Mineralogy, geochemistry, and radiocarbon ages of deep sea sediments from the Gulf of Mexico, Mexico

NASA Astrophysics Data System (ADS)

Armstrong-Altrin, John S.; Machain-Castillo, María Luisa

2016-11-01

The mineralogy, geochemistry, and radiocarbon ages of two sediment cores (GMX1 and GMX2) collected from the deep sea area of the Southwestern Gulf of Mexico (∼876-1752 m water depth) were studied to infer the sedimentation rate, provenance, heavy metal contamination, and depositional environment. The sediments are dominated by silt and clay fractions. The mineralogy determined by X-Ray diffractometry for the sediment cores reveals that montmorillonite and muscovite are the dominant clay minerals. The sections between 100 and 210 cm of the sediment cores GMX1 and GMX2, respectively, are characterized by the G. menardii group and G. Inflata planktonic foraminiferal species, which represent the Holocene and Pleistocene, respectively. The radiocarbon-age measurements of mixed planktonic foraminifera varied from ∼268 to 45,738 cal. years B.P and ∼104 to 25,705 cal. years B.P, for the sediment cores GMX1 and GMX2, respectively. The variation in age between the two sediment cores is due to a change in sediment accumulation rate, which was lowest at the location GMX1 (0.006 cm/yr) and highest at the location GMX2 (0.017 cm/yr). The chemical index of alteration (CIA), chemical index of weathering (CIW), and index of chemical maturity (ICV) values indicated a moderate intensity of weathering in the source area. The total rare earth element concentrations (∑REE) in the cores GMX1 and GMX2 vary from ∼94 to 171 and ∼78 to 151, respectively. The North American Shale Composite (NASC) normalized REE patterns showed flat low REE (LREE), heavy REE (HREE) depletion with low negative to positive Eu anomalies, which suggested that the sediments were likely derived from intermediate source rocks. The enrichment factor of heavy metals indicated that the Cd and Zn concentrations in the sediment cores were impacted by an anthropogenic source. The redox-proxy trace element ratios such as V/Cr, Ni/Co, Cu/Zn, (Cu + Mo)/Zn, and Ce/Ce* indicated that the sediments were deposited under an oxic depositional environment. The similarity in major element concentrations, REE content, and the NASC normalised REE patterns between the cores GMX1 and GMX2 revealed that the provenance of sediments remained relatively uniform or constant during deposition for ∼4.5 Ma. The major and trace element based multidimensional discrimination diagrams showed a rift setting for the core sediments, which is consistent with the geology of the Gulf of Mexico.

Nitrate removal in deep sediments of a nitrogen-rich river network: A test of a conceptual model

USGS Publications Warehouse

Stelzer, Robert S.; Bartsch, Lynn

2012-01-01

Many estimates of nitrogen removal in streams and watersheds do not include or account for nitrate removal in deep sediments, particularly in gaining streams. We developed and tested a conceptual model for nitrate removal in deep sediments in a nitrogen-rich river network. The model predicts that oxic, nitrate-rich groundwater will become depleted in nitrate as groundwater upwelling through sediments encounters a zone that contains buried particulate organic carbon, which promotes redox conditions favorable for nitrate removal. We tested the model at eight sites in upwelling reaches of lotic ecosystems in the Waupaca River Watershed that varied by three orders of magnitude in groundwater nitrate concentration. We measured denitrification potential in sediment core sections to 30 cm and developed vertical nitrate profiles to a depth of about 1 m with peepers and piezometer nests. Denitrification potential was higher, on average, in shallower core sections. However, core sections deeper than 5 cm accounted for 70%, on average, of the depth-integrated denitrification potential. Denitrification potential increased linearly with groundwater nitrate concentration up to 2 mg NO3-N/L but the relationship broke down at higher concentrations (> 5 mg NO3-N/L), a pattern that suggests nitrate saturation. At most sites groundwater nitrate declined from high concentrations at depth to much lower concentrations prior to discharge into the surface water. The profiles suggested that nitrate removal occurred at sediment depths between 20 and 40 cm. Dissolved oxygen concentrations were much higher in deep sediments than in pore water at 5 cm sediment depth at most locations. The substantial denitrification potential in deep sediments coupled with the declines in nitrate and dissolved oxygen concentrations in upwelling groundwater suggest that our conceptual model for nitrate removal in deep sediments is applicable to this river network. Our results suggest that nitrate removal rates can be high in deep sediments of upwelling stream reaches, which may have implications for efforts to understand and quantify nitrogen transport and removal at larger scales.

A 59-year sedimentary record of metal pollution in the sediment core from the Huaihe River, Huainan, Anhui, China.

PubMed

Wang, Jie; Liu, Guijian; Zhang, Jiamei; Liu, Houqi; Lam, Paul K S

2016-12-01

An approximately 59-year (1955-2014) sedimentary record of metal elements (Cu, Pb, Zn, Ni, Co, Mn, and Fe) in a sediment core, collected from the Huaihe River, Huainan City, Anhui Province, China, was reconstructed by using 210 Pb geochronology. Copper, Zn, Ni, Co, and Mn evaluated by enrichment factor (EF) indicated minor contamination due to water pollution accidents of the Huaihe River that occurred in 1990s and 2004. Lead presented the most severe pollution among the metals studied, especially during 1957-1974. The use of leaded petrol and atmospheric deposition of coal combustion flue gases could have contributed to Pb contamination. In spite of the general good quality (mean sediment pollution index (SPI) 35.69) of the sediment core evaluated by SPI based on the principal component analysis, worse sediment qualities in the upper section (<6 cm, 2004) were still observed, suggesting intensive human activities causing the increasing concentrations of metals in recent decades.

Fish Lake, Utah - a promising long core site straddling the Great Basin to Colorado Plateau transition zone

NASA Astrophysics Data System (ADS)

Marchetti, D. W.; Abbott, M. B.; Bailey, C.; Wenrich, E.; Stoner, J. S.; Larsen, D. J.; Finkenbinder, M. S.; Anderson, L.; Brunelle, A.; Carter, V.; Power, M. J.; Hatfield, R. G.; Reilly, B.; Harris, M. S.; Grimm, E. C.; Donovan, J.

2015-12-01

Fish Lake (~7x1.5 km and 2696 m asl) is located on the Fish Lake Plateau in central Utah. The Lake occupies a NE-striking tectonic graben; one of a suite of grabens on the Plateau that cut 21-26 Ma volcanic rocks. The lake outflows via Lake Creek to the NE where it joins Sevenmile Creek to become the Fremont River, a tributary to the Colorado River. A bathymetric survey reveals a mean depth of 27 m and a max depth of 37.2 m. The lake bottom slopes from NW to SE with the deepest part near the SE wall, matching the topographic expression of the graben. Nearby Fish Lake Hightop (3545 m) was glaciated with an ice field and outlet glaciers. Exposure ages indicate moraine deposition during Pinedale (15-23 ka) and Bull Lake (130-150 ka) times. One outlet glacier at Pelican Canyon deposited moraines and outwash into the lake but the main basin of the lake was never glaciated. Gravity measurements indicate that lake sediments thicken toward the SE side of the lake and the thickest sediment package is modeled to be between 210 and 240 m. In Feb 2014 we collected cores from Fish Lake using a 9-cm diameter UWITECH coring system in 30.5 m of water. A composite 11.2-m-long core was constructed from overlapping 2 m drives that were taken in triplicate to ensure total recovery and good preservation. Twelve 14C ages and 3 tephra layers of known age define the age model. The oldest 14C age of 32.3±4.2 cal ka BP was taken from 10.6 m. Core lithology, CT scans, and magnetic susceptibility (ms) reveal three sediment packages: an organic-rich, low ms Holocene to post-glacial section, a fine-grained, minerogenic glacial section with high ms, and a short section of inferred pre-LGM sediment with intermediate composition. Extrapolating the age model to the maximum estimated sediment thicknesses suggest sediments may be older than 500-700 ka. Thus Fish Lake is an ideal candidate for long core retrieval as it likely contains paleoclimatic records extending over multiple glacial cycles.

High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

USGS Publications Warehouse

Powars, David S.; Catchings, Rufus D.; Goldman, Mark R.; Gohn, Gregory S.; Horton, J. Wright; Edwards, Lucy E.; Rymer, Michael J.; Gandhok, Gini

2009-01-01

The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (~5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientific Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderate-amplitude, discontinuous, dipping reflections below ~527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ~527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fill sediments and postimpact Eocene to Pleistocene sediments. Reflections with ~20-30 m of relief in the uppermost part of the crater-fill and lowermost part of the postimpact section suggest differential compaction of the crater-fill materials during early postimpact time. The top of the crater-fill section also shows ~20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostrati-graphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the first possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postim-pact section unrelated to structures in the crater fill indicates postimpact sediment compaction.

Reconstructed Sediment Mobilization Processes in a Large Reservoir Using Short Sediment Cores

NASA Astrophysics Data System (ADS)

Cockburn, J.; Feist, S.

2014-12-01

Williston Reservoir in northern British Columbia (56°10'31"N, 124°06'33") was formed when the W.A.C. Bennett Dam was created in the late 1960s, is the largest inland body of water in BC and facilitates hydroelectric power generation. Annually the reservoir level rises and lowers with the hydroelectric dam operation, and this combined with the inputs from several river systems (Upper Peace, Finlay, Parsnip, and several smaller creeks) renews suspended sediment sources. Several short-cores retrieved from shallow bays of the Finlay Basin reveal near-annual sedimentary units and distinct patterns related to both hydroclimate variability and the degree to which the reservoir lowered in a particular year. Thin section and sedimentology from short-cores collected in three bays are used to evaluate sediment mobilization processes. The primary sediment sources in each core location is linked to physical inputs from rivers draining into the bays, aeolian contributions, and reworked shoreline deposits as water levels fluctuate. Despite uniform water level lowering across the reservoir, sediment sequences differed at each site, reflecting the local stream inputs. However, distinct organic-rich units, facilitated correlation across the sites. Notable differences in particle size distributions from each core points to important aeolian derived sediment sources. Using these sedimentary records, we can evaluate the processes that contribute to sediment deposition in the basin. This work will contribute to decisions regarding reservoir water levels to reduce adverse impacts on health, economic activities and recreation in the communities along the shores of the reservoir.

Anisotropy of magnetic susceptibility used to detect coring-induced sediment disturbance and filter palaeomagnetic secular variation data: IODP sites M0061 and M0062 (Baltic Sea)

NASA Astrophysics Data System (ADS)

Snowball, Ian; Almqvist, Bjarne; Lougheed, Bryan; Svensson, Anna; Wiers, Steffen; Herrero-Bervera, Emilio

2017-04-01

Inspired by palaeomagnetic data obtained from two sites (M0061 and M0062) cored during IODP Expedition 347 - Baltic Sea Paleoenvironment we studied the Hemsön Alloformation, which is a series of brackish water muds consisting of horizontal planar and parallel laminated (varved) silty clays free from bioturbation. We determined the anisotropy of magnetic susceptibility (AMS) and characteristic remanence (ChRM) directions of a total of 1,102 discrete samples cut from (i) IODP cores recovered by an Advanced Piston corer and (ii) a series of six sediment cores recovered from the same sites by a Kullenberg piston corer. Systematic core splitting, sub-sampling methods and measurements were applied to all sub-samples. We experimentally tested for field-impressed AMS of these muds, in which titanomagnetite carries magnetic remanence and this test was negative. The AMS is likely determined by paramagnetic minerals. As expected for horizontally bedded sediments, the vast majority of the K1 (maximum) and K2 (intermediate) axes had inclinations close to 0 degrees and the AMS shape parameter (T) indicates an oblate fabric. The declinations of the K1 and K2 directions of the sub-samples taken from Kullenberg cores showed a wide distribution around the bedding plane, with no preferred alignment along any specimen axis. Exceptions are samples from the upper 1.5 m of some of these cores, in which the K1 and K2 directions were vertical, the K3 (minimum) axis shallow and T became prolate. We conclude that the Kullenberg corer, which penetrated the top sediments with a pressure of approximately 15 bar, occasionally under-sampled during penetration and vertically stretched the top sediments. Sub-samples from the upper sections of Kullenberg cores had relatively steep ChRM inclinations and we rejected samples that had a prolate, vertically oriented AMS ellipsoid. Surprisingly, the declinations of the K1 axis of all sub-samples taken from IODP APC core sections, which were not oriented relative to each other with respect to azimuth, clustered tightly within the 90-270 degree specimen axis (K2 is within the 0-180 degree axis). This axis is the direction across each cores' split surface (i.e. perpendicular to the "push" direction of the sub-sampling boxes). The APC cores were characterized by various degrees of downwards bending of the planar varves towards the inner surface of the core liner. We conclude that the initial hydraulic pressure applied by the APC, which was consistently above 50 bar during Expedition 347, was needlessly high and created a conical sediment structure and the distinct alignment of the magnetic susceptibility axes along specimen axes. APC core sections with marked disturbances were characterized by ChRM inclinations below 65 degrees, which is a lower limit predicted by time varying geomagnetic field models for the duration of the Hemsö Alloformation (the most recent 6000 years). We rejected samples for palaeomagnetic purposes if the K1 inclination was steeper than 10 degrees. Our study highlights the added value of measuring AMS of discrete sub-samples as an independent control of the suitability of sediments as a source of palaeomagnetic data.

Trends in chlorinated hydrocarbon levels in Hudson River basin sediments.

PubMed

Bopp, R F; Chillrud, S N; Shuster, E L; Simpson, H J; Estabrooks, F D

1998-08-01

Analysis of sections from dated sediment cores were used to establish geographic distributions and temporal trends of chlorinated hydrocarbon contaminant levels in sediments from natural waters of the Hudson River basin. Radiometric dating was based primarily on the depth distribution of 137(Cs) in the cores and on the occurrence of detectable levels of 7(Be) in surface sediment samples. Eighteen sampling sites included several along the main stem of the Hudson, its major tributaries, and components of the New York/New Jersey (NY/NJ) harbor complex. Drinking-water reservoirs were sampled to place upper limits on atmospheric inputs. Core sections were analyzed for polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT)-derived compounds, chlordane, and dioxins. Sediment concentrations of most contaminants at most sites have decreased significantly since the mid-1960s. The data provide a basinwide perspective on major point-source inputs of PCBs to the upper Hudson River and of 2,3,7,8-tetrachlorodibenzo-p-dioxin and DDT to the lower Passaic River. Evidence was found for significant but poorly characterized sources of PCBs and chlordane to the western NY/NJ harbor, and of highly chlorinated dioxins to the upstream sites on the main stem of the Hudson. The results indicate that analysis of dated sediment samples is a most effective and efficient monitoring tool for the study of large-scale geographic and temporal trends in levels of particle-associated contaminants.

Preliminary cross section of Englebright Lake sediments

USGS Publications Warehouse

Snyder, Noah P.; Hampton, Margaret A.

2003-01-01

Overview -- The Upper Yuba River Studies Program is a CALFED-funded, multidisciplinary investigation of the feasibility of introducing anadromous fish species to the Yuba River system upstream of Englebright Dam. Englebright Lake (Figure 1 on poster) is a narrow, 14-km-long reservoir located in the northern Sierra Nevada, northeast of Marysville, CA. The dam was completed in 1941 for the primary purpose of trapping sediment derived from mining operations in the Yuba River watershed. Possible management scenarios include lowering or removing Englebright Dam, which could cause the release of stored sediments and associated contaminants, such as mercury used extensively in 19th-century hydraulic gold mining. Transport of released sediment to downstream areas could increase existing problems including flooding and mercury bioaccumulation in sport fish. To characterize the extent, grain size, and chemistry of this sediment, a coring campaign was done in Englebright Lake in May and June 2002. More than twenty holes were drilled at 7 different locations along the longitudinal axis of the reservoir (Figure 4 on poster), recovering 6 complete sequences of post-reservoir deposition and progradation. Here, a longitudinal cross section of Englebright Lake is presented (Figure 5 on poster), including pre-dam and present-day topographic profiles, and sedimentologic sections for each coring site. This figure shows the deltaic form of the reservoir deposit, with a thick upper section consisting of sand and gravel overlying silt, a steep front, and a thinner lower section dominated by silt. The methodologies used to create the reservoir cross section are discussed in the lower part of this poster.

Molluscan shell communities: a window into the ecological history of the northern Adriatic Sea

NASA Astrophysics Data System (ADS)

Gallmetzer, Ivo; Haselmair, Alexandra; Tomasovych, Adam; Stachowitsch, Michael; Zuschin, Martin

2015-04-01

The historical ecology approach used in the present study sheds light on the younger ecological history of the northern Adriatic Sea, targeting the period of the last 500 to 1500 years. We focus on down-core changes in molluscan death assemblages, where differences between community structures serve as a proxy for ecological shifts over time. The northern Adriatic Sea, with its densely populated shoreline, is among the most degraded marine ecosystems worldwide and is therefore particularly suited to study ecosystem modification under human pressure. Multiple cores of 1.5 m length and diameters of 90 and 160 mm were taken at seven sampling stations throughout the northern Adriatic Sea, covering different sediment types, nutrient conditions and degrees of exploitation. For the mollusc analyses, the cores were sliced into smaller subsamples and analysed for species composition, abundance, taxonomic similarity, evidence for ecological interactions (i.e., frequencies of drilling predation) and taphonomic condition of shells. Sediment analyses include granulometry and radiometric sediment dating using Pb 210. Sediment age analysis revealed one-order-of-magnitude differences in sedimentation rates between stations (34 mm/yr at the Po delta, Italy, 1.5 mm/yr at Brijuni islands, Croatia). In total, 114 bivalve and 112 gastropod species were recorded. Bivalve assemblages showed significant interregional differences that are strongly correlated with sedimentation rates and sediment composition. Down-core changes in molluscan communities are conspicuous in all cores, particularly in the uppermost core sections. This information, together with radiometric shell dating for selected species, helps to specify the timing of major ecological changes in the past and define pristine benthic communities as references for future conservation and management efforts.

Polychaete Tubes, Turbulence, and Erosion of Fine-Grained Sediment

NASA Astrophysics Data System (ADS)

Kincke-Tootle, A.; Frank, D. P.; Briggs, K. B.; Calantoni, J.

2016-02-01

The role of polychaete tubes protruding through the benthic boundary layer in promoting or hindering erosion of fine-grained sediment was examined in laboratory experiments. Diver core samples of the top 10cm of sediment were collected west of Trinity Shoal off the Louisiana coast in 10-m depth. Diver cores were used in laboratory experiments conducted in a unidirectional flume. Tubes that were constructed by polychaetes, which comprised 70% of the species from the study area, were inserted into the core sediment surface. The sediment cores were then placed in the 2-m long test section of a small oscillatory flow tunnel and high-speed, stereo particle image velocimetry was used to determine the 2-dimensional, 3-component fluid velocity at high temporal (100 Hz) and spatial (< 1mm vector spacing) resolution. The tubes that protruded above the boundary layer allowed vortices to be initiated. Tubes are made up of shell fragments and fine-grained sediment, allowing for some rigidity and resistance to the flow. Rigidity determines the resistance causing small-scale eddies to form. The small-scale turbulence incited scour erosion, allowing fine-grained particles to be suspended into the water and in some cases coarser particles to be mobilized. Less-rigid tubes succumb to the shear stress, inhibit the formation of small-scale eddies, limit sediment erodibility, and increase the critical shear stress of the sediment. Discussion will focus on a modification to the critical Shields parameter to account for the effects of benthic biological activity.

A Comparison of Naturally-Occurring and Artificially Stimulated Uranium(VI) Bioreduction in Sediment from a Field-scale Experiment in Rifle, CO

NASA Astrophysics Data System (ADS)

Campbell, K. M.; Williams, K. H.; Lesher, E.; Davis, J. A.; Long, P. E.

2007-12-01

Long-term remediation of uranium (U)-contaminated groundwater poses one of the greatest challenges in the clean-up of impacted sites. One solution is to reduce dissolved U(VI) to insoluble U(IV) precipitates by stimulating indigenous metal reducing bacterial populations in situ. Contamination from a former U mine tailings repository (Rifle, CO) provides a research site to study the efficacy of biostimulated U(VI) reduction at the field scale. Several cores were drilled in June 2007 across a region of naturally-occurring U(VI) bioreduction. The cores represent a cross section of sediment that ranges from minimally reducing to highly reducing. Anaerobic sediment samples from the cores were analyzed for labile U(VI) content by carbonate extraction in anoxic conditions (pH 9.4, 14 mM NaHCO3, 2.8 mM Na2CO¬3). A subset of the same core sections were dried and oxidized by exposure to air for 2 weeks. The carbonate extraction was repeated, and the amount of U(IV) present in the anaerobic sample was calculated by difference between the anoxic and oxidized extractions. An acid extraction was also performed on the oxidized sediments to compare the carbonate extractable and the acid extractable U fractions. The highest U concentrations were found in the highly bioreduced sediment, with the majority of U present as U(IV) (66-92%). The regions of highest bioreduction also correspond to elevated concentrations of solid phase organic carbon, suggesting that natural bioreduction is stimulated by zones of increased organic carbon content. The same field site was then used for an artificially stimulated bioreduction experiment, where the indigenous bacterial community was stimulated by injecting acetate upgradient of the core collection location. Carbonate and acid extractions were performed on core samples taken after the completion of the acetate injection. This work evaluates the composition of the sediment before and after biostimulation as a way of directly comparing the extent of natural U(VI) bioreduction to acetate-stimulated bioreduction in order to facilitate the design of a more effective bioremediation strategy for this site.

High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

USGS Publications Warehouse

Powars, D.S.; Catchings, R.D.; Goldman, M.R.; Gohn, G.S.; Horton, J. Wright; Edwards, L.E.; Rymer, M.J.; Gandhok, G.

2009-01-01

The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (??5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientifi c Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderateamplitude, discontinuous, dipping reflections below ??527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ??527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fi ll sediments and postimpact Eocene to Pleistocene sediments. Refl ections with ??20-30 m of relief in the uppermost part of the crater-fi ll and lowermost part of the postimpact section suggest differential compaction of the crater-fi ll materials during early postimpact time. The top of the crater-fi ll section also shows ??20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostratigraphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the fi rst possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postimpact section unrelated to structures in the crater fi ll indicates postimpact sediment compaction. ?? 2009 The Geological Society of America.

Paleoclimatological analysis of Late Eocene core, Manning Formation, Brazos County, Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yancey, T.; Elsik, W.

1994-09-01

A core of the basal part of the Manning Formation was drilled to provide a baseline for paleoclimate analysis of the expanded section of siliciclastic sediments of late Eocene age in the outcrop belt. The interdeltaic Jackson Stage deposits of this area include 20+ cyclic units containing both lignite and shallow marine sediments. Depositional environments can be determined with precision and the repetitive nature of cycles allows comparisons of the same environment throughout, effectively removing depositional environment as a variable in interpretation of climate signal. Underlying Yegua strata contain similar cycles, providing 35+ equivalent environmental transacts within a 6 m.y.more » time interval of Jackson and Yegua section, when additional cores are taken. The core is from a cycle deposited during maximum flooding of the Jackson Stage, with deposits ranging from shoreface (carbonaceous) to midshelf, beyond the range of storm sand deposition. Sediments are leached of carbonate, but contain foram test linings, agglutinated forams, fish debris, and rich assemblages of terrestrial and marine palynomorphs. All samples examined contain marine dinoflagellates, which are most abundant in transgressive and maximum flood zones, along with agglutinated forams and fish debris. This same interval contains two separate pulses of reworked palynomorphs. The transgressive interval contains Glaphyrocysta intricata, normally present in Yegua sediments. Pollen indicates fluctuating subtropical to tropical paleoclimates, with three short cycles of cooler temperatures, indicated by abundance peaks of alder pollen (Alnus) in transgressive, maximum flood, and highstand deposits.« less

Geomagnetic Excursions and High-Latitude Paleomagnetic Records of Glaciomarine Sediments from the Western Greenland Margin (Baffin Bay)

NASA Astrophysics Data System (ADS)

Richter, C.; Jensen, S. R.; Acton, G. D.; Evans, H. F.

2017-12-01

We present new paleomagnetic results from Quaternary sediment samples recovered during the Baffin Bay Scientific Coring Expedition conducted by the JOIDES Resolution in 2012. The expedition recovered well-preserved core material from the Arctic Basin, providing an outstanding opportunity for the study of the behavior of the geomagnetic field at high latitude. We analyzed material from 12 sites cored at latitudes between 74°45.32'N and 75°46.68'N in the Melville Bay region (Cape York and Melville Ridge) of Baffin Bay located at an average water depth of 394 m. The Quaternary glaciomarine sediments are up to 150 m thick and consist of very soft diatom-bearing muds to clast-rich sandy and muddy diamicts, which suggest deposition in a subglacial to ice-procimal environment. We carried out paleomagnetic and rock magnetic measurements on the shipboard cryogenic magnetometer at 5-cm resolution on 32 split-core sections and a selected number of discrete samples, and recently processed measurements taken at 1-cm resolution on eight U-channel samples from the uppermost Holocene part of the section. Stepwise demagnetization of the NRM demonstrates excellent demagnetization behavior, with a viscous isothermal remanent magnetization overprint, induced by the coring and sampling process, and typically removed by the 20 mT demagnetization step. The magnetic inclination data are characterized by steep, 80°, normal inclinations, consistent with the site position near the North Pole. Thermal demagnetization, magnetic susceptibility, isothermal remanent magnetization, and hysteresis parameters indicate that the primary magnetic carrier consists of a low-coercivity mineral, e.g., magnetite and/or titanomagnetite, with minor traces of higher-coercivity minerals. Well-developed geomagnetic excursions in the upper part of the section can be correlated between several sites. Although dating of these sediments remains a challenge because of the lack of carbonates we will discuss possible age models and use them to assign ages to the geomagnetic excursions.

Trends in chlorinated hydrocarbon levels in Hudson River basin sediments.

PubMed Central

Bopp, R F; Chillrud, S N; Shuster, E L; Simpson, H J; Estabrooks, F D

1998-01-01

Analysis of sections from dated sediment cores were used to establish geographic distributions and temporal trends of chlorinated hydrocarbon contaminant levels in sediments from natural waters of the Hudson River basin. Radiometric dating was based primarily on the depth distribution of 137(Cs) in the cores and on the occurrence of detectable levels of 7(Be) in surface sediment samples. Eighteen sampling sites included several along the main stem of the Hudson, its major tributaries, and components of the New York/New Jersey (NY/NJ) harbor complex. Drinking-water reservoirs were sampled to place upper limits on atmospheric inputs. Core sections were analyzed for polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT)-derived compounds, chlordane, and dioxins. Sediment concentrations of most contaminants at most sites have decreased significantly since the mid-1960s. The data provide a basinwide perspective on major point-source inputs of PCBs to the upper Hudson River and of 2,3,7,8-tetrachlorodibenzo-p-dioxin and DDT to the lower Passaic River. Evidence was found for significant but poorly characterized sources of PCBs and chlordane to the western NY/NJ harbor, and of highly chlorinated dioxins to the upstream sites on the main stem of the Hudson. The results indicate that analysis of dated sediment samples is a most effective and efficient monitoring tool for the study of large-scale geographic and temporal trends in levels of particle-associated contaminants. Images Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 PMID:9703496

Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

USGS Publications Warehouse

Stern, Laura A.; Lorenson, T.D.; Pinkston, John C.

2011-01-01

Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA–DOE–USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5 m to 760.1 m depth, and sections investigated here were retrieved from 619.9 m and 661.0 m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70–75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20–120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas.

Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

USGS Publications Warehouse

Stern, L.A.; Lorenson, T.D.; Pinkston, J.C.

2011-01-01

Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5. m to 760.1. m depth, and sections investigated here were retrieved from 619.9. m and 661.0. m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70-75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20-120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas. ?? 2009.

Geoacoustic Characterization of the Mud Drape at the New England Mud Patch

NASA Astrophysics Data System (ADS)

Reed, A. H.

2016-02-01

The New England Mud Patch is an extensive deposit of fine-grained sediments that extends from an area south of Cape Cod, MA to south of Montauk Point Long Island, NY out on the continental shelf in water depths of 60 to 90 meters. The mud patch has a remarkable accumulation of up to a 13 meter thick sequence of mud that overlays a transgressive surface of Pleistocene Age and then thins out on the periphery where surficial sediments convert from mud to sand and sand/gravel. The deposit likely accumulated in this region due to the coalescing of shelf currents that had oppositional flow. This work focuses on a section of the mud patch that is centered over the thickest portion of mud and extends east-west for 30 km and north south for 10 km. Gravity cores were collected throughout this region and the cores penetrated the upper 2-4 m of mud at 28 different sites with multiple cores collected in several locations. The mud thickness in these regions exceeded the core barrel length, therefore the cores did not penetrate into the basal sand sediment layer, a relict transgressional horizon, which displays prominently in the acoustic data for this selected region. These cores were evaluated for compressional sound speed (averaging 1480 m/s) and density (1580 kg/m3) and found to be largely homogeneous and similar throughout the study area. The largest source of inhomogeneity was due to dispersed shell hash and disarticulated bivalves, but these inclusions represent minor components in the total sediment volume. The overlying sediment that characterizes the New England Mud Patch can be readily classified as mud, silty mud, or sandy-silty mud. This fine-grained sediment deposit reflects upon the low-energy nature of the hydrodynamics within this region.

The Varved Sediments of Lake Bosumtwi, Ghana and Implications for a new Chronology of West African Hydrologic Change During the Late Quaternary

NASA Astrophysics Data System (ADS)

Wheeler, C. W.; Overpeck, J. T.; Beck, J. W.; Arko, J.; Sharp, W. E.

2002-12-01

Lake Bosumtwi is a small (8-km diameter), deep (78-m) crater lake in the lowland forest of southern Ghana (West Africa) that offers tremendous potential for high-resolution environmental reconstruction. Lying in the path of the seasonal Intertropical Convergence Zone (ITCZ) monsoonal precipitation procession, as well as the dry Harmattan winds of the Sahel in winter, this lake is uniquely located to provide potential proxy records of these dominate climatic phenomena effecting West Africa's hydrologic cycle. The lake exhibits excellent sediment preservation, with finely laminated sediments through most of the ca. 24,000 years of core material recovered thus far. We present a detailed chronological analysis of the uppermost 1.1 meters of laminated sediment, obtained via a recently collected suite of freeze- and piston-cores. Utilizing digital images and petrographic thin-section transects of six freeze-cores and two piston cores, we identified 400 diagnostic marker laminations common among the cores, thus enabling cross correlation of the cores to a sub-centimeter scale. The marker laminations also serve as anchor points for counts of organic-rich fine-laminations that were hypothesized to be annual. Excellent agreement between our lamination counts and independent radiometric sediment age models (lead-210 and bomb radiocarbon) verify that these counted laminations are in fact annual (i.e. varves). Thus, we are able to present an annual chronology for the last 800 years of sedimentation (prior to 2000 AD)ñ ~4%. Though anthroprogenic changes have probably effected the local environment within the last 100 years, as we interpret anomalous increases in %organic carbon, %inorganic carbon and %nitrogen to indicate, the varve appearance does not seem to change across the 1.1 m section analyzed. Pre-nuclear weapon testing radiocarbon values, derived from bulk organic carbon, were examined in relation to the varve and lead-210 age-models to assess radiocarbon age offset due to reservoir effects and the redeposition of old-carbon; the data suggest that anomalously old radiocarbon ages ranging from ~430 to 3000 years are possible. The size of the radiocarbon bias may vary with lake status, indicating the role of old-carbon redeposition from ancient lake sediments currently at shallow depths or above current lake level in the crater catchment. Our study shows that 1) varves have excellent potential for creating a high-resolution chronology for Lake Bosumtwi, and 2) caution must be taken in using radiocarbon results to date the sediments of Lake Bosumtwi

Postimpact deposition in the Chesapeake Bay impact structure: Variations in eustasy, compaction, sediment supply, and passive-aggressive tectonism

USGS Publications Warehouse

Kulpecz, A.A.; Miller, K.G.; Browning, J.V.; Edwards, L.E.; Powars, D.S.; McLaughlin, P.P.; Harris, A.D.; Feigenson, M.D.

2009-01-01

The Eyreville and Exmore, Virginia, core holes were drilled in the inner basin and annular trough, respectively, of the Chesapeake Bay impact structure, and they allow us to evaluate sequence deposition in an impact crater. We provide new high-resolution geochronologic (<1 Ma) and sequence-stratigraphic interpretations of the Exmore core, identify 12 definite (and four possible) postimpact depositional sequences, and present comparisons with similar results from Eyreville and other mid- Atlantic core holes. The concurrence of increases in ??18O with Chesapeake Bay impact structure sequence boundaries indicates a primary glacioeustatic control on deposition. However, regional comparisons show the differential preservation of sequences across the mid-Atlantic margin. We explain this distribution by the compaction of impactites, regional sediment-supply changes, and the differential movement of basement structures. Upper Eocene strata are thin or missing updip and around the crater, but they thicken into the inner basin (and offshore to the southeast) due to rapid crater infilling and concurrent impactite compaction. Oligocene sequences are generally thin and highly dissected throughout the mid-Atlantic region due to sediment starvation and tectonism, except in southeastern New Jersey. Regional tectonic uplift of the Norfolk Arch coupled with a southward decrease in sediment supply resulted in: (1) largely absent Lower Miocene sections around the Chesapeake Bay impact structure compared to thick sections in New Jersey and Delaware; (2) thick Middle Miocene sequences across the Delmarva Peninsula that thin south of the Chesapeake Bay impact structure; and (3) upper Middle Miocene sections that pinch out just north of the Chesapeake Bay impact structure. Conversely, the Upper Miocene-Pliocene section is thick across Virginia, but it is poorly represented in New Jersey because of regional variations in relative subsidence. ?? 2009 The Geological Society of America.

Synthetic Musk Fragrances in Lake Erie and Lake Ontario Sediment Cores

PubMed Central

Peck, Aaron M.; Linebaugh, Emily K.; Hornbuckle, Keri C.

2009-01-01

Two sediment cores collected from Lake Ontario and Lake Erie were sectioned, dated, and analyzed for five polycyclic musk fragrances and two nitro musk fragrances. The polycyclic musk fragrances were HHCB (Galaxolide), AHTN (Tonalide), ATII (Traseolide), ADBI (Celestolide), and AHMI (Phantolide). The nitro musk fragrances were musk ketone and musk xylene. Chemical analysis was performed by gas chromatography/mass spectrometry (GC/MS) and results from Lake Erie were confirmed using gas chromatography/triple-quadrupole mass spectrometry (GC/MS/MS). The chemical signals observed at the two sampling locations were different from each other due primarily to large differences in the sedimentation rates at the two sampling locations. HHCB was detected in the Lake Erie core while six compounds were detected in the Lake Ontario core. Using measured fragrance and 210Pb activity, the burden of synthetic musk fragrances estimated from these sediment cores is 1900 kg in Lake Erie and 18000 kg in Lake Ontario. The input of these compounds to the lakes is increasing. The HHCB accumulation rates in Lake Erie for 1979-2003 and 1990-2003 correspond to doubling times of 16 ± 4 yr and 8 ± 2 yr, respectively. The results reflect current U.S. production trends for the sum of all fragrance compounds. PMID:17007119

VARIATIONS IN MINERAL MATTER CONTENT OF A PEAT DEPOSIT IN MAINE RESTING ON GLACIO-MARINE SEDIMENTS.

USGS Publications Warehouse

Cameron, Cornelia C.; Schruben, Paul

1983-01-01

The Great Heath, Washington County, Maine, is an excellent example of a multidomed ombrotrophic peatland resting on a gently undulating surface of glacio-marine sediments and towering above modern streams. A comprehensive study sponsored by the Geological Survey of Maine in cooperation with the U. S. Geological Survey included preparation of a contoured surficial geology map on which are located 81 core sites. Eight cross sections accompany the map showing occurrence and thickness of three types of organic material and locations of cored sample analyses. Refs.

Sedimentological and geochemical investigations to understand source of sediments and processes of recent past in Schirmacher Oasis, East Antarctica

NASA Astrophysics Data System (ADS)

Choudhary, Shabnam; Tiwari, Anoop Kumar; Nayak, G. N.; Bejugam, Purnima

2018-03-01

Three sediment cores collected from GL-1, V-1(Vetehiya) and L-6 lakes of Schirmacher Oasis, East Antarctica were studied for sediment components (sand, silt, clay, total organic carbon, total nitrogen, TOC/TN ratio and biogenic silica), major elements (Aluminium, Iron and Manganese) and trace metals (Chromium, Zinc, Lead, Cobalt, Cadmium and Nickel). High sand content in all the three cores revealed the release of coarser sediments through mechanical weathering in fluvio-glacial environment. Relatively, high biogenic silica along with high total organic carbon associated with high clay in some sections indicated high primary productivity due to the warming and exposure of the lakes to the ice-melt water influx. TOC/TN ratio for all the cores was found to be < 10 which indicated that the major source of organic matter was autochthonous. Metals were found to be strongly associated with clay and organic carbon in core V-1, with sand and clay in core L-6 while, with silt and organic matter in core GL-1 indicating their role in regulating the distribution of metals. Cadmium in lake GL-1 was found to be associated with total organic carbon and showed largely biogenic origin, while, Cd and Pb in lakes L-6 and V-1 were found to be of anthropogenic origin. All the other metals showed signatures of lithogenic origin.

Core logs from five holes near Kramer, in the Mojave Desert, California

USGS Publications Warehouse

Benda, William K.; Erd, Richard C.; Smith, Ward C.

1958-01-01

In 1957, five test holes were drilled near Kramer, California, in =he western Mojave Desert. The drill sites are in topographic basins where gravimetric and geologic surveys indicated the presence, beneath alluvium, of a thick section of Quaternary and Tertiary sedimentary and volcanic rocks. Two holes which were deeper tests at sites drilled in 1954 cored only silts, sands and gravels: Four Corners test hole No. 1 was drilled in sec. 20, T. I0 N., R. 6 W., to a depth of 3,500 feet. Four Corners No. 2, in sec. 5, T. I0 N., R. 8 W., was drilled to 2,328 feet. Three holes which were drilled at new sites north of the intersection of U. S. Highways 395 and 466, locally known as Four Corners, encountered colemanite-bearing sediments. The locations and total depths of these holes are as follows: Four Corners No. 3, sec. T. 11 N., R. 6 W., depth 2,568 feet; Four Corners No. 4, near northern edge of sec. 30, T. ll N., R. 6 W., depth 3,500 feet; Four Corners No. 5, near southern edge of sec. 30, depth 1,604 feet. The sections of rocks encountered in these three holes are similar. In each, the colemanite is in fine-grained sediments that lie below sands and gravels, which are about 600 to 800 feet thick, and are underlain by sandstones and conglomerates. Colemanite is most abundant in the cores from Four Corners to hole No. 5, particularly in the 76 feet of core recovered between depths of 1,051 and 1,131 feet. Chemical analysis shows that in this section of core the average content of B203 is above 14 percent. In addition to colemanite, the cores contain sulfides of arsenic, an unusual iron sulfide, and zeolites. This mineralogy of the colemanite-bearing sediments north of Four Corners, together with the general lake bed lithology and the occurrence as a tilted section of beds below sands and gravels, supports correlation with the upper or marginal parts of the borate-bearin8 sediments at the Kramer borate mining district, which have similar features. There is, however, no evidence that any beds are exactly equivalent in age.

Benthic and Plankton Foraminifers in Hydrothermally Active Zones of the Mid-Atlantic Ridge (MAR)

NASA Astrophysics Data System (ADS)

Khusid, T. A.; Os'kina, N. S.; Lukashina, N. P.; Gablina, I. F.; Libina, N. V.; Matul, A. G.

2018-01-01

Comparison of benthic foraminiferal assemblages from the core obtained within the Peterburgskoe ore field (Mid-Atlantic Ridge) and from the core taken five kilometers away from the ore field revealed evident differences in their composition, in the appearance of their shells, and also in the benthic-plankton species ratio. It was noted that the foraminiferal assemblage from the ore-bearing sediments of the Petersburg field was characterized by a higher relative content of benthic species and a large number of chemically altered and broken shells. The first occurrence of the species Osangularia umbonifera, which is able to exist in lowoxygen and CaCO3-undersaturated bottom waters at the boundary of biogenic sediments surrounding the ore field and in the ore-bearing sediments, was established. In the core section sampled beyond the ore field, the composition of foraminiferal assemblages differs insignificantly from typical oceanic ones.

Tulelake, California: The last 3 million years

USGS Publications Warehouse

Adam, D.P.; Sarna-Wojcicki, A. M.; Rieck, Hugh J.; Bradbury, J.P.; Dean, W.E.; Forester, R.M.

1989-01-01

The Tulelake basin, formed by east-west extension and faulting during the past several million years, contains at least 550 m of lacustrine sediment. Interdisciplinary studies of a 334 m-long cored section from the town of Tulelake, California, near the center of the basin, document a 3-m.y. record of environmental changes. The core consists of a thick sequence of diatomaceous clayey, silty, and marly lacustrine sediments interbedded with numerous tephra layers. Paleomagnetic study puts the base of the core at about 3.0 Ma. Twelve widespread silicic tephra units provide correlations with other areas and complement age control provided by magnetostratigraphy; mafic and silicic tephra units erupted from local sources are also common in the core. Widespread tephra units include the Llao Rock pumice (=Tsoyawata, 7 ka), the Trego Hot Springs Bed (23 ka), and the Rockland (0.40 Ma), Lava Creek (0.62 Ma), and Rio Dell (1.5 Ma) ash beds, as well as several ash beds also found at Summer Lake, Oregon, and an ash bed originally recognized in DSDP hole 173 in the northeastern Pacific. Several tephra layers found in the core also occur in lacustrine beds exposed around the margins of the basin and elsewhere in the ancestral lacustrine system. Diatoms are present throughout the section. Pollen is present in most of the section, but some barren zones are found in the interval between 50 and 140 m; the greatest change in behavior of the pollen record takes place just above the top of the Olduvai Normal-Polarity Subchronozone. Ostracodes are present only in high-carbonate (>10% CaCO3) intervals. Evolutionary changes are found in the diatom and ostracode records. Bulk geochemical analyses show significant changes in elemental composition of the sediment through time. ?? 1989.

Understanding Mississippi Delta Subsidence through Stratigraphic and Geotechnical Analysis of a Continuous Holocene Core at a Subsidence Superstation

NASA Astrophysics Data System (ADS)

Bridgeman, J.; Tornqvist, T. E.; Jafari, N.; Allison, M. A.

2017-12-01

Land-surface subsidence can be a major contributor to the relative sea-level rise that is threatening coastal communities. Loosely constrained subsidence rate estimates across the Mississippi Delta make it difficult to differentiate between subsidence mechanisms and complicate modeling efforts. New data from a nearly 40 m long, 12 cm diameter core taken during the installation of a subsidence monitoring superstation near the Mississippi River, SW of New Orleans, provides insight into the stratigraphic and geotechnical properties of the Holocene succession. Stratigraphically, the core can be grouped into three sections. The top 12 m is dominated by clastic overbank sediment with interspersed organic-rich layers. The middle section, 12-35 m consists predominately of mud, and the bottom section, 35-38.7 m, is marked by a transition into a Holocene-aged basal peat (11,350-11,190 cal BP) which overlies densely packed Pleistocene sediment. Radiocarbon and OSL ages show up to 6 m of vertical displacement since 3,000 cal BP. We infer that most of this was due to compaction of the thick underlying mud package. The top ­­­­­ 70 cm of the core is a peat that represents the modern marsh surface and is inducing minimal surface loading. This is consistent with the negligible shallow subsidence rate as seen at a nearby rod-surface elevation table - marker horizon station and the initial strainmeter data. Future compaction scenarios for the superstation can be modeled from the stratigraphic and geotechnical properties of the core, including the loading from the planned Mid-Barataria sediment diversion which is expected to dramatically change the coastal landscape in this region.

A detailed Holocene glacial-periglacial reconstruction based on multidisciplinary studies of a 60 m permafrost core from central Svalbard

NASA Astrophysics Data System (ADS)

Hvidtfeldt Christiansen, Hanne; Elberling, Bo; Gilbert, Graham L.; Thiel, Christine; Murray, Andrew; Buylaert, Jan-Pieter; Dypvik, Henning; Lomstein, Bente; Hovgaard, Jonas; Christensen, Anne T.; Mørkved, Pål T.; Reigstad, Laila J.; Fromreide, Siren; Seidenkrantz, Marit-Solveig

2014-05-01

During summer 2012, a 60 m sedimentary permafrost core was retrieved from the lower part of the Adventdalen Valley, central Svalbard, as part of the Longyearbyen CO2 project. The core was taken in 3 m long sections, with 20 % core loss, and reached the sedimentary bedrock (Lower Cretaceous). Thus our samples had the potential to represent the entire Quaternary and reflect changes in the sedimentary environments through time. The stratigraphy and sedimentology of the core was first investigated, to establish an overall geological model for the sampling site. The general stratigraphy encompasses a layer of basal till at the bottom of the core. This is overlain by marine sediments documenting a transition from glacial-proximal to open-marine conditions. Subsequently, a thick package of deltaic sediments records the progradation of the local river system. Finally, aeolian sediments, characterizing the modern environment, form the top few meters of the core. The ice content of the permafrost is generally low. Gravimetric water content generally ranges between 20% and 40%, but is considerably higher in some ice-rich layers. High resolution optically stimulated luminescence dating of the core sediment shows that deposition was very fast and took place primarily during the mid Holocene, with very rapid sedimentation of around 4 m/ka. With the onset of aeolian deposition (around 3-4 ka) the sedimentation rate decreased significantly to 1m/ka. The microbial diversity and activity of the core are being studied displaying decreasing activity with depth. Microbial community and functional gene numbers indicate variations with depth and geochemistry. Incubation studies have been performed primarily on the upper 30 m, and indicate a potential CO2 production from all depth intervals being studied. The potential for using foraminifer studies for both dating and palaeoenvironmental reconstructions are evaluated with the intension of comparison with previous studies of marine sediment cores both from the fjords in the Svalbard area and from the Barents Sea and Fram Strait region. This multidisciplinary approach is allowing us to build the first detailed palaeoenvironmental reconstruction of the Holocene glacial-periglacial interaction in the lowlands of central Svalbard; this includes a detailed reconstruction of the permafrost conditions.

Late Quaternary sediment-accumulation rates within the inner basins of the California Continental Borderland in support of geologic hazard evaluation

USGS Publications Warehouse

Normark, W.R.; McGann, M.; Sliter, R.W.

2009-01-01

An evaluation of the geologic hazards of the inner California Borderland requires determination of the timing for faulting and mass-movement episodes during the Holocene. Our effort focused on basin slopes and turbidite systems on the basin floors for the area between Santa Barbara and San Diego, California. Dating condensed sections on slopes adjacent to fault zones provides better control on fault history where high-resolution, seismic-reflection data can be used to correlate sediment between the core site and the fault zones. This study reports and interprets 147 radiocarbon dates from 43 U.S. Geological Survey piston cores as well as 11 dates from Ocean Drilling Program Site 1015 on the floor of Santa Monica Basin. One hundred nineteen dates from 39 of the piston cores have not previously been published. Core locations were selected for hazard evaluation, but despite the nonuniform distribution of sample locations, the dates obtained for the late Quaternary deposits are useful for documenting changes in sediment-accumulation rates during the past 30 ka. Cores from basins receiving substantial sediment from rivers, i.e., Santa Monica Basin and the Gulf of Santa Catalina, show a decrease in sediment supply during the middle Holocene, but during the late Holocene after sea level had reached the current highstand condition, rates then increased partly in response to an increase in El Ni??o-Southern Oscillation events during the past 3.5 ka. ?? 2009 The Geological Society of America.

A record of hydrocarbon input to San Francisco Bay as traced by biomarker profiles in surface sediment and sediment cores

USGS Publications Warehouse

Hostettler, F.D.; Pereira, W.E.; Kvenvolden, K.A.; VanGeen, A.; Luoma, S.N.; Fuller, C.C.; Anima, R.

1999-01-01

San Francisco Bay is one of the world's largest urbanized estuarine systems. Its water and sediment receive organic input from a wide variety of sources; much of this organic material is anthropogenically derived. To document the spatial and historical record of the organic contaminant input, surficial sediment from 17 sites throughout San Francisco Bay and sediment cores from two locations Richardson Bay and San Pablo Bay were analyzed for biomarker constituents. Biomarkers, that is, 'molecular fossils', primarily hopanes, steranes, and n-alkanes, provide information on anthropogenic contamination, especially that related to petrogenic sources, as well as on recent input of biogenic material. The biomarker parameters from the surficial sediment and the upper horizons of the cores show a dominance of anthropogenic input, whereas the biomarker profiles at the lower horizons of the cores indicate primarily biogenic input. In the Richardson Bay core the gradual upcore transition from lower maturity background organics to a dominance of anthropogenic contamination occurred about 70-100 years ago and corresponds to the industrial development of the San Francisco Bay area. In San Pablo Bay, the transition was very abrupt, reflecting the complex depositional history of the area. This sharp transition, perhaps indicating a depositional hiatus or erosional period, dated at pre-1952, is clearly visible. Below, the hiatus the biomarker parameters are immature; above, they are mature and show an anthropogenic overlay. Higher concentrations of terrigenous n-alkanes in the upper horizons in this core are indicative of an increase in terrigenous organic matter input in San Pablo Bay, possibly a result of water diversion projects and changes in the fresh water flow into the Bay from the Delta. Alternatively, it could reflect a dilution of organic material in the lower core sections with hydraulic mining debris.

Mercury in Long Island Sound sediments

USGS Publications Warehouse

Varekamp, J.C.; Buchholtz ten Brink, Marilyn R.; Mecray, E.I.; Kreulen, B.

2000-01-01

Mercury (Hg) concentrations were measured in 394 surface and core samples from Long Island Sound (LIS). The surface sediment Hg concentration data show a wide spread, ranging from 600 ppb Hg in westernmost LIS. Part of the observed range is related to variations in the bottom sedimentary environments, with higher Hg concentrations in the muddy depositional areas of central and western LIS. A strong residual trend of higher Hg values to the west remains when the data are normalized to grain size. Relationships between a tracer for sewage effluents (C. perfringens) and Hg concentrations indicate that between 0-50 % of the Hg is derived from sewage sources for most samples from the western and central basins. A higher percentage of sewage-derived Hg is found in samples from the westernmost section of LIS and in some local spots near urban centers. The remainder of the Hg is carried into the Sound with contaminated sediments from the watersheds and a small fraction enters the Sound as in situ atmospheric deposition. The Hg-depth profiles of several cores have well-defined contamination profiles that extend to pre-industrial background values. These data indicate that the Hg levels in the Sound have increased by a factor of 5-6 over the last few centuries, but Hg levels in LIS sediments have declined in modern times by up to 30 %. The concentrations of C. perfringens increased exponentially in the top core sections which had declining Hg concentrations, suggesting a recent decline in Hg fluxes that are unrelated to sewage effluents. The observed spatial and historical trends show Hg fluxes to LIS from sewage effluents, contaminated sediment input from the Connecticut River, point source inputs of strongly contaminated sediment from the Housatonic River, variations in the abundance of Hg carrier phases such as TOC and Fe, and focusing of sediment-bound Hg in association with westward sediment transport within the Sound.

Sedimentological and geochemical support for a large flood ca. 4400 cy BP in the coastal southwest United States (Lake Elsinore, CA): Evidence for a Drought Buster Atmospheric River Storm?

NASA Astrophysics Data System (ADS)

Kirby, M. E.; Patterson, W. P.

2015-12-01

As serious a threat drought is to the coastal southwest United States (US), floods represent an equally formidable threat. So significant is this risk that the USGS has created the ARkStorm Project. This project aims to prepare California for a future storm(s) on the scale of the disastrous 1861-1862 A.D. events. Unfortunately, our knowledge of pre-measurement floods in the coastal southwest US is not well known, excepting seven identified flood layers in the Santa Barbara Basin, which span the past 2000 years. As an alternative to marine archives, the lakes of the coastal southwest US represent untapped resources for pre-measurement flood reconstructions. Here, we present evidence for a flood ca. 4400 cal yrs BP using sediments from Lake Elsinore. Core LEGC03-4 was collected in 4.0 m water depth using a push core with a hollow stemmed augur; the core is 994 cm in length. The core is predominantly clayey silt with occasional sandy silt units of variable cm-scale thickness. Here we focus on a specific core section between 315 and 350 cm where a ~11 cm thick "unusual" sediment unit (319-330 cm) is well preserved and complete. The core section was digitally photographed, described, and sampled at 1 cm contiguous intervals for a variety of physical and chemical properties including: magnetic susceptibility, loss-on-Ignition (LOI) 550 and 950 °C, grain size, CN ratios, and d13Cbulk organics. The data suggest rapid deposition of sediment with classic "Bouma" sequence preservation. The unit is characterized by an erosional basal contact and flame structures. It is normally graded with laminae occurring in the upper section of the unit. It contains predominantly terrestrial organic matter and the upper boundary is gradational. The cause of this event unit is speculative but potentially associated with San Jacinto River flooding in response to a large atmospheric river storm. Curiously, the 1861-1862 A.D. events are not observed in the sediment core suggesting that this 4400 yr event was different (larger magnitude?) than anything observed in historic times. This event's timing is compared to regional paleoclimatic reconstructions and examined in the context of potential forcings.

Using recent hurricanes and associated event layers to evaluate regional storm impacts on estuarine-wetland systems

NASA Astrophysics Data System (ADS)

Smith, C. G.; Marot, M. E.; Osterman, L. E.; Adams, C. S.; Haller, C.; Jones, M.

2016-12-01

Tropical cyclones are a major driver of change in coastal and estuarine environments. Heightened waves and sea level associated with tropical cyclones act to erode sediment from one environment and redistribute it to adjacent environments. The fate and transport of this redistributed material is of great importance to the long-term sediment budget, which in turns affects the vulnerability of these coastal systems. The spatial variance in both storm impacts and sediment redistribution is large. At the regional-scale, difference in storm impacts can often be attributed to natural variability in geologic parameters (sediment availability/erodibility), coastal geomorphology (including fetch, shoreline tortuosity, back-barrier versus estuarine shoreline, etc.), storm characteristics (intensity, duration, track/approach), and ecology (vegetation type, gradient, density). To assess storm characteristics and coastal geomorphology on a regional-scale, cores were collected from seven Juncus marshes located in coastal regions of Alabama and Mississippi (i.e., Mobile Bay, Bon Secour Bay, Mississippi Sound, and Grand Bay) expected to have been impacted by Hurricane Frederic (1979). All cores were sectioned and processed for water content, organic matter (loss-on-ignition), and select cores analyzed for foraminiferal assemblages, stable isotopes and bulk metals to aid in the identification of storm events. Excess lead-210 and cesium-137 were used to develop chronologies for the cores and evaluate mass accumulation rates and sedimentation rates. Temporal variations in accumulation rates of inorganic and organic sediments were compared with shoreline and areal change rates derived from historic aerial imagery to evaluate potential changes in sediment exchange prior to, during, and following the storm. A combined geospatial and geologic approach will improve our understanding of coastal change in estuarine marsh environments, as well help refine the influence of storms on regional sediment budgets.

The chemistry and mineralogy of haloed burrows in pelagic sediment at DOMES Site A: The equatorial North Pacific

USGS Publications Warehouse

Piper, D.Z.; Rude, P.D.; Monteith, S.

1987-01-01

The chemical and mineralogical composition of burrowed sediment, recovered in 66 box cores at latitude 9??25???N and longitude 151??15???W in the equatorial Pacific, demonstrates the important role of infauna in determining the geochemistry of pelagic sediment. Haloed burrows, approximately 3 cm across, were present in many of the cores. Within early Tertiary sediment that was covered by less than 5 cm of surface Quaternary sediment in several cores, the burrows in cross-section consist of three units: (1) a dark yellowish-brown central zone of Quaternary sediment surrounded, by (2) a pale yellowish-orange zone (the halo) of Tertiary sediment, which is surrounded by (3) a metal-oxide precipitate; the enclosing Tertiary sediment is dusky brown. Several elements - Mn, Ni, Cu, Co, Zn, Sb and Ce - have been leached from the light-colored halo, whereas Cr, Cs, Hf, Rb, Sc, Ta, Th, U, the rare earth elements exclusive of Ce, and the major oxides have not been leached. The metal-oxide zone, 1-5 mm thick, contains as much as 16% MnO2, as the mineral todorokite. The composition of the todorokite, exclusive of the admixed Tertiary sediment, resembles the composition of the metal deficit of the halo and also the composition of surface ferromanganese nodules that have been interpreted as having a predominantly diagenetic origin. Thus bioturbation contributes not only to the redistribution of metals within pelagic sediment, but also to the accretion of ferromanganese nodules on the sea floor. ?? 1987.

SlamZ: Slide activity on the Hikurangi margin, New Zealand - First results of the RV Sonne expedition SO247

NASA Astrophysics Data System (ADS)

Huhn, Katrin; Kukowski, Nina; Freudenthal, Tim; Crutchley, Gareth; Goepel, Andreas; Henrys, Stuart; Kasten, Sabine; Kaul, Norbert; Kuhlmann, Jannis; Mountjoy, Joshu; Orpin, Alan; Pape, Thomas; Schwarze, Cornelius; Totsche, Kai-Uwe; Torres, Marta; Villinger, Heiner

2017-04-01

Submarine landslides are important geologic hazards. Although they have been the focus of research for decades, there is still a clear lack in knowledge with respect to the interplay between tectonic movements, slope architecture and sediment physical properties of slope strata, as well as gas hydrate dissociation as controlling factors of slope stability or respectively slope failure processes. The main scientific goal of the Sonne expedition SO247 undertaken in spring 2016 was to gain a better understanding of the factors controlling slope destabilization, especially the interaction of tectonic steepening and gas hydrate transformation, at different tectonic settings along the Hikurangi subduction zone east of New Zealand's North Island. This active continental margin is characterized by various potential triggers for slope failure, e.g. (I) a wide range of tectonic movements which are associated with high seismicity, numerous active faults, sediment uplift and slope over-steepening, and (II) large gas hydrate deposits whose current upper stability limit in some places correlates with the breakoff points of slides. The target areas of SO247 were the frontal accretionary ridge at Rock Garden and the Tuaheni landslide complex (TLC) further north offshore Gisborne. Bathymetric as well as high-resolution seismic reflection and Parasound data were used to select suitable position for 53 gravity cores with a total length of 150 m which were recovered along systematic transects from the undisturbed slope sections to the slid masses in both working areas. In addition, six long sediment cores (three in both working areas) with a total length of approx. 470 m were drilled utilizing the MARUM Bremen drill rig MeBo200. These include a 105 m long continuous sediment core (core recovery > 95%) from an undisturbed slope section in the vicinity of the Tuaheni slide complex. This core represented the first long (i.e. longer than 50 m) sediment record from the Hikurangi margin. This drilling operation was paired with dense in-situ heat-flow measurements. Sedimentological, geotechnical, geophysical and geochemical analysis of the core material as well as sampled pore fluids and gases will enable a deeper insight into the slide kinematics, potential trigger mechanisms and timing of failure events. Furthermore, these data allow us to test hypotheses regarding the key role of sediment physical properties and/or gas hydrate dissociation and therewith the mechanics of submarine landslides; what are potential trigger mechanisms: uplift and over-steepening vs. sediment physical behaviour.

An historical assessment of trace metal accumulation in Lake Champlain, Vermont

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mecray, E.L.; King, J.W.

1993-03-01

The Lake Champlain watershed, with its increased land use, shoreline development, and population, is being threatened by pollutants in the water column and bottom sediments. A comprehensive study is currently being conducted to characterize the bottom sediments of the lake for toxicity and to reconstruct the history of pollutant inputs. Surface sediment samples were collected from 30 stations and analyzed for metal (Cu, Zn, Cr, Pb, Ni, Mn, Fe, Cd, Al, and Ag) concentrations to determine the contaminated regions of the lake. Once the contaminated regions were determined, a Nemesis corer was used to retrieve sediments cores averaging 1 metermore » in length from 10 sites within Lake Champlain. Grain size and metal analyses were conducted at one and two cm intervals down the cores. Grain size data, in combination with metal and radiometric stratigraphy, can serve as an indicator of changing land use in the watershed. The grain size in some cores has a fining upward trend indicating increased land use and soil erosion. Downcore variations in metal concentrations reveal two different regimes. The concentration at depth remain consistently low and are inferred to correspond with the natural background levels. In contrast, the upper section of the cores show abrupt increases in metal concentrations which are attributed to increased anthropogenic inputs. Radiometric ([sup 210] and [sup 137]Cs) and pollen chronostratigraphy of these cores indicates that the increased metal concentrations and the changes in grain size recorded in the upper most sediments is related to increased human disturbance beginning in the late 18th and early 19th centuries. This study demonstrates that the historical record of pollution inputs to Lake Champlain can be reconstructed from the sediment sequences.« less

Measurements of mercury methylation rates and bioavailability in the Allequash Creek Wetland, Northern Wisconsin

NASA Astrophysics Data System (ADS)

Creswell, J. E.; Babiarz, C. L.; Shafer, M. M.; Armstrong, D. E.

2008-12-01

Wetlands are known to be hot spots for the production of methylmercury (MeHg) and subsequent export into other aquatic ecosystems. Because MeHg is a bioaccumulative neurotoxin, and because the primary route of human exposure to mercury is through the consumption of contaminated fish, understanding the processes by which MeHg is produced in the aquatic environment is important to the protection of human health. Inorganic Hg(II) is known to be methylated by bacteria in the anoxic zones of wetland sediments, but bioavailability plays a role in this process, as certain chemical complexes of mercury are unavailable to the microbial community. In the Allequash Creek wetland, a strong relationship has been observed between MeHg and Dissolved Organic Carbon (DOC) concentrations, but the observed relationship between MeHg and total Hg is weak. This observation implicates factors other than Hg(II) concentration as drivers of methylation. In this study, depth-resolved estimates of the bioavailability of inorganic Hg(II) were made by measuring the net mercury methylation rate potential in the hyporheic zone of the wetland. Gross mercury methylation was measured in sediment cores amended with stable isotope-enriched Hg(II), by analyzing isotopically-enriched methylmercury produced during an incubation. Demethylation was measured by amending replicate cores with stable isotope-enriched methylmercury and analyzing the amount consumed over the incubation period. Analyses were conducted using an inductively coupled plasma-quadrupole mass spectrometer. A method comparison was made between incubating cores intact, with mercury amendments injected through core tube walls, and incubating sectioned cores, with mercury amendments mixed into homogenized sediments. The value of incubating intact cores is that disturbance to the sediment and the microbial community is minimized, resulting in experimental conditions that more accurately mimic in situ conditions. The value of mixing mercury amendments into homogenized sediments is that this spreads the amended mercury throughout the core section, avoiding injection channel effects. The influence of Hg(II) speciation on methylation is also being examined. Preliminary results show gross mercury methylation occurring at both sites sampled, although net methylation is negative throughout most of the depth profile, suggesting that the chemical conditions controlling the bioavailability of Hg(II) are highly variable. Because this is the first time such measurements have been made in this system, these data provide an important baseline for future studies of mercury bioavailability in northern wetlands.

Vertical distribution of trace-element concentrations and occurrence of metallurgical slag particles in accumulated bed sediments of Lake Roosevelt, Washington, September 2002

USGS Publications Warehouse

Cox, S.E.; Bell, P.R.; Lowther, J.S.; Van Metre, P.C.

2005-01-01

Sediment cores were collected from six locations in Lake Roosevelt to determine the vertical distributions of trace-element concentrations in the accumulated sediments of Lake Roosevelt. Elevated concentrations of arsenic, cadmium, copper, lead, mercury, and zinc occurred throughout much of the accumulated sediments. Concentrations varied greatly within the sediment core profiles, often covering a range of 5 to 10 fold. Trace-element concentrations typically were largest below the surficial sediments in the lower one-half of each profile, with generally decreasing concentrations from the 1964 horizon to the surface of the core. The trace-element profiles reflect changes in historical discharges of trace elements to the Columbia River by an upstream smelter. All samples analyzed exceeded clean-up guidelines adopted by the Confederated Tribes of the Colville Reservation for cadmium, lead, and zinc and more than 70 percent of the samples exceeded cleanup guidelines for mercury, arsenic, and copper. Although 100 percent of the samples exceeded sediment guidelines for cadmium, lead, and zinc, surficial concentrations of arsenic, copper, and mercury in some cores were less than the sediment-quality guidelines. With the exception of copper, the trace-element profiles of the five cores collected along the pre-reservoir Columbia River channel typically showed trends of decreasing concentrations in sediments deposited after the 1964 time horizon. The decreasing concentrations of trace elements in the upper half of cores from along the pre-reservoir Columbia River showed a pattern of decreasing concentrations similar to reductions in trace-element loading in liquid effluent from an upstream smelter. Except for arsenic, trace-element concentrations typically were smaller at downstream reservoir locations along the pre-reservoir Columbia River. Trace-element concentration in sediments from the Spokane Arm of the reservoir showed distinct differences compared to the similarities observed in cores from along the pre-reservoir Columbia River. Particles of slag, which have physical and chemical characteristics of slag discharged to the Columbia River by a lead-zinc smelter upstream of the reservoir at Trail, British Columbia, were found in sediments of Lake Roosevelt. Slag particles are more common in the upstream reaches of the reservoir. The chemical composition of the interior matrix of slag collected from Lake Roosevelt closely approximated the reported elemental concentrations of fresh smelter slag, although evidence of slag weathering was observed. Exfoliation flakes were observed on the surface of weathered slag particles isolated from the core sediments. The concentrations of zinc on the exposed surface of slag grains were smaller than concentrations on interior surfaces. Weathering rinds also were observed in the cross section of weathered slag grains, indicating that the glassy slag material was undergoing hydration and chemical weathering. Trace elements observed in accumulated sediments in the middle and lower reaches of the reservoir are more likely due to the input from liquid effluent discharges compared to slag discharges from the upstream smelter.

Unravelling the Paleoenvironmental and Diagenetic History of Fluviolacustrine Sediments from a Northern Kenya Rift Basin Through Analysis of HSPDP West Turkana-Kaitio Core Material

NASA Astrophysics Data System (ADS)

Rabideaux, N. M.; Chaudhary, M. S.; Deocampo, D.; Feibel, C. S.; Cohen, A. S.

2016-12-01

The Hominin Sites and Paleolakes Drilling Project (HSPDP) collected sediment cores from six rift basins in Ethiopia and Kenya. The goal of HSPDP is to construct high-resolution records of environmental change, and to understand how those changes relate to early human evolution and cultural adaptations. The West Turkana-Kaitio (WTK) site was targeted due to the abundant archeological and paleontological artifacts and fossils discovered around the basin. We conducted XRD and XRF analyses on HSPDP-WTK core material to construct a high-resolution record of paleoenvironmental conditions in the Kenya Rift during the Early Pleistocene ( 1.9-1.35 Ma). Mineralogical and geochemical trends were also used to identify the diagenetic history of fluviolacustrine sediments in the basin. The bulk mineralogy is comprised of mostly detrital feldspars, muscovite, α-quartz, and carbonates. Zeolites are present in intervals throughout the core, possibly suggesting pulses of increased salinity. Oxides and S-bearing minerals are abundant from 100-170 mbs, which may be indicative of redox and or hydrothermal processes in that interval. The lowermost portion of the core contains α- and β-quartz, pyrite and zeolites, suggesting either low-oxygen saline conditions or hydrothermal activity. Oriented clay analysis indicated multiple intervals of diagenesis, with the illitization of smectite related to hydrothermal and or microbial activity. Clay analysis provided evidence for a low degree of illitization in the upper portion of the core, whereas mixed-layered illite-smectite (I/S) contained 30-50% illite proximal to fault breccia and up to 70% illite below the faulted section, indicative of significant alteration in the lowermost portion of the core. Coupled mineralogical and geochemical analysis revealed a complex alteration history in the basin indicated by: 1) the presence of mixed-layer I/S throughout the 216 m core; 2) pronounced alteration proximal to faulting; and 3) authigenic silicates and pyrite in the basal section of the core.

Sedimentology and Permafrost Characteristics of Pingo-Like Features (PLFs) from the Beaufort Sea shelf, NWT, Canada

NASA Astrophysics Data System (ADS)

Medioli, B. E.; Dallimore, S. R.; Nixon, F. M.; Dallimore, A.; Blasco, S.; Paull, C. K.; McLaughlin, F.; Ussler, W.; Davies, E.

2004-12-01

Pingo-like features (PLFs) are rounded positive relief features commonly found on Beaufort Sea shelf, NWT. PLFs occur in water depths from 20 to 200m, are typically a few hundred meters in diameter and rise 10 to 35m above the seafloor. In the fall of 2003, an MBARI-USGS-GSC-DFO coring and geophysical study was undertaken of a number of PLFs. The crests, flanks and moats of 8 PLFs, as well as background shelf sites, were vibra-cored. Upon recovery, core temperatures of moat sediments ranged from 2.0 to -0.5 deg C and no ice bonding was observed. Sediments consisted of dark-olive-grey to black muds with shells. Sedimentary structures were rare with some finely laminated to finely-color-banded beds. Intense bioturbation, in situ marine shells and a lack of terriginous macrofossils suggest moat sediments were deposited in a shallow coastal environment. In some instances, a down core grain size coarsening was observed with higher organic content suggesting a gradational environment towards more lagoonal conditions. Core temperatures from the 8 PLFs were 0 to -1.7 deg C, significantly colder than the moat sediments. Ice-bonded permafrost was encountered within 1m of the seabed with visible ice content up to 40% by volume. Several ice-bonded intervals were preserved frozen for detailed investigation in the lab. The observed ground ice in the cores was quite unique when compared with visible ice forms commonly seen in regional terrestrial sections. The ice gave the core a vuggy texture with individual ice-filled vugs 10 to 200 mm3. Vugs were typically flattened to ovoid. When thawed, the ice produced excess water resulting in a very soft texture. In many cases the vuggy texture was maintained with sediment voids forming where the ice was. PLF crest sediments were massive silty clays with clayey silts and muddy fine sand interbeds. They generally lack sedimentary structures, although this may have been due to sediment structure loss upon thawing. The background seafloor sediments consisted of unfrozen, massive silty sands and sandy silts and were distinct from the crest and moat sediments. In several cores, a sharp transition was noted to well-sorted sands. This lower unit may represent a transgressed terrestrial sequence. Research continues to determine the origin of the PLFs and quantify the role of permafrost and ice formation.

Terrestrial Palynology of Paleocene and Eocene Sediments Above the Chicxulub Impact Crater

NASA Astrophysics Data System (ADS)

Smith, V.; Warny, S.; Bralower, T. J.; Jones, H.; Lowery, C. M.; Smit, J.; Vajda, V.; Vellekoop, J.; 364 Scientists, E.

2017-12-01

International Ocean Discovery Program (IODP) Expedition 364, with support from the International Continental Scientific Drilling Program, cored through Paleocene and Eocene sediments and into the impact structure of the Chicxulub impact crater. Three palynological studies of the post-impact section are currently underway. The two other studies are investigating the dinoflagellate palynology and terrestrial palynology of the K/Pg boundary section, while this study focuses on the early Eocene terrestrial palynology of the IODP 364 core, which has yielded a diverse and well preserved pollen assemblage. A few samples from the Early Paleocene have also been examined but organic microfossil preservation is quite poor. Samples from this core are the oldest palynological record from the Yucatan peninsula. Sample preparation and detailed abundance counts of sixty samples throughout the post-impact section are in progress, with a particular focus on the Paleocene-Eocene Thermal Maximum (PETM) and the Early Eocene Climatic Optimum (EECO). Terrestrial palynomorph assemblages will be used to reconstruct paleoclimatological conditions throughout this time period. Floral response to hyperthermal events in the IODP 364 core will be compared with records from other Gulf of Mexico and Caribbean sections. In addition to the biological and paleoclimatological implications of this research, age control from foraminiferal and nannofossil biostratigraphy, paleomagnetism, and radiometric dating will provide a chronological framework for the terrestrial pollen biostratigraphy, with applications to hydrocarbon exploration in the Wilcox Formation and age equivalent sections in the Gulf of Mexico.

The Baltic Sea: Geophysical and geochemical properties of Holocene sediment sequences as indicators of past environmental variability

NASA Astrophysics Data System (ADS)

Lenz, Conny; Reinholdsson, Maja; Zillén, Lovisa; Conley, Daniel J.; Snowball, Ian

2010-05-01

The Baltic Sea has undergone large environmental changes since the retreat of the Weischselian Ice-sheet. In the Late Glacial Period and the early Holocene these changes were most likely caused by natural environmental changes (i.e. changes in the morphology and depths of the Baltic basin and the sills). In more recent time anthropogenic impacts have become more important as a possible and likely cause for changes. During the whole Holocene period climate variability played an important role. However, the relative importance between humans and nature is largely unknown. Here we present the results of a combined geophysical and geochemical study on selected sediment sequences from the Baltic Sea within the two BONUS (Baltic Organisations Network For Funding Science) funded projects HYPER (HYPoxia mitigation for Baltic Sea Ecosystem Restoration) and Baltic GAS (GAS storage and effects of climate change and eutrophication). The over-all aim of these projects is to understand large-scale Baltic Sea ecosystem responses to environmental, climate and anthropogenic forcing. During two Baltic Sea research cruises in 2009 long sediment cores from 8 different locations were recovered. We present preliminary results from one site (LL19) located in the north central Baltic Proper at 169 m water depth. The Littorina Sea sediment record (i.e. the last c. 8000 years) is characterised by alternating periods of homogenised sediments (indicative of oxic conditions) and laminated sediments (indicative of hypoxic/anoxic conditions). Mineral magnetic properties illustrate clear changes between laminated and non-laminated sections of the core. The concentration of ferrimagnetic minerals, as revealed by initial magnetic susceptibility (χ) and saturation isothermal remanent magnetization (SIRM) is variable. The laminated sections in particular show high concentrations and to reveal the origin of the ferrimagnetic signal additional magnetic properties were measured, specifically the acquisition of rotational remanent magnetization (RRM), frequency dependency of susceptibility (χfd) and magnetic loops. These data show that magnetic assemblage of the laminated sections is dominated by a single-domain magnetic grain size. The elemental composition was measured with a high resolution Itrax XRF-scanner throughout the core. In addition, biogenic silica (BSi) and total organic carbon (TOC) were determined. Distinct changes of elemental contents between the laminated and homogenous sections in the Littorina Sea sediments were identified. A combination of the physical and geochemical properties of the sediment sequences and the construction of geochronologies will provide information about past environmental variability to identify casual relationships to climate and human impact in the Baltic Sea.

On the preservation of laminated sediments along the western margin of North America

USGS Publications Warehouse

VanGeen, A.; Zheng, Yen; Bernhard, J.M.; Cannariato, K.G.; Carriquiry, J.; Dean, W.E.; Eakins, B.W.; Ortiz, J.D.; Pike, J.

2003-01-01

Piston, gravity, and multicores as well as hydrographic data were collected along the Pacific margin of Baja California to reconstruct past variations in the intensity of the oxygen-minimum zone (OMZ). Gravity cores collected from within the OMZ north of 24??N did not contain laminated surface sediments even though bottom water oxygen (BWO) concentrations were close to 5 ??mol/kg. However, many of the cores collected south of 24??N did contain millimeter- to centimeter-scale, brown to black laminations in Holocene and older sediments but not in sediments deposited during the Last Glacial Maximum. In addition to the dark laminations, Holocene sediments in Soledad Basin, silled at 290 m, also contain white coccolith laminae that probably represent individual blooms. Two open margin cores from 430 and 700 m depth that were selected for detailed radiocarbon dating show distinct transitions from bioturbated glacial sediment to laminated Holocene sediment occurring at 12.9 and 11.5 ka, respectively. The transition is delayed and more gradual (11.3-10.0 ka) in another dated core from Soledad Basin. The observations indicate that bottom-water oxygen concentrations dropped below a threshold for the preservation of laminations at different times or that a synchronous hydrographic change left an asynchronous sedimentary imprint due to local factors. With the caveat that laminated sections should therefore not be correlated without independent age control, the pattern of older sequences of laminations along the North American western margin reported by this and previous studies suggests that multiple patterns of regional productivity and ventilation prevailed over the past 60 kyr. Copyright 2003 by the American Geophysical Union.

The Influence of Sampling Density on Bayesian Age-Depth Models and Paleoclimatic Reconstructions - Lessons Learned from Lake Titicaca - Bolivia/Peru

NASA Astrophysics Data System (ADS)

Salenbien, W.; Baker, P. A.; Fritz, S. C.; Guedron, S.

2014-12-01

Lake Titicaca is one of the most important archives of paleoclimate in tropical South America, and prior studies have elucidated patterns of climate variation at varied temporal scales over the past 0.5 Ma. Yet, slow sediment accumulation rates in the main deeper basin of the lake have precluded analysis of the lake's most recent history at high resolution. To obtain a paleoclimate record of the last few millennia at multi-decadal resolution, we obtained five short cores, ranging from 139 to 181 cm in length, from the shallower Wiñaymarka sub-basin of of Lake Titicaca, where sedimentation rates are higher than in the lake's main basin. Selected cores have been analyzed for their geochemical signature by scanning XRF, diatom stratigraphy, sedimentology, and for 14C age dating. A total of 72 samples were 14C-dated using a Gas Ion Source automated high-throughput method for carbonate samples (mainly Littoridina sp. and Taphius montanus gastropod shells) at NOSAMS (Woods Hole Oceanographic Institute) with an analytical precision higher than 2%. The method has lower analytical precision compared with traditional AMS radiocarbon dating, but the lower cost enables analysis of a larger number of samples, and the error associated with the lower precision is relatively small for younger samples (< ~8,000 years). A 172-cm-long core was divided into centimeter long sections, and 47 14C dates were obtained from 1-cm intervals, averaging one date every 3-4 cm. The other cores were radiocarbon dated with a sparser sampling density that focused on visual unconformities and shell beds. The high-resolution radiocarbon analysis reveals complex sedimentation patterns in visually continuous sections, with abundant indicators of bioturbated or reworked sediments and periods of very rapid sediment accumulation. These features are not evident in the sparser sampling strategy but have significant implications for reconstructing past lake level and paleoclimatic history.

Age depth model construction of the upper section of ICDP Dead Sea Deep Drilling Project based on the high-resolution 14C dating

NASA Astrophysics Data System (ADS)

Kitagawa, H.; Nakamura, T.; Neugebauer, I.; Schwab, M. J.; Brauer, A.; Goldstein, S. L.; Stein, M.

2014-12-01

To reconstruct environmental, climatic and tectonic histories of the Levant, a deep drilling has been accomplished in the northern basin of the Dead Sea during the fall winter of 2010-2011 by the Dead Sea Deep Drilling Project (DSDDP) in the framework of the ICDP program. The sediment cores from site 5017-1 (water depth of ~300 m) recorded the paleoenvironmental and paleohydrological changes in the Dead Sea and the Levant during the last two glacial-interglacial cycles (Neugebauer et al., QSR in press). To provide precise timing of sedimentological - limnological events in the lake and its watershed, and more critically the relative timing of these events, radiocarbon dating of >70 well-preserved terrestrial plants and some carbonate deposits from the upper 150 m long section of the sediment core were performed. Based on the high-resolution radiocarbon dating, a statistical age-depth model was constructed with assumptions on the deposition condition and the radiocarbon age offset of carbonate samples. We discuss the practicality and the limitation of the age-depth model toward interpreting the high-resolution records of environmental, climatic and tectonic events recorded in the long sediment cores from site 5017-1.

Surface sediment remobilization triggered by earthquakes in the Nankai forearc region

NASA Astrophysics Data System (ADS)

Okutsu, N.; Ashi, J.; Yamaguchi, A.; Irino, T.; Ikehara, K.; Kanamatsu, T.; Suganuma, Y.; Murayama, M.

2017-12-01

Submarine landslides triggered by earthquakes generate turbidity currents (e.g. Piper et al., 1988; 1999). Recently several studies report that the remobilization of the surface sediment triggered by earthquakes can also generate turbidity currents. However, studies that proposed such process are still limited (e.g. Ikehara et al., 2016; Mchugh et al., 2016; Moernaut et al., 2017). The purpose of this study is to examine those sedimentary processes in the Nankai forearc region, SW Japan using sedimentary records. We collected 46 cm-long multiple core (MC01) and a 6.7 m-long piston core (PC03) from the small basin during the R/V Shinsei Maru KS-14-8 cruise. The small confined basin, which is our study site, block the paths of direct sediment supply from river-submarine canyon system. The sampling site is located at the ENE-WSW elongated basin between the accretionary prism and the forearc basin off Kumano without direct sediment supply from river-submarine canyon system. The basin exhibits a confined basin that captures almost of sediments supplied from outside. Core samples are mainly composed of silty clay or very fine sand. Cs-137 measurement conducted on a MC01 core shows constantly high value at the upper 17 cm section and no detection below it. Moreover, the sedimentary structure is similar to fine-grained turbidite described by Stow and Shanmgam (1980), we interpret the upper 17 cm of MC01 as muddy turbidite. Grain size distribution and magnetic susceptibility also agree to this interpretation. Rapid sediment deposition after 1950 is assumed and the most likely event is the 2004 off Kii peninsula earthquakes (Mw=6.6-7.4). By calculation from extent of provenance area, which are estimated by paleocurrent analysis and bathymetric map, and thickness of turbidite layer we conclude that surface 1 cm of slope sediments may be remobilized by the 2004 earthquakes. Muddy turbidites are also identified in a PC03 core. The radiocarbon age gap of 170 years obtained around 2 mbsf of PC03 core also indicates similar sedimentary process. However, we also obtained large age gap in a thick turbidite layer, indicating remobilization of deeper sediments by landslide. Our results revealed that the studied basin recorded various scales and styles of sediment remobilizations by earthquake shakings.

Rock-avalanche and ocean-resurge deposits in the late Eocene Chesapeake Bay impact structure: Evidence from the ICDP-USGS Eyreville cores, Virginia, USA

USGS Publications Warehouse

Gohn, G.S.; Powars, D.S.; Dypvik, H.; Edwards, L.E.

2009-01-01

An unusually thick section of sedimentary breccias dominated by target-sediment clasts is a distinctive feature of the late Eocene Chesapeake Bay impact structure. A cored 1766-m-deep section recovered from the central part of this marine-target structure by the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) drilling project contains 678 m of these breccias and associated sediments and an intervening 275-m-thick granite slab. Two sedimentary breccia units consist almost entirely of Cretaceous nonmarine sediments derived from the lower part of the target sediment layer. These sediments are present as coherent clasts and as autoclastic matrix between the clasts. Primary (Cretaceous) sedimentary structures are well preserved in some clasts, and liquefaction and fluidization structures produced at the site of deposition occur in the clasts and matrix. These sedimentary breccias are interpreted as one or more rock avalanches from the upper part of the transient-cavity wall. The little-deformed, unshocked granite slab probably was transported as part of an extremely large slide or avalanche. Water-saturated Cretaceous quartz sand below the slab was transported into the seafloor crater prior to, or concurrently with, the granite slab. Two sedimentary breccia units consist of polymict diamictons that contain cobbles, boulders, and blocks of Cretaceous nonmarine target sediments and less common shocked-rock and melt ejecta in an unsorted, unstratified, muddy, fossiliferous, glauconitic quartz matrix. Much of the matrix material was derived from Upper Cretaceous and Paleogene marine target sediments. These units are interpreted as the deposits of debris flows initiated by the resurge of ocean water into the seafloor crater. Interlayering of avalanche and debris-flow units indicates a partial temporal overlap of the earlier avalanche and later resurge processes. A thin unit of stratified turbidite deposits and overlying laminated fine-grained deposits at the top of the section represents the transition to normal shelf sedimentation. ?? 2009 The Geological Society of America.

Tracing salt provenance in McMurdo Dry Valley soils by using magnesium isotopes

NASA Astrophysics Data System (ADS)

Cuozzo, N.; Sletten, R. S.; Hu, Y.; Teng, F. Z.

2016-12-01

The McMurdo Dry Valleys (MDV) are a hyper-arid polar desert that contain a rich geologic record in permafrost that has been preserved over millions of years. Soluble salts accumulate through the surface and subsurface of MDV soils. Sources of salt accumulation include mineral weathering, transport of marine aerosols, and possible glacial meltwater. This project seeks to study the provenance of these salts in a 30-meter ice cemented permafrost core collected in Beacon Valley. The ice-rich core was thawed and water extracted by centrifugation using a double bottom centrifuge tube. The extracted water was analyzed for ionic composition, pH, and Mg isotopes (δ26Mg), which are useful in interpreting provenance. The ionic and δ26Mg values show a disconformity at around 7 meters. Above 7 meters, δ26Mg values vary between -0.76 to -0.52, indicating rock-water interactions. These samples are isotopically heavier than the lower section of the core and can be explained by a slow accumulation of sediment and warmer near-surface temperatures that allow for greater chemical weathering of dolerite in the ice-cemented, debris-rich permafrost core. This interpretation is also supported by the more alkaline pH values (7.07 - 7.54) above 7 meters, which is consistent with chemical weathering of dolerite. In comparison, salt samples below 7 meters have δ26Mg values between -0.95 to -0.84, which overlaps with modern seawater (δ26Mg = -0.83 ± 0.09) and is fairly consistent throughout the rest of the core. Furthermore, below a depth of 7 meters, Mg/Na and Mg/K ratios are also similar to modern seawater. In summary, these results indicate differing sources of salts along the depth of the Dry Valley permafrost core, changing from a marine-dominant signature in the deeper section to a stronger weathered signal in the upper section. Additional work dating the sediment using cosmogenic nuclides provides a history for the burial of the sediments in the permafrost core and may provide broad scale paleoclimatic implications.

ACEX: A First Look at Arctic Ocean Cenozoic History

NASA Astrophysics Data System (ADS)

Moran, K.; Backman, J.

2004-12-01

The first Integrated Ocean Drilling Program mission specificplatform expedition (ACEX - Arctic Coring Expedition) drilled and recovered core from five holes at four sites through Cenozoic sediments draping the crest of the Lomonosov Ridge in the central Arctic Ocean. Coring continued into the underlying Cretaceous sedimentary bedrock. Sites are located only a few nautical miles apart along a single seismic line (AWI-91090), showing an identical and coherent Cenozoic seismostratigraphy. Preliminary results from shipboard investigations of core-catcher-based bio- and lithostratigraphy, pore water analyses and core logger data describe a thick (~160 m) middle Miocene through Pleistocene sequence that shows large amplitude, cyclic variability in the density, magnetic susceptibility and acoustic velocity of the sediments. Sediments are largely carbonate free. Pleistocene sedimentation rates are close to 3 cm/ka, whereas Pliocene sediments are by-and-large missing. A sharp change in physical properties at ~200 m defines the transition into a 200+ m thick Paleogene sequence that is initially dominated by large numbers of dinoflagellate cysts. The early Miocene, Oligocene and late Eocene appear to be largely missing in a hiatus. However, a 32 m thick interval separates the overlying middle Miocene from the underlying middle Eocene and presumably preserves some of the early Neogene and late Paleogene sections. Dinoflagellate cysts, diatoms, ebridians and silicoflagellates are common to abundant in the middle Eocene section, which bottoms in a spectacular layer showing massive occurrences of glochidia and massulae (megaspores) of the freshwater hydropterid fern Azolla (duckweed) at the early/middle Eocene boundary (~306 m), suggesting strongly reduced surface water salinity or perhaps even a brief episode of fresh water conditions at the surface. Biosilica is not present prior to the late early Eocene (~320 m). The (sub-) tropical dinoflagellate species Apectodinium augustum occurs abundantly at around 380m in pyrite-rich mudstones, indicating that the Paleocene/Eocene boundary and the associated Carbon Isotope Excursion (CIE) interval were recovered, and that the Arctic Ocean experienced surface temperatures on the order of 20°C during the Paleocene Eocene Thermal Maximum (PETM). Benthic foraminifers indicate that the early Eocene through latest Paleocene sediments were deposited in shallow-marine, neritic to inner neritic, environments. The mudstone of late Paleocene age rests unconformably on Campanian marine sands, sandstone and mudstone.

Downhole well log and core montages from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

USGS Publications Warehouse

Collett, T.S.; Lewis, R.E.; Winters, W.J.; Lee, M.W.; Rose, K.K.; Boswell, R.M.

2011-01-01

The BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well was an integral part of an ongoing project to determine the future energy resource potential of gas hydrates on the Alaska North Slope. As part of this effort, the Mount Elbert well included an advanced downhole geophysical logging program. Because gas hydrate is unstable at ground surface pressure and temperature conditions, a major emphasis was placed on the downhole-logging program to determine the occurrence of gas hydrates and the in-situ physical properties of the sediments. In support of this effort, well-log and core data montages have been compiled which include downhole log and core-data obtained from the gas-hydrate-bearing sedimentary section in the Mount Elbert well. Also shown are numerous reservoir parameters, including gas-hydrate saturation and sediment porosity log traces calculated from available downhole well log and core data. ?? 2010.

Geologic columns for the ICDP-USGS Eyreville A and C cores, Chesapeake Bay impact structure: Postimpact sediments, 444 to 0 m depth

USGS Publications Warehouse

Edwards, L.E.; Powars, D.S.; Browning, J.V.; McLaughlin, P.P.; Miller, K.G.; ,; Kulpecz, A.A.; Elbra, T.

2009-01-01

A 443.9-m-thick, virtually undisturbed section of postimpact deposits in the Chesapeake Bay impact structure was recovered in the Eyreville A and C cores, Northampton County, Virginia, within the "moat" of the structure's central crater. Recovered sediments are mainly fine-grained marine siliciclastics, with the exception of Pleistocene sand, clay, and gravel. The lowest postimpact unit is the upper Eocene Chickahominy Formation (443.9-350.1 m). At 93.8 m, this is the maximum thickness yet recovered for deposits that represent the return to "normal marine" sedimentation. The Drummonds Corner beds (informal) and the Old Church Formation are thin Oligocene units present between 350.1 and 344.7 m. Above the Oligocene, there is a more typical Virginia coastal plain succession. The Calvert Formation (344.7-225.4 m) includes a thin lower Miocene part overlain by a much thicker middle Miocene part. From 225.4 to 206.0 m, sediments of the middle Miocene Choptank Formation, rarely reported in the Virginia coastal plain, are present. The thick upper Miocene St. Marys and Eastover Formations (206.0-57.8 m) appear to represent a more complete succession than in the type localities. Correlation with the nearby Kiptopeke core indicates that two Pliocene units are present: Yorktown (57.8-32.2 m) and Chowan River Formations (32.2-18.3 m). Sediments at the top of the section represent an upper Pleistocene channel-fill and are assigned to the Butlers Bluff and Occohannock Members of the Nassawadox Formation (18.3-0.6 m). ?? 2009 The Geological Society of America.

Water column and bed-sediment core samples collected from Brownlee Reservoir near Oxbow, Oregon, 2012

USGS Publications Warehouse

Fosness, Ryan L.; Naymik, Jesse; Hopkins, Candice B.; DeWild, John F.

2013-01-01

The U.S. Geological Survey, in cooperation with Idaho Power Company, collected water-column and bed-sediment core samples from eight sites in Brownlee Reservoir near Oxbow, Oregon, during May 5–7, 2012. Water-column and bed-sediment core samples were collected at each of the eight sites and analyzed for total mercury and methylmercury. Additional bed-sediment core samples, collected from three of the eight sites, were analyzed for pesticides and other organic compounds, trace metals, and physical characteristics, such as particle size. Total mercury and methylmercury were detected in each of the water column and bed-sediment core samples. Only 17 of the 417 unique pesticide and organic compounds were detected in bed-sediment core samples. Concentrations of most organic wastewater compounds detected in bed sediment were less than the reporting level. Trace metals detected were greater than the reporting level in all the bed-sediment core samples submitted for analysis. The particle size distribution of bed-sediment core samples was predominantly clay mixed with silt.

Hydrothermal alteration in research drill hole Y-3, Lower Geyser Basin, Yellowstone National Park, Wyoming

USGS Publications Warehouse

Bargar, Keith E.; Beeson, Melvin H.

1985-01-01

Y-3, a U.S. Geological Survey research diamond-drill hole in Lower Geyser Basin, Yellowstone National Park, Wyoming, reached a depth of 156.7 m. The recovered drill core consists of 42.2 m of surficial (mostly glacial) sediments and two rhyolite flows (Nez Perce Creek flow and an older, unnamed rhyolite flow) of the Central Plateau Member of the Pleistocene Plateau Rhyolite. Hydrothermal alteration is fairly extensive in most of the drill core. The surficial deposits are largely cemented by silica and zeolite minerals; and the two rhyolite flows are, in part, bleached by thermal water that deposited numerous hydrothermal minerals in cavities and fractures. Hydrothermal minerals containing sodium as a dominant cation (analcime, clinoptilolite, mordenite, Na-smectite, and aegirine) are more abundant than calcium-bearing minerals (calcite, fluorite, Ca-smectite, and pectolite) in the sedimentary section of the drill core. In the volcanic section of drill core Y-3, calcium-rich minerals (dachiardite, laumontite, yugawaralite, calcite, fluorite, Ca-smectite, pectolite, and truscottite) are predominant over sodium-bearing minerals (aegirine, mordenite, and Na-smectite). Hydrothermal minerals that contain significant amounts of potassium (alunite and lepidolite in the sediments and illitesmectite in the rhyolite flows) are found in the two drill-core intervals. Drill core y:.3 also contains hydrothermal silica minerals (opal, [3-cristobalite, chalcedony, and quartz), other clay minerals (allophane, halloysite, kaolinite, and chlorite), gypsum, pyrite, and hematite. The dominance of calcium-bearing hydrothermal minerals in the lower rhyolitic section of the y:.3 drill core appears to be due to loss of calcium, along with potassium, during adiabatic cooling of an ascending boiling water.

Unexpected spontaneous ignition of Late Glacial sediments from the palaeolake Wukenfurche (NE Germany)

NASA Astrophysics Data System (ADS)

Dräger, Nadine; Brademann, Brian; Theuerkauf, Martin; Wulf, Sabine; Tjallingii, Rik; Słowiński, Michał; Schlaak, Norbert; Błaszkiewicz, Mirosław; Brauer, Achim

2015-04-01

A new finely laminated sediment archive has been recovered from the palaeolake Wukenfurche, NE Germany, comprising the last Glacial to Interglacial transition. The site is located within the Eberswalde ice-marginal valley and south of the terminal moraine that was formed during the Pomeranian phase of the Weichselian glaciation. Two sediment cores were obtained from the presently swampy area in July 2014. From these individual profiles a 14.7 m long continuous composite profile has been compiled by correlation of distinct marker layers. Glacial sand deposits covered by basal peat are found at the base of the cores. A visible volcanic ash layer 6 cm above the transition from basal peat into the overlaying finely laminated lake sediments corresponds most likely to the late Allerød Laacher See Tephra (LST). Preliminary counting on core photographs of the 3.5 m thick package of reddish and black alternating laminae above the LST yields a total of ca. 2500 layer couplets. Further micro-facies analyses on large-scale thin sections will be applied to test if these couplets are of annual origin (i.e. varves). Standard preparation for large-scale thin sections involves freeze-drying (for 48 hours) of 10 cm-long sediment slabs stored in aluminum boxes. Immediately after releasing the vacuum of the freeze-dryer chamber we observed an unexpected spontaneous combustion of the sediment from a particular interval of the profile. The exothermic combustion process lasted for approximately 10 to 20 minutes during which temperatures of up to 350°C have been measured with an infrared camera. Preliminary results suggest that oxidation of iron sulfides contributes to the observed reaction. To our knowledge this is the first time that such spontaneous combustion of lake sediments after freeze-drying has been observed. Details of the combustion process and sediment characteristics will be provided. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis -ICLEA- of the Helmholtz Association, grant number VH-VI-415.

[Concentrations and Distribution of Metals in the Core Sediments from Estuary and City Section of Liaohe River].

PubMed

Wang, Wei-jie; Zhou, Jun-li; Pei, Shu-wei; Liu, Zheng-tao

2016-01-15

The particle size, total organic carbon (TOC), total nitrogen (TN), C/N ratio and metal concentrations as well as activities of 210Pb were determined in Liaohe River estuary area (LN-2) and Shenyang area (LN-5), and the organic matter resources were discussed in two core sediments. Also the index of geoaccumulation (Igeo) and enrichment factors (EFs) methods were applied to evaluate the state of heavy metal contamination in the studied sties. The study showed that both sediment cores LN-2 and LN-5 were dominated by silts, and the vertical variations of grain-size composition and organic matter were well distributed in LN- 2 while fluctuated in LN-5. According to the organic matter source analysis through C/N ratio, C/N ratio varied in the scale of 5. 24-7.93 in LN-2 which was dominated by river source, and 9.94-14.21 in LN-5 which was dominated by terrestrial input. Al, Ca, Fe, Mn, Ni, Cu, Zn, Cd, Pb and Cr in two sediment cores had different vertical changing rules, Ni and Zn in LN-2 as well as Pb and Zn in LN-5 were affected by both natural and human factors, other elements had similar distributions to those of organic matters, which showed that these elements were mainly affected by the natural activities. Based on Igeo and EFs, both sediment cores were more severely polluted with Ni, Zn and Pb than other metals. The effects of human activities on the environment were also discussed in this study, combined with the economical development of Liaoning Province and the studied sites in the past 20 years.

Laboratory investigation of the erosion of cohesive sediments under oscillatory flows using a synchronized imaging technique

NASA Astrophysics Data System (ADS)

Sou, I.; Calantoni, J.; Reed, A. H.; Furukawa, Y.

2012-12-01

A synchronized dual stereo particle image velocimetry (PIV) measurement technique is used to examine the erosion process of a cohesive sediment core in the Small Oscillatory Flow Tunnel (S-OFT) in the Sediment Dynamics Laboratory at the Naval Research Laboratory, Stennis Space Center, MS. The PIV system uses four cameras and a dual cavity Nd:YAG laser. The system allows for a pair of stereo PIV windows of about 10 cm by 10 cm each to be arbitrarily located within a single light sheet. Image pairs were acquired with all four cameras at 50 Hz for 50 consecutive seconds for each flow condition. The stereo PIV windows were positioned on either side of sediment cores inserted along the centerline of the S-OFT allowing for a total measurement window of about 20 cm long by 10 cm high with sub-millimeter spacing on resolved velocity vectors. The oscillatory flows are generated by two types of driving mechanism (scotch yoke and crank lever) for converting the rotational motion of the flywheel into the linear motion of a piston. The period of oscillation ranged from 2.86 to 6.12 seconds with constant semi-excursion amplitude in the test section of 9 cm. Two kinds of inorganic sediment samples were examined. One was a mixture of 50% kaolinite and 50% 500-micron sand under flows driven by the crank lever mechanism. Another sediment core was a mixture of 50% mud collected in Galveston Bay, TX, and 50% 250-micron sand under flows driven by the scotch-yoke mechanism. During the erosion process, Kelvin-Helmholtz instabilities were observed as the flow accelerated in each direction and eventually were broken down when the flow reversed. An example of the instantaneous velocity field superimposed on the raw image is shown in Figure 1. The relative concentration of suspended sediments under different flow conditions was estimated using the intensity of light scattered from the sediment particles in suspension. By subtracting the initial light scattered from the mud core, the residual light intensity was assumed to be scattered from suspended sediments eroded from the core. Relative comparisons were only made using the same sample mixture since it is difficult, if not impossible, to calibrate the light scattering from different sediments.; Figure 1. An example of the instantaneous time-resolved velocity field superimposed on the raw image.

Microstructural study of natural fractures in Cape Roberts Project 3 core, Western Ross Sea, Antarctica

USGS Publications Warehouse

Millan, C.; Wilson, T.; Paulsen, T.

2007-01-01

Microstructures in natural fractures in core recovered offshore from Cape Roberts, Ross Sea, Antarctica, provide new constraints on the relative timing of faulting and sedimentation in the Victoria Land Basin along the Transantarctic Mountain rift flank. This study characterizes the textures, fabrics and grain-scale structures from thin section analysis of samples of microfaults, veins, and clastic dikes. Microfaults are abundant and display two different types of textures, interpreted to record two different deformation modes: pre-lithification shearing and brittle faulting of cohesive sediment. Both clastic dikes and calcite veins commonly follow fault planes, indicating that injections of liquefied sediment and circulating fluids used pre-existing faults as conduits. The close association of clastic injections, diagenetic mineralization, and faulting indicates that faulting was synchronous with deposition in the rift basin

Historical record of mercury contamination in sediments from the Babeni Reservoir in the Olt River, Romania.

PubMed

Bravo, Andrea Garcia; Loizeau, Jean-Luc; Ancey, Lydie; Ungureanu, Viorel Gheorghe; Dominik, Janusz

2009-08-01

Mercury (Hg) is a ubiquitous and hazardous contaminant in the aquatic environment showing a strong biomagnification effect along the food chain. The most common transfer path of Hg to humans is contaminated fish consumption. In severely exposed humans, Hg poisoning may lead to damage in the central nervous system. Thus, it is important to examine current and past contamination levels of Hg in aquatic milieu. The Olt River is the largest Romanian tributary of the Danube River. The use of Hg as an electrode in a chlor-alkali plant contributed to the contamination of the aquatic environment in the Rm Valcea region. The purpose of this study was to compare the current state of Hg contamination with the past contamination using a historical record obtained from a dated sediment core from one of the Olt River reservoirs (Babeni) located downstream from the chlor-alkali plant. To our knowledge, no published data on Hg contamination in this region are available. The Babeni Reservoir was selected for this study because it is situated downstream from the chlor-alkali plant, whilst the other reservoirs only retain the pollutants coming from the upstream part of the watershed. Preliminary analyses (unpublished) showed high Hg concentrations in the surface sediment of the Babeni Reservoir. One core was taken in the upstream Valcea Reservoir to provide a local background level of Hg concentrations in sediments. Sediment texture was uniform in the cores from both reservoirs. Laminated sediment structure, without any obvious discontinuities, was observed. Hg concentrations in the sediment core from the Valcea Reservoir were low and constant (0.01-0.08 mg/kg). In Babeni Reservoir sediments, Hg concentrations were very high in the deeper core section (up to 45 mg/kg in the longest core) and decreased to lower concentrations toward the top of the cores (1.3-2.4 mg/kg). This decrease probably reflects technological progress in control of emissions from the Hg-cell-based chlor-alkali industry. Two strong peaks could be distinguished in older sediments. The mean rate of sedimentation (5.9 cm/year) was calculated from the depth of the (137)Cs Chernobyl peak. This was in good agreement with the sedimentation rate estimated at this site from a bathymetric study. Assuming a constant sedimentation rate, the two Hg peaks would reflect two contamination events in 1987 and 1991, respectively. However, it is also possible that the two peaks belong to the same contamination event in 1987 but were separated by a sediment layer richer in sand and silt. This layer had a low Hg concentration, which can be interpreted as a mass deposition event related to a major flood bringing Hg-free sediments. Whilst the chlor-alkali plant partly switched to a cleaner technology in 1999, no obvious decrease of Hg concentrations was observed in recent decade. Results from the sediment core reflected the historical trend of Hg release from the chlor-alkali plant, revealed important contamination episodes and confirmed a legacy of contamination of Hg in recent sediments even if the concentrations of Hg decreased toward the surface due to a more efficient emission control. Although the Hg concentrations in Babeni Reservoir sediments were extremely high in the late eighties and they remain one order of magnitude higher in the surface sediments than in sediments from the upstream reservoir, little is known about the transfer of Hg to the biota and human population. Our initial measurements indicate the presence of monomethyl-Hg (MMHg) in pore water, but further studies are necessary to evaluate fluxes of MMHg at the sediment-water interface. Samples of fish and hair from various groups of the local population were recently collected to evaluate the potential hazard of Hg contamination to human health in the Rm Valcea region.

3D Chirp Sonar Images on Fluid Migration Pathways and Their Implications on Seafloor Stability East of the Fangliao Submarine Canyon Offshore SW Taiwan

NASA Astrophysics Data System (ADS)

Lu, Y. W.; Liu, C. S.; Su, C. C.; Hsu, H. H.; Chen, Y. H.

2015-12-01

This study utilizes both chirp sonar images and coring results to investigate the unstable seafloor strata east of the Fangliao Submarine Canyon offshore southwestern Taiwan. We have constructed 3D chirp sonar images from a densely surveyed block to trace the attitude of an acoustic transparent layer and features caused by fluid activities. Based on the distribution of this transparent layer and fluid-related features, we suggest that this transparent layer forms a pathway for fluid migration which induces fluid-related characters such as acoustic blanking and fluid chimneys in the 3D chirp sonar images. Cored seafloor samples are used in this study to investigate the sediment compositions. The 210Pb activity profiles of the cores show oscillating and unsteady values at about 20~25 cm from core top. The bulk densities of the core samples in the same section (about 20~25 cm from core top) give values lower than those at deeper parts of the cores. These results indicate that the water content is much higher in the shallow sediments than in the deeper strata. From core sample analyses, we deduce that the local sediments are disturbed by liquefaction. From the analyses of 3D chirp sonar images and core data, we suggest that the seafloor east of the Fangliao Submarine Canyon is in an unstable condition, if disturbed by earthquakes, submarine landslides and gravity flows could be easily triggered and cause some geohazards, like breaking submarine cables during the 2006 Pingtung earthquake event.

Geological controls on the occurrence of gas hydrate from core, downhole log, and seismic data in the Shenhu area, South China Sea

USGS Publications Warehouse

Xiujuan Wang,; ,; Collett, Timothy S.; Lee, Myung W.; Yang, Shengxiong; Guo, Yiqun; Wu, Shiguo

2014-01-01

Multi-channel seismic reflection data, well logs, and recovered sediment cores have been used in this study to characterize the geologic controls on the occurrence of gas hydrate in the Shenhu area of the South China Sea. The concept of the "gas hydrate petroleum system" has allowed for the systematic analysis of the impact of gas source, geologic controls on gas migration, and the role of the host sediment in the formation and stability of gas hydrates as encountered during the 2007 Guangzhou Marine Geological Survey Gas Hydrate Expedition (GMGS-1) in the Shenhu area. Analysis of seismic and bathymetric data identified seventeen sub-linear, near-parallel submarine canyons in this area. These canyons, formed in the Miocene, migrated in a northeasterly direction, and resulted in the burial and abandonment of canyons partially filled by coarse-grained sediments. Downhole wireline log (DWL) data were acquired from eight drill sites and sediment coring was conducted at five of these sites, which revealed the presence of suitable reservoirs for the occurrence of concentrated gas hydrate accumulations. Gas hydrate-bearing sediment layers were identified from well log and core data at three sites mainly within silt and silt clay sediments. Gas hydrate was also discovered in a sand reservoir at one site as inferred from the analysis of the DWL data. Seismic anomalies attributed to the presence of gas below the base of gas hydrate stability zone, provided direct evidence for the migration of gas into the overlying gas hydrate-bearing sedimentary sections. Geochemical analyses of gas samples collected from cores confirmed that the occurrence of gas hydrate in the Shenhu area is controlled by the presence thermogenic methane gas that has migrated into the gas hydrate stability zone from a more deeply buried source.

Presence of Nitrate-Accumulating Sulfur Bacteria and Their Influence on Nitrogen Cycling in a Shallow Coastal Marine Sediment

PubMed Central

Sayama, Mikio

2001-01-01

Nitrate flux between sediment and water, nitrate concentration profile at the sediment-water interface, and in situ sediment denitrification activity were measured seasonally at the innermost part of Tokyo Bay, Japan. For the determination of sediment nitrate concentration, undisturbed sediment cores were sectioned into 5-mm depth intervals and each segment was stored frozen at −30°C. The nitrate concentration was determined for the supernatants after centrifuging the frozen and thawed sediments. Nitrate in the uppermost sediment showed a remarkable seasonal change, and its seasonal maximum of up to 400 μM was found in October. The directions of the diffusive nitrate fluxes predicted from the interfacial concentration gradients were out of the sediment throughout the year. In contrast, the directions of the total nitrate fluxes measured by the whole-core incubation were into the sediment at all seasons. This contradiction between directions indicates that a large part of the nitrate pool extracted from the frozen surface sediments is not a pore water constituent, and preliminary examinations demonstrated that the nitrate was contained in the intracellular vacuoles of filamentous sulfur bacteria dwelling on or in the surface sediment. Based on the comparison between in situ sediment denitrification activity and total nitrate flux, it is suggested that intracellular nitrate cannot be directly utilized by sediment denitrification, and the probable fate of the intracellular nitrate is hypothesized to be dissimilatory reduction to ammonium. The presence of nitrate-accumulating sulfur bacteria therefore may lower nature's self-purification capacity (denitrification) and exacerbate eutrophication in shallow coastal marine environments. PMID:11472923

Impact of early diagenesis and bulk particle grain size distribution on estimates of relative geomagnetic palaeointensity variations in sediments from Lama Lake, northern Central Siberia

NASA Astrophysics Data System (ADS)

Nowaczyk, Norbert R.; Harwart, Stefanie; Melles, Martin

2001-04-01

High-resolution analyses of rock magnetic and sedimentological parameters were conducted on an 11m long sediment core from Lama Lake, Northern Siberia, which encompasses the late Pleistocene and the Holocene epochs. The results reveal a strong link between the median grain size of the magnetic particles, identified as magnetite, and the oxidation state of the sediment. Reducing conditions associated with a relative high total organic carbon (TOC) content of the sediment characterize the upper 7m of the core (~Holocene), and these have led to a partial dissolution of detrital magnetite grains, and a homogenization of grain-size-related rock magnetic parameters. The anoxic sediments are characterized by significantly larger median magnetic grain sizes, as indicated, for example, by lower median destructive fields of the natural remanent magnetization (MDFNRM) and lower ratios of saturation remanence to saturation magnetization (MSR/MS). Consequently, estimates of relative geomagnetic palaeointensity variations yielded large amplitude shifts associated with anoxic/oxic boundaries. Despite the partial reductive dissolution of magnetic particles within the anoxic section, and consequent minimal variations in magnetic concentration and grain size, palaeointensity estimates for this part of the core were still lithologically distorted by the effects of particle size (and subsidiary TOC) variations. Anomalously high values coincide with an interval of significantly more fine-grained sediment, which is also associated with a decrease in TOC content, which may thus imply a decreased level of magnetite dissolution in this interval. Calculation of relative palaeointensity estimates therefore seems to be compromised by a combined effect of shifts in the particle size distribution of the bulk sediment and by partial magnetite dissolution varying in association with the TOC content of the sediment.

Is the Core Top Really Modern? A Story of Chemical Erosion, Bioturbation, and Lateral Sediment Redistribution from the Eastern Equatorial Pacific

NASA Astrophysics Data System (ADS)

Mekik, F.

2016-12-01

Paleoceanographic work is based on calibrating paleo-environmental proxies using well-preserved core top sediments which represent the last one thousand years or less. However, core top sediments may be in places as old as 9000 years due to various sedimentary and diagenetic processes, such as chemical erosion, bioturbation and lateral sediment redistribution. We hypothesize that in regions with high surface ocean productivity, high organic carbon to calcite ratios reaching the seabed promote calcite dissolution in sediments, even in regions above the lysocline. This process may lead to chemical erosion of core tops which in turn may result in core top aging. The eastern equatorial Pacific (EEP), a popular site for calibration of paleoceanographic proxies, is such a place. Better understanding the relationship between core top age and dissolution will help correct biases inherent in proxy calibration because dissolution of foraminifers alters shell chemistry, and wholesale dissolution of sediments leads to core top aging and loss. We present both new and literature-based core top data of radiocarbon ages from the EEP. We created regional maps of both core top radiocarbon age and calcite preservation measured with the Globorotalia menardii Fragmentation Index (MFI; over 100 core tops). Our maps show a clear pattern of deep sea sedimentary calcite dissolution mimicking the pattern of surface ocean productivity observed from satellites and sediment traps in the EEP. Core top radiocarbon ages generally parallel the dissolution patterns observed in the region. Where this relationship does not hold true, bioturbation and/or lateral sediment redistribution may play a role. Down core radiocarbon and 230Th-normalized sediment accumulation rate data from several cores in the EEP support this hypothesis. Better understanding the role of diagenesis promotes the development of more reliable paleo-environmental proxies.

INNOVATIVE TECHNOLOGY EVALUATION REPORT ...

EPA Pesticide Factsheets

The Split Core Sampler for Submerged Sediments (Split Core Sampler) designed and fabricated by Arts Manufacturing & Supply, Inc., was demonstrated under the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation Program in April and May 1999 at sites in EPA Regions 1 and 5, respectively. In addition to assessing ease of sampler operation, key objectives of the demonstration included evaluating the samplers ability to (1) consistently collect a given volume of sediment, (2) consistently collect sediment in a given depth interval, (3) collect samples with consistent characteristics from a homogenous layer of sediment, and (4) collect samples under a variety of site conditions. This report describes the demonstration results for the Split Core Sampler and two conventional samplers (the Hand Corer and Vibrocorer) used as reference samplers. During the demonstration, the Split Core Sampler performed as well as or better than the reference samplers. Based on visual observations, both the Split Core Sampler and reference samplers collected partially compressed samples of consolidated and unconsolidated sediments from the sediment surface downward; sample representativeness may be questionable because of core shortening and core compression. Sediment stratification was preserved for both consolidated and unconsolidated sediment samples collected by the Split Core Sampler and reference samplers. No sampler was able to collect samples

Preserving Geological Samples and Metadata from Polar Regions

NASA Astrophysics Data System (ADS)

Grunow, A.; Sjunneskog, C. M.

2011-12-01

The Office of Polar Programs at the National Science Foundation (NSF-OPP) has long recognized the value of preserving earth science collections due to the inherent logistical challenges and financial costs of collecting geological samples from Polar Regions. NSF-OPP established two national facilities to make Antarctic geological samples and drill cores openly and freely available for research. The Antarctic Marine Geology Research Facility (AMGRF) at Florida State University was established in 1963 and archives Antarctic marine sediment cores, dredge samples and smear slides along with ship logs. The United States Polar Rock Repository (USPRR) at Ohio State University was established in 2003 and archives polar rock samples, marine dredges, unconsolidated materials and terrestrial cores, along with associated materials such as field notes, maps, raw analytical data, paleomagnetic cores, thin sections, microfossil mounts, microslides and residues. The existence of the AMGRF and USPRR helps to minimize redundant sample collecting, lessen the environmental impact of doing polar field work, facilitates field logistics planning and complies with the data sharing requirement of the Antarctic Treaty. USPRR acquires collections through donations from institutions and scientists and then makes these samples available as no-cost loans for research, education and museum exhibits. The AMGRF acquires sediment cores from US based and international collaboration drilling projects in Antarctica. Destructive research techniques are allowed on the loaned samples and loan requests are accepted from any accredited scientific institution in the world. Currently, the USPRR has more than 22,000 cataloged rock samples available to scientists from around the world. All cataloged samples are relabeled with a USPRR number, weighed, photographed and measured for magnetic susceptibility. Many aspects of the sample metadata are included in the database, e.g. geographical location, sample description, collector, rock age, formation, section location, multimedia images as well structural data, field observations, logistics, surface features, etc. The metadata are entered into a commercial, museum based database called EMu. The AMGRF houses more than 25,000m of deep-sea cores and drill cores as well as nearly 3,000 meters of rotary cored geological material from Antarctica. Detailed information on the sediment cores including location, sediment composition are available in cruise reports posted on the AMGRF web-site. Researchers may access the sample collections through the online websites (http://www-bprc.mps.ohio-state.edu/emuwebusprr and http://www.arf.fsu.edu). Searches may be done using multiple search terms or by use of the mapping feature. The on-line databases provide an essential resource for proposal preparation, pilot studies and other sample based research that should make fieldwork more efficient.

A 1500-year holocene caribbean climate archive from the Blue Hole, lighthouse reef, belize

USGS Publications Warehouse

Gischler, E.; Shinn, E.A.; Oschmann, W.; Fiebig, J.; Buster, N.A.

2008-01-01

Sediment cores (up to 6 m in length) from the bottom of the Blue Hole, a 125 m deep Pleistocene sinkhole located in the lagoon of Lighthouse Reef Atoll, Belize, consist of undisturbed, annually layered biogenic carbonate muds and silts with intercalated coarser grained storm beds. The sedimentation rate of the layered sections is 2.5 mm/y on average, and the long cores span the past 1500 years. Oxygen isotopes of laminated sediment provide a late Holocene climate proxy: A high-resolution ??18O time series traces the final Migration Period Pessimum, the Medieval Warm Period, the Little Ice Age, and the subsequent temperature rise. Carbon isotopes (??13C) decrease up core and show the impacts of the decline of the Mayan culture and the Suess effect. Time series analyses of ??18O and ??13C content reveal 88-, 60-, 52-, and 32-year cyclicities, and suggest solar forcing. Storm event beds are most common during AD 650-850, around AD 1000, during AD 1200-1300, and AD 1450-1550. Major storm beds are rare during the past 500 years BP.

Estimating selenium removal by sedimentation from the Great Salt Lake, Utah

USGS Publications Warehouse

Oliver, W.; Fuller, C.; Naftz, D.L.; Johnson, W.P.; Diaz, X.

2009-01-01

The mass of Se deposited annually to sediment in the Great Salt Lake (GSL) was estimated to determine the significance of sedimentation as a permanent Se removal mechanism. Lake sediment cores were used to qualitatively delineate sedimentation regions (very high to very low), estimate mass accumulation rates (MARs) and determine sediment Se concentrations. Sedimentation regions were defined by comparison of isopach contours of Holocene sediment thicknesses to linear sedimentation rates determined via analysis of 210Pb, 226Ra, 7Be and 137Cs activity in 20 short cores (<5 cm), yielding quantifiable results in 13 cores. MARs were developed via analysis of the same radioisotopes in eight long cores (>10 cm). These MARs in the upper 1-2 cm of each long core ranged from 0.019 to 0.105 gsed/cm2/a. Surface sediment Se concentrations in the upper 1 or 2 cm of each long core ranged from 0.79 to 2.47 mg/kg. Representative MARs and Se concentrations were used to develop mean annual Se removal by sedimentation in the corresponding sedimentation region. The spatially integrated Se sedimentation rate was estimated to be 624 kg/a within a range of uncertainty between 285 and 960 kg/a. Comparison to annual Se loading and other potential removal processes suggests burial by sedimentation is not the primary removal process for Se from the GSL. ?? 2009 Elsevier Ltd.

Description and hydrogeologic implications of cored sedimentary material from the 1975 drilling program at the radioactive waste management complex, Idaho

USGS Publications Warehouse

Rightmire, C.T.

1984-01-01

Samples of sedimentary material from interbeds between basalt flows and from fractures in the flows, taken from two drill cores at the Radioactive Waste Management Complex at the Idaho National Engineering Laboratory were analyzed for (1) particle-size dribution, (2) bulk mineralogy, (3) clay mineralogy, (4) cation-exchange capacity, and (5) carbonate content. Thin sections of selected sediment material were made for petrographic examination. Preliminary interpretations indicate that (1) it may be possible to distinguish the various sediment interbeds on the basis of their mineralogy, (2) the presence of carbonate horizons in sedimentary interbeds may be utilized to approximate the time of exposure and the climate while the surface was exposed (which affected the hydrogeologic character of the sediment), and the type and orientation of fracture-filling material may be utilized to determine the mechanism by which fractures were filled. (USGS)

Pore fluid geochemistry from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

USGS Publications Warehouse

Torres, M.E.; Collett, T.S.; Rose, K.K.; Sample, J.C.; Agena, W.F.; Rosenbaum, E.J.

2011-01-01

The BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well was drilled and cored from 606.5 to 760.1. m on the North Slope of Alaska, to evaluate the occurrence, distribution and formation of gas hydrate in sediments below the base of the ice-bearing permafrost. Both the dissolved chloride and the isotopic composition of the water co-vary in the gas hydrate-bearing zones, consistent with gas hydrate dissociation during core recovery, and they provide independent indicators to constrain the zone of gas hydrate occurrence. Analyses of chloride and water isotope data indicate that an observed increase in salinity towards the top of the cored section reflects the presence of residual fluids from ion exclusion during ice formation at the base of the permafrost layer. These salinity changes are the main factor controlling major and minor ion distributions in the Mount Elbert Well. The resulting background chloride can be simulated with a one-dimensional diffusion model, and the results suggest that the ion exclusion at the top of the cored section reflects deepening of the permafrost layer following the last glaciation (???100 kyr), consistent with published thermal models. Gas hydrate saturation values estimated from dissolved chloride agree with estimates based on logging data when the gas hydrate occupies more than 20% of the pore space; the correlation is less robust at lower saturation values. The highest gas hydrate concentrations at the Mount Elbert Well are clearly associated with coarse-grained sedimentary sections, as expected from theoretical calculations and field observations in marine and other arctic sediment cores. ?? 2009 Elsevier Ltd.

Sedimentation of the mud belt along the coast of China from the mouth of the Yangtze (Changjiang) River to northern Taiwan Strait: An Source-to-Sink Perspective

NASA Astrophysics Data System (ADS)

Chien, C. C.; Liu, J. T.; Yang, R.; Huh, C. A.; Su, C. C.

2016-02-01

Sediments in the Taiwan Strait are originated from Mainland China and Taiwan. The China Coastal Current, influenced by the northeast monsoon in winter, becomes enhanced, which caries the sediments exported from the Yangtze River to the southern East China Sea and the Taiwan Strait along the Zhemin-Taiwan Strait mud belt. The sediment transport process is also influenced by tidal current and Kuroshio Branch Current and Taiwan Warm Current, making the seafloor sediment signals complex. This study used R/V Ocean Researcher V (Cruise 0032), to collect six box cores and three gravity cores along the Zhemin mud belt and the mud belt in northern Taiwan Strait in the winter of 2014. From the core samples, grain-size distribution, Multi-Sensor Core Logger, and 7Be activity were measured to investigate the sedimentation process along the mud belts. The box core taken at the mouth of the Changjiang- is composed of homogeneous clay and rich in shell fragments. The core off the mouth of Ou River is composed of homogeneous clay, but showing horizontal laminations. Near the Taishan Island off the coast of Zhejiang the core is consisted of a homogeneous sandy sediments that turned into clay. Off the mouth of the Min River the core consists of clay with shell fragments. Off the coast of the Wu River on the west coast of the Taiwan, the core is mainly composed of muddy sediments, which has the siltstone layers of oblique bedding. Off the mouth of Zhuoshui River in central Taiwan, the core is composed of sandy sediments. From the mouth of the Changhjiang, Zhemin mud belt, the northern Taiwan Strait mud belt, to the central Taiwan Strait, 7Be activity in the seafloor sediment indicates that the freshness of the terrigenous sediments decreased. The Mass Magnetic Susceptiblity (MSI) demonstrates that the terrigenous sediments decreased from north to south. The MSI signals in the core off the mouth of the Minjiang are different from those in the neighboring cores. This is suspected due to the convergence of sediments from the Changjiang and Taiwan. The particle sizes of the cores show that the sediment became coarser from the north to south. In the future the study will make use of 210Pbex, and other environmental and provenance such as water dynamic mechanism variables to explore the sediment source and sink patterns along with the Zhemin-Taiwan Strait mud belts.

Compositional classification and sedimentological interpretation of the laminated lacustrine sediments at Baumkrichen (Western Austria) using XRF core scanning data

NASA Astrophysics Data System (ADS)

Barrett, Samuel; Tjallingii, Rik; Bloemsma, Menno; Brauer, Achim; Starnberger, Reinhard; Spötl, Christoph; Dulski, Peter

2015-04-01

The outcrop at Baumkirchen (Austria) encloses part of a unique sequence of laminated lacustrine sediments deposited during the last glacial cycle. A ~250m long composite sediment record recovered at this location now continuously covers the periods ~33 to ~45 ka BP (MIS 3) and ~59 to ~73 ka BP (MIS 4), which are separated by a hiatus. The well-laminated (mm-cm scale) and almost entirely clastic sediments reveal alternations of clayey silt and medium silt to very-fine sand layers. Although radiocarbon and optically stimulated luminescence (OSL) dating provide a robust chronology, accurate dating of the sediment laminations appears to be problematic due to very high sedimentation rates (3-8 cm/yr). X-ray fluorescence (XRF) core scanning provided a detailed ~150m long record of compositional changes of the sediments at Baumkirchen. Changes in the sediments are subtle and classification into different facies based on individual elements is therefore subjective. We applied a statistically robust clustering analysis to provide an objective compositional classification without prior knowledge, based on XRF measurements for 15 analysed elements (all those with an acceptable signal-noise ratio: Zr, Sr, Ca, Mn, Cu, Zn, Rb, Ni, Fe, K, Cr, V, Si, Ba, T). The clustering analysis indicates a distinct compositional change between sediments deposited below and above the stratigraphic hiatus, but also differentiates between individual different laminae. Preliminary results suggest variations in the sequence are largely controlled by the relative occurrence of different kinds of sediment represented by different clusters. Three clusters identify well-laminated sediments, visually similar in appearance, each dominated by an anti-correlation between Ca and one or more of the detrital elements K, Zr, Ti, Si and Fe. Two of these clusters occur throughout the entire sequence, one frequently and the other restricted to short sections, while the third occurs almost exclusively below the hiatus, indicating a geochemically distinct component that possibly represents a specific sediment source. In a similar manner, three other clusters identify event layers with different compositions of which two occur exclusively above the hiatus and one exclusively below. The variations in the occurrence of these clusters revealing distinct event layers suggest variations in dominant sediment source both above and below the hiatus and within the section above it. More detailed comparisons between compositional variations of the individual clusters obtained from biplots and microscopic observations on thin sections, grain-size analyses, and mineralogical analyses are needed to further differentiate between sediment sources and transport mechanisms.

Effects of spatial and temporal variation of acid-volatile sulfide on the bioavailability of copper and zinc in freshwater sediments

USGS Publications Warehouse

Besser, John M.; Ingersoll, Christopher G.; Giesty, John P.

1996-01-01

Variation in concentrations of acid-volatile sulfide (AVS) in sediments from the upper Clark Fork River of Montana, USA, was associated with differences in bioaccumulation of Cu and Zn and growth of larvae of the midge, Chironomus tentans. Growth of midge larvae was significantly greater and bioaccumulation of Cu was significantly less in surface sections (0–3 cm depth) of sediment cores, which had greater concentrations of AVS and lesser ratios of simultaneously extracted metals to AVS (SEM:AVS ratios) than in subsurface sediments (6–9 cm). Concentrations of AVS were significantly less in sediments incubated with oxic overlying water for 9 weeks than in the same sediments incubated under anoxic conditions. Bioaccumulation of Cu differed significantly between incubation treatments, corresponding to differences in concentrations of AVS and SEM:AVS ratios, although midge growth did not. Bioaccumulation of Zn did not differ significantly between depth strata of sediment cores or between incubation treatments. When results from the two sets of bioassays were combined, bioaccumulation of Cu and Zn, but not growth, was significantly correlated with SEM:AVS ratios and other estimates of bioavailable metal fractions in sediments. Growth of midge larvae was significantly correlated with bioaccumulation of Zn, but not Cu, suggesting that Zn was the greater contributor to the toxicity of these sediments. Assessments of the toxicity of metal-contaminated freshwater sediments should consider the effects of spatial and temporal variation in AVS concentrations on metal bioavailability.

The distribution of sediments grain size along the depth in source of the Yangtze River, Tibetan Plateau, China

NASA Astrophysics Data System (ADS)

Zhou, Y.; Yao, S.; Zhou, S.; Liu, X.; Yan, X.; Lu, J.

2017-12-01

Sediment was the one result of river process, in alluvial rive, it can reflect the hydrodynamic characteristic, even the hydrology and climate. In the source region of the Yangtze River with few human activities, The Qumalai Reach of the Tongtianhe River was selected to research the distribution of sediments grain size along the depth. The vertical drilling tools were used to obtain 7 boreholes along the river cross section, and the sedimentary cores were made analysis of stratification and granularity. The results show: The sediments are dominated by sand and grail, the sediment transport capacity of river sources is strong; the grain size frequency distribution curve with 2 3 kurtosis, main peak is sharp, it is typical deposit sediment of the suspended load; The grain size coarsen from the stream terrace to the main channel, sediment transport capacity of main stream is bigger; There are several coarse and fine sediments layers in the sedimentary core of the terrace and flood plain, medium diameters of each layer are various from 0.4mm to 80mm, different layer with different grain size can reflect the different hydrodynamic characteristic of each historical period. This result can provide the original data and enlightenment to support the research for historical river process and hydrology so much as the climate change.

A database of paleoceanographic sediment cores from the North Pacific, 1951-2016

NASA Astrophysics Data System (ADS)

Borreggine, Marisa; Myhre, Sarah E.; Mislan, K. Allison S.; Deutsch, Curtis; Davis, Catherine V.

2017-09-01

We assessed sediment coring, data acquisition, and publications from the North Pacific (north of 30° N) from 1951 to 2016. There are 2134 sediment cores collected by American, French, Japanese, Russian, and international research vessels across the North Pacific (including the Pacific subarctic gyre, Alaskan gyre, Japan margin, and California margin; 1391 cores), the Sea of Okhotsk (271 cores), the Bering Sea (123 cores), and the Sea of Japan (349 cores) reported here. All existing metadata associated with these sediment cores are documented here, including coring date, location, core number, cruise number, water depth, vessel metadata, and coring technology. North Pacific sediment core age models are built with isotope stratigraphy, radiocarbon dating, magnetostratigraphy, biostratigraphy, tephrochronology, % opal, color, and lithological proxies. Here, we evaluate the iterative generation of each published age model and provide comprehensive documentation of the dating techniques used, along with sedimentation rates and age ranges. We categorized cores according to the availability of a variety of proxy evidence, including biological (e.g., benthic and planktonic foraminifera assemblages), geochemical (e.g., major trace element concentrations), isotopic (e.g., bulk sediment nitrogen, oxygen, and carbon isotopes), and stratigraphic (e.g., preserved laminations) proxies. This database is a unique resource to the paleoceanographic and paleoclimate communities and provides cohesive accessibility to sedimentary sequences, age model development, and proxies. The data set is publicly available through PANGAEA at https://doi.org/10.1594/PANGAEA.875998.

Lake Sediment Records as an Indicator of Holocene Fluctuations of Quelccaya Ice Cap, Peru and Regional Climate

NASA Astrophysics Data System (ADS)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.; Baranes, H. E.

2012-12-01

The past fluctuations of Quelccaya Ice Cap, (QIC; 13°S, 70°W, 5200 m asl) located in the southeastern Peruvian Andes, provide a record of tropical climate since the last glacial-interglacial transition. A detailed surficial geomorphic record of past glacial extents developed over the last several decades (e.g. Mercer and Palacios 1977; Buffen et al. 2009; Kelly et al. 2012 accepted) demonstrates that QIC is a dynamic glacial system. These records show that the ice cap was larger than present and retreating by ~11,500 yr BP, and smaller than present between ~7,000 and ~4,600 yr BP. The most recent advance occurred during the late Holocene (Little Ice Age;LIA), dated with 10Be surface exposure ages (510±90 yrs (n = 8)) (Stroup et al. in prep.). This overrode earlier deposits obscuring a complete Holocene record; we aim to address the gaps in glacial chronology using the sedimentary record archived in lakes. We retrieved two sets cores (8 and 5 m-long) from Laguna Challpacocha (13.91°S, 70.86°W, 5040 m asl), a lake that currently receives meltwater from QIC. Four radiocarbon ages from the cores suggest a continuous record dating to at least ~10,500 cal. yr BP. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, grayscale and X-ray fluorescence chemistry indicate changes in the amount of clastic sediment deposition. We interpret clastic sediments to have been deposited from ice cap meltwater, thus indicating more extensive ice. Clastic sediments compose the top of the core from 4 to 30 cm depth, below there is a sharp transition to organic sediments radiocarbon dated to (500±30 and 550±20 cal. yr BP). The radiocarbon ages are similar to the 10Be dated (LIA) glacial position. At least three other clastic units exist in the core; dating to ~2600-4300, ~4800-7300 and older then ~10,500 cal. yr BP based on a linear age model with four radiocarbon dates. We obtained two, ~4 m long, cores from Laguna Yanacocha (13.95°S,70.87°W, 4910 m asl), a lake that has not received glacial meltwater since late glacial time. We used the clastic sediment record to determine the input from non-glacial sources, representing ambient climate. This information tests our hypothesis that increased clastic sediment is from a glacial source in the Challpacocha record. The Yanacocha cores are composed primarily of organic-rich sediment with little clastic sediment. Eight radiocarbon ages in stratigraphic order indicate a continuous sedimentation in the lake since 11,240±90 cal. yr BP. Till at the base of the core indicates likely ice recession from the basin at this time. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, and gray scale suggest only minor changes in sedimentation relative to those in the Challpacocha core. Our new continuous lake sediment record provides complementary data to the discontinuous records of QIC Holocene extents as marked by moraines and exposed sections (e.g. Buffen et al. 2009; Thompson et al. 2006). Our record has some similarities with the nearby lacustrine record from Laguna Pacococha, which also receives meltwater from QIC (Rodbell and Seltzer, 2000; Abbott et al., 2003).

Evaluation of surficial sediment toxicity and sediment physico-chemical characteristics of representative sites in the Lagoon of Venice (Italy)

NASA Astrophysics Data System (ADS)

Losso, C.; Arizzi Novelli, A.; Picone, M.; Marchetto, D.; Pessa, G.; Molinaroli, E.; Ghetti, P. F.; Volpi Ghirardini, A.

2004-11-01

Toxic hazard in sites with varying types and levels of contamination in the Lagoon of Venice was estimated by means of toxicity bioassays based on the early life-stages of the autochthonous sea urchin Paracentrotus lividus. Elutriate was chosen as the test matrix, due to its ability to highlight potential toxic effects towards sensitive biological components of the water column caused by sediment resuspension phenomena affecting the Lagoon. Surficial sediments (core-top 5 cm deep), directly influenced by resuspension/redeposition processes, and core sediments (core 20 cm deep), recording time-mediated contamination, were sampled in some sites located in the lagoonal area most greatly influenced by anthropogenic activities. Particle size, organic matter and water content were also analysed. In two sites, the results of physical parameters showed that the core-top sediments were coarser than the 20-cm core sediments. Sperm cell toxicity test results showed the negligible acute toxicity of elutriates from all investigated sites. The embryo toxicity test demonstrated a short-term chronic toxicity gradient for elutriates from the 20-cm core sediments, in general agreement both with the expected contamination gradient and with results of the Microtox® solid-phase test. Elutriates of the core-top 5-cm sediments revealed a totally inverted gradient, in comparison with that for the 20-cm core sediments, and the presence of a "hot spot" of contamination in the site chosen as a possible reference. Investigations on ammonia and sulphides as possible confounding factors excluded their contribution to this "hot spot". Integrated physico-chemical and toxicity results on sediments at various depths demonstrated the presence of disturbed sediments in the central basin of the Lagoon of Venice.

Estimating accumulation rates and physical properties of sediment behind a dam: Englebright Lake, Yuba River, northern California

USGS Publications Warehouse

Snyder, Noah P.; Rubin, David M.; Alpers, Charles N.; Childs, Jonathan R.; Curtis, Jennifer A.; Flint, Lorraine E.; Wright, Scott A.

2004-01-01

Studies of reservoir sedimentation are vital to understanding scientific and management issues related to watershed sediment budgets, depositional processes, reservoir operations, and dam decommissioning. Here we quantify the mass, organic content, and grain-size distribution of a reservoir deposit in northern California by two methods of extrapolating measurements of sediment physical properties from cores to the entire volume of impounded material. Englebright Dam, completed in 1940, is located on the Yuba River in the Sierra Nevada foothills. A research program is underway to assess the feasibility of introducing wild anadromous fish species to the river upstream of the dam. Possible management scenarios include removing or lowering the dam, which could cause downstream transport of stored sediment. In 2001 the volume of sediments deposited behind Englebright Dam occupied 25.5% of the original reservoir capacity. The physical properties of this deposit were calculated using data from a coring campaign that sampled the entire reservoir sediment thickness (6–32 m) at six locations in the downstream ∼3/4 of the reservoir. As a result, the sediment in the downstream part of the reservoir is well characterized, but in the coarse, upstream part of the reservoir, only surficial sediments were sampled, so calculations there are more uncertain. Extrapolation from one-dimensional vertical sections of sediment sampled in cores to entire three-dimensional volumes of the reservoir deposit is accomplished via two methods, using assumptions of variable and constant layer thickness. Overall, the two extrapolation methods yield nearly identical estimates of the mass of the reservoir deposit of ∼26 × 106 metric tons (t) of material, of which 64.7–68.5% is sand and gravel. Over the 61 year reservoir history this corresponds to a maximum basin-wide sediment yield of ∼340 t/km2/yr, assuming no contribution from upstream parts of the watershed impounded by other dams. The uncertainties and limitations of the estimates of overall sediment quantities are discussed. Implications for watershed management and future reservoir sedimentation studies are also presented.

Susceptibility of synthetic long-chain alkylbenzenes to degradation in reducing marine sediments

USGS Publications Warehouse

Eganhouse, Robert P.; Pontolillo, James

2008-01-01

Long-chain alkylbenzenes (LCABs) synthesized for production of alkylbenzene sulfonate surfactants have been used as molecular markers of anthropogenic waste for 25 years. Synthetic LCABs comprise two classes, the tetrapropylene-based alkylbenzenes (TABs) and the linear alkylbenzenes (LABs). LABs supplanted TABs in the mid-1960s because of improved biodegradability of their sulfonated analogs. Use of LCABs for molecular stratigraphy depends on their preservation in sediments over decadal time scales. Most laboratory and field studies suggest that LABs degrade rapidly under aerobic conditions but are resistant to degradation when oxygen is absent. However, recent work indicates that LABs may not be as persistent under reducing conditions as previously thought. To assess the potential for degradation of LCABs in reducing sediments, box cores collected in 1992 and 2003 near a submarine wastewater outfall system were analyzed using gas chromatography/mass spectrometry. The TABs were effectively preserved; differences between whole-core inventories were within analytical error. By contrast, whole-core inventories of the LABs decreased by about 50-60% during the same time interval. Based on direct comparison of chemical inventories in coeval core sections, LAB transformation rates are estimated at 0.07 ±. 0.01 yr-1. These results indicate that caution should be exercised when using synthetic LCABs for reconstruction of depositional records.

Temporal Geochemical Variations in Glass and Minerals from Early Oligocene to Miocene Volcanic Sediments, DSDP Site 296, Kyushu Palau Ridge: Is There a Geochemical Signal for Arc Rifting?

NASA Astrophysics Data System (ADS)

Hickey-Vargas, R.; Samajpati, E.

2015-12-01

Volcaniclastic sediments and sedimentary rocks from DSDP Site 296, located within a basin at the crest of the northern Kyushu Palau ridge (KPR), record the latter part of the first stage of Izu Bonin Mariana (IBM) arc evolution, up to the cessation of volcanism caused by arc rifting and opening of the Shikoku basin. The lower section consists of early to late Oligocene coarse volcaniclastic sedimentary rocks, and is overlain by late Oligocene to Pleistocene nannofossil chalks and oozes with volcanic sand and ash-rich layers. We have studied the chemical composition of pyroxene, feldspar and glass grains separated from the coarse volcaniclastic rocks at depths from 435 to 1082 meters below sea floor, and of glass shards in layers in the overlying sediments of late Oligocene to early Miocene age. Overall, pyroxene and feldspar compositions show little systematic variation with depth in the core, although for pyroxene, highest En and highest Al2O3 contents are found in the interval from 600-900 meters bsf. An contents in feldspars show a bimodal distribution throughout the core, with most values > 90 or in the range 60-70, with more abundant intermediate compositions in the 600-900 meter interval. Compositions of glass shards vary widely, from basalt to rhyolite, and from low K, light rare earth (LREE)-depleted to high K, strongly LREE-enriched character, without systematic variation with depth in the core. However, all cores sampled from early Oligocene to early Miocene contain relatively low K basalt and basaltic andesite glass. Like the pyroxenes, a wider range of compositions is found in glass from the 600 to 900 mbsf interval. The Site 296 sequence overlaps in age with the uppermost sedimentary section of recently drilled IODP Site 1438, located 230 km to the southwest in the Amami Sankaku basin, thus the two sites may contain volcanic debris shed from contemporaneous sections of the KPR.

Locations and descriptions of gravity, box, and push cores collected in San Francisco Bay between January and February, 1990 and 1991

USGS Publications Warehouse

Anima, Roberto J.; Clifton, H. Edward; Reiss, Carol; Wong, Florence L.

2005-01-01

A project to study San Francisco Bay sediments collected over 300 sediment gravity cores; six push cores, and three box cores in San Francisco Bay during the years 1990-91. The purpose of the sampling effort is to establish a database on the Holocene sediment history of the bay. The samples described and mapped are the first effort to catalog and present the data collected. Thus far the cores have been utilized in various cooperative studies with state colleges and universities, and other USGS divisions. These cores serve as a base for ongoing multidisciplinary studies. The sediment studies project has initiated subsequent coring efforts within the bay using refined coring techniques to attain deeper cores.

Multivariate analysis and geochemical approach for assessment of metal pollution state in sediment cores.

PubMed

Jamshidi-Zanjani, Ahmad; Saeedi, Mohsen

2017-07-01

Vertical distribution of metals (Cu, Zn, Cr, Fe, Mn, Pb, Ni, Cd, and Li) in four sediment core samples (C 1 , C 2 , C 3 , and C 4 ) from Anzali international wetland located southwest of the Caspian Sea was examined. Background concentration of each metal was calculated according to different statistical approaches. The results of multivariate statistical analysis showed that Fe and Mn might have significant role in the fate of Ni and Zn in sediment core samples. Different sediment quality indexes were utilized to assess metal pollution in sediment cores. Moreover, a new sediment quality index named aggregative toxicity index (ATI) based on sediment quality guidelines (SQGs) was developed to assess the degree of metal toxicity in an aggregative manner. The increasing pattern of metal pollution and their toxicity degree in upper layers of core samples indicated increasing effects of anthropogenic sources in the study area.

Mercury contamination history of an estuarine floodplain reconstructed from a 210Pb-dated sediment core (Berg River, South Africa).

PubMed

Kading, T J; Mason, R P; Leaner, J J

2009-01-01

Mercury deposition histories have been scarcely documented in the southern hemisphere. A sediment core was collected from the ecologically important estuarine floodplain of the Berg River (South Africa). We establish the concentration of Hg in this (210)Pb-dated sediment core at <50 ng g(-1) Hg(T) throughout the core, but with 1.3 ng g(-1) methylmercury in surface sediments. The (210)Pb dating of the core provides a first record of mercury deposition to the site and reveals the onset of enhanced mercury deposition in 1970. The ratio of methylmercury to total mercury is relatively high in these sediments when compared to other wetlands.

Site 765: Sediment Lithostratigraphy

USGS Publications Warehouse

,

1990-01-01

A 935-m-thick succession of Quaternary through Lower Cretaceous sediments was recovered at Site 765 (Fig. 10). A single core of Quaternary sediment was obtained from Hole 765A; drilling terminated and a new hole was drilled in an attempt to establish the mud line. Quaternary through middle Miocene sediments were cored in Hole 765B down to a depth of 395.6 mbsf. Middle Miocene through Lower Cretaceous sediments were cored in Hole 765C, after washing the interval between 0 and 350.2 mbsf. Exact lithologic correlation of the basal cores from Hole 765B with the upper cores from Hole 765C is not possible because of poor recovery; hence, correlation is based solely on matching sub-bottom depths.

Biostratigraphic data for the Cretaceous marine sediments in the USGS-St. George no. 1 core (DOR-211), Dorchester County, South Carolina

USGS Publications Warehouse

Self-Trail, Jean M.; Gohn, Gregory S.

1997-01-01

The USGS-St. George corehole was drilled for the U.S. Geological Survey (USGS) by a commercial drilling company during 1982. The corehole is located within the Coastal Plain Province in northern Dorchester County, South Carolina, about three miles southeast of the town of St. George near the village of Byrd (fig. 1). Coordinates for the corehole are 33o09'25'N latitude and 80o31'18'W longitude; ground elevation at the site is +78 feet (Reid and others, 1986). The St. George corehole is designated as USGS drill hole DOR-211. The St. George corehole was drilled to a total depth of 2,067 ft. The hole was cored continuously with generally good recovery from 300 ft to its total depth. Spot cores were taken at selected intervals between the top of the hole and a depth of 300 ft (50-55 ft, 100-110 ft, 150-165 ft, 200-205 ft, and 250-255 ft); however, recovery was poor in most of these intervals. The St. George core currently is stored at the USGS National Center, Reston, VA (March, 1997). The St. George corehole bottomed in basalt of probable early Mesozoic age beneath an Upper Cretaceous and Cenozoic sedi-mentary section. Reid and others (1986) placed the top of basalt saprolite at 1,962 ft in the hole. Our examination of the geophysical logs and original core descriptions suggests that the top of the saprolite is higher in the hole, at about 1,939 ft. The Cretaceous-Tertiary boundary was placed at or near 550 ft in the core by Reid and others (1986) and by Habib and Miller (1989). In this report, we provide paleontologic data for marine sediments in the upper part of the Upper Cretaceous section in the St. George core. Biostratigraphic and paleoenvironmental data and interpretations based on the study of calcareous nannofossils and ostracodes from the Cretaceous section are discussed.

Inorganic nitrogen transformations in the bed of the Shingobee River, Minnesota: Integrating hydrologic and biological processes using sediment perfusion cores

USGS Publications Warehouse

Sheibley, R.W.; Duff, J.H.; Jackman, A.P.; Triska, F.J.

2003-01-01

Inorganic N transformations were examined in streambed sediments from the Shingobee River using sediment perfusion cores. The experimental design simulated groundwater-stream water mixing within sediment cores, which provided a well-defined one-dimensional representation of in situ hydrologic conditions. Two distinct hydrologic and chemical settings were preserved in the sediment cores: the lowermost sediments, perfused with groundwater, remained anaerobic during the incubations, whereas the uppermost sediments, perfused with oxic water pumped from the overlying water column, simulated stream water penetration into the bed. The maintenance of oxic and anoxic zones formed a biologically active aerobic-anaerobic interface. Ammonium (NH4+) dissolved in groundwater was transported conservatively through the lower core zone but was removed as it mixed with aerated recycle water. Concurrently, a small quantity of nitrate (NO3-) equaling ???25% of the NH4+ loss was produced in the upper sediments. The NH4+ and NO3- profiles in the uppermost sediments resulted from coupled nitrification-denitrification, because assimilation and sorption were negligible. We hypothesize that anaerobic microsites within the aerated upper sediments supported denitrification. Rates of nitrification and denitrification in the perfusion cores ranged 42-209 and 53-160 mg N m-2 day-1, respectively. The use of modified perfusion cores permitted the identification and quantification of N transformations and verified process control by surface water exchange into the shallow hyporheic zone of the Shingobee River.

Wetland paleoecological study of southwest coastal Louisiana: sediment cores and diatom calibration dataset

USGS Publications Warehouse

Smith, Kathryn E. L.; Flocks, James G.; Steyer, Gregory D.; Piazza, Sarai C.

2015-01-01

Wetland sediment data were collected in 2009 and 2010 throughout the southwest Louisiana Chenier Plain as part of a pilot study to develop a diatom-based proxy for past wetland water chemistry and the identification of sediment deposits from tropical storms. The complete dataset includes forty-six surface sediment samples and nine sediment cores. The surface sediment samples were collected in fresh, intermediate, and brackish marsh and are located coincident with Coastwide Reference Monitoring System (CRMS) sites. The nine sediment cores were collected at the Rockefeller Wildlife Refuge (RWR) located in Grand Chenier, La.

Sedimentological characteristics of lake sediment of the Lake Jelonek (North Poland)

NASA Astrophysics Data System (ADS)

Kramkowski, Mateusz; Filbrandt-Czaja, Anna; Ott, Florian; Słowiński, Michał; Tjallingii, Rik; Błaszkiewicz, Mirosław; Brauer, Achim

2016-04-01

Lake Jelonek is located in Northern Poland (53°45'58N, 18°23'30E). The lake is surrounded by forest, covers an area of 19,9 ha and has a maximum depth of 13,8 m. In 2013 and 2014 three overlapping and parallel series of long sediment cores JEL14-A-(1445 cm), JEL14-B-(1430 cm), JEL14-C-(1435 cm) and seven short gravity cores JEL13 (K1-K7) have been recovered from the deepest part of the lake. A continuous composite profile JEL14 covering 1426 cm has been established by correlation based on 28 distinct macroscopic marker layers. The sediment sequence can be divided into 15 (I-XV) lithological units. These units comprise biochemical calcite varves, homogeneous calcite-rich gyttja, homogeneous organic-diatomaceous gyttja, and sandy layers. The chronology established so far is based on 14 AMS 14C dates from terrestrial plant remains and tephrochronology (Askja AD-1875) and covers the interval from the Younger Dryas to present times. Based on the chronology and sedimentological characteristics the composite profile has been correlated to a previous core from which a detailed pollen diagram had been established (Filbrandt-Czaja 2009). Here we present initial results from thin section analyses for two intervals from the new composite record JEL14, (I) the uppermost 0-256 cm and (II) the interval from 768-1296 cm. Intercalated between these two varved interval is a thick section (512 cm) of homogeneous organic-ditomaceous sediments. We present varve micro-facies data in combination with μ-XRF element scanning for comprehensive reconstruction of the sedimentation processes in Lake Jelonek. Preliminary varve counting reveals that the uppermost 256 cm varved sediments comprise ca 925 years (2008-1083 AD), while the lower floating varve interval covers the time period from 1850 - 10500 cal a BP. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis -ICLEA- of the Helmholtz Association; grant number VH-VI-415. References: Filbrandt-Czaja, A. 2009: Studia nad historią szaty roślinnej i krajobrazu Borów Tucholskich. pp. Wydawnictwo Naukowe Uniwersytetu Mikołaja Kopernika.

Sediment and water chemistry of the San Juan River and Escalante River deltas of Lake Powell, Utah, 2010-2011

USGS Publications Warehouse

Hornewer, Nancy J.

2014-01-01

Recent studies have documented the presence of trace elements, organic compounds including polycyclic aromatic hydrocarbons, and radionuclides in sediment from the Colorado River delta and from sediment in some side canyons in Lake Powell, Utah and Arizona. The fate of many of these contaminants is of significant concern to the resource managers of the National Park Service Glen Canyon National Recreation Area because of potential health impacts to humans and aquatic and terrestrial species. In 2010, the U.S. Geological Survey began a sediment-core sampling and analysis program in the San Juan River and Escalante River deltas in Lake Powell, Utah, to help the National Park Service further document the presence or absence of contaminants in deltaic sediment. Three sediment cores were collected from the San Juan River delta in August 2010 and three sediment cores and an additional replicate core were collected from the Escalante River delta in September 2011. Sediment from the cores was subsampled and composited for analysis of major and trace elements. Fifty-five major and trace elements were analyzed in 116 subsamples and 7 composited samples for the San Juan River delta cores, and in 75 subsamples and 9 composited samples for the Escalante River delta cores. Six composited sediment samples from the San Juan River delta cores and eight from the Escalante River delta cores also were analyzed for 55 low-level organochlorine pesticides and polychlorinated biphenyls, 61 polycyclic aromatic hydrocarbon compounds, gross alpha and gross beta radionuclides, and sediment-particle size. Additionally, water samples were collected from the sediment-water interface overlying each of the three cores collected from the San Juan River and Escalante River deltas. Each water sample was analyzed for 57 major and trace elements. Most of the major and trace elements analyzed were detected at concentrations greater than reporting levels for the sediment-core subsamples and composited samples. Low-level organochlorine pesticides and polychlorinated biphenyls were not detected in any of the samples. Only one polycyclic aromatic hydrocarbon compound was detected at a concentration greater than the reporting level for one San Juan composited sample. Gross alpha and gross beta radionuclides were detected at concentrations greater than reporting levels for all samples. Most of the major and trace elements analyzed were detected at concentrations greater than reporting levels for water samples.

Microplastics in Sediment Cores from Asia and Africa as Indicators of Temporal Trends in Plastic Pollution.

PubMed

Matsuguma, Yukari; Takada, Hideshige; Kumata, Hidetoshi; Kanke, Hirohide; Sakurai, Shigeaki; Suzuki, Tokuma; Itoh, Maki; Okazaki, Yohei; Boonyatumanond, Ruchaya; Zakaria, Mohamad Pauzi; Weerts, Steven; Newman, Brent

2017-08-01

Microplastics (<5 mm) were extracted from sediment cores collected in Japan, Thailand, Malaysia, and South Africa by density separation after hydrogen peroxide treatment to remove biofilms were and identified using FTIR. Carbonyl and vinyl indices were used to avoid counting biopolymers as plastics. Microplastics composed of variety of polymers, including polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethyleneterphthalates (PET), polyethylene-polypropylene copolymer (PEP), and polyacrylates (PAK), were identified in the sediment. We measured microplastics between 315 µm and 5 mm, most of which were in the range 315 µm-1 mm. The abundance of microplastics in surface sediment varied from 100 pieces/kg-dry sediment in a core collected in the Gulf of Thailand to 1900 pieces/kg-dry sediment in a core collected in a canal in Tokyo Bay. A far higher stock of PE and PP composed microplastics in sediment compared with surface water samples collected in a canal in Tokyo Bay suggests that sediment is an important sink for microplastics. In dated sediment cores from Japan, microplastic pollution started in 1950s, and their abundance increased markedly toward the surface layer (i.e., 2000s). In all sediment cores from Japan, Thailand, Malaysia, and South Africa, the abundance of microplastics increased toward the surface, suggesting the global occurrence of and an increase in microplastic pollution over time.

Microanalysis (micro-XRF, micro-XANES, and micro-XRD) of a tertiary sediment using microfocused synchrotron radiation.

PubMed

Denecke, Melissa A; Somogyi, Andrea; Janssens, Koen; Simon, Rolf; Dardenne, Kathy; Noseck, Ulrich

2007-06-01

Micro-focused synchrotron radiation techniques to investigate actinide elements in geological samples are becoming an increasingly used tool in nuclear waste disposal research. In this article, results using mu-focus techniques are presented from a bore core section of a U-rich tertiary sediment collected from Ruprechtov, Czech Republic, a natural analog to nuclear waste repository scenarios in deep geological formations. Different methods are applied to obtain various, complementary information. Elemental and element chemical state distributions are obtained from micro-XRF measurements, oxidation states of As determined from micro-XANES, and the crystalline structure of selected regions are studied by means of micro-XRD. We find that preparation of the thin section created an As oxidation state artifact; it apparently changed the As valence in some regions of the sample. Results support our previously proposed hypothesis of the mechanism for U-enrichment in the sediment. AsFeS coating on framboid Fe nodules in the sediment reduced mobile groundwater-dissolved U(VI) to less-soluble U(IV), thereby immobilizing the uranium in the sediment.

Is the core top modern? Observations from the eastern equatorial Pacific

NASA Astrophysics Data System (ADS)

Mekik, Figen; Anderson, Robert

2018-04-01

A compilation of ages from 67 core tops in the eastern equatorial Pacific (EEP) does not display an easily discernible regional pattern. The ages range from 790 to over 15,000 years. The youngest core tops with the highest sediment focusing factors are located in the Panama Basin. There are weak but statistically significant inverse relationships between core top age and age-model based mass accumulation rates, bioturbation depth, linear sedimentation rate and sediment focusing factors. However, we found no statistically significant relationship between core top age and calcite dissolution in sediments or 230Th-normalized mass accumulation rates. We found evidence suggesting that greater amount of sediment focusing helps to preserve the carbonate fraction of the sediment where focusing is taking place. When focusing factors are plotted against percent calcite dissolved, we observe a strong inverse relationship, and core tops younger than 4500 years tend to occur where focusing factors are high and percent calcite dissolved values are low. Using labile organic carbon fluxes to estimate bioturbation depth in the sediments results in the observation that where bioturbation depth is shallow (<4 cm), the core top age has a strong, inverse relationship with sediment accumulation rate. We used the Globorotalia menardii Fragmentation Index (MFI) as an indicator of percent calcite dissolved in deep sea sediments. There is a distinct pattern to core top calcite dissolution in the EEP which delineates bands of high surface ocean productivity as well as the clear increase in dissolution downward on the flanks of the East Pacific Rise.

Paleoclimatic investigations during the late Quaternary using gravity core sediments of Lake Hovsgol in Mongolia

NASA Astrophysics Data System (ADS)

Cheong, Daekyo; Shin, Seungwon; Park, Yong-Hee; Nam, Seung Il

2010-05-01

The Lake Hovsgol is located in northeast Eurasia which is a tectonic lake formed by rifting, and its thick bottom sediments record climatic change of the past. The lake is a suitable site to study a rapid Quaternary climate change. This study includes analysis of smear slides, particle size analysis, data of spectrophotometer and magnetic susceptibility, trace element analysis using XRF core scanner for HS-3, 5 gravity core sediments from the middle southern Lake Hovsgol. HS-3 core sediments were measured for TOC, and HS-5 core was scrutinized for species analysis of ostracods. HS-3 core was obtained at 160 m water depth, and is divided into three sedimentary units. Unit A of HS-3 is characterized by distinct lamination, high sand contents considerably decreasing towards the upper part, and the ostracods are rarely discovered at the upper part of Unit A. Unit B is characterized by weakly lamination, and some ostracods are observed in the lower part, but diatoms are observed in the upper part of Unit B. Also grain size is getting smaller toward the upper part. Unit C consists of fine diatomaceous ooze and contains abundant diatoms. Overall organic contents are high, and lamination with black-colored organic layer is observed in the lower part of Unit C. HS-5 core was obtained at 210 m water depth and is divided into two sedimentary units with faint boundary. Unit A of HS-5 is characterized by lamination and contains abundant diatoms and ostracods. At Unit B, grain size is getting smaller toward the upper part, and occurrence change of ostracods is observed in the upper part. Framboidal pyrite were formed during the diagenesis. Four species of ostracods are observed in the core sediments, i.e. Cytherissa lacustris, Limnocythere inopinate dominate in the lower part, and Candona lepnevae, Leucocythere sp dominates in the upper part. Carbon age dating results show that sediment unit B of HS-5 and unit C of HS-3 containing rare ostracods are similar in age. The reason of low occurrence of ostracods fossils and high content of sand is consistent with that ostracods disappeared as temperature rise or inhabitant change since late LGM. An age of sediment unit B of HS-3 is the Last Deglacial period when organic contents increased obviously and contents of sand decreased as the lake level rose. The change of magnetic susceptibility and Fe/Al, Ca/Al and Si/Al ratio values are observed at 90 cm depth section of HS-3, which indicates that input sediments changed as the lake level fell due to a temporal cooling at Younger Dryas during the Last Deglacial. The age of the sediment unit C of HS-3 is Holocene. At this period, high contents of organic materials were caused by increase of nutrition input because of a thick vegetation cover as temperature rose, and thus diatom blooming. The organic strata containing mica minerals at early Holocene have been formed during fall or stagnation periods of the lake level. We interpreted that those are closely related to the global environmental change.

Facies and Depositional History of Arc-Related, Deep-Marine Volcaniclastic Rocks in Core Recovered on International Ocean Discovery Program Expedition 351, Philippine Sea

NASA Astrophysics Data System (ADS)

Johnson, K. E.; Waldman, R.; Marsaglia, K. M.

2016-12-01

The Izu-Bonin-Mariana (IBM) Arc System, south of Japan, hosts a multitude of active and extinct (remnant) volcanic arcs and associated basins partly filled with volcanic sediment. Core extracted adjacent to the proto-IBM arc (Kyushu-Palau Ridge; KPR), in the Amami-Sankaku Basin (ASB) during International Ocean Discovery Program (IODP) Expedition 351, contains an incredibly well-preserved record of backarc sedimentation resulting from changing tectonic regimes during arc development and decline. Approximately 1000 meters of Eocene to Oligocene volcaniclastic sedimentary rocks were analyzed via shipboard core photos, core descriptions, and thin sections with the intention of understanding the depositional history at this site. A database of stratigraphic columns, 539 section and 147 core summaries, was created to display grain size trends, sedimentary structures, bedding characteristics, and facies changes. Individual depositional events were classified using existing and slightly modified classification schemes for muddy, sandy, and gravel-rich gravity flow deposits, as well as muddy deposits and tuffs. Downhole trends show repeating coarsening-upward intervals that grade from fine-grained turbidites to coarser turbidites and debrites. These trends indicate how the active depositional systems evolved upsection as the arc matured. Following arc initiation, facies deposited were primarily mud-rich; these coarsened-upward into 12 stacked sequences of submarine lobe and channel facies with sediment from one or more volcanic sources. These are interpreted to represent the building of the arc edifice that began 41 Ma. Four distinct periods of coarse lobe accumulation created a thick submarine fan over a period of nearly 13 million years. An abrupt shift to muddy turbidites at 30 Ma represents the onset of rifting of the paleo-IBM arc as backarc spreading in the Shikoku Basin was initiated and volcaniclastic supply to the ASB waned with formation of the KPR remnant arc.

Contaminant trends in reservoir sediment cores as records of influent stream quality

USGS Publications Warehouse

Van Metre, P.C.; Mahler, B.J.

2004-01-01

When reconstructing water-quality histories from lake and reservoir cores, it is sometimes assumed that the chemical signatures in the cores reflect historical water quality in the influent streams. To investigate this assumption, concentrations of metals, PAHs, and organochlorine compounds in sediment cores were compared to those associated with an influent-stream suspended sediment for three reservoirs in Fort Worth, TX, and two reservoirs in Boston, MA, U.S.A., and interpreted in light of land-use and regulation histories. In evaluating relations between suspended sediments and cores, three levels of preservation were indicated: (1) influent concentrations and historical trends are preserved in cores (metals at all sites; some organic contaminants at some sites); (2) some loss occurs during transport and initial deposition but relative historical trends are preserved in cores (some organic contaminants at some sites); and (3) neither stream concentrations nor relative historical trends are preserved (dieldrin and p,p???-DDT). The degree of preservation of influent concentration histories varied between lakes, particularly for PAHs. The results support the use of sediment cores to infer streamwater-quality histories for many contaminants but indicate that reservoir-bottom sediment samples might underestimate concentrations of organic contaminants in some streams.

Identification of water-quality trends using sediment cores from Dillon Reservoir, Summit County, Colorado

USGS Publications Warehouse

Greve, Adrienne I.; Spahr, Norman E.; Van Metre, Peter C.; Wilson, Jennifer T.

2001-01-01

Since the construction of Dillon Reservoir, in Summit County, Colorado, in 1963, its drainage area has been the site of rapid urban development and the continued influence of historical mining. In an effort to assess changes in water quality within the drainage area, sediment cores were collected from Dillon Reservoir in 1997. The sediment cores were analyzed for pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and trace elements. Pesticides, PCBs, and PAHs were used to determine the effects of urban development, and trace elements were used to identify mining contributions. Water-quality and streambed-sediment samples, collected at the mouth of three streams that drain into Dillon Reservoir, were analyzed for trace elements. Of the 14 pesticides and 3 PCBs for which the sediment samples were analyzed, only 2 pesticides were detected. Low amounts of dichloro-diphenyldichloroethylene (DDE) and dichloro-diphenyldichloroethane (DDD), metabolites of dichlorodiphenyltrichloroethane (DDT), were found at core depths of 5 centimeters and below 15 centimeters in a core collected near the dam. The longest core, which was collected near the dam, spanned the entire sedimentation history of the reservoir. Concentrations of total combustion PAH and the ratio of fluoranthene to pyrene in the core sample decreased with core depth and increased over time. This relation is likely due to growth in residential and tourist populations in the region. Comparisons between core samples gathered in each arm of the reservoir showed the highest PAH concentrations were found in the Tenmile Creek arm, the only arm that has an urban area on its shores, the town of Frisco. All PAH concentrations, except the pyrene concentration in one segment in the core near the dam and acenaphthylene concentrations in the tops of three cores taken in the reservoir arms, were below Canadian interim freshwater sediment-quality guidelines. Concentrations of arsenic, cadmium, chromium, copper, lead, and zinc in sediment samples from Dillon Reservoir exceeded the Canadian interim freshwater sediment-quality guidelines. Copper, iron, lithium, nickel, scandium, titanium, and vanadium concentrations in sediment samples decreased over time. Other elements, while no trend was evident, displayed concentration spikes in the down-core profiles, indicating loads entering the reservoir may have been larger than they were in 1997. The highest concentrations of copper, lead, manganese, mercury, and zinc were detected during the late 1970's and early 1980's. Elevated concentrations of trace elements in sediment in Dillon Reservoir likely resulted from historical mining in the drainage area. The downward trend identified for copper, iron, lithium, nickel, scandium, titanium, and vanadium may be due in part to restoration efforts in mining-affected areas and a decrease in active mining in the Dillon Reservoir watershed. Although many trace-element core-sediment concentrations exceeded the Canadian probable effect level for freshwater lakes, under current limnological conditions, the high core-sediment concentrations do not adversely affect water quality in Dillon Reservoir. The trace-element concentrations in the reservoir water column meet the standards established by the Colorado Water Quality Control Commission. Although many trace-element core-sediment concentrations exceeded the Canadian probable effect level for freshwater lakes, under current limnological conditions, the high core-sediment concentrations do not adversely affect water quality in Dillon Reservoir. The trace-element concentrations in the reservoir water column meet the standards established by the Colorado Water Quality Control Commission.

Analysis of Fluvial Bed Sediments Along the Apalachicola River, Florida through Field Reconnaissance Studies

NASA Astrophysics Data System (ADS)

Passeri, D.; Hagen, S. C.; Daranpob, A.; Smar, D. E.

2011-12-01

River competence is an important parameter in understanding sediment transport in fluvial systems. Competence is defined as the measure of a stream's ability to transport a certain maximum grain size of sediment. Studies have shown that bed sediment particle size in rivers and streams tends to vary spatially along the direction of stream flow. Over a river section several reaches long, variability of sediment particle sizes can be seen, often becoming finer downstream. This phenomenon is attributed to mechanisms such as local control of stream gradient, coarse tributary sediment supply or particle breakdown. Average particle size may also be smaller in tributary sections of rivers due to river morphology. The relationship between river mean velocity and particle size that can be transported has also been explored. The Hjulstrom curve classifies this relationship by relating particle size to velocity, dividing the regions of sedimentation, transportation, and erosion. The curve can also be used to find values such as the critical erosion velocity (the velocity required to transport particles of various sizes in suspension) and settling velocity (the velocity at which particles of a given size become too heavy to be transported and fall out of suspension, consequently causing deposition). The purpose of this research is to explore the principles of river competence through field reconnaissance collection and laboratory analysis of fluvial sediment core samples along the Apalachicola River, FL and its distributaries. Sediment core samples were collected in the wetlands and estuarine regions of the Apalachicola River. Sieve and hydrometer analyses were performed to determine the spatial distribution of particle sizes along the river. An existing high resolution hydrodynamic model of the study domain was used to simulate tides and generate river velocities. The Hjulstrom curve and the generated river velocities were used to define whether sediment was being transported, eroded or deposited at the different locations in the river and its distributaries. Parameters such as critical erosion velocity and settling velocity were also calculated to describe sediment transport along the channel. This research provides a better understanding of the fluvial geomorphic system, particularly sediment transport in channels. It also provides excellent validation data for future sediment transport studies in similar fluvial study domains.

Historical trends of perfluoroalkyl substances (PFASs) in dated sediments from semi-enclosed bays of Korea.

PubMed

Shen, Aihua; Lee, Sunggyu; Ra, Kongtae; Suk, Dongwoo; Moon, Hyo-Bang

2018-03-01

Information is scarce on historical trends of perfluoroalkyl substances (PFASs) in the coastal environment. In this study, four sediment cores were collected from semi-enclosed bays of Korea to investigate the pollution history, contamination profiles, and environmental burden of PFASs. The total PFAS concentrations in sediment cores ranged from 6.61 to 821 pg/g dry weight. The highest concentrations of PFASs were found in surface or sub-surface sediments, indicating on-going contamination by PFASs. Historical trends in PFASs showed a clear increase since the 1980s, which was consistent with the global PFAS consumption pattern. Concentrations of PFASs were dependent on the organic carbon content in sediment cores. PFOS and longer-chain PFASs were predominant in all of the sediment cores. In particular, a large proportion of longer-chain PFASs was observed in the upper layers of the sediment cores from industrialized coastal regions. Inventories and fluxes estimated for PFASs were similar to those for PCDD/Fs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sedimentology of cores recovered from the Canada Basin of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Edwards, B. D.; Saint-Ange, F.; Pohlman, J.; Higgins, J.; Mosher, D. C.; Lorenson, T. D.; Hart, P.

2011-12-01

Researchers from the United States and Canada are collaborating to understand the tectonic and sedimentary history of the Arctic Ocean between Canada and Alaska. As part of this on-going study, a joint US-Canadian ice breaker expedition operated in parts of the Canada Basin during August 2010. Occasional interruptions of the seismic data acquisition provided the ship time to collect gravity and piston cores at five sites-of-opportunity throughout the basin. High-resolution multibeam bathymetry and chirp sub-bottom profiler data collected immediately prior to coring reveal the fine-scale morphology of each site. Core photographs, X-ray radiographs, and physical property data support the following descriptions. Two piston cores were collected from the Beaufort Sea continental margin in a region of known bottom simulating reflectors (BSRs). Site 1 (2538 m water depth): This core recovered 5.72 m of gas-charged, gray sticky clay and silty-clay from an approximately 1100 m diameter, 130 m high conical mound overlying the crest of a buried anticline. Gas hydrate recovered in the core catcher combined with cracks and voids, methane and other hydrocarbon gasses, pyrite concretions, chemosynthetic clams, carbonate nodules, and soft carbonate masses indicate the likely upward migration of deep-seated fluids. Site 2 (1157 m water depth): This core, positioned 40 km upslope from the gas hydrate core, recovered 3 m of gray sticky silty clay and clayey silt near the base of an erosional scarp. Some voids and fracturing are apparent but carbonate masses and pyrite concretions are absent. Site 3 (3070 m water depth): This core from the top of a seamount discovered in 2009 in the north-central part of the Canada Basin recovered 4.94 m of sediment. More than 3 m of dark brown to yellowish brown, massive interbedded silty clays with sands and matrix-supported gravels (ice rafted debris [IRD]) occur in abrupt contact with underlying reddish yellow to brownish yellow silty clay and gravelly sandy clay interpreted to be altered hydrothermally. Successions of IRD layers create a thinly- to medium-bedded sequence throughout the lower section. Site 4 (3700 m water depth; central Canada Basin): This core recovered 3.4 m of sediment typified by decimeter-thick sequences of stacked graded beds with erosional basal contacts (Bouma sequences) characteristic of turbidite deposition. Site 5 (2081 m water depth; continental slope west of the Canadian archipelago): This core recovered 4.96 m of sediment of which the upper 2 m is silty clay to clayey silt with dispersed sand and granules. This upper section has an irregular, sharp basal contact with an underlying 16-cm-thick clast-supported massive gravel. The gravel has a scoured basal contact and overlies a monotonous gray clayey silt containing dispersed granules of IRD. Sparse and poorly preserved fauna throughout all the cores make age determination difficult; however, given the paucity of sediment cores in the Arctic Ocean, these samples provide vital geophysical groundtruth and sedimentological information about the basin.

Earthquake Signatures in the Modern Sediment Record of Prince William Sound, Alaska

NASA Astrophysics Data System (ADS)

Marshall, N. R.; Kuehl, S. A.; Dellapenna, T. M.; Miller, E. J.

2016-02-01

Geochemical signatures of earthquake-generated sediment gravity flows are investigated using X-ray fluorescence core scanning on a suite of sediment cores from Prince William Sound, Alaska. This study focused on the development of geochemical proxies for earthquake deposits with an emphasis on interpreting deposits initiated from large subduction earthquakes. A north-south transect of sediment cores from Prince William Sound, between Hinchinbrook Island and the Columbia Glacier, was used to examine a record of earthquakes in this tectonically active region for the past century. The sediments in Prince William Sound are sourced from two geologically distinct regions: the metamorphosed turbidites of coastal Prince William Sound, and the Copper River Basin that contains a significant amount of volcanic rocks. Geochemical studies of sediment cores and end-member sediment samples using X-ray fluorescence and inductively coupled plasma mass spectrometry allowed for the development of geochemical proxies for sediment provenance during the past 100 years. Downcore peaks in Sr/Pb are indicative of Copper River Basin sediments, whereas peaks in K/Ca are indicative of inputs of Prince William Sound sediments. Large subduction earthquakes in northern Prince William Sound initiate gravity flows of Prince William Sound provenance into the deep channel. Particularly robust provenance signatures are seen in the northernmost cores in the core transect, which are closer to the earthquake epicenters and the Columbia Glacier source region. The ages of the deposits, from core-averaged 210Pb sediment accumulation rates, correspond to large earthquakes that occurred in 1912, 1964, and 1983. A similar deposit from 1895 in northern Prince William Sound, prior to historical earthquake records, may have also been initiated from a large earthquake in the 1890's.

X-ray fluorescence results from IODP Expedition 355 sediments in Laxmi Basin, eastern Arabian Sea: Insights into late Miocene and Pleistocene carbonate production and burial and possible variations in monsoon intensit

NASA Astrophysics Data System (ADS)

Bowen, M. G.; Kulhanek, D. K.; Lyle, M. W.; Hahn, A.

2017-12-01

Variations in CaCO3 accumulation on the seafloor depend on a number of factors, including productivity of carbonate-producing organisms in the overlying water column, input of siliciclastic material from nearby continents, and changes in ocean chemistry. These factors are affected by variations in tectonics and climate. Here we use X-ray fluorescence (XRF) core scanning data to develop high-resolution chemical profiles calibrated with discrete samples to examine changes in carbonate production and burial in the eastern Arabian Sea. International Ocean Discovery Program (IODP) Expedition 355 cored two sites in the Indus Fan in Laxmi Basin. We scanned the Pleistocene composite sections from both sites at 2 cm resolution ( 150-300 year sampling resolution) using the Avaatech XRF core scanner at the IODP Gulf Coast Repository. In addition, we scanned a hemipelagic interval dated to the late Miocene ( 8 to 6 Ma) that spans the late Miocene climate transition to drier conditions globally, as documented by an expansion in C4 plants. The 2 cm scanning resolution represents 500 years between samples for the upper Miocene section. We used carbonate measurements on discrete samples to calibrate the XRF data, supplemented by analysis using a quantitative benchtop XRF at the University of Bremen. We find large variability in carbonate content in the Pleistocene and upper Miocene, varying from 15-80 wt%, with higher carbonate content correlating with lighter colored sediment. The aluminosilicate composition varies in part because of carbonate dilution but also because of changes in the source of clays and turbidites through the section. We also explore the use of chemical ratios to better understand the variations through the section. Changes in Ca/Fe (biogenic/terrestrial component) and Rb/Zr (fine/coarse grained) match well with visual observation of sediment composition in the cores. We can combine these with the oxygen isotope-derived age model for the Pleistocene section to examine orbital-scale variations in carbonate production and terrigenous input at the sites. We also explore proxies for precipitation (Ti/Ca) and weathering (Fe/K and Al/K) to elucidate changes in monsoon strength during the Pleistocene, although these results are preliminary.

INNOVATIVE TECHNOLOGY EVALUATION REPORT, SEDIMENT SAMPLING TECHNOLOGY, ART'S MANUFACTURING, SPLIT CORE SAMPLER FOR SUBMERGED SEDIMENTS

EPA Science Inventory

The Split Core Sampler for Submerged Sediments (Split Core Sampler) designed and fabricated by Arts Manufacturing & Supply, Inc., was demonstrated under the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation Program in April and May 1999 at ...

Sediment Core Descriptions: R/V KANA KEOKI 1972 Cruise, Eastern and Western Pacific Ocean,

DTIC Science & Technology

1976-06-01

of ship tracks and coring stations are shown. Corrected satellite navigation-determined coordinates for each coring operation are indicated, and water depth, length of core, and age of oldest sediment in the cores are given.

Identifying water-quality trends in the Trinity River, Texas, USA, 1969-1992, using sediment cores from Lake Livingston

USGS Publications Warehouse

Van Metre, P.C.; Callender, E.

1996-01-01

Chemical analyses were done on cores of bottom sediment from three locations in Lake Livingston, a reservoir on the Trinity River in east Texas to identify trends in water quality in the Trinity River using the chemical record preserved in bottom sediments trapped by the reservoir. Sediment cores spanned the period from 1969, when the reservoir was impounded, to 1992, when the cores were collected. Chemical concentrations in reservoir sediment samples were compared to concentrations for 14 streambed sediment samples from the Trinity River Basin and to reported concentrations for soils in the eastern United States and shale. These comparisons indicate that sediments deposited in Lake Livingston are representative of the environmental setting of Lake Livingston within the Trinity River Basin. Vertical changes in concentrations within sediment cores indicate temporal trends of decreasing concentrations of lead, sodium, barium, and total DDT (DDT plus its metabolites DDD and DDE) in the Trinity River. Possible increasing temporal trends are indicated for chlordane and dieldrin. Each sediment-derived trend is related to trends in water quality in the Trinity River or known changes in environmental factors in its drainage basin or both.

Sediment studies in the Assabet River, central Massachusetts, 2003

USGS Publications Warehouse

Zimmerman, Marc J.; Sorenson, Jason R.

2005-01-01

From its headwaters in Westborough, Massachusetts, to its confluence with the Sudbury River, the 53-kilometer-long Assabet River passes through a series of small towns and mixed land-use areas. Along the way, wastewater-treatment plants release nutrient-rich effluents that contribute to the eutrophic state of this waterway. This condition is most obvious where the river is impounded by a series of dams that have sequestered large amounts of sediment and support rooted and floating macrophytes and epiphytic algae. The water in parts of these impoundments may also have low concentrations of dissolved oxygen, another symptom of eutrophication. All of the impoundments had relatively shallow maximum water depths, which ranged from approximately 2.4 to 3.4 meters, and all had extensive shallow areas. Sediment volumes estimated for the six impoundments ranged from approximately 380 cubic meters in the Aluminum City impoundment to 580,000 cubic meters in the Ben Smith impoundment. The other impoundments had sediment volumes of 120,000 cubic meters (Powdermill), 67,000 cubic meters (Gleasondale), 55,000 cubic meters (Hudson), and 42,000 cubic meters (Allen Street). The principal objective of this study was the determination of sediment volume, extent, and chemistry, in particular, the characterization of toxic inorganic and organic chemicals in the sediments. To determine the bulk-sediment chemical-constituent concentrations, more than one hundred sediment cores were collected in pairs from the six impoundments. One core from each pair was sampled for inorganic constituents and the other for organic constituents. Most of the cores analyzed for inorganics were sectioned to provide information on the vertical distribution of analytes; a subset of the cores analyzed for organics was also sectioned. Approximately 200 samples were analyzed for inorganic constituents and 100 for organics; more than 10 percent were quality-control replicate or blank samples. Maximum bulk-sediment phosphorus concentrations in surface samples from the impoundments increased along a downstream gradient, with the exception of samples from the last impoundment, where the concentrations decreased. In addition, the highest phosphorus concentrations were generally in the surface samples; this finding may prove helpful if surface dredging is selected as a means to control phosphorus release from sediments. There is no known relation, however, between bulk-sediment concentration of phosphorus and the concentrations of phosphorus available to biota. Potentially toxic metals, including arsenic, cadmium, chromium, copper, nickel, lead, and zinc were frequently measured at concentrations that exceeded U.S. Environmental Protection Agency sediment-quality guidelines for the protection of aquatic life and that occasionally exceeded Massachusetts Department of Environmental Protection guidelines governing landfill disposal (reuse). Due to the effects of matrix interference and sample dilution on laboratory analyses, neither pesticides nor volatile organic compounds were detected at any sites. However, samples collected in other studies from nearby streams indicated the possibility that pesticides might have been detected in the impoundments if not for these analytical problems. Although polychlorinated biphenyl concentrations, as individual Aroclors, generally exceeded published U.S. Environmental Protection Agency guideline concentrations for potential effects on aquatic life, the U.S. Environmental Protection Agency guideline concentrations for human contact or the Massachusetts guidelines for landfill reuse were rarely exceeded. Concentrations of polycyclic aromatic hydrocarbons, both individually and total, frequently were greater than guideline concentrations. Concentrations of total extractable petroleum hydrocarbons did not exceed Massachusetts guideline concentrations in any samples. When the sediment analytes from surface samples are considered togethe

Identifying sediment discontinuities and solving dating puzzles using monitoring and palaeolimnological records

NASA Astrophysics Data System (ADS)

Dong, Xuhui; Sayer, Carl D.; Bennion, Helen; Maberly, Stephen C.; Yang, Handong; Battarbee, Richard W.

2016-12-01

Palaeolimnological studies should ideally be based upon continuous, undisturbed sediment sequences with reliable chronologies. However for some lake cores, these conditions are not met and palaeolimnologists are often faced with dating puzzles caused by sediment disturbances in the past. This study chooses Esthwaite Water from England to illustrate how to identify sedimentation discontinuities in lake cores and how chronologies can be established for imperfect cores by correlation of key sediment signatures in parallel core records and with long-term monitoring data (1945-2003). Replicated short cores (ESTH1, ESTH7, and ESTH8) were collected and subjected to loss-on-ignition, radiometric dating (210Pb, 137Cs, and 14C), particle size, trace metal, and fossil diatom analysis. Both a slumping and a hiatus event were detected in ESTH7 based on comparisons made between the cores and the long-term diatom data. Ordination analysis suggested that the slumped material in ESTH7 originated from sediment deposited around 1805-1880 AD. Further, it was inferred that the hiatus resulted in a loss of sediment deposited from 1870 to 1970 AD. Given the existence of three superior 14C dates in ESTH7, ESTH1 and ESTH7 were temporally correlated by multiple palaeolimnological proxies for age-depth model development. High variability in sedimentation rates was evident, but good agreement across the various palaeolimnological proxies indicated coherence in sediment processes within the coring area. Differences in sedimentation rates most likely resulted from the natural morphology of the lake basin. Our study suggests that caution is required in selecting suitable coring sites for palaeolimnological studies of small, relatively deep lakes and that proximity to steep slopes should be avoided wherever possible. Nevertheless, in some cases, comparisons between a range of contemporary and palaeolimnological records can be employed to diagnose sediment disturbances and establish a chronology.

Sedimentological and geochemical characteristic of varved lake sediment of the Lake Jelonek (North Poland)

NASA Astrophysics Data System (ADS)

Kramkowski, M. A.; Filbrandt-Czaja, A.; Ott, F.; Slowinski, M. M.; Tjallingii, R.; Błaszkiewicz, M.; Brauer, A.

2016-12-01

Lake Jelonek is located in Northern Poland. The lake covers an area of 19,9 ha and has a maximum depth of 13,8 m. Three overlapping series of 14,3 m - long sediment records have been cored with an UWITEC 90 mm diameter piston corer from the deepest part of the lake. The cores were split in half, lithologically described, photographed and correlated with each other by 28 marker layers to construct a composite profile covering 1426cm. Here we present detailed varve micro-facies for different sediment intervals and the preliminary chronology based on AMS 14C dating of 10 terrestrial macro remains samples and the Askja AD-1875 tephra. Here we present initial results from thin section analyses for two intervals. First (I) the uppermost 0-256 cm and second (II) the interval from 768-1296 cm. Intercalated between these two varved interval is a thick section (512 cm) of homogeneous organic-ditomaceous sediments. We present varve micro-facies data in combination with µ-XRF element scanning for comprehensive reconstruction of the sedimentation processes in Lake Jelonek. Varve counting reveals that the lower floating varve interval covers the time period from 1850 - 10500 cal a BP, while the uppermost 256 cm varved sediments comprise ca 925 years (2008-1083 AD). The main goal is to synchronize the sediment record from Lake Jelonek with European and Worldly records, to achieve a comprehensive knowledge of landscape forming processes and to distinguish between local, regional and global impacts during the past. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis -ICLEA- of the Helmholtz Association; grant number VH-VI-415, National Science Centre, Poland grant 2015/19/N/ST10/02655 and from the Science and Research Funds for 2015-2016 allocated to a co-financed international project, CONTRACT No. 3500/ICLEA/15/2016/0.

Preliminary results of the first scientific Drilling on Lake Baikal, Buguldeika site, southeastern Siberia

USGS Publications Warehouse

Williams, Douglas F.; Colman, S.; Grachev, M.; Hearn, P.; Horie, Shoji; Kawai, T.; Kuzmin, Mikhail I.; Logachov, N.; Antipin, V.; Bardardinov, A.; Bucharov, A.; Fialkov, V.; Gorigljad, A.; Tomilov, B.; Khakhaev, B.N.; Kochikov, S.; Logachev, N.; Pevzner, L.A.; Karabanov, E.B.; Mats, V.; Baranova, E.; Khlystov, O.; Khrachenko, E.; Shimaraeva, M.; Stolbova, E.; Efremova, S.; Gvozdkov, A.; Kravchinski, A.; Peck, J.; Fileva, T.; Kashik, S.; Khramtsova, T.; Kalashnikova, I.; Rasskazova, T.; Tatarnikova, V.; Yuretich, Richard; Mazilov, V.; Takemura, K.; Bobrov, V.; Gunicheva, T.; Haraguchi, H.; Ito, S.; Kocho, T.; Markova, M.; Pampura, V.; Proidakova, O.; Ishiwatari, R.; Sawatari, H.; Takeuchi, A.; Toyoda, K.; Vorobieva, S.; Ikeda, A.; Marui, A.; Nakamura, T.; Ogura, K.; Ohta, Takeshi; King, J.; Sakai, H.; Yokoyama, T.; Hayashida, A.; Bezrukova, E.; Fowell, S.; Fujii, N.; Letunova, P.; Misharina, V.; Miyoshi, N.; Chernyaeva, G.; Ignatova, I.; Likhoshvai, E.; Granina, L.; Levina, O.; Dolgikh, P.; Lazo, F.; Lutskaia, N.; Orem, W.; Wada, E.; Yamada, K.; Yamada, S.; Callander, E.; Golobokoval, L.; Shanks, W. C. Pat; Dorofeeva, R.; Duchkov, A.

1997-01-01

The Baikal Drilling Project (BDP) is a multinational effort to investigate the paleoclimatic history and tectonic evolution of the Baikal sedimentary basin during the Late Neogene. In March 1993 the Baikal drilling system was successfuly deployed from a barge frozen into position over a topographic high, termed the Buguldeika saddle, in the southern basin of Lake Baikal. The BDP-93 scientific team, made up of Russian, American and Japanese scientists, successfully recovered the first long (>100 m) hydraulic piston cores from two holes in 354 m of water. High quality cores of 98 m (Hole 1) and 102 m (Hole 2), representing sedimentation over the last 500,000 years, were collected in 78 mm diameter plastic liners with an average recovery of 72% and 90%, respectively. Magnetic susceptibility logging reveals an excellent hole-to-hole correlation. In this report the scientific team describes the preliminary analytical results from BDP-93 hole 1 cores. Radiocarbon dating by accelerator mass spectrometry provides an accurate chronology for the upper portion of Hole 1. Detailed lithologic characteristics, rock magnetic properties and inorganic element distributions show a significant change to the depositional environment occuring at 50 m subbottom depth, approximately 250,000 BP. This change may be due to uplift and rotation of the horst block in the Buguldeika saddle. The sedimentary section above 50 m is pelitic with varve-like laminae, whereas the section below 50 m contains a high proportion of sand and gravel horizons often organized into turbidite sequences. Accordingly, high resolution seismic records reveal a change in sonic velocity at this depth. It is inferred that sedimentation prior to 250 ka BP was from the west via the Buguldeika river system. After 250 ka BP the Buguldeika saddle reflects an increase in hemipelagic sediments admixed with fine-grained material from the Selenga River drainage basin, east of Lake Baikal. Variations in the spore-pollen assemblage, diatoms, biogenic silica content, rock magnetic properties, clay mineralogy and organic carbon in the upper 50 m of BDP-93-1 reveal a detailed record of climate change over approximately the last 250,000 years. These variables alternate in a pattern characteristic of glacial/interglacial climatic fluctuations. The present age model suggests that the climate signal recorded in Lake Baikal sediments is similar to Late Quaternary signals recorded in Chinese loess sections and in marine sediments.

Adjustable shear stress erosion and transport flume

DOEpatents

Roberts, Jesse D.; Jepsen, Richard A.

2002-01-01

A method and apparatus for measuring the total erosion rate and downstream transport of suspended and bedload sediments using an adjustable shear stress erosion and transport (ASSET) flume with a variable-depth sediment core sample. Water is forced past a variable-depth sediment core sample in a closed channel, eroding sediments, and introducing suspended and bedload sediments into the flow stream. The core sample is continuously pushed into the flow stream, while keeping the surface level with the bottom of the channel. Eroded bedload sediments are transported downstream and then gravitationally separated from the flow stream into one or more quiescent traps. The captured bedload sediments (particles and aggregates) are weighed and compared to the total mass of sediment eroded, and also to the concentration of sediments suspended in the flow stream.

Mercury profiles in sediment from the marginal high of Arabian Sea: an indicator of increasing anthropogenic Hg input.

PubMed

Chakraborty, Parthasarathi; Vudamala, Krushna; Chennuri, Kartheek; Armoury, Kazip; Linsy, P; Ramteke, Darwin; Sebastian, Tyson; Jayachandran, Saranya; Naik, Chandan; Naik, Richita; Nath, B Nagender

2016-05-01

Total Hg distributions and its speciation were determined in two sediment cores collected from the western continental marginal high of India. Total Hg content in the sediment was found to gradually increase (by approximately two times) towards the surface in both the cores. It was found that Hg was preferentially bound to sulfide under anoxic condition. However, redox-mediated reactions in the upper part of the core influenced the total Hg content in the sediment cores. This study suggests that probable increase in authigenic and allogenic Hg deposition attributed to the increasing Hg concentration in the surface sediment in the study area.

Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod.

PubMed

Schwing, Patrick T; Romero, Isabel C; Larson, Rebekka A; O'Malley, Bryan J; Fridrik, Erika E; Goddard, Ethan A; Brooks, Gregg R; Hastings, David W; Rosenheim, Brad E; Hollander, David J; Grant, Guy; Mulhollan, Jim

2016-08-17

Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, this resolution provides records at the annual to decadal scale, at best. An extrusion method, using a calibrated, threaded-rod is presented here, which allows for millimeter-scale subsampling of aquatic sediment cores of varying diameters. Millimeter scale subsampling allows for sub-annual to monthly analysis of the sedimentary record, an order of magnitude higher than typical sampling schemes. The extruder consists of a 2 m aluminum frame and base, two core tube clamps, a threaded-rod, and a 1 m piston. The sediment core is placed above the piston and clamped to the frame. An acrylic sampling collar is affixed to the upper 5 cm of the core tube and provides a platform from which to extract sub-samples. The piston is rotated around the threaded-rod at calibrated intervals and gently pushes the sediment out the top of the core tube. The sediment is then isolated into the sampling collar and placed into an appropriate sampling vessel (e.g., jar or bag). This method also preserves the unconsolidated samples (i.e., high pore water content) at the surface, providing a consistent sampling volume. This mm scale extrusion method was applied to cores collected in the northern Gulf of Mexico following the Deepwater Horizon submarine oil release. Evidence suggests that it is necessary to sample at the mm scale to fully characterize events that occur on the monthly time-scale for continental slope sediments.

Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod

PubMed Central

Schwing, Patrick T.; Romero, Isabel C.; Larson, Rebekka A.; O'Malley, Bryan J.; Fridrik, Erika E.; Goddard, Ethan A.; Brooks, Gregg R.; Hastings, David W.; Rosenheim, Brad E.; Hollander, David J.; Grant, Guy; Mulhollan, Jim

2016-01-01

Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, this resolution provides records at the annual to decadal scale, at best. An extrusion method, using a calibrated, threaded-rod is presented here, which allows for millimeter-scale subsampling of aquatic sediment cores of varying diameters. Millimeter scale subsampling allows for sub-annual to monthly analysis of the sedimentary record, an order of magnitude higher than typical sampling schemes. The extruder consists of a 2 m aluminum frame and base, two core tube clamps, a threaded-rod, and a 1 m piston. The sediment core is placed above the piston and clamped to the frame. An acrylic sampling collar is affixed to the upper 5 cm of the core tube and provides a platform from which to extract sub-samples. The piston is rotated around the threaded-rod at calibrated intervals and gently pushes the sediment out the top of the core tube. The sediment is then isolated into the sampling collar and placed into an appropriate sampling vessel (e.g., jar or bag). This method also preserves the unconsolidated samples (i.e., high pore water content) at the surface, providing a consistent sampling volume. This mm scale extrusion method was applied to cores collected in the northern Gulf of Mexico following the Deepwater Horizon submarine oil release. Evidence suggests that it is necessary to sample at the mm scale to fully characterize events that occur on the monthly time-scale for continental slope sediments. PMID:27585268

Current status and historical variations of DDT-related contaminants in the sediments of Lake Chaohu in China and their influencing factors.

PubMed

Kang, Lei; He, Qi-Shuang; He, Wei; Kong, Xiang-Zhen; Liu, Wen-Xiu; Wu, Wen-Jing; Li, Yi-Long; Lan, Xin-Yu; Xu, Fu-Liu

2016-12-01

The temporal-spatial distributions of DDT-related contaminants (DDXs), including DDT (dichlorodiphenyltrichloroethane), DDE (dichlorodiphenyldichloroethylene) and DDD (dichlorodiphenyldichloroethane), in the sediments of Lake Chaohu and their influencing factors were studied. p,p-DDE and p,p-DDD were found to be the two dominant components of DDXs in both surface and core sediments. The parent DDT compounds were still detectable in sediment cores after the late 1930s. Historical usage of technical DDT was identified as the primary source of DDXs in sediments, as indicated by DDT/(DDD + DDE) ratios of less than one. The residual levels of DDXs were higher in the surface and core sediments in the western lake area than in other lake areas, which might be due to the combined inflow effects of municipal sewage, industrial wastewater and agricultural runoff. The DDX residues in the sediment cores reached peak values in the late 1970s or early 1980s. There were significant positive relationships between DDX residues in sediment cores with annual DDT production and with fine particulate sizes (<4.5 μm). The relationship between the DDXs and TOC in sediment was complex, as indicated by the significant differences among the surface and core sediments. The algae-derived organic matter significantly influenced the amount of residue, composition and distribution of DDXs in the sediments. The DDD/DDE ratios responded well to the anaerobic conditions in the sediments that were caused by algal blooms after the late 1970s in the western lake area. This suggests that the algae-derived organic matter was an important factor and served as a biomarker of eutrophication and also affected the DDX residues and lifecycle in the lake ecosystem. Copyright © 2016 Elsevier Ltd. All rights reserved.

SedCT: MATLAB™ tools for standardized and quantitative processing of sediment core computed tomography (CT) data collected using a medical CT scanner

NASA Astrophysics Data System (ADS)

Reilly, B. T.; Stoner, J. S.; Wiest, J.

2017-08-01

Computed tomography (CT) of sediment cores allows for high-resolution images, three-dimensional volumes, and down core profiles. These quantitative data are generated through the attenuation of X-rays, which are sensitive to sediment density and atomic number, and are stored in pixels as relative gray scale values or Hounsfield units (HU). We present a suite of MATLAB™ tools specifically designed for routine sediment core analysis as a means to standardize and better quantify the products of CT data collected on medical CT scanners. SedCT uses a graphical interface to process Digital Imaging and Communications in Medicine (DICOM) files, stitch overlapping scanned intervals, and create down core HU profiles in a manner robust to normal coring imperfections. Utilizing a random sampling technique, SedCT reduces data size and allows for quick processing on typical laptop computers. SedCTimage uses a graphical interface to create quality tiff files of CT slices that are scaled to a user-defined HU range, preserving the quantitative nature of CT images and easily allowing for comparison between sediment cores with different HU means and variance. These tools are presented along with examples from lacustrine and marine sediment cores to highlight the robustness and quantitative nature of this method.

Enantiomer fractions of chlordane components in sediment from U.S. Geological Survey sites in lakes and rivers

USGS Publications Warehouse

Ulrich, E.M.; Foreman, W.T.; Van Metre, P.C.; Wilson, J.T.; Rounds, S.A.

2009-01-01

Spatial, temporal, and sediment-type trends in enantiomer signatures were evaluated for cis- and trans-chlordane (CC, TC) in archived core, suspended, and surficial-sediment samples from six lake, reservoir, and river sites across the United States. The enantiomer fractions (EFs) measured in these samples are in good agreement with those reported for sediment, soil, and air samples in previous studies. The chlordane EFs were generally close to the racemic value of 0.5, with CC values ranging from 0.493 to 0.527 (usually >0.5) and TC values from 0.463 to 0.53 (usually <0.5). EF changes with core depth were detected for TC and CC in some cores, with the most non-racemic values near the top of the core. Surficial and suspended sediments generally have EF values similar to the top core layers but are often more non-racemic, indicating that enantioselective degradation is occurring before soils are eroded and deposited into bottom sediments. We hypothesize that rapid losses (desorption or degradation) from suspended sediments of the more bioavailable chlordane fraction during transport and initial deposition could explain the apparent shift to more racemic EF values in surficial and top core sediments. Near racemic CC and TC in the core profiles suggest minimal alteration of chlordane from biotic degradation, unless it is via non-enantioselective processes. EF values for the heptachlor degradate, heptachlor epoxide (HEPX), determined in surficial sediments from one location only were always non-racemic (EF ??? 0.66), were indicative of substantial biotic processing, and followed reported EF trends.

Questa baseline and premining ground-water quality investigation. 8. Lake-sediment geochemical record from 1960 to 2002, Eagle Rock and Fawn Lakes, Taos County, New Mexico

USGS Publications Warehouse

Church, S.E.; Fey, D.L.; Marot, M.E.

2005-01-01

Geochemical studies of lake sediment from Eagle Rock Lake and upper Fawn Lake were conducted to evaluate the effect of mining at the Molycorp Questa porphyry molybdenum deposit located immediately north of the Red River. Two cores were taken, one from each lake near the outlet where the sediment was thinnest, and they were sampled at 1-cm intervals to provide geochemical data at less than 1-year resolution. Samples from the core intervals were digested and analyzed for 34 elements using ICP-AES (inductively coupled plasma-atomic emission spectrometry). The activity of 137Cs has been used to establish the beginning of sedimentation in the two lakes. Correlation of the geochemistry of heavy-mineral suites in the cores from both Fawn and Eagle Rock Lakes has been used to develop a sedimentation model to date the intervals sampled. The core from upper Fawn Lake, located upstream of the deposit, provided an annual sedimentary record of the geochemical baseline for material being transported in the Red River, whereas the core from Eagle Rock Lake, located downstream of the deposit, provided an annual record of the effect of mining at the Questa mine on the sediment in the Red River. Abrupt changes in the concentrations of many lithophile and deposit-related metals occur in the middle of the Eagle Rock Lake core, which we correlate with the major flood-of-record recorded at the Questa gage at Eagle Rock Lake in 1979. Sediment from the Red River collected at low flow in 2002 is a poor match for the geochemical data from the sediment core in Eagle Rock Lake. The change in sediment geochemistry in Eagle Rock Lake in the post-1979 interval is dramatic and requires that a new source of sediment be identified that has substantially different geochemistry from that in the pre-1979 core interval. Loss of mill tailings from pipeline breaks are most likely responsible for some of the spikes in trace-element concentrations in the Eagle Rock Lake core. Enrichment of Al2O3, Cu, and Zn occurred as a result of chemical precipitation of these metals from ground water upstream in the Red River. Comparisons of the geochemistry of the post-1979 sediment core with both mine wastes and with premining sediment from the vicinity of the Questa mine indicate that both are possible sources for this new component of sediment. Existing data have not resolved this enigma.

Rapid sedimentation of iron oxyhydroxides in an active hydrothermal shallow semi-enclosed bay at Satsuma Iwo-Jima Island, Kagoshima, Japan

NASA Astrophysics Data System (ADS)

Kiyokawa, Shoichi; Ueshiba, Takuya

2015-04-01

Hydrothermal activity is common in the fishing port of Nagahama Bay, a small semi-enclosed bay located on the southwest coast of Satsuma Iwo-Jima Island (38 km south of Kyushu Island, Japan). The bay contains red-brown iron oxyhydroxides and thick deposits of sediment. In this work, the high concentration and sedimentation rates of oxyhydroxide in this bay were studied and the sedimentary history was reconstructed. Since dredging work in 1998, a thickness of 1.0-1.5 m of iron oxyhydroxide-rich sediments has accumulated on the floor of the bay. To estimate the volume of iron oxyhydroxide sediments and the amount discharged from hydrothermal vents, sediment traps were operated for several years and 13 sedimentary core samples were collected to reconstruct the 10-year sedimentary history of Nagahama Bay. To confirm the timing of sedimentary events, the core data were compared with meteorological records obtained on the island, and the ages of characteristic key beds were thus identified. The sedimentation rate of iron oxyhydroxide mud was calculated, after correcting for sediment input from other sources. The sediments in the 13 cores from Nagahama Bay consist mainly of iron oxyhydroxide mud, three thick tephra beds, and a topmost thick sandy mud bed. Heavy rainfall events in 2000, 2001, 2002, and 2004-2005 coincide with tephra beds, which were reworked from Iwo-Dake ash deposits to form tephra-rich sediment. Strong typhoon events with gigantic waves transported outer-ocean-floor sediments and supplied quartz, cristobalite, tridymite, and albite sands to Nagahama Bay. These materials were redeposited together with bay sediments as the sandy mud bed. Based on the results from the sediment traps and cores, it is estimated that the iron oxyhydroxide mud accumulated in the bay at the relatively rapid rate of 33.3 cm/year (from traps) and 2.8-4.9 cm/year (from cores). The pore water contents within the sediment trap and core sediments are 73%-82% and 47%-67%, respectively. The estimated production of iron oxyhydroxide for the whole fishing port from trap cores is 142.7-253.3 t/year/5000 m2. From sediment cores, however, the accumulation of iron oxyhydroxide sediments on the sea floor is 39-95 t/year/5000 m2. This finding indicates that the remaining 63%-73% of iron was transported out to sea from Nagahama Bay. Even with a high rate of iron oxyhydroxide production, the sedimentation rate of iron oxyhydroxides in the bay is considerably higher than that observed in modern deep-ocean sediments. This example of rapid and abundant oxyhydroxide sedimentation might provide a modern analog for the formation of iron deposits in the geological record, such as ironstones and banded iron formations.

Trace element fluxes during the last 100 years in sediment near a nuclear power plant

NASA Astrophysics Data System (ADS)

Bojórquez-Sánchez, S.; Marmolejo-Rodríguez, A. J.; Ruiz-Fernández, A. C.; Sánchez-González, A.; Sánchez-Cabeza, J. A.; Bojórquez-Leyva, H.; Pérez-Bernal, L. H.

2017-11-01

The Salada coastal lagoon is located in Veracruz (Mexico) near the Laguna Verde Nuclear Power Plant (LVNPP). Currently, the lagoon receives the cooling waters used in the LVNPP. To evaluate the fluxes and mobilization of trace elements due to human activities in the area, two sediment cores from the coastal flood plains of Salada Lagoon were analysed. Cores were collected using PVC tubes. Sediments cores were analysed every centimetre for dating (210Pb by alpha detector) and trace metal analysis using ICP-Mass Spectrometry. The dating of both sediment cores covers the period from 1900 to 2013, which includes the construction of the LVNPP (1970's). The Normalized Enrichment Factor shows enrichment of Ag, As and Cr in both sediment cores. These enrichments correspond to the extent of mining activity (which reached a maximum in the 1900's) and to the geological setting of the coastal zone. The profiles of the element fluxes in both sediment cores reflected the construction and operation of the LVNPP; however, the elements content did not show evidence of pollution coming from the LVNPP.

Estimating growth rates of uncultivated clades of archaea and bacteria in marine sediments

NASA Astrophysics Data System (ADS)

Lloyd, K. G.

2016-12-01

The vast majority of microbes present in marine sediments have never been cultivated in laboratory conditions. It is therefore difficult to estimate the growth rates of these organisms in situ. Quantitative PCR (qPCR) and 16S rRNA gene libraries from sediments below 10 cm show very little change in abundance of these organisms with depth or with redox conditions. Therefore, we hypothesized that uncultivated clades of bacteria and archaea that are ubiquitous in marine sediments, actually grow in the upper 10 cm of marine sediments. We collected sediment cores from the White Oak River estuary, sectioned them in 1 cm intervals, and examined the changes in abundance of uncultivated microbes with depth using 16S rRNA gene libraries and qPCR. We found that some of the key clades associated with the deep subsurface microbiome, such as Bathyarchaeota and MBG-D, increase in abundance with depth, demonstrating extremely slow growth in these shallow subsurface sediments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simpson, H.J.; Williams, S.C.

We have obtained a large set of cores from the Hudson Estuary covering nearly all of the ambient salinity range. A number of core sections have been analyzed for /sup 137/Cs, /sup 134/Cs, /sup 60/Co and /sup 40/K by direct gamma counting and for /sup 239/,/sup 240/Pu and /sup 238/Pu by alpha-spectrometry. Rapid accumulation, up to 20 cm/year, of sediments containing /sup 239/,/sup 240/Pu, /sup 137/Cs, /sup 134/Cs and /sup 60/Co occurs in New York Harbor. Marginal coves upstream from the harbor also serve as depositional environments. The ratio of sediment /sup 239,240/Pu to /sup 137/Cs is higher than themore » fallout ratio in the seaward end of New York Harbor, despite the presence of a significant component of reactor /sup 137/Cs in the sediments, but lower than the range of ratios observed by others for nearshore environments with low sediment deposition rates. A substantial portion of gamma emitting fission product and activation nuclides released from the Indian Point nuclear facility have accumulated in New York Harbor, more than 60 km downstream from the release area. We have not yet established whether local transuranic releases to the Hudson have occurred.« less

Sediment Relative Paleointensity Record With Slow-sedimentation Rates: Implication For a Chronological Tool In The Slow-sedimentation Sequence

NASA Astrophysics Data System (ADS)

Kanamatsu, T.

2006-12-01

Usefulness of paleointensity records with high-sedimentation rates in stratigraphic correlation have been proved (e.g. Stoner et al., 1998, Laj et al., 2000, Stoner et al., 2000), because the sediment geomagnetic paleointensity data makes possible the fine time correlation between cores on the older sediment than the range of AMS 14C. As father application of the sediment paleointensity for chronological tool, we examined the paleointensity record of much slower sedimentation rate. The paleointensity record of the slower sedimentation sequence is supposed to show the convoluted record by the filtering effect of the post- depositional remanent magnetization, then a unique and different pattern depending on the sedimentation rate (e.g. Guyodo and Channell, 2002). We studied the record of the cores obtained from the West Philippine Sea Basin (Water depth ca. 5000 to 6000 m). The analyses of paleomagnetic direction proved that the cores contain Jaramillo and Olduvai Events. The sedimentation rates of cores estimated from magnetostratigraphy are less than 1cm/kyr (0.6-0.4 cm/kyr). Proxy of paleointensity (NRM20mT/ARM20mT) applied to cores reveals the variations in the records are dominate in c.a. 100 ky cycle. Comparing to other published paleointensity record, it is clear that the record includes ca.100-ky cycle in spite of slower sedimentation rates, although other high frequency records were not identified. It is suggests that geomagnetic events of a few to several kys are recordable in the sediment. The paleointensity in the slow-sedimentation record is still useful for the age control utilizing the lower frequency signal, especially for investigating of less age information sequence such as the deep sea sediment below CCD, but not for fine correlation by high frequency data.

Toxicity of sediment cores collected from the Ashtabula River in northeastern Ohio, USA, to the amphipod Hyalella azteca

USGS Publications Warehouse

Ingersoll, C.G.; Kemble, N.E.; Kunz, J.L.; Brumbaugh, W.G.; MacDonald, D.D.; Smorong, D.

2009-01-01

This study was conducted to support a Natural Resource Damage Assessment and Restoration project associated with the Ashtabula River in Ohio. The objective of the study was to evaluate the chemistry and toxicity of 50 sediment samples obtained from five cores collected from the Ashtabula River (10 samples/core, with each 10-cm-diameter core collected to a total depth of about 150 cm). Effects of chemicals of potential concern (COPCs) measured in the sediment samples were evaluated by measuring whole-sediment chemistry and whole-sediment toxicity in the sediment samples (including polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], organochlorine pesticides, and metals). Effects on the amphipod Hyalella azteca at the end of a 28-day sediment toxicity test were determined by comparing survival or length of amphipods in individual sediment samples in the cores to the range of responses of amphipods exposed to selected reference sediments that were also collected from the cores. Mean survival or length of amphipods was below the lower limit of the reference envelope in 56% of the sediment samples. Concentrations of total PCBs alone in some samples or concentrations of total PAHs alone in other samples were likely high enough to have caused the reduced survival or length of amphipods (i.e., concentrations of PAHs or PCBs exceeded mechanistically based and empirically based sediment quality guidelines). While elevated concentrations of ammonia in pore water may have contributed to the reduced length of amphipods, it is unlikely that the reduced length was caused solely by elevated ammonia (i.e., concentrations of ammonia were not significantly correlated with the concentrations of PCBs or PAHs and concentrations of ammonia were elevated both in the reference sediments and in the test sediments). Results of this study show that PAHs, PCBs, and ammonia are the primary COPCs that are likely causing or substantially contributing to the toxicity to sediment-dwelling organisms. ?? 2009 US Government.

A Composite Depth Scale for Sediments from Crevice Lake, Montana

USGS Publications Warehouse

Rosenbaum, J.G.; Skipp, G.; Honke, J.; Chapman, C.

2010-01-01

As part of a study to derive records of past environmental change from lake sediments in the western United States, a set of cores was collected from Crevice Lake, Montana, in late February and early March 2001. Crevice Lake (latitude 45.000N, longitude 110.578W, elevation 1,713 meters) lies adjacent to the Yellowstone River at the north edge of Yellowstone National Park. The lake is more than 31 meters deep and has a surface area of 7.76 hectares. The combination of small surface area and significant depth promote anoxic bottom-water conditions that preserve annual laminations (varves) in the sediment. Three types of cores were collected through the ice. The uppermost sediments were obtained in freeze cores that preserved the sediment water interface. Two sites were cored with a 5-centimeter diameter corer. Five cores were taken with a 2-meter-long percussion piston corer. The percussion core uses a plastic core liner with an inside diameter of 9 centimeters. Coring was done at two sites. Because of the relatively large diameter of the percussion cores, samples from these cores were used for a variety of analyses including pollen, charcoal, diatoms, stable isotopes, organic and inorganic carbon, elemental analyses, and magnetic properties.

Contaminated Sediment Core Profiling

EPA Science Inventory

Evaluating the environmental risk of sites containing contaminated sediments often poses major challenges due in part to the absence of detailed information available for a given location. Sediment core profiling is often utilized during preliminary environmental investigations ...

Benthic foraminiferal responses to operational drill cutting discharge in the SW Barents Sea - a case study.

NASA Astrophysics Data System (ADS)

Aagaard-Sørensen, Steffen; Junttila, Juho; Dijkstra, Noortje

2016-04-01

Petroleum related exploration activities started in the Barents Sea 1980, reaching 97 exploration wells drilled per January 2013. The biggest operational discharge from drilling operations in the Barents Sea is the release of drill cuttings (crushed seabed and/or bedrock) and water based drilling muds including the commonly used weighing material barite (BaSO4). Barium (Ba), a constituent of barite, does not degrade and can be used to evaluate dispersion and accumulation of drill waste. The environmental impact associated with exploration drilling within the Goliat Field, SW Barents Sea in 2006 was evaluated via a multiproxy investigation of local sediments. The sediments were retrieved in November 2014 at ~350 meters water depth and coring sites were selected at distances of 5, 30, 60, 125 and 250 meters from the drill hole in the eastward downstream direction. The dispersion pattern of drill waste was estimated via measurements of sediment parameters including grain size distribution and water content in addition to heavy metal and total organic carbon contents. The environmental impact was evaluated via micro faunal analysis based on benthic foraminiferal (marine shell bearing protists) fauna composition and concentration changes. Observing the sediment parameters, most notably Ba levels, reveals that dispersion of drill waste was limited to <125 meters from the drill site with drill waste thicknesses decreasing downstream. The abruptness and quantity of drill waste sedimentation initially smothered the foraminiferal fauna at ≤ 30 meters from the drill site, while at a distance of 60 meters, the fauna seemingly survived and bioturbation persisted. Analysis of the live (Nov 2014) foraminiferal fauna reveals a natural species composition at all distances from the drill site within the top sediments (0-5 cm core depth). Furthermore, the fossil foraminiferal fauna composition found within post-impacted top sediment sections, particularly in the cores situated at 30 and 60 meters from the drill site, suggests that reestablishment of the foraminiferal fauna likely commenced shortly after cessation of drilling activity.

Mineralogic Causes of Variations in Magnetic Susceptibility of Late Pleistocene and Holocene Sediment from Great Salt Lake, Utah

USGS Publications Warehouse

Reynolds, Richard L.; Rosenbaum, Joseph G.; Thompson, Robert S.

2008-01-01

We describe here results of magnetic susceptibility (MS) measurements and magnetic mineralogy of sediments sampled in three cores from the south basin of Great Salt Lake. The cores were obtained in 1996 with a Kullenburg-type piston corer at sites in close proximity: core 96-4 at 41 deg 01.00' N, 112 deg 28.00' W and cores 96-5 and 96-6 at 41 deg 00.09' N, 112 deg 23.05' W. Cores 96-5 (2.16 m long) and -6 combine to make a composite 11.31-m sediment record. Sediments in core 96-4 (5.54 m long) correspond to the approximate depth interval of 3.9-9.6 m in the composite core of 96-5 and -6 based on similarities in the MS records as described below. The central goal of the research was to provide a sediment record of paleoenvironmental change in the northeastern Basin and Range Province over the past 40,000 years. Specific targets included a sedimentologic record of lake-level change combined with a pollen record of climatic change.

Vertical profile, source apportionment, and toxicity of PAHs in sediment cores of a wharf near the coal-based steel refining industrial zone in Kaohsiung, Taiwan.

PubMed

Chen, Chih-Feng; Chen, Chiu-Wen; Ju, Yun-Ru; Dong, Cheng-Di

2016-03-01

Three sediment cores were collected from a wharf near a coal-based steel refining industrial zone in Kaohsiung, Taiwan. Analyses for 16 polycyclic aromatic hydrocarbons (PAHs) of the US Environmental Protection Agency priority list in the core sediment samples were conducted using gas chromatography-mass spectrometry. The vertical profiles of PAHs in the core sediments were assessed, possible sources and apportionment were identified, and the toxicity risk of the core sediments was determined. The results from the sediment analyses showed that total concentrations of the 16 PAHs varied from 11774 ± 4244 to 16755 ± 4593 ng/g dry weight (dw). Generally, the vertical profiles of the PAHs in the sediment cores exhibited a decreasing trend from the top to the lower levels of the S1 core and an increasing trend of PAHs from the top to the lower levels of the S2 and S3 cores. Among the core sediment samples, the five- and six-ring PAHs were predominantly in the S1 core, ranging from 42 to 54 %, whereas the composition of the PAHs in the S2 and S3 cores were distributed equally across three groups: two- and three-ring, four-ring, and five- and six-ring PAHs. The results indicated that PAH contamination at the site of the S1 core had a different source. The molecular indices and principal component analyses with multivariate linear regression were used to determine the source contributions, with the results showing that the contributions of coal, oil-related, and vehicle sources were 38.6, 35.9, and 25.5 %, respectively. A PAH toxicity assessment using the mean effect range-median quotient (m-ERM-q, 0.59-0.79), benzo[a]pyrene toxicity equivalent (TEQ(carc), 1466-1954 ng TEQ/g dw), and dioxin toxicity equivalent (TEQ(fish), 3036-4174 pg TEQ/g dw) identified the wharf as the most affected area. The results can be used for regular monitoring, and future pollution prevention and management should target the coal-based industries in this region for pollution reduction.

Methane Hydrate Recovered From A Mud Volcano in Santa Monica Basin, Offshore Southern California

NASA Astrophysics Data System (ADS)

Normark, W. R.; Hein, J. R.; Powell, C. L.; Lorenson, T. D.; Lee, H. J.; Edwards, B. D.

2003-12-01

In July 2003, a short (2.1 m) piston core from the summit of a mud volcano recovered methane hydrate at a water depth of 813 m in Santa Monica Basin. The discovery core penetrated into in the hydrate as evidenced by chunks of ice and violent degassing of the core section between 162 and 212 cm depth. The core consists of shell hash and carbonate clasts (to 7-cm long) in silty mud. The methanogenic carbonates are of two types: massive, recrystallized nodular masses with an outer mm-thick sugary patina and a bivalve coquina with carbonate cement. Living clams including the genus Vesicomya, commonly found at cold-seep sites elsewhere, were recovered from the top of the core. Further sampling attempts using piston, gravity, and box corers, all of which were obtained within 15 m of the discovery core, recovered olive-brown silty mud with variable amounts of whole and fragmented bivalve shells and methanogenic carbonate fragments characteristic of cold-seep environments. Gases collected in cores adjacent to the discovery core contain elevated amounts of methane and trace amounts of heavier hydrocarbon gases, indicating some component from thermogenic sources. Hydrogen sulfide was also detected in these sediment samples. Vertical channels in one core may have served as fluid pathways. The existence of hydrate at such a shallow depth in the sediment was unexpected, however, the presence of Vesicomya and hydrogen sulfide indicate that the mud volcano is a site of active methane venting. The mud volcano, which is about 24 km west-southwest of Redondo Beach, is about 300 m in diameter at the base. No internal structure is resolved on either high resolution deep-tow boomer or single-channel air-gun profiles, most likely as a result of the gas content and sediment deformation. The diapiric structure has ascended through well-bedded sediment on the lower slope of the basin, producing as much as 30 m of bathymetric relief. It is located in an area where strike-slip motion along the San Pedro Basin fault zone to the south is replaced by convergent motion to the north. The source horizon for the gas in the hydrate is unknown but appears to be collecting in beds as shallow as 200 m below the regional seafloor based on the presence of a strong and irregular reflection interval.

Perfluoroalkyl substances and extractable organic fluorine in surface sediments and cores from Lake Ontario.

PubMed

Yeung, Leo W Y; De Silva, Amila O; Loi, Eva I H; Marvin, Chris H; Taniyasu, Sachi; Yamashita, Nobuyoshi; Mabury, Scott A; Muir, Derek C G; Lam, Paul K S

2013-09-01

Fourteen perfluoroalkyl substances (PFASs) including short-chain perfluorocarboxylates (PFCAs, C4-C6) and perfluoroalkane sulfonates (PFSAs, C4 and C6) were measured in surface sediment samples from 26 stations collected in 2008 and sediment core samples from three stations (Niagara, Mississauga, and Rochester basins) collected in 2006 in Lake Ontario. Perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), and perfluoroundecanoate (PFUnDA) were detected in all 26 surface sediment samples, whereas perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonamide (FOSA), perfluorododecanoate (PFDoDA) and perfluorobutanoate (PFBA) were detected in over 70% of the surface sediment samples. PFOS was detected in all of the sediment core samples (range: 0.492-30.1ngg(-1) d.w.) over the period 1952-2005. The C8 to C11 PFCAs, FOSA, and PFBA increased in early 1970s. An overall increasing trend in sediment PFAS concentrations/fluxes from older to more recently deposited sediments was evident in the three sediment cores. The known PFCAs and PFSAs accounted for 2-44% of the anionic fraction of the extractable organic fluorine in surface sediment, suggesting that a large proportion of fluorine in this fraction remained unknown. Sediment core samples collected from Niagara basin showed an increase in unidentified organic fluorine in recent years (1995-2006). These results suggest that the use and manufacture of fluorinated organic compounds other than known PFCAs and PFSAs has diversified and increased. © 2013.

The PASADO core processing strategy — A proposed new protocol for sediment core treatment in multidisciplinary lake drilling projects

NASA Astrophysics Data System (ADS)

Ohlendorf, Christian; Gebhardt, Catalina; Hahn, Annette; Kliem, Pierre; Zolitschka, Bernd

2011-07-01

Using the ICDP (International Continental Scientific Drilling Program) deep lake drilling expedition no. 5022 as an example, we describe core processing and sampling procedures as well as new tools developed for subsampling. A manual core splitter is presented that is (1) mobile, (2) able to cut plastic core liners lengthwise without producing swarf of liner material and (3) consists of off-the-shelf components. In order to improve the sampling of sediment cores, a new device, the core sampling assembly (CSA), was developed that meets the following targets: (1) the partitioning of the sediment into discs of equal thickness is fast and precise, (2) disturbed sediment at the inner surface of the liner is discarded during this sampling process, (3) usage of the available sediment is optimised, (4) subsamples are volumetric and oriented, and (5) identical subsamples are taken. The CSA can be applied to D-shaped split sediment cores of any diameter and consists of a divider and a D-shaped scoop. The sampling plan applied for ICDP expedition 5022 is illustrated and may be used as a guideline for planning the efficient partitioning of sediment amongst different lake research groups involved in multidisciplinary projects. For every subsample, the use of quality flags is suggested (1) to document the sample condition, (2) to give a first sediment classification and (3) to guarantee a precise adjustment of logging and scanning data with data determined on individual samples. Based on this, we propose a protocol that might be applied across lake drilling projects in order to facilitate planning and documentation of sampling campaigns and to ensure a better comparability of results.

Holocene provenance shift of suspended particulate matter in the Amazon River basin

NASA Astrophysics Data System (ADS)

Höppner, Natalie; Lucassen, Friedrich; Chiessi, Cristiano M.; Sawakuchi, André O.; Kasemann, Simone A.

2018-06-01

The strontium (Sr), neodymium (Nd) and lead (Pb) isotope signatures of suspended particulate matter (SPM) in rivers reflect the radiogenic isotope signatures of the rivers' drainage basin. These signatures are not significantly affected by weathering, transport or depositional cycles, but document the sedimentary contributions of the respective sources. We report new Sr, Nd and Pb isotope ratios and element concentrations of modern SPM from the Brazilian Amazon River basin and document the past evolution of the basin by analyzing radiogenic isotopes of a marine sediment core from the slope off French Guiana archiving the last 40 kyr of Amazon River SPM, and the Holocene section of sediment cores raised between the Amazon River mouth and the slope off French Guiana. The composition of modern SPM confirms two main source areas, the Andes and the cratonic Shield. In the marine sediment core notable changes occurred during the second phase of Heinrich Stadial 1 (i.e. increased proportion of Shield rivers SPM) and during the last deglaciation (i.e. increased proportion of Madeira River SPM) together with elsewhere constant source contributions. Furthermore, we report a prominent offset in Sr and Nd isotopic composition between the average core value (εNd: -11.7 ± 0.9 (2SD), 87Sr/86Sr: 0.7229 ± 0.0016 (2SD)) and the average modern Amazon River SPM signal (εNd: -10.5 ± 0.5 (2SD), 87Sr/86Sr: 0.7213 ± 0.0036 (2SD)). We suggest that a permanent change in the Amazon River basin sediment supply during the late Holocene to a more Andean dominated SPM was responsible for the offset.

Accretion rate of extraterrestrial matter: Iridium deposited over the last 70 million years

NASA Technical Reports Server (NTRS)

Kyte, Frank T.

1988-01-01

In order to quantify the accretion rate of extraterrestrial matter during the Cenozoic, Ir concentrations were measured in a continuous series of 450 samples across most of the length of piston core LL44-GPC3. LL44-GPC3 is a 25-meter-long, large-diameter piston core of abyssal clay from the central North Pacific. This core contains a nearly continuous record of sedimentation over the last 70 Ma, as this site migrated from a region near the Equator in the late Cretaceous to its present position north of Hawaii. The first-cut survey across the core is nearing completion, and all of the conclusions of the earlier study, in which was reported the concentrations of Ir, Co, and Sb across 9 meters of this core, remain unchanged. The only strongly enhanced Ir concentrations occur at the Cretaceous-Tertiary (K-T) boundary and outside the K-T boundary Ir correlates well with Co, a terrestrial element which is largely present in hydrogenous ferromanganese oxide precipitates from seawater. Concentrations of both elements appear to be inversely correlated with the sedimentation rate. Although the K-T Ir anomaly is unique in magnitude in this core, there are several small bumps in the Ir profile which may reflect smaller accretionary events. The most promising Ir enhancement was observed in a 30 cm section approximately 1 m below the K-T boundary. Preliminary data suggest deposition of an excess across this interval at a time estimate to be approximate 1 Ma before the K-T impact event, but there is insufficient evidence at present to prove that this reflects enhanced accretion of extraterrestrial matter. A detailed model is being prepared of the chemical record of sedimentation in this core using a combined database of 39 elements in approximately 450 samples across the Cenozoic. Preliminary working model indicates that the only sedimentary sources which contribute significantly to the Ir budget in this core are the hydrogenous precipitates and extraterrestrial particulates.

Vertical Geochemical Variations and Speciation Studies of As, Fe, Mn, Zn, and Cu in the Sediments of the Central Gangetic Basin: Sequential Extraction and Statistical Approach

PubMed Central

Ramanathan, AL.

2018-01-01

A geochemical and speciation study of As, Fe, Mn, Zn, and Cu was performed using sequential extraction and statistical approaches in the core sediments taken at two locations—Rigni Chhapra and Chaube Chhapra—of the central Gangetic basin (India). A gradual increase in the grain size (varying from clay to coarse sands) was observed in both the core profiles up to 30.5 m depth. The concentrations of analyzed elements ranged as follows: 6.9–14.2 mg/kg for As, 13,849–31,088 mg/kg for Fe, 267–711 mg/kg for Mn, 45–164 mg/kg for Cu for Rigni Chhapra while for Chaube Chhapra the range was 7.5–13.2 mg/kg for As, 10,936–37,052 mg/kg for Fe, 267–1052 mg/kg for Mn, 60–198 mg/kg for Zn and 60–108 mg/kg for Cu. Significant amounts (53–95%) of all the fractionated elemental concentrations were bound within the crystal structure of the minerals as a residual fraction. The reducible fraction was the second most dominant fraction for As (7% and 8%), Fe (3%), Mn (20% and 26%), and Cu (7% and 6%) respectively for both the cores. It may be released when aquifers subjected to changing redox conditions. The acid soluble fraction was of most interest because it could quickly mobilize into the water system which formed the third most dominating among all three fractions. Four color code of sediments showed an association with total As concentration and did not show a relation with any fraction of all elements analyzed. The core sediment was observed enriched with As and other elements (Cu, Fe, Mn, and Zn). However, it fell under uncontaminated to moderately contaminate which might exhibit a low risk in prevailing natural conditions. X-ray diffraction analyses indicated the availability of siderite and magnetite minerals in the core sediments in a section of dark grey with micaceous medium sand with organic matter (black). PMID:29360767

An exploratory method to detect tephras from quantitative XRD scans: Examples from Iceland and east Greenland marine sediments

USGS Publications Warehouse

Andrews, John T.; Eberl, D.D.; Kristjansdottir, G.B.

2006-01-01

Tephras, mainly from Iceland, are becoming increasingly important in interpreting leads and lags in the Holocene climate system across NW Europe. Here we demonstrate that Quantitative Phase Analysis of x-ray diffractograms of the 150 um fraction and identify these same peaks in XRD scans - two of these correlate geochemically and chronologically with Hekla 1104 and 3. At a distal site to the WNW of Iceland, on the East Greenland margin (core MD99-2317), the weight% of volcanic glass reaches values of 11% at about the time of the Saksunarvatn tephra. The XRD method identifies the presence of volcanic glass but not its elemental composition; hence it will assist in focusing attention on specific sections of sediment cores for subsequent geochemical fingerprinting of tephras. ?? 2006 SAGE Publications.

Environmental History on a Central Mediterranean Island

NASA Astrophysics Data System (ADS)

Gambin, Belinda; Medail, Frederic; Andrieu-Ponel, Valerie; Djamali, Morteza; Marriner, Nick; Morhange, Christophe; Gambin, Timmy

2013-04-01

Through the PaleoMed project a number of cores have been taken from key locations on the Maltese Islands with the aim of establishing various aspects related to the archipelago's historical environment. A multi-disciplinary team have been investigating a number of bodies of evidence including sediments, charcoal and shells. Through this poster I will present the results from pollen samples extracted from a section of one of the cores. The core, taken from Burmarrad, has a section that has been carbon dated to 7200-3200BP. Preliminary results from this site, one of the largest flood plains on Malta, will provide an indication of the local vegetation during this chronological window. Pollen was extracted from sediment deposits following the classical treatment method (eg Moore et al., 1990). Furthermore, identification was undertaken through the use of pollen atlases of Europe and North Africa (Reille, 1992, 1995, 1998) and Beug (2004) along with IMBE's international pollen reference collection. Pollen percentages were calculated in TILIA and the pollen percentage diagram constructed using TGView software (Grimm 2004, 2005). Current results indicate that prior to 7000BP there was a high percentage of aquatic plants, while tree and shrub counts were low. At 6900BP a large increase in Pistacia pollen is recorded, with moderate increase in Plantago (especially lanceolata), Asphodelus, Dinaflagelates and Mirco Foraminifera. At this time there is also a reduction in Cichorioideae & Charcoal in the section. A similar increase in Pistacia at around this time has also been recorded from another core in Burmarrad (Djamali et al., 2012) and in southern Sicily (Tinner et al., 2009). The date of this increase corresponds to the first recorded settlement on the Maltese Islands (circa 5500BC) as well as the climatic optimum of forest cover in the Mediterranean region (Noti et al., 2009).

Effects of sulfate-reducing bacteria on methylmercury at the sediment-water interface.

PubMed

Zeng, Lingxia; Luo, Guangjun; He, Tianrong; Guo, Yanna; Qian, Xiaoli

2016-08-01

Sediment cores (containing sediment and overlying water) from Baihua Reservoir (SW China) were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria (SRB) on mercury (Hg) methylation at sediment-water interfaces. Concentrations of dissolved methyl mercury (DMeHg) in the overlying water of the control cores with bioactivity maintained (BAC) and cores with only sulfate-reducing bacteria inhibited (SRBI) and bacteria fully inhibited (BACI) were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMeHg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations (r=-0.5311 and r=-0.4977 for BAC and SRBI, respectively). The water DMeHg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment-water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster (hgcAB), besides SRB, causing Hg methylation in the sediment-water system. Copyright © 2016. Published by Elsevier B.V.

Offshore sediments record the history of onshore iron ore mining in Goa State, India.

PubMed

Sebastian, Tyson; Nath, B Nagender; Naik, Sangeeta; Borole, D V; Pierre, Salou; Yazing, Armoury Kazip

2017-01-30

Environmental magnetic and geochemical analyses combined with 210 Pb dating were carried out on a sediment core off Goa from Arabian Sea to reconstruct the sedimentation history of last three and a half centuries and to investigate the impact of onshore iron ore mining on the offshore sedimentation. A drastic increase in sedimentation rate and mineral magnetic concentration parameters divides the core into two units (1 & 2) at a depth of 41cm (1982CE). The high magnetic susceptibility values in Unit 1 sediments are coeval with increased iron ore production on land and illustrate the role of terrestrial mining on the increased offshore sedimentation. The early diagenetic signals were observed in Unit 2 of the core with low concentration parameters, coarse magnetic grain size and magnetically hard mineralogy. The geochemical data of the core also record the Little Ice Age (LIA) climatic events of Dalton and Maunder solar minima. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigation of mechanical properties of hydrate-bearing pressure core sediments recovered from the Eastern Nankai Trough using transparent acrylic cell triaxial testing system (TACTT-system)

NASA Astrophysics Data System (ADS)

Yoneda, J.; Masui, A.; Konno, Y.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Tenma, N.; Nagao, J.

2014-12-01

Natural gas hydrate-bearing pressure core sediments have been sheared in compression using a newly developed Transparent Acrylic Cell Triaxial Testing (TACTT) system to investigate the geophysical and geomechanical behavior of sediments recovered from the deep seabed in the Eastern Nankai Trough, the first Japanese offshore production test region. The sediments were recovered by hybrid pressure core system (hybrid PCS) and pressure cores were cut by pressure core analysis tools (PCATs) on board. These pressure cores were transferred to the AIST Hokkaido centre and trimmed by pressure core non-destructive analysis tools (PNATs) for TACTT system which maintained the pressure and temperature conditions within the hydrate stability boundary, through the entire process of core handling from drilling to the end of laboratory testing. An image processing technique was used to capture the motion of sediment in a transparent acrylic cell, and digital photographs were obtained at every 0.1% of vertical strain during the test. Analysis of the optical images showed that sediments with 63% hydrate saturation exhibited brittle failure, although nonhydrate-bearing sediments exhibited ductile failure. In addition, the increase in shear strength with hydrate saturation increase of natural gas hydrate is in agreement with previous data from synthetic gas hydrate. This research was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) that carries out Japan's Methane Hydrate R&D Program by the Ministry of Economy, Trade and Industry (METI).

Investigation of Sediment Pathways and Concealed Sedimentological Features in Hidden River Cave, Kentucky

NASA Astrophysics Data System (ADS)

Feist, S.; Maclachlan, J. C.; Reinhardt, E. G.; McNeill-Jewer, C.; Eyles, C.

2016-12-01

Hidden River Cave is part of a cave system hydrogeologically related to Mammoth Cave in Kentucky and is a multi-level active cave system with 25km of mapped passages. Upper levels experience flow during flood events and lower levels have continuously flowing water. Improper industrial and domestic waste disposal and poor understanding of local hydrogeology lead to contamination of Hidden River Cave in the early 1940s. Previously used for hydroelectric power generation and as a source of potable water the cave was closed to the public for almost 50 years. A new sewage treatment plant and remediation efforts since 1989 have improved the cave system's health. This project focuses on sedimentological studies in the Hidden River Cave system. Water and sediment transport in the cave are being investigated using sediment cores, surface sediment samples and water level data. An Itrax core scanner is used to analyze sediment cores for elemental concentrations, magnetic susceptibility, radiography, and high resolution photography. Horizons of metal concentrations in the core allow correlation of sedimentation events in the cave system. Thecamoebian (testate amoebae) microfossils identified in surface samples allow for further constraint of sediment sources, sedimentation rates, and paleoclimatic analysis. Dive recorders monitor water levels, providing data to further understand the movement of sediment through the cave system. A general time constraint on the sediment's age is based on the presence of microplastic in the surface samples and sediment cores, and data from radiocarbon and lead-210 dating. The integration of various sedimentological data allows for better understanding of sedimentation processes and their record of paleoenvironmental change in the cave system. Sediment studies and methodologies from this project can be applied to other karst systems, and have important applications for communities living on karst landscapes and their water management policies.

Trace Metals and Lead Isotopes in modern Sediments Near Rio de Janeiro, Brazil

NASA Astrophysics Data System (ADS)

Boyle, E. A.; Lazzari, L.; Wagener, A. L.; Carreira, R.; Godoy, J. M.; Noble, A.; Carrasco, G. G.; Moos, S. B.

2014-12-01

This work focuses on the export of trace metals and combustion residues from land to ocean and on the Southeast continental margin of Brazil and its historical variability using stable lead isotopes. Two sediment cores were collected, one in highly impacted Guanabara Bay and the other on the Southeast continental shelf. Continental shelf samples were analyzed for trace element concentrations [Mn (117±50 ppm), Ni (6.5±2.3 ppm), Zn (5.0±1.5), (233±46 ppm), ], Pb (5.4±2.4 ppm), as well as Cu, Ag, Cd, Sr, Ba, Tl, U and Pb isotope ratios & Pb-210. Most of the elements show higher concentrations on the upper part of the core compared to the bottom. Downcore changes of the concentrations of these elements were similar. The sediments of adjacent rivers and bays around the upper section of the southeast continental shelf of Brazil are considered highly enriched with Pb, Zn, Cu and Cr such as Guanabara Bay, Sepetiba Bay and Paraíba do Sul River compared with the natural concentrations and other regions in the world. A [Pb] maximum is seen between samples from 24 to 43 cm (~8 ppm). Utilization of tetraethyl lead (TEL) gasoline in Brazil was phased out beginning in 1983 and was largely completed by 1988. Continental shelf Pb-206/Pb-207 varies between 1.174 near the core top to 1.190 at 100 cm, with a sharp difference between samples at 6 and 8 cm. Higher core top Pb, Zn, and Ni corroborate the recent anthropogenic influence on the southeast continental shelf of Brazil. For Guanabara Bay sediment samples [Pb] varies between 90 ppm near the top to 1 ppm at the bottom. Pb-206/Pb-207 varies between 1.161 near the core top to 1.165 near the bottom. Using triple isotope plots we can discern different sources of lead to the region and how these vary with time.

Distribution and transport of total mercury and methylmercury in mercury-contaminated sediments in reservoirs and wetlands of the Sudbury River, east-central Massachusetts

USGS Publications Warehouse

Colman, John A.; Waldron, Marcus C.; Breault, Robert F.; Lent, Robert M.

1999-01-01

Total mercury and methylmercury were measured in 4 reservoir cores and 12 wetland cores from Sudbury River. The distribution of total mercury and methylmercury in these cores was evaluated to determine the potential for total mercury and methylmercury transport from reservoir and wetlands sediments to the water column. Concentrations of methylmercury were corrected for an analytical artifact introduced during the separation distillation used in the analysis procedure. Corrected methylmercury concentrations correlated with total mercury concentrations in bulk sediment from below the top layers of reservoir and wetland cores; methylmercury concentrations at the top layers of cores were relatively high, however, and were not correlated with total mercury concentrations. Concentrations of methylmercury in pore water were positively correlated with methylmercury concentrations in the bulk sediment. High concentrations of total mercury and methylmercury in sediment (73 and 0.047 micrograms per gram dry-weight basis, respectively) contributed less to the water column in the reservoir than in the wetlands probably because of burial by low concentration sediment and differences in the processes available to transport mercury from the sediments to the water in the reservoirs, as compared to the wetlands .

Historical ecology of the northern Adriatic Sea: Field methods and coring device

NASA Astrophysics Data System (ADS)

Haselmair, Alexandra; Gallmetzer, Ivo; Tomasovych, Adam; Stachowitsch, Michael; Zuschin, Martin

2014-05-01

For an ongoing study on the historical ecology of the northern Adriatic Sea, the objective was to retrieve a high number of sediment cores at seven sampling stations spread across the entire basin. One set of cores is intended for sediment analyses including radiometric Pb-sediment-dating, grain size, TOC, TAC and heavy metal analyses. The other set of cores delivered enough shelly remains of endo- or epibenthic hard part producers (e.g. molluscs, crustaceans, echinoderms) to enable the reconstruction of death assemblages in core layers from top to bottom. The down-core changes of such assemblages record ecological shifts in a marine environment that has endured strong human impacts over several centuries. A 1.5 m-long core could, according to the available sedimentation data for the area, cover up to 2000 or even more years of ecological history. The coring method had to meet the following requirements: a) deliver 1.5-m-long cores from different sediment settings (mud to sand, reflecting a wide range of benthic habitats in the northern Adriatic); b) enable quick and easy deployment to ensure that multiple cores can be taken at the individual sampling stations within a short time; c) be relatively affordable and allow handling by the researchers themselves, potentially using a small vessel in order to further contain the operating costs. Two types of UWITEC™ piston corers were used to meet these requirements. A model with 90 mm of diameter (samples for sediment analysis) and another one with 160 mm, specifically designed to obtain the large amount of material needed for shell analysis, successfully delivered a total of 54 cores. The device consists of a stabilizing tripod and the interchangeable coring cylinders. It is equipped with a so-called hammer action that makes it possible, at least for the smaller cylinder, to penetrate even harder sediments. A closing mechanism of the corer retains the sediment in the cylinder upon extraction; it works either automatically through hydraulic pressure once the final core-length is reached, or can be triggered manually anytime from the surface using a connected hose and water pump. The whole coring device weighs less than 300 kg and can readily be transported in a van. It can easily be assembled, disassembled and operated by two to three persons after a brief training. With a newly designed, very simple and effective slicing device, the cores can be sliced in an upright position directly on board after extraction. This type of corer can be highly recommended for any smaller coring operations on lakes, streams, or at sea.

River-plume sedimentation and 210Pb/7Be seabed delivery on the Mississippi River delta front

NASA Astrophysics Data System (ADS)

Keller, Gregory; Bentley, Samuel J.; Georgiou, Ioannis Y.; Maloney, Jillian; Miner, Michael D.; Xu, Kehui

2017-06-01

To constrain the timing and processes of sediment delivery and submarine mass-wasting events spanning the last few decades on the Mississippi River delta front, multi-cores and gravity cores (0.5 and <3 m length respectively) were collected seaward of the Mississippi River Southwest Pass in 25-75 m water depth in 2014. The cores were analyzed for radionuclide activity (7Be, 210Pb, 137Cs), grain size, bulk density, and fabric (X-radiography). Core sediments are faintly bedded, sparsely bioturbated, and composed mostly of clay and fine silt. Short-term sedimentation rates (from 7Be) are 0.25-1.5 mm/day during river flooding, while longer-term accumulation rates (from 210Pb) are 1.3-7.9 cm/year. In most cores, 210Pb activity displays undulatory profiles with overall declining activity versus depth. Undulations are not associated with grain size variations, and are interpreted to represent variations in oceanic 210Pb scavenging by river-plume sediments. The 210Pb profile of one gravity core from a mudflow gully displays uniform basal excess activity over a zone of low and uniform bulk density, interpreted to be a mass-failure event that occurred 9-18 years before core collection. Spatial trends in sediment deposition (from 7Be) and accumulation (from 210Pb) indicate that proximity to the river mouth has stronger influence than local facies (mudflow gully, depositional lobe, prodelta) over the timeframe and seabed depth represented by the cores (<40 years, <3 m length). This may be explained by rapid proximal sediment deposition from river plumes coupled with infrequent tropical cyclone activity near the delta in the last 7 years (2006-2013), and by the location of most sediment failure surfaces (from mass flows indicated by parallel geophysical studies) deeper than the core-sampling depths of the present study.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simpson, H.J.; Trier, R.M.

We have obtained a large set of sediment cores from the Hudson estuary through much of the ambient salinity range. A number of core sections and samples of suspended particles have been analyzed for /sup 137/Cs, /sup 134/Cs and /sup 60/Co by direct gamma counting, and /sup 239/Pu, /sup 240/Pu, and /sup 238/Pu by alpha spectrometry. The distribution of both /sup 137/Cs and /sup 239/Pu, /sup 240/Pu indicates rapid accumulation in marginal cover areas, and especially in the harbor region adjacent to New York City. The distributions of both /sup 137/Cs and /sup 239/Pu, /sup 240/Pu are similar in surfacemore » sediments and with depth in cores, but there are deviations from the fallout ratio due to addition of reactor /sup 137/Cs and loss of /sup 137/Cs from the particle phases at higher salinities. Measureable amounts of reactor-derived /sup 134/Cs and /sup 60/Co are found in nearly all sediment samples containing appreciable /sup 137/Cs, between 15 km upstream of Indian Point and the downstream extent of our sampling, 70 km south of the reactor. Accumulations of /sup 239/Pu, /sup 240/Pu in New York harbor sediments are more than an order of magnitude greater than the fallout delivery rate. The most likely explanation is accumulation of fine particles in the harbor which have been transported from upstream areas of the Hudson. Our evidence so far indicates that Indian Point is probably not a significant source of /sup 239/Pu, /sup 240/Pu or /sup 238/Pu compared with the fallout burden of these nuclides already in the sediments.« less

A high-resolution paleosecular variation record from Black Sea sediments indicating fast directional changes associated with low field intensities during marine isotope stage (MIS) 4

NASA Astrophysics Data System (ADS)

Nowaczyk, Norbert R.; Jiabo, Liu; Frank, Ute; Arz, Helge W.

2018-02-01

A total of nine sediment cores recovered from the Archangelsky Ridge in the SE Black Sea were systematically subjected to intense paleo- and mineral magnetic analyses. Besides 16 accelerator mass spectrometry (AMS) 14C ages available for another core from this area, dating was accomplished by correlation of short-term warming events during the last glacial monitored by high-resolution X-ray fluorescence (XRF) scanning as maxima in both Ca/Ti and K/Ti ratios in Black Sea sediments to the so-called 'Dansgaard-Oeschger events' recognized from Greenland ice cores. Thus, several hiatuses could be identified in the various cores during the last glacial/interglacial cycle. Finally, core sections documenting marine isotope stage (MIS) 4 at high resolution back to 69 ka were selected for detailed analyses. At 64.5 ka, according to obtained results from Black Sea sediments, the second deepest minimum in relative paleointensity during the past 69 ka occurred, with the Laschamp geomagnetic excursion at 41 ka being associated with the lowest field intensities. The field minimum during MIS 4 is associated with large declination swings beginning about 3 ka before the minimum. While a swing to 50°E is associated with steep inclinations (50-60°) according to the coring site at 42°N, the subsequent declination swing to 30°W is associated with shallow inclinations of down to 40°. Nevertheless, these large deviations from the direction of a geocentric axial dipole field (I = 61 °, D = 0 °) still can not yet be termed as 'excursional', since latitudes of corresponding virtual geomagnetic poles (VGP) only reach down to 51.5°N (120°E) and 61.5°N (75°W), respectively. However, these VGP positions at opposite sides of the globe are linked with VGP drift rates of up to 0.2° per year in between. These extreme secular variations might be the mid-latitude expression of a geomagnetic excursion with partly reversed inclinations found at several sites much further North in Arctic marine sediments between 69°N and 81°N. Thus, the pronounced intensity minimum at 64.5 ka and described directional variations might be the effect of a weak geomagnetic field with a multi-polar geometry in the middle of MIS 4.

Geochemical data for core and bottom-sediment samples collected in 2007 from Grand Lake O' the Cherokees, northeast Oklahoma

USGS Publications Warehouse

Fey, David L.; Becker, Mark F.; Smith, Kathleen S.

2010-01-01

Grand Lake O' the Cherokees is a large reservoir in northeast Oklahoma, below the confluence of the Neosho and Spring Rivers, both of which drain the Tri-State Mining District to the north. The Tri-State district covers an area of 1,200 mi2 (3,100 km2) and comprises Mississippi Valley-type lead-zinc deposits. A result of 120 years of mining activity is an estimated 75 million tons of processed mine tailings (chat) remaining in the district. Concerns of sediment quality and the possibility of human exposure to cadmium and lead through eating fish have led to several studies of the sediments in the Tri-State district. In order to record the transport and deposition of metals from the Tri-State district by the Spring and Neosho Rivers into Grand Lake O' the Cherokees, the U.S. Geological Survey collected 11 sediment cores and 15 bottom-sediment samples in September 2007. Subsamples from five selected cores and the bottom-sediment samples were analyzed for major and trace elements and forms of carbon. The sediment samples collected from the sediment-water interface had larger average concentrations of zinc, cadmium, and lead than local background. The core collected from the Spring River had the largest concentrations of mining-related elements. A core collected just south of Twin Bridges State Park, at the confluence of the Spring and Neosho Rivers, showed a mixing zone with more mining-related elements coming from the Spring River side. The element zinc showed the most definitive patterns in graphs depicting concentration-versus-depth profiles. A core collected from the main body of the reservoir showed affected sediment down to a depth of 85 cm (33 in). This core and two others appear to have penetrated to below mining-affected sediment.

Late-Holocene Environmental Reconstruction and Depositional History from a Taxodium Swamp near Lake Pontchartrain in Southern Louisiana

NASA Astrophysics Data System (ADS)

Ryu, J.; Bianchette, T. A.; Liu, K. B.; Yao, Q.; Maiti, K.

2017-12-01

The hydrological and environmental history of estuarine wetlands in Louisiana is not well-documented. To better understand the depositional processes in coastal wetlands, this study aims to reconstruct the environmental changes and document the occurrence of event deposits found in a bald cypress (Taxodium distichum) swamp approximately 800 m west of Lake Pontchartrain, a site susceptible to wind-generated storm surges as well as inundation from other fluvial and lacustrine processes. 210Pb analysis of a 59 cm sediment core (WMA-1) suggests that it has a sedimentation rate of 0.39 cm/year, consistent with the detection of a 137Cs peak at 17 cm from the core top. Results of sedimentological, geochemical, and palynological analyses reveal that the core contains two distinct sediment facies: an organic-rich dark brown peat unit from 0 to 29 cm containing low concentrations of terrestrial elements (e.g., Ti, Fe, and K), and a clay unit from 30 to 59 cm with elevated concentrations of most elements. Two thin clay layers, at 3-5 cm and 14-19 cm, embedded in the upper peat section are probably attributed to two recent storm events, Hurricane Isaac (2012) and Hurricane Gustav (2008), because both hurricanes caused heavy rain and significant storm-surge flooding at the study site. The pollen assemblage in the clay section is dominated by TCT (mainly Taxodium), but it is replaced by Salix and wetland herbaceous taxa in the overlying peat section. The multi-proxy data suggest that a cypress swamp has been present at the site for at least several hundred years but Taxodium was being replaced by willow (Salix) and other bottomland hardwood trees and wetland herbs as the water level dropped. Human activities may have been an important factor causing the hydrological and ecological changes at the site during the past century.

ELSA flood stack for MIS 2-3 from dry maar lakestructure Auel (Eifel/Germany)

NASA Astrophysics Data System (ADS)

Brunck, Heiko; Sirocko, Frank

2015-04-01

Lacustrine sediments are very sensitive to natural and anthropogenically enviromental changes. Thus, lake sediments are excellent climate archives and can be used for reconstructions of past precipitation and flood events. However, until now, there is no continous flood record for the entire last 60 000 years for Central Europe. The present study reconstructs paleo floods from event layers in the sediment, of dry maar lakestructure Auel (Eifel). This silted up basin has an inflow by a local stream. Accordingly the sedimentation rate is directly linked to runoff activity. The bioturbation was low so that event layers become visible, but varves are not preserved. The maar site is near to the town of Gerolstein in the Eifel; the core AU2 was drilled in the ELSA (Eifel Laminated Sediment archive) project and is 123m long. AU2 has the highest sedimentation rate of all ELSA cores, due to abundant fluvial input. The Eifel area is well suited to approximate Central European weather, because modern water level gauge data from Eifel rivers correlate with respective data from the Rhine (Wernli and Pfahl, 2009). Due to the high inflow into the maar, Auel has the highest number of botanical macro remains of all ELSA cores. These specific conditions explain why only in AU2 all 21 Greenland interstadials can be observed in the abundance of wood remains and the organic carbon concentration. In a final stratigraphic step the time series of Corg was tuned to the Greenland ice core chronology to link the central European landscape evolution directly to the Greenland climate curve (Svensson et al., 2008). Combined sedimentological, paleobotanical and geochemical data received from AU2 builds the foundation of the 14C based chronology. The synchronisation of the record with other cores is controlled by tephra time markers and pollen. Both are used to align the main cores of the ELSA project and construct an integrated age model for the last 220 000 years [b2k] (Förster and Sirocko, 2014). To study the past flood events in detail, 10 cm long thin sections were analyzed to distinguish flood layers from distal turbidites. Turbidites have a continuous grain size gradation; the grains size profile of flood events is in contrast characterized by several grain size maxima over the entire layer thickness. A flood event over several days shows numerous peaks of intense discharge, which lead to a discontinuous grain size gradient. The thickness of each flood layer was measured for the classification of the event intensity. As a consequence, 88 flood layers over 7.5 mm thickness were detected. Our time-series represents the first highly-resolved chronology for flood events from 60 000 years until present times and indicates variable periodicities of flood activity linked to predominant climatic development. The fore main sections of all flood layers are: 44 000 - 45 500, 30 000 - 37 000, 20 000 - 22 500 and 11 000 - 17 000 years [b2k].

High resolution analysis of northern Patagonia lake sediments

NASA Astrophysics Data System (ADS)

Jarvis, S. W.; Croudace, I. W.; Langdon, P. G.; Rindby, A.

2009-04-01

Sediment cores covering the period from the last glacial maximum through the Holocene to the present have been collected from sites in the Chacubuco valley, southern Chile (around 47°08'S, 72°25'W, to the east of the North Patagonian Icecap). Cores were taken from five lakes and one recently dried lake bed. Short cores (0.2 to 0.5m), covering approximately the last two hundred years, were taken from all the lakes. Additionally, long sequences were obtained from one of the lakes and from the dried lake bed, the latter sequence extending back to the last glacial maximum as indicated by thick clay at the base. Each of the lakes are small-medium sized and are open systems situated at 300-1000m above sea level. The shorter cores comprise predominantly clastic gyttja but show a number of distinct changes in colour and chemical composition that suggest major environmental changes over the period of sediment accumulation. This is also reflected in variations in the loss on ignition of samples from the cores and in elemental profiles produced by scanning the cores with the Itrax micro-XRF corescanner at 200μm resolution. The long sequence from the dried lake bed has very low organic content glacial clay at the base, interpreted as last glacial maximum basal clay following determination in the field that this layer exceeded 2m in thickness. Similar sediments occur within a stratigraphically discrete section of approximately 14cm and may relate to a stadial event. The latter section also shows a drop in organic content and appears to be glacial clay incorporating some coarse sandy components indicative of detrital input from the catchment. The second long sequence, from a carbonate lake, includes two mineral layers indicating increased detrital input from the catchment. The deeper and thicker of these layers appears similar to the 14cm layer in the first long sequence, while the upper layer comprises a fine grain size indicative of rock flour and hence also of glacial activity in the catchment. Variation of elemental composition of these ‘glacial' layers is also clear from the Itrax data. It therefore appears that there have been significant reglaciation events in the catchment since the last glacial maximum. Many cores contain tephra layers, identified both visually and from the Itrax scans. Some of these have been confirmed as volcanic ash from the 1991 eruption of Mt Hudson, which at 45°54'S, 72°58'W is the southern-most volcano in the Chilean Andes and only 140km from the study area. Further work is underway to confirm and identify the source and age of other suspected tephra layers. Sediment accumulation rates in the upper parts of the cores are of the order of 1mm/yr (as determined by lead-210, caesium-137 dating and the 1991 Hudson tephra). Given XRF scan resolutions of up to 200μm there is thus the potential for investigation of sub-annual variability. Funding has been obtained to determine carbon-14 dates for the lower parts of the longer cores. The reproducibility and accuracy of the Itrax data has been validated using conventional WD-XRF spectrometry and the work presented will also include geochemical interpretation of the XRF data and comparison with recorded and proxy-inferred climate data for the region.

A new sediment core from the early Aptian OAE1a: the Cau section (Prebetic Zone, Spain)

NASA Astrophysics Data System (ADS)

Alejandro Ruiz-Ortiz, Pedro; Castro, José Manuel; de Gea, Ginés A.; Jarvis, Ian; Loeser, Hannes; Molina, José Miguel; Nieto, Luis Miguel; Pancost, Richard; Quijano, María Luisa; Reolid, Matías; Skelton, Peter; Weissert, Helmut

2016-04-01

The occurrence of time intervals of enhanced deposition of organic matter (OM) during the Cretaceous, defined as Oceanic Anoxic Events (OAE), reflect abrupt changes in global carbon cycling. The exemplary Aptian OAE1a (120 Ma), is recorded in all the main ocean basins and associated with massive burial of OM in marine sediments [1]. OAE1a is concomitant with the 'nannoconid crisis', which represents a major biotic turnover [2], and also with widespread demise of carbonate platforms [1]. Much research has been done on the OAE1a from different sections in the world over the last decades, since the definition of the C-isotope stratigraphy of the event [3]. Notwithstanding, high-resolution studies across the entire event will be crucial to elucidate the precise timing and rates of the different environmental and biotic changes involved. In order to perform high-resolution studies, drill-cores can represent the best option. Previous cores with successful scientific results has been performed in two reference sections, the Cismon Apti-core [4], and more recently in La Bédoule [5]. Here we present a new drill-core from southern Spain, the Cau section core, drilled in the last quarter of 2015. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents the platform deposits of the Southern Iberian Palaeomargin. The lower Aptian of the Cau section is represented by an hemipelagic unit (Almadich Formation, ca. 200 m thick), deposited in a highly subsiding sector of a tilted block, located in the distal parts of the Prebetic Platform. Previous studies of the early Aptian of the Cau section have focused on the stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry [6], [7], among others. A recent study on the Cau section based on biomarkers has presented a detailed record of the PCO2, [8]. All these studies reveal that the Cau section represents an excellent site to investigate the OAE1a, based on its exceptional thickness and stratigraphic continuity, the quality and preservation of fossils and the geochemical signatures. Acknowledgements: This work is a contribution of the research project CGL2014-55274-P (Gov. of Spain). [1] Föllmi (2012). Cret. Res. 35, 230-257. [2] Erba et al. (2010). Science. 329, 428-432. [3] Menegatti et al. (1998). Paleoceanography 13, 530-545. [4] Erba et al. (1999). Jour. For. Res. 29, 371-391. [5] Lorenzen et al. (2013). Cret. Res. 39, 6-16. [6] Gea et al. (2003) Palaeo3. 200, 207-219. [7] Quijano et al. (2012). Palaeo3. 365-366, 276-293. [8] Naafs et al. (2016). Nat. Geosc. DOI: 10.1038/NGEO2627.

Assessing Sedimentation Issues Within Aging Flood Control Reservoirs in Oklahoma

NASA Astrophysics Data System (ADS)

Bennet, Sean J.; Cooper, Charles M.; Ritchie, Jerry C.; Dunbar, John A.; Allen, Peter M.; Caldwell, Larry W.; McGee, Thomas M.

2002-10-01

Since 1948, the USDA-NRCS has constructed nearly 11,000 flood control dams across the United States, and many of the reservoirs are rapidly filling with sediment. To rehabilitate these structures, the impounded sediment must be assessed to determine the volume of accumulated sediment and the potential hazard this sediment may pose if reintroduced to the environment. An assessment of sedimentation issues within two reservoirs, Sugar Creek No. 12, Hinton, Oklahoma, and Sergeant Major No. 4, Cheyenne, Oklahoma, is presented. Sediment cores obtained using a vibracoring system were composed of alternating layers of gravel, sand, silt, and clay. Stratigraphic analysis coupled with 137Cs dating techniques enabled the discrimination of pre-construction sediment from post-construction deposition. An acoustic profiling system was unencumbered by the relatively shallow water depth at Sugar Creek No. 12 and the seismic horizons agreed well with the sediment core data. Total sediment volume determined from the acoustic survey and the sediment core data for comparable areas differed by only 1.4 percent. The seismic profiling system worked well in the relatively deeper lake of Sergeant Major No. 4 and showed good correspondence to the collected core data. Detailed chemical analyses showed that overall sediment quality was good at both locations and that chemical composition was spatially invariant. Implementation of these techniques will aid action agencies such as the USDA-NRCS in their assessment and effective management of aging flood control reservoirs.

Geochemical evidence for enhanced preservation of organic matter in the oxygen minimum zone of the continental margin of northern California during the Late Pleistocene

USGS Publications Warehouse

Dean, Walter E.; Gardner, James V.; Anderson, Roger Y.

1994-01-01

The present upper water mass of the northeastern Pacific Ocean off California has a well-developed oxygen minimum zone between 600 and 1200 m wherein concentrations of dissolved oxygen are less than 0.5 mL/L. Even at such low concentrations of dissolved oxygen, benthic burrowing organisms are abundant enough to thoroughly bioturbate the surface and near-surface sediments. These macro organisms, together with micro organisms, also consume large quantities of organic carbon produced by large seasonal stocks of plankton in the overlying surface waters, which are supported by high concentrations of nutrients within the California Current upwelling system. In contrast to modern conditions of bioturbation, laminated sediments are preserved in upper Pleistocene sections of cores collected on the continental slope at water depths within the present oxygen minimum zone from at least as far north as the California-Oregon border and as far south as Point Conception. Comparison of sediment components in the laminae with those delivered to sediment traps as pelagic marine “snow” demonstrates that the dark-light lamination couplets are indeed annual (varves). These upper Pleistocene varved sediments contain more abundant lipid-rich “sapropelic” (type II) organic matter than the overlying bioturbated, oxidized Holocene sediments. The baseline of stable carbon isotopic composition of the organic matter in these slope cores does not change with time, indicating that the higher concentrations of type II organic matter in the varved sediments represent better preservation of organic matter rather than any change in the source of organic matter.

Drilling, construction, geophysical log data, and lithologic log for boreholes USGS 142 and USGS 142A, Idaho National Laboratory, Idaho

USGS Publications Warehouse

Twining, Brian V.; Hodges, Mary K.V.; Schusler, Kyle; Mudge, Christopher

2017-07-27

Starting in 2014, the U.S. Geological Survey in cooperation with the U.S. Department of Energy, drilled and constructed boreholes USGS 142 and USGS 142A for stratigraphic framework analyses and long-term groundwater monitoring of the eastern Snake River Plain aquifer at the Idaho National Laboratory in southeast Idaho. Borehole USGS 142 initially was cored to collect rock and sediment core, then re-drilled to complete construction as a screened water-level monitoring well. Borehole USGS 142A was drilled and constructed as a monitoring well after construction problems with borehole USGS 142 prevented access to upper 100 feet (ft) of the aquifer. Boreholes USGS 142 and USGS 142A are separated by about 30 ft and have similar geology and hydrologic characteristics. Groundwater was first measured near 530 feet below land surface (ft BLS) at both borehole locations. Water levels measured through piezometers, separated by almost 1,200 ft, in borehole USGS 142 indicate upward hydraulic gradients at this location. Following construction and data collection, screened water-level access lines were placed in boreholes USGS 142 and USGS 142A to allow for recurring water level measurements.Borehole USGS 142 was cored continuously, starting at the first basalt contact (about 4.9 ft BLS) to a depth of 1,880 ft BLS. Excluding surface sediment, recovery of basalt, rhyolite, and sediment core at borehole USGS 142 was approximately 89 percent or 1,666 ft of total core recovered. Based on visual inspection of core and geophysical data, material examined from 4.9 to 1,880 ft BLS in borehole USGS 142 consists of approximately 45 basalt flows, 16 significant sediment and (or) sedimentary rock layers, and rhyolite welded tuff. Rhyolite was encountered at approximately 1,396 ft BLS. Sediment layers comprise a large percentage of the borehole between 739 and 1,396 ft BLS with grain sizes ranging from clay and silt to cobble size. Sedimentary rock layers had calcite cement. Basalt flows ranged in thickness from about 2 to 100 ft and varied from highly fractured to dense, and ranged from massive to diktytaxitic to scoriaceous, in texture.Geophysical logs were collected on completion of drilling at boreholes USGS 142 and USGS 142A. Geophysical logs were examined with available core material to describe basalt, sediment and sedimentary rock layers, and rhyolite. Natural gamma logs were used to confirm sediment layer thickness and location; neutron logs were used to examine basalt flow units and changes in hydrogen content; gamma-gamma density logs were used to describe general changes in rock properties; and temperature logs were used to understand hydraulic gradients for deeper sections of borehole USGS 142. Gyroscopic deviation was measured to record deviation from true vertical at all depths in boreholes USGS 142 and USGS 142A.

Constraints on the Pleistocene chronology of sediments from the Lomonosov Ridge

USGS Publications Warehouse

O'Regan, M.; King, J.; Backman, J.; Jakobsson, M.; Palike, H.; Moran, K.; Heil, C.; Sakamoto, T.; Cronin, T. M.; Jordan, R.W.

2008-01-01

Despite its importance in the global climate system, age-calibrated marine geologic records reflecting the evolultion of glacial cycles through the Pleistocene are largely absent from the central Arctic Ocean. This is especially true for sediments older than 200 ka. Three sites cored during the Integrated Ocean Drilling Program's Expedition 302, the Arctic Coring Expedition (ACEX), provide a 27 m continuous sedimentary section from the Lomonosov Ridge in the central Arctic Ocean. Two key biostratigraphic datums and constraints from the magnetic inclination data are used to anchor the chronology of these sediments back to the base of the Cobb Mountain subchron (1215 ka). Beyond 1215 ka, two best fitting geomagnetic models are used to investigate the nature of cyclostratigraphic change. Within this chronology we show that bulk and mineral magnetic properties of the sediments vary on predicted Milankovitch frequencies. These cyclic variations record "glacial" and "interglacial" modes of sediment deposition on the Lomonosov Ridge as evident in studies of ice-rafted debris and stable isotopic and faunal assemblages for the last two glacial cycles and were used to tune the age model. Potential errors, which largely arise from uncertainties in the nature of downhole paleomagnetic variability, and the choice of a tuning target are handled by defining an error envelope that is based on the best fitting cyclostratigraphic and geomagnetic solutions. Copyright 2008 by the American Geophysical Union.

Clostridium perfringens in Long Island Sound sediments: An urban sedimentary record

USGS Publications Warehouse

Buchholtz ten Brink, Marilyn R.; Mecray, E.L.; Galvin, E.L.

2000-01-01

Clostridium perfringens is a conservative tracer and an indicator of sewage-derived pollution in the marine environment. The distribution of Clostridium perfringens spores was measured in sediments from Long Island Sound, USA, as part of a regional study designed to: (1) map the distribution of contaminated sediments; (2) determine transport and dispersal paths; (3) identify the locations of sediment and contaminant focusing; and (4) constrain predictive models. In 1996, sediment cores were collected at 58 stations, and surface sediments were collected at 219 locations throughout the Sound. Elevated concentrations of Clostridium perfringens in the sediments indicate that sewage pollution is present throughout Long Island Sound and has persisted for more than a century. Concentrations range from undetectable amounts to 15,000 spores/g dry sediment and are above background levels in the upper 30 cm at nearly all core locations. Sediment focusing strongly impacts the accumulation of Clostridium perfringens spores. Inventories in the cores range from 28 to 70,000 spores/cm2, and elevated concentrations can extend to depths of 50 cm. The steep gradients in Clostridium perfringens profiles in muddier cores contrast with concentrations that are generally constant with depth in sandier cores. Clostridium perfringens concentrations rarely decrease in the uppermost sediment, unlike those reported for metal contaminants. Concentrations in surface sediments are highest in the western end of the Sound, very low in the eastern region, and intermediate in the central part. This pattern reflects winnowing and focusing of Clostridium perfringens spores and fine-grained sediment by the hydrodynamic regime; however, the proximity of sewage sources to the westernmost Sound locally enhances the Clostridium perfringens signals.

Results of Laboratory Tests on Surficial Sediments from the Upper Continental Slope Northern Gulf of Mexico

USGS Publications Warehouse

Booth, James S.

1979-01-01

The purpose of this report is to present the results of geo­technical, textural, and chemical tests performed on samples from the upper Continental Slope, northern Gulf of Mexico.The samples were collected by a piston corer up to 12 m (40 ft.} in length with a head weight of 908 kg (one ton}. The inside diameter of the C. A. B. liner was 89 mm (3.5 inches}. Upon retrieval, the cores were cut in 1.5 m sections, examined for evidence of disturbance, then, if in acceptable condition, were sealed and placed in their in situ vertical position in a refrigerated van. Once ashore, the sections were opened, sealed with wax, recapped and stored as before.The cores were split lengthwise for analysis. One half of the core was X-rayed and the radiograph was carefully examined as a further check for disturbance. This half was then archived. The other half of the core was used for the laboratory work.

Oscillatory erosion and transport flume with superimposed unidirectional flow

DOEpatents

Jepsen, Richard A.; Roberts, Jesse D.

2004-01-20

A method and apparatus for measuring erosion rates of sediments and at high shear stresses due to complex wave action with, or without, a superimposed unidirectional current. Water is forced in a channel past an exposed sediment core sample, which erodes sediments when a critical shear stress has been exceeded. The height of the core sample is adjusted during testing so that the sediment surface remains level with the bottom of the channel as the sediments erode. Complex wave action is simulated by driving tandom piston/cylinder mechanisms with computer-controlled stepper motors. Unidirectional flow, forced by a head difference between two open tanks attached to each end of the channel, may be superimposed on to the complex wave action. Sediment traps may be used to collect bedload sediments. The total erosion rate equals the change in height of the sediment core sample divided by a fixed period of time.

Lead contamination and source in Shanghai in the past century using dated sediment cores from urban park lakes.

PubMed

Li, H B; Yu, S; Li, G L; Deng, H

2012-08-01

Lead contamination becomes of importance to urban resident health worldwide, especially for child health and growth. Undisturbed lake sediment cores are increasingly employed as a useful tool to backdate environmental contamination history. Five intact sediment cores collected from lakes in five urban parks were dated using (210)Pb and analyzed for total Pb content and isotope ratio to reconstruct the Pb contamination history over the last century in Shanghai, China. Total Pb content in the sediment cores increased by about 2- to 3-fold since 1900s. The profile of Pb flux in each sediment core revealed a remarkable increase of Pb contamination in Shanghai over the past century, especially in the latest three decades when China was experiencing a rapid economic and industrial development. Significant correlations were found between Pb fluxes in sediment cores and Pb emission from coal combustion in Shanghai. Coal combustion emission dominated anthropogenic Pb sources during the past century contributing from 52% to 69% of total Pb in cores, estimated by a three-end member model of Pb isotope ratios. Leaded gasoline emission generally contributed <30% of total Pb, which was banned by 1997 in the Shanghai region. Our results implicate that coal combustion-based energy consumption should be replaced, or at least partially replaced, to reduce health risks of Pb contamination in Shanghai. Copyright © 2012 Elsevier Ltd. All rights reserved.

Methodological issues and preliminary results from a combined sediment fingerprinting and radioisotope dating approach to explore changes in sediment sources with land-use change in the Brantian Catchment, Borneo.

NASA Astrophysics Data System (ADS)

Walsh, Rory; Higton, Sam; Marshall, Jake; Bidin, Kawi; Blake, William; Nainar, Anand

2015-04-01

This paper reports some methodological issues and early results of a project investigating the erosional impacts of land use changes (multiple selective logging and progressive, partial conversion to oil palm) over the last 25-40 years in the 600km2 Brantian river catchment in Sabah, Borneo. A combined sediment fingerprinting and radioisotope dating approach is being applied to sediment cores taken in stream hierarchical fashion across the intermediate catchment scale. Changes in sediment sources and sedimentation rates over time can be captured by changes in the relative importance of geochemical elements with depth in downstream sediment cores, which in turn can be linked to parallel changes in upstream cores by the application of unmixing models and statistical techniques. Radioisotope analysis of the sediment cores allows these changes to be dated and sedimentation rates to be estimated. Work in the neighbouring Segama catchment had successfully demonstrated the potential of such an approach in a rainforest environment (Walsh et al. 2011). The paper first describes steps taken to address methodological issues. The approach relies on taking continuous sediment cores which have aggraded progressively over time and remain relatively undisturbed and uncontaminated. This issue has been tackled (1) through careful core sampling site selection with a focus on lateral bench sites and (2) deployment of techniques such as repeat-measurement erosion bridge transects to assess the contemporary nature of sedimentation to validate (or reject) candidate sites. The issue of sediment storage and uncertainties over lag times has been minimised by focussing on sets of above- and below-confluence sites in the intermediate zone of the catchment, thus minimising sediment transit times between upstream contributing and downstream destination core sites. This focus on the intermediate zone was also driven by difficulties in finding suitable core sites in the mountainous headwaters area due to the prevalence of steep, incised channels without even narrow floodplains. Preliminary results are reported from (1) a field visit to investigate potential sampling sites in July 2014 and (2) initial analysis of a sediment core at a promising lateral bench site. Marked down-profile geochemistry changes of the core indicate a history of phases of high deposition and lateral growth of the channel caused by mobilisation of sediment linked to logging and clearance upstream. Recent channel bed degradation suggests the system has been adjusting a decline in sediment supply with forest recovery since logging in 2005, but a renewed sedimentation phase heralded by > 10 cm deposition at the site in a flood in July 2014 appears to have started linked to partial forest clearance for oil palm. These preliminary results support the ability of a combined fingerprinting and dating approach to reflect the spatial history of land-use change in a catchment undergoing disturbance. Walsh R. P. D. , Bidin K., Blake W.H., Chappell N.A., Clarke M.A., Douglas I., Ghazali R., Sayer A.M., Suhaimi J., Tych W. & Annammala K.V. (2011) Long-term responses of rainforest erosional systems at different spatial scales to selective logging and climatic change. Philosophical Transactions of the Royal Society B, 366, 3340-3353.

A chronicle of organochlorine contamination in Clear Creek, Galveston and Harris Counties, Texas, 1960-2002, as recorded in sediment cores

USGS Publications Warehouse

Mahler, Barbara J.; Van Metre, Peter

2003-01-01

Clear Creek flows through the Texas Coastal Plain from its headwaters southeast of Houston, Texas, to Clear Lake, which empties into Galveston Bay. Segments of Clear Creek were on the State of Texas 303(d) list for 1998, 1999, and 2000 as a result of a fish consumption advisory issued by the Texas Department of Health. One of the contaminants for which the fish consumption advisory was issued is the organochlorine pesticide chlordane. Chlordane is a hydrophobic (“waterfearing”) contaminant; that is, it adsorbs to sediment at concentrations much greater than those found in water. The study described here sought to answer three questions:Does chlordane occur in Clear Creek sediments at present?Is there current loading of chlordane to Clear Creek?How has occurrence of chlordane in Clear Creek changed over time?To answer these questions, the U.S. Geological Survey (USGS), in cooperation with the U.S. Environmental Protection Agency (USEPA), collected and analyzed sediment cores from Clear Creek (fig. 1). Sediment cores sometimes can be used to reconstruct historical trends in concentrations of hydrophobic contaminants (Eisenreich and others, 1989; Van Metre and others, 1997). Cores were collected from five ponds connected to Clear Creek but out of the main channel (fig. 1). Cesium-137 (137Cs) was analyzed in the cores to determine if the sediments in the cores were undisturbed and if the cores reached sediment predating 1964. The two cores that appeared most undisturbed on the basis of 137Cs profiles (see sidebar, p. 2) were further subsampled and additional samples analyzed for 137Cs, organic carbon, selected organochlorine pesticides (including chlordane), and total polychlorinated biphenyls (PCB).

The effects of Hurricanes Katrina and Rita on seabed polycyclic aromatic hydrocarbon dynamics in the Gulf of Mexico.

PubMed

Mitra, Siddhartha; Lalicata, Joseph J; Allison, Mead A; Dellapenna, Timothy M

2009-06-01

To assess the extent to which Hurricanes Katrina and Rita affected polycyclic aromatic hydrocarbons (PAH) in the Gulf of Mexico (GOM), sediment cores were analyzed in late 2005 from: a shallow shelf, a deeper shelf, and a marsh station. Sediment geochronology, fabric, and geochemistry show that the 2005 storms deposited approximately 10cm of sediment to the surface of a core at 5-12A. Bulk carbon geochemistry and PAH isomers in this top layer suggest that the source of sediment to the top portion of core 5-12A was from a relatively more marine area. Particulate PAHs in the marsh core (04M) appeared unaffected by the storms while sediments in the core from Station 5-1B (deeper shelf) were affected minimally (some possible storm-derived deposition). Substantial amounts of PAH-laden particles may have been displaced from the seabed in shallow areas of the water column in the GOM by these 2005 storms.

Recent marine deposits reconstruction of two depositional environments of the French Atlantic coast

NASA Astrophysics Data System (ADS)

Pouzet, Pierre; Maanan, Mohamed; Schmidt, Sabine; Athimon, Emmanuelle; Robin, Marc

2017-04-01

This work provides a 300-yr high-resolution record of past storm and/or tsunami events using a multi-proxy analysis (137Cs and 210Pb dating, chemical composition and grain size) of sedimentary deposits from two coastal depositional environments of the French Atlantic coast. We analyse two wetland areas situated just behind a narrow coastal sand strip: 1) the Mer Blanche and 2) the Turballe. Evidence for strong extratropical storms and /or tsunamis events can be identified in this central part of the Bay of Biscay from the XIXth to the XXth century. Nine short sediment cores were collected in August 2016 using gravity type corer of 10 inner diameter and 100 cm length. Each core was longitudinally sliced, each half section photographed and described. High-resolution elemental analyses of split sediment cores were done using an Avaatech XRF core scanner. Then sediment cores were sampled every 0.5 cm. Grain size analysis was done using a Malvern 2600 laser beam grain sizer; organic carbon was measured by Leco induction furnace. 137Cs, 210Pb and 226Ra activities were measured on about 2 g dried sediment using a low background, well-type γ spectrometer (Canberra). The 210Pb in excess, which is used for dating, was calculated as the difference of measured 210Pb and of its supported activities (226Ra). The history information is performed using historical documents including narrative sources, ancient maps, records of cities repairs, surveys conducted after a disaster, newspaper from different departmental and national archives, and meteorological data. Coastal depositional environments were affected hardest by extreme environmental and climatological events during the last century. In the Mer Blanche core, three extreme episodes can be observed: i) at 36 cm, sediment is characterized by coarser sand and higher Sr/Al ratio, this episode coincides with a high tidal wave in spring 1937; ii) at 55 cm, we observe the presence of many gravels, they dates back to the high tidal wave of 1924 and iii) at 65 cm, the presence of another coarse pebble layer is attributed to a series of severe storms associated with coastal flooding episodes between 1910 and 1913. Acknowledgements The authors gratefully acknowledge Isabelle Billy (EPOC, University of Bordeaux 1) for XRF spectrometric core scanner analysis. This work was supported by grants from the Fondation de France through the research program « Quels littoraux pour demain? » and OR2C PDL regional framework.

Current status and historical variations of phthalate ester (PAE) contamination in the sediments from a large Chinese lake (Lake Chaohu).

PubMed

Kang, Lei; Wang, Qing-Mei; He, Qi-Shuang; He, Wei; Liu, Wen-Xiu; Kong, Xiang-Zhen; Yang, Bin; Yang, Chen; Jiang, Yu-Jiao; Xu, Fu-Liu

2016-06-01

The residual levels of phthalate esters (PAEs) in the surface and two core sediments from Lake Chaohu were measured with a gas chromatograph-mass spectrometer (GC-MS). The temporal-spatial distributions, compositions of PAEs, and their effecting factors were investigated. The results indicated that di-n-butyl phthalate (DnBP), diisobutyl phthalate (DIBP), and di(2-ethylhexyl) phthalate (DEHP) were three dominant PAE components in both the surface and core sediments. The residual level of total detected PAEs (∑PAEs) in the surface sediments (2.146 ± 2.255 μg/g dw) was lower than that in the western core sediments (10.615 ± 9.733 μg/g) and in the eastern core sediments (5.109 ± 4.741 μg/g). The average content of ∑PAEs in the surface sediments from the inflow rivers (4.128 ± 1.738 μg/g dw) was an order of magnitude higher than those from the lake (0.323 ± 0.093 μg/g dw), and there were similar PAE compositions between the lake and inflow rivers. This finding means that there were important effects of PAE input from the inflow rivers on the compositions and distributions of PAEs in the surface sediments. An increasing trend was found for the residual levels of ΣPAEs, DnBP, and DIBP from the bottom to the surface in both the western and eastern core sediments. Increasing PAE usage with the population growth, urbanization, and industrial and agricultural development in Lake Chaohu watershed would result in the increasing production of PAEs and their resulting presence in the sediments. The significant positive relationships were also found between the PAE contents and the percentage of sand particles, as well as TOC contents in the sediment cores.

High-Resolution Magnetic Properties and Cyclicity of Contourites from IODP Site U1389 (West Iberian Margin)

NASA Astrophysics Data System (ADS)

Richter, C.; Adesiyun, O.; Acton, G.; Sidorovskaia, N.; Sierro, F. J.; Xuan, C.; Verosub, K. L.

2015-12-01

We present high-resolution paleomagnetic and rock magnetic results from the lower part of the APC-cored section (36 - 107 meters composite depth) of Integrated Ocean Drilling Program (IODP) Site U1389 (36º 25.515'N; 7º 16.683'W, 644 m water depth). This site was cored as part of the IODP Mediterranean Outflow Expedition to address paleoceanographic questions about the evolution of the North Atlantic Mediterranean and climate system over the past 6 million years. The recovered section at Site U1389 consists of a thick, rapidly accumulated (~40 cm/kyr), and very uniform series of contouritic sediment. Ages were obtained by tuning the planktonic foraminifer oxygen isotope data to the NGRIP ice core record. We collected rock magnetic and paleomagnetic measurements at 1-cm resolution on 71-m of U-channel samples (representing ~145 k.yr.), with the goal of extracting a high-resolution record of paleoenvironmental variability, relative geomagnetic paleointensity, and paleosecular variation. Stepwise demagnetization of the natural remanence (NRM) demonstrates the successful removal of a secondary, predominantly drill-string induced, magnetization and identification of a stable and strong primary magnetization carried by the sediment samples (average MAD calculated by principal component analysis: ~1º). Excellent behavior of the samples during alternating field demagnetization and isothermal remanent magnetization (IRM) acquisition suggest magnetite as the main carrier of magnetic remanence. Relative paleointensity estimates were determined by normalizing the NRM by the ARM, IRM, and magnetic susceptibility. Time-frequency analyses of high-resolution concentration and grain-size dependent paleomagnetic proxy data for the entire 107-m (200 k.yr.) long APC section of Site U1389 will be presented with the goal of identifying the driver of cyclic changes in the sedimentary section.

Occurrence, compositional distribution, and toxicity assessment of pyrethroid insecticides in sediments from the fluvial systems of Chaohu Lake, Eastern China.

PubMed

Wang, Ji-Zhong; Bai, Ya-Shu; Wu, Yakton; Zhang, Shuo; Chen, Tian-Hu; Peng, Shu-Chuan; Xie, Yu-Wei; Zhang, Xiao-Wei

2016-06-01

Surface sediment-associated synthetic pyrethroid insecticides (SPs) are known to pose high risks to the benthic organisms in Chaohu Lake, a shallow lake of Eastern China. However, the pollution status of the lake's tributaries and estuaries is still unknown. The present study was conducted to investigate the occurrence, compositional distribution, and toxicity of 12 currently used SPs in the surface sediments from four important tributaries, as well as in the sediment cores at their estuaries, using GC-MS for quantification. All SPs selected were detectable, with cypermethrin, es/fenvalerate, and permethrin dominant in both surface and core sediments, suggesting that these compounds were extensively applied. Urban samples contained the highest summed concentrations of the 12 SPs analyzed (Σ12SP) in both surface and core sediments compared with rural samples, suggesting that urban areas near aquatic environments posed high risks for SPs. The mean concentration of Σ12SP in surface sediments of each river was generally higher than that found in core sediments from its corresponding estuary, perhaps implying recent increases in SP usage. Surface sediments were significantly dominated by cypermethrin and permethrin, whereas core sediments were dominated by permethrin and es/fenvalerate. The compositional distributions demonstrated a spatial variation for surface sediments because urban sediments generally contained greater percentages of permethrin and cypermethrin, but rural sediments had significant levels of es/fenvalerate and cypermethrin. In all sediment cores, the percentage of permethrin gradually increased, whereas es/fenvalerate tended to decrease, from the bottom sediments to the top, indicating that the former represented fresh input, whereas the latter represented historical residue. Most urban samples would be expected to be highly toxic to benthic organisms due to the residue of SPs based on a calculation of toxic units (TUs) using toxicity data of the amphipod Hyalella azteca. However, low TU values were found for the samples from rural areas. These results indicate that the bottom sediments were exposed to high risk largely by the residual SPs from urban areas. The summed TUs were mostly attributable to cypermethrin, followed by λ-cyhalothrin and es/fenvalerate. Despite permethrin contributing ∼28.7 % of the Σ12SP concentration, it only represented 6.34 % of the summed TUs. Therefore, our results suggest that high levels of urbanization can increase the accumulation of SPs in aquatic environments.

City Core - detecting the anthropocene in urban lake cores

NASA Astrophysics Data System (ADS)

Kjaer, K. H.; Ilsøe, P.; Andresen, C. S.; Rasmussen, P.; Andersen, T. J.; Frei, R.; Schreiber, N.; Odgaard, B.; Funder, S.; Holm, J. M.; Andersen, K.

2011-12-01

Here, we presents the preliminary results from lake cores taken in ditches associated with the historical fortifications enclosing the oldest - central Copenhagen to achieve new knowledge from sediment deposits related to anthropogenic activities. We have examined sediment cores with X-ray fluorescence (XRF) analyzers to correlate element patterns from urban and industrial emissions. Thus, we aim to track these patterns back in time - long before regular routines of recording of atmospheric environment began around 1978. Furthermore, we compare our data to alternative sources of information in order to constrain and expand the temporal dating limits (approximately 1890) achieved from 210Pb activity. From custom reports and statistic sources, information on imported volumes from coal, metal and oil was obtained and related contaminants from these substances to the sediment archives. Intriguingly, we find a steep increase in import of coal and metals matching the exponential increase of lead and zinc counts from XRF-recordings of the sediment cores. In this finding, we claim to have constrain the initiation of urban industrialization. In order to confirm the age resolution of the lake cores, DNA was extracted from sediments, sedaDNA. Thus we attempt to trace plantation of well documented exotic plants to, for instance, the Botanical Garden. Through extraction and sampling of sedaDNA from these floral and arboreal specimens we intend to locate their strataigraphic horizons in the sediment core. These findings may correlate data back to 1872, when the garden was established on the area of the former fortification. In this line of research, we hope to achieve important supplementary knowledge of sedaDNA-leaching frequencies within freshwater sediments.

Paleoenvironmental reconstructions of Nettilling Lake area (Baffin Island, Nunavut): A multi-proxy analysis.

NASA Astrophysics Data System (ADS)

Beaudoin, Anne; Pienitz, Reinhard; Francus, Pierre; Zdanowicz, Christian; St-Onge, Guillaume

2014-05-01

The paleoclimate and paleolimnological history of several Arctic regions remains poorly known. This is the case for the area around Nettilling Lake (Baffin Island, Nunavut), the largest lake of the Canadian Arctic Archipelago. To reconstruct the past environmental history of this area, a highly innovative multi-proxy approach combining physical, magnetic, chemical and biological properties preserved in lake sediments was used. One particular goal of this study was to investigate the possible coupling between sedimentation processes observed in the lake and melt rates of nearby Penny Ice Cap. A 1-m long sediment core was retrieved from a small bay in the northeastern part of Nettilling Lake during the summer of 2010. This sampling area was chosen based on the hypothesis that incoming glacial meltwaters from Penny Ice Cap would leave a strong climate-modulated signal that would be reflected in the sedimentary sequence. The core was analyzed by both non-destructive (X-radiography (X-ray), microfluorescence-X (µ-XRF), magnetic susceptibility) and destructive (Loss On Ignition, grain size, water content, thin sections, diatoms) techniques. Radiometric AMS 14C and 210Pb/137Cs age determinations, as well as paleomagnetic measurements, were used to develop the core chronology, yielding an estimated bottom age of approximately 1365 AD. The sedimentation rate (0.15 cm.yr-1) in Nettilling Lake was found to be high compared to other Arctic lakes, due to inputs of highly turbid meltwaters from Penny Ice Cap with high suspended sediment loads. Significant correlations were found between geochemical profiles of elements linked to detrital inputs (Si, Ti, K, Ca) and melt rates from Penny Ice Cap since the 19th century. This suggests that variations in detrital elements in Nettilling Lake sediments might be used as an indirect indicator of regional climate fluctuations (e.g., summer temperatures) that determine glacier melt rates.

Dual-core mass-balance approach for evaluating mercury and210Pb atmospheric fallout and focusing to lakes

USGS Publications Warehouse

Van Metre, P.C.; Fuller, C.C.

2009-01-01

Determining atmospheric deposition rates of mercury and other contaminants using lake sediment cores requires a quantitative understanding of sediment focusing. Here we present a novel approach that solves mass-balance equations for two cores algebraically to estimate contaminant contributions to sediment from direct atmospheric fallout and from watershed and in-lake focusing. The model is applied to excess 210Pb and Hg in cores from Hobbs Lake, a high-altitude lake in Wyoming. Model results for excess 210Pb are consistent with estimates of fallout and focusing factors computed using excess 210Pb burdens in lake cores and soil cores from the watershed and model results for Hg fallout are consistent with fallout estimated using the soil-core-based 210Pb focusing factors. The lake cores indicate small increases in mercury deposition beginning in the late 1800s and large increases after 1940, with the maximum at the tops of the cores of 16-20 ??g/m 2year. These results suggest that global Hg emissions and possibly regional emissions in the western United States are affecting the north-central Rocky Mountains. Hg fallout estimates are generally consistent with fallout reported from an ice core from the nearby Upper Fremont Glacier, but with several notable differences. The model might not work for lakes with complex geometries and multiple sediment inputs, but for lakes with simple geometries, like Hobbs, it can provide a quantitative approach for evaluating sediment focusing and estimating contaminant fallout.

Anthropogenically induced changes in sediment and biogenic silica fluxes in Chesapeake Bay

USGS Publications Warehouse

Colman, Steven M.; Bratton, John F.

2003-01-01

Sediment cores as long as 20 m, dated by 14C, 210Pb, and 137Cs methods and pollen stratigraphy, provide a history of diatom productivity and sediment-accumulation rates in Chesapeake Bay. We calculated the flux of biogenic silica and total sediment for the past 1500 yr for two high-sedimentation-rate sites in the mesohaline section of the bay. The data show that biogenic silica flux to sediments, an index of diatom productivity in the bay, as well as its variability, were relatively low before European settlement of the Chesapeake Bay watershed. In the succeeding 300–400 yr, the flux of biogenic silica has increased by a factor of 4 to 5. Biogenic silica fluxes still appear to be increasing, despite recent nutrient-reduction efforts. The increase in diatom-produced biogenic silica has been partly masked (in concentration terms) by a similar increase in total sediment flux. This history suggests the magnitude of anthropogenic disturbance of the estuary and indicates that significant changes had occurred long before the twentieth century.

Antropogenically induced changes in sediment and biogenic silica fluxes in Chesapeake Bay

USGS Publications Warehouse

Colman, Steven M.; Bratton, J.F.

2003-01-01

Sediment cores as long as 20 m, dated by 14C, 210Pb, and 137Cs methods and pollen stratigraphy, provide a history of diatom productivity and sediment-accumulation rates in Chesapeake Bay. We calculated the flux of biogenic silica and total sediment for the past 1500 yr for two high-sedimentation-rate sites in the mesohaline section of the bay. The data show that biogenic silica flux to sediments, an index of diatom productivity in the bay, as well as its variability, were relatively low before European settlement of the Chesapeake Bay watershed. In the succeeding 300-400 yr, the flux of biogenic silica has increased by a factor of 4 to 5. Biogenic silica fluxes still appear to be increasing, despite recent nutrient-reduction efforts. The increase in diatom-produced biogenic silica has been partly masked (in concentration terms) by a similar increase in total sediment flux. This history suggests the magnitude of anthropogenic disturbance of the estuary and indicates that significant changes had occurred long before the twentieth century.

Aragonite preservation in late Quaternary sediment cores on the Brazilian Continental Slope: implications for intermediate water circulation

NASA Astrophysics Data System (ADS)

Gerhardt, S.; Groth, H.; Rühlemann, C.; Henrich, R.

We present late Quaternary records of aragonite preservation determined for sediment cores recovered on the Brazilian Continental Slope (1790-2585m water depth) where North Atlantic Deep Water (NADW) dominates at present. We have used various indirect dissolution proxies (carbonate content, aragonite/calcite contents, and sand percentages) as well as gastropodal abundances and fragmentation of Limacina inflata to determine the state of aragonite preservation. In addition, microscopic investigations of the dissolution susceptibility of three Limacina species yielded the Limacina Dissolution Index which correlates well with most of the other proxies. Excellent preservation of aragonite was found in the Holocene section, whereas aragonite dissolution gradually increases downcore. This general pattern is attributed to an overall increase in aragonite corrosiveness of pore waters. Overprinted on this early diagenetic trend are high-frequency fluctuations of aragonite preservation, which may be related to climatically induced variations of intermediate water masses.

Textural analysis of marine sediments at the USGS Woods Hole Science Center; methodology and data on DVD

USGS Publications Warehouse

Poppe, Lawrence J.; Williams, S. Jeffress; Paskevich, Valerie F.

2006-01-01

Marine sediments off the eastern United States vary markedly in texture (i.e., the size, shape, composition, and arrangement of their grains) due to a complex geologic history. For descriptive purposes, however, it is typically most useful to classify these sediments according to their grain-size distributions. In 1962, the U.S. Geological Survey began a program to study the marine geology of the continental margin off the Atlantic coast of the United States. As part of this program and numerous subsequent projects, thousands of sediment grab samples and cores were collected and analyzed for grain size at the Woods Hole Science Center. USGS Open-File Report 2005-1001 (Poppe et al., 2005), available on DVD and online, describes the field methods used to collect marine sediment samples as well as the laboratory methods used to determine and characterize grain-size distributions, and presents these data in several formats that can be readily employed by interested parties. The report is divided into three sections. The first section discusses procedures and contains pictures of the equipment, analytical flow diagrams, video clips with voice commentary, classification schemes, useful forms and compiled and uncompiled versions of the data-acquisition and data-processing software with documentation. The second section contains the grain-size data for more than 23,000 analyses in two “flat-file” formats, a data dictionary, and color-coded browse maps. The third section provides a GIS data catalog of the available point, interpretive, and baseline data layers, with FGDC-compliant metadata to help users visualize the textural information in a geographic context.

Paleomagnetic and rock magnetic study of the IODP Site U1332 sediments - relative paleointensity during Eocene and Oligocene

NASA Astrophysics Data System (ADS)

Yamamoto, Y.; Acton, G.; Channell, J. E.; Palmer, E. C.; Richter, C.; Yamazaki, T.

2011-12-01

Integrated Ocean Drilling Program (IODP) Expeditions 320 and 321 recovered sediment cores from equatorial Pacific. Cores were taken at eight Sites (U1331-U1338) and onboard measurements showed that those from Sites U1331, U1332, U1333 and U1334 covered Eocene and/or Oligocene (Expedition 320/321 Scientists, 2010). Although many efforts have been made to reveal relative geomagnetic paleointensity variations in geologic time, those prior to ca. 3 m.y. have been not yet reported except a few studies (e.g. ca. 23-34 Ma, Tauxe and Hartl, 1997). This study concentrates on paleomagnetic and rock magnetic measurements on the Site U1332 sediment core. The measurements include stepwise alternating field demagnetization of the natural remanent magnetization (NRM), the anhysteretic remanent magnetization (ARM) and the isothermal remanent magnetization (IRM). The magnetostrartigraphy constructed from the NRM data show that the sedimentary section extends from the early Oligocene to middle Eocene (23.030-41.358 Ma). Intensity variation of ARM and IRM is within about a factor of six throughout the core. Magnetic grain size proxy, ARM/IRM, differ between Eocene (about 0.11) and Oligocene (about 0.14). These suggest that relative paleointensity (RPI) estimation is basically possible if we divide the core into Eocene and Oligocene periods. RPI estimates have been done by using ARM and IRM as normalizers for NRM. RPIs by ARM and IRM generally show consistent variations. However, several experimental results imply that RPI by IRM may be more preferable. We will compare the U1332 RPI record with the U1331, U1333 and U1334 RPI records.

Analytical and sampling constraints in ²¹⁰Pb dating.

PubMed

MacKenzie, A B; Hardie, S M L; Farmer, J G; Eades, L J; Pulford, I D

2011-03-01

²¹⁰Pb dating provides a valuable, widely used means of establishing recent chronologies for sediments and other accumulating natural deposits. The Constant Rate of Supply (CRS) model is the most versatile and widely used method for establishing ²¹⁰Pb chronologies but, when using this model, care must be taken to account for limitations imposed by sampling and analytical factors. In particular, incompatibility of finite values for empirical data, which are constrained by detection limit and core length, with terms in the age calculation, which represent integrations to infinity, can generate erroneously old ages for deeper sections of cores. The bias in calculated ages increases with poorer limit of detection and the magnitude of the disparity increases with age. The origin and magnitude of this effect are considered below, firstly for an idealized, theoretical ²¹⁰Pb profile and secondly for a freshwater lake sediment core. A brief consideration is presented of the implications of this potential artefact for sampling and analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

Natural thorium isotopes in marine sediment core off Labuan port

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hafidz, B. Y.; Asnor, A. S.; Terence, R. C.

2014-02-12

Sediment core was collected from Labuan port and analyzed to determine the radioactivity of thorium (Th) isotopes. The objectives of this study are to determine the possible sources of Th isotopes at Labuan port and estimates the sedimentation rate based on {sup 228}Th/{sup 232}Th model. The results suggest the {sup 230}Th and {sup 232}Th might be originated from terrestrial sedimentary rock while {sup 228}Th originated by authigenic origin. High ratio value of {sup 230}Th/{sup 232}Th detected at the top surface sediment indicates the increasing of {sup 230}Th at the recent years which might be contributed from the anthropogenic sources. Themore » sedimentation rate of core sediment from Labuan Port was successfully estimated by using {sup 228}Th/{sup 232}Th model. The result show high sedimentation rate with 4.67 cm/year indicates rapid deposition occurred at this study area due to the high physical activity at the Labuan port. By assume the constant sedimentation rate at this area; we estimated the age of 142 cm core sediment obtained from Labuan port is 32 years started from 1981 to 2012. This chronology will be used in forthcoming research to investigate the historical profile of anthropogenic activities affecting the Labuan port.« less

ENANTIOMERIC RATIOS OF CHIRAL PCB ATROPISOMERS IN RADIODATED SEDIMENT CORES

EPA Science Inventory

Enantiomeric ratios (ERs)) of chiral polychlorinated biphenyl (PCB) atropisomers were quantified in radiodated sediment cores of Lake Hartwell SC, a reservoir heavily impacted by PCBS, to study spatial and temporal changes in chirality. A chiral analysis of cores showed accumulat...

Long-term recovery of PCB-contaminated surface sediments at the Sangamo-westonl Twelvemile Creek/lake Hartwell Superfund Site.

PubMed

Brenner, Richard C; Magar, Victor S; Ickes, Jennifer A; Foote, Eric A; Abbott, James E; Bingler, Linda S; Crecelius, Eric A

2004-04-15

Natural recovery of contaminated sediments relies on burial of contaminated sediments with increasingly clean sediments over time (i.e., natural capping). Natural capping reduces the risk of resuspension of contaminated surface sediments, and it reduces the potential for contaminant transport into the food chain by limiting bioturbation of contaminated surface or near-surface sediments. This study evaluated the natural recovery of surface sediments contaminated with polychlorinated biphenyls (PCBs) at the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site (Lake Hartwell), Pickens County, SC. The primary focus was on sediment recovery resulting from natural capping processes. Total PCB (t-PCB), lead-210 (210Pb), and cesium-137 (137Cs) sediment core profiles were used to establish vertical t-PCB concentration profiles, age date sediments, and determine surface sedimentation and surface sediment recovery rates in 18 cores collected along 10 transects. Four upgradient transects in the headwaters of Lake Hartwell were impacted by historical sediment releases from three upgradient sediment impoundments. These transects were characterized by silt/ clay and sand layering. The highest PCB concentrations were associated with silt/clay layers (1.8-3.5% total organic carbon (TOC)), while sand layers (0.05-0.32% TOC) contained much lower PCB concentrations. The historical sediment releases resulted in substantial burial of PCB-contaminated sediment in the vicinity of these four cores; each core contained less than 1 mg/kg t-PCBs in the surface sand layers. Cores collected from six downgradient Lake Hartwell transects consisted primarily of silt and clay (0.91-5.1% TOC) and were less noticeably impacted by the release of sand from the impoundments. Vertical t-PCB concentration profiles in these cores began with relatively low PCB concentrations at the sediment-water interface and increased in concentration with depth until maximum PCB concentrations were measured at approximately 30-60 cm below the sediment-water interface, ca. 1960-1980. Maximum t-PCB concentrations were followed by progressively decreasing concentrations with depth until the t-PCB concentrations approached the detection limit, where sediments were likely deposited before the onset of PCB use at the Sangamo-Weston plant. The sediments containing the maximum PCB concentrations are associated with the period of maximum PCB release into the watershed. Sedimentation rates averaged 2.1 +/- 1.5 g/(cm2 yr) for 12 of 18 cores collected. The 1994 Record of Decision cleanup requirement is 1.0 mg/kg; two more goals (0.4 and 0.05 mg/kg t-PCBs) also were identified. Average surface sedimentation requirements to meet the three goals were 1.4 +/- 3.7, 11 +/- 4.2, and 33 +/- 11 cm, respectively. Using the age dating results, the average recovery dates to meet these goals were 2000.6 +/- 2.7, 2007.4 +/- 3.5, and 2022.7 +/- 11 yr, respectively. (The 95% prediction limits for these values also are provided.) Despite the reduction in surface sediment PCB concentrations, PCB concentrations measured in largemouth bass and hybrid bass filets continue to exceed the 2.0 mg/kg FDA fish tolerance level.

Sediment Dating With 210Pb and 137Cs In Monterey Canyon, California Reveal the extent of recent sediment movement down canyon

NASA Astrophysics Data System (ADS)

Lorenson, T. D.; Maier, K. L.; Gwiazda, R.; Paull, C. K.; McGann, M.

2017-12-01

Submarine canyons are major vectors of sediment transport off the continent into the deep sea. Recent results from the Monterey Coordinated Canyon Experiment document fifteen sediment transport events occurred during an 18-month period from 2015 to 2017, and three of them reached at least to 1850m. In an attempt to constrain the timing and rate in which sediments were transported down canyons in these and earlier events we have collected sediment cores and measured the sedimentation rates using 210Pb and 137Cs dating techniques along the axis of Monterey Canyon. We employed transects of precisely located ROV collected push cores and vibracores collected at water depths ranging from 300m to 2900m perpendicular to the canyon axis using a remotely operated vehicle (ROV). Some cores were taken in 2013 and compared with those taken in 2017. We focused on cores from terraces that are between 60m and 75m above the canyon thalweg in water depths between 300 and 1500 m and in cores collected form the canyon's axial channel between 1800 and 2900 m water depths where the canyon widens considerably. Generally sedimentation rates vary with depth, with the highest sedimentation rate closest to land, but vary substantially across successive terraces. Sawtooth-shaped excess 210Pb and 137Cs profiles with depth at almost all sites at least to 1500m imply several episodes of deposition and reworking of sediment on the terraces suggesting multiple sediment transport events. The excess 210Pb in many cores reach depths of up to 1m implying sedimentation rates greater than 10mm per year. At the deepest site (2900m) about 10 cm of fine hemipelagic sediment overlies sand indicating a high-energy sediment flow event. In 2014 the measured 210Pb sedimentation rate of 0.6 to 0.8mm per year indicates that the last 10 cm of sediment have been deposited and undisturbed since about the year 1910 showing that recent events have not reached this depth. Measurements are on going to determine if the 2015-2017 sediment transport events have travelled down to 2900m [RG1] and if the timing of these sediment flow events were triggered by external factors, like earthquakes, winter storms, or by seafloor failures within the Canyon. [RG1]This seem to contradict the previous sentence where it says that it did not reach 2900 m

Hydrocarbon Degradation in Caspian Sea Sediment Cores Subjected to Simulated Petroleum Seepage in a Newly Designed Sediment-Oil-Flow-Through System.

PubMed

Mishra, Sonakshi; Wefers, Peggy; Schmidt, Mark; Knittel, Katrin; Krüger, Martin; Stagars, Marion H; Treude, Tina

2017-01-01

The microbial community response to petroleum seepage was investigated in a whole round sediment core (16 cm length) collected nearby natural hydrocarbon seepage structures in the Caspian Sea, using a newly developed Sediment-Oil-Flow-Through (SOFT) system. Distinct redox zones established and migrated vertically in the core during the 190 days-long simulated petroleum seepage. Methanogenic petroleum degradation was indicated by an increase in methane concentration from 8 μM in an untreated core compared to 2300 μM in the lower sulfate-free zone of the SOFT core at the end of the experiment, accompanied by a respective decrease in the δ 13 C signal of methane from -33.7 to -49.5‰. The involvement of methanogens in petroleum degradation was further confirmed by methane production in enrichment cultures from SOFT sediment after the addition of hexadecane, methylnapthalene, toluene, and ethylbenzene. Petroleum degradation coupled to sulfate reduction was indicated by the increase of integrated sulfate reduction rates from 2.8 SO 4 2- m -2 day -1 in untreated cores to 5.7 mmol SO 4 2- m -2 day -1 in the SOFT core at the end of the experiment, accompanied by a respective accumulation of sulfide from 30 to 447 μM. Volatile hydrocarbons (C2-C6 n -alkanes) passed through the methanogenic zone mostly unchanged and were depleted within the sulfate-reducing zone. The amount of heavier n -alkanes (C10-C38) decreased step-wise toward the top of the sediment core and a preferential degradation of shorter (C30) was seen during the seepage. This study illustrates, to the best of our knowledge, for the first time the development of methanogenic petroleum degradation and the succession of benthic microbial processes during petroleum passage in a whole round sediment core.

Hydrocarbon Degradation in Caspian Sea Sediment Cores Subjected to Simulated Petroleum Seepage in a Newly Designed Sediment-Oil-Flow-Through System

PubMed Central

Mishra, Sonakshi; Wefers, Peggy; Schmidt, Mark; Knittel, Katrin; Krüger, Martin; Stagars, Marion H.; Treude, Tina

2017-01-01

The microbial community response to petroleum seepage was investigated in a whole round sediment core (16 cm length) collected nearby natural hydrocarbon seepage structures in the Caspian Sea, using a newly developed Sediment-Oil-Flow-Through (SOFT) system. Distinct redox zones established and migrated vertically in the core during the 190 days-long simulated petroleum seepage. Methanogenic petroleum degradation was indicated by an increase in methane concentration from 8 μM in an untreated core compared to 2300 μM in the lower sulfate-free zone of the SOFT core at the end of the experiment, accompanied by a respective decrease in the δ13C signal of methane from -33.7 to -49.5‰. The involvement of methanogens in petroleum degradation was further confirmed by methane production in enrichment cultures from SOFT sediment after the addition of hexadecane, methylnapthalene, toluene, and ethylbenzene. Petroleum degradation coupled to sulfate reduction was indicated by the increase of integrated sulfate reduction rates from 2.8 SO42-m-2 day-1 in untreated cores to 5.7 mmol SO42-m-2 day-1 in the SOFT core at the end of the experiment, accompanied by a respective accumulation of sulfide from 30 to 447 μM. Volatile hydrocarbons (C2–C6 n-alkanes) passed through the methanogenic zone mostly unchanged and were depleted within the sulfate-reducing zone. The amount of heavier n-alkanes (C10–C38) decreased step-wise toward the top of the sediment core and a preferential degradation of shorter (C30) was seen during the seepage. This study illustrates, to the best of our knowledge, for the first time the development of methanogenic petroleum degradation and the succession of benthic microbial processes during petroleum passage in a whole round sediment core. PMID:28503172

Sediment characteristics and configuration within three dam impoundments on the Kalamazoo River, Michigan, 2000

USGS Publications Warehouse

Rheaume, S.J.; Rachol, C.M.; Hubbell, D.L.; Simard, Andreanne

2002-01-01

The removal of the remnants of three hydroelectric dams on the Kalamazoo River near Plainwell, Otsego, and Allegan, Michigan, has been proposed. The benefits of this removal include returning the Kalamazoo River to its pre-dam flow, increasing recreational use and safety on the river, and improving aquatic habitat. The U.S. Environmental Protection Agency has designated this reach of the Kalamazoo River as a Federal Superfund site because of the historical discharge of papermill waste containing polychlorinated biphenyls. Much of this waste material remains concentrated in organic sediment and kaolinite clay deposited upstream from the three dam foundations. Sediment containing up to 150 milligrams per kilogram polychlorinated biphenyls could move if dam foundations are removed; therefore, it is necessary to estimate the characteristic and configuration of the sediment before work begins. Data collected from augered sections and sediment cores show that impoundment sediments were deposited in two distinctly different sedimentary environments. Interbedded lacustrine sediments that overlie the pre-dam channel surface consist of organic-rich silt and clay, fine to medium sand, and some gravel. These materials were deposited in a repetitive, cyclic fashion related to former stream velocities when the impoundment water levels were 5-10 feet higher. Lowering of these water levels and demolition of the superstructures of these dams resulted in erosion of much of these instream lacustrine sediments and subsequent deposition of coarse-grained alluvium in the impounded channel behind the remaining dam foundations. The composite thicknesses of the lacustrine deposits and overlying alluvium was determined from sediment cores collected from each impoundment. The volume of instream sediment contained in each impoundment is estimated to be about 77,600 cubic yards at the Plainwell impoundment; 268,900 cubic yards at the Otsego impoundment; and 1,192,600 cubic yards at the Trowbridge impoundment. Estimates do not include bank or flood-plain deposits.

Use of sediment source fingerprinting to assess the role of subsurface erosion in the supply of fine sediment in a degraded catchment in the Eastern Cape, South Africa.

PubMed

Manjoro, Munyaradzi; Rowntree, Kate; Kakembo, Vincent; Foster, Ian; Collins, Adrian L

2017-06-01

Sediment source fingerprinting has been successfully deployed to provide information on the surface and subsurface sources of sediment in many catchments around the world. However, there is still scope to re-examine some of the major assumptions of the technique with reference to the number of fingerprint properties used in the model, the number of model iterations and the potential uncertainties of using more than one sediment core collected from the same floodplain sink. We investigated the role of subsurface erosion in the supply of fine sediment to two sediment cores collected from a floodplain in a small degraded catchment in the Eastern Cape, South Africa. The results showed that increasing the number of individual fingerprint properties in the composite signature did not improve the model goodness-of-fit. This is still a much debated issue in sediment source fingerprinting. To test the goodness-of-fit further, the number of model repeat iterations was increased from 5000 to 30,000. However, this did not reduce uncertainty ranges in modelled source proportions nor improve the model goodness-of-fit. The estimated sediment source contributions were not consistent with the available published data on erosion processes in the study catchment. The temporal pattern of sediment source contributions predicted for the two sediment cores was very different despite the cores being collected in close proximity from the same floodplain. This highlights some of the potential limitations associated with using floodplain cores to reconstruct catchment erosion processes and associated sediment source contributions. For the source tracing approach in general, the findings here suggest the need for further investigations into uncertainties related to the number of fingerprint properties included in un-mixing models. The findings support the current widespread use of ≤5000 model repeat iterations for estimating the key sources of sediment samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

Determining rates of sediment accumulation on the Mekong shelf: Timescales, steady-state assumptions, and radiochemical tracers

NASA Astrophysics Data System (ADS)

DeMaster, D. J.; Liu, J. P.; Eidam, E.; Nittrouer, C. A.; Nguyen, T. T.

2017-09-01

Thirty-two kasten cores, collected from the proximal Mekong continental shelf, have been analyzed for their excess 210Pb distributions in an effort to establish rates of sediment accumulation over the past 100 years. The length of the cores varied from 0.5 to 3 m, and stations sampled topset, foreset, and bottomset beds (water depths 7-21 m). Apparent excess 210Pb sediment accumulation rates ranged from > 10 cm/y (no down-core decrease of excess activity over 300 cm core length) near the Song Hau river mouth, to 1-3 cm/y in topset and foreset beds within 20-50 km of the river mouth, to rates as low as 0.4 cm/y in cores from bottomset beds. The 210Pb sediment accumulation rates yield an overall sediment burial rate of 6.1 × 1013 g/y for the proximal deltaic deposits, which corresponds to 43% of the total modern Mekong sediment burial on the southern Vietnam shelf (1.4 × 1014 g/y; based on our 210Pb and seismic data and 210Pb data from the literature). This shelf burial rate is in reasonable agreement with current long-term estimates of Mekong River sediment discharge (1.3-1.6 × 1014 g/y) from the literature. The inventory of excess 210Pb in the proximal Mekong deltaic deposits indicates that the shoreward flow of offshore water (entrained during river/ocean mixing) is approximately twice the flow of the Mekong freshwater discharge. Organic-carbon 14C ages were measured on 10 cores from the proximal Mekong delta and compared to 210Pb sediment accumulation rates in the same core. The 210Pb accumulation rates in all 10 cores were considered to be more robust and accurate than the 14C geochronologies, primarily because of down-core variations in the source of organic carbon deposited on the seafloor (old terrestrial carbon versus younger marine carbon). Variations in the source of organic carbon accumulating in the seabed were resolved by measuring the δ13C value of the seabed organic carbon.

The effect of mining on the sediment - trace element geochemistry of cores from the Cheyenne River arm of Lake Oahe, South Dakota, U.S.A.

USGS Publications Warehouse

Horowitz, A.J.; Elrick, K.A.; Callender, E.

1988-01-01

Six cores, ranging in length from 1 to 2 m, were collected in the Cheyenne River arm of Lake Oahe, South Dakota, to investigate potential impacts from gold-mining operations around Lead, South Dakota. Sedimentation rates in the river arm appear to be event-dominated and rapid, on the order of 6-7 cm yr.-1. All the chemical concentrations in the core samples fall within the wide ranges previously reported for the Pierre Shale of Cretaceous age and with the exception of As, generally are similar to bed sediment levels in the Cheyenne River, Lake Oahe and Foster Bay. Based on the downcore distribution of Mn, it appears that reducing conditions exist in the sediment column of the river arm below 2-3 cm. The reducing conditions do not appear to be severe enough to produce differentiation of Fe and Mn throughout the sediment column in the river arm. Cross-correlations for high-level metal-bearing strata within the sediment column can be made for several strata and for several cores; however, cross-correlations for all the high-level metal-bearing strata are not feasible. As is the only element which appears enriched in the core samples compared to surface sediment levels. Well-crystallized arsenopyrite was found in high-As bearing strata from two cores and probably was transported in that form from reducing sediment-storage sites in the banks or floodplains of Whitewood Creek and the Belle Fourche River. It has not oxidized due to the reducing conditions in the sediment column of the Cheyenne River arm. Some As may also be transported in association with Fe- and Mn-oxides and -hydroxides, remobilized under the reducing conditions in the river arm, and then reprecipitated in authigenic sulfide phases. In either case, the As appears to be relatively immobile in the sediment column. ?? 1988.

Identifying heavy metal levels in historical flood water deposits using sediment cores.

PubMed

Lintern, Anna; Leahy, Paul J; Heijnis, Henk; Zawadzki, Atun; Gadd, Patricia; Jacobsen, Geraldine; Deletic, Ana; Mccarthy, David T

2016-11-15

When designing mitigation and restoration strategies for aquatic systems affected by heavy metal contamination, we must first understand the sources of these pollutants. In this study, we introduce a methodology that identifies the heavy metal levels in floodplain lake sediments deposited by one source; fluvial floods. This is done by comparing sediment core heavy metal profiles (i.e., historical pollution trends) to physical and chemical properties of sediments in these cores (i.e., historical flooding trends). This methodology is applied to Willsmere and Bolin Billabongs, two urban floodplain lakes (billabongs) of the Yarra River (South-East Australia). Both billabongs are periodically inundated by flooding of the Yarra River and one billabong (Willsmere Billabong) is connected to an urban stormwater drainage network. 1-2-m long sediment cores (containing sediment deposits up to 500 years old) were taken from the billabongs and analysed for heavy metal concentrations (arsenic, chromium, copper, lead, nickel, zinc). In cores from both billabongs, arsenic concentrations are high in the flood-borne sediments. In Bolin Billabong, absolute metal levels are similar in flood and non-flood deposits. In Willsmere Billabong, absolute copper, lead and zinc levels were generally lower in fluvial flood-borne sediments in the core compared to non-fluvial sediments. This suggests that heavy metal concentrations in Bolin Billabong sediments are relatively similar regardless of whether or not fluvial flooding is occurring. However for Willsmere Billabong, heavy metal concentrations are high when overland runoff, direct urban stormwater discharges or atmospheric deposition is occurring. As such, reducing the heavy metal concentrations in these transport pathways will be of great importance when trying to reduce heavy metal concentrations in Willsmere Billabong sediments. This study presents a proof-of-concept that can be applied to other polluted aquatic systems, to understand the importance of river floods in the contamination of the bed sediments of aquatic systems. As a cost effective and less time consuming alternative to extensive field monitoring, our proposed method can be used to identify the key sources of pollution and therefore support the development of effective management strategies. Copyright © 2016 Elsevier Ltd. All rights reserved.

A sample-freezing drive shoe for a wire line piston core sampler

USGS Publications Warehouse

Murphy, F.; Herkelrath, W.N.

1996-01-01

Loss of fluids and samples during retrieval of cores of saturated, noncohesive sediments results in incorrect measures of fluid distributions and an inaccurate measure of the stratigraphic position of the sample. To reduce these errors, we developed a hollow drive shoe that freezes in place the lowest 3 inches (75 mm) of a 1.88-inch-diameter (48 mm), 5-foot-long (1.5 m) sediment sample taken using a commercial wire line piston core sampler. The end of the core is frozen by piping liquid carbon dioxide at ambient temperature through a steel tube from a bottle at the land surface to the drive shoe where it evaporates and expands, cooling the interior surface of the shoe to about -109??F (-78??C). Freezing a core end takes about 10 minutes. The device was used to collect samples for a study of oil-water-air distributions, and for studies of water chemistry and microbial activity in unconsolidated sediments at the site of an oil spill near Bemidji, Minnesota. Before freezing was employed, samples of sandy sediments from near the water table sometimes flowed out of the core barrel as the sampler was withdrawn. Freezing the bottom of the core allowed for the retention of all material that entered the core barrel and lessened the redistribution of fluids within the core. The device is useful in the unsaturated and shallow saturated zones, but does not freeze cores well at depths greater than about 20 feet (6 m) below water, possibly because the feed tube plugs with dry ice with increased exhaust back-pressure, or because sediment enters the annulus between the core barrel and the core barrel liner and blocks the exhaust.

Fluid Pressure in the Shallow Plate Interface at the Nankai Trough Subduction Zone

NASA Astrophysics Data System (ADS)

Tobin, H. J.; Saffer, D.

2003-12-01

The factors controlling the occurrence, magnitude, and other characteristics of great earthquakes is a fundamental outstanding question in fault physics. Pore fluid pressure is perhaps the most critical yet poorly known parameter governing the strength and seismogenic character of plate boundary faults, but unfortunately cannot be directly inferred through available geophysical sensing methods. Moreover, true in situ fluid pressure has proven difficult to measure even in boreholes. At the Nankai Trough, several hundred meters of sediment are subducted beneath the frontal portion of the accretionary prism. The up-dip portion of the plate interface is therefore hosted in these fine-grained marine sedimentary rocks. ODP Leg 190 and 196 showed that these rapidly-loaded underthrust sediments are significantly overpressured near the deformation front. Here, we attempt to quantitatively infer porosity, pore pressure, and effective normal stress at the plate interface at depths currently inaccessible to drilling. Using seismic reflection interval velocity calibrated at the boreholes to porosity, we quantitatively infer pore pressure to ˜ 20 km down-dip of the deformation front, to a plate interface depth of ˜ 6 km. We have developed a Nankai-specific velocity-porosity transform using ODP cores and logs. We use this function to derive a porosity profile for each of two down-dip seismic sections extracted from a 3-D dataset from the Cape Muroto region. We then calculate pore fluid pressure and effective vertical (fault-normal) stress for the underthrust sediment section using a compaction disequilibrium approach and core-based consolidation test data. Because the pore fluid pressure at the fault interface is likely controlled by that of the top of the underthrust section, this calculation represents a quantitative profile of effective stress and pore pressure at the plate interface. Results show that seismic velocity and porosity increase systematically downdip in the underthrust section, but the increase is suppressed relative to that expected from normally consolidating sediments. The computed pore pressure increases landward from an overpressure ratio (λ * = hydrostatic pressure divided by the lithostatic overburden) of ˜ 0.6 at the deformation front to ˜ 0.77 where sediments have been subducted 15 km. The results of this preliminary analysis suggest that a 3-dimensional mapping of predicted effective normal stress in the seismic data volume is possible.

User Friendly Processing of Sediment CT Data: Software and Application in High Resolution Non-Destructive Sediment Core Data Sets

NASA Astrophysics Data System (ADS)

Reilly, B. T.; Stoner, J. S.; Wiest, J.; Abbott, M. B.; Francus, P.; Lapointe, F.

2015-12-01

Computed Tomography (CT) of sediment cores allow for high resolution images, three dimensional volumes, and down core profiles, generated through the attenuation of X-rays as a function of density and atomic number. When using a medical CT-Scanner, these quantitative data are stored in pixels using the Hounsfield scale, which are relative to the attenuation of X-rays in water and air at standard temperature and pressure. Here we present MATLAB based software specifically designed for sedimentary applications with a user friendly graphical interface to process DICOM files and stitch overlapping CT scans. For visualization, the software allows easy generation of core slice images with grayscale and false color relative to a user defined Hounsfield number range. For comparison to other high resolution non-destructive methods, down core Hounsfield number profiles are extracted using a method robust to coring imperfections, like deformation, bowing, gaps, and gas expansion. We demonstrate the usefulness of this technique with lacustrine sediment cores from the Western United States and Canadian High Arctic, including Fish Lake, Oregon, and Sawtooth Lake, Ellesmere Island. These sites represent two different depositional environments and provide examples for a variety of common coring defects and lithologies. The Hounsfield profiles and images can be used in combination with other high resolution data sets, including sediment magnetic parameters, XRF core scans and many other types of data, to provide unique insights into how lithology influences paleoenvironmental and paleomagnetic records and their interpretations.

3D anatomy of Heinrich Layer 2

NASA Astrophysics Data System (ADS)

van Rooij, D.; Zaazi, N.; Fagel, N.; Boone, M.; Cnudde, V.; Dewanckele, J.; Pirlet, H.; Rohl, U.; Blamart, D.; Henriet, J.-P.; Jacobs, P.; Houbrechts, H.; Duyck, P.; Swennen, R.

2009-04-01

Heinrich Layers are found in the North Atlantic Ocean as well-constrained markers of catastrophic iceberg surges from the Pan-Atlantic ice sheets during the last glacial cycle. Their physical and geochemical characteristics allow for relatively fast diagnostics using the state-of-the-art core scanners such as a Multi-Sensor Core Logger and an XRF core scanner. The nature of these characteristics are predominantly due to the source sediments of the ice-rafted debris (IRD) on the one hand (magnetic susceptibility, color, carbonate content) and the response of the palaeo-environment on the other hand (carbonate content, foraminiferal assemblage). However, changes in (gamma) bulk density of the sediment within a Heinrich Layer cannot solely be explained due to the higher content of IRD. Sediment cores in the Porcupine Seabight (West off Ireland) have shown the presence of Heinrich Events without the diagnostic changes in magnetic susceptibility (MS), suggesting a more drastic change in oceanography which could cause widespread diagenesis on the seabed during Heinrich Events. In order to better understand the physical behavior of a Heinrich Layer, 2 cores were studied taken from the northern Porcupine Seabight by R/V Marion Dufresne campaign MD123 in September 2001. More specifically HL2 was studied since it carries the most typical HL signature. The main anatomical information, with a resolution of 0.5 mm, was obtained by means of medical computed tomography of half-core sections of 50 cm length from the Ghent University Hospital. This information was used for detailed sampling for mineralogy, grainsize measurements and palaeoenvironmental analyses. On one core section, XRF core scanning was performed at a 0.5 cm interval. Higher-resolution information was obtained from five 8 cc subsamples which underwent µCT scanning and cold-cathode luminescence microscopy. The results of this unique approach show a rather surprising 3D view of a Heinrich Layer. As expected, the concentration of ice-rafted debris (commonly referred to as the fraction > 150 µm) increases towards the culmination of HL2, marked by an increase in MS, XRF Ca and the percentage of N. pachyderma s. However, the zone where the density increases is marked by a cloud of fine and highly dense particles surrounding the IRD. It seems as if the fine clayey "background" matrix throughout the core consolidates near the centre of HL2. The same feature has been observed within the µCT samples, where the cold-cathode luminescence microscopy has indicated the presence of zoned dolomites. These dolomites might be the result of a diagenetic process that might explain the elevated density. Moreover, the mineralogical analyses show for a predominant volcanic source for the magnetic susceptibility. Contrastingly, both XRF Fe and Ti show significant decreases near the HL culmination, which calls again for diagenetic alteration of the sediment during or just after the Heinrich Event. At this stage of the research, the mechanisms of these diagenetic processes remain unclear. Nevertheless, these results call for a wider view on the depositional processes of Heinrich Layers and their impact upon the seabed geochemistry.

Compositional Variations of Paleogene and Neogene Tephra From the Northern Izu-Bonin-Mariana Arc

NASA Astrophysics Data System (ADS)

Tepley, F. J., III; Barth, A. P.; Brandl, P. A.; Hickey-Vargas, R.; Jiang, F.; Kanayama, K.; Kusano, Y.; Li, H.; Marsaglia, K. M.; McCarthy, A.; Meffre, S.; Savov, I. P.; Yogodzinski, G. M.

2014-12-01

A primary objective of IODP Expedition 351 was to evaluate arc initiation processes of the Izu-Bonin-Mariana (IBM) volcanic arc and its compositional evolution through time. To this end, a single thick section of sediment overlying oceanic crust was cored in the Amami Sankaku Basin where a complete sediment record of arc inception and evolution is preserved. This sediment record includes ash and pyroclasts, deposited in fore-arc, arc, and back-arc settings, likely associated with both the ~49-25 Ma emergent IBM volcanic arc and the evolving Ryukyu-Kyushu volcanic arc. Our goal was to assess the major element evolution of the nascent and evolving IBM system using the temporally constrained record of the early and developing system. In all, more than 100 ash and tuff layers, and pyroclastic fragments were selected from temporally resolved portions of the core, and from representative fractions of the overall core ("core catcher"). The samples were prepared to determine major and minor element compositions via electron microprobe analyses. This ash and pyroclast record will allow us to 1) resolve the Paleogene evolutionary history of the northern IBM arc in greater detail; 2) determine compositional variations of this portion of the IBM arc through time; 3) compare the acquired data to an extensive whole rock and tephra dataset from other segments of the IBM arc; 4) test hypotheses of northern IBM arc evolution and the involvement of different source reservoirs; and 5) mark important stratigraphic markers associated with the Neogene volcanic history of the adjacent evolving Ryukyu-Kyushu arc.

Uncertainties in historical pollution data from sedimentary records from an Australian urban floodplain lake

NASA Astrophysics Data System (ADS)

Lintern, A.; Leahy, P.; Deletic, A.; Heijnis, H.; Zawadzki, A.; Gadd, P.; McCarthy, D.

2018-05-01

Sediment cores from aquatic environments can provide valuable information about historical pollution levels and sources. However, there is little understanding of the uncertainties associated with these findings. The aim of this study is to fill this knowledge gap by proposing a framework for quantifying the uncertainties in historical heavy metal pollution records reconstructed from sediment cores. This uncertainty framework consists of six sources of uncertainty: uncertainties in (1) metals analysis methods, (2) spatial variability of sediment core heavy metal profiles, (3) sub-sampling intervals, (4) the sediment chronology, (5) the assumption that metal levels in bed sediments reflect the magnitude of metal inputs into the aquatic system, and (6) post-depositional transformation of metals. We apply this uncertainty framework to an urban floodplain lake in South-East Australia (Willsmere Billabong). We find that for this site, uncertainties in historical dated heavy metal profiles can be up to 176%, largely due to uncertainties in the sediment chronology, and in the assumption that the settled heavy metal mass is equivalent to the heavy metal mass entering the aquatic system. As such, we recommend that future studies reconstructing historical pollution records using sediment cores from aquatic systems undertake an investigation of the uncertainties in the reconstructed pollution record, using the uncertainty framework provided in this study. We envisage that quantifying and understanding the uncertainties associated with the reconstructed pollution records will facilitate the practical application of sediment core heavy metal profiles in environmental management projects.

n-Alkanes in sediments from the Yellow River Estuary, China: Occurrence, sources and historical sedimentary record.

PubMed

Wang, Shanshan; Liu, Guijian; Yuan, Zijiao; Da, Chunnian

2018-04-15

A total of 21 surface sediments from the Yellow River Estuary (YRE) and a sediment core from the abandoned Old Yellow River Estuary (OYRE) were analyzed for n-alkanes using gas chromatography-mass spectrometry (GC-MS). n-Alkanes in the range C 12 -C 33 and C 13 -C 34 were identified in the surface sediments and the core, respectively. The homologous series were mainly bimodal distribution pattern without odd/even predominance in the YRE and OYRE. The total n-alkanes concentrations in the surface sediments ranged from 0.356 to 0.572mg/kg, with a mean of 0.434mg/kg on dry wt. Evaluation of n-alkanes proxies indicated that the aliphatic hydrocarbons in the surface sediments were derived mainly from a petrogenic source with a relatively low contribution of submerged/floating macrophytes, terrestrial and emergent plants. The dated core covered the time period 1925-2012 and the mean sedimentation rate was ca. 0.5cm/yr. The total n-alkanes concentrations in the core ranged from 0.0394 to 0.941mg/kg, with a mean of 0.180mg/kg. The temporal evolution of n-alkanes reflected the historical input of aliphatic hydrocarbons and was consistent with local and regional anthropogenic activity. In general, the investigation on the sediment core revealed a trend of regional environmental change and the role of anthropogenic activity in environmental change. Copyright © 2017 Elsevier Inc. All rights reserved.

Trends in chemical concentration in sediment cores from three lakes in New Jersey and one lake on Long Island, New York

USGS Publications Warehouse

Long, Gary R.; Ayers, Mark A.; Callender, Edward; Van Metre, Peter C.

2003-01-01

Data from this study indicate that changes in population, land use, and chemical use in the urbanized watersheds over the period of sedimentary record have contributed to upward trends in concentrations of trace elements and hydrophobic organic compounds. Although downward trends were observed for some constituents in the years after their concentrations peaked, concentrations of most constituents in urban lake cores were higher in the most recently deposited sediments than at the base of each respective core and in the reference lake cores. Similar trends in concentrations of these constituents have been observed in sediment cores from other urban lakes across the United States.

Fault architecture and deformation processes within poorly lithified rift sediments, Central Greece

NASA Astrophysics Data System (ADS)

Loveless, Sian; Bense, Victor; Turner, Jenni

2011-11-01

Deformation mechanisms and resultant fault architecture are primary controls on the permeability of faults in poorly lithified sediments. We characterise fault architecture using outcrop studies, hand samples, thin sections and grain-size data from a minor (1-10 m displacement) normal-fault array exposed within Gulf of Corinth rift sediments, Central Greece. These faults are dominated by mixed zones with poorly developed fault cores and damage zones. In poorly lithified sediment deformation is distributed across the mixed zone as beds are entrained and smeared. We find particulate flow aided by limited distributed cataclasis to be the primary deformation mechanism. Deformation may be localised in more competent sediments. Stratigraphic variations in sediment competency, and the subsequent alternating distributed and localised strain causes complexities within the mixed zone such as undeformed blocks or lenses of cohesive sediment, or asperities at the mixed zone/protolith boundary. Fault tip bifurcation and asperity removal are important processes in the evolution of these fault zones. Our results indicate that fault zone architecture and thus permeability is controlled by a range of factors including lithology, stratigraphy, cementation history and fault evolution, and that minor faults in poorly lithified sediment may significantly impact subsurface fluid flow.

Historical trends of polycyclic aromatic hydrocarbons in the reservoir sediment core at Osaka

NASA Astrophysics Data System (ADS)

Moriwaki, Hiroshi; Katahira, Kenshi; Yamamoto, Osamu; Fukuyama, Joji; Kamiura, Toshikazu; Yamazaki, Hideo; Yoshikawa, Shusaku

The historical trends of polycyclic aromatic hydrocarbons (PAHs) in the sediment core of the moat in Osaka Castle, located at the center of Osaka city, Japan, were studied. The moats in Osaka Castle were built in the 1620s, and the undisturbed sediment core, which consists of atmospheric deposits in Osaka city from 1671 to 1976, was withdrawn from the moat. PAHs in the sediment core were identified and quantified in the total concentration range of 0.053-26 mg kg -1 dry wt. The highest content of PAHs was found in the sample, which was dated to 1944 during World War II. Osaka Castle was exposed to intense bombing raids during World War II, and the spiked peak of the PAH concentration during the mid-1940s was due to the air attacks. The total PAH concentration in the sediment core sample during World War II was about two-fold greater than the average after the war. This study made it appear that the largest impact of PAHs on the atmospheric environment in Osaka city in almost 300 years was caused by modern warfare.

The impacts of tracer selection and corrections for organic matter and particle size on the results of quantitative sediment fingerprinting. A case study from the Nene basin, UK.

NASA Astrophysics Data System (ADS)

Pulley, Simon; Ian, Foster; Paula, Antunes

2014-05-01

In recent years, sediment fingerprinting methodologies have gained widespread adoption when tracing sediment provenance in geomorphological research. A wide variety of tracers have been employed in the published literature, with corrections for particle size and organic matter applied when the researcher judged them necessary. This paper aims to explore the errors associated with tracer use by a comparison of fingerprinting results obtained using fallout and lithogenic radionuclides, geochemical, and mineral magnetic tracers in a range of environments located in the Nene basin, UK. Specifically, fingerprinting was undertaken on lake, reservoir and floodplain sediment cores, on actively transported suspended sediment and on overbank and channel bed sediment deposits. Tracer groups were investigated both alone and in combination to determine the differences between their sediment provenance predictions and potential causes of these differences. Additionally, simple organic and particle size corrections were applied to determine if they improve the agreement between the tracer group predictions. Key results showed that when fingerprinting contributions from channel banks to actively transported or recently deposited sediments the tracer group predictions varied by 24% on average. These differences could not be clearly attributed to changes in the sediment during erosion or transport. Instead, the most likely cause of differences was the pre-existing spatial variability in tracer concentrations within sediment sources, combined with highly localised erosion. This resulted in the collected sediment source samples not being representative of the actual sediment sources. Average differences in provenance predictions between the different tracer groups in lake, reservoir and floodplain sediment cores were lowest in the reservoir core at 19% and highest in some floodplain cores, with differences in predictions in excess of 50%. In these latter samples organic enrichment of the sediment, selective transport of fine particles and post-depositional chemical changes to the sediment were determined to be the likely cause of the differences. It was determined that organic and particle size corrections made the differences between tracer groups larger in most cases, although differences between tracer group predictions were reduced in two of the four floodplain cores.

Late Holocene sedimentation in coastal areas of the northwestern Ross Sea (Antarctica)

NASA Astrophysics Data System (ADS)

Colizza, Ester; Finocchiaro, Furio; Kuhn, Gerhard; Langone, Leonardo; Melis, Romana; Mezgec, Karin; Severi, Mirko; Traversi, Rita; Udisti, Roberto; Stenni, Barbara; Braida, Martina

2013-04-01

Sediment cores and box cores collected in two coastal areas of the northwestern Ross Sea (Antarctica) highlight the possibility of studying the Late Holocene period in detail. In this work we propose a study on two box cores and two gravity cores collected in the Cape Hallett and Wood Bay areas during the 2005 PNRA oceanographic cruise. The two sites are feed by Eastern Antarctic Ice Shelf (EAIS) and previous studies have highlighted a complex postglacial sedimentary sequence, also influenced by local morphology. This study is performed within the framework of the PNRA-ESF PolarCLIMATE HOLOCLIP (Holocene climate variability at high-southern latitudes: an integrated perspective) Project. The data set includes: magnetic susceptibility, X-ray analyses, 210Pb, 14C dating, diatoms and foraminifera assemblages, organic carbon, and grain-size analyses. Furthermore XRF core scanner analyses, colour analysis from digital images, and major, minor and trace element concentration analyses (ICP-AES) are performed. Data show that the box core and upper core sediments represent a very recent sedimentation in which it is possible to observe the parameter variability probably linked to climate variability/changes: these variation will be compared with isotopic record form ice cores collected form the same Antarctic sector.

Bacteria in deep coastal plain sediments of Maryland: A possible source of CO2 to groundwater

NASA Astrophysics Data System (ADS)

Chapelle, Francis H.; Zelibor, Joseph L., Jr.; Grimes, D. Jay; Knobel, Leroy L.

1987-08-01

Nineteen cores of unconsolidated Coastal Plain sediments obtained from depths of 14 to 182 m below land surface near Waldorf, Maryland, were collected and examined for metabolically active bacteria. The age of the sediments cored range from Miocene to Early Cretaceous. Acridine orange direct counts of total (viable and nonviable) bacteria in core subsamples ranged from 108 to 104 bacteria/g of dry sediment. Direct counts of viable bacteria ranged from 106 to 103 bacteria/g of dry sediment. Three cores contained viable methanogenic bacteria, and seven cores contained viable sulfate-reducing bacteria. The observed presence of bacteria in these sediments suggest that heterotrophic bacterial metabolism, with lignitic organic material as the primary substrate, is a plausible source of CO2 to groundwater. However, the possibility that abiotic processes also produce CO2 cannot be ruled out. Estimated rates of CO2 production in the noncalcareous Magothy/Upper Patapsco and Lower Patapsco aquifers based on mass balance of dissolved inorganic carbon, groundwater flow rates, and flow path segment lengths are in the range 10-3 to 10-5 mmol L-1 yr-1. Isotope balance calculations suggest that aquifer-generated CO2 is much heavier isotopically (˜—10 to + 5 per mil) than lignite (˜-24 per mil) present in these sediments. This may reflect isotopic fractionation during methanogenesis and possibly other bacterially mediated processes.

Late Pliocene age control and composite depths at ODP Site 982, revisited

NASA Astrophysics Data System (ADS)

Khélifi, N.; Sarnthein, M.; Naafs, B. D. A.

2011-05-01

Ocean Drilling Program (ODP) Site 982 provided a key sediment section at Rockall Plateau for reconstructing northeast Atlantic paleoceanography and monitoring benthic δ18O stratigraphy over the Late Pliocene to Quaternary onset of major Northern Hemisphere Glaciation. A renewed hole-specific inspection of magnetostratigraphic events and the addition of epibenthic δ18O records for short Pliocene sections in holes 982A, B, and C, crossing core breaks in the δ18O record published for Hole 982B, now imply a major revision of composite core depths. After tuning to the orbitally tuned reference record LR04 the new composite δ18O record results in a hiatus, where the Kaena magnetic event might been lost, and in a significant age reduction for all proxy records by 130 to 20 ka over the time span 3.2-2.7 million yr ago (Ma). Our study demonstrates the significance of reliable composite-depth scales and δ18O stratigraphies in ODP sediment records for ocean-wide correlations in paleoceanography and makes Late Pliocene trends found at Site 982 much better comparable to those published from elsewhere in the North Atlantic.

Multivariate analysis of heavy metal contamination using river sediment cores of Nankan River, northern Taiwan

NASA Astrophysics Data System (ADS)

Lee, An-Sheng; Lu, Wei-Li; Huang, Jyh-Jaan; Chang, Queenie; Wei, Kuo-Yen; Lin, Chin-Jung; Liou, Sofia Ya Hsuan

2016-04-01

Through the geology and climate characteristic in Taiwan, generally rivers carry a lot of suspended particles. After these particles settled, they become sediments which are good sorbent for heavy metals in river system. Consequently, sediments can be found recording contamination footprint at low flow energy region, such as estuary. Seven sediment cores were collected along Nankan River, northern Taiwan, which is seriously contaminated by factory, household and agriculture input. Physico-chemical properties of these cores were derived from Itrax-XRF Core Scanner and grain size analysis. In order to interpret these complex data matrices, the multivariate statistical techniques (cluster analysis, factor analysis and discriminant analysis) were introduced to this study. Through the statistical determination, the result indicates four types of sediment. One of them represents contamination event which shows high concentration of Cu, Zn, Pb, Ni and Fe, and low concentration of Si and Zr. Furthermore, three possible contamination sources of this type of sediment were revealed by Factor Analysis. The combination of sediment analysis and multivariate statistical techniques used provides new insights into the contamination depositional history of Nankan River and could be similarly applied to other river systems to determine the scale of anthropogenic contamination.

A method for estimation of historic contaminant loads using dated sediment cores

EPA Science Inventory

Dated sediment cores were used to assess the history of contaminant loads. The contaminant selected must be one that is not significantly remobilized by post depositional processes such as diagenesis. In addition, the core must be from an area with a high deposition rate and litt...

St. Petersburg Coastal and Marine Science Center's Core Archive Portal

USGS Publications Warehouse

Reich, Chris; Streubert, Matt; Dwyer, Brendan; Godbout, Meg; Muslic, Adis; Umberger, Dan

2012-01-01

This Web site contains information on rock cores archived at the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center (SPCMSC). Archived cores consist of 3- to 4-inch-diameter coral cores, 1- to 2-inch-diameter rock cores, and a few unlabeled loose coral and rock samples. This document - and specifically the archive Web site portal - is intended to be a 'living' document that will be updated continually as additional cores are collected and archived. This document may also contain future references and links to a catalog of sediment cores. Sediment cores will include vibracores, pushcores, and other loose sediment samples collected for research purposes. This document will: (1) serve as a database for locating core material currently archived at the USGS SPCMSC facility; (2) provide a protocol for entry of new core material into the archive system; and, (3) set the procedures necessary for checking out core material for scientific purposes. Core material may be loaned to other governmental agencies, academia, or non-governmental organizations at the discretion of the USGS SPCMSC curator.

Multi-proxy dating of Holocene maar lakes and Pleistocene dry maar sediments in the Eifel, Germany

NASA Astrophysics Data System (ADS)

Sirocko, Frank; Dietrich, Stephan; Veres, Daniel; Grootes, Pieter M.; Schaber-Mohr, Katja; Seelos, Klemens; Nadeau, Marie-Josée; Kromer, Bernd; Rothacker, Leo; Röhner, Marieke; Krbetschek, Matthias; Appleby, Peter; Hambach, Ulrich; Rolf, Christian; Sudo, Masafumi; Grim, Stephanie

2013-02-01

During the last twelve years the ELSA Project (Eifel Laminated Sediment Archive) at Mainz University has drilled a total of about 52 cores from 27 maar lakes and filled-in maar basins in the Eifel/Germany. Dating has been completed for the Holocene cores using 6 different methods (210Pb and 137Cs activities, palynostratigraphy, event markers, varve counting, 14C). In general, the different methods consistently complement one another within error margins. Event correlation was used for relating typical lithological changes with historically known events such as the two major Holocene flood events at 1342 AD and ca 800 BC. Dating of MIS2-MIS3 core sections is based on greyscale tuning, radiocarbon and OSL dating, magnetostratigraphy and tephrochronology. The lithological changes in the sediment cores demonstrate a sequence of events similar to the North Atlantic rapid climate variability of the Last Glacial Cycle. The warmest of the MIS3 interstadials was GI14, when a forest with abundant spruce covered the Eifel area from 55 to 48 ka BP, i.e. during a time when also other climate archives in Europe suggested very warm conditions. The forest of this "Early Stage 3 warm phase" developed subsequently into a steppe with scattered birch and pine, and finally into a glacial desert at around 25 ka BP. Evidence for Mono Lake and Laschamp geomagnetic excursions is found in two long cores. Several large eruptions during Middle and Late Pleistocene (Ulmener Maar - 11,000 varve years BP, Laacher See - 12,900 varve years BP, Mosenberg volcanoes/Meerfelder Maar 41-45 cal ka BP, Dümpel Maar 116 ka BP, Glees Maar - 151 ka BP) produced distinct ash-layers crucial for inter-core and inter-site correlations. The oldest investigated maar of the Eifel is 40Ar/39Ar dated to the time older than 520 ka BP.

A Long Pleistocene Paleoclimate Record from Stoneman Lake, Arizona

NASA Astrophysics Data System (ADS)

Fawcett, P. J.; Anderson, R. S.; Brown, E. T.; Werne, J. P.; Jimenez-Moreno, G.; Toney, J. L.; Garcia, D.; Garrett, H. L.; Dunbar, N. W.

2015-12-01

Long continuous lake sediment cores provide enormous potential for interpreting climate change. In the American Southwest, long records are revolutionizing our understanding of megadroughts, which have occurred in the past and will most certainly occur in the future with rapidly changing climate. One site with the potential to study ancient megadroughts is Stoneman Lake, central Arizona, whose basin is a circular depression formed by a collapse in late Tertiary volcanics. The lake is spring fed, most recently alternating between a marsh and a lake, with water levels having fluctuated by > 3 meters over the last 25 years. Its small closed drainage basin (ca. 2.5 km2) with one small inflowing stream is key to the sensitivity of the record. Two parallel lacustrine sediment cores (70 m and 30 m deep) were recovered in October of 2014. Our preliminary chronology includes 8 AMS dates in the upper 7 m and two distinct tephras at 30.8 m depth and 36.3 m depth. Radiocarbon dates show a 2.7-m-thick Holocene section, and then a low Pleistocene SAR with an age of 11,000 cal yr B.P. at ~2.8 m to an age of 46,500 cal yr B.P. at 4.2 m depth. We estimate that the 70-m deep hole will provide a climate record back to ~1.3 million years ago. Of particular interest are the interglacials that serve as good analogs for future climate including MIS 11 and MIS 19. Initial core description includes MS, bulk density and high-resolution images. Holocene sediments are characterized by massive, dark organic rich silty clays with no distinct lamination. Sediments from the Last Glacial Maximum are well-laminated, light brown silty clays with few organics present. The distinctive laminations probably represent a very deep lake and therefore a wet cold climate, also verified by pollen data. There are several repeated intervals of laminated sediments deeper in the core that may represent older glacial maxima. Future work will include detailed pollen, plant macrofossil and charcoal analysis, scanning XRF, TOC and carbon isotopic analyses as well as compound specific carbon and hydrogen work.

Ultra-high-resolution paleoenvironmental records via direct laser-based analysis of lipid biomarkers in sediment core samples

PubMed Central

Wörmer, Lars; Elvert, Marcus; Fuchser, Jens; Lipp, Julius Sebastian; Buttigieg, Pier Luigi; Zabel, Matthias; Hinrichs, Kai-Uwe

2014-01-01

Marine microorganisms adapt to their habitat by structural modification of their membrane lipids. This concept is the basis of numerous molecular proxies used for paleoenvironmental reconstruction. Archaeal tetraether lipids from ubiquitous marine planktonic archaea are particularly abundant, well preserved in the sedimentary record and used in several molecular proxies. We here introduce the direct, extraction-free analysis of these compounds in intact sediment core sections using laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LDI FTICR-MS can detect the target lipids in single submillimeter-sized spots on sediment sections, equivalent to a sample mass in the nanogram range, and could thus pave the way for biomarker-based reconstruction of past environments and ecosystems at subannual to decadal resolution. We demonstrate that ratios of selected archaeal tetraethers acquired by LDI FTICR-MS are highly correlated with values obtained by conventional liquid chromatography/MS protocols. The ratio of the major archaeal lipids, caldarchaeol and crenarchaeol, analyzed in a 6.2-cm intact section of Mediterranean sapropel S1 at 250-µm resolution (∼4-y temporal resolution), provides an unprecedented view of the fine-scale patchiness of sedimentary biomarker distributions and the processes involved in proxy signal formation. Temporal variations of this lipid ratio indicate a strong influence of the ∼200-y de Vries solar cycle on reconstructed sea surface temperatures with possible amplitudes of several degrees, and suggest signal amplification by a complex interplay of ecological and environmental factors. Laser-based biomarker analysis of geological samples has the potential to revolutionize molecular stratigraphic studies of paleoenvironments. PMID:25331871

A ground penetrating radar investigation of a glacial-marine ice- contact delta, Pineo Ridge, eastern coastal Maine

USGS Publications Warehouse

Tary, A.K.; Duncan, M. FitzGerald; Weddle, T.K.

2007-01-01

In eastern coastal Maine, many flat-topped landforms, often identified as glacial-marine deltas, are cultivated for blueberry production. These agriculturally valuable features are not exploited for aggregate resources, severely limiting stratigraphic exposure. Coring is often forbidden; where permissible, coarse-grained surficial sediments make coring and sediment retrieval difficult. Ground penetrating radar (GPR) has become an invaluable tool in an ongoing study of the otherwise inaccessible subsurface morphology in this region and provides a means of detailing the large-scale sedimentary structures comprising these features. GPR studies allow us to reassess previous depositional interpretations and to develop alternative developmental models. The work presented here focuses on Pineo Ridge, a large, flat-topped ice-marginal glacial-marine delta complex with a strong linear trend and two distinct landform zones, informally termed East Pineo and West Pineo. Previous workers have described each zone separately due to local morphological variation. Our GPR work further substantiates this geomorphic differentiation. East Pineo developed as a series of deltaic lobes prograding southward from an ice-contact margin during the local marine highstand. GPR data do not suggest postdepositional modification by ice-margin re-advance. We suggest that West Pineo has a more complex, two-stage depositional history. The southern section of the feature consists of southward-prograding deltaic lobes deposited during retreat of the Laurentide ice margin, with later erosional modification during marine regression. The northern section of West Pineo formed as a series of northward-prograd- ing deltaic lobes as sediment-laden meltwater may have been diverted by the existing deposits of the southern section of West Pineo. ?? 2007 The Geological Society of America. All rights reserved.

Water-quality trends using sediment cores from White Rock Lake, Dallas, Texas

USGS Publications Warehouse

Van Metre, Peter C.; Land, Larry F.; Braun, C.L.

1996-01-01

The purpose of this fact sheet is to summarize the principal findings documented in a report on water-quality trends in White Rock Creek Basin using dated sediment cores from White Rock Lake (Van Metre and Callender, in press). The study used dated sediment cores to reconstruct water-quality conditions. More specifically, the changes in water quality associated with the watershed’s change from agricultural to urban land use and with the implementation of environmental regulations were identified.

Geomorphology-based interpretation of sedimentation rates from radiodating, lower Passaic River, New Jersey, USA.

PubMed

Erickson, Michael J; Barnes, Charles R; Henderson, Matthew R; Romagnoli, Robert; Firstenberg, Clifford E

2007-04-01

Analysis of site geomorphology and sedimentation rates as an indicator of long-term bed stability is central to the evaluation of remedial alternatives for depositional aquatic environments. In conjunction with various investigations of contaminant distribution, sediment dynamics, and bed stability in the Passaic River Estuary, 121 sediment cores were collected in the early 1990s from the lower 9.7 km of the Passaic River and analyzed for lead-210 (210Pb), cesium-137 (137Cs), and other analytes. This paper opportunistically uses the extensive radiochemical dataset to examine the spatial patterns of long-term sedimentation rates in, and associated geomorphic aspects of, this area of the river. For the purposes of computing sedimentation rates, the utility of the 210Pb and 137Cs depositional profiles was assessed to inform appropriate interpretation. Sedimentation rates were computed for 90 datable cores by 3 different methods, depending on profile utility. A sedimentation rate of 0 was assigned to 17 additional cores that were not datable and for which evidence of no deposition exists. Sedimentation patterns were assessed by grouping results within similar geomorphic areas, delineated through inspection of bathymetric data. On the basis of channel morphology, results reflect expected patterns, with the highest sedimentation rates observed along point bars and channel margins. The lowest rates of sedimentation (and the largest percentage of undatable cores) were observed in the areas along the outer banks of channel bends. Increasing sedimentation rates from upstream to downstream were noted. Average and median sedimentation rates were estimated to be 3.8 and 3.7 cm/y, respectively, reflecting the highly depositional nature of the Passaic River estuary. This finding is consistent with published descriptions of long-term geomorphology for Atlantic Coastal Plain estuaries.

Are lake sediments mere archives of degraded organic matter? - evidence of rapid biotic changes tracked in sediments of pre-alpine Lake Lunz, Austria

NASA Astrophysics Data System (ADS)

Hollaus, Lisa-Maria; Khan, Samiullah; Schelker, Jakob; Ejarque, Elisabet; Battin, Tom; Kainz, Martin

2016-04-01

Lake sediments are used as sentinels of changes in organic matter composition and dynamics within lakes and their catchments. In an effort to investigate how past and recent hydrological extreme events have affected organic matter composition in lake sediments, we investigated the biogeochemical composition of sediment cores and settling particles, using sediment traps in the pre-alpine, oligotrophic Lake Lunz, Austria. We assessed annual sedimentation rates using 137Cs and 210Pb, time integrated loads of settling particles, analyze stable carbon (δ13C) and nitrogen (δ15N) isotopes to track changes of carbon sources and trophic compositions, respectively, and use source-specific fatty acids as indicators of allochthonous, bacterial, and algal-derived organic matter. Preliminary results indicate that settling particles of Lake Lunz (33 m depth) contain high algae-derived organic matter, as assessed by long-chain polyunsaturated fatty acids (LC-PUFA), indicating low degradation of such labile organic matter within the water column of this lake. However, LC-PUFA decreased rapidly in sediment cores below the sediment-water interface. Concentrations of phosphorous remained stable throughout the sediment cores (40 cm), suggesting that past changes in climatic forcing did not alter the load of this limiting nutrient in lakes. Ongoing work reveals dramatic biotic changes within the top layers of the sediment cores as evidenced by high numbers of small-bodied cladocerans (e.g., Bosmina) and large-bodied zooplankton (e.g., Daphnia) are only detected at lower sediment layers. Current research on these lake sediments is aimed at investigating how organic matter sources changed during the past century as a result of recorded weather changes.

Autigenic and Anthropogenic Uranium in the Marine Sediments of the Gulf of California in Front of Santa Rosalia Mining District

NASA Astrophysics Data System (ADS)

Choumiline, K.; Rodríguez-Figueroa, G.; Shumilin, E.; Sapozhnikov, D.

2007-05-01

To verify the possibilities of U enrichments in the marine sedimentary environment of the eastern sector of the central Gulf of Califoria (GC), eleven sediment cores were collected in front of the Santa Rosalia mining region, peninsula of Baja California. Uranium and some other trace element contents in sliced core layers, dried and homogenized, were determined using instrumental neutron activation analysis. Average total U contents in sediments of five cores collected in the open GC in front of Santa Rosalía at sites with water depths from 265 m to 1030 m and in the Guaymas Basin with 2019 m, ranged from 1.36±0.26 mg kg-1 (Guaymas Basin) to 9.31±3.03 mg kg-1 (SR63 core, depth 630 m). To distinguish non-lithogenic U from the lithogenic one, the normalization of total U contents to the concentrations of Sc in the samples was used. That because this element is a reliable indicator of crustal materials, mainly aluminosilicates in the marine sediments. The relative contribution of non-lithogenic (authigenic) U varied from 49.8±3 % (Guaymas Basin) to 84.2±8.2 % (SR62 core) of the total U content in the sediments of the open central GC. Surprisingly, in three sediment cores from the coastal zone adjacent to the town of Santa Rosalía in water depth range 3-6 m very high concentrations of total U were found, ranging from 54.2±7.3 mg kg-1 (SR4 core) to 110±13 mg kg-1 (SR2 core) and exceeding not only U average abundance in the earth´s crust (2.7 mg kg-1), but also its levels found for SR62 core, as well as those reported for natural enrichments of U in suboxic-anoxic environments, e.g. at Mexico and Peru margin sites (3.04 mg kg-1 - 24.54 mg kg-1, McManus et al., 2006). The relative contribution of non-lithogenic U in the sediments of these three anomalous cores varied from 97.2±0.4 % (SR4 core) to 98.80.2 % (SR1 and SR2 cores) of their total U content. The sediments were also depleted in organic C (0.05 % - 0.18 %), which is not typical for marine solid phases enriched in authigenic U. Additional surface sampling around the cores with high levels of U, helped to define the spatial distribution of this element, as well as Co, Cu, Zn, light lanthanides and europium, which also showed "anomalies". The association with anthropogenic impact is discussed because the geochemical fingerprints of these sediments are the same as for solid wastes of copper smelting, which has occurred in Santa Rosalía in the past century till 1984.

Polycyclic aromatic hydrocarbons (PAHs) in the water column and sediment core of Deep Bay, South China

NASA Astrophysics Data System (ADS)

Qiu, Yao-Wen; Zhang, Gan; Liu, Guo-Qing; Guo, Ling-Li; Li, Xiang-Dong; Wai, Onyx

2009-06-01

The levels of 15 polycyclic aromatic hydrocarbons (PAHs) were determined in seawater, suspended particulate matter (SPM), surface sediment and core sediment samples of Deep Bay, South China. The average concentrations Σ 15PAHs were 69.4 ± 24.7 ng l -1 in seawater, 429.1 ± 231.8 ng g -1 in SPM, and 353.8 ± 128.1 ng g -1 dry weight in surface sediment, respectively. Higher PAH concentrations were observed in SPM than in surface sediment. Temporal trend of PAH concentrations in core sediment generally increased from 1948 to 2004, with higher concentrations in top than in sub-surface, implying a stronger recent input of PAHs owing to the rapid economic development in Shenzhen. Compared with historical data, the PAH levels in surface sediment has increased, and this was further confirmed by the increasing trend of PAHs in the core sediment. Phenanthrene, fluoranthene and pyrene dominated in the PAH composition pattern profiles in the Bay. Compositional pattern analysis suggested that PAHs in the Deep Bay were derived from both pyrogenic and petrogenic sources, and diesel oil leakage, river runoff and air deposition may serve as important pathways for PAHs input to the Bay. Significant positive correlations between partition coefficient in surface sediment to that in water ( KOC) of PAH and their octanol/water partition coefficients ( KOW) were observed, suggesting that KOC of PAHs in sediment/water of Deep Bay may be predicted by the corresponding KOW.

Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment.

PubMed

Wurzbacher, Christian; Fuchs, Andrea; Attermeyer, Katrin; Frindte, Katharina; Grossart, Hans-Peter; Hupfer, Michael; Casper, Peter; Monaghan, Michael T

2017-04-08

Lake sediments harbor diverse microbial communities that cycle carbon and nutrients while being constantly colonized and potentially buried by organic matter sinking from the water column. The interaction of activity and burial remained largely unexplored in aquatic sediments. We aimed to relate taxonomic composition to sediment biogeochemical parameters, test whether community turnover with depth resulted from taxonomic replacement or from richness effects, and to provide a basic model for the vertical community structure in sediments. We analyzed four replicate sediment cores taken from 30-m depth in oligo-mesotrophic Lake Stechlin in northern Germany. Each 30-cm core spanned ca. 170 years of sediment accumulation according to 137 Cs dating and was sectioned into layers 1-4 cm thick. We examined a full suite of biogeochemical parameters and used DNA metabarcoding to examine community composition of microbial Archaea, Bacteria, and Eukaryota. Community β-diversity indicated nearly complete turnover within the uppermost 30 cm. We observed a pronounced shift from Eukaryota- and Bacteria-dominated upper layers (<5 cm) to Bacteria-dominated intermediate layers (5-14 cm) and to deep layers (>14 cm) dominated by enigmatic Archaea that typically occur in deep-sea sediments. Taxonomic replacement was the prevalent mechanism in structuring the community composition and was linked to parameters indicative of microbial activity (e.g., CO 2 and CH 4 concentration, bacterial protein production). Richness loss played a lesser role but was linked to conservative parameters (e.g., C, N, P) indicative of past conditions. By including all three domains, we were able to directly link the exponential decay of eukaryotes with the active sediment microbial community. The dominance of Archaea in deeper layers confirms earlier findings from marine systems and establishes freshwater sediments as a potential low-energy environment, similar to deep sea sediments. We propose a general model of sediment structure and function based on microbial characteristics and burial processes. An upper "replacement horizon" is dominated by rapid taxonomic turnover with depth, high microbial activity, and biotic interactions. A lower "depauperate horizon" is characterized by low taxonomic richness, more stable "low-energy" conditions, and a dominance of enigmatic Archaea.

High Resolution Measurements In U-Channel Technique And Implications For Sedimentological Purposes

NASA Astrophysics Data System (ADS)

Acar, Dursun; Cagatay, Namık; Sarı, Erol; Eris, Kadir; Biltekin, Demet; Akcer, Sena; Meydan Gokdere, Feray; Makaroglu, Ozlem; Bulkan, Ozlem; Arslan, Tugce; Albut, Gulum; Yalamaz, Burak; Yakupoglu, Nurettin; Sabuncu, Asen; Fillikci, Betul; Yıldız, Guliz

2016-04-01

Mechanical features in-stu drilling for sediment cores and vacuum forces that affect while obtaining the sediments to the core tube are formed concave shaped deformations. Even in the half sections, concave deformation form still appears. During MCSL measurements, Laminae which forms concave shaped deformation, show interference thus, values indicate overall results for several laminae instead of single lamina. These interferenced data is not appropriate for paleoceanography studies which require extend accuracy and high frequency data set to describe geochemical and climatological effects in high resolution. U-Channel technique provides accurate location and isolated values for each lamina. In EMCOL Laboratories, U-channel provide well saturated and air-free environment for samples and, by using these technique U-channels are prepared with modificated MCSL for data acquisition. Even below millimeter scale sampling rate provides the separation of each lamina and, physical properties of every each lamina. Cover of u-channel is made by homogenous plastic in shape of rectangular prism geometry. Thus, during measurement, MSCL sensors may harm the sediment; however u-channel covers the sediment from this unwanted deformation from MSCL itself. U-channel technique can present micro scale angular changes in the laminae. Measurements that have been taken from U-channel are compared with the traditional half core measurements. Interestingly, accuracy of the positions for each lamina is much more detailed and, the resolution is progressively higher. Results from P Wave and Gamma ray density provide removed interference effects on each lamina. In this technique, it is high recommended that U-channel widens the resolution of core logging and generates more cleansed measurements in MCSL. For P- Wave Used Synthetic seismograms that modelled by MSCL data set which created from U-channel technique dictates each anomalies related with climatological and geological changes. Keywords: u channel , P-Wave, Gamma Ray Density, High resolution measurements, Data accuracy

Geochemical Dataset of the Rhone River Delta (Lake Geneva) Sediments - Disentangling Human Impacts from Climate Change

NASA Astrophysics Data System (ADS)

Silva, T. A.; Girardclos, S.; Loizeau, J. L.

2016-12-01

Lake sediment records are often the most complete continental archives. In the last 200 years, in addition to climatic variability, humans have strongly impacted lake watersheds around the world. During the 20th century the Rhone River and its watershed upstream Lake Geneva (Switzerland/France) have been subject to river channelization, dam construction, water flow regulation, water and sediment abstraction as well as various land use changes. Under the scope of the SEDFATE project (Swiss National Science Foundation nº147689) we address human and climatic impact on the sediment transfer from the Rhone River watershed to Lake Geneva. Nineteen short sediment cores were collected in the Rhone River delta area in May 2014. Cores have been scanned with MSCL and XRF, sub-sampled every 1cm and 8 cores were dated by radiometric methods (137Cs and 210Pb). Photographs taken right after core opening were used for lithological description and in addition to MSCL data were used to correlate cores. Core dating shows that mass accumulation rates decreased in the 1964-1986 interval and then increased again in the interval between 1986-2014. XRF elements and ratios, known to indicate detrital sources (Al, Al/Si, Fe, K, Mn, Rb, Si, Ti, Ti/Ca), show that clastic input diminished from 1964 to 1986 and re-increased to the present. Other elemental (Zr/Rb, Zr/K, Si/Ti) and geophysical data (magnetic susceptibility) combined with lithology identify density flow deposits vs hemipelagic sedimentation. Changes in frequency of these event deposits indicate changes in the sedimentation patterns in the Rhone River sublacustrine delta during the last century. From these results we hypothesize that a significant sediment amount was abstracted from the system after the major dam constructions in the 1950's and that, since the 1990's, a contrary signal is due to increased sediment loads that follows glacial melting due to global warming.

Paleomagnetism of late Quaternary drift sediments off the west Antarctica Peninsula

NASA Astrophysics Data System (ADS)

Channell, J. E. T.; Xuan, C.; Hillenbrand, C. D.; Larter, R. D.

2016-12-01

Natural remanant magnetization of a series of piston cores (typically 10 m in lengtth) collected during the JR298 Expedition (January-March 2015) to the west Antarctica Peninsula shows well-defined magnetic components (maximum angular deviations 1°-3°) that potentially record paleomagnetic changes at high southern latitudes. Rock magnetic experiments on the sediments conducted at room and high (up to 700°C) temperatures demonstrate the presence of a low- and a high-coercivity component (mean coercivity of 50-60 mT and 130-140 mT respectively). Paleomagnetic directions from the piston cores are primarily carried by the low-coercivity detrital (titano)magnetite, and are affected by authigenic growth of the high-coercivity maghemite. Maghematization in these sediments is attributed to the low concentrations of labile organic matter and lack of sulfate reduction in an extended oxic zone not penetrated by the piston cores. Despite the varying degree of maghematization, some of the recovered cores yield relative paleointensity (RPI) records that can be matched to a reference RPI record constructed mainly from North Atlantic cores. The resulting age models yield mean sedimentation rates of 4-12 cm/kyr for the JR298 piston cores. RPI may serve as a stratigraphic tool to date sediment cores from the region where traditional isotope stratigraphy is challenging due to the rarity of foraminiferal carbonate.

A Holocene record of endogenic iron and manganese precipitation, isotopic composition of endogenic carbonate, and vegetation history in a lake-fen complex in northwestern Minnesota

USGS Publications Warehouse

Dean, Walter E.; Doner, Lisa A.

2011-01-01

Little Shingobee Lake and Fen are part of an extensive network of lakes and wetlands in the Shingobee River headwaters area of northwestern Minnesota. Prior to about 9800 radiocarbon years, most of the lakes in the Shingobee watershed area were interconnected to form glacial Lake Willobee. From 9800 to 7700 radiocarbon years, the level of Lake Willobee fell as a result of breaching of a dam, leaving small separated basins containing the existing lakes and wetlands. The dominant components in the sediments in a 9-meter core from Little Shingobee Lake (LSL-B), and lacustrine sediments under 3.3 meters of peat in a 17-meter core from Little Shingobee Fen (LSF-10) are detrital clastic material, endogenic CaCO3, and organic matter. The detrital fraction in the Holocene section in core LSL-B varies considerably from 7 weight percent to 82 weight percent and closely parallels the concentration of detrital quartz measured by X-ray diffraction. The CaCO3 concentration, which also varies considerably from 10 weight percent to 70 weight percent, is generally antithetic to the detrital concentration owing to the dilution of detrital material by CaCO3, particularly during the early to middle Holocene (about 9000-6500 calendar years). The organic-matter content varies from 5 weight percent to 25 weight percent and, together with CaCO3, serves to dilute the allogenic detrital fraction. In both cores almost all of the iron (Fe) and manganese (Mn) is in endogenic minerals, presumed to be oxyhydroxide minerals, that are important components throughout the core; little Fe and Mn are contributed by detrital aluminosilicate minerals. The endogenic Fe mineral, calculated as Fe(OH)3, forms a larger percentage of the sediment than endogenic organic material throughout most of the Holocene section in the LSL-B core and in the lacustrine sediments below the peat in the LSF-10 core. Biogenic silica as opal (biopal; diatom debris) was not measured, but the average calculated biopal is 5 percent in the LSL-B core and 15.5 percent in the LSF-10 core. Values of delta18O in mollusk (Pisidium) and ostracode shells increase by only about 20 per mil from the bottom to the top of the LSL-B core (about 12600-2200 calendar years). The remarkably constant oxygen-isotope composition throughout the Holocene suggests that environmental conditions affecting values of delta18O (temperature, salinity, composition of the water, composition of precipitation) did not change greatly. Values of delta13C in carbonate shells generally decreased by about 2 per mil from 9000 calendar years to 6000 calendar years, but they did not increase in organic carbon. This mid-Holocene increase in delta13C in shells but not in organic carbon is likely due to an increase in residence time. A late Pleistocene forest dominated by spruce was replaced in the early Holocene by a pine forest. The pine forest migrated east during the middle Holocene and was replaced by an open sagebrush-oak savanna. The western migration of forests into northwestern Minnesota is marked first by a hardwood forest and finally a pine forest.

Sedimentological and geochemical record of submarine mine tailing footprint in Repparfjorden (Northern Norway)

NASA Astrophysics Data System (ADS)

Sternal, Beata; Junttila, Juho; Pedersen, Kristine Bondo; Skirbekk, Kari; Forwick, Matthias; Carroll, JoLynn

2016-04-01

The knowledge on understanding the physical, chemical and biological processes dominating in marine system affected by submarine tailings disposal (STD) remains limited and further knowledge to make reliable long-term predictions of future environmental impacts is needed. One way of contributing to this is by investigation of marine environments already affected by the tailings discharge in the past. We present preliminary results from a multidisciplinary study of marine sediments from Repparfjorden in northern Norway, a fjord that was influenced by the deposition of tailings from a copper mine during the 1970's. The study is a part of the competence cluster Environmental Waste Management (EWMA) that as one of its important aims has advancing the knowledge of spreading of mine-tailing related contaminants. Here we give particular attention to the reconstruction of sedimentation style, rate of sediment accumulation, as well as potential sediment transport paths (contaminants dispersion). Seventeen short cores (up to 21 cm long) were retrieved from sites covering the entire area of Repparfjorden. The cores were sliced into 1-cm intervals that are and will be analysed for grain-size, concentration of heavy metals and total organic carbon content of bulk sediment. Sediment chronologies are and will be derived using 210Pb and 137Cs dating techniques. An approximately 7-cm thick interval which is different from present fjord sedimentation was observed below c. 10 cm depth in three of the cores retrieved from the area of tailings deposition in the 1970's. Sediments of this discrete depth interval are mainly composed of mud or sandy mud with bimodal grain-size distribution (first mode: medium silt fraction; second mode: very coarse silt). They are characterised by very high Cu concentrations (>250 mg/kg). Preliminary measurements of the 210Pb activity indicate an increase in sediment accumulation rate during the deposition of this interval. Therefore, we interpret it to be mainly composed of mine tailing sediments. As this sediment interval was only observed in 3 of 17 cores, we suggest that the lateral extent of the tailings is restricted to a relatively small area of the fjord. However, elevated concentrations of Cu (40-80 mg/kg) were also detected in a discrete sediment interval (3-10 cm) in one core ˜3 km beyond the tailing deposition site. In addition, high Cu concentrations (60-190 mg/kg) in sediments between the seafloor and the tailing deposit, as well as some centimetres below the deposit (in all cores from the old tailing deposition site) suggest possible dispersion of Cu to the immediate surrounding sediments in the cores.

Lake Chad sedimentation and environments during the late Miocene and Pliocene: New evidence from mineralogy and chemistry of the Bol core sediments

NASA Astrophysics Data System (ADS)

Moussa, Abderamane; Novello, Alice; Lebatard, Anne-Elisabeth; Decarreau, Alain; Fontaine, Claude; Barboni, Doris; Sylvestre, Florence; Bourlès, Didier L.; Paillès, Christine; Buchet, Guillaume; Duringer, Philippe; Ghienne, Jean-François; Maley, Jean; Mazur, Jean-Charles; Roquin, Claude; Schuster, Mathieu; Vignaud, Patrick; Brunet, Michel

2016-06-01

This study presents mineralogical and geochemical data from a borehole drilled near the locality of Bol (13°27‧N, 14°44‧E), in the eastern archipelago of the modern Lake Chad (Chad). Samples were taken from a ∼200 m long core section forming a unique sub-continuous record for Central Africa. Among these samples, 25 are dated between 6.4 and 2.4 Ma. Dominant minerals are clays (66% average) mixed with varying amounts of silt and diatomite. The clay fraction consists of Fe-beidellite (87% average), kaolinite, and traces of illite. Clay minerals originate from the erosion of the vertisols that surrounded the paleolake Chad. Sedimentological data indicate that a permanent lake (or recurrent lakes) existed from 6.7 until 2.4 Ma in the vicinity of Bol. By comparison with modern latitudinal distribution of vertisols in Africa the climate was Sudanian-like. Changes in the sedimentation rate suggest a succession of wetter and dryer periods during at least six million years in the region during the critical time period covering the Miocene-Pliocene transition.

Evidence of Historical Mining Impacts on Saltmarshes from east Cornwall, UK

NASA Astrophysics Data System (ADS)

Iurian, Andra-Rada; Taylor, Alex; Millward, Geoff; Blake, William

2016-04-01

In landscapes with extensive mining history, saltmarshes can become sinks for contaminants that are vulnerable to release with sea-level rise and increased storminess. Given the prolonged residence time of heavy metals in the environment, data is urgently required to contextualise the impacts of past and present mining and pollution events and provide a baseline against which to assess Water Framework Directive (WFD) (2000/60/EC) compliance within an integrated catchment management framework. The geology of east Cornwall, UK (with intrusions of granite into the surrounding sedimentary rocks) was favourable for a prosperous mining industry, although large scale operations did not start until about 1830. Tin, cooper, lead and tungsten were the most important ores in the region. In order to quantify the spatial and temporal extent of contamination from past mining, sediment cores were collected from three saltmarshes, namely: Antony Marsh and Treluggan Marsh on the Lower Basin of River Lynher, and Port Eliot Marsh on the Lower Basin of River Tiddy. Core sections at 1 cm intervals were analysed by gamma-ray spectrometry for Pb-210, Ra-226, Cs-137 and Am-241, and the well-established Constant Rate of Supply (CRS) model was employed to derive Pb-210 geochronology with bomb-derived Cs-137 and Am-241 as independent chronological markers. The geochronological data provided the sedimentary accumulation and temporal context for the study. In terms of sediment quality with respect to mining pollution, core sections were analysed using Q-ICP-MS techniques and, additionally, WD-XRF instrumentation at Plymouth University. Measurements were performed for target elements that are normally associated with mining and smelting activities (e.g. Pb, Cu, Sn, Zn, Cr, Cd, etc.), and lithogenic elements (e.g. Fe, Al, Ti) that allow enrichment factors for the anthropogenically-derived elements to be determined. The grain size distribution was determined to identify storminess events and to detect discontinuities in the sediment record. Downcore trends in metal pollutants are discussed in the context of the chronological data, sediment composition and historic meteorological and river flow records. Acknowledgements: Andra-Rada Iurian acknowledges the support of a Marie Curie Fellowship (H2020-MSCA-IF-2014, Grant Agreement number: 658863) within the Horizon 2020.

Surface (sea floor) and near-surface (box cores) sediment mineralogy in Baffin Bay as a key to sediment provenance and ice sheet variations

USGS Publications Warehouse

Andrews, John T.; Eberl, D.D.

2011-01-01

To better understand the glacial history of the ice sheets surrounding Baffin Bay and to provide information on sediment pathways, samples from 82 seafloor grabs and core tops, and from seven box cores were subjected to quantitative X-ray diffraction weight percent (wt.%) analysis of the 2000 m) all show an abrupt drop in calcite wt.% (post-5 cal ka BP?) following a major peak in detrital carbonate (mainly dolomite). This dolomite-rich detrital carbonate (DC) event in JR175BC06 is possibly coeval with the Younger Dryas cold event. Four possible glacial-sourced end members were employed in a compositional unmixing algorithm to gain insight into down core changes in sediment provenance at the deep central basin. Estimates of the rates of sediment accumulation in the central basin are only in the range of 2 to 4 cm/cal ka, surprisingly low given the glaciated nature of the surrounding land.

Sediment Coring of the Proglacial Lake Donguz-Orun (northern Caucasus, Russia)

NASA Astrophysics Data System (ADS)

Alexandrin, Mikhail; Solomina, Olga; Kalugin, Ivan; Darin, Andrey; Nesje, Atle

2014-05-01

So far, no high-resolution reconstructions of climate and glacier variations based on lake sediment properties are available in Caucasus Mountains. In other presently glaciated regions this approach is proved to be very useful for this purpose (e.g. Nesje et al., 2001, 2011; Bakke, 2005, Nesje, 2009) In this paper we report the first results of the sediment coring of Donguz-Orun Lake (N 43°13'26", E 42°29'35") situated in the upper reaches of Donguz-Orun-Kyol, a tributary of Baksan river in the Elbrus region of Northern Caucasus, a typical proglacial lake dammed by a lateral moraine deposited by the Donguz-Orun Glacier. It is a drainage lake with several inflowing glacial streams and effluent river Donguz-Orun. The surface area is around 105 000 m2 with a water volume of 465 000m3. The average water depth is around 4.5 m, with a maximum water depth of 14 m. The deepest part is found close to the moraine dam in the narrow northern part of the lake. This is normally consistent with this type of glacial lake systems. An intensive gravitational drift of the moraine material towards the lake is observed. These non-rounded moraine boulders constitute a significant part of the lakebed. Lacustrine sediments are present though. The coring campaign from Institute of Geography, Russian Academy of Sciences (August 2012) used a modified piston corer with a 110 mm-diameter plastic tube (Nesje, 1992) mounted on the inflatable catamaran to obtain lake sediments from Lake Donguz-Orun. A 28-cm long core was retrieved from a water depth of around 7 m. The sediments consist of regularly laminated, fine beige clay, with several interlayers of sand. The coring process appeared to be challenging due to the stiffness of clay, which led to extreme bending of the sediment layers in the basal part of the core. The original thickness of the sediments was obviously higher than observed in the core. In order to clarify the recent history of the Donguz-Orun glacier, we used lichenometry and dendrochronology for dating its lateral and terminal moraines. The upper part of the core (0-170 mm) was scanned applying X-ray fluorescent microanalysis using synchrotron radiation and sampled for dating using 137Cs and 210Pb. The assumption that the sediment stratification represents annual layering (spring flood) is generally confirmed with correlation of the Rb/Sr-ratio (that supposedly marks grain-size variations in the sediments) curve and the image of the sediment core. Calculations of Rb/Sr peaks or visual layers yield an accumulation rate of around 2 mm/yr. Analogous results (1.73 mm/yr) are derived from 137Cs-dating. With this high accumulation rate, the sediment core of Lake Donguz-Orun represents an important source of information for high-resolution reconstructions of climatic parameters and glacier variations of the region. The research project of Mikhail Alexandrin is supported by grant# 227470/F11 issued by The Research Council of Norway.

Geochemical data for mercury, methylmercury, and other constituents in sediments from Englebright Lake, California, 2002

USGS Publications Warehouse

Alpers, Charles N.; Hunerlach, Michael P.; Marvin-DePasquale, Mark C.; Antweiler, Ronald C.; Lasorsa, Brenda K.; De Wild, John F.; Snyder, Noah P.

2006-01-01

Deep coring penetrated the full thickness of material deposited after 1940 at six locations in the reservoir; the cores reached a maximum depth of 32.8 meters below the reservoir floor. At the three deep coring sites closest to Englebright Dam, concentrations of HgT (dry basis) were consistently in the range of 100 to 500 ng/g (nanogram per gram), in sediment dominantly of silt size (median grain size of 0.004 to 0.063 mm [millimeter]). At the deep coring sites located farther upstream, the upper parts of the profile had lower concentrations of HgT, generally ranging from 2 to 100 ng/g, in sediment dominantly of sand size (median grain size from 0.063 to 2 mm). The lower part of the vertical profiles at three upstream coring sites had higher concentrations of HgT than the upper and middle parts of these profiles, and had finer median grain size. The highest median concentration of MeHg (1.1 ng/g) was in the top 2 cm (centimeter) of the shallow box cores. This vertical interval also had the highest value of the ratio of MeHg to HgT, 0.41 percent. Median concentrations of MeHg and median values of MeHg/HgT decreased systematically with depth from 0-4 to 4-8 to 8-12 cm in the shallow cores. However, similar systematic decreases were not observed at the meter scale in the deep cores of the MEM (MEthylMercury) series. The overall median of the ratio MeHg/HgT in the deep cores was 0.25 percent, not much less than the overall median value for the shallow cores (0.33 percent). Mercury-203 radiotracer divalent inorganic mercury (203Hg(II)) was used to determine microbial mercury-methylation potential rates for 11 samples collected from three reservoir locations and various depths in the sediment profile. For the five shallow mercury-methylation subsamples, ancillary geochemical parameters were assayed, including microbial sulfate reduction rates, sulfur speciation (sediment acid volatile sulfide, total reduced sulfur, and pore-water sulfate), iron speciation (sediment acid extractable iron(II), amorphous iron(III), crystalline iron(III) and pore-water iron(II)), pore-water chloride and dissolved organic carbon, and pH, oxidation-reduction potential (Eh) and whole-sediment organic content. The highest potential rates of microbial mercury methylation were measured in shallow (0 to 8 cm depth) sediments (5 to 30 nanograms of mercury per gram dry sediment per day), whereas potential rates for subsamples collected from depths greater than 500 cm were consistently below the detection limit of the radiotracer method (< 0.02 nanogram of mercury per gram dry sediment per day). Chemical analyses of trace and major elements in bed sediment are presented for 202 samples from deep cores from five locations in Englebright Lake. The mean values and standard deviations for selected trace elements were as follows (in micrograms per gram): antimony, 2.4 ? 1.6; arsenic, 69 ? 48; chromium, 134 ? 23; lead, 33 ? 25; and nickel, 87 ? 24. Concentrated samples of heavy-mineral grains, prepared using nine large-volume composite samples from

Mineralogical and Geochemical Analyses of Antarctic Lake Sediments: A Reflectance and Moessbauer Spectroscopy Study with Applications for Remote Sensing on Mars

NASA Technical Reports Server (NTRS)

Froeschl, Heinz; Lougear, Andre; Trautwein, Alfred X.; Newton, Jason; Doran, Peter T.; Koerner, Wilfried; Koeberl, Christian; Bishop, Janice (Technical Monitor); DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

Lakebottom sediments from the Dry Valleys region of Antarctica have been analyzed here in order to study the influence of water chemistry on the mineralogy and geochemistry of these sediments, as well as to evaluate techniques for remote spectral identification of potential biomarker minerals on Mars. Lakes from the Dry Valleys region of Antarctica have been investigated as possible analogs for extinct lake environments on early Mars. Sediment cores were collected in the present study from perennially ice-covered Lake Hoare in the Taylor Valley. These sediments were taken from a core in an oxic region of the lake and another core in an anoxic zone. Differences between the two cores were observed in the sediment color, Fe(II)/Fe(III) ratio, the presence of pyrite, the abundance of Fe, S and some trace elements, and the C, N and S isotope fractionation patterns. The results of visible-infrared reflectance spectroscopy (0.3-25 microns) Mossbauer spectroscopy (77 and 4 K) and X-ray diffraction are combined to determine the mineralogy and composition of these samples. The sediments are dominated by plagioclase, K-feldspar, quartz and pyroxene. Algal mats grow on the bottom of the lake and organic material has been found throughout the cores. Calcite is abundant in some layers of the aerobic core (shallow region) and pyrite is abundant in some layers of the anaerobic core (deep region). Analysis of the spectroscopic features due to organics and carbonates with respect to the abundance of organic C and carbonate contents was performed in order to select optimal spectral bands for remote identification of these components in planetary regoliths. Carbonate bands near 4 and 6.8 microns (approx.2500 and 1500/cm) were detected for carbonate abundances as low as 0.1 wt.% CO2. Organic features at 3.38, 3.42 and 3.51 microns (2960, 2925 and 2850/cm) were detected for organic C abundances as low as 0.06 wt.% C. The d13C trends show a more complex organic history for the anaerobic sediments than for the aerobic sediments. The biogenic pyrite found in the anaerobic core is associated with lighter d34S values and high organic C levels and could be used as a biomarker mineral for paleolakes on Mars.

Sedimentation and chronology of heavy metal pollution in Oslo harbor, Norway.

PubMed

Lepland, Aivo; Andersen, Thorbjørn J; Lepland, Aave; Arp, Hans Peter H; Alve, Elisabeth; Breedveld, Gijs D; Rindby, Anders

2010-09-01

Stratigraphic profiles of Cu, Cd and Hg in ten sediment cores from the Oslo harbor, Norway, combined with results of radiometric dating demonstrate that pollution by these metals peaked between 1940 and 1970. Dating results indicate that Hg discharges peaked between 1940 and 1950, Cd reached maximum ca. 1955-1960, and Cu has the highest concentration in sediment interval corresponding to ca. 1970. Geochemical profiles and maxima of Cu, Cd and Hg concentrations can be used as chronostratigraphic markers for sediment cores from the Oslo harbor. Acoustic backscatter and sediment core data indicate that propeller wash affects the seabed in the Oslo harbor. The propeller-induced turbulence causes erosion, and in places exposes and remobilizes contaminated sediments that accumulated in the harbor during previous decades. Such re-exposure of contaminated sediments could be detrimental to local ecosystems and offset remediation efforts, warranting further impact studies and potential mitigation strategies to prevent redistribution. Copyright 2010 Elsevier Ltd. All rights reserved.

A new high-resolution sediment record from Lake Gościąż (central Poland)

NASA Astrophysics Data System (ADS)

Bonk, Alicja; Błaszkiewicz, Mirosław; Brauer, Achim; Brykała, Dariusz; Gierszewski, Piotr; Kramkowski, Mateusz; Plessen, Brigit; Schwab, Markus; Słowiński, Michał; Tjallingii, Rik

2017-04-01

The varved sediments from Lake Gościąż, located in the Vistula Valley in Central Poland, are an iconic record for palaeoclimate and palaeoenvironmental reconstruction (Goslar et al. 2000, Hajdas et al. 1995, Ralska-Jasiewiczowa et al. 1998). Recently, we obtained a set of new sediment cores from Lake Gościąż and established a 21 m long sediment profile. Except of the topmost part of the core, it is continuously laminated down to glacial sands. We aim at applying a comprehensive multi-proxy core analyses combined with monitoring of present-day sedimentation processes. Sediment investigations will include new methods that have been developed or advanced since the previous studies on the Lake Gościąż sediments including continuous micro-facies analyses, μXRF core scanning and tephrochronology. The main aims of our new project are a revision of the existing floating chronology and to synchronise the Lake Gościąż sediment record based on independent isochrones with other European varved lake records like, e.g. Lake Meerfelder Maar, in order to investigate in detail proxy responses to climate change and to decipher regional leads and lags in climate change. Here, we will present (1) the objectives of our new project on this key record of past climate and environmental change and, (2) preliminary results including magnetic susceptibility, μ-XRF core scanning and microfacies images. This study is a contribution to scientific project financed by the National Science Centre, Poland - No DEC-2015/19/B/ST10/03039.

Geochemical assessment of metals and dioxin in sediment from the San Carlos Reservoir and the Gila, San Carlos, and San Francisco Rivers, Arizona

USGS Publications Warehouse

Church, Stan E.; Choate, LaDonna M.; Marot, Marci E.; Fey, David L.; Adams, Monique; Briggs, Paul H.; Brown, Zoe Ann

2005-01-01

In October 2004, we sampled stream-bed sediment, terrace sediment, and sediment from the San Carlos Reservoir to determine the spatial and chronological variation of six potentially toxic metals-Cu, Pb, Zn, Cd, As, and Hg. Water levels in the San Carlos Reservoir were at a 20-year low at an elevation of 2,409 ft (734.3 m). Four cores were taken from the reservoir: one from the San Carlos River arm, one from the Gila River arm, and two from the San Carlos Reservoir just west of the Pinal County line. Radioisotope chronometry (7Be, 137Cs, and 210Pb) conducted on sediment from the reservoir cores provides a good chronological record back to 1959. Chronology prior to that, during the 1950s, is based on our interpretation of the 137Cs anomaly in reservoir cores. During and prior to the 1950s, the reservoir was dry and sediment-accumulation rates were irregular; age control based on radioisotope data was not possible. We recovered sediment at the base of one 4-m-long core that may date back to the late 1930s. The sedimentological record contains two discrete events, one about 1978-83 and one about 1957, where the Cu concentration in reservoir sediment exceeded recommended sediment quality guidelines and should have had an effect on sensitive aquatic and benthic organisms. Concentrations of Zn determined in sediment deposited during the 1957(?) event also exceeded recommended sediment quality guidelines. Concentration data for Cu from the four cores clearly indicate that the source of this material was upstream on the Gila River. Lead isotope data, coupled with the geochemical data from a 2M HCl-1 percent H2O2 leach of selected sediment samples, show two discrete populations of data. One represents the dominant sediment load derived from the Safford Valley, and a second reflects sediment derived from the San Francisco River. The Cu concentration spikes in the reservoir cores have chemical and Pb isotope signatures that indicate that deposits in a porphyry copper deposit from the Morenci district is the likely source of these Cu-rich sedimentary deposits. Copper concentrations and Pb isotope data in premining terrace-sediment deposits indicate that the Cu peaks could not have resulted from erosion of premining sediment from terrace deposits downstream on the Gila River. The chemical and Pb isotope data also indicate that agricultural practices in the Safford Valley have resulted in an increased sediment load to the Gila River since large-scale farming began, prior to the time when the San Carlos Reservoir was built. Analyses of dioxin, which is an impurity in one of the herbicides used in the late 1960s and early 1970s, were completed in sediment from one of the cores in the reservoir to determine whether any of these pesticide residues have accumulated in the reservoir sediment. Dioxin concentration is expressed in terms of its toxicity (toxic equivalent concentration or TEQ). Concentrations of dioxin in the sediment ranged from 0.68 to 1.37 pg/g and are less than any of the benchmark concentrations recommended as threshold values for adverse effects of dioxin in sediment (> 2.5-10 pg/g).

Estimation of a Historic Mercury Load Function for Lake Michigan using Dated Sediment Cores

EPA Science Inventory

Box cores collected between 1994 and 1996 were used to estimate historic mercury loads to Lake Michigan. Based on a kriging spatial interpolation of 54 Pb-210 dated cores, 228 metric tons of mercury are stored in the lake’s sediments (excluding Green Bay). To estimate the time ...

IODP Expedition 351 Izu-Bonin-Mariana Arc Origins: Preliminary Results

NASA Astrophysics Data System (ADS)

Ishizuka, O.; Arculus, R. J.; Bogus, K.

2014-12-01

Understanding how subduction zones initiate and continental crust forms in intraoceanic arcs requires knowledge of the inception and evolution of a representative intraoceanic arc, such as the Izu-Bonin-Mariana (IBM) Arc system. This can be obtained by exploring regions adjacent to an arc, where unequivocal pre-arc crust overlain by undisturbed arc-derived materials exists. IODP Exp. 351 (June-July 2014) specifically targeted evidence for the earliest evolution of the IBM system following inception. Site U1438 (4711 m water depth) is located in the Amami Sankaku Basin (ASB), west of the Kyushu-Palau Ridge (KPR), a paleo-IBM arc. Primary objectives of Exp. 351 were: 1) determine the nature of the crust and mantle pre-existing the IBM arc; 2) identify and model the process of subduction initiation and initial arc crust formation; 3) determine the compositional evolution of the IBM arc during the Paleogene; 4) establish geophysical properties of the ASB. Seismic reflection profiles indicate a ~1.3 km thick sediment layer overlying ~5.5 km thick igneous crust, presumed to be oceanic. This igneous crust seemed likely to be the basement of the IBM arc. Four holes were cored at Site U1438 spanning the entire sediment section and into basement. The cored interval comprises 5 units: uppermost Unit I is hemipelagic sediment with intercalated ash layers, presumably recording explosive volcanism mainly from the Ryukyu and Kyushu arcs; Units II and III host a series of volcaniclastic gravity-flow deposits, likely recording the magmatic history of the IBM Arc from arc initiation until 25 Ma; Siliceous pelagic sediment (Unit IV) underlies these deposits with minimal coarse-grained sediment input and may pre-date arc initiation. Sediment-basement contact occurs at 1461 mbsf. A basaltic lava flow section dominantly composed of plagioclase and clinopyroxene with rare chilled margins continues to the bottom of the Site (1611 mbsf). The expedition successfully recovered pre-IBM Arc basement, a volcanic and geologic record spanning pre-Arc, Arc initiation to remnant Arc stages, which permits testing for subduction initiation and subsequent Arc evolution.

Climate signals in Late Holocene sediments from Maxwell Bay and English Strait (South Shetland Islands, Antarctica)

NASA Astrophysics Data System (ADS)

Hass, H. Christian; Schröder, Simon; Kuhn, Gerhard

2017-04-01

Climate fluctuations of the past two millennia such as the Little Ice Age and the Medieval Warm Period are reported mainly from the Northern Hemisphere. Evidence from Antarctica is comparably sparse and reveals regional and temporal differences, which are particularly evident at the western and eastern sides of the Antarctic Peninsula. High-resolution coastal-marine sediment cores from the northernmost tip of the West Antarctic Peninsula reveal periods dominated by finer sediments between periods that lack the finer sediment component. In Maxwell Bay this fine sediment (grain size mode around 16 µm) has been traced back to sediment related to the occurrence of glacial meltwater. It was found in sheltered places and meltwater creeks of Potter Cove, a small tributary fjord to Maxwell Bay. In the sediment core this sediment occurs predominantly between 600 and 1250 AD (Medieval Warm Period) whereas it is only sparsely affecting the record between 1450 and 1900 AD (Little Ice Age). The temporal pattern is very similar to global-temperature reconstructions and even resembles temperature reconstructions from the Northern Hemisphere. To avoid local effects that may occur in Maxwell Bay more sediment cores were taken from bays and straits further south of King George Island during Cruise PS97 of RV "Polarstern" in 2016. A core from English Strait reveals completely different sedimentary conditions with no detectable meltwater signal (16 µm). However, the mean grain size record resembles that of the cores from Maxwell Bay. The lack of a clear-cut meltwater sediment class as it occurs further north is likely the result of a much smaller hinterland (Greenwich and Robert islands) when compared to Maxwell Bay between Nelson Island and the much bigger King George Island where glaciers and ice sheets discharge large quantities of very turbid meltwater directly into the bay. It is concluded that during the warmer climate periods a large amount of meltwater was released along the NW Antarctic Peninsula. The related plume sediments were distributed downstream to overprint coastal sediments even though the amount was likely not sufficient to produce a discrete sediment class.

Concentration of Antifouling Biocides and Metals in Sediment Core Samples in the Northern Part of Hiroshima Bay

PubMed Central

Tsunemasa, Noritaka; Yamazaki, Hideo

2014-01-01

Accumulation of Ot alternative antifoulants in sediment is the focus of this research. Much research had been done on surface sediment, but in this report, the accumulation in the sediment core was studied. The Ot alternative antifoulants, Diuron, Sea-Nine211, and Irgarol 1051, and the latter’s degradation product, M1, were investigated in five samples from the northern part of Hiroshima Bay. Ot compounds (tributyltin (TBT) and triphenyltin (TPT)) were also investigated for comparison. In addition, metal (Pb, Cu, Zn, Fe and Mn) levels and chronology were measured to better understand what happens after accumulation on the sea floor. It was discovered that Ot alternative antifoulant accumulation characteristics in sediment were like Ot compounds, with the concentration in the sediment core being much higher than surface sediment. The concentration in sediment seems to have been affected by the regulation of Ot compounds in 1990, due to the concentration of Ot alternative antifoulants and Ot compounds at the survey point in front of the dock, showing an increase from almost the same layer after the regulation. PMID:24901529

An automated full waveform logging system for high-resolution P-wave profiles in marine sediments

NASA Astrophysics Data System (ADS)

Breitzke, Monika; Spieβ, Volkhard

1993-11-01

An automated, PC-based logging system has been developed to investigate marine sediment cores by full waveform transmission seismograms. High-resolution P-wave velocity and amplitude attenuation profiles are simultaneously derived from the transmission data to characterize the acoustic properties of the sediment column. A pair of ultrasonic, piezoelectric wheel probes is used to generate and record the transmission signals travelling radially through the sediment core. Both unsplit and split cores are allowed. Mounted in a carriage driven by a stepping motor via a shaft the probes automatically move along the core liner, stopping at equidistant spacings to provide a quasi-continuous inspection of the core by the transmission data. The axial travel distance and the core diameter are determined by digital measuring tools. First arrivals are picked automatically from the transmission seismograms using either a threshold in the seismogram's envelope or a cross-correlation algorithm taking the ‘zero-offset’ signal of both wheel probes into account. Combined with the core diameter these first arrivals lead to a P-wave velocity profile with a relative precision of 1 to 2 m s-1. Simultaneously, the maximum peak-to-peak amplitudes of the transmission seismograms are evaluated to get a first idea on the amplitude attenuation along the sediment core. Two examples of gravity cores taken during a recent cruise of R.V. METEOR in the Western Equatorial Atlantic are presented. They yield that the P-wave profiles can be used for locating strong and fine-scale lithological changes, e.g. turbidite layers and slight variations in the sand, silt or clay content. In addition, the transmission seismograms and their amplitude spectra obviously seem to reveal a correlation between the relative amount of low-frequency spectral components and the sediment grain size, and thus provide a tool for the determination of additional, related physical or sedimentological parameters in future investigations.

Copper and cadmium in bottom sediments dredged from Wyścigi Pond, Warsaw, Poland--contamination and bioaccumulation study.

PubMed

Wojtkowska, Małgorzata; Karwowska, Ewa; Chmielewska, Iwona; Bekenova, Kundyz; Wanot, Ewa

2015-12-01

This research covered an evaluation of the copper and cadmium concentrations in bottom sediments dredged from one of the ponds in Warsaw. The samples of sediments, soil, and plants were analyzed in terms of Cu and Cd content. The research concerned the heap of dredged bottom sediments from Wyścigi Pond, Warsaw, Poland. Two boreholes were made to obtain sediment cores with depths of A 162.5 cm and B 190.0 cm. The cores were divided into 10 sub-samples with a thickness of about 15-20 cm. A control sample of soil was taken from the horse racecourse several hundred meters away from the heap. The vegetation was sampled directly from the heap. The predominating plants were tested: Urtica dioica, Glechoma hederacea, Euonymus verrucosus, and Drepanocladus aduncus. A control sample of U. dioica taken outside of the heap was also tested. The commercial PHYTOTOXKIT microbiotest was applied to evaluate the influence of heavy metal-contaminated sediments (used as soil) on germination and growth of the chosen test plants. The analyses of cadmium and copper concentrations revealed that the metal concentration in sediments was diverse at different depths of sampling, probably reflecting their concentration in stored layers of sediments. Moreover, the metal content in core A was four to five times lower than that in core B, which reveals heterogeneity of the sediments in the tested heap. In core A, the copper concentration ranged from 4.7 to 13.4 mg/kg d.w. (average 8.06 ± 0.71 mg/kg d.w.), while in core B, it ranged from 9.2 to 82.1 mg/kg d.w. (average 38.56 ± 2.6 mg/kg d.w.). One of the results of the heavy metal presence in soils is their bioaccumulation in plants. Comparing plant growth, more intensive growth of roots was observed in the case of plants growing on the control (reference) soil than those growing on sediments. The intensive development of both primary and lateral roots was noticed. During this early growth, metal accumulation in plants occurred.

Fast elemental screening of soil and sediment profiles using small-spot energy-dispersive X-ray fluorescence: application to mining sediments geochemistry.

PubMed

Gonzalez-Fernandez, Oscar; Queralt, Ignacio

2010-09-01

Elemental analysis of different sediment cores originating from the Cartagena-La Union mining district in Spain was carried out by means of a programmable small-spot energy-dispersive X-ray fluorescence (EDXRF) spectrometer to study the distribution of heavy metals along soil profiles. Cores were obtained from upstream sediments of a mining creek, from the lowland sedimentation plain, and from a mining landfill dump (tailings pile). A programmable two-dimensional (2D) stage and a focal spot resolution of 600 μm allow us to obtain complete core mapping. Geochemical results were verified using a more powerful wavelength-dispersion X-ray fluorescence (WDXRF) technique. The data obtained was processed in order to study the statistical correlations within the elemental compositions. The results obtained allow us to observe the differential in-depth distribution of heavy metals among the sampled zones. Dump site cores exhibit a homogeneous distribution of heavy metals, whereas the alluvial plain core shows accumulation of heavy metals in the upper part. This approach can be useful for the fast screening of heavy metals in depositional environments around mining sites.

Geochemical, radiometric, and environmental approaches for the assessment of the intensity and chronology of metal contamination in the sediment cores from Oualidia lagoon (Morocco).

PubMed

Mejjad, Nezha; Laissaoui, Abdelmourhit; El-Hammoumi, Ouafa; Fekri, Ahmed; Amsil, Hamid; El-Yahyaoui, Adil; Benkdad, Azzouz

2018-06-01

The present study evaluates the distribution of metals over the last 100 years in the Oualidia lagoon by examining their concentrations in the sediment cores. The samples were analyzed by instrumental neutron activation analysis and inductively coupled plasma mass spectrometry. Activities of 210 Pb, 226 Ra, and 137 Cs were determined by gamma-ray spectrometry for establishing the age-depth relationships throughout the sediment cores by applying conventional models. The results indicated that the study area is contaminated by As and Cd revealing a detectable anthropogenic input of occurring metals as a consequence of the continuous development of human activities around the lagoon since 1950. The enrichment factor calculated for each layer of the three cores revealed that the studied sediments present no enrichment by Pb, K, and Mn; minor enrichment by Zn, Cr, Co, Cu, V, and Ni; and a moderately to severe enrichment by As and Cd. The pollution load index values increase from the bottom to the top of cores, and ranged from 0.9 to 2.8, which indicates levels of pollutants ranging from background to relatively high concentrations in the investigated sediments.

Composition and depth distribution of hydrocarbons in Barataria Bay marsh sediments after the Deepwater Horizon oil spill.

PubMed

Dincer Kırman, Zeynep; Sericano, José L; Wade, Terry L; Bianchi, Thomas S; Marcantonio, Franco; Kolker, Alexander S

2016-07-01

In 2010, an estimate 4.1 million barrels of oil were accidentally released into the Gulf of Mexico (GoM) during the Deepwater Horizon (DWH) Oil Spill. One and a half years after this incident, a set of subtidal and intertidal marsh sediment cores were collected from five stations in Barataria Bay, Louisiana, USA, and analyzed to determine the spatial and vertical distributions and source of hydrocarbon residues based on their chemical composition. An archived core, collected before the DWH oil spill from the same area, was also analyzed to assess the pre-spill hydrocarbon distribution in the area. Analyses of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs) and stable carbon isotope showed that the distribution of petroleum hydrocarbons in Barataria Bay was patchy and limited in areal extent. Significant TPH and ΣPAH concentrations (77,399 μg/g and 219,065 ng/g, respectively) were detected in the surface sediments of one core (i.e., core A) to a depth of 9 cm. Based on a sedimentation rate of 0.39 cm yr(-1), determined using (137)Cs, the presence of anthropogenic hydrocarbons in these sediment core deposited ca. 50 to 60 years ago. The historical background hydrocarbon concentrations increased significantly at the sediment surface and can be attributed to recent inputs. Although the oil present in the bay's sediments has undergone moderate weathering, biomarker analyses performed on core A samples likely indicated the presence of hydrocarbons from the DWH oil spill. The effects of oiling events on Barataria Bay and other marsh ecosystems in this region remain uncertain, as oil undergoes weathering changes over time. Copyright © 2016 Elsevier Ltd. All rights reserved.

Phosphorus speciation and its bioavailability in sediments of the Jiaozhou Bay

NASA Astrophysics Data System (ADS)

Kang, Xuming; Song, Jinming; Yuan, Huamao; Shi, Xin; Yang, Weifeng; Li, Xuegang; Li, Ning; Duan, Liqin

2017-03-01

Phosphorus (P) is an important macronutrient that can limit primary productivity in coastal marine ecosystems. In this study, four sediment cores were collected in the Jiaozhou Bay to study the phosphorus forms and their bioavailability, including exchangeable or loosely sorbed P (Ex-P), iron-bound P (Fe-P), authigenic P (Ca-P), detrital P (De-P) and organic P (OP), which were separated and quantified using a sequential extraction method (SEDEX). The results showed that the concentration of total P (TP) in core sediments ranged from 6.23 to 10.46 μmol/g, and inorganic P (IP) was the dominated P form. Fe-P and De-P were the main chemical forms of IP in core sediments. The profile variation of OP presented the most significant among the phosphorus forms. Whereas the concentrations of Ex-P, Fe-P, and Ca-P varied slightly with depth, indicating that the transformation of Ex-P, Fe-P, Ca-P, and OP could occur during sedimentary P burial. Moreover, the distribution of P species was influenced by many factors, including terrigenous input, biological processes, organic matter degradation and increasing human activities. High total organic carbon (TOC)/OP ratio occurred in the Jiaozhou Bay, ranging from 73 to 472 (average, 180 ± 81) in core sediments, which was caused by the increasing terrestrial organic matter. The ratio of TOC/Preactive ranged from 24 to 101 (average 46 ± 15) in core sediments (lower than the Redfield ratio), implying a surplus of sedimentary reactive P compared with TOC. Potential bioavailable P (BAP) accounted for about 28.2-60.8% (average, 47.1 ± 7.4%) of TP in core sediments, and presented an increasing trend since 1980s, which might be responsible for the shift of phytoplankton community composition during these decades.

Marsh soils as potential sinks for Bacteroides fecal indicator bacteria, Waccamaw National Wildlife Refuge, Georgetown, SC, USA

USGS Publications Warehouse

Drexler, Judith Z.; Johnson, Heather E.; Duris, Joseph W.; Krauss, Ken W.

2014-01-01

A soil core collected in a tidal freshwater marsh in the Waccamaw National Wildlife Refuge (Georgetown, SC) exuded a particularly strong odor of cow manure upon extrusion. In order to test for manure and determine its provenance, we carried out microbial source tracking using DNA markers for Bacteroides, a noncoliform, anaerobic bacterial group that represents a broad group of the fecal population. Three core sections from 0-3 cm, 9-12 cm and 30-33 were analyzed for the presence of Bacteroides. The ages of core sediments were estimated using 210Pb and 137Cs dating. All three core sections tested positive for Bacteroides DNA markers related to cow or deer feces. Because cow manure is stockpiled, used as fertilizer, and a source of direct contamination in the Great Pee Dee River/Winyah Bay watershed, it is very likely the source of the Bacteroides that was deposited on the marsh. The mid-points of the core sections were dated as follows: 0-3 cm: 2009; 9-12 cm: 1999, and 30-33 cm: 1961. The presence of Bacteroides at different depths/ages in the soil profile indicates that soils in tidal freshwater marshes are, at the least, capable of being short-term sinks for Bacteroides and, may have the potential to be long-term sinks of stable, naturalized populations.

Gas Hydrate Petroleum System Analysis

NASA Astrophysics Data System (ADS)

Collett, T. S.

2012-12-01

In a gas hydrate petroleum system, the individual factors that contribute to the formation of gas hydrate accumulations, such as (1) gas hydrate pressure-temperature stability conditions, (2) gas source, (3) gas migration, and (4) the growth of the gas hydrate in suitable host sediment can identified and quantified. The study of know and inferred gas hydrate accumulations reveal the occurrence of concentrated gas hydrate is mostly controlled by the presence of fractures and/or coarser grained sediments. Field studies have concluded that hydrate grows preferentially in coarse-grained sediments because lower capillary pressures in these sediments permit the migration of gas and nucleation of hydrate. Due to the relatively distal nature of the deep marine geologic settings, the overall abundance of sand within the shallow geologic section is usually low. However, drilling projects in the offshore of Japan, Korea, and in the Gulf of Mexico has revealed the occurrence of significant hydrate-bearing sand reservoirs. The 1999/2000 Japan Nankai Trough drilling confirmed occurrence of hydrate-bearing sand-rich intervals (interpreted as turbidite fan deposits). Gas hydrate was determined to fill the pore spaces in these deposits, reaching saturations up to 80% in some layers. A multi-well drilling program titled "METI Toaki-oki to Kumano-nada" also identified sand-rich reservoirs with pore-filling hydrate. The recovered hydrate-bearing sand layers were described as very-fine- to fine-grained turbidite sand layers measuring from several centimeters up to a meter thick. However, the gross thickness of the hydrate-bearing sand layers were up to 50 m. In 2010, the Republic of Korea conducted the Second Ulleung Basin Gas Hydrate (UBGH2) Drilling Expedition. Seismic data clearly showed the development of a thick, potential basin wide, sedimentary sections characterized by mostly debris flows. The downhole LWD logs and core data from Site UBGH2-5 reveal that each debris flows is characterized by basal silt- to sand-rich clay dominated stratigraphic units. The upper most debris flow at Site UBGH2-5 extends into the overlying gas hydrate stability zone and IR core scans indicate that this section contains some amount of gas hydrate. The UBGH2 LWD and coring program also confirmed the occurrence of numerous volcaniclastic and siliciclastic sand reservoirs that were deposited as part of local to basin-wide turbidite events. Gas hydrate saturations within the turbidite sands ranged between 60-80 percent. In 2009, the Gulf of Mexico (GOM) Joint Industry Project (JIP) drilled seven wells at three sites, finding gas hydrate at high concentration in sands in four wells, with suspected gas hydrate at low to moderate saturations in two other wells. In the northern GOM, high sedimentation rates in conjunction with salt tectonism, has promoted the formation of complex seafloor topography. As a result, coarse-grained deposition can occur as gravity-driven sedimentation traversing the slope within intra-slope "ponded" accommodation spaces.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gardiner, W.W.; Barrows, E.S.; Antrim, L.D

Buttermilk Channel was one of seven waterways that was sampled and evaluated for dredging and sediment disposal. Sediment samples were collected and analyses were conducted on sediment core samples. The evaluation of proposed dredged material from the channel included bulk sediment chemical analyses, chemical analyses of site water and elutriate, water column and benthic acute toxicity tests, and bioaccumulation studies. Individual sediment core samples were analyzed for grain size, moisture content, and total organic carbon. A composite sediment samples, representing the entire area proposed for dredging, was analyzed for bulk density, polynuclear aromatic hydrocarbons, and 1,4-dichlorobenzene. Site water and elutriatemore » were analyzed for metals, pesticides, and PCBs.« less

Inexpensive, easy-to-construct suction coring devices usable from small boats

USGS Publications Warehouse

Onuf, Christopher P.; Chapman, Duane C.; Rizzo, William M.

1996-01-01

Collection of sediment cores in depths of 1-5 m is difficult with traditional sampling gear. Here we describe three suction coring devices constructed with readily available plumbing supplies and parts easily made from acrylic plastic and silicone sealant. The samplers have been used successfully in sediments ranging from coarse sands and shell hash to muds, highly organic deposits, and dense clays. Successful applications have ranged from contaminants analysis, toxicity testing, seagrass mapping, and assessment of sediment-microfloral interactions to sampling the infauna of surf-swept beaches.

Testing a laser-induced breakdown spectroscopy technique on the Arctic sediments

NASA Astrophysics Data System (ADS)

Han, D.; Nam, S. I.

2017-12-01

Physical and geochemical investigations coupled with the Laser-induced Breakdown Spectroscopy (LIBS) were performed on three surface sediment cores (ARA03B/24BOX, ARA02B/01(A)MUC, ARA02B/02MUC and ARA02B/03(A)MUC) recovered from the western Arctic Ocean (Chukchi Sea) during IBRV ARON expeditions in 2012. The LIBS technique was applied to carry out elemental chemical analysis of the Arctic sediments and compared with that measured by ITRAX X-ray fuorescence (XRF) core scanning. LIBS and XRF have shown similar elemental composition within each sediment core. In this study, mineral composition (XRD), grain size distribution and organic carbon content as well as elemental composition (LIBS) were all considered to understand paleoenvironmental changes (ocean circulation, sea-ice drift, iceberg discharge, and etc.) recorded in the Arctic Holocene sediment. Quantitative LIBS analysis shows a gradually varying distribution of the elements along the sampled core and clear separation between the cores. The cores are geochemically characterized by elevated Mn profile. The gradient of mineral composition and grain sizes among the cores shows regional distribution and variation in sedimentary condition due to geological distance between East Siberian and North America. The present study reveals that a LIBS technique can be employed for in-situ sediment analyses for the Arctic Ocean. Furthermore, LIBS does not require costly equipment, trained operators, and complicated sample pre-treatment processes compared to Atomic absorption spectroscopy (AAS) and inductively coupled plasma emission spectroscopy (ICP), and also known to show relatively high levels of sensitivity, precision, and distinction than XRF analysis, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and electron probe X-ray microanalysis (EPMA).

New radiocarbon ages from cirques in Colorado Front Range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, P.T.; Birkeland, P.W.; Caine, N.

The authors recovered sediment cores 3.1 m long from Blue Lake ([approximately]37m water depth, [approximately]3,445m a.s.l., 40[degree]5 minutes 20 seconds N, 105[degree]37 minutes 08 seconds W) and 2.7m long from Lake Dorothy ([approximately]35m water depth, [approximately]3,675m a.s.l., 40[degree]00 minutes 46 seconds N, 105[degree]41 minutes 11 seconds W). A light-weight percussion coring system suspended from perlon ropes was used because of sediment thicknesses, water depths, and ski-backpacking requirements. Lake ice provided a stable coring platform. One purpose of the project is provision of a high-resolution record of environmental change in the subalpine/alpine ecotone during the Holocene, under the auspices of themore » Niwot Ridge Long-Term Ecological Research program. The sediment cores also provide minimum-limiting radiocarbon ages for deglaciation of cirques and the deposits that impound their tarns. Here the authors report on this second purpose. The Blue Lake core bottomed in sandy, gray, inorganic sediment, presumably glacial diamict. A bulk sample from 2.8--2.9m depth yielded a conventional radiocarbon age of 12,275[+-]345 yrs BP. Thus, ice retreated from the site by 12 ka. Since 12 ka both glacial and rock-glacial sediments have been deposited upvalley; some of these events may be recognized in the core. In contrast, the Lake Dorothy core did not penetrate gray inorganic diamict and is entirely organic-rich. A bulk sample from 2.65--2.7m depth yielded a conventional radiocarbon age of 10,910 [+-] 320 yrs BP. Thus, the moraines impounding the lake are 2--3 times older than suggested by a combination of relative-age methods and one radiocarbon age from surface sediments.« less

Historical reconstruction of atmospheric lead pollution in central Yunnan province, southwest China: an analysis based on lacustrine sedimentary records.

PubMed

Liu, Enfeng; Zhang, Enlou; Li, Kai; Nath, Bibhash; Li, Yanling; Shen, Ji

2013-12-01

Atmospheric lead (Pb) pollution during the last century in central Yunnan province, one of the largest non-ferrous metal production centers in China, was reconstructed using sediment cores collected from Fuxian and Qingshui Lakes. Lead concentrations and isotopic ratios ((207)Pb/(206)Pb and (208)Pb/(206)Pb) were measured in sediment cores from both lakes. The operationally defined chemical fractions of Pb in sediment core from Fuxian Lake were determined by the optimized BCR procedure. The chronology of the cores was reconstructed using (210)Pb and (137)Cs dating methods. Similar three-phase variations in isotopic ratios and enrichment factors of Pb were observed in the sediment cores from both lakes. Before the 1950s, the sediment data showed low (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios and enrichment factors (EFs=~1), indicating that the sedimentary Pb was predominantly of lithogenic origin. However, these indices were increased gradually between the 1950s and the mid-1980s, implying an atmospheric Pb deposition. The EFs and isotopic ratios of Pb reached their peak during recent years, indicating aggravating atmospheric Pb pollution. The average anthropogenic Pb fluxes since the mid-1980s were estimated to be 0.032 and 0.053 g m(-2) year(-1) recorded in Fuxian and Qingshui cores, respectively. The anthropogenic Pb was primarily concentrated in the reducible fraction. Combining the results of Pb isotopic compositions and chemical speciations in the sediment cores and in potential sources, we deduced that recent aggravating atmospheric Pb pollution in central Yunnan province should primarily be attributed to regional emissions from non-ferrous metal production industries.

Geochronology and sources of heavy metal pollution in sediments of Istanbul Strait (Bosporus) outlet area, SW Black Sea, Turkey.

PubMed

Sarı, Erol; Çağatay, M Namık; Acar, Dursun; Belivermiş, Murat; Kılıç, Önder; Arslan, Tuğçe Nagihan; Tutay, Ali; Kurt, Mehmet Ali; Sezer, Narin

2018-08-01

Geochemical and sedimentological analyses and radionuclide ( 210 Pb and 137 Cs) dating of three cores from the Bosporus outlet area of the Black Sea, north of Istanbul, were conducted to assess the sources and history of heavy metal pollution. The sedimentary succession in the shelf core KD12-01 consists mainly of clay (49-80%) and silt (15-41%). Radionuclide dating of the core indicates that it consists of old sediments that are uncontaminated with heavy metals. In contrast, cores KD12-04 and KD12-07 recovered from -350 m and -304 mm in the upper slope area represent sediments consisting of silt and clay that were deposited since at least the last 120 years and 60 years, respectively. The latter core contains two mass-flow units represented by relatively old sedimentary material according to the low 210 Pb activity and relatively low heavy metal contents. The upper 40 and 48 cm of cores KD 12-04 and KD 12-07 represent sediments deposited since 1970s and 1980s that are significantly polluted with Cu, Ni, Zn, Mo, Pb and Cr, Cu, Co, Ni, Mo, Pb, Zn, respectively. However, high Pb and Cr concentrations with high TOC contents date back to early part of the 20th century in core KD 12-04. The geochemical data, together with the high 137 Cs concentrations of the contaminated sediments, strongly suggest that the pollution is mainly delivered to the western and north western Black Sea by the large European rivers, from there transported to the study area by the rim current, and deposited in the sediments under anoxic conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Regional patterns of labile organic carbon flux in North American Arctic Margin (NAAM) as reflected by redox sensitive-elements distributions in sediments

NASA Astrophysics Data System (ADS)

Gobeil, C.; Kuzyk, Z. Z. A.; Goni, M. A.; Macdonald, R. W.

2016-02-01

Concentrations of elements (S, Mn, Mo, U, Cd, Re) providing insights on organic C metabolized through oxidative processes at the sea floor were measured in 27 sediment cores collected along a section extending from the North Bering Sea to Davis Strait via the Canadian Archipelago. Sedimentary distributions and accumulation rates of these elements were used to i) document the relative importance of aerobic versus anaerobic degradation of organic C in NAAM sediments, ii) infer variations in water column carbon flux and iii) estimate the importance of this margin as a sink for key elements in the Arctic and global ocean. Distributions of Mn, total S and reduced inorganic S demonstrated that most sediments along the NAAM had relatively thick (>1 cm) surface oxic layers, underlain by sediments with weakly reducing conditions and limited sulphate reduction. Strongly reducing conditions accompanied by substantial sedimentary pyrite burial occurred only in certain subregions, including the Bering-Chukchi Shelves, shallow portions of Barrow Canyon. Estimated accumulation rates of authigenic S, Mo, Cd and U, and total Re displayed marked spatial variability that was related to sedimentary redox conditions induced by the supply of labile C to the seabed, as shown by significant relationships between the accumulation rates and vertical C flux, estimated from regional primary production values and water depth at the coring sites. High primary production combined with shallow water columns drive elevated rates of authigenic trace element accumulation in sediments from the Bering-Chukchi Shelves whereas low production combined with moderately deep conditions drive low rates of accumulation in sediments in the Beaufort Shelf, Davis Strait and Canadian Archipelago. Using the average authigenic trace element accumulation rates in sediments from the various regions, we submit that the shelves along the NAAM margin are important sinks in global marine biogeochemical budgets.

Collection, analysis, and age-dating of sediment cores from 56 U.S. lakes and reservoirs sampled by the U.S. Geological Survey, 1992-2001

USGS Publications Warehouse

Van Metre, Peter; Wilson, Jennifer T.; Fuller, Christopher C.; Callender, Edward; Mahler, Barbara J.

2004-01-01

The U.S. Geological Survey Reconstructed Trends National Synthesis study collected sediment cores from 56 lakes and reservoirs between 1992 and 2001 across the United States. Most of the sampling was conducted as part of the National Water-Quality Assessment (NAWQA) Program. The primary objective of the study was to determine trends in particle-associated contaminants in response to urbanization; 47 of the 56 lakes are in or near one of 20 U.S. cities. Sampling was done with gravity, piston, and box corers from boats and push cores from boats or by wading, depending on the depth of water and thickness of sediment being sampled. Chemical analyses included major and trace elements, organochlorine pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, cesium-137, and lead-210. Age-dating of the cores was done on the basis of radionuclide analyses and the position of the pre-reservoir land surface in the reservoir and, in a few cases, other chemical or lithologic depth-date markers. Dates were assigned in many cores on the basis of assumed constant mass accumulation between known depth-date markers. Dates assigned were supported using a variety of other date markers including first occurrence and peak concentrations of DDT and polychlorinated biphenyls and peak concentration of lead. A qualitative rating was assigned to each core on the basis of professional judgment to indicate the reliability of age assignments. A total of 122 cores were collected from the 56 lakes and age dates were assigned to 113 of them, representing 54 of the 56 lakes. Seventy-four of the 122 cores (61 percent) received a good rating for the assigned age dates, 28 cores (23 percent) a fair rating, and 11 cores (9 percent) a poor rating; nine cores (7 percent) had no dates assigned. An analysis of the influence of environmental factors on the apparent quality of age-dating of the cores concluded that the most important factor was the mass accumulation rate (MAR) of sediment: the greater the MAR, the better the temporal discretization in the samples and the less important the effects of postdepositional sediment disturbance. These age-dated sediment cores provide the basis for local-, regional-, and national-scale interpretations of water-quality trends.

Sediment data collected in 2013 from the northern Chandeleur Islands, Louisiana

USGS Publications Warehouse

Buster, Noreen A.; Kelso, Kyle W.; Bernier, Julie C.; Flocks, James G.; Miselis, Jennifer L.; DeWitt, Nancy T.

2014-01-01

This data series serves as an archive of sediment data collected in July 2013 from the Chandeleur Islands sand berm and adjacent barrier-island environments. Data products include descriptive core logs, core photographs and x-radiographs, results of sediment grain-size analyses, sample location maps, and Geographic Information System data files with accompanying formal Federal Geographic Data Committee metadata.

Holocene Paleolimnological Records from Thule, Northwestern Greenland

NASA Astrophysics Data System (ADS)

Corbett, L.; Osterberg, E. C.; Kelly, M. A.; Axford, Y.

2012-12-01

Assessing Holocene climatic and environmental variability around the margin of the Greenland Ice Sheet provides important information against which to compare ice sheet margin fluctuations. Here, we report preliminary results from ongoing research in northwestern Greenland. We present records of physical properties of lake sediments and use these to make inferences about the evolution of the lake and its surroundings over the latter half of the Holocene. We collected two sediment cores, 90 and 72 cm in length, from a small (surface area ~0.3 km2), shallow (maximum depth ~4.5 m) lake at 76°33'40''N 68°26'31''W near Thule Air Base in July 2012. The length of the cores was limited by the length of the core barrel and does not reflect the total thickness of sediment in the lake. The lake is situated within the glacial limit and likely formed subsequent to deglaciation of the region during early Holocene time. No glaciers exist within the lake's catchment today; the primary modern source of sediment is a perennial inflow from the west. We developed a preliminary depth-age model using radiocarbon ages of terrestrial organic macrofossils. Thus far, we have analyzed the sediments for magnetic susceptibility and loss-on-ignition. A radiocarbon age of 6069 ± 90 cal yr BP at the base of the core indicates that the sediments preserve a continuous record of middle to late Holocene conditions. The top of both cores consists of a thick (~12 cm) layer of dark gray unlaminated sediments, while the rest of the material in both cores is lighter brown to olive, finely laminated sediment. The upper layer is characterized by low water content (<25%), low loss-on-ignition (<5%), and high magnetic susceptibility (~150-250 x10-6). Conversely, the laminated sediments beneath have higher water content (~40-50%), higher loss-on-ignition (~5-10%), and much lower magnetic susceptibility (<50 x10-6). We hypothesize that the upper, less organic unit may represent a single event in the lake's recent history. We are refining the depth-age model with more radiocarbon ages, measuring grain size and carbon to nitrogen ratios of the sediments, and evaluating possible linkages between the sediment physical properties and precipitation as recorded by annual accumulation in ice cores in northwestern Greenland and Arctic Canada. This project will provide a foundation for future work in Thule investigating Holocene fluctuations of local ice cap and ice sheet margin positions.

Fluvial landscapes evolution in the Gangkou River basin of southern Taiwan: Evidence from the sediment cores

NASA Astrophysics Data System (ADS)

Chen, Jia-Hong; Chyi, Shyh-Jeng; Yen, Jiun-Yee; Lin, Li-Hung; Yen, I.-Chin; Yu, Neng-Ti; Ho, Lih-Der; Jen, Chia-Hung

2017-04-01

The Gangkou River basin is the largest basin in the eastern Hengchun Peninsula of Taiwan. Its main river length is 31km and the basin area is 102sq. km. The width of the active channel is relatively narrow, but the valley from the middle to downstream is remarkably wide, indicating a feature of underfit stream. We drilled two sediment cores in the downstream area, including a 30m core (core-A) from a higher terrace, which is 14m above mean sea level, and a 20m core (core-B) from a lower terrace, which is 4m above mean sea level. Most of the sediments in the core-A are mud, which represents the flood plain facies, and 14C dates in the core-A range from 11ka to 7ka BP. Furthermore, the sediment layers reveal signals of marine events at the core depths of 5m to 11m by X-ray fluorescence. In the core-B, there is an erosional surface at the core depth of 5m. The age of the fluvial gravel layer above the erosional surface is about 0.4ka BP, and the mud layer top the surface is about 8.5ka BP. The preliminary results show that (1) as the tectonic uplift rate induced by the marine terraces around the basin is 1.0 to 2.5 mm/yr, and the accumulation rate of the mud layer in the basin is 6.7 to 8.7 mm/yr, the sediments infilling (more than 30-meters-thick) in the downstream area of the basin should be the results of the lower tectonic uplifting and the higher post-glacial sea level rise and; (2) the marine sediment layer with 14C dates of 7.5ka to 8.5ka BP is very likely the remain of the maximum flooding surface (MFS) in the early Holocene. These results indicate that the fluvial landscapes evolution of the basin was controlled by the sea-level; (3) the erosional surface in the core-B indicates the Gangkou River continuously erode the infilling sediments from 7ka to 0.4ka BP. Previous studies show that the sea-level around Taiwan gradually declined from its high stand since 6ka, we proposed that the continuous erosion was probably the results of tectonic uplifting and eustatic sea-level fall.

Benthic macrofaunal colonization patterns and preservation of laminated sediments: Observations in an extreme coastal basin environment in the lower Gulf of California

NASA Astrophysics Data System (ADS)

Herguera, J.; Paull, C. K.; Anderson, K.; Gwiazda, R.; Lundsten, E. M.; Kundz, L.; Edwards, B. D.; McGann, M. L.

2012-12-01

New observations and cores obtained with the ROV Doc Ricketts operated from the RV/Western Flyer provide a glimpse into a macrofauna barren sea-floor where laminated sediments are known to accumulate on the sea-floor of Alfonso Basin. This basin, located north of La Paz Bay, Baja California, is known to be an important repository of laminated sediments due to a combination of the relatively high input of terrigenous sediments brought in by summer rains, a moderate to high export productivity from its surface waters, and the very low oxygen concentrations at depth bathed by tropical subsurface waters. These laminated sediments are unique repositories of paleoceanographic and paleoclimatic information for its very high resolution records of past conditions comparable to ice core, tree ring, coral and cave records although spanning continuously much further back in time. However, the paleoceanographic community rarely has had the opportunity to visualize the seafloor surface where these sediments are accumulating and examine the biological abundance patterns in these extreme environments. Here we will show results from ROV Doc Ricketts quantitative video transects providing benthic faunal abundance patterns on the seafloor in these highly oxygen depleted bottom waters. These observations are further compared with the underlying stratigraphy. A coring system carried on the ROV allowed us to replicate cores and to collect a transect of 5 closely spaced cores to evaluate the horizontal extent of the observed variability down-core. We will also show some preliminary results from x-radiographs showing the nature of the laminations and its sediment composition based on elemental analysis on organic carbon, carbonate and biogenic opal analysis. New XRF results from a box core will be used to calibrate its terrigenous components with the historical rainfall record and evaluate its potential to reconstruct summer precipitation patterns in this region.

Geochemical characteristics of organic compounds in a permafrost sediment core sample from northeast Siberia, Russia

NASA Technical Reports Server (NTRS)

Matsumoto, G. I.; Friedmann, E. I.; Gilichinsky, D. A.

1995-01-01

We studied total organic carbon (TOC), hydrocarbons and fatty acids in a permafrost sediment core sample (well 6-90, length 32.0 m, 1.5-2.5 Ma BP) from northeast Siberia (approximately 70 degrees N, 158 degrees E), Russia, to elucidate their geochemical features in relation to source organisms and paleoenvironmental conditions. Long-chain n-alkanes and n-alkanoic acids (>C19) were most predominant hydrocarbons and fatty acids, respectively, so organic matter in the sediment core was derived mainly from vascular plants and, to a much smaller extent, from bacteria. Low concentrations of unsaturated fatty acids revealed that organic matter in the sediment core was considerably degraded during and/or after sedimentation. The predominance of vascular plant components, the major ionic components of nonmarine sources, and geological data strongly implied that the sediment layers were formed in shallow lacustrine environments, such as swamp with large influences of tundra or forest-tundra vegetation. Also, no drastic changes in paleoenvironmental conditions for biological activity or geological events, such as sea transgressions or ice-sheet influences, occurred at the sampling site approximately 100 km from the coast of the East Siberian Sea during the late Pliocene an early Pleistocene periods.

Post-Glacial and Paleo-Environmental History of the West Coast of Vancouver Island

NASA Astrophysics Data System (ADS)

Dallimore, A.; Enkin, R. J.

2005-12-01

Annually laminated sediments in anoxic fjords are potentially ideal paleoclimate recorders, particularly once proxy measurements for atmospheric, oceanographic and sedimentological conditions have been calibrated. On the west coast of Canada, these sediments also record the changing environment as glaciers retreated from this area about 12 ka y BP. In Effingham Inlet, a 40 m core taken from the French ship the Marion Dufresne as part of the international IMAGES/PAGES program, gives evidence of an isolation basin at maximum glacial isostatic rebound and lowest paleo-sea level followed by eustatic sea level rise about 10 ka y BP. The Late Pleistocene record also marks dramatic changes in glacial sedimentary source and transport. Excellent chronological control is provided by complementary yet independent dating methods including radiocarbon dates on both plants and shells, identification of the Mazama Ash, varve counting and paleomagnetic, paleosecular variation correlations in the lower, pro-glacial section of the core which does not contain organic material. Paleoenvironmental evidence from this core provides information on immediate post-glacial conditions along the coast and rapid climatic changes throughout the Holocene, with implications for the possibility of early human migration routes and refugia.

Active Urbanization and Channel Adjustment in Apple Creek, Appleton, WI

NASA Astrophysics Data System (ADS)

Clark, J. J.

2002-12-01

Headwaters of the Apple Creek watershed have been and continue to be rapidly developed as part of the City of Appleton's long-term growth plan. Concurrent with early development, and prior to development over the past 4 years, two regional stormwater management facilities were constructed. Cross-sectional surveys and core transects were used to determine channel response to urbanization mitigated by stormwater management. The reach immediately downstream of the first pond complex has a narrow, but well established, wooded riparian zone and has not changed in size or shape over the past two years. An engineered reach approximately one mile downstream, however has exhibited widespread bed aggradation. Cross-sectional area decreased an average of 51% over the past four years. Despite the use of sediment and erosion control BMPs, sediment concentrations exceeding 1000 mg/L during base flow are not uncommon downstream of construction sites adjacent to the stream. The artificially widened channel, a reduction in stream gradient, and the backwater effect from downstream ponds caused much of this sediment to remain within the engineered reach. It is estimated that approximately 21,000 Mg of sediment is stored in this mile-long reach. As this sediment migrates downstream, the forebay of the second set of stormwater ponds will begin to fill, reducing storage capacity and thereby limiting its effectiveness in mitigating peak discharges and sequestering nutrients.

Recent sedimentary records from the Arabian Sea

NASA Astrophysics Data System (ADS)

Somayajulu, B. L. K.; Yadav, D. N.; Sarin, M. M.

1994-06-01

An attempt is made to understand the redox conditions that prevailed in the north eastern continental margins of the Arabian Sea and in the nearby deep water regions during the past few centuries using short undisturbed sediment cores. The geochronology is accomplished using210Pb excess method and the proxy indicators chosen for productivity and associated redox changes are CaCO3, organic matter (OM), Mn and U along with major elements Fe and Al. Such changes in principle are related to high productivity in the overlying waters which in turn depend on monsoonal intensity that causes upwelling responsible for increase in productivity. Alongwith the published data on gravity cores from the same region, our measurements suggest the following: At ˜ 300 m water depth, south of 21°N, the sediment-water interface at depths of ˜ 300 m had been anoxic during the time span represented by the presently studied cores for approximately ˜ 700y as evidenced by low Mn/Al (< 0.7 × 10-2) and high U/Al (> 10-4) weight ratios. In some adjacent deeper regions, however, the environment turned oxic around ˜ 200 y BP. Whereas both Mn and Ra were lost to the overlying waters in the anoxic regions (depth ˜340m), the Mn that diffused from deeper sections appears to have mineralized at the sediment-water-interface. Studies of this type on long undisturbed cores from the margins of the Arabian Sea and the Bay of Bengal, involving several proxies and geochronology by more than one method are needed to understand short term environmental (and monsoonal intensity) changes of the recent past with high resolution.

Lithostratigraphy, biostratigraphy and chemostratigraphy of Upper Cretaceous and Paleogene sediments from southern Tanzania: Tanzania Drilling Project Sites 27-35

NASA Astrophysics Data System (ADS)

Jimènez Berrocoso, Àlvaro; Huber, Brian T.; MacLeod, Kenneth G.; Petrizzo, Maria Rose; Lees, Jacqueline A.; Wendler, Ines; Coxall, Helen; Mweneinda, Amina K.; Falzoni, Francesca; Birch, Heather; Singano, Joyce M.; Haynes, Shannon; Cotton, Laura; Wendler, Jens; Bown, Paul R.; Robinson, Stuart A.; Gould, Jeremy

2012-07-01

The 2008 Tanzania Drilling Project (TDP) expedition recovered common planktonic foraminifera (PF), calcareous nannofossils (CN) and calcareous dinoflagellates with extraordinary shell preservation at multiple Cenomanian-Campanian sites that will be used for paleoclimatic, paleoceanographic, and biostratigraphic studies. New cores confirm the existence of a more expanded and continuous Upper Cretaceous sequence than had previously been documented in the Lindi and Kilwa regions of southeastern coastal Tanzania. This TDP expedition cored 684.02 m at eight Upper Cretaceous sites (TDP Sites 28-35) and a thin Paleocene section (TDP Site 27). TDP Sites 29, 30, 31 and 34 together span the lowermost Turonian to Coniacian (PF Whiteinella archaeocretacea to Dicarinella concavata Zones and CN Zones UC6a-9b), with TDP Site 31 being the most biostratigraphically complete Turonian section found during TDP drilling. A discontinuous section from the Santonian-upper Campanian (PF D. asymetrica to Radotruncana calcarata Zones and CN Zones UC12-16) was collectively recovered at TDP Sites 28, 32 and 35, while thin sequences of the lower Cenomanian (PF Thalmanninella globotruncanoides Zone and CN subzones UC3a-b) and middle Paleocene (Selandian; PF Zone P3a and CN Zone NP5) were cored in TDP Sites 33 and 27, respectively. Records of δ13Corg and δ13Ccarb from bulk sediments generated for all the Cretaceous sites show largely stable values through the sections. Only a few parallel δ13Corg and δ13Ccarb shifts have been found and they are interpreted to reflect local processes. The δ18Ocarb record, however, is consistent with Late Cretaceous cooling trends from the Turonian into the Campanian. Lithologies of these sites include thick intervals of claystones and siltstones with locally abundant, finely-laminated fabrics, irregular occurrences of thin sandstone layers, and sporadic bioclastic debris (e.g., inoceramids, ammonites). Minor lithologies represent much thinner units of up to medium-grained, massive sandstones. The %CaCO3 (∼5-40%) and %Corg (∼0.1-2%) are variable, with the highest %CaCO3 in the lower Campanian and the highest %Corg in the Turonian. Lithofacies analysis suggests that deposition of these sediments occurred in outer shelf-upper slope, a setting that agrees well with inferences from benthic foraminifera and calcareous dinoflagellates.

Late Holocene sedimentary environments of south San Francisco Bay, California, illustrated in gravity cores

USGS Publications Warehouse

Woodrow, Donald L.; Fregoso, Theresa A.; Wong, Florence L.; Jaffe, Bruce E.

2014-01-01

Data are reported here from 51 gravity cores collected from the southern part of San Francisco Bay by the U.S. Geological Survey in 1990. The sedimentary record in the cores demonstrates a stable geographic distribution of facies and spans a few thousand years. Carbon-14 dating of the sediments suggests that sedimentation rates average about 1 mm/yr. The geometry of the bay floor and the character of the sediment deposited have remained about the same in the time spanned by the cores. However, the sedimentary record over periods of centuries or decades is likely to be much more variable. Sediments containing a few bivalve shells and bivalve or oyster coquinas are most often found west of the main channel and near the San Mateo Bridge. Elsewhere in the south bay, shells are rare except in the southernmost reaches where scattered gastropod shells are found.

Pore Water Transport of Enterococci out of Beach Sediments

PubMed Central

Phillips, Matthew C.; Solo-Gabriele, Helena M.; Reniers, Adrianus J. H. M.; Wang, John D.; Kiger, Russell T.; Abdel-Mottaleb, Noha

2011-01-01

Enterococci are used to evaluate the safety of beach waters and studies have identified beach sands as a source of these bacteria. In order to study and quantify the release of microbes from beach sediments, flow column systems were built to evaluate flow of pore water out of beach sediments. Results show a peak in enterococci (average of 10% of the total microbes in core) released from the sand core within one pore water volume followed by a marked decline to below detection. These results indicate that few enterococci are easily removed and that factors other than simple pore water flow control the release of the majority of enterococci within beach sediments. A significantly larger quantity and release of enterococci were observed in cores collected after a significant rain event suggesting the influx of fresh water can alter the release pattern as compared to cores with no antecedent rainfall. PMID:21945015

Rare earth element compositions of core sediments from the shelf of the South Sea, Korea: Their controls and origins

NASA Astrophysics Data System (ADS)

Jung, Hoi-Soo; Lim, Dhongil; Choi, Jin-Yong; Yoo, Hae-Soo; Rho, Kyung-Chan; Lee, Hyun-Bok

2012-10-01

Rare earth elements (REEs) of bulk sediments and heavy mineral samples of core sediments from the South Sea shelf, Korea, were analyzed to determine the constraints on REE concentrations and distribution patterns as well as to investigate their potential applicability for discriminating sediment provenance. Bulk sediment REEs showed large variation in concentrations and distribution patterns primarily due to grain size and carbonate dilution effects, as well as due to an abundance of heavy minerals. In the fine sandy sediments (cores EZ02-15 and 19), in particular, heavy minerals (primarily monazite and titanite/sphene) largely influenced REE compositions. Upper continental crust-normalized REE patterns of these sand-dominated sediments are characterized by enriched light REEs (LREEs), because of inclusion of heavy minerals with very high concentrations in LREEs. Notably, such a strong LREE enrichment is also observed in Korean river sediments. So, a great care must be taken when using the REE concentrations and distribution patterns of sandy and coarse silty shelf sediments as a proxy for discriminating sediment provenance. In the fine-grained muddy sediments with low heavy mineral abundance, in contrast, REE fractionation ratios and their UCC-normalized patterns seem to be reliable proxies for assessing sediment provenance. The resultant sediment origin suggested a long lateral transportation of some fine-grained Chinese river sediments (probably the Changjiang River) to the South Sea of Korea across the shelf of the northern East China Sea.

Procedures for Handling and Chemical Analysis of Sediment and Water Samples,

DTIC Science & Technology

1981-05-01

silts. Particularly suitable for studies of the sediment/ water interface, for studies on depositonal sediment structures. Al pi ne- ravity Cores of 2 m...adverse water quality impacts would occur. Elemental partitioning or sedimentation fractionation studies are the most complex of the tests considered...8217 water %nd blend the core or dredge sample. Place a{js roximalel-i 00 cc of’ the blended sample in an oxygen-free, poly - ca rbor’~ [ ’-l centrifuge bottle

Examples of Mass Wasting and Hemipelagic Sedimentation of Brazos-Trinity Basin #4 and Ursa Basin, Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Schneider, J.; Moerz, T.; Bartetzko, A.; Iturrino, G. J.; Edeskar, T. M.; Flemings, P. B.; Behrmann, J. H.; John, C. M.

2005-12-01

Pleistocene sea level changes influenced the sedimentation history on the passive continental margin of the northern Gulf of Mexico coast. During IODP Expedition 308, the Brazos-Trinity #4 and Ursa Basin were drilled to study -overpressure, fluid flow and deformation processes in a passive margin setting. The Brazos-Trinity Basin #4 is located 200 km south of Galveston, Texas (USA) in ~1400 m water depth below an extended shelf section. Ursa Basin is located 150 km south of New Orleans, Louisiana (USA) in ~1000 m water depth south of the Mississippi river mouth. Despite their similar geotectonic setting both basins show fundamental differences in their style of mass wasting and drape sedimentation. Here we use core descriptions, core photographs, Formation MicroScanner (FMS) data and selected physical properties measurements (magnetic susceptibility, GRAPE density) to illustrate and compare styles of mass wasting and drape sedimentation on selected intervals for the first 4 Marine Isotope Stages. Special emphasis is given to the thickness and frequency of single depositional events. One aim is to estimate the mass wasting / hemipelagic accumulation ratio for both basins and compare it to the average sedimentation rates based on the preliminary shipboard age models. This information will be used in the future to study how sedimentation processes control permeability and pore pressure. In this upcoming project, starting in mid 2006, will use well-logging data to compute continuous porosity, permeability, and pore pressure profiles. These computations require input and reference data obtained from petrophysical and geotechnical core analyses and in situ measurements (e.g. matrix density to calculate porosity from the density log, permeability and porosity to derive porosity-permeability relations, effective stress to calculate pore pressure). Permeability and effective stress will be measured using oedometer tests on undisturbed samples. The detailed lithostratigraphic information, particularly turbidite thickness, and the permeability and pore pressure profiles will be used as input data for one-dimensional modeling of the compression history of two Sites using the civil engineering modeling software PLAXIS.

Lake and Bog Sediment Records of Holocene Climate and Glacier Variability in the Cordillera Vilcabamba of Southern Peru

NASA Astrophysics Data System (ADS)

Schweinsberg, A.; Licciardi, J. M.; Rodbell, D. T.; Stansell, N.

2013-12-01

Records of past fluctuations in climatically sensitive tropical glaciers are among the best indicators of regional paleoclimatic trends and forcings. However, continuous sediment records in this region remain limited, particularly during the Holocene. Here we present the first continuous records of glacier activity in the Cordillera Vilcabamba (13°20'S) of southern Peru from lake and bog sediment cores in stratigraphic contact with 10Be-dated moraines. Completed analyses include sediment lithostratigraphy, magnetic susceptibility, and biogenic silica, in conjunction with AMS radiocarbon dates on charcoal. Carbon measurements, bulk density, and bulk sedimentation rates are used to derive a record of clastic sediment flux that serves as a proxy indicator of former glacier activity. Visually distinct sedimentological variations, magnetic susceptibility peaks, and radiocarbon dates were correlated among adjacent cores to construct one composite record representative of each coring site. Three composite cores are presented: two from the Rio Blanco valley and one from the Yanama valley. Sediment records from these two glaciated valleys suggest a series of environmental changes during the last ~12,000 calendar years BP. Clastic sediment flux trends are broadly consistent with published evidence that the early to middle Holocene was relatively warm and arid in the southern Peruvian Andes. An episode of high clastic flux in the late Holocene may reflect enhanced glacial activity in response to the onset of cooler and wetter conditions. A prominent peak in magnetic susceptibility at 1660 cal yr BP is present in all composite cores and serves as a chronostratigraphic marker. In addition, our new basal radiocarbon ages place limits on the cosmogenic 10Be production rate in the high Andes, suggesting the cosmogenic 10Be production rate is considerably lower than previously published estimates.

The preglacial sediment record of Lake Ladoga, Russia - first results from a seismic survey and sediment coring in 2013

NASA Astrophysics Data System (ADS)

Melles, Martin; Krastel, Sebastian; Fedorov, Grigory; Subetto, Dmitry A.; Savelieva, Larisa A.; Andreev, Andrej; Wagner, Bernd

2014-05-01

The new German-Russian project PLOT (Paleolimnological Transect) aims at investigating the Late Quaternary climatic and environmental history along a more than 6000 km long longitudinal transect crossing northern Eurasia. Special emphasis is put on the preglacial history. For this purpose shallow and deep seismic surveys shall be carried out on five lakes, which potentially host preglacial sediment records, followed by sediment coring based on the results of the seismic campaigns. The well-studied Lake El'gygytgyn represents the eastern-most location of the transect and acts as reference site. Within the scope of a pilot phase for the PLOT project, funded by the German Federal Ministry of Education and Research, we were able to investigate Lake Ladoga, which is located close to St. Petersburg at the western end of the transect. Lake Ladoga is the largest lake in Europe, covering an area of almost 18.000 km2. The modern sedimentation as well as the late glacial and Holocene history of the lake were already studied in detail over the past decades. The older, preglacial lake history, however, is only rudimentary known from a core transect drilled in the southern lake in the 1930th. The cores of up to about 60 m length were only briefly described and are not existing any more. The results from these cores, known from unpublished reports only, suggest the existence of marine sediments of presumably Eemian age, representing a time when Lake Lagoga was part of a precursor of the Baltic Sea, which had a connection via Ladoga and Onega Lakes to the White Sea and further to the Arctic Ocean. In late August/early September 2013 we carried out a seismic survey on Lake Ladoga using a Mini-GI-Gun and a 32-channel seismic streamer. In total, 1500 km of seismic profiles were measured, covering most parts of the lake. The seismic lines typically show acoustically well stratified Holocene muds overlaying rather transparent postglacial varves. These sediment successions can reach more than 10 m in thickness. They usually are bordered by a hard reflector underneath that may represent coarse-grained sediments or a till, which in most areas is not penetrated by the acoustic waves. In particular in the western part of the lake, however, these sediment successions can be underlain by sedimentary strata of up to 60 m thickness that fill steeply sloped depressions or channels. Sediment coring at two sites in western Ladoga Lake confirmed the seismic interpretation of the postglacial sediment succession. At one of these sites, the basal reflector at about 13 m depth was penetrated another ca. 10 m into preglacial sediments. According to initial pollen data, these sediments were formed during an interglacial with a slightly warmer climate than that of the Holocene. Further work is currently carried out, for instance, to identify which of the Quaternary interglacials is respresented by the sediments cored in 2013.

Glacial-marine sediments record ice-shelf retreat during the late Holocene in Beascochea Bay on the western margin of the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Hardin, L. A.; Wellner, J. S.

2010-12-01

Beascochea Bay has an overall rapid rate of sedimentation due to retreating fast-flowing ice, and thus contains high-resolution records of Antarctica’s glacial and climate history. Beascochea Bay is a 16 km long by 8 km wide bay located on the western margin of the Antarctica Peninsula, centered between Anvers Island and Renaud Island, but open to the Bellingshausen Sea. Currently, three tidewater glaciers draining the Bruce Plateau of Graham Land enter into the fjords of Beascochea Bay, releasing terrigenous sediments which have left a record of the fluctuations of the Antarctic Peninsula Ice Cap since the grounded ice decoupled from the seafloor after the last glacial maximum. These three glaciers have played a significant role in providing sediment to the main basin, allowing a detailed sediment facies analysis to be conducted from eight sediment cores which were collected during the austral summer of 2007. Pebbly silty clay sediment cores, along with 3.5 kHz seismic data and multibeam swath bathymetry data, are integrated to reconstruct a glacial retreat timeline for the middle to late Holocene, which can be compared to the recent retreat rates over the last century. Paleoenvironment of deposition is determined by mapping lateral facies changes from the side fjords (proximal) to the outer basin (distal), as each region records the transition from glacial-marine sediments to open-marine sediments. As the ice retreated from the outer basin to the inner basin, and most recently leaving the side fjords, each facies deposited can be age-constrained by radiocarbon, 210Pb, and 137Cs dating methods. A distinct 137Cs signal is readily seen in two kasten cores from a side fjord and the inner basin of Beascochea Bay. This dating method revealed an average sedimentation rate of 2.7 mm per year for approximately the last century, which is comparable to 210Pb rates obtained in other studies. Lithology variations in each sediment core record indications of ice-shelf influence in Beascochea Bay throughout the Holocene deglaciation. The distinctively laminated sub-ice shelf facies can be clearly seen in the x-rays of these cores, and can be easily distinguished from the poorly sorted glacial-marine facies and the greenish finer-grained facies deposited in open-marine conditions. A 14 m long sediment core taken from the outer basin of Beascochea Bay recovered the greatest length of sediment and dates back to the middle Holocene. X-rays of this core show a possible mid-Holocene retreat of the ice shelf followed by intermittent advance and retreat that precedes the most recent retreat. The inner basin of Beascochea Bay has been without an ice shelf for the last 200 years, based on the sedimentation rates of the last century projected downcore.

The Varve Record of Puyehue Lake (Meridional Chile), AD 1412-2002 .

NASA Astrophysics Data System (ADS)

Boes, X.; Arnaud, F.; Fagel, N.

2004-12-01

Puyehue Lake is located in the Southern Volcanic Zone of Chile (Southern Lake District, 40°S). This monomictic lake is under the influence of the oceanic winter polar front (WPF) and constitutes a powerful sedimentary archive for paleoenvironmental reconstruction. The underflow (PUI) and interflow (PUII) coring sites were selected by a high resolution seismic survey (RUG). The sedimentation is driven by the annual blooms of diatoms in association with thermal lake cycles. For each site, one short core (50-60 cm) is analyzed by continuous cover of thin sections for varve counting and chronology for the AD 1412-2002 time window. The varve chronology is constrained by 210Pb,137Cs sedimentation rate estimates, and by the AD 1960 Valdivia'seismite. The sediment laminations are especially emphasized by the continuous grey-scale measurements from thin sections. Detrital clayey material characterizes the dark levels, and biogenic diatom mud defines the light levels. Varve counting is derived from the occurrence of light layers, i.e. formed at the end of winter after nutrient turn-over. In both cores, the grey-scale is influenced by instantaneous tephra layers related to the regional volcanic activity (Puyehue and Cordon Caulle volcanoes). For instance, in PUII, we identify major historical eruptions (AD 1921, 1837, 1790, 1564, and 1544) in accordance with the varve age model. In addition, we measure the total varve thickness. Lower than 500 µm until AD 1780, the varve thickness gradually increases by a factor of four in PUII. The first period suggests a decrease of lake productivity, in agreement with a cooling. The age fits with the end of Little Ice Age in Southern America. Between AD 1780-2002, the thicker varves could be driven by a reinforcement of the WPF since the 19e century. Our local observations require further investigations to be extrapolated over regional or global scale.

Responses to the 2800 years BP climatic oscillation in shallow- and deep-basin sediments from the Dead Sea

NASA Astrophysics Data System (ADS)

Neugebauer, Ina; Brauer, Achim; Schwab, Markus; Dulski, Peter; Frank, Ute; Hadzhiivanova, Elitsa; Kitagawa, Hiroyuki; Litt, Thomas; Schiebel, Vera; Taha, Nimer; Waldmann, Nicolas

2015-04-01

Laminated lake sediments from the Dead Sea basin provide high-resolution records of climatic variability in the eastern Mediterranean region, which is considered being especially sensitive to changing climatic conditions. In the study presented here, we aim to reconstruct palaeoclimatic changes and their relation to the frequency of flood/erosion and dust deposition events as archived in the Dead Sea basin for the time interval from ca 3700 to 1700 years BP. A ca 4 m thick, mostly annually laminated (varved) sediment section from the western margin of the Dead Sea (shallow-water DSEn - Ein Gedi profile) was analysed and correlated to the new ICDP Dead Sea Deep Drilling Project core 5017-1 from the deep basin. To detect even single event layers, we applied a multi-proxy approach of high-resolution microscopic thin section analyses, µXRF element scanning and magnetic susceptibility measurements, supported by grain size and palynological analyses. Based on radiocarbon and varve dating two pronounced dry periods were detected at ~3500-3300 yrs BP and ~2900-2400 yrs BP that are characterized by a sand deposit during the older dry period and enhanced frequency of coarse detrital layers during the younger dry period in the shallow-water DSEn core, both interpreted as increased erosion processes. In the 5017-1 deep-basin core these dry periods are depicted by halite deposits. The timing of the younger dry period broadly coincides with the Homeric Minimum of solar activity at ca 2800 yrs BP. Our results suggest that during this period the Dead Sea region experienced a change in synoptic weather patterns leading to an increased occurrence of flash-flood events, overprinting the overall dry climatic conditions. Following this dry spell, a 250-yrs period of increased dust deposition is observed, coinciding with more regular aragonite precipitation during less arid climatic conditions.

The origin, historical variations, and distribution of heavy metals in the Qiongzhou Strait and nearby marine areas

NASA Astrophysics Data System (ADS)

Zhang, Zhiqiang; Chen, Liang; Wang, Weiping; Li, Tuanjie; Zu, Tingting

2017-04-01

We analyzed heavy metal concentrations in a number of surface sediments and cores from the Qiongzhou Strait and surrounding marine areas. The areas of high concentrations are primarily outside the eastern mouth of the Qiongzhou Strait and on the west side of the Leizhou Peninsula, whereas the areas of low concentrations are located primarily in the eastern Qiongzhou Strait. The maximum Cd, Pb and Zn concentrations in the samples collected in our study do not exceed the official standards for marine sediments, whereas the concentrations of Cr and Cu slightly exceed the standards. Correlations exist between the concentrations of Cu, Pb, Zn, Cr and Cd, and the concentrations of these metals are positively correlated with the mean particle size (φ value), indicating that the finer sediments have adsorbed greater amounts of heavy metal elements than the coarser sediments. An evaluation of the potential environmental risks demonstrates that certain indices of heavy metal pollution and environmental risks are relatively low and may be assigned low risk levels, thereby indicating that, in terms of heavy metals, the marine sedimentary environment in this region is only mildly impacted. Our analysis of the contaminant origins shows that the heavy metals in this region primarily originate in the Pearl River Estuary and that a small amount of them is derived from local runoff. The elevated heavy metal concentrations from the upper sections of the cores started 130 years ago, which indicats that heavy metals in the surface sediments are primarily due to human activities associated with industrialization.

Amino acid epimerization implies rapid sedimentation rates in Arctic Ocean cores

USGS Publications Warehouse

Sejrup, H.P.; Miller, G.H.; Brigham-Grette, J.; Lovlie, R.; Hopkins, D.

1984-01-01

The palaeooceanography of the Arctic Ocean is less well known than any other ocean basin, due to difficulties in obtaining cores and in providing a secure chronological framework for those cores that have been raised. Most recent investigators have suggested that low sedimentation rates (0.05-0.1 cm kyr-1) have characterized the deep basins over the past 5 Myr (refs 1,2) despite the glacial-marine character of the sediment and proximity to major centres of shelf glaciation. These calculations have been primarily based on the down-core pattern in the inclination of magnetic minerals, supported by uranium-series, 14C and micropalaeontological evidence. Here we analyse amino acid diagnesis in foraminifera from two gravity cores raised from the floor of the Arctic Ocean, our results suggest that these cores span <200 kyr., conflicting with the earlier estimate of 3 Myr based on palaeomagnetic data. The chronology of other Arctic Ocean cores and previous palaeoenvironmental interpretations need re-evaluation. ?? 1984 Nature Publishing Group.

Grain-size distribution and selected major and trace element concentrations in bed-sediment cores from the Lower Granite Reservoir and Snake and Clearwater Rivers, eastern Washington and northern Idaho, 2010

USGS Publications Warehouse

Braun, Christopher L.; Wilson, Jennifer T.; Van Metre, Peter C.; Weakland, Rhonda J.; Fosness, Ryan L.; Williams, Marshall L.

2012-01-01

Fifty subsamples from 15 cores were analyzed for major and trace elements. Concentrations of trace elements were low, with respect to sediment quality guidelines, in most cores. Typically, major and trace element concentrations were lower in the subsamples collected from the Snake River compared to those collected from the Clearwater River, the confluence of the Snake and Clearwater Rivers, and Lower Granite Reservoir. Generally, lower concentrations of major and trace elements were associated with coarser sediments (larger than 0.0625 millimeter) and higher concentrations of major and trace elements were associated with finer sediments (smaller than 0.0625 millimeter).

Variation of heavy metals in recent sediments from Piratininga Lagoon (Brazil): interpretation of geochemical data with the aid of multivariate analysis

NASA Astrophysics Data System (ADS)

Huang, W.; Campredon, R.; Abrao, J. J.; Bernat, M.; Latouche, C.

1994-06-01

In the last decade, the Atlantic coast of south-eastern Brazil has been affected by increasing deforestation and anthropogenic effluents. Sediments in the coastal lagoons have recorded the process of such environmental change. Thirty-seven sediment samples from three cores in Piratininga Lagoon, Rio de Janeiro, were analyzed for their major components and minor element concentrations in order to examine geochemical characteristics and the depositional environment and to investigate the variation of heavy metals of environmental concern. Two multivariate analysis methods, principal component analysis and cluster analysis, were performed on the analytical data set to help visualize the sample clusters and the element associations. On the whole, the sediment samples from each core are similar and the sample clusters corresponding to the three cores are clearly separated, as a result of the different conditions of sedimentation. Some changes in the depositional environment are recognized using the results of multivariate analysis. The enrichment of Pb, Cu, and Zn in the upper parts of cores is in agreement with increasing anthropogenic influx (pollution).

Uranium series isotopes concentration in sediments at San Marcos and Luis L. Leon reservoirs, Chihuahua, Mexico

NASA Astrophysics Data System (ADS)

Méndez-García, C.; Renteria-Villalobos, M.; García-Tenorio, R.; Montero-Cabrera, M. E.

2014-07-01

Spatial and temporal distribution of the radioisotopes concentrations were determined in sediments near the surface and core samples extracted from two reservoirs located in an arid region close to Chihuahua City, Mexico. At San Marcos reservoir one core was studied, while from Luis L. Leon reservoir one core from the entrance and another one close to the wall were investigated. 232Th-series, 238U-series, 40K and 137Cs activity concentrations (AC, Bq kg-1) were determined by gamma spectrometry with a high purity Ge detector. 238U and 234U ACs were obtained by liquid scintillation and alpha spectrometry with a surface barrier detector. Dating of core sediments was performed applying CRS method to 210Pb activities. Results were verified by 137Cs AC. Resulting activity concentrations were compared among corresponding surface and core sediments. High 238U-series AC values were found in sediments from San Marcos reservoir, because this site is located close to the Victorino uranium deposit. Low AC values found in Luis L. Leon reservoir suggest that the uranium present in the source of the Sacramento - Chuviscar Rivers is not transported up to the Conchos River. Activity ratios (AR) 234U/overflow="scroll">238U and 238U/overflow="scroll">226Ra in sediments have values between 0.9-1.2, showing a behavior close to radioactive equilibrium in the entire basin. 232Th/overflow="scroll">238U, 228Ra/overflow="scroll">226Ra ARs are witnesses of the different geological origin of sediments from San Marcos and Luis L. Leon reservoirs.

Gas and porewater composition of shallow sediments in the Tuaheni Basin, New Zealand

NASA Astrophysics Data System (ADS)

Rose, P. S.; Coffin, R. B.; Yoza, B.; Boyd, T. J.; Crutchley, G. J.; Mountjoy, J. J.; Pecher, I. A.

2015-12-01

Seismic profiles collected during previous investigations on the Hikurangi Margin, off the North Island, New Zealand showed bottom simulating reflectors (BSRs), which are generally indicative of the presence of free gas. Further, double BSRs clearly identified in the Tuaheni Basin were hypothesized to result from differences in gas composition and fluid migration. During a cruise on the RV Tangaroa in June 2015 (TAN 1508) additional seismic data were collected and used to identify piston coring targets. Coring locations were selected to sample around BSR pinch-outs and possible fluid migration pathways to determine gas composition and flux. Shallow sediments collected in June 2015 in the Tuaheni Basin had relatively low sediment headspace CH4 concentrations (6000ppm. Higher molecular weight alkanes were not detected in the sediment headspace gas at any location. Sediment porewater sulfate, chloride and sulfide concentrations will be presented with CH4concentration profiles and geophysical data.

Return to the Strangelove Ocean?: Preliminary results of carbon and oxygenisotope compositions of post-impact sediments, IODP Expedition 364 "Chicxulub Impact Crater"

NASA Astrophysics Data System (ADS)

Yamaguchi, K. E.; Ikehara, M.; Hayama, H.; Takiguchi, S.; Masuda, S.; Ogura, C.; Fujita, S.; Kurihara, E.; Matsumoto, T.; Oshio, S.; Ishihata, K.; Fuchizawa, Y.; Noda, H.; Sakurai, U.; Yamane, T.; Morgan, J. V.; Gulick, S. P. S.

2017-12-01

The Chicxulub crater in the northern Yucatan Peninsula, Mexico was formed by the asteroid impact at the Cretaceous-Paleogene boundary (66.0 Ma). In early 2016 the IODP Exp. 364 successfully drilled the materials from the topographic peak ring within the crater that was previously identified by seismological observations. A continuous core was recovered. The 112m-thick uppermost part of the continuous core (505.7-1334.7 mbsf) is post-impact sediments, including the PETM, that are mainly composed of carbonate with intercalation of siliciclastics and variable contents of organic carbon. More than 300 samples from the post-impact section were finely powdered for a variety of geochemical analysis. Here we report their carbon and oxygen isotope compositions of the carbonate fraction (mostly in the lower part of the analyzed section) and carbon and nitrogen isotope compositions of organic matter (mostly in the middle-upper part of the analyzed section). Isotope mass spectrometer Isoprime was used for the former analysis, and EA-irMS (elemental analyzer - isotope ratio mass spectrometer) was used for the latter analysis, both at CMCR, Kochi Univ. Depth profile of oxygen isotope compositions of carbonate fraction is variable and somewhat similar to those of Zachos et al. (2001; Science). Carbon isotope compositions of carbonate and organic carbon in the lower part of the analyzed section exhibit some excursions that could correspond to the hyperthemals in the early Paleogene. Their variable nitrogen isotope compositions reflect temporal changes in the style of biogeochemical cycles involving denitrification and nitrogen fixation. Coupled temporal changes in the carbon isotope compositions of organic and carbonate carbon immediately after the K-Pg boundary might support a Strangelove ocean (Kump, 1991; Geology), however high export production (Ba/Ti, nannoplankton and calcisphere blooms, high planktic foram richness, and diverse and abundant micro- and macrobenthic organisms) at the base of the Danian limestone cored during Exp. 364 contradict a Strangelove Ocean.

Uranium and Its Decay Products in Floodplain Sediments from the River Fal

NASA Astrophysics Data System (ADS)

Millward, G. E.; Blake, W. H.; Little, R.; Couldrick, L.

2012-04-01

European river basins are subject to longer-term storage of legacy contaminants in sedimentary sinks and their potential release presents a credible risk to achieving water quality targets required by the EU Water Framework Directive. The catchment of the River Fal, south west England, is extensively mineralised and has been greatly impacted by heavy metal mining. Uranium and radium were extracted and processed between 1870 and 1930 and spoil tips along the channel banks are assumed to have been a source of radionuclides into the river. Radionuclides were determined in five cores obtained from the river floodplain, including a reference core positioned upstream of the uranium mine enabling evaluation of its impact on past and contemporary sediment quality. The core was sectioned into 1 cm thick slices and they were analysed by gamma spectrometry for products of the U-238 decay series, i.e. Th-234 (a surrogate for U-238), Pb-214 (a surrogate for Ra-226), Pb-210 and fallout Am-241 and Cs-137. Peak Cs-137 concentrations at mid-depth were associated with fallout after atmospheric nuclear tests in 1963 and were used to estimate sedimentation rates. However, the activity concentrations of Pb-210 were elevated at all depths and the result indicated a significant input of unsupported Pb-210 (linked to processed spoil material) throughout the period of deposition. At some sites, peak activity concentrations of Th-234 suggested inputs from mining activity during major release and/or flood events. The cores downstream of the mine all had higher radionuclide inventories, of the order 105 Bq m-2, compared to the reference core due to the presences of products from the U-238 decay series. In addition, the inventories did not decrease systematically downstream indicating storage regions within the river channel. Storage of such legacy contaminants at levels in excess of contemporary environmental quality guidelines raises important questions and challenges for floodplain use and management.

Evaluation of dredged material proposed for ocean disposal from Gravesend Bay Anchorage, New York

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barrows, E.S.; Gruendell, B.D.

1996-09-01

The Gravesend Bay Anchorage was one of seven waterways that the US Army Corps of Engineers-New York District (USACE-NYD) requested the Battelle Marine Sciences Laboratory (MSL) to sample and evaluate for dredging and disposal in February 1994. Sediment samples were submitted for physical and chemical analyses to provide baseline sediment chemistry data on the Gravesend Bay Anchorage. Individual sediment core samples collected at the Gravesend Bay Anchorage were analyzed for grain size, moisture content, and total organic carbon (TOC). Two samples, one of composited sediment cores representing the southeast corner of the anchorage (COMP GR), and one sediment core representingmore » the northeast corner of the anchorage (Station GR-1 0), were analyzed for bulk density, specific gravity, metals, chlorinated pesticides, polychlorinated biphenyl (PCB) congeners, polynuclear aromatic hydrocarbons (PAH), and 1,4-dichlorobenzene.« less

Shallow stratigraphy of the Skagit River Delta, Washington, derived from sediment cores

USGS Publications Warehouse

Grossman, Eric E.; George, Douglas A.; Lam, Angela

2011-01-01

Sedimentologic analyses of 21 sediment cores, ranging from 0.4 to 9.6 m in length, reveal that the shallow geologic framework of the Skagit River Delta, western Washington, United States, has changed significantly since 1850. The cores collected from elevations of 3.94 to -2.41 m (relative to mean lower low water) along four cross-shore transects between the emergent marsh and delta front show relatively similar environmental changes across an area spanning ~75 km2. Offshore of the present North Fork Skagit River and South Fork Skagit River mouths where river discharge is focused by diked channels through the delta, the entire 5–7-km-wide tidal flats are covered with 1–2 m of cross-bedded medium-to-coarse sands. The bottoms of cores, collected in these areas are composed of mud. A sharp transition from mud to a cross-bedded sand unit indicates that the tidal flats changed abruptly from a calm environment to an energetic one. This is in stark contrast to the Martha's Bay tidal flats north of the Skagit Bay jetty that was completed in the 1940s to protect the newly constructed Swinomish Channel from flooding and sedimentation. North of the jetty, mud ranging from 1 to 2 m thick drapes a previously silt- and sand-rich tidal flat. The silty sand is a sediment facies that would be expected there where North Fork Skagit River sedimentation occurred prior to jetty emplacement. This report describes the compositional and textural properties of the sediment cores by using geophysical, photographic, x-radiography, and standard sediment grain-size and carbon-analytical methods. The findings help to characterize benthic habitat structure and sediment transport processes and the environmental changes that have occurred across the nearshore of the Skagit River Delta. The findings will be useful for quantifying changes to nearshore marine resources, including impacts resulting from diking, river-delta channelization, shoreline development, and natural variations in fluvial-sediment inputs. These results also provide important quantitative data on the amount of sediment delivered to the nearshore from the Skagit River for use in calculating sediment budgets for application to watershed planning and wetland and coastal-ecosystem restoration.

A carbon, nitrogen, and sulfur elemental and isotopic study in dated sediment cores from the Louisiana Shelf

USGS Publications Warehouse

Rosenbauer, R.J.; Swarzenski, P.W.; Kendall, C.; Orem, W.H.; Hostettler, F.D.; Rollog, M.E.

2009-01-01

Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine variable organic matter inputs, and to assess the sediment record for possible evidence of hypoxic events. Sediment from site MRJ03-3, which is located close to the Mississippi Canyon and generally not influenced by summer-time hypoxia, is typical of marine sediment in that it contains mostly marine algae and fine-grained material from the erosion of terrestrial C4 plants. Sediment from site MRJ03-2, located closer to the mouth of the Mississippi River and at the periphery of the hypoxic zone (annual recurrence of summer-time hypoxia >50%), is similar in composition to core MRJ03-3, but exhibits more isotopic and elemental variability down-core, suggesting that this site is more directly influenced by river discharge. Site MRJ03-5 is located in an area of recurring hypoxia (annual recurrence >75%), and is isotopically and elementally distinct from the other two cores. The carbon and nitrogen isotopic composition of this core prior to 1960 is similar to average particulate organic matter from the lower Mississippi River, and approaches the composition of C3 plants. This site likely receives a greater input of local terrestrial organic matter to the sediment. After 1960 and to the present, a gradual shift to higher values of ??13C and ??15N and lower C:N ratios suggests that algal input to these shelf sediments increased as a result of increased productivity and hypoxia. The values of C:S and ??34S reflect site-specific processes that may be influenced by the higher likelihood of recurring seasonal hypoxia. In particular, the temporal variations in the C:S and ??34S down-core are likely caused by changes in the rate of sulfate reduction, and hence the degree of hypoxia in the overlying water column. Based principally on the down-core C:N and C:S ratios and ??13C and ??34S profiles, sites MRJ03-3 and MRJ03-2 generally reflect more marine organic matter inputs, while site MRJ03-5 appears to be more influenced by terrestrial deposition. ?? 2009 Springer-Verlag.

Technical note: Late Pliocene age control and composite depths at ODP Site 982, revisited

NASA Astrophysics Data System (ADS)

Khélifi, N.; Sarnthein, M.; Naafs, B. D. A.

2012-01-01

Ocean Drilling Program (ODP) Site 982 provided a key sediment section at Rockall Plateau for reconstructing northeast Atlantic paleoceanography and monitoring benthic δ18O stratigraphy over the late Pliocene to Quaternary onset of major Northern Hemisphere glaciation. A renewed hole-specific inspection of magnetostratigraphic reversals and the addition of epibenthic δ18O records for short Pliocene sections in holes 982A, B, and C, crossing core breaks in the δ18O record published for Hole 982B, now imply a major revision of composite core depths. After tuning to the orbitally tuned reference record LR04, the new composite δ18O record results in a hiatus, where the Kaena magnetic subchron might have been lost, and in a significant age reduction for all proxy records by 130 to 20 ky over the time span 3.2-2.7 million years ago (Ma). Our study demonstrates the general significance of reliable composite-depth scales and δ18O stratigraphies in ODP sediment records for generating ocean-wide correlations in paleoceanography. The new concept of age control makes the late Pliocene trends in SST (sea surface temperature) and atmospheric pCO2 at Site 982 more consistent with various paleoclimate trends published from elsewhere in the North Atlantic.

Lignin geochemistry of a Late Quaternary sediment core from Lake Washington

NASA Astrophysics Data System (ADS)

Hedges, John I.; Ertel, John R.; Leopold, Estella B.

1982-10-01

Long-term lignin stability and paleovegetation patterns were investigated using CuO oxidation products of sediments from an 11 m core of Late Quaternary sediment collected from the mid-basin of Lake Washington, Washington State. Relatively constant yields of lignin-derived phenols (normalized to organic carbon) from the entire core indicate minimal in situ lignin degradation over the last 13,000 years. Compositional patterns within the phenolic suite and increased corresponding yields from baseextracted sediments indicate that sedimentary lignins are present predominantly as well preserved plant tissue fragments. Abundance patterns of vanillyl, syringyl, and cinnamyl phenols record four distinct sequences within the core characterized by: (a) high concentrations of gymnosperm wood in a basal horizon of glacial flour, 11-10 m; (b) an essentially pure mixture of nonwoody angiosperm tissues in late Pleistocene sediments, 10-8 m; (c) relatively high concentrations of angiosperm woods in the bottom half of a limnic peat sequence deposited approximately 10,000-7,000 years B.P., 8-4 m; and (d) a progressive enrichment in gymnosperm woods at the expense of angiosperm woods over the last 7,000 years in the upper limnic peat, 4-0 m. Vascular plant tissues account for less than half the total sedimentary organic carbon throughout the core.

Abrupt Changes at the Permian/Triassic Boundary: Tempo of Events from High-Resolution Cyclostratigraphy

NASA Technical Reports Server (NTRS)

Rampino, M. R.; Prokoph, A.; Adler, A. C.

2000-01-01

The Permian/Triassic (P/Tr) boundary (251.4 +/- 3 Myr) is marked by the most severe mass extinction in the geologic record. Recently, precise absolute dating has bracketed the marine extinctions and associated carbon-isotope anomaly within less than 1 Myr. We improve this resolution through high-resolution stratigraphy across the P/Tr boundary in the 331-m Gartnerkofel-1 core and nearby Reppwand outcrop section (Carnic Alps, Austria) utilizing FFT and wavelet timeseries analyses of cyclic components in down-hole core logs of density and natural gamma-ray intensity, and carbon-isotopic ratios of bulk samples. The wavelet analysis indicates continuity of deposition across the P/Tr boundary interval, and the timeseries analyses show evidence for persistent cycles in the ratio of approximately 40: 10: 4.7: 2.3 meters, correlated with Milankovitch-band orbital cycles of approximately 412: 100: 40: 20 kyr (eccentricity 1 and 2, obliquity, and precession), and giving a consistent average sedimentation rate of approximately 10 cm/1,000 yr. Milankovitch periods in delta C-13 and density in these shallow-water carbonates were most likely the result of climatically induced oscillations of sea level and climate, coupled with changes in ocean circulation and productivity, that affected sedimentation. Fluctuations in gamma radiation reflect varying input of clay minerals and the presence of shaly interbeds. Throughout the P/Tr boundary interval in the core, the 100,000-year eccentricity cycle seems to be dominant. Weaker obliquity and precession cycles are in line with the location of the Austrian section in the latest Permian, close to the Equator in the western bight of the Tethys, where obliquity and precessional effects on seasonal contrast might be subdued. Using the improved resolution provided by cycle analysis in the GK-1 core, we find that the dramatic change in the faunal record that marks the P/Tr boundary takes place over less than 6m, or less than 60,000 years. In the nearby Reppwand outcrop section, the same faunal changes occurs over only 0.8 m or about 8,000 years, close to the limit of time-resolution induced by bioturbation and reworking in these sediments. The sharp negative global carbon-isotope shift took place within less than or equal to 40,000 yr, and the isotope excursions persisted for approximately 480,000 yr into the Early Triassic. The results indicate that the severe marine faunal event that marks the P/Tr boundary was very sudden, perhaps less than the resolution window in the GK-1 core, and suggest a catastrophic cause. The wavelet-analysis approach to high-resolution cyclostratigraphy can be applied to other P/Tr boundary sections, and when combined with precise absolute dating and magnetostratigraphic methods promises a significant increase in resolution in determining the correlation and tempo of the end-Permian extinctions and related events worldwide.

Non-destructive X-ray Computed Tomography (XCT) Analysis of Sediment Variance in Marine Cores

NASA Astrophysics Data System (ADS)

Oti, E.; Polyak, L. V.; Dipre, G.; Sawyer, D.; Cook, A.

2015-12-01

Benthic activity within marine sediments can alter the physical properties of the sediment as well as indicate nutrient flux and ocean temperatures. We examine burrowing features in sediment cores from the western Arctic Ocean collected during the 2005 Healy-Oden TransArctic Expedition (HOTRAX) and from the Gulf of Mexico Integrated Ocean Drilling Program (IODP) Expedition 308. While traditional methods for studying bioturbation require physical dissection of the cores, we assess burrowing using an X-ray computed tomography (XCT) scanner. XCT noninvasively images the sediment cores in three dimensions and produces density sensitive images suitable for quantitative analysis. XCT units are recorded as Hounsfield Units (HU), where -999 is air, 0 is water, and 4000-5000 would be a higher density mineral, such as pyrite. We rely on the fundamental assumption that sediments are deposited horizontally, and we analyze the variance over each flat-lying slice. The variance describes the spread of pixel values over a slice. When sediments are reworked, drawing higher and lower density matrix into a layer, the variance increases. Examples of this can be seen in two slices in core 19H-3A from Site U1324 of IODP Expedition 308. The first slice, located 165.6 meters below sea floor consists of relatively undisturbed sediment. Because of this, the majority of the sediment values fall between 1406 and 1497 HU, thus giving the slice a comparatively small variance of 819.7. The second slice, located 166.1 meters below sea floor, features a lower density sediment matrix disturbed by burrow tubes and the inclusion of a high density mineral. As a result, the Hounsfield Units have a larger variance of 1,197.5, which is a result of sediment matrix values that range from 1220 to 1260 HU, the high-density mineral value of 1920 HU and the burrow tubes that range from 1300 to 1410 HU. Analyzing this variance allows us to observe changes in the sediment matrix and more specifically capture where, and to what extent, the burrow tubes deviate from the sediment matrix. Future research will correlate changes in variance due to bioturbation to other features indicating ocean temperatures and nutrient flux, such as foraminifera counts and oxygen isotope data.

Pliocene and Pleistocene geologic and climatic evolution in the San Luis Valley of south-central Colorado

USGS Publications Warehouse

Rogers, K.L.; Larson, E.E.; Smith, G.; Katzman, D.; Smith, G.R.; Cerling, T.; Wang, Y.; Baker, R.G.; Lohmann, K.C.; Repenning, C.A.; Patterson, P.; Mackie, G.

1992-01-01

Sediments of the Alamosa Formation spanning the upper part of the Gauss and most of the Matuyama Chrons were recovered by coring in the high (2300 m) San Luis Valley of south-central Colorado. The study site is located at the northern end of the Rio Grande rift. Lithologic changes in the core sediments provide evidence of events leading to integration of the San Luis drainage basin into the Rio Grande. The section, which includes the Huckleberry Ridge Ash (2.02 Ma) and spans the entire Matuyama Chron, contains pollen, and invertebrate and vertebrate fossils. Stable isotope analyses of inorganic and biogenic carbonate taken over most of the core indicate substantially warmer temperatures than occur today in the San Luis Valley. At the end of the Olduvai Subchron, summer precipitation decreased, summer pan evaporation increased, and temperatures increased slightly compared to the earlier climate represented in the core. By the end of the Jaramillo Subchron, however, cold/wet and warm/dry cycles become evident and continue into the cold/wet regime associated with the deep-sea oxygen-isotope Stage 22 glaciation previously determined from outcrops at the same locality. Correspondence between the Hansen Bluff climatic record and the deep-sea oxygen-isotope record (oxygen-isotope stages from about 110-18) is apparent, indicating that climate at Hansen Bluff was responding to global climatic changes. ?? 1992.

Trace element distribution in the water and sediments of certain storage lakes from the Jijia catchment, (Romania)

NASA Astrophysics Data System (ADS)

Dughila, A.; Iancu, O. G.; Romanescu, G. T.

2012-04-01

The present study aims at investigating the concentrations and distribution levels of a series of trace elements in water and sediment samples collected from six storage lakes located in the Jijia catchment - NE of Romania. The lakes are multi-purpose water reservoirs, three of them being mainly used as a source of municipal drinking water, or for fishing, irrigation for the farms in the area, protection against floods and the regulation of river flows. By contrast, agricultural wastes, fertilizers, raw sewage effluents and road runoff constitute the predominant anthropogenic sources, which supply the lakes in question with Cd, Cu, Pb and Zn. The present study was conducted on a series of 63 sediment samples and 18 water samples, collected from the same locations, in order to establish the distribution levels of certain trace elements from the water through sediments. Sediment cores were collected from two sections across each lake by means of a motor boat, using a system that consists of a graduated sampling tube (0.9 m in length and 72.5 mm in diameter) made of Plexiglas (Eijkelkamp sample tube guide). Prior to the analyses, the samples were air-dried, ground and homogenized using an agate mortar, oven-dried at 50 °C for 6 days and then sieved through 63 µm sieves. The sediment and water samples were subjected to a digestion technique with concentrated nitric acid using a microwave oven (Berghof type), and analyzed for the following elements: Pb, Zn, Cu, Cd, Cr and Ni. The total concentration of the elements was measured through atomic absorption spectrometry (AAS) with an RSD of < 10 % from solutions. The vertical distribution of most elements in the cores examined could be characterized as relatively uniform, with higher concentrations for those collected from the lakes which are more influenced by anthropogenic factors, compared to those situated in forested areas. The lake-water quality characteristics were below the recommended drinking water standards imposed by the current legislation (MMGA Ord. No. 161/16.02.2006 - Normative regarding the classification of surface waters in order to establish the ecological status of water bodies, which combines European and Romanian provisions), with the exception of copper (with very high concentrations in all the water samples), lead and cadmium. Keywords: AAS, Jijia catchment (Romania), lake water, sediment core, trace elements

INNOVATIVE TECHNOLOGY EVALUATION REPORT ...

EPA Pesticide Factsheets

The Russian Peat Borer designed and fabricated by Aquatic Research Instruments was demonstrated under the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation Program in April and May 1999 at sites in EPA Regions 1 and 5, respectively. In addition to assessing ease of sampler operation, key objectives of the demonstration included evaluating the sampler?s ability to (1) consistently collect a given volume of sediment, (2) consistently collect sediment in a given depth interval, (3) collect samples with consistent characteristics from a homogenous layer of sediment, and (4) collect samples under a variety of site conditions. This report describes the demonstration results for the Russian Peat Borer and two conventional samplers (the Hand Corer and Vibrocorer) used as reference samplers. During the demonstration, the Russian Peat Borer was the only sampler that collected samples in the deep depth interval (4 to 11 feet below sediment surface). It collected representative and relatively uncompressed core samples of consolidated sediment in discrete depth intervals. The reference samplers collected relatively compressed samples of both consolidated and unconsolidated sediments from the sediment surface downward; sample representativeness may be questionable because of core shortening and core compression. Sediment stratification was preserved only for consolidated sediment samples collected by the Russian Peat Borer but for bo

Barium and calcium analyses in sediment cores using µ-XRF core scanners

NASA Astrophysics Data System (ADS)

Acar, Dursun; Çaǧatay, Namık; Genç, S. Can; Eriş, K. Kadir; Sarı, Erol; Uçarkus, Gülsen

2017-04-01

Barium and Ca are used as proxies for organic productivity in paleooceanographic studies. With its heavy atomic weight (137.33 u), barium is easily detectable in small concentrations (several ppm levels) in marine sediments using XRF methods, including the analysis by µ-XRF core scanners. Calcium has an intermediate atomic weight (40.078 u) but is a major element in the earth's crust and in sediments and sedimentary rocks, and hence it is easily detectable by µ-XRF techniques. Normally, µ-XRF elemental analysis of cores are carried out using split half cores or 1-2 cm thich u-channels with an original moisture. Sediment cores show variation in different water content (and porosity) along their length. This in turn results in variation in the XRF counts of the elements and causes error in the elemental concentrations. We tried µ-XRF elemental analysis of split half cores, subsampled as 1 cm thick u-channels with original moisture and 0.3 mm-thin film slices of the core with original wet sample and after air drying with humidity protector mylar film. We found considerable increase in counts of most elements, and in particular for Ba and Ca, when we used 0.3 mm thin film, dried slice. In the case of Ba, the counts increased about three times that of the analysis made with wet and 1 cm thick u-channels. The higher Ba and Ca counts are mainly due to the possible precipitation of Ba as barite and Ca as gypsum from oxidation of Fe-sulphides and the evaporation of pore waters. The secondary barite and gypsum precipitation would be especially serious in unoxic sediment units, such as sapropels, with considerable Fe-sulphides and bio-barite.It is therefore suggested that reseachers should be cautious of such secondary precipitation on core surfaces when analyzing cores that have long been exposed to the atmospheric conditions.

Subdivision of Holocene Baltic sea sediments by their physical properties [Gliederung holozaner ostseesedimente nach physikalischen Eigenschaften

USGS Publications Warehouse

Harff, Jan; Bohling, Geoffrey C.; Endler, R.; Davis, J.C.; Olea, R.A.

1999-01-01

The Holocene sediment sequence of a core taken within the centre of the Eastern Gotland Basin was subdivided into 12 lithostratigraphic units based on MSCL-data (sound velocity, wet bulk density, magnetic susceptibility) using a multivariate classification method. The lower 6 units embrace the sediments until the Litorina transgression, and the upper 6 units subdivide the brackish-marine Litorina- and post-Litorina sediments. The upper lithostratigraphic units reflect a change of anoxic (laminated) and oxic (non-laminated) sediments. By application of a numerical stratigraphic correlation method the zonation was extended laterally onto contiguous sediment cores within the central basin. Consequently the change of anoxic and oxic sediments can be used for a general lithostratigraphic subdivision of sediments of the Gotland Basin. A quantitative criterion based on the sediment-physical lithofacies is added to existing subdivisions of the Holocene in the Baltic Sea.

An overview of the refinements and improvements to the USEPA’s sediment toxicity methods for freshwater sediment

EPA Science Inventory

Sediment toxicity tests are used for contaminated sediments, chemical registration, and water quality criteria evaluations and can be a core component of ecological risk assessments at contaminated sediments sites. Standard methods for conducting sediment toxicity tests have been...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapelle, F.H.; Zelibor, J.L. Jr.; Grimes, D.J.

Nineteen cores of unconsolidated Coastal Plain sediments obtained from depths of 14 to 182 m below land surface near Waldorf, Maryland, were collected and examined for metabolically active bacteria. The age of the sediments cored range from Miocene to Early Cretaceous. Acridine orange direct counts of total (viable and nonviable) bacteria in core subsamples ranged from 10/sup 8/ to 10/sup 4/ bacteria/g of dry sediment. Direct counts of viable bacteria ranged from 10/sup 6/ to 10/sup 3/ bacteria/g of dry sediment. Three cores contained viable methanogenic bacteria, and seven cores contained viable sulfate-reducing bacteria. The observed presence of bacteria inmore » these sediments suggest that hetrotrophic bacterial metabolism, with lignitic organic material as the primary substrate, is a plausible source of CO/sub 2/ to ground water. However, the possibility that abiotic processes also produce CO/sub 2/ cannot be rules out. Estimated rates of CO/sub 2/ production in the noncalcareous Magothy/Upper Patapsco and Lower Patapsco aquifers based on mass balance of dissolved inorganic carbon, ground water flow rates, and flow path segment lengths are in the range 10/sup -3/ to 10/sup -5/ mmol L/sup -1/ yr/sup -1/. Isotope balance calculations suggest that aquifer-generated CO/sub 2/ is much heavier isotopically ( approx. - 10 to + 5 per mil) than lignite ( approx. - 24 per mil) present in these sediments. This may reflect isotopic fractionation during methanogenesis and possibly other bacterially mediated processes.« less

An innovative piston corer for large‐volume sediment samples

PubMed Central

Haselmair, Alexandra; Stachowitsch, Michael; Zuschin, Martin

2016-01-01

Abstract Coring is one of several standard procedures to extract sediments and their faunas from open marine, estuarine, and limnic environments. Achieving sufficiently deep penetration, obtaining large sediment volumes in single deployments, and avoiding sediment loss upon retrieval remain problematic. We developed a piston corer with a diameter of 16 cm that enables penetration down to 1.5 m in a broad range of soft bottom types, yields sufficient material for multiple analyses, and prevents sediment loss due to a specially designed hydraulic core catcher. A novel extrusion system enables very precise slicing and preserves the original sediment stratification by keeping the liners upright. The corer has moderate purchase costs and a robust and simple design that allows for a deployment from relatively small vessels as available at most marine science institutions. It can easily be operated by two to three researchers rather than by specially trained technicians. In the northern Adriatic Sea, the corer successfully extracted more than 50 cores from a range of fine mud to coarse sand, at water depths from three to 45 m. The initial evaluation of the cores demonstrated their usefulness for fauna sequences along with heavy metal, nutrient and pollutant analyses. Their length is particularly suited for historical ecological work requiring sedimentary and faunal sequences to reconstruct benthic communities over the last millennia. PMID:28111529

A giant sediment trap in the Florida keys

USGS Publications Warehouse

Shinn, E.A.; Reich, C.D.; Locker, S.D.; Hine, A.C.

1996-01-01

Aerial photography, high-resolution seismic profiling, coring and jet probing have revealed a large sediment-filled sinkhole in the Key Largo National Marine Sanctuary off Key Largo, Florida. The 600-m-diameter feature straddles coral reef and carbonate-sand facies and contains >55 m of marine lime sand and aragonite mud. Bulk 14C age determinations of mud from a 30- m sediment core indicate infilling rates exceeding 20 m/ka between 3 and 5.6 ka. The total thickness and nature of the sediment near the base of the sinkhole are not known.

Facies-dependent variations in sediment physical properties on the Mississippi River Delta Front, USA: evidence for depositional and post-depositional processes

NASA Astrophysics Data System (ADS)

Smith, J. E., IV; Bentley, S. J.; Courtois, A. J.; Obelcz, J.; Chaytor, J. D.; Maloney, J. M.; Georgiou, I. Y.; Xu, K.; Miner, M. D.

2017-12-01

Recent studies on Mississippi River Delta have documented sub-aerial land loss, driven in part by declining sediment load over the past century. Impacts of changing sediment load on the subaqueous delta are less well known. The subaqueous Mississippi River Delta Front is known to be shaped by extensive submarine mudflows operating at a range of temporal and spatial scales, however impacts of changing sediment delivery on mudflow deposits have not been investigated. To better understand seabed morphology and stratigraphy as impacted by plume sedimentation and mudflows, an integrated geological/geophysical study was undertaken in delta front regions offshore the three main passes of the Mississippi River Delta. This study focuses on stratigraphy and physical properties of 30 piston cores (5-9 m length) collected in June 2017. Coring locations were selected in gully, lobe and prodelta settings based on multibeam bathymetry and seismic profiles collected in mid-May 2017. Cores were analyzed for density, magnetic susceptibility, P-wave speed, and resistivity using a Geotek multi sensor core logger; here, we focus on density data. Core density profiles generally vary systematically across facies. Density profiles of gully cores are nearly invariant with some downward stepwise increases delineating units meters thick, and abundant gaps likely caused by gas expansion. Lobe cores generally have subtle downward increases in density, some stepwise density increases, and fewer gaps. Prodelta cores show more pronounced downward density increases, decimeter-scale peaks and valleys in density profiles, but stepwise increases are less evident. We hypothesize that density profiles in gully and lobe settings (uniform profiles except for stepwise increases) reflect remolding by mudflows, whereas density variations in prodelta settings instead reflect grain size variations (decimeter-scale) and more advanced consolidation (overall downward density increase) consistent with slower sediment deposition. These hypotheses will be evaluated by a more detailed study of seismic stratigraphy and core properties, including geochronology, grain size distribution and X-radiographic imaging, to further relate important sedimentary processes with resulting deposits.

Persistence, temporal and spatial profiles of ultraviolet absorbents and phenolic personal care products in riverine and estuarine sediment of the Pearl River catchment, China.

PubMed

Peng, Xianzhi; Xiong, Songsong; Ou, Weihui; Wang, Zhifang; Tan, Jianhua; Jin, Jiabin; Tang, Caiming; Liu, Jun; Fan, Yujuan

2017-02-05

A variety of personal care products have been classified as emerging contaminants (ECs). Occurrence, fate, spatial and vertical profiles of 13 ultraviolet absorbents, triclocarban (TCC) and its dechlorinated products, triclosan (TCS), 2-phenylphenol and parabens were investigated in riverine and estuarine sediment of the Pearl River catchment, China. Bisphenol A (BPA), a widely applied plasticizer, was also investigated. The ECs were widely present in the bed sediment. TCC was the most abundant with a maximum concentration of 332ngg -1 dry weight. The other prominent ECs included BPA, TCS, octocrylene, and benzotriazole UV stabilizers UV326 and UV328. Treated wastewater effluent was the major source of the ECs in the riverine sediment. TCC, BPA, TCS, methyparaben, UV531, UV326, and UV328 were also detected throughout the estuarine sediment cores, indicating their persistence in the sediment. Temporal trends of the ECs in the sediment cores reflected a combined effect of industrial development, population growth, human life quality improvement, and waste treatment capacity in the Pearl River Delta over the last decades. TCC dechlorination products were frequently detected in the bed sediment with higher levels near treated effluent outlets but only occasionally observed in the sediment cores, suggesting insignificant in-situ TCC dechlorination in the sediment. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantifying and overcoming bioturbation in marine sediment cores: dual 14C and δ18O analysis on single foraminifera

NASA Astrophysics Data System (ADS)

Lougheed, Bryan; Metcalfe, Brett; Wacker, Lukas

2017-04-01

Marine sediment cores used in palaeoceanography form the basis of our current understanding of past global climate and ocean chemistry. Precision and accuracy of geochronological control in these sediment cores are crucial in unravelling the timing of rapid shifts in palaeoclimate and, ultimately, the interdependency of global climate mechanisms and their causality. Aware of the problems associated with bioturbation (the mixing of ocean sediments by benthic organisms) palaeoceanographers generally aim to retrieve sediment cores from locations with high sediment accumulation rates, thus minimising the influence of bioturbation as much as possible. However, the practice of concentrating only on areas of the ocean floor with high sedimentation accumulation rates has the potential to introduce a geographical bias into our understanding of global palaeoclimate. For example, global time averaged sediment accumulation rates for the ocean floor (excluding continental margins) indicate that vast areas of the ocean floor have sediment accumulation rates less than the recommended minimum advised sediment accumulation rates of 10 cm/ka or greater. Whilst many studies have focussed on quantifying the impact of bioturbation on our understanding of the past, few have attempted to overcome the problems associated with bioturbation. Recent pioneering developments in 14C AMS at the Laboratory of Ion Beam Physics at ETH Zürich have led to the development of the Mini Carbon Dating System (MICADAS). This compact 14C AMS system can be coupled to a carbonate handling system, thus enabling the direct AMS measurement of gaseous samples, i.e. without graphitisation, allowing for the analysis of carbonate samples of <100 μg. Likewise, while earlier isotope ratio mass spectrometry (IRMS) technology required a minimum of 100 μg of carbonate to produce a successful δ18O measurement, more recent advances in IRMS technology have made routine measurements of as little as 5 μg possible. Combining both analytical techniques enables palaeoclimate reconstructions that are independent of depth. Here, we present work on a low sedimentation core ( 2 cm/ka) core in the North Atlantic (core T86-10P, 37° 8.13' N, 29° 59.15' W) on single shells of the benthic species of foraminifera, Cibicidoides wuellerstorfi. Preliminary downcore single specimen 14C data display a large scatter in 14C ages for the various discrete 1 cm depth intervals analysed. In the case of depth intervals where three or more single specimens have been analysed, we find that the standard deviation in 14C age varies between 1210 and 9437 14C yr, with the mean variation for all such discrete depths being 3384 14C yr.

Natural gas geochemistry of sediments drilled on the 2005 Gulf of Mexico JIP cruise

USGS Publications Warehouse

Lorenson, T.D.; Claypool, G.E.; Dougherty, J.A.

2008-01-01

In April and May 2005, cores were acquired and sub-sampled for gases in lease blocks Atwater Valley 13 and 14 and Keathley Canyon 151 during deep subseafloor drilling conducted as part of the JIP study of gas hydrates in the northern Gulf of Mexico. Sample types included sediment headspace gas, free gas derived from sediment gas exsolution, and gas exsolution from controlled degassing of pressurized cores. The gases measured both onboard and in shore-based labs were nitrogen, oxygen, hydrogen sulfide, carbon dioxide, and the hydrocarbons methane through hexane. The presence of seafloor mounds, seismic anomalies, a shallow sulfate-methane interface, and similar gas compositions and isotopic compositions near the seafloor and at depth suggest an upward flux of methane at both sites. Sediment gases at the Atwater Valley sites, where seafloor mounds and adjacent sediments were cored, strongly suggest a microbial source of methane, with very little thermogenic gas input. Sediment gas from all cores contained from about 96 to 99.9% methane, with the balance composed primarily of carbon dioxide. Methane to ethane ratios were greater than 1000, and often over 10,000. Gases from cores at Keathley Canyon were similar to those at Atwater Valley, however, deeper cores from Keathley Canyon contained more ethane, propane, and butane suggesting mixing with minor concentrations thermogenic gas. The isotopic composition of methane, ethane, and carbon dioxide were measured, and ??13C values range from -84.3 to -71.5???, -65.2 to -46.8???, and -23.5 to -3.0???, respectively, all consistent with microbial gas sources, early diagenesis of organic matter and perhaps biodegradation of petroleum. The presence of deep microbial gas at these sites here and elsewhere highlights a potentially significant, predominantly microbial gas source in the northern Gulf of Mexico.

Morphobathymetric analysis of the large fine-grained sediment waves over the Gulf of Valencia continental slope (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Ribó, Marta; Puig, Pere; Muñoz, Araceli; Lo Iacono, Claudio; Masqué, Pere; Palanques, Albert; Acosta, Juan; Guillén, Jorge; Gómez Ballesteros, María

2016-01-01

Detailed analysis of recently acquired swath bathymetry, together with high-resolution seismic profiles and bottom sediment samples, revealed the presence of large-scale fine-grained sediment waves over the Gulf of Valencia continental slope. As many other deep-water sediment waves, these features were previously attributed to gravitational slope failure, related to creep-like deformation, and are here reinterpreted as sediment wave fields extending from 250 m depth to the continental rise, at 850 m depth. Geometric parameters were computed from the high-resolution multibeam dataset. Sediment wave lengths range between 500 and 1000 m, and maximum wave heights of up to 50 m are found on the upper slope, decreasing downslope to minimum values of 2 m high. Sediment waves on the lower part of the slope are quasi-stationary vertically accreting, whereas they show an upslope migrating pattern from the mid-slope to the upper part of the continental slope. High-resolution seismic profiles show continuous internal reflectors, with sediment waves merging down-section and sediment wave packages decreasing in thickness downslope. These sediment packages are thicker on the crest of each individual sediment wave and thinner on the downslope flank. 210Pb analyses conducted on sediment cores collected over the sediment wave fields also indicate slightly higher sediment accumulation rates on the wave crests. Sediment wave formation processes have been inferred from contemporary hydrodynamic observations, which reveal the presence of near-inertial internal waves interacting with the Gulf of Valencia continental slope. Internal wave activity is suggested to be the preferential mechanism for the transport and deposition of sediment, and the maintenance of the observed sediment wave fields.

Application of individual foraminifera Mg/Ca and δ18O analyses for paleoceanographic reconstructions in the Bay of Bengal and other active depositional environments

NASA Astrophysics Data System (ADS)

Fritz-Endres, T.; Dekens, P.; Fehrenbacher, J. S.; Spero, H. J.; Stine, A.

2017-12-01

Paleoceanographic research traditionally focuses on regions where sediment deposition is minimally affected by transport. However, sediment fans near tectonically active regions provide an opportunity to link oceanographic climate to terrestrial processes. Sediment cores recovered during IODP Expedition 354 in the Bay of Bengal include hemipelagic sections that record the history of tectonic uplift and the development of the Indian Monsoon through the last 10 Ma. Although these cores provide a unique opportunity to link marine and terrestrial climate, the complex depositional environment requires that the source of foraminifera is carefully considered before using these proxies to reconstruct oceanographic conditions. Foraminifera in Bengal Fan sediments may have been transported via turbidity currents from the northern Bay of Bengal, where the seasonal variability of SST and SSS is larger compared to the southern Bay of Bengal. We measured single Globigerinoides sacculifer Mg/Ca and δ18O from mudline samples of IODP Site U1454 (8.4°N, 85.5°E, 3721 m water depth) near the modern active channel and Site U1449 (8.4°N, 88.7°E, 3653 m water depth) far from channel activity. We compare these sites to single G. sacculifer from the core-top sample of Site 342KL (20.6°N, 90.1°E, 1256 m water depth) located on the continental shelf. Each foraminifera lives 2-4 weeks and the distribution of 60 to 80 data points reflects the seasonal range of SST and SSS at the location where the foraminifera calcified. Measurements in foraminifera from Site U1449 (away from active channel) are statistically different from the site in the northern Bay of Bengal and more consistent with local conditions. Conversely, foraminifera from the site near the active channel reflect a combined signal of local conditions recorded from the site far from channel activity and those recorded from the continental shelf. This suggests a portion of foraminifera from the active channel site have been transported from the northern Bay of Bengal. Our data show that foraminifera can be used to reconstruct SST and δ18O in this complex depositional environment, but caution must be taken when the down-core lithology indicates turbidites and possible sediment transport

The Late Pleistocene Contourites on Ceara Rise: Stratigraphy, Sedimentology and Paleoceanography

NASA Astrophysics Data System (ADS)

Ivanova, E. V.; Murdmaa, I.; Borisov, D.; Seitkalieva, E.; Ovsepyan, E.

2016-12-01

The study of sediment cores obtained during the cruises 35 (2012) and 50 (2015) of RV Akademic Ioffe from the Ceara Rise in the western tropical Atlantic strongly supports a significant influence of bottom (contour) currents on the Late Quaternary sedimentation. Seismic evidence of contourites in the study area (migrating contourite sediment waves, furrows) was previously described by Kumar and Embley (1977) and Curry et al. (1995). Widespread distribution of seismic waves on the rise and adjacent areas was suggested by Murdmaa et al (2014) based on the results of high-resolution seismic profiling with SES-2000 deep (4-5 kHz) in 2012. Our sediment cores recovered intercalation of bioturbated clays and silty clays with thin linear or wavy sand and silt layers and lenses implying strong bottom current control on sedimentation. The stratigraphic frame of the reference core AI-3426 retrieved near the summit of the Ceara Rise, at the water depth of 3046 m is based on the foraminiferal (Globorotalia menardii zones), oxygen isotope and AMS-14C data. The core recovered sediments of the last 140 ka with very rich and well-preserved tropical planktic foraminiferal assemblages. G. menardii is common within MIS 1 and 5 and is almost absent in MIS 2-4 and upper MIS 6. The abundance of benthic foraminifers is rather low. However, dominance of Globocassidulina subglobosa in benthic assemblages likely indicates a moderate bottom-current activity on the Ceara Rise during the last glacial. The other 4-5m long sediment cores collected along the seismic profile from the northern and southern slopes demonstrate the similar contourite sedimentological features and insignificant reworking of the Neogene foraminiferal species as inferred from the core AI-3426 along with the significant variations in foraminiferal preservation during the Pleistocene. The study is supported by the projects RSF 14-50-00095, RFBR 14-05-00744 and RFBR 16-35-60111, and Program I3P by RAS.

Mercury Cycling in Sediments of the Northeast Pacific Continental Margin Between Southern California and Central Oregon, USA

NASA Astrophysics Data System (ADS)

Heim, W. A.; Coale, K. H.; Chiswell, H.; Olson, A.; Martenuk, S.; Bonnema, A.; Weiss-Penzias, P. S.

2017-12-01

Monomethylmercury (MMHg) production by anaerobic bacteria in sediments is considered to be a dominate source of MMHg to sediments and overlying surface water in the coastal environment. In this study, we measured total mercury (Hgt) and MMHg sediment and pore water concentrations and calculated diffusive sediment water exchange fluxes in samples collected on the coastal shelf in the California Current System. Sediment cores and overlying water were collected from 20 stations using a slow-entry multi-corer deployed during 4 oceanographic cruises over two years. The upper few centimeters of undisturbed cores were sectioned at the following depth increments: 0.5, 1, 1.5, 2, 3, 4, 5 cm. Pore waters were extracted via centrifugation and the Hgt and MMHg gradients were used to calculate fluxes into the overlying water column based upon molecular diffusion alone. Sediment concentrations for Hgt and MMHg ranged from 50 to 2338 pmoles g-1 and 0.1 to 9 pmoles g-1 respectively. Pore water and overlying water MMHg concentrations ranged from 0.1 to 2.2 pM and 0.03 to 0.3 pM respectively. Diffusional Hgt and MMHg sediment water fluxes ranged from 1.4 to 7.3 pmoles m-2 d-1 and -0.03 to 1.7 pmoles m-2 d-1 respectively. While the gradients in MMHg showed significant and widespread flux that would indicate an input into the waters of the shelf these fluxes were insufficient to sustain elevated concentrations at the sediment boundary layer, or at the depth of the shelf in general. Measurements made on the northwestern Atlantic shelf are in general an order of magnitude greater than those observed here. We suggest that the narrow eastern shelf of the California Current with little allochthonous inputs contrasts sharply with the broad shelf of the Eastern Seaboard with significant organic carbon, riverine and anthropogenic inputs. In general, the narrow shelf of the California Current seems to reflect the pelagic processes of the off shore regions for this element where water column production predominates the formation of the methylated forms.

Dendrogeochronologic and Anatomic Analysis of Excavated Plains Cottonwoods Determine Overbank Sedimentation Rates and Historical Channel Positions Along the Interior of a Migrating Meander Bend, Powder River, Montana

NASA Astrophysics Data System (ADS)

Metzger, T. L.; Pizzuto, J. E.; Schook, D. M.; Hasse, T. R.; Affinito, R. A.

2017-12-01

Dendrochronological dating of buried trees precisely determines the germination year and identifies the stratigraphic context of germination for the trees. This recently developed application of dendrochronology provides accurate time-averaged sedimentation rates of overbank deposition along floodplains and can be used to identify burial events. Previous studies have demonstrated that tamarisk (Tamarix ramosissima) and sandbar willow (Salix exigua) develop anatomical changes within the tree rings (increased vessel size and decreased ring widths) on burial, but observations of plains cottonwood (Populus deltoides ssp. monilifera) are lacking. In September 2016 and June 2017, five buried plains cottonwoods were excavated along a single transect of the interior of a meander bend of the Powder River, Montana. Sediment samples were obtained near each tree for 210Pb and 137Cs dating, which will allow for comparison between dendrochronological and isotopic dating methods. The plains cottonwood samples collected exhibit anatomical changes associated with burial events that are observed in other species. All trees germinated at the boundary between thinly bedded fine sand and mud and coarse sand underlain by sand and gravel, indicating plains cottonwoods germinate on top of point bars prior to overbank deposition. The precise germination age and depth provide elevations and minimum age constraints for the point bar deposits and maximum ages for the overlying sediment, helping constrain past channel positions and overbank deposition rates. Germination years of the excavated trees, estimated from cores taken 1.5 m above ground level, range from 2014 to 1862. Accurate establishment years determined by cross-dating the buried section of the tree can add an additional 10 years to the cored age. The sedimentation rate and accumulation thickness varied with tree age. The germination year, total sediment accumulation, and average sedimentation rate at the five sampled trees is: 2011, 35 cm, 7.0 cm/year; 1973, 77 cm, 1.8 cm/year; 1962, 140 cm, 2.6 cm/year; 1960, 123 cm, 2.2 cm/year; and 1862, 112 cm, 0.7 cm/year. These sedimentation rates indicate that the cumulative sedimentation decreases as a power law with increasing tree age.

Sediment storage quantification and postglacial evolution of an inner-alpine sedimentary basin (Gradenmoos, Schober Mountains, Austria)

NASA Astrophysics Data System (ADS)

Götz, J.; Buckel, J.; Otto, J. C.; Schrott, L.

2012-04-01

Knickpoints in longitudinal valley profiles of alpine headwater catchments can be frequently assigned to the lithological and tectonical setting, to damming effects through large (rockfall) deposits, or to the impact of Pleistocene glaciations causing overdeepened basins. As a consequence various sedimentary sinks developed, which frequently interrupt sediment flux in alpine drainage basins. Today these locations may represent landscape archives documenting a sedimentary history of great value for the understanding of alpine landscape evolution. The glacially overdeepened Gradenmoos basin at 1920 m a.s.l. (an alpine lake mire with adjacent floodplain deposits and surrounding slope storage landforms; approx. 4.1 km2) is the most pronounced sink in the studied Gradenbach catchment (32.5 km2). The basin is completely filled up with sediments delivered by mainly fluvial processes, debris flows, and rock falls, it is assumed to be deglaciated since Egesen times and it is expected to archive a continuous stratigraphy of postglacial sedimentation. As the analysis of denudation-accumulation-systems is generally based on back-calculation of stored sediment volumes to a specific sediment delivering area, most reliable results will be consequently obtained (1) if sediment output of the system can be neglected for the investigated period of time, (2) if - due to spatial scale - sediment storage can be assessed quantitatively with a high level of accuracy, and (3) if the sediment contributing area can be clearly delimited. All three aspects are considered to be fulfilled to a high degree within the Gradenmoos basin. Sediment storage is quantified using geophysical methods, core drillings and GIS modelling whereas postglacial reconstruction is based on radiocarbon dating and palynological analyses. Subject to variable subsurface conditions, different geophysical methods were applied to detect bedrock depth. Electrical resistivity surveying (2D/3D) was used most extensively as it delivered detailed and realistic subsurface models with low residual errors in the fine grained and water saturated central and distal part of the basin. With a lower data density, ground penetrating radar and refraction seismic supplied bedrock depths underneath adjacent debris and talus slope deposits. Additionally extracted sediment cores (up to 22 m depth) yielded a detailed stratigraphic record of the basin comprising a basal till layer underneath lake sediments (sandy-silty, partly varved), a sandy matrix with several oxidised layers in the upper sections, and layers of peat towards the surface. As bedrock was reached several times, core drilling further enabled to calibrate resistivity models. On the base of geophysical derived bedrock points, the shape of the assumed bedrock basin was modelled using a thin-plate-spline interpolation. Sediment volumes were calculated by subtracting the bedrock model from a surface DEM derived from terrestrial laser scanning. Since sediment delivering areas can be clearly assigned to single storage landform volumes, denudation rates could be calculated in detail and related to sedimentation rates obtained by radiocarbon dating results. An integrated analysis of surface, subsurface and temporal information finally yielded a model of postglacial basin evolution which will be discussed in a paraglacial context. This presentation is supported by the EUROCORES programme TOPO-EUROPE of the European Science Foundation.

Uranium series isotopes concentration in sediments at San Marcos and Luis L. Leon reservoirs, Chihuahua, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Méndez-García, C.; Montero-Cabrera, M. E., E-mail: elena.montero@cimav.edu.mx; Renteria-Villalobos, M.

2008-01-01

Spatial and temporal distribution of the radioisotopes concentrations were determined in sediments near the surface and core samples extracted from two reservoirs located in an arid region close to Chihuahua City, Mexico. At San Marcos reservoir one core was studied, while from Luis L. Leon reservoir one core from the entrance and another one close to the wall were investigated. ²³²Th-series, ²³⁸U-series, ⁴⁰K and ¹³⁷Cs activity concentrations (AC, Bq kg⁻¹) were determined by gamma spectrometry with a high purity Ge detector. ²³⁸U and ²³⁴U ACs were obtained by liquid scintillation and alpha spectrometry with a surface barrier detector. Dating ofmore » core sediments was performed applying CRS method to ²¹⁰Pb activities. Results were verified by ¹³⁷Cs AC. Resulting activity concentrations were compared among corresponding surface and core sediments. High ²³⁸U-series AC values were found in sediments from San Marcos reservoir, because this site is located close to the Victorino uranium deposit. Low AC values found in Luis L. Leon reservoir suggest that the uranium present in the source of the Sacramento – Chuviscar Rivers is not transported up to the Conchos River. Activity ratios (AR) ²³⁴U/²³⁸U and ²³⁸U/²²⁶Ra in sediments have values between 0.9–1.2, showing a behavior close to radioactive equilibrium in the entire basin. ²³²Th/²³⁸U, ²²⁸Ra/²²⁶Ra ARs are witnesses of the different geological origin of sediments from San Marcos and Luis L. Leon reservoirs.« less

Sedimentological, mineralogical, and geochemical results from surface sediments and the sediment record from Site 2 of the ICDP drilling project at Lake Towuti, Indonesia

NASA Astrophysics Data System (ADS)

Hasberg, A. K.; Melles, M.; Wennrich, V.; Vogel, H.; Just, J.; Russell, J. M.; Bijaksana, S.; Morlock, M.; Opitz, S.

2017-12-01

More than 1000 m of sediment core were recovered in spring 2015 from three different drill sites in tropical Lake Towuti (2.5°S, 121°E), Indonesia, during the Towuti Drilling Project (TDP) of the International Continental Scientific Drilling Program (ICDP). Furthermore, a set of 84 lake surface sediment samples, distributed over the entire lake, was collected in order to better understand modern sedimentary processes. The surface samples were investigated for physical, chemical, mineralogical, and biological properties at the University of Cologne (UoC), Germany. On the sediment cores macro- and microscopical lithological descriptions, line-scan imaging, logging of physical properties (MSCL), and subsampling was conducted at the National Lacustrine Core Facility of the University of Minnesota, USA, in November 2015 and January 2016. Afterwards, the archive core halves and 672 subsamples of TDP Site 2 were shipped to the UoC for X-Ray Fluorescence (XRF) scanning and sedimentological, geochemical, and mineralogical analyses, respectively, supplemented by visible to near-infrared spectroscopy (VNIR) at Brown University, USA. The data from the surface samples evidence that allochthonous sedimentation in Lake Towuti today is dominated by fluvial supply from five distinguishable source areas: (i) the Mahalona River to the north, which drains lakes Mahalona and Matano, (ii) inlets around the village of Timampu to the northwest, (iii) the Loeha River to the east, (iv) the Lengke River to the south, and (v) the Lemo-Lemo River to the northeast of Lake Towuti. Of these, source areas (ii) and (iii) as well as (iv) and (v) have similar geochemical compositions, respectively. In addition, the lake sedimentation is significantly influenced by gravitational sediment supply from steep slopes as well as lake-internal gravitational and density-driven processes. The uppermost 41 m of sediment core 2A consist of pelagic sediments (totaling 11 m) and event layers from mass movement ( 30 m) that were formed during the past 50 cal kyr. In this period, the data reflect significant climatic and environmental changes, in particular in precipitation and lake level. These changes seem to be coupled to prominent paleoclimatic events.

Pre-aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records

NASA Astrophysics Data System (ADS)

Douglas, Peter M. J.; Pagani, Mark; Eglinton, Timothy I.; Brenner, Mark; Hodell, David A.; Curtis, Jason H.; Ma, Keith F.; Breckenridge, Andy

2014-09-01

Sedimentary records of plant-wax hydrogen (δDwax) and carbon (δ13Cwax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of plant waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of plant-wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon (14Cwax) data for n-alkanoic acid plant waxes (n-C26 to n-C32) from: (1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, (2) soils in the Lake Chichancanab catchment, and (3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14Cwax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14Cwax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged plant waxes, which are likely delivered to lake sediments through subsurface transport. Plant waxes in the Lake Chichancanab core are 350-1200 years older than corresponding ages of bulk sediment deposition, determined by 14C dates on terrestrial plant macrofossils in the core. A δDwax time series is in closer agreement with other regional proxy hydroclimate records when a plant-wax 14C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of plant-wax age distribution parameters suggests that plant waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (<200 years). Our findings demonstrate that high-temporal-resolution climate records inferred from stable isotope measures on plant waxes in lacustrine sediments may suffer from possible chronologic distortions as a consequence of long residence times of plant waxes in soils. They also underscore the importance of direct radiocarbon dating of these organic molecules.

Quantifying the origin of different sediment types in a catchment of the Southern French Alps by combining hydro-sedimentary records and fingerprinting

NASA Astrophysics Data System (ADS)

Evrard, Olivier; Navratil, Oldrich; Ayrault, Sophie; Esteves, Michel; Legout, Cédric; Némery, Julien; Lefèvre, Irène; Bonté, Philippe

2013-04-01

Soil erosion and subsequent sediment supply to rivers are particularly massive and episodic in mountainous environments, such as in the Southern French Alps. Those processes typically lead to an increase in water turbidity and a rapid filling of reservoirs in downstream areas. This situation is particularly problematic in regions where reservoirs are used to provide clear water to hydroelectric power plants. Sediment source areas must first be delineated and sediment fluxes between hillslopes and the river system must be better understood to implement efficient sediment management. We therefore combined traditional monitoring techniques (i.e., installation of river gauges and sediment samplers in several subcatchments) and sediment fingerprinting using elemental geochemistry and fallout radionuclides as potential discriminant properties to quantify the supply of sediment provided by different lithological sources (i.e., black marls, marly limestones, conglomerates, Quaternary deposits) to the River Bléone (905 km²). Those analyses were conducted on different material types collected within the catchment (i.e. suspended and riverbed sediment), and at the catchment outlet (i.e. on a sequence of sections of a 3-m long sediment core). Sediment exports at the river catchment outlet (330±100 t km-2 yr-1) were mainly driven (80%) by the occurrence of widespread rainfall events (long duration, low intensities). In contrast, heavy, local and short duration storms generated high peak discharges and suspended sediment concentrations, but they were restricted to small upstream torrents. Our study (2007-2009) confirmed the important contribution of black marls (up to 70% at the flood scale) to sediment transported in rivers, although this substrate only occupies c. 10% of the total catchment surface. However, the contribution of other lithological sources varied at both intra- and inter-flood scales. Sediment exports generated by local convective storms were dominated by black marls/marly limestones. In contrast, widespread flood events that generate the bulk of annual sediment supply at the outlet were characterized by a more stable lithologic composition and by a larger contribution of limestones, Quaternary deposits and conglomerates, which corroborated the analysis of riverbed sediment. Finally, we found that black marls and marly limestone sources provided the main fraction of sediment analysed throughout the outlet core sequence (40 and 22 %, respectively, for the period 1962-2009). However, we also found evidence for the occurrence of major floods carrying large quantities of sediment originating from Quaternary deposits and conglomerates (25 and 16 %, respectively). The variability of sediment sources throughout the sequence may reflect the spatial variability of rainfall within the catchment, which in turn reflects its origin. This study emphasizes the importance of using archival data to validate the results of sediment fingerprinting studies conducted during short contemporary monitoring programmes.

Mercury flux from salt marsh sediments: Insights from a comparison between 224Ra/228Th disequilibrium and core incubation methods

NASA Astrophysics Data System (ADS)

Shi, Xiangming; Mason, Robert P.; Charette, Matthew A.; Mazrui, Nashaat M.; Cai, Pinghe

2018-02-01

In aquatic environments, sediments are the main location of mercury methylation. Thus, accurate quantification of methylmercury (MeHg) fluxes at the sediment-water interface is vital to understanding the biogeochemical cycling of mercury, especially the toxic MeHg species, and their bioaccumulation. Traditional approaches, such as core incubations, are difficult to maintain at in-situ conditions during assays, leading to over/underestimation of benthic fluxes. Alternatively, the 224Ra/228Th disequilibrium method for tracing the transfer of dissolved substances across the sediment-water interface, has proven to be a reliable approach for quantifying benthic fluxes. In this study, the 224Ra/228Th disequilibrium and core incubation methods were compared to examine the benthic fluxes of both 224Ra and MeHg in salt marsh sediments of Barn Island, Connecticut, USA from May to August, 2016. The two methods were comparable for 224Ra but contradictory for MeHg. The radiotracer approach indicated that sediments were always the dominant source of both total mercury (THg) and MeHg. The core incubation method for MeHg produced similar results in May and August, but an opposite pattern in June and July, which suggested sediments were a sink of MeHg, contrary to the evidence of significant MeHg gradients between overlying water and porewater at the sediment-water interface. The potential reasons for such differences are discussed. Overall, we conclude that the 224Ra/228Th disequilibrium approach is preferred for estimating the benthic flux of MeHg and that sediment is indeed an important MeHg source in this marshland, and likely in other shallow coastal waters.

Effect of abalone farming on sediment geochemistry in the Shallow Sea near Wando, South Korea

NASA Astrophysics Data System (ADS)

Kang, Jeongwon; Lee, Yeon Gyu; Jeong, Da Un; Lee, Jung Sick; Choi, Yang Ho; Shin, Yun Kyung

2015-12-01

Wando County has grown up to 93% of the total abalone produced in South Korea since the late 1990s; however, this production has been decreasing in recent years. The objectives of this study were to understand the potential contamination risks of abalone farming and to examine the influence of intensive abalone farming on sediment quality by analyzing grain-size composition, organic matter (total organic carbon (TOC), total nitrogen (TN), total sulfur (TS)) and heavy metal content, pH, and 210Pb geochronology. The results of organic matter analysis from surface and core sediment (length: 64 cm) showed that the area around the abalone farm had oxic marine-to-brackish conditions, but that the area directly below an abalone cage (location 7) had reductive conditions, with a C/S ratio of ~2. The average TN levels in the surface and core sediments were 0.25% and 0.29%, respectively, and this was predominantly due to the use of seaweed for feed. The low sediment pH (surface, 7.23; core, 7.04), indicates that acidification of the bottom sediment has gradually increased since the initiation of abalone farming and is likely due to the continuous accumulation of uneaten feed and feces. Heavy metal pollution was not apparent based on the examination of EF and Igeo, although the excess metal flux of Ni, Pb, Cu, Co, As, and Cd increased toward surface of the sediment core. These sediment changes may be caused by the rapid accumulation (sedimentation rate: 1.45 cm/year) of sludge discharged from the abalone farm and may be controlled by tidal currents, physiography, water depth, and tidal ranges.

Strontium Isotope Dating of Metalliferous Sediment in the SW Pacific Basin

NASA Astrophysics Data System (ADS)

Stancin, A. M.; Gleason, J. D.; Owen, B. M.; Rea, D. K.; Moore, T. C.; Hendy, I. L.; Lyle, M. W.; Blum, J. D.

2007-12-01

A 2 million km2 region virtually devoid of sediment was identified in the remote SW Pacific Basin during the TUIM- 3 2005 drill site survey cruise. This region, termed the "South Pacific Bare Zone", comprises ocean floor dating back to the Late Cretaceous. Within the Bare Zone, a small (1km2) abyssal valley containing sediment to a depth of 24 m was sampled using a large diameter piston core (MV0502-15JC, 31 ° 42.194'S, 143 ° 30.331'W), leading to recovery of 8.35 m of metalliferous sediment at 5082 m water depth. Fish-teeth Sr-isotope stratigraphy reveals a continuous record of sedimentation from 31 Ma to present at this site. The fish teeth age-depth profile and INAA geochemistry reveal an exponentially decreasing hydrothermal flux, with sedimentation rates approaching 0.05 mm/kyr after 20 Ma. The source of hydrothermal activity at this site was likely the Pacific- Farallon Ridge, which went extinct at 20 Ma. A second piston core (MV0502-16JC; 28 ° 05.151'S, 140 ° 14.140'W) was collected near MacDonald Seamounts located on the southeastern end of the Cook-Austral island chain outside the Bare Zone and recovered 10.5 m of hydrothermal sediment and biogenic ooze. The lower 65 cm of the core consists of a coccolith ooze. From 10 mbsf depth to 1.5 mbsf depth, the core contians reddish black zeolitic clay, while the upper 1.5 mbsf contains biogenic ooze associated with abundant Late Pleistocene foraminifera remains. Concordant nannofossil and fish teeth ages at the base of the core (27-28 Ma), and Pleistocene ages near the top of the core reinforce the validity of the Sr fish teeth method for dating hydrothermal cores. These independent records suggest that regional hydrothermal activity during the Oligocene may have been related to a series of late Eocene/early Oligocene ridge jumps, propagating rifts and seafloor spreading centers that accompanied large-scale plate tectonic reorganization of South Pacific seafloor.

Marine historical ecology at the Brijuni Islands, Croatia: preliminary results from down-core changes of foraminiferal assemblages

NASA Astrophysics Data System (ADS)

Vidovic, Jelena; Cosovic, Vlasta; Gallmetzer, Ivo; Haselmair, Alexandra; Zuschin, Martin

2015-04-01

The Late Holocene in the northern Adriatic is characterized by the eustatic peak of the sea-level rise, followed by the equilibrium between the regional tectonic subsidence and hydro-isostatic emergence and relatively stable sea level for a few thousand years. During this period the area experienced changes in sedimentation rate, food/oxygen availability in the benthic ecosystem and eutrophication with seasonal hypoxic and anoxic events. In order to reconstruct the marine paleoecology in the Brijuni Islands area during this period, a multidisciplinary study was carried out, including geochemical (TOC, trace metals, carbonate content), micropaleontological analyses (benthic foraminifera) and dating of sediments and mollusc shells. The principal aim of this study is to observe the effects of ecological shifts on foraminiferal assemblages during the Late Holocene. One core of 1.5 m length was taken at a sampling station south of Veli Brijuni Island, located within a marine protected area with no fishing/dredging pressure (Croatian national park). The core was sliced into smaller subsamples, and four sediment fractions of each subsample (63, 125, 250 and 500 µm) were analyzed for standard properties of the foraminiferal community (species richness, faunal composition, biodiversity indices), in comparison with relevant physical and geochemical properties of the sediment. The results concerning changes in foraminiferal species composition and abundance point to differences within the core: surface sediments are dominated by suspension feeders (Planorbulina mediterranensis, Lobatula lobatula, Cibicides variabilis, Cibicides refulgens), whereas deposit feeders (genera Textularia, Siphonaperta, Adelosina, Trioculina) appear in higher abundances at approximately 30 cm of the sediment depth and dominate down-core. Species richness in the first 30 cm is lower (10 to 34 species per sample) in comparison to the middle part of the core (39 to 53 species), and decreases again at 100 cm to 25 to 42 species per sample. Diversity indices follow the pattern of species richness and point to normal marine conditions. Similarity indices rise with core depth. The radiometric dating of the sediments together with carbon-calibrated amino acid- racemisation of mollusc shells from selected species will help to determine the timing of major ecological changes.

Triolein embedded cellulose acetate membrane as a tool to evaluate sequestration of PAHs in lake sediment core at large temporal scale.

PubMed

Tao, Yuqiang; Xue, Bin; Yao, Shuchun; Deng, Jiancai; Gui, Zhifan

2012-04-03

Although numerous studies have addressed sequestration of hydrophobic organic compounds (HOCs) in laboratory, little attention has been paid to its evaluation method in field at large temporal scale. A biomimetic tool, triolein embedded cellulose acetate membrane (TECAM), was therefore tested to evaluate sequestration of six PAHs with various hydrophobicity in a well-dated sediment core sampled from Nanyi Lake, China. Properties of sediment organic matter (OM) varying with aging time dominated the sequestration of PAHs in the sediment core. TECAM-sediment accumulation factors (MSAFs) of the PAHs declined with aging time, and significantly correlated with the corresponding biota-sediment accumulation factors (BSAFs) for gastropod (Bellamya aeruginosa) simultaneously incubated in the same sediment slices. Sequestration rates of the PAHs in the sediment core evaluated by TECAM were much lower than those obtained from laboratory study. The relationship between relative availability for TECAM (MSAF(t)/MSAF(0)) and aging time followed the first order exponential decay model. MSAF(t)/MSAF(0) was well-related to the minor changes of the properties of OM varying with aging time. Compared with chemical extraction, sequestration reflected by TECAM was much closer to that by B. aeruginosa. In contrast to B. aeruginosa, TECAM could avoid metabolism and the influences from feeding and other behaviors of organisms, and it is much easier to deploy and ready in laboratory. Hence TECAM provides an effective and convenient way to study sequestration of PAHs and probably other HOCs in field at large temporal scale.

Distribution and sources of polychlorinated biphenyls in Woods Inlet, Lake Worth, Fort Worth, Texas, 2003

USGS Publications Warehouse

Besse, Richard E.; Van Metre, Peter C.; Wilson, Jennifer T.

2005-01-01

Woods Inlet is a flooded stream channel on the southern shore of Lake Worth along the western boundary of Air Force Plant 4 in Fort Worth, Texas, where elevated polychlorinated biphenyl (PCB) concentrations in sediment were detected in a previous study. In response, the U.S. Geological Survey, in cooperation with the U.S. Air Force, conducted a study in 2003 to map the extent of elevated PCB concentrations in Woods Inlet and to identify possible sources (or more specifically, source areas) of PCBs in the watershed of Woods Inlet. Three gravity cores (penetration to pre-reservoir sediment at three sites) and 17 box cores (surficial bottom sediment samples) were collected in Woods Inlet. Suspended sediment in stormwater runoff and streambed sediment were sampled in tributaries to Woods Inlet following storms. Assemblages of PCB congeners in surficial inlet sediments and suspended and streambed sediments were analyzed to indicate sources of PCBs in the inlet sediments on the basis of chemical signatures of PCBs. Woods Inlet receives runoff primarily from three tributaries: (1) Gruggs Park Creek, (2) the small unnamed creek that drains a Texas National Guard maintenance facility, called TNG Creek for this report, and (3) Meandering Road Creek. Twenty-seven of 209 possible PCB congeners were analyzed. The sum of the congeners was used as a measure of total PCB. The spatial distribution of total PCB concentrations in the inlet indicates that most PCBs are originating in the Meandering Road Creek watershed. Peak total PCB concentrations in the three gravity cores occurred at depths corresponding to sediment deposition dates of about 1960 for two of the cores and about 1980 for the third core. The magnitudes of peak total PCB concentrations in the gravity cores followed a spatial distribution generally similar to that of surficial bottom sediment concentrations. Total PCB concentrations in suspended and streambed sediment varied greatly between sites and indicated a likely source of PCBs associated with a sampling site that receives runoff from Air Force Plant 4. Three approaches to the analyses of congener assemblages indicate that PCBs in surficial bottom sediment of Woods Inlet primarily enter Lake Worth from Meandering Road Creek and that runoff from Air Force Plant 4 is a source of the PCBs in Meandering Road Creek. Although current (2003) transport of PCBs from Air Force Plant 4 to the creek is occurring, large decreases in PCB concentrations with decreasing age in two cores indicate that PCB loading to the inlet has decreased greatly since the 1960s. Because runoff entering Meandering Road Creek from some parts of Air Force Plant 4 was not measured or sampled in this study, it cannot be said with certainty that the Air Force Plant 4 site sampled is the only source of PCBs to Meandering Road Creek.

Porosity and Mineralogy Control on the Thermal Properties of Sediments in Off-Shimokita Deep-Water Coal Bed Basin

NASA Astrophysics Data System (ADS)

Tanikawa, W.; Tadai, O.; Morita, S.; Lin, W.; Yamada, Y.; Sanada, Y.; Moe, K.; Kubo, Y.; Inagaki, F.

2014-12-01

Heat transport properties such as thermal conductivity, heat capacity, and thermal diffusivity are significant parameters that influence on geothermal process in sedimentary basins at depth. We measured the thermal properties of sediment core samples at off-Shimokita basin obtained from the IODP Expedition 337 and Expedition CK06-06 in D/V Chikyu shakedown cruise. Overall, thermal conductivity and thermal diffusivity increased with depth and heat capacity decreased with depth, although the data was highly scattered at the depth of approximately 2000 meters below sea floor, where coal-layers were formed. The increase of thermal conductivity is mainly explained by the porosity reduction of sediment by the consolidation during sedimentation. The highly variation of the thermal conductivity at the same core section is probably caused by the various lithological rocks formed at the same section. Coal shows the lowest thermal conductivity of 0.4 Wm-1K-1, and the calcite cemented sandstone/siltstone shows highest conductivity around 3 Wm-1K-1. The thermal diffusivity and heat capacity are influenced by the porosity and lithological contrast as well. The relationship between thermal conductivity and porosity in this site is well explained by the mixed-law model of Maxwell or geometric mean. One dimensional temperature-depth profile at Site C0020 in Expedition 337 estimated from measured physical properties and radiative heat production data shows regression of thermal gradient with depth. Surface heat flow value was evaluated as 29~30 mWm-2, and the value is consistent with the heat flow data near this site. Our results suggest that increase of thermal conductivity with depth significantly controls on temperature profile at depth of basin. If we assume constant thermal conductivity or constant geothermal gradient, we might overestimate temperature at depth, which might cause big error to predict the heat transport or hydrocarbon formation in deepwater sedimentary basins.

New Progress on Radiocarbon Geochronology in Southern Lake Tanganyika (East Africa)

NASA Astrophysics Data System (ADS)

McGlue, M. M.; Soreghan, M. J.

2017-12-01

Our limnogeological research in Lake Tanganyika focuses on elucidating the patterns of sediment accumulation on deepwater horsts, outer platforms, and littoral environments in the lake's southern basin ( 6-8°S latitude). Here, we present new radiocarbon (14C) dates from high-quality surface sediment cores, in order to make comparisons with previously published age models, to address the presence and spatiotemporal variability of a reservoir effect, and to constrain sedimentation rates and facies at sites that may be important targets for future scientific drilling. Plant macrofossils are rare in deepwater sediment cores, so charcoal and bulk organic matter have been the primary materials used for dating. On the Kavala Island Ridge (KIR) horst, initial core descriptions revealed variations in laminae presence, thickness, and chemistry. Sediment cores from the KIR at 172m water depth consist of thickly laminated diatom oozes. Charcoal from the bases of these cores returned median ages of 2.1-2.2 cal ka, suggesting linear accumulation rates on the order of 0.51 mm/yr. By contrast, a core from 420 m water depth on the KIR exhibited very thin laminations and diatom layers were much less prominent. Charcoal at the base of this core produced a median age of 8.1 cal ka, suggesting a linear accumulation rate of 0.11 mm/yr. These initial results suggest that sedimentation rates may vary considerably over sublacustrine horst blocks. We will test this initial discovery with additional sedimentation rate information from the Kalya and Nitiri horsts. In addition, we report new 14C dates made on both dead and live-collected shells of the endemic gastropod Neothauma tanganyicense. These shells form vast accumulations along shallow-water platforms of the lake and form an important substrate for a number of other endemic species. The discovery of living snails in southern Lake Tanganyika may allow for the development of a species-specific reservoir correction. A limited N. tanganyicense shell 14C dataset from the lake's northern basin exhibits time averaged over the past 1600 cal yrs; results from this project will begin to address spatial variability in time averaging, and therefore improve our understanding of shell bed formation and the extent to which anthropogenic sedimentation is impacting shell bed persistence.

Geological and paleontological results from the WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) Project

NASA Astrophysics Data System (ADS)

Scherer, R. P.; Powell, R. D.; Coenen, J. J.; Hodson, T. O.; Puttkammer, R.; Tulaczyk, S. M.

2015-12-01

The WISSARD project recovered sediment cores and other geological materials from beneath the Whillans Ice Stream in West Antarctica during two drilling seasons; Subglacial Lake Whillans (SLW) in 2013 and 100km downstream at the ice stream grounding-zone (WGZ) in 2015. SLW is characterized by 2 m of freshwater with a high suspended-sediment load, whereas WGZ has a 10 m column of clear, fully marine water with an active community of marine organisms. Three coring devices were deployed as part of WISSARD, including (1) a multicorer, which recovers 3 unaltered sediment-water interface cores, up to 0.5m, (2) a piston corer, also deployed as a gravity corer, with a 3m core barrel, and (3) a percussion coring system with a 5m core barrel. Sediments recovered from SLW are muddy diamicton with minimal stratification. The sediments are characteristic of active till, not water-column deposition. The till is weak and effective stresses very low, thus till flux from deformation must also be low. Water through flow is sufficient to carry suspended clays and silts, but not transfer large volumes of sediment in the current glaciological regime. Microfossils and geochemical tracers (e.g., biomarkers, 10Be and 14C) in SLW sediments indicate Pleistocene input from open water conditions, plus input and mixing of components derived from older Cenozoic strata. Diatoms and other sedimentary characteristics of SLW are entirely consistent with material previously recovered from upstream sites on the Whillans Ice Stream (UpB), but show evidence of further cumulative subglacial shear strain, suggesting downstream translation as deforming till. Sedimentary components from WGZ indicate significant input from sources other than from the Whillans Ice Stream. Sediment cores include distinct stratigraphic variability, with differing geochemical and sedimentary components indicative of input from changing source beds. Components indicate a mixture of Quaternary and older components. The lower ca. 10m of ice at WGZ contained abundant sedimentary debris, and active melting and rainout of basal debris was observed. We attribute much of the stratigraphy of the upper sedimentary layers at WGZ, which include soft mud and rock clasts, to ongoing basal melting. This may represent recent grounding line retreat.

Quantitative degassing of gas hydrate-bearing pressure cores from Green Canyon 955, Gulf of Mexico

NASA Astrophysics Data System (ADS)

Phillips, S. C.; Holland, M. E.; Flemings, P. B.; Schultheiss, P. J.; Waite, W. F.; Petrou, E. G.; Jang, J.; Polito, P. J.; O'Connell, J.; Dong, T.; Meazell, K.

2017-12-01

We present results from 20 quantitative degassing experiments of pressure-core sections collected during Expedition UT-GOM2-1 from Green Canyon 955 in the northern Gulf of Mexico. These experiments highlight an average pore-space methane hydrate saturation, Sh, of 59% (min: 12%; max 87%) in sediments between 413 and 440 mbsf in 2032 m water depth. There is a strong lithofacies control of hydrate saturation within the reservoir, with a high saturation sandy silt facies (Sh of 65 to 87%) interbedded with a low saturation clayey silt facies (Sh of 12 to 30%). Bedding occurs on the scale of tens of centimeters. Outside of the main hydrate reservoir, methane hydrate occurs in low saturations (Sh of 0.8 to 3%). Hydrate saturations exhibit a strong correlation (R2=0.89) with the average P-wave velocity measured through the degassed sections. These preliminary hydrate saturations were calculated assuming a porosity of 40% with core filling the full internal diameter of the core liner. Gas recovered during these experiments is composed of almost entirely methane, with an average of 94 ppm ethane and detectable, but not quantifiable, propane. Degassed pressure cores were depressurized through a manifold by the stepwise release of fluid, and the volumes of produced gas and water were monitored. The core's hydrostatic pressure was measured and recorded continuously at the manifold. Pressure and temperature were also measured by data storage tags within the sample chambers. Two slow, multi-day degassing experiments were performed to estimate the in situ salinity within core sections. Based on temperature and pressure observations at the point of the initial pressure rebound due to hydrate dissociation, we estimate the salinity within these samples to be between 33 and 42 g kg-1.

Vergleich von hydraulischen und chemischen Sedimenteigenschaften aus Spül- und Kernbohrungen im Raum Peine (Norddeutschland)

NASA Astrophysics Data System (ADS)

Konrad, C.; Walther, W.; Reimann, T.; Rogge, A.; Stengel, P.; Well, R.

2008-03-01

Comparison of hydraulic and chemical properties of sediments from flush- and core drillings in the area of Peine (Germany). Because of financial constraints, investigations of nitrate metabolism are often based on disturbed borehole samples. It is arguable, however, whether disturbed samples are suitable for these types of investigations. Disadvantages of disturbed samples in comparison to undisturbed core samples are well known and include possible contamination of the sample by mud additives, destruction of the sediment formation and the insecurity concerning the correct depth allocation. In this study, boreholes were drilled at three locations to a maximum depth of 50 m. The extracted samples, as intact sediment cores and drill cuttings, were studied with regard to chemical and hydraulic parameters of the aquifer sediments. The results show: 1. hydraulic parameters are not affected by clay-based mud; 2. disturbed samples contain less fine grain material relative to the core samples, and the hydraulic conductivity can only be estimated from catch samples; 3. catch samples contain fewer reducing agents (sulphides, organic carbon) than core samples in hydraulically passive zones (defined as K < 10 6 m · s 1); 4. the results of analyses of disturbed and undisturbed core samples are in good agreement for hydraulically active zones (K ≥ 10 6 m · s 1).

Results of chemical and isotopic analyses of sediment and water from alluvium of the Canadian River near a closed municipal landfill, Norman, Oklahoma

USGS Publications Warehouse

Breit, George N.; Tuttle, Michele L.W.; Cozzarelli, Isabelle M.; Christenson, Scott C.; Jaeschke, Jeanne B.; Fey, David L.; Berry, Cyrus J.

2005-01-01

Results of physical and chemical analyses of sediment and water collected near a closed municipal landfill at Norman, Oklahoma are presented in this report. Sediment analyses are from 40 samples obtained by freeze-shoe coring at 5 sites, and 14 shallow (depth <1.3 m) sediment samples. The sediment was analyzed to determine grain size, the abundance of extractable iron species and the abundances and isotopic compositions of forms of sulfur. Water samples included pore water from the freeze-shoe core, ground water, and surface water. Pore water from 23 intervals of the core was collected and analyzed for major and trace dissolved species. Thirteen ground-water samples obtained from wells within a few meters of the freeze-shoe core sites and one from the landfill were analyzed for major and trace elements as well as the sulfur and oxygen isotope composition of dissolved sulfate. Samples of surface water were collected at 10 sites along the Canadian River from New Mexico to central Oklahoma. These river-water samples were analyzed for major elements, trace elements, and the isotopic composition of dissolved sulfate.

Chemical gradients in sediment cores from an EPA reference site off the Farallon Islands - Assessing chemical indicators of dredged material disposal in the deep sea

USGS Publications Warehouse

Bothner, Michael H.; Gill, P.W.; Boothman, W.S.; Taylor, B.B.; Karl, Herman A.

1998-01-01

Heavy metal and organic contaminants have been determined in undisturbed sediment cores from the US Environmental Protection Agency reference site for dredged material on the continental slope off San Francisco. As expected, the concentrations are significantly lower than toxic effects guidelines, but concentrations of PCBs, PAHs, Hg, Pb, and Clostridium perfringens (a bacterium spore found in sewage) were nearly two or more times greater in the surface sediments than in intervals deeper in the cores. These observations indicate the usefulness of measuring concentration gradients in sediments at the San Francisco deep ocean disposal site (SF-DODS) where a thin (0.5 cm thick) layer of dredged material has been observed beyond the boundary. This thin layer has not been chemically characterized by the common practice of homogenizing over the top 10 cm. An estimated 300 million cubic yards of dredged material from San Francisco Bay are expected to be discharged at the SF-DODS site during the next 50 years. Detailed depth analysis of sediment cores would add significant new information about the fate and effects of dredged material in the deep sea.

Microbial diversity in Cenozoic sediments recovered from the Lomonosov Ridge in the Central Arctic basin.

PubMed

Forschner, Stephanie R; Sheffer, Roberta; Rowley, David C; Smith, David C

2009-03-01

The current understanding of microbes inhabiting deeply buried marine sediments is based largely on samples collected from continental shelves in tropical and temperate latitudes. The geographical range of marine subsurface coring was expanded during the Integrated Ocean Drilling Program Arctic Coring Expedition (IODP ACEX). This expedition to the ice-covered central Arctic Ocean successfully cored the entire 428 m sediment stack on the Lomonosov Ridge during August and September 2004. The recovered cores vary from siliciclastic sediment low in organic carbon (< 0.2%) to organic rich ( approximately 3%) black sediments that rapidly accumulated in the early middle Eocene. Three geochemical environments were characterized based on chemical analyses of porewater: an upper ammonium oxidation zone, a carbonate dissolution zone and a deep (> 200 m below sea floor) sulfate reduction zone. The diversity of microbes within each zone was assessed using 16S rRNA phylogenetic markers. Bacterial 16S rRNA genes were successfully amplified from each of the biogeochemical zones, while archaea was only amplified from the deep sulfate reduction zone. The microbial communities at each zone are phylogenetically different and are most closely related to those from other deep subsurface environments.

Bayesian integration of radioisotope dating (210Pb, 137Cs, 241Am, 14C) and an 18-20th century mining history of Brotherswater, English Lake District

NASA Astrophysics Data System (ADS)

Schillereff, Daniel; Chiverrell, Richard; Macdonald, Neil; Hooke, Janet; Welsh, Katharine; Piliposyan, Gayane; Appleby, Peter

2014-05-01

Lake sediment records are often a useful tool for investigating landscape evolution as geomorphic changes in the catchment are reflected by altered sediment properties in the material transported through the watershed and deposited at the lake bed. Recent research at Brotherswater, an upland waterbody in the Lake District, northwest England, has focused on reconstructing historical floods from their sedimentary signatures and calculating long-term sediment and carbon budgets from fourteen sediment cores extracted from across the basin. Developing accurate chronological control is essential for these tasks. One sediment core (BW11-2; 3.5 m length) from the central basin has been dated using artificial radionuclide measurements (210Pb, 137Cs, 241Am) for the uppermost sediments and radiocarbon (14C) for lower sediments. The core appears to span the past 1500 years, however a number of problems have arisen. We present our explanations for these errors, the independent chronological techniques used to generate an accurate age-depth model for this core and methods for its transferral to the other 13 cores extracted from the basin. Two distinct 137Cs markers, corresponding to the 1986 Chernobyl disaster and 1960s weapons testing, confirm the 210Pb profile for sediment deposition since ~1950, but calculations prior to this appear erroneous, possibly due to a hiatus in the sediment record. We used high-resolution geochemical profiles (measured by XRF) to cross-correlate with a second 210Pb-dated chronology from a more distal location, which returned more sensible results. Unfortunately, the longer 14C sequence exhibits two age-reversals (radiocarbon dates that are too old). We believe the uppermost two dates are erroneous, due to a shift in inflow location as a flood prevention method ~1900 A.D., dated using information from historical maps. The lower age-reversal coincides with greater supply of terrigenous material to the lake (increased Zr, K, Ti concentrations), pointing to a hillslope clearance event. A widespread concurrent hillslope gullying phase in northwest England triggering enhanced soil erosion is thus the most likely explanation, as the presence of old carbon is a known issue for lakes in the region at this time. Applying a Bayesian age-depth modelling protocol is able to account for these age-reversals with some success. However, the greatest uncertainty in the model occurs across the 1700 -1900 A.D. time window as the radiocarbon percentages offer multiple age solutions due to fluctuating atmospheric 14C concentrations from fossil fuel emissions. We address this issue by incorporating into the model geochemical markers in the sediment core related to local point-source Pb mining of known-age; the most-likely age-depth curve is subsequently much more definitively resolved. Usefully, these mining-derived chronological markers bridge the temporal gap between artificial radionuclide and conventional radiocarbon dating which is a common problem in palaeolimnology. These distinctive geochemical mining profiles (Pb, Zn, Cu) have been mapped across all cores, enabling precise core correlation and confident transferral of the age-depth model, and reveal highly spatially variable sediment accumulation rates. This has enabled more accurate sediment and carbon budgets to be calculated and some insight into palaeoflood frequency to be obtained from the Brotherswater sediment sequence.

Mineralogy and Geochemistry from Trollveggen Vent Field Chimneys and Metalliferous Sediments (Mohns Ridge, West Jan Mayen Fracture Zone at 71°N)

NASA Astrophysics Data System (ADS)

Dias, S.; Cruz, I.; Fonseca, R.; Barriga, F. J.; Pedersen, R.

2010-12-01

The Jan Mayen vent fields were discovered in the Mohns Ridge during an expedition with the Norwegian research vessel "G.O. Sars" in July 2005. They comprise two main active areas: (1) Soria Moria and (2) Gallionella Garden & Trollveggen. The Trollveggen vent field is located at depths of 700-750 m. Venting takes place mainly through white smoker chimneys with fluid temperatures reaching up to 260-270°C. Here we present mineralogical and geochemical data from vent chimneys and metalliferous sediments collected at the Trollveggen vent field with an ROV. Cross-sections of chimneys present evident mineralogical zonation, showing acicular barite crystals in the outer parts and sulfide enrichments in the interior (Sph + Cpy +/- Py - Po). Sediments are mainly formed by vent fragments but also by minerals precipitated by diffuse fluid circulation, showing a mineral assemblage similar to that of chimneys. Microprobe analyses were obtained both in sulfates and sulphides revealing a particular sphalerite composition, characterized by low Fe (< 2%) and high total trace metal contents (up to 4%, including Cu, Ag and Au). Geochemical profiles of gravity cores collected in the area surrounding Jan Mayen were also performed in order to investigate the presence of additional hydrothermal activity in the area. Total geochemical analyses showed a slight enrichment in trace metals, such as Cu, Zn and Fe, with exception of one core that reached 85 ppm for Cu, 150 ppm for Zn and 20% for Fe. The metal enrichment in this core suggests hydrothermal activity in the neighboring area.

Iridium Concentrations and Abundances of Meteoritic Ejecta from the Eltanin Impact in Sediment Cores from Polarstern Expedition ANT XII/4

NASA Technical Reports Server (NTRS)

Kyte, Frank T.

2002-01-01

The abundances of meteoritic ejecta from the Eltanin asteroid impact have been examined in several sediment cores recovered by the FS Polarstern during expedition ANT XII/4 using elemental concentrations of iridium and weights of coarse ejecta debris. Three cores with well-preserved impact deposits, PS204-1, PS2708-1, and PS2709-1, each contain Ir and ejecta fluences similar to those found in USNS Eltanin core E13-4. Small Ir anomalies and traces of ejecta were found in cores PS2706-1 and PS2710-1, but since these cores lack well-defined deposits, these are considered to be reworked and not representative of the fallout. No evidence of ejecta was found in cores PS2802-1 and PS2705-1. These results confirm earlier speculation that the Eltanin impact resulted in deposits of ejecta with up to 1 gram/sq centimeter of depris over a wide area of the ocean floor. However, there are sill large uncertainties over the actual regional or global extent of this unique sediment deposit.

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations.

PubMed

Owens, Michael S; Cornwell, Jeffrey C

2016-08-03

The measurement of sediment-water exchange of gases and solutes in aquatic sediments provides data valuable for understanding the role of sediments in nutrient and gas cycles. After cores with intact sediment-water interfaces are collected, they are submerged in incubation tanks and kept under aerobic conditions at in situ temperatures. To initiate a time course of overlying water chemistry, cores are sealed without bubbles using a top cap with a suspended stirrer. Time courses of 4-7 sample points are used to determine the rate of sediment water exchange. Artificial illumination simulates day-time conditions for shallow photosynthetic sediments, and in conjunction with dark incubations can provide net exchanges on a daily basis. The net measurement of N2 is made possible by sampling a time course of dissolved gas concentrations, with high precision mass spectrometric analysis of N2:Ar ratios providing a means to measure N2 concentrations. We have successfully applied this approach to lakes, reservoirs, estuaries, wetlands and storm water ponds, and with care, this approach provides valuable information on biogeochemical balances in aquatic ecosystems.

Structural architecture and petrophysical properties of the Rocca di Neto extensional fault zone developed in the shallow marine sediments of the Crotone Basin (Southern Apennines, Italy).

NASA Astrophysics Data System (ADS)

Pizzati, Mattia; Balsamo, Fabrizio; Iacumin, Paola; Swennen, Rudy; Storti, Fabrizio

2017-04-01

In this contribution we describe the architecture and petrophysical properties of the Rocca di Neto extensional fault zone in loose and poorly lithified sediments, located in the Crotone forearc basin (south Italy). To this end, we combined fieldwork with microstructural observations, grain size analysis, and in situ permeability measurements. The studied fault zone has an estimated maximum displacement of 80-90 m and separates early Pleistocene age (Gelasian) sands in the footwall from middle Pleistocene (Calabrian) silty clay in the hangingwall. The analysed outcrop consists of about 70 m section through the fault zone mostly developed in the footwall block. Fault zone consists of four different structural domains characterized by distinctive features: (1) <1 m-thick fault core (where the majority of the displacement is accommodated) in which bedding is transposed into foliation imparted by grain preferential orientation and some black gouges decorate the main slip surfaces; (2) zone of tectonic mixing characterized by a set of closely spaced and anastomosed deformation bands parallel to the main slip surface; (3) about 8 m-thick footwall damage zone characterized by synthetic and antithetic sets of deformation bands; (4) zone of background deformation with a few, widely-spaced conjugate minor faults and deformation bands. The boundary between the relatively undeformed sediments and the damage zone is not sharp and it is characterized by a progressive decrease in deformation intensity. The silty clay in the hangingwall damage zone is characterized by minor faults. Grain size and microstructural data indicate that particulate flow with little amount of cataclasis is the dominant deformation mechanism in both fault core rocks and deformation bands. Permeability of undeformed sediments is about 70000 mD, whereas the permeability in deformation bands ranges from 1000 to 18000 mD; within the fault core rocks permeability is reduced up to 3-4 orders of magnitude respect to the undeformed domains. Structural and petrophysical data suggest that the Rocca di Neto fault zone may compartmentalize the footwall block due to both juxtaposition of clay-rich lithology in the hangingwall and the development of low permeability fault core rocks.

Sediment Carbon Accumulation in Southern Latitude Saltmarsh Communities of Tasmania, Australia.

PubMed

Ellison, Joanna C; Beasy, Kim M

2018-05-02

Carbon sequestration values of wetlands are greatest in their sediments. Northern hemisphere research dominates the earlier saltmarsh carbon sequestration literature, recently augmented by analyses across mainland Australia where species assemblages, catchment histories and environmental settings differ. No previous assessment has been made for Tasmania. Carbon stores and accumulation rates in saltmarsh sediments of the Rubicon estuary, Tasmania, were investigated. Carbon was determined from sediment cores by Elemental Analyser, combined with analysis of organic content and bulk density. Carbon accumulation was determined using short-term and long-term sediment accretion indicators. Results showed carbon densities to be lower than global averages, with variation found between carbon stores of native and introduced species zones. Cores from introduced Spartina anglica indicated a trend of higher sediment carbon percentages relative to cores from native saltmarsh Juncus kraussii and Sarcocornia quinqueflora , and in finer grain sizes. Sediment carbon stock of 30 cm depths was 49.5 Mg C ha −1 for native saltmarsh and 55.5 Mg C ha −1 for Spartina . Carbon percentages were low owing to high catchment inorganic sediment yields, however carbon accumulation rates were similar to global averages, particularly under Spartina . Covering 85% of saltmarsh area in the estuary, Spartina contributes the majority to carbon stores, potentially indicating a previously unrecognized value for this invasive species in Australia.

Sediment accumulation and mixing in the Penobscot River and estuary, Maine.

PubMed

Yeager, K M; Schwehr, K A; Schindler, K J; Santschi, P H

2018-04-16

Mercury (Hg) was discharged in the late 1960s into the Penobscot River by the Holtra-Chem chlor-alkali production facility, which was in operation from 1967 to 2000. To assess the transport and distribution of total Hg, and recovery of the river and estuary system from Hg pollution, physical and radiochemical data were assembled from sediment cores collected from 58 of 72 coring stations sampled in 2009. These stations were located throughout the lower Penobscot River, and included four principal study regions, the Penobscot River (PBR), Mendall Marsh (MM), the Orland River (OR), and the Penobscot estuary (ES). To provide the geochronology required to evaluate sedimentary total Hg profiles, 58 of 72 sediment cores were dated using the atmospheric radionuclide tracers 137 Cs, 210 Pb, and 239,240 Pu. Sediment cores were assessed for depths of mixing, and for the determination of sediment accumulation rates using both geochemical (total Hg) and radiochemical data. At most stations, evidence for significant vertical mixing, derived from profiles of 7 Be (where possible) and porosity, was restricted to the upper ~1-3cm. Thus, historic profiles of both total Hg and radionuclides were only minimally distorted, allowing a reconstruction of their depositional history. The pulse input tracers 137 Cs and 239,240 Pu used to assess sediment accumulation rates agreed well, while the steady state tracer 210 Pb exhibited weaker agreement, likely due to irregular lateral sediment inputs. Copyright © 2018. Published by Elsevier B.V.

Short Term Sediment Exchange Between Marshes and Bays Using Beryllium-7 as a Tracer, Fourleague Bay, Louisiana.

NASA Astrophysics Data System (ADS)

Restreppo, G. A.; Bentley, S. J.; Xu, K.; Wang, J.

2016-12-01

Modern delta models focus on the availability and exchange of coarse sediment as one of the major factors of deltaic growth or decay. Fine-grained sediment exchange within a river's delta is relatively poorly understood, as is the impact that this exchange has on land building and land loss. To better understand the dynamics of fine grain sediment exchange between river mouth, adjacent bays, and marshland, sediment cores from Fourleague Bay, LA, were collected and analyzed for 7Be, a naturally occurring radioisotope that serves as a marker for recently deposited sediment. Time-series push cores were collected every two months at ten sites, five located across a longitudinal transect in the middle bay and five located along adjacent marshes, from May 2015 to May 2016. All sites fall within 11 to 28 km of the Atchafalaya Delta, along a gradient extending towards the open ocean. Cores were extruded in 2 cm intervals, dried, ground, and analyzed via gamma spectrometry for the presence of 7Be. Inventories of 7Be were then calculated and used to determine bimonthly sedimentation rates over the course twelve months. Sediment deposition on the bay floor and marsh surface were then compared to Atchafalaya River discharge, wind speed and direction, and wave action. Preliminary results indicate patterns of initial fluvial sediment transfer from river to bay floor, then bay floor to marsh surface, with decreasing fluvial influence towards the open ocean. Sediment transport from bay to marsh appears to be coupled with meteorological forcing that induces bay-floor sediment resuspension and the flooding of marsh surfaces. This indirect mechanism of fluvial sediment supply to wetland surfaces may extend the region of influence for sediment delivery from man-made river-sediment diversions.

Grain Size Biasing of 230Th-derived Focusing Factors in the Panama Basin

NASA Astrophysics Data System (ADS)

Loveley, M. R.; Marcantonio, F.; Lyle, M. W.; Ibrahim, R.; Wang, J. K.; Hertzberg, J. E.

2014-12-01

In this study, we attempt to understand how differing grain size classes in Panama Basin sediments may create biasing of 230Th as a constant-flux proxy. Greater amounts of 230Th are contained in fine grained particles, which, if fractionated from coarser grained counterparts may lead to biasing of 230Th-derived mass accumulation rates (MARs) and sediment focusing factors. We examined sediments that span the past 25 kyr from four new sediment cores retrieved from two different localities close to the ridges that bound the Panama Basin. Each locality contained paired sites that were seismically interpreted to have undergone sediment redistribution, i.e., thick focused sites versus thin winnowed sites. Two sediment cores were retrieved from the northern part of the Panama basin, Cocos Ridge, (MV1014-01-"4JC", 5° 44.7'N 85° 45.5' W, 1730 m depth; MV1014-01-"8JC", 6° 14.0'N 86° 2.6' W, 1993 m depth), and two were retrieved from the southern part of the basin, Carnegie Ridge, (MV1014-02-"11JC", 0° 41.6'S 85° 20.0' W, 2452 m depth; MV1014-02-"17JC" 0° 10.8'S 85° 52.0' W, 2846 m depth). Cores 4JC and 11JC lie closer to the ridge tops of the Cocos and Carnegie Ridges, respectively, and have thin sediment drapes, while deeper cores, 8JC (Cocos) and 17JC (Carnegie), have thicker sediment drapes and lie downslope from the ridge top cores. Age-model-derived sand MARs, which likely represent the vertical rain of particles that cannot be transported by bottom currents, are similar at each of the paired sites in Holocene and glacial time slices. However, 230Th-normalized MARs are about 50% lower, on average at each of the paired sites during the same time slices. Both Holocene and glacial samples from "thin" cores (4,11JC) contain, surprisingly, significant amounts (up to 50%) of the 230Th within the coarse grained (>63 μm) fraction which makes up 40-70% of the bulk samples analyzed. On the contrary, Holocene and glacial samples from "thick" cores, (8,17JC), contain the greatest amounts of 230Th (up to 49%) in the finest grain-sized fraction (<4μm), which makes up 26-40% of the bulk samples analyzed. Although, redistribution of sediment has taken place, our analysis indicates that 230Th-derived focusing factors are being overestimated at thick sites and underestimated at thin sites.

Historical trends of metals in the sediments of San Francisco Bay, California

USGS Publications Warehouse

Hornberger, Michelle I.; Luoma, S.N.; VanGeen, A.; Fuller, C.; Anima, R.

1999-01-01

Concentrations of Ag, Al, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn were determined in six sediment cores from San Francisco Bay (SFB) and one sediment core in Tomales Bay (TB), a reference estuary. SFB cores were collected from between the head of the estuary and its mouth (Grizzly Bay, GB; San Pablo Bay, SP; Central Bay, CB; Richardson Bay, RB, respectively) and ranged in length from 150 to 250 cm. Concentrations of Cr, V and Ni are greater than mean crustal content in SFB and TB sediments, and greater than found in many other coastal sediments. However, erosion of ultramafic rock formations in the watershed appears to be the predominant source. Baseline concentrations of other metals were determined from horizons deposited before sediments were influenced by human activities and by comparing concentrations to those in TB. Baseline concentrations of Cu co-varied with Al in the SFB sediments and ranged from 23.7 ?? 1.2 ??g/g to 41.4 ?? 2.4 ??g/g. Baseline concentrations of other metals were less variable: Ag, 0.09 ?? 0.02 ??g/g; Pb, 5.2 ?? 0.7 ??g/g; Hg, 0.06 ?? 0.01 ??g/g; Zn, 78 ?? 7 ??g/g. The earliest anthropogenic influence on metal concentrations appeared as Hg contamination (0.3-0.4 ??g/g) in sediments deposited at SP between 1850 and 1880, apparently associated with debris from hydraulic gold mining. Maximum concentrations of Hg within the cores were 20 times baseline. Greater inventories of Hg at SP and GB than at RB verified the importance of mining in the watershed as a source. Enrichment of Ag, Pb, Cu and Zn first appeared after 1910 in the RB core, later than is observed in Europe or eastern North America. Maximum concentrations of Ag and Pb were 5-10 times baseline and Cu and Zn concentrations were less than three times baseline. Large inventories of Pb to the sediments in the GB and SP cores appeared to be the result of the proximity to a large Pb smelter. Inventories of Pb at RB are similar to those typical of atmospheric inputs, although influence from the Pb smelter is also suspected. Concentrations of Hg and Pb have decreased since the 1970s (to 0.30 ??g/g and 25 ??g/g, respectively) and were similar among all cores in 1990. Early Ag contamination was perhaps a byproduct of the Pb smelting process, but a modem source of Ag is also indicated, especially at RB and CB.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lockhart, L.; Ramial, K.; Wilkinson, P.

Mercury concentrations were measured in sediment cores from lakes in central and northern Canada. Typically cores spanned periods of one hundred to several hundred years, as judged by profiles of unsupported lead-210 and cesium-137. Mercury in the uppermost slices of sediment from lakes in more easterly locations was consistently elevated above that in deeper slices from the same lakes. The authors have interpreted this surface enrichment as evidence of increased recent loadings in agreement with similar studies in Ontario, Quebec, USA and Scandinavia. Western sites showed less surface enrichment with mercury, sometimes almost none, in agreement with experience in Alaska.more » Surface grab samples and two deep cores from Lake Winnipeg indicated that mercury in surface sediments exceeded that at depths corresponding to several thousand years in the history of the lake. The current indication from the cores is a regional difference in loadings of mercury with higher enrichments over basal values in the East than in the West. Recent literature, however, has raised the possibility of vertical mobility of mercury in sediments. This has suggested that processes controlling the well-known concentration of iron and manganese in oxidized surface sediments may also concentrate mercury. A number of the cores were analyzed for iron and manganese but mercury (or lead or cadmium) failed to correlate with iron or manganese. Efforts are underway to develop ways to distinguish rigorously between natural mercury and contamination.« less

Recurrence of water bodies in the hyperarid core of the Atacama Desert - New insights into the Late Pleistocene paleoclimate history of Northern Chile

NASA Astrophysics Data System (ADS)

Diederich, J. L.; Wennrich, V.; Fernández Galego, E.; Ritter, B.; Brill, D.; Niemann, K.; Rolf, C.; Melles, M.

2017-12-01

The Atacama Desert of northern Chile is regarded as the driest desert on Earth. Although still controversially discussed, overall arid to hyperarid conditions in the Atacama are thought to have persisted at least since the early Miocene, but were frequently punctuated by pluvial phases. The knowledge of past changes in humidity is strongly hampered by the fact that sediment records from the central Atacama Desert, which enable longer-scale precipitation reconstructions, are rare and mostly restricted to the Miocene/Pliocene or the late Pleistocene <50 kyrs. In this study, we focus on a sediment record from the hyperarid core of the Atacama Desert, derived from a tectonically blocked clay pan in the Coastal Cordillera (20°04'33.64"S, 69°55'01.75"W). This clay pan `Huara' has been initially investigated by a geophysical survey in spring 2015, followed by drilling of a short core (HU-III) covering the uppermost 4 m of sediment. Initial results of the ground penetrating radar (GPR) and horizontal to vertical (H/V) spectral ratio measurements indicate well-stratified sediment bodies in the basin with a maximum sediment infill of 30 ± 4 m. The chronology of core HU-III was established by a combination of optically stimulated luminescence (OSL) and paleomagnetic dating. The sedimentological and geochemical data of core HU-III as well as it's sediment geophysical properties indicate the primary accumulation of fine-grained sediments over the past ca. 50 kyrs, interpreted to be deposited under arid conditions with only sporadic precipitation. Intercalated coarser horizons indicate several periods of semiarid climate conditions, causing multiple phases of local alluvial deposition from the interior catchment area into the clay pan. The results are in agreement with a cosmogenic nuclide study from an adjacent meander system, indicating that the whole sediment sequence of the Huara clay pan covers the regional climate history of the past 500 - 700 kyrs.

Efficacy of 230Th normalization in sediments from the Juan de Fuca Ridge, northeast Pacific Ocean

NASA Astrophysics Data System (ADS)

Costa, Kassandra; McManus, Jerry

2017-01-01

230Th normalization is an indispensable method for reconstructing sedimentation rates and mass fluxes over time, but the validity of this approach has generated considerable debate in the paleoceanographic community. 230Th systematics have been challenged with regards to grain size bias, sediment composition (CaCO3), water column advection, and other processes. In this study, we investigate the consequences of these effects on 230Th normalization from a suite of six cores on the Juan de Fuca Ridge. The proximity of these cores (<30 km) suggests that they should receive the same particle rain rate of sediment, but the steep bathymetry of the ridge leads to substantial sediment redistribution and variable carbonate preservation, both of which may limit the usage of 230Th in this region. Despite anticipated complications, 230Th normalization effectively reconstructs nearly identical particle rain rates from all six cores, which are summarily unrelated to the total sedimentation rates as calculated from the age models. Instead the total sedimentation rates are controlled almost entirely by sediment focusing and winnowing, which are highly variable even over the short spatial scales investigated in this study. Furthermore, no feedbacks on 230Th systematics were detected as a consequence of sediment focusing, coarse fraction variability, or calcium carbonate content, supporting the robustness of the 230Th normalization technique.

Dissimilatory arsenate and sulfate reduction in sediments of two hypersaline, arsenic-rich soda lakes: Mono and Searles Lakes, California

USGS Publications Warehouse

Kulp, T.R.; Hoeft, S.E.; Miller, L.G.; Saltikov, C.; Murphy, J.N.; Han, S.; Lanoil, B.; Oremland, R.S.

2006-01-01

A radioisotope method was devised to study bacterial respiratory reduction of arsenate in sediments. The following two arsenic-rich soda lakes in California were chosen for comparison on the basis of their different salinities: Mono Lake (???90 g/liter) and Searles Lake (???340 g/liter). Profiles of arsenate reduction and sulfate reduction were constructed for both lakes. Reduction of [73As] arsenate occurred at all depth intervals in the cores from Mono Lake (rate constant [k] = 0.103 to 0.04 h-1) and Searles Lake (k = 0.012 to 0.002 h-1), and the highest activities occurred in the top sections of each core. In contrast, [35S] sulfate reduction was measurable in Mono Lake (k = 7.6 ?? 104 to 3.2 ?? 10-6 h-1) but not in Searles Lake. Sediment DNA was extracted, PCR amplified, and separated by denaturing gradient gel electrophoresis (DGGE) to obtain phylogenetic markers (i.e., 16S rRNA genes) and a partial functional gene for dissimilatory arsenate reduction (arrA). The amplified arrA gene product showed a similar trend in both lakes; the signal was strongest in surface sediments and decreased to undetectable levels deeper in the sediments. More arrA gene signal was observed in Mono Lake and was detectable at a greater depth, despite the higher arsenate reduction activity observed in Searles Lake. A partial sequence (about 900 bp) was obtained for a clone (SLAS-3) that matched the dominant DGGE band found in deeper parts of the Searles Lake sample (below 3 cm), and this clone was found to be closely related to SLAS-1, a novel extremophilic arsenate respirer previously cultivated from Searles Lake. Copyright ?? 2006, American Society for Microbiology. All Rights Reserved.

Paleoenvironmental reconstruction of lagoonal strata from Sri Lanka using multiple physical properties proxies to assure stratigraphic continuity

NASA Astrophysics Data System (ADS)

Ranasinghage, P. N.; Ortiz, J. D.; Moore, A.; Siriwardana, C.

2009-12-01

Core collapsing is a common problem in studies of lagoonal sediment cores. Coring liquefied sediments below the water table can lead to collapse of material from upper core drives in to the hole. This can be prevented by casing the hole. But casing is not always possible due to practical issues such as coring device type, resources, or time constraints. In such cases identifying the collapsed material in each drive is necessary to ensure accurate results. Direct visual identification of collapsed portion is not always possible and may not be precise. This study successfully recognized collapsed material using a suite of physical properties measurements including: visible (VIS) reflectance spectroscopy, magnetic susceptibility and grain size spectra. This enables us to use the verified stratigraphically continuous records for paleo-environmental studies. Sediment cores were collected from three coastal lagoons and a swale along south eastern and eastern Sri Lanka. Cores were collected using a customized AMS soil coring device with a 1-m long sample barrel. The metal barrel of this instrument collects a 2.5 cm diameter sample in 1-m long plastic tubes. Coring was conducted to refusal, with a maximum depth of 5 m. Casing was not applied to the holes due to small core diameter and time constrains. Drill holes were placed at locations situated both below and above the water level of the lagoons. A total of 100 m of sediment core were obtained from these locations. After opening the cores, suspected collapsed material was initially identified by visual observation using a high power binocular microscope. Particle size, magnetic susceptibility, X-ray fluorescence (XRF) and Diffuse Spectral Reflectance (DSR) was then measured on all cores at 1-2 cm resolution to precisely define the repeated sediment intervals. Down core variation plots of magnetic susceptibility, CIE L* (lightness), a*(red/green difference), b* (blue and yellow difference) clearly record abrupt changes at core drive boundaries at the presence of collapsed material. The correlation of grain-size spectra from the bottom and top of consecutive drives was used to precisely determine the thickness of the collapsed material between drives. Our analysis of 48 m of core material thus far indicates that ~4.4m or ~9% of the record represents collapsed material which can be excluded from further study. The remaining continuous record was analyzed for paleoenvironmental studies. Down core variation of grain size, geochemical ratios, principle components of DSR and geochemical data, and magnetic susceptibility from all locations indicate a gradual filling of these deep lagoons and a transition from reducing to oxic conditions. According to an age model constructed for a nearby lagoon the onset of regression began ~6,000 years BP. Several instantaneous sedimentation events were recorded in all lagoons. Further studies will be carried out to determine whether these represent tsunami, storm surge, or flood deposits.

Multi-core, multi-constraint chronostratigraphic framework over past 50,000 years places high-resolution Gulf of Alaska ocean-ice-sediment history into a global framework

NASA Astrophysics Data System (ADS)

Mix, A. C.; Walczak, M.; Asahi, H.; Belanger, C. L.; Cowan, E. A.; Du, J.; Fallon, S.; Fifield, L. K.; Hobern, T.; Jaeger, J. M.; Jensen, B. J. L.; McKay, J. L.; Padman, J.; Ross, A.; Sharon, S.; Stoner, J. S.; Zellers, S.

2017-12-01

Development of precise chronologies extending older than late glacial time in the subpolar North Pacific has been notoriously difficult due to limited record length in sediment cores, poor carbonate preservation, and (in many cases) relatively low resolution records. This is a key gap in our understanding of Northern Hemisphere and global paleoclimate change, now addressed with results from IODP Expedition 341 in the Gulf of Alaska. Here we utilize marine core and drill sites (U1417, U1418, U1419, U1421 and co-located site-survey cores) some of which provide exceptionally high sustained sedimentation rates (up to 2 cm per year in extended glacial intervals). This facilitates a multifaceted approach to chronology development over the past 50,000 years including radiocarbon, foraminiferal stable isotopes and other geochemical proxies, sediment physical properties, sedimentology, and tephrochronology. Given high sedimentation rates and the superb preservation this provides, we have developed marine time series that rival the resolution of the polar ice core records, which allows us to compare radiocarbon-based chronologies with several strategies involving signal tuning. Such a multifaceted approach mitigates weaknesses in any of the individual methods and allows a rigorous analysis of uncertainties in ages and sediment accumulation rates. The resulting record reveals dynamic changes in the Cordilleran Ice Sheet and North Pacific Ocean and most importantly facilitates placing these records into the context of global climate changes. (We acknowledge the contributions of J. Addison and S. Praetorius, who were not listed as co-authors due to USGS submission rules).

Extracting paleo-climate signals from sediment laminae: A new, automated image processing method

NASA Astrophysics Data System (ADS)

Gan, S. Q.; Scholz, C. A.

2010-12-01

Lake sediment laminations commonly represent depositional seasonality in lacustrine environments. Their occurrence and quantitative attributes contain various signals of their depositional environment, limnological conditions and climate. However, the identification and measurement of laminae remains a mainly manual process that is not only tedious and labor intensive, but also subjective and error prone. We present a batch method to identify laminae and extract lamina properties automatically and accurately from sediment core images. Our algorithm is focused on image enhancement that improves the signal-to-noise ratio and maximizes and normalizes image contrast. The unique feature of these algorithms is that they are all direction-sensitive, i.e., the algorithms treat images in the horizontal direction and vertical direction differently and independently. The core process of lamina identification is to use a one-dimensional (1-D) lamina identification algorithm to produce a lamina map, and to use image blob analyses and lamina connectivity analyses to aggregate and smash two-dimensional (2-D) lamina data for the best representation of fine-scale stratigraphy in the sediment profile. The primary output datasets of the system are definitions of laminae and primary color values for each pixel and each lamina in the depth direction; other derived datasets can be retrieved at users’ discretion. Sediment core images from Lake Hitchcock , USA and Lake Bosumtwi, Ghana, were used for algorithm development and testing. As a demonstration of the utility of the software, we processed sediment core images from the top of 50 meters of drill core (representing the past ~100 ky) from Lake Bosumtwi, Ghana.

Diagenetic effects on magnetic minerals in a Holocene lacustrine sediment core from Huguangyan maar lake, southeast China

NASA Astrophysics Data System (ADS)

Wu, Xudong; Wang, Yong; Bian, Liu; Shen, Ji

2016-09-01

Post-depositional reductive diagenesis usually results in partial or entire cleansing of the pristine palaeomagnetic signal, therefore, its intensity is important to be assessed for sediments that are in the purpose of retrieving palaeomagnetic information. Grain size, rock magnetic and geochemical studies on the entire core, along with scanning electron microscope observations and X-ray diffraction analyses for representative samples were carried out on a Holocene sediment core retrieved from the deep water part of Huguangyan maar lake (HGY), southeast China. The pristine magnetic mineral assemblage of the studied core is domianted by superparamagnetic (SP) and stable single domain titanomagnetite, and high coercivity minerals are not detectable. Based on down-core variations of the average grain size (MZ), total organic carbon (TOC), detrital elements (Al, Ti, Fe and Mn) and the concentration and mineralogy of magnetic minerals, the studied core could be divided into three subsections. The uppermost subsection is the least affected by diagenesis, with detrital titanomagnetite as the dominant magnetic mineral. This is owing to low TOC contents, but high detrital input generated by weak Asian summer monsoon intensity during the late Holocene. The intermediate subsection shows down-core progressively enhanced dissolution of detrital titanomagnetite, and concomitant formation of authigenic pyrite and siderite, which indicates down-core progressively enhanced diagenesis generated by down-core progressive increasing TOC content, but decreasing detrital input as the result of down-core progressively strengthened Asian summer monsoon intensity. The pristine magnetic mineral assemblage has been profoundly modified in the lowermost subsection. At certain positions of the lowermost subsection, detrital titanomagnetite has been even completely dissolved via diagenesis, giving place to authigenic pyrite and siderite. High TOC content, but low detrital input generated from strong Asian summer monsoon intensity during the early Holocene are accountable for intensive diagenesis in the lowermost subsection. Complete erasing of detrital magnetic input signal at certain positions of the lowermost subsection, and considerable formation of authigenic siderite indicate that palaeomagnetic records of the studied core have been significantly compromised. The studied core has relatively higher TOC content, lower detrital matter content, calmer sedimentary environments, and less DO available at its water-sediment interface than the cores retrieved at relatively shallower water depths, which all contribute to its relatively stronger diagenesis. Progressive thickening of the upper two subsections with increasing water depth is owing to progressive increase in sedimentation rate with increasing water depth, which is the key factor in determining the thickness of each diagenetic subsection of cores from HGY. It would be better that lake sediments for palaeomagnetic investigations collected at a water depth shallower than the depth of its thermocline.

Experimental Simulations of Methane Gas Migration through Water-Saturated Sediment Cores

NASA Astrophysics Data System (ADS)

Choi, J.; Seol, Y.; Rosenbaum, E. J.

2010-12-01

Previous numerical simulations (Jaines and Juanes, 2009) showed that modes of gas migration would mainly be determined by grain size; capillary invasion preferably occurring in coarse-grained sediments vs. fracturing dominantly in fine-grained sediments. This study was intended to experimentally simulate preferential modes of gas migration in various water-saturated sediment cores. The cores compacted in the laboratory include a silica sand core (mean size of 180 μm), a silica silt core (1.7 μm), and a kaolin clay core (1.0 μm). Methane gas was injected into the core placed within an x-ray-transparent pressure vessel, which was under continuous x-ray computed tomography (CT) scanning with controlled radial (σr), axial (σa), and pore pressures (P). The CT image analysis reveals that, under the radial effective stress (σr') of 0.69 MPa and the axial effective stress (σa') of 1.31 MPa, fracturings by methane gas injection occur in both silt and clay cores. Fracturing initiates at the capillary pressure (Pc) of ~ 0.41 MPa and ~ 2.41 MPa for silt and clay cores, respectively. Fracturing appears as irregular fracture-networks consisting of nearly invisibly-fine multiple fractures, longitudinally-oriented round tube-shape conduits, or fine fractures branching off from the large conduits. However, for the sand core, only capillary invasion was observed at or above 0.034 MPa of capillary pressure under the confining pressure condition of σr' = 1.38 MPa and σa' = 2.62 MPa. Compared to the numerical predictions under similar confining pressure conditions, fracturing occurs with relatively larger grain sizes, which may result from lower grain-contact compression and friction caused by loose compaction and flexible lateral boundary employed in the experiment.

Abyssal ostracods from the South and Equatorial Atlantic Ocean: Biological and paleoceanographic implications

USGS Publications Warehouse

Yasuhara, Moriaki; Cronin, T. M.; Martinez, Arbizu P.

2008-01-01

We report the distribution of ostracods from ???5000 m depth from the Southeast and Equatorial Atlantic Ocean recovered from the uppermost 10 cm of minimally disturbed sediments taken by multiple-corer during the R/V Meteor DIVA2 expedition M63.2. Five cores yielded the following major deep-sea genera: Krithe, Henryhowella, Poseidonamicus, Legitimocythere, Pseudobosquetina, and Pennyella. All genera are widely distributed in abyssal depths in the world's oceans and common in Cenozoic deep-sea sediments. The total number of ostracod specimens is higher and ostracod shell preservation is better near the sediment-water interface, especially at the 0-1 cm core depths. Core slices from ???5 to 10 cm were barren or yielded a few poorly preserved specimens. The DIVA2 cores show that deep-sea ostracod species inhabit corrosive bottom water near the carbonate compensation depth (CCD) even though their calcareous valves are rarely preserved as fossils in sediment cores due to postmortem dissolution. Their occurrence at great water depths may partially explain the well-known global distributions of major deep-sea taxa in the world's oceans, although further expeditions using minimal-disturbance sampling devices are needed to fill geographic gaps. ?? 2008 Elsevier Ltd. All rights reserved.

Evolution of Metallic Trace Elements in Contaminated River Sediments: Geochemical Variation Along River Linear and Vertical Profile

NASA Astrophysics Data System (ADS)

Kanbar, Hussein; Montarges-Pelletier, Emmanuelle; Mansuy-Huault, Laurence; Losson, Benoit; Manceau, Luc; Bauer, Allan; Bihannic, Isabelle; Gley, Renaud; El Samrani, Antoine; Kobaissi, Ahmad; Kazpard, Veronique; Villieras, Frédéric

2015-04-01

Metal pollution in riverine systems poses a serious threat that jeopardizes water and sediment quality, and hence river dwelling biota. Since those metallic pollutants can be transported for long distances via river flow, river management has become a great necessity, especially in times where industrial activities and global climate change are causing metal release and spreading (by flooding events). These changes are able to modify river hydrodynamics, and as a consequence natural physico-chemical status of different aquatic system compartments, which in turn alter metal mobility, availability and speciation. Vertical profiles of sediments hold the archive of what has been deposited for several tenths of years, thus they are used as a tool to study what had been deposited in rivers beds. The studied area lies in the Orne river, northeastern France. This river had been strongly modified physically and affected by steelmaking industrial activities that had boosted in the middle of the last century. This study focuses on several sites along the linear of the Orne river, as well as vertical profiles of sediments. Sediment cores were collected at sites where sedimentation is favoured, and in particular upstream two dams, built in the second half of the XXth century for industrial purposes. Sediment cores were sliced into 2-5cm layers, according to suitability, and analysed for physical and physico-chemical properties, elemental content and mineralogy. Data of the vertical profile in a sediment core is important to show the evolution of sediments as a function of depth, and hence age, in terms of nature, size and constituents. The physical properties include particle size distribution (PSD) and water content. In addition, the physico-chemical properties, such as pH and oxido-reduction potential (ORP) of interstitial water from undisturbed cores were also detected. Total elemental content of sediment and available ones of extracted interstitial waters was detected using ICP-MS and ICP-OES for trace and major elements respectively. Well crystallized minerals were detected by X-Ray Diffraction (XRD), while amorphous and poorly crystallized phases were identified with scanning and transmission electron microscope (SEM and TEM respectively), combined with Energy Dispersive X-Ray Spectroscopy (EDXS). Such microscopic techniques also provided information about metal carriers. To have an insight about the metal speciation at molecular level, X-Ray Absorption spectroscopy (XAS) was performed at Zn K-edge. The first analyses of Orne sediment cores evidenced different particle size distribution and sediment consolidation levels. Yet the cores showed that below a layer of apparently recent sediments (about 10-20 cm), lie highly contaminated ones. Zn and Pb content in deep sediment layers reach several thousands ppm, where they appeared mainly as Zn and Pb sulphides. Also, the high content of iron in deep sediments resulted in the presence of different iron phases: hematite, wuestite, magnetite, goethite, sulphides (pyrite), as well as undefined iron-silicate. In addition, interstitial waters contained high values of available metals (Zn: 500-35000 ppm, Pb: 150-5700 ppm, Cd: 1-10ppm), which might cause a greater concern than solid-bound metals, especially when river bed sediments are disturbed.

Magnetic properties of Japan Sea sediments in areas which host shallow gas hydrates and in relation to the the amount of gas hydrate

NASA Astrophysics Data System (ADS)

Shimono, T.; Matsumoto, R.

2016-12-01

Shallow gas hydrate is known to occur as massive nodular aggregates in subsurface and/or shallow marine sediments (e.g. Matsumoto et al. 2009). We conducted a rock magnetic study of marine core sediments to clarify the relationship between shallow gas hydrate and the surrounding sediments. The core samples were taken from around Oki area and offshore Joetsu, the eastern margin of Japan Sea, during PS15 cruise in 2015. We mainly report magnetic susceptibility measurement of whole-round core samples. From the onboard measurements, the magnetic susceptibilities of gas hydrates indicated diamagnetic mineral like water or ice ( -0.9 x 10-5 vol. SI). Moreover, we introduce a method to assess the amount of gas hydrate present within marine sediments using magnetic susceptibility and rock magnetic analyses. This study was conducted under the commission from AIST as a part of the methane hydrate research project of METI (the Ministry of Economy, Trade and Industry, Japan).

Electrogenic sulfur oxidation in a northern saltmarsh (St. Lawrence Estuary, Canada).

PubMed

Rao, Alexandra; Risgaard-Petersen, Nils; Neumeier, Urs

2016-06-01

Measurements of porewater O2, pH, and H2S microprofiles in intact sediment cores collected in a northern saltmarsh in the St. Lawrence Estuary (Quebec, Canada) revealed the occurrence of electrogenic sulfur oxidation (e-SOx) by filamentous "cable" bacteria in submerged marsh pond sediments in the high marsh. In summer, the geochemical fingerprint of e-SOx was apparent in intact cores, while in fall, cable bacteria were detected by fluorescence in situ hybridization and the characteristic geochemical signature of e-SOx was observed only upon prolonged incubation. In exposed, unvegetated creek bank sediments sampled in the low marsh in summer, cable bacteria developed only in repacked cores of sieved (500 μm), homogenized sediments. These results suggest that e-SOx is suppressed by the activity of macrofauna in exposed, unvegetated marsh sediments. A reduced abundance of benthic invertebrates may promote e-SOx development in marsh ponds, which are dominant features of subarctic saltmarshes as in the St. Lawrence Estuary.

RECONSTRUCTION OF CONTAMINANT TRENDS IN A SALT WEDGE ESTUARY WITH SEDIMENT CORES DATED USING A MULTIPLE PROXY APPROACH

EPA Science Inventory

The Taunton River is a partially mixed tidal estuary in southeastern Massachusetts (USA) which has received significant contaminant inputs, yet little information exists on the history of discharge and the subsequent fate of these contaminants. Three sediment cores taken along a...

Investigating Holocene Glacial and Pluvials Events in the Sierra Nevada of California

NASA Astrophysics Data System (ADS)

Ashford, J.; Sickman, J. O.; Lucero, D. M.; Kirby, M.; Gray, A. B.

2016-12-01

Understanding interannual and decadal variation in snowfall and extreme hydrologic events in the Sierra Nevada is hampered by short instrumental record and uncertainty caused by extrapolating paleoclimate data from lower elevation systems to the alpine snow deposition zone. Longer paleo records from high elevation systems are necessary to provide a more accurate record of snow water content and extreme precipitation events over millennial timescales that can be used to test hypotheses regarding teleconnections between Pacific climate variability and water supply and flood risk in California. In October 2013 we collected sediment cores from Pear Lake, an alpine lake in Sequoia National Park. The cores were split and characterized by P-wave velocity, magnetic susceptibility and density scanning along with grain-size analysis at 1-2 cm increments. Radiocarbon dates indicate that the Pear Lake cores contain a 13.5K year record of lake sediment. In contrast to other Sierra Nevada lakes previously cored by our group, high-resolution scanning revealed alternating fine grained, light-dark bands (1 mm to 5 mm thick) for most of the Pear Lake core length. This pattern was interrupted at intervals by homogenous clasts (up to 75 mm thick) ranging in grain size from sand to gravel up to 1 cm diameter. The sand to gravel sized clasts are most likely associated with extreme precipitation events. Preliminary grain-size analysis results show evidence of isolated extreme hydrologic events and sections of increased event frequency which we hypothesize are the result of atmospheric rivers intersecting the southern Sierra Nevada outside of the snow covered period.

Planktic foraminifer census data from Northwind Ridge Core 5, Arctic Ocean

USGS Publications Warehouse

Foley, Kevin M.; Poore, Richard Z.

1991-01-01

The U.S. Geological Survey recovered 9 piston cores from the Northwind Ridge in the Canada Basin of the Arctic Ocean from a cruise of the USCGC Polar Star during 1988. Preliminary analysis of the cores suggests sediments deposited on Northwind Ridge preserve a detailed record of glacial and interglacial cycles for the last few hundred-thousand to one million years. This report includes quantitative data on foraminifers and selected sediment size-fraction data in samples from Northwind Ridge core PI-88AR P5.

Speciation and isotopic composition of sedimentary sulfur in the Everglades, Florida, USA

USGS Publications Warehouse

Bates, A.L.; Spiker, E. C.; Holmes, C.W.

1998-01-01

We have studied the sulfur speciation and isotopic composition of two peat cores from Water Conservation Area 2A (WCA 2A) in the Florida Everglades. Core site E1 is affected by agricultural runoff from the Hillsboro Canal which drains the Everglades Agricultural Area; Core site U3 is distant from the canal and relatively unaffected by agricultural runoff. Depth profiles of the total sulfur content of both cores show fairly constant levels (??0.7 wt.%) below about 25-30 cm depth in Core E1 and below 40-45 cm in Core U3. Above these depths, total sulfur increases to as much as 1.52 wt.% in Core E1 and 1.74 wt.% in Core U3, suggesting that more sulfur has entered the sediments and/or that more sulfur is being retained in recent times at both sampling sites. These changes in total sulfur content with depth in Core E1 correlate with changes in total phosphorus that have been observed in other studies at core sites near the Hillsboro Canal. This correlation of total sulfur with phosphorus with depth is not seen in Core U3 located away from the canal, possibly because phosphorus is more effectively retained than sulfur in the organic sediment near the canal. Organic-sulfur (OS) concentrations are at least twice as high as the dusulfide-sulfur (DS) concentrations in the upper parts of both cores suggesting that iron is presently limiting the amount of dusulfide minerals formed in these sediments. The degree of pyritization (DOP) in the upper parts of the cores suggest that sulfide mineralization is limited by the availability of highly reactive iron during the earliest stages of diagenesis. Positive ??34S values for reduced sulfur forms in both cores indicate a relatively restricted sulfate reservoir, consistent with nearly complete reduction of the sulfate available in the sediment at any given time. Differences between the two core appear in the ??34S values for the near-surface sediments. The DS ??34S values in the upper 10.0 cm of sediment are more posotive at site E1, with a mean ??34S value of +12.9???, than at site U3, with a mean ??34S value of +2.9???. These reuslts may indicate that increased rates of organic deposition due to nutrient loading near the canal have increased the rate of sulfate reduction at the E1 site in recent times. Acid-volatile-sulfide (AVS) concentrations are lower than DS and OS concentrations by at least a factor of 10. Increasing ??34S values for AVS with increasing depth in both cores suggests ongoing reduction of a limited porewater sulfate reservoir after deposition. The disulfide and organic-sulfur ??34S values diverge from the ??34S values for AVS with depth, suggesting that most of the transformation of AVS into disulfide minerals or incorporation of sulfur into orgnaic matter occurs in the near-surface sediments. A comparison of organic-sulfur ??34S values in the dominant flora at the U3 site (sawgrass leaves and periphyton) with organic-sulfur ??34S values at the top of the U3 core indicates that there was early incorporation of an isotopically light sulfide species into the orgnaic matter.

Stable lead isotopic analyses of historic and contemporary lead contamination of San Francisco Bay estuary

USGS Publications Warehouse

Ritson, P.I.; Bouse, R.M.; Flegal, A.R.; Luoma, S.N.

1999-01-01

Variations in stable lead isotopic composition (240Pb, 206Pb, 207Pb, 208Pb) in three sediment cores from the San Francisco Bay estuary document temporal changes in sources of lead during the past two centuries. Sediment, with lead from natural geologic sources, and relatively homogeneous lead isotopic compositions are overlain by sediments whose isotopic compositions indicate change in the sources of lead associated with anthropogenic modification of the estuary. The first perturbations of lead isotopic composition in the cores occur in the late 1800s concordant with the beginning of industrialization around the estuary. Large isotopic shifts, toward lower 206Pb/207Pb, occur after the turn of the century in both Richardson and San Pablo Bays. A similar relationship among lead isotopic compositions and lead concentrations in both Bays suggest contamination from the same source (a lead smelter). The uppermost sediments (post 1980) of all cores also have a relatively homogenous lead isotopic composition distinct from pre-anthropogenic and recent aerosol signatures. Lead isotopic compositions of leachates from fourteen surface sediments and five marsh samples from the estuary were also analyzed. These analyses suggest that the lead isotopic signature identified in the upper horizons of the cores is spatially homogeneous among recently deposited sediments throughout the estuary. Current aerosol lead isotopic compositions [Smith, D.R., Niemeyer, S., Flegal, A.R., 1992. Lead sources to California sea otters: industrial inputs circumvent natural lead biodepletion mechanisms. Environmental Research 57, 163-175] are distinct from the isotopic compositions of the surface sediments, suggesting that the major source of lead is cycling of historically contaminated sediments back through the water column. Both the upper core sediments and surface sediments apparently derive their lead predominantly from sources internal to the estuary. These results support the idea that geochemical cycling of lead between sediments and water accounts for persistently elevated lead concentrations in the water column despite 10-fold reduction of external source inputs to San Francisco Bay [Flegal, A.R., Rivera-Duarte, I., Ritson, P.I., Scelfo, G., Smith, G.J., Gordon, M., Sanudo-Wilhelmy, S.A., 1996. Metal contamination in San Francisco Waters: historic perturbations, contemporary concentrations, and future considerations in San Francisco Bay. In: Hollobaugh, J.T. (Ed.), The Ecosystem. AAAS, pp. 173-188].

Physical Properties of Sediment Related to Gas Hydrate in the Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Winters, W. J.; Novosel, I.; Boldina, O. M.; Waite, W. F.; Lorenson, T. D.; Paull, C. K.; Bryant, W.

2002-12-01

Eighteen giant piston cores, up to 38-m long, were recovered during July 2002 to determine the distribution of gas hydrate in widely different geologic environments of the Northern Gulf of Mexico. Physical properties, including electrical resistivity, three different shear strengths, P-wave velocity, and thermal conductivity were measured on split and whole-round cores at sea. Water content, grain density, and related properties are being determined in a shore-based laboratory from shipboard-acquired subsamples. These physical property data are important for two primary reasons: (1) to relate the presence of gas hydrate to the natural host sediment; and (2) to correlate with shallow seismic reflection records so they can be interpreted more accurately within and below the depth of coring. Preliminary results indicate that porosity and water content typically decrease rapidly to a subbottom depth of about 8 to 9 m, but then decrease at a much lower rate to the base of the core - often 30 or more mbsf. Although higher water contents are measured in the sediments that were recovered in association with gas hydrates, they are probably an artifact of post-sampling hydrate dissociation rather than an in-situ characteristic. The hydrate recovered during the cruise, was present either as particles distributed throughout the sediment or as massive chunks that filled the entire 10-cm diameter of the core liner. The sediments immediately adjacent to the recovered gas hydrates are visually similar to surrounding sediments, and thus primary lithologic differences do not appear to control the distribution of these gas hydrates. Vane shear strength measurements correlate better to subbottom depth than to water content. The strength values typically increase from less than 10 kPa near the seafloor to as much as 80 to 90 kPa at the base of some cores. Electrical resistivity appears to be related to water content (and probably porewater salinity) since a break in slope with depth is often recorded in the upper 8 to 15 m of sediment. Electrical resistivity typically increases from about 0.4 to 0.5 ohm-m near the top of many cores, to about 0.7 ohm-m near the base of the deeper recovered sediment. These values are typical for clay-rich fine-grained sediment with high water content. Although the amount of gas hydrate in the natural environment is enormous, little is known about its distribution in sea-floor sediment or even exactly how it forms. A goal of this cruise was to find evidence for the existence of gas hydrate away from obvious seafloor gas-hydrate mounds and at depth in the sediment. This international, multi-discipline coring cruise was conducted jointly by the Institut Polaire Francais, Paul-Emile Victor (IPEV) and the USGS aboard the 120-m-long French research vessel, Marion Dufresne. Partial funding was provided by the U.S. Dept. of Energy and considerable at-sea help was provided by an international group of about 40 scientists under the IMAGES (International Marine Past Global Changes Study) and PAGE (Paleoceanography of the Atlantic and Geochemistry) programs.

Geologic, geotechnical, and geophysical properties of core from the Acme Fire-Pit-1 drill hole, Sheridan County, Wyoming

USGS Publications Warehouse

Collins, Donley S.

1983-01-01

A preliminary core study from the Acme Fire-Pit-1 drill hole, Sheridan County, Wyoming, revealed that the upper portion of the core had been baked by a fire confined to the underlying Monarch coal bed. The baked (clinkered) sediment above the Monarch coal bed was determined to have higher point-load strength values (greater than 2 MPa) than the sediment under the burned coal

Leg 67: the Deep Sea Drilling Project Mid-America Trench transect off Guatemala.

USGS Publications Warehouse

von Huene, Roland E.

1980-01-01

Drilling on the Cocos plate recovered a basal chalk sequence deposited during early and mid-Miocene time, a short interval of abyssal red clay, and an upper sequence of late Miocene and younger sediment deposited within an area influenced by a terrigenous source. In the trench, a mud and sand fill less than 400,000 yr old overlies the oceanic sequence. The entire section shows no evidence of compressive deformation. In contrast, the section cored on the trench's landward slope 3 km from the trench axis is affected by tectonism. The section contains a Cretaceous to Pliocene claystone sequence capped by Pliocene to Quaternary hemipelagic slope deposits.- from Authors

Distribution and origin of authigenic smectite clays in Cape Roberts Project Core 3, Victoria Land Basin, Antarctica

USGS Publications Warehouse

Priestas, A.W.; Wise, S.W.

2007-01-01

Of some 800 m of lower Oligocene marine sediments cored continuously from the seafloor in the Victoria Land Basin of Antarctica at Cape Roberts Site CRP-3, the lower 500 m exhibit authigenic smectite clay coats on shallow-water sandstone grains. A scanning electron microscope/EDS study of 46 fracture sections confirms that the distribution of the clay coats through the unit is not uniform or evenly distributed, but rather varies with depth, original porosity, and the kinds and abundance of source materials. Our results suggest that smectite emplacement resulted from in-situ, low-temperature burial diagenesis rather than hydrothermal or fault-focused thermobaric fluids.

Patterns in bacterial and archaeal community structure and diversity in western Beaufort Sea sediments and waters

NASA Astrophysics Data System (ADS)

Hamdan, L. J.; Sikaroodi, M.; Coffin, R. B.; Gillevet, P. M.

2010-12-01

A culture-independent phylogenetic study of microbial communities in water samples and sediment cores recovered from the Beaufort Sea slope east of Point Barrow, Alaska was conducted. The goal of the work was to describe community composition in sediment and water samples and determine the influence of local environmental conditions on microbial populations. Archaeal and bacterial community composition was studied using length heterogeneity-polymerase chain reaction (LH-PCR) and multitag pyrosequencing (MTPS). Sediment samples were obtained from three piston cores on the slope (~1000m depth) arrayed along an east-west transect and one core from a depth of approximately 2000m. Discrete water samples were obtained using a CTD-rosette from three locations adjacent to piston core sites. Water sample were selected at three discrete depths within a vertically stratified (density) water column. The microbial community in near surface waters was distinct from the community observed in deeper stratified layers of the water column. Multidimensional scaling analysis (MDS) revealed that water samples from mid and deep stratified layers bore high similarity to communities in cores collected in close proximity. Overall, the highest diversity (bacteria and archaea) was observed in a core which had elevated methane concentration relative to other locations. Geochemical (e.g., bulk organic and inorganic carbon pools, nutrients, metabolites) and physical data (e.g. depth, water content) were used to reveal the abiotic factors structuring microbial communities. The analysis indicates that sediment water content (porosity) and inorganic carbon concentration are the most significant structuring elements on Beaufort shelf sedimentary microbial communities.

Assessment of sediments in the riverine impoundments of national wildlife refuges in the Souris River Basin, North Dakota

USGS Publications Warehouse

Tangen, Brian A.; Laubhan, Murray K.; Gleason, Robert A.

2014-01-01

Accelerated sedimentation of reservoirs and riverine impoundments is a major concern throughout the United States. Sediments not only fill impoundments and reduce their effective life span, but they can reduce water quality by increasing turbidity and introducing harmful chemical constituents such as heavy metals, toxic elements, and nutrients. U.S. Fish and Wildlife Service national wildlife refuges in the north-central part of the United States have documented high amounts of sediment accretion in some wetlands that could negatively affect important aquatic habitats for migratory birds and other wetland-dependent wildlife. Therefore, information pertaining to sediment accumulation in refuge impoundments potentially is important to guide conservation planning, including future management actions of individual impoundments. Lands comprising Des Lacs, Upper Souris, and J. Clark Salyer National Wildlife Refuges, collectively known as the Souris River Basin refuges, encompass reaches of the Des Lacs and Souris Rivers of northwestern North Dakota. The riverine impoundments of the Souris River Basin refuges are vulnerable to sedimentation because of the construction of in-stream dams that interrupt and slow river flows and because of post-European settlement land-use changes that have increased the potential for soil erosion and transport to rivers. Information regarding sediments does not exist for these refuges, and U.S. Fish and Wildlife Service personnel have expressed interest in assessing refuge impoundments to support refuge management decisions. Sediment cores and surface sediment samples were collected from impoundments within Des Lacs, Upper Souris, and J. Clark Salyer National Wildlife Refuges during 2004–05. Cores were used to estimate sediment accretion rates using radioisotope (cesium-137 [137Cs], lead-210 [210Pb]) dating techniques. Sediment cores and surface samples were analyzed for a suite of elements and agrichemicals, respectively. Examination of core characteristics along the depth profile suggests that there has been regular sediment mixing and removal, as well as non-uniform sediment deposition with time. Estimated mean accretion rates based on the three methods of determination (two time markers for 137Cs, 210Pb) ranged from 0.22–0.35 centimeters per year, and approximately 70 percent of cores had less 137Cs than expected. Concentrations of sediment-associated elements generally were within reported reference ranges, and all agrichemicals analyzed were below detection limits. Results suggest that there does not appear to be widespread sediment accumulation in impoundments of the Souris River Basin refuges. In addition, there were no identifiable patterns among sedimentation rates from the upstream (Des Lacs, Upper Souris) to the downstream (J. Clark Salyer) refuges. There were, however, apparent upstream to downstream patterns of increased concentrations of some elements (for example, aluminum, boron, and vanadium) that may warrant further exploration. Future related monitoring and research efforts should focus on areas with high potential for sediment accumulation, such as upstream areas adjacent to dams, to identify potential sediment problems before they become too severe. Further, assessments of suspended sediments transported in the Des Lacs and Souris Rivers would augment interpretation of sedimentation data by identifying potential sediment sources and areas with the greatest potential for accumulation.

Analysis of archaeal communities in Gulf of Mexico dead zone sediments.

EPA Science Inventory

Sediments may contribute significantly to Louisiana continental shelf “dead zone” hypoxia but limited information hinders comparison of sediment biogeochemistry between norm-oxic and hypoxic seasons. Dead zone sediment cores collected during hypoxia (September 2006) had higher l...

A New Method for the Determination of Annual Sediment Fluxes from Varved Lake Sediments

NASA Astrophysics Data System (ADS)

Francus, P.; Massa, C.; Lapointe, F.

2013-12-01

Calculation of sediment mass accumulation rates instead of thickness accumulation is preferable for paleoclimatic reconstruction as it eliminates the effects of dilution and compaction. Annually laminated lake sediment sequences (varved) theoretically allow for the estimation of sediment fluxes at annual scale, but the calculation is limited by discrete bulk density measurements, often carried out at a much lower resolution (usually 1 cm) than the varves (ranging from 0.07 to 27.3 mm, average 1.84 mm according to Ojala et al. 2012). Since many years the development of automated logging instruments made available continuous and high resolution sediment property data, in a non-destructive fashion. These techniques can easily be used to extract the physical and chemical parameters of sediments at the varve scale (down to 100 μm). Here we present a robust method to calculate annual sediment fluxes from varved lake sediments by combining varves thickness measurements to core logging data, and provide an example for its applications. Several non-destructive densitometric methods applied to the Strathcona Lake sediment, northern Ellesmere Island, Canada (78°33'N; 82°05'W) were compared: Hounsfield Units from a CT-Scan, coherent/incoherent ratio and X-ray radiography (of both split core and sediment slabs, from an Itrax core Scanner), and gamma ray attenuation density. Core logging data were statistically compared to 400 discrete measurements of dry bulk density, wet bulk density and water content performed at 2 mm contiguous intervals. A very strong relationship was found between X-ray grey level on sediment slab and dry bulk density. Relative X-ray densities, at 100μm resolution, were then successfully calibrated against real densities. The final step consisted in binning the calibrated densities to the corresponding varve thickness and then to calculate the annual mass accumulation rates by multiplying the two parameters for each varve year. Strathcona Lake is located directly downstream of the Agassiz ice cap and contains laminated sediments whose accumulation is directly related to hydrological inputs generated by the melting of the ice cap. Over the last 65 years, annual sediment accumulation rates in Strathcona Lake documented an increase in high-energy hydrologic discharge events from 1990 to 2009. This timing is in agreement with evidence for an increase in the amount of melt on the adjacent Agassiz Ice Cap, as recorded in ice cores. A good correspondence was also found between annual mass accumulation rates and Eureka air temperature records, suggesting that temperature changes affected the extent of summer melting on the Agassiz Ice Cap, leading to high sediment yield to Strathcona Lake. Ojala, A.E.K., Francus, P., Zolitschka, B., Besonen, M. and Lamoureux, S.F. (2012) Characteristics of sedimentary varve chronologies - A review. Quaternary Science Reviews, 43, 45-60.

Vertical accumulation of potential toxic elements in a semiarid system that is influenced by an abandoned gold mine

NASA Astrophysics Data System (ADS)

Sánchez-Martínez, Martha A.; Marmolejo-Rodríguez, Ana J.; Magallanes-Ordóñez, Víctor R.; Sánchez-González, Alberto

2013-09-01

The mining zone at El Triunfo, Baja California Sur, Mexico, was exploited for gold extraction for 200 years. This area includes more than 100 abandoned mining sites. These sites contain mine tailings that are highly contaminated with potential toxic elements (PTE), such as As, Cd, Pb, Sb, Zn, and other associated elements. Over time, these wastes have contaminated the sediments in the adjacent fluvial systems. Our aim was to assess the vertical PTE variations in the abandoned mining zone and in the discharge of the main arroyo into a small lagoon at the Pacific Ocean. Sediments were collected from the two following locations in the mining zone near the arroyo basin tailings: 1) an old alluvial terrace (Overbank) and a test pit (TP) and 2) two sediment cores locations at the arroyo discharge into a hypersaline small lagoon. Samples were analyzed by ICP-MS, ICP-OES, and INAA and the methods were validated. The overbank was the most contaminated and had As, Cd, Pb, Sb, and Zn concentrations of 8690, 226, 84,700, 17,400, and 42,600 mg kg-1, respectively, which decreased with depth. In addition, the TP contained elevated As, Cd, Pb, Sb, and Zn concentrations of 694, 18.8, 5001, 39.2, and 4170 mg kg-1, respectively. The sediment cores were less contaminated. However, the As, Cd, Pb, Sb, and Zn concentrations were greater than the concentrations that are generally found in the Earth's crust. The normalized enrichment factors (NEFs), which were calculated from the background concentrations of these elements in the system, showed that extremely severe As, Cd, Pb, Sb, and Zn (NEF > 50) enrichment occurred at the overbank. The TP was severe to very severely enriched with As, Cd, Pb, Sb, and Zn (NEF = 10-50). The sediment cores had a severe enrichment of As, Pb, and Zn (NEF = 10-25). Their vertical profiles showed that anthropogenic influences occurred in the historic sediment deposition at the overbank and TP and in the sediment cores. In addition, the As, Pb, and Zn concentrations in the sediment cores were related to the deposition of fine sediments and organic carbon.

Diagenetic changes of lignin compounds in a more than 0.6 million-year-old lacustrine sediment (Lake Biwa, Japan)

NASA Astrophysics Data System (ADS)

Ishiwatari, Ryoshi; Uzaki, Minoru

1987-02-01

A vertical profile of lignin in the upper 700 m layer of a 1400 m sediment core of Lake Biwa, an oligotrophic freshwater lake in Japan, was determined using a CuO oxidative degradation method. The results indicated that lignin is found throughout the core, demonstrating lignin to be very stable for over 0.6 million years. Moreover, the upper 250 m (approximately 0.6 million years old) segment of the sediment core was investigated to determine the apparent long term degradation rate of lignin. A downward lignin concentration decrease is observed over the upper 250 m of the core which corresponds to a calculated half life of at least approximately 40 × 10 4 years, assuming that lignin decrease is due to its in situ degradation (diagenesis).

a Mineralogical Analysis of Hspdp Core Samples from the Northern Awash Pliocene Hadar Formation, Ethiopia: the tale of AN East African Paleolake

NASA Astrophysics Data System (ADS)

Davis, D. M.; Deocampo, D.; Rabideaux, N. M.; Campisano, C. J.

2017-12-01

The Northern Awash Valley is located in the southwestern portion of the Afar Depression in Ethiopia. During the 2014 field season, two core sites were drilled as part of the Hominin Sites and Paleolakes Drilling Project (HSPDP), recovering a total of 600 m of sediment from both localities (NAO and NAW). Mineralogical analyses of the bulk sediments and clays from the Hadar Formation have helped to begin constructing a more complete picture of the paleoenvironmental conditions of the Northern Awash during the Pliocene. This work is an attempt to begin to answer the questions about salinity/alkalinity of Hadar Paleolake as well as its sulfur content. The two sites, NAW and NAO, are about 3 kilometers apart and presumably part of the same paleolake basin. The data has shown that this area was much more humid during the Pliocene than it is today and that most of the minerals in the paleolake basin are detrital, save for calcite, Mg-calcite, gypsum, pyrite, and a few zeolites. 060 analyses of the clays in the cores show that the lake was a freshwater lake three million years ago, up until its eventual evaporation. Interestingly, the lack of trioctahedral clays is an indication that the lake water did not become highly saline and alkaline during its evaporation. An interesting contrast between the two cores shows that NAO contains gypsum, but so far, no pyrite. NAW, on the other hand, contains both pyrite and gypsum. The pyrite in NAW is mostly at the bottom of the core, whereas, the gypsum is intermittent throughout the core and much more sparse toward the bottom. This line of evidence suggests that the two sites within the lake may have experienced different redox conditions. It may be that the NAO core was sampled in a shallower part of the lake whereas the NAW core sampled a deeper section.

Sedimentary Environment and Climate Evolution at the Northern Continental Margin of the South China Sea During the Last Glacial Cycle and Holocene

NASA Astrophysics Data System (ADS)

Tomczak, M.; Kaiser, J.; Borowka, R. K.; Chen, H.; Zhang, J.; Harff, J.; Qiu, Y.; Witkowski, A.

2014-12-01

Climate, oceanographic and sea level history during last glacial cycle (LGC) and Holocene at the NW continental margin of the South China Sea (SCS) are investigated within the SECEB project. For that purpose two sediment cores (HDQ2 & 83PC) and single-channel seismic sections were selected to serve as a proxy data source for paleoceanographic and paleoclimatic reconstructions. The sedimentary facies is interpreted by multi-proxy approaches considering micropaleontological, sedimentological and geochemical analyses. According to 14C and OSL datings, sediments of shallow water drill core HDQ2 (88.3 m) cover a time span of ca. 115 kyr BP. Seismic images of the sampling site show a series of reflectors which can be correlated with coarse layers of core HDQ2. These layers are interpreted as transgression / regression horizons. Due to the age model it is possible to correlate these horizons with the general sea level dynamics within the SCS as it is displayed in relative sea level excursions for the MIS 5 to 2 from the Sunda Shelf (Hanebuth et al. 2011). Core 83PC (8.6 m) retrieved from the continental slope provide constant record and calm environment. Therefore, this core is used as a source for data proxy for environmental reconstructions. According to δ18O and paleomagnetic analysis, a good age model which indicate age of this core to ca. 110 kyr BP was elaborated and help correlate the paleoenvironmental data with core HDQ2. Alkenones, δ18O, the Mg/Ca ratio, and microfossil proxies serve for paleo-SST curves and monsoon variability reconstructions. δ15N and δ13C indicate nutrient supply to the marine environment. Diatomological analysis outlines the environmental evolution and interrelations between their parameters during the LGC. Interpretation of seismic profiling allowed identification of submarine paleo-delta. It's anticipated that deposited sediments descent from the Hainan Island and allow correlation of the source and sink area.Hanebuth, T.J.J, Voris, H.K., Yokoyama, Y., Saito, Y., Okuno, J., 2011. Formation and fate of sedimentary depocentres on Southeast Asia's Sunda Shelf over the past sea-level cycle and biogeographic implications. Earth-Science Reviews 104, p. 92-110The project was funded by the Polish National Science Centre allocated on the basis of the decision no. DEC-2011/01/N/ST10/07708

Integrated stratigraphy of a shallow marine Paleocene-Eocene boundary section, MCBR cores, Maryland (USA)

NASA Astrophysics Data System (ADS)

Self-Trail, J. M.; Robinson, M. M.; Edwards, L. E.; Powars, D. S.; Wandless, G. A.; Willard, D. A.

2013-12-01

An exceptional Paleocene-Eocene boundary section occurs in a cluster of six short (<15m) coreholes (MCBR 1 through 6) drilled near Mattawoman Creek in western Charles County, Maryland. The sediments consist of glauconite-rich sand of the upper Paleocene Aquia Formation and silty clay of the lower Eocene Marlboro Clay. Sediment samples were analyzed for carbon and oxygen isotopes, percent calcium carbonate, calcareous nannofossils, planktic and benthic foraminifera, dinoflagellates, pollen, and lithology. A well-defined carbon isotope excursion (CIE) documents a gradual negative shift in δ13C values that starts below the lithologic break between the Aquia Formation and the Marlboro Clay. A benthic foraminifer extinction event, reduction of calcareous nannofossil assemblages, and change in core color from gray to alternating gray and pink also occurs within the CIE transition. These alternating changes in color coincide with cyclic peaks in the carbon isotope and percent calcium carbonate curves, where gray color corresponds to a positive shift in carbon isotope values and to a corresponding increase in percent benthic and planktic foraminifera. The upper third of the Marlboro Clay is barren of all calcareous microfossil material, although the presence of foraminiferal molds and linings proves that deposition occurred in a marine environment. Co-occurrence of the dinoflagellates Apectodinium augustum and Phthanoperidinium crenulatum at the top of the Marlboro Clay suggests that the Marlboro Clay at Mattawoman Creek is truncated. This is corroborated by the absence in the Marlboro of specimens of the calcareous nannofossil Rhomboaster-Discoaster assemblage, which is restricted to early Eocene Zone NP9b. Based on planktic/benthic foraminifera ratios, deposition of sediments at Mattawoman Creek occurred predominantly in an inner neritic environment, at water depths between 25-50 m. Occasional deepening to approximately 75m (middle neritic environment) occurred in the early Eocene, as represented by the basal Marlboro Clay. The planktic/benthic ratio, however, could also be affected by surface productivity and/or river runoff. The gradual shift up-section in core color from gray to alternating gray and red, to dark red, coupled with dissolution of calcareous microfossil assemblages, is possibly secondary and may represent lysocline shoaling in a nearshore environment. This would suggest that lysocline shoaling continued after the CIE and well into the early Eocene.

Tracking Changes in Iron Mineralogy Through Time in Gale Crater and Terrestrial Analogues

NASA Astrophysics Data System (ADS)

Sheppard, R.; Milliken, R.; Russell, J. M.

2017-12-01

Iron and other redox-sensitive elements measured in ancient mudstones of Gale Crater, Mars by the Curiosity rover can provide information on past climate and interactions between water and the early atmosphere. Preserved ferrous mineralogy can constrain lake bottom water conditions and potentially the relative position of the oxycline and/or shoreline through the stratigraphic section. Multiple oxidation states in a given assemblage may also indicate a potential energy source for microbes. The X-ray amorphous fraction of all rocks measured in Gale Crater to date is also enigmatic: it can constitute up to 50 wt% of the sediment but the precise composition and formation conditions are unknown. Features similar to those in the martian mudstones are seen in sediments from the terrestrial redox-stratified Lake Towuti, including alternating ferrous and ferric mineralogy and an abundant Fe-rich X-ray amorphous phase. To constrain conditions in the water column and early diagenetic processes, we present trends in chemistry and mineralogy for sediment acquired from soils in the mafic/ultramafic catchment and lake bottom/core samples. The soils contain high abundances of crystalline Fe-oxides (e.g. magnetite, goethite, hematite), whereas sediment from the very surface of the lake bottom maintain high Fe but not in crystalline form based on XRD. This suggests Fe is being rapidly cycled to form amorphous phases after entering the lake. Sequential extractions to isolate highly reactive iron (e.g. ferrihydrite) will be used to confirm the relative abundance of poorly crystalline phases in catchment versus lake sediment. Sediments from a 150 m core representing 1 Myr lake history also maintain high Fe content and distinct alternating bands of red and green sediment, but there are no crystalline Fe-oxides discernible in XRD data. The process(es) and timescale for this switching is not yet known, but understanding the conditions that allow ferrous vs. ferric iron to form, and what other changes happen concurrently with silicates such as clay minerals, may help constrain how to interpret lake sediment chemistry and mineralogy in terms of climate on Earth and Mars.

Middle Pleistocene infill of Hinkley Valley by Mojave River sediment and associated lake sediment: Depositional architecture and deformation by strike-slip faults

USGS Publications Warehouse

Miller, David; Haddon, Elizabeth; Langenheim, Victoria; Cyr, Andrew J.; Wan, Elmira; Walkup, Laura; Starratt, Scott W.

2018-01-01

Hinkley Valley in the Mojave Desert, near Barstow about 140 km northeast of Los Angeles and midway between Victorville Valley and the Lake Manix basin, contains a thick sedimentary sequence delivered by the Mojave River. Our study of sediment cores drilled in the valley indicates that Hinkley Valley was probably a closed playa basin with stream inflow from four directions prior to Mojave River inflow. The Mojave River deposited thick and laterally extensive clastic wedges originating from the southern valley that rapidly filled much of Hinkley Valley. Sedimentary facies representing braided stream, wetland, delta, and lacustrine depositional environments all are found in the basin fill; in some places, the sequence is greater than 74 m (245 ft) thick. The sediment is dated in part by the presence of the ~631 ka Lava Creek B ash bed low in the section, and thus represents sediment deposition after Victorville basin was overtopped by sediment and before the Manix basin began to be filled. Evidently, upstream Victorville basin filled with sediment by about 650 ka, causing the ancestral Mojave River to spill to the Harper and Hinkley basins, and later to Manix basin.Initial river sediment overran wetland deposits in many places in southern Hinkley Valley, indicating a rapidly encroaching river system. These sediments were succeeded by a widespread lake (“blue” clay) that includes the Lava Creek B ash bed. Above the lake sediment lies a thick section of interlayered stream sediment, delta and nearshore lake sediment, mudflat and/or playa sediment, and minor lake sediment. This stratigraphic architecture is found throughout the valley, and positions of lake sediment layers indicate a successive northward progression in the closed basin. A thin overlapping sequence at the north end of the valley contains evidence for a younger late Pleistocene lake episode. This late lake episode, and bracketing braided stream deposits of the Mojave River, indicate that the river avulsed through the valley, rather than continuing toward Lake Manix, during the late Pleistocene. Two dextral strike-slip fault zones, the Lockhart and the Mt. General, fold and displace the distinctive stratigraphic units, as well as surficial late Pleistocene and Holocene deposits. The sedimentary architecture and the two fault zones provide a framework for evaluating groundwater flow in Hinkley Valley.

Slope and basinal deposits adjacent to isolated carbonate platforms in the Indian Ocean: Sedimentology, geomorphology, and a new 1.2 Ma record of highstand shedding

NASA Astrophysics Data System (ADS)

Counts, J. W.; Jorry, S.; Jouet, G.

2017-12-01

Newly analyzed bathymetric, seismic, and core data from carbonate-topped seamounts in the Mozambique Channel reveals a variety of depositional processes and products operating on platform slopes and adjacent basins. Mass transport complexes (including turbidites and debrites), leveed channel systems with basin-floor fans, and contourites are imaged in high resolution in both seafloor maps and cross-section, and show both differences and similarities compared with platform slopes in the Bahamas and elsewhere. In some, though not all, platforms, increased sedimentation can be observed on the leeward margins, and slope rugosity may be asymmetric with respect to prevailing wind direction. Deposition is also controlled by glacial-interglacial cycles; cores taken from the lower slopes (3000+ m water depth) of carbonate platforms reveal a causative relationship between sea level and aragonite export to the deep ocean. δ18O isotopes from planktonic and benthic foraminifera of two 27-meter cores, reveal a high-resolution, continuous depositional record of carbonate sediment dating back to 1.2 Ma. Sea level rise, as determined by correlation with the LR04 benthic stack, is coincident with increased aragonite flux from platform tops. Gravity flow deposits are also affected by platform flooding—the frequency of turbidite/debrite deposits on pinnacle slopes increases during highstand, although such deposits are also present during glacial episodes. The results reported here are the first record of highstand shedding in the southern Indian Ocean, and provide the longest Quaternary sediment record to date in the region, including the Mid-Brunhes transition (MIS 11) that serves as an analog for the current climate conditions. In addition, this is the first study to describe sedimentation on the slopes of these platforms, providing an important point of comparison that has the potential to influence source-to-sink carbonate facies models.

Benthic foraminifera as indicators of hydrologic and environmental conditions in the Ross Sea (Antarctica)

NASA Astrophysics Data System (ADS)

Bertoni, E.; Bertello, L.; Capotondi, L.; Bergami, C.; Giglio, F.; Ravaioli, M.; Rossi, C.; Ferretti, A.

2012-04-01

This study, present data on benthic foraminiferal assemblages from four box cores collected in different areas of the Ross Sea during the 2005 oceanographic cruise in the framework of the Italian Antarctic Research National Programme (PNRA). Based on magnetic susceptibility, biosiliceous content, and micropaleontological analysis, the sediment cores provide a record of glacial retreat and Holocene environmental changes in the Ross Sea during the last 11 kyr BP. Sediment lithologies range between diamicton to surficial diatomaceous mud, the intermediate levels being glacial-marine sediment. The sedimentary sections include diatomaceous glacial-marine deposit over transitional (proximal grounding zone) glacial-marine sediment. The study revealed that the Ross Sea contains typical Antarctic foraminifera fauna with the dominance of agglutinated taxa. Relatively elevated abundances, richness and diversity were common in the northernmost site, where the water column was characterized by relatively warmer intermediate waters and by the presence of the colder High Salinity Shelf Water (HSSW) occupying the deepest part of the basin. Here, the assemblage was dominated by Miliammina arenacea and the more abundant species were Trochammina quadricamerata and Lagenammina difflugiformis. In the southernmost site and in the eastern Ross Sea, richness and diversity were low and the most significant species were Trochammina sp., and Reophax sp. M. arenacea was ubiquitous in all the samples and sites, confirming its tolerance to cold corrosive bottom waters and salinity fluctuations as well as its uniquely high preservation potential. Moreover, elevated abundances, richness and diversity were common in the upper portion of the core which represents the youngest climatic phase characterized by the presence of some calcareous specimens too. This may indicate a deeper Carbonate Compensation Depth, probably due to relatively stable and warmer environmental conditions. Results document that diversity of benthic foraminifera, number of specimens and variations in test morphology are related to regional differences in water properties (temperature, salinity, carbonate chemistry).

Structure and builtup of the Middle Bengal Fan at 8°N from multichannel seismic surveys and the IODP Expedition 354 drilling transect

NASA Astrophysics Data System (ADS)

Spiess, V.; Bergmann, F.; Schwenk, T.; Lantzsch, H.; Bahk, J. J.; Weber, M. E.; France-Lanord, C.; Klaus, A.

2016-12-01

IODP Expedition 354 to the Bengal Fan drilled a 320 km long e-W transect at 8°N with 7 drill sites, fully covering the uppermost 150-200 meters of fan deposits at distances of 50 km, originating from Himalayan mountain ranges and the Ganges-Brahmaputra river system. A major goal of this transect approach was to ensure a continuous record of turbiditic material delivered over the last appx. 1 million year, considering frequent longitudinal depocenter shifts of the active channel. By extensively utilizing the new half-APC coring technique, high quality and high recovery cores could be retrieved representing a wide range of grain sizes from hemipelagic deposits through clay rich turbidites to coarse silt and sandy units. Up to medium sand grain sizes were retrieved within the basal units of levees, which correspond to high-reflectivity units in high-resolution multichannel seismic profiles. Finely laminated sections with mm to cm-thick turbidites represents levee formations. At Site U1453 for example, core logging and downhole logging data confirm the representative sampling based on a very good match of several physical property data sets. An expanded section was cored at Site U1454, where the presumably currently active channel has built a levee, which likely represents major sediment supply within the last 30 kyr. A spatial grid of seismic and echosounder data in the vicinity of the active channel reveals a high spatial variability in sedimentation rates and distinct depocenter shifts in response to changes in channel geometry. Site U1452 has provided a full record a levee growth including interlevee sedimentation, sandy basal units characterized by a lobe formation, and a pronounced fining upward trend following the phase of channel erosion and levee builtup. From all sites, detailed comparisons of physical and sedimentological shipboard results with seismic data will be presented. Expedition 354 has provided a unique sample and data set to better understand fan deposition and channel-levee growth including silt and sand grain sizes. It will also provide valuable constraints on the volume, nature and composition of suspension flows contributing to fan growth in the Middle Bengal Fan.

Source, conveyance and fate of suspended sediments following Hurricane Irene. New England, USA

USGS Publications Warehouse

Yellen, Brian; Woodruff, Jon D.; Kratz, Laura N.; Mabee, Steven B.; Morrison, Jonathan; Martini, Anna M.

2014-01-01

Hurricane Irene passed directly over the Connecticut River valley in late August, 2011. Intense precipitation and high antecedent soil moisture resulted in record flooding, mass wasting and fluvial erosion, allowing for observations of how these rare but significant extreme events affect a landscape still responding to Pleistocene glaciation and associated sediment emplacement. Clays and silts from upland glacial deposits, once suspended in the stream network, were routed directly to the mouth of the Connecticut River, resulting in record-breaking sediment loads fifteen-times greater than predicted from the pre-existing rating curve. Denudation was particularly extensive in mountainous areas. We calculate that sediment yield during the event from the Deerfield River, a steep tributary comprising 5% of the entire Connecticut River watershed, exceeded at minimum 10–40 years of routine sediment discharge and accounted for approximately 40% of the total event sediment discharge from the Connecticut River. A series of surface sediment cores taken in floodplain ponds adjacent to the tidal section of the Connecticut River before and after the event provides insight into differences in sediment sourcing and routing for the Irene event compared to periods of more routine flooding. Relative to routine conditions, sedimentation from Irene was anomalously inorganic, fine grained, and enriched in elements commonly found in chemically immature glacial tills and glaciolacustrine material. These unique sedimentary characteristics document the crucial role played by extreme precipitation from tropical disturbances in denuding this landscape.

Source, conveyance and fate of suspended sediments following Hurricane Irene. New England, USA

NASA Astrophysics Data System (ADS)

Yellen, B.; Woodruff, J. D.; Kratz, L. N.; Mabee, S. B.; Morrison, J.; Martini, A. M.

2014-12-01

Hurricane Irene passed directly over the Connecticut River valley in late August, 2011. Intense precipitation and high antecedent soil moisture resulted in record flooding, mass wasting and fluvial erosion, allowing for observations of how these rare but significant extreme events affect a landscape still responding to Pleistocene glaciation and associated sediment emplacement. Clays and silts from upland glacial deposits, once suspended in the stream network, were routed directly to the mouth of the Connecticut River, resulting in record-breaking sediment loads fifteen-times greater than predicted from the pre-existing rating curve. Denudation was particularly extensive in mountainous areas. We calculate that sediment yield during the event from the Deerfield River, a steep tributary comprising 5% of the entire Connecticut River watershed, exceeded at minimum 10-40 years of routine sediment discharge and accounted for approximately 40% of the total event sediment discharge from the Connecticut River. A series of surface sediment cores taken in floodplain ponds adjacent to the tidal section of the Connecticut River before and after the event provides insight into differences in sediment sourcing and routing for the Irene event compared to periods of more routine flooding. Relative to routine conditions, sedimentation from Irene was anomalously inorganic, fine grained, and enriched in elements commonly found in chemically immature glacial tills and glaciolacustrine material. These unique sedimentary characteristics document the crucial role played by extreme precipitation from tropical disturbances in denuding this landscape.

Benchscale Assessment of the Efficacy of a Reactive Core Mat to Isolate PAH-spiked Aquatic Sediments.

PubMed

Meric, Dogus; Barbuto, Sara; Sheahan, Thomas C; Shine, James P; Alshawabkeh, Akram N

2014-01-01

This paper describes the results of a benchscale testing program to assess the efficacy of a reactive core mat (RCM) for short term isolation and partial remediation of contaminated, subaqueous sediments. The 1.25 cm thick RCM (with a core reactive material such as organoclay with filtering layers on top and bottom) is placed on the sediment, and approximately 7.5 - 10 cm of overlying soil is placed on the RCM for stability and protection. A set of experiments were conducted to measure the sorption characteristics of the mat core (organoclay) and sediment used in the experiments, and to determine the fate of semi-volatile organic contaminants and non-reactive tracers through the sediment and reactive mat. The experimental study was conducted on naphthalene-spiked Neponset River (Milton, MA) sediment. The results show nonlinear sorption behavior for organoclay, with sorption capacity increasing with increasing naphthalene concentration. Neponset River sediment showed a notably high sorption capacity, likely due to the relatively high organic carbon fraction (14%). The fate and transport experiments demonstrated the short term efficiency of the reactive mat to capture the contamination that is associated with the post-capping period during which the highest consolidation-induced advective flux occurs, driving solid particles, pore fluid and soluble contaminants toward the reactive mat. The goal of the mat placement is to provide a physical filtering and chemically reactive layer to isolate contamination from the overlying water column. An important finding is that because of the high sorption capacity of the Neponset River sediment, the physical filtering capability of the mat is as critical as its chemical reactive capacity.

Sediment mineralogy based on visible and near-infrared reflectance spectroscopy

USGS Publications Warehouse

Jarrard, R.D.; Vanden Berg, M.D.; ,

2006-01-01

Visible and near-infrared spectroscopy (VNIS) can be used to measure reflectance spectra (wavelength 350-2500 nm) for sediment cores and samples. A local ground-truth calibration of spectral features to mineral percentages is calculated by measuring reflectance spectra for a suite of samples of known mineralogy. This approach has been tested on powders, core plugs and split cores, and we conclude that it works well on all three, unless pore water is present. Initial VNIS studies have concentrated on determination of relative proportions of carbonate, opal, smectite and illite in equatorial Pacific sediments. Shipboard VNIS-based determination of these four components was demonstrated on Ocean Drilling Program Leg 199. ?? The Geological Society of London 2006.

Archive of sediment data from vibracores collected in 2010 offshore of the Mississippi barrier islands

USGS Publications Warehouse

Kelso, Kyle W.; Flocks, James G.

2015-01-01

Selection of the core site locations was based on geophysical surveys conducted around the islands from 2008 to 2010. The surveys, using acoustic systems to image and interpret the nearsurface stratigraphy, were conducted to investigate the geologic controls on island evolution. This data series serves as an archive of sediment data collected from August to September 2010, offshore of the Mississippi barrier islands. Data products, including descriptive core logs, core photographs, results of sediment grain-size analyses, sample location maps, and geographic information system (GIS) data files with accompanying formal Federal Geographic Data Committee (FDGC) metadata can be downloaded from the data products and downloads page.

Deposition and chemistry of bottom sediments in Cochiti Lake, north-central New Mexico

USGS Publications Warehouse

Wilson, Jennifer T.; Van Metre, Peter C.

2000-01-01

Bottom sediments were sampled at seven sites in Cochiti Lake in September 1996. Sediment cores penetrating the entire lacustrine sediment sequence were collected at one site near the dam. Surficial sediments were sampled at the near-dam site and six other sites located along the length of the reservoir. Analyses included grain size, major and trace elements, organochlorine compounds, polycyclic aromatic hydrocarbons (PAH's), and radionuclides. Concentrations of trace elements, organic compounds, and radionuclides are similar to those in other Rio Grande reservoirs and are low compared to published sediment-quality guidelines. Most elements and compounds that were detected did not show trends in the age estimated sediment cores with the exception of a decreasing trend in total DDT concentrations from about 1980 to 1992. The mixture of PAH's suggests that the increase is caused by inputs of fuel-related PAH and not combustion- related PAH.

Marine reservoir age variability and water mass distribution in the Iceland Sea

NASA Astrophysics Data System (ADS)

Eiríksson, Jón; Larsen, Gudrún; Knudsen, Karen Luise; Heinemeier, Jan; Símonarson, Leifur A.

2004-11-01

Lateglacial and Holocene tephra markers from Icelandic source volcanoes have been identified in five sediment cores from the North Icelandic shelf and correlated with tephra layers in reference soil sections in North Iceland and the GRIP ice core. Land-sea correlation of tephra markers, that have been radiocarbon dated with terrestrial material or dated by documentary evidence, provides a tool for monitoring reservoir age variability in the region. Age models developed for the shelf sediments north of Iceland, based on offshore tephrochronology on one hand and on calibrated AMS 14C datings of marine molluscs on the other, display major deviations during the last 4500 years. The inferred temporal variability in the reservoir age of the regional water masses exceeds by far the variability expected from the marine model calculations. The observed reservoir ages are generally considerably higher, by up to 450 years, than the standard model ocean. It is postulated that the intervals with increased and variable marine reservoir age reflect incursions of Arctic water masses derived from the East Greenland Current to the Iceland Sea and the North Icelandic shelf.

Recent increases in sediment and nutrient accumulation in Bear Lake, Utah/Idaho, USA

USGS Publications Warehouse

Smoak, J.M.; Swarzenski, P.W.

2004-01-01

This study examines historical changes in sediment and nutrient accumulation rates in Bear Lake along the northeastern Utah/Idaho border, USA. Two sediment cores were dated by measuring excess 210Pb activities and applying the constant rate of supply (CRS) dating model. Historical rates of bulk sediment accumulation were calculated based on the ages within the sediment cores. Bulk sediment accumulation rates increased throughout the last 100 years. According to the CRS model, bulk sediment accumulation rates were <25mg cm-2 year-1 prior to 1935. Between 1935 and 1980, bulk sediment accumulation rates increased to approximately 40mg cm -2 year-1. This increase in sediment accumulation probably resulted from the re-connection of Bear River to Bear Lake. Bulk sediment accumulation rates accelerated again after 1980. Accumulation rates of total phosphorus (TP), total nitrogen (TN), total inorganic carbon (TIC), and total organic carbon (TOC) were calculated by multiplying bulk sediment accumulation rates times the concentrations of these nutrients in the sediment. Accumulation rates of TP, TN, TIC, and TOC increased as a consequence of increased bulk sediment accumulation rates after the re-connection of Bear River with Bear Lake.

Role of storms and forest practices in sedimentation of an Oregon Coast Range lake

NASA Astrophysics Data System (ADS)

Richardson, K.; Hatten, J. A.; Wheatcroft, R. A.; Guerrero, F. J.

2014-12-01

The design of better management practices in forested watersheds to face climate change and the associated increase in the frequency of extreme events requires a better understanding of watershed responses to extreme events in the past and also under management regimes. One of the most sensitive watershed processes affected is sediment yield. Lake sediments record events which occur in a watershed and provide an opportunity to examine the interaction of storms and forest management practices in the layers of the stratigraphy. We hypothesize that timber harvesting and road building since the 1900s has resulted in increases in sedimentation; however, the passage of the Oregon Forest Practices Act (OFPA) in 1972 has led to a decrease in sedimentation. Sediment cores were taken at Loon Lake in the Oregon Coast Range. The 32-m deep lake captures sediment from a catchment highly impacted by recent land use and episodic Pacific storms. We can use sedimentological tools to measure changes in sediment production as motivated by extreme floods before settlement, during a major timber harvesting period, and after installation of forestry Best Management Practices. Quantification of changes in particle size and elemental composition (C, N, C/N) throughout the cores can elucidate changes in watershed response to extreme events, as can changes in layer thickness. Age control in the cores is being established by Cesium-137 and radiocarbon dating. Given the instrumental meteorological data and decadal climate reconstructions, we will disentangle climate driven signals from changes in land use practices. The sediment shows distinct laminations and varying thickness of layers throughout the cores. Background deposition is composed of thin layers (<0.5 cm) of fine silts and clays, punctuated by thicker layers (3-25 cm) every 10 to 75 cm. These thick layers consist of distinctly textured units, generally fining upward. We interpret the thick layers in Loon Lake to be deposited by sediment-producing floods throughout much of the 1500-year lifespan of this lake. We will explore the relationship between sedimentation, land use, and climate forcing events to determine if the OFPA is having an effect on reducing sedimentation rates as a result of extreme magnitude storm events.

Occurrence, trends, and sources in particle-associated contaminants in selected streams and lakes in Fort Worth, Texas

USGS Publications Warehouse

Van Metre, Peter C.; Wilson, Jennifer T.; Harwell, Glenn R.; Gary, Marcus O.; Heitmuller, Franklin T.; Mahler, Barbara J.

2003-01-01

Several lakes and stream segments in Fort Worth, Texas, have fish consumption bans because of elevated levels of chlordane, dieldrin, DDE, and polychlorinated biphenyls (PCBs). This study was undertaken to evaluate current loading, trends, and sources in these long-banned contaminants and other particle-associated contaminants commonly found in urban areas. Sampling included suspended sediments at 11 sites in streams and bottom-sediment cores in three lakes. Samples were analyzed for chlorinated hydrocarbons, major and trace elements, and polycyclic aromatic hydrocarbons (PAHs). All four legacy pollutants responsible for fish consumption bans were detected frequently. Concentrations of chlordane, lead, and PAHs most frequently exceeded sediment-quality guidelines. Trends in DDE and PCBs since the 1960s generally are decreasing; and trends in chlordane are mixed with a decreasing trend in Lake Como, no trend in Echo Lake, and an increasing trend in Fosdic Lake. All significant trends in trace elements are decreasing, and most significant trends in PAHs are increasing. Sedimentation surveys were conducted on each of the three lakes and used in combination with sediment core data to compute sediment mass balances for the lakes, to estimate long-term-average loads and yields of sediment, and to estimate recent loads and yields of selected contaminants.Concentrations of most trace elements in suspended sediments were similar to those at the tops of cores, but concentrations of many hydrophobic organic contaminants were two to three times larger. As a result, for these fluvial systems, sediment cores probably provide a historical record of trace element contamination but could underestimate historical concentrations of organic contaminants. However, down-core profiles suggest that relative concentration histories are preserved in these sediment cores for many organic contaminants (such as chlordane and total DDT) but not for all (such as dieldrin).Percent urban land use correlates strongly with selected contaminant concentrations in sediments. Organochlorine pesticides had significant correlations to residential land use, whereas PCBs, cadmium, lead, zinc, and PAHs more often correlate significantly with commercial and industrial land uses, which suggests different urban sources for different contaminants. The amount of enrichment in these contaminants associated with urban land use predicted from regression equations, expressed as the ratio of concentrations predicted for 100 percent urban to 30 percent urban, ranges from 3.6 to 6.9 for PCBs and heavy metals to about 15 for chlordane, total DDT, and PAHs. These data indicate that urbanization is having a substantial negative effect on sediment and water quality and that legacy pollutants are being actively transported to streams and lakes 13 to 30 years after their use was restricted or banned. They further suggest that fish in the lakes and these water bodies will continue to be exposed to legacy pollutants in sediment for many years to come.

Organic Geochemistry of Sediments in Nearshore Areas of the Mississippi and Atchafalaya Rivers: I. General Organic Characterization

USGS Publications Warehouse

Orem, William H.; Rosenbauer, Robert J.; Swarzenski, Peter W.; Lerch, Harry E.; Corum, Margo D.; Bates, Anne L.

2007-01-01

This report presents results on the general organic characteristics of sediment cores collected from the coastal zone of the Mississippi River system, including distributions of the important nutrient elements (C, N, P, and S). This was part of a larger study conducted from 2001-2005 to examine the delivery of sediment-associated contaminants to the Gulf of Mexico by the Mississippi River system, funded by the USGS Coastal and Marine Geology Program. Companion reports emphasize organic contaminants (Rosenbauer and others, 2006), and metals (Swarzenski and others, 2006). The level of contamination within the deltaic system of the Mississippi River system was determined through the collection of sediment cores from interdistributary bays, and offshore in the Gulf of Mexico, including the zone of hypoxia. Results provide the basis for reconstructing contaminant inventories from which to develop historic perspectives on nutrient loading and hypoxia, and to better understand how sediment-hosted contaminants either directly or indirectly move through biota and ultimately affect ecosystem health. Concentrations of C, N, P, and S in sediments varied by a factor of 10 between sites, and in down core profiles. Nearshore cores collected in 2001 proved to have erratic downcore C, N, P, and S profiles and sediment deposition rates, suggesting a high energy regime controlled more by variability in river flow rather than by geochemical processes and reactions within the system. These results focused further coring activities further offshore. Atomic C/N ratios suggest that organic matter deposited at all sites is a mix of microbial (algal) and terrestrial (vascular plant) remains, but with algal material dominant. Concentrations of total sulfur in sediments from cores in the zone of hypoxia were often higher than those in nearby zones with oxic water columns. Corresponding atomic C/S ratios were typically lower in sediments from sites in the zone of hypoxia compared to nearby sites with oxic water columns, and thus atomic C/S values may be useful as a proxy for identifying sites impacted by hypoxic conditions in the water column and for examining historical trends in hypoxia. At one site examined in this study, maximum hypoxic conditions were observed in the mid 1960's. The organic elemental composition (C, N, P, and S) of sediments was also used to guide sample selection for contaminant analysis, and to normalize the contaminant data to organic C content of the sediments. Dissolved hydrocarbon gases in sediments showed a dominance of methane, but identifiable concentrations of ethane and hexane, and trace concentrations of propane, butane, and pentane were also detected. All dissolved gases except hexane were dominated by 'bound' gas, gas released only after agitation of the sediment in a blender. Hexane, in contrast was observed mostly as free gas, determined by headspace analysis.

Microbial diversity in methane hydrate-bearing deep marine sediments core preserved in the original pressure.

NASA Astrophysics Data System (ADS)

Takahashi, Y.; Hata, T.; Nishida, H.

2017-12-01

In normal coring of deep marine sediments, the sampled cores are exposed to the pressure of the atmosphere, which results in dissociation of gas-hydrates and might change microbial diversity. In this study, we analyzed microbial composition in methane hydrate-bearing sediment core sampled and preserved by Hybrid-PCS (Pressure Coring System). We sliced core into three layers; (i) outside layer, which were most affected by drilling fluids, (ii) middle layer, and (iii) inner layer, which were expected to be most preserved as the original state. From each layer, we directly extracted DNA, and amplified V3-V4 region of 16S rRNA gene. We determined at least 5000 of nucleotide sequences of the partial 16S rDNA from each layer by Miseq (Illumina). In the all layers, facultative anaerobes, which can grow with or without oxygen because they can metabolize energy aerobically or anaerobically, were detected as majority. However, the genera which are often detected anaerobic environment is abundant in the inner layer compared to the outside layer, indicating that condition of drilling and preservation affect the microbial composition in the deep marine sediment core. This study was conducted as a part of the activity of the Research Consortium for Methane Hydrate Resources in Japan [MH21 consortium], and supported by JOGMEC (Japan Oil, Gas and Metals National Corporation). The sample was provided by AIST (National Institute of Advanced Industrial Science and Technology).

Geochemical characteristics of Holocene laminated sapropel (unit II) and underlying lacustrine unit III in the Black Sea

USGS Publications Warehouse

Dean, Walter E.; Arthur, Michael A.

2011-01-01

eg 1 of the 1988 R/V Knorr expeditions to the Black Sea recovered 90 gravity and box cores. The longest recovery by gravity cores was about 3 meters, with an average of about 2.5 meters, recovering all of the Holocene and upper Pleistocene sections in the Black Sea. During the latest Pleistocene glaciation, sea level dropped below the 35-meters-deep Bosporus outlet sill of the Black Sea. Therefore throughout most of its history the Black Sea was a lake, and most of its sediments are lacustrine. The oldest sediments recovered (older than 8,000 calendar years) consist of massive to coarsely banded lacustrine calcareous clay designated as lithologic Unit III, generally containing less than 1 percent organic carbon (OC). The base of overlying Unit II marks the first incursion of Mediterranean seawater into the Black Sea, and the onset of bottom-water anoxia about 7,900 calendar years. Unit II contains as much as 15 percent OC in cores from the deepest part of the Black Sea (2,200 meters). The calcium carbonate (CaCO3) remains of the coccolith Emiliania huxleyi form the distinctive white laminae of overlying Unit I. The composition of Unit III and Unit II sediments are quite different, reflecting different terrigenous clastic sources and increased contributions from hydrogenous and biogenic components in anoxic Unit II sapropel. In Unit II, positive covariance between OC and three trace elements commonly concentrated in OC-rich sediments where sulfate reduction has occurred (molybdenum, nickel, and vanadium) and a nutrient (phosphorus) suggest a large marine source for these elements although nickel and vanadium also have a large terrigenous clastic source. The marine sources may be biogenic or hydrogenous. A large biogenic source is also suggested for copper and cobalt. Because abundant pyrite forms in the water column and sediments of the Black Sea, we expected to find a large hydrogenous iron component, but a strong covariance of iron with aluminum suggests that the dominant source of iron is from terrigenous clastic material. Most elements in lacustrine Unit III sediments have a strong covariance with Al indicating a very dominant terrigenous source. In Unit II, some elements, especially nickel, molybdenum, vanadium, and zinc, do not correlate with aluminum and have concentrations well above terrigenous clastic material, indicating a marine source.

Lead in Lake Michigan and Green Bay Surficial Sediments

EPA Science Inventory

Sediment cores were collected in 1987-1989 in Green Bay using a box corer and in 1994-1996 in Lake Michigan using a box corer and a PONAR. Core samples were segmented and dated. Historic background lead concentrations were determined for Green Bay (range=1.8-39.3 mg/kg, mean=14...

Characteristics of hydrocarbons in sediment core samples from the northern Okinawa Trough.

PubMed

Huang, Xin; Chen, Shuai; Zeng, Zhigang; Pu, Xiaoqiang; Hou, Qinghua

2017-02-15

Sediment core samples from the northern Okinawa Trough (OT) were analyzed to determine abundances and distributions of hydrocarbons by gas chromatography-mass spectrometer (GC-MS). The results show that the n-alkanes in this sediment core conform to a bimodal distribution, and exhibit an odd-to-even predominance of high molecular weights compared to an even-to-odd predominance in low molecular weight n-alkanes with maxima at C 16 and C 18 . The concentrations of bitumen, alkanes and polyaromatic hydrocarbons (PAHs) were higher in samples S10-07 than all others. Three maturity parameters as well as the ratios between parent phenanthrenes (Ps) and methylphenanthrenes (MPs) in samples S10-07 and S10-17 were higher. The distribution and composition of hydrocarbons in sample S10-07 suggest that one, or several, undetected hydrothermal fields may be present in the region of this sediment core. Results also suggest that volcanism may be the main reason for the observed distribution and composition of hydrocarbons in S10-17 sample. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preliminary report on the Late Pleistocene and Holocene diatoms of Swamp Lake, Yosemite National Park, California, USA

USGS Publications Warehouse

Starratt, Scott W.; Anderson, R. Scott

2013-01-01

Swamp Lake, Yosemite National Park, is the only known lake in California containing long sequences of varved sediments and thus has the potential to provide a high-resolution record of climate variability. This preliminary analysis of the diatom assemblages from a 947-cm-long composite sediment core (freeze core FZ02–05; 0–67 cm, Livingstone core 02–05; 53–947 cm) shows that the lake has been freshwater, oligotrophic, and circumneutral to alkaline throughout its ~16,000-year-long history. The first sediments deposited in the lake show that the vegetation in the watershed was sparse, allowing organic matter-poor silt and clay to be deposited in the basin. The basin filled quickly to a depth of at least 5 m and remained at least that deep for most of the sediment record. Several short intervals provided evidence of large fluctuations in lake level during the Holocene. The upper 50 cm of the core contains evidence of the Medieval Climate Anomaly and Little Ice Age.

Anisotropy of magnetic susceptibility as a tool for recognizing core deformation: reevaluation of the paleomagnetic record of Pleistocene sediments from drill hole OL-92, Owens Lake, California

USGS Publications Warehouse

Rosenbaum, Joseph; Reynolds, Richard T.; Smoot, Joseph; Meyer, Robert

2000-01-01

At Owens Lake, California, paleomagnetic data document the Matuyama/Brunhes polarity boundary near the bottom of a 323-m core (OL-92) and display numerous directional fluctuations throughout the Brunhes chron. Many of the intervals of high directional dispersion were previously interpreted to record magnetic excursions. For the upper ~120 m, these interpretations were tested using the anisotropy of magnetic susceptibility (AMS), which typically defines a subhorizontal planar fabric for sediments deposited in quiet water. AMS data from intervals of deformed core, determined from detailed analysis of sedimentary structures, were compared to a reference AMS fabric derived from undisturbed sediment. This comparison shows that changes in the AMS fabric provide a means of screening core samples for deformation and the associated paleomagnetic record for the adverse effects of distortion. For that portion of core OL-92 studied here (about the upper 120 m), the combined analyses of sedimentary structures and AMS data demonstrate that most of the paleomagnetic features, previously interpreted as geomagnetic excursions, are likely the result of core deformation.

Application of Rhizon Porewater Samplers to Shipboard Operations, IODP Expedition 308, Northeast Gulf of Mexico

NASA Astrophysics Data System (ADS)

Gilhooly, W. P.; Macko, S. A.; Flemings, P. B.

2005-12-01

Pleistocene and Recent sediments within the Brazos-Trinity and Ursa Basins (northwestern Gulf of Mexico) were largely deposited by turbidity currents and have been deformed by a number of mass transport events. The geochemical composition of interstitial waters was determined in order to assess fluid flow within these sediments. Typical porewater sampling resolution, using advanced piston coring and the traditional Manheim squeezer technique, is approximately one sample every other core (20m) with the highest working resolution at one sample every 1.5m. In this study, Rhizon soil moisture samplers were used to attain high-resolution porewater profiles within sea floor surface sediments and for permeable sediments at depth. The small dimensions (2mm x 30mm) and pore-size (1μm) of the devices enable high-frequency placement within a core, specific targeting of the sequence of interest, and do not require sediment removal from the core, or filtering of extracted porewaters. Initial shipboard analyses derived from sediments at the Ursa Basin (Site 1322) indicate a linear decrease in salinity with depth at U1322 where the overpressure gradient is thought to be greatest. The less saline waters with depth lends evidence for potential mixing between deep-seated fluids and low salinity ones derived from the Blue Unit and seawater. Isotopic composition and concentrations of sulfur species (SO4 and H2S) dissolved in porewaters, as well as, ionic compositions (Cl, Na, K, Ca, Mg) and chemical composition of associated sediments (%C, %N, 13C, and 15N) are compared with chemical results obtained with squeezers.

Evidence for gassy sediments on the inner shelf of SE Korea from geoacoustic properties

NASA Astrophysics Data System (ADS)

Gorgas, Thomas J.; Kim, Gil Y.; Park, Soo C.; Wilkens, Roy H.; Kim, Dae C.; Lee, Gwang H.; Seo, Young K.

2003-05-01

The inner shelf of SE Korea is characterized by an up to 40 m thick blanket of soft sediments often characterized by acoustic turbidity (AT). This AT is caused by a layer of sub-surface gas, which prohibits the identification of geological structures below that gas layer. Sound speeds were measured directly in these sediments using the Acoustic Lance (AL) in both mid- and late-September 1999. In situ sound speeds obtained in mid-September varied between 1400 and 1550 m/s, and thus did not confirm the presence of gas within the top 3.5 m of the seafloor. However, signal waveforms suggested that a gassy layer might have been just below the depth penetrated by the Lance. In late-September, on the other hand, two sites showed an abrupt decrease in signal amplitudes and in sound speed (less than 800 m/s) at depths as shallow as 2 m below seafloor, indicating the presence of free gas bubbles. Piston-cored sediments were retrieved at the same sites in February 1999. X-radiographs of some of the cores revealed numerous microcracks caused by the expansion of gas bubbles during core retrieval. In contrast to in situ acoustic data, ultrasonic sound speeds acquired in the laboratory in May 1999 on those cores did not differentiate convincingly between gas-bearing and gas-free sediments. Our measurements on the SE Korean shelf with the AL provide new data on the in situ acoustic behavior of gassy sediments and the sediments that overlie them in zones of AT.

Enhanced Sulfate Reduction and Carbon Sequestration in Sediments Underlying the Core of the Arabian Sea Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Fernandes, S. Q.; Mazumdar, A.; Peketi, A.; Bhattacharya, S.; Carvalho, M.; Da Silva, R.; Roy, R.; Mapder, T.; Roy, C.; Banik, S. K.; Ghosh, W.

2017-12-01

The oxygen minimum zone (OMZ) of the Arabian Sea in the northern Indian Ocean is one of the three major global sites of open ocean denitrification. The functionally anoxic water column between 150 to 1200 mbsl plays host to unique biogeochemical processes and organism interactions. Little is known, however, about the consequence of the low dissolved oxygen on the underlying sedimentary biogeochemical processes. Here we present, for the first time, a comprehensive investigation of sediment biogeochemistry of the Arabian Sea OMZ by coupling pore fluid analyses with microbial diversity data in eight sediment cores collected across a transect off the west coast of India in the Eastern Arabian Sea. We observed that in sediments underlying the core of the OMZ, high organic carbon sequestration coincides with a high diversity of all bacteria (the majority of which are complex organic matter hydrolyzers) and sulfate reducing bacteria (simple organic compound utilizers). Depth-integrated sulfate reduction rate also intensifies in this territory. These biogeochemical features, together with the detected shallowing of the sulfate-methane interface and buildup of pore-water sulfide, are all reflective of heightened carbon-sulfur cycling in the sediments underlying the OMZ core. Our data suggests that the sediment biogeochemistry of the OMZ is sensitive to minute changes in bottom water dissolved oxygen, and is dictated by the potential abundance and bioavailability of complex to simple carbon compounds which can stimulate a cascade of geomicrobial activities pertaining to the carbon-sulfur cycle. Our findings hold implications in benthic ecology and sediment diagenesis.

Environmental implications of the use of sulfidic back-bay sediments for dune reconstruction — Lessons learned post Hurricane Sandy

USGS Publications Warehouse

Plumlee, Geoffrey S.; Benzel, William M.; Hoefen, Todd M.; Hageman, Philip L.; Morman, Suzette A.; Reilly, Timothy J.; Adams, Monique; Berry, Cyrus J.; Fischer, Jeffrey; Fisher, Irene

2016-01-01

Some barrier-island dunes damaged or destroyed by Hurricane Sandy's storm surges in October 2012 have been reconstructed using sediments dredged from back bays. These sand-, clay-, and iron sulfide-rich sediments were used to make berm-like cores for the reconstructed dunes, which were then covered by beach sand. In November 2013, we sampled and analyzed partially weathered materials collected from the cores of reconstructed dunes. There are generally low levels of metal toxicants in the reconstructed dune materials. However oxidation of reactive iron sulfides by percolating rainwater produces acid-sulfate pore waters, which evaporate during dry periods to produce efflorescent gypsum and sodium jarosite salts. The results suggest use of sulfidic sediments in dune reconstruction has both drawbacks (e.g., potential to generate acid runoff from dune cores following rainfall, enhanced corrosion of steel bulwarks) and possible benefits (e.g., efflorescent salts may enhance structural integrity).

Dynamics of sediments along with their core properties in the Monastir-Bekalta coastline (Tunisia, Central Mediterranean)

NASA Astrophysics Data System (ADS)

Khiari, Nouha; Atoui, Abdelfattah; Khalil, Nadia; Charef, Abdelkrim; Aleya, Lotfi

2017-10-01

The authors report on two campaigns of high-resolution samplings along the shores of Monastir Bay in Tunisia: the first being a study of sediment dynamics, grain size and mineral composition in surface sediment, and the second, eight months later, using four sediment cores to study grain-size distribution in bottom sediments. Particle size analysis of superficial sediment shows that the sand in shallow depths is characterized by S-shaped curves, indicating a certain degree of agitation, possible transport by rip currents near the bottom and hyperbolic curves illustrating heterogeneity of sand stock. The sediments settle in a relatively calm environment. Along the bay shore (from 0 to 2 m depth), the bottom is covered by medium sand. Sediment transport is noted along the coast; from north to south and from south to north, caused by longshore drift and a rip current in the middle of the bay. These two currents are generated by wind and swell, especially by north to northeast waves which transport the finest sediment. Particle size analysis of bottom sediment indicates a mean grain size ranging from coarse to very fine sands while vertical distribution of grain size tends to decrease from surface to depth. The increase in particle size of sediment cores may be due to the coexistence of terrigenous inputs along with the sedimentary transit parallel to the coast due to the effect of longshore drift. Mineralogical analysis shows that Monastir's coastal sands and bottom sediment are composed of quartz, calcite, magnesium calcite, aragonite and hematite. The existence of a low energy zone with potential to accumulate pollutants indicates that managerial action is necessary to help preserve Monastir Bay.

Technogenic and natural radionuclides in the bottom sediments of the Sea of Azov: regularities of distribution and application to the study of pollutants accumulation chronology

NASA Astrophysics Data System (ADS)

Kuznetsov, A. N.; Fedorov, Yu A.; Yaroslavtsev, V. M.

2018-01-01

The study of pollutants vertical distribution in seabed sediments is of high interest as they conserve the information on the chronology of pollution level in the past. In the present paper, the results of layer by layer study of Cs-137, Am-241, Pb-210 specific activities as well as concentrations of petroleum components, lead and mercury in 48 sediment cores of the Sea of Azov, the Don River and the Kuban River are examined. In most sediment cores, two peaks of Cs-137 and Am-241 are detected. The upper of them was formed due to the Chernobyl accident in 1986 and the other is related to the global nuclear fallout of 1960s. The specific activity of naturally occurring atmospheric Lead-210 decreases exponentially with the sediment core depth. However, it is influenced by fluvial run-off, coastal erosion, Radium-226 and Radon-222 decay. The data on the radionuclides distribution in the seabed sediments is used to date them. According to the results of dating, most of petroleum components, lead and mercury quantities are concentrated in the upper sediment layer formed in the last 50 to 70 years i.e. in the period of the most important anthropogenic pressure.

Time Matters: Increasing the Efficiency of Antarctic Marine Geology and Paleoceanography Expeditions by Providing Improved Sediment Chronology

NASA Astrophysics Data System (ADS)

Rosenheim, B. E.; Domack, E. W.; Shevenell, A.; Subt, C.

2015-12-01

To maximize the areal extent of Antarctic sedimentary records of past deglaciation, it is necessary to ensure more sediment cores can be adequately dated. Antarctic margin sediment is challenging to date due to the lack of preserved calcium carbonate, but the records contained in these sediments readily recount the history of deglaciation. Recent and continued development of new chronological methods for Antarctic margin sediments have allowed better use of the efforts of marine geological coring expeditions to the region. The development of Ramped PyrOx radiocarbon dating has allowed us to 1. improve dates in deglacial sediments where no carbonate is preserved, 2. date glacial sediments lying below the tills marking the last glaciation, and 3. compile core chronologies into a regional framework of ice shelf collapse that has eluded many marine geology campaigns over the last few decades. These advances in a fundamental aspect of geological sciences will put the U.S. and international community on a better foothold to interpret the past as it relates to our warming future. We will present these advances in chronology as well as the science that is enabled by them, while arguing that the future of Antarctic marine science also depends on investments in shore-based technologies that come at a relatively low cost.

Tidal and flood signatures of settling particles in the Gaoping submarine canyon (SW Taiwan) revealed from radionuclide and flow measurements

USGS Publications Warehouse

Huh, C.-A.; Liu, J.T.; Lin, H.-L.; Xu, J. P.

2009-01-01

Sediment transport and sedimentation processes in the Gaoping submarine canyon were studied using sediment trap and current meter moorings deployed at a location during the winter (January-March) and the summer (July-September) months in 2008. At the end of each deployment, sediment cores were also collected from the canyon floor at the mooring site. Samples from sediment traps and sediment cores were analyzed for 210Pb and 234Th by gamma spectrometry. In conjunction with particle size and flow measurements, the datasets suggest that sediment transport in the canyon is tidally-modulated in the drier winter season and flood (river)-dominated in the wetter summer season. From the magnitude and temporal variation of sediment flux in the canyon with respect to the burial flux and sediment budget on the open shelf and slope region, we reaffirm that, on annual or longer timescales, the Gaoping submarine canyon is an effective conduit transporting sediments from the Gaoping River's drainage basin (the source) to the deep South China Sea (the ultimate sink). ?? 2009 Elsevier B.V.

Western Tropical Atlantic Hydrologic change during the last 130,000 years

NASA Astrophysics Data System (ADS)

McGrath, S. M.; Lavoie, N.; Oppo, D.

2016-12-01

Abrupt climate changes in the North Atlantic during the last 130,000 years are associated with hydrologic changes in the western tropical Atlantic Ocean. Previous studies on marine sediment cores from between 4°S and the equator have documented pulses of terrigenous sediment recording increased precipitation and weathering on the Brazilian Nordeste associated with Heinrich events. We worked on cores KNR197-3-11CDH (7°40'N, 53°49'W, water depth 550 m) and KNR 197-3-46CDH (7°50.1621'N, 53°39.8051'W, 947m water depth) located farther north along the South American continental slope, where sediment derives from the Amazon river basin and is transported by the North Brazilian Current. Preliminary stratigraphy based on magnetic susceptibility shows a possible correlation with the Greenland ice core δ18O stratigraphy. We use sediment elemental composition, determined by x-ray fluorescence (XRF) to evaluate variations in terrigenous sediment runoff and δ18O of the planktonic foraminifers Globierinoides ruber to evaluate variations in western tropical North Atlantic surface hydrography across North Atlantic abrupt climate events. Similarities and differences among our records and the records from the more southerly cores will help understand the mechanisms of hydrologic changes in the regions on abrupt climate time scales.

Sedimentary processes on the Mekong subaqueous delta: Clay mineral and geochemical analysis

NASA Astrophysics Data System (ADS)

Xue, Zuo; Paul Liu, J.; DeMaster, Dave; Leithold, Elana L.; Wan, Shiming; Ge, Qian; Nguyen, Van Lap; Ta, Thi Kim Oanh

2014-01-01

Sedimentary processes on the inner Mekong Shelf were investigated by examining the characteristics of sediments sampled in gravity cores at 15 locations, including grain size, clay mineralogy, sediment accumulation rates, and the elemental and stable carbon isotopic composition of organic matter (atomic C/N ratios and δ13C). Deltaic deposits exhibit contrasting characteristics along different sides of the delta plain (South China Sea, SCS hereafter, to the east and Gulf of Thailand, GOT hereafter, to the west) as well as on and off the subaqueous deltaic system. On one hand, cores recovered from the subaqueous delta in the SCS/GOT are consisted of poorly/well sorted sediments with similar/different clay mineral assemblage with/from Mekong sediments. Excess 210Pb profiles, supported by 14C chronologies, indicate either "non-steady" (SCS side) or "rapid accumulation" (GOT side) processes on the subaqueous delta. The δ13C and C/N ratio indicate a mixture of terrestrial and marine-sourced organic matter in the deltaic sediment. On the other hand, cores recovered from areas with no deltaic deposits or seaward of the subaqueous delta show excess 210Pb profiles indicating "steady-state" accumulation with a greater proportion of marine-sourced organic matter. Core analysis's relevance with local depositional environment and previous acoustic profiling are discussed.

Refining the Subseafloor Circulation Model of the Middle Valley Hydrothermal System Using Fluid Geochemistry

NASA Astrophysics Data System (ADS)

Inderbitzen, K. E.; Wheat, C. G.; Baker, P. A.; Fisher, A. T.

2014-12-01

Currently, fluid circulation patterns and the evolution of rock/fluid compositions as circulation occurs in subseafloor hydrothermal systems are poorly constrained. Sedimented spreading centers provide a unique opportunity to study subsurface flow because sediment acts as an insulating blanket that traps heat from the cooling magma body and limits: (a) potential flow paths for seawater to recharge the aquifer in permeable upper basaltic basement and (b) points of altered fluid egress. This also allows for a range of thermal and geochemical gradients to exist near the sediment-water interface. Models of fluid circulation patterns in this type of hydrologic setting have been generated (eg. Stein and Fisher, 2001); however fluid chemistry datasets have not previously been used to test the model's viability. We address this issue by integrating the existing circulation model with fluid compositional data collected from sediment pore waters and high temperature hydrothermal vents located in Middle Valley on the Juan de Fuca Ridge. Middle Valley hosts a variety of hydrologic regimes: including areas of fluid recharge (Site 855), active venting (Site 858/1036; Dead Dog vent field), recent venting (Site 856/1035; Bent Hill Massive Sulfide deposit) and a section of heavily sedimented basement located between recharge and discharge sites (Site 857). We will present new results based on thermal and geochemical data from the area of active venting (Sites 858 and 1036), that was collected during Ocean Drilling Program Legs 139 and 169 and a subsequent heat flow/gravity coring effort. These results illuminate fine scale controls on secondary recharge and fluid flow within the sediment section at Site 858/1036. The current status of high temperature vents in this area (based on observations made in July, 2014) will also be outlined.

Fungi in deep-sea sediments of the Central Indian Basin

NASA Astrophysics Data System (ADS)

Damare, Samir; Raghukumar, Chandralata; Raghukumar, S.

2006-01-01

Although a great amount of information is available on bacteria inhabiting deep-sea sediments, the occurrence of fungi in this environment has been poorly studied and documented. We report here the occurrence of fungi in deep-sea sediments from ˜5000 m depth in the Central Indian Basin (9-16°S and 73-76°E). A total of 181 cultures of fungi, most of which belong to terrestrial sporulating species, were isolated by a variety of isolation techniques. Species of Aspergillus and non-sporulating fungi were the most common. Several yeasts were also isolated. Maximum species diversity was observed in 0-2 cm sections of the sediment cores. Direct staining of the sediments with Calcofluor, a fluorescent optical brightener, revealed the presence of fungal hyphae in the sediments. Immunofluorescence using polyclonal antibodies raised against a deep-sea isolate of Aspergillus terreus (# A 4634) confirmed its presence in the form of hyphae in the sub-section from which it was isolated. A total of 25 representative species of fungi produced substantial biomass at 200 bar pressure at 30° as well as at 5 °C. Many fungi showed abnormal morphology at 200 bar/5 °C. A comparison of terrestrial isolates with several deep-sea isolates indicated that the former could grow at 200 bar pressure when growth was initiated with mycelial inocula. However, spores of a deep-sea isolate A. terreus (# A 4634), but not the terrestrial ones, showed germination at 200 bar pressure and 30 °C. Our results suggest that terrestrial species of fungi transported to the deep sea are initially stressed but may gradually adapt themselves for growth under these conditions.

Clastic sediment flux to tropical Andean lakes: records of glaciation and soil erosion

NASA Astrophysics Data System (ADS)

Rodbell, Donald T.; Seltzer, Geoffrey O.; Mark, Bryan G.; Smith, Jacqueline A.; Abbott, Mark B.

2008-08-01

We developed records of clastic sediment flux to 13 alpine lakes in Peru, Ecuador, and Bolivia, and compared these with independently dated records of regional glaciation. Our objectives are to determine whether a strong relationship exists between the extent of ice cover in the region and the rate of clastic sediment delivery to alpine lakes, and thus whether clastic sediment records serve as reliable proxies for glaciation during the late Pleistocene. We isolated the clastic component in lake sediment cores by removing the majority of the biogenic and authigenic components from the bulk sediment record, and we dated cores by a combination of radiocarbon and tephrochronology. In order to partially account for intra-basin differences in sediment focusing, bedrock erosivity, and sediment availability, we normalized each record to the weighted mean value of clastic sediment flux for each respective core. This enabled the stacking of all 13 lake records to produce a composite record that is generally representative of the tropical Andes. There is a striking similarity between the composite record of clastic sediment flux and the distribution of ˜100 cosmogenic radionuclide (CRN) exposure ages for erratics on moraine crests in the central Peruvian and northern Bolivian Andes. The extent of ice cover thus appears to be the primary variable controlling the delivery of clastic sediment to alpine lakes in the region, which bolsters the increasing use of clastic sediment flux as a proxy for the extent of ice cover in the region. The CRN moraine record and the stacked lake core composite record together indicate that the expansion of ice cover and concomitant increase in clastic sediment flux began at least 40 ka, and the local last glacial maximum (LLGM) culminated between 30 and 20 ka. A decline in clastic sediment flux that began ˜20 ka appears to mark the onset of deglaciation from the LLGM, at least one millennium prior to significant warming in high latitude regions. The interval between 20 and 18 ka was marked by near-Holocene levels of clastic sediment flux, and appears to have been an interval of much reduced ice extent. An abrupt increase in clastic sediment flux 18 ka heralded the onset of an interval of expanded ice cover that lasted until ˜14 ka. Clastic sediment flux declined thereafter to reach the lowest levels of the entire length of record during the early-middle Holocene. A middle Holocene climatic transition is apparent in nearly all records and likely reflects the onset of Neoglaciation and/or enhanced soil erosion in the tropical Andes.

Historical deposition of mercury and selected trace elements to high-elevation National Parks in the Western U.S. inferred from lake-sediment cores

USGS Publications Warehouse

Mast, M. Alisa; Manthorne, David J.; Roth, David A.

2010-01-01

Atmospheric deposition of Hg and selected trace elements was reconstructed over the past 150 years using sediment cores collected from nine remote, high-elevation lakes in Rocky Mountain National Park in Colorado and Glacier National Park in Montana. Cores were age dated by 210Pb, and sedimentation rates were determined using the constant rate of supply model. Hg concentrations in most of the cores began to increase around 1900, reaching a peak sometime after 1980. Other trace elements, particularly Pb and Cd, showed similar post-industrial increases in lake sediments, confirming that anthropogenic contaminants are reaching remote areas of the Rocky Mountains via atmospheric transport and deposition. Preindustrial (pre-1875) Hg fluxes in the sediment ranged from 5.7 to 42 μg m−2 yr−1 and modern (post-1985) fluxes ranged from 17.7 to 141 μg m−2 yr−1. The average ratio of modern to preindustrial fluxes was 3.2, which is similar to remote lakes elsewhere in North America. Estimates of net atmospheric deposition based on the cores were 3.1 μg m−2 yr−1 for preindustrial and 11.7 μg m−2 yr−1for modern times. Current-day measurements of wet deposition range from 5.0 to 8.6 μg m−2 yr−1, which are lower than the modern sediment-based estimate of 11.7 μg m−2 yr−1, perhaps owing to inputs of dry-deposited Hg to the lakes.

Chlorinated hydrocarbon pesticides and polychlorinated biphenyls in sediment cores from San Francisco Bay

USGS Publications Warehouse

Venkatesan, M.I.; De Leon, R. P.; VanGeen, A.; Luoma, S.N.

1999-01-01

Sediment cores of known chronology from Richardson and San Pablo Bays in San Francisco Bay, CA, were analyzed for a suite of chlorinated hydrocarbon pesticides and polychlorinated biphenyls to reconstruct a historic record of inputs. Total DDTs (DDT = 2,4'- and 4,4'-dichlorodiphenyltrichloroethane and the metabolites, 2,4'- and 4,4'-DDE, -DDD) range in concentration from 4-21 ng/g and constitute a major fraction (> 84%) of the total pesticides in the top 70 cm of Richardson Bay sediment. A subsurface maximum corresponds to a peak deposition date of 1969-1974. The first measurable DDT levels are found in sediment deposited in the late 1930's. The higher DDT inventory in the San Pablo relative to the Richardson Bay core probably reflects the greater proximity of San Pablo Bay to agricultural activities in the watershed of the Sacramento and San Joaquin rivers. Total polychlorinated biphenyls (PCBs) occur at comparable levels in the two Bays (< 1-34 ng/g). PCBs are first detected in sediment deposited during the 1930's in Richardson Bay, about a decade earlier than the onset of detectable levels of DDTs. PCB inventories in San Pablo Bay are about a factor of four higher in the last four decades than in Richardson Bay, suggesting a distribution of inputs not as strongly weighed towards the upper reaches of the estuary as DDTs. The shallower subsurface maximum in PCBs compared to DDT in the San Pablo Bay core is consistent with the imposition of drastic source control measures four these constituents in 1970 and 1977 respectively. The observed decline in DDT and PCB levels towards the surface of both cores is consistent with a dramatic drop in the input of these pollutants once the effect of sediment resuspension and mixing is taken into account.

Varying sediment sources (Hudson Strait, Cumberland Sound, Baffin Bay) to the NW Labrador Sea slope between and during Heinrich events 0 to 4

USGS Publications Warehouse

Andrews, John T.; Barber, D.C.; Jennings, A.E.; Eberl, D.D.; Maclean, B.; Kirby, M.E.; Stoner, J.S.

2012-01-01

Core HU97048-007PC was recovered from the continental Labrador Sea slope at a water depth of 945 m, 250 km seaward from the mouth of Cumberland Sound, and 400 km north of Hudson Strait. Cumberland Sound is a structural trough partly floored by Cretaceous mudstones and Paleozoic carbonates. The record extends from ∼10 to 58 ka. On-board logging revealed a complex series of lithofacies, including buff-colored detrital carbonate-rich sediments [Heinrich (H)-events] frequently bracketed by black facies. We investigate the provenance of these facies using quantitative X-ray diffraction on drill-core samples from Paleozoic and Cretaceous bedrock from the SE Baffin Island Shelf, and on the < 2-mm sediment fraction in a transect of five cores from Cumberland Sound to the NW Labrador Sea. A sediment unmixing program was used to discriminate between sediment sources, which included dolomite-rich sediments from Baffin Bay, calcite-rich sediments from Hudson Strait and discrete sources from Cumberland Sound. Results indicated that the bulk of the sediment was derived from Cumberland Sound, but Baffin Bay contributed to sediments coeval with H-0 (Younger Dryas), whereas Hudson Strait was the source during H-events 1–4. Contributions from the Cretaceous outcrops within Cumberland Sound bracket H-events, thus both leading and lagging Hudson Strait-sourced H-events.

Results of the Chemical and Isotopic Analyses of Sediment and Ground Water from Alluvium of the Canadian River Near a Closed Municipal Landfill, Norman, Oklahoma, Part 2

USGS Publications Warehouse

Breit, George N.; Tuttle, Michele L.W.; Cozzarelli, Isabelle M.; Berry, Cyrus J.; Christenson, Scott C.; Jaeschke, Jeanne B.

2008-01-01

Analytical results on sediment and associated ground water from the Canadian River alluvium collected subsequent to those described in Breit and others (2005) are presented in this report. The data presented herein were collected primarily to evaluate the iron and sulfur species within the sediment at well sites IC 36, IC 54, and IC South located at the USGS Norman Landfill study site. Cored sediment and water samples were collected during October 2004 and April 2005. The 52 sediment samples collected by coring were analyzed to determine grain size, the abundance of extractable iron species, and the abundance of sulfur forms and their isotopic compositions. Ground water was collected from cluster wells that sampled ground water from 11 to 15 screened intervals at each of the three sites. The depth range of the wells overlapped the interval of cored sediment. Concentrations of major ions, dissolved organic carbon (DOC), ammonium, and iron are reported with pH, specific conductance, and the isotopic composition of the water for the 75 water samples analyzed. Dissolved sulfate in selected water samples was analyzed to determine its sulfur and oxygen isotope composition.

[Study on trace elements of lake sediments by ICP-AES and XRF core scanning].

PubMed

Cheng, Ai-Ying; Yu, Jun-Qing; Gao, Chun-Liang; Zhang, Li-Sha; He, Xian-Hu

2013-07-01

It is the first time to study sediment of Toson lake in Qaidam Basin. Trace elements including Cd, Cr, Cu, Zn and Pb in lake sediment were measured by ICP-AES method, studied and optimized from different resolution methods respectively, and finally determined a optimum pretreatment system for sediment of Toson lake, namely, HCl-HNO3-HF-HClO4-H2O2 system in the proportions of 5 : 5 : 5 : 1 : 1 was determined. At the same time, the data measured by XRF core scanning were compared, the use of moisture content correction method was analyzed, and the influence of the moisture content on the scanning method was discussed. The results showed that, compared to the background value, the contents of Cd and Zn were a little higher, the content of Cr, Cu and Pb was within the background value limits. XRF core scanning was controlled by sediment elements as well as water content in sediment to some extent. The results by the two methods showed a significant positive correlation, with the correlation coefficient up to 0.673-0.925, and they have a great comparability.

Planktic foraminifer census data from Northwind Ridge cores PI-88-AP P3, PI-88-AR P7 and PI-88-AR P9, Arctic Ocean

USGS Publications Warehouse

Foley, Kevin M.; Poore, Richard Z.

1993-01-01

The U.S. Geological Survey recovered 9 piston cores from the Northwind Ridge in the Canada Basin of the Arctic Ocean from a cruise of the USCGC Polar Star during 1988. Preliminary analysis of the cores suggests sediments deposited on Northwind Ridge preserve a detailed record of glacial and interglacial cycles for the last few hundred-thousand to one million years. This report includes quantitative data on foraminifers and selected sediment size-fraction data in 98 samples from Northwind Ridge core PI-88AR P3, 51 samples from core PI-88-AR P7 and 117 samples from core PI-88-AR P9.

Mercury accumulation in Devils Lake, North Dakota effects of environmental variation in closed-basin lakes on mercury chronologies

USGS Publications Warehouse

Lent, R.M.; Alexander, C.R.

1997-01-01

Sediment cores were collected from lakes in the Devils Lake Basin in North Dakota to determine if mercury (Hg) accumulation chronologies from sediment-core data are good indicators of variations in Hg accumulation rates in saline lakes. Sediment cores from Creel Bay and Main Bay, Devils Lake were selected for detailed analysis and interpretation. The maximum Hg concentration in the Creel Bay core was 0.15 micrograms per gram at 8 to 9 centimeters. The maximum Hg concentration in the Main Bay core was 0.07 micrograms per gram at 5 to 7 centimeters. The general decreases in Hg concentrations with depth are attributed to historic variations in atmospheric Hg deposition rate. Hg stratigraphies combined with 210Pb and 137Cs dating analyses yield Hg chronologies that indicate a general increase in Hg accumulation rates in Devils Lake since the middle of the 19th century. Mean modern Hg accumulation rates in Creel Bay were 4.9 nanograms per square centimeter per year, and rates in Main Bay were 1.8 nanograms per square centimeter per year. Mean preindustrial Hg accumulation rates in Creel Bay were 1.2 nanograms per square centimeter per year, and rates in Main Bay were 1.6 nanograms per square centimeter per year. Relatively low Hg concentrations in recent sediments in the Devils Lake Basin, along with similarities in Hg accumulation rates between lakes in the Devils Lake Basin and other lakes in the northern interior of North America, indicate that local sources of Hg are not important sources of Hg. Results of the study indicate that accurate Hg chronologies are discernible in sediment cores collected from saline lakes. However, spatial and temporal variations in lake level and water chemistry common to saline lakes make interpretation of radioisotopic and geochemical chronologies difficult. Hg geochemistry in Devils Lake, and presumably in other saline lakes, is dynamic. The results of this study indicate that the absolute amount of sediment transported to Devils Lake, along with the associated Hg and total organic carbon, and the distribution of sedimentation patterns in Devils Lake may be affected by changing lake levels.

Use of reservoir deposits to reconstruct the recent changes in sediment yields from a small granite catchment in the Yimeng Mountain region, China

NASA Astrophysics Data System (ADS)

Zhang, Yunqi; Long, Yi; Li, Bao; Xu, Shujian; Wang, Xiaoli; Liao, Jia

2017-09-01

Information on recent changes in sediment yields from small catchments provides a better understanding of temporal trends in soil loss from certain physical and human-influenced landscapes that have been subjected to recent environmental changes, and will help bridge the current knowledge gap that exists between hillslope erosion and sediment transport in rivers. The Yimeng Mountain region, characterized by alternating granite and limestone, is one of the most susceptible regions to soil erosion in northern China, and has been subjected to intensive anthropogenic activity in recent years. Soil loss from areas underlain by granite is particularly obvious, and is the main sediment source for the Yihe River. In this study, we used reservoir deposits to estimate the changes in sediment yields over the past 50 years from a small catchment underlain by granite, namely the Jiangzhuang catchment in the Yimeng Mountain region. Three cores were collected from the Jiangzhuang Reservoir in the catchment. The activities of 137Cs and 210Pbex at different depths, clay (grain size < 5 μm) contents, and sedimentary organic carbon (SOC) contents in the cores were analysed with reference to human activity and environmental change in the catchment. The chronologies of the cores were established by 137Cs and 210Pbex dating. The area-specific sediment yield (SSY) for different time periods since dam construction was estimated from each core by referring to the original capacity curve of the reservoir. The results indicate that the depth profiles of 137Cs, 210Pbex, clay, and SOC contents in cores from the Jiangzhuang Reservoir reflect the general history of human disturbances on the catchment over the past 50 years. The estimated SSY value from each core for each period ranged from 7.2 ± 2.7 to 23.7 ± 8.3 t ha- 1 y- 1, with a mean of 12.5 ± 4.6 t ha- 1 y- 1. SSY decreased during 1954-1972, and then showed a general tendency to increase. The temporal pattern of the sediment yield largely reflects the history of environmental change influenced by human activity in the catchment.

A Brunhes-Matuyama polarity transition record from anoxic sediments in the South Atlantic (Ocean Drilling Program Hole 1082C)

NASA Astrophysics Data System (ADS)

Yamazaki, T.; Oda, H.

2001-08-01

A paleomagnetic study was performed on Hole 1082C sediment cores taken during the Ocean Drilling Program (ODP) Leg 175 in the South Atlantic in order to obtain a high-resolution Brunhes-Matuyama (B/M) polarity transition record. An average sedimentation rate was as high as 10 cm/kyr. The cores consist of strongly anoxic sediments, which is common for the areas of large material supply. Anoxic sediments, which are geochemically quite active, were considered to be unsuitable for studies on detailed behavior of the geomagnetic field such as polarity transitions. For global site distribution, however, it is necessary to make efforts to retrieve paleomagnetic records from such sediments. A continuous record of directional changes around the transition was obtained from U-channel samples after cleaning by stepwise alternating-field (AF) demagnetization. Consistency of the record was checked using discrete samples taken from the other half of the cores. The coring-induced magnetic overprint of radial-inward direction, which has often been reported from ODP piston-cores, was negligibly small in our cores. Relative paleointensity variation was estimated from remanent intensities of the discrete samples normalized by artificial remanences. Our record shows following features of the B/M transition similar to those already reported by previous studies. A zone of large directional fluctuations with low paleointensities occurs just before the main transition (788 to 795 ka based on the oxygen-isotope stratigraphy), which would correspond to the "precursor" of Hartl and Tauxe (1996). The virtual geomagnetic poles (VGPs) at the precursor lie along the so-called preferred longitudinal bands over the north-south Americas and Australia-east Asia. After the main transition from the reversed to normal polarity, VGPs stayed in the middle-to-high latitudes over the North America with an intermediate paleointensity for about 5~kyrs, and then moved in the vicinity of the North Pole with full recovery of intensity. Such behavior was reported by Oda et al. (2000). These similarities suggest that the anoxic sediments at Site 1082 could record the behavior of the geomagnetic field rather faithfully, although the remanence may be of chemical origin.

Comparative Paleomagnetic Study of the Quaternary-Pliocene Sedimentation Rates in the Arctic Basin: First Results

NASA Astrophysics Data System (ADS)

Elkina, D.; Piskarev, A.

2017-12-01

Accurate dating of marine sediments from the Arctic Basin continues to remain a subject of great debates over the last decades. Due to the lack of adequate materials for biostratigraphy, and isotope analyses, paleomagnetic reconstructions came on line here but still yielded ambivalent interpretations. Moreover, sedimentation rates, estimated for isolated morphological features in the Arctic Ocean, are often extended to the whole Basin and, therefore, lead to significant approximations of the sedimentation pattern distribution. Paleomagnetic study of two sediment cores up to 8 meter long, collected at the Mendeleev Rise, and the Lomonosov Ridge, have provided the opportunity to compare sedimentation regimes on these two profound structures of the Arctic Basin. Cores PS72/396 and PS87/023 were carried out along the cruises of RV Polarstern at the Mendeleev Rise (Stein et. al, 2010), and the Lomonosov Ridge (Stein, 2015) respectively. Measurements of natural remanent magnetization (NRM) and anhysteretic remanence (ARM) acquisition with the following alternating field (AF) demagnetization were performed on u-channel samples, obtained from the cores, at the Center for Geo-Environmental Research and Modeling (GEOMODEL) of the Research Park, St. Petersburg State University. According to preliminary results, core PS72/396 has shown a change from positive to negative inclinations at ca. 120 cm below sea floor (cmbsf), prevailed up to ca. 360 cmbsf where it gets back to the positive ones. This trend is comparable with some previous paleomagnetic results, conducted on cores from the Mendeleev Rise (Piskarev et al., 2013; Elkina, 2014). In contrast, for core PS87/023, a relevant drop to negative inclinations can be observed only after 330 cmbsf. That could signify a dramatic difference in sedimentation rates between the sites during the Quaternary and Pliocene. Nevertheless, a rather complicated picture of the AF data assumes effects of secondary overprints, having influenced the initial magnetization pattern for the both regions studied, manifested for the Lomonosov Ridge in great measure. AcknowledgmentsThe current study is conducted in collaboration with the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research.

The Late Glacial Chronology from Lake Suigestu: A new approach to varve interpolation using frequency distributions of annual sub-layers

NASA Astrophysics Data System (ADS)

Schlolaut, Gordon; Marshall, Michael; Brauer, Achim; Nakagawa, Takeshi; Lamb, Henry; Staff, Richard; Bronk Ramsey, Christopher; Brock, Fiona; Bryant, Charlotte; 2006 Project Members, Suigetsu

2010-05-01

The 1993 sediment core from Lake Suigetsu is one of the most comprehensive terrestrial radiocarbon records. It is extremely rich in leaf fossils, providing a unique, truly atmospheric record of radiocarbon for the last 10-50 kyr BP (Kitagawa & van der Plicht, 2000). Since the Lake Suigetsu sediment is annually laminated (varved) for much of its depth it is suitable for extending the terrestrial radiocarbon calibration model up to 50 kyr BP. However, the data presented by Kitagawa & van der Plicht (2000) significantly diverged from alternative, marine-based calibration datasets, due to gaps in the sediment profile and varve counting uncertainties (Staff et al., 2009). In 2006 four new parallel cores were recovered from Lake Suigetsu and combined to construct a new complete and continuous master profile (SG06). Along with a new program of AMS radiocarbon measurement, varve counting is being carried out using two different techniques: i) thin section microscopy and ii) high-resolution X-ray fluorescence and X-radiography. In addition, a novel interpolation approach has been developed. First results are presented for the Late Glacial (10,200 - 15,000 kyr BP). The U-Oki Tephra at the top of this interval is used as tie point for the floating varve count chronology. Initially, the two counting methods are carried out independently. The results are then compared in detail to identify the differences down to the sub-mm scale. This new approach substantially reduces internal error and results in a greater degree of accuracy than previously possible. Due to poor varve preservation in some sediment intervals, the counts of these sections have to be interpolated. Commonly, interpolation is carried out manually using sedimentation rate estimates from neighbouring sections. The new approach presented here is based on an automated analysis of frequency distributions of annual sub-layers from the compromised section itself, allowing an estimate of the sedimentation rate unbiased by neighbouring sections or by subjective interpretation. Sedimentation rates are calculated from the independent varve counts and are then combined. The application of these sedimentation rates (combined and independent) to the raw counts yields a varve count synthesis as well as an error estimate for the age model. Comparison of the varve count synthesis with the Late Glacial radiocarbon dates calibrated using Intcal04 (Reimer et al. 2004) and Fairbanks et al. (2005) shows a good agreement between the chronologies. Reference: R.G. Fairbanks, R.A. Mortlock, T.-C. Chiu, L. Cao, A. Kaplan, T.P. Guilderson, T.W. Fairbanks, A.L. Bloom, P.M. Grootes, M.-J. Nadeau, (2005), Radiocarbon calibration curve spanning 0 to 50,000 years bp based on paired 230Th/234U/238U and 14C dates on pristine corals, Quaternary Science Reviews 24 H. Kitagawa, J. van der Plicht, (2000), Atmospheric radiocarbon calibration beyond 11,900 cal BP from Lake Suigetsu laminated sediments, Radiocarbon 42(3) P.J. Reimer, M.G.L. Baillie, E. Bard, A. Bayliss, J.W. Beck, C.J.H. Bertrand, P.G. Blackwell, C.E. Buck, G.S. Burr, K.B. Cutler, P.E. Damon, R.L. Edwards, R.G. Fairbanks, M. Friedrich, T.P. Guilderson, A.G. Hogg, K.A. Hughen, B. Kromer, G. McCormac, S. Manning, C. Bronk Ramsey, R.W. Reimer, S. Remmele, J.R. Southon, M. Stuiver, S. Talamo, F.W. Taylor, J. van der Plicht, C.E. Weyhenmeyer, (2004), IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr bp, Radiocarbon 46(3) R.A. Staff, C. Bronk Ramsey, T. Nakagawa and Suigetsu 2006 Project members, (2009), A re-analysis of the Lake Suigetsu terrestrial radiocarbon calibration dataset, Nuclear Instruments and Methods in Physics Research B

Determination of subsurface fluid contents at a crude-oil spill site

USGS Publications Warehouse

Hess, K.M.; Herkelrath, W.N.; Essaid, H.I.

1992-01-01

Measurement of the fluid-content distribution at sites contaminated by immiscible fluids, including crude oil, is needed to better understand the movement of these fluids in the subsurface and to provide data to calibrate and verify numerical models and geophysical methods. A laboratory method was used to quantify the fluid contents of 146 core sections retrieved from boreholes aligned along a 120-m longitudinal transect at a crude-oil spill site near Bemidji, Minnesota, U.S.A. The 47-mm-diameter, minimally disturbed cores spanned a 4-m vertical interval contaminated by oil. Cores were frozen on site in a dry ice-alcohol bath to prevent redistribution and loss of fluids while sectioning the cores. We gravimetrically determined oil and water contents using a two-step method: (1) samples were slurried and the oil was removed by absorption onto strips of hydrophobic porous polyethylene (PPE); and (2) the samples were oven-dried to remove the water. The resulting data show sharp vertical gradients in the water and oil contents and a clearly defined oil body. The subsurface distribution is complex and appears to be influenced by sediment heterogeneities and water-table fluctuations. The center of the oil body has depressed the water-saturated zone boundary, and the oil is migrating laterally within the capillary fringe. The oil contents are as high as 0.3 cm3 cm-3, which indicates that oil is probably still mobile 10 years after the spill occurred. The thickness of oil measured in wells suggests that accumulated thickness in wells is a poor indicator of the actual distribution of oil in the subsurface. Several possible sources of error are identified with the field and laboratory methods. An error analysis indicates that adsorption of water and sediment into the PPE adds as much as 4% to the measured oil masses and that uncertainties in the calculated sample volume and the assumed oil density introduce an additional ??3% error when the masses are converted to fluid contents.

Integration of Well & Core Data of Carbonate Reservoirs with Surface Seismic in Garraf Oil Field, Southern Iraq

NASA Astrophysics Data System (ADS)

Mhuder, J. J.; Muhlhl, A. A.; Basra Geologiests

2013-05-01

The Garraf Field is situated in Southern Iraq in Nasiriya area, is located in Mesopotamian basin. The carbonate facies are dominant in main reservoirs in Garraf field (Mishrif and Yammama Formations) which is Cretaceous in age. The structure of the reservoir in this field are low relief gentle anticlinal structure aligned in NW to SE direction, and No fault were observed and interpreted in 3D seismic section. 3D seismic survey by Iraqi Oil Exploration Company No 2 was successfully conducted on the Garraf field at 2008-2009 using recording system SERCEL 408UL and Vibrators Nomad 65. Bin size: 25*25, Fold: 36, SP Interval: 50m, Lines Interval: 300m, 3 wells were drilled Ga (1, 2, 3) and it used for seismic to well tie in Petrel. Data analysis was conducted for each reservoirs for Lithological and sedimentological studies were based on core and well data .The study showed That the Mishrif Formation deposited in a broad carbonate platform with shallowing upward regressive succession and The depositional environment is extending from outer marine to shallow middle-inner shelf settings with restricted lagoons as supported by the present of Miliolid fossils. The fragmented rudist biostromes accumulated in the middle shelf. No rudist reef is presence in the studied cores. While the Major sequences are micritic limestone of lagoonal and oolitic/peloidal grainstone sandy shoal separated by mudstone of Yamama formation. Sedimentation feature are seen on seismic attributes and it is help for understanding of sedimentation environment and suitable structure interpretation. There is good relationship between Acustic Impedance and porosity, Acustic Impedance reflects porosity or facies change of carbonate rather than fluid content. Data input used for 3D Modeling include 3D seismic and AI data, petrophysical analysis, core and thin section description. 3D structure modeling were created base on the geophysical data interpretation and Al analysis. Data analysis for Al data were run as secondary input for 3D properties modeling.

Facies And Bedding Analysis of Deep-Marine, Arc-Related, Sediementary Rocks Cored on International Ocean Drilling Program Expedition 351.

NASA Astrophysics Data System (ADS)

Johnson, K. E.; Marsaglia, K. M.

2015-12-01

The Izu-Bonin-Mariana (IBM) Arc System, south of Japan, hosts a multitude of active and extinct (remnant) arc volcanic sediment sources. Core extracted adjacent to the proto-IBM arc (Kyushu-Palau Ridge; KPR) in the Amami-Sankaku Basin on International Ocean Discovery Program (IODP) Expedition 351 contains evidence of the variety of sediment sources that have existed in the area as a result of changing tectonic regimes through arc development, backarc basin formation and remnant arc abandonment. Approximately 1000 meters of Eocene to Oligocene volcaniclastic sedimentary rocks were analyzed via shipboard core photos, core descriptions, and thin sections with the intention of understanding the depositional history at this site. These materials contain a crucial record of arc development complementary to the Neogene history preserved in the active reararc (Expedition 350) and compressed whole-arc record in the current forearc (Expedition 352). A database of stratigraphic columns was created to display grain size trends, facies changes, and bedding characteristics. Individual beds (depositional events) were classified using existing and slightly modified classification schemes for muddy, sandy and gravel-rich gravity flow deposits, as well as muddy debris flows and tuffs. Utilizing the deep marine facies classes presented by Pickering et al. (1986), up section changes are apparent. Through time, as the arc developed, facies and bedding types and their proportions change dramatically and relatively abruptly. Following arc initiation facies are primarily mud-rich with intercalated tuffaceous sand. In younger intervals, sand to gravel gravity-flow deposits dominate, becoming more mud-rich. Muddy gravity flow deposits, however, dominate farther upsection. The overall coarsening-upward pattern (Unit III) is consistent with building of the arc edifice. Farther upsection (Unit II) an abrupt fining-upward trend represents the onset of isolation of the KPR as backarc spreading in the Shikoku Basin was initiated. This information will be combined with volcanic provenance and geochemical information from other studies, ultimately creating a deep-marine facies model for intraoceanic arc systems.

Sediment DIN fluxes and preferential recycling of benthic microalgal nitrogen in a shallow macrotidal estuary

USGS Publications Warehouse

Tobias, C.; Giblin, A.; McClelland, J.; Tucker, J.; Peterson, B.

2003-01-01

Sediment-water fluxes of NH4+, NO3-, dissolved inorganic carbon, and O2 were measured in cores collected from the upper Rowley River estuary, Massachusetts, and used to calculate rates of organic nitrogen (N) mineralization, nitrification, and coupled and direct denitrification (DNF). The cores contained 15N label in benthic microalgae (BMA) and in NO3- in the overlying water as a result of an ongoing whole-estuary 15NO 3- enrichment study (NISOTREX II). The tracer allowed for estimation of gross NO3- regeneration in sediments and the contribution of BMA derived N to total mineralization. The mean mineralization rate between sites was 16.0 ?? 2.0 mmol N m-2 d-1. Approximately 13 to 56% of the mineralized N was nitrified at rates ranging from 1.8 to 10.1 mmol N m-2 d-1. Total denitrification was dominated by direct DNF (3.6 mmol N m-2 d -1) furthest upstream, where NO3- concentrations were highest. Coupled DNF was most important (8.0 mmol N m -2 d-1) in the sediments with high nitrification and low water column NO3-. A gross NO3- flux from sediments to water of 0.9 to 2.1 mmol N m-2 d-1 was estimated from the isotope dilution of ??15NO 3- in the overlying water of the cores. The isotope dilution seen in the cores was also detected as a deviation from conservative ??15NO3- mixing along estuarine transects. Incorporation of this NO3- regeneration into the DNF calculations effectively increased the estimate of direct DNF by up to 50% and decreased the coupled DNF estimate by up to 220%. Increasing ?? 15NH4+ in the water of the cores indicated that the 15N-labelled BMA were preferentially mineralized over bulk sediment organic N. Additional 15N enrichments in the sediment bacterial biomarker diaminopimelic acid showed a link among 15N-labeled BMA, active bacteria, and 15NH 4+released to the overlying water. Based on ?? 15NH4+ enrichments in the cores, BMA accounted for approximately 50 to 100% of the N mineralized. An isotopic enrichment of ??15NH4+ above background in the estuary was observed at a magnitude consistent with the core-based rates of BMA mineralization. These results provide further evidence that BMA are not unidirectional sinks for water column-dissolved organic nitrogen, but instead act to turn over N between sediments and estuarine water on the scale of days.

Determining Historical Pesticide Deposition on Cape Cod through Sediment Core Analysis:A Validation of GIS as An Exposure Assessment Tool

NASA Astrophysics Data System (ADS)

Feingold, B. J.; Benoit, G.; Rudel, R.

2006-12-01

Geographic Information Systems (GIS) has emerged as a powerful tool to assess current and historical exposure to environmental pollutants. GIS aids in the visualization and understanding of associations between exposure to contaminants and disease. This study is an example of the bridge between environmental science and public health and of how new technology such as GIS can be incorporated into these fields to strengthen both the research and the communication of scientific results. It attempts to validate a GIS-based aerial drift model which predicts the residential exposure to and boundaries of historical organochlorine pesticide (OCP) drift from applications on cranberry bogs, tree pest sprayings and others by analytically quantifying the historical pesticide deposition in a transect of lakes radiating from a distinct spray source. This model was previously used to assess historical residential exposure to OCPs in an environmental epidemiological case-control study of breast cancer incidence on Cape Cod, MA, where the incidence rate of the disease is significantly higher than in the rest of the state. The model's validation in this current study is essential to establishing its predictive ability and thus, its further use. Ground truthing of the model was done through the collection and analysis of sediment cores along a transect of five hydrologically independent kettle ponds radiating from a distinct OCP tree-pest spray area. Measurements of OCP concentrations, total carbon and total organic carbon were determined, and dating of the sediments was completed using 210Pb and verified using 137Cs. Each 50-cm core was sliced into 25 2- cm sections for the analyses, creating a fine-scale depositional history in each pond. Information gathered from each core allows for the determination of the extent and degree of dissipation of individual spray events of a known source area and determine how well the model fits the actual data.

Comparison of hydraulic conductivities for a sand and gravel aquifer in southeastern Massachusetts, estimated by three methods

USGS Publications Warehouse

Warren, L.P.; Church, P.E.; Turtora, Michael

1996-01-01

Hydraulic conductivities of a sand and gravel aquifer were estimated by three methods: constant- head multiport-permeameter tests, grain-size analyses (with the Hazen approximation method), and slug tests. Sediment cores from 45 boreholes were undivided or divided into two or three vertical sections to estimate hydraulic conductivity based on permeameter tests and grain-size analyses. The cores were collected from depth intervals in the screened zone of the aquifer in each observation well. Slug tests were performed on 29 observation wells installed in the boreholes. Hydraulic conductivities of 35 sediment cores estimated by use of permeameter tests ranged from 0.9 to 86 meters per day, with a mean of 22.8 meters per day. Hydraulic conductivities of 45 sediment cores estimated by use of grain-size analyses ranged from 0.5 to 206 meters per day, with a mean of 40.7 meters per day. Hydraulic conductivities of aquifer material at 29 observation wells estimated by use of slug tests ranged from 0.6 to 79 meters per day, with a mean of 32.9 meters per day. The repeatability of estimated hydraulic conductivities were estimated to be within 30 percent for the permeameter method, 12 percent for the grain-size method, and 9.5 percent for the slug test method. Statistical tests determined that the medians of estimates resulting from the slug tests and grain-size analyses were not significantly different but were significantly higher than the median of estimates resulting from the permeameter tests. Because the permeameter test is the only method considered which estimates vertical hydraulic conductivity, the difference in estimates may be attributed to vertical or horizontal anisotropy. The difference in the average hydraulic conductivities estimated by use of each method was less than 55 percent when compared to the estimated hydraulic conductivity determined from an aquifer test conducted near the study area.

Title: Biogenic Magnetite Prevails in Oxic Pelagic Red Clay Core in the South Pacific Gyre

NASA Astrophysics Data System (ADS)

Shimono, T.; Yamazaki, T.

2012-12-01

Magnetotactic bacteria have been observed in wide variety of environments, including soils, freshwater lakes, and marine sediments, since Blakemore (1975) first described in 1975. Magnetotactic bacteria, which most commonly live within the oxic-anoxic transition zone (OATZ) of aquatic environments, produce intracellular crystals of magnetic minerals, specifically magnetite or greigite. It is considered that the magnetite/greigite crystals facilitate the bacteria's search for optimal conditions within the sharp chemical gradients of the OATZ. Petermann and Bleil (1993) reported living magnetotactic bacteria in pelagic and hemipelagic sediments near OATZ in the eastern South Atlantic at water depths to about 3,000 m, but they couldn't find actively swimming magnetotactic bacteria in sediments of deeper water depths. The South Pacific Gyre (SPG) is far from continents and the lowest productivity region on Earth. IODP site U1365 (water depth ~5,700 m) cored pelagic red clay of 75.5 m thick above ~100 Ma basement (except for the chart layer from ~42 to 63.5 m) in the western edge of the SPG. The core mainly consists of iron rich clay. The color is dark reddish and/or dark brown throughout the core. We conducted a paleomagnetic and environmental rock magnetic study of the pelagic clay core. The magnetostratigraphy revealed the top 5 m sediments cover the last 5 My, and sedimentation rate decreases downward from 1.7 to 0.6 m/m.y. Geochemical measurements of pore water indicate that dissolved oxygen was present throughout the core (>50 μM). Thus oxygen penetrates through the entire sediment column to the sediment/basalt interface, and there is no OATZ. Magnetic mineral assemblage of this core is dominated by biogenic magnetite despite no OATZ. First-order reversal curve (FORC) diagrams of all specimens have a narrow central ridge along the Hc axis with very small vertical spread. This indicates very weak magnetostatic interaction (Roberts et al., 2000), and is the characteristic of biogenic magnetite (Egli et al., 2010; Roberts et al., 2011). Presence of biogenic magnetite was confirmed by TEM observation. Occurrence of biogenic magnetite was reported also in pelagic red clay of the North Pacific with TEM observations (Yamazaki and Ioka, 1997), and these samples also display the characteristic FORC diagrams. These observations suggest that biogenic magnetites commonly occur in oxic pelagic red clay without OATZ.

Nitrogen fluxes across hydrogeomorphic zones in coastal deltaic floodplain using flow-through technique

NASA Astrophysics Data System (ADS)

Li, S.; Twilley, R.; Christensen, A.

2017-12-01

Coastal floodplain deltas are the region of continental margins of major river basins that can remove excess nitrogen before entering the coastal ocean. We propose that the processing of nitrogen in active deltaic wetlands varies with soil organic content in response to different hydrogeomorphic zones. Continuous flow-through core system was used to incubate sediment cores from supratidal, intertidal, and subtidal hydrogeomorphic zones along a chronosequence in Wax Lake Delta during summer of 2017. Ambient water from Wax Lake Outlet was continuously pumped through sealed cores to estimate fluxes of inorganic nitrogen and phosphorus across the sediment-water interface by calculating the difference between inflow and outflow concentrations. The average respiration rate of sediment cores from intertidal zone was about 1.5 g m-2 d-1 while the rate in supratidal zone was more than doubled to 3.7 g m-2 d-1. Under the constant inflow concentration of nitrate (about 107.1 umol/L), sediment cores in supratidal zone exhibited greater NO3- uptake (1329.7 umol m-2 h-1) and N2 release (499.0 umol N m-2 h-1) than that in intertidal zone (421.5 umol m-2 h-1 of NO3- uptake and 67.6 umol N m-2 h-1 of N2 flux respectively). These results indicate greater rate of net denitrification in supratidal zone than intertidal zone in the older chronosequence of the active delta (which formed approximately in 1980). Also, lower NH4 flux (mean 70.0 umol m-2 h-1) from sediment to water column in supratidal zone together with higher NO2- flux (mean 94.2 umol m-2 h-1) illustrated strong signal of nitrification. In conclusion, sediment cores at the intertidal zone helped to remove 12% of NO3- from the water column while cores at supratidal zone removed 35% of NO3-. Based on the correlation between NO3- and N2 fluxes, about 60% of NO3- removed could be converted to N2 under sediment organic concentrations of about 12%. Comparisons of NO3 removal and conversion to N2 by denitrification will be compared along the chronosequence to test the effects of shifts from mineral to organic soils as active deltas develop at the mouths of major river basins.

Dominant molluscan taxa in the northern Adriatic Sea over the last centuries: down-core changes in shell communities and their implications for an ecological history

NASA Astrophysics Data System (ADS)

Haselmair, Alexandra; Gallmetzer, Ivo; Tomasovych, Adam; Stachowitsch, Michael; Zuschin, Martin

2015-04-01

The northern Adriatic Sea, with its densely populated shoreline, is among the most degraded marine ecosystems worldwide and therefore particularly suited to study ecosystem modification under human pressure. In particular, the period of the last 500 to 1500 years witnessed major anthropogenic impacts here. The present study reconstructs major ecological shifts over this timespan by identifying down-core changes in molluscan death assemblages that can serve as proxies for changing environmental conditions. Here, we focus on taxonomical down-core fluctuations and changes in abundance of key bivalve and gastropod taxa found at seven sampling stations spread throughout the northern Adriatic basin. At these stations, which were chosen in order to cover different sediment types, nutrient conditions and degrees of exploitation, several cores of 1.5 m length and diameters of 90 and 160 mm were taken and sliced into smaller subsamples of 2 and 5 cm, respectively. The samples were sieved through a 1 mm mesh size and all the shells found counted and identified to species level if possible. In total, 114 bivalve and 112 gastropod species were recorded. At the Po delta and Panzano bay stations, characterized by muddy sediments, Corbula gibba and Kurtiella bidentata were the dominant bivalve species, Nassarius pygmaeus and Turritella communis the most abundand gastropods. In the sandy mud from the Brijuni islands, the bivalves Timoclea ovata and Striarca lactea were very numerous, whereas at the Piran station, characterized by a similar sediment composition, Gouldia minima and Corbula gibba reached the highest numbers. Overall abundances of bivalve and gastropod species differed markedly between stations. In all cores, the incidence of individual species varied down-core. Opposite trends were recorded for Brijuni and Piran station: at Piran, the abundance peaked in the uppermost sediment layers while at the Brijuni islands the number of most gastropod and bivalve species increased with depth. The down-core changes in species abundance and dominance can be correlated with shifts in the environmental parameters such as sedimentation rates and sediment composition and may also indicate anthropogenic influence. The available data from a radiometric sediment dating performed for all the seven sampling stations help to specify the timing of these past ecological changes.

Late Pleistocene and Holocene paleoclimate and alpine glacier fluctuations recorded by high-resolution grain-size data from an alpine lake sediment core, Wind River Range, Wyoming, USA

NASA Astrophysics Data System (ADS)

Thompson Davis, P.; Machalett, Björn; Gosse, John

2013-04-01

Varved lake sediments, which provide ideal high-resolution climate proxies, are not commonly available in many geographic areas over long time scales. This paper utilizes high-resolution grain-size analyses (n = 1040) from a 520-cm long sediment core from Lower Titcomb Lake (LTL), which lies just outside the type Titcomb Basin (TTB) moraines in the Wind River Range, Wyoming. The TTB moraines lie between Lower Titcomb Lake and Upper Titcomb Lake (UTL), about 3 km beyond, and 200 m lower than the modern glacier margin and Gannett Peak (Little Ice Age) moraines in the basin. Based on cosmogenic exposure dating, the TTB moraines are believed to be Younger Dryas (YD) age (Gosse et al., 1995) and lie in a geomorphic position similar to several other outer cirque moraines throughout the western American Cordillera. Until recently, many of these outer cirque moraines were believed to be Neoglacial age. The sediment core discussed here is one of five obtained from the two Titcomb Lakes, but is by the far the longest with the oldest sediment depositional record. Two AMS radiocarbon ages from the 445- and 455-cm core depths (about 2% loss on ignition, LOI) suggest that the lake basin may have been ice-free as early as 16.1 or even 16.8 cal 14C kyr, consistent with 10Be and 26Al exposure ages from boulders and bedrock surfaces outside the TTB moraines. The 257-cm depth in the core marks an abrupt transition from inorganic, sticky gray silt below (<1% LOI) to more organic, less sticky, light brown silt above (4-10% LOI). Eight AMS radiocarbon ages on bulk sediment and macrofossils date the transition to about 11.6 cal 14C kyr. Thus, sampling resolution above the transition is about 22.57 yr and below the transition is about 12.56 yr, consistent with a decreased sediment accumulation rate in LTL when Younger Dryas ice pulled back from the TTB moraines opening up UTL as a sediment depositional basin. The presented high-resolution grain size record reveals amplitudes and other structural features similar to delta 18O records from deep-lake ostracods in southern Germany, the Greenland ice core record, and speleothems in China. Major increases in the 2 - 8 µm grain size fraction indicative of increased glacier rock flour production between the 257 and 466 cm core depths appear to be roughly correlative with the YD-Alleröd-Bölling-Meiendorf-Heinrich 1 climate events recognized in other terrestrial records and Northern Atlantic Ocean marine cores, but provide much higher resolution than most of those records from a climate-sensitive alpine region in North America.

Mercury contamination chronologies from Connecticut wetlands and Long Island Sound sediments

USGS Publications Warehouse

Varekamp, J.C.; Kreulen, B.; Buchholtz ten Brink, Marilyn R.; Mecray, E.L.

2003-01-01

Sediment cores were used to investigate the mercury deposition histories of Connecticut and Long Island Sound. Most cores show background (pre-1800s) concentrations (50–100 ppb Hg) below 30–50 cm depth, strong enrichments up to 500 ppb Hg in the core tops with lower Hg concentrations in the surface sediments (200–300 ppb Hg). A sediment core from the Housatonic River has peak levels of 1,500 ppb Hg, indicating the presence of a Hg point source in this watershed. The Hg records were translated into Hg contamination chronologies through 210Pb dating. The onset of Hg contamination occurred in ~1840–1850 in eastern Connecticut, whereas in the Housatonic River the onset is dated at around 1820. The mercury accumulation profiles show periods of peak contamination at around 1900 and at 1950–1970. Peak Hg* (Hg*= Hg measured minus Hg background) accumulation rates in the salt marshes vary, dependent on the sediment character, between 8 and 44 ng Hg/cm2 per year, whereas modern Hg* accumulation rates range from 4–17 ng Hg/cm2 per year; time-averaged Hg* accumulation rates are 15 ng Hg/cm2 per year. These Hg* accumulation rates in sediments are higher than the observed Hg atmospheric deposition rates (about 1–2 ng Hg/cm2 per year), indicating that contaminant Hg from the watershed is focused into the coastal zone. The Long Island Sound cores show similar Hg profiles as the marsh cores, but time-averaged Hg* accumulation rates are higher than in the marshes (26 ng Hg/cm2 a year) because of the different sediment characteristics. In-situ atmospheric deposition of Hg in the marshes and in Long Island Sound is only a minor component of the total Hg budget. The 1900 peak of Hg contamination is most likely related to climatic factors (the wet period of the early 1900s) and the 1950–1970 peak was caused by strong anthropogenic Hg emissions at that time. Spatial trends in total Hg burdens in cores are largely related to sedimentary parameters (amount of clay) except for the high inventories of the Housatonic River, which are related to Hg releases from hat-making in the town of Danbury. Much of the contaminated sediment transport in the Housatonic River Basin occurs during floods, creating distinct layers of Hg-contaminated sediment in western Long Island Sound. The drop of about 40% in Hg accumulation rates between the 1960s and 1990s seems largely the result of reduced Hg emissions and to a much lesser extent of climatic factors.

Luminescence signal profiling: a new proxy for sedimentologically "invisible" marine Mass Transport Deposits (MTDs)

NASA Astrophysics Data System (ADS)

López, Gloria I.; Bialik, Or; Waldmann, Nicolas

2017-04-01

When dealing with fine-grained, organic-rich, colour-monotone, underwater marine sediment cores retrieved from the continental shelf or slope, the initial visual impression, upon split-opening the vessels, is often of a "disappointing" homogeneous, monotonous, continuous archive. Only after thorough, micro- to macro-scale, multi-parameter investigations the sediment reveals its treasures, initially by performing some measurements on the intact core itself, hence depicting for the first time its contents, and subsequently by carrying out the destructive, multi-proxy sample-based analyses. Usually, routine Multi-Sensor Core Logger (MSCL) measurements of petrophysical parameters (e.g. magnetic susceptibility, density, P-Wave velocity) on un-split sediment cores are the first undertaken while still on-board in the field or back at the laboratory. Less often done, but equally valuable, are continuous X-Ray and CT scan imaging of the same intact archives. Upon splitting, routine granulometry, micro- and macro-fossil and invertebrate identification, total organic / inorganic carbon content (TOC / TIC), amid other analyses take place. The geochronology component is also established usually by AMS 14C on selected organic-rich units, and less common is Optically Stimulated Luminescence (OSL) dating used on the coarser-grained, siliciclastic layers. A relatively new tool used in Luminescence, the Portable OSL Reader, employed to rapidly assess the luminescence signal of untreated poly-mineral samples to assist with targeted field sampling for full OSL dating, was used for the first time in marine sediment cores as a novel petrophysical characterization tool with astonishing results. In this study, two 2 m-long underwater piston sediment cores recovered from 200 m depths on the continental shelf off-southern Israel, were subjected to pulsed-photon stimulation (PPSL) obtaining favourable luminescence signals along their entire lengths. Astoundingly, luminescence signals were obtained on both, already split-opened cores. Both cores depicted the monotonous characteristics of homogeneousness down-core as per most of the results obtained from the non-destructive and destructive tests. One of the cores showed several small higher energy events, including a Mass Transport Deposit (MTD) within its first 10 cm, only fully visible on the CT scan imaging, the PPSL profile and particle size distribution plot. This initial investigation demonstrates the feasibility and usefulness of luminescence profiling as a new sedimentological and petrophysical proxy to better visualize homogeneous yet complex, fine-grained, underwater archives. Moreover, it helps to understand the continuity of the stratigraphy and linearity of deposition of the sediment, besides assisting on the estimation of relative ages provided that good OSL ages are obtained throughout the recovered archive.

Radiocarbon dating Arctic deep marine sediment to refine the usage of Mn pattern as a stratigraphic tool

NASA Astrophysics Data System (ADS)

Chiu, Pin-Yao Bernie; Löwemark, Ludvig

2016-04-01

The distinctive pattern of Mn content in Arctic deep marine sediment has been used as a proxy to indicate glacial-interglacial cyclicity (Löwemark et al., 2014). As has been observed in many sediment cores, Mn peaks correspond to warm interglacial periods. In order to improve the preciseness of Mn pattern as a proxy, we collected the foraminifera Neogloboquadrina pachyderma (sinistral) from brownish, Mn-rich layers, and performed radiocarbon dating on selected cores collected during the LOMROG07, LOMROG09 and LOMROG12 expeditions. Additional cores form the YMER and AO96 expeditions are also included. Based on our general understanding of the Mn system in the Arctic Ocean, we predicted a Mn pattern with a high peak in the uppermost core top, representing the Holocene. This Holocene peak in Mn is separated from the underlying warm period MIS 3 by a Mn-poor interval also characterized by a drop in Ca. This Mn and Ca poor interval reperesents MIS 2 and the LGM. Older warm periods, such as MIS 3, 5, 7 etc will display a similar pattern with distinct Mn peaks, separated by Mn minima representing cold iperiods For example, the MIS 5 sometimes shown a distinct pattern with three Mn peaks representing MIS 5a, 5c and 5e. However, there are still some limitations in the applicability of Mn stratigraphy, such as the remobilization of the Mn layer and the core-top loss during coring. We performed AMS carbon 14 dating on more than 10 cores, and the result revealed several cases of lost core tops, leading to depletion or complete loss of the Holocene interval. In several cores, our AMS dating revealed a hiatus in the MIS2 interval. The complete lack of MIS2 sediment likely is the result of extremely slow sedimentation rate due to severe sea ice conditions, while places with records of LGM may be the result of polynyas within the sea ice, or certain circulation pattern. Consequently, although Mn pattern can be used as a preliminary tool to identify glacial-interglacial cycles, the loss core tops and glacial hiatuses limits the usage and accuracy of the correlation of Mn stratigraphies. Therefore, additional radiocarbon dating can refine our understanding of the Mn patterns in Arctic marine sediment and help to make it a better proxy for both paleoenvironmental reconstructions and for the age models. Further study on the cause of hiatus often encountered in the LGM interval is necessary to ensure the usefulness of Mn stratigraphy.

Current and historical concentrations of poly and perfluorinated compounds in sediments of the northern Great Lakes - Superior, Huron, and Michigan.

PubMed

Codling, Garry; Hosseini, Soheil; Corcoran, Margaret B; Bonina, Solidea; Lin, Tian; Li, An; Sturchio, Neil C; Rockne, Karl J; Ji, Kyunghee; Peng, Hui; Giesy, John P

2018-05-01

Current and historical concentrations of 22 poly- and perfluorinated compounds (PFASs) in sediment collected from Lake Superior and northern Lake Michigan in 2011 and Lake Huron in 2012 are reported. The sampling was performed in two ways, Ponar grabs of surface sediments for current spatial distribution across the lake and dated cores for multi-decadal temporal trends. Mean concentrations of the sum of PFASs (∑PFASs) were 1.5, 4.6 and 3.1 ng g -1 dry mas (dm) in surface sediments for Lakes Superior, Michigan and Huron, respectively. Of the five Laurentian Lakes, the watersheds of Superior and Huron are the less densely populated by humans, and concentrations observed were typically less and from more diffuse sources, due to lesser urbanization and industrialization. However, some regions of greater concentrations were observed and might indicate more local, point sources. In core samples concentrations ranged from 7 that include perfluoro-n-octane sulfonate (PFOS) bind more strongly to sediment, which resulted in more accurate analyses of temporal trends. Shorter-chain PFASs, such as perfluoro-n-butanoic acid which is the primary replacement for C8 PFASs that have been phased out, are more soluble and were identified in some core layers at depths corresponding to pre-production periods. Thus, analyses of temporal trends of these more soluble compounds in cores of sediments were less accurate. Total elemental fluorine (TF) and extractable organic fluorine (EOF) indicated that identified PFASs were not a significant fraction of fluorine containing compounds in sediment (<0.01% in EOF). Copyright © 2018 Elsevier Ltd. All rights reserved.

Microbiological and Geochemical Characterization of Fluvially Deposited Sulfidic Mine Tailings

PubMed Central

Wielinga, Bruce; Lucy, Juliette K.; Moore, Johnnie N.; Seastone, October F.; Gannon, James E.

1999-01-01

The fluvial deposition of mine tailings generated from historic mining operations near Butte, Montana, has resulted in substantial surface and shallow groundwater contamination along Silver Bow Creek. Biogeochemical processes in the sediment and underlying hyporheic zone were studied in an attempt to characterize interactions consequential to heavy-metal contamination of shallow groundwater. Sediment cores were extracted and fractionated based on sediment stratification. Subsamples of each fraction were assayed for culturable heterotrophic microbiota, specific microbial guilds involved in metal redox transformations, and both aqueous- and solid-phase geochemistry. Populations of cultivable Fe(III)-reducing bacteria were most prominent in the anoxic, circumneutral pH regions associated with a ferricrete layer or in an oxic zone high in organic carbon and soluble iron. Sulfur- and iron-oxidizing bacteria were distributed in discrete zones throughout the tailings and were often recovered from sections at and below the anoxic groundwater interface. Sulfate-reducing bacteria were also widely distributed in the cores and often occurred in zones overlapping iron and sulfur oxidizers. Sulfate-reducing bacteria were consistently recovered from oxic zones that contained high concentrations of metals in the oxidizable fraction. Altogether, these results suggest a highly varied and complex microbial ecology within a very heterogeneous geochemical environment. Such physical and biological heterogeneity has often been overlooked when remediation strategies for metal contaminated environments are formulated. PMID:10103249

Quantity of dates trumps quality of dates for dense Bayesian radiocarbon sediment chronologies - Gas ion source 14C dating instructed by simultaneous Bayesian accumulation rate modeling

NASA Astrophysics Data System (ADS)

Rosenheim, B. E.; Firesinger, D.; Roberts, M. L.; Burton, J. R.; Khan, N.; Moyer, R. P.

2016-12-01

Radiocarbon (14C) sediment core chronologies benefit from a high density of dates, even when precision of individual dates is sacrificed. This is demonstrated by a combined approach of rapid 14C analysis of CO2 gas generated from carbonates and organic material coupled with Bayesian statistical modeling. Analysis of 14C is facilitated by the gas ion source on the Continuous Flow Accelerator Mass Spectrometry (CFAMS) system at the Woods Hole Oceanographic Institution's National Ocean Sciences Accelerator Mass Spectrometry facility. This instrument is capable of producing a 14C determination of +/- 100 14C y precision every 4-5 minutes, with limited sample handling (dissolution of carbonates and/or combustion of organic carbon in evacuated containers). Rapid analysis allows over-preparation of samples to include replicates at each depth and/or comparison of different sample types at particular depths in a sediment or peat core. Analysis priority is given to depths that have the least chronologic precision as determined by Bayesian modeling of the chronology of calibrated ages. Use of such a statistical approach to determine the order in which samples are run ensures that the chronology constantly improves so long as material is available for the analysis of chronologic weak points. Ultimately, accuracy of the chronology is determined by the material that is actually being dated, and our combined approach allows testing of different constituents of the organic carbon pool and the carbonate minerals within a core. We will present preliminary results from a deep-sea sediment core abundant in deep-sea foraminifera as well as coastal wetland peat cores to demonstrate statistical improvements in sediment- and peat-core chronologies obtained by increasing the quantity and decreasing the quality of individual dates.

Major refit of R/V MARION DUFRESNE and giant sediment corer improvements

NASA Astrophysics Data System (ADS)

Leau, Hélène; Réaud, Yvan

2015-04-01

The french Research Vessel MARION DUFRESNE is equipped with a unique sediment coring facility, called CALYPSO, developed initially by Yvon BALUT at the French Polar Institute, Paul-Emile Victor (IPEV) that operates the vessel 217 days per year in all oceans. The CALYPSO sediment corer retrieves routinely 50 m long undisturbed sediment cores in any water depths, and presently holds the worldwide record of the longest core ever retrieved, that is 64.5 m. This vessel is then a fantastic opportunity for the paleoceanographic community to carry out expeditions at sea. Over the last 20 years, many international IMAGES coring expeditions were organized in all the ocean basins around the world on board the R/V MARION DUFRESNE. More than 1500 cores were retrieved, leading to major advances in the paleoceanography and paleoclimatology of the Late Quaternary. The vessel will celebrate her 20th anniversary in 2015 and will undergo a major refit on hull & machineries, public spaces, as well as scientific equipment. The coring capacity is currently being developed to further improve - The length of the retrievable core, with an objective of 75 m long core in routine - The quality of the sediment un-disturbance with a specially designed coring cable with controlled minimum elasticity - The safety of the operations at sea - The quality control of the operations with a suite of sensors and software allowing a detailed monitoring of the coring operation - The time requested for each operation - The environment data collection, in the same time as the coring operations The detailed description of the upgrades will be presented. They consist in a new suite of acoustic sensors that will be integrated on board the vessel during the 4 months ship yard stay from April to July 2015, amongst which a KONSBERG EM122 multibeam echo-sounder and a SBP 120-3 sub-bottom profiler, both mounted on a gondola fitted under the hull of the vessel. This equipment will allow the highest quality images of the seabed and upper sediment, allowing accurate survey of the coring targets. Scientific deck equipment, such as coring winch and associated A frame, hydrological winch and deployment system, will be upgraded, the coring operating equipment being brought up to 45 t SWL. The ship side will be modified to allow the deployment of 75 m long corer. Finally, the laboratories will be renovated and the main PC room will be redistributed in order to offer more space to the scientific party and secure a new IT dedicated room. The vessel will undergo a series of tests at sea before being available to the scientific community again from January 2016. As before her midlife refit, IPEV wishes to carry on training programs such as "University at Sea" and EGU supported "Teachers at sea" program in association with future paleoceanographic activities.

Comparison of Radiocarbon Ages of Sediments, Plants, and Shells From Coastal Lakes in North Florida

NASA Astrophysics Data System (ADS)

Wang, Y.; Das, O.; Liu, J.; Xu, X.; Roy, R.; Donoghue, J. F.; Means, G. H.

2017-12-01

Coastal lakes sediments are valuable archives of paleo-hurricanes and environmental changes during the late Quaternary provided that they can be accurately dated. Here, we report new radiocarbon (14C) dates derived from various organic and inorganic substrates, including bulk sediment organic matter, plants, shells, particulate organic matter (POM) and dissolved organic matter (DOM), from three coastal lakes in Florida, and compare these ages to evaluate the "reservoir effect" on 14C dating of both organic and inorganic carbon in these lakes. Bulk sediment organic matter yielded consistently older 14C ages than contemporaneous plants and shell fragments, indicating significant radiocarbon deficiencies in sedimentary organic matter in these coastal lakes, caused by influx of old organic carbon from terrestrial sources (such as soils and ancient peat deposits) in the watershed. Several reversals are observed in the 14C ages of bulk sediment organic matter in sediment cores from these lakes, indicating that input of aged organic matter from terrestrial sources into these lakes can vary considerably over time. DOM and POM samples collected at different times also yielded variable 14C signatures, further confirming the temporal variability in the contribution of old organic carbon from terrestrial sources to the lakes. The 14C age discrepancy between bulk sediment organic matter and co-occurring plant fragments or shells varies from less than one hundred years to nearly three thousand years in sediment cores examined in this study. The results show that 14C ages obtained from bulk sediment organic matter in these coastal lakes are unreliable. Analyses of both modern and fossil shells from one of the lakes suggest that the 14C reservoir effect on inorganic carbon in the lake is small and thus freshwater shells (if preserved in the sediment cores) may serve as a good substrate for 14C dating in the absence of plant fragments. However, unidentifiable shell fragments, especially those associated with sand pockets (or sand layers), in coastal lake sediment cores are not suitable for 14C dating as they are likely of marine origin and affected by significant marine 14C reservoir effect.

Exploring mechanisms of compaction in salt-marsh sediments using Common Era relative sea-level reconstructions

NASA Astrophysics Data System (ADS)

Brain, Matthew J.; Kemp, Andrew C.; Hawkes, Andrea D.; Engelhart, Simon E.; Vane, Christopher H.; Cahill, Niamh; Hill, Troy D.; Donnelly, Jeffrey P.; Horton, Benjamin P.

2017-07-01

Salt-marsh sediments provide precise and near-continuous reconstructions of Common Era relative sea level (RSL). However, organic and low-density salt-marsh sediments are prone to compaction processes that cause post-depositional distortion of the stratigraphic column used to reconstruct RSL. We compared two RSL reconstructions from East River Marsh (Connecticut, USA) to assess the contribution of mechanical compression and biodegradation to compaction of salt-marsh sediments and their subsequent influence on RSL reconstructions. The first, existing reconstruction ('trench') was produced from a continuous sequence of basal salt-marsh sediment and is unaffected by compaction. The second, new reconstruction is from a compaction-susceptible core taken at the same location. We highlight that sediment compaction is the only feasible mechanism for explaining the observed differences in RSL reconstructed from the trench and core. Both reconstructions display long-term RSL rise of ∼1 mm/yr, followed by a ∼19th Century acceleration to ∼3 mm/yr. A statistically-significant difference between the records at ∼1100 to 1800 CE could not be explained by a compression-only geotechnical model. We suggest that the warmer and drier conditions of the Medieval Climate Anomaly (MCA) resulted in an increase in sediment compressibility during this time period. We adapted the geotechnical model by reducing the compressive strength of MCA sediments to simulate this softening of sediments. 'Decompaction' of the core reconstruction with this modified model accounted for the difference between the two RSL reconstructions. Our results demonstrate that compression-only geotechnical models may be inadequate for estimating compaction and post-depositional lowering of susceptible organic salt-marsh sediments in some settings. This has important implications for our understanding of the drivers of sea-level change. Further, our results suggest that future climate changes may make salt marshes more susceptible to the impacts of RSL rise by enhancing sediment compressibility. We stress, however, that the cause of the softening remains enigmatic. Until this is better constrained, it is premature to widely extrapolate our findings to existing core-based reconstructions of Holocene RSL.

The Impacts of Episodic Storm and Flood Events on Carbon and Sediment Delivery to Gulf of Mexico Sediments

NASA Astrophysics Data System (ADS)

Schreiner, K. M.; Carlin, J. A.; Sayers, L.; Swenson, J.

2017-12-01

Marine sediments are an important long-term reservoir for both recently fixed organic carbon (OC) and ancient rock derived OC, much of which is delivered by rivers. The ratio between these two sources of OC in turn regulates atmospheric levels of oxygen and carbon dioxide over geologic time, making this riverine delivery of OC, primarily carried by sediments, an important flux in the global carbon cycle. However, while the overall magnitude of these fluxes are relatively well known, it remains to be determined the importance of episodic events, like storms and floods, in the flux of OC from terrestrial to marine environments. Here, we present data from a 34 cm core collected from the Gulf of Mexico at a mid-shelf distal depocenter for the Brazos River in 2015, during a strong El Nino when that area of the country was experiencing 100-year flood events and anomalously high river flow. Based on analysis of the radioactive isotope 7Be, approximately the top 7-8 cm of the sediment in this core was deposited during this flood event. Both bulk elemental (C, N, and stable carbon isotopes) and chemical biomarker (lignin-phenol) data has been combined to provide information of the origin and chemistry of the OC in this core both before and during flooding. C:N and d13C indicate a mixture of marine-sourced and terrestrially-sourced OC throughout the length of the core with very little variation between the flood layer and deeper sediments. However, lignin-phenol concentrations are higher in flood-deposited sediment, indicating that this sediment is likely terrestrially-sourced. Lignin-phenol indicators of OC degradation state (Acid:Aldehyde ratios) indicate that flood sediment is fresher and less degraded than deeper sediments. Taken together, these results indicate that 1. Bulk analyses are not enough to determine OC source and the importance of flood events in OC cycling and 2. Episodic events like floods could have an oversized impact on OC storage in marine sediments.

The Characteristics of Turbidite Beds of Southwest Ryukyu Trench Floor: A new Approach From the X-ray Fluorescence Core Scanning Analysis

NASA Astrophysics Data System (ADS)

Hsiung, K. H.; Kanamatsu, T.; Ikehara, K.; Usami, K.; Saito, S.; Murayama, M.

2017-12-01

The southwest Ryukyu Trench near Taiwan is an ideal place for source-to-sink studies based on the distinctive sediment transport route between the terrestrial sediment source in Taiwan and the marine sink in the Ryukyu Trench. Using the bathymetric and seismic reflection data, we develop a sediment transport routes for understanding the ultimate sink of the southwest Ryukyu Trench floor. The southwest Ryukyu Trench floor can be regarded as the most distal depositional basin and isolated from the Ryukyu forearc basins. In addition, part of sediment from the proximal sources of the Ryukyu Islands and Yaeyama accretionary prism could be transported to the trench floor. We collected the piston core, PC04, from the southwest Ryukyu Trench floor of 6,147 m water depth in 3.23 m core length from cruise KR15-18, 2015. The coring site locates behind the natural levee of an obvious channel in the Ryukyu trench floor. The PC04 is composed of gray silty clay interbedded with numerous silt layers. Most of the silt layers are less than 2 cm in thickness. Based upon the core observation, X-ray fluorescence core scanning analysis and 14C age determinations, thirty-seven individual and thin beds were determined as turbidites. The results of X-ray fluorescence core scanning analysis provide continuous and high-resolution (1.0 mm of each point) assessment of relative change in the elemental ratios. Ca/Fe is a proxy for the terrigenous component of the sediment, indicating the High Ca and low Fe of each turbidite layers. Zr/Rb ratios of the marine sediments commonly used in the reflection of the original grain size variation. A large part of deep-sea turbidite beds are characterized by high Ca/Fe and Zr/Rb ratio values. These turbidite beds can be linked spatially over a distance of ˜200 km via submarine canyons within the Taiwan orogen. However, it is difficult to be linked temporally to certain events.

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

USGS Publications Warehouse

Santamarina, J.C.; Dai, Shifeng; Terzariol, M.; Jang, Jeonghwan; Waite, William F.; Winters, William J.; Nagao, J.; Yoneda, J.; Konno, Y.; Fujii, T.; Suzuki, K.

2015-01-01

Natural hydrate-bearing sediments from the Nankai Trough, offshore Japan, were studied using the Pressure Core Characterization Tools (PCCTs) to obtain geomechanical, hydrological, electrical, and biological properties under in situ pressure, temperature, and restored effective stress conditions. Measurement results, combined with index-property data and analytical physics-based models, provide unique insight into hydrate-bearing sediments in situ. Tested cores contain some silty-sands, but are predominantly sandy- and clayey-silts. Hydrate saturations Sh range from 0.15 to 0.74, with significant concentrations in the silty-sands. Wave velocity and flexible-wall permeameter measurements on never-depressurized pressure-core sediments suggest hydrates in the coarser-grained zones, the silty-sands where Sh exceeds 0.4, contribute to soil-skeletal stability and are load-bearing. In the sandy- and clayey-silts, where Sh < 0.4, the state of effective stress and stress history are significant factors determining sediment stiffness. Controlled depressurization tests show that hydrate dissociation occurs too quickly to maintain thermodynamic equilibrium, and pressure–temperature conditions track the hydrate stability boundary in pure-water, rather than that in seawater, in spite of both the in situ pore water and the water used to maintain specimen pore pressure prior to dissociation being saline. Hydrate dissociation accompanied with fines migration caused up to 2.4% vertical strain contraction. The first-ever direct shear measurements on never-depressurized pressure-core specimens show hydrate-bearing sediments have higher sediment strength and peak friction angle than post-dissociation sediments, but the residual friction angle remains the same in both cases. Permeability measurements made before and after hydrate dissociation demonstrate that water permeability increases after dissociation, but the gain is limited by the transition from hydrate saturation before dissociation to gas saturation after dissociation. In a proof-of-concept study, sediment microbial communities were successfully extracted and stored under high-pressure, anoxic conditions. Depressurized samples of these extractions were incubated in air, where microbes exhibited temperature-dependent growth rates.

Methane and Carbon Dioxide Production Rates in Lake Sediments from Sub-Arctic Sweden

NASA Astrophysics Data System (ADS)

DeStasio, J.; Halloran, M.; Erickson, L. M.; Varner, R. K.; Johnson, J. E.; Setera, J.; Prado, M. F.; Wik, M.; Crill, P. M.

2013-12-01

Ecosystems at high latitudes are undergoing rapid change due to amplified arctic warming. Lakes in these regions are sources of both methane (CH4) and carbon dioxide (CO2) to the atmosphere and will likely be impacted by elevated temperatures. Because of the potential increase in the release of organic carbon due to thawing permafrost, it is believed that methanogenesis rates within neighboring fresh water sediments will display a positive feedback response, by increasing CH4 emission to the atmosphere. We studied CH4 production potential of sediments using cores from three lakes in the Stordalen Mire complex in sub-Arctic, Sweden: Inre Harrsjön, Mellan Harrsjön, and Villasjön. Sediment cores were incubated to determine CO2 and CH4 production rates and were analyzed for CH4 concentrations, dissolved inorganic carbon (DIC) concentrations, total organic carbon (TOC) concentrations, as well as carbon, nitrogen and sulfur content. Our results from the Villasjön cores indicate that CH4 production rates were highest at the same sediment depths as peak dissolved CH4 concentrations, with maximum values between depths of approximately 10cm and 30cm. Additionally, the highest observed CH4 production rates were in sediments from areas within Villasjön known to have the highest rates of CH4 ebullition. CO2 production rates were generally highest within surface sediments ranging from about 4cm to 11cm in depth, with production rates displaying a steady decrease below 11cm. Additionally, observed CO2 production rates correlated with total organic carbon (TOC) concentrations with respect to sediment depth, but displayed no relationship with dissolved inorganic carbon (DIC). Further analysis will be conducted to determine how CH4 and CO2 production characteristics vary between sediment core samples, as well as isotopic analysis of select samples taken from each lake.

Assessing environmental impact from gas and oil exploration in the SW Barents Sea using benthic foraminiferal assemblages

NASA Astrophysics Data System (ADS)

Dijkstra, N.; Junttila, J.; Husum, K.; Carroll, J.; Hald, M.

2012-04-01

During the last decades petroleum industry and shipping activities have increased in the SW Barents Sea. Oil exploration wells were drilled in the 1980s with production starting in 2007. These activities are projected to expand in the coming years. As part of the Northern Environmental Waste Management (EWMA) project, a competence cluster for petroleum industry related waste handling, we investigate the impacts of enhanced anthropogenic activities on benthic foraminiferal assemblages in the SW Barents Sea. Sediment cores (0-20 cm) from sites in proximity to two oil- and gas fields are under investigation. These sediment cores, dated with the 210Pb method, represent the last 90 to 150 years. Both dead and living benthic foraminifera (100 µm-1 mm) were counted to elucidate differences in foraminiferal assemblages between pre-impact and recent conditions. In addition, the heavy metal concentrations, persistent organic pollutant (POP) concentrations, grain size and total organic content (TOC) of the sediment cores have been analyzed. Pollution levels of the surface sediments (0-1 cm) are of background to good level (level I-II) according to the definitions of the Water Framework Directorate (WFD). Patterns in living benthic foraminiferal assemblages identified in the sea floor surface sediments, are the result of natural environmental changes such as depth, water mass and sediment composition. Further downcore (1-20 cm) pollution levels are in general of background environmental status (WFD level I). However, at some depth intervals, especially in sediment cores from the near proximity of the oil- and gas- fields, pollution levels are slightly enhanced (WFD level II). Further work will include statistical comparison of dead and living foraminiferal assemblages with sediment pollution levels, sediment properties, and oceanographic conditions. This research contributes to the development of foraminifera as a useful bio-monitoring technique for the Arctic region as industrial activities increase in the coming years.

Paleontological interpretations of crater processes and infilling of synimpact sediments from the Chesapeake Bay impact structure

USGS Publications Warehouse

Self-Trail, Jean M.; Edwards, Lucy E.; Litwin, Ronald J.

2009-01-01

Biostratigraphic analysis of sedimentary breccias and diamictons in the Chesapeake Bay impact structure provides information regarding the timing and processes of late-stage gravitational crater collapse and ocean resurge. Studies of calcareous nannofossil and palynomorph assemblages in the International Continental Scientific Drilling Program (ICDP)–U.S. Geological Survey (USGS) Eyreville A and B cores show the mixed-age, mixed-preservation microfossil assemblages that are typical of deposits from the upper part of the Chesapeake Bay impact structure. Sparse, poorly preserved, possibly thermally altered pollen is present within a gravelly sand interval below the granite slab at 1392 m in Eyreville core B, an interval that is otherwise barren of calcareous nannofossils and dinocysts. Gravitational collapse of water- saturated sediments from the transient crater wall resulted in the deposition of sediment clasts primarily derived from the nonmarine Cretaceous Potomac Formation. Collapse occurred before the arrival of resurge. Low pollen Thermal Alteration Index (TAI) values suggest that these sediments were not thermally altered by contact with the melt sheet. The arrival of resurge sedimentation is identified based on the presence of diamicton zones and stringers rich in glauconite and marine microfossils at 866.7 m. This horizon can be traced across the crater and can be used to identify gravitational collapse versus ocean-resurge sedimentation. Glauconitic quartz sand diamicton dominates the sediments above 618.2 m. Calcareous nannofossil and dino-flagellate data from this interval suggest that the earliest arriving resurge from the west contained little or no Cretaceous marine input, but later resurge pulses mined Cretaceous sediments east of the Watkins core in the annular trough. Additionally, the increased distance traveled by resurge to the central crater in turbulent flow conditions resulted in the disaggregation of Paleogene unconsolidated sediments. As a result, intact Paleogene clasts in Eyreville cores are rare, but clasts of semilithified Potomac Formation silts and clays are common.

Paleontological interpretations of crater processes and infilling of synimpact sediments from the Chesapeake Bay impact structure

USGS Publications Warehouse

,; Edwards, L.E.; Litwin, R.J.

2009-01-01

Biostratigraphic analysis of sedimentary breccias and diamictons in the Chesapeake Bay impact structure provides information regarding the timing and processes of late-stage gravitational crater collapse and ocean resurge. Studies of calcareous nannofossil and palynomorph assemblages in the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville A and B cores show the mixed-age, mixed-preservation microfossil assemblages that are typical of deposits from the upper part of the Chesapeake Bay impact structure. Sparse, poorly preserved, possibly thermally altered pollen is present within a gravelly sand interval below the granite slab at 1392 m in Eyreville core B, an interval that is otherwise barren of calcareous nannofossils and dinocysts. Gravitational collapse of watersaturated sediments from the transient crater wall resulted in the deposition of sediment clasts primarily derived from the nonmarine Cretaceous Potomac Formation. Collapse occurred before the arrival of resurge. Low pollen Thermal Alteration Index (TAI) values suggest that these sediments were not thermally altered by contact with the melt sheet. The arrival of resurge sedimentation is identified based on the presence of diamicton zones and stringers rich in glauconite and marine microfossils at 866.7 m. This horizon can be traced across the crater and can be used to identify gravitational collapse versus ocean-resurge sedimentation. Glauconitic quartz sand diamicton dominates the sediments above 618.2 m. Calcareous nannofossil and dinoflagellate data from this interval suggest that the earliest arriving resurge from the west contained little or no Cretaceous marine input, but later resurge pulses mined Cretaceous sediments east of the Watkins core in the annular trough. Additionally, the increased distance traveled by resurge to the central crater in turbulent flow conditions resulted in the disaggregation of Paleogene unconsolidated sediments. As a result, intact Paleogene clasts in Eyreville cores are rare, but clasts of semilithified Potomac Formation silts and clays are common. ?? 2009 The Geological Society of America.

The Seno Otway pockmark field and its relationship to thermogenic gas occurrence at the western margin of the Magallanes Basin (Chile)

NASA Astrophysics Data System (ADS)

Kilian, R.; Breuer, S.; Behrmann, J. H.; Baeza, O.; Diaz-Michelena, M.; Mutschke, E.; Arz, H.; Lamy, F.

2017-12-01

Pockmarks are variably sized crater-like structures that occur in young continental margin sediments. They are formed by gas eruptions and/or long-term release of fluid or gas. So far no pockmarks were known from the Pacific coast of South America between 51°S and 55°S. This article documents an extensive and previously unknown pockmark field in the Seno Otway (Otway Sound, 52°S) with multibeam bathymetry and parametric echosounding as well as sediment drill cores. Up to 31 pockmarks per square kilometer occur in water depths of 50 to >100 m in late glacial and Holocene sediments. They are up to 150 m wide and 10 m deep. Below and near the pockmarks, echosounder profiles image acoustic blanking as well as gas chimneys often crosscutting the 20 to >30 m thick glacial sediments above the acoustic basement, in particular along fault zones. Upward-migrating gas is trapped within the sediment strata, forming dome-like features. Two 5 m long piston cores from inside and outside a typical pockmark give no evidence for gas storage within the uppermost sediments. The inside core recovered poorly sorted glacial sediment, indicating reworking and re-deposition after several explosive events. The outside core documents an undisturbed stratigraphic sequence since 15 ka. Many buried paleo-pockmarks occur directly below a prominent seismic reflector marking the mega-outflow event of the Seno Otway at 14.3 ka, lowering the proglacial lake level by about 80 m. This decompression would have led to frequent eruptions of gas trapped in reservoirs below the glacial sediments. However, the sediment fill of pockmarks formed after this event suggests recurrent events throughout the Holocene until today. Most pockmarks occur above folded hydrocarbon-bearing Upper Cretaceous and Paleogene rocks near the western margin of the Magallanes Basin, constraining them as likely source rocks for thermogenic gas.

The Seno Otway pockmark field and its relationship to thermogenic gas occurrence at the western margin of the Magallanes Basin (Chile)

NASA Astrophysics Data System (ADS)

Kilian, R.; Breuer, S.; Behrmann, J. H.; Baeza, O.; Diaz-Michelena, M.; Mutschke, E.; Arz, H.; Lamy, F.

2018-06-01

Pockmarks are variably sized crater-like structures that occur in young continental margin sediments. They are formed by gas eruptions and/or long-term release of fluid or gas. So far no pockmarks were known from the Pacific coast of South America between 51°S and 55°S. This article documents an extensive and previously unknown pockmark field in the Seno Otway (Otway Sound, 52°S) with multibeam bathymetry and parametric echosounding as well as sediment drill cores. Up to 31 pockmarks per square kilometer occur in water depths of 50 to >100 m in late glacial and Holocene sediments. They are up to 150 m wide and 10 m deep. Below and near the pockmarks, echosounder profiles image acoustic blanking as well as gas chimneys often crosscutting the 20 to >30 m thick glacial sediments above the acoustic basement, in particular along fault zones. Upward-migrating gas is trapped within the sediment strata, forming dome-like features. Two 5 m long piston cores from inside and outside a typical pockmark give no evidence for gas storage within the uppermost sediments. The inside core recovered poorly sorted glacial sediment, indicating reworking and re-deposition after several explosive events. The outside core documents an undisturbed stratigraphic sequence since 15 ka. Many buried paleo-pockmarks occur directly below a prominent seismic reflector marking the mega-outflow event of the Seno Otway at 14.3 ka, lowering the proglacial lake level by about 80 m. This decompression would have led to frequent eruptions of gas trapped in reservoirs below the glacial sediments. However, the sediment fill of pockmarks formed after this event suggests recurrent events throughout the Holocene until today. Most pockmarks occur above folded hydrocarbon-bearing Upper Cretaceous and Paleogene rocks near the western margin of the Magallanes Basin, constraining them as likely source rocks for thermogenic gas.

Summary of Results from Analyses of Deposits of the Deep-Ocean Impact of the Eltanin Asteroid

NASA Technical Reports Server (NTRS)

Kyte, Frank T.; Kuhn, Gerhard; Gersonde, Rainer

2005-01-01

Deposits of the late Pliocene (2.5 Ma) Eltanin impact are unique in the known geological record. The only known example of a km-sized asteroid to impact a deep-ocean (5 km) basin, is the most meterorite-rich locality known. This was discovered as an Ir anomaly in sediments from three cores collected in 1965 by the USNS Eltanin. These cores contained mm-sized shock-melted asteroid materials and unmelted meteorite fragments. Mineral chemistry of meteorite fragments, and siderophole concentrations in melt rocks, indicate that the parent asteroid was a low-metal (4\\%) mesosiderite. A geological exploration of the impact in 1995 by Polarstern expedition ANT-XIV4 was near the Freeden Seamounts (57.3S, 90.5 W), and successfully collected three cores with impact deposits. Analyses showed that sediments as old as Eocene were eroded by the impact disturbance and redeposited in three distinct units. The lowermost is a chaotic assemblage of sediment fragments up to 50 cm in size. Above this is a laminated sand-rich unit that deposited as a turbulent flow, and this is overlain by a more fine-grained deposit of silts and clays that settled from a cloud of sediment suspended in the water column. Meteoritic ejecta particles were concentrated near the base of the uppermost unit, where coarse ejecta caught up with the disturbed sediment. Here we will present results from a new suite of cores collected on Polarstern expedition ANT-XVIIU5a. In 2001, the Polarstern returned to the impact area and explored a region of 80,000 sq-km., collecting at least 16 sediment cores with meteoritic ejecta. The known strewn field extends over a region 660 by 200 km. The meteoritic ejecta is most concentrated in cores on the Freeden seamounts, and in the basins to the north, where the amount of meteoritic material deposited on the ocean floor was as much as 3 g/sq-cm. These concentrations drop off to the north and the east to levels as low as approximately 0.1 g/sq-cm. We were unable to sample the impact south and west of the seamounts, as the deposit was buried beyond the reach of our 25 m piston corer. We estimate that ground zero was in the region just north, or northwest, of the seamounts. There is no evidence that the impactor penetrated the ocean floor or formed a crater. The composition of the melted ejecta is inconsistent with mixing between projectile and terrestrial materials other than seawater salts. X-ray radiographs of sediments reveal details not seen in earlier cores. The uppermost impact unit is well-preserved in several cores, found as much as 50 km from the seamounts to the east, north, and west of the seamounts, where at least 25 cm of this unit is preserved. At greater distances burrowing organisms have mixed the sediments so if this unit did exist, it was too thin to survive bioturbation. These finegrained sediments are clearly laminated, and show alternating layers of low- and high-density (meteoritic) sediments, consistent with ripple formation in an energetic flow regime. We have extracted 35 g of meteoritic melt rock and 3 g of meteorite fragments from sieved sediments. Additionally a 9 g, 2.2 cm meteorite was recovered during opening of one core. The fact that 9\\% of the coarse ejecta is unmelted meteorites may be characteristic of deep-ocean impacts. This may have significance for delivery of organic matter to the early Earth by small impacts into primordial oceans, where actual meteorite fragments can survive in significant amounts. However, a large portion of the meteoritic debris is buried rapidly by the sediments disturbed by the impact.

Recovery and Lithologic Analysis of Sediment from Hole UT-GOM2-1-H002, Green Canyon 955, Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Kinash, N.; Cook, A.; Sawyer, D.; Heber, R.

2017-12-01

In May 2017 the University of Texas led a drilling and pressure coring expedition in the northern Gulf of Mexico, UT-GOM2-01. The holes were located in Green Canyon Block 955, where the Gulf of Mexico Joint Industry Project Leg II identified an approximately 100m thick hydrate-filled course-grained levee unit in 2009. Two separate wells were drilled into this unit: Holes H002 and H005. In Hole H002, a cutting shoe drill bit was used to collect the pressure cores, and only 1 of the 8 cores collected was pressurized during recovery. The core recovery in Hole H002 was generally poor, about 34%, while the only pressurized core had 45% recovery. In Hole H005, a face bit was used during pressure coring where 13 cores were collected and 9 cores remained pressurized. Core recovery in Hole H005 was much higher, at about 75%. The type of bit was not the only difference between the holes, however. Drilling mud was used throughout the drilling and pressure coring of Hole H002, while only seawater was used during the first 80m of pressure cores collected in Hole H005. Herein we focus on lithologic analysis of Hole H002 with the goal of documenting and understanding core recovery in Hole H002 to compare with Hole H005. X-ray Computed Tomography (XCT) images were collected by Geotek on pressurized cores, mostly from Hole H005, and at Ohio State on unpressurized cores, mostly from Hole H002. The XCT images of unpressurized cores show minimal sedimentary structures and layering, unlike the XCT images acquired on the pressurized, hydrate-bearing cores. Only small sections of the unpressurized cores remained intact. The unpressurized cores appear to have two prominent facies: 1) silt that did not retain original sedimentary fabric and often was loose within the core barrel, and 2) dense mud sections with some sedimentary structures and layering present. On the XCT images, drilling mud appears to be concentrated on the sides of cores, but also appears in layers and fractures within intact core sections. On microscope images, the drilling mud also appears to saturate the pores in some silt intervals. Further analysis of the unpressurized cores is planned, including X-ray diffraction, grain size analysis and porosity measurements. These results will be compared to the pressurized cores to understand if further lithologic factors could have affected core recovery.

Sedimentary properties of shallow marine cores collected in June and September 2006, Hanalei Bay, Kaua‘i, Hawai‘i

USGS Publications Warehouse

Draut, Amy E.; Bothner, Michael H.; Reynolds, Richard L.; Buchan, Olivia C.; Cochran, Susan A.; Casso, Michael A.; Baldwin, Sandra M.; Goldstein, Harland L.; Xiao, Jiang; Field, Michael E.; Logan, Joshua B.

2007-01-01

Sedimentary facies, short-lived isotopes 7Be, 137Cs, and 210Pb, and magnetic properties of sediment cores in Hanalei Bay, Kaua‘i, Hawai‘i, were used to assess sediment sources and patterns of deposition associated with seasonal flooding of the Hanalei River. Sediment cores were collected from the seafloor in June and September of 2006 to supplement similar data collected during the summer of 2005. The youngest and thickest terrigenous sediment was observed on the east side of the bay: near the Hanalei River mouth and in a bathymetric depression, known locally as the Black Hole, that acts as a temporary sediment sink. Deposits from floods that occurred between February and April 2006 left flood deposits in the eastern bay that, by June of 2006, were on the order of 10 cm thick. A flood occurred on August 7, 2006, that was smaller than floods that occurred the previous winter but was a substantial discharge event for the summer season. Deposits from the winter 2006 floods continued to dominate the sedimentary record in the eastern bay through early fall, even after the addition of newer sediment during the August 7 flood; this is consistent with the much higher sediment input of the winter floods compared with the August 7 flood. Broad variations in magnetic grain size and relative magnetite-hematite abundance in several sediment cores indicate many sources of upland terrigenous sediment. As a group, recent flood deposits show much less variation in these properties compared with older deposits, implying either that the 2006 winter–spring flood sediment originated from one or more distinct upland settings, or that substantial mixing of sediment from multiple sources occurred during transport. Sediment is most readily remobilized and advected out of the bay during winter, when oceanic conditions are energetic. In summer, wave and current measurements made concurrently with this study showed weak currents and little wave energy, indicating that sediment delivered during summer floods most likely remains in the bay until winter storms can remove it. Increased turbidity and sedimentation on corals resulting from floods of the Hanalei River could affect the sustainability of coral reefs and their many associated species. This possibility is of particular concern during summer months when wave energy is low and sediment is not readily remobilized and transported out of the bay. The timing (seasonality) and magnitude of sediment input to the coastal ocean relative to seasonal variations in wave and current energy could have significant ecological consequences for coral-reef communities in the Hawaiian Islands.

The Role of Anthropogenic Stratigraphy in River Restoration Projects

NASA Astrophysics Data System (ADS)

Evans, J. E.; Webb, L. D.

2012-12-01

As part of a river restoration project and removal of a low-head dam on the Ottawa River (northwestern Ohio and southeastern Michigan) in 2007, a longer-term project was initiated to assess anthropogenic changes of the Ottawa River fluvial system. A composite stratigraphic section 4.5 m in length was constructed by stratigraphic correlation from three trenches up to 2.5 m in depth and 14 vibracores up to 2.5 m in length, all within a small region (<0.5 km2 in area). At various stratigraphic levels, the cores contain a suite of anthropogenic materials including fragments of bricks and cement blocks, pieces of modern ceramics, fragments of plastic and rubber tires, intact or pieces of glass bottles, and one horizon of displaced railroad ties. Age control for the composite section is provided by 4 14C dates, 6 OSL dates, and one bottle with a date stamp. Two prominent flood horizons are indicated in multiple trenches or cores, and identified as the historic floods of 1913 and 1959. The data show the following major changes in the fluvial system over time: (1) prior to approximately 5 Ka, the river system was transporting mineral-rich sediment and formed meandering point-bar sequences approximately 1.5 m thick; (2) between approximately 5 Ka and 200 YBP, the river system was transporting organic-rich sediment (i.e., blackwater stream) bordered by riparian wetlands accumulating peat (part of the regional "Great Black Swamp" discovered by settlers from eastern North America); (3) between approximately 200 YBP and the early 1960s the river system was transporting mineral-rich sediment (i.e., brownwater stream), probably sourced from extensive land clearance for agriculture, which backfilled and overtopped the previous riparian wetlands and produced an series of thin channel fills interpreted as rapidly shifting avulsional channels; (4) since the early 1960s, sediment supply has exceeded sediment conveyance capacity, leading to vertical aggradation of approximately 1.7 m, creating the fill-terrace morphology evident today; and (5) overlapping with the previous stage, channel incision and lateral channel migration has produced a fluvial system dominated by bank erosion, logjams due to tree fall, and degraded substrate with fluvial pavements. Stage 4 is interpreted as a time-specific (1950s-1960s) sediment pulse related to extensive urbanization of the lower drainage basin, while the partly overlapping stage 6 is interpreted as fluvial reworking of intrabasinal storage of legacy sediment under conditions of lower sediment input (reforested suburban housing developments) but higher water inputs (increasingly urbanized stormwater networks). Regarding river restoration, it is clear that most of the modern fluvial system is a recent and highly manipulated system that may not be sustainable.

Sedimentary Records of the Paleohurricane Activity in the Bahamas

NASA Astrophysics Data System (ADS)

Wallace, E. J.; Donnelly, J. P.; Wiman, C.; Cashman, M.

2015-12-01

Hurricanes pose a threat to human lives and can cause significant destruction of coastal areas. This threat has become more pronounced with recent rises in sea level and coastal populations. Currently, there is a large degree of uncertainty surrounding future changes in tropical cyclone activity. This is due to the limitations of climate models as well as the scarcity and unreliability of the current observational record. With so much uncertainty surrounding the current projections of hurricane activity, it is crucial to establish a longer and more accurate historical record. This study uses sediment cores extracted from blueholes in the Bahamas to develop a record of intense hurricane landfalls in the region dating back more than a millennia. The collected cores were sectioned, split, and scanned on an X-ray fluorescence scanner to obtain a high resolution core profile of the sediments' elemental composition and to identify potential sedimentary structures. Age control of the samples was determined using radiocarbon dating, coarse fraction was measured every centimeter, and hurricane event bed frequency was established for each core. We assess the statistical significance of the patterns observed in the sedimentary record using a coupled ocean-atmosphere hurricane model to simulate storms representative of modern climatology. Cores extracted from two blue holes near South Andros Island provide approximately a 1600 year and a 600 year record respectively, with sedimentation rates exceeding 1 cm/year. Both records contain coarse grained event deposits that correlate with known historical intense hurricane strikes in the Bahamas within age uncertainties. The 1600 year record confirms previous hurricane reconstructions from the Caribbean indicating higher tropical cyclone activity from 500 to 1400 CE. In addition, these new high-resolution records indicate elevated intense hurricane activity in the 17th and 18th centuries CE, when activity is also elevated in lower resolution records from Abaco, Bahamas and Vieques, Puerto Rico. However, records from the northeast United States and Gulf of Mexico are relatively inactive. This spatial variability in intense hurricane landfalls suggests significant regional controls on hurricane activity.

Paleomagnetic constrains in the reconstruction of the recent stratigraphic evolution of the Po delta

NASA Astrophysics Data System (ADS)

Correggiari, Annamaria; Vigliotti, Luigi; Remia, Alessandro; Perini, Luisa; Calabrese, Lorenzo; Luciani, Paolo

2014-05-01

The delta and prodelta deposits are characterized by a complex stratigraphic architecture that can be approached with several multidisciplinary tools. We present an example from the Po delta system characterized by alternating phases of rapid advance and abandonment of its multiple deltaic lobes that has been investigated through: (1) a review of historical cartography extending back several centuries; (2) integrated surveys of VHR seismic profiles recorded offshore of the modern delta from water depths as shallow as 5 m to the toe of the prodelta in about 30 m; and (3) sedimentological and geochronological data from precisely positioned sediment cores. Within this well known stratigraphic framework we have acquired seismic data and sediment cores in the area of the post roman Po delta system. However a precise dating of the recent evolution of depositional delta lobes is difficult because of the lack of suitable dating methods. To constrain the emplacement timing of the Renaissance lobes a paleomagnetic studies was carried out on a sedimentary sequence representing a seismic facies well correlated in the cores by whole core magnetic susceptibility profile. Forty eight samples were collected from a core section (RER96-1) characterized by a fine grained lithology suitable for paleomagnetic investigations. The characteristic remanent magnetization (ChRM) of the sediments has been obtained by applying an AF cleaning between 10 and 30 millitesla. The results have been compared with the directions recorded by the historical lavas of the Etna and Vesuvius. The combination of the trends observed in the declination and inclination suggests that the results can be compatible with the directions of the secular variation of the earth magnetic field occurring during the XVII century. This allow to date the sismic unit as representative of the beginning of the new delta following the Porto Viro avulsion made by the Venice Republic in 1604 AD. This delta history reflects the forcing of high-frequency climate change, autocyclic avulsions, and anthropogenic factors, acting on variable, but typically short, time scales. By using multidisciplinary methods of investigation is possible to detect the sedimentary response forced by anthropic impact at centennial/decadal time scale.

Assessment of heavy metal contamination in the sediments of Nansihu Lake Catchment, China.

PubMed

Liu, Enfeng; Shen, Ji; Yang, Liyuan; Zhang, Enlou; Meng, Xianghua; Wang, Jianjun

2010-02-01

At present, anthropogenic contribution of heavy metals far exceeds natural input in some aquatic sediment, but the proportions are difficult to differentiate due to the changes in sediment characters. In this paper, the metal (Al, Fe, K, Mg, Ca, Cr, Cu, Ni, and Zn) concentrations, grain size, and total organic carbon (TOC) content in the surface and core sediments of Nansihu Lake Catchment (the open lake and six inflow rivers) were determined. The chemical speciations of the metals (Al, Fe, Cr, Cu, Ni, and Zn) in the surface sediments were also analyzed. Approaches of factor analysis, normalized enrichment factor (EF) and the new non-residual fractions enrichment factor (K(NRF)) were used to differentiate the sources of the metals in the sediments, from detrital clastic debris or anthropogenic input, and to quantify the anthropogenic contamination. The results indicate that natural processes were more dominant in concentrating the metals in the surface and core sediments of the open lake. High concentration of Ca and deficiency of other metals in the upper layers of the sediment core were attributed to the input of carbonate minerals in the catchment with increasing human activities since 1980s. High TOC content magnified the deficiency of the metals. Nevertheless, the EF and K(NRF) both reveal moderate to significant anthropogenic contamination of Cr, Cu, Ni, and Zn in the surface sediments of Laoyun River and the estuary and Cr in the surface sediments of Baima River. The proportion of non-residual fractions (acid soluble, reducible, and oxidizable fractions) of Cr, Cu, Ni, and Zn in the contaminated sediments increased to 37-99% from the background levels less than 30%.

Hudson River Paleoclimate, Sea Level, and Human Impact: A Record From Piermont Marsh, NY

NASA Technical Reports Server (NTRS)

Kurdyla; Peteet, Dorothy; Liberman, Louisa; Sugar; Wong; Hansen, James E. (Technical Monitor)

2001-01-01

A 13.77 meter sediment core from Piermont Marsh, NY (40 00 N, 73 55W) records the local and regional vegetational and foraminiferal history of the Hudson Estuary. The sediments were sampled every 4 cm, which represents a decadal to centuryscale resolution. Basal sediment dating is in progress, and the 11-m depth represents about 4000 years. Changes in plant macrofossils and charcoal appear to indicate differences in salinIty and drought, suggesting changes in climate. Scirpus, Salicornia, and high levels of charcoal seem to indicate drier/more saline conditions, while lack of these macrofossils and increases in Chara/Nitella, aquatic leaves, and very little charcoal suggests wetter conditions. Other macrofossils include Carex, Juncus, Polygonum, Zanichellia, Ruppia. High resolution AMS dating of plant macrofossils is in progress, and will be compared with changes in Hudson River sediment cores offshore. Foraminiferal assemblages from key intervals of the core will be presented. Human impact in the upper sediments is visible from the influx of grass seeds, primarily Phragmites, and the ragweed pollen rise.

TEMPORAL TRENDS OF AROCLOR 1268 IN THE TAUNTON RIVER ESTUARY: EVIDENCE OF EARLY PRODUCTION, USE AND RELEASE TO THE ENVIRONMENT

EPA Science Inventory

Sediment cores were collected at three sites from the Lower Taunton River in Narragansett Bay, MA, dated and examined for PCBs. At each site, PCBs first appear in the sediment cores at depths corresponding to 1929 based on a combination of radiometric and anthropogenic dating pr...

Depositional history and inventories of polychlorinated biphenyls (PCBs) in sediment cores from an Antarctic Specially Managed Area (Admiralty Bay, King George Island).

PubMed

Combi, Tatiane; Martins, César C; Taniguchi, Satie; Leonel, Juliana; Lourenço, Rafael André; Montone, Rosalinda Carmela

2017-05-15

Temporal patterns, fluxes and inventories of polychlorinated biphenyls (PCBs) were assessed in nine sediment cores collected from selected areas of Admiralty Bay off the Antarctic Peninsula. Concentrations of total PCBs were low, but slightly higher in comparison to low-impacted, remote environments in the world, ranging from below the detection limit to 11.9ngg -1 in dry weight. PCB concentrations and inventories suggest a possible minor influence related to the nearby logistic activities, especially in the sediment core collected close to the Ferraz Station. Despite being the most remote and protected area on the planet, the Antarctic continent is no longer a pristine environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spatial and Vertical Distribution of Dechlorane Plus in Mangrove Sediments of the Pearl River Estuary, South China.

PubMed

Sun, Yu-Xin; Zhang, Zai-Wang; Xu, Xiang-Rong; Hao, Qin-Wei; Hu, Yong-Xia; Zheng, Xiao-Bo; Luo, Xiao-Jun; Diao, Zeng-Hui; Mai, Bi-Xian

2016-10-01

Thirty surface sediments and three sediment cores were collected from mangrove wetlands in the Pearl River Estuary of South China to investigate the spatial and vertical distribution of Dechlorane Plus (DP). DP concentrations in the mangrove surface sediments ranged from 0.0130 to 1.504 ng/g dry weight (dw). DP concentrations in sediments from Shenzhen were significantly greater than those from Guangzhou and Zhuhai. Anti-Cl11-DP, the dechlorinated product of anti-DP, was also detected in the mangrove sediments with concentrations ranged from not detected to 0.0198 ng/g dw. Significant positive relationship between anti-Cl11-DP and anti-DP levels was observed in the mangrove sediments, suggesting that photo and/or microbial degradation of anti-DP might occur in the sediments. The f anti values in the mangrove sediments were close to those in the technical DP products, suggesting that stereoselective enrichment of anti-DP may not exist in the mangrove sediments. DP concentrations in the mangrove sediment cores generally showed an increasing trend from the bottom to top layers. This is the first study to report the occurrence of DP and its degradation product in the mangrove wetlands.

Magnetic properties of sediments in cores from the Mandovi estuary, western India: Inferences on provenance and pollution.

PubMed

Prajith, A; Rao, V Purnachandra; Kessarkar, Pratima M

2015-10-15

Magnetic properties of sediments were investigated in 7 gravity cores recovered along a transect of the Mandovi estuary, western India to understand their provenance and pollution. The maximum magnetic susceptibility of sediments was at least 6 times higher in the upper/middle estuary than in lower estuary/bay. The χfd% and χARM/SIRM of sediments indicated coarse, multi-domain and pseudo-single domain magnetic grains, resembling ore material in the upper/middle estuary and coarse stable single domain (SSD) to fine SSD grains in the lower estuary/bay. Mineralogy parameters indicated hematite and goethite-dominated sediments in the upper/middle estuary and magnetite-dominated sediments in the lower estuary/bay. Two sediment types were discernible because of deposition of abundant ore material in the upper/middle estuary and detrital sediment in the lower estuary/bay. The enrichment factor and Index of geo-accumulation of metals indicated significant to strong pollution with respect to Fe and Mn in sediments from the upper/middle estuary. Copyright © 2015 Elsevier Ltd. All rights reserved.

Understanding Mississippi Delta Subsidence through Stratigraphic and Geotechnical Analysis of a Continuous Holocene Core at a Subsidence Superstation

NASA Astrophysics Data System (ADS)

Bridgeman, J.; Tornqvist, T. E.; Allison, M. A.; Jafari, N.

2016-12-01

Land-surface subsidence is a major contributor to recent Mississippi Delta land loss. Despite significant research efforts, the primary mechanisms and rates of delta subsidence remain the subject of debate. This has led to a broad range of subsidence rate estimates across the delta, making differentiating between subsidence mechanisms as well as coastal restoration efforts more challenging. New data from a continuous 39 m long, 12 cm diameter core taken during the installation of a subsidence monitoring superstation near the Mississippi River, SW of New Orleans, provides insight into the grain size, bulk density, geochronology, and geotechnical parameters of the entire Holocene succession. The core consists of three major sections. The top 11 m contain a modern marsh peat, followed by a silty clay loam with interspersed humic clays (14C age 1250 BP), a peat bed (14C age 2200-2950 BP), and silt loams. The middle section from 11 to 35 m is dominated by clay and silty clay, with a relative bulk density of 1.5 g/cc, which gradually becomes denser with depth and the bottom section (35 to 39 m) is marked by a high energy, shell-rich sand facies and a basal peat (14C age 9850 BP), which terminates at the core base in a densely packed, blue-gray silty clay loam, characteristic of the Pleistocene. The radiocarbon ages of marsh peat beds, combined with sea-level markers derived from basal peat elsewhere in the delta, enable the reconstruction of the local subsidence history at this site. Notably, the data shows a significant amount of vertical displacement from the dated organics in the top section of the core; 3.5 m in the humic clays and up to 5 m in the peat bed. The subsidence rates measured by the superstation apparatus, and the geotechnical measurements of core sediments, will aid in determining the dominant subsidence mechanisms (shallow vs. deep) in the region.

Impacts of pollution derived from ship wrecks on the marine environment on the basis of s/s "Stuttgart" (Polish coast, Europe).

PubMed

Rogowska, Justyna; Wolska, Lidia; Namieśnik, Jacek

2010-11-01

In 1943 the German hospital ship s/s Stuttgart (Lazaretschiff "C") was sunk close to the port of Gdynia (Gulf of Gdańsk - Polish coast). This and other actions (undertaken after the war to remove the wreck) led to pollution of the sea bottom with oil derivatives. During our studies (2009) 11 surface sediment and water samples were collected as well as sediment core samples at 4 locations in order to determine the concentration levels of priority pollutants belonging to polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB). The concentrations of 16 PAH and 7 PCB were analysed with GC-MS. ΣPAH varied between 11.54 ± 0.39 and 206.7 ± 6.5mg/kg dry weight in the surface sediments, and from 0.686 ± 0.026 to 1291 ± 53 mg/kg dry weight in the core samples. Contamination in the core samples collected may reach a depth of at least 230-240 cm (deepest sample studied). The PAH-group profiles in all surface sediment samples suggest a pyrolytic source of PAH, while the results obtained for core samples indicate a mixed pattern of pyrolytic and petrogenic inputs of PAH. Results obtained may suggest also that fuel residues being present at sea bottom is not crude oil derived but results from coal processing (synthetic fuel). The sum of PCB in surface sediments ranged from 0.761 ± 0.068 to 6.82 ± 0.28 μg/kg dry weight (except for sampling point W2, where ΣPCB was 108.8 ± 4.4 μg/kg dry weight). The strong correlation between PAH and PCB levels, and the fact that PCB are present only in the surface sediments, suggest that the compounds in these sediments got there as a result of emission from urban areas, entering the aquatic environment via atmospheric deposition. PCB levels in the sediment core samples were generally very low and in most cases did not exceed the method quantification limit. Copyright © 2010 Elsevier B.V. All rights reserved.

Reconstruction of atmospheric trace metals pollution in Southwest China using sediments from a large and deep alpine lake: Historical trends, sources and sediment focusing.

PubMed

Lin, Qi; Liu, Enfeng; Zhang, Enlou; Nath, Bibhash; Shen, Ji; Yuan, Hezhong; Wang, Rong

2018-02-01

Atmospheric pollution, one of the leading environmental problems in South and East Asia, and its impact on the terrestrial environmental quality remain poorly understood particularly in alpine areas where both historical and present-day mining and smelting operations might leave an imprint. Here, we reconstructed atmospheric trace metals pollution during the past century using core sediments from a large and deep alpine lake in Southwest China. The implication of in lake and/or in watershed sediment focusing in pollution quantification is discussed by analyzing 15 sediment cores. Factor analysis and enrichment factor indicated Cd, Pb and Sb as the typical pollutants. Distinct peaks of Pb and Sb pollution were observed around the 1920s, but little Pb pollution was detected in recent decades, different from other studies in similar regions. Cadmium pollution was observed until the mid-1980s synchronized with Sb. The distinctive variations in atmospheric trace metal pollution process in Southwest China highlight the regional and sub-regional sources of metal pollutants, which should be primarily attributed to non-ferrous metal smelting emissions. Both natural and anthropogenic metals showed wide concentration ranges though exhibited similar temporal trends in the 15 cores. Spatial variations of anthropogenic metals were influenced by the in-watershed pollutants remobilization, whereas, natural metals were regulated by the detrital materials in the sub-basin. In-lake sediment focusing had little influence on the spatial distributions of all metals, different from the traditional sediment focusing pattern observed in small lakes. Anthropogenic Cd accumulation in sediments ranged from 1.5 to 10.1mgm -2 in a specific core with an average of 6.5mgm -2 for the entire lake, highlighting that a reliable whole-lake pollutant budget requires an analysis of multiple cores. Our study suggests that the management of aquatic ecosystem health should take the remobilization of in-watershed stored pollutants into consideration especially under increasing human perturbation. Copyright © 2017 Elsevier B.V. All rights reserved.

Radiocarbon ages and age models for the past 30,000 years in Bear Lake, Utah and Idaho

USGS Publications Warehouse

Colman, Steven M.; Rosenbaum, J.G.; Kaufman, D.S.; Dean, W.E.; McGeehin, J.P.

2009-01-01

Radiocarbon analyses of pollen, ostracodes, and total organic carbon (TOC) provide a reliable chronology for the sediments deposited in Bear Lake over the past 30,000 years. The differences in apparent age between TOC, pollen, and carbonate fractions are consistent and in accord with the origins of these fractions. Comparisons among different fractions indicate that pollen sample ages are the most reliable, at least for the past 15,000 years. The post-glacial radiocarbon data also agree with ages independently estimated from aspartic acid racemization in ostracodes. Ages in the red, siliclastic unit, inferred to be of last glacial age, appear to be several thousand years too old, probably because of a high proportion of reworked, refractory organic carbon in the pollen samples. Age-depth models for five piston cores and the Bear Lake drill core (BL00-1) were constructed by using two methods: quadratic equations and smooth cubic-splinefits. The two types of age models differ only in detail for individual cores, and each approach has its own advantages. Specific lithological horizons were dated in several cores and correlated among them, producing robust average ages for these horizons. The age of the correlated horizons in the red, siliclastic unit can be estimated from the age model for BL00-1, which is controlled by ages above and below the red, siliclastic unit. These ages were then transferred to the correlative horizons in the shorter piston cores, providing control for the sections of the age models in those cores in the red, siliclastic unit. These age models are the backbone for reconstructions of past environmental conditions in Bear Lake. In general, sedimentation rates in Bear Lake have been quite uniform, mostly between 0.3 and 0.8 mm yr-1 in the Holocene, and close to 0.5 mm yr-1 for the longer sedimentary record in the drill core from the deepest part of the lake. Copyright ?? 2009 The Geological Society of America.

Quaternary displacement rates on the Meeman‐Shelby fault and Joiner ridge horst, eastern Arkansas: Results from coring Mississippi River alluvium

USGS Publications Warehouse

Ward, Alex; Counts, Ronald C.; Van Arsdale, Roy; Larsen, Daniel; Mahan, Shannon

2017-01-01

This research used coring and optically stimulated luminescence (OSL) dating of displaced, deeply buried Quaternary alluvium to determine vertical displacement rates for the Meeman‐Shelby fault and the Joiner ridge horst, two structures in northeastern Arkansas that have no modern seismicity associated with them. We drilled continuous cores of the entire alluvial section in the hanging wall of each structure, performed detailed core descriptions and analyses, and obtained three OSL ages from each core. The Meeman‐Shelby fault core consists of 36 m of 4.3–5.2‐ka Holocene alluvium overlying 4 m of 14.3‐ka Kennett alluvium that in turn overlies the upper part of Eocene Claiborne Group sediments at a depth of 41 m. Seismic reflection indicates that the basal (Kennett) alluvium at the Meeman‐Shelby fault is displaced ∼28  m across the Meeman‐Shelby fault, which equates to a time‐averaged vertical displacement rate of 2  mm/yr within the last 14.3 ka. The Joiner ridge horst core consists, in descending order, of 11 m of 6.3‐ka Holocene alluvium, 14 m of 11.5‐ka Morehouse alluvium, a paleosol, 6 m of Kennett alluvium, and 4 m of 20.3‐ka Sikeston alluvium that in turn overlies the upper part of Eocene Claiborne Group sediments at a depth of 36 m. Lignite exploration drilling conducted in the 1970s indicates that basal (Sikeston) alluvium is displaced ∼20  m across the eastern bounding fault of the Joiner ridge horst, resulting in a time‐averaged vertical displacement rate of ∼1  mm/yr within the last 20.3 ka. These late Quaternary displacement rates are comparable to time‐averaged displacement rates of faults within the active New Madrid seismic zone.

Natural and Anthropocene fluxes of trace elements in estuarine sediments of Galician Rias

NASA Astrophysics Data System (ADS)

Álvarez-Vázquez, Miguel Ángel; Caetano, Miguel; Álvarez-Iglesias, Paula; Pedrosa-García, María del Canto; Calvo, Susana; De Uña-Álvarez, Elena; Quintana, Begoña; Vale, Carlos; Prego, Ricardo

2017-11-01

The Anthropocene has been proposed as a new geo-stratigraphic epoch where humans have become a global factor affecting the ecosystems. Estuarine sediments constitute a biogeochemical reservoir where trace elements (TEs) from natural sources mix with a fraction generated by human activities. This study assessed the natural lithogenic imprint of TEs from uncontaminated sedimentary records to study anthropogenic changes. Sediment cores were sampled in the estuarine part of the low populated and low industrialized rias of Ares (A), Betanzos (B) and Cedeira (C), which are located in the NW of the Iberian Peninsula. Cores were dated by the 210Pb method, covering up to the last century period. Sedimentation rates (in mm yr-1) were 3.4 ± 0.6 (older than 1961) and 8.2 ± 3.2 (younger than 1961) for core A, 0.9 ± 0.2 (<1940) and 4.2 ± 2.3 for core B, and 13.4 ± 1.4 for core C. The background fluxes of TEs were in the ranges of (in g m-2 yr-1) 50-560 for Al and Fe, 20-320 for POC and 8-100 for PS, and (in mg m-2 yr-1) 20-120 for As, 0.2-2.0 for Cd, 7-110 for Co, 40-870 for Cr, 20-230 for Cu, 0.1-0.6 for Hg, 290-2800 for Mn, 4-24 for Mo, 20-410 for Ni, 20-150 for Pb, 60-800 for V and 70-700 for Zn. The three cores showed an anthropogenic influence since the mid-20th century. The detected human impact during the Anthropocene was due to the Eume River damming and As-Pontes lignite mining (the largest mine open-pit in the Iberian Peninsula) in core A, by bridge/road constructions, vehicles emissions and river mouth urbanization in core B, and changes in land use in core C. Sediment accumulation rates increased 2.4 (core A) and 4.7 times (core B) while TEs fluxes increased 2.4 times in core A and between 3.6 and 5.1 times in core B. Pre-industrial sedimentary records showed the lithogenic differences of the drainage basins, mainly granitic watersheds for cores A and B and the prevalence of basic rocks of the Ortegal Geological Complex for core C. This explains the high concentrations and fluxes of Cr, Ni and V of core C. The different lithogenic imprints highlight the value of using local background references in contamination studies, such as those on the Anthropocene influence in estuaries, which occurred after the Spanish Civil War in the studied rias.

High-resolution past environmental reconstruction in East Asia using annually laminated lake sediments of Lake Megata in northeastern Japan

NASA Astrophysics Data System (ADS)

Yamada, K.; Gotanda, K.; Yonenobu, H.; Shinozuka, Y.; Kitagawa, J.; Makohonienko, M.; Schwab, M.; Haraguchi, T.; Yasuda, Y.

2007-12-01

37 m-long non-glacial varved sequences were taken from Ichi-no-Megata maar in Oga Peninsula, Akita, northern part of Japan. Ichi-no-Megata maar occupies 0.25 km2 with a maximum water depth of ca. 45.1 m. The shape of lake is a kettle-type basin and the deepest bottom basin is very flat. We took core samples (named IMG06 core) at the center of the lake in November to December in 2006. In order to take completely continuous maar sediment, we drilled three holes and take every sample from each hole which apart only few meters. In this drilling campaign, we can 37 m-long continuous maar sediment except thick volcanic deposits from 26.5 to 31.7m in core. The sedimentological feature of IMG06 core is dominated by thin lamination clay/silt from most top part up to 37 m with turbidites characterized upward fining structure. The SEM image observation of lamination reveals that sponge-like lamina consists of diatom assemblage against dark colored lamina consists of mixture of detritus minerals, clay minerals, and diatom. It means sponge-like lamina deposits during spring season, and later one deposits during another three seasons, and then these thin lamination of IMG06 core could be identified as annual lamination (varves). This interpretation is supported by the correlation of historic event as earthquake and tunnel construction. In this IMG06 core, six volcanic ashes are found and we have also analyzed radiocarbon dating from 38 horizons of the core to use leaf and seeds inter-bedded varves. As the results, the IMG06 core covers from 25,000 to 4,000 14C yr BP with stable sedimentation rates (0.71mm/year).

Changes in the northern Adriatic molluscan community from the Holocene transgression up to the present

NASA Astrophysics Data System (ADS)

Gallmetzer, Ivo; Haselmair, Alexandra; Tomasovych, Adam; Stachowitsch, Michael; Zuschin, Martin

2016-04-01

The northern Adriatic Sea is one of the few modern, epicontinental seas comparable to typical Palaeozoic shelf environments. It has a shallow average water depth (<50 m) and was formed at the end of the last glaciation when the sea level rose. Since historical times this part of the Adriatic has been strongly influenced by human activities through multiple direct or indirect impacts (e.g. fishing, coastal building development, pollution, eutrophication, increased sedimentation), making it one of the most degraded marine ecosystems worldwide. Our study was designed to reconstruct major environmental changes here since the onset of the Holocene transgression using down-core changes in death assemblages of molluscs as indicators for ecological shifts. The sediment cores were taken at three different stations (Brijuni Islands, Croatia, off Piran, Slovenia, and off Venice, Italy), each representative of specific sediment and nutrient conditions and degrees of habitat exploitation. The cores were 1.5 m long and had diameters of 90 or 160 mm. For the molluscan shell analyses, sediment subsamples were examined for species composition, abundance, taxonomic similarity and ecological interactions (e.g. frequencies of drilling predation). In total, 98,700 valves and shells were investigated and 113 bivalve and 178 gastropod species recorded. Sedimentation rates derived from 210Pb dating are very low, between 0.15 cm/yr at Brijuni and 0.25 cm/yr at Piran. The dating of Lucinella divaricata, Timoclea ovata and Gouldia minima shells with 14C calibrated amino-acid racemisation (AAR) revealed that the cores at all three stations cover at least 6000 to 8000 years, i.e. the whole Holocene transgression period. Time averaging is high, especially in the lower core layers of Piran station, probably due to strong bioturbation. Surface mixed-layer assemblages tend to show right-skewed postmortem age-frequency distributions, whereas subsurface assemblages show unimodal or uniform shapes. Molluscan assemblages show significant interregional differences that correlate with sedimentation rate, grain size, and the occurrence of organic pollutants and heavy metals. Down-core changes in molluscan communities are also conspicuous in all cores. They partly reflect long-term changes in water depth, vegetation cover or grain size distribution caused by natural fluctuations of environmental conditions over the past millennia. In the uppermost core layers, however, these changes can be interpreted as indicators of anthropogenic impacts.

Geotechnical properties of core sample from methane hydrate deposits in Eastern Nankai Trough

NASA Astrophysics Data System (ADS)

Yoneda, J.; Masui, A.; Egawa, K.; Konno, Y.; Ito, T.; Kida, M.; Jin, Y.; Suzuki, K.; Nakatsuka, Y.; Tenma, N.; Nagao, J.

2013-12-01

To date, MH extraction has been simulated in several ways to help ensure the safe and efficient production of gas, with a particular focus on the investigation of landsliding, uneven settlement, and production well integrity. The mechanical properties of deep sea sediments and gas-hydrate-bearing sediments, typically obtained through material tests, are essential for the geomechanical response simulation to hydrate extraction. We conducted triaxial compression tests and the geotechnical properties of the sediments was investigated. Consolidated undrained compression tests were performed for silty sediments. And consolidated drained tests were performed for sandy samples. In addition, permeability was investigated from isotropic consolidation results. These core samples recovered from methane hydrate deposits of Daini Atsumi Knoll in Eastern Nankai Trough during the 2012 JOGMEC/JAPEX Pressure coring operation. The pressure core samples were rapidly depressurized on the ship and it were frozen using liquid nitrogen to prevent MH dissociation. Undrained shear strength of the core samples increase linearly with depth from sea floor. These core samples should be normally consolidated sample in-situ. Drained shear strength increases dramatically with hydrate saturation increases. Peak stress ratio q/p' of the core sample which has 73% of hydrate saturation was approximately 2.0 and it decrease down to 1.3 at the critical state. Dilatancy also changed from compressive tendency to dilative tendency with hydrate saturation increase. This study was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) that carries out Japan's Methane Hydrate R&D Program conducted by the Ministry of Economy, Trade and Industry (METI).

Cyclicity and reservoir properties of Lower-Middle Miocene sediments of South Kirinsk oil and gas field

NASA Astrophysics Data System (ADS)

Kurdina, Nadezhda

2017-04-01

Exploration and additional exploration of oil and gas fields, connected with lithological traps, include the spreading forecast of sedimentary bodies with reservoir and seal properties. Genetic identification and forecast of geological bodies are possible in case of large-scale studies, based on the study of cyclicity, structural and textural features of rocks, their composition, lithofacies and depositional environments. Porosity and permeability evaluation of different reservoir groups is also an important part. Such studies have been successfully completed for productive terrigenous Dagi sediments (Lower-Middle Miocene) of the north-eastern shelf of Sakhalin. In order to identify distribution of Dagi reservoirs with different properties in section, core material of the one well of South Kirinsk field has been studied (depth interval from 2902,4 to 2810,5 m). Productive Dagi deposits are represented by gray-colored sandstones with subordinate siltstones and claystones (total thickness 90,5 m). Analysis of cyclicity is based on the concepts of Vassoevich (1977), who considered cycles as geological body, which is the physical result of processes that took place during the sedimentation cycle. Well section was divided into I-X units with different composition and set of genetic features due to layered core description and elementary cyclites identification. According to description of thin sections and results of cylindrical samples porosity and permeability studies five groups of reservoirs were determined. There are coarse-grained and fine-coarse-grained sandstones, fine-grained sandstones, fine-grained silty sandstones, sandy siltstones and siltstones. It was found, in Dagi section there is interval of fine-coarse-grained and coarse-grained sandstones with high petrophysical properties: permeability 3000 mD, porosity more than 25%, but rocks with such properties spread locally and their total thickness is 6 meters only. This interval was described in the IV unit. In the IV unit lower cyclites elements consist of conglomerates and upper by above-mentioned sandstones. The appearance of conglomerates indicates a coastal-marine depositional environment. The most widely spread reservoir type of Dagi section is fine-grained sandstones and fine-grained silty sandstones with porosity value 22-24% and permeability 100-500 mD. They present the lower elements of cyclites in I, II, VII and VIII units. These sandstones contain fragments of pelecypods shells and marks of bioturbation. There are long (up to 1 m) vertical burrows, which means shallow basin and a weak hydrodynamics. The most clayey section parts (units V and VI) that are presented by wavy-horizontal interlayering of clayey siltstones and clayey-silty rocks contain reservoirs but of poorer petrophysical properties. Sandy siltstones with 14-23% porosity and permeability value 1-10 mD. In general, units V and VI are characterized by conditions of active hydrodynamic and sandy siltstones appearance - with additional supply of sediments with temporary flows. Presence of different reservoir groups in Dagi section is controlled by sedimentation factors and reflects succession of vertical genetic series. According to the preliminary assessment, rocks accumulated predominantly in coastal-marine and shallow-marine environment. Frequent change of lithotypes in Dagi section in well 5 of South Kirinsk field indicates significant changes of depositional environment whose diagnostic and identification are an integral part of the field exploration works.

Data on sediment quality and concentrations of polychlorinated biphenyls from the Lower Neponset River, Massachusetts, 2002-03

USGS Publications Warehouse

Breault, Robert F.; Cooke, Matthew G.; Merrill, Michael

2004-01-01

The U.S. Geological Survey, in cooperation with the Massachusetts Executive Office of Environmental Affairs Department of Fish and Game Riverways Program, and the U.S. Environmental Protection Agency, studied sediment and water quality in the lower Neponset River, which is a tributary to Boston Harbor. Grab and core samples of sediment were tested for elements and organic compounds including polyaromatic hydrocarbons, organochlorine pesticides, and polychlorinated biphenyls. Physical properties of sediment samples, including grain size, were also measured. Selected sediment-core samples were tested for reactive sulfides and metals by means of the toxicity characteristic leaching procedure, which are sediment-disposal-related tests. Water quality, with respect to polychlorinated biphenyl contamination, was determined by testing samples collected by PISCES passive-water-column samplers for polychlorinated biphenyl congeners. Total concentrations of polychlorinated biphenyls were calculated by congener and by Aroclor.

The 3.6 ka Aniakchak tephra in the Arctic Ocean: A constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea

USGS Publications Warehouse

Pearce, Christof; Varhelyi, Aron; Wastegård, Stefan; Muschitiello, Francesco; Barrientos Macho, Natalia; O'Regan, Matt; Cronin, Thomas M.; Gemery, Laura; Semiletov, Igor; Backman, Jan; Jakobsson, Martin

2017-01-01

The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid–late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed across a more than 1.5 m long sediment sequence. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca. 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major influence of typically "carbon-old" Pacific waters, and it agrees well with recent estimates of ΔR along the northwest Alaskan coast, possibly indicating stable oceanographic conditions during the second half of the Holocene. Our use of a volcanic absolute age marker to obtain the marine reservoir age offset is the first of its kind in the Arctic Ocean and provides an important framework for improving chronologies and correlating marine sediment archives in this region. Core 2PC has a high sediment accumulation rate averaging 200 cm kyr throughout the last 4000 years, and the chronology presented here provides a solid base for high-resolution reconstructions of late Holocene climate and ocean variability in the Chukchi Sea.

The Towuti Drilling Project: A new, long Pleistocene record of Indo-Pacific Climate

NASA Astrophysics Data System (ADS)

Russell, James M.; Vogel, Hendrik; Bijaksana, Satria; Melles, Martin

2016-04-01

Lake Towuti is the largest tectonic lake in Indonesia, and the longest known terrestrial sediment archive in Southeast Asia. Lake Towuti's location in central Indonesia provides an important opportunity to reconstruct long-term changes in terrestrial climate in the Western Pacific warm pool, heart of the El Niño-Southern Oscillation. Lake Towuti has extremely high rates of floral and faunal endemism and is surrounded by one of the most diverse tropical forests on Earth making it a hotspot of Southeast Asian biodiversity. The ultramafic rocks and soils surrounding Lake Towuti provide high concentrations of metals to the lake and its sediments that feed a diverse, exotic microbial community. From May - July, 2015, the Towuti Drilling Project, consisting of more than 30 scientists from eight countries, recovered over 1,000 meters of new sediment core from 3 different drill sites in Lake Towuti, including cores through the entire sediment column to bedrock. These new sediment cores will allow us to investigate the history of rainfall and temperature in central Indonesia, long-term changes in the composition of the region's rainforests and diverse aquatic ecosystems, and the micro-organisms living in Towuti's exotic, metal-rich sediments. The Indo-Pacific region plays a pivotal role in the Earth's climate system, regulating critical atmospheric circulation systems and the global concentration of atmospheric water vapor- the Earth's most important greenhouse gas. Changes in seasonal insolation, greenhouse gas concentrations, ice volume, and local sea level are each hypothesized to exert a dominant control on Indo-Pacific hydroclimate variations through the Pleistocene. Existing records from the region are short and exhibit fundamental differences and complexity in orbital-scale climate patterns that limit our understanding of the regional climate responses to climate boundary conditions. Our sediment cores, which span much of the past 1 million years, allow new tests of these hypotheses. Sediment core logging and lithostratigraphic data document major shifts in sediment composition, including alterations of lake clays and calcareous sediments in the upper ~100m and peats and gravels in the basal units of our records. These data show excellent agreement with major lithological transitions recorded in seismic reflection data, and indicate large changes in lake levels and hydroclimate through the late Quaternary. Prior work on Lake Towuti indicated a dominant control by global ice volume on regional hydroclimate, a hypothesis we now test through the analysis of these new cores. This presentation will review existing records from the region and show the first long geochemical and sedimentological records from Lake Towuti to understand orbital-scale Indo-Pacific hydrologic change during the late Pleistocene.

The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea

NASA Astrophysics Data System (ADS)

Pearce, Christof; Varhelyi, Aron; Wastegård, Stefan; Muschitiello, Francesco; Barrientos, Natalia; O'Regan, Matt; Cronin, Thomas M.; Gemery, Laura; Semiletov, Igor; Backman, Jan; Jakobsson, Martin

2017-04-01

The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid-late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed across a more than 1.5 m long sediment sequence. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca. 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major influence of typically carbon-old Pacific waters, and it agrees well with recent estimates of ΔR along the northwest Alaskan coast, possibly indicating stable oceanographic conditions during the second half of the Holocene. Our use of a volcanic absolute age marker to obtain the marine reservoir age offset is the first of its kind in the Arctic Ocean and provides an important framework for improving chronologies and correlating marine sediment archives in this region. Core 2PC has a high sediment accumulation rate averaging 200 cm kyr-1 throughout the last 4000 years, and the chronology presented here provides a solid base for high-resolution reconstructions of late Holocene climate and ocean variability in the Chukchi Sea.

Estuarine sedimentation, sediment character, and foraminiferal distribution in central San Francisco Bay, California

USGS Publications Warehouse

Chin, John L.; Woodrow, Donald L.; McGann, Mary; Wong, Florence L.; Fregoso, Theresa A.; Jaffe, Bruce E.

2010-01-01

Central San Francisco Bay is the deepest subembayment in the San Francisco Bay estuary and hence has the largest water volume of any of the subembayments. It also has the strongest tidal currents and the coarsest sediment within the estuary. Tidal currents are strongest over the west-central part of central bay and, correspondingly, this area is dominated by sand-size sediment. Much of the area east of a line from Angel Island to Alcatraz Island is characterized by muddy sand to sandy mud, and the area to the west of this line is sandy. The sand-size sediment over west-central bay furthermore is molded by the energetic tidal currents into bedforms of varying sizes and wavelengths. Bedforms typically occur in water depths of 15-25 m. High resolution bathymetry (multibeam) from 1997 and 2008 allow for subdivision of the west-central bayfloor into four basic types based on morphologic expression: featureless, sand waves, disrupted/man-altered, and bedrock knobs. Featureless and sand-wave morphologies dominate the bayfloor of west-central bay. Disrupted bayfloor has a direct association with areas that are undergoing alteration due to human activities, such as sand-mining lease areas, dredging, and disposal of dredge spoils. Change detection analysis, comparing the 1997 and 2008 multibeam data sets, shows that significant change has occurred in west-central bay during the roughly 10 years between surveys. The surveyed area lost about 5.45 million m3 of sediment during the decade. Sand-mining lease areas within west-central bay lost 6.77 million m3 as the bayfloor deepened. Nonlease areas gained 1.32 million m3 of sediment as the bayfloor shallowed slightly outside of sand-mining lease areas. Furthermore, bedform asymmetry did not change significantly, but some bedforms did migrate some tens of meters. Gravity cores show that the area east of Angel and Alcatraz Islands is floored by clayey silts or silty sand whereas the area to the west of the islands is floored dominantly by sand- to coarse sand-sized sediment. Sandy areas also include Raccoon Strait, off Point Tiburon, and on the subtidal Alcatraz, Point Knox, and Presidio Shoals. Drab-colored silty clays are the dominant sediment observed in gravity cores from central bay. Their dominance along the length of the core suggests that silty clays have been deposited consistently over much of this subembayment for the time period covered by the recovered sediments (Woodrow and others, this report). Stratification types include weakly-defined laminae, 1-3 mm thick. Few examples of horizontal lamination in very fine sand or silt were observed. Cross lamination, including ripples, was observed in seven cores. Erosional surfaces were evident in almost every core where x-radiographs were available (they are very difficult to observe visually). Minor cut-and-fill structures also were noted in three cores and inclined strata were observed in three cores. Textural patterns in central bay indicate that silts and clays dominate the shallow water areas and margins of the bay. Sand dominates the tidal channel just east of Angel and Alcatraz Islands and to the west of the islands to the Golden Gate. The pattern of sand-sized sediment, as determined by particle-size analysis, suggests that sand movement is easterly from the west-central part of the bay. A second pattern of sand movement is to the south from the southwestern extremity of San Pablo Bay (boundary approximated by the location of the Richmond-San Rafael Bridge). Age dates for central bay sediment samples were obtained by carbon-14 radiometric age dating. Age dates were determined from shell material that was interpreted to be largely in-place (not transported). Age dates subsequently were reservoir corrected and then converted to calendar years. Sediments sampled from central bay cores range in age from 330 to 4,155 years before present. Foraminiferal distribution in the San Francisco Bay estuary is fairly well

High resolution HH-XRF scanning and XRD modelling as a tool in sedimentological analysis - A case study from the Enreca-3 core, Bach Long Vi Island, Vietnam

NASA Astrophysics Data System (ADS)

Rizzi, Malgorzata; Hemmingsen Schovsbo, Niels; Korte, Christoph; Bryld Wessel Fyhn, Michael

2017-04-01

To improve the understanding and interpretation of the depositional environment of a late Oligocene lacustrine organic rich oil-prone source rock succession, 2464 hand held (HH)-XRF measurements were made systematically on the 500 m long, continuous core from the fully cored Enreca-3 well. This core, drilled on the remote Bach Long Vi Island, northern Gulf of Tonkin, offshore Vietnam, represents a deep lake succession alternating between lacustrine pelagic dominated sediments interrupted by hyperpycnal turbidites, high density turbidites and debris flows [1, 2]. From a combined HH-XRF-XRD data set, multivariate data analysis and regression models are used to type the rock and to predict the XRD mineral composition based on HH-XRF composition. The rock types and the modelled mineral composition highlight the geochemical variations of the sediment and allows for direct comparison with sedimentological processes and facies changes. The modeling also depicts the cyclic alteration of rock types that are present on many different scales ranging from centimeters to hundreds of meters [1, 2]. The sedimentological and geochemical variations observed throughout the cored section reflects fluctuating paleoclimate, tectonism and hinterland condition controlling the depositional setting, which may provide a deeper understanding of the deposition of this and similar Paleogene syn-rift succession in the South China Sea region. It allows furthermore the development of a more generalized depositional model relevant for other deep-lacustrine syn-rift basins. [1] Petersen et al. (2014) Journal of Petroleum Geology, 37: 373-389. [2] Hovikoski et al. (2016) Journal of Sedimentary Research, 86(8): 982-1007.

Chronicling ice shelf history in the sediments left behind

NASA Astrophysics Data System (ADS)

Rosenheim, B. E.; Subt, C.; Shevenell, A.; Guitard, M.; Vadman, K. J.; DeCesare, M.; Wellner, J. S.; Bart, P. J.; Lee, J. I.; Domack, E. W.; Yoo, K. C.; Hayes, J. M.

2017-12-01

Collapsing and retreating ice shelves leave unmistakable sediment sequences on the Antarctic margin. These sequences tell unequivocal stories of collapse or retreat through a typical progression of sub-ice shelf diamicton (marking the past positions of grounding lines), sequentially overlain by a granulated facies from beneath the ice shelf, ice rafted debris from the calving line, and finally open marine sediment. The timelines to these stories, however, are troublesome. Difficulties in chronicling these stories recorded in sediment have betrayed their importance to our understanding of a warming world in many cases. The difficulties involve the concerted lack of preservation/production of calcium carbonate tests from the water column above and admixture of relict organic material from older sources of carbon. Here, we summarize our advances in the last decade of overcoming difficulties associated with the paucity of carbonate and creating chronologies of ice shelf retreat into the deglacial history of Antarctica by exploiting the range of thermochemical stability in organic matter (Ramped PyrOx) from these sediment sequences. We describe our success in comparing Ramped PyrOx 14C dates with foraminiferal dates, the relationship between sediment facies and radiocarbon age spectrum, and our ability to push limits of dating sediments deposited underneath ice shelves. With attention to the caveats of recent dating developments, we summarize expectations that geologist should have when coring the Antarctic margins to discern deglacial history. Perhaps most important among these expectations is the ability to design coring expeditions without regard to our ability to date calcium carbonate microfossils within the cores, in essence removing suspense of knowing whether cores taken from crucial paleo ice channels and other bathymetric features will ultimately yield a robust chronology for its sedimentary sequence.

Microbial community structure and methane-cycling activity of subsurface sediments at Mississippi Canyon 118 before the Deepwater Horizon disaster

NASA Astrophysics Data System (ADS)

Underwood, Sarah; Lapham, Laura; Teske, Andreas; Lloyd, Karen G.

2016-07-01

The Deepwater Horizon disaster caused a shift in microbial communities in Gulf of Mexico seawater, but less is known about the baseline for microbial communities in the underlying sediments. We compared 16S rRNA and functional gene sequences deriving from DNA and RNA with geochemical profiles (sulfate and methane concentrations, δ13C of methane and carbon dioxide, and chloride concentrations) of a sediment gravity core from the upper continental slope of the northwestern Gulf of Mexico (MC118) in 2008, 15 km from the spill site. The highest number of archaeal sequences were ANME-1 and ANME-2 archaea in the sulfate-reducing upper core segments (12 and 42 cmbsf), ANME-1 and Methanomicrobiales in the middle methanogenic depths (200 and 235 cmbsf), and ANME-1 at the deepest depths (309, 400, and 424 cmbsf). The presence of mcrA gene transcripts showed that members of the ANME-1 group are active throughout the core and transcribe the mcrA gene, a key gene of methanogenesis and anaerobic methane oxidation. The bacterial community consists mostly of members of the Deltaproteobacteria, Chloroflexi, Cytophaga, Epsilonproteobacteria, and the Japan Sea Group 1 throughout the core. The commonly detected genera of gammaproteobacterial hydrocarbon-degrading bacteria in the water column are not found in this sediment survey, indicating that the benthic sediment is an unlikely reservoir for these aerobes. However, the sediments contain members of the sulfate-reducing families Desulfobulbaceae and Desulfobacteraceae, some members of which degrade and completely oxidize aromatic hydrocarbons and alkanes, and the Desulfobacterium anilini lineage of obligately aromatics-degrading sulfate reducers. Thus, the benthic sediments are the most likely reservoir for the active deltaproteobacterial populations that were observed repeatedly after the Deepwater Horizon spill in the fall of 2010.

Characteristics of Air Core and Surface Velocity for Water Flow in a Vortex Sediment-Extraction Chamber Measured by Using Photo Images and PTV Technique.

NASA Astrophysics Data System (ADS)

Yao, Hou Chang; Chyan Deng, Jan; Chao, Hsu Yu; Chih Yuan, Yang

2017-04-01

A vortex sediment-extraction chamber, consisted of cylindrical chamber, inflow system, bottom orifice and overflow weir, is used to separate sediment from sediment-laden water flow. A tangential inflow is introduced into a cylindrical chamber with a bottom orifice; thus, a strong vortex flow is produced there. Under actions of gravity and centrifugal force, heavier sediment particles are forced to move towards the bottom orifice, and relatively clear water flows over through the top overflow weir. The flow field in the cylindrical chamber consists of forced vortex and free vortex. When the bottom orifice is opened during the sediment-extraction process, an air core appears and changes with different settings. In this study, the air core and water surface velocity in the cylindrical chamber were measured by using a photo image process and particle tracking velocimetry (PTV), as well as numerically simulated by using a commercial software, Flow-3D.Laboratory experiments were conducted in a vortex chamber, having height of 130 cm and diameter of 48 cm. Five kinds of bottom orifice size from 1.0 cm to 3.0 cm and four kinds of inflow water discharge from 1,300cm3/s to 1,700 cm3/s were used while the inflow pipe of 3 cm in diameter was kept the same for all experiments. The characteristics of the air core and water surface velocity, and the inflow and outflow ratios under different experimental arrangements were observed and discussed so as to provide a better design and application for a vortex sediment-extraction chamber in the future.

Use of the [(14)C]leucine incorporation technique to measure bacterial production in river sediments and the epiphyton.

PubMed

Fischer, H; Pusch, M

1999-10-01

Bacterial production is a key parameter for the understanding of carbon cycling in aquatic ecosystems, yet it remains difficult to measure in many aquatic habitats. We therefore tested the applicability of the [(14)C]leucine incorporation technique for the measurement of bulk bacterial production in various habitats of a lowland river ecosystem. To evaluate the method, we determined (i) extraction efficiencies of bacterial protein from the sediments, (ii) substrate saturation of leucine in sediments, the biofilms on aquatic plants (epiphyton), and the pelagic zone, (iii) bacterial activities at different leucine concentrations, (iv) specificity of leucine uptake by bacteria, and (v) the effect of the incubation technique (perfused-core incubation versus slurry incubation) on leucine incorporation into protein. Bacterial protein was best extracted from sediments and precipitated by hot trichloroacetic acid treatment following ultrasonication. For epiphyton, an alkaline-extraction procedure was most efficient. Leucine incorporation saturation occurred at 1 microM in epiphyton and 100 nM in the pelagic zone. Saturation curves in sediments were difficult to model but showed the first level of leucine saturation at 50 microM. Increased uptake at higher leucine concentrations could be partly attributed to eukaryotes. Addition of micromolar concentrations of leucine did not enhance bacterial electron transport activity or DNA replication activity. Similar rates of leucine incorporation into protein calculated for whole sediment cores were observed after slurry and perfused-core incubations, but the rates exhibited strong vertical gradients after the core incubation. We conclude that the leucine incorporation method can measure bacterial production in a wide range of aquatic habitats, including fluvial sediments, if substrate saturation and isotope dilution are determined.

Use of the [14C]Leucine Incorporation Technique To Measure Bacterial Production in River Sediments and the Epiphyton

PubMed Central

Fischer, Helmut; Pusch, Martin

1999-01-01

Bacterial production is a key parameter for the understanding of carbon cycling in aquatic ecosystems, yet it remains difficult to measure in many aquatic habitats. We therefore tested the applicability of the [14C]leucine incorporation technique for the measurement of bulk bacterial production in various habitats of a lowland river ecosystem. To evaluate the method, we determined (i) extraction efficiencies of bacterial protein from the sediments, (ii) substrate saturation of leucine in sediments, the biofilms on aquatic plants (epiphyton), and the pelagic zone, (iii) bacterial activities at different leucine concentrations, (iv) specificity of leucine uptake by bacteria, and (v) the effect of the incubation technique (perfused-core incubation versus slurry incubation) on leucine incorporation into protein. Bacterial protein was best extracted from sediments and precipitated by hot trichloroacetic acid treatment following ultrasonication. For epiphyton, an alkaline-extraction procedure was most efficient. Leucine incorporation saturation occurred at 1 μM in epiphyton and 100 nM in the pelagic zone. Saturation curves in sediments were difficult to model but showed the first level of leucine saturation at 50 μM. Increased uptake at higher leucine concentrations could be partly attributed to eukaryotes. Addition of micromolar concentrations of leucine did not enhance bacterial electron transport activity or DNA replication activity. Similar rates of leucine incorporation into protein calculated for whole sediment cores were observed after slurry and perfused-core incubations, but the rates exhibited strong vertical gradients after the core incubation. We conclude that the leucine incorporation method can measure bacterial production in a wide range of aquatic habitats, including fluvial sediments, if substrate saturation and isotope dilution are determined. PMID:10508068

Analytical Results for 42 Fluvial Tailings Cores and 7 Stream Sediment Samples from High Ore Creek, Northern Jefferson County, Montana

USGS Publications Warehouse

Fey, David L.; Church, Stan E.

1998-01-01

Metal-mining related wastes in the Boulder River basin study area in northern Jefferson County, Montana have been implicated in their detrimental effects on water quality with regard to acid-generation and toxic-metal solubility. Sediments, fluvial tailings and water from High Ore Creek have been identified as significant contributors to water quality degradation of the Boulder River below Basin, Montana. A study of 42 fluvial tailings cores and 7 stream sediments from High Ore Creek was undertaken to determine the concentrations of environmentally sensitive elements (i.e. Ag, As, Cd, Cu, Pb, Zn) present in these materials, and the mineral phases containing those elements. Two sites of fluvial deposition of mine-waste contaminated sediment on upper High Ore Creek were sampled using a one-inch soil probe. Forty-two core samples were taken producing 247 subsamples. The samples were analyzed by ICP-AES (inductively coupled-plasma atomic emission spectroscopy) using a total mixed-acid digestion. Results of the core analyses show that the elements described above are present at very high concentrations (to 22,000 ppm As, to 460 ppm Ag, to 900 ppm Cd, 4,300 ppm Cu, 46,000ppm Pb, and 50,000 ppm Zn). Seven stream-sediment samples were also analyzed by ICP-AES for total element content and for leachable element content. Results show that the sediment of High Ore Creek has elevated levels of ore-related metals throughout its length, down to the confluence with the Boulder River, and that the metals are, to a significant degree, contained in the leachable phase, namely the hydrous amorphous iron- and manganese-hydroxide coatings on detrital sediment particles.

Evaluating the potential effects of hurricanes on long-term sediment accumulation in two micro-tidal sub-estuaries: Barnegat Bay and Little Egg Harbor, New Jersey, U.S.A.

USGS Publications Warehouse

Marot, Marci E.; Smith, Christopher G.; Ellis, Alisha M.; Wheaton, Cathryn J.

2016-06-23

This report serves as an archive for sedimentological and radiochemical data derived from the surface sediments and box cores. Downloadable data are available as Excel spreadsheets, PDF files, and JPEG files, and include sediment core data plots and x-radiographs, as well as physical-properties, grain-size, alpha-spectroscopy, and gamma-spectroscopy data. Federal Geographic Data Committee metadata are available for analytical datasets in the data downloads page of this report.

Data report: Permeabilities of eastern equatorial Pacific and Peru margin sediments

USGS Publications Warehouse

Gamage, Kusali; Bekins, Barbara A.; Screaton, Elizabeth; Jørgensen, Bo B.; D'Hondt, Steven L.; Miller, D. Jay

2006-01-01

Constant-flow permeability tests were conducted on core samples from Ocean Drilling Program Leg 201 from the eastern equatorial Pacific and the Peru margin. Eighteen whole-round core samples from Sites 1225, 1226, 1227, 1230, and 1231 were tested for vertical permeabilities. Sites 1225, 1226, and 1231 represent sediments of the open ocean, whereas Sites 1227 and 1230 represent sediments of the ocean margin. Measured vertical permeabilities vary from ~8 x 10–19 m2 to ~1 x 10–16 m2 for a porosity range of 45%–90%.

Biostratigraphic and morphometric analyses of specimens from the calcareous nannofossil genus Tribrachiatus

USGS Publications Warehouse

Self-Trail, Jean; Seefelt, Ellen L.; Shepherd, Claire L.; Martin, Victoria A.

2017-01-01

Biostratigraphic and morphometric analyses of calcareous nannofossil assemblages from one outcrop and two cored sections of lower Eocene sediments reveal the presence of two new species: Tribrachiatus lunatus sp. nov., and Tribrachiatus absidatus sp. nov. Differences between the new species and Tribrachiatus orthostylus are discussed. The first occurrence of the two new species is just below the calcareous nannofossil Zone NP11/NP12 boundary, close to the Chron 24r/23n boundary, and thus they are globally useful biostratigraphic markers.

Optically stimulated luminescence dating of sediments

NASA Astrophysics Data System (ADS)

Troja, S. O.; Amore, C.; Barbagallo, G.; Burrafato, G.; Forzese, R.; Geremia, F.; Gueli, A. M.; Marzo, F.; Pirnaci, D.; Russo, M.; Turrisi, E.

2000-04-01

Optically stimulated luminescence (OSL) dating methodology was applied on the coarse grain fraction (100÷500 μm thick) of quartz crystals (green light stimulated luminescence, GLSL) and feldspar crystals (infrared stimulated luminescence, IRSL) taken from sections at different depths of cores bored in various coastal lagoons (Longarini, Cuba, Bruno) in the south-east coast of Sicily. The results obtained give a sequence of congruent relative ages and maximum absolute ages compatible with the sedimentary structure, thus confirming the excellent potential of the methodology.

Chronology from sediment cores collected in southwestern Everglades National Park, Florida

USGS Publications Warehouse

Bernhardt, C.E.; Wingard, G.L.; Willard, D.A.; Marot, M.E.; Landacre, B.; Holmes, C.W.

2013-01-01

Age model data are presented for 10 cores from the southwestern coastal mangrove zone of Everglades National Park, Florida, collected in Common Era (CE) 2004 and 2005 and used for paleoecological analysis. Carbon-14 (14C), lead-210 (210Pb), cesium-137 (137Cs), radium-226 (226Ra), and pollen biostratigraphic information is included, and age models were generated for 6 of the 10 cores. Age reversals and sediment disturbance prevented construction of age models on the remaining four cores. Four cores present a continuous record of the last 50 to 100 years, making them useful for analyzing the impacts caused by changes in water management in south Florida. These cores are Harney River 2A and Harney River 1A, Shark River 2A, and Roberts River.

Postimpact heat conduction and compaction-driven fluid flow in the Chesapeake Bay impact structure based on downhole vitrinite reflectance data, ICDP-USGS Eyreville deep core holes and Cape Charles test holes

USGS Publications Warehouse

Malinconico, M.L.; Sanford, W.E.; Wright, Horton W.J.J.

2009-01-01

Vitrinite reflectance data from the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville deep cores in the centralcrater moat of the Chesapeake Bay impact structure and the Cape Charles test holes on the central uplift show patterns of postimpact maximum-temperature distribution that result from a combination of conductive and advective heat flow. Within the crater-fill sediment-clast breccia sequence at Eyreville, an isoreflectance (-0.44% Ro) section (525-1096 m depth) is higher than modeled background coastal-plain maturity and shows a pattern typical of advective fluid flow. Below an intervening granite slab, a short interval of sediment-clast breccia (1371-1397 m) shows a sharp increase in reflectance (0.47%-0.91% Ro) caused by conductive heat from the underlying suevite (1397-1474 m). Refl ectance data in the uppermost suevite range from 1.2% to 2.1% Ro. However, heat conduction alone is not sufficient to affect the temperature of sediments more than 100 m above the suevite. Thermal modeling of the Eyreville suevite as a 390 ??C cooling sill-like hot rock layer supplemented by compaction- driven vertical fluid flow (0.046 m/a) of cooling suevitic fluids and deeper basement brines (120 ??C) upward through the sediment breccias closely reproduces the measured reflectance data. This scenario would also replace any marine water trapped in the crater fill with more saline brine, similar to that currently in the crater, and it would produce temperatures sufficient to kill microbes in sediment breccias within 450 m above the synimsuevite. A similar downhole maturity pattern is present in the sediment-clast breccia over the central uplift. High-reflectance (5%-9%) black shale and siltstone clasts in the suevite and sediment-clast breccia record a pre-impact (Paleozoic?) metamorphic event. Previously published maturity data in the annular trough indicate no thermal effect there from impact-related processes. ?? 2009 The Geological Society of America.

Freeze shoe sampler for the collection of hyporheic zone sediments and porewater.

PubMed

Bianchin, M; Smith, L; Beckie, R

2015-01-01

The Starr and Ingleton (1992) drive point piston sampler (DPPS) design was modified by fitting it with a Murphy and Herkelrath (1996) type sample-freezing drive shoe (SFDS), which uses liquid carbon dioxide as a cryogen. Liquid carbon dioxide was used to freeze sediments in the lower 0.1 m of the core and the drive-point piston sealed the core at the top preserving the reductive-oxidation (redox) sensitive sediments from the atmosphere and maintaining natural stratigraphy. The use of nitrogen gas to provide positive pressure on the gas system blocked the ingress of water which froze on contact with the cryogen thus blocking the gas lines with ice. With this adaptation to the gas system cores could be collected at greater depths beneath the static water level. This tool was used to collect intact saturated sediment cores from the hyporheic zone of the tidally influenced Fraser River in Vancouver, British Columbia, Canada where steep geochemical and microbial gradients develop within the interface between discharging anaerobic groundwater and recharging aerobic river water. In total, 25 cores driven through a 1.5 m sampling interval were collected from the river bed with a mean core recovery of 75%. The ability to deploy this method from a fishing vessel makes the tool more cost effective than traditional marine-based drilling operations which often use barges, tug boats, and drilling rigs. © 2014, National Ground Water Association.

Sediment records of Yellow River channel migration and Holocene environmental evolution of the Hetao Plain, northern China

NASA Astrophysics Data System (ADS)

Wang, Jingzhong; Wu, Jinglu; Pan, Baotian; Jia, Hongjuan; Li, Xiao; Wei, Hao

2018-05-01

The origin and evolution of lakes in the Hetao Plain, northern China, were influenced by climate variation, channel migration, and human activity. We analyzed a suite of sediment cores from the region to investigate Yellow River channel migration and environmental change in this region over the Holocene. Short sediment cores show that environmental indicators changed markedly around CE 1850, a time that corresponds to flood events, when large amounts of river water accumulated in the western part of the Hetao Plain, giving rise to abundant small lakes. Multiple sediment variables (environmental proxies) from two long cores collected in the Tushenze Paleolake area show that sediments deposited between 12.0 and 9.0 cal ka BP were yellow clay, indicative of fluvial deposition and channel migration. From 9.0 to 7.5 cal ka BP, sand was deposited, reflecting a desert environment. From 7.5 to 2.2 cal ka BP, however, the sediments were blue-gray clay that represents lacustrine facies of Lake Tushenze, which owes its origin to an increase in strength of the East Asian monsoon. At about 2.2 cal ka BP, the north branch of the Yellow River was flooded, and the Tushenze Paleolake developed further. Around 2.0 cal ka BP, the paleolake shrank and eolian sedimentation was recorded. The analyzed sediment records are consistent with the written history from the region, which documents channel migration and environmental changes in the Hetao Plain over the Holocene.

Magnetic Hysteresis of Deep-Sea Sediments in Korea Deep Ocean Study(KODOS) Area, NE Pacific

NASA Astrophysics Data System (ADS)

Kim, K.; Park, C.; Yoo, C.

2001-12-01

The KODOS area within the Clarion-Clipperton fracture zone (C-C zone) is surrounded by the Hawaiian and Line Island Ridges to the west and the central American continent to the east. Topography of the seafloor consists of flat-topped abyssal hills and adjacent abyssal troughs, both of which run parallel in N-S direction. Sediments from the study area consist mainly of biogenic sediments. Latitudinal zonation of sedimentary facies was caused by the accumulation of biogenic materials associated with the equatorial current system and movement of the Pacific plate toward the north or northwest. The KODOS area belongs to the latitudinal transition zone having depositional characteristics between non-fossiliferous pelagic clay-dominated zone and calcareous sediment-dominated zone. The box core sediments of the KODOS area are analyzed in an attempt to obtain magnetic hysteresis information and to elucidate the relationship between hysteresis property and lithological facies. Variations in magnetic hysteresis parameters with unit layers reflect the magnetic grain-size and concentrations within the sediments. The ratios of remanant coercivity/coercive force (Hcr/Hc) and saturation remnance/saturation magnetization (Mrs/Ms) indicate that coarse magnetic grains are mainly distributed in dark brown sediments (lower part of the sediment core samples) reflecting high Hcr/Hc and low Mrs/Ms ratios. These results are mainly caused by dissolution differences with core depth. From the plotting of the ratios of hyteresis parameters, it is indicated that magnetic minerals in cubic samples are in pseudo-single domain (PSD) state.

Trace metal concentrations in tropical mangrove sediments, NE Brazil.

PubMed

Miola, Brígida; Morais, Jáder Onofre de; Pinheiro, Lidriana de Souza

2016-01-15

Sediment cores were taken from the mangroves of the Coreaú River estuary off the northeast coast of Brazil. They were analyzed for grain size, CaCO3, organic matter, and trace metal (Cd, Pb, Zn, Cu, Al, and Fe) contents. Mud texture was the predominant texture. Levels of trace metals in surface sediments indicated strong influence of anthropogenic processes, and diagenetic processes controlled the trace metal enrichment of core sediments of this estuary. The positive relationships between trace metals and Al and Fe indicate that Cu, Zn, Pb, and Cd concentrations are associated mainly with Al and Fe oxy-hydroxides and have natural sources. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sediment characteristics and configuration within the Otsego City Dam impoundment on the Kalamazoo River, Michigan, 2001-02

USGS Publications Warehouse

Rheaume, S.J.; Hubbell, D.L.; Rachol, C.M.; Simard, A.; Fuller, L.M.

2004-01-01

The removal of the Otsego City Dam on the Kalamazoo River at Otsego, Mich., is under consideration by the Michigan Department of Environmental Quality and the city of Otsego. The historical discharge of papermill waste containing polychlorinated biphenyls from sources upstream from the dam has led the U.S. Environmental Protection Agency to designate the Kalamazoo River from Morrow Dam near Comstock to its mouth near Saugatuck as a Federal Superfund site. The papermill waste is concentrated in organic sediment and kaolinite clay, with the sediment containing as much as 94 milligrams per kilogram polychlorinated biphenyls. This contaminated sediment could move if the dam is removed; therefore, it is necessary to estimate the characteristics and configuration of the sediment before removal plans begin. Data from augered sections and sediment cores show that the current Otsego City impoundment sediments were deposited in two distinctly different sedimentary environments: (1) lacustrine sediments consisting of organic-rich silt and clay, fine to medium sand, and some gravel deposited in a repetitive, cyclic fashion related to former stream velocities when the Otsego City impoundment water levels were 2-4 feet higher (1880s-1960s), and from downstream movement of lacustrine sediments during the removal of the upstream Plainwell Dam superstructure in the 1980s; and (2) more recent (1980s-2002) coarse-grained alluvium deposited on top of the lacustrine sediments. The volume of instream sediment contained within the Otsego City impoundment is estimated to be about 457,270 cubic yards. This estimate is based on the composite thicknesses of the lacustrine deposits and overlying alluvium, which were determined to contain PCBs, and does not include bank or flood-plain deposits.

Polychlorinated biphenyl congeners in sediment cores from the Upper Mississippi River

PubMed Central

Martinez, Andres; Schnoebelen, Douglas J.; Hornbuckle, Keri C.

2015-01-01

We determined polychlorinated biphenyls (PCBs) and radionuclide 137Cs in sediment cores from the Upper Mississippi River (UMR) and the Iowa River, Iowa, at their confluence. Vertical distribution of 137Cs indicated negligible mixing in the UMR core, while the Iowa River core showed signs of mixing. A clear 137Cs peak was found in the UMR core, which was correlated to 1963. The PCB vertical distribution in UMR core was similar to the historical trend in Aroclor production observed in Great Lakes cores, with a peak close to the 137Cs peak, suggesting a date near 1960. In general, PCB congener profiles in both cores resembled the Iowa soil background signal. We concluded that despite evidence of mixing in the Iowa River core, both cores retain the PCB signature of historical and regional environmental exposure. Further, our results indicate that this iconic waterway has a long history of PCBs that reflects national production and use. PMID:26547030

Distributions, Early Diagenesis, and Spatial Characteristics of Amino Acids in Sediments of Multi-Polluted Rivers: A Case Study in the Haihe River Basin, China.

PubMed

Zhao, Yu; Shan, Baoqing; Tang, Wenzhong; Zhang, Hong; Rong, Nan; Ding, Yuekui

2016-02-19

The Haihe River Basin, which is one of the most water-scarce and polluted river basins in China, has abnormally high nitrogen levels. In this study, total hydrolyzable amino acids (THAAs) were measured in surface sediment and sediment core samples in the Haihe River Basin to determine if amino acids were potential sources of ammonium, organic nitrogen, and organic carbon. The rivers were found to be in a state of hypoxia and contain abnormally high levels of ammonium and organic nitrogen. Additionally, NH₃-N was the predominant form of inorganic nitrogen in the surface sediments, while organic nitrogen accounted for 92.53% of sedimentary nitrogen. THAAs-C accounted for 14.92% of the total organic carbon, while THAAs-N accounted for more than 49.59% of organic nitrogen and 45.68% of total nitrogen. The major fraction of THAAs were protein amino acids. Three sediment cores of the most heavily polluted rivers also showed high levels of THAAs. Evaluation of the degradation index (DI) of sedimentary organic matter in sediments evaluated based on the THAAs revealed that most positive DI values were found in the downstream portion of the Ziya River Watershed. Additionally, the DI of surface sediment was correlated with THAAs (r² = 0.763, p < 0.001), as was the DI of sediment cores (r² = 0.773, p < 0.001). Overall, amino acids in sediments were found to be an important potential source of ammonium, organic nitrogen, and organic carbon.

Spatial and temporal variations of Rb/Sr ratios of the bulk surface sediments in Lake Qinghai

PubMed Central

2010-01-01

The Rb/Sr ratios of lake sediments have been suggested as indicators of weathering intensity by increasing work. However, the geochemistry of Rb/Sr ratios of lake sediments is variable between different lakes. In this study, we investigated the spatial and temporal patterns of Rb/Sr ratios, as well as those of other major elements in surface sediments of Lake Qinghai. We find that the spatial pattern of Rb/Sr ratios of the bulk sediments correlates well with that of the mass accumulation rate, and those of the terrigenous fractions, e.g., SiO2, Ti, and Fe. The temporal variations of Rb/Sr ratios also synchronize with those of SiO2, Ti, and Fe of each individual core. These suggest that Rb/Sr ratios of the surface sediments are closely related to terrigenous input from the catchment. Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal scales; however, the other cores do not show such relationship. The result of this study suggests that physical weathering and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales. Therefore, it is necessary to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before it is used as an indicator of weathering intensity of the catchment. PMID:20615264