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Sample records for abyssal plain sediments

  1. Northwest African Continental Margin: History of sediment accumulation, landslide deposits, and hiatuses as revealed by drilling the Madeira Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Weaver, P. P. E.

    2003-03-01

    ODP drill sites in the Madeira Abyssal Plain reveal sequences of organic-rich turbidites derived from the northwest African margin, in which each turbidite has a volume of tens to hundreds of cubic kilometers. The frequency of turbidite emplacement has been combined with core and seismic data to show the volume of redeposited sediment. The basin began to fill about 22 Ma with numerous small turbidites, up to 100 per million years, each with volumes of a few cubic kilometers. The total volume of turbidites deposited increased between 16 and 11 Ma, as did their individual volumes, and then declined to 7 Ma. At 7 Ma, there was a dramatic increase in the amount of turbidite input to 768 km3/Myr and a rise in the average volume of each unit to 59 km3. These high values have been maintained to the present day. The variations in the amount of redeposited sediment most likely reflect the rates of sedimentation on the northwest African margin since high sedimentation leads to oversteepening of the slopes and eventual mass wasting. The dramatic changes at about 7 Ma may be due to a large increase in upwelling off northwest Africa caused by circulation changes associated with increased glaciation of the poles. Up to 20% of sediment may be remobilized by landslides, with each event leaving a hiatus. Each of these hiatuses extends over an average area of 4800 km2 and represents removal of sediment layers several tens of meters thick and of several hundred thousand years duration.

  2. Acoustic environment of the Hatteras and Nares Abyssal Plains, western North Atlantic Ocean, determined from velocities and physical properties of sediment cores

    SciTech Connect

    Tucholke, B.E.

    1980-11-01

    Seventeen piston cores up to 13 m long were recovered from representative acoustic and lithologic environments of the Hatteras and Nares Abyssal Plains in the western North Atlantic. Compressional-wave velocities (corrected to in situ conditions) and bulk physical properties measured on the cores are used to characterize the acoustic framework of these areas. For correlation with conventional seismic data, whole-core averages of properties are a better index to the acoustic nature of abyssal plain sediments than properties of the upper few centimeters of the seafloor because (1) strong changes in lithofacies (and acoustic properties) occur over depth scales of tens of centimeters to meters in the sediment column, and (2) conventional seismic frequencies of 3.5 kHz or less sample these variations to subbottom depths of tens of meters and more. Whole-core properties are a function of the thickness and distribution of high-velocity silt and sand layers in the core; they vary in a complex fashion with proximity to the source of turbidity currents, distance from axial paths of turbidity-current flows, local and regional basin geometry, and seafloor slope. Thus strongly reflective seabed regions with numerous high-velocity layers are not restricted simply to near-source areas nor are weakly reflective seabed regions (clay sediments only) limited to ''distal'' areas. Whole-core properties show a good qualitative correlation to variations in 3.5-kHz reflection profiles, and 3.5-kHz echo character therefore provides a useful means of mapping general acoustic properties over large regions of abyssal plains.

  3. Bioturbation, geochemistry and geotechnics of sediments affected by the oxygen minimum zone on the Oman continental slope and abyssal plain, Arabian Sea

    NASA Astrophysics Data System (ADS)

    Meadows, Azra; Meadows, Peter S.; West, Fraser J. C.; Murray, John M. H.

    2000-01-01

    We investigate the way the oxygen minimum zone (OMZ) alters interactions between bioturbation and sediment geochemistry, and geotechnical properties. Sediments are compared within and below the OMZ on the Oman continental slope and adjacent abyssal plain during the post monsoonal autumn season. Quantitative measurements were made of Eh and pH, of total organic matter (TOM) and carbonate, of water content and shear strength, and of bioturbation structures in vertical profiles of subcores taken from spade-box core samples. The OMZ stations had distinctively low redox conditions and high carbonate content, and different geotechnical properties and different bioturbation structures than stations below the OMZ on the abyssal plain. These differences are related to the degree of anoxia and to water depth. Within the OMZ, Eh, pH and carbonate increased with water depth, and TOM and water content decreased. We also noted the presence of subsurface sediment heterogeneity on the continental slope within the OMZ. In the OMZ, Eh, water content and bioturbation decreased with increasing sediment depth. There was a slight decrease in pH in the top 5 cm at all stations. Shear strength nearly always increased with increasing sediment depth. At each water depth correlations show down-core trends in these parameters, while across all water depths correlations were significant at deeper sediment depths (20-30 cm). An Eh-pH diagram identified two water-depth groupings: 391-1008 and 1265-3396 m. Cluster analysis showed the upper and lower sediment depths form separate clusters, the break occurring at 4-7.5 cm; while there are also distinct clusters related to water depth. We relate our results to bottom-water oxygen concentrations reported by other investigators, and to regional-scale geochemical processes.

  4. Abyssal plains heat exchange could explain global deficit

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-07-01

    When researchers measure the amount of heat flowing conductively from the seafloor to the ocean waters and then compare that value against a theoretical prediction of that heat loss, they observe that the global average measured heat flow is lower than expected. Researchers think that advection, a heat transfer mechanism that is difficult to measure, makes up this difference between predicted and observed heat exchange. They suggest that as seawater circulates through the permeable upper layers of the seafloor crust, driven by a thermal gradient, the water accumulates heat, drawing it into the ocean. Scientists have recently proposed that seafloor sediment plays an important role in controlling the geometry of such intraocean crust circulation. In the abyssal plains, the accumulation of millions of years' worth of low permeability sediment limits direct contact between the ocean and the crust. Where the sediment is thin or absentfor example, at outcropswater is thought to be able to move between the ocean and the crust. Scientists propose that seawater can travel through the crust for tens of kilometers beneath the sediment, moving laterally from outcrop to outcrop.

  5. GLORIA side-scan imagery of Aleutian basin, Bering Sea slope and Abyssal plain

    SciTech Connect

    Carlson, P.R.; Cooper, A.K.; Gardner, J.V.; Karl, H.A.; Marlow, M.S.; Stevenson, A.J.; Huggett, Q.; Kenyon, N.; Parson, L.

    1987-05-01

    During July-September 1986, about 700,000 km/sup 2/ of continental slope and abyssal plain of the Aleutian basin, Bering Sea, were insonified with GLORIA (Geological Long Range Inclined Asdic) side-scane sonar. A sonar mosaic displays prominent geomorphic features including the massive submarine canyons of the Beringian and the northern Aleutian Ridge slopes and shows well-defined sediment patterns including large deep-sea channels and fan systems on the Aleutian basin abyssal plain. Dominant erosional and sediment transport processes on both the Beringian and the Aleutian Ridge slopes include varieties of mass movement that range from small debris flows and slides to massive slides and slumps of blocks measuring kilometers in dimension. Sediment-flow patterns that appear to be formed by sheet flow rather than channelized flow extend basinward from the numerous canyons and gullies that incise the slopes of the Beringian margin and of Bowers Ridge and some places along the Aleutian Ridge. These Beringian and Bowers canyon sediment sources, however, appear to have contributed less modern sediment to the Aleutian basin than the large, well-defined channel systems that emanate from Bering, Umnak, and Amchitka submarine canyons and extend for several hundred kilometers across the abyssal plain. This GLORIA imagery emphasizes the important contribution of the Aleutian Ridge to modern sedimentation in the deep Bering Sea.

  6. An abyssal hill fractionates organic and inorganic matter in deep-sea surface sediments

    NASA Astrophysics Data System (ADS)

    Turnewitsch, Robert; Lahajnar, Niko; Haeckel, Matthias; Christiansen, Bernd

    2015-09-01

    Current estimates suggest that more than 60% of the global seafloor are covered by millions of abyssal hills and mountains. These features introduce spatial fluid-dynamic "granularity" whose influence on deep-ocean sediment biogeochemistry is unknown. Here we compare biogeochemical surface-sediment properties from a fluid-dynamically well-characterized abyssal hill and upstream plain: (1) In hill sediments, organic-carbon and -nitrogen contents are only about half as high as on the plain while proteinaceous material displays less degradation; (2) on the hill, more coarse-grained sediments (reducing particle surface area) and very variable calcite contents (influencing particle surface charge) are proposed to reduce the extent, and influence compound-specificity, of sorptive organic-matter preservation. Further studies are needed to estimate the representativeness of the results in a global context. Given millions of abyssal hills and mountains, their integrative influence on formation and composition of deep-sea sediments warrants more attention.

  7. Late Quarternary evolution of the northern Hatteras Abyssal Plain. [LLW Ocean Disposal Program

    SciTech Connect

    Dickson, S.M.; Laine, E.P.

    1986-05-01

    The sedimentary history and seismic structure of a deep-water turbidite basin in the Western North Atlantic Ocean has been investigated to understand further the evolution of abyssal plains. This study integrates analyses of sedimentary and seismic facies in order to examine the temporal and spatial patterns of sedimentation on the northern Hatteras Abyssal Plain during the Late Quaternary. Forty deep-sea sediment cores and 6000 km of high resolution (3.5 kHz) seismic reflection profiles from within 31-34/sup 0/N and 69-74/sup 0/W include portions of the Hatteras Outer Ridge, Lower Continental Rise and Bermuda Rise as well as the northern Hatteras Abyssal Plain. Seismic profiles (within 32-33/sup 0/N, 70-71.5/sup 0/W) define two acoustically-transparent seismic units beneath the Plain. The composition of these seismic units has been investigated with sediment cores. This study has found two notable features in the sedimentary framework of the Plain that appear to have resulted from temporal changes in sediment supply. The most recent change, a postglacial decline in turbidity current activity, produced a diagenetic iron enrichment at the Pleistocene-Holocene boundary. The stratigraphic thickness affected by diagenesis is related spatially to patterns of turbidite sedimentation. An earlier change, discovered in this research, occurred during the Wisconsinian glaciation and brought coarser-grained turbidity currents to the northern Plain. Deposition of sands from these flows appears to have been locally controlled by a broad topographic feature with less than ten meters relief. As a result of the topographic influence, there are abrupt boundaries, both verically and laterally, between an older mud facies and a younger sandy turbidite facies of the Plain.

  8. Unexpectedly higher metazoan meiofauna abundances in the Kuril-Kamchatka Trench compared to the adjacent abyssal plains

    NASA Astrophysics Data System (ADS)

    Schmidt, Christina; Martínez Arbizu, Pedro

    2015-01-01

    We studied meiofauna standing stocks and community structure in the Kuril-Kamchatka Trench and its adjacent abyssal plains in the northwestern Pacific Ocean. In general, the Nematoda were dominant (93%) followed by the Copepoda (4%). Nematode abundances ranged from 87% to 96%; those of copepods from 2% to 7%. The most diverse deployment yielded 17 taxa: Acari, Amphipoda, Annelida, Bivalvia, Coelenterata, Copepoda, Cumacea, Gastrotricha, Isopoda, Kinorhyncha, Loricifera, Nematoda, Ostracoda, Priapulida, Tanaidacea, Tantulocarida, and Tardigrada. Nauplii were also present. Generally, the trench slope and the southernmost deployments had the highest abundances (850-1392 individuals/cm2). The results of non-metric multidimensional scaling indicated that these deployments were similar to each other in meiofauna community structure. The southernmost deployments were located in a zone of higher particulate organic carbon (POC) flux (g Corg m-2 yr-1), whereas the trench slope should have low POC flux due to depth attenuation. Also, POC and abundance were significantly correlated in the abyssal plains. This correlation may explain the higher abundances at the southernmost deployments. Lateral transport was also assumed to explain high meiofauna abundances on the trench slope. Abundances were generally higher than expected from model results. ANOSIM revealed significant differences between the trench slope and the northern abyssal plains, between the central abyssal plains and the trench slope, between the trench slope and the southern abyssal plains, between the central and the southern abyssal plains, and between the central and northern deployments. The northern and southern abyssal plains did not differ significantly. In addition, a U-test revealed highly significant differences between the trench-slope and abyssal deployments. The taxa inhabited mostly the upper 0-3 cm of the sediment layer (Nematoda 80-90%; Copepoda 88-100%). The trench-slope and abyssal did not differ in occupancy of the top layer. Furthermore, sediment depth and abundance were strongly correlated, but the sediment texture itself and the grain sizes showed only slight correlations with abundance. In the trench slope no correlation between sediment texture and abundance was found. We suggest that sediment is not the only factor that affects meiofauna abundance in the study area. The results of our study were compared with other trench and nontrench studies, and in most cases, the abundance decreases with depth initially but increases again below a certain depth, especially in deep-sea trenches below productive waters. No generalization can be made, however, about the depth at which the reversal occurs; it depends on the area of investigation and on a mixture of many other factors (e.g., sediment heterogeneity, oxygen, redox potential, proximity to land masses, and season).

  9. An Evaluation of Neogene Sedimentation on the Surveyor Fan, Gulf of Alaska: Geochemical, Mineralogical, and Rock Magnetic Provenance Variation in Alaskan Abyssal Plain Sediments

    NASA Astrophysics Data System (ADS)

    Jaeger, J. M.; Ullrich, A. D.

    2011-12-01

    Glaciated orogenic belts such as those of southeastern Alaska provide ideal environments in which to investigate climate-tectonic interactions because of significant glacigenic sediment production and transport along an active plate boundary. The sedimentary record of this interaction has a high potential for preservation in adjacent basins like the Gulf of Alaska because of a reduced transport distance from sediment source to deepwater sink. The Surveyor Fan in the northern Gulf of Alaska contains seismic stratigraphic evidence of a substantial shift in sedimentation type and source. Based on limited age control from DSDP Site 178 this shift occurs at ~1 Ma, which approximately correlates to increased glacial sediment input and accelerated exhumation of onshore terranes. This coincides with significantly increased global glaciation following the Mid-Pleistocene Transition (MPT). We hypothesize that the compositional changes in Surveyor Fan fine-grain sediments observed at Site 178 are related to intensified glaciation at 1 Ma, which resulted in focused erosion along the windward side of the St. Elias Range, as well as formation of cross-shelf sea valleys that isolated sediment transport pathways to the Surveyor Channel. Here, we address this hypothesis by developing preliminary source terrane signatures of fine-grained sediment and applying them to offshore sediments of the Surveyor Fan at DSDP Site 178. This is done by employing multiple analytical tools shown to be effective in previous provenance studies, including trace and major elemental geochemistry, quantitative mineralogy, and environmental magnetic properties. The results of these analyses indicate that the provenance of the likely source end-members (Orca and Valdez Groups of the Prince William Terrane, the Chugach Terrane, and the Kulthieth/Poul Creek Formations) along the windward side of the St. Elias Range can be differentiated using a combination of these techniques. Fine-grained sediments from the Orca and Valdez Groups (OVG) of the Prince William Terranes and the Kulthieth Formation of the Yakutat Terrane represent relatively more mafic and felsic compositional end members, respectively, with Chugach Terrane samples of intermediate composition, but with distinct environmental magnetic properties. Poul Creek Formation samples are most similar to the Kultieth, but with the addition from a more mafic source. Samples of the youngest onshore source, the Yakataga Formation, reflect a mixing of sources. DSDP 178 samples are of an intermediate composition between felsic and mafic end members, but with no apparent bulk fine-grain compositional difference between Upper and Mid-Lower Fan constituents. However, the variability in elemental composition is significantly decreased in Upper Fan sediments supporting the hypothesis that transport pathways to Site 178 were isolated following the MPT at ~ 1 Ma.

  10. Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Phillips, R.L.; Mullen, M.W.; Starratt, S.W.; Jones, Glenn A.; Naidu, A.S.; Finney, B.P.

    1996-01-01

    Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010??120 yr has consisted of a continuing rain of pelagic organic and ice-rafted elastic sediment with a net accumulation rate during the late Holocene of ???10 mm/1000 yr, and episodically emplaced turbidites 1-5 m thick deposited at intervals of 830 to 3450 yr (average 2000 yr). The average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1.2 m/1000 yr. Physiography suggests that the turbidites originated on the Mackenzie Delta or its clinoform, and ??13C values of -27 to - 25??? in the turbidites are compatible with a provenance on a delta. Extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units. Their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the Canada Abyssal Plain. The presence of Middle Pleistocene diatoms in the turbidites suggests, in addition, that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf. Small but consistent differences in organic carbon content and ??13C values between the turbidite units suggest that they did not share an identical provenance, which is at least compatible with an origin in slope failures. The primary provenance of the ice-rafted component of the pelagic beds was the glaciated terrane of northwestern Canada; and the provenance of the turbidite units was Pleistocene and Holocene sedimentary deposits on the outer continental shelf and upper slope of the Mackenzie Delta. Largely local derivation of the sediment of the Canada Abyssal Plain indicates that sediment accumulation rates in the Arctic Ocean are valid only for regions with similar depositional sources and processes, and that these rates cannot be extrapolated regionally. The location of an elliptical zone of active seismicity over the inferred provenance of the turbidites suggests that they were triggered by large earthquakes. Distal turbidite sediment accumulation rates were more than two orders of magnitude greater than pelagic sediment accumulation rates on the Canada Abyssal Plain during the last 8000 years. This disparity reconciles the discrepancy between the high accumulation rates assumed by some for the Arctic Ocean because of the numerous major rivers and large ice sheets that discharge into this small mediterranean basin and the low pelagic sedimentation rates that have been reported from the Arctic Ocean.

  11. Seafloor Mapping of the Southeast Iberian Continental Slope and Western Algero-Balearic Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Lastras, G.; Canals, M.; León, C.; Elvira, E.; Pascual, L.; Muñoz, A.; de Cárdenas, E.; Acosta, J.

    2014-12-01

    We present the multibeam bathymetry and derived maps of the southeast Iberian margin from Cabo de Palos to Cabo de Gata, 37º35'N to 35º45'N and 2º10'W to 0º20'E, from the coastline down to the Algero-Balearic abyssal plain at depths exceeding 2,600 m. Data were obtained during different surveys in 2004, 2006 and 2007 on board R/V Vizconde de Eza with a Simrad EM300 multibeam echo-sounder, as part of the CAPESME Project, a collaboration between the Spanish Institute of Oceanography (IEO) and General Secretariat of Fisheries (SGP), aiming at creating maps of the fishing grounds of the Mediterranean continental margins of Spain. The edition of the maps has been carried out within the Complementary Action VALORPLAT (Scientific valorisation of multibeam bathymetry data from the Spanish continental shelf and slope), funded by the Spanish Ministry of Economy and Competitivity. Multibeam bathymetry data from the continental shelf obtained within the ESPACE project, also in a cooperative frame between IEO and SGP, completes the whole picture from the coastline to the deep abyssal plain. The map series is constituted by a general map at 1:400,000 scale and 14 detailed maps at 1:75,000 scale, which include inset maps on slope gradients and seafloor nature (rock or sediment type), the later obtained with rock dredges and Shipeck sediment dredges. Both the detailed maps and the general map are available in paper print, and the whole collection is also distributed in an edited USB. The geological features displayed in the different maps include the continental shelf, with abundant geomorphic features indicative of past sea-level changes, the continental slope carved by a large number of submarine canyons and gullies, including Palos, Tiñoso, Cartagena Este, Cartagena Oeste, Águilas, Almanzora, Alias, Garrucha and Gata submarine canyons, the Mazarrón, Palomares and Al-Mansour escarpments of probable tectonic origin, the Abubácer, Maimonides and Yusuf ridges, the Águilas and Al-Mansour seamounts, and the Algero-Balearic abyssal plain where prominent halokinetic deformation structures have been observed.

  12. Variability in ultraplankton at the Porcupine Abyssal Plain study site

    NASA Astrophysics Data System (ADS)

    Martin, Adrian P.; Zubkov, Mikhail V.; Holland, Ross J.; Tarran, Glen; Burkill, Peter

    2010-08-01

    Observations of the ultraplankton (<5 μm) are presented from a 4 day mesoscale survey centred on the Porcupine Abyssal Plain (PAP) study site (49°00'N 16°30'W), in July 2006. The organisms enumerated include two groups of phytoplankton, Synechococcus cyanobacteria, heterotrophic bacteria, large viruses, and two size classes of heterotrophic protist. The dataset comprises over 400 samples from the mixed layer taken over a 100 × 100 km 2 area at a spatial resolution of typically 2-3 km. For phytoplankton and heterotrophic bacteria there is a clear bimodal structure to the histograms of abundance indicative of two distinct communities in the region. Using the strong bimodality of one of the phytoplankton groups' histogram as a basis, the dataset is split into two subsets, with roughly 200 points in each, corresponding to the two histogram peaks. Doing so provides evidence that Synechococcus and viruses may also have a bimodal structure. Correlations between all pairings of these five organisms (both phytoplankton groups, Synechococcus, heterotrophic bacteria and viruses) are positive and quite high (r>0.7). The two communities can therefore be characterised as high and low abundance. Although there is a coincidence of low abundances with high temperatures in the southwest corner of the region, where there was known to be an eddy present, the spatial distributions of these organisms over the whole region is poorly predicted by temperature (or salinity or density). Furthermore, the spatial distributions of heterotrophic protists are found to differ strongly from those of the other organisms, having a unimodal structure and no obvious large scale structure. The more random structure of the heterotrophs' spatial distribution compared to their prey is consistent with previous results from the continental shelf, but is demonstrated for the open ocean here for the first time. Spatial variability is a large potential source of error in point samples, such as those comprising time series or transect cruises, unless a sufficient number of samples are taken. This large dataset is further used to provide guidance on the number of samples that would be required to estimate the mean abundance for the organisms accurately in this spatially variable region. Even if the bimodal structure was known initially, many of the organisms would require 10 or more samples to estimate the mean with 25% accuracy.

  13. Distribution and diversity of holothuroids (Echinodermata) on Cascadia Basin and Tufts Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Carney, Robert S.; Carey, Andrew G.

    1982-05-01

    The pattern of diversity, species composition, and inter-sample similarity of the holothuroid fauna was examined for 95 beam trawl samples from below 2000 m on the Cascadia Basin and Tufts Abyssal Plain off Oregon, U.S.A. Abundance as inferred from catch size, diversity, species composition, and zonation all showed major change over the sampled area where there was a depth change. Where depth remained relatively constant across the floor of Cascadia Basin, faunal changes were minor in spite of progressive isolation from land. Overall bathymetric patterns of zonation and diversity were basically like those found for other faunal groups in the deep-sea depth. The distribution of minor species indicated that the holothuroid fauna at the base of the continental slope, the apron of Astoria Fan, and near Cascadia Channel might be slightly different from that at similar depths elsewhere in the sampled area. The marked uniformity of the holothuroid fauna across the basin floor appeared to be restricted to epifaunal sediment-feeding species. Infaunal forms were more abundant at the slope base, similar to previous findings for the macro-infauna.

  14. Links between surface productivity and deep ocean particle flux at the Porcupine Abyssal Plain sustained observatory

    NASA Astrophysics Data System (ADS)

    Frigstad, H.; Henson, S. A.; Hartman, S. E.; Omar, A. M.; Jeansson, E.; Cole, H.; Pebody, C.; Lampitt, R. S.

    2015-10-01

    In this study we present hydrography, biogeochemistry and sediment trap observations between 2003 and 2012 at Porcupine Abyssal Plain (PAP) sustained observatory in the Northeast Atlantic. The time series is valuable as it allows for investigation of the link between surface productivity and deep ocean carbon flux. The region is a perennial sink for CO2, with an average uptake of around 1.5 mmol m-2 day-1. The average monthly drawdowns of inorganic carbon and nitrogen were used to quantify the net community production (NCP) and new production. Seasonal NCP and new production were found to be 4.57 0.85 mol C m-2 and 0.37 0.14 mol N m-2, respectively. The C : N ratio was high (12) compared to the Redfield ratio (6.6), and the production calculated from carbon was higher than production calculated from nitrogen, which is indicative of carbon overconsumption. The export ratio and transfer efficiency were 16 and 4 %, respectively, and the site thereby showed high flux attenuation. Particle tracking was used to examine the source region of material in the sediment trap, and there was large variation in source regions, both between and within years. There were higher correlations between surface productivity and export flux when using the particle-tracking approach, than by comparing with the mean productivity in a 100 km box around the PAP site. However, the differences in correlation coefficients were not significant, and a longer time series is needed to draw conclusions on applying particle tracking in sediment trap analyses.

  15. Long-term change in the megabenthos of the Porcupine Abyssal Plain (NE Atlantic)

    NASA Astrophysics Data System (ADS)

    Billett, D. S. M.; Bett, B. J.; Rice, A. L.; Thurston, M. H.; Galron, J.; Sibuet, M.; Wolff, G. A.

    A radical change in the abundance of invertebrate megafauna on the Porcupine Abyssal Plain is reported over a period of 10 years (1989-1999). Actiniarians, annelids, pycnogonids, tunicates, ophiuroids and holothurians increased significantly in abundance. However, there was no significant change in wet weight biomass. Two holothurian species, Amperima rosea and Ellipinion molle, increased in abundance by more than two orders of magnitude. Samples from the Porcupine Abyssal Plain over a longer period (1977-1999) show that prior to 1996 these holothurian species were always a minor component of the megafauna. From 1996 to 1999 A. rosea was abundant over a wide area of the Porcupine Abyssal Plain indicating that the phenomenon was not a localised event. Several dominant holothurian species show a distinct trend in decreasing body size over the study period. The changes in megafauna abundance may be related to environmental forcing (food supply) rather than to localised stochastic population variations. Inter-annual variability and long-term trends in organic matter supply to the seabed may be responsible for the observed changes in abundance, species dominance and size distributions.

  16. Evidences of intraplate deformation in the West Madeira Abyssal Plain (eastern North Atlantic) from seismic reflection and multibeam swath bathymetry data

    NASA Astrophysics Data System (ADS)

    Roque, C.; Simões, M.; Lourenço, N.; Pinto de Abreu, M.

    2009-04-01

    The West Madeira Abyssal Plain is located in the eastern North Atlantic off Madeira Islands, forming part of the Canary Basin and reaching a mean water depth of 5300 m. This region is also located within Africa plate at about 500 km southwards from the Açores-Gibraltar plate boundary, and for that reason lacks seismic activity. Although this region being located in an intraplate setting, the presence of faulted sediments was reported in several works published during the eighties of last century following a study conducted in late 1970s to evaluate the feasibility of disposal of high-level radioactive wastes in the ocean. According these works, the Madeira Abyssal Plain sediments are cut by many normal growth faults and this deformation is a result of compaction and dewatering of the sediments. Evidences of tectonic deformation of oceanic sediments in intraplate settings are uncommon, but folded sediments and reverse faults extending into the basement, were recognized in the equatorial Indian Ocean and in the West African continental margin. Recently, during 2006 multi-channel seismic reflection and multibeam swath bathymetry surveys were carried out in the West Madeira Abyssal Plain by EMEPC in order to prepare the Portuguese proposal for the extension of the continental shelf. The seismic lines were acquired onboard R/V Akademik Shatskiy using a source of 5720 cu in bolt gun array, cable length of 7950 m and shot interval of 50.00 m. The multibeam swath bathymetry was acquired onboard NRP Gago Coutinho, and allowed a high resolution mapping of the main geomorphological features. The multichannel seismic lines, oriented WNW-ESE, image the Madeira island lower slope located at about 4000 m water depth and the almost flat abyssal plain at about 5300 m water depth. These seismic lines show a thick sedimentary succession that reaches a maximum thickness of about 1.5 sec twt in the deepest parts of the West Madeira Abyssal Plain, overlying an irregular diffractive Late Cretaceous oceanic basement. This basement is outcropping in some places originating small highs, which top is placed at 4700-4800 m water depth, about 500 m above the surrounding flat abyssal plain. The acoustic facies shown by the sedimentary record suggests the presence of a great thickness of turbidites within the sedimentary succession. The sismostratigraphy interpretation allowed the identification of four distinctive seismic units named from bottom to top U1 to U4. A theoretical stratigraphic correlation model between these seismic units and the ODP 157 data (Sites 950, 951 and 952) is proposed in the present work. The oldest seismic units U1 and U2 rest above the oceanic basement and could be correlated with the Late Cretaceous to Early Miocene sediments drilled during ODP 157. The youngest seismic units U3 and U4 show a succession of very continuous and parallel reflections alternating between low and high amplitude. Such type of seismic facies could be correlated with alternating turbidites and pelagic sediments possibly of Middle-Upper Miocene to Pleistocene age considering the ODP 157 data. The Cenozoic sedimentary succession is cut by several normal faults, close spaced, possibly related to compaction and dewatering processes. The acoustic record suggests the occurrence of fluid circulation along these faults, which are rooted in the oceanic basement. In some places these faults cut though the entire sedimentary sequence, almost reaching the seafloor. Evidences of recent compressional deformation are shown by reverse faults that affected the sedimentary sequence and also deform the seafloor by buckling and high amplitude folding. A large pop-up structure is recognized, generating a seafloor high, suggesting the occurrence of recent compressional events in the West Madeira Abyssal Plain region.

  17. Tectonic evolution of the Perth Abyssal Plain's Quiet Zone, Southeast Indian Ocean

    NASA Astrophysics Data System (ADS)

    Ehrlich, Zohar Louis; Granot, Roi; Williams, Simon E.

    2013-04-01

    During the Late Jurassic period, the Greater-Indian plate was torn away from Australia, dissociating East Gondwanaland. The Perth Abyssal Plain (PAP) is the southernmost rift segment along the western Australian margin, and has an onset age of ~136 Ma. New marine magnetic and swath bathymetry data, crossing the entire PAP, were acquired recently on geophysical cruise ss2011v06 aboard the R/V Southern Surveyor. These have lead to the outline of conjugate Indian and Australian M-series isochrons in the east and west PAP, respectively [1]. Yet, most of the PAP was created during the Cretaceous Normal Superchron (CNS, 121-83 Ma), a period of no geomagnetic field reversals, hence no comprehensive tectonic model for the PAP exists . Here we present preliminary findings of an analytic bathymetric and magnetic investigation aimed at elucidating the PAP's quiet zone. Recent discoveries regarding the evolution of the geomagnetic field during the CNS [2] provide new time markers that can be utilized to date the oceanic crust. The magnetic anomaly data exhibit the Q2 anomaly marker (~108 Ma), further constraining the spreading history of the PAP. Together with the ridgelet transform method [3] for automated abyssal hill delineation, we present new constraints on the development of crustal construction processes (spreading location, direction and rates) that took place along the PAP spreading center. References: [1] S.E. Williams, J.M. Whittaker, R. Granot, R.D. Muller (in preparation), New constraints on the seafloor spreading history in the Perth Abyssal Plain. [2] Granot, R., J. Dyment, and Y. Gallet (2012), Geomagnetic field variability during the Cretaceous Normal Superchron, Nature Geoscience, 5(3), 220-223. [3] Downey, N. J. and R. W. Clayton (2007), A ridgelet transform method for constraining tectonic models via abyssal-hill morphology, Geochemistry Geophysics Geosystems, 8, Q03004, doi: 10.1029/2006GC001440.

  18. STUDY OF ABYSSAL SEAFLOOR ISOLATION OF CONTAMINATED SEDIMENTS CONCLUDED

    EPA Science Inventory

    Recognizing the rapidly decreasing availability of disposal sites on land, in 1993 Congress directed the Department of Defense to assess the technical and scientific feasibility of isolating contaminated dredged material on the abyssal seafloor. The Naval Research Laboratory (NRL...

  19. Links between surface productivity and deep ocean particle flux at the Porcupine Abyssal Plain (PAP) sustained observatory

    NASA Astrophysics Data System (ADS)

    Frigstad, H.; Henson, S. A.; Hartman, S. E.; Omar, A. M.; Jeansson, E.; Cole, H.; Pebody, C.; Lampitt, R. S.

    2015-04-01

    In this study we present hydrography, biogeochemistry and sediment trap observations between 2003 and 2012 at Porcupine Abyssal Plain (PAP) sustained observatory in the northeast Atlantic. The time series is valuable as it allows for investigation of the link between surface productivity and deep ocean carbon flux. The region is a perennial sink for CO2, with an average uptake of around 1.5 mmol m-2 d-1. The average monthly drawdowns of inorganic carbon and nitrogen were used to quantify the net community production (NCP) and new production, respectively. Seasonal NCP and new production were found to be 4.57 0.27 mol C m-2 and 0.37 0.14 mol N m-2. The Redfield ratio was high (12), and the production calculated from carbon was higher than production calculated from nitrogen, which is indicative of carbon overconsumption. The export ratio and transfer efficiency were 16 and 4%, respectively, and the site thereby showed high flux attenuation. Particle tracking was used to examine the source region of material in the sediment trap, and there was large variation in source regions, both between and within years. There were higher correlations between surface productivity and export flux when using the particle-tracking approach, than by comparing with the mean productivity in a 100 km box around the PAP site. However, the differences in correlation coefficients were not significant, and a longer time series is needed to draw conclusions on applying particle tracking in sediment trap analyses.

  20. Meiobenthos of the hatteras abyssal plain and Puerto Rico trench: abundance, biomass and associations with bacteria and particulate fluxes

    NASA Astrophysics Data System (ADS)

    Tietjen, John H.; Deming, Jody W.; Rowe, Gilbert T.; Macko, Stephen; Wilke, Richard J.

    1989-10-01

    An abyssal station on the Hatteras Abyssal Plain (5411 m) and two hadal stations in the Puerto Rico Trench (7460 and 8189 m) were sampled to obtain quantitative information on the abundance and biomass of metazoan meiofauna and, for comparative purposes, bacteria and measurements of particulate flux rates. Average meiofauna abundance (no./10 cm 2 1 S.E. integrated over a sediment depth of 15 cm) was lowest at the 7460 m site (44 10) and highest at the 8189 m (96 15) and Hatteras sites (114 26), the latter two not being statistically significant from each other. Biomasses (?g dry wt/10 cm2 1 S.E., also integrated over a 15 cm depth) at the Hatteras and 7460 and 8189 m Trench sites were 38.4 10.3, 3.8 1.6 and 14.3 5.1, respectively; all differences were statistically significant. High biomass at the Hatteras site was due to large, burrowing harpacticoid copepods that were found to depths of 10-15 cm below the sediment surface, and which were most abundant below the surface (0-2 cm) layer of sediment. Nematodes, the numerically dominant taxon, were most abundant in the upper 6 cm of sediment at all sites, as were copepods at the two Trench sites. Average abundances of bacteria (no. of cells 10 9 per 10 cm 2 of sediment to a depth of 15 cm), determined by epifluorescence microscopy, were 11.0, 10.5 and 5.6 at the Hatteras, 7460 and 8189 m Trench sites, respectively. Flux rates of organic carbon and total nitrogen (mg m -2 day -1) were about four times higher at the Hatteras site (e.g. 25.8 and 3.8) than at the 7460 m site in the Trench (6.3 and 0.8). An analysis of the meiofaunal and bacterial abundances obtained at the three sites revealed no significant associations between the two organismal groups, though abundances of both groups did decrease significantly and predictably with sediment depth at each station. Associations between particulate flux rates and meiofauna biomass were highly significant, suggesting that flux rates measured in near-bottom traps may be useful indicators of general resources available to the meiobenthos.

  1. New insights into the abyssal sponge fauna of the Kurile-Kamchatka plain and Trench region (Northwest Pacific)

    NASA Astrophysics Data System (ADS)

    Downey, Rachel V.; Janussen, Dorte

    2015-01-01

    The under-explored abyssal depths of the Kurile-Kamchatka region have been re-examined during the KuramBio (Kurile-Kamchatka Biodiversity Study) expedition. Combining new KuramBio data with previous expedition data in this region has enhanced our understanding abyssal sponge fauna, in particular, the patchiness, rarity, and exceptional richness of the Cladorhizidae family. In total, 14 sponge species, from 7 genera, in 5 families, within two classes (Demospongiae and Hexactinellida) were collected. Of the 14 species, 29% (4 spp.) have been found previously in this region, 36% (5 spp.) were new to the regional abyssal fauna, and 21% (3 spp.) were new to science. The number of abyssal species in this region has now been increased by 26% (8 spp.) and genera by nearly 15% (2 genera). Rarity is a prominent feature of this abyssal fauna, with more than half of species only found at one station, and 83% (19 spp.) of species found previously in this region were not re-found during KuramBio. Cladorhizid sponges dominate demosponge species and genera richness in the abyssal Kurile-Kamchatka region; accounting for 87% (20 spp.) of all demosponge species, and accounting for over 60% (5 genera) of all demosponge genera. Sponge richness in this region is potentially aided by the productivity of the ocean waters, the geological age of the Pacific Ocean, low population densities, and the varied topographic features (ridges, trenches, and seamounts) found in this region. Unusually, the dominance of demosponges in the Kurile-Kamchatka sponge faunal composition is not replicated in other well-sampled abyssal regions, which tend to be richer in deep-sea hexactinellid fauna. Broad depth, latitudinal and longitudinal ranges in Kurile-Kamchatka abyssal fauna are a key characteristic of this faunal assemblage. Strong abyssal faunal connectivity is found between the Kurile-Kamchatka region and North Pacific abyssal fauna, with weaker faunal connections found with the adjacent semi-enclosed seas of Japan and Okhotsk. The importance of the dominant sub-Polar Gyre currents, the vast area of abyssal plain and similar levels of productivity, are likely to be driving the strong faunal connectivity in the North Pacific. The importance of utilising several forms of sampling equipment has been illustrated in this study, with half of all specimens caught with non-AGT (Agassiz trawl) equipment.

  2. Study of abyssal seafloor isolation of contaminated sediments concluded

    SciTech Connect

    Valent, P.

    1998-12-31

    Recognizing the rapidly decreasing availability of disposal sites on land, in 1993 Congress directed the Department of Defense to assess the technical and scientific feasibility of isolating contaminated dredged material on the abyssal seafloor. The Naval Research Laboratory (NRL) conducted and managed the assessment, which was funded during its first year by the Strategic Environmental Research and Development Program and in the following two years by the Defense Advanced Research Projects Agency. NRL carried out the projects in collaboration with participants from academic institutions and industrial organizations. The seafloor isolation concept is an attractive management option for contaminated dredged material because, if abyssal isolation is feasible and environmentally sound, air, land, or water supplies would not be contaminated. The participants concluded that it is technically and environmentally feasible. In ports where shipping costs are high, abyssal seafloor isolation is a cost-competitive strategy. They also outlined the architecture of a system to monitor conditions at the site and to detect and measure possible leaks of contaminated material.

  3. Characteristics of sinking particles in the upper ocean at the Porcupine Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Riley, Jennifer; Sanders, Richard; Achterberg, Eric

    2010-05-01

    Sinking particles play an important role in the biological carbon pump, transferring carbon from the surface to the deep ocean. Data from deep ocean sediment traps suggest biominerals influence particle settling velocity, by increasing their density. However it is unclear whether this biomineral facilitated sinking applies to the upper ocean and if shape also plays a critical role on the rate at which particles sink. Measurements of particle settling velocity, density and drag were made in order to determine their influences on the particle sinking rate in the upper water column. Samples were taken during a cruise in summer 2009 from the Porcupine Abyssal Plain (PAP site) in the northwest Atlantic. Particles were collected from the base of the mixed layer (approximately 50m) using the Marine Snow Catcher. This instrument samples 100L of water and collects any settling particles in a 5L base chamber over 2 - 3 hours. After settling, the top 95L of water was drained off and any particles collected in the base chamber were transferred to the lab. Particles were individually picked using a Pasteur pipette and subdivided, into categories on the basis of appearance. Settling experiments were conducted in a 2L glass measuring cylinder filled with surface sea water, kept at a constant temperature of 15 C. After each experiment particles were preserved individually in buffered formalin for high quality image analysis back on land. Calculations of both excess density and drag were undertaken using data from microscopic measurements. Five main particle categories were identified; (1) diffuse fluff aggregates, (2) dense fluff aggregates, (3) centred particles (fluff aggregated around a central biomineral test), (4) organisms (biomineralising protists including foraminifera) and (5) calcareous tests. Statistical analysis suggested a significant difference in the rate at which the centred and calcareous particles sank (approximately 248 m day-1 and 1070 m day-1respectively) in relation to the other classes (142 - 184 m day-1). Excess densities and drag coefficients were respectively; 0.015 g cm-3 and 126, for organisms, 0.044 g cm-3 and 204 for centred particles and 1.68 g cm-3 and 1823 for calcareous tests. To determine whether particle density or drag, governs settling velocity, calculations were made of how typical (defined using averaged values from the observed data) sinking speeds vary with, (1) excess density and (2) drag coefficient. Comparison of the observed and typical particle characteristics suggested the differences observed in excess density were too small to account for the variation in measured sinking speed. However the change in calculated drag was larger than required to account for the observed variation in settling velocity. The results imply it is the process of aggregate formation and the resulting particle shape that has the greatest influence upon the rate at which particles sink in the upper ocean. This contrasts with the deep ocean ballast hypothesis, which suggests the incorporation of biominerals into aggregates influences particle sinking speeds.

  4. A qualitative zoogeographic analysis of decapod crustaceans of the continental slopes and abyssal plain of the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Wicksten, Mary K.; Packard, Jane M.

    2005-09-01

    Occurrence of 130 species of decapod crustaceans was compared between the continental slope (200-2500 m) and the abyssal plain (2500-3840 m) of the Gulf of Mexico. We compiled records of these species from published literature and from the crustacean catalogue of the Marine Invertebrate Collection of Texas A&M University. Each species was scored as present or absent in each of 10 polygons that were defined by physiographic features of the sea floor. Using cluster analysis, we identified inherent patterns of species richness. A distinct faunal assemblage occurred in the Sigsbee Abyssal Plain. This deep plain was a potential "coldspot" in terms of the number of species in the basin, compared to a "hotspot" in the vicinity of De Soto Canyon. Polygons of the eastern upper slopes (i.e. calcareous substrate of western Florida) contained the most species that were not found elsewhere in the Gulf of Mexico. Using an inductive approach, we identified the following hypotheses: (1) most crustacean species of the deep Sigsbee Abyssal Plain occur in oceans world-wide, (2) overall, almost a quarter of the deep sea species in the Gulf of Mexico range from the western Atlantic (south of Cape Hatteras) to the Caribbean, and (3) the Gulf of Mexico is particularly rich in species of Munidopsis (25 species).

  5. Organic matter accumulation, sulfate reduction, and methane generation in a turbidite sequence on the Iberia Abyssal Plain

    SciTech Connect

    Meyers, P.A.; Silliman, J.E. ); Shaw, T.J. )

    1996-01-01

    Organic matter can be transferred and redeposited from continental margins to the deep-sea by turbidity currents and slumps. An opportunity to investigate the consequences of turbidite deposition on sediment organic matter was provided by a transect of four closely spaced drill sites sampled during ODP Leg 149 in a Pliocene-Pleistocene distal turbidite sequence on the landward edge of the Iberia Abyssal Plain. Organic carbon concentrations average ca 0.7% in sediments from Sites 897 and 898 and ca 0.4% at Sites 899 and 900. Headspace concentrations of interstitial methane exceed 100,000 ppm in sediments from Sites 897 and 898 but are essentially zero in those from Sites 899 and 900. Methane concentrations do not rise until interstitial sulfate concentrations are virtually depleted, suggesting the presence of deep in situ methanogenic bacterial activity at Sites 897 and 898 and its absence at Sites 899 and 900. Two factors associated with the turbidity flows that created the sedimentary sequence evidently influenced post-depositional diagenesis at these sites. The principal factor is that the rapidly deposited turbidite sequences at Sites 897 and 898 protected organic matter from oxic, early degradation and thereby permitted anoxic, later degradation to proceed. In contrast, organic matter in the more slowly deposited turbidites at Sites 899 and 900 was oxidized soon after deposition and was therefore not available for later microbial utilization. A lesser factor is that the turbidity flows may have obtained their entrained organic matter from different environments and consequently delivered organic matter with different characteristics.

  6. Organic matter accumulation, sulfate reduction, and methane generation in a turbidite sequence on the Iberia Abyssal Plain

    SciTech Connect

    Meyers, P.A.; Silliman, J.E.; Shaw, T.J.

    1996-12-31

    Organic matter can be transferred and redeposited from continental margins to the deep-sea by turbidity currents and slumps. An opportunity to investigate the consequences of turbidite deposition on sediment organic matter was provided by a transect of four closely spaced drill sites sampled during ODP Leg 149 in a Pliocene-Pleistocene distal turbidite sequence on the landward edge of the Iberia Abyssal Plain. Organic carbon concentrations average ca 0.7% in sediments from Sites 897 and 898 and ca 0.4% at Sites 899 and 900. Headspace concentrations of interstitial methane exceed 100,000 ppm in sediments from Sites 897 and 898 but are essentially zero in those from Sites 899 and 900. Methane concentrations do not rise until interstitial sulfate concentrations are virtually depleted, suggesting the presence of deep in situ methanogenic bacterial activity at Sites 897 and 898 and its absence at Sites 899 and 900. Two factors associated with the turbidity flows that created the sedimentary sequence evidently influenced post-depositional diagenesis at these sites. The principal factor is that the rapidly deposited turbidite sequences at Sites 897 and 898 protected organic matter from oxic, early degradation and thereby permitted anoxic, later degradation to proceed. In contrast, organic matter in the more slowly deposited turbidites at Sites 899 and 900 was oxidized soon after deposition and was therefore not available for later microbial utilization. A lesser factor is that the turbidity flows may have obtained their entrained organic matter from different environments and consequently delivered organic matter with different characteristics.

  7. Heat flow in the western abyssal plain of the Gulf of Mexico: Implications for thermal evolution of the old oceanic lithosphere

    NASA Astrophysics Data System (ADS)

    Nagihara, S.; Sclater, J. G.; Phillips, J. D.; Behrens, E. W.; Lewis, T.; Lawver, L. A.; Nakamura, Y.; Garcia-Abdeslem, J.; Maxwell, A. E.

    1996-02-01

    The seafloor depth of an oceanic basin reflects the average temperature of the lithosphere. Thus the western abyssal plain of the Gulf of Mexico, which has tectonically subsided much (>1 km) deeper than other basins of comparable ages (late Jurassic), should be underlain by an anomalously cold lithosphere. In order to examine this hypothesis, we made suites of high-accuracy heat flow measurements at 10 sites along a line connecting Deep Sea Drilling Project (DSDP) sites 90 and 91 in the Sigsbee abyssal plain. The new heat flow sites were initially surveyed by 3.5-kHz echo sounding, 4-channel seismic reflection, seismic refraction with eight ocean bottom seismometers, and nine piston cores. We occupied a total of 48 heat flow stations along the seismic survey line (3 to 6 at each site), including 28 where we measured in situ thermal conductivities over the practical depth interval (4 m) of the new multioutrigger bow heat flow probe. We determined the heat flow associated with the lithosphere by correcting the values measured at the seafloor (41 to 45 mW/m2) for (1) the thermal effect of the sedimentation and (2) the additional heat from the radioactive elements within the sediments. The sedimentation history, required for the first, was reconstructed at each heat flow site based on ages and thicknesses of the major seismic stratigraphical sequences, age data from the DSDP cores, 3.5-kHz subbottom reflectors, and correlation of turbidite units found in the piston cores. Radiogenic heat production was measured for 55 sediment samples from four DSDP holes in the gulf, whose age ranged from present to Early Cretaceous (0.83 ?W/m3 on the average). This provided the correction for the second. The effects of these two secondary factors approximately cancel one another. The lithospheric heat flow under the abyssal plain thus estimated ranges from 40 to 47 mW/m2. These heat flow values are among the lowest in the Mesozoic ocean basins where highly reliable data (45 to 55 mW/m2) have been reported. Therefore the lithosphere under the gulf seems indeed colder than that under other old ocean basins. However, it is not as cold as expected from the large tectonic subsidence. The inconsistency between the depth and heat flow may imply an anomaly in the regional thermal isostasy.

  8. Seismicity and seismotectonics of the diffusive Iberian/African plate boundary: Horseshoe Abyssal Plain and Gorringe Bank

    NASA Astrophysics Data System (ADS)

    Grevemeyer, Ingo; Lange, Dietrich; Matias, Luis

    2014-05-01

    In the area to the west of the Gibraltar Arc the plate boundary between Africa and Iberia is poorly defined. The deformation in the area is forced by the slow NW-SE convergence of 4 mm/yr between the oceanic domains of Iberia/Eurasia and Africa and is accommodated over a 200 km broad tectonically-active deformation zone. The region, however, is also characterized by large earthquakes and tsunamis, such as the 1969 Mw=7.9 Horseshoe Abyssal Plain earthquake and the November 1, 1755 Great Lisbon earthquake with an estimated magnitude of Mw~8.5. The exact location of the source of the 1755 Lisbon earthquake is still unknown. Recent work may suggest that the event occurred in the vicinity of the Horseshoe fault, an oblique thrust fault. However, estimates of tsunami arrival times suggested a source near the Gorringe Bank, a ~180 km-long and ~70 km-wide ridge that has a relieve of ~5000 m. Deep Sea Drilling (DSDP) and rock samples indicated that the bank is mainly composed of serpentinized peridotites with gabbroic intrusions, perhaps being created by overthrusting of the Horseshoe Abyssal Plain onto the Tagus Abyssal Plain in NW direction. Further, the Horseshoe Abyssal Plain is marked by the presence of compressive structures with a roughly NE-SW orientation and E-W trending, segmented, crustal-scale, strike slip faults that extend from the Gorringe Bank to the Gibraltar Arc in the eastern Gulf of Cadiz, which were called "South West Iberian Margin" or SWIM faults. The fault system may mark a developing Eurasia-Africa plate boundary. Two local seismic networks were operated in the area. First, a network of 14 ocean-bottom seismometers (OBS) was operated between April and October 2012 in the vicinity of the Horseshoe fault between 10W to 11W, and 3550'N to 3610'N. From October 2013 to March 2014 a second network of 15 OBS monitored seismicity at the Gorringe Bank. Both networks benefitted from seismic stations operated in Portugal. The first network provided in the order of 100 locale earthquakes occurring with the network. Most earthquakes in the Horseshoe occurred at a depth of 40-60 km, either in oceanic or unroofed continental mantle. The large source depth of events observed in the Horseshoe Abyssal Plain supports the idea that large catastrophic earthquakes, like the Great Lisbon earthquake of 1755, may indeed occur in the area.

  9. Subbottom Profile of Abyssal Sediments in the Central Equatorial Pacific.

    PubMed

    Heath, G R; Moore, T C

    1965-08-13

    A north-south subbottom acoustic profile made in the central Pacific Ocean shows that the first layer (unconsolidated and semiconsolidated sediments) increases in thickness from less than 200 meters at about 14 degrees N to more than 600 meters near the equator. Two major faults, one of which lies on the extension of the Clipperton fracture zone, have produced vertical separations of about 400 meters in the base of the first layer. PMID:17779182

  10. Connections between climate, food limitation, and carbon cycling in abyssal sediment communities

    PubMed Central

    Ruhl, Henry A.; Ellena, Jacob A.; Smith, Kenneth L.

    2008-01-01

    Diverse faunal groups inhabit deep-sea sediments over much of Earth's surface, but our understanding of how interannual-scale climate variation alters sediment community components and biogeochemical processes remains limited. The vast majority of deep-sea communities depend on a particulate organic carbon food supply that sinks from photosynthetically active surface waters. Variations in food supply depend, in part, on surface climate conditions. Proposed ocean iron fertilization efforts are also intended to alter surface production and carbon export from surface waters. Understanding the ecology of the abyssal sediment community and constituent metazoan macrofauna is important because they influence carbon and nutrient cycle processes at the seafloor through remineralization, bioturbation, and burial of the sunken material. Results from a 10-year study in the abyssal NE Pacific found that climate-driven variations in food availability were linked to total metazoan macrofauna abundance, phyla composition, rank-abundance distributions, and remineralization over seasonal and interannual scales. The long-term analysis suggests that broad biogeographic patterns in deep-sea macrofauna community structure can change over contemporary timescales with changes in surface ocean conditions and provides significant evidence that sediment community parameters can be estimated from atmospheric and upper-ocean conditions. These apparent links between climate, the upper ocean, and deep-sea biogeochemistry need to be considered in determining the long-term carbon storage capacity of the ocean. PMID:18974223

  11. Structural Iron (II) of Basaltic Glass as an Energy Source for Zetaproteobacteria in an Abyssal Plain Environment, Off the Mid Atlantic Ridge

    PubMed Central

    Henri, Pauline A.; Rommevaux-Jestin, Céline; Lesongeur, Françoise; Mumford, Adam; Emerson, David; Godfroy, Anne; Ménez, Bénédicte

    2016-01-01

    To explore the capability of basaltic glass to support the growth of chemosynthetic microorganisms, complementary in situ and in vitro colonization experiments were performed. Microbial colonizers containing synthetic tholeitic basaltic glasses, either enriched in reduced or oxidized iron, were deployed off-axis from the Mid Atlantic Ridge on surface sediments of the abyssal plain (35°N; 29°W). In situ microbial colonization was assessed by sequencing of the 16S rRNA gene and basaltic glass alteration was characterized using Scanning Electron Microscopy, micro-X-ray Absorption Near Edge Structure at the Fe-K-edge and Raman microspectroscopy. The colonized surface of the reduced basaltic glass was covered by a rind of alteration made of iron-oxides trapped in a palagonite-like structure with thicknesses up to 150 μm. The relative abundance of the associated microbial community was dominated (39% of all reads) by a single operational taxonomic unit (OTU) that shared 92% identity with the iron-oxidizer Mariprofundus ferrooxydans PV-1. Conversely, the oxidized basaltic glass showed the absence of iron-oxides enriched surface deposits and correspondingly there was a lack of known iron-oxidizing bacteria in the inventoried diversity. In vitro, a similar reduced basaltic glass was incubated in artificial seawater with a pure culture of the iron-oxidizing M. ferrooxydans DIS-1 for 2 weeks, without any additional nutrients or minerals. Confocal Laser Scanning Microscopy revealed that the glass surface was covered by twisted stalks characteristic of this iron-oxidizing Zetaproteobacteria. This result supported findings of the in situ experiments indicating that the Fe(II) present in the basalt was the energy source for the growth of representatives of Zetaproteobacteria in both the abyssal plain and the in vitro experiment. In accordance, the surface alteration rind observed on the reduced basaltic glass incubated in situ could at least partly result from their activity. PMID:26834704

  12. Structural Iron (II) of Basaltic Glass as an Energy Source for Zetaproteobacteria in an Abyssal Plain Environment, Off the Mid Atlantic Ridge.

    PubMed

    Henri, Pauline A; Rommevaux-Jestin, Céline; Lesongeur, Françoise; Mumford, Adam; Emerson, David; Godfroy, Anne; Ménez, Bénédicte

    2015-01-01

    To explore the capability of basaltic glass to support the growth of chemosynthetic microorganisms, complementary in situ and in vitro colonization experiments were performed. Microbial colonizers containing synthetic tholeitic basaltic glasses, either enriched in reduced or oxidized iron, were deployed off-axis from the Mid Atlantic Ridge on surface sediments of the abyssal plain (35°N; 29°W). In situ microbial colonization was assessed by sequencing of the 16S rRNA gene and basaltic glass alteration was characterized using Scanning Electron Microscopy, micro-X-ray Absorption Near Edge Structure at the Fe-K-edge and Raman microspectroscopy. The colonized surface of the reduced basaltic glass was covered by a rind of alteration made of iron-oxides trapped in a palagonite-like structure with thicknesses up to 150 μm. The relative abundance of the associated microbial community was dominated (39% of all reads) by a single operational taxonomic unit (OTU) that shared 92% identity with the iron-oxidizer Mariprofundus ferrooxydans PV-1. Conversely, the oxidized basaltic glass showed the absence of iron-oxides enriched surface deposits and correspondingly there was a lack of known iron-oxidizing bacteria in the inventoried diversity. In vitro, a similar reduced basaltic glass was incubated in artificial seawater with a pure culture of the iron-oxidizing M. ferrooxydans DIS-1 for 2 weeks, without any additional nutrients or minerals. Confocal Laser Scanning Microscopy revealed that the glass surface was covered by twisted stalks characteristic of this iron-oxidizing Zetaproteobacteria. This result supported findings of the in situ experiments indicating that the Fe(II) present in the basalt was the energy source for the growth of representatives of Zetaproteobacteria in both the abyssal plain and the in vitro experiment. In accordance, the surface alteration rind observed on the reduced basaltic glass incubated in situ could at least partly result from their activity. PMID:26834704

  13. Composition and distribution of bivalves of the abyssal plain adjacent to the Kuril-Kamchatka Trench (Pacific Ocean)

    NASA Astrophysics Data System (ADS)

    Kamenev, Gennady M.

    2015-01-01

    The KuramBio German-Russian deep-sea expedition ("Sonne", 2012) revealed a rich fauna of bivalves (55 species belonging to 21 families) on the abyssal plain (4861-5787 m) adjacent to the Kuril-Kamchatka Trench. Per station species richness varied from 18 to 33 species. The richest families were Cuspidariidae (7 species), Tindariidae (6 species), Thyasiridae (6 species), and Xylophagidae (5 species). The families Nuculidae, Malletidae, Yoldiidae, Mytilidae, Protocuspidariidae, and Verticordiidae were represented by a single species. Representatives of the family Siliculidae were recorded in the northwestern Pacific for the first time. Thirteen species (23.6%) were most common in the investigated northwestern Pacific region. Nine species (16.4%) were only found at one of the stations. Eight species (14.5%) are first records for the northwestern Pacific, of which Yoldiella cf. jeffreysi (Hidalgo, 1877), Pristigloma cf. albaSanders and Allen, 1973, and Syssitomya cf. pourtalesianaOliver, 2012 were previously known only for the Atlantic Ocean. The high diversity and richness of the bivalve fauna on the abyssal plain in the Kuril-Kamchatka Trench area may be connected to the favorable feeding conditions in this, one of the most highly productive areas of the Pacific Ocean.

  14. Epibenthic megacrustaceans from the continental margin, slope and abyssal plain of the Southwestern Gulf of Mexico: Factors responsible for variability in species composition and diversity

    NASA Astrophysics Data System (ADS)

    Escobar-Briones, Elva G.; Gaytn-Caballero, Adriana; Legendre, Pierre

    2008-12-01

    The community structure of megacrustaceans (orders Lophogastrida, Isopoda, and Decapoda) collected in trawls on the continental margin, upper slope and abyssal plain of the southern Gulf of Mexico was studied to determine to what extent broad-scale variation in community composition and diversity was influenced by geographic regions environmental variability and depth. Trawls were collected in the Mexican Ridges, the Campeche Bank, and the Sigsbee abyssal plain. There was variability in species composition, density and diversity among geographic regions and along the depth gradient. A total of 106 species were identified and grouped in three orders; five infraorders, 40 families, and 70 genera. This study extends the known geographic ranges of the species Homolodromia monstrosa and Ephyrina benedicti. The largest number of species was recorded in the Mexican Ridges and on the upper continental shelf; lower values were found on the continental margin and in the abyssal plain. The largest densities were recorded on the continental margin in the Mexican Ridges. Megacrustaceans show in general low frequencies and low abundances in trawls, characterizing them as rare components of benthic assemblages. Contrary to an accepted paradigm about deep-sea biodiversity, the highest H' diversity values were recorded in the Sigsbee abyssal plain, followed by values from the upper continental slope; diversity values were correlated with evenness. Canonical Redundancy analysis results showed a significant affinity to regions for 18 crustacean species; 33 species showed a significant affinity to both regions and depth zones within regions.

  15. A Geo-traverse at a Passive Continental Margin: the Tagus Abyssal Plain, West Iberia

    NASA Astrophysics Data System (ADS)

    Afilhado, A.; Matias, L.; Mendes-Victor, L.

    2006-12-01

    The crustal and lithospheric mantle structure was investigated along a 370km profile at the south segment of the west Iberian margin, from 12.9W to 8.7W, at approximately 38N. The profile crosses from inland unthinned continental to oceanic crust, IAM5. Both MCS data and wide-angle, WA, data were considered. WA data set includes 6 OBSs and 2 inland seismic stations. Free air and total field magnetic anomalies profiles were extracted from available grided data. WA data cinematic and dynamic modeling provided a 2D velocity model that proved to be consistent with the free air anomaly profile. 2.5D generalized inversion on pseudo- susceptibility was performed. A Bouguer anomaly grid was calculated and a similar procedure was performed for the undulation of the geoid grid. First and second derivatives grids of this surface and its upward continued surfaces were calculated to locate lineated lows and highs. MCS and WA data sets indicate four main crustal domains. East of 9.4W the complete crustal section of slightly thinned continental crust is present. From 9.4W to 9.7W crustal thinning is abrupt and the lower continental crust pinches out. From 9.7W to 10.5W the transitional crust has a complex structure that varies both horizontally and vertically. Within the eastern most transitional domain the exhumed mid continental crust thins to zero; small scale heterogeneities exist at its lower interface; the under-laying lower crust nature is unknown, correlating both to exhumed continental mantle and to continental gabbros. From 10.2W to 10.5W the transitional crust is very heterogeneous, having higher than usual density at its upper levels; the absence of Moho reflections suggests that exhumed and intruded mantle might be present at the lower transitional crust. West of 10.5W thin oceanic crust is found, probably generated in a slow spreading environment; around 12W the data suggests a very thin or even absent layer 3. Deep reflectors imaged within the oceanic domain and transitional domain suggests a layered structure for the lithospheric mantle. The location of the main features and trend changes seen on the magnetic anomaly and the Bouguer anomaly maps are compatible to the seismically defined transition to the oceanic domain. Both magnetic and free air profiles modeling are also consistent to a major rock property contrast at this location. Minor features within the oceanic domain indicate some variability of the mass and magnetic dipoles distribution that might be related to different cross cutting of the segment axis and/or non stationary thermo-mechanical conditions of the sea floor spreading process. From 9.4W to the foot of the continental slope, at 10.2W, in a 65km distance, the Bouguer anomaly strongly increases due both to continental crust thinning and Moho shallowing. Magnetic anomalies having peak to peak values of 30 to 90nT and wave length of at least 30km plus the high density blocks modeled at shallow levels, indicate that dense and magnetic rocks should be present at the continental margin. A large body of exhumed continental mantle at the OCT is hardly supported by the data. Even so, the eastern 35km segment of the abyssal plain adjacent to the continental margin is a mass excess segment, bordered by significant magnetic anomalies, in good agreement to an intruded and partly ultramafic lower transitional crust, as suggested by the seismic data.

  16. The response of Oneirophanta mutabilis (Holothuroidea) to the seasonal deposition of phytopigments at the Porcupine Abyssal Plain in the Northeast Atlantic

    NASA Astrophysics Data System (ADS)

    Witbaard, R.; Duineveld, G. C. A.; Kok, A.; van der Weele, J.; Berghuis, E. M.

    The impact of seasonal pulses of phytodetritus on the grazing behaviour of Oneirophanta mutabilis was assessed on the Porcupine Abyssal Plain (PAP) in the NE Atlantic. Sediment and sediment trap samples were analysed by HPLC to estimate the quantity and quality of the organic material in terms of phytopigments and nucleic acids. Food selection by Oneirophanta was estimated by analysing these constituents in the gut contents. The study area is characterised by large interannual variations in the deposition of fresh organic material. The mass fluxes at 10 m above bottom (mab) varied from 0.25 g DW m -2 d -1 in September 1996 to <0.1 g DW m -2 d -1 in March 1997. The material caught in the sediment trap in September 1996 had a relative fresh signature with a chlorophyll -a:phaeophorbide ratio of 1.33. During the other seasons (March 1997, July 1997 and October 1997) the chlorophyll -a:phaeophorbide ratio remained low. In sediment cores this ratio showed a similar seasonal and inter-annual pattern, and again September 1996 was the period of maximum abundance of fresh organic material in the surficial sediment. The analyses of the gut contents of Oneirophanta mirrored exactly the seasonal variation of the phytopigments in both the sediment and the sediment trap material. Concentrations of pigments in the fore-gut were 5 to 15 times higher than in the sediment and the nucleic acid concentrations were up to 80 times higher. This discrepancy between pigments and nucleic acids concentrations suggests that the latter are indigenous to the gut of Oneirophanta, either because the gut contains high numbers of actively-dividing bacteria or as a result of cell lysis of the gut epithelium. The seasonal differences in the pigment concentration factor suggest that Oneirophanta does not actively search for hotspots where pigment concentrations are enriched. By using the degradation rate of chlorophyll- a in the PAP sediments, the minimum residence time of chlorophyll in the sediment within the gut of Oneirophanta was calculated. In combination with gut volume and density data it was estimated that each year the Oneirophanta population skims a third of the sediment surface at the PAP site.

  17. Triticella minini - a new ctenostome bryozoan from the abyssal plain adjacent to the Kuril-Kamchatka Trench

    NASA Astrophysics Data System (ADS)

    Grischenko, Andrei V.; Chernyshev, Alexei V.

    2015-01-01

    A new species of ctenostome bryozoan, Triticella minini sp. nov., is described from the abyssal plain adjacent to the Kuril-Kamchatka Trench, based on material collected by the Russian-German deep-sea expedition KuramBio 2012. Colonies of T. minini sp. nov. were found attached to the oral spines of irregular sea urchin Echinosigra (Echinogutta) amphoraMironov, 1974 by means of rhizoid fibers that penetrated the substratum through circular borings. The specimens were examined by light microscopy, scanning electron microscopy, and confocal laser scanning microscopy with phalloidin and nuclear labeling. The description of T. minini sp. nov. combines a general taxonomic description with a description of the anatomy of the muscular system. The new species differs from congeners in lacking a stolon. It has an intertentacular organ. T. minini sp. nov. is the eleventh species described in the genus TriticellaDalyell, 1848, and the first record for this genus from the northwestern Pacific. The new species is the fifth ctenostome bryozoan known to occur in 5001-5500 m depth interval worldwide, and the deepest record reported for Triticella.

  18. Fatty acid compositions and trophic relationships of shelled molluscs from the Kuril-Kamchatka Trench and the adjacent abyssal plain

    NASA Astrophysics Data System (ADS)

    Kharlamenko, Vladimir I.; Würzberg, Laura; Peters, Janna; Borisovets, Evgeny E.

    2015-01-01

    Fatty acid (FA) compositions of 12 species of shelled molluscs (gastropods, bivalves, and scaphopods) from the Kuril-Kamchatka Trench and the adjacent abyssal plain were studied. According to the results of multivariate statistical analysis, molluscs were divided into three groups. Group I consisted of three scaphopod species, the bivalve Nucula profundorum and the gastropod Solariella delicata. FA compositions of this group were characterized by high levels of 20:4(n-6). We suggest that the FA pattern found in scaphopods with high values of 20:4(n-6) is most likely typical for that of benthic organisms feeding preferentially on foraminiferans. Group II included the bivalves Neilonella politissima, Bentharca asperula, and Rhinoclama filatovae. Bivalves from the second group had elevated concentrations of 22:6(n-3), and the ratio of 20:4(n-6) to 20:5(n-3) was lower than 1. Bivalves from the second group had elevated concentrations of 22:6(n-3). We propose that high concentrations of this FA can be used as a specific marker for a carnivorous feeding mode of deep-sea benthic invertebrates. The bivalve Bathyspinula calcarella as well as the scaphopod Polyschides sakuraii could not unambiguously be assigned to one group. Within the similarity analysis they rather clustered together with the foraminiferans feeders (group I), but forming an own subgroup. In the PCA on the other hand, P. sakuraii showed a position close to the other bivalves, while B. calcarella had an intermediate position between all three groups. Group III consisted of the gastropods Tacita holoserica and Paracteocina sp., which contained high concentrations of 20:5(n-3) and 22:5(n-3). Both are known to exhibit a carnivorous/scavenging feeding strategy. The very low content of DHA in both species is on first sight not consistent with the suggested carnivorous feeding behavior. A characteristic feature of Paracteocina sp. and T. holoserica was a high level of 22:5(n-3), and HUFA ratios indicate that DHA might be replaced by DPA and EPA in the structural lipids. The comparison of FA compositions of abyssal molluscs showed that different FA patterns are related more to the feeding type than to taxonomic classification.

  19. Deep-sea epibiotic hydroids from the abyssal plain adjacent to the Kuril-Kamchatka Trench with description of Garveia belyaevi sp. nov. (Hydrozoa, Bougainvilliidae)

    NASA Astrophysics Data System (ADS)

    Stepanjants, Sofia D.; Chernyshev, Alexey V.

    2015-01-01

    Examination of material collected by the German-Russian KuramBio Deep-Sea Expedition to the abyssal plain adjacent to the Kuril-Kamchatka Trench revealed about 17 hydroid species, including two species presumably new to science. Before the KuramBio Expedition only fragments of the unidentified hydroids and Cryptolaria sp. were collected in the Kuril-Kamchatka Trench from depths exceeding 3000 m. Descriptions of three species of epibiotic hydroids (including one new species, Garveia belyaevi sp. nov.) are presented herein. A colony of G. belyaevi sp. nov. (the third deep-sea and deepest species of the wide distributed genus Garveia) was attached to the spines of unidentified irregular sea urchins from depths 5217 to 5229 m. Нalitholus (?) sp. (Hydrozoa, Anthoathecata) colonized the skin of spoon worms (Echiura) but could not be identified to species level because the mature medusa stage was absent in the material. An unidentified juvenile polyp (Pandeidae) was found on the bryozoan Tricitella minini attached to spines of irregular sea urchins Echinosigra amphora. Colonial sedentary organisms inhabiting abyssal plains with soft bottoms may colonize invertebrates which are seldom used as substrates for epibiota in shallow waters. Epibiosis among abyssal colonial invertebrates, though extremely poorly studied, appears to be rather frequent.

  20. Temporal and depth-related differences in prokaryotic communities in abyssal sediments associated with particulate organic carbon flux

    NASA Astrophysics Data System (ADS)

    Moeseneder, M. M.; Smith, K. L.; Ruhl, H. A.; Jones, D. O. B.; Witte, U.; Prosser, J. I.

    2012-12-01

    Particulate organic carbon (POC) flux is hypothesized to be the most important parameter influencing activity and biomass of prokaryotic and faunal communities in the abyssal seafloor, but there is little evidence of POC-related changes in community composition of prokaryotes. This hypothesis was tested by 16S rRNA-gene-based analysis of prokaryotic DNA and RNA extracted from abyssal seafloor sediments during periods of low and high POC flux. Fingerprint analysis of prokaryotic communities indicated that approximately 50% of the phylotypes were identical at each sediment horizon, regardless of the temporal variations in POC flux. However, phylotypes were also detected that represented a relatively dynamic component of these communities and were probably strongly influenced by the prevalent POC flux regime. These patterns were also detected in deeper sediment horizons. DNA- and RNA-based community profiles differed, although both approaches had similar community dynamics. Crenarchaeota showed the strongest shift in community composition in response to availability of labile POC, indicating that POC flux may have a more pronounced impact on crenarchaeal communities than on bacterial communities. The high number of phylotypes common to each sample time suggests that both standing stock and active prokaryotic communities are stable.

  1. Controls on sediment delivery in coastal plain rivers.

    PubMed

    Slattery, Michael C; Phillips, Jonathan D

    2011-02-01

    Rivers crossing coastal plains are often inefficient conveyors of sediment, so that changes in upstream sediment dynamics are not evident at the river mouth. Extensive accommodation space and low stream power often result in extensive alluvial storage upstream of estuaries and correspondingly low sediment loads at the river mouth. However, gaging stations with sediment records are typically well upstream of the coast, and thus tend to overestimate sediment yields by under-representing the lower coastal plain and because there is often a net loss of sediment in lower coastal plain reaches. Studies of alluvial sediment storage have generally focused on accommodation space, but, using examples from Texas, we show that low transport capacity controlled largely by slope is a crucial factor. PMID:19892459

  2. Benthic foraminifera living in Gulf of Mexico bathyal and abyssal sediments: Community analysis and comparison to metazoan meiofaunal biomass and density

    NASA Astrophysics Data System (ADS)

    Bernhard, Joan M.; Sen Gupta, Barun K.; Baguley, Jeffrey G.

    2008-12-01

    Benthic foraminiferal biomass, density, and species composition were determined at 10 sites in the Gulf of Mexico. During June 2001 and 2002, sediment samples were collected with a GoMex box corer. A 7.5-cm diameter subcore was taken from a box core collected at each site and sliced into 1-cm or 2-cm sections to a depth of 2 or 3 cm; the >63-?m fraction was examined shipboard for benthic foraminifera. Individual foraminifers were extracted for adenosine triphosphate (ATP) using a luciferin-luciferase assay, which indicated the total ATP content per specimen; that data was converted to organic carbon. Foraminiferal biomass and density varied substantially (2-53 mg C m -2; 3600-44,500 individuals m -2, respectively) and inconsistently with water depth: although two 1000-m deep sites were geographically separated by only 75 km, the foraminiferal biomass at one site was relatively low (9 mg C m -2) while the other site had the highest foraminiferal biomass (53 mg C m -2). Although most samples from Sigsbee Plain (>3000 m) had low biomass, one Sigsbee site had >20 mg foraminiferal C m -2. The foraminiferal community from all sites (i.e. bathyal and abyssal locales) was dominated by agglutinated, rather than calcareous or tectinous, species. Foraminiferal density never exceeded that of metazoan meiofauna at any site. Foraminiferal biomass, however, exceeded metazoan meiofaunal biomass at 5 of the 10 sites, indicating that foraminifera constitute a major component of the Gulf's deep-water meiofaunal biomass.

  3. Chemistry and mineralogy of pyrite-enriched sediments at a passive margin sulfide brine seep: abyssal Gulf of Mexico

    USGS Publications Warehouse

    Commeau, R.F.; Paull, C.K.; Commeau, J.A.; Poppe, L.J.

    1987-01-01

    Pyrite is rapidly accumulating at the contact between the Cretaceous limestones of the Florida Platform and the hemipelagic sediments of the abyssal Gulf of Mexico. Sediments sampled with the submersible "Alvin" in 3266 m of water are associated with a dense community of organisms that depend on chemosynthetic primary production as a food source. Analysis of the chemistry, mineralogy, and textural composition of these sediments indicate that iron sulfide mineralization is occurring at the seafloor within an anoxic micro-habitat sustained by the advection of hydrogen sulfide-charged saline brines from the adjacent platform. The chemosynthetic bacteria that directly overlie the sediments oxidize hydrogen sulfide for energy and provide elemental sulfur that reacts with iron monosulfide to form some of the pyrite. The sediments are mixtures of pyrite (??? 30 wt.%), BaSr sulfates (??? 4 wt.%), clays, and locally derived biogenic carbonates and are progressively being cemented by iron sulfides. Oxidation of hydrogen sulfide produces locally acidic conditions that corrode the adjacent limestones. Potential sources of S, H2S, Fe, Ba, and Sr are discussed. ?? 1987.

  4. Depth-related distribution and abundance of seastars (Echinodermata: Asteroidea) in the Porcupine Seabight and Porcupine Abyssal Plain, N.E. Atlantic

    NASA Astrophysics Data System (ADS)

    Howell, Kerry L.; Billett, David S. M.; Tyler, Paul A.

    2002-10-01

    The depth-related distribution of seastar (Echinodermata: Asteroidea) species between 150 and 4950 m in the Porcupine Seabight and Porcupine Abyssal Plain is described. 47 species of asteroid were identified from 14,000 individuals collected. The bathymetric range of each species is recorded. What are considered quantitative data, from an acoustically monitored epibenthic sledge and supplementary data from otter trawls, are used to display the relative abundance of individuals within their bathymetric range. Asteroid species are found to have very narrow centres of distribution in which they are abundant, despite much wider total adult depth ranges. Centres of distribution may be skewed. This might result from competition for resources or be related to the occurrence of favourable habitats at particular depths. The bathymetric distributions of the juveniles of some species extend outside the adult depth ranges. There is a distinct pattern of zonation with two major regions of faunal change and six distinct zones. An upper slope zone ranges from 150 to 700 m depth, an upper bathyal zone between 700 and 1100 m, a mid-bathyal zone from 1100 to1700 m and a lower bathyal zone between 1700 and 2500 m. Below 2500 m the lower continental slope and continental rise have a characteristic asteroid fauna. The abyssal zone starts at about 2800 m. Regions of major faunal change are identified at the boundaries of both upper and mid-bathyal zones and at the transition of bathyal to abyssal fauna. Diversity is greatest at 1800 m, decreasing with depth to 2600 m before increasing again to high levels at 4700 m.

  5. Polychaete composition from the abyssal plain adjacent to the Kuril-Kamchatka Trench with the description of a new species of Sphaerephesia (Polychaeta: Sphaerodoridae)

    NASA Astrophysics Data System (ADS)

    Alalykina, Inna L.

    2015-01-01

    During the KuramBio expedition, the abyssal plain adjacent to the Kuril-Kamchatka Trench was sampled in July-August 2012. More than 5200 individuals of Polychaeta belonging to 38 families, 108 genera and about 144 species were found. Six genera have been reported for the Northwest Pacific for the first time. About 50% of the collected polychaete species are considered as new to science. One of these, Sphaerephesia lesliae sp. n., is described herein. The detailed description of the new species is presented and its differences from similar species are shown. This eighth species of the genus is characterized by the presence of macrotubercles with two paired terminal papillae. The genus Sphaerephesia Fauchald, 1972 is newly recorded in the Northwest Pacific. An updated key to the species of the genus Sphaerephesia is provided.

  6. Geochemical indicators of subsidence in sediment, Terrebonne coastal plain, Louisiana

    SciTech Connect

    Bailey, A.M. ); Roberts, H.H. )

    1990-09-01

    Sediments comprising the Terrebonne Coastal Plain consist primarily of clays, silts, and peats that fill the depressions between alluvial ridges created by former Mississippi River courses. These sediments are subsiding at variable rates. Depositional history, sedimentation rates, and environment of deposition affect both the types and abundances of diagenetic products found in deltaic sediments. Early diagenesis influences the geotechnical properties of these coastal plain deposits and their local subsidence rates. Diagenetic mineralogy and elemental geochemistry therefore offer clues to understanding some of the variability associated with subsidence in the lower deltaic plain. Results show that diagenetic minerals consist of carbonates (siderite, calcite, dolomite, and rhodochrosite), iron sulfides, vivianite, and iron oxides. In general, siderite and other carbonates as well as pyrite are higher in the fine-grained swamp and lacustrine clays of the upper/middle deltaic plain environments where sediment compaction and subsidence rates are considerably lower than rapidly deposited lower delta and marine deposits. Prodelta clays, for example, contain fewer varieties and lower abundances of diagenetic inclusions than their freshwater fine-grained counterparts. Oxidized sediments of well-drained swamp and natural levee deposits that contain goethite, iron oxides, manganese oxides, and carbonates are stabilized early in their depositional history and therefore do not lend themselves to rapid volume reduction associated with dewatering and compaction. Elemental concentrations can also be interpreted to reflect relative diagenetic activity in the sediments. These preliminary results indicate that close examination of diagenetic mineralogical and geochemical features can provide valuable information concerning the subsidence history of delta plain areas.

  7. Sediments in Semi-arid Wetlands: US Southern High Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Playas are ephemeral wetlands on the semi-arid U.S. Southern High Plains that serve as runoff catchment basins and are thought to be focal points of Ogallala aquifer recharge. Sediments in playas alter biodiversity and hydroperiods. The purpose of this study was to evaluate the effects of outerbas...

  8. Current-controlled, abyssal microtopography and sedimentation in Mozambique Basin, southwest Indian Ocean

    USGS Publications Warehouse

    Kolla, V.; Eittreim, S.; Sullivan, L.; Kostecki, J.A.; Burckle, L.H.

    1980-01-01

    The Antarctic Bottom Water (AABW) activity and the variations in the abundance and grain size of the terrigenous sediments, derived from Africa and Madagascar land masses, are reflected in different types of microtopography in the Mozambique Basin. In southerly areas, where the sediment supply is much less, the bottom-current activity has resulted in the presence of manganese nodules, a thin veneer of sediments, and the absence of sediment waves. Farther north, along the marginal areas of the basin where the fine-grained sediments from the Africa-Madagascar source have been supplied in abundance, wavy bedforms have been generated by AABW. Wavy bedforms do not exist even in the northerly areas if coarse-grained, turbidite sediments are present on the sea floor. The continuation of acoustic reflectors from the zone of turbidites in the central areas of the basin into the zone of sediment waves along the margins, and the lithology and structures in sediment cores from these zones suggest that the turbidity-current-fed, fine-grained sediments were deposited as wavy bedforms by AABW flow. Thus, sediment waves formed readily during Pleistocene times. The enrichment of quartz and displaced Antarctic diatoms, and the relatively low kaolinite/chlorite ratios in the sediments, the north-pointing current lineations on the sea floor, the lack of any perceptible sedimentary fill in the troughs of waves, and the dense nepheloid layer in the westerly areas of the Mozambique Basin, attest to the current-controlled sedimentation and generation of wavy bedforms during Holocene time also. The formation of sediment waves in the Mozambique Basin can be modeled after a fluvial antidune mechanism. This model envisages that internal waves, focussed on a benthic boundary layer cap, have been locked in phase with sediment waves in the presence of an 8-10 cm/sec current in the Mozambique Basin. A density contrast of 2??10-6 g/cm3 appears to exist at the tops of benthic boundary layers in the Mozambique Basin and is quite sufficient for supporting the internal waves. The densiometric Froude number calculated for a 60-280 m thick boundary layer in the basin is close to unity or greater, and is compatible with the antidune model. ?? 1980.

  9. Coupling Between Fluid Flow and Brittle/semi-brittle Deformation: A Comparison Between The Skyttorp-vattholma Fault Zone, Sweden and The Iberia Abyssal Plain (odp Site 1067)

    NASA Astrophysics Data System (ADS)

    Engstrm, A.; Skelton, A.

    The Skyttorp-Vattholma Fault Zone (SVFZ) is situated in northern Uppland, south- central Sweden, near the villages of Skyttorp and Vattholma. The zone exposes ev- idence of both brittle and ductile deformation. Brittle deformation is manifest by large-scale faults, breccias and brittle macro- to microscale structures such as frac- tures, small-scale faults, deformed grains and cataclastic flow. Brittle deformation en- hanced fluid circulation, which generated hydrothermal minerals, e.g. chlorite, lau- montite, epidote and prehnite, concentrating in veins or on slickenside surfaces. Dur- ing brittle deformation, semi-brittle structures, including kinkbands and boxfolds, formed and eventually overprinted ductile as well as brittle structures. Folded brec- cias and deformed calcite and chlorite indicate a transition from brittle to semi-brittle behaviour, most likely caused by invading fluids weakening the rock. Fluid-rock inter- action appears very local, or alternatively, semi-brittle structures have been obscured by subsequent brittle deformation during the fault evolution. We conclude that fluid- deformation interaction in the SVFZ was cyclic and related to the large-scale evolution of the fault zone. The fault zone initially served as a conduit for fluids, which softened the material and enhanced semi-brittle deformation. With time, precipitated miner- als acted as barriers for fluids promoting renewed brittle deformation, opening new conduits (Engstrm and Sjstrm, 2002). Similar coupling between fluid flow and brittle/semi-brittle deformation is observed in drill core samples from ODP Site 1067, which is situated at the eastern boundary of the ocean-continent transition zone beneath the Iberia Abyssal Plain. Here fluid-rock in- teraction is manifested by growth of hydrothermal minerals, e.g. epidote, chlorite and calcite, occurring in tectonised amphibolites. Spatial correlation of hydrothermal and cataclastic "fronts" at Site 1067 argues for coupling between brittle deformation and fluid-rock interaction. Ongoing microstructural studies indicate the presence of semi- brittle features such as kinkbands and reactivated veins and faults. These observation, together with evidence for recrystallisation of hydrothermal epidote, indicating two or 1 more phases of fluid-rock interaction, suggest that (1) two or more deformation/fluid- rock interaction cycles occurred, and (2) a similar pattern to that observed in the SVFZ, where fluid-induced softening resulted in enhanced semi-brittle deformation, is ob- served at the Iberia Abyssal Plain. 2

  10. Abyssal hills - hidden source of increased habitat heterogeneity, benthic megafaunal biomass and diversity in the deep sea

    NASA Astrophysics Data System (ADS)

    Durden, Jennifer M.; Bett, Brian J.; Jones, Daniel O. B.; Huvenne, Veerle A. I.; Ruhl, Henry A.

    2015-09-01

    Abyssal hills are the most abundant landform on Earth, yet the ecological impact of the resulting habitat heterogeneity on the wider abyss is largely unexplored. Topographic features are known to influence food availability and the sedimentary environment in other deep-sea habitats, in turn affecting the species assemblage and biomass. To assess this spatial variation, benthic assemblages and environmental conditions were compared at four hill and four plain sites at the Porcupine Abyssal Plain. Here we show that differences in megabenthic communities on abyssal hills and the adjacent plain are related to environmental conditions, which may be caused by local topography and hydrodynamics. Although these hills may receive similar particulate organic carbon flux (food supply from the surface ocean) to the adjacent plain, they differ significantly in depth, slope, and sediment particle size distribution. We found that megafaunal biomass was significantly greater on the hills (mean 13.45 g m-2, 95% confidence interval 9.25-19.36 g m-2) than the plain (4.34 g m-2, 95% CI 2.08-8.27 g m-2; ANOVA F(1, 6) = 23.8, p < 0.01). Assemblage and trophic compositions by both density and biomass measures were significantly different between the hill and plain, and correlated with sediment particle size distributions. Hydrodynamic conditions responsible for the local sedimentary environment may be the mechanism driving these assemblage differences. Since the ecological heterogeneity provided by hills in the abyss has been underappreciated, regional assessments of abyssal biological heterogeneity and diversity may be considerably higher than previously thought.

  11. Styles of interdistributary basin sedimentation: Mississippi delta plain, Louisiana

    SciTech Connect

    Tye, R.S.; Kosters, E.C.

    1986-09-01

    Analyses of sedimentary processes in the Barataria and Atchafalaya basins of the Louisiana delta plain reveal two contrasting styles of sediment accumulation. The deposits are largely controlled by the relative rates of subsidence and the amount of sediment transported into the basins. Marine delta progradation and subsequent abandonment on approximately a 1000 to 1500-year cycle isolate extensive backswamp and marshy areas between major distributary channels. The resulting interdistributary basins areally occupy a large part of the lower alluvial valley and upper delta plain. Extensive well-drained and poorly drained backswamp environments occur at the apex of these basins and grade seaward into fresh, brackish, and saline marshes. Following delta-lobe abandonment, high subsidence rates combined with low sediment input lead to basin flooding, both by marine incursion and the enlargement of lakes.

  12. Tanaidacean fauna of the Kuril-Kamchatka Trench and adjacent abyssal plain - abundance, diversity and rare species

    NASA Astrophysics Data System (ADS)

    B?a?ewicz-Paszkowycz, Magdalena; Pabis, Krzysztof; J?wiak, Piotr

    2015-01-01

    Here we examine the distribution patterns, abundance, and species richness of tanaidacean peracarids in the abyssal-hadal transition zone. Material was collected in the region of Kuril-Kamchatka Trench during the German-Russian KuramBio Expedition with use of a giant boxcorer (GKG) of sampling area 0.25 m2. In the 23 samples collected from depths 4900 to 5800 m 48 species of Tanaidacea belonging to 11 families have been identified; most of the species (80%) are new to science. There was no evidence of a distribution pattern associated with depth or geographic location of stations in the nMDS analysis. Frequency of occurrence of twelve species was high (at 34-78% of stations) although the stations were distributed along a distance of about 1000 km. This observation is rationalized by the uniform environmental conditions of temperature, hydrostatic pressure, salinity, conductivity, and character of bottom deposits in the investigated area. Mean tanaidacean densities were 25.018.0 ind./0.25 m2, with mean values of species richness (number of species per sample) and diversity (Shannon Index) as high as 9.74.6 and 1.90.3 respectively. Singletons constituted about 20% of all species and more than one third of the species occurred as low counts per sample. The species accumulation curve did not reach the asymptotic level suggesting under-sampling of the studied area.

  13. An account of the Ischnomesidae (Peracarida, Isopoda) from the Kuril-Kamchatka Trench and abyssal plain (Northwest Pacific) with the description of two new species

    NASA Astrophysics Data System (ADS)

    Brandt, Angelika; Kristin Stven, Jana; Caurant, Cyril; Oskar Elsner, Nikolaus

    2015-01-01

    During the German-Russian expedition KuramBio (Kuril-Kamchatka Biodiversity Studies) from board of the RV Sonne to the Kuril-Kamchatka Trench and adjacent abyssal plain, benthic samples were taken by means of a camera-epibenthic sledge. Amongst one of the most diverse macrobenthic taxa, the Isopoda (Crustacea, Malacostraca), Ischnomesidae were the fifth most abundant isopod family in the Kuril-Kamchatka area and were sampled with 24 species from 5 genera in 21 hauls at 12 stations. Fortimesus occurs most frequently in the samples (36% of all Ischnomesidae sampled), followed by Stylomesus (26%), Heteromesus (23%), Ischnomesus (10%) and Gracilimesus (4%). Number of ischnomesid individuals is highest at station 10-12 with 35 specimens, followed by station 12-4 (30 ind.), station 6-12 (29 ind.), station 9-9 (28), and station 1-11 (24). At station 4-3 only 1 specimen was found. A key to all genera of Ischnomesidae is provided. Two new species from two genera: StylomesusWolff, 1956 and FortimesusKavanagh and Wilson, 2007 are described from the KuramBio material. Stylomesus malyutinae sp. nov. is distinguished by the smooth body surface, the shape of pleotelson and the length of uropods from other species of the genus from the Northwest Pacific Ocean. Fortimesus trispiculum sp. nov. is characterised by anterolateral projections of pereonites 1-3 which are forming an angle of about 45 with the longitudinal body axis decreasing in length from anterior to posterior.

  14. Effect on the macrobenthic community structure of an abyssal salt diapir in the central Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Martinez, M.; Escobar, E.; Mortera, C.

    2007-05-01

    A salt diapir was mapped in the Sigsbee abyssal plain in the central Gulf of Mexico and studied to evaluate the effect on the variability of the macrobenthic community structure. Samples were collected along a linear transect in 6 stations associated with the salt diapir, including abyssal stations. The diapir affects sediment factors such as percentage of sand and silt and the elemental C/N ratio and percentage of organic carbon and nitrogen determining the distribution of the macrobenthic taxonomic richness and biomass. The densities of taxa such as ostracods, cumaceans, nematodes, polychaetes and turbelarids respond specifically to the availability of organic carbon and nitrogen in sediment. This salt diapir acts as a topography feature that modifies the superficial sediment conditions and food availability affecting the composition and taxonomic richness, density and biomass of the abyssal benthos.

  15. Biogeochemical variations at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the northeast Atlantic Ocean, from weekly to inter-annual time scales

    NASA Astrophysics Data System (ADS)

    Hartman, Susan; Lampitt, Richard

    2015-04-01

    We present high-resolution autonomous measurements of carbon dioxide partial pres- sure p(CO2) taken in situ at the Porcupine Abyssal Plain sustained observatory (PAP- SO) in the northeast Atlantic (49N, 16.5W; water depth of 4850 m) for the period 2010 to 2012. Measurements of p(CO2) made at 30 m depth on a sensor frame are compared with other autonomous biogeochemical measurements at that depth (including chlorophyll a-fluorescence and nitrate concentration data) to analyse weekly to seasonal controls on p(CO2) flux in the inter-gyre region of the North Atlantic. Comparisons are also made with in situ regional time-series data from a ship of opportunity and mixed layer depth (MLD) measurements from profiling Argo floats. There is a persistent under saturation of CO2 in surface waters throughout the year which gives rise to a perennial CO2 sink. Comparison with an earlier dataset collected at the site (2003 to 2005) confirms seasonal and inter-annual changes in surface seawater chemistry. There is year-to-year variability in the timing of deep winter mixing and the intensity of the spring bloom. The 2010-2012 period shows an overall increase in p(CO2) values when compared to the 2003-2005 period as would be expected from increases due to anthropogenic CO2 emissions. The surface temperature, wind speed and MLD measurements are similar for both periods of time. Future work should incorporate daily CO2 flux measurements made using CO2 sensors at 1 m depth and the in situ wind speed data now available from the UK Met Office Buoy.

  16. Biogeochemical variations at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the northeast Atlantic Ocean, from weekly to inter-annual time scales

    NASA Astrophysics Data System (ADS)

    Hartman, S. E.; Jiang, Z.-P.; Turk, D.; Lampitt, R. S.; Frigstad, H.; Ostle, C.

    2014-08-01

    We present high-resolution autonomous measurements of carbon dioxide partial pressure p(CO2) taken in situ at the Porcupine Abyssal Plain sustained observatory (PAP-SO) in the Northeast Atlantic (49 N, 16.5 W; water depth of 4850 m) for the period 2010 to 2012. Measurements of p(CO2) made at 30 m depth on a sensor frame are compared with other autonomous biogeochemical measurements at that depth (including chlorophyll a-fluorescence and nitrate concentration data) to analyse weekly to seasonal controls on p(CO2) flux in the inter-gyre region of the North Atlantic. Comparisons are also made with in situ regional time-series data from a ship of opportunity and mixed layer depth (MLD) measurements from profiling Argo floats. There is a persistent under saturation of CO2 in surface waters throughout the year which gives rise to a perennial CO2 sink. Comparison with an earlier dataset collected at the site (2003 to 2005) confirms seasonal and inter-annual changes in surface seawater chemistry. There is year-to-year variability in the timing of stratification and deep winter mixing. The 2010 to 2012 period shows an overall increase in p(CO2) values when compared to the 2003-2005 period. This is despite similar surface temperature, wind speed and MLD measurements between the two periods of time. Future work should incorporate daily CO2 flux measurements made using CO2 sensors at 1 m depth and the in situ wind speed data now available from the UK Met Office Buoy.

  17. Biogeochemical variations at the Porcupine Abyssal Plain sustained Observatory in the northeast Atlantic Ocean, from weekly to inter-annual timescales

    NASA Astrophysics Data System (ADS)

    Hartman, S. E.; Jiang, Z.-P.; Turk, D.; Lampitt, R. S.; Frigstad, H.; Ostle, C.; Schuster, U.

    2015-02-01

    We present high-resolution autonomous measurements of carbon dioxide partial pressure p(CO2) taken in situ at the Porcupine Abyssal Plain sustained Observatory (PAP-SO) in the northeast Atlantic (49 N, 16.5 W; water depth of 4850 m) for the period 2010-2012. Measurements of p(CO2) made at 30 m depth on a sensor frame are compared with other autonomous biogeochemical measurements at that depth (including chlorophyll a fluorescence and nitrate concentration data) to analyse weekly to seasonal controls on p(CO2) flux in the inter-gyre region of the North Atlantic. Comparisons are also made with in situ regional time series data from a ship of opportunity and mixed layer depth (MLD) measurements from profiling Argo floats. There is a persistent under-saturation of CO2 in surface waters throughout the year which gives rise to a perennial CO2 sink. Comparison with an earlier data set collected at the site (2003-2005) confirms seasonal and inter-annual changes in surface seawater chemistry. There is year-to-year variability in the timing of deep winter mixing and the intensity of the spring bloom. The 2010-2012 period shows an overall increase in p(CO2) values when compared to the 2003-2005 period as would be expected from increases due to anthropogenic CO2 emissions. The surface temperature, wind speed and MLD measurements are similar for both periods of time. Future work should incorporate daily CO2 flux measurements made using CO2 sensors at 1 m depth and the in situ wind speed data now available from the UK Met Office Buoy.

  18. Sonnenemertes cantelli gen. et sp. nov. (Heteronemertea)-A new Oxypolella-like nemertean from the abyssal plain adjacent to the Kuril-Kamchatka Trench

    NASA Astrophysics Data System (ADS)

    Chernyshev, Alexei V.; Abukawa, Shushi; Kajihara, Hiroshi

    2015-01-01

    Approximately 129 nemertean specimens were obtained in the material collected by the Russian-German KuramBio expedition 2012 to the abyssal plain adjacent to the Kuril-Kamchatka Trench (KKT). Due to deformed, fragmentary condition of most of the collected nemerteans they were identified to the order level only. Both archi- and heteronemerteans were very rare, and tubulanid palaeonemerteans and hoplonemerteans were predominant in the KuramBio epibenthic sledge (EBS) samples. Before the KuramBio expedition, only three species of the World fauna of benthic nemerteans had been known from depths exceeding 3000 m; according to data of Vityaz expedition in the KKT, published in 1955, unidentified nemerteans were found in all trawl samples from depths 1000 to 4640 m, but only one specimen of unidentified nemertean was collected from depths exceeding 5000 m. A reliable estimation of the actual species diversity of the present KuramBio samples could have been made primarily based on molecular genetic analyses; almost all the collected specimens are likely to represent undescribed species. In this study, a new species of the heteronemertean, Sonnenemertes cantelli gen. et sp. nov., from a depth of approximately 4870 m is described. This is the deepest record for an identified benthic nemertean, as well as the first species of the subfamily Oxypolellinae from the North Pacific. A single specimen was examined by light microscopy, scanning electron microscopy, and confocal laser scanning microscopy with phalloidin and antibody labeling. Morphologically, this species is similar to those in the genus Oxypolella. A preliminary molecular phylogenetic analysis based on partial 16S rDNA among the selected heteronemertean species indicated that S. cantelli formed a monophyletic group with Oxypolella alba Bergendal, 1903 together as a sister to the genus Baseodiscus. Systematic positioning of Oxypolella, Sonnenemertes, and related genera is discussed.

  19. Abyssal seafloor waste isolation: the concept

    NASA Astrophysics Data System (ADS)

    Valent, Philip J.; Young, David K.; Sawyer, William B.; Wright, Thomas D.

    1998-05-01

    The Naval Research Laboratory (NRL), with industry and university participation, conducted an assessment of the concept of isolating certain wastes (i.e., sewage sludge, fly ash from municipal incinerators, and contaminated dredged material) on the oceans' abyssal seafloor. In this assessment the advantages, disadvantages, and economic and environmental viability of potential engineering methods for achieving abyssal waste isolation were identified and compared. This paper presents background to the Abyssal Plains Waste Isolation (APWI) Project, describes the characteristics of the waste streams and quantities potentially available for disposal via the abyssal isolation concept, summarizes regulations affecting use of the abyssal seafloor for disposal of wastes, and introduces the technical and scientific premises underlying implementation of the concept.

  20. Desmosomatidae (Isopoda: Asellota) from the abyssal plain to the east of the Kuril-Kamchatka Trench: New data on diversity with the description of two new species

    NASA Astrophysics Data System (ADS)

    Golovan, Olga A.

    2015-01-01

    In the material from the KuramBio expedition (Kuril-Kamchatka Biodiversity Study) Desmosomatidae constituted 20% of all isopod specimens (Crustacea: Malacostraca). 29 species in 10 genera (Desmosoma, Chelator, Eugerda, Eugerdella, Mirabilicoxa, Momedossa, Parvochelus, Prochelator, Pseudomesus and Torwolia) were found in the Pacific Ocean to the east of the Kuril-Kamchatka Trench at depth of 4830-5780 m. From these taxa five genera are reported for the first time in the Northwest Pacific, 26 species (90%) are new to science. Two species, Chelator michaeli sp.nov. and Prochelator keenani sp.nov. are described. Both described species appear to be very close to the two species previously known from the abyssal of the North Atlantic. Keys to the species of ChelatorHessler, 1970a and ProchelatorHessler, 1970a and the discussion of the genera are provided. The discussion of the Northwest Pacific desmosomatid fauna is presented. The diversity and the generic composition of the Desmosomatidae in the open abyssal of the Northwest Pacific are comparable with those known in other non-isolated deep-sea regions. On the contrary, the generic composition of Desmosomatidae in the adjacent semi-isolated Sea of Japan is impoverished versus the open Pacific abyssal.

  1. Spatial distribution and morphology of sediments in Texas Southern High Plains playa wetlands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Playas are depressional geomorphic features on the U.S. High Plains. About 20,000 Southern High Plains playa wet¬lands serve as runoff catchment basins, which are thought to be focal points of Ogallala aquifer recharge. Sediments in playas can alter biodiversity services, impede aquifer recharge, an...

  2. Spatial Distribution and Morphology of Sediments in Texas Southern High Plains Playa Wetlands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Playas are depressional geomorphic features on the U.S. High Plains and about 20,000 Southern High Plains playa wetlands serve as runoff catchment basins, which are thought to be focal points of Ogallala aquifer recharge. Sediments in playas can alter biodiversity services, impede aquifer recharge,...

  3. Sediment deposition in the flood plain of Stemple Creek Watershed, northern California

    NASA Astrophysics Data System (ADS)

    Ritchie, Jerry C.; Finney, Vernon L.; Oster, Kenneth J.; Ritchie, Carole A.

    2004-08-01

    Over the past 150 years, major land use changes have occurred in the Stemple Creek Watershed in northern California that have caused erosion to move soils from the upland to the flood plain, stream channels, and the bay. The purpose of this study is to document the recent (1954 to present) sediment deposition patterns in the flood plain area adjacent to Stemple Creek using the 137Cesium technique. Sediment deposition ranged from 0.26 to 1.84 cm year -1 for the period from 1964 to 2002 with an average of 0.850.41 cm year -1. Sediment deposition rates were higher for the 1954 to 1964 period with a range of 0.31-3.50 cm year -1 and an average of 1.291.04 cm year -1. These data indicate that sediment deposition in the flood plain has decreased since the middle 1950s, probably related to reduction in row crop agriculture and an increase in pasturelands. This study shows that the flood plains in the Stemple Creek Watershed are a significant sink for the soils being eroded from the upland area. Given the significance of the flood plain for trapping eroded materials before they reach the stream channels or the bay, efforts need to be made to manage these flood plain areas to insure that they do not change and become a source rather than a sink for eroded materials as improved management practices on the upland areas reduce sediment input to the flood plain.

  4. Exchanges of sediment between the flood plain and channel of the Amazon River in Brazil

    USGS Publications Warehouse

    Dunne, T.; Mertes, L.A.K.; Meade, R.H.; Richey, J.E.; Forsberg, B.R.

    1998-01-01

    Sediment transport through the Brazilian sector of the Amazon River valley, a distance of 2010 km, involves exchanges between the channel and the flood plain that in each direction exceed the annual flux of sediment out of the river at O??bidos (???1200 Mt yr-1). The exchanges occur through bank erosion, bar deposition, settling from diffuse overbank flow, and sedimentation in flood-plain channels. We estimated the magnitude of these exchanges for each of 10 reaches of the valley, and combined them with calculations of sediment transport into and out of the reaches based on sediment sampling and flow records to define a sediment budget for each reach. Residuals in the sediment budget of a reach include errors of estimation and erosion or deposition within the channel. The annual supply of sediment entering the channel from bank erosion was estimated to average 1570 Mt yr-1 (1.3 ?? the O??bidos flux) and the amount transferred from channel transport to the bars (380 Mt yr-1) and the flood plain (460 Mt yr-1 in channelized flow; 1230 Mt yr-1 in diffuse overbank flow) totaled 2070 Mt yr-1 (1.7 ?? the O??bidos flux). Thus, deposition on the bars and flood plain exceeded bank erosion by 500 Mt yr-1 over a 10-16 yr period. Sampling and calculation of sediment loads in the channel indicate a net accumulation in the valley floor of approximately 200 Mt yr-1 over 16 yr, crudely validating the process-based calculations of the sediment budget, which in turn illuminate the physical controls on each exchange process. Another 300-400 Mt yr-1 are deposited in a delta plain downstream of O??bidos. The components of the sediment budget reflect hydrologie characteristics of the valley floor and geomorphic characteristics of the channel and flood plain, which in turn are influenced by tectonic features of the Amazon structural trough.

  5. Composite refraction-reflection stack sections: Tracing faults in the Atlantic coastal plain sediments

    SciTech Connect

    Stephenson, D.E.; Coruh, C.; Costain, J.K.

    1993-05-01

    Seismic data from the Atlantic Coastal Plain are reprocessed and composite refraction-reflection stack sections produced to investigate basement faults that penetrate upward into Atlantic Coastal Plain sediments in South Carolina. Reprocessing recovered reflections from within the deep crust to the Moho as well as from within thin veneer (300) of the Atlantic Coastal Plain sediments. One of the major objectives of this paper is to discuss the use of shallow refracted arrivals to construct a composite refraction- reflection stack that allows better imaging of the subsurface at shallow depths.

  6. A census of abyssal polychaetes

    NASA Astrophysics Data System (ADS)

    Paterson, Gordon L. J.; Glover, Adrian G.; Barrio Frojn, Christopher R. S.; Whitaker, Amoret; Budaeva, Nataliya; Chimonides, Jim; Doner, Stacy

    2009-09-01

    As part of the Census of Marine Life's programme of summarising existing knowledge of the oceans, records of all polychaete species collected below 2000 m have been collated from the literature. A total of 3633 records was assembled into a database, revealing that 768 species, 358 of which were new to science, have been reported from the deep sea over the past 200 years. The limitations of the dataset are also discussed. Most of the records were obtained from between 2000 m, the upper depth range of the study, and 4000 m. Analyses of the distribution of records with time reveals that the majority of records were added in the 1960s to early 1980s, coincidental with the introduction of new collecting technologies. However, following this period there was a gap between the collecting of samples and the publication of taxonomic results. To reduce this time lag we are encouraging the use of the world-wide web with new tools and protocols to bring together taxonomists working on different sample sets and allow them to share and compare taxonomic data. As this is the first collation of abyssal polychaetes, the records were analysed to determine whether there is a distinct hadal fauna and whether the fauna of individual trenches was distinctive or a subset of the abyssal plain fauna. The results suggest that the hadal fauna contains few endemic species and that the majority are elements of the abyssal fauna that have extended their bathymetric range.

  7. Geochemical signature of provenance, tectonics and chemical weathering in the Quaternary flood plain sediments of the Hindon River, Gangetic plain, India

    NASA Astrophysics Data System (ADS)

    Mondal, M. E. A.; Wani, H.; Mondal, Bulbul

    2012-09-01

    The Ganga basin in the Himalayan foreland is a part of the world's largest area of modern alluvial sedimentation. Flood plain sediments of the Hindon River of the Gangetic plain have been analyzed for sediment texture, major and trace elements including rare earth elements (REEs). The results have been used to characterize the source rock composition and to understand the intensity of chemical weathering, tectonics and their interplay in the Hindon flood plain. The sediments of the Hindon flood plain dominantly consist of sand sized particles with little silt and clay. The geochemistry of the Hindon sediments has been compared to the Siwalik mudstone of the Siwalik Group (Siwaliks). The Siwalik sedimentary rocks like sandstones, mudstones and conglomerates are the known source rocks for the Hindon flood plain sediments. Mudstone geochemistry has been considered best to represent the source rock characteristics. The UCC (Upper Continental Crust) normalized major and trace elements of the Hindon flood plain sediments are very similar to the Siwalik mudstone except for Th and Cr. Furthermore, the average chondrite normalized REE pattern of the Hindon flood plain sediments is similar to the Siwalik mudstone. Textural immaturity, K/Rb ratios and the average CIA (Chemical Index of Alteration) and PIA (Plagioclase Index of Alteration) values of the Hindon flood plain sediments indicate that the sediments have not been affected by chemical weathering. Our study suggests that the active tectonics of the Himalayas and monsoon climate enhances only physical erosion of the source rocks (Siwaliks) rather than the chemical alteration. These factors help the Hindon sediments to retain their parental and tectonic signature even after recycling.

  8. The role of outcrop-to-outcrop fluid flow in off-axis oceanic hydrothermal systems under abyssal sedimentation conditions

    NASA Astrophysics Data System (ADS)

    Anderson, B. W.; Coogan, L. A.; Gillis, K. M.

    2012-05-01

    It has been proposed that ridge flank hydrothermal circulation by outcrop-to-outcrop (lateral) flow may be the dominant mode of oceanic hydrothermal circulation globally. In this model, the upper igneous crust is an aquifer overlain by low permeability sediments, and aquifer-ocean fluid exchange occurs through basement outcrops. Thermally induced pressure gradients drive fluid laterally from recharge outcrops to discharge outcrops. To test the global applicability of outcrop-to-outcrop flow, models of synthetic basement bathymetry representative of crust formed at different spreading rates, pelagic sediment supply and post depositional transport, and sediment hydraulic impedance are used to quantify the time-varying distribution of sediment and basement outcrops globally. Results suggest that basement outcrops may be 40-50% closer together than previously estimated. The modeled sediment and outcrop results are coupled with a two-dimensional model of outcrop-to-outcrop fluid flow and heat exchange in a vertically isothermal crustal aquifer to predict the spatial distributions of seafloor heat flow within the simulation region under this mode of hydrothermal circulation. It is found that both the time-varying average and standard deviation of modeled seafloor heat flow required by outcrop-to-outcrop flow simultaneously fit the global heat flow data if the average aquifer permeability decreases from 10-9 m2 to 10-11 m2 over the duration of the global heat flow deficit (to 65 Myr). This permeability range is consistent with other estimates of upper crustal permeability on comparable spatial scales, and supports the proposition that outcrop-to-outcrop fluid flow may be the dominant mode of off-axis hydrothermal circulation globally.

  9. Lineaments in coastal plain sediments as seen in ERTS imagery

    NASA Technical Reports Server (NTRS)

    Withington, C. F.

    1973-01-01

    Examination of satellite imagery over the Atlantic Coastal Plain near Washington, D. C. shows numerous lineaments, which cannot be accounted for by any known cultural or natural features. At least some of these lineaments represent the surface expression of faults, for one of them has been correlated with the outcrop of a fault that had been traced for several miles in southern Prince Georges County, Maryland. If a substantial number of these lineaments do indeed represent fault traces, the fact that they show on the surface suggests that the geologic history of the Coastal Plain is much more complex than has previously been recognized, and that faulting may have occurred in the Holocene, much later than has generally been recognized. The importance that such recent movements could have on future development of the Coastal Plain should be emphasized.

  10. Direct observation of episodic growth in an abyssal xenophyophore (Protista)

    NASA Astrophysics Data System (ADS)

    Gooday, A. J.; Bett, B. J.; Pratt, D. N.

    1993-11-01

    Three specimens of the xenophyophore Reticulammina labyrinthica were photographed on the Madeira Abyssal Plain (316.1'N, 2110.9'W; 4944 m) using the Bathysnap time-lapse camera system. During the 8 month observation period, the specimens underwent an estimated 3-10 fold increase in volume. Growth occurred episodically in several distinct phases, each lasting 2-3 days, during which sediment was collected and incorporated into the test. These phases were separated by fairly regular periods of about 2 months when the organisms showed little obvious activity. The growth phases were approximately synchronous between specimens. However, it is not clear whether the periodicity and apparent synchronization of these events resulted from an external (environmental) cue or whether growth is internally controlled and the synchronization arose by chance. These unique observations, which represent the first direct measurement of growth in any abyssal organism living outside a hydrothermal vent field, suggest that xenophyophores combine test growth with deposit feeding. The tests appear to grow more quickly, and to be more active, dynamic structures, than previously believed.

  11. Functional diversity patterns of abyssal nematodes in the Eastern Mediterranean: A comparison between cold seeps and typical deep sea sediments

    NASA Astrophysics Data System (ADS)

    Kalogeropoulou, V.; Keklikoglou, K.; Lampadariou, N.

    2015-04-01

    Spatial patterns in deep sea nematode biological trait composition and functional diversity were investigated between chemosynthetic and typical deep sea ecosystems as well as between different microhabitats within the chemosynthetic ecosystems, in the Eastern Mediterranean. The chemosynthetic ecosystems chosen were two mud volcanoes, Napoli at 1950 m depth and Amsterdam at 2040 m depth which are cold seeps characterized by high chemosynthetic activity and spatial heterogeneity. Typical deep sea ecosystems consisted of fine-grained silt-clay sediments which were collected from three areas located in the south Ionian Sea at 2765 to 2840 m depth, the southern Cretan margin at 1089 to 1998 m depth and the Levantine Sea at 3055 to 3870 m depth. A range of biological traits (9 traits; 31 categories) related to buccal morphology, tail shape, body size, body shape, life history strategy, sediment position, cuticle morphology, amphid shape and presence of somatic setae were combined to identify patterns in the functional composition of nematode assemblages between the two habitats, the two mud volcanoes (macroscale) and between the microhabitats within the mud volcanoes (microscale). Data on trait correspondence was provided by biological information on species and genera. A total of 170 nematode species were allocated in 67 different trait combinations, i.e. functional groups, based on taxonomic, morphological and behavioral characteristics. The Biological Trait Analysis (BTA) revealed significant differences between the mud volcanoes and the typical deep sea sediments indicating the presence of different biological functions in ecologically very different environments. Moreover, chemosynthetic activity and habitat heterogeneity within mud volcanoes enhance the presence of different biological and ecological functions in nematode assemblages of different microhabitats. Functional diversity and species richness patterns varied significantly across the different environmental gradients prevailing in the study areas. Biological trait analysis, with the addition of newly introduced trait categories, and functional diversity outcomes provided greater explanatory power of ecosystem functioning than species richness and taxonomic diversity.

  12. Retention of riverine sediment and nutrient loads by coastal plain floodplains

    USGS Publications Warehouse

    Noe, G.B.; Hupp, C.R.

    2009-01-01

    Despite the frequent citation of wetlands as effective regulators of water quality, few quantitative estimates exist for their cumulative retention of the annual river loads of nutrients or sediments. Here we report measurements of sediment accretion and associated carbon, nitrogen, and phosphorus accumulation as sedimentation over feldspar marker horizons placed on floodplains of the non-tidal, freshwater Coastal Plain reaches of seven rivers in the Chesapeake Bay watershed, USA. We then scale these accumulation rates to the entire extent of non-tidal floodplain in the Coastal Plain of each river, defined as riparian area extending from the Fall Line to the upper limit of tidal influence, and compare them to annual river loads. Floodplains accumulated a very large amount of material compared to their annual river loads of sediment (median among rivers = 119%), nitrogen (24%), and phosphorus (59%). Systems with larger floodplain areas and longer floodplain inundation retained greater proportions of riverine loads of nitrogen and phosphorus, but systems with larger riverine loads retained a smaller proportion of that load on floodplains. Although the source and long-term fate of deposited sediment and associated nutrients are uncertain, these fluxes represent the interception of large amounts of material that otherwise could have been exported downstream. Coastal Plain floodplain ecosystems are important regulators of sediment, carbon, and nutrient transport in watersheds of the Chesapeake Bay.

  13. Amazonis Planitia: The role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on Mars

    NASA Astrophysics Data System (ADS)

    Fuller, Elizabeth R.; Head, James W.

    2002-10-01

    Amazonis Planitia, located between the two main volcanic provinces on Mars (Tharsis and Elysium), is characterized by extremely smooth topography at several scale lengths, as smooth as oceanic abyssal plains topography on Earth. We use Mars Global Surveyor (MGS) data (primarily very high resolution Mars Orbiter Laser Altimeter (MOLA) topography and derivative slope maps, gradient maps, and detrended maps) to examine the surface morphology of Amazonis Planitia and the stratigraphic relationships among previously mapped and newly defined units. These new data reveal the presence of a 1300 km diameter Noachian impact basin in northwest Amazonis Planitia and an extensive Late Hesperian lava flow unit that appears to have originated from the Olympus Mons source area prior to aureole formation. The presence of this previously unrecognized flow unit strongly suggests that Olympus Mons activity dates back to at least the Hesperian, as did activity on the Tharsis Montes. Emplacement of this ~100 meter thick flow unit formed a barrier along the northern margin of Amazonis Planitia which had a profound influence on the subsequent geologic history of the region. Formation of Olympus Mons aureole deposits created an eastern topographic barrier, and subsequent Tharsis Montes lava flows entered the basin from the south, flowing around the aureole. These three barriers (degraded Noachian crater rim, proto-Olympus Mons flow unit, and Olympus Mons aureole) caused subsequent lava flows and outflow channel effluents, primarily from the Elysium region to the west, to pond on the floor of Amazonis Planitia, preferentially smoothing the terrain there. Mars Orbiter Camera (MOC) images substantiate that at least two very fluid lava flows alternated with fluvial episodes from Elysium Planitia, flowing through Marte Valles onto the floor of the Amazonis Planitia basin. Within Amazonis Planitia, MOC images show flow-like textures heavily mantled by sediments, and radar data reveal the presence of rough lava flow surfaces underlying the sedimentary debris. These data thus suggest that the unique smoothness of Amazonis Planitia is the result of deposition of thin fluid lava flows and fluvial sediments in an enclosed basin. Crater counts suggest that the most recent resurfacing may have occurred in the latest Amazonian Period, in the last 1% of the history of Mars. In light of its unique history, it is somewhat ironic to note that Amazonis Planitia was originally thought to be a typical young Martian surface and therefore used to name the Amazonian era.

  14. Arsenic fractionation and contamination assessment in sediments of thirteen lakes from the East Plain and Yungui Plateau Ecoregions, China.

    PubMed

    Zan, Fengyu; Huo, Shouliang; Zhang, Jingtian; Zhang, Li; Xi, Beidou; Zhang, Lieyu

    2014-10-01

    Arsenic (As) fractions in the sediments of seven lakes from East Plain Ecoregion and six lakes from Yungui Plateau Ecoregion, China, were investigated. Results indicated that the total As concentrations in sediment samples of lakes of the East Plain Lake Ecoregion are higher than those of Yungui Plateau Lake Ecoregion. Residual As is the main fraction in sediment samples of lakes from both ecoregions, followed by reducible As and soluble or oxidizable As. The total As is correlated to oxidizable As and residual As in sediment samples from both lake ecoregions. As distribution in sediment samples of lakes of the East Plain Ecoregion appears to be affected by human activity, while the As origin mainly comes from natural sources in sediment samples of lakes in the Yungui Plateau Ecoregion. The potential ecological risk index and geoaccumulation index values suggest "low to moderate" risk degree and "unpolluted to moderately polluted" for As in the studied lake sediments. PMID:25288540

  15. Distributions, sources, and ecological risks of hexachlorocyclohexanes in the sediments from Haihe Plain, Northern China.

    PubMed

    Xu, Fu-Liu; Kong, Xiang-Zhen; He, Wei; Qin, Ning; Zhu, Ying; Tao, Shu

    2013-04-01

    The levels of hexachlorocyclohexanes (HCHs) in the sediments from Haihe Plain, China, were measured by a gas chromatograph with a (63)Ni microelectron capture detector. The spatial distributions, possible sources, and potential ecological risks of these compounds were analyzed. The residual level of total HCHs was 33.84 173.37 ng g(-1) dry weight (d.w.) with ranges of 0.13 ~ 1,107.41 ng g(-1) d.w. Much higher ?HCH contents were found in the lower reaches of some rivers and in the mouth of the main stream receiving tributaries. The predominance of ?-HCH (36%) in the sediments was similar to that in the soils from Haihe Plain. The high percentages of ?-HCH (23-41%) could be detected at 25% of the sampling sites in the seven river systems. There were statistically significant positive relationships between the contents of HCHs and total organic carbon. Lindane was identified as the primary source of HCHs in the sediments, and it seemed that recent illegal lindane inputs still existed in some areas in Haihe Plain, as indicated by the ?-/?-HCH and ?-/(? + ?)-HCH ratios. Severe potential ecological risks of ?-HCH to benthic organisms at some sampling sites were found based on the consensus-based sediment quality guidelines. PMID:23054791

  16. Calculation of the mercury accumulation in the Idrijca River alluvial plain sediments.

    PubMed

    Zibret, Gorazd; Gosar, Mateja

    2006-09-01

    From the historic literature on the Idrija mercury mine, it is evident that part of the smelting and mining waste was dumped into the Idrijca River. This waste was transported downstream during floods. The amount of mercury which has accumulated in the alluvial sediments of the Idrijca River until the present was studied. Mapping of Holocene river terraces of the Idrijca River was performed in order to estimate the volume of the alluvial sediment. For the purpose of the assessment of the mercury concentration, we sampled the alluvial sediments on different levels and performed an analysis of variance. The greatest variability is between the floodplain and terraces inside the same alluvial plain. Considering this fact, which determined the methodology employed for calculation, we estimated that about 2029 tons of mercury is stored in the Idrijca River alluvial sediments. PMID:16274733

  17. Low-energy Beach ridge sedimentation in the Mississippi River delta plain

    SciTech Connect

    Gerdes, R.G.; Penland, S.

    1985-01-01

    Regressive beach ridge plains, such as Cheniere Caminada, Cheniere Caillou, and Cheniere Ronquille, are common depositional features within the Mississippi River delta plain in southeastern Louisiana. Vibracored sequences indicate beach ridge formation is a 3 stage process: Stage 1: Distributary Progradation, followed by Stage 2: Longshore Transport Interception, and completed by Stage 3: Beach Ridge Progradation. Cheniere Caminada is the largest beach ridge plain and is associated with the Late Lafourche delta. Radiocarbon dates indicate beach ridge building began approximately 720 years BP, when the Bayou Lafourche distributaries built seaward of the older, retreating Bayou Blue shoreline and intercepted westward longshore sediment transport, resulting in the progradation of Cheniere Caminada. Near the fan apex, beach ridges are 7-8 m thick and thin westward 2-3 m thick against the levees of Bayou Moreau. A typical beach ridge vertical sequence coarsens upward, with shoreface silty sands overlain by a thin cap of beach, washover, and aeolian sands. Beach ridge progradation in this area ceased approximately 300 years BP with the abandonment of Bayou Lafourche. The documentation of multiple regressive beach ridge plains suggest these deposits are stratigraphically more significant in the Mississippi River delta plain than recognized previously. The regressive beach ridge sequence documented in this study both stratigraphically and genetically contrasts with the classic transgressive chenier ridges of southwestern Louisiana.

  18. Transport and deposition of plutonium in the ocean: evidence from Gulf of Mexico sediments

    NASA Astrophysics Data System (ADS)

    Scott, M. R.; Salter, P. F.; Halverson, J. E.

    1983-05-01

    A study of sediments in the Gulf of Mexico shows dramatic gradients in Pu content and isotope ratios from the continental shelf to the Sigsbee Abyssal Plain. In terms of predicted direct fallout inventory of Pu, one shelf core contains 745% of the predicted inventory, while abyssal plain sediments contain only 15-20% of the predicted value. Absolute Pu concentrations of shelf sediments are also conspicuously high, up to 110 dpm/kg, compared to 13.5 dpm/kg in Mississippi River suspended sediment. There is no evidence of Pu remobilization in Gulf of Mexico shelf sediments, based on comparison of Pu profiles with Mn/Al and Fe/Al profiles. Horizontal transport of fallout nuclides from the open ocean to removal sites in ocean margin sediments is concluded to be the source of both the high concentrations and high inventories of Pu reported here. The shelf sediments show 240Pu/ 239Pu ratios close to 0.179, the average stratospheric fallout value, but the ratios decrease progressively across the Gulf to low values of 0.06 in abyssal plain sediments. The source of low-ratio Pu in deep-water sediments may be debris from low yield tests transported in the troposphere. Alternatively, it may represent a fraction of the Pu from global stratospheric fallout which has been separated in the water column from the remainder of the Pu in the ocean. In either case, the low-ratio material must have been removed rapidly to the sea floor where it composes a major fraction of the Pu in abyssal plain sediments. Pu delivered by global atmospheric fallout from the stratosphere has apparently remained for the most part in the water or has been transported horizontally and removed into shallow-water sediments.

  19. Linking suspended sediment transport metrics with fish functional traits in the Northwestern Great Plains (Invited)

    NASA Astrophysics Data System (ADS)

    Schwartz, J. S.; Simon, A.; Klimetz, L.

    2009-12-01

    Loss of ecological integrity due to excessive suspended sediment in rivers and streams is a major cause of water quality impairment in the United States. Although 32 states have developed numeric criteria for turbidity or suspended solids, or both according to the USEPA (2006), criteria is typically written as a percent exceedance above background and what constitutes background is not well defined. Defining a background level is problematic considering suspended sediments and related turbidity levels change with flow stage and season, and limited scientific data exists on relationships between sediment exposure and biotic response. Current assessment protocols for development of sediment total maximum daily loads (TMDLs) lack a means to link temporally-variable sediment transport rates with specific losses of ecological functions as loads increase. This study, within the in Northwestern Great Plains Ecoregion, co-located 58 USGS gauging stations with existing flow and suspended sediment data, and fish data from federal and state agencies. Suspended sediment concentration (SSC) transport metrics were quantified into exceedance frequencies of a given magnitude, duration as the number of consecutive days a given concentration was equaled or exceeded, dosage as concentration x duration, and mean annual suspended sediment yields. A functional traits-based approach was used to correlate SSC transport metrics with site occurrences of 20 fish traits organized into four main groups: preferred rearing mesohabitat, trophic structure, feeding habits, and spawning behavior. Negative correlations between SSC metrics and trait occurrences were assumed to represent potential conditions for impairment, specifically identifying an ecological loss by functional trait. Potential impairment conditions were linked with presence of the following traits: habitat preferences for stream pool and river shallow waters; feeding generalists, omnivores, piscivores; and several spawning behaviors. Using these results, TMDL targets were proposed such as < 19 mg/l SSC and 1,500 mg/l-day dosage at the 95% recurrence frequency for feeding generalists and omnivores. In general, traits correlated with: 1) a broad range of SSC exceedance frequencies and flow stages, 2) exceedance frequencies near 90-95% occurring at moderate flow stages; and 3) exceedance frequencies near 0.01-10 % occurring during floods. Unstable channels were found to be greater in transported suspended sediment than stable channels over a range of concentration exceedance frequencies, and likely influence physical habitat quality. Pool-preference and gravel spawner traits were greater in stable channels than unstable channels. Overall, a functional traits-based approach utilizing concentration-duration-frequency characteristics of suspended sediment transport was successful in identifying potential “targets” for biological impairment due to excessive sediment, and will aid in developing sediment TMDLs.

  20. Occurrence of arsenic in sediment pore waters in the central Kanto Plain, Japan

    NASA Astrophysics Data System (ADS)

    Hachinohe, Shoichi; Hamamoto, Hideki; Ishiyama, Takashi; Hossain, Sushmita; Oguchi, Chiaki T.

    2014-05-01

    The Kanto Plain is known as the largest plain in Japan, where marine sediments are widely developed because of cyclic iteration of global sea-level changes even 50 km or more inland from the present shoreline. In this area, dependence on groundwater for water requirements is relatively high; in particular, around 40 % of the municipal water supply is dependent on groundwater. Arsenic levels greater than that permitted by the environmental standards of Japan have been detected in groundwater in this area. Therefore, to evaluate occurrences of arsenic and other related elements in pore waters contained in natural sediment layers, we measured the levels of various inorganic chemical substances such as arsenic (As), iron (Fe), and sulfur (S) and major dissolved ions such as sulfate (SO42-), calcium (Ca2+), and sodium (Na+). Pore waters were collected from sediment samples that were obtained by a drilling from the river bottom down to 44 m depth; pore water samples were obtained immediately after extraction of sediments. The sedimentary facies in the vertical profile are continental, transitional, and marine, including two aquifers. The upper aquifer (15-20 m) contains fine to medium sand, whereas the lower aquifer (37-44 m) contains medium to coarse and gravelly sand. Arsenic and other inorganic elements were measured by an inductively coupled plasma mass spectrometer (ICP/MS) and an inductively coupled plasma atomic emission spectrometer (ICP/AES), and major dissolved ions were measured by an ion chromatograph analyzer. The total content of chemical elements was measured by X-ray fluorescence analysis using solid sediment samples. We obtained the following results. The arsenic concentrations in pore waters in marine silt and clay sediments (approximately 0.04 mg/L) were about five times higher than that in continental sediments (approximately 0.008 mg/L). The highest concentration of arsenic (0.074 mg/L) was detected at a depth of 13 m, which is immediately above the upper aquifer. Visual observations confirmed that this level is under oxidizing conditions. Thus, it regards that arsenic was adsorbed to iron hydroxide in the sediments. On the other hand, in the top part of the section, from the river bottom to a depth of approximately 3 m, arsenic concentrations in the pore waters were clearly high and decreased gradually and continuously with depth. This is considered to be the result of anthropogenic impact on the river.

  1. Identification of trends and patterns in sediment geochemistry from the Aare delta plain, Swiss Alps.

    NASA Astrophysics Data System (ADS)

    Carvalho, Filipe; Schulte, Lothar

    2015-04-01

    The study of fluvial systems by means of sediment cores is one of the most interesting approaches to understand the spatial and temporal pattern of river dynamics under the influence of different driving forces such as climate variability and human activities. This work focuses on the analysis of the geochemistry of fluvial sediments from the Aare delta plain in the Swiss Alps.The analysis of sediment cores allowed the identification of trends and patterns in sediment geochemistry. It was possible to identify diverse sedimentation phases in the delta plain, marked by differences in sedimentation processes and characterized by decreasing grain size sequences. It is worth mentioning the importance of peat formations in this sedimentary environment, reaching several centimeters thick in some cases. These horizons are normally associated with very low concentrations of chemical elements from the mineral fraction, such as Si, Al, Fe, and K. The general trends in geochemistry indicate the dominance of elements such as Al and Si, which have similar variability in all cores. It is noted that these elements have a reasonably good correlation with grain size and inverse relation with organic matter content. Factor analysis was used to study the geochemical data set of 3 sediment cores. This analysis is based on a statistical description of the variability of the correlated data where a smaller number of not observed variables are obtained (factors). Factor analysis attempts to find joint variation of the data series and presents that response as unobservable latent variables. In this study, factor analysis was conducted with the major chemical elements: Al, Si, P, K, Ca, Ti, Mn, Fe, Cu, Zn, Pb and also the percentage of TOC. Variations of these 12 inorganic and organic elements are reflected in two unobserved variables, factor 1 and factor 2. Factor analysis has enabled the recognition of two clusters: 1) a group of elements that include the TOC and metals, which are associated with organic horizons and 2) a group of inorganic elements, where the main response seems to be associated with phyllosilicate and siliciclastic minerals. A paleoclimatic analysis was also carried out using the main observed trends of the geochemistry analysis. This helped to identify a possible link between phases of increased fluvial activity and cold climatic periods. These phases are supported by an accumulation of coarser materials (sand-dominated layers) and may be influenced by glacier dynamics. It is assumed that during cold climatic periods, glaciers have greater erosive capacity. In warm periods there is strong evidence of an increase of peat formation.

  2. Sedimentation along the Eastern Chenier Plain Coast: Down Drift Impact of a Delta Complex Shift

    NASA Technical Reports Server (NTRS)

    Huh, Oscar K.; Walker, Nan D.; Moeller, Christopher

    2001-01-01

    The Mississippi River Chenier Plain is a shore parallel landform (down-drift from the Atchafalaya distributary of the Mississippi River) consisting of an alternating series of transgressive sand-shell ridges and regressive, progradational mudflats. The late 1940s shift of 1/3 of the flow of the Mississippi to the newly developing Atchafalaya delta complex to the west has resulted in injection of the river waters and suspended sediment into the westward flowing currents of the coastal current system. This has reactivated the dormant processes of mud accumulation along this coast. These environmental circumstances have provided the opportunity to: (1) investigate the depositional processes of the prograding, fine grained, mud flat facies of the open Chenier main coast and (2) to test the hypothesis that the impacts of the frequent cold front passages of fall, winter and spring exceed those of the occasional and more localized hurricane in shaping the coast and powering the dominant sedimentary processes. We conducted field investigations with the benefit of multi - scale, time series environmental surveillance by remote sensing systems, including airborne and satellite sensors. These systems provided invaluable new information on areal geomorphic patterns and the behavior of the coastal waters. This is a classic case of weather impacting inner shelf waters and sediments and causing the development of a new landform. It is clear that mud flats of the eastern chenier plain are prograding seaward, as well as progressively growing in a westerly direction.

  3. Paleochannels and Sediment Characteristics of the Chenier Plain Inner Shelf, Louisiana

    NASA Astrophysics Data System (ADS)

    Garcia-Garcia, A.; Fagherazzi, S.; Orange, D.

    2011-12-01

    In the last 3000 yrs, sediments from the Mississippi Delta have been transported to the western part of the Louisiana shelf, triggering beach progradation through a series of shell and sandy ridges (cheniers) separated by muddy hollows. Distinct events of chenier plain development have been explained as being the result of delta lobe switching in the Mississippi delta combined to local processes responsible for formation of beach ridges, recurved spits, eolian deposits, storm berms, and natural levees. In the present work we investigate the recent infill of the inner shelf off the Chenier Plain coast, just west of the recent deltaic deposits of the Mississippi River. We use shallow seismic analysis and the identification of paleochannels to understand their relationship with current rivers off the present coastline. We have been able to identify four seismic units U1 to U4 and their associated surfaces and discontinuities. A tentative reconstruction for the last 20 ky sedimentary infill is provided, correlating well with the datations available for the area. The identification and tracking of several buried channels across the shelf in units U1 and U3 let us track the position of the Mermentau-Calcasieu hydrological system in previous lowstands. It is interpreted that the Mermentau river was flowing more eastward during the Wisconsinan, occupying the location of our study and was then diverted to the west as a result of coastal processes and the development of the Chenier plains. Also, the Mermentau was re-occupying almost the same location at different lowstands, and only when the Chenier formed (due to reactivation of the west Mississippi lobe), the Mermentau was deviated westward due to sediment accumulation at the shoreline.

  4. The Surface of Venus is Saturated With Ancient Impact Structures, and its Plains are Marine Sediments

    NASA Astrophysics Data System (ADS)

    Hamilton, W. B.

    2009-05-01

    Conventional interpretations of Venus are forced to fit dubious pre-Magellan conjectures that the planet is as active internally as Earth and preserves no ancient surface features. Plate tectonics obviously does not operate, so it is commonly assumed that the surface must record other endogenic processes, mostly unique to Venus. Imaginative systems of hundreds of tiny to huge rising and sinking plumes and diapirs are invoked. That much of the surface in fact is saturated with overlapping large circular depressions with the morphology of impact structures is obscured by postulating plume origins for selected structures and disregarding the rest. Typical structures are rimmed circular depressions, often multiring, with lobate debris aprons; central peaks are common. Marine-sedimentation features are overlooked because dogma deems the plains to be basalt flows despite their lack of source volcanoes and fissures. The unearthly close correlation between geoid and topography at long to moderate wavelengths requires, in conventional terms, dynamic maintenance of topography by up and down plumes of long-sustained precise shapes and buoyancy. A venusian upper mantle much stronger than that of Earth, because it is cooler or poorer in volatiles, is not considered. (The unearthly large so-called volcanoes and tessera plateaus often are related to rimmed circular depressions and likely are products of impact fluidization and melting.) Plains-saturating impact structures (mostly more obvious in altimetry than backscatter) with diameters of hundreds of km are superimposed as cookie-cutter bites, are variably smoothed and smeared by apparent submarine impact and erosion, and are differentially buried by sediments compacted into them. Marine- sedimentation evidence includes this compaction; long sinuous channels and distributaries with turbidite- channel characteristics and turbidite-like lobate flows (Jones and Pickering, JGSL 2003); radar-smooth surfaces and laminated aspect in lander images; and widespread minor structures with neither terrestrial volcanic analogues nor plausible volcanic explanations. Broad tracts of polygonal reticulations 100 m to 5 km in diameter have dimensional and geometric terrestrial analogues in the polygonal faulting shown by 3-D reflection-seismic surveys of dewatered fine-grained sediments in marine basins. Impact-comminuted basaltic crust may dominate the fine sediment. Vast numbers of small low so-called shield volcanoes have geometric analogues in terrestrial mud volcanoes, not magmatic constructs. Less than half of the 1000 small misnamed pristine craters, the only venusian craters accepted by all as of impact origin, in fact are pristine. The rest are variably eroded, their craters partly filled by sediments that often display polygonal faulting, and their aprons partly covered by sediments of surrounding plains. All gradations are displayed between these structures and the more modified but otherwise similar structures from which they are arbitrarily and inconsistently separated. Lunar analogy dates the thousands of large venusian craters, 300-2000 km in rim diameter, as older than 3.8 Ga. Marine sedimentation began before late-stage accretion was complete. The nominally pristine craters are commonly assumed to be younger than 1 Ga but may go back to 3.8 Ga. Venusian oceans persisted long after that, without stillstands sufficient for development of global shorelines and shelves, before complete greenhouse evaporation, deep desiccation, and top-down metamorphism of sediments.

  5. Sediment distribution, hydrolytic enzyme profiles and bacterial activities in the guts of Oneirophanta mutabilis, Psychropotes longicauda and Pseudostichopus villosus: what do they tell us about digestive strategies of abyssal holothurians?

    NASA Astrophysics Data System (ADS)

    Roberts, D.; Moore, H. M.; Berges, J.; Patching, J. W.; Carton, M. W.; Eardly, D. F.

    This paper describes inter-specific differences in the distribution of sediment in the gut compartments and in the enzyme and bacterial profiles along the gut of abyssal holothurian species - Oneirophanta mutabilis, Psychropotes longicauda and Pseudostichopus villosus sampled from a eutrophic site in the NE Atlantic at different times of the year. Proportions of sediments, relative to total gut contents, in the pharynx, oesophagus, anterior and posterior intestine differed significantly in all the inter-species comparisons, but not between inter-seasonal comparisons. Significant differences were also found between the relative proportions of sediments in both the rectum and cloaca of Psychropotes longicauda and Oneirophanta mutabilis. Nineteen enzymes were identified in either gut-tissue or gut-content samples of the holothurians studied. Concentrations of the enzymes in gut tissues and their contents were highly correlated. Greater concentrations of the enzymes were found in the gut tissues suggesting that they are the main source of the enzymes. The suites of enzymes recorded were broadly similar in each of the species sampled collected regardless of the time of the year, and they were similar to those described previously for shallow-water holothurians. Significant inter-specific differences in the gut tissue concentrations of some of the glycosidases suggest dietary differences. For example, Psychropotes longicauda and Pseudostichopus villosus contain higher levels of chitobiase than Oneirophanta mutabilis. There were no seasonal changes in bacterial activity profiles along the guts of O. mutabilis and Pseudostichopus villosus. In both these species bacterial activity and abundance declined between the pharynx/oesophagus and anterior intestine, but then increased along the gut and became greatest in the rectum/cloaca. Although the data sets were more limited for Psychropotes longicauda, bacterial activity increased from the anterior to the posterior intestine but then declined slightly to the rectum/cloaca. These changes in bacterial activity and densities probably reflect changes in the microbial environment along the guts of abyssal holothurians. Such changes suggest that there is potential for microbial breakdown of a broader range of substrates than could be otherwise be achieved by the holothurian itself. However, the present study found no evidence for sedimentary (microbial) sources of hydrolytic enzymes.

  6. Ridgelet and Curvelet Analysis of Abyssal-hill Fabric

    NASA Astrophysics Data System (ADS)

    Downey, N. J.; Clayton, R. W.

    2006-12-01

    Abyssal-hill shape correlates with spreading rate and direction. Therefore analysis of abyssal-hill fabric may be useful for determining the tectonic history of regions where spreading rate and direction cannot be determined from magnetic reversal anomalies. One such region is the area of seafloor east of the Tonga- Kermadec trench that contains the Osbourn Trough. This region was created during the Cretaceous Long Normal Polarity Interval (Chron C34, 83-121 Ma). We present a new method of abyssal-hill analysis based on the ridgelet and curvelet transforms, relatives of the 2D wavelet transform. This technique is spatially local and therefore especially useful for detecting changes in abyssal-hill shape. These changes may correspond to changes in tectonic configuration at the time of seafloor creation. However several post-creation processes can affect the results of any abyssal-hill analysis. Three such process are sedimentation, post-creation seafloor faulting and intraplate volcanism. In the Tonga-Kermadec region the most sediment-free area is located on the forebulge of the Pacific plate. This region, however, has been subjected to subduction-related trench-parallel faulting. Fortunately, the abyssal-hill fabric in this region trends nearly perpendicular to the strike of the faulting. Ridgelet-domain filtering of the bathymetry of this region therefore makes it possible to separate the linear features due to sea floor spreading from those due to post-creation faulting. The Tonga- Kermadec region has also been subjected to extensive intraplate volcanism resulting in the creation of many seamounts. By utilizing the ridgelet/curvelet transform and the isotropic 2D wavelet transform in a morphological component analysis (MCA) it is possible to filter the relatively conical seamounts from the elongate abyssal-hills so that the latter can be analyzed independently.

  7. Geochemical Fractionations and Mobility of Arsenic, Lead and Cadmium in Sediments of the Kanto Plain, Japan.

    NASA Astrophysics Data System (ADS)

    Hossain, Sushmita; Oguchi, Chiaki T.; Hachinohe, Shoichi; Ishiyama, Takashi; Hamamoto, Hideki

    2014-05-01

    Lowland alluvial and floodplain sediment play a major role in transferring heavy metals and other elements to groundwater through sediment water interaction in changing environmental conditions. However identification of geochemical forms of toxic elements such as arsenic (As), lead (Pb) and cadmium (Cd) requires risk assessment of sediment and subsequent groundwater pollution. A four steps sequential extraction procedure was applied to characterize the geochemical fractionations of As, Pb and Cd for 44 sediment samples including one peat sample from middle basin area of the Nakagawa river in the central Kanto plain. The studied sediment profile extended from the bottom of the river to 44 m depth; sediment samples were collected at 1m intervals from a bored core. The existing sedimentary facies in vertical profile are continental, transitional and marine. There are two aquifers in vertical profile; the upper aquifer (15-20m) contains fine to medium sand whereas medium to coarse sand and gravelly sand contain in lower aquifer (37-44m). The total As and Pb contents were measured by the X-Ray Fluorescence analysis which ranged from 4 to 23 mg/kg of As and 10 to 27 mg/kg of Pb in sediment profile. The three trace elements and major heavy metals were determined by ICP/MS and ICP/AES, and major ions were measured by an ion chromatograph. The marine sediment is mainly Ca-SO4 type. The Geochemical analysis showed the order of mobility trends to be As > Pb > Cd for all the steps. The geochemical fractionations order was determined to be Fe-Mn oxide bound > carbonate bound > ion exchangeable > water soluble for As and Pb whereas the order for Cd is carbonate bound > Fe-Mn oxide bound > ion exchangeable > water soluble. The mobility tendency of Pb and Cd showed high in fine silty sediment of marine environment than for those from continental and transitional environments. In the case of As, the potential mobility is very high (>60%) in the riverbed sediments and clayey silt sediment at 13m depth which is just above the upper aquifer. This potential mobility may pose a threat to upper aquifer and riverbed aquatic system. The overall geochemical analysis revealed that the dissolution of Fe-Mn oxide is the most effective mechanism for As, Pb in groundwater however the mobility of Cd is mainly carbonate bound. In the present study, the pollution level is much below from leaching environmental standards (0.01 mg/L) for all three elements and the total content is within the natural abundance of As, Pb and Cd in sediment. The potential mobility of these elements in oxidized fine silty sediment and the possible further effect to the aquifer suggest that shallow groundwater abstraction should be restricted to protect seasonal groundwater fluctuation. Moreover marine sediment containing high total toxic element contents and mobility tendency at changing oxidation and reduction environments requires proper management when sediments are excavated for construction purpose.

  8. Source-To-Sink Perspectives On The Mississippi River System, Miocene To Present, Mountain To Abyss

    NASA Astrophysics Data System (ADS)

    Bentley, S. J.; Blum, M. D.

    2013-12-01

    . The objective of this study is to present a synthesis of the Mississippi River source-to-sink system, from montane source to abyssal sink, to elucidate specific geomorphic components and boundaries in the system, controls on mass transfer, and resultant geomorphic and statigraphic development. The Mississippi River source-to-sink system constitutes one of the largest sources, conduits, and depocenters of sediment on Earth, extending from elevations of 3.7 km in the Rocky Mountains to the Gulf of Mexico abyssal plain. Despite being one of the most intensely studied fluvial-marine systems in the world, comprehensive understanding and management of the system's resources remain a challenge. The system is valuable in many ways: it provides navigation and water to the heart of North America, and sustains extensive marine fisheries. The river has built a delta that is home to millions of people and yet is subsiding rapidly. Ancestral Mississippi fluvial-marine deposits continue to yield high-value petroleum resources to exploration. To address the range of temporal and spatial scales over which the system has developed and continues to evolve, we will focus on three geological time spans that display contrasting geologic forcing and response: Miocene, Pleistocene, and late Holocene. The present configuration of source, conduit, and sink were established during the Miocene epoch, when tectonics (via the uplifting southern Rockies, and later the rejuvenated Appalachians) and climate (wet in the east and dry in the west) provided abundant water and sediment to prograde the shelf margin and initiate deep-sea fan growth. Pleistocene continental glaciation, eustasy, and catastrophic drainage events further sculpted the alluvial valley, and extended the shelf margin, and fan. Studies of Modern processes and Holocene delta development have provided keys to both the delta's past and future evolution, in terms of cyclic autogenic lobe-switching, mass-transport events, storm-driven sediment delivery to canyon heads, and allogenic/anthropogenic controls on sediment supply and subsidence.

  9. Effects of waste disposal on benthic faunal succession on the abyssal seafloor

    NASA Astrophysics Data System (ADS)

    Young, David K.; Richardson, Michael D.

    1998-05-01

    Strategies to predict, and thus limit, potentially detrimental environmental impacts of abyssal disposal of wastes are severely limited by our lack of knowledge of deep-sea processes and lack of opportunity to directly study waste disposal in abyssal environments. Probable successional sequences following burial of benthic faunas by sewage sludge and dredged material on the abyssal seafloor are drawn by analogy with well-known processes in shallow-marine water. Scales of change and recovery of abyssal benthic faunas from episodic deposition of waste material are examined by extrapolation from what is currently known about turbidite sedimentary provinces, in particular, the Venezuela Abyssal Plain and the Great Meteor East area of the Madeira Abyssal Plain. Results suggest that initial benthic faunal recolonization would take place within years following episodic depositions of waste on the abyssal seafloor. Anoxic conditions or chemical inhibitory effects may delay initial benthic recolonization for hundreds of years. Establishment of equilibrium benthic faunal assemblages probably takes hundreds to potentially thousands of years. Potentially detrimental effects dictate that the surface areas of individual waste deposits should be minimized and the deposits should be isolated by capping with nontoxic materials or chemical barriers.

  10. Runoff and sediment responses to grazing native and introduced species on highly erodible Southern Great Plains soil.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Rolling Red Plains of western Oklahoma have highly erodible soils that are subject to rapid erosion under inappropriate land use. Understanding the hydrologic effects of different land uses is pivotal for managing this landscape to minimize runoff and sediment discharge and to improve stream-wat...

  11. Physiological Diversity and Distributions of Heterotrophic Bacteria in Deep Cretaceous Sediments of the Atlantic Coastal Plain

    PubMed Central

    Fredrickson, James K.; Balkwill, David L.; Zachara, John M.; Li, Shu-Mei W.; Brockman, Fred J.; Simmons, Mary A.

    1991-01-01

    A series of 23 intact core segments was obtained from two distinct deep subsurface geological formations, the Middendorf and the Cape Fear formations, underlying the southeastern coastal plain of South Carolina. The Middendorf formation in this region consists of permeable, saturated, sandy sediments; the Cape Fear formation consists mainly of less permeable sediments. The core segments were separated by vertical distances ranging from several centimeters to 48 m. Aerobic chemoheterotrophic bacteria were enumerated on a dilute medium, and populations ranged from 3.1 to 6.4 log CFU g of sediment-1 in the Middendorf cores and from below detection to 4.3 log CFU g-1 in the Cape Fear cores. A total of 198 morphologically distinct colony types were isolated, purified, and subjected to 108 different physiological measurements. The isolates from the two formations were distinct (i.e., they produced substantially different response patterns to the various physiological measurements), as were those in different core samples from the same formation. Cluster analysis revealed 21 different biotypes based on similarities of 75% or higher in response patterns to 21 physiological assays. One biotype contained 57 (29%) of the subsurface isolates, 10 biotypes contained 5 or more isolates, and the remainder had 4 or fewer. The organic compounds that were most commonly metabolized by the subsurface bacteria included Tween 40 (85%) and β-hydroxybutyric acid (60%). Organic acids, in general, were also commonly metabolized by the subsurface bacteria. Isolates from the Cape Fear core segments were capable of metabolizing a higher percentage of the substrates than were bacteria isolated from the Middendorf formation. Although the heterogeneous distributions of bacteria in deep subsurface sediments may make it difficult to use aquifer microcosms to predict in situ biotransformation rates, the diversity of the physiological properties of these organisms offers promise for in situ remediation of contaminants. PMID:16348407

  12. Thermal, chemical, and mass-transport processes induced in abyssal sediments by the emplacement of nuclear waste: experimental and modeling results

    SciTech Connect

    McVey, D.F.; Erickson, K.L.; Seyfried, W.

    1980-01-01

    This paper discusses heat and mass transport studies of marine red clay sediments being considered as a nuclear waste isolation medium. Numerical models indicate that for a maximum allowable sediment/canister interface temperature of 200 to 250/sup 0/C, the sediment can absorb about 1.5 kW initial power from waste in a 3 m long by 0.3 m dia canister buried 30 m in the sediment. Fluid displacement due to convection is found to be less than 1 m. Laboratory studies of the geochemical effects induced by heating sediment/seawater mixtures indicate that the canister and waste form must be designed to resist a hot, acid (pH 3 to 4) oxidizing environment. Since the thermally altered sediment volume of about 5.5 m/sup 3/ is small relative to the sediment volume overlying the canister, the acid and oxidizing conditions are not anticipated to effect the properties of the far field. Using sorption coefficient correlations, the migration of four nuclides /sup 239/Pu, /sup 137/Cs, /sup 129/I, and /sup 99/Tc were computer for a canister buried 30 m deep in a 60 m thick red clay sediment layer. It was found that the /sup 239/Pu and /sup 137/Cs are essentially completely contained in the sediments, while /sup 129/I and /sup 99/Tc broke through the 30 m of sediment in about 5000 years. The resultant peak injection rates of 4.6 x 10/sup -5/ ..mu..Ci/year-m/sup 2/ for /sup 129/I and 1.6 x 10/sup -2/ ..mu..Ci/year-m/sup 2/ for /sup 99/Tc were less than the natural radioactive flux of /sup 226/Ra (3.5 to 8.8 x 10/sup -4/ ..mu..Ci/year-m/sup 2/) and /sup 222/Rn (0.26 to 0.88 ..mu..Ci/year-m/sup 2/).

  13. Sedimentation of lithogenic particles in the deep ocean

    USGS Publications Warehouse

    Honjo, S.; Manganini, S.J.; Poppe, L.J.

    1982-01-01

    Investigation of lithogenic particles collected by sediment traps in open-ocean stations revealed that the sediment flux increased linearly with depth in the water column. This rate of increase decreased with distance of the station from the continent; it was largest at the Panama Basin station and almost negligible at the E. Hawaii Abyssal Plain station. At the Panama Basin station, smectite flux increased with depth. We suggest that smectite resuspended from bottom sediments of the continental slope west of the sediment-trap station is advected by easterly deep currents, and the suspended particles are then possibly entrapped by large settling particles. On the other hand, the flux of hemipelagic clay particles, kaolinite and chlorite, was nearly constant at all depths; this can be explained by incorporation of these particles in fecal pellets which then settle from the surface water. At the Demerara Abyssal Basin Station, flux of illite and chlorite particles increased with depth and the flux of smectite was constant. A sudden increase of the flux of illite and chlorite was observed near the bottom traps at the So??hm Abyssal Plain station. The flux of quartz and feldspar was 10 to 15% of the clay flux. ?? 1982.

  14. The feeding behaviour of an abyssal echiuran revealed by in situ time-lapse photography

    NASA Astrophysics Data System (ADS)

    Bett, B. J.; Rice, A. L.

    1993-09-01

    A time-lapse camera (IOSDL "Bathysnap") deployed on the Porcupine Abyssal Plain (4850.1'N, 1629.9'W, 4839 m), from 16 to 27 May 1991, recorded the sediment surface activity of what appeared to be an echiuran proboscis. The proboscis emerged from a hole formed during the period of observation to make seven sweeping, feeding excursions. These excursions, which occured over three consecutive days, averaged 73 min duration, with an average interval between excursions of 9 h, 22 min. The proboscis was not observed in the remaining eight days of the deployment. No change in the size or shape of near-by sediment mounds was observed at any time; there was no evidence of the return of material collected by the proboscis to the sediment surface. Proboscis activity appeared to occur preferentially at higher near-bottom current speeds, a possible advantage where phytodetritus is subject to redistribution by water currents (as was observed throughout the deployment). These observations are discussed in relation to the known behaviour of echiurans, particularly the mode of feeding, periodicity, quiescence, and sediment surface trace formation.

  15. Trends in nutrient and sediment retention in Great Plains reservoirs (USA).

    PubMed

    Cunha, Davi Gasparini Fernandes; do Carmo Calijuri, Maria; Dodds, Walter Kennedy

    2014-02-01

    Reservoirs are artificial ecosystems with physical, chemical, and biological transitional characteristics between rivers and lakes. Greater water retention time in reservoirs provides conditions for cycling materials inputs from upstream waters through sedimentation, biological assimilation and other biogeochemical processes. We investigated the effects of reservoirs on the water quantity and quality in the Great Plains (Kansas, USA), an area where little is known about these dominant hydrologic features. We analyzed a 30-year time-series of discharge, total phosphorus (TP), nitrate (NO3(-)), and total suspended solids (TSS) from six reservoirs and estimated overall removal efficiencies from upstream to downstream, testing correlations among retention, discharge, and time. In general, mean removal of TP (42-74%), TSS (0-93%), and NO3(-) (11-56%) from upstream to downstream did not change over 30 years. TP retention was associated with TSS removal, suggesting that nutrient substantial portion of P was adsorbed to solids. Our results indicated that reservoirs had the effect of lowering variance in the water quality parameters and that these reservoirs are not getting more or less nutrient-rich over time. We found no evidence of temporal changes in the yearly mean upstream and downstream discharges. The ratio upstream/downstream discharge was analyzed because it allowed us to assess how much contribution of additional unsampled tributaries may have biased our ability to calculate retention. Nutrient and sediment removal was less affected by hydraulic residence time than expected. Our study demonstrates that reservoirs can play a role in the removal and processing of nutrient and sediments, which has repercussions when valuing their ecological services and designing watershed management plans. PMID:24061791

  16. Importance of flood-plain sedimentation for river sediment budgets and terrigenous input to the oceans: Insights from the Brahmaputra-Jamuna River

    NASA Astrophysics Data System (ADS)

    Allison, M. A.; Kuehl, S. A.; Martin, T. C.; Hassan, A.

    1998-02-01

    Recent authors have suggested that a significant proportion of the worldwide terrigenous sediment budget is trapped landward of the river-ocean boundary in high-load, tectonically active basins. To test this idea, modern flood-plain sediment accumulation rates were determined along a 110 km reach of the Brahmaputra (locally Jamuna) River using 137Cs geochronology of sediment cores and geographic information system (GIS) extrapolation to adjacent areas. 137Cs accumulation rates decrease exponentially away from the channel, from >4 cm/yr on the natural levees to <1 cm/yr within a few tens of kilometers basinward. Important controls on sedimentation in this area include proximity to distributary channels, local topography, and interannual variability of the flood pulse. Model results indicate that an average of 23 m.t./yr of sediment are sequestered in this section of the flood plain. Extrapolated basinwide, as much as 39% 71% of the river sediment budget may be trapped landward of the Ganges-Brahmaputra mouth.

  17. Geostatistical modeling of the spatial distribution of sediment oxygen demand within a Coastal Plain blackwater watershed

    PubMed Central

    Todd, M. Jason; Lowrance, R. Richard; Goovaerts, Pierre; Vellidis, George; Pringle, Catherine M.

    2010-01-01

    Blackwater streams are found throughout the Coastal Plain of the southeastern United States and are characterized by a series of instream floodplain swamps that play a critical role in determining the water quality of these systems. Within the state of Georgia, many of these streams are listed in violation of the states dissolved oxygen (DO) standard. Previous work has shown that sediment oxygen demand (SOD) is elevated in instream floodplain swamps and due to these areas of intense oxygen demand, these locations play a major role in determining the oxygen balance of the watershed as a whole. This work also showed SOD rates to be positively correlated with the concentration of total organic carbon. This study builds on previous work by using geostatistics and Sequential Gaussian Simulation to investigate the patchiness and distribution of total organic carbon (TOC) at the reach scale. This was achieved by interpolating TOC observations and simulated SOD rates based on a linear regression. Additionally, this study identifies areas within the stream system prone to high SOD at representative 3rd and 5th order locations. Results show that SOD was spatially correlated with the differences in distribution of TOC at both locations and that these differences in distribution are likely a result of the differing hydrologic regime and watershed position. Mapping of floodplain soils at the watershed scale shows that areas of organic sediment are widespread and become more prevalent in higher order streams. DO dynamics within blackwater systems are a complicated mix of natural and anthropogenic influences, but this paper illustrates the importance of instream swamps in enhancing SOD at the watershed scale. Moreover, our study illustrates the influence of instream swamps on oxygen demand while providing support that many of these systems are naturally low in DO. PMID:20938491

  18. Physiological diversity and distributions of heterotrophic bacteria in deep cretaceous sediments of the Atlantic coastal plain

    SciTech Connect

    Fredrickson, J.K.; Zachara, J.M.; Li, S.W.; Brockman, F.J.; Simmons, M.A. ); Balkwill, D.L. )

    1991-02-01

    A series of 23 intact core segments was obtained from two distinct deep subsurface geological formations, the Middendorf and the Cape Fear formations, underlying the southeastern coastal plain of South Carolina. Aerobic chemoheterotrophic bacteria were enumerated on a dilute medium, and populations ranged from 3.1 to 6.4 log CFU g of sediment[sup [minus]1] in the Middendorf cores and from below detection to 4.3 log CFU g[sup [minus]1] in the Cape Fear cores. A total of 198 morphologically distinct colony types were isolated, purified, and subjected to 108 different physiological measurements. The isolates from the two formations were distinct as were those in different core samples from the same formation. Cluster analysis revealed 21 different biotypes based on similarities of 75% or higher in response patterns to 21 physiological assays. One biotype contained 57 of the subsurface isolates, 10 biotypes contained 5 or more isolates, and the remainder had 4 or fewer. The organic compounds that were most commonly metabolized by the subsurface bacteria included Tween 40 and [beta]-hydroxybutyric acid. Organic acids, in general, were also commonly metabolized by the subsurface bacteria. Isolates from the Cape Fear core segments were capable of metabolizing a higher percentage of the substrates than were bacteria isolated from the Middendorf formation. Although the heterogeneous distributions of bacteria in deep subsurface sediments may make it difficult to use aquifer microcosms to predict in situ biotransformation rates, the diversity of the physiological properties of these organisms offers promise for in situ remediation of contaminants.

  19. Sediments in marsh ponds of the Gulf Coast Chenier Plain: Effects of structural marsh management and salinity

    USGS Publications Warehouse

    Bolduc, F.; Afton, A.D.

    2005-01-01

    Physical characteristics of sediments in coastal marsh ponds (flooded zones of marsh associated with little vegetation) have important ecological consequences because they determine compositions of benthic invertebrate communities, which in turn influence compositions of waterbird communities. Sediments in marsh ponds of the Gulf Coast Chenier Plain potentially are affected by (1) structural marsh management (levees, water control structures and impoundments; SMM), and (2) variation in salinity. Based on available literature concerning effects of SMM on sediments in emergent plant zones (zones of marsh occasionally flooded and associated with dense vegetation) of coastal marshes, we predicted that SMM would increase sediment carbon content and sediment hardness, and decrease oxygen penetration (O2 depth) and the silt-clay fraction in marsh pond sediments. Assuming that freshwater marshes are more productive than are saline marshes, we also predicted that sediments of impounded freshwater marsh ponds would contain more carbon than those of impounded oligohaline and mesohaline marsh ponds, whereas C:N ratio, sediment hardness, silt-clay fraction, and O2 depth would be similar among pond types. Accordingly, we measured sediment variables within ponds of impounded and unimpounded marshes on Rockefeller State Wildlife Refuge, near Grand Chenier, Louisiana. To test the above predictions, we compared sediment variables (1) between ponds of impounded (IM) and unimpounded mesohaline marshes (UM), and (2) among ponds of impounded freshwater (IF), oligohaline (IO), and mesohaline (IM) marshes. An a priori multivariate analysis of variance (MANOVA) contrast indicated that sediments differed between IM and UM marsh ponds. As predicted, the silt-clay fraction and O2 depth were lower and carbon content, C:N ratio, and sediment hardness were higher in IM than in UM marsh ponds. An a priori MANOVA contrast also indicated that sediments differed among IF, IO, and IM marsh ponds. As predicted, carbon content was higher in IF marsh ponds than in ponds of other impounded marsh types. In contrast to our predictions, C:N ratio and sediment hardness were lowest and silt-clay fraction and O2 depth were highest in IO and IM marsh ponds. Our results indicated that SMM has affected physical properties of sediments in coastal marsh ponds. Moreover, sediments in IF marsh ponds were affected more so than were those in IO and IM marsh ponds. Our results, in conjunction with those of previous studies, indicated that sediments of marsh ponds and emergent plant zones differed greatly. We predict that changes in pond sediments due to SMM will promote greater epifaunal macroinvertebrate biomass, which in turn should attract larger populations of wintering waterbirds. However, waterbirds that filter or probe soft sediments may be negatively affected by SMM because of the expected decrease in infaunal invertebrate biomass. ?? Springer 2005.

  20. Vertical variation of potential mobility of heavy metal in sediment to groundwater of the Kanto plain, Japan

    NASA Astrophysics Data System (ADS)

    Hossain, S.; Hachinohe, S.; Ishiyama, T.; Hamamoto, H.; Oguchi, C. T.

    2014-12-01

    Heavy metals release from sediment may occur due to sediment water interaction under different changing environmental conditions. This has substantial influence on groundwater quality. However, identification of potentially mobile fractions of metals like Cu, Cr, Ni, Pb, Zn, Fe, Mn and Ti requires for the sustainable land and groundwater development and pollution management. 44 sediment and pore water samples at 1 m interval were analyzed from a vertical profile beneath the Naka river at the bottom of Central Kanto plain, Japan. Sequential extraction method was applied to determine potentially mobile forms of metals such as water soluble, ion exchangeable, acid soluble and Fe-Mn oxide bound. Metals were determined using X-Ray Fluorescence, Inductively coupled plasma atomic emission and mass spectrometer. Analyses show that potential mobility is high in river bed, volcanic ash mix, marine and transitional clayey silt. Metal mobility was higher in lower gravelly aquifer than upper sandy aquifer. Potential mobility and bioavailability of Zn, Cu, Ni, Pb and Mn are very high in river bed sediment which may pose threat to river bottom aquatic system. Zn, Cu and Ni concentration in pore water is high in river bed and peat bearing sediment. In pore water of marine and transitional sediment ion concentration such as Ca2+ and SO42- is very high indicating high mobility of Calcium and Sulfur from sediment as no significant variation observed in total content. In vertical profile, potential mobility tendency of metal in sediment trends to be Zn > Cu > Ni > Cr > Pb > Mn > Fe > Ti. Current study indicates low potential mobility and pollution risk to groundwater due to overall low metal concentration in pore water and high portion of metals attached with sediment as Fe-Mn oxide bound. More over under strong reducing condition considerable amount of metals will release and pollute groundwater.

  1. Invertebrate colonization of leaves and roots within sediments of intermittent coastal plain streams across hydrologic phases

    EPA Science Inventory

    We compared benthic invertebrate assemblages colonizing three types of buried substrates (leaves, roots and plastic roots) among three intermittent Coastal Plain streams over a one year period. Invertebrate density was significantly lower in root litterbags than in plastic root l...

  2. Use of U-series nuclides to constrain sediments transfer-times in the alluvial plains: example of the Ganges and Bramaputra river system.

    NASA Astrophysics Data System (ADS)

    Chabaux, Franois; Granet, Mathieu; Blaes, Estelle; Stille, Peter; France-Lanord, Christian; Dosseto, Antony

    2010-05-01

    U-series nuclides have the potential to bring important information on the transfer time of sediments in the alluvial plains. This is a consequence of the dual property of these nuclides 1) to be fractionated during physical denudation and chemical weathering processes and 2) to have radioactive decay periods of the same order of magnitude as the time-scales of these processes (e.g. Chabaux et al., 2003b, 2008). We have illustrated such a potential with the analysis of U-series disequilibria in sediments collected in the Ganges and Bramaputra river basin. The approach relies on the analysis of U-series in river sediments collected along the streams. Indeed, as illustrated in Granet et al. (2007), in large alluvial plains where sediments are only transferred and not affected by additional inputs of new weathering products from fresh rocks, the intensity of 238U-234U-230Th disequilibria in river sediments will only depend on two parameters: (a) the duration of the transfer including the time spent in soils and in the river, and (b) the nature and the intensity of U-Th fractionations occurring in sediments during their transfer into alluvial plains. Recovering time information from the variation of U-Th disequilibria in such sediments requires therefore the use of realistic models accounting for the U-Th fractionation of sediments during their transfers into the plain. From the data, it is proposed for the Ganges and Bramaputra river sediments, that the main U-Th fractionation process is connected with the sediment weathering during their transit and storage in the plain. In this case the U-Th variation in sediments along the two main rivers lead to quite long sediment transfer time in the alluvial plains, of 100-150 ky for Bramaputra plain and of 400 or 500 ky for the Ganges river. Chabaux F., Riotte J., Dequincey O. (2003) U-Th-Ra fractionation during weathering and river transport, Rev Mineral. Geochem. 52, 533-576. Chabaux, F., Bourdon, B., Riotte, J., 2008. U-series Geochemistry in weathering profiles, river waters and lakes. In : S. Krishnaswami and J.K. Cochran (Eds.), U/Th Series Radionuclides in Aquatic Systems, Elsevier, Radioactivity in the Environment, 13, 49-104 M. Granet, F. Chabaux, C. France-Lanord, P. Stille, E. Pelt (2007). Time-scales of sedimentary transfer and weathering processes from U-series nuclides: Clues from the Himalayan rivers, Earth and Planetary Science Letters, 261, 389-406.

  3. A DERIVED-DISTRIBUTION APPROACH TO DAILY LOADS OF SEDIMENT IN COASTAL PLAIN STREAMFLOW

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Estimates of allowable total maximum daily loads (TMDLs) of sediment must be developed for selected streams and rivers across the US. The sediment TMDLs are required to quantify total daily assimilative loads for those streams which are deemed to have impaired water quality due to sediment, and are ...

  4. Pathways for arsenic from sediments to groundwater to streams: Biogeochemical processes in the Inner Coastal Plain, New Jersey, USA

    USGS Publications Warehouse

    Barringer, Julia L.; Mumford, Adam; Young, Lily Y.; Reilly, Pamela A.; Bonin, Jennifer L.; Rosman, Robert

    2010-01-01

    The Cretaceous and Tertiary sediments that underlie the Inner Coastal Plain of New Jersey contain the arsenic-rich mineral glauconite. Streambed sediments in two Inner Coastal Plain streams (Crosswicks and Raccoon Creeks) that traverse these glauconitic deposits are enriched in arsenic (1525 mg/kg), and groundwater discharging to the streams contains elevated levels of arsenic (>80 ?g/L at a site on Crosswicks Creek) with arsenite generally the dominant species. Low dissolved oxygen, low or undetectable levels of nitrate and sulfate, detectable sulfide concentrations, and high concentrations of iron and dissolved organic carbon (DOC) in the groundwater indicate that reducing environments are present beneath the streambeds and that microbial activity, fueled by the DOC, is involved in releasing arsenic and iron from the geologic materials. In groundwater with the highest arsenic concentrations at Crosswicks Creek, arsenic respiratory reductase gene (arrA) indicated the presence of arsenic-reducing microbes. From extracted DNA, 16s rRNA gene sequences indicate the microbial community may include arsenic-reducing bacteria that have not yet been described. Once in the stream, iron is oxidized and precipitates as hydroxide coatings on the sediments. Arsenite also is oxidized and co-precipitates with or is sorbed to the iron hydroxides. Consequently, dissolved arsenic concentrations are lower in streamwater than in the groundwater, but the arsenic contributed by groundwater becomes part of the arsenic load in the stream when sediments are suspended during high flow. A strong positive relation between concentrations of arsenic and DOC in the groundwater samples indicates that any processnatural or anthropogenicthat increases the organic carbon concentration in the groundwater could stimulate microbial activity and thus increase the amount of arsenic that is released from the geologic materials.

  5. Distribution of phthalate esters in alluvial sediment: a case study at JiangHan Plain, Central China.

    PubMed

    Liu, Hui; Liang, Hecheng; Liang, Ying; Zhang, Dan; Wang, Cheng; Cai, Hesheng; Shvartsev, Stepan L

    2010-01-01

    This study aimed to investigate the sources and distribution of phthalate esters (PAEs) in alluvial sediment of humid climate regions where water cycle is very active in order to reveal their behavior of transport from topsoil and/or surface water to deep sediment and groundwater. Topsoil and deeper sediment samples were collected from nine and seventeen sites in July 2007, and January 2008, respectively, from the eastern part of JiangHan Plain, Central China. On each site, samples were collected at every 20-40cm depth within the sediment profiles. Contents of 16 PAEs were detected for each sample. summation operator(16)PAEs contents in the topsoil ranged from 252.6 to 2515.7ngg(-1), with an average value of 926.8ngg(-1). Di(2-ethylhexyl) phthalate (DEHP), di-isobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), and diethyl phthalate (DEP) were the dominant PAE species. The horizontal distribution of PAEs was related to time (season), cultivation type, distance and exact position from surface water. DEP existed only on the upper layer of soil due to its rapid degradation. However, DEHP, DnBP, and DiBP could be transported downward into deep sediment even though large amount of them were lost due to biodegradation and adsorption. On the other hand, DEHP, DnBP, and DiBP could be transported into deep sediment along with the horizontal flow of shallow groundwater from surface water, such as Yangtze River, Hanjiang River, and Honghu Lake. PMID:20006896

  6. FACTORS AFFECTING SEDIMENT OXYGEN DEMAND DYNAMICS IN BLACKWATER STREAMS OF GEORGIA'S COASTAL PLAIN

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many coastal plain streams have impaired water quality because of low dissolved oxygen (DO) levels at certain times of the year. These streams are required to have Total Maximum Daily Load (TMDL) plans that often include reduction of nutrient loads. This approach assumes that low DO is due to exce...

  7. Antecedent Water Content Effects on Runoff and Sediment Yields From Two Coastal Plain Utisols

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The highly-weathered, low-carbon, intensively cropped, drought-prone Coastal Plain soils of Georgia are susceptible to runoff and soil loss, especially at certain times of the year when soil water contents are elevated. Our objective was to quantify the effects of antecedent water content (AWC) on r...

  8. Sediment sources and sedimentation processes of 2011 Tohoku-oki tsunami deposits on the Sendai Plain, Japan — Insights from diatoms, nannoliths and grain size distribution

    NASA Astrophysics Data System (ADS)

    Szczuciński, Witold; Kokociński, Mikołaj; Rzeszewski, Michał; Chagué-Goff, Catherine; Cachão, Mario; Goto, Kazuhisa; Sugawara, Daisuke

    2012-12-01

    The 11th March 2011 Tohoku-oki tsunami inundated the low-lying Sendai Plain (Japan) more than 5 km inland leaving sand and mud deposits over most of the area. In order to establish the sources of the tsunami deposits and interpret processes of their sedimentation, samples were collected from the deposits, underlying soils and the beach along a shore-perpendicular transect and analysed for grain size, diatom assemblages and nannoliths. The fining-inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2 km of the coastline and very poorly to poorly sorted mud farther inland. More specifically, there was a slight fining of the coarse to medium sand mode within the sandy deposits and an increased contribution of the coarse and very coarse silt fraction in the mud deposits. The tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening-fining upward trends. Few diatoms were present in beach sediments, soils and tsunami deposits within 1 km of the coastline, while diatoms were more abundant farther inland. Diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater-brackish habitats, while no typically marine species were encountered. Nannoliths were generally absent in the studied sediments, except for few specimens. Our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami. The sandy tsunami deposits within ~ 1 km of the coastline were mostly derived from beach and dune erosion. From 1 to 2 km landward the contribution of these sources decreased, while sources comprising local soil erosion and the entrainment of sediments from the Teizan-bori canal increased. Farther inland, local soil erosion was the major sediment source for the mud deposits. The tsunami deposits were most likely deposited during at least two inundations, mostly out from suspension resulting in an upward grain size fining trend. However, bed load deposition was also important in the sandy deposits as suggested by a common grain size upward coarsening, position on C-M diagrams and frequent horizontal lamination. The present study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin (marine diatoms, foraminifera, nannoliths, marine sediments) may be of limited use.

  9. Effects of sediment depositional environment and ground-water flow on the quality and geochemistry of water in aquifers in sediments of Cretaceous age in the coastal plain of South Carolina

    USGS Publications Warehouse

    Speiran, Gary K.; Aucott, Walter R.

    1994-01-01

    The quality and geochemistry of ground water are significantly affected by the depositional environment of aquifer sediments. Cretaceous sediments in the Coastal Plain of South Carolina have been deposited in fluvial, delta-plain, marginal-marine, and marine environments. Depositional environments of sediments within a single aquifer may grade from nonmarine, fluvial, or upper delta plain near the updip limit of the aquifer to transitional, lower delta plain and to marine toward the coast. In nonmarine sediments the major source of inorganic carbon in the water is the decomposition of organic material. The major aqueous geochemical processes are the dissolution and alteration of silicate minerals. Silica makes up a major part of the dissolved constituents in water from these sediments. In transitional and marine sediments the major aqueous geochemical processes are (1) the dissolution of calcium carbonate by hydrolysis and by carbonic acid derived from the decomposition of organic material and (2) the exchange of calcium in solution for sodium on the marine-clay minerals. The clay minerals may also serve as buffers by neutralizing the hydroxyl ion produced by hydrolysis. The effects of incompletely flushed dilute saltwater on water quality increase toward the coast and toward the northeast.

  10. Temperature and humidity conditions of Macocha Abyss

    NASA Astrophysics Data System (ADS)

    Litschmann, Tom; Ronovsk, Jaroslav; St?eda, Tom; St?edov, Hana; Hebelka, Ji?

    2012-09-01

    The paper deals with the evaluation of temperature and humidity measurements in the vertical profile of Macocha Abyss (Moravian Karst, South Moravia, Czech Republic). The measuring profile on a rock wall is made up of seven HOBO-PRO sensors. Two other meteorological stations are installed at the bottom and near the upper edge of the abyss. The evaluation was designed separately for warm season (June 1, 2008 to August 31, 2008) and cold season (November 1, 2008 to February 28, 2009). In the warm season, distribution of inverse temperatures dominated in the abyss. Temperature differences between the bottom of the abyss and its upper edge reached about 10 C. At the bottom of the abyss, the minimum temperatures proved to be higher than at its upper edge and in its vicinity. Thermal circulation is evident to the depth of about 60 m. The highest temperatures were observed in the deeper layers of the abyss in the warm period at around 10 a.m. of Central European Summer Time. Towards the upper edge of the abyss, the hour of daily maximum temperature shifts to 2 to 4 p.m. In the cold season, the minimum temperature was observed between 6 and 7 a.m. of Central European Time. A decrease in the accumulation of cold air (cold-air pool formation) was not found in the lower floors of the abyss. This phenomenon does not occur even during clear nights. The depth of 60 m from the upper edge of the area maintains a high relative humidity (above 95%) in the warm season. However, humidity decreases from this depth towards the top of the abyss. In the cold season, the whole abyss is filled with air with relative humidity of 90 to 95%.

  11. Long-term change in the abyssal NE Atlantic: The Amperima Event revisited

    NASA Astrophysics Data System (ADS)

    Billett, D. S. M.; Bett, B. J.; Reid, W. D. K.; Boorman, B.; Priede, I. G.

    2010-08-01

    The results from a time series study (1989-2005) at a depth of 4850 m on the Porcupine Abyssal Plain, NE Atlantic, are presented, showing radical changes in the density of large invertebrates (megafauna) over time. Major changes occurred in a number of different taxa between 1996 and 1999 and then again in 2002. One species of holothurian, Amperima rosea, was particularly important, increasing in density by over three orders of magnitude. There were no significant changes in total megafaunal biomass during the same period. Peaks in density were correlated to reductions in mean body size, indicating that the increases were related to large-scale recruitment events. The changes occurred over a wide area of the Porcupine Abyssal Plain. Comparisons made with changes in the density of protozoan and metazoan meiofauna, and with macrofauna, showed that major changes in community structure occurred in all size fractions of the benthic community at the same time. This suggests that the faunal changes were driven by environmental factors rather than being stochastic population imbalances of one or two species. Large-scale changes in the flux of organic matter to the abyssal seafloor have been noted in the time series, particularly in 2001, and may be related to the sudden mass occurrence of A. rosea the following year. Time-varying environmental factors are important in influencing the occurrence of megafauna on the abyssal seafloor.

  12. Temporal variability in polychaete assemblages of the abyssal NE Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Soto, Eulogio H.; Paterson, Gordon L. J.; Billett, David S. M.; Hawkins, Lawrence E.; Galron, Joelle; Sibuet, Myriam

    2010-08-01

    Temporal variability in deep-sea polychaete assemblages was assessed at the Porcupine Abyssal Plain Sustained Observatory, NE Atlantic, over a 9-year period (eight cruises between August 1989 and September 1998). The polychaete communities were characterized by large number of individuals (abundance) and high family richness. The highest abundances occurred in the upper 1 cm sediment layer (53.2% of total abundance). The most abundant families were the Cirratulidae, Spionidae, Opheliidae and Paraonidae. Surface deposit feeders were the dominant trophic group (67.4% of total abundance). Significant temporal variability was evident in polychaete abundance with significant differences in polychaete abundance between sampling periods (cruises; p<0.01). Stepwise increases in abundance in September 1996 and March 1997 coincided with similar increases in abundance in large invertebrates (megafauna) in the same area (known as the ' Amperima Event' after a species of holothurian that increased in abundance by over three orders of magnitude). Similar patterns were observed for abundances across different layers of the sediment, main families and trophic groups showing significant differences between cruises ( p<0.05). A comparison of samples taken (1) before the ' Amperima Event' (1989-1994) and (2) during the ' Amperima Event' (1996-1998) showed significant differences in the polychaete abundance in the upper 3 cm of the sediment. There were significant differences in some trophic groups (predators, deposit feeders and burrowers) and the dominant families (Cirratulidae, Spionidae and Opheliidae). Not all elements of the polychaete community showed a response (e.g. the Paraonidae). Changes in surface deposit feeders were particularly evident. The temporal variability is likely to be related to seasonal and interannual variability in organic matter input. Greater food supply in some years may allow the growth and development of deposit-feeding polychaetes.

  13. Organic carbon cycling in abyssal benthic food chains: numerical simulations of bioenhancement by sewage sludge

    NASA Astrophysics Data System (ADS)

    Rowe, Gilbert T.

    1998-05-01

    The hypothetical bioenhancement of the endemic benthic biota on an oligotrophic abyssal plain by organic carbon has been investigated with mathematical simulation experiments. First, the responses of the biomass and respiration to seasonal variations in the rain of organic carbon (POC) have been simulated in a simplified benthic assemblage (sediment organic carbon, sediment-dwelling heterotrophs (bacteria, meiofauna, macrofauna and detritus feeding megafauna) and predatory megafauna), with no added organic matter. These calculations were based on measured standing stocks and respiration in the central North Pacific (5.8 km depth, 31°N Lat.×159°W Long.). The dynamic relationships in this natural "oligotrophic" food chain were then subjected to added inputs of organic carbon presumed to be in sewage sludge. Two examples are presented: a modest but continuous input of organic carbon (100 mg C m -2 d -1) and a year-long pulse of the same intensity. The continuous input forced the biomass and community respiration to steadily increase until they reached steady state in 15 years at values similar to those found on a typical continental shelf. The pulse exhibited the same pattern, but biomass and respiration returned to levels found under natural oligotrophic conditions several years after cessation of intensified carbon loading. The responses of the sediment community to added organic matter were validated using information from a deep-ocean sewage disposal site (DWD106) off the coast of New Jersey. The models are also used to illustrate an approach for estimating possible transfers of potentially toxic contaminants, such as total polycyclic aromatic hydrocarbons (tPAHs), in lipid-rich eggs. In the future it will be necessary to validate model results with deep-ocean in situ experiments.

  14. Sediment Sources, Sedimentation Processes and Post-Depositional Changes of the 2011 Tohoku-Oki Tsunami Deposits on the Sendai Plain, Japan

    NASA Astrophysics Data System (ADS)

    Szczucinski, W.; Chague-Goff, C.; Goto, K.; Sugawara, D.; Jagodzinski, R.; Kokocinski, M.; Cachao, M.; Sternal, B.; Rzeszewski, M.; Goff, J. R.; Jaffe, B. E.

    2012-12-01

    The 11th March 2011 Tohoku-oki tsunami inundated the low-lying Sendai Plain (Japan) more than 5 km inland leaving sand and mud deposits over most of the area. In order to establish the sources of the tsunami deposits and interpret processes of their sedimentation, samples were collected from the deposits, underlying soils and the beach along a shore-perpendicular transect and analysed for grain size, heavy minerals, diatom assemblages and nannoliths. Surveys were undertaken 2, 5 and 7 months after the tsunami to assess the importance of post-depositional changes in tsunami deposits. The last survey took place shortly after a major typhoon. The fining-inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2 km of the coastline and very poorly to poorly sorted mud farther inland. The tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening-fining upward trends. Heavy minerals comprised on average 35% of the tsunami deposit in the 0.125 - 0.25 mm grain size fraction. Heavy mineral concentrations and assemblages were similar in the tsunami deposits, beach and underlying soils. Diatoms were rare in beach sediments, soils and tsunami deposits within 1 km of the coastline, while they were more abundant farther inland. Diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater-brackish habitats, while no typically marine species were encountered. Nannoliths were generally absent in the studied sediments, except for few specimens. Our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami. The sandy tsunami deposits within ~1 km of the coastline were mostly derived from beach and dune erosion. From 1 to 2 km landward the contribution of these sources decreased, while sources comprising local soil and inland canal sediments increased. Farther inland, mud deposits were mostly derived from local soil erosion. The tsunami deposits were most likely deposited during at least two inundations, mostly from suspension resulting in an upward grain size fining trend. However, bed load deposition was also important in the sandy deposits. The tsunami deposits were generally well preserved after 2 months but sandy sediments in exposed areas were redeposited by wind action. After 7 months, preservation was still good. On the coastal dune slopes there was limited redeposition of sediment by flowing water. Plant recolonisation was slow. The surface of the tsunami deposits was commonly stabilised by an algal mat cover. In places where the deposits were thinner than 1 cm their visual discrimination from the underlying soil was problematic, however, the deposits were still relatively well preserved for about 80% of their original extent. The study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin may be of limited use. Preservation of tsunami deposits in a coastal plain setting primarily depends on their thickness and land topography. Most erosion and redeposition of the deposits take place shortly after tsunami inundation and depend on climate (wind, rain) and topography.

  15. Late Pleistocene to Holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments, southwestern Taiwan

    USGS Publications Warehouse

    Chen, Y.-G.; Liu, J.C.-L.; Shieh, Y.-N.; Liu, T.-K.

    2004-01-01

    A core, drilled at San-liao-wan in the southwestern coastal plain of Taiwan, has been analyzed for total sulfur contents, isotopic values, as well as ratios of pyritic sulfur to organic carbon. Our results demonstrate a close relationship between late Pleistocene sea-level change and the proxies generated in this study. The inorganic sulfur contents indicate that at our study site, the Holocene transgression started at ???11 ka and remained under seawater for thousands of years until the late Holocene, corresponding to a depth of 20 m in the study core. The uppermost 20 m of core shows relatively high total organic carbon (TOC) and ??34S of inorganic sulfur, suggesting a transitional environment such as muddy lagoon or marsh, before the site turned into a modern coastal plain. In the lower part of the core, at depths of 110-145 m (corresponding ages of ???12-30 ka), low sulfur contents are recorded, probably indicating fluvial sediments deposited during the oceanic isotope stage (OIS) 2, a sea-level lowstand. The lower part of the core, roughly within OIS 3, records at least two transgressions, although the transgressional signals may be somewhat obscured by subsequent weathering. The reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data; however, the marine organic source was periodically dominant. The modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments, probably indicating that the sulfate migrated into the site subsequent to early diagenesis. ?? 2003 Elsevier Ltd. All rights reserved.

  16. Eolian sedimentation and soil development on a semiarid to subhumid grassland, Tertiary Ogallala and Quaternary Blackwater Draw Formations, Texas and New Mexico High Plains

    SciTech Connect

    Gustavson, T.C.; Holliday, V.T.

    1999-05-01

    Eolian sediments have accumulated as non-glacigenic loess and thin sand sheets on the Central and Southern High Plains grasslands of Texas and new mexico since the late Miocene. Locally as much as 110 m of eolian sediments with numerous paleosols are preserved in the Quaternary Blackwater Draw formation and the upper part of the Miocene-Pleiocene Ogallala formation. These sediments and paleosols, which cover more than 130,000 km{sup 2}, are similar to recent surface sediments and soils and record a long period of episodic eolian transport and sedimentation, and pedogenesis on a stable low-relief grass-covered landscape. Eolian sections, which comprise the fine sand to coarse silt lithofacies of the Ogallala formation, and the very fine to fine sand and sandy mud lithofacies of the Blackwater Draw formation, generally lack primary sedimentary structures. Grain size of Ogallala sediments decreases from west to east and grain size of Blackwater Draw sediments decreases from southwest to northeast. Soil horizonation is well developed in most sections, and buried calcic and argillic horizons are common. Calcic horizons are characterized by sharply increased CaCO{sub 3} content in the form of filaments, nodules, and petrocalcic horizons (calcretes). Argillic horizons are characterized by increased illuvial clay, pedogenic structure, and darker reddish hues. Rhizocretions are common locally. Open root tubules, which are typically less than 1 mm in diameter and characteristic of small plants like grasses, are present in all Ogallala and Blackwater Draw eolian sediments. Paleosols preserved in eolian sediments of the High Plains reflect periods of sedimentation followed by episodes of landscape stability and pedogenesis, and negligible sedimentation. Episodes of sedimentation and soil development likely resulted from cyclic decreases and increases in available moisture and vegetative cover. Eolian sediments were eroded and transported eastward during dry periods when vegetation was sparse in source areas, such as the western High Plains and the Pecos Valley. During humid periods more abundant vegetation probably protected source areas from deflation, and resulted in landscape stability across the High Plains.

  17. Arsenic in sediments, groundwater, and streamwater of a glauconitic Coastal Plain terrain, New Jersey, USA-Chemical " fingerprints" for geogenic and anthropogenic sources

    USGS Publications Warehouse

    Barringer, J.L.; Reilly, P.A.; Eberl, D.D.; Blum, A.E.; Bonin, J.L.; Rosman, R.; Hirst, B.; Alebus, M.; Cenno, K.; Gorska, M.

    2011-01-01

    Glauconite-bearing deposits are found worldwide, but As levels have been determined for relatively few. The As content of glauconites in sediments of the Inner Coastal Plain of New Jersey can exceed 100mg/kg, and total As concentrations (up to 5.95??g/L) found historically and recently in streamwaters exceed the State standard. In a major watershed of the Inner Coastal Plain, chemical " fingerprints" were developed for streambed sediments and groundwater to identify contributions of As to the watershed from geologic and anthropogenic sources. The fingerprint for streambed sediments, which included Be, Cr, Fe and V, indicated that As was predominantly of geologic origin. High concentrations of dissolved organic C, nutrients (and Cl-) in shallow groundwater indicated anthropogenic inputs that provided an environment where microbial activity released As from minerals to groundwater discharging to the stream. Particulates in streamwater during high flow constituted most of the As load; the chemical patterns for these particulates resembled the geologic fingerprint of the streambed sediments. The As/Cr ratio of these suspended particles likely indicates they derived not only from runoff, but from groundwater inputs, because As contributed by groundwater is sequestered on streambed sediments. Agricultural inputs of As were not clearly identified, although chemical characteristics of some sediments indicated vehicle-related inputs of metals. Sediment sampling during dry and wet years showed that, under differing hydrologic conditions, local anthropogenic fingerprints could be obscured but the geologic fingerprint, indicating glauconitic sediments as an As source, was robust. ?? 2011.

  18. Evaluation of natural radioactivity in soil, sediment and water samples of Niger Delta (Biseni) flood plain lakes, Nigeria.

    PubMed

    Agbalagba, E O; Onoja, R A

    2011-07-01

    This paper presents the findings of a baseline study undertaken to evaluate the natural radioactivity levels in soil, sediment and water samples in four flood plain lakes of the Niger Delta using a hyper pure germanium (HPGe) detector. The activity profile of radionuclides shows low activity across the study area. The mean activity level of the natural radionuclides (226)Ra, (232)Th and (40)K is 203, 203 and 18050Bqkg(-1), respectively. These values are well within values reported elsewhere in the country and in other countries with similar environments. The study also examined some radiation hazard indices. The mean values obtained are, 7614Bqkg(-1), 305.5?Gyh(-1), 376.8?Svy(-1), 0.17 and 0.23 for Radium Equivalent Activity (Ra(eq)), Absorbed Dose Rates (D), Annual Effective Dose Rates (E(ff) Dose), External Hazard Index (H(ex)) and Internal Hazard Index (H(in)) respectively. All the health hazard indices are well below their recommended limits. The soil and sediments from the study area provide no excessive exposures for inhabitants and can be used as construction materials without posing any significant radiological threat to the population. The water is radiologically safe for domestic and industrial use. The paper recommends further studies to estimate internal and external doses from other suspected radiological sources to the population of the Biseni kingdom. PMID:21514983

  19. Sediment-Chlorophyll Relationship in Oxbow Lakes in the Mississippi River Alluvial Plain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    During of the past century, aquatic habitats have declined worldwide, primarily due to draining and clearing for agriculture and urban development. These activities often result in increased erosion and sedimentation with detrimental impacts on stream and lake water quality. Oxbow lakes are importa...

  20. PHOSPHORUS SORPTION BY SEDIMENTS IN A SOUTHEASTERN COASTAL PLAIN IN-STREAM WETLAND

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A close relationship has been reported between sediment organic carbon (sed. OC) content and its phosphorus sorption capacity (Pmax) and total phosphorus (TP) concentration. Phosphorus (P) sorbed to organically-complexed cations is a proposed explanation for this relationship, however; few studies h...

  1. Chromium and nickel as indicators of source-to-sink sediment transfer in a Holocene alluvial and coastal system (Po Plain, Italy)

    NASA Astrophysics Data System (ADS)

    Amorosi, Alessandro

    2012-12-01

    A reliable quantitative estimate of changes in source-to-sink sediment transfer requires that high-resolution stratigraphic studies be coupled with accurate reconstructions of spatial and temporal variability of the sediment-routing system through time. Source-to-sink patterns from the contributing upland river catchments to the deltaic and coastal system are reconstructed from the Holocene succession of the Po Plain on the basis of selected geochemical indicators. Sediment supplied to the delta area by the major trunk river (the Po) exhibits naturally high Cr and Ni values, which invariably exceed the maximum permissible concentrations for unpolluted sites. This 'anomaly' reflects remarkable sediment contribution from ultramafic (ophiolitic) parent rocks cropping out in the Po drainage basin (Western Alps and NW Apennines). In contrast, alluvial and coastal plain deposits supplied by ophiolite-free, Apenninic catchments invariably display lower Cr and Ni contents. For constant sediment provenance domain, Cr and Ni distribution is observed to be controlled primarily by hydraulic sorting. Clay-silt deposits (floodplain, swamp and lagoon/bay facies associations) invariably show higher metal concentrations than their sandy counterparts (fluvial-channel, distributary-channel and beach-ridge facies associations). From a stratigraphic perspective, in sedimentary basins characterized by strong differences in sediment composition geochemical fingerprinting of individual facies associations framed by surfaces of chronostratigraphic significance is proposed as an invaluable approach towards an accurate quantitative assessment of sediment storage in alluvial and coastal depositional systems as opposed to volumetric reconstructions based on lithologic or geometric criteria alone.

  2. [Distribution of sediment iron of the ditch system in Sanjiang Plain, northeast China].

    PubMed

    Zou, Yuan-Chun; L, Xian-Guo; Jiang, Ming; Xi, Min

    2009-03-15

    The iron distribution of the multi-level ditch system (hair canal-field canal-lateral canal-branch canal-main canal) was studied through total iron determination of the sediments (0-60 cm). The results showed that the mean concentration was (3.02 +/- 0.10) x 10(4) mg x kg(-1). Extremely significant difference was obseved between different ditch level (F = 6.261, p < 0.001), and the highest and the lowest concentration were present in the farmland lateral canal (3.71 x 10(4) mg x kg(-1)) and wetland canal (2.43 x 10(4) mg x kg(-1)), respectively. The difference of different sediment layers was not significant (F = 0.093, p = 0.693), while the iron concentrations of 0-10 cm and 10-20 cm sediments were 51.96% and 62.22% higher than that of the natural wetland soil nearby, respectively. Iron can transfer with the runoff in a certain extent, but it was not cumulated along the ditch system with the largest cumulation location at the third level. The runoff containing iron decreased gradully because of the wetland protection and climate change nowadays. The horizontal transfer of iron along the ditch system indicated the timing and intensity of iron loss in the past since the canals were dredged. PMID:19432346

  3. Effects of agricultural tillage and sediment accumulation on emergent plant communities in playa wetlands of the U.S. High Plains.

    PubMed

    O'Connell, Jessica L; Johnson, Lacrecia A; Daniel, Dale W; McMurry, Scott T; Smith, Loren M; Haukos, David A

    2013-05-15

    Identifying community assembly filters is a primary ecological aim. The High Plains, a 30 million ha short-grass eco-region, is intensely cultivated. Cultivation disturbance, including plowing and eroded soil deposition down-slope of plowing, influences plant composition in depressional wetlands, such as playas, within croplands. We evaluated influences of wetland cultivation and sediment deposition on plant composition in playas embedded within croplands (46 plowed and 32 unplowed) and native grasslands (79) across 6 High Plains' states. Sediment accumulation ranged from 7 to 78 cm in cropland and 1 to 35 cm in grassland playas. Deeper sediments and plowing each decreased wetland plant richness, 28% and 70% respectively in cropland wetlands. Sediment depth reduced richness 37% in small grasslands playas while it increased richness 22% in larger ones, suggesting moderate disturbance increased richness when there were nearby propagule sources. Sediment depth was unrelated to species richness in plowed wetlands, probably because plowing was a strong disturbance. Plowing removed perennial plants from vegetation communities. Sediment accumulation also influenced species composition in cropland playas, e.g., probability of Eleocharis atropurpurea increased with sediment depth, while probability of Panicum capillare decreased. In grassland playas, observed lighter sediment depths did not influence species composition after accounting for wetland area. Sediment accumulation and plowing shift wetland plant communities toward annual species and decrease habitat connectivity for wetland-dependent organisms in cropland playas over 39,000 and 23,400 ha respectively. Conservation practices lessening sediment accumulation include short-grass buffer strips surrounding wetlands. Further, wetland tillage, allowed under federal agricultural conservation programs, should be eliminated. PMID:23500104

  4. Sediment facies and Holocene deposition rate of near-coastal fluvial systems: An example from the Nobi Plain, Japan

    NASA Astrophysics Data System (ADS)

    Hori, Kazuaki; Usami, Shogo; Ueda, Hiroki

    2011-05-01

    Floodplains are a major component of present near-coastal fluvial systems that have evolved in response to postglacial changes in climate and sea level. Knowledge of sedimentary facies and deposition rates on a centennial to millennial time scale is required for considering floodplain evolution. Two cores, AP1 and AP2, were acquired from an abandoned channel of the Ibi River and its natural levee on the Nobi Plain, central Japan. Sediment facies analysis, electrical conductivity, and radiocarbon dating of borehole samples showed that in both cores organic-rich dark gray floodbasin mud overlies deltaic deposits dating to after approximately 3200 years calibrated radiocarbon age (cal BP) in relation to delta progradation. The accumulation of floodbasin mud continued at the both sites until about 400 cal BP. Around 400 cal BP, the mud was eroded by the overlying channel sand and gravel at AP1 and was covered by fine-grained natural levee deposits at AP2 with an abrupt contact. This timing is concordant with the historical record of avulsion of the Ibi River during the Keicho Era (AD 1596-1615). Averaged aggradation rates at the AP1 and AP2 sites were approximately 2.2 and 3.2 mm/yr, respectively. Faulting-related subsidence along the western edge of the plain has influenced these rates by creating accommodation. Averaged deposition rates differed greatly between the floodbasin and the levee, suggesting that rapid aggradation of the natural levee also occurred on a centennial to millennial scale. These empirical data may be useful for testing models of the architecture and evolution of near-coastal fluvial systems.

  5. Aminostratigraphy of surface and subsurface Quaternary sediments, North Carolina coastal plain, USA

    USGS Publications Warehouse

    Wehmiller, J. F.; Thieler, E.R.; Miller, D.; Pellerito, V.; Bakeman, Keeney V.; Riggs, S.R.; Culver, S.; Mallinson, D.; Farrell, K.M.; York, L.L.; Pierson, J.; Parham, P.R.

    2010-01-01

    The Quaternary stratigraphy and geochronology of the Albemarle Embayment of the North Carolina (NC) Coastal Plain is examined using amino acid racemization (AAR) in marine mollusks, in combination with geophysical, lithologic, and biostratigraphic analysis of 28 rotasonic cores drilled between 2002 and 2006. The Albemarle Embayment is bounded by structural highs to the north and south, and Quaternary strata thin westward toward the Suffolk paleoshoreline, frequently referred to as the Suffolk Scarp. The Quaternary section is up to ???90. m thick, consists of a variety of estuarine, shelf, back-barrier, and lagoonal deposits, and has been influenced by multiple sea-level cycles. The temporal resolution of the amino acid racemization method is tested statistically and with the stratigraphic control provided by this geologic framework, and it is then applied to the correlation and age estimation of subsurface units throughout the region. Over 500 specimens (primarily Mercenaria and Mulinia) from the subsurface section have been analyzed using either gas chromatographic (GC) or reverse-phase liquid chromatographic (RPLC) techniques. The subsurface stratigraphic data are compared with AAR results from numerous natural or excavated exposures from the surrounding region, as well as results from NC beach collections, to develop a comprehensive aminostratigraphic database for the entire Quaternary record within the NC coastal system. Age mixing, recognized in the beach collections, is also seen in subsurface sections, usually where major seismic reflections or core lithology indicate the presence of stratigraphic discontinuities. Kinetic models for racemization are tested within the regional stratigraphic framework, using either radiocarbon or U-series calibrations or comparison with regional biostratigraphy. Three major Pleistocene aminozones [AZ2, AZ3, and AZ4] are found throughout the region, all being found in superposition in several cores. Each can be subdivided, yielding a total of at least eight stratigraphically and statistically distinct aminozones. Kinetic modeling, supplemented with local calibration, indicates that these aminozones represent depositional events ranging from ???80. ka to nearly 2. Ma. Three prominent seismic reflections are interpreted to represent the base of the early, middle, and late Pleistocene, respectively, roughly 2. Ma, 800. ka, and 130. ka. The large number of samples and the available stratigraphic control provide new insights into the capabilities and limitations of aminostratigraphic methods in assessing relative and numerical ages of Atlantic Coastal Plain Quaternary deposits. ?? 2009 Elsevier B.V.

  6. Black carbon's long trip to the abyssal plain

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2014-08-01

    Black carbon, or soot, is the second most important anthropogenic driver of global climate change, taking a backseat only to carbon dioxide. Whether from wood in a cookstove, coal in a power plant, or trees charred by a wildfire, black carbon is produced by the incomplete combustion of organic matter. Once it gets into the environment, black carbon lowers the albedo when it settles on land, increasing warming and enhancing snow and ice melt. In the atmosphere, black carbon both helps and inhibits the formation of clouds.

  7. Pleistocene paleosols in the loess and loess-like sediments of the central part of the russian plain

    NASA Astrophysics Data System (ADS)

    Yakimenko, E. Y.

    The Central part of the Russian Plain is a key region because of the complex interrelation of the Pleistocene glacials and interglacials. Fossil soils are not continuous in this region due to cryoturbation, erosion and other later processes. Morphological, chemical and micromorphological features of the Upper (Eemian) and Middle (Treenian) Pleistocene paleosols were investigated in the sections of loess and loess-like sediments on the plateau on the right bank of the River Oka. The Eemian soils studied have a humic (A1) horizon with typical biogenic multiordered microstructure and illuvial (B) horizon. The soil morphology is similar to that of the modern Grey-forest soils, which are widespread in this region. The Middle and Upper Pleistocene paleosols are separated by the Moscow (Warta) loess, but sometimes the Eemian fossil soil lies directly on the podzolic layer of the Treenian soil. The investigated Treenian paleosol exposed in the loess has no humic horizon and is very similar to the modern spodosol, indicating colder forest conditions in the region during this interglacial.

  8. Sediment community oxygen consumption in the deep Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Rowe, Gilbert T.; Morse, John; Nunnally, Clifton; Boland, Gregory S.

    2008-12-01

    Sediment community oxygen consumption (SCOC) has been measured from the continental shelf out to the Sigsbee Abyssal Plain in the NE Gulf of Mexico (GoM). SCOC rates on the continental shelf were an order of magnitude higher than those on the adjacent continental slope (450-2750 m depth) and two orders of magnitude higher than those on the abyssal plain at depths of 3.4-3.65 km. Oxygen penetration depth into the sediment was inversely correlated with SCOC measured within incubation chambers, but rates of SCOC calculated from either the gradient of the [O 2] profiles or the total oxygen penetration depth were generally lower than those derived from chamber incubations. SCOC rates seaward of the continental shelf were lower than at equivalent depths on most continental margins where similar studies have been conducted, and this is presumed to be related to the relatively low rates of pelagic production in the GoM. The SCOC, however, was considerably higher than the input of organic detritus from the surface-water plankton estimated from surface-water pigment concentrations, suggesting that a significant fraction of the organic matter nourishing the deep GoM biota is imported laterally down slope from the continental margin.

  9. Cost assessment for abyssal seafloor waste isolation

    NASA Astrophysics Data System (ADS)

    Jin, Di; Kite-Powell, Hauke L.

    1998-05-01

    We develop an integrated model for estimating the internal cost of abyssal seafloor waste isolation. The model captures the major economic, engineering, geographic and social factors that influence the management cost for sewage sludge and municipal incinerator ash. Considering five representative metropolitan areas and five proposed abyssal study sites, we apply this model to produce cost estimates for four deep-ocean waste delivery system concepts. The results show that the unit cost depends primarily on regional waste volume, the marine delivery system and transportation distance. Based on available data, the abyssal ocean option may be competitive with present land-based disposal costs in New York City. The option is less competitive in other metropolitan areas.

  10. Algal pigments in Southern Ocean abyssal foraminiferans indicate pelagobenthic coupling

    NASA Astrophysics Data System (ADS)

    Cedhagen, Tomas; Cheah, Wee; Bracher, Astrid; Lejzerowicz, Franck

    2014-10-01

    The cytoplasm of four species of abyssal benthic foraminiferans from the Southern Ocean (around 51S; 12W and 50S; 39W) was analysed by High Performance Liquid Chromatography (HPLC) and found to contain large concentrations of algal pigments and their degradation products. The composition of the algal pigments in the foraminiferan cytoplasm reflected the plankton community at the surface. Some foraminiferans contained high ratios of chlorophyll a/degraded pigments because they were feeding on fresher phytodetritus. Other foraminiferans contained only degraded pigments which shows that they utilized degraded phytodetritus. The concentration of algal pigment and corresponding degradation products in the foraminiferan cytoplasm is much higher than in the surrounding sediment. It shows that the foraminiferans collect a diluted and sparse food resource and concentrate it as they build up their cytoplasm. This ability contributes to the understanding of the great quantitative success of foraminiferans in the deep sea. Benthic foraminiferans are a food source for many abyssal metazoans. They form a link between the degraded food resources, phytodetritus, back to the active metazoan food chains.

  11. Diversity and Biogeography of Bathyal and Abyssal Seafloor Bacteria

    PubMed Central

    Bienhold, Christina; Zinger, Lucie; Boetius, Antje; Ramette, Alban

    2016-01-01

    The deep ocean floor covers more than 60% of the Earth’s surface, and hosts diverse bacterial communities with important functions in carbon and nutrient cycles. The identification of key bacterial members remains a challenge and their patterns of distribution in seafloor sediment yet remain poorly described. Previous studies were either regionally restricted or included few deep-sea sediments, and did not specifically test biogeographic patterns across the vast oligotrophic bathyal and abyssal seafloor. Here we define the composition of this deep seafloor microbiome by describing those bacterial operational taxonomic units (OTU) that are specifically associated with deep-sea surface sediments at water depths ranging from 1000–5300 m. We show that the microbiome of the surface seafloor is distinct from the subsurface seafloor. The cosmopolitan bacterial OTU were affiliated with the clades JTB255 (class Gammaproteobacteria, order Xanthomonadales) and OM1 (Actinobacteria, order Acidimicrobiales), comprising 21% and 7% of their respective clades, and about 1% of all sequences in the study. Overall, few sequence-abundant bacterial types were globally dispersed and displayed positive range-abundance relationships. Most bacterial populations were rare and exhibited a high degree of endemism, explaining the substantial differences in community composition observed over large spatial scales. Despite the relative physicochemical uniformity of deep-sea sediments, we identified indicators of productivity regimes, especially sediment organic matter content, as factors significantly associated with changes in bacterial community structure across the globe. PMID:26814838

  12. Diversity and Biogeography of Bathyal and Abyssal Seafloor Bacteria.

    PubMed

    Bienhold, Christina; Zinger, Lucie; Boetius, Antje; Ramette, Alban

    2016-01-01

    The deep ocean floor covers more than 60% of the Earth's surface, and hosts diverse bacterial communities with important functions in carbon and nutrient cycles. The identification of key bacterial members remains a challenge and their patterns of distribution in seafloor sediment yet remain poorly described. Previous studies were either regionally restricted or included few deep-sea sediments, and did not specifically test biogeographic patterns across the vast oligotrophic bathyal and abyssal seafloor. Here we define the composition of this deep seafloor microbiome by describing those bacterial operational taxonomic units (OTU) that are specifically associated with deep-sea surface sediments at water depths ranging from 1000-5300 m. We show that the microbiome of the surface seafloor is distinct from the subsurface seafloor. The cosmopolitan bacterial OTU were affiliated with the clades JTB255 (class Gammaproteobacteria, order Xanthomonadales) and OM1 (Actinobacteria, order Acidimicrobiales), comprising 21% and 7% of their respective clades, and about 1% of all sequences in the study. Overall, few sequence-abundant bacterial types were globally dispersed and displayed positive range-abundance relationships. Most bacterial populations were rare and exhibited a high degree of endemism, explaining the substantial differences in community composition observed over large spatial scales. Despite the relative physicochemical uniformity of deep-sea sediments, we identified indicators of productivity regimes, especially sediment organic matter content, as factors significantly associated with changes in bacterial community structure across the globe. PMID:26814838

  13. Cenozoic Ridge Crest Sediments From the Central Arctic Ocean Yield cm/ka-Scale Sedimentation Rates

    NASA Astrophysics Data System (ADS)

    Backman, J.; Moran, K.; Moore, T.; King, J.; Gattacecca, J.; Brinkhuis, H.; Matthiessen, J.; Jakobsson, M.; Paelike, H.; O'Regan, M.; Frank, M.; Kubik, P.

    2005-12-01

    Estimates of long-term sedimentation rates derived from total sediment thickness and bedrock ages based on current tectonic models consistently yield cm/ka-scale average sedimentation rates in the central Arctic Ocean, including the Lomonosov Ridge. The physiographic setting of the Arctic Basin is that of a small basin surrounded by huge landmasses since its initial opening during Early Cretaceous times, a setting that has contributed to yielding 2-6 km thick sediment deposits on Arctic's abyssal plains at average rates of about 4-5 cm/ka. This as sedimentation rate scenario is in contrast to the long-held belief that central Arctic Plio-Pleistocene sedimentation rates have been on the mm/ka-scale, or even sub-mm/ka-scale, estimated from numerous short gravity or piston cores. ACEX drilled through a nearly 410 m thick latest Paleocene to Recent sediment section on the Lomonosov Ridge near 88N at about 1200 m water depth, with a recovery of 68 %. A combination of paleomagnetic, biostratigraphic and 10-Be data derived from the ACEX cores finally solved the Arctic Basin sedimentation rate ambiguity, in showing an average middle Miocene to Recent rate of about 1.3 cm/ka and Pleistocene rates of nearly 2 cm/ka. The ACEX record is interrupted by a hiatus encompassing the interval between about 17 Ma and 43 Ma. Average middle Eocene through latest Paleocene rates are on the order of about 1.5 cm/ka.

  14. Vertical and Horizontal Variations in the Physiological Diversity of the Aerobic Chemoheterotrophic Bacterial Microflora in Deep Southeast Coastal Plain Subsurface Sediments

    PubMed Central

    Balkwill, D. L.; Fredrickson, J. K.; Thomas, J. M.

    1989-01-01

    Aerobic chemoheterotrophic bacteria were isolated from surface soils and coastal plain subsurface (including deep aquifer) sediments (depths to 265 m) at a study site near Aiken, S.C., by plating on concentrated and dilute media. Morphologically distinct colonies were purified, and their responses to 21 selected physiological tests were determined. These isolates were quite diverse; 626 physiologically distinct types (i.e., types with a unique pattern of responses to the 21 tests) were detected among the 1,112 isolates obtained. Physiologically distinct types were isolated on concentrated and dilute media (only 11% overlap between the groups); isolates from surface soils and subsurface sediments were also quite different (only 3% overlap). The surface soil isolates more readily utilized all but 1 of 12 carbon sources offered, and a significantly larger proportion of them hydrolyzed esculin and gelatin. Only 4% of the subsurface isolates fermented glucose, even though 82% of them could use it aerobically. l-Malate and d-gluconate were utilized by at least 75% of the subsurface isolates, and seven other carbon sources were used by at least 40% of them. Subsurface isolates from different geological formations (depths) and, to a lesser extent, from the same geological formation at different boreholes differed distinctly in their group responses to certain physiological tests. Moreover, sediments from different depths and boreholes contained physiologically distinct types of bacteria. Thus, considerable bacterial diversity was observed in coastal plain subsurface sediments, even within defined geological formations. PMID:16347902

  15. Chemistry of bottom sediments from the Cal-Sag channel and the Des Plaines and Illinois Rivers between Joliet and Havana, Illinois

    SciTech Connect

    Harrison, W.; Kucera, E.T.; Tome, C.; Van Loon, L.S.; Van Luik, A.

    1981-02-01

    Cores were taken in 28 actual or proposed maintenance-dredging areas. Sixty-one core samples were analyzed to provide a data base for subsequent studies of the suitability of the potential dredged material for reclamation of abandoned surface-mined land bordering the Illinois Waterway. Samples were composited over 2-ft depth increments, up to a maximum 8-ft depth where possible. Parameters determined for each sample were: volatile solids, flash point, polyaromatic hydrocarbons (PAHs), base/neutral organic compounds, pH, total phosphorus, total phenols, oil and grease, polychlorinated biphenyls (PCBs), cyanide, arsenic, barium, cadmium, chromium, copper, lead, mercury, zinc, silver, nickel, selenium, and sulfide. Results showed PCBs to be higher in the Cal-Sag Channel sediments (..mu..=7.0 mg/kg) than in the Des Plaines River (..mu..=1.6 mg/kg), or Illinois River (..mu..=0.5 mg/kg) sediments. Concentrations of metals including arsenic, barium, cadmium, copper, lead, nickel, and silver were higher in the Des Plaines River samples than in the Cal-Sag Channel or Illinois River samples. Illinois River sediments were, generally, the least contaminated in terms of the measured parameters. Leach tests for arsenic, chromium, copper, lead, nickel, and zinc indicated low leachate-metal concentrations relative to total metal concentrations; thus, these metals exist in relatively insoluble solid states in the sediments.

  16. Holocene environmental and climatic change in the Northern Great Plains as recorded in the geochemistry of sediments in Pickerel Lake, South Dakota

    USGS Publications Warehouse

    Dean, W.E.; Schwalb, A.

    2000-01-01

    The sediments in Pickerel Lake, northeastern South Dakota, provide a continuous record of climatic and environmental change for the last 12000 yr. Sediments deposited between 12 and 6 ka (radiocarbon) show extreme variations in composition, oxygen and carbon isotopic composition of bulk carbonate, carbon isotopic composition of organic matter, and magnetic susceptibility. These variations reflect changes in sources of moisture, regional vegetation types, precipitation-evaporation balance, ground- and surface-water influx, water residence time, erosion, lake productivity, water level, and water temperature. The total carbonate content of late Pleistocene sediments steadily increased from <20% at the base of the core to as much as 80% in sediments deposited between 11 and 9 ka. By about 8 ka, the total carbonate content of the sediments had declined to about 40% where it remained with little variation for the past 8 kyr, suggesting relatively stable conditions. There are marked increases in values of ??13C and ??18O in bulk carbonate, and ??13C of organic matter, in sediments deposited between 10 and 6 ka as evaporation increased, and the vegetation in the watershed changed from forest to prairie. This shift toward more 18O-enriched carbonate may also reflect a change in source or seasonality of precipitation. During this early Holocene interval the organic carbon (OC) content of the sediments remained relatively low (2-3%), but then increased rapidly to 4.5% between 7 and 6 ka, reflecting the rapid transition to a prairie lake. The OC content fluctuates slightly between 4 and 6% in sediments deposited over the past 6 kyr. Like OC and total carbonate, most variables measured show little variation in the 13 m of sediment deposited over the past 6 kyr, particularly when compared with early Holocene variations. Although the magnetic susceptibility of this upper 13 m of sediment is generally low (<10 SI units), the upper six meters of the section is marked by striking 1 m cycles (ca. 400-500 yr periodicity) in susceptibility. These cycles are interpreted as being due to variations in the influx of eolian detrital-clastic material. Century-scale cyclic variations in different proxy variables for aridity and eolian activity from sediments deposited over the past 2000 yr in other lakes in the northern Great Plains, as well as in sand dune activity, suggest that aridity cycles were the dominant feature of late Holocene climate of the northern Great Plains. (C) 2000 Elsevier Science Ltd and INQUA. All rights reserved.

  17. Arsenic in New Jersey Coastal Plain streams, sediments, and shallow groundwater: effects from different geologic sources and anthropogenic inputs on biogeochemical and physical mobilization processes

    USGS Publications Warehouse

    Barringer, Julia L.; Reilly, Pamela A.; Eberl, Dennis D.; Mumford, Adam C.; Benzel, William M.; Szabo, Zoltan; Shourds, Jennifer L.; Young, Lily Y.

    2013-01-01

    Arsenic (As) concentrations in New Jersey Coastal Plain streams generally exceed the State Surface Water Quality Standard (0.017 micrograms per liter (µg/L)), but concentrations seldom exceed 1 µg/L in filtered stream-water samples, regardless of geologic contributions or anthropogenic inputs. Nevertheless, As concentrations in unfiltered stream water indicate substantial variation because of particle inputs from soils and sediments with differing As contents, and because of discharges from groundwater of widely varying chemistry. In the Inner Coastal Plain, streams draining to lower reaches of the Delaware River traverse As-rich glauconitic sediments of marine origin in which As contents typically are about 20 milligrams per kilogram (mg/kg) or greater. In some of these sedimentary units, As concentrations exceed the New Jersey drinking-water maximum contaminant level (5 µg/L) in shallow groundwater that discharges to streams. Microbes, fueled by organic carbon beneath the streambed, reduce iron (Fe) and As, releasing As and Fe into solution in the shallow groundwater from geologic materials that likely include (in addition to glauconite) other phyllosilicates, apatite, and siderite. When the groundwater discharges to the stream, the dissolved Fe and As are oxidized, the Fe precipitates as a hydroxide, and the As sorbs or co-precipitates with the Fe. Because of the oxidation/precipitation process, dissolved As concentrations measured in filtered stream waters of the Inner Coastal Plain are about 1 µg/L, but the total As concentrations (and loads) are greater, substantially amplified by As-bearing suspended sediment in stormflows. In the Outer Coastal Plain, streams draining to the Atlantic Ocean traverse quartz-rich sediments of mainly deltaic origin where the As content generally is low ( With a history of agriculture in the New Jersey Coastal Plain, anthropogenic inputs of As, such as residues from former pesticide applications in soils, can amplify any geogenic As in runoff. Such inputs contribute to an increased total As load to a stream at high stages of flow. As a result of yet another anthropogenic influence, microbes that reduce and mobilize As beneath the streambeds are stimulated by inputs of dissolved organic carbon (DOC). Although DOC is naturally occurring, anthropogenic contributions from wastewater inputs may deliver increased levels of DOC to subsurface soils and ultimately groundwater. Arsenic concentrations may increase with the increases in pH of groundwater and stream water in developed areas receiving wastewater inputs, as As mobilization caused by pH-controlled sorption and desorption reactions are likely to occur in waters of neutral or alkaline pH (for example, Nimick and others, 1998; Barringer and others, 2007b). Because of the difference in As content of the geologic materials in the two sub-provinces of the Coastal Plain, the amount of As that is mobile in groundwater and stream water is, potentially, substantially greater in the Inner Coastal Plain than in the Outer Coastal Plain. In turn, streams within the Inner and Outer Coastal Plain can receive substantially more As in groundwater discharge from developed areas than from environments where DOC appears to be of natural origin.

  18. Tectonic and Sedimentation Interactions in the East Caribbean Subduction Zone: AN Overview from the Orinoco Delta to the Barbados Accretionary Prism

    NASA Astrophysics Data System (ADS)

    Deville, E.

    2011-12-01

    Recent marine geophysical acquisitions and piston-coring allow to better understand the close interactions between the sand-rich Orinoco turbidite system and the compressional structures of the Barbados prism. Because of the morphologic and tectonic control in the east-Caribbean active margin, the Orinoco turbiditic pattern system does not exhibit a classic fan geometry. The sea-floor geometry between the slope of the front of the Barbados prism and the slope of the South-American margin induces the convergence of the turbidite channels toward the abyssal plain, at the front of the accretionary prism. Also, whereas in most passive margins the turbidite systems are organized upstream to downstream as canyon, then channel-levee, then lobes, here, due to the tectonic control, the sedimentary system is organized as channel-levee, then canyons, then channelized lobes. At the edge of the Orinoco platform, the system has multiple sources with several distributaries and downward the channel courses are complex with frequent convergences or divergences that are emphasized by the effects of the undulating seafloor tectonic morphologies associated with active thrust tectonics and mud volcanism. On top of the accretionary prism, turbidite sediments are filling transported piggy-back basins whose timing of sedimentation vs. deformation is complex. Erosion processes are almost absent on the highly subsiding Orinoco platform and in the upper part of the turbidite system. Erosion processes develop mostly between 2000 and 4000 m of water depth, above the compressional structures of the Barbados prism (canyons up to 3 km wide and 300 m deep). In the abyssal plain, turbiditic channels develop on very long distance (> 1000 km) joining the mid-Atlantic channel (sourced mostly by the Amazon), filling several elongated basins corresponding to transform faults (notably the Barracuda Basin), and finally sourcing the Puerto-Rico trench, the deepest morphologic depression of this region. Piston-core surveys have demonstrated that turbidite sediments above the accretionary prism and in the abyssal plain are mostly coarse sandy deposits covered by recent pelagic planktonic-rich sediments, which indicate that sand deposition has slow down during the post-glacial sea level rise. Numerical stratigraphic modeling suggests that during the last glacial event, the main depocenters were located above the tectonic prism and in the abyssal plain, at the front of the prism and that, during the Holocene eustatic rise, a large accommodation space formed on the shelf confining sedimentation mostly on the Orinoco deltaic platform and producing a starvation downstream in the turbidite system. This is in good agreement with the piston coring results which show low deep turbidite sedimentation rates during recent times.

  19. Response of Late Cretaceous migrating deltaic facies systems to sea level, tectonics, and sediment supply changes, New Jersey Coastal Plain, U.S.A.

    USGS Publications Warehouse

    Kulpecz, A.A.; Miller, K.G.; Sugarman, P.J.; Browning, J.V.

    2008-01-01

    Paleogeographic, isopach, and deltaic lithofacies mapping of thirteen depositional sequences establish a 35 myr high resolution (> 1 Myr) record of Late Cretaceous wave- and tide-influenced deltaic sedimentation. We integrate sequences defined on the basis of lithologic, biostratigraphic, and Sr-isotope stratigraphy from cores with geophysical log data from 28 wells to further develop and extend methods and calibrations of well-log recognition of sequences and facies variations. This study reveals the northeastward migration of depocenters from the Cenomanian (ca. 98 Ma) through the earliest Danian (ca. 64 Ma) and documents five primary phases of paleodeltaic evolution in response to long-term eustatic changes, variations in sediment supply, the location of two long-lived fluvial axes, and thermoflexural basement subsidence: (1) Cenomanian-early Turonian deltaic facies exhibit marine and nonmarine facies and are concentrated in the central coastal plain; (2) high sediment rates, low sea level, and high accommodation rates in the northern coastal plain resulted in thick, marginal to nonmarine mixed-influenced deltaic facies during the Turonign-Coniacian; (3) comparatively low sediment rates and high long-term sea level in the Santonian resulted in a sediment-starved margin with low deltaic influence; (4) well-developed Campanian deltaic sequences expand to the north and exhibit wave reworking and longshore transport of sands, and (5) low sedimentation rates and high long-term sea level during the Maastrichtian resulted in the deposition of a sediment-starved glauconitic shelf. Our study illustrates the widely known variability of mixed-influence deltaic systems, but also documents the relative stability of deltaic facies systems on the 106-107 yr scale, with long periods of cyclically repeating systems tracts controlled by eustasy. Results from the Late Cretaceous further show that although eustasy provides the template for sequences globally, regional tectonics (rates of subsidence and accommodation), changes in sediment supply, proximity to sediment input, and flexural subsidence from depocenter loading determines the regional to local preservation and facies expression of sequences. Copyright ?? 2008, SEPM (Society for Sedimentary Geology).

  20. Environmental factors affecting distribution and abundance of bacteria, fungi and protozoa in subsurface sediments of the Upper Atlantic Coastal Plain, USA

    SciTech Connect

    Levine, S.N.; Ghiorse, W.C.

    1990-12-31

    Exploratory statistical analyses of microbiological, hydrological and geochemical data for samples from four boreholes drilled into Upper Atlantic Coastal Plain sediments near the Savannah River Site, SC, showed highly significant correlations between bacterial abundance (AODC and CFU) and hydraulic conductivity (K). Sediment texture variables (% sand (S), % silt, % clay (C), and S/C) were strongly interrelated with K and, therefore, also correlated with bacterial abundance. AODC did not correlate with the concentrations of dissolved inorganic nitrogen (DIN) or dissolved organic carbon (DOC) in pore water. CFU also did not correlate with DIN, but a negative relationship was found between the CFU and DOC for sandy sediments, suggesting that microbial activity may control pore water DOC concentration. In some, but not all boreholes, AODC and CFU correlated negatively with pore water concentrations of metals and positively with pH. Protozoan abundance correlated strongly with AODC and CFU in the two boreholes closest to the recharge areas for their major aquifers. It also correlated with sediment texture variables, but not with K. Fungal abundance did not correlate with the abundance of other microbial types when data from individual boreholes were considered; however it did correlate with both bacterial and protozoan abundance when data from all four boreholes were combined. There was no relationship between fungal abundance and either K or sediment texture.

  1. Environmental factors affecting distribution and abundance of bacteria, fungi and protozoa in subsurface sediments of the Upper Atlantic Coastal Plain, USA

    SciTech Connect

    Levine, S.N.; Ghiorse, W.C.

    1990-01-01

    Exploratory statistical analyses of microbiological, hydrological and geochemical data for samples from four boreholes drilled into Upper Atlantic Coastal Plain sediments near the Savannah River Site, SC, showed highly significant correlations between bacterial abundance (AODC and CFU) and hydraulic conductivity (K). Sediment texture variables (% sand (S), % silt, % clay (C), and S/C) were strongly interrelated with K and, therefore, also correlated with bacterial abundance. AODC did not correlate with the concentrations of dissolved inorganic nitrogen (DIN) or dissolved organic carbon (DOC) in pore water. CFU also did not correlate with DIN, but a negative relationship was found between the CFU and DOC for sandy sediments, suggesting that microbial activity may control pore water DOC concentration. In some, but not all boreholes, AODC and CFU correlated negatively with pore water concentrations of metals and positively with pH. Protozoan abundance correlated strongly with AODC and CFU in the two boreholes closest to the recharge areas for their major aquifers. It also correlated with sediment texture variables, but not with K. Fungal abundance did not correlate with the abundance of other microbial types when data from individual boreholes were considered; however it did correlate with both bacterial and protozoan abundance when data from all four boreholes were combined. There was no relationship between fungal abundance and either K or sediment texture.

  2. Dredged material isolation on the abyssal seafloor: A feasibility study. Final report

    SciTech Connect

    Valent, P.J.; Young, D.K.

    1997-12-01

    This report is the result of an examination of the feasibility of isolating contaminated dredged material on the abyssal seafloor. The focus is on the technical and environmental factors that constrain the considerations of feasibility. A thorough conceptual design of a dredging to abyssal deposition system is analyzed with regard to each subsystem and to the entire operational concept. These subsystems include: (1) a low leakage dredge, (2) equipment for material handling and loading into geosynthetic fabric containers (GFCs), (3) the barge for transport and navigation, and (4) the subsystem for releasing the GFCs to sink to the abyssal seafloor isolation site. Particular consideration is given to the exclusion of dredged material from the ocean`s productive zone in the upper 1000 m. New theoretical models and previous empirical results are used to predict GFC motion through the water column and response to impact on the abyssal seafloor, including the case of potential release of contaminated, turbid water at impact. A geochemical model of the temporal and spatial evolution of the post-deposition geochemistry of the water column, the GFC contents and the sediments below is developed and analyzed; the results show that release of metals into the ocean waters would be insignificant. A model of the biological impacts of the introduction of dredged material in the abyssal environment is used to infer that: (1) biological diversity in the vicinity of the deposition site will be diminished, (2) biomass will be increased by dominance of a few fast growing, opportunistic benthic species, and (3) concentrations of trace elements and organic contaminant.

  3. Global variations in abyssal peridotite compositions

    NASA Astrophysics Data System (ADS)

    Warren, Jessica M.

    2016-04-01

    Abyssal peridotites are ultramafic rocks collected from mid-ocean ridges that are the residues of adiabatic decompression melting. Their compositions provide information on the degree of melting and melt-rock interaction involved in the formation of oceanic lithosphere, as well as providing constraints on pre-existing mantle heterogeneities. This review presents a compilation of abyssal peridotite geochemical data (modes, mineral major elements, and clinopyroxene trace elements) for > 1200 samples from 53 localities on 6 major ridge systems. On the basis of composition and petrography, peridotites are classified into one of five lithological groups: (1) residual peridotite, (2) dunite, (3) gabbro-veined and/or plagioclase-bearing peridotite, (4) pyroxenite-veined peridotite, and (5) other types of melt-added peridotite. Almost a third of abyssal peridotites are veined, indicating that the oceanic lithospheric mantle is more fertile, on average, than estimates based on residual peridotites alone imply. All veins appear to have formed recently during melt transport beneath the ridge, though some pyroxenites may be derived from melting of recycled oceanic crust. A limited number of samples are available at intermediate and fast spreading rates, with samples from the East Pacific Rise indicating high degrees of melting. At slow and ultra-slow spreading rates, residual abyssal peridotites define a large (0-15% modal clinopyroxene and spinel Cr# = 0.1-0.6) compositional range. These variations do not match the prediction for how degree of melting should vary as a function of spreading rate. Instead, the compositional ranges of residual peridotites are derived from a combination of melting, melt-rock interaction and pre-existing compositional variability, where melt-rock interaction is used here as a general term to refer to the wide range of processes that can occur during melt transport in the mantle. Globally, ~ 10% of abyssal peridotites are refractory (0% clinopyroxene, spinel Cr# > 0.5, bulk Al2O3 < 1 wt.%) and some ridge sections are dominated by harzburgites while lacking a significant basaltic crust. Abyssal ultramafic samples thus indicate that the mantle is multi-component, probably consisting of at least three components (lherzolite, harzburgite, and pyroxenite). Overall, the large compositional range among residual and melt-added peridotites implies that the oceanic lithospheric mantle is heterogeneous, which will lead to the generation of further heterogeneities upon subduction back into the mantle.

  4. Isotope and trace element geochemistry of sediments from the Barbados Ridge-Demerara Plain region, Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    White, William M.; Dupr, Bernard; Vidal, Philippe

    1985-09-01

    Twenty-four piston core sediment samples and 13 sediments and 3 basalts from DSDP Leg 78 Site 543 were analyzed for Sr, Nd and Pb isotopic compositions. The results show sediment with highly radiogenic Pb 206Pb /204Pb up to 19.8) and rather radiogenic Sr and unradiogenic Nd has been deposited in the region since the Cretaceous. The source of this sediment is probably the Archean Guiana Highland, which is drained by the Orinoco River. Pb and Sr isotopic compositions and sediment thickness decrease and 143Nd /144Nd increases northward due to a decrease in turbiditic component. This decrease is partly due to the damming action of basement ridges. Rare earth concentrations in the sediments are somewhat low, due to the abundance of detrital and biogenic components in the sediment and rapid sedimentation rates. Both positive and negative Ce anomalies occur in the surface sediments, but only positive Ce anomalies occur in the Site 543 sediments. It is unlikely that sediment subducted to the source region of Lesser Antilles arc magmas could be the cause of negative Ce anomalies in those magmas. Isotopic compositions of Site 543 basalts show some effect of contamination by seawater-basalt reaction products and sediments. Beyond this, however, they are typical of "normal" depleted MORB.

  5. A 200,000-year record of late Quaternary Aeolian sedimentation on the Southern High Plains and nearby Pecos River Valley, USA

    NASA Astrophysics Data System (ADS)

    Rich, J.; Stokes, S.

    2011-03-01

    Presently stabilized Southern High Plains (SHP) dune systems have been repeatedly re-activated during the past 200,000 years, providing an archive of environmental and related climatic change for the late Quaternary. Our data set of 38 optically dated samples from four different localities identifies eolian activity from late-middle Pleistocene to the historic period. Oldest eolian sediments are from the Blackwater Draw Formation and indicate accretion during late-middle to late Pleistocene. Younger sediments dating from the later Pleistocene through the Holocene are found in the Muleshoe, Lea-Yoakum, Mescalero, and Monahans dunes that overlie the Blackwater Draw Formation. Muleshoe dunes accreted during the Late Pleistocene between 31 ± 3 and 27 ± 2 ka, while Holocene deposition transpired 7.5 ± 0.4, 4.0 ± 0.7 ka through 3.6 ± 0.4 ka, and between 1.3 ± 0.2 and 1.1 ± 0.1 ka. A period of dune building for Lea-Yoakum dune sediments occurred during the late Pleistocene (48 ± 5 ka), and the later Holocene (3.6 ± 0.4 ka). Mescalero and Monahans dunes were accreting during the later Pleistocene between 29 ± 3 and 22 ± 2 ka followed by a sequence of eolian sand deposited ca. 15 ka. Holocene eolian sedimentation for the Mescalero and Monahans dunes occurred 7.5 ± 0.8, 5.1 ± 0.5, 4.3 ± 0.4, and 2.0 ± 0.3 ka. Historic eolian deposition is identifiable in the dune chronology with multiple optical age estimates overlapping established drought events recorded ca. 1890, 1910, 1920, and during the 1930's when the North American "Dust Bowl" transpired. These Quaternary eolian deposits mantling the Southern High Plains are an important component of the surficial material of the region and provide a rich archive of past climatic change.

  6. 200,000 years of climate change recorded in eolian sediments of the High Plains of eastern Colorado and western Nebraska

    USGS Publications Warehouse

    Muhs, Daniel R.; Swinehart, James B.; Loope, David B.; Aleinikoff, John N.; Been, Josh

    1999-01-01

    Loess and eolian sand cover vast areas of the western Great Plains of Nebraska, Kansas and Colorado (Fig. 1). In recent studies of Quaternary climate change, there has been a renewed interest in loess and eolian sand. Much of the attention now given to loess stems from new studies of long loess sequences that contain detailed records of Quaternary glacial-interglacial cycles, thought to be a terrestrial equivalent to the foraminiferal oxygen isotope record in deep-sea sediments (Fig. 2). Loess is also a direct record of atmospheric circulation, and identification of loess paleowinds in the geologic record can test atmospheric general circulation models. Until recently, eolian sand on the Great Plains had received little attention from Quaternary geologists. The past decade has seen a proliferation of studies of Great Plains dune sands, and many studies, summarized below, indicate that landscapes characterized by eolian sand have had dynamic histories. On this field trip, we will visit some key eolian sand and loess localities in eastern Colorado and southwestern Nebraska (Fig. 1). Stratigraphic studies at some of these localities have been conducted for more than 50 years, but others have been systematically studied only in the past few years. Many of the data which appear in this guidebook have been derived from previous studies (Swinehart and Diffendal, 1990; Madole, 1994; Loope and others, 1995; Maat and Johnson, 1996; Muhs and others, 1996, 1997a, 1999; Mason and others, 1997; Aleinikoff and others, 1999), but some are presented here for the first time.

  7. Laboratory-Measured and Property-Transfer Modeled Saturated Hydraulic Conductivity of Snake River Plain Aquifer Sediments at the Idaho National Laboratory, Idaho

    USGS Publications Warehouse

    Perkins, Kim S.

    2008-01-01

    Sediments are believed to comprise as much as 50 percent of the Snake River Plain aquifer thickness in some locations within the Idaho National Laboratory. However, the hydraulic properties of these deep sediments have not been well characterized and they are not represented explicitly in the current conceptual model of subregional scale ground-water flow. The purpose of this study is to evaluate the nature of the sedimentary material within the aquifer and to test the applicability of a site-specific property-transfer model developed for the sedimentary interbeds of the unsaturated zone. Saturated hydraulic conductivity (Ksat) was measured for 10 core samples from sedimentary interbeds within the Snake River Plain aquifer and also estimated using the property-transfer model. The property-transfer model for predicting Ksat was previously developed using a multiple linear-regression technique with bulk physical-property measurements (bulk density [pbulk], the median particle diameter, and the uniformity coefficient) as the explanatory variables. The model systematically underestimates Ksat,typically by about a factor of 10, which likely is due to higher bulk-density values for the aquifer samples compared to the samples from the unsaturated zone upon which the model was developed. Linear relations between the logarithm of Ksat and pbulk also were explored for comparison.

  8. Diversity of Thiosulfate-Oxidizing Bacteria from Marine Sediments and Hydrothermal Vents†

    PubMed Central

    Teske, A.; Brinkhoff, T.; Muyzer, G.; Moser, D. P.; Rethmeier, J.; Jannasch, H. W.

    2000-01-01

    Species diversity, phylogenetic affiliations, and environmental occurrence patterns of thiosulfate-oxidizing marine bacteria were investigated by using new isolates from serially diluted continental slope and deep-sea abyssal plain sediments collected off the coast of New England and strains cultured previously from Galapagos hydrothermal vent samples. The most frequently obtained new isolates, mostly from 103- and 104-fold dilutions of the continental slope sediment, oxidized thiosulfate to sulfate and fell into a distinct phylogenetic cluster of marine alpha-Proteobacteria. Phylogenetically and physiologically, these sediment strains resembled the sulfate-producing thiosulfate oxidizers from the Galapagos hydrothermal vents while showing habitat-related differences in growth temperature, rate and extent of thiosulfate utilization, and carbon substrate patterns. The abyssal deep-sea sediments yielded predominantly base-producing thiosulfate-oxidizing isolates related to Antarctic marine Psychroflexus species and other cold-water marine strains of the Cytophaga-Flavobacterium-Bacteroides phylum, in addition to gamma-proteobacterial isolates of the genera Pseudoalteromonas and Halomonas-Deleya. Bacterial thiosulfate oxidation is found in a wide phylogenetic spectrum of Flavobacteria and Proteobacteria. PMID:10919760

  9. Biogenic silica in surface sediments of the South China Sea: Controlling factors and paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Zhang, Lanlan; Wang, Rujian; Chen, Muhong; Liu, Jianguo; Zeng, Lili; Xiang, Rong; Zhang, Qiang

    2015-12-01

    We mapped the spatial distribution of biogenic silica (BSi) based on a total of 355 surface sediment samples from the South China Sea to provide a basin-wide BSi data set for paleoenvironmental reconstruction in the region. The results show that BSi relative abundance, calcium carbonate percentage, siliceous test total abundance, grain size and sediment magnetic susceptibility all show distinct spatial distribution patterns that are affected by environmental drivers. The gradual increase in BSi from the continental shelf to the abyssal plain suggests that decreased dilution of terrigenous sediments plays a greater role in BSi preservation than does increasing dilution by CaCO3, decreasing productivity or siliceous dissolution. The BSi correlation is weak for diatom abundance but relatively good for radiolarians, confirming that radiolarians are the primary contributor to BSi fluxes in the low-latitude South China Sea. In contrast, increased dissolution results in a decrease in CaCO3 with increasing water depth, reflecting the different preservation patterns of these two biogenic components. Correlation analysis also reveals a positive correlation between BSi and fine grain size, perhaps reflecting the ability of clay minerals to protect BSi from dissolution; volcanic ash and glass also can retard dissolution by increasing the pore-water saturation of SiO2 in abyssal basin sediments.

  10. Sediment capture in flood plains of the Mississippi River: A case study in Cat Island National Wildlife Refuge, Louisiana

    NASA Astrophysics Data System (ADS)

    Smith, M.; Bentley, S. J., Sr.

    2015-03-01

    To plan restoration of the Mississippi River Delta, it is imperative to know how much sediment the Mississippi River currently provides. Recent research has demonstrated that between Tarbert Landing and St Francisville on the Mississippi, as much as 67 million metric tons (Mt) per year is lost from river transport, of which ~16 Mt is muddy suspended sediment. So where does this sediment go? Two pathways for loss have been proposed: riverbed storage, and overbank deposition in regions that lack manmade levées. Cat Island National Wildlife Refuge, on the unleveed Mississippi River east bank near St Francisville, Louisiana, consists of undisturbed bottomland forest that is inundated most years by river flooding. To determine fluvial sediment accumulation rates (SAR) from flooding, pushcores 40-50 cm long were collected then dated by Pb-210 and Cs-137 geochronology. Preliminary data suggests that muddy sediment accumulation is 10-13% of muddy suspended sediment lost from river transport along this river reach.

  11. Results of analyses performed on soil adjacent to penetrators emplaced into sediments at McCook, Nebraska, January 1976. [simulated penetration into wind-deposited sediments on Martian plains

    NASA Technical Reports Server (NTRS)

    Blanchard, M.; Bunch, T.; Davis, A.; Kyte, F.; Shade, H.; Erlichman, J.; Polkowski, G.

    1977-01-01

    During 1976 several penetrators (full and 0.58 scale) were dropped into a test site McCook, Nebraska. The McCook site was selected because it simulated penetration into wind-deposited sediments (silts and sands) on Martian plains. The physical and chemical modifications found in the sediment after the penetrators' impact are described. Laboratory analyses have shown mineralogical and elemental changes are produced in the sediment next to the penetrator. Optical microscopy studies of material next to the skin of the penetrator revealed a layer of glassy material about 75 microns thick. Elemental analysis of a 0-1-mm layer of sediment next to the penetrator revealed increased concentrations for Cr, Fe, Ni, Mo, and reduced concentrations for Mg, Al Si, P, K, and Ca. The Cr, Fe, Ni, and Mo were in fragments abraded from the penetrator. Mineralogical changes occurring in the sediment next to the penetrator included the introduction of micron-size grains of alpha iron and several hydrated iron oxide minerals. The newly formed silicate minerals include metastable phases of silica (cristobalite, lechatelierite, and opal). The glassy material was mostly opal which formed when the host minerals (mica, calcite, and clay) decomposed. In summary, contaminants introduced by the penetrator occur up to 2 mm away from the penetrator's skin. Although volatile elements do migrate and new minerals are formed during the destruction of host minerals in the sediment, no changes were observed beyond the 2-mm distance. The analyses indicate 0.58-scale penetrators do effectively simulate full-scale testing for soil modification effects.

  12. Surface Sediments in the Marsh-Sandy Land Transitional Area: Sandification in the Western Songnen Plain, China

    PubMed Central

    Yu, Xiaofei; Grace, Michael; Zou, Yuanchun; Yu, Xuefeng; Lu, Xianguo; Wang, Guoping

    2014-01-01

    The development of sandification process was studied, by monitoring the changes of sediment characteristics, at marsh-sandy land intersections in China's Songnen region. A series of sediment collection plates were deployed in the region; after one year, sediments in these plates were analyzed for changes of mass and chemical characteristics. The sediment flux and the sand content of the sediments decreased with the increasing longitudinal distance between the sampling site and the centre line of a sand dune. The mean sediment flux was 29±14 kg m−2 yr−1 and 0.6±0.3 kg m−2 yr−1 in the sandy land and marsh, respectively. Strong, positive correlations were found between the concentrations of organic matter, total nitrogen, P, Fe, Ti, V and Zr, all of which were also negatively correlated with the sand content. The concentrations of organic matter, total nitrogen, P, Fe, Ti, V and Zr in the marsh sediment samples were all significantly greater than the corresponding concentrations of the sandy land (p<0.001). Sand content and Ti, V and Zr concentrations all proved to be valid indicators of sandification intensity, and they showed that the marsh could be divided into three distinct zones. Sand expansion extended about 88 m into the marsh. The mean sand content in the sediments of the sandy land was 91% and then 64% in the marsh, which in turn was higher than that of marshes outside the influence of sandification, suggesting that the marsh in the marsh-sandy land transitional area has already undergone extensive sandification in the past. The study results provide information on the wetland's function of indicating and buffering the sandification process. PMID:24932717

  13. Recent deformation of Quaternary sediments as inferred from GPR images and shallow P-wave velocity tomograms: Northwest Canterbury Plains, New Zealand

    NASA Astrophysics Data System (ADS)

    Carpentier, S. F. A.; Green, A. G.; Doetsch, J.; Dorn, C.; Kaiser, A. E.; Campbell, F.; Horstmeyer, H.; Finnemore, M.

    2012-06-01

    Prior to the recent highly damaging M 7.1 earthquake near the city of Christchurch on the South Island of New Zealand, we recorded coincident high-resolution seismic and ground-penetrating radar (GPR) data across parts of the northwest Canterbury Plains. The seismic reflection images reveal a vast network of interconnected faults and folds below a seemingly undisturbed flat surface. To complement the seismic images, which only provide limited information on the very shallow subsurface (i.e., < 20 m), we have now processed and analysed the GPR data. The migrated GPR images are dominated by complex reflection patterns characteristic of glaciofluvial sediments. Such sediments eroded from the Southern Alps are observed at the surface throughout our study site. Although it is difficult to distinguish between complexities associated with complicated sedimentation processes and disruptions and offsets of GPR reflections associated with recent movements on faults and folds, we identify a number of regions where the GPR data are consistent with tectonic deformation of Holocene sediments. Two of these regions straddle an interpolated connection between active faults mapped at the surface. In a third region, the development of river terraces imaged in the GPR data may have been affected by slip on newly discovered underlying faults. The most significant near-surface deformation, which is apparent on a coincident seismic reflection image, P-wave tomogram and GPR image, is observed on the flank of a major anticline that appears to have been thrust close to the surface along a reverse fault. Some of the faults and folds resolved in our seismic and GPR data may have been reactivated during the recent period of intense seismicity.

  14. Eukaryotic Richness in the Abyss: Insights from Pyrotag Sequencing

    PubMed Central

    Pawlowski, Jan; Christen, Richard; Lecroq, Batrice; Bachar, Dipankar; Shahbazkia, Hamid Reza; Amaral-Zettler, Linda; Guillou, Laure

    2011-01-01

    Background The deep sea floor is considered one of the most diverse ecosystems on Earth. Recent environmental DNA surveys based on clone libraries of rRNA genes confirm this observation and reveal a high diversity of eukaryotes present in deep-sea sediment samples. However, environmental clone-library surveys yield only a modest number of sequences with which to evaluate the diversity of abyssal eukaryotes. Methodology/Principal Findings Here, we examined the richness of eukaryotic DNA in deep Arctic and Southern Ocean samples using massively parallel sequencing of the 18S ribosomal RNA (rRNA) V9 hypervariable region. In very small volumes of sediments, ranging from 0.35 to 0.7 g, we recovered up to 7,499 unique sequences per sample. By clustering sequences having up to 3 differences, we observed from 942 to 1756 Operational Taxonomic Units (OTUs) per sample. Taxonomic analyses of these OTUs showed that DNA of all major groups of eukaryotes is represented at the deep-sea floor. The dinoflagellates, cercozoans, ciliates, and euglenozoans predominate, contributing to 17%, 16%, 10%, and 8% of all assigned OTUs, respectively. Interestingly, many sequences represent photosynthetic taxa or are similar to those reported from the environmental surveys of surface waters. Moreover, each sample contained from 31 to 71 different metazoan OTUs despite the small sample volume collected. This indicates that a significant faction of the eukaryotic DNA sequences likely do not belong to living organisms, but represent either free, extracellular DNA or remains and resting stages of planktonic species. Conclusions/Significance In view of our study, the deep-sea floor appears as a global DNA repository, which preserves genetic information about organisms living in the sediment, as well as in the water column above it. This information can be used for future monitoring of past and present environmental changes. PMID:21483744

  15. Biogeochemical, Isotopic and Bacterial Distributions Trace Oceanic Abyssal Circulation.

    PubMed

    Rubino, Angelo; Bensi, Manuel; Hainbucher, Dagmar; Zanchettin, Davide; Mapelli, Francesca; Ogrinc, Nives; Marchetto, Davide; Borin, Sara; Cardin, Vanessa; Fajon, Vesna; Horvat, Milena; Taricco, Carla; Baldi, Franco

    2016-01-01

    We explore the possibility of tracing routes of dense waters toward and within the ocean abyss by the use of an extended set of observed physical and biochemical parameters. To this purpose, we employ mercury, isotopic oxygen, biopolymeric carbon and its constituents, together with indicators of microbial activity and bacterial diversity found in bottom waters of the Eastern Mediterranean. In this basin, which has been considered as a miniature global ocean, two competing sources of bottom water (one in the Adriatic and one in the Aegean seas) contribute to the ventilation of the local abyss. However, due to a recent substantial reduction of the differences in the physical characteristics of these two water masses it has become increasingly complex a water classification using the traditional approach with temperature, salinity and dissolved oxygen alone. Here, we show that an extended set of observed physical and biochemical parameters allows recognizing the existence of two different abyssal routes from the Adriatic source and one abyssal route from the Aegean source despite temperature and salinity of such two competing sources of abyssal water being virtually indistinguishable. Moreover, as the near-bottom development of exogenous bacterial communities transported by convectively-generated water masses in the abyss can provide a persistent trace of episodic events, intermittent flows like those generating abyssal waters in the Eastern Mediterranean basin may become detectable beyond the availability of concomitant measurements. PMID:26761666

  16. Biogeochemical, Isotopic and Bacterial Distributions Trace Oceanic Abyssal Circulation

    PubMed Central

    Rubino, Angelo; Bensi, Manuel; Hainbucher, Dagmar; Zanchettin, Davide; Mapelli, Francesca; Ogrinc, Nives; Marchetto, Davide; Borin, Sara; Cardin, Vanessa; Fajon, Vesna; Horvat, Milena; Taricco, Carla; Baldi, Franco

    2016-01-01

    We explore the possibility of tracing routes of dense waters toward and within the ocean abyss by the use of an extended set of observed physical and biochemical parameters. To this purpose, we employ mercury, isotopic oxygen, biopolymeric carbon and its constituents, together with indicators of microbial activity and bacterial diversity found in bottom waters of the Eastern Mediterranean. In this basin, which has been considered as a miniature global ocean, two competing sources of bottom water (one in the Adriatic and one in the Aegean seas) contribute to the ventilation of the local abyss. However, due to a recent substantial reduction of the differences in the physical characteristics of these two water masses it has become increasingly complex a water classification using the traditional approach with temperature, salinity and dissolved oxygen alone. Here, we show that an extended set of observed physical and biochemical parameters allows recognizing the existence of two different abyssal routes from the Adriatic source and one abyssal route from the Aegean source despite temperature and salinity of such two competing sources of abyssal water being virtually indistinguishable. Moreover, as the near-bottom development of exogenous bacterial communities transported by convectively-generated water masses in the abyss can provide a persistent trace of episodic events, intermittent flows like those generating abyssal waters in the Eastern Mediterranean basin may become detectable beyond the availability of concomitant measurements. PMID:26761666

  17. Results of rainfall simulation to estimate sediment-bound carbon and nitrogen loss from an Atlantic Coastal Plain (USDA) ultisol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The impact of erosion on soil and carbon loss and redistribution within landscapes is an important component for developing estimates of carbon sequestration potential, management plans to maintain soil quality, and transport of sediment bound agrochemicals. Soils of the Southeastern U.S. Coastal Pl...

  18. Global sediment thickness data set updated for the Australian-Antarctic Southern Ocean

    NASA Astrophysics Data System (ADS)

    Whittaker, Joanne M.; Goncharov, Alexey; Williams, Simon E.; Mller, R. Dietmar; Leitchenkov, German

    2013-08-01

    We present a new, 5 min sediment thickness grid for the Australian-Antarctic region (60E-155E, 30S-70S). New seismic reflection and refraction data have been used to add detail to the conjugate Australian and Antarctic margins and intervening ocean floor where regional sediment thickness patterns were poorly known previously. On the margins, sediment thickness estimates were computed from velocity-depth functions from sonobuoy/refraction velocity solutions ground-truthed against seismic reflection data. For the Southeast Indian Ridge abyssal plains, sediment thickness contours from Geli et al. (2007) were used. The new regional minimum sediment thickness grid was combined with the global National Geophysical Data Center (NGDC) sediment grid to create an updated global grid. Even using the minimum estimates, sediment accumulations on the extended Australian and Antarctic continental margins are 2 km thicker across large regions and up to 9 km thicker in the Ceduna Basin compared to the global NGDC compilation of sediment thickness data.

  19. Strath terraces on the western High Plains indicate climatically-driven variations in sediment supply from source basins in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Dhnforth, M.; Anderson, R. S.

    2013-12-01

    Large strath terraces adjacent to the Colorado Front Range record the local history of fluvial planation and incision into the erodible rocks of the Denver basin over the last 2 million years. Terrace surfaces have been correlated into ~6 alluvial units using elevation and soil development; each alluvial unit was thought to represent a fairly consistent elevation of the Denver basin during various stages of exhumation, driven by base-level fall of the South Platte River. Here we show instead that (1) strath terraces in the western High Plains cannot be correlated based on elevation alone and (2) exhumation of the Denver basin is likely spatially and temporally variable due to climatically-driven variations in sediment supply from the source basins. We collected samples for cosmogenic radionuclide (CRN) profiles (10Be and 26Al) and a soil chronosequence from three strath terraces adjacent to Lefthand Creek near Boulder, CO. 10Be profile data on the upper- and middle-elevation terraces yield dates of 95 ka and 91 ka; these dates are much younger than the correlative alluvial units to the south of Boulder, which date to 1.5 Ma and 250 ka, respectively. Soils on the upper and middle terraces are similar in soil development and clast weathering, consistent with the narrow time window obtained from CRN dating of the two units. 10Be-derived rates for catchment-wide paleo-denudation are ~8.0 cm/ka from the flat and broad upper-terrace gravels and ~3.5 cm/ka from the steeper and narrower middle-terrace gravels. Young terraces at Lefthand Canyon are more consistent with a model of fluvial incision and aggradation driven by climate-controlled variations in sediment production from source basins in the Front Range. High catchment-wide denudation rates generate a high sediment supply, leading to aggradation and lateral planation. Terrace sediments are likely deposited and eroded multiple times during periods of lateral planation; the most recent occupation is preserved in the gravel caps on strath terraces. Lower catchment-wide denudation rates, and thus low sediment supply, lead to vertical bedrock incision and abandonment of terrace surfaces. Our data indicate that Front Range rivers experience a complex and basin-specific history where long periods of aggradation and lateral planation are punctuated by brief episodes of rapid incision through the soft Cretaceous shale underlying the Boulder area.

  20. Pb isotopes in surficial pelagic sediments from the North Atlantic

    SciTech Connect

    Hamelin, B.; Grousset, F. ); Sholkovitz, E.R. )

    1990-01-01

    The authors measured Pb isotopic composition and concentration in sediment samples close to the sea water interface in 6 box-cores from the NE Atlantic, 2 box-cores from the Sargasso Sea, and one from the US continental shelf. The anthropogenic Pb input to marine sediments due to the increase of Pb contamination over the ocean during the last century can be identified in all these cores. In the eastern part of the Atlantic, i.e., in regions under aeolian influence from Europe, Pb pollution can be recognized using its distinctive unradiogenic composition, clearly different from the upper-crustal values commonly found in pre-Holocene sediments. In contrast, Pb pollution in regions influenced by North American sources can be identified only in detailed concentration profiles because the American Pb pollution has an isotopic composition much closer to that of the natural detrital Pb input coming from weathering of the continental crust. Pb excess inventories are in good agreement with fluxes estimated from sediment-trap data and with the time record of Pb-contamination increase given by analyses in coral growth bands. Inventories of Pb contamination to the sediments of the Mud Patch (American shelf) are tenfold higher (84 {mu}g/cm{sup 2}) than those to Hatteras and Bermuda abyssal plains (4.3 and 2.8 {mu}g/cm{sup 2}).

  1. Internal tide generation by abyssal hills using analytical theory

    NASA Astrophysics Data System (ADS)

    Melet, Anglique; Nikurashin, Maxim; Muller, Caroline; Falahat, S.; Nycander, Jonas; Timko, Patrick G.; Arbic, Brian K.; Goff, John A.

    2013-11-01

    Internal tide driven mixing plays a key role in sustaining the deep ocean stratification and meridional overturning circulation. Internal tides can be generated by topographic horizontal scales ranging from hundreds of meters to tens of kilometers. State of the art topographic products barely resolve scales smaller than 10 km in the deep ocean. On these scales abyssal hills dominate ocean floor roughness. The impact of abyssal hill roughness on internal-tide generation is evaluated in this study. The conversion of M2 barotropic to baroclinic tidal energy is calculated based on linear wave theory both in real and spectral space using the Shuttle Radar Topography Mission SRTM30_PLUS bathymetric product at 1/120 resolution with and without the addition of synthetic abyssal hill roughness. Internal tide generation by abyssal hills integrates to 0.1 TW globally or 0.03 TW when the energy flux is empirically corrected for supercritical slope (i.e., 10% of the energy flux due to larger topographic scales resolved in standard products in both cases). The abyssal hill driven energy conversion is dominated by mid-ocean ridges, where abyssal hill roughness is large. Focusing on two regions located over the Mid-Atlantic Ridge and the East Pacific Rise, it is shown that regionally linear theory predicts an increase of the energy flux due to abyssal hills of up to 100% or 60% when an empirical correction for supercritical slopes is attempted. Therefore, abyssal hills, unresolved in state of the art topographic products, can have a strong impact on internal tide generation, especially over mid-ocean ridges.

  2. Abyssal fauna of the UK-1 polymetallic nodule exploration claim, Clarion-Clipperton Zone, central Pacific Ocean: Echinodermata.

    PubMed

    Glover, Adrian G; Wiklund, Helena; Rabone, Muriel; Amon, Diva J; Smith, Craig R; O'Hara, Tim; Mah, Christopher L; Dahlgren, Thomas G

    2016-01-01

    We present data from a DNA taxonomy register of the abyssal benthic Echinodermata collected as part of the Abyssal Baseline (ABYSSLINE) environmental survey cruise 'AB01' to the UK Seabed Resources Ltd (UKSRL) polymetallic-nodule exploration claim 'UK-1' in the eastern Clarion-Clipperton Zone (CCZ), central Pacific Ocean abyssal plain. Morphological and genetic data are presented for 17 species (4 Asteroidea, 4 Crinoidea, 2 Holothuroidea and 7 Ophiuroidea) identified by a combination of morphological and genetic data. No taxa matched previously published genetic sequences, but 8 taxa could be assigned to previously-described species based on morphology, although here we have used a precautionary approach in taxon assignments to avoid over-estimating species ranges. The Clarion-Clipperton Zone is a region undergoing intense exploration for potential deep-sea mineral extraction. We present these data to facilitate future taxonomic and environmental impact study by making both data and voucher materials available through curated and accessible biological collections. PMID:26929713

  3. Abyssal fauna of the UK-1 polymetallic nodule exploration claim, Clarion-Clipperton Zone, central Pacific Ocean: Echinodermata

    PubMed Central

    Glover, Adrian G; Wiklund, Helena; Rabone, Muriel; Amon, Diva J; Smith, Craig R; O'Hara, Tim; Mah, Christopher L

    2016-01-01

    Abstract We present data from a DNA taxonomy register of the abyssal benthic Echinodermata collected as part of the Abyssal Baseline (ABYSSLINE) environmental survey cruise ‘AB01’ to the UK Seabed Resources Ltd (UKSRL) polymetallic-nodule exploration claim ‘UK-1’ in the eastern Clarion-Clipperton Zone (CCZ), central Pacific Ocean abyssal plain. Morphological and genetic data are presented for 17 species (4 Asteroidea, 4 Crinoidea, 2 Holothuroidea and 7 Ophiuroidea) identified by a combination of morphological and genetic data. No taxa matched previously published genetic sequences, but 8 taxa could be assigned to previously-described species based on morphology, although here we have used a precautionary approach in taxon assignments to avoid over-estimating species ranges. The Clarion-Clipperton Zone is a region undergoing intense exploration for potential deep-sea mineral extraction. We present these data to facilitate future taxonomic and environmental impact study by making both data and voucher materials available through curated and accessible biological collections. PMID:26929713

  4. A source-sink hypothesis for abyssal biodiversity.

    PubMed

    Rex, Michael A; McClain, Craig R; Johnson, Nicholas A; Etter, Ron J; Allen, John A; Bouchet, Philippe; Warn, Anders

    2005-02-01

    Bathymetric gradients of biodiversity in the deep-sea benthos constitute a major class of large-scale biogeographic phenomena. They are typically portrayed and interpreted as variation in alpha diversity (the number of species recovered in individual samples) along depth transects. Here, we examine the depth ranges of deep-sea gastropods and bivalves in the eastern and western North Atlantic. This approach shows that the abyssal molluscan fauna largely represents deeper range extensions for a subset of bathyal species. Most abyssal species have larval dispersal, and adults live at densities that appear to be too low for successful reproduction. These patterns suggest a new explanation for abyssal biodiversity. For many species, bathyal and abyssal populations may form a source-sink system in which abyssal populations are regulated by a balance between chronic extinction arising from vulnerabilities to Allee effects and immigration from bathyal sources. An increased significance of source-sink dynamics with depth may be driven by the exponential decrease in organic carbon flux to the benthos with increasing depth and distance from productive coastal systems. The abyss, which is the largest marine benthic environment, may afford more limited ecological and evolutionary opportunity than the bathyal zone. PMID:15729648

  5. Influence of internal tides on Antarctic Bottom Water propagation through abyssal channels

    NASA Astrophysics Data System (ADS)

    Morozov, Eugene

    2010-05-01

    Antarctic Bottom Water (AABW) propagates in the Atlantic Ocean from the Weddell Sea to the north through narrow passages in submarine ridges. Submarine ridges are regions of strong internal tide generation in the ocean that causes mixing and eventually AABW loses its distinguishing properties such as low temperature and salinity. The Vema Fracture Zone (11? N) and Romanche Fracture Zone (equator) in the Mid-Atlantic Ridge (MAR) are pathways for AABW to the Northeast Atlantic. The deep basin of the Northeast Atlantic (Canary Basin and Gambia Abyssal Plain) are filled with the bottom water propagating through the Vema FZ rather than through the equatorial fracture zones because strong internal tides and mixing over the slopes of the MAR near the equator cause warming of AABW and decrease of its density. Further propagation of AABW through the Kane Gap is low. Recent field measurements in the fracture zones confirm this concept based on modeling results. Results of recent cruises are presented.

  6. Kuril-Kamchatka deep sea revisited - insights into the amphipod abyssal fauna

    NASA Astrophysics Data System (ADS)

    Ja?d?ewska, Anna

    2015-01-01

    During the KuramBIO expedition to the Kuril-Kamchatka Trench and abyssal plain, benthic samples from the depths from 4987 to 5422 m were collected using a camera-epibenthic sledge. In this collection more than 1200 individuals of Amphipoda were found. They were assigned to 60 taxa (including 47 morphospecies) and 21 families. Until now 28 species being new to science have been found: six in the superfamily Eusiroidea and in the Oedicerotidae and Synopiidae families, four in the Phoxocephalidae, three in the Pardaliscidae, two in the Stenothoidae and one in the Pachynidae. The Synopiidae, Stenothoidae and Pachynidae were recorded for the first time in North-West Pacific area. The dominant and most speciose families were Oedicerotidae, Phoxocephalidae, Synopiidae, Eusiridae s.l. and Lysianassidae. The cluster analysis clearly separated the shallowest sample from the others, which were divided further into two groups. The shallowest sample was characterized by the highest number of species and number of individuals.

  7. Pedobacter nyackensis sp. nov., Pedobacter alluvionis sp. nov. and Pedobacter borealis sp. nov., isolated from Montana flood-plain sediment and forest soil.

    PubMed

    Gordon, Nathan S; Valenzuela, Alejandra; Adams, Sandra M; Ramsey, Philip W; Pollock, Jarrod L; Holben, William E; Gannon, James E

    2009-07-01

    Three Gram-negative, rod-shaped, non-spore-forming eubacterial strains were isolated in western Montana, USA, and subjected to taxonomic studies. Strains NWG-II14(T) and NWER-II11(T) were isolated from hyporheic sediments of a large alluvial flood plain, whereas strain G-1(T) was isolated from a conifer forest soil. On the basis of 16S rRNA gene sequence similarity, strains NWG-II14(T), NWER-II11(T) and G-1(T) were shown to belong to the family Sphingobacteriaceae and are most closely related to various species of the genus Pedobacter. The results of molecular, physiological and biochemical tests allowed genotypic and phenotypic differentiation of these three strains from 23 Pedobacter species with validly published names. The three isolates therefore represent novel species, for which the names Pedobacter nyackensis sp. nov. (type strain NWG-II14(T) =DSM 19625(T) =LMG 24260(T)), Pedobacter alluvionis sp. nov. (type strain NWER-II11(T) =DSM 19624(T) =LMG 24258(T)) and Pedobacter borealis sp. nov. (type strain G-1(T) =DSM 19626(T) =LMG 24259(T)) are proposed. PMID:19542109

  8. Role of naturally occurring gas hydrates in sediment transport

    SciTech Connect

    McIver, R.D.

    1982-06-01

    Naturally occurring gas hydrates have the potential to store enormous volumes of both gas and water in semi-solid form in ocean-bottom sediments and then to release that gas and water when the hydrate's equilibrium condition are disturbed. Therefore, hydrates provide a potential mechanism for transporting large volumes of sediments. Under the combined low bottom-water temperatures and moderate hydrostatic pressures that exist over most of the continental slopes and all of the continental rises and abyssal plains, hydrocarbon gases at or near saturation in the interstitial waters of the near-bottom sediments will form hydrates. The gas can either be autochthonous, microbially produced gas, or allochthonous, catagenic gas from deeper sediments. Equilibrium conditions that stabilize hydrated sediments may be disturbed, for example, by continued sedimentation or by lowering of sea level. In either case, some of the solid gas-water matrix decomposes. Released gas and water volume exceeds the volume occupied by the hydrate, so the internal pressure rises - drastically if large volumes of hydrate are decomposed. Part of the once rigid sediment is converted to a gas- and water-rich, relatively low density mud. When the internal pressure, due to the presence of the compressed gas or to buoyancy, is sufficiently high, the overlying sediment may be lifted and/or breached, and the less dense, gas-cut mud may break through. Such hydrate-related phenomena can cause mud diapirs, mud volcanos, mud slides, or turbidite flows, depending on sediment configuration and bottom topography. 4 figures.

  9. Adult antarctic krill feeding at abyssal depths.

    PubMed

    Clarke, Andrew; Tyler, Paul A

    2008-02-26

    Antarctic krill (Euphausia superba) is a large euphausiid, widely distributed within the Southern Ocean [1], and a key species in the Antarctic food web [2]. The Discovery Investigations in the early 20(th) century, coupled with subsequent work with both nets and echosounders, indicated that the bulk of the population of postlarval krill is typically confined to the top 150 m of the water column [1, 3, 4]. Here, we report for the first time the existence of significant numbers of Antarctic krill feeding actively at abyssal depths in the Southern Ocean. Biological observations from the deep-water remotely operated vehicle Isis in the austral summer of 2006/07 have revealed the presence of adult krill (Euphausia superba Dana), including gravid females, at unprecedented depths in Marguerite Bay, western Antarctic Peninsula. Adult krill were found close to the seabed at all depths but were absent from fjords close inshore. At all locations where krill were detected they were seen to be actively feeding, and at many locations there were exuviae (cast molts). These observations revise significantly our understanding of the depth distribution and ecology of Antarctic krill, a central organism in the Southern Ocean ecosystem. PMID:18302926

  10. Growth, reproduction and possible recruitment variability in the abyssal brittle star Ophiocten hastatum (Ophiuroidea: Echinodermata) in the NE Atlantic

    NASA Astrophysics Data System (ADS)

    Gage, John D.; Anderson, Roslyn M.; Tyler, Paul A.; Chapman, Rachel; Dolan, Emily

    2004-06-01

    Growth was studied from skeletal growth markers in the cosmopolitan abyssal brittle star Ophiocten hastatm. Samples for analysis were taken at five sites located in the southern (2900 m) and central (2000 m) Rockall Trough, at ca. 3000 and 4000 m in the Porcupine Seabight, and at 4850 m on the Porcupine Abyssal Plain. Growth bands were assumed to reflect an annual cycle in skeletal growth. Band measurements on arm vertebrae, standardised to disc diameter, were used to provide size-at-age data and size-increment data that took into account overgrowth of early bands in older individuals. The Richards growth function marginally provides best fit to pooled size-at-age data, although the asymptote-less Tanaka function and the Gompertz growth function also provided good fit to size-at-age data which showed a rather linear growth pattern with little indication of a growth asymptote. Log e transformed size-increment data were linearised by applying the Ford-Walford method to approximate Gompertz growth so that growth could be compared at the five sites. Grouped linear regression and analysis of covariance showed no significant differences between growth at the sites and a common fitted regression. However, pairwise comparisons suggest growth differences with increasing bathymetric separation. Oocyte size frequencies measured from histological preparations of the gonad of specimens from the Porcupine Abyssal Plain indicate marked reproductive periodicity, with spawn-out in late winter that is likely followed by planktotrophic early development in spring with benthic settlement in summer. Although usually rare in the trawl and epibenthic sled samples, several years of successful recruitment followed by a period when recruitment was low or absent might explain size structure observed in a single unusually large sample from the Rockall Trough. This is consistent with previous observations during the late 1990s of a large population increase on the Porcupine Abyssal Plain. Analysis of growth bands of these specimens sampled in 1997 suggest the population increase derives from a single or small number of year classes recruited during the early 1990s.

  11. Abyssal benthos of the central Indian Ocean

    NASA Astrophysics Data System (ADS)

    Parulekar, A. H.; Harkantra, S. N.; Ansari, Z. A.; Matondkar, S. G. P.

    1982-12-01

    Quantitative studies of the abyssal benthos (3600 to 5300 m) of the central Indian Ocean show a rich fauna and high standing crops. Density of 3 meiofaunal and 12 macrofaunal taxa are large (2175 to 15233; x = 6441 m -2) Polychaetes (41.6%), peracarid crustaceans (31.7%), ophiuroids (12.2%), echiuroid-bryozoa (9.7%), molluscs (4.8%), and agglutinating rhizopod protozoans form the macrofauna. Meiofaunal taxa are nematodes (69.4%), harpacticoid copepods (26.6%), and ostracods (4%). Meiofauna abundances are positively correlated with distance from shore, whereas the distribution and abundance of macrofauna are independent of variations in depth and distance from the shore. Ratio of macro to meiofauna in the total population is 1 to 31. The benthic standing crop is uniformly high (0.54 to 13.73 g m -2; x = 2.70 g m -2) and many times larger than previously reported for comparable depths in other oceans and from the same region. Biomass values are significantly related to distance from shore and the type of substratum. Contribution of macro and meiofauna to the total standing crop was in the ratio of 31 to 1. High benthic biomass and rich fauna are consequences of high organic production in the euphotic zone. The correlation between biomass of the total oxidizable organic matter in the water column and the benthic standing crop is statistically significant ( r = -0.64) at the P < 0.05 level. Rich fauna and high standing crop were associated with the occurrence of polymetallic nodules.

  12. Internal wave structures in abyssal cataract flows

    NASA Astrophysics Data System (ADS)

    Makarenko, Nikolay; Liapidevskii, Valery; Morozov, Eugene; Tarakanov, Roman

    2014-05-01

    We discuss some theoretical approaches, experimental results and field data concerning wave phenomena in ocean near-bottom stratified flows. Such strong flows of cold water form everywhere in the Atlantic abyssal channels, and these currents play significant role in the global water exchange. Most interesting wave structures arise in a powerful cataract flows near orographic obstacles which disturb gravity currents by forced lee waves, attached hydraulic jumps, mixing layers etc. All these effects were observed by the authors in the Romanche and Chain fracture zones of Atlantic Ocean during recent cruises of the R/V Akademik Ioffe and R/V Akademik Sergei Vavilov (Morozov et al., Dokl. Earth Sci., 2012, 446(2)). In a general way, deep-water cataract flows down the slope are similar to the stratified flows examined in laboratory experiments. Strong mixing in the sill region leads to the splitting of the gravity current into the layers having the fluids with different densities. Another peculiarity is the presence of critical layers in shear flows sustained over the sill. In the case under consideration, this critical level separates the flow of near-bottom cold water from opposite overflow. In accordance with known theoretical models and laboratory measurements, the critical layer can absorb and reflect internal waves generated by the topography, so the upward propagation of these perturbations is blocked from above. High velocity gradients were registered downstream in the vicinity of cataract and it indicates the existence of developed wave structures beyond the sill formed by intense internal waves. This work was supported by RFBR (grants No 12-01-00671-a, 12-08-10001-k and 13-08-10001-k).

  13. Cross-equatorial flow through an abyssal channel under the complete Coriolis force: Two-dimensional solutions

    NASA Astrophysics Data System (ADS)

    Stewart, A. L.; Dellar, P. J.

    The component of the Coriolis force due to the locally horizontal component of the Earth's rotation vector is commonly neglected, under the so-called traditional approximation. We investigate the role of this "non-traditional" component of the Coriolis force in cross-equatorial flow of abyssal ocean currents. We focus on the Antarctic Bottom Water (AABW), which crosses from the southern to the northern hemisphere through the Ceara abyssal plain in the western Atlantic ocean. The bathymetry in this region resembles a northwestward channel, connecting the Brazil Basin in the south to the Guyana Basin in the north. South of the equator, the AABW leans against the western continental rise, consistent with a northward flow in approximate geostrophic balance. The AABW then crosses to the other side of the abyssal channel as it crosses the equator, and flows into the northern hemisphere leaning towards the east against the Mid-Atlantic Ridge. The non-traditional component of the Coriolis force is strongest close to the equator. The traditional component vanishes at the equator, being proportional to the locally vertical component of the Earth's rotation vector. The weak stratification of the abyssal ocean, and subsequent small internal deformation radius, defines a relatively short characteristic horizontal lengthscale that tends to make non-traditional effects more prominent. Additionally, the steep gradients of the channel bathymetry induce large vertical velocities, which are linked to zonal accelerations by the non-traditional components of the Coriolis force. We therefore expect non-traditional effects to play a substantial role in cross-equatorial transport of the AABW. We present asymptotic steady solutions for non-traditional shallow water flow through an idealised abyssal channel, oriented at an oblique angle to the equator. The current enters from the south, leaning up against the western side of the channel in approximate geostrophic balance, and crosses the channel as it crosses the equator. The "non-traditional" contribution to the planetary angular momentum must be balanced by stronger westward flow in the channel, which leads to an increased transport in a northwestward channel, and a reduced transport in a northeastward channel. Our results suggest that as much as 10-30% of the cross-equatorial flow of the AABW may be attributed to the non-traditional components of the Coriolis force.

  14. Vesicomyinae (Bivalvia: Vesicomyidae) of the Kuril-Kamchatka Trench and adjacent abyssal regions

    NASA Astrophysics Data System (ADS)

    Krylova, Elena M.; Kamenev, Gennady M.; Vladychenskaya, Irina P.; Petrov, Nikolai B.

    2015-01-01

    Representatives of the subfamily Vesicomyinae (Bivalvia, Vesicomyidae) are tiny deep-sea molluscs distributed worldwide and reaching huge abundances of hundreds and thousands of specimens in trawl catches. During the German-Russian deep-sea expedition KuramBio (R/V Sonne, 2012) for the first time two vesicomyin species were collected from the abyssal plain adjacent to the Kuril-Kamchatka Trench from the depths of 4861-5787 m, Vesicomya pacifica (Smith, 1885) and "Vesicomya" filatovae sp.n. Two species of vesicomyins, V. sergeeviFilatova, 1971 and V. profundiFilatova, 1971, which were previously reported from the hadal of the Kuril-Kamchatka Trench, were not collected at the abyssal depth despite of the close geographical proximity of the sampling area to their distribution ranges. Altogether nine species of vesicomyins are recorded now from the West and Indo-West Pacific; data on distribution and morpho-anatomical characters of these species are provided. Taxonomic description of V. pacifica is revised including information on its soft part anatomy, new localities and COI sequences. For the first time for a vesicomyin bivalve molecular data is given for a species with an explicit morphological description and unambiguous taxonomic affiliation. Molecular analysis of 160 published COI sequences of vesicomyids and newly obtained molecular data on V. pacifica showed that V. pacifica and two undescribed vesicomyin species forming a monophyletic clade which exhibits sister relationships with the Pliocardiinae, the group of chemosymbiotic vesicomyids. "Vesicomya" filatovae sp.n. is provisionally assigned to the genus Vesicomya (s.l.) until additional morphological and molecular data are obtained. It differs from Vesicomya s.s. by a broader hinge margin with more radiating teeth and the presence of only one pair of demibranchs.

  15. The sedimentation pattern around the Atlantis-Meteor seamount complex: a model study

    NASA Astrophysics Data System (ADS)

    Verhoef, J.

    1985-04-01

    The Atlantis-Meteor seamount group forms a large volcanic complex situated about 700 km to the south of the Azores. Not counting the turbidite sedimentation of the Madeira abyssal plain to the east, the area around the complex is characterized by a relatively thick sedimentary layer containing a strong and often shielding reflector. The thickness of the sediments above the strong reflector, as well as the total sediment thickness, shows an asymmetry with respect to the seamount complex: west of the seamounts a thick sedimentary cover can be found, while virtually no sediments occur to the east of the seamounts. The depth anomaly in the area around the seamount complex is positive. The depth anomaly contours correlate well with the regional isopachs of the sediment above the strong reflector. This correlation led to the construction of a simple carbonate sedimentation model. In this model paleodepth reconstructions were used to calculate the carbonate sedimentation. The model explains the most important aspects of the sedimentation pattern. Besides it led to the conclusion that the age of the strongly reflecting layer cannot be much older than Miocene. This conclusion is sustained by the absence of sediments in the southwestern part of the area. Therefore it is unlikely that the volcanism in this area and the anomalous depth originated on the spreading centre. The model is not sensitive enough to detect variations in age between the different seamounts. Since there are no DSDP sites in this area the age determination based on the sedimentation pattern forms a useful alternative for the time being.

  16. 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.

  17. Sediment structures and sediment ages of the Chukchi region, Amerasia Basin

    NASA Astrophysics Data System (ADS)

    Hegewald, A.; Jokat, W.

    2011-12-01

    In 2008, the Alfred Wegener Institute (AWI) of Germany, using the RV Polarstern, collected multichannel seismic reflection data in the eastern Arctic Ocean (73-79°N and 170°E-165°W), namely the East Siberian Shelf, the Chukchi Shelf, - Plateau, and - Abyssal Plain, and the southern part of the Mendeleev Ridge. For the seismic data acquisition an air gun array with up to six air guns (48 ltr. total volume fired at 200 bar) was used. With a 3000 m long streamer including 240 active channels and a 600 m long streamer including 96 active channels the seismic signals were recorded. Obtaining the ages of the sediments, the information of five exploration wells near the coast of Alaska were correlated into the new seismic lines. For this correlation an existing network of more than 200 seismic reflection lines on the East Siberian Shelf and Chukchi Shelf from the USGS, TGS-NOPEC and ION-GX Technology were used. The research area is dominated by two different sediment packages ranging from the Paleocene to the Jurassic. The upper part is an undisturbed unit with low amplitudes and flat-lying reflections. In contrast, the lower package is dominated by an undulated stratification with many fractures and faults. Moreover, the lower unit consists of higher amplitudes with strong reflection bands. The sedimentary thickness varied from the East Siberian Shelf to the Chukchi Plateau from more than 8 km to 4 km. In the basin between the Chukchi Plateau and the Mendeleev Ridge the sedimentary thickness is about 2 km. Furthermore, a series of prograding sequences at the continental margin of the Chukchi Shelf with ages of 65 Ma and younger were analysed. These sequences are the result of an enormous sediment influx from Siberia and Alaska and can be explained by variations in the sedimentation rate over time.

  18. Reconstructing past plate motions with abyssal hill topography

    NASA Astrophysics Data System (ADS)

    Dahn, M. R.; Pockalny, R. A.; King, C.

    2013-12-01

    The seafloor spreading history of oceanic plates is primarily reconstructed by using a combination of dated seafloor magnetic anomalies and fracture zone trends to locate Euler poles and determine rotation rates. In some regions, these conventional measures of determining spreading history do not exist and alternative methods are required. Abyssal hills are elongate, topographic highs that are created at and form parallel to the ridge axis of spreading centers. Once formed, the abyssal hills are transported onto the ridge flank and provide a record of ridge axis orientation. We propose using the orientation of abyssal hill topography to supplement existing plate motion reconstruction methods and to serve as a stand-alone method for regions where conventional methods will not apply. Our new method uses high-resolution bathymetry grids created with multibeam data with grid-node spacing of 100-200 m, determined by regional water depths. The bathymetric grids are detrended to remove depth-age relationships and spatially filtered to remove anomalous regions where seafloor age is unknown. The detrended grids are then clipped to remove anomalously deep (e.g., fracture zones) or anomalously shallow topography (e.g., seamounts). Abyssal hill orientations are determined by calculating the modal frequencies of slope azimuth for pre-defined sub-regions (e.g., 50 km x 50 km) of these modified grids. The Euler Pole is then found by an iterative least-squares method from a grid of potential Euler Poles; first a coarse grid and then a fine grid are utilized to avoid local minima. At each potential Euler Pole, the sum of the differences between predicted and observed abyssal hill trends is squared and the minimum value identifies the location of the best-fit Euler Pole. Our method was applied to the well-mapped Cocos-Pacific plate boundary along the northern East Pacific Rise for the past 3 Ma and the poorly constrained Mid-Cretaceous seafloor (84 - 120 Ma) in the southwest Pacific Ocean. The results for the northern East Pacific Rise are very encouraging and our calculated Euler Poles are within 4 degrees of the NUVEL 1a and 2 degrees of the MORVEL global relative motion models. We also applied our method to the EMAG2 magnetic anomaly intensity grids with similar encouraging results; 17 degrees NUVEL 1a & 11 degrees MORVEL. The results for the southwest Pacific are still preliminary, but the method effectively identifies regions with similar abyssal hill trends and may be useful for more detailed tectonic reconstructions of the enigmatic region.

  19. Identification of dredged sediment-derived soils in the alluvial plains of the Leie and the Upper and Sea Scheldt rivers (Belgium) based on physico-chemical soil properties.

    PubMed

    Vandecasteele, Bart; De Vos, Bruno; Tack, Filip M G

    2002-04-01

    An approach was developed to identify surface soils affected by historical dredged sediment disposal in the alluvial plains of the Upper Scheldt, the Sea Scheldt and the Leie river. Dredged sediment-derived soils were identified based on field observations, comparative granulometric analyses and chemical analyses. Criteria developed were based on a comparison between reference data from 102 aerobic soil samples of areas known to be affected by dredged sediment disposal and 104 samples from undisturbed alluvial soils along the studied rivers. A comparative grain size analysis with optical laser diffractometry between the A and C horizon proved useful for the identification of levelled-up sites. The chemical soil characteristics that were most useful in identifying dredged sediment-derived soils were CaCO3, sulfur (S), organic carbon (OC) and phosphorus (P) contents, electrical conductivity (EC), and the C/P and C/S ratios. Criteria for concluding the origin of an investigated soil were specific for the studied area, but the approach presented may provide useful guidelines for developing criteria valid for different regions. PMID:11993775

  20. Teaching the abyss: living the art-science of nursing.

    PubMed

    Ramey, Sandra L; Bunkers, Sandra Schmidt

    2006-10-01

    This column addresses how nurse educators can provide the teaching-learning experiences for novice nurses to develop the leadership competence to effectively practice nursing in an extremely demanding healthcare environment. The authors delve into Mitchell and Bunkers' use of the metaphor of an abyss to explore the lived experience of risking being with others in extremely intense interpersonal situations. Using reflection, students' journal narratives affirm connections made among past experiences and the new knowledge gleaned from exploring and naming the phenomenon of the abyss. Several teaching-learning strategies are offered as ways for addressing the leadership issues related to dealing with intense relational experiences in nursing practice, including exploring nurse theorist Rosemarie Rizzo Parse's essentials of leadership. PMID:16982716

  1. Orphan strontium-87 in abyssal peridotites: daddy was a granite.

    PubMed

    Snow, J E; Hart, S R; Dick, H J

    1993-12-17

    The (87)Sr/(86)Sr ratios in some bulk abyssal and alpine peridotites are too high to be binary mixtures of depleted mantle and seawater components. The apparent excess, or "orphan," (87)Sr appears to be separated from its radioactive parent. Such observations were widely held to be analytical artifacts. Study of several occurrences of orphan (87)Sr shows that the orphan component in abyssal peridotite is located in the alteration products of olivine and enstatite in the peridotite. The orphan (87)Sr is most likely introduced by infiltration of low-temperature (<200 degrees C) seawater bearing suspended detrital particulates. These particulates include grains of detrital clay that are partly derived from continental (that is, granitic) sources and thus are highly radiogenic. Orphan (87)Sr and other radiogenic isotopes may provide a tracer for low-temperature seawater penetrating into the oceanic crust. PMID:17829634

  2. Feeding preferences of abyssal macrofauna inferred from in situ pulse chase experiments.

    PubMed

    Jeffreys, Rachel M; Burke, Ciara; Jamieson, Alan J; Narayanaswamy, Bhavani E; Ruhl, Henry A; Smith, Kenneth L; Witte, Ursula

    2013-01-01

    Climatic fluctuations may significantly alter the taxonomic and biochemical composition of phytoplankton blooms and subsequently phytodetritus, the food source for the majority of deep-sea communities. To examine the response of abyssal benthic communities to different food resources we simulated a food sedimentation event containing diatoms and coccolithophorids at Station M in the NE Pacific. In one set of experiments we measured incorporation of diatomC and coccoN into the macrofauna using isotopically enriched (13)C-diatoms and (15)N-coccolithophores. In a second experiment we measured incorporation of C and N from dual-labelled ((13)C and (15)N) diatoms. The second experiment was repeated 2 months later to assess the effect of seasonality. The simulated food pulses represented additions of 650 - 800 mg C m(-2) and 120 mg N m(-2) to the seafloor. In all cases rapid incorporation of tracer was observed within 4 days, with between 20% and 52% of the macrofauna displaying evidence of enrichment. However, incorporation levels of both diatomC and coccoN were low (<0.05% and 0.005% of the added C and N). Incorporation of labelled diatoms was similar during both June and September suggesting that the community was not food limited during either period. We found no evidence for selective ingestion of the different food types in the metazoan fauna suggesting that macrofauna do not have strong preferences for diatom vs. coccolithophore dominated phytodetrital pulses. C∶N ratios from both experiments suggest that the metazoan macrofauna community appear to have higher C demands and/or assimilation efficiencies compared to N. Concomitantly, the foraminifera preferentially selected for diatomN over coccoN, and we suggest that this may be related to foraminiferal requirements for intracellular nitrate. These experiments provide evidence that abyssal faunal feeding strategies are in part driven by an organism's internal stoichiometric budgets and biochemical requirements. PMID:24303022

  3. Feeding Preferences of Abyssal Macrofauna Inferred from In Situ Pulse Chase Experiments

    PubMed Central

    Jeffreys, Rachel M.; Burke, Ciara; Jamieson, Alan J.; Narayanaswamy, Bhavani E.; Ruhl, Henry A.; Smith, Kenneth L.; Witte, Ursula

    2013-01-01

    Climatic fluctuations may significantly alter the taxonomic and biochemical composition of phytoplankton blooms and subsequently phytodetritus, the food source for the majority of deep-sea communities. To examine the response of abyssal benthic communities to different food resources we simulated a food sedimentation event containing diatoms and coccolithophorids at Station M in the NE Pacific. In one set of experiments we measured incorporation of diatomC and coccoN into the macrofauna using isotopically enriched 13C-diatoms and 15N-coccolithophores. In a second experiment we measured incorporation of C and N from dual-labelled (13C and 15N) diatoms. The second experiment was repeated 2 months later to assess the effect of seasonality. The simulated food pulses represented additions of 650 – 800 mg C m−2 and 120 mg N m−2 to the seafloor. In all cases rapid incorporation of tracer was observed within 4 days, with between 20% and 52% of the macrofauna displaying evidence of enrichment. However, incorporation levels of both diatomC and coccoN were low (<0.05% and 0.005% of the added C and N). Incorporation of labelled diatoms was similar during both June and September suggesting that the community was not food limited during either period. We found no evidence for selective ingestion of the different food types in the metazoan fauna suggesting that macrofauna do not have strong preferences for diatom vs. coccolithophore dominated phytodetrital pulses. C∶N ratios from both experiments suggest that the metazoan macrofauna community appear to have higher C demands and/or assimilation efficiencies compared to N. Concomitantly, the foraminifera preferentially selected for diatomN over coccoN, and we suggest that this may be related to foraminiferal requirements for intracellular nitrate. These experiments provide evidence that abyssal faunal feeding strategies are in part driven by an organism's internal stoichiometric budgets and biochemical requirements. PMID:24303022

  4. A hydrodynamically modified, abyssal isopod fauna

    NASA Astrophysics Data System (ADS)

    Thistle, David; Wilson, George D. F.

    1987-01-01

    At the High Energy Benthic Boundary Layer Experiment (HEBBLE) site (4820 m depth in the western North Atlantic) periods of strong currents and sediment erosion alternate with periods of weak flow and massive deposition. We investigated the impact of this atypical hydrodynamic environment on the isopod fauna by testing for a difference in composition between the HEBBLE site and a tranquil location, the Deep Ocean Mining Environmental Study (DOMES) site A ( ca. 5000 m) in the equatorial Pacific. Epifaunal isopods were significantly less abundant at the HEBBLE site than at the comparison site despite significantly greater total isopod numbers at the HEBBLE site. We suggest that the hydrodynamic regime puts epifaunal isopods at risk, making them rare at the HEBBLE site.

  5. Can the source-sink hypothesis explain macrofaunal abundance patterns in the abyss? A modelling test.

    PubMed

    Hardy, Sarah M; Smith, Craig R; Thurnherr, Andreas M

    2015-06-01

    Low food availability is a major structuring force in deep-sea benthic communities, sustaining only very low densities of organisms in parts of the abyss. These low population densities may result in an Allee effect, whereby local reproductive success is inhibited, and populations are maintained by larval dispersal from bathyal slopes. This slope-abyss source-sink (SASS) hypothesis suggests that the abyssal seafloor constitutes a vast sink habitat with macrofaunal populations sustained only by an influx of larval 'refugees' from source areas on continental slopes, where higher productivity sustains greater population densities. Abyssal macrofaunal population densities would thus be directly related to larval inputs from bathyal source populations. We evaluate three predictions derived from the SASS hypothesis: (i) slope-derived larvae can be passively transported to central abyssal regions within a single larval period, (ii) projected larval export from slopes to the abyss reproduces global patterns of macrofaunal abundance and (iii) macrofaunal abundance decreases with distance from the continental slope. We find that abyssal macrofaunal populations are unlikely to be sustained solely through influx of larvae from slope sources. Rather, local reproduction probably sustains macrofaunal populations in relatively high-productivity abyssal areas, which must also be considered as potential larval source areas for more food-poor abyssal regions. PMID:25948686

  6. Phytodetritus at the abyssal seafloor across 10 of latitude in the central equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Smith, Craig R.; Hoover, Daniel J.; Doan, Shawn E.; Pope, Robin H.; Demaster, David J.; Dobbs, Fred C.; Altabet, Mark A.

    Fresh phytoplankton detritus (or phytodetritus) has been reported from numerous deep seafloor sites in the temperate North Atlantic and Pacific Oceans following seasonal phytoplankton blooms. Here we report the first strong evidence for abyssal accumulations of phytodetritus in the tropics, in the central equatorial Pacific. In November-December 1992 we obtained photographs and/or sediment-core samples from 61 abyssal stations (water depths of 4280-5012 m) between 12S and 9N along 140W. Greenish flocculent material was recovered from the top of multiple-core samples from 5S to 5N; this material was most abundant from 2S to 2N, in some areas forming continuous layers at least 5 mm thick, and individual aggregates > 1 cm in diameter. The greenish material was clearly visible in bottom photographs as a green veneer that covered >95% of the seafloor near the equator, and as individual cm-scale aggregates covering <1% of the seafloor. Occasionally, thick accumulations of cm-scale aggregates occurred in biogenic pits. Cleared trails and feeding traces suggest that surface-deposit-feeding holothurians and echiurans grazed the greenish material. Microscopic examination of greenish material recovered from core tops and a burrow lumen revealed relatively intact diatoms (including Rhizosolenia sp.) and other microalgae with chloroplasts containing chlorophyll. The greenish material was 1-12.5% organic carbon by weight, i.e. 5-39 times richer than associated seafloor sediments. It also contained high excess activities of 234Th, suggesting arrival from the water column in the previous 100 days. Samples of the greenish flocculent material from 0 and 5N incubated at simulated environmental pressure and temperature with 14C-labeled glutamate exhibited ? 5-fold higher rates of microbial activity than underlying sediments or brown floc from 9N. Surface-sediment samples (which included the greenish flocculent material) from 5S to 5N also contained significant concentrations of chlorophyll a and other chloropigments; the chloropigment concentrations were roughly comparable to deep-sea phytodetritus collected in the North Atlantic. We conclude that fresh, organic-rich phytodetritus was present on the seafloor from 5S to 5N along 140W in November-December 1992, with highest concentrations within 2-3 of the equator. This material is likely to be a concentrated, high-quality food resource for deep-sea microbes and metazoans. We estimate an upper limit for the standing stock of this phytodetritus to be 2.6 mmol C org/m 2; this corresponds to 3% of the annual flux of organic carbon to the seafloor at these latitudes in 1992. Because the degradation rate of this material appears to be very high, its presence at the seafloor for several months per year could yield significant phytodetrital contributions to the annual seafloor organic-carbon budget. We also suggest that the phytodetrital aggregates are formed at intense convergence zones resulting from seasonal passage of tropical instability waves within 5 of the equator; if so, phytodetrital accumulations are likely to recur seasonally over broad areas of the abyssal equatorial Pacific.

  7. Reproductive patterns of the abyssal asteroid Styracaster elongatus from the N.E. Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Bentez-Villalobos, Francisco; Daz-Martnez, Julia P.

    2010-01-01

    We analysed the reproductive biology of the asteroid species Styracaster elongatus based on time-series samples from a 5000-m-deep site on the Porcupine Abyssal Plain (N.E. Atlantic). The ratio of males to females, the gonadosomatic index (GI), and pyloric caecum index (PCI) were determined and the results were corroborated by histological examination of the gonads. Fecundity and oocyte-size distribution were determined by histological and image analyses. Styracaster elongatus is a gonochoric asteroid and the ratio of males to females was not significantly different throughout the year. Oogenesis was asynchronous. The previtellogenic oocytes grew to a size of 230 ?m before undergoing vitellogenesis. Maximum oocyte size was 620 ?m. The ovary volume was mainly occupied by small previtellogenic oocytes (100-150 ?m) at any one time. Mean GI was 6.383.30 for females and 9.044.1 for males. Mean PCI was 7.441.66 for females and 7.661.46 for males. Mean fecundity was 16,3735988 oocites per female. There were no seasonal variations in GI and fecundity. There was evidence of a pyiloric caecum seasonal development for females and males. For S. elongatus there is no direct relationship among seasonal primary production at the surface and production of vitellogenic oocytes. Nevertheless, this species takes advantage of the pulse of phytodetritus to the seabed by increasing the storage of nutrients in the pyloric caecum in order to maintain a constant production of eggs and sperm.

  8. Estimated post-Messinian sediment supply and sedimentation rates on the Ebro continental margin, Spain

    USGS Publications Warehouse

    Nelson, C.H.

    1990-01-01

    Because of the extensive data base of seismic profiles, radiometric ages, and stratigraphic time markers such as the subaerial Messinian surface, sedimentation rates and Ebro River sediment discharge can be estimated for different periods and environments of the Ebro continental margin. New values for sediment discharge (i.e., 6.2 versus previous estimates of 2-3.5 million t/yr) for the Holocene highstand are more reliable but remain minimum estimates because a small proportion of Ebro sediment advected to the Balearic Rise and Abyssal Plain cannot be accounted for, especially during lowstands. The general highstand conditions of the Pliocene, which were similar to those of the Holocene, resulted in a low discharge of Ebro River sediment (ca. 6.5 million t/yr) and an even thickness of sediment across the margin that deposited at rates of about 24-40 cm/ky. In contrast, sediment supply increased two-three times during the Pleistocene, the margin prograded rapidly and deposition occurred at rates of 101-165 cm/ky on the outer shelf and slope, but basin floor rates remained anomalously low (21-26 cm/ky) because sediment was drained and broadly dispersed eastward in Valencia Trough. During the late Pleistocene rise of sea level, the main depocenters progressively shifted shoreward and sedimentation rates greatly decreased from 175 cm/ky on the upper slope during the early transgression to 106 cm/ky on the outer shelf and then to 63 cm/ky on the mid-shelf during the late transgression as the river sediment discharge dropped to half by Holocene time. Maximal sedimentation rates occurred in active depocenters of sediment dispersal such as the Holocene delta (370 cm/ky) or the youngest Pleistocene Oropesa channel-levee complex (705 cm/ky) where deposition rates increased by an order of magnitude or more compared to average Ebro shelf (38 cm/ky) or base-of-slope rates in the Pleistocene (21 cm/ky). The sedimentation rates verify the importance of sea-level control on the progressive change in location of depocenters and amount of sediment supply, but Pleistocene climatic change and deforestation alone can be observed to double river sediment discharge. The latter observation helps explain the anomalously high deposition rates in Pleistocene turbidite systems compared with older systems that may be controlled more by tectonic and sea-level changes alone. During the past 2000 years, in contrast, man has controlled deposition in the Ebro margin system, first by deforestation that more than doubled river sediment discharge and shelf deposition rates to equal those of Pleistocene time; and second by dam contruction that reduced sediment discharge to less than 5% of the normal Holocene discharge. Similar recent discharge reductions from the Nile and Rhone Rivers suggest that loss of the majority of the river sediment supply in the Mediterranean Sea may result in significant erosion of biologically and agriculturally important lobate delta areas. ?? 1990.

  9. Meiofauna communities along an abyssal depth gradient in the Drake Passage

    NASA Astrophysics Data System (ADS)

    Gutzmann, E.; Martnez Arbizu, P.; Rose, A.; Veit-Khler, G.

    2004-07-01

    Meiofauna standing stocks and community structure are reported for the first time for abyssal soft-sediment samples in Antarctic waters. At seven stations within a depth range of 2274-5194 m a total of 128 sediment cores were retrieved with a multiple corer (MUC) on board of the R.V. Polarstern during the ANDEEP-1 cruise (ANT XIX/3). The metazoan meiofauna (defined by a lower size limit of 40 ?m) was identified and counted, and one core per station was preserved for CPE, C/N, TOM and grain size analyses. Meiofauna densities are in the range of 2731 Ind./10 cm 2 at 2290 m depth and 75 Ind./10 cm 2 at 3597 m depth, with nematodes being the dominant group at all stations. Nematodes account for 84-94% followed by copepods with 2-8% of the total meiofauna. Other frequent taxa found at each station are kinorhynchs, loriciferans, tantulocarids, ostracods and tardigrades. There is a general tendency of decreasing abundances of metazoan meiofauna with increasing depth, but not all higher level taxa displayed this pattern. In addition, a tendency of decreasing higher taxon density with increasing depth was observed. Standing stocks are higher than the average found at similar depths in other oceans.

  10. Summertime trends in pelagic biogeochemistry at the Porcupine Abyssal Plain study site in the northeast Atlantic

    NASA Astrophysics Data System (ADS)

    Painter, Stuart C.; Lucas, Michael I.; Stinchcombe, Mark C.; Bibby, Thomas S.; Poulton, Alex J.

    2010-08-01

    Measurements of nitrate and carbon uptake made in July 2006 in the Northeast Atlantic Ocean are evaluated with reference to the photophysiology of the attendant phytoplankton population. Over the 11-day observation period integrated chlorophyll concentrations and carbon fixation rates decreased by 76% and 60%, respectively. Integrated nitrate uptake decreased by 50% from initial to final rates but was generally less variable than carbon fixation and chlorophyll in the intervening period. Satellite derived estimates of surface chlorophyll concentrations reveal the uptake observations to be coincident with, and subsequent to, a peak in summer time production. Large reductions in diatom and dinoflagellate abundance were also seen at this time, with indications that increased grazing, due to an increase in ciliate abundance, was an important mechanism terminating summertime production in the NE Atlantic. Meanwhile, the presence of consistently low values of Fv/Fm (<0.3), particularly in surface waters, suggests that production occurs, or is inhibited, with suboptimal photochemical efficiency widespread amongst the phytoplankton population. Furthermore, the low values of Fv/Fm were not alleviated by day-to-day variability in macronutrient concentration. The timing of our observations places them within the seasonal period recognised for the widespread phenomena of carbon overconsumption, and we estimate C:N uptake ratios at this time could be as high as 13:1.

  11. Enzyme activities of demersal fishes from the shelf to the abyssal plain

    NASA Astrophysics Data System (ADS)

    Drazen, Jeffrey C.; Friedman, Jason R.; Condon, Nicole E.; Aus, Erica J.; Gerringer, Mackenzie E.; Keller, Aimee A.; Elizabeth Clarke, M.

    2015-06-01

    The present study examined metabolic enzyme activities of 61 species of demersal fishes (331 individuals) trawled from a 3000 m depth range. Citrate synthase, lactate dehydrogenase, malate dehydrogenase, and pyruvate kinase activities were measured as proxies for aerobic and anaerobic activity and metabolic rate. Fishes were classified according to locomotory mode, either benthic or benthopelagic. Fishes with these two locomotory modes were found to exhibit differences in metabolic enzyme activity. This was particularly clear in the overall activity of citrate synthase, which had higher activity in benthopelagic fishes. Confirming earlier, less comprehensive studies, enzyme activities declined with depth in benthopelagic fishes. For the first time, patterns in benthic species could be explored and these fishes also exhibited depth-related declines in enzyme activity, contrary to expectations of the visual interactions hypothesis. Trends were significant when using depth parameters taken from the literature as well as from the present trawl information, suggesting a robust pattern regardless of the depth metric used. Potential explanations for the depth trends are discussed, but clearly metabolic rate does not vary simply as a function of mass and habitat temperature in fishes as shown by the substantial depth-related changes in enzymatic activities.

  12. The fish fauna of Ampre Seamount (NE Atlantic) and the adjacent abyssal plain

    NASA Astrophysics Data System (ADS)

    Christiansen, Bernd; Vieira, Rui P.; Christiansen, Sabine; Denda, Anneke; Oliveira, Frederico; Gonalves, Jorge M. S.

    2015-03-01

    An inventory of benthic and benthopelagic fishes is presented as a result of two exploratory surveys around Ampre Seamount, between Madeira and the Portuguese mainland, covering water depths from 60 to 4,400 m. A total of 239 fishes were collected using different types of sampling gear. Three chondrichthyan species and 31 teleosts in 21 families were identified. The collections showed a vertical zonation with little overlap, but indications for an affinity of species to certain water masses were only vague. Although most of the species present new records for Ampre Seamount, all of them have been known for the NE Atlantic; endemic species were not found. The comparison with fish communities at other NE Atlantic seamounts indicates that despite a high ichthyofaunal similarity, which supports the "stepping stone" hypothesis of species dispersal, some differences can be attributed to the local features of the seamounts.

  13. Evaluation of Cross-Hole Seismic Tomography for Imaging Low Resistance Intervals and Associated Carbonate Sediments in Coastal Plain Sequences on the Savannah River Site, South Carolina

    SciTech Connect

    Cumbest, R. J.

    1999-01-05

    The objectives of the pilot study were to investigate the limitations of the technique for imaging the presence, extent, and boundaries of the low-resistance intervals and associated carbonate sediments.

  14. Physical and chemical data on sediments deposited in the Missouri and the Mississippi River flood plains during the July through August 1993 flood

    USGS Publications Warehouse

    Schalk, Gregg K.; Holmes, Jr., Robert R.; Johnson, Gary P.

    1998-01-01

    Because sediments deposited by the 1993 floods on the Missouri and Mississippi rivers were thought to contain elevated concentrations of nutrients and trace elements, sediment deposits were sampled at 25 floodplain locations. The samples were analyzed for particle size, water content, volatile solids, nutrients, carbon, selected trace elements, pesticides, and semivolatile organic compounds. Preflood soil samples were analyzed for particle size only. Procedures for selecting sites, techniques developed for sampling, laboratory and analytical methods, and quality assurance methods also are described.

  15. Geochemical and micropaleontological character of Deep-Sea sediments from the Northwestern Pacific near the Kuril-Kamchatka Trench

    NASA Astrophysics Data System (ADS)

    Sattarova, Valentina V.; Artemova, Antonina V.

    2015-01-01

    Sediments from the abyssal plain adjacent to the Kuril-Kamchatka Trench were collected during the German-Russian cruise for the Kuril Kamchatka Biodiversity Study, and the chemical composition, quantitative content, and species composition of collected diatoms were studied. The collected sediments are silt and clayey silt, the SiO2 am and Corg contents range 7.58-19.38% and 0.44-1.55%, respectively. The enrichment of silts by amorphous silica indicates the presence of a significant number of organisms (predominantly diatoms) with an opal skeleton. High Corg content in sediments reflects biological productivity, which is controlled by factors such as water circulation and the distribution of nutrients. Interrelation trends among chemical constituents is investigated via multi-component statistics. Diatom assemblages reflect present-day water masses characterized by high nutrient content, surface water circulation, and sedimentation conditions for different parts of the study area. Analysis of this new data also highlights changes in the response of diatom flora due to abiotic factors.

  16. Ammonia-oxidizing Bacteria of the Nitrosospira cluster 1 dominate over ammonia-oxidizing Archaea in oligotrophic surface sediments near the South Atlantic Gyre.

    PubMed

    Lagostina, Lorenzo; Goldhammer, Tobias; Ry, Hans; Evans, Thomas W; Lever, Mark A; Jrgensen, Bo B; Petersen, Dorthe G; Schramm, Andreas; Schreiber, Lars

    2015-06-01

    Sediments across the Namibian continental margin feature a strong microbial activity gradient at their surface. This is reflected in ammonium concentrations of abyssal plain sediments near the South Atlantic Gyre compared with ammonium concentrations of >?700??M in upwelling areas near the coast. Here we address changes in apparent abundance and structure of ammonia-oxidizing archaeal and bacterial communities (AOA and AOB) along a transect of seven sediment stations across the Namibian shelf by analysing their respective ammonia monooxygenase genes (amoA). The relative abundance of archaeal and bacterial amoA (g(-1) DNA) decreased with increasing ammonium concentrations, and bacterial amoA frequently outnumbered archaeal amoA at the sediment-water interface [0-1?cm below seafloor (cmbsf)]. In contrast, AOA were apparently as abundant as AOB or dominated in several deeper (>?10?cmbsf), anoxic sediment layers. Phylogenetic analyses showed a change within the AOA community along the transect, from two clusters without cultured representatives at the gyre to Nitrososphaera and Nitrosopumilus clusters in the upwelling region. AOB almost exclusively belonged to the Nitrosospira cluster 1. Our results suggest that this predominantly marine AOB lineage without cultured representatives can thrive at low ammonium concentrations and is active in the marine nitrogen cycle. PMID:25581373

  17. Hydrothermal Mineral Deposits From a Young (0.1Ma) Abyssal Hill on the Flank of the Fast-Spreading East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Benjamin, S. B.; Haymon, R. M.

    2004-12-01

    It has been estimated from heat flow measurements that at least 40% of the total hydrothermal heat lost from oceanic lithosphere is removed from 0.1-5 Ma abyssal hill terrain on mid-ocean ridge flanks. Despite the large magnitude of estimated hydrothermal heat loss from young abyssal hills, little is known about characteristics of hydrothermal vents and mineral deposits in this setting. This study describes the first abyssal hill hydrothermal samples to be collected on the flank of a fast-spreading ridge. The mineral deposits were discovered at "Tevnia Site" on the axis-facing fault scarp of an abyssal hill, located on 0.1 Ma lithosphere 5 km east of the East Pacific Rise (EPR) axis at 10\\deg 20'N. Observations of Galatheid crabs, "dandelion" siphonophores, and colonies of dead, yet still intact, Tevnia worm tubes at this site during Alvin dives in 1994 suggests relatively recent hydrothermal activity. The deposits are friable hydrothermal precipitates incorporating volcanic clasts brecciated at both the micro and macro scales. The petrographic sequence of brecciation, alteration, and cementation exhibited by the samples suggests that they formed from many pulses of hydrothermal venting interspersed with, and perhaps triggered by, repeated tectonic events as the abyssal hill was uplifted and moved off-axis (see also Haymon et al., this session). Observed minerals include x-ray amorphous opaline silica and Fe-oxide phases, crystalline Mn-oxides (birnessite and todorokite), an irregularly stratified mixed layer nontronite-celadonite, and residual calcite in sediment-derived microfossils incorporated into the breccia matrix. This mineral assemblage suggests that the deposits precipitated from moderately low-temperature (<140\\deg C) fluids, enriched in K, Fe, Si, and Mn, with a near-neutral pH. The presence of tubeworm casings at the site is evidence that the hydrothermal fluids carried H2S, however no metal sulfide phases were identified in the samples. Although the fluids were actively venting from an abyssal hill distal to the ridge crest, the presence of Fe- and K-rich nontronite-celadonite suggests an axial fluid source. However, the observed textures, minerals, and microfossils, combined with the absence of copper, zinc, and sulfur minerals, clearly distinguishes these near-axis samples from hydrothermal deposits formed at higher temperatures (>350\\deg C) on the mid-ocean ridge crest.

  18. A Deep Cabled Observatory: Biology and Physics in the Abyss

    NASA Astrophysics Data System (ADS)

    Howe, Bruce M.

    2014-11-01

    The ALOHA Cabled Observatory (ACO) is the deepest operating observatory on the planet, providing power and communications to scientific instruments on the seafloor. In the future, ACO will add water column measurements, from the seafloor to the surface, using moorings and undersea vehicles. Recent results from video monitoring of deep-sea life and from temperature sensors illustrate the benefit of and need for long-term, sustained, continuous sampling in this abyssal context. The observatory is located at Station ALOHA (A Long-Term Oligotrophic Habitat Assessment), 100 kilometers north of Oahu, at 4728-meter water depth (Figure 1, top).

  19. Impact of bedrock surface topography on spatial distribution of Quaternary sediments and on the flow pattern of late Weichselian glaciers on the East European Craton (Russian Plain)

    NASA Astrophysics Data System (ADS)

    Kalm, Volli; Gorlach, Aleksandr

    2014-02-01

    This paper presents the first high quality maps of the bedrock surface topography and the Quaternary sediment distribution for the Late Weichselian glaciation area on the East European Craton (EEC) and the reasoning behind the estimated sediment distribution. Geographic information system (GIS)-based three-dimensional model of the bedrock surface topography, the current digital terrain model (DTM), and the ice flow pattern of the last glaciation provided the main source data for the analyses and interpretations. In the current continental area of the western EEC, which was covered by the last Scandinavian Ice Sheet (SIS), the bedrock lies overwhelmingly (85%) above the contemporary sea level, with an average altitude of ~ 54 m above sea level. The topography of the bedrock surface is very well reflected in the current topography, and an 80-m difference in the ice bed surface altitudes results in the topographic focusing of the ice flow, and thus all late Weichselian ice streams were accommodated to the depressions in the subglacial surface. Such depressions are characterised by a thin (< 10-m) layer of sediment with one till bed. Just 50 m upslope from the bottom of the depressions, the thickness of the sediment increases two- to threefold and comprises five or more till layers, indicating relief enhancement through subsequent glaciations. The average calculated thickness of the Quaternary deposits in the study area was ~ 49 m, and the total volume of sediments was ~ 20,280 km3.

  20. Plains Traveler

    NASA Technical Reports Server (NTRS)

    2006-01-01

    10 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dust devil traveling across a plain west-southwest of Schiaparelli Crater, in far eastern Sinus Meridiani. The dust devil is casting a shadow toward the northeast, just south (below) of an egg-shaped crater.

    Location near: 6.4oS, 349.3oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Southern Summer

  1. Abyssal ocean warming around Antarctica strengthens the Atlantic overturning circulation

    NASA Astrophysics Data System (ADS)

    Patara, Lavinia; Bning, Claus W.

    2014-06-01

    The abyssal warming around Antarctica is one of the most prominent multidecadal signals of change in the global ocean. Here we investigate its dynamical impacts on the Atlantic Meridional Overturning Circulation (AMOC) by performing a set of experiments with the ocean-sea ice model NEMO-LIM2 at horizontal resolution. The simulations suggest that the ongoing warming of Antarctic Bottom Water (AABW), already affecting much of the Southern Hemisphere with a rate of up to 0.05C decade-1, has important implications for the large-scale meridional overturning circulation in the Atlantic Ocean. While the abyssal northward flow of AABW is weakening, we find the upper AMOC cell to progressively strengthen by 5-10% in response to deep density changes in the South Atlantic. The simulations suggest that the AABW-induced strengthening of the AMOC is already extending into the subtropical North Atlantic, implying that the process may counteract the projected decrease of the AMOC in the next decades.

  2. Mobility of authigenic rhenium, silver, and selenium during postdepositional oxidation in marine sediments

    NASA Astrophysics Data System (ADS)

    Crusius, John; Thomson, John

    2003-01-01

    Sedimentary records of redox-sensitive trace elements hold significant potential as indicators of paleoceanographic environmental conditions. Records of Re can reveal the intensity of past reducing conditions in sediments at the time of deposition, whereas records of Ag may record the magnitude of past diatom fluxes to the seafloor. Confidence in paleoenvironmental reconstruction from records of either metal, however, requires it to have experienced negligible redistribution since deposition. This study examines diagenetic rearrangements of Re and Ag that occur in response to exposure to bottom-water O 2 in environments of low sedimentation rate, including Madeira Abyssal Plain turbidites and eastern Mediterranean basin sapropels. Authigenic Re was remobilized quantitatively by oxidation but poorly retained by the underlying sediments. All records are consistent with previous work demonstrating that only a limited reimmobilization of Re occurs preferentially in C org-rich, reducing sediments. Silver was also mobilized quantitatively by oxidation, but it was subsequently immobilized more efficiently in all cases as sharp peaks immediately into anoxic conditions below active oxidation fronts, and these peaks remain immobile in anoxic conditions during long-term burial. Comparison of Ag, S, and Se records from various cores suggests that Ag is likely to have been immobilized as a selenide, a mechanism previously proposed for Hg in similar situations (Mercone et al., 1999). Coexisting narrow peaks of Ag and Hg with Se offer a means of assessing whether oxidative burndown has ever occurred at the top of C org- and sulfide-rich sedimentary units. Although these results suggest that caution must be used when inferring paleoenvironmental information from records of Ag and Re in cores with low sediment accumulation rates (<5 cm ka -1), they should not affect the promise that authigenic Ag and Re records hold for paleoenvironmental reconstruction in sediments with higher accumulation rates and where anoxic conditions have been maintained continuously.

  3. Mobility of authigenic rhenium, silver, and selenium during postdepositional oxidation in marine sediments

    USGS Publications Warehouse

    Crusius, John; Thomson, John

    2003-01-01

    Sedimentary records of redox-sensitive trace elements hold significant potential as indicators of paleoceanographic environmental conditions. Records of Re can reveal the intensity of past reducing conditions in sediments at the time of deposition, whereas records of Ag may record the magnitude of past diatom fluxes to the seafloor. Confidence in paleoenvironmental reconstruction from records of either metal, however, requires it to have experienced negligible redistribution since deposition. This study examines diagenetic rearrangements of Re and Ag that occur in response to exposure to bottom-water O2 in environments of low sedimentation rate, including Madeira Abyssal Plain turbidites and eastern Mediterranean basin sapropels. Authigenic Re was remobilized quantitatively by oxidation but poorly retained by the underlying sediments. All records are consistent with previous work demonstrating that only a limited reimmobilization of Re occurs preferentially in Corg-rich, reducing sediments. Silver was also mobilized quantitatively by oxidation, but it was subsequently immobilized more efficiently in all cases as sharp peaks immediately into anoxic conditions below active oxidation fronts, and these peaks remain immobile in anoxic conditions during long-term burial. Comparison of Ag, S, and Se records from various cores suggests that Ag is likely to have been immobilized as a selenide, a mechanism previously proposed for Hg in similar situations (Mercone et al., 1999). Coexisting narrow peaks of Ag and Hg with Se offer a means of assessing whether oxidative burndown has ever occurred at the top of Corg- and sulfide-rich sedimentary units. Although these results suggest that caution must be used when inferring paleoenvironmental information from records of Ag and Re in cores with low sediment accumulation rates (−1), they should not affect the promise that authigenic Ag and Re records hold for paleoenvironmental reconstruction in sediments with higher accumulation rates and where anoxic conditions have been maintained continuously.

  4. Mercury net methylation in five tropical flood plain regions of Brazil: high in the root zone of floating macrophyte mats but low in surface sediments and flooded soils.

    PubMed

    Guimares, J R; Meili, M; Hylander, L D; de Castro e Silva, E; Roulet, M; Mauro, J B; de Lemos, R

    2000-10-16

    In aquatic systems, bottom sediments have often been considered as the main methylmercury (MeHg) production site. In tropical floodplain areas, however, floating meadows and flooded forests extend over large areas and can be important Hg methylating sites. We present here a cross-system comparison of the Hg net methylation capacity in surface sediments, flooded soils and roots of floating aquatic macrophytes, assayed by in situ incubation with 203Hg and extraction of formed Me203 Hg by acid leaching and toluene. The presence of mono-MeHg was confirmed by thin layer chromatography and other techniques. Study areas included floodplain lakes in the Amazon basin (Tapajs, Negro and Amazon rivers), the Pantanal floodplain (Paraguay river basin), freshwater coastal lagoons in Rio de Janeiro and oxbow lakes in the Mogi-Gua river, So Paulo state. Different Hg levels were added in assays performed in 1994-1998, but great care was taken to standardise all other test parameters, to allow data comparisons. Net MeHg production was one order of magnitude higher (mean 13.8%, range 0.28-35) in the living or decomposing roots of floating or rooted macrophyte mats (Eichhornia azurea, E. crassipes, Paspalum sp., Eleocharis sellowiana, Salvinia sp., S. rotundifolia and Scirpus cubensis) than in the surface layer of underlying lake sediments (mean 0.6%, range 0.022-2.5). Methylation in flooded soils presented a wide range and was in some cases similar to the one found in macrophyte roots but usually much lower. In a Tapajs floodplain lake, natural concentrations of MeHg in soil and sediment cores taken along a lake-forest transect agreed well with data on net methylation potentials in the same samples. E. azurea, E. crassipes and Salvinia presented the highest methylation potentials, up to 113 times higher than in sediments. Methylation in E. azurea from six lakes of the Paraguay and Cuiab rivers, high Pantanal, was determined in the 1998 dry and wet seasons and ranged from 1.8 to 35%. Methylation was lower in washed roots than in untreated roots of E. azurea and methylation in solids isolated from the roots, was higher than in sediments but lower than in untreated roots. This indicates that the methylation in roots zones occurs mainly in the root-associated solids. Floating meadows are sites of intense production of biomass and of highly bioavailable MeHg and appear to be an essential link of the MeHg cycle in tropical aquatic systems. PMID:11036981

  5. Abyssal macrofauna of the Kuril-Kamchatka Trench area (Northwest Pacific) collected by means of a camera-epibenthic sledge

    NASA Astrophysics Data System (ADS)

    Brandt, A.; Elsner, N. O.; Malyutina, M. V.; Brenke, N.; Golovan, O. A.; Lavrenteva, A. V.; Riehl, T.

    2015-01-01

    Abyssal macrofaunal composition of 21 epibenthic sledge hauls from twelve stations taken in the Kuril-Kamchatka Trench (KKT) and at the adjacent abyssal plain, Northwest Pacific, is presented. Sampling with the fine meshed epibenthic sledge yielded higher abundances and species richness than was reported from previous expeditions from board of RV Vityaz. In total 84,651 invertebrates were sampled with RV Sonne between July and September of 2012 (31,854 invertebrates if standardised for 1000 m2 trawled distances) from 41 taxa of different taxonomic ranks (15 phyla, 28 classes, 7 orders) were sampled from a trawled area of 53,708 m² and have been analyzed. Few taxa were frequent and most taxa were rare in the samples, twelve taxa occurred with more than 1% frequency. Of these, the Polychaeta were most abundant followed by the benthic Copepoda and Isopoda. Total numbers of individuals varied between stations and were highest with 4238 individuals at station 2-10 close to the KKT in 4865 m depth and lowest with 374 individuals at station 6-11 in 5305 m depth. At this station also the lowest number of taxa occurred (18 taxa) while the highest number occurred with 31 taxa at station 3-9 in 4991 m depth. Numbers of individuals decreased with increasing depth between 4830 and 5780 m. Crustaceans of the superorder Peracarida were one of the dominating taxa with four orders occurring frequently in most samples. In total, Isopoda were most important and occurred with 59% of all peracarid orders sampled, followed by Amphipoda with 21%, Tanaidacea with 11%, Cumacea with 9%, and Mysidacea with <1%. The communities of the stations (and hauls) of the KKT abyssal area differ in terms of taxon composition from each other. A cluster analysis (nMDS) performed for all sampled stations revealed no clear pattern of community similarity between stations or hauls. All hauls close to the trench (2-9 and 2-10 close to the eastern slope of the KKT; and 3-9 and 4-3 at the western slope) were most different to the other hauls. Hauls 8-9 and 8-12 as well as 5-10 and 7-10 in the approximate centre of the overall research area were most similar (88% similarity). The non-isolated KKT area is characterized by higher abundances and higher benthic species richness than the geographically isolated and young deep-sea basin of the Sea of Japan.

  6. Revisiting Plain Language.

    ERIC Educational Resources Information Center

    Mazur, Beth

    2000-01-01

    Discusses the plain language movement and its origins. Reviews past and current resources related to plain language writing. Examines criticism of the movement while examining past and current plain language literature, with particular attention to the information design field. (SR)

  7. Glacial-interglacial sedimentation rates and turbidite frequency in the Bahamas: a clear case of carbonate shedding during high sea level stands

    SciTech Connect

    Droxler, A.W.; Schlager, W.

    1985-01-01

    Vail's sea level curve is built on a basic principle that siliciclastic continental shelves and implicitly carbonate platforms mainly export sediment toward the surrounding basins during sea level low stands. The authors late Quaternary Bahamian data demonstrate however, that sediment export from carbonate banks is just the opposite. Five, 8-13 m long, piston cores were studied from the southern Tongue of the Ocean, a 1300 m deep flat-floored basin in the Bahamas, surrounded on its three sides by wide shallow carbonate banks. Turbidite layers were visually distinguished from intervening periplatform ooze. Glacial cyclic variations of aragonite content in the periplatform ooze, along with nannoplankton stratigraphy were used to identified the last two glacial and interglacial intervals, low and high stand situations respectively. On average, turbidite frequency and accumulation rates were much higher, 14 times and 45 to 22 times respectively, during interglacial than glacial stages. The Bahamian carbonate banks export therefore more material during sea level high stands when the platform tops are flooded and produce sediment. This is in direct opposition with siliciclastic ocean margins, where sediment is stored on the inner shelf during high stands and passed on to continental rises and abyssal plains during low stands. In addition, aragonite dissolution as postulated by Droxler et al. (Geology April 1983) is working in phase with the input signal by removing material during glacial intervals.

  8. The Late Pliocene Eltanin Impact: Documentation From Sediment Core Analyses

    NASA Technical Reports Server (NTRS)

    Gersonde, R.; Kyte, F.; Flores, J. A.; Becquey, S.

    2002-01-01

    The expeditions ANT-XII/4 (1995) and ANT-XVIII/5a (2001) of the RV POLARSTERN collected extensive bathymetric and seismic data sets as well as sediment cores from an area in the Bellingshausen Sea (eastern Pacific Southern Ocean) that allow the first comprehensive geoscientific documentation of an asteroid impact into a deep ocean (approx. 5 km) basin, named the Eltanin impact. Impact deposits have now been recovered from a total of more than 20 sediment cores collected in an area covering about 80,000 km2. Combined biomagnetostratigraphic dating places the impact event into the earliest Matuyama Chron, a period of enhanced climate variability. Sediment texture analyses and studies of sediment composition including grain size and microfossil distribution reveal the pattern of impact- related sediment disturbance and the sedimentary processes immediately following the impact event. The pattern is complicated by the San Martin Seamounts (approx. 57.5 S, 91 W), a large topographic elevation that rises up to 3000 m above the surrounding abyssal plain in the area affected by the Eltanin impact. The impact ripped up sediments as old as Eocene and probably Paleocene that have been redeposited in a chaotic assemblage. This is followed by a sequence sedimented from a turbulent flow at the sea floor, overprinted by fall-out of airborne meteoritic ejecta that settled trough the water column. Grain size distribution reveals the timing and interaction of the different sedimentary processes. The gathered estimate of ejecta mass deposited over the studied area, composed of shock-melted asteroidal material and unmelted meteorites including fragments up to 2.5 cm in diameter, point to an Eltanin asteroid larger than the 1 km in diameter size originally suggested as a minimum based on the ANT-XII/4 results. This places the energy released by the impact at the threshold of those considered to cause environmental disturbance at a global scale and it makes the impact a likely transport mechanism explaining the presence of extinct Cenozoic microfossils in the transantarctic Sirius Unit. Although a crater structure representing Eltanin ground zero has not been discovered, the distribution pattern of sediment disturbance and ejecta deposits now allows to better determine the central target area north of the San Martin Seamounts.

  9. Abyssal ?-S Observations at Hawaii Ocean Time-series Station ALOHA

    NASA Astrophysics Data System (ADS)

    Lukas, R.; Santiago-Mandujano, F.; Fumar, C.; McCoy, D.; Deppe, R. W.; Gum, J.; Snyder, J.; Chee, B.; Howe, B. M.; Potemra, J. T.; Duennebier, F. K.

    2014-12-01

    Abyssal ?-S variations observed since June 2011 by the ALOHA Cabled Observatory (ACO) reveal a potential temperature range of 0.025C, and a salinity range of more than 0.0025 g kg-1. The very large temperature range is associated with episodic cold events (Lukas et al.2001; Alford et al. 2011). The salinity range, while not large in absolute terms, is an order of magnitude larger than the precision of the Sea-Bird Microcat. The absolute salinity is calibrated against simultaneous Hawaii Ocean Time-series (HOT) full-depth CTD profiles that have an accuracy of ~10-3 g kg-1. A slow drift of the SBE-37 conductivity sensor is seen, along with a sudden offset that may have been caused by a nearby glass ball implosion. ?-S variations are dominated by changes in density that are associated with dynamic processes. Large cooling events are associated with increases of salinity ultimately deriving from the neighboring Maui Deep. The slopes of these excursions in ?-S space are consistent with the slopes of HOT CTD depth profiles, suggesting that these are vertical changes due either to gravity currents associated with cold, salty overflow events from the Maui Deep, or to internal seiches within the Kauai Deep. ?-S variations that are nearly isopycnal are also seen during the slow recovery from a major cooling event in 2011. This may be due to diapycnal mixing with fresher waters above the controlling sill depth. It cannot be ruled out that some apparent salinity changes may be associated with sediment resuspension events, with subsequent deviations from the PSS-78 empirical relationship between conductivity, salinity, temperature and pressure. ADCP records show large vacillations of along- and cross-isobath flow. Large vertical current variations are measured that are correlated with horizontal flows, likely due to the bottom slope, even after minimizing correlations to account for the unknown orientation of the ADCP. The primary conclusion is that abyssal dynamics preclude the use of a time-invariant ?-S relationship for calibrating instantaneous CTD profiles.

  10. Aged black carbon in marine sediments and sinking particles

    NASA Astrophysics Data System (ADS)

    Coppola, Alysha I.; Ziolkowski, Lori A.; Masiello, Caroline A.; Druffel, Ellen R. M.

    2014-04-01

    We report measurements of oceanic black carbon (BC) to determine the sources of BC to abyssal marine sediments in the northeast Pacific Ocean. We find that the average 14C age of BC is older (by 6200 2200 14C years) than that of the concurrently deposited non-BC sedimentary organic carbon. We investigate sources of aged BC to sediments by measuring a sample of sinking particulate organic carbon (POC) and find that POC may provide the main transport mechanism of BC to sediments. We suggest that aged BC is incorporated into POC from a combination of resuspended sediments and sorption of ancient dissolved organic carbon BC onto POC. Our BC flux estimate represents ~8-16% of the global burial flux of organic carbon to abyssal sediments and constitutes a minimum long-term removal estimate of 6-32% of biomass-derived BC using the present day emission flux.

  11. First steps of integrated spatial modeling of titanium, zirconium, and rare earth element resources within the Coastal Plain sediments of the southeastern United States

    USGS Publications Warehouse

    Ellefsen, Karl J.; Van Gosen, Bradley S.; Fey, David L.; Budahn, James R.; Smith, Steven M.; Shah, Anjana K.

    2015-01-01

    The Coastal Plain of the southeastern United States has extensive, unconsolidated sedimentary deposits that are enriched in heavy minerals containing titanium, zirconium, and rare earth element resources. Areas favorable for exploration and development of these resources are being identified by geochemical data, which are supplemented with geological, geophysical, hydrological, and geographical data. The first steps of this analysis have been completed. The concentrations of lanthanum, yttrium, and titanium tend to decrease as distance from the Piedmont (which is the likely source of these resources) increases and are moderately correlated with airborne measurements of equivalent thorium concentration. The concentrations of lanthanum, yttrium, and titanium are relatively high in those watersheds that adjoin the Piedmont, south of the Cape Fear Arch. Although this relation suggests that the concentrations are related to the watersheds, it may be simply an independent regional trend. The concentration of zirconium is unrelated to the distance from the Piedmont, the equivalent thorium concentration, and the watershed. These findings establish a foundation for more sophisticated analyses using integrated spatial modeling.

  12. Inter-annual dynamics of abyssal polychaete communities in the North East Pacific and North East AtlanticA family-level study

    NASA Astrophysics Data System (ADS)

    Laguionie-Marchais, C.; Billett, D. S. M.; Paterson, G. L. D.; Ruhl, H. A.; Soto, E. H.; Smith, K. L., Jr.; Thatje, S.

    2013-05-01

    Characterising how deep-sea communities change on contemporary time-scales and understanding underlying ecosystem processes has become important under changing climate and the rise in the exploitation of deep-sea resources. However, little is known about these dynamics and processes. Long-term observations from which inter-annual variations can be detected are scarce in the deep sea. This study examines inter-annual changes in density, family richness and evenness, family and functional group rank abundance distributions of infaunal polychaetes at two abyssal stations in the North East Pacific (Station M, 1991 to 2005) and in the North East Atlantic (Porcupine Abyssal Plain, 1991 to 1999). The two long-term data sets were used to investigate not only if polychaete community structure and composition varied at inter-annual scales in terms of diversity and rank abundance distributions but also if any changes were related to previous observations in megafauna and environmental factors at each locality. The polychaete community structure at each locality was analysed using univariate statistics as well as multivariate ordination techniques based on Bray-Curtis similarity of the yearly family density. Sub-surface deposit feeders, such as Paraonidae, dominated the North East Pacific, whereas surface deposit feeders, such as Cirratulidae, dominated the North East Atlantic. Both stations showed inter-annual variations in density, family evenness and rank abundance distributions. The greatest changes occurred in 1998 in both time series when polychaete densities peaked, and switches in the rank abundance of the most abundant families and functional groups took place. Inter-annual variations in the polychaete community were correlated with a limited number of holothurian species changes, but no correlation was found with particulate organic matter flux or climate indices. Ecological and environmental factors behind the family-level changes remain elusive. Overall, changes in the dominance of functional groups imply changes in abyssal ecosystem functioning with potential consequences on carbon cycling at the seabed.

  13. Mesozoic and Early Cenozoic sediment influx in the Mozambique basin.

    NASA Astrophysics Data System (ADS)

    Castelino, Jude; Reichert, Christian; Klingelhoefer, Frauke; Aslanian, Daniel; Jokat, Wilfried

    2015-04-01

    Mozambique Basin is together with the Somali Basin the oldest rifted sedimentary basin developed along the eastern African margin in Jurassic times. The basin hosts a continuous record of sediments since Jurassic times, when Antarctica separated from Africa. The primary objectives of this study were to extend the regional stratigraphic framework north of the Zambezi Delta and to review geological events documented in the Mozambique Basin. Nine Multi-Channel seismic reflection profiles are used to extend the regional stratigraphy in to the deep abyssal plains of the basin. We identify six major stratigraphic units that correlate to Jurassic, Early Cretaceous, Late Cretaceous, Paleogene, Neogene and Quaternary periods. Mesozoic sedimentation rates of 3-5 cm/kyr are observed in the deeper basin and 1-2 cm /kyr during Paleogene (neither compensated for compaction). The presence of Domo shales from existing wells point to a restricted circulation in the basin until mid-Cretaceous. Mesozoic sediments have a high velocity that exceed 4.5 km/s with an exception of a distinct low-velocity zone of 3.7 km/s in the mid-Cretaceous that may indicate under-compacted overpressured shales. Higher sedimentation rate in Late Cretaceous can be attributed to rapid denudation of the African continent after a major tectonic uplift episode at approximately 90 Ma and simultaneous increase in the catchment area of the proto-Zambezi. Increased sediment influx into the basin from the Zambezi in Late Cretaceous resulted in the formation a submarine delta fan lobe progressing into the Mozambique Channel around the northern periphery of Beira High. Strong north-south bottom currents commenced within the channel in Late Cretaceous that forced the aggradation of sediments of the submarine fan lobe on the southern flank. In addition, we observe several current-controlled drift bodies in the deeper basin that are influenced by the north-south bottom current. Low sedimentation rates in Paleogene are attributed to a relative quiet tectonic phase onshore and erosion during global marine regression in mid-Oligocene.

  14. [The role of antarctica in formation of the cenozoic climate and contemporary open sea abyssal fauna].

    PubMed

    Kuznetsov, A P

    2001-01-01

    The key role of the Antarctic continent in the formation of the contemporary (Cenozoic) zonal-contrast climate and related geologically "young" (Postmesozoic) contemporary abyssal fauna of the World Ocean is discussed on the basis of the current concepts of pleitectonics, history of planetary climates, paleobiooceanology, and bioevolution. It has been shown that the flows of cold aerated near-Antarctic waters that started to descend in the open sea abyssal in the middle of Cenozoic were capable of substituting for previously (in Mesozoic) heated (up to 15-20 degrees C) abyssal waters within only 1500-2000 years. Following the descending near-Antarctic waters, the shallow and cold water oxyphilic fauna assimilated the abyssal zone that had been warm water and weakly populated. PMID:15926327

  15. Description and phylogenetic position of the first abyssal solitary kamptozoan species from the Kuril-Kamchatka Trench area: Loxosomella profundorum sp. nov. (Kamptozoa: Loxosomatidae)

    NASA Astrophysics Data System (ADS)

    Borisanova, Anastasia O.; Chernyshev, Alexei V.; Neretina, Tatyana V.; Stupnikova, Alexandra N.

    2015-01-01

    One of two orders of a small phylum Kamptozoa, Solitaria, consisting of one family Loxosomatidae of about 140 species, has never been recorded deeper than 700 m. All known for the north-western Pacific loxosomatids (about 17 species) occur in shallow waters. The first abyssal solitary kamptozoan, Loxosomella profundorum sp. nov. is described herein. It was collected during the German-Russian deep-sea expedition KuramBio aboard RV Sonne in the summer of 2012 in the abyssal plain adjacent to the Kuril-Kamchatka Trench. It is the deepest finding of Kamptozoa to date. The new species was found living on the anthozoan polyp Corallimorpharia. L. profundorum sp. nov. is a largest solitary kamptozoan species, up to 4 mm in length, with a stalk of up to 3.5 mm, with 10-12 tentacles, with two conspicuous lateral papillae, and a row of glandular cells in its stalk. A preliminary molecular phylogenetic analysis based on partial 18S rDNA indicated that L. profundorum sp. nov. is a sister clade to the clade, which includes other Loxosomella and two species of Loxomitra.

  16. Carbonate to siliciclastic periplatform sediments: southwest Florida

    USGS Publications Warehouse

    Holmes, Charles W.

    1988-01-01

    Geophysical, geochemical, and sedimentological data suggest that the spatial relationships of these deposits are related to sea-level variations. During extreme lowstands, with much of the shelf exposed, the dominant sedimentation was in the form of siliciclastic deposition on the abyssal floor, and slope talus development at the edge of the shelf. During a subsequent rise in sea level, after carbonate production on the shelf was initiated, sediment was transported southward to the head of the canyons and funneled to the abyssal floor. Subsequent rising sea level shifted the axis of transport farther to the shelf, bypassing the canyons and funneling the sediment through breaks in the carbonate reef banks at the southern edge of the platform. At the sites of both the hemipelagic and the turbidite deposition, high-resolution seismic data indicate that at least three cycles of deposition have occurred. In the abyss, this cyclic nature has produced alternating layers of carbonate and noncarbonate sediments, recognizable in the sedimentary record as limestone units interlayered with fine shales. In the geologic record the hemipelagic deposits would be almost indistinguishable from deep-sea foraminiferal oozes.

  17. Peculiarities of Environment Pollution as a Special Type of Radioactive Waste: Field Means for Comprehensive Characterization of Soil and Bottom Sediments and their Application in the Survey at the Flood plain of Techa River - 13172

    SciTech Connect

    Ivanov, Oleg; Danilovich, Alexey; Potapov, Victor; Stepanov, Vyacheslav; Smirnov, Sergey; Volkovich, Anatoly

    2013-07-01

    Contamination of natural objects - zone alarm fallout, zones and flood plains near production sites (the result of technological accidents and resource extraction) occupy large areas. Large area and volume of contaminated matter, moderate specific activity (as low - medium-level wastes) make such objects specific types of radioactive waste. These objects exist for a long time, now they are characterized by a bound state of nuclides with the matrix. There is no cost-effective ways to remove these waste, the only solution for the rehabilitation of such areas is their isolation and regular monitoring through direct and indirect measurements. The complex of instruments was developed to field mapping of contamination. It consists of a portable spectrometric collimated detector, collimated spectrometric borehole detector, underwater spectrometer detector, spectrometer for field measurements of the specific activity of Sr-90, connected to a portable MCA 'Colibry (Hummingbird)'. The complex was used in settlements of Bryansk region, rivers Techa and Yenisei. The effectiveness of the developed complex considered by the example of characterization of the reservoir 10 (artificial lake) in Techinsky cascade containing a huge amount of radioactive waste. The developed field means for comprehensive characterization of soil and bottom sediments contamination are very effective for mapping and monitoring of environment contamination after accidents. Especially in case of high non-uniformity of fallout and may be very actual in Fukushima area. (authors)

  18. Taphonomy and paleoecology of nonmarine mollusca: indicators of alluvial plain lacustrine sedimentation, upper part of the Tongue River Member, Fort Union Formation ( Paleocene), Northern Powder River Basin, Wyoming and Montana ( USA).

    USGS Publications Warehouse

    Hanley, J.H.; Flores, R.M.

    1987-01-01

    The composition, species abundances, and spatial and temporal distributions of mollusc assemblages were controlled by the environments in which they lived and the depositional processes that affected the molluscs after death and before final burial. Post-mortem transport, reworking and concentration of shells, and mixing of faunal elements from discrete habitats produced a taphonomic 'overprint' on assemblage characteristics that directly reflects the processes of alluvial plain and floodbasin lacustrine sedimentation. The 'overprint' can be interpreted from outcrop analysis of molluscan biofabric, which consists of: 1) orientation, fragmentation, size-sorting, abrasion, density, and dispersion of shells, 2) the nature and extent of shell-infilling, and 3) ratio of articulated to disarticulated bivalves. Taphonomic characteristics were used with sedimentological properties to differentiate in-place, reworked, transported, and ecologically mixed mollusc assemblages. This study also defines the paleoecology of habitat preferences of mollusc species as a basis for recognition of the environments in which these assemblages were deposited: 1) large floodbasin lakes, 2) small floodbasin lakes, and 3) crevasse deltas and splays. Integration of sedimentology and paleoecology provides an interdisciplinary approach to the interpretation of alluvial environments through time in the Tongue River Member. -Authors

  19. A ridgelet transform method for constraining tectonic models via abyssal-hill morphology

    NASA Astrophysics Data System (ADS)

    Downey, Nathan J.; Clayton, Robert W.

    2007-03-01

    Abyssal-hill shape and orientation are related to the direction and spreading rate of paleo-spreading centers. Therefore analyzing abyssal-hill shape and trend is useful for constraining tectonic models of regions devoid of magnetic reversal anomalies. Detecting systematic changes of abyssal-hill shapes or trends, due to changes in spreading rate or direction, is not straightforward, which makes it difficult to determine appropriate regions over which to average abyssal-hill parameters. Often, however, detecting these systematic changes, where they occur, and the scale over which they occur, is of primary importance for tectonic reconstructions. We present a new method of abyssal-hill analysis that is based on the ridgelet transform, a relative of the two-dimensional wavelet transform. Our method is capable of locally estimating the width, azimuth, and root-mean-square (RMS) amplitude of abyssal-hill fabric and highlights changes in these parameters across a survey area, making it possible to identify regions created with a constant spreading rate and direction. We use three multibeam swaths, one crossing the Osbourn Trough in the southwest Pacific Basin, one crossing the East Pacific Rise, and one crossing the Mid-Atlantic Ridge, to demonstrate the utility and performance of our method.

  20. Benthic foraminiferal response to trophic changes across the last glacial-Holocene transition in the abyssal eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Müller-Navarra, K.; Lochte, A.; Schmiedl, G.

    2012-04-01

    Benthic foraminifers have been studied in high temporal resolution in a well-dated abyssal sediment record from the Levantine Basin of the eastern Mediterranean Sea. Major target was to document the exact temporal sequence of changes in quantity and quality of organic matter fluxes and reconstruction of nutrient cycling during the last glacial, glacial termination and Holocene intervals and to evaluate its role in the formation of sapropel S1 during the early Holocene. The low-diverse modern benthic foraminiferal faunas of the abyssal eastern Mediterranean Sea are dominated by miliolids, and a few epifaunal arenaceous and hyaline taxa reflecting low food availability and ultra-oligotrophic conditions in the open-marine surface waters of this region. Specifically, the presence of the small opportunistic species Eponides pusillus and Anomalinoides minimus are associated with seasonal phytoplankton blooms and related phytodetritus pulses to the deep-sea. During the last glacial period, elevated proportions of shallow infaunal taxa indicate relatively higher organic matter fluxes than at present. The inferred glacial increase in surface water productivity can be attributed to intensified wind-induced vertical mixing of surface waters and related nutrient cycling. With the transition to Holocene boundary conditions, surface water productivity decreased and the abyssal faunas lack evidence for eutrophication with onset of sapropel S1 formation. This finding corroborates results from recent studies on the stable nitrogen isotope signature of organic matter but is in contrast to previous geochemical evidence. Comparison with faunal records from marginal areas of the eastern Mediterranean basins suggests that increased productivity in surface waters during the early Holocene was restricted to areas in the vicinity of riverine nutrient fluxes. Enhanced productivity in surface waters and related organic matter fluxes did obviously not contribute to the formation of sapropel S1 in the deeper basins. In addition, the record of the small opportunistic taxa allowed a detailed reconstruction of changes in the seasonality of surface water production and phytodetritus pulses that will aid to map the spatial and temporal variability of trophic changes in the eastern Mediterranean Sea during the transition from the last glacial to the Holocene.

  1. Abyssal Sequestration of Nuclear Waste in Earth's Crust

    NASA Astrophysics Data System (ADS)

    Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.

    2013-12-01

    This work outlines a new method for disposing of hazardous (e.g., nuclear) waste. The technique is called Abyssal Sequestration, and it involves placing the waste at extreme depths in Earth's crust where it could achieve the geologically-long period of isolation. Abyssal Sequestration involves storing the waste in hydraulic fractures driven by gravity, a process we term gravity fracturing. In short, we suggest creating a dense fluid (slurry) containing waste, introducing the fluid into a fracture, and extending the fracture downward until it becomes long enough to propagate independently. The fracture will continue to propagate downward to great depth, permanently isolating the waste. Storing solid wastes by mixing them with fluids and injecting them into hydraulic fractures is a well-known technology. The essence of our idea differs from conventional hydraulic fracturing techniques only slightly in that it uses fracturing fluid heavier than the surrounding rock. This difference is fundamental, however, because it allows hydraulic fractures to propagate downward and carry wastes by gravity instead of or in addition to being injected by pumping. An example of similar gravity-driven fractures with positive buoyancy is given by magmatic dikes that may serve as an analog of Abyssal Sequestration occurring in nature. Mechanics of fracture propagation in conditions of positive (diking) and negative (heavy waste slurry) buoyancy is similar and considered in this work for both cases. Analog experiments in gelatin show that fracture breadth (horizontal dimension) remains nearly stationary when fracturing process in the fracture 'head' (where breadth is 'created') is dominated by solid toughness, as opposed to the viscous fluid dissipation dominant in the fracture tail. We model propagation of the resulting 'buoyant' or 'sinking' finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response of the crack to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to unit crack extension and the rock fracture toughness. It allows to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, which breadth is known a priori, the final breadth of a finger-like fracture is a result of the fracturing process in the fracture head. To resolve the breadth, we relax the local elasticity assumption in the fracture head by neglecting viscous pressure drop there. The resulting fracture head model is a 3D analog of the Weertman's hydrostatic pulse, and yields expressions for the terminal breadth, b = 0.34 (K / Delta rho g))^(2/3), and for the head volume, V = 10.4 K b^(5/2) / E'. We then combine the finger crack solution for the viscous tail with the 3-D pulse solution for the fracture head. The obtained closed-form solution is compared to numerical simulations. Based on this solution, we analyzed the gravity fracture propagation in conditions of either continuous injection or finite volume release for sets of parameters representative of the heavy waste injection technique and low viscosity magma diking.

  2. Morphology and Late Quaternary sedimentation in the Gulf of Oman Basin

    NASA Astrophysics Data System (ADS)

    Uchupi, Elazar; Swift, S. A.; Ross, D. A.

    The morphology of the Gulf of Oman Basin, a 3,400 m deep oceanic basin between Oman and southern Pakistan and southern Iran, ranges from a convergent margin (Makran margin) along the north side, a passive type (Oman margin) along the south side, translation types along the basin's west (Zendan Fault-Oman Line) and east (Murray Ridge) sides and a narrow continental rise and a wide abyssal plain in the centre of the basin. Sediment input into the basin during the Late Quaternary has been mainly from the north as a result of the uplift of the Coast Makran Mountains in the Late Miocene-Pliocene. Today most of this detritrus is deposited on the shelf and upper continental slope and perched basins behind the fold/fault ridges on the lower slope. The presence of fans and channels on the continental rise on the north side of the basin indicate, however, that continental derived debris was, and possibly is, being transported to the deep-sea by turbidity currents via gaps in the ridges on the lower slope. In addition to land derived terrigenous sediments, the basin deposits also contain biogenic (organic matter and calcium carbonate), eolian detritus and hydrates and authigenic carbonates from the tectonic dewatering of the Makran accretionary wedge. The eolian sediment is carried into the Gulf of Oman Basin from Arabia and the Mesopotamia Valley by the northwesterly Shamal winds. This type of detritus was particularly abundant during the glacial arid periods 21,000-20,000 and 11,000 (Younger Dryas) years ago when exposure of the Persian (Arabian) Gulf increased the area of dust entrainment and shifted the position of the source of the eolian sediments closer to the basin.

  3. Three new species and one new genus of abyssal Cumacea (Crustacea, Malacostraca, Peracarida) from the Kuril-Kamchatka Trench area

    NASA Astrophysics Data System (ADS)

    Lavrenteva, Anna V.; Mhlenhardt-Siegel, Ute

    2015-01-01

    Only two species of crustacean Cumacea have been reported in publications for the Kuril-Kamchatka Trench area after nine expeditions on board of the RV "Vityaz". During the KuramBio expedition 2012 to the Kuril-Kamchatka Trench and the adjacent abyssal plain at depths 4830-5780 m no less than 72 species of cumaceans from 23 genera and 6 families were sampled. Five genera were recorded for the first time in the studied region: the genera Pseudoleptostyloides and Platycuma were detected for the first time for the Pacific Ocean; Cyclaspoides, Bathylamprops and Styloptocuma were firstly sampled in North Pacific. About 90% of the sampled species appear to be new to science. Three new deep-sea cumacean species and one new genus from the Kurile Kamchatka area are described in the present paper: Abyssoleucon tzarevae gen. n., sp. n. belonging to the family Leuconidae, Cyclaspoides borisovetsi sp. n. and Bathycuma sonne sp. n. of the family Bodotriidae. A distribution map for the species of the genus Cyclaspoides is provided.

  4. Organic-Carbon Sequestration in Soil/Sediment of the Mississippi River Deltaic Plain - Data; Landscape Distribution, Storage, and Inventory; Accumulation Rates; and Recent Loss, Including a Post-Katrina Preliminary Analysis (Chapter B)

    USGS Publications Warehouse

    Markewich, Helaine W.; Buell, Gary R.; Britsch, Louis D.; McGeehin, John P.; Robbins, John A.; Wrenn, John H.; Dillon, Douglas L.; Fries, Terry L.; Morehead, Nancy R.

    2007-01-01

    Soil/sediment of the Mississippi River deltaic plain (MRDP) in southeastern Louisiana is rich in organic carbon (OC). The MRDP contains about 2 percent of all OC in the surface meter of soil/sediment in the Mississippi River Basin (MRB). Environments within the MRDP differ in soil/sediment organic carbon (SOC) accumulation rate, storage, and inventory. The focus of this study was twofold: (1) develop a database for OC and bulk density for MRDP soil/sediment; and (2) estimate SOC storage, inventory, and accumulation rates for the dominant environments (brackish, intermediate, and fresh marsh; natural levee; distributary; backswamp; and swamp) in the MRDP. Comparative studies were conducted to determine which field and laboratory methods result in the most accurate and reproducible bulk-density values for each marsh environment. Sampling methods included push-core, vibracore, peat borer, and Hargis1 sampler. Bulk-density data for cores taken by the 'short push-core method' proved to be more internally consistent than data for samples collected by other methods. Laboratory methods to estimate OC concentration and inorganic-constituent concentration included mass spectrometry, coulometry, and loss-on-ignition. For the sampled MRDP environments, these methods were comparable. SOC storage was calculated for each core with adequate OC and bulk-density data. SOC inventory was calculated using core-specific data from this study and available published and unpublished pedon data linked to SSURGO2 map units. Sample age was estimated using isotopic cesium (137Cs), lead (210Pb), and carbon (14C), elemental Pb, palynomorphs, other stratigraphic markers, and written history. SOC accumulation rates were estimated for each core with adequate age data. Cesium-137 profiles for marsh soil/sediment are the least ambiguous. Levee and distributary 137Cs profiles show the effects of intermittent allochthonous input and/or sediment resuspension. Cesium-137 and 210Pb data gave the most consistent and interpretable information for age estimations of soil/sediment deposited during the 1900s. For several cores, isotopic 14C and 137Cs data allowed the 1963-64 nuclear weapons testing (NWT) peak-activity datum to be placed within a few-centimeter depth interval. In some cores, a too old 14C age (when compared to 137Cs and microstratigraphic-marker data) is the probable result of old carbon bound to clay minerals incorporated into the organic soil/sediment. Elemental Pb coupled with Pb source-function data allowed age estimation for soil/sediment that accumulated during the late 1920s through the 1980s. Exotic pollen (for example, Vigna unguiculata and Alternanthera philoxeroides) and other microstratigraphic indicators (for example, carbon spherules) allowed age estimations for marsh soil/sediment deposited during the settlement of New Orleans (1717-20) through the early 1900s. For this study, MRDP distributary and swamp environments were each represented by only one core, backswamp environment by two cores, all other environments by three or more cores. MRDP core data for the surface meter soil/sediment indicate that (1) coastal marshes, abandoned distributaries, and swamps have regional SOC-storage values >16 kg m-2; (2) swamps and abandoned distributaries have the highest SOC storage values (swamp, 44.8 kg m-2; abandoned distributary, 50.9 kg m-2); (3) fresh-to-brackish marsh environments have the second highest site-specific SOC-storage values; and (4) site-specific marsh SOC storage values decrease as the salinity of the environment increases (fresh-marsh, 36.2 kg m-2; intermediate marsh, 26.2 kg m-2; brackish marsh, 21.5 kg m-2). This inverse relation between salinity and SOC storage is opposite the regional systematic increase in SOC storage with increasing salinity that is evident when SOC storage is mapped by linking pedon data to SSURGO map units (fresh marsh, 47 kg m-2; intermediate marsh, 67 kg m-2; brackish marsh, 75 kg m-2; and salt marsh, 80 kg m-2). MRDP core data for this study also indicate that levees and backswamp have regional SOC-storage values <16 kg m-2. Group-mean SOC storage for cores from these environments are natural levee (17.0 kg m-2) and backswamp (14.1 kg m-2). An estimate for the SOC inventory in the surface meter of soil/sediment in the MRDP can be made using the SSURGO mapped portion of the coastal-marsh vegetative-type map (13,236 km2, land-only area) published by the Louisiana Department of Wildlife and Fisheries and U.S. Geological Survey (1997). This area has a SOC inventory (surface meter) of 677 Tg (slightly more than 2 percent of the 30,289 Tg SOC inventory for the MRB). The MRDP (6,180 km2, land-only area) has an estimated SOC inventory of 397 Tg. Most of the MRDP is located within the SSURGO mapped coastal marshlands. The entire MRDP, including water, has an area of about 10,800 km2. Using the ratio of total MRDP area to SSURGO mapped MRDP area as an adjustment, the MRDP SOC inventory is estimated at 694 Tg. This larger estimate of 694 Tg for the SOC inventory is probably more realistic, because it is reasonable to assume that the marsh sediments overlain by shallow water have comparable SOC storage to that of the adjacent land areas. MRDP core data for this study indicate that there is some variability in long-term SOC mass-accumulation rates for centuries and millennia and that this variability may indicate important geologic changes or changes in land use. However, the consistency of the range in rates of SOC accumulation through time suggests a remarkable degree of marsh sustainability throughout the Holocene, including the recent period of significant marsh modification/channelization for human use. One example of marsh sustainability is its present ability to function as a SOC sink even with Louisiana's large-scale coastal land loss during the last several decades. With coastal-marsh restoration efforts, this sink potential will increase. Looking to the future, a total of 1,101 g m-2 yr-1 SOC is projected to be lost from all of coastal Louisiana (U.S. Army Corps of Engineers, Louisiana Coastal Area (LCA) subprovinces 1-4; not just the MRDP) through coastal erosion from year 2000 to 2050. This translates to a projected SOC-loss rate of about 0.20 percent per year. The recent Hurricanes Katrina and Rita, which devastated the Louisiana coast during late August and late September 2005, transformed about 259 km2 (100 mi2) of marsh to open water (U.S. Geological Survey, 2005). To the extent that some or all of this land loss is permanent, this result equates to a SOC loss of about 15 Tg. This estimate is based on the year-2000 15,153-km2 land area for the LCA study area that includes LCA subprovince 4. Using the year-2000 land area, the LCA study area had an estimated SOC inventory of 858 Tg. The estimated 15 Tg SOC loss attributable to Hurricanes Katrina and Rita is 1.7 percent of the year-2000 LCA inventory and 2.3 percent of the year-2000 MRDP inventory. If this SOC loss is included in the projection for the year 2050, then the MRDP would either remain a source with a net SOC loss of 3 Tg or become a weak sink with a net SOC gain of 4 Tg. These estimates are lower bounds for potential SOC flux because they are only for the surface meter of landmass.

  5. The response of abyssal organisms to low pH conditions during a series of CO2-release experiments simulating deep-sea carbon sequestration

    NASA Astrophysics Data System (ADS)

    Barry, J. P.; Buck, K. R.; Lovera, C.; Brewer, P. G.; Seibel, B. A.; Drazen, J. C.; Tamburri, M. N.; Whaling, P. J.; Kuhnz, L.; Pane, E. F.

    2013-08-01

    The effects of low-pH, high-pCO2 conditions on deep-sea organisms were examined during four deep-sea CO2 release experiments simulating deep-ocean C sequestration by the direct injection of CO2 into the deep sea. We examined the survival of common deep-sea, benthic organisms (microbes; macrofauna, dominated by Polychaeta, Nematoda, Crustacea, Mollusca; megafauna, Echinodermata, Mollusca, Pisces) exposed to low-pH waters emanating as a dissolution plume from pools of liquid carbon dioxide released on the seabed during four abyssal CO2-release experiments. Microbial abundance in deep-sea sediments was unchanged in one experiment, but increased under environmental hypercapnia during another, where the microbial assemblage may have benefited indirectly from the negative impact of low-pH conditions on other taxa. Lower abyssal metazoans exhibited low survival rates near CO2 pools. No urchins or holothurians survived during 30-42 days of exposure to episodic, but severe environmental hypercapnia during one experiment (E1; pH reduced by as much as ca. 1.4 units). These large pH reductions also caused 75% mortality for the deep-sea amphipod, Haploops lodo, near CO2 pools. Survival under smaller pH reductions (ΔpH<0.4 units) in other experiments (E2, E3, E5) was higher for all taxa, including echinoderms. Gastropods, cephalopods, and fish were more tolerant than most other taxa. The gastropod Retimohnia sp. and octopus Benthoctopus sp. survived exposure to pH reductions that episodically reached -0.3 pH units. Ninety percent of abyssal zoarcids (Pachycara bulbiceps) survived exposure to pH changes reaching ca. -0.3 pH units during 30-42 day-long experiments.

  6. Edwardsia sojabio sp. n. (Cnidaria: Anthozoa: Actiniaria: Edwardsiidae), a new abyssal sea anemone from the Sea ofJapan

    NASA Astrophysics Data System (ADS)

    Sanamyan, Nadya; Sanamyan, Karen

    2013-02-01

    The paper describes new deep-water edwardsiid sea anemone Edwardsia sojabio sp. n. which is very common on soft muddy bottoms at lower bathyal and upper abyssal depths in the Sea of Japan. It was recorded in high quantity in depths between 2545 and 3550 m and is the second abyssal species of the genus Edwardsia.

  7. Temperatures and cooling rates recorded in REE in coexisting pyroxenes in ophiolitic and abyssal peridotites

    NASA Astrophysics Data System (ADS)

    Dygert, Nick; Liang, Yan

    2015-06-01

    Mantle peridotites from ophiolites are commonly interpreted as having mid-ocean ridge (MOR) or supra-subduction zone (SSZ) affinity. Recently, an REE-in-two-pyroxene thermometer was developed (Liang et al., 2013) that has higher closure temperatures (designated as TREE) than major element based two-pyroxene thermometers for mafic and ultramafic rocks that experienced cooling. The REE-in-two-pyroxene thermometer has the potential to extract meaningful cooling rates from ophiolitic peridotites and thus shed new light on the thermal history of the different tectonic regimes. We calculated TREE for available literature data from abyssal peridotites, subcontinental (SC) peridotites, and ophiolites around the world (Alps, Coast Range, Corsica, New Caledonia, Oman, Othris, Puerto Rico, Russia, and Turkey), and augmented the data with new measurements for peridotites from the Trinity and Josephine ophiolites and the Mariana trench. TREE are compared to major element based thermometers, including the two-pyroxene thermometer of Brey and Khler (1990) (TBKN). Samples with SC affinity have TREE and TBKN in good agreement. Samples with MOR and SSZ affinity have near-solidus TREE but TBKN hundreds of degrees lower. Closure temperatures for REE and Fe-Mg in pyroxenes were calculated to compare cooling rates among abyssal peridotites, MOR ophiolites, and SSZ ophiolites. Abyssal peridotites appear to cool more rapidly than peridotites from most ophiolites. On average, SSZ ophiolites have lower closure temperatures than abyssal peridotites and many ophiolites with MOR affinity. We propose that these lower temperatures can be attributed to the residence time in the cooling oceanic lithosphere prior to obduction. MOR ophiolites define a continuum spanning cooling rates from SSZ ophiolites to abyssal peridotites. Consistent high closure temperatures for abyssal peridotites and the Oman and Corsica ophiolites suggests hydrothermal circulation and/or rapid cooling events (e.g., normal faulting, unroofing) control the late thermal histories of peridotites from transform faults and slow and fast spreading centers with or without a crustal section.

  8. A three-dimensional map of tidal dissipation over abyssal hills

    NASA Astrophysics Data System (ADS)

    Lefauve, Adrien; Muller, Caroline; Melet, Angélique

    2015-07-01

    The breaking of internal tides is believed to provide a large part of the power needed to mix the abyssal ocean and sustain the meridional overturning circulation. Both the fraction of internal tide energy that is dissipated locally and the resulting vertical mixing distribution are crucial for the ocean state, but remain poorly quantified. Here we present a first worldwide estimate of mixing due to internal tides generated at small-scale abyssal hills. Our estimate is based on linear wave theory, a nonlinear parameterization for wave breaking and uses quasi-global small-scale abyssal hill bathymetry, stratification, and tidal data. We show that a large fraction of abyssal-hill generated internal tide energy is locally dissipated over mid-ocean ridges in the Southern Hemisphere. Significant dissipation occurs above ridge crests, and, upon rescaling by the local stratification, follows a monotonic exponential decay with height off the bottom, with a nonuniform decay scale. We however show that a substantial part of the dissipation occurs over the smoother flanks of mid-ocean ridges, and exhibits a middepth maximum due to the interplay of wave amplitude with stratification. We link the three-dimensional map of dissipation to abyssal hills characteristics, ocean stratification, and tidal forcing, and discuss its potential implementation in time-evolving parameterizations for global climate models. Current tidal parameterizations only account for waves generated at large-scale satellite-resolved bathymetry. Our results suggest that the presence of small-scale, mostly unresolved abyssal hills could significantly enhance the spatial inhomogeneity of tidal mixing, particularly above mid-ocean ridges in the Southern Hemisphere.

  9. Methane in water columns and sediments of the north western Sea of Japan

    NASA Astrophysics Data System (ADS)

    Vereshchagina, Olga F.; Korovitskaya, Elena V.; Mishukova, Galina I.

    2013-02-01

    This paper presents the results of methane measurements in water and sediments, first performed along the north western continental slope and abyssal plain of the Sea of Japan. Methane concentrations in the study area were very low. However, some features of its distribution are revealed. The highest dissolved methane concentrations (10-14 nmol kg-1) are characteristic of the pycnocline layer at a depth of 30-50 m in the northern shallow stations. With increasing depth, the methane is reduced to minimum values (0.5-1.0 nmol kg-1). The greatest variability in methane concentrations was observed in the layers at 0-500 m, which can be explained by the hydrodynamic conditions of the environment on the slope. Methane plumes (1.7 and 1.3 nmol kg-1) on the northern section were recorded at the depth of 1250 and 1495 m, respectively. Plumes (1.2 nmol kg-1) are also observed on near bottom layers at the deepest (more than 3000 m) stations. CH4 concentration in bottom sediments is also low (from 1 nmol kg-1 at 7 cm level to 752 nmol kg-1 at the 53 cm level of the core sediment in the northern part). Reduced sediments in the southern part of the study region have maximal methane concentration for sediment (2549 nmol kg-1) at the horizon 44 cm bsf (below sea floor) with a smell of H2S. These results assume a close relation of CH4 with sediment properties. A few stations with maximum methane (86-101 nmol kg-1) in the surface sediment layer are at the foot of a steep slope. Herewith, the highest abundance of some pericarid species was observed at the points with the highest values of methane concentrations in the surface sediment layer. Weak methane seepage can cause anoxic marine waters. Methane emission from water to the atmosphere is low because its concentration is close to equilibrium in surface water. An improved formula for calculating the methane flux of water into the atmosphere, taking into account high wind speeds, is presented in the paper.

  10. Sediment recycling at convergent plate margins (Indo-Burman Ranges and Andaman-Nicobar Ridge)

    NASA Astrophysics Data System (ADS)

    Garzanti, Eduardo; Limonta, Mara; Resentini, Alberto; Bandopadhyay, Pinaki C.; Najman, Yani; Andò, Sergio; Vezzoli, Giovanni

    2013-08-01

    Subduction complexes large enough to be exposed subaerially and become significant sources of terrigenous detritus are formed by tectonic accretion above trenches choked with thick sections of remnant-ocean turbidites. They thus need to be connected along strike to a major collision zone, where huge volumes of orogenic detritus are produced and conveyed via a major fluvio-deltaic system to the deep sea. In this article we investigate sediment generation and recycling in the archetype of such settings, the eastern prolongation of the Himalayan collisional system. We illustrate the petrographic and heavy-mineral suites of modern sands produced all along the Indo-Burman-Andaman-Nicobar subduction complex, which includes accreted abyssal-plain sediments overthrust by ophiolites and unconformably overlain by volcaniclastic forearc strata. "Subduction Complex Provenance" is thus composite, and overwhelmingly consists of detritus recycled from largely turbiditic parent rocks (Recycled Clastic Provenance), with local supply from obducted ultramafic and mafic rocks of forearc lithosphere (Ophiolite Provenance) or recycled paleovolcanic to neovolcanic sources (Volcanic Arc Provenance). In order to specifically investigate the effect of recycling, we characterize the diverse detrital signatures of Cenozoic sandstones originally deposited during subsequent stages of "soft" and "hard" Himalayan collision and presently exposed from Bangladesh to the Andaman Islands, and discuss the reasons for compositional discrepancies between parent sandstones and their recycled daughter sands. Long-distance, multistep and multicyclic sediment transfer along and across convergent plate boundaries follows complex trajectories in space and time, which must be resolved whenever we want to obtain a reasonably faithful paleogeographic reconstruction for the recent and less recent geological past.

  11. Chenier Plain Sediment Burial Pipe Measurements

    NASA Technical Reports Server (NTRS)

    Moeller, Chris; Gunshor, Mat; Huh, Oscar; Winch, Dale

    2000-01-01

    These field notes describe the logistical circumstances and field conditions experienced by the researchers, who measured the waterlines on a series of vertical pipes previously buried in shallow coastal water. The purpose of the measurements was to monitor a portion of the Gulf coast in Louisiana for erosion.

  12. Sources and controls for the mobility of arsenic in oxidizing groundwaters from loess-type sediments in arid/semi-arid dry climates - evidence from the Chaco-Pampean plain (Argentina).

    PubMed

    Nicolli, Hugo B; Bundschuh, Jochen; Garca, Jorge W; Falcn, Carlos M; Jean, Jiin-Shuh

    2010-11-01

    In oxidizing aquifers, arsenic (As) mobilization from sediments into groundwater is controlled by pH-dependent As desorption from and dissolution of mineral phases. If climate is dry, then the process of evaporative concentration contributes further to the total concentration of dissolved As. In this paper the principal As mobility controls under these conditions have been demonstrated for Sal River alluvial basin in NW Argentina (Tucumn Province; 7000 km(2)), which is representative for other basins or areas of the predominantly semi-arid Chaco-Pampean plain (1,000,000 km(2)) which is one of the world's largest regions affected by high As concentrations in groundwater. Detailed hydrogeochemical studies have been performed in the Sal River basin where 85 groundwater samples from shallow aquifers (42 samples), deep samples (26 samples) and artesian aquifers (17 samples) have been collected. Arsenic concentrations range from 11.4 to 1660 ?g L(-1) leaving 100% of the investigated waters above the provisional WHO guideline value of 10 ?g L(-1). A strong positive correlation among As, F, and V in shallow groundwaters was found. The correlations among those trace elements and U, B and Mo have less significance. High pH (up to 9.2) and high bicarbonate (HCO(3)) concentrations favour leaching from pyroclastic materials, including volcanic glass which is present to 20-25% in the loess-type aquifer sediments and yield higher trace element concentrations in groundwater from shallow aquifers compared to deep and artesian aquifers. The significant increase in minor and trace element concentrations and salinity in shallow aquifers is related to strong evaporation under semi-arid climatic conditions. Sorption of As and associated minor and trace elements (F, U, B, Mo and V) onto the surface of Fe-, Al- and Mn-oxides and oxi-hydroxides, restricts the mobilization of these elements into groundwater. Nevertheless, this does not hold in the case of the shallow unconfined groundwaters with high pH and high concentrations of potential competitors for adsorption sites (HCO(3), V, P, etc.). Under these geochemical conditions, desorption of the above mentioned anions and oxyanions occurs as a key process for As mobilization, resulting in an increase of minor and trace element concentrations. These geochemical processes that control the concentrations of dissolved As and other trace elements and which determine the groundwater quality especially in the shallow aquifers, are comparable to other areas with high As concentrations in groundwater of oxidizing aquifers and semi-arid or arid climate, which are found in many parts of the world, such as the western sectors of the USA, Mexico, northern Chile, Turkey, Mongolia, central and northern China, and central and northwestern Argentina. PMID:21035830

  13. Northern Plains Buried Craters

    NASA Technical Reports Server (NTRS)

    2004-01-01

    22 December 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows three circular features on the martian northern plains near 70.7oN, 311.7oW. These circular features are the locations of meteor impact craters that have been buried beneath the plains. Much of the northern plains shares this story, in which thousands of old craters have been filled or partially filled and then thinly buried beneath textured plains. The picture covers an area 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  14. The role of the geothermal heat flux in driving the abyssal ocean circulation

    NASA Astrophysics Data System (ADS)

    Mashayek, A.; Ferrari, R.; Vettoretti, G.; Peltier, W. R.

    2013-06-01

    The results presented in this paper demonstrate that the geothermal heat flux (GHF) from the solid Earth into the ocean plays a non-negligible role in determining both abyssal stratification and circulation strength. Based upon an ocean data set, we show that the map of upward heat flux at the ocean floor is consistent (within a factor of 2) with the ocean floor age-dependent map of GHF. The observed buoyancy flux above the ocean floor is consistent with previous suggestions that the GHF acts to erode the abyssal stratification and thereby enhances the strength of the abyssal circulation. Idealized numerical simulations are performed using a zonally averaged single-basin model which enables us to address the GHF impact as a function of the depth dependence of diapycnal diffusivity. We show that ignoring this vertical variation leads to an under-prediction of the influence of the GHF on the abyssal circulation. Independent of the diffusivity profile, introduction of the GHF in the model leads to steepening of the Southern Ocean isopycnals and to strengthening of the eddy-induced circulation and the Antarctic bottom water cell. The enhanced circulation ventilates the GHF derived heating to shallow depths, primarily in the Southern Ocean.

  15. Flow of grounded abyssal ocean currents along zonally-varying topography in spherical geometry

    NASA Astrophysics Data System (ADS)

    Swaters, G. E.

    2013-05-01

    Many of the abyssal currents in the oceans, associated with the equatorward motion of deep water masses produced by atmospheric cooling in high latitudes, are organized as mesoscale topographically-steered geostrophically-balanced grounded gravity currents, which flow along sloping continental boundaries. These currents form an important component in the deep "leg" of the meridional overturning circulation in the oceans. The spatial extent of these abyssal currents is hemispheric in scale. This raises the question of the role of planetary sphericity and differential rotation (from the viewpoint of the underlying local geostrophic balance) in determining the large scale kinematic structure of these flows. A steady nonlinear planetary-geostrophic model in spherical coordinates is presented describing the hemispheric-scale meridional flow of grounded abyssal currents on a sloping bottom. The model, which corresponds mathematically to a quasi-linear hyperbolic partial differential equation, can be solved explicitly for a cross-slope isopycnal field that is grounded (i.e., intersects the bottom on the up slope and down slope sides). The solutions possess decreasing abyssal current height in the equatorward direction while maintaining constant meridional mass flux and exhibit westward intensification as they flow toward the equator.

  16. Monologue or Dialogue? Stepping Away from the Abyss in Higher Education

    ERIC Educational Resources Information Center

    Stern, Julian

    2009-01-01

    This paper investigates the possibilities of the use of dialogue, and the dangers of the use of monologue, in higher education in the early twenty-first century, in a period facing a number of smaller- and larger-scale crises--each interpreted as an "abyss" of some kind. How does higher education contribute, positively or negatively, to personal…

  17. SEDIMENT SAMPLING GUIDELINES

    EPA Science Inventory

    The guidance document will detail the measures needed to collect and analyze soils/sediments from flood plains, wetlands, bogs, rivers, and streams that are impacted by high moisture content. High moisture in the above matrices can manifest itself as increased detection limits a...

  18. Observation of the abyssal western boundary current in the Philippine Sea

    NASA Astrophysics Data System (ADS)

    Zhai, Fangguo; Wang, Qingye; Hu, Dunxin; Guo, Xiaogang

    2014-09-01

    Mooring observations were conducted from July 16, 2011 to March 30, 2012 east of Mindanao, Philippines (1272.8'E, 80.3'N) to observe the abyssal current at about 5 600 m deep and 500 m above the ocean bottom. Several features were revealed: 1) the observed abyssal current was highly variable with standard deviations of 57.3 mm/s and 34.0 mm/s, larger than the mean values of -31.9 and 16.6 mm/s for the zonal and meridional components, respectively; 2) low-frequency current longer than 6 days exhibited strong seasonal variation, flowing southeastward (mean flow direction of 119.0 clockwise from north) before about October 1, 2011 and northwestward (mean flow direction of 60.5 counter-clockwise from north) thereafter; 3) the high-frequency flow bands were dominated by tidal currents O1, K1, M2, and S2, and near-inertial currents, whose frequencies were higher than the local inertial frequency. The two diurnal tidal constituents were much stronger than the two semidiurnal ones. This study provides for the first time an observational insight into the abyssal western boundary current east of Mindanao based on long-term observations at one site. It is meaningful for further research into the deep and abyssal circulation over the whole Philippine Sea and the 3D structure of the western boundary current system in this region. More observational and high-resolution model studies are needed to examine the spatial structure and temporal variation of the abyssal current over a much larger space and longer period, their relation to the upper-layer circulation, and the underlying dynamics.

  19. Abundance, diversity, and latitudinal gradients of southeastern Atlantic and Antarctic abyssal gastropods

    NASA Astrophysics Data System (ADS)

    Schrödl, M.; Bohn, J. M.; Brenke, N.; Rolán, E.; Schwabe, E.

    2011-03-01

    Mollusca are widely used for deriving concepts on deep-sea biology and biodiversity, yet abyssal collections are limited to only a few regions of the world ocean and biased toward the northern Atlantic. The present study compares gastropod molluscs sampled along a transect through the southern Atlantic from the equator to Antarctica. The DIVA I and II expeditions concentrated on the hardly explored Guinea, Angola, and Cape Basins. Of the 145 deep-sea deployments (5025-5656 m depth) analyzed to date, 20 have yielded 68 specimens of benthic gastropods, representing 27 species. Only five abyssal species were previously known, four of them from the northern Atlantic deep sea; the remainder appear to be undescribed. Interestingly, there is no faunal overlap with the nearby Antarctic deep-sea. Most of these DIVA species (63%) are represented by single individuals, or limited to one or two stations. The rarity (i.e. 0.55 specimens m -2 calculated from quantitative corers) and still undetectable patchiness of southeastern Atlantic abyssal gastropods may indicate "source-sink" dynamics, but comparison is needed with thus far hardly explored regional bathyal faunas. The BRENKE-epibenthic sledge (EBS) may be efficient at surveying the abyssal gastropod species richness, but is shown to drastically underestimate true abundances. Low diversity values throughout the three southern Atlantic ocean basins do further challenge earlier estimates of a hyperdiverse global abyssal macrofauna. Comparative EBS data available from the southern hemisphere indicate a gradient from the equatorial Guinea Basin towards higher gastropod abundances and diversity in Antarctica. This is in clear contrast to the paradigm of a globally strongly decreasing marine diversity from lower to higher latitudes, highlighting the importance of further exploring the southern fauna from the tropics to Antarctica.

  20. The Plains City Story

    ERIC Educational Resources Information Center

    van Olphen, Marcela; Rios, Francisco; Berube, William; Dexter, Robin; McCarthy, Robert

    2006-01-01

    This case study portrays a contemporary phenomenon that affects many U.S. school districts. Specifically, the authors address the challenges that the superintendent of the Plains City school district faced as a result of a change in the demographic distribution of his district. The gradual development of the pig farming industry in Plains City…

  1. The Plains City Story

    ERIC Educational Resources Information Center

    van Olphen, Marcela; Rios, Francisco; Berube, William; Dexter, Robin; McCarthy, Robert

    2006-01-01

    This case study portrays a contemporary phenomenon that affects many U.S. school districts. Specifically, the authors address the challenges that the superintendent of the Plains City school district faced as a result of a change in the demographic distribution of his district. The gradual development of the pig farming industry in Plains City

  2. Agriculture on the Chaco Plain, Paraguay, South America

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This view of extensive agriculture on the Chaco Plain, Paraguay, (22.5S, 60.5W) depicts the fertility of the soils between the Andes Mountains and the Paraguay - Parana Rivers in the northwestern Paraguay. The Gran Chaco Plain is flat landscape built up by sediments. Frontier settlements like Marsical Estigarribia, seen in the image, are dominated by agriculture along the stream courses that abound in the area.

  3. A comparative study on arsenic and humic substances in alluvial aquifers of Bengal delta plain (NW Bangladesh), Chianan plain (SW Taiwan) and Lanyang plain (NE Taiwan): implication of arsenic mobilization mechanisms.

    PubMed

    Selim Reza, A H M; Jean, Jiin-Shuh; Yang, Huai-Jen; Lee, Ming-Kuo; Hsu, Hua-Fen; Liu, Chia-Chuan; Lee, Yao-Chang; Bundschuh, Jochen; Lin, Kao-Hong; Lee, Chi-Yu

    2011-06-01

    Humic substances in groundwater and aquifer sediments from the arsenicosis and Blackfoot disease (BFD) affected areas in Bangladesh (Bengal delta plain) and Taiwan (Lanyang plain and Chianan plain) were characterized using fluorescence spectrophotometry and Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the mean concentration of As and relative intensity of fluorescent humic substances are higher in the Chianan plain groundwater than those in the Lanyang plain and Bengal delta plain groundwater. The mean As concentrations in Bengal delta plain, Chianan plain, and Lanyang plain are 50.65 ?g/l (2.8-170.8 ?g/l, n=20), 393 ?g/l (9-704 ?g/l, n=5), and 104.5 ?g/l (2.51-543 ?g/l, n = 6), respectively. Average concentrations and relative fluorescent intensity of humic substances in groundwater are 25.381 QSU (quinine standard unit) and 17.78 in the Bengal delta plain, 184.032 QSU and 128.41 in the Chianan plain, and 77.56 QSU and 53.43 in the Lanyang plain. Moreover, FT-IR analysis shows that the humic substances extracted from the Chianan plain groundwater contain phenolic, alkanes, aromatic ring and amine groups, which tend to form metal carbon bonds with As and other trace elements. By contrast, the spectra show that humic substances are largely absent from sediments and groundwater in the Bengal delta plain and Lanyang plain. The data suggest that the reductive dissolution of As-adsorbed Mn oxyhydroxides is the most probable mechanism for mobilization of As in the Bengal delta plain. However, in the Chianan plain and Lanyang plain, microbially mediated reductive dissolution of As-adsorbed amorphous/crystalline Fe oxyhydroxides in organic-rich sediments is the primary mechanism for releasing As to groundwater. High levels of As and humic substances possibly play a critical role in causing the unique BFD in the Chianan plain of SW Taiwan. PMID:20706862

  4. Assessment and estimation of streambank erosion rates in the Southeastern Plains ecoregion of Mississippi

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sediment loads from watersheds located in the Southeastern Plain Ecoregion can have contributions from stream channel degradation as large as 90%. Monitoring and modeling techniques to assess the contribution of channel sediment to overall sediment load are needed to determine the reductions necessa...

  5. Marine geology of the hess rise, 1, bathymetry, surface sediment distribution, and environment of deposition

    SciTech Connect

    Nemoto, K.; Kroenke, L.W.

    1981-11-10

    New charts of bathymetry, acoustic character, and sediment distribution describe the Hess Rise, a large oceanic plateau in the central north Pacific. Discrete physiographic provinces on the Hess Rise are the High Plateau, shallower than 3900 m, trending N30/sup 0/W; the Northeastern Flank, a smooth, gentle slope gradually increasing in depth to the northeast; the Woollard Abyssal Plain, extending farther to the northeast; the Volcanic Province with its high peaks and ridges along the southern margin of the Hess Rise; the Mendocino Fracture Zone to the south, expressed by broad, planar seafloor regions bordered by ridges and scarps; the Western Steps, formed by structural benches on the western side of the Rise; and the Emperor Deep, between the rise and the Emperor Seamounts. Five types of acoustic units have been mapped and interpreted: a transparent layer, predominantly of biosiliceous pelagic clay; a stratified layer, predominantly of nannofossil ooze; a diffuse layer of debris flows that seem to have originated mostly in the Volcanic Province; an opaque horizon commonly formed of volcaniclastic sediments that are usually found on the seafloor of the Mendocino Fracture Zone; and a hyperbolic horizon, indicating outcrops of igneous rock. The pronounced effect of bottom currents on the present-day environment of deposition in the Hess Rise is evidenced by the presence of the opaque horizon, which is interpreted as an erosion surface, and by current moating, abrupt thinning of surface layers and truncation of subbottom reflectors. The widespread erosion on the seafloor of the Mendocino Fracture Zone is attributed to the flow of Antarctic bottom water.

  6. Geology, geochemistry, and tectonostratigraphic relations of the crystalline basement beneath the coastal plain of New Jersey and contiguous areas

    USGS Publications Warehouse

    Volkert, Richard A.; Drake, Avery Ala, Jr.; Sugarman, Peter J.

    1996-01-01

    Coastal plain sediments are underlain by pre-Mesozoic crystalline rocks. The inner coastal plain is underlain by schist that is correlated with the Potomac Terrane, as well as by mafic rocks probably equivalent to the Wilmington or Bel Air-Rising Sun terranes. The northern and central outer coastal plain is underlain by metasedimentary rocks similar to the Brompton-Cameron Terrane. Rocks beneath the southern coastal plain probably correlate with those of the Chopawamsic and Roanoke Rapids terranes.

  7. River sediments.

    PubMed

    Williams, Martin

    2012-05-13

    River history is reflected in the nature of the sediments carried and deposited over time. Using examples drawn from around the world, this account illustrates how river sediments have been used to reconstruct past environmental changes at a variety of scales in time and space. Problems arising from a patchy alluvial record and from influences external to the river basin can make interpretation difficult. The Nile is treated in some detail because its history is further complicated by tectonic, volcanic and climatic events in its headwaters and by enduring human impacts. It arose soon after 30 Ma. Since that time approximately 100,000 km(3) of rock have been eroded from its Ethiopian sources and deposited in the eastern Mediterranean, with minor amounts of sediment laid down along its former flood plains in Egypt and Sudan. From these fragmentary alluvial remains, a detailed history of Nile floods and droughts has been reconstructed for the last 15 kyr, and, with less detail, for the past 150 kyr, which shows strong accordance with global fluctuations in the strength of the summer monsoon, which are in turn perhaps modulated by changes in solar insolation caused by changes in the Earth's orbit and by variations in solar irradiance. PMID:22474677

  8. Billing in Plain English.

    ERIC Educational Resources Information Center

    Hughes, Sarah Jane

    1987-01-01

    The author describes the efforts of the Federal Trade Commission to make credit communications more readable and informative. The group working on the project uses "plain English" as the writing model for forms and manuals. (CH)

  9. Depositional environments of late glacial to Holocene sediments on the deep water levees of Setbal and Nazar Canyons, offshore Portugal: preliminary results

    NASA Astrophysics Data System (ADS)

    Pascoletti, F. C.; Masson, D.; Innocenti, C.

    2010-12-01

    The west Iberian margin is indented by a network of submarine canyons that create rugged seafloor morphology and act as major pathways for the transport of sediment from land to the abyssal plains. The Setbal and Nazar Canyons are part of this complex environment and strongly influence sediment distribution, capturing sediments from the Tagus River and the littoral cell transport respectively. Deep submarine sedimentary sequences thus reflect changes in sediment input and depositional environments. The high-resolution sedimentological study here presented was applied in four cores of the deep water levees of Nazar and Setbal Canyons in order to explore how sediment input to the canyons changed during the last glacial - interglacial transition, and how this reflects changing environmental conditions on land. By means of non-destructive corelogger measurements and analyses of spectral signatures, geochemical compositions and colour variations, it was possible to identify ice-rafted debris (IRD) deposits, to characterize hemipelagic and turbidite layers and to investigate terrestrial-derived sediments input variation during the last 26 ka. Preliminary results from the sedimentological and turbidite frequency analyses show that highest turbidite occurrence is recorded during the glacial stage, confirming that the generation of turbidity flows in submarine canyons is tightly related to low sea-level stands. We found that major peaks in frequency and thickness of turbidite deposits in the deep Portuguese margin are mainly coeval with abrupt climatic (H2 and 1) and sea-level changes (~ 19 and ~ 23 ka BP), as a consequence of which a major amount of continentally-derived material was transported into the deep sea. During the Holocene, the inception of sea-level rises, independent of their magnitude, has been found to be sufficient to generate turbidity currents, particularly in the Nazar system. Moreover, a multiple regression analysis was attempted in order to estimate the sediment carbonate content from VIS reflectance spectrophotometry data acquired with a Konica Minolta spectrophotometer (39 bands, wavelength range from 360 nm to 740 nm). The equation obtained for recent mostly hemipelagic sediments, has an adjusted coefficient of determination of 0.97 and a root main squared error (RMSE) of 4.02 %, indicating a very good correspondence between analytically determined percent calcium carbonate and reflectance-based calcium carbonate estimates. However the spectral technique failed on deeper and older core sections, characterized by a general higher variability in sediment components, including a major terrestrial input and carbonate from a variety of biogenic and nonbiogenic sources.

  10. Spatially heterogeneous diapycnal mixing in the abyssal ocean: A comparison of two parameterizations to observations

    NASA Astrophysics Data System (ADS)

    Decloedt, Thomas; Luther, Douglas S.

    2012-11-01

    The spatial distributions of the diapycnal diffusivity predicted by two abyssal mixing schemes are compared to each other and to observational estimates based on microstructure surveys and large-scale hydrographic inversions. The parameterizations considered are the tidal mixing scheme by Jayne, St. Laurent and co-authors (JSL01) and the Roughness Diffusivity Model (RDM) by Decloedt and Luther. Comparison to microstructure surveys shows that both parameterizations are conservative in estimating the vertical extent to which bottom-intensified mixing penetrates into the stratified water column. In particular, the JSL01 exponential vertical structure function with fixed scale height decays to background values much nearer topography than observed. JSL01 and RDM yield dramatically different horizontal spatial distributions of diapycnal diffusivity, which would lead to quite different circulations in OGCMs, yet they produce similar basin-averaged diffusivity profiles. Both parameterizations are shown to yield smaller basin-mean diffusivity profiles than hydrographic inverse estimates for the major ocean basins, by factors ranging from 3 up to over an order of magnitude. The canonical 10-4 m2 s-1abyssal diffusivity is reached by the parameterizations only at depths below 3 km. Power consumption by diapycnal mixing below 1 km of depth, between roughly 32°S and 48°N, for the RDM and JSL01 parameterizations is 0.40 TW & 0.28 TW, respectively. The results presented here suggest that present-day mixing parameterizations significantly underestimate abyssal mixing. In conjunction with other recently published studies, a plausible interpretation is that parameterizing the dissipation of bottom-generated internal waves is not sufficient to approximate the global spatial distribution of diapycnal mixing in the abyssal ocean.

  11. A glimpse into the deep of the Antarctic Polar Front - Diversity and abundance of abyssal molluscs

    NASA Astrophysics Data System (ADS)

    Jrger, K. M.; Schrdl, M.; Schwabe, E.; Wrzberg, L.

    2014-10-01

    Our knowledge of the biodiversity and distribution patterns of benthic deep-sea faunas is still limited, with large parts of the world's abyss unexplored, lacking ?-taxonomic data across oceans basins and especially of biogeographic transition zones between oceans. The Antarctic Polar Frontal Zone has been discussed as major biogeographic barrier hindering faunal exchange between Subantarctic and Antarctic provinces and conserving high rates of endemism in the Southern Ocean benthos. In the present study we report first, exploratory ?-taxonomy on the malacofauna sampled by means of an epibenthic sledge from four bathyal respectively abyssal stations (2732-4327 m depth) in the vicinity of the Antarctic Polar Front during the SYSTCO II expedition (SYSTem COupling in the Southern Ocean, RV Polarstern cruise ANT XXVIII/3). We identified 58 distinct molluscan taxa based on external morphology ('morphospecies'); of the 33 taxa successfully assigned to described species 94% were previously reported from the Southern Ocean, but 24% exhibit distribution ranges crossing the Polar Front. One North Atlantic scaphopod is reported for the first time in Antarctic waters. Our study supports that the Antarctic Polar Front does not serve as effective barrier preventing gene flow in deep-sea molluscs. The present dataset shows the general characteristics of deep-sea sampling: patchiness in distribution and a high degree of singletons. Overall molluscan abundances were generally low ranging between 3.60 and 24.65 ind./1000 m, but in comparison with equatorial and subtropic abyssal basins, gastropod species richness and abundance were reaching high values similar to high Antarctic stations. Comparison between high productivity and low productivity zones along the Polar Front suggests increased abundances and species richness in high productivity zones. Intensified sampling is needed, however, to outweigh stochastic errors and to evaluate the influence of carbon flux as driving factor to faunal composition and abundances of abyssal molluscs.

  12. Demographic indicators of change in a deposit-feeding abyssal holothurian community (Station M, 4000 m)

    NASA Astrophysics Data System (ADS)

    Huffard, Christine L.; Kuhnz, Linda A.; Lemon, Larissa; Sherman, Alana D.; Smith, Kenneth L.

    2016-03-01

    Holothurians are among the most abundant benthic megafauna at abyssal depths, and important consumers and bioturbators of organic carbon on the sea floor. Significant fluctuations in abyssal holothurian density are often attributed to species-specific responses to variable particulate organic carbon flux (food supply) stemming from surface ocean events. We report changes in densities of 19 holothurian species at the abyssal monitoring site Station M in the northeast Pacific, recorded during 11 remotely operated vehicle surveys between Dec 2006 and Oct 2014. Body size demographics are presented for Abyssocucumis abyssorum, Synallactidae sp. 1, Paelopatides confundens, Elpidia sp. A, Peniagone gracilis, Peniagone papillata, Peniagone vitrea, Peniagone sp. A, Peniagone sp. 1, and Scotoplanes globosa. Densities were lower and species evenness was higher from 2006-2009 compared to 2011-2014. Food supply of freshly-settled phytodetritus was exceptionally high during this latter period. Based on relationships between median body length and density, numerous immigration and juvenile recruitment events of multiple species appeared to take place between 2011 and 2014. These patterns were dominated by elpidiids (Holothuroidea: Elasipodida: Elpidiidae), which consistently increased in density during a period of high food availability, while other groups showed inconsistent responses. We considered minimum body length to be a proxy for size at juvenile recruitment. Patterns in density clustered by this measure, which was a stronger predictor of maximum density than median and mean body length.

  13. Abyssal Scavenging Communities attracted to Sargassum and fish in the Sargasso Sea

    NASA Astrophysics Data System (ADS)

    Fleury, Aharon G.; Drazen, Jeffrey C.

    2013-02-01

    Deep-sea communities rely on epipelagic surface production as a primary source of energy and food. The flux of phytodetritus drives many abyssal ecological processes but the flux of large particles such as nekton carcasses, macroalgae, and wood may also be important. Recent baited camera experiments noted that some abyssal fish consumed spinach and phytoplankton placed on the seafloor. To evaluate if fish or other scavengers would consume natural plant or macroalgal material falling to the deep-sea floor we conducted camera experiments using Sargassum or mackerel bait in the Sargasso Sea. A benthic community of invertebrates was attracted to Sargassum, which naturally falls to the seafloor in this area. In five instances it was observed that an isopod Bathyopsurus sp. removed a piece of Sargassum from the main clump and left the field of view with it. An ophiuroid is also observed handling a piece of Sargassum. The group of scavengers attracted to mackerel bait was very different and was dominated by large ophidiid fish. In contrast to studies elsewhere in the abyssal North Atlantic, only a small number of rattails are observed, which could be related to water depth or an ichthyofaunal zonal change between oligotrophic and eutrophic regions.

  14. The Plains of Venus

    NASA Astrophysics Data System (ADS)

    Sharpton, V. L.

    2013-12-01

    Volcanic plains units of various types comprise at least 80% of the surface of Venus. Though devoid of topographic splendor and, therefore often overlooked, these plains units house a spectacular array of volcanic, tectonic, and impact features. Here I propose that the plains hold the keys to understanding the resurfacing history of Venus and resolving the global stratigraphy debate. The quasi-random distribution of impact craters and the small number that have been conspicuously modified from the outside by plains-forming volcanism have led some to propose that Venus was catastrophically resurfaced around 725375 Ma with little volcanism since. Challenges, however, hinge on interpretations of certain morphological characteristics of impact craters: For instance, Venusian impact craters exhibit either radar dark (smooth) floor deposits or bright, blocky floors. Bright floor craters (BFC) are typically 100-400 m deeper than dark floor craters (DFC). Furthermore, all 58 impact craters with ephemeral bright ejecta rays and/or distal parabolic ejecta patterns have bright floor deposits. This suggests that BFCs are younger, on average, than DFCs. These observations suggest that DFCs could be partially filled with lava during plains emplacement and, therefore, are not strictly younger than the plains units as widely held. Because the DFC group comprises ~80% of the total crater population on Venus the recalculated emplacement age of the plains would be ~145 Ma if DFCs are indeed volcanically modified during plains formation. Improved image and topographic data are required to measure stratigraphic and morphometric relationships and resolve this issue. Plains units are also home to an abundant and diverse set of volcanic features including steep-sided domes, shield fields, isolated volcanoes, collapse features and lava channels, some of which extend for 1000s of kilometers. The inferred viscosity range of plains-forming lavas, therefore, is immense, ranging from the extremely fluid flows (i.e., channel formers), to viscous, possibly felsic lavas of steep-sided domes. Wrinkle ridges deform many plains units and this has been taken to indicate that these ridges essentially form an early stratigraphic marker that limits subsequent volcanism to a minimum. However, subtle backscatter variations within many ridged plains units suggest (but do not prove) that some plains volcanism continued well after local ridge deformation ended. Furthermore, many of volcanic sources show little, if any, indications of tectonic modification and detailed analyses have concluded that resurfacing rates could be similar to those on Earth. Improving constraints on the rates and styles of volcanism within the plains could lend valuable insights into the evolution of Venus's internal heat budget and the transition from thin-lid to thick-lid tectonic regimes. Improved spatial and radiometric resolution of radar images would greatly improve abilities to construct the complex local stratigraphy of ridged plains. Constraining the resurfacing history of Venus is central to understanding how Earth-sized planets evolve and whether or not their evolutionary pathways lead to habitability. This goal can only be adequately addressed if broad coverage is added to the implementation strategies of any future mapping missions to Venus.

  15. Radiocarbon evidence for a possible abyssal front near 3.1 km in the glacial equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Keigwin, L. D.; Lehman, S. J.

    2015-09-01

    We investigate the radiocarbon ventilation age in deep equatorial Pacific sediment cores using the difference in conventional 14C age between coexisting benthic and planktonic foraminifera, and integrate those results with similar data from around the North Pacific Ocean in a reconstruction for the last glaciation (15 to 25 conventional 14C ka). Most new data from both the Equatorial Pacific and the Emperor Seamounts in the northwestern Pacific come from maxima in abundance of benthic taxa because this strategy reduces the effect of bioturbation. Although there remains considerable scatter in the ventilation age estimates, on average, ventilation ages in the Equatorial Pacific were significantly greater below 3.2 km (∼ 3080 ± 1125 yrs, n = 15) than in the depth interval 1.9 to 3.0 km (∼ 1610 ± 250 yrs, n = 12). When compared to the average modern seawater Δ14C profile for the North Pacific, the Equatorial Pacific glacial data suggest an abyssal front located somewhere between 3.0 and 3.2 km modern water depth. Above that depth, the data may indicate slightly better ventilation than today, and below that depth, glacial Equatorial Pacific data appear to be as old as last glacial maximum (LGM) deep water ages reported for the deep southern Atlantic. This suggests that a glacial reservoir of aged waters extended throughout the circumpolar Southern Ocean and into the Equatorial Pacific. Renewed ventilation of such a large volume of aged (and, by corollary, carbon-rich) water would help to account for the rise in atmospheric pCO2 and the fall in Δ14C as the glaciation drew to a close.

  16. Composition of the abyssal infauna of the Kuril-Kamchatka area (NW Pacific) collected with a box corer

    NASA Astrophysics Data System (ADS)

    Fischer, Viola; Brandt, Angelika

    2015-01-01

    During the German-Russian KuramBio (Kuril-Kamchatka Biodiversity Studies) expedition with the RV Sonne from July to September 2012, a 0.25 m2 box corer was used to sample the benthic fauna of the Kuril-Kamchatka area. 23 cores were deployed at 12 stations, and in total 36,648 individuals could be identified from a combined surface area of 5.75 m2. Total faunal densities ranged from 1024 to 16,592 ind. m-2, respectively, for the macrofauna from 436 to 3520 ind. m-2. The fauna was dominated by Nematoda (65%), even though this group and other meiofaunal taxa were only partially retained by the 300 ?m screen that was used as the smallest screen for this study. The remaining part of the fauna was dominated by polychaetes (23%), followed by peracarid crustaceans (6%) and molluscs (3%). Most of the collected taxa occurred very patchily. Over 80% of the animals were extracted from the upper 2 centimeters of the sediment. Compared to other regions of the Pacific the density of the benthic fauna was unusually high. At the upper slope of the continental margin of the trench and at the southern part of the area the benthic fauna was most taxon rich. Station 3 from the continental slope of the trench was also most rich in terms of faunal density (total numbers of ind. m-2), followed by the station 11 and 12 from that the southernmost part of the abyss. Although the Kuril-Kamchatka area has been sampled on several expeditions during the last century, and some studies on the biomass of the benthic fauna have been published, this study offers the first quantitative community analysis of the benthic fauna in terms of abundance and taxon richness.

  17. Outwash plains and thermokarst on Mars.

    NASA Astrophysics Data System (ADS)

    Costard, F. M.; Kargel, J. S.

    1995-03-01

    The spatial distribution of different types of rampart craters on Mars suggests a hemispheric asymmetry in the distribution of ground ice. The northern plains, especially major topographic depressions near the terminations of outflow channels, have high percentages of rampart craters. Two of these basins, Acidalia and Utopia Planitiae, received extraordinarily large amounts of water and sediment from the Chryse and Elysium outflow channels. In both regions, the analysis of high-resolution Viking pictures (12 m/pixel) indicates a concentration of kilometer-scale depressions that are similar in size and form to thermokarstic features in Yakutia (Siberia) and parts of the arctic coastal plain of North America. Accordingly, we infer that (1) Utopia Planitia and Acidalia Planitia may contain thick, laterally continuous, ice-rich sedimentary deposits related to outflow channel-forming floods, and (2) these areas of Mars may have experienced thermokarstic processes similar to modern thermokarstic processes in some periglacial regions of Earth.

  18. Outwash plains and thermokarst on Mars

    USGS Publications Warehouse

    Costard, F.M.; Kargel, J.S.

    1995-01-01

    The spatial distribution of different types of rampart craters on Mars suggests a hemispheric asymmetry in the distribution of ground ice. The northern plains, especially major topographic depressions near the terminations of outflow channels, have high percentages of rampart craters. Two of these basins, Acidalia and Utopia Planitiae, received extraordinarily large amounts of water and sediment from the Chryse and Elysium outflow channels. In both regions, the analysis of high-resolution Viking pictures (12 m/pixel) indicates a concentration of kilometer-scale depressions that are similar in size and form to thermokarstic features in Yakutia (Siberia) and parts of the arctic coastal plain of North America. Accordingly, we infer that (1) Utopia Planitia and Acidalia Planitia may contain thick, laterally continuous, ice-rich sedimentary deposits related to outflow channel-forming floods, and (2) these areas of Mars may have experienced thermokarstic processes similar to modern thermokarstic processes in some periglacial regions of Earth.

  19. Hydrologic impacts of strip tillage for a Coastal Plain soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Strip till is a growing practice among many Coastal Plain cotton growers which can lead to reduced surface runoff and reduced transport of sediment and agrichemicals. This research examines nine years of rainfall-runoff data from a paired conventional till / strip till research site. Annual water ...

  20. Northern Plains 'Crater'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    10 December 2004 The lower left (southwest) corner of this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the location of a somewhat filled and buried meteor impact crater on the northern plains of Mars. The dark dots are boulders. A portion of a similar feature is seen in the upper right (northeast) corner of the image. This picture, showing landforms (including the odd mound north/northeast of the crater) that are typical of the martian northern lowland plains, was obtained as part of the MGS MOC effort to support the search for a landing site for the Phoenix Mars Scout lander. Phoenix will launch in 2007 and land on the northern plains in 2008. This image is located near 68.0oN, 227.4oW, and covers an area approximately 3 km (1.9 mi) wide. The scene is illuminated by sunlight from the lower left.

  1. Long-term maintenance and public exhibition of deep-sea hydrothermal fauna: The AbyssBox project

    NASA Astrophysics Data System (ADS)

    Shillito, Bruce; Ravaux, Juliette; Sarrazin, Jozée; Zbinden, Magali; Sarradin, Pierre-Marie; Barthelemy, Dominique

    2015-11-01

    The AbyssBox project aims to provide the first permanent public exhibition of live deep-sea hydrothermal fauna maintained at in situ pressure. AbyssBox is a pressurized aquarium designed to function permanently. Here we present details of the project after the public exhibition functioned for more than three years at Océanopolis aquarium in Brest, France. We also describe the AbyssBox pressure aquarium, and provide data and observations on vent shrimp (Mirocaris fortunata) and crabs (Segonzacia mesatlantica) that were sampled from 1700 m depth at the Lucky Strike vent field (Mid-Atlantic Ridge) during different cruises. While mortalities exceeded 50% during the first days following sampling, the remaining animals appeared to acclimate fairly well. Some crabs have now been kept for more than 2 years, and some shrimp have spent more than 3 years in captivity. Primarily designed for a public exhibition, the AbyssBox is already used for scientific purposes, since it provides one of the most effective tools for long-term rearing of deep-sea fauna. AbyssBox is a first step towards maintaining a variety of deep-sea fauna year-round at in situ pressure, which will serve both scientific and public interests.

  2. Coastal Plain Near Kalapana

    USGS Multimedia Gallery

    This composite image of the coastal plain near Kalapana combines a thermal image and a conventional photograph. The majority of lava is traveling through the lava tube system to the ocean and is not easily detectable in the image. Sometimes, however, the lava tubes do show a clear thermal sign...

  3. Plains Tectonics on Venus

    NASA Technical Reports Server (NTRS)

    Banerdt, W. B.; McGill, G. E.; Zuber, M. T.

    1996-01-01

    Tectonic deformation in the plains of Venus is pervasive, with virtually every area of the planet showing evidence for faulting or fracturing. This deformation can be classified into three general categories, defined by the intensity and areal extent of the surface deformation: distributed deformation, concentrated deformation, and local fracture patterns.

  4. Mountain-Plains Curriculum.

    ERIC Educational Resources Information Center

    Mountain-Plains Education and Economic Development Program, Inc., Glasgow AFB, MT.

    The document lists the Mountain-Plains curriculum by job title (where applicable), including support courses. The curriculum areas covered are mathematics skills, communication skills, office education, lodging services, food services, marketing and distribution, welding support, automotive, small engines, career guidance, World of Work, health

  5. Mountain-Plains Curriculum.

    ERIC Educational Resources Information Center

    Mountain-Plains Education and Economic Development Program, Inc., Glasgow AFB, MT.

    The document lists the Mountain-Plains curriculum by job title (where applicable), including support courses. The curriculum areas covered are mathematics skills, communication skills, office education, lodging services, food services, marketing and distribution, welding support, automotive, small engines, career guidance, World of Work, health…

  6. An abyssal mobilome: viruses, plasmids and vesicles from deep-sea hydrothermal vents.

    PubMed

    Lossouarn, Julien; Dupont, Samuel; Gorlas, Aurore; Mercier, Coraline; Bienvenu, Nadege; Marguet, Evelyne; Forterre, Patrick; Geslin, Claire

    2015-12-01

    Mobile genetic elements (MGEs) such as viruses, plasmids, vesicles, gene transfer agents (GTAs), transposons and transpovirions, which collectively represent the mobilome, interact with cellular organisms from all three domains of life, including those thriving in the most extreme environments. While efforts have been made to better understand deep-sea vent microbial ecology, our knowledge of the mobilome associated with prokaryotes inhabiting deep-sea hydrothermal vents remains limited. Here we focus on the abyssal mobilome by reviewing accumulating data on viruses, plasmids and vesicles associated with thermophilic and hyperthermophilic Bacteria and Archaea present in deep-sea hydrothermal vents. PMID:25911507

  7. New paedomorphic brachiopods from the abyssal zone of the north-eastern Pacific Ocean.

    PubMed

    Bitner, Maria Aleksandra; Melnik, Vjacheslav P; Zezina, Olga N

    2013-01-01

    New Recent very small but sexually mature brachiopods have been found at abyssal depths (4580-4850 m) in the Clarion- Clipperton Zone of the Pacific Ocean. They are characterized by simple (under-developed, juvenile) morphological features, which are interpreted here as paedomorphic, indicating the importance of heterochrony in the evolution of deep-sea brachiopods. We have described these brachiopods as representing two new genera and species, i.e. Oceanithyris juveniformis Bitner & Zezina (Family ?Dyscoliidae) and Simpliciforma profunda Bitner & Zezina (Superfamily Gwynioidea). PMID:24698918

  8. Seawater-derived rare earth element addition to abyssal peridotites during serpentinization

    NASA Astrophysics Data System (ADS)

    Frisby, Carl; Bizimis, Michael; Mallick, Soumen

    2016-04-01

    Serpentinized abyssal peridotites are evidence for active communication between the Earth's hydrosphere and the upper mantle, where exchange and retention of both major and trace elements occur. Bulk rock Nd isotopes in serpentinized abyssal peridotites imply interaction of seawater with the peridotite. In contrast, the Nd isotopes of clinopyroxenes from serpentinized abyssal peridotites retain their primary magmatic signature. It is currently unclear if, how and where seawater-derived Nd and other REE are being added or exchanged with the mantle peridotite minerals during serpentinization. To remedy this knowledge gap, we present in situ trace and major element concentrations, bulk rock and sequential leaching experiment trace element concentrations as well as Nd, Sr isotope data on refertilized and depleted serpentinized abyssal peridotites from the Southwest Indian Ridge. The secondary serpentine matrix and magnetite veins in these peridotites have elevated LREE concentrations, with variable negative Ce anomalies and large Rb, Sr, Pb and U enrichments that resemble seawater trace element patterns. The LREE concentrations in the serpentine phase are higher than those expected for the primary mantle mineralogy (olivine, orthopyroxene) based on data from relic clinopyroxenes and equilibrium partition coefficients. These data are consistent with seawater-derived REE addition to the peridotite during serpentinization. The bulk rocks have more radiogenic Sr and more unradiogenic Nd isotopes than their clinopyroxene (up to 8 εNd units lower than clinopyroxene). Sequential leaching experiments designed to mobilize secondary carbonates and Fe-oxides show even more unradiogenic Nd isotope ratios in the leachates than the bulk rock and clinopyroxene, approaching seawater compositions (up to 15 εNd units lower than clinopyroxene). Mass balance calculations using trace elements or Nd isotopes suggest that up to 30% of the bulk peridotite Nd budget is of seawater origin and was added to the peridotite, as opposed to being exchanged. These data allows for more accurate constraints of the water/rock mass exchange ratios during serpentinization in these rocks (~ 1000 to 17,000) that are at least an order of magnitude lower than using typical mantle and seawater endmembers. These data provide strong evidence that serpentinization may also be a sink for the light REE, with implications for the refertilization of the peridotite during serpentinization, and the cycling of these elements through the subduction system and into the upper mantle.

  9. Flood hydrology and methylmercury availability in Coastal Plain rivers

    USGS Publications Warehouse

    Bradley, Paul M.; Journey, Celeste A.; Chapelle, Francis H.; Lowery, Mark A.; Conrads, Paul A.

    2010-01-01

    Mercury (Hg) burdens in top-predator fish differ substantially between adjacent South Carolina Coastal Plain river basins with similar wetlands coverage. In the Congaree River, floodwaters frequently originate in the Blue Ridge and Piedmont regions, where wetlands coverage and surface water dissolved methylmercury (MeHg) concentrations are low. Piedmont-driven flood events can lead to downward hydraulic gradients in the Coastal Plain riparian wetland margins, inhibiting MeHg transport from wetland sediments, and decreasing MeHg availability in the Congaree River habitat. In the adjacent Edisto River basin, floodwaters originate only within Coastal Plain sediments, maintaining upward hydraulic gradients even during flood events, promoting MeHg transport to the water column, and enhancing MeHg availability in the Edisto River habitat. These results indicate that flood hydrodynamics contribute to the variability in Hg vulnerability between Coastal Plain rivers and that comprehensive regional assessment of the relationship between flood hydrodynamics and Hg risk in Coastal Plain streams is warranted.

  10. The absence of sharks from abyssal regions of the world's oceans

    PubMed Central

    Priede, Imants G; Froese, Rainer; Bailey, David M; Bergstad, Odd Aksel; Collins, Martin A; Dyb, Jan Erik; Henriques, Camila; Jones, Emma G; King, Nicola

    2006-01-01

    The oceanic abyss (depths greater than 3000?m), one of the largest environments on the planet, is characterized by absence of solar light, high pressures and remoteness from surface food supply necessitating special molecular, physiological, behavioural and ecological adaptations of organisms that live there. Sampling by trawl, baited hooks and cameras we show that the Chondrichthyes (sharks, rays and chimaeras) are absent from, or very rare in this region. Analysis of a global data set shows a trend of rapid disappearance of chondrichthyan species with depth when compared with bony fishes. Sharks, apparently well adapted to life at high pressures are conspicuous on slopes down to 2000?m including scavenging at food falls such as dead whales. We propose that they are excluded from the abyss by high-energy demand, including an oil-rich liver for buoyancy, which cannot be sustained in extreme oligotrophic conditions. Sharks are apparently confined to ca 30% of the total ocean and distribution of many species is fragmented around sea mounts, ocean ridges and ocean margins. All populations are therefore within reach of human fisheries, and there is no hidden reserve of chondrichthyan biomass or biodiversity in the deep sea. Sharks may be more vulnerable to over-exploitation than previously thought. PMID:16777734

  11. Evidence for deep-water deposition of abyssal Mediterranean evaporites during the Messinian salinity crisis

    NASA Astrophysics Data System (ADS)

    Christeleit, Elizabeth C.; Brandon, Mark T.; Zhuang, Guangsheng

    2015-10-01

    Scientific drilling of the abyssal evaporites beneath the deepest parts of the Mediterranean basin gave rise to the idea that the Mediterranean sea completely evaporated at the end of the Messinian. Herein, we show, using new organic geochemical data, that those evaporites were deposited beneath a deep-water saline basin, not in a subaerial saltpan, as originally proposed. Abundant fossil organic lipids were extracted from evaporites in Mediterranean Deep Sea Drilling Project cores. The archaeal lipid distribution and new analyses, using the ACE salinity proxy and TEX86 temperature proxy, indicate that surface waters at the time of evaporite deposition had normal marine salinity, ranging from ∼26 to 34 practical salinity units, and temperatures of 25-28 °C. These conditions require a deep-water setting, with a mixed layer with normal marine salinity and an underlying brine layer at gypsum and halite saturation. After correction for isostatic rebound, our results indicate maximum drawdown of ∼2000 m and ∼2900 m relative to modern sea level in the western and eastern Mediterranean basins, respectively. Our results are consistent with previously proposed scenarios for sea level drawdown based on both subaerial and submarine incision and backfilling of the Rhone and Nile rivers, which require Messinian sea level drops of ∼1300 m and ∼200 m, respectively. This study provides new evidence for an old debate and also demonstrates the importance of further scientific drilling and sampling of deeper part of the abyssal Messinian units.

  12. "First" abyssal record of Stenosemus exaratus (G.O.Sars, 1878) (Mollusca, Polyplacophora) intheNorth-Atlantic Ocean.

    PubMed

    Allcock, Louise; Schwabe, Enrico

    2013-01-01

    The first proven abyssal record of Stenosemus exaratus (G.O. Sars, 1878) is presented on the basis of an ROV study in the Irish Sea. For the first time in situ images of the species and data on the environmental parameters are provided. PMID:23794838

  13. On the morphodynamics of a channel on a small proglacial braid plain (Fagge River, tztal Alps, Austria)

    NASA Astrophysics Data System (ADS)

    Schuchardt, Anne; Morche, David; Baewert, Henning; Dubberke, Karolin

    2015-04-01

    Braid plains are important sediment stores in high mountain regions, particularly in glacier forefields of Alpine glaciers. Proglacial braid plains receive sediment input from glacial meltwater and paraglacial sediment sources. The channel morphodynamics on a braid plains are strongly related to the sediment transport and flow regime of the proglacial river. This study deals with channel morphodynamics on a small proglacial braid plain in the European Alps. The Fagge River originates at the glacier Gepatschferner. In 1953 the glacier covered the whole 300 m long braid plain. Geophysical surveys on the glacier tongue carried out in the 1950s showed the existence of a subglacial basin filled with sediments. After glacier "retreat" a proglacial braid plain developed there. In 2014, the glacier snout was 1250 m upstream of the braid plain (mean annual "retreat" of 25 m/year). This study focusses on two different time scales. Decadal channel planform changes were assessed by remote sensing approaches. Ten orthophoto sequences (1953-2014) were analysed in a GIS. Those channel planform changes were mapped and different braiding indices were calculated. The recent channel bed changes were investigated by cross sectional surveys and particle counts in 2013 as well as terrestrial laserscanning campaigns in June 2012 and September 2013. This study is part of the DFG/FWF funded interdisciplinary research project PROSA (High-resolution measurements of morphodynamics in rapidly changing PROglacial Systems of the Alps).

  14. Implications of spinel compositions for the petrotectonic history of abyssal peridotite from Southwest Indian Ridge (SWIR)

    NASA Astrophysics Data System (ADS)

    Chen, T.; Jin, Z.; Wang, Y.; Tao, C.

    2012-12-01

    Abyssal peridotites generate at mid-ocean ridges. Lherzolite and harzburgite are the main rock types of peridotites in the uppermost mantle. The lherzolite subtype, less depleted and less common in ophiolites, characterizes mantle diapirs and slow-spreading ridges. Along the Earth's mid-ocean ridges, abyssal peridotites undergo hydration reactions to become serpentinite minerals, especially in slow to ultraslow spreading mid-ocean ridges. Spinel is common in small quantities in peridotites, and its compositions have often been used as petrogenetic indicators [1]. The Southwest Indian Ridge (SWIR) is one of the two ultraslow spreading ridges in the world. The studied serpentinized peridotite sample was collected by the 21st Voyage of the Chinese oceanic research ship Dayang Yihao (aka Ocean No. 1) from a hydrothermal field (63.5E, 28.0S, and 3660 m deep) in SWIR. The studied spinels in serpentinized lherzolite have four zones with different compositions: relic, unaltered core is magmatic Al-spinels; micro- to nano- sized ferrichromite zoned particles; narrow and discontinuous magnetite rim; and chlorite aureoles. The values Cr# of the primary Al-spinels indicate the range of melting for abyssal peridotites from SWIR extends from ~4% to ~7% [2]. The alteration rims of ferrichromite have a chemical composition characterized by Fe enrichment and Cr# increase indicating chromite altered under greenschist-amphibolite facies. Magnetites formed in syn- and post- serpentinization. Chlorite (clinochlore) formed at the boundary and crack of spinel indicating it had undergone with low-temperature MgO- and SiO2-rich hydrothermal fluids [3]. It suggests that serpentinized lherzolite from SWIR had undergone poly-stage hydration reactions with a wide range of temperature. Acknowledgments: EMPA experiment was carried out by Xihao Zhu and Shu Zheng in The Second Institute of Oceanography and China University of Geosciences, respectively. The work was supported by NSFC. References [1] Dick, H.J.B., et al., Contrib Mineral Petr., 86:54, 1984. [2] Hellebrand et al., Nature, 410: 677, 2001. [3] Hamdy, M.M. , et al., JGMR, 3(9): 232, 2011.

  15. Rich and rare—First insights into species diversity and abundance of Antarctic abyssal Gastropoda (Mollusca)

    NASA Astrophysics Data System (ADS)

    Schwabe, Enrico; Michael Bohn, Jens; Engl, Winfried; Linse, Katrin; Schrödl, Michael

    2007-08-01

    The abyssal depths of the polar oceans are thought to be low in diversity compared with the shallower polar shelves and temperate and tropical deep-sea basins. Our recent study on the gastropod fauna of the deep Southern Ocean gives evidence of the existence of a rich gastropod assemblage at abyssal depths. During the ANDEEP I and II expeditions to the southern Drake Passage, Northwestern Weddell Sea, and South Sandwich Trench, gastropods were collected by bottom and Agassiz trawls, epibenthic sledge, and multicorer, at 40 stations in depths between 127 and 5194 m. On the whole, 473 specimens, corresponding to 93 species of 36 families, were obtained. Of those, 414 specimens were caught below 750 m depth and refer to 84 (90%) benthic species of 32 (89%) families. Most families were represented by a single species only. The numerically dominant families were Skeneidae and Buccinidae (with 10 and 11 species, respectively), Eulimidae and Trochidae (with 9 species each), and Turridae (6 species). Thirty-Seven benthic deep-sea species (44%) were represented by a single specimen, and another 20 species (24%) were found at a single station, suggesting that more than two thirds of Antarctic deep-sea gastropod species are very rare or have a very scattered distribution. Of the 27 species occurring at two or more deep-sea stations, 14 were collected with different gear. Approximately half of the deep-water species are new to science or have been recently described. The present investigation increases the total number of recorded benthic Antarctic deep-sea gastropods (below 750 m) from 115 to 177. The previously known depth ranges have been extended, often considerably, for 31 species. The collected deep-sea gastropods comprise both eurybathic shelf species (29%) and apparently true deep-sea species (58%); some of the latter may belong to a so far unknown Antarctic abyssal fauna. Geographical ranges of the collected Antarctic benthic deep-sea gastropod species appear limited, and all these 84 species seem endemic to Antarctica south of the Polar Front. Comparing diversity and abundances based on epibenthic sledge samples, there is no clear relationship between Antarctic deep-sea gastropod abundance and species richness with depth. However, both Antarctic and adjacent deep-sea areas are still far from being adequately sampled to allow more comprehensive conclusions.

  16. Engineering concepts for the placement of wastes on the abyssal seafloor

    NASA Astrophysics Data System (ADS)

    Valent, Philip J.; Palowitch, Andrew W.; Young, David K.

    1998-05-01

    The Naval Research Laboratory (NRL), with industry and academic participation, has completed a study of the concept of isolating industrial wastes (i.e., sewage sludge, fly ash from municipal incinerators, and dredged material) on the abyssal seafloor. This paper presents results of the technical and economic assessment of this waste management concept. The results of the environmental impacts portion of the study are presented in a companion paper. The technical assessment began with identification of 128 patents addressing waste disposal in the ocean. From these 128 patents, five methods for transporting wastes through the water column and emplacing wastes within an easily monitored area on the abyssal seafloor were synthesized for technical assessment. In one method waste is lowered to the seafloor in a bucket of 190 m 3. In a second method waste is pumped down to the seafloor in pipes, 1.37 m in diameter and 6100 m in length. In a third method waste is free-fallen from the ocean surface in 380-m 3 geosynthetic fabric containers (GFCs). In the fourth and fifth methods, waste is carried to near the seafloor in GFCs transported in (a) a 20,000 metric ton displacement (loaded), unpowered, unmanned submersible glider, or (b) a 2085 metric ton displacement (loaded) disk-shaped transporter traversing to and from the seafloor much like an untethered elevator. In the last two methods the transporter releases the GFCs to free-fall the last few hundred meters to the seafloor. Two reliability analyses, a Fault Tree Analysis (FTA), and a Failure Modes, Effects, and Criticality Analysis (FMECA), showed that the free-fall GFC method posed the least overall relative risk, provided that fabric container and transporter designs eliminate the potential for tearing of the containers on release from the surface transporter. Of the five methods, the three GFC methods were shown to offer cost-effective waste management options when compared with present-day waste management techniques in higher-priced areas, such as the New York-New Jersey area. In conclusion, the abyssal seafloor waste isolation concept is technically feasible and cost-effective for many waste sources.

  17. Controls of sedimentary supply and gravity driven deformation on the eastern Niger delta (Plio-Pleistocene) from the shoreline to the deep sea plain

    NASA Astrophysics Data System (ADS)

    Robin, Cécile; Guillocheau, François; Rouby, Delphine; Nalpas, Thierry; Jermannaud, Paul; Raillard, Stéphane

    2013-04-01

    We studied the evolution of the gravity flow sedimentary within a large shelf-edge delta (Eastern Niger delta) over the last 2,5Myr taking into account the influence of the contemporaneous gravity driven deformation and sedimentary supply. To do this, we mapped (i) the shoreline geometry and (ii) the associated turbiditic systems for 9 intervals using a classification based on three morphological end-members: erosive, constructive and depositional modes. We characterized the depositional profile of the passive margin delta from the littoral domain to the abyssal plain and its spatial and temporal variability. We showed that, at the scale of the delta, the depositional profile varied from (i) a shelf edge delta profile with a slope break at the location of the shoreline during progradation to (ii) a ramp profile characteristic of a mid-shelf delta during retrogradation. Thus, during a stratigraphic cycle, the delta front evolved from a prograding slope break during the development of the HST, to steepening clinoforms during the development of the LST that progressively flattened out during the TST to reach a ramp profile at the MFS. The turbiditic systems (including MTC) initiate near the shoreline, at the toe of the delta front. Also, they form preferentially down slope synthetic faults or within antithetic fault relays. They are initially erosive, becoming constructive further down slope and eventually depositional. They may become erosive again as they cut through the compressional structures. We showed that the stratigraphic state (progradation/retrogradation) controls the amount of sediment reaching the platform and strongly impacts the density of gravity flow sedimentary systems (low density during progradation and high density during progradation). On the other hand, the gravity driven deformation controls the slope of the sea-floor and, in doing so, their morphology (erosive/constructive/depositional). Within this framework, lateral migrations of the delta impact both the spatial distribution of gravity driven deformation and gravity flow sedimentary systems. We think these results may be extrapolated to many shelf-edge deltas affected by gravity-driven deformation. Also, these results provide us with a tool to predict the spatial distribution of the domains in erosion/transit/sedimentation of the gravity flow sedimentary systems as well as their expected lithologies.

  18. Ice in the northern plains: Relic of a frozen ocean?

    NASA Technical Reports Server (NTRS)

    Lucchitta, B. K.

    1993-01-01

    Viking images revealed many features in the northern plains and along their boundary that early investigators believed to be formed by ice-related processes. The features are possible pingos, pseudocraters, table mountains and moberg ridges, thermokarst depressions, moraines, patterned ground, and lobate aprons that suggest viscous flow such as that of ice or rock glaciers. More recently, many of these features were reinterpreted as related to sedimentation in hypothetical former polar lakes, oceans, or alluvial plains or as shoreline features of associated water bodies. Some evidence that points toward the existence of former bodies of standing water in the northern plains, but is also consistent with the idea that these bodies were ice covered or completely frozen is reviewed.

  19. Wet coastal plain tundra

    SciTech Connect

    Myers, J.P.; McCaffery, B.J.; Pitelka, F.A.

    1980-01-01

    This years's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSW of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 43'W; Barrow Quadrangle, USGS, reflect an increase in breeding species of 31% over the 5-year average, while breeding density was up 22%. Ten species increased and only 4 decreased. There was a total of 17 species; 61.5 territorial males or females (171/km/sup 2/, 69/100 acres).

  20. Regional variation of total microbial biomass in sediments of the deep Arabian Sea

    NASA Astrophysics Data System (ADS)

    Boetius, Antje; Lochte, Karin

    2000-01-01

    Eight different sites from 2300 to 4420 m water depth in the Arabian Sea were sampled for a biochemical quantification of phospholipid concentrations in the sediments. This method serves as a measure of microbial biomass in marine sediments comprising all small-sized organisms, including bacteria, fungi, protozoa and metazoa. Phospholipid concentrations can be converted to carbon units as an estimate of total microbial biomass in the sediments. The average phospholipid concentrations in the surface sediments (0-1 cm) of the 4 abyssal sites ranged from 7 nmol cm -3 at the southern site (SAST, 10N 65E, 4425 m) to 29 nmol cm -3 at the western site (WAST, 16N 60E, 4045 m). The high values detected at the abyssal station WAST exceeded those in the literature for other abyssal sites and were comparable to values from the upper continental slope of the NE-Atlantic and the Arctic. At the four continental slope sites in the Arabian Sea, average phospholipid concentrations ranged from 9 to 53 nmol cm -3 with the maximum values at stations A (2314 m) and D (3142 m) close to the Omani coast. Records of particulate organic carbon flux to the deep sea are available for four of the investigated locations, allowing a test of the hypothesis that the standing stock of benthic microorganisms in the deep sea is controlled by substrate availability, i.e. particle sedimentation. Total microbial biomass in the surface sediments of the Arabian Sea was positively correlated with sedimentation rates, consistent with previous studies of other oceans. The use of the measurement of phospholipid concentrations as a proxy for input of particulate organic matter is discussed.

  1. Geohydrologic framework of the coastal plain aquifers of South Carolina

    USGS Publications Warehouse

    Aucott, Walter R.; Davis, Marvin E.; Speiran, Gary K.

    1987-01-01

    The U.S. Geological Survey is conducting a series of investigations of aquifers throughout the United States as a part of the RASA (Regional Aquifer System Analysis) program. These investigations provide a comprehensive regional understanding of groundwater resources throughout the Nation. The Coastal Plain aquifers in South Carolina are being studied as a part of this program. An important part of a description of the groundwater resources is the development of a geohydrologic framework. Such a framework delineates the aquifers through which groundwater flows and the confining units which retard the flow of groundwater between aquifers. The Coastal Plain of South Carolina is underlain by a wedge of sediments that thickens from its inner margin, the Fall Line, to the coast and consists of sand, silt, clay, and limestone of Late Cretaceous to Holocene age. These sediments are underlain by pre-Cretaceous rocks consisting of consolidated sedimentary rocks of Triassic age and a complex of metamorphic and igneous rocks similar to those found near the surface in the Piedmont province of the State. The geohydrologic framework that divides the sediments of the South Carolina Coastal Plain into the Coastal Plain aquifer system is delineated by eleven geohydrologic sections and four maps showing the configuration of the top or base of individual aquifers. Although flow within the Coastal Plain aquifer system is three dimensional, simplifying the system by dividing it into a framework of discrete hydrologic units can aid significantly in understanding the hydrology of the system. This framework is the basis for the aquifers used in potentiometric mapping, transmissivity mapping, geochemical analysis, and groundwater flow modeling for the South Carolina RASA program. (Lantz-PTT)

  2. Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean.

    PubMed

    Smith, Kenneth L; Ruhl, Henry A; Kahru, Mati; Huffard, Christine L; Sherman, Alana D

    2013-12-01

    The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (~4,000-m depth). Here we show that previous findings of food deficits are now punctuated by large episodic surpluses of particulate organic carbon reaching the sea floor, which meet utilization. Changing surface ocean conditions are translated to the deep ocean, where decadal peaks in supply, remineralization, and sequestration of organic carbon have broad implications for global carbon budget projections. PMID:24218565

  3. Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean

    PubMed Central

    Smith, Kenneth L.; Ruhl, Henry A.; Kahru, Mati; Huffard, Christine L.; Sherman, Alana D.

    2013-01-01

    The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (∼4,000-m depth). Here we show that previous findings of food deficits are now punctuated by large episodic surpluses of particulate organic carbon reaching the sea floor, which meet utilization. Changing surface ocean conditions are translated to the deep ocean, where decadal peaks in supply, remineralization, and sequestration of organic carbon have broad implications for global carbon budget projections. PMID:24218565

  4. Northern Plains Patterns

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-513, 14 October 2003

    Patterns are common on the northern plains of Mars. Like their terrestrial counterparts in places like Siberia, Alaska, and northern Canada, patterned ground on Mars might be an indicator of the presence of ground ice. Whether it is true that the patterns on Mars are related to ground ice and whether the ice is still present beneath the martian surface are unknown. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows an example of patterned ground on the martian northern plains near 72.4oN, 252.6oW. The dark dots and lines are low mounds and chains of mounds. The circular feature near the center of the image is the location of a buried meteor impact crater; its presence today is marked only by the dark boulders on its rim and ejecta blanket that have managed to remain uncovered at the martian surface. The area shown is 3 km (1.9 mi) wide and illuminated by sunlight from the lower left.

  5. Particle export from the euphotic zone: Estimates using a novel drifting sediment trap, 234Th and new production

    NASA Astrophysics Data System (ADS)

    Lampitt, R. S.; Boorman, B.; Brown, L.; Lucas, M.; Salter, I.; Sanders, R.; Saw, K.; Seeyave, S.; Thomalla, S. J.; Turnewitsch, R.

    2008-11-01

    We describe the first results obtained using a novel free-drifting neutrally buoyant sediment trap called PELAGRA (Particle Export measurement using a LAGRAngian trap). The trap uses an APEX float (Autonomous Profiling EXplorer) to maintain its location at a predetermined depth or density horizon and is designed to be deployed in the depth range 100-600 m for periods of up to a week. PELAGRA was deployed into a well characterised region of the Northeast (NE) Atlantic over the Porcupine Abyssal Plain (PAP) during the summers of 2003, 2004, 2005 and 2006 in post-bloom conditions. In parallel, measurements were made of total and new primary production and estimates of particle export based on 234Th deficits in the upper water column. Samples of sinking material from PELAGRA were recovered almost uncontaminated by "swimmers". The material collected differed from that obtained using water bottles and an in situ filtration system and this indicated selective export of centric diatoms. Fluxes of 234Th into the traps were less than that calculated from the deficit of this isotope in the upper water column. It is concluded that this reflects export events that had occurred prior to these deployments. Fluxes of organic carbon into the PELAGRA traps were similar to those expected from measurements of new production in the upper mixed layer. During 2006, simultaneous PELAGRA deployments at depths of 150 and 250 m provided a direct measurement of the decrease in flux with depth. This decrease was substantially more than that predicted by the often-used "Martin equation" and yielded a " b value" of 1.7. Using this value in the NE Atlantic about 14% of the total production reaches a depth of 150 m during the post-bloom period under nutrient limitation.

  6. Organic matter budget in the Southeast Atlantic continental margin close to the Congo Canyon: In situ measurements of sediment oxygen consumption

    NASA Astrophysics Data System (ADS)

    Rabouille, C.; Caprais, J.-C.; Lansard, B.; Crassous, P.; Dedieu, K.; Reyss, J. L.; Khripounoff, A.

    2009-12-01

    A study of organic carbon mineralization from the Congo continental shelf to the abyssal plain through the Congo submarine channel and Angola Margin was undertaken using in situ measurements of sediment oxygen demand as a tracer of benthic carbon recycling. Two measurement techniques were coupled on a single autonomous platform: in situ benthic chambers and microelectrodes, which provided total and diffusive oxygen uptake as well as oxygen microdistributions in porewaters. In addition, sediment trap fluxes, sediment composition (Org-C, Tot-N, CaCO 3, porosity) and radionuclide profiles provided measurements of, respectively input fluxes and burial rate of organic and inorganic compounds. The in situ results show that the oxygen consumption on this margin close to the Congo River is high with values of total oxygen uptake (TOU) of 40.6, 3.60.5 mmol m -2 d -1 at 1300 and 3100 m depth, respectively, and between 1.90.3 and 2.40.2 mmol m -2 d -1 at 4000 m depth. Diffusive oxygen uptakes (DOU) were 2.81.1, 2.30.8, 0.80.3 and 1.20.1 mmol m -2 d -1, respectively at the same depths. The magnitude of the oxygen demands on the slope is correlated with water depth but is not correlated with the proximity of the submarine channel-levee system, which indicates that cross-slope transport processes are active over the entire margin. Comparison of the vertical flux of organic carbon with its mineralization and burial reveal that this lateral input is very important since the sum of recycling and burial in the sediments is 5-8 times larger than the vertical flux recorded in traps. Transfer of material from the Congo River occurs through turbidity currents channelled in the Congo valley, which are subsequently deposited in the Lobe zone in the Congo fan below 4800 m. Ship board measurements of oxygen profiles indicate large mineralization rates of organic carbon in this zone, which agrees with the high organic carbon content (3%) and the large sedimentation rate (19 mm y -1) found on this site. The Lobe region could receive as high as 19 mol C m -2 y -1, 1/3 being mineralized and 2/3 being buried and could constitute the largest depocenter of organic carbon in the South Atlantic.

  7. Quails on the High Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Southern High Plains of Texas are on the southern end of the North American Great Plains and occupy about 20 million acres. The climate is semi-arid, with long-term (90-year) average annual precipitation at Lubbock of 18.9 inches. Two species of quail, northern bobwhite (Colinus virginianus) and...

  8. Denitrification in Agriculturally Influenced Coastal Plain Streams

    NASA Astrophysics Data System (ADS)

    McMillan, S. K.; Ensign, S. H.; Thompson, S. P.; Paerl, H. W.; Piehler, M. F.

    2005-05-01

    Agricultural runoff from coastal plain watersheds contributes nitrogen to downstream estuarine and coastal waters. Nitrogen fuels eutrophication, which has resulted in increased algal biomass, hypoxia, and fish kills in the Neuse River Estuary, North Carolina. Denitrification is the sole mechanism of permanent nitrogen removal along the riverine to estuarine continuum, but its contribution to nitrogen attenuation in this system is not well understood. Denitrification rates measured seasonally in stream bed sediments were variable but showed a distinct spring maximum, which was likely associated with rising temperatures and added nitrogen from fertilizer application (0-150 umol N m-2 h-1 during the summer, fall and winter and 150-300 umol N m-2 h-1 in the spring). Reach-scale uptake experiments showed the potential for 65-98% retention of the watershed DIN load in ephemeral drainage ditches. Results indicated that nitrogen retention was high despite low hyporheic exchange that is typically associated with channelized streams with low gradients, straight channels and homogenous stream bed sediments. Comparison of direct denitrification rate measurements to reach scale uptake rates and a watershed mass balance showed considerable potential for nitrogen removal via denitrification in agricultural stream sediments.

  9. Sources of fine-grained sediment in the Linganore Creek watershed, Frederick and Carroll Counties, Maryland, 2008-10

    USGS Publications Warehouse

    Gellis, Allen C.; Noe, Gregory B.; Clune, John W.; Myers, Michael K.; Hupp, Cliff R.; Schenk, Edward R.; Schwarz, Gregory E.

    2015-01-01

    Management implications of this study indicate that both agriculture and streambanks are important sources of sediment in Linganore Creek where the delivery of agriculture sediment was 4 percent and the delivery of streambank sediment was 44 percent. Fourth order streambanks, on average, had the highest rates of bank erosion. Combining the sediment fingerprinting and sediment budget results indicates that 96 percent of the eroded fine-grained sediment from agriculture went into storage. Flood plains and ponds are effective storage sites of sediment in the Linganore Creek watershed. Flood plains stored 8 percent of all eroded sediment with 4th and 5th order flood plains, on average, storing the most sediment. Small ponds in the Linganore Creek watershed, which drained 16 percent of the total watershed area, stored 15 percent of all eroded sediment. Channel beds were relatively stable with the greatest erosion generally occurring in 4th and 5th order streams.

  10. Holocene delta plain development in the Song Hong (Red River) delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Funabiki, Ayako; Haruyama, Shigeko; Quy, Nguyen Van; Hai, Pham Van; Thai, Dinh Hung

    2007-05-01

    Holocene delta plain development was investigated based on three sediment cores analyzed in detail from the Song Hong (Red River) delta plain in Vietnam. Two cores (DA and PD) from the western delta plain showed both the landward limit of the transgressive estuarine system in the valley incised during the last glacial maximum and floodplain evolution since the middle Holocene. On the other hand, a core (TL) from the eastern delta plain revealed a Pleistocene terrace buried under the deltaic sediments and a slow accumulation rate compared with that in the west. At 8 cal ky BP, the shoreline migrated very close to the present Hanoi city area, and the sedimentary environment changed to tidal flat or salt marsh. Hanoi city marks the northern limit of shoreline transgression. The mangrove swamp expanded from 8 to 5 cal ky BP to the landward limit of the delta plain. Subsequently, the shoreline migrated seaward as a result of delta progradation and sea-level lowering. From 5 cal ky BP, the emerged area evolved into a floodplain and natural levees formed along the abandoned river channels on the western delta plain, but at 2 cal ky, archeological sites indicate that the Holocene terrace in the eastern delta plain was still inundated.

  11. Two depositional models for Pliocene coastal plain fluvial systems, Goliad Formation, south Texas Gulf Coastal plain

    SciTech Connect

    Hoel, H.D.; Galloway, W.E.

    1983-03-01

    The Goliad Formation consists of four depositional systems-the Realitos and Mathis bed-load fluvial systems in the southwest and the Cuero and Eagle Lake mixed-load fluvial systems in the northeast. Five facies are recognized in the Realitos and Mathis bed-load fluvial systems: (1) primary channel-fill facies, (2) chaotic flood channel-fill facies, (3) complex splay facies, (4) flood plain facies, and (5) playa facies. A model for Realitos-Mathis depositional environments shows arid-climate braided stream complexes with extremely coarse sediment load, highly variable discharge, and marked channel instability. Broad, shallow, straight to slightly sinuous primary channels were flanked by wide flood channels. Flood channels passed laterally into broad, low-relief flood plains. Small playas occupied topographic lows near large channel axes. Three facies are recognized in the Cuero and Eagle Lake mixed-load fluvial systems: (1) channel-fill facies, (2) crevasse splay facies, and (3) flood plain facies. A model for Cuero-Eagle Lake depositional environments shows coarse-grained meander belts in a semi-arid climate. Slightly to moderately sinuous meandering streams were flanked by low, poorly developed natural levees. Crevasse splays were common, but tended to be broad and ill-defined. Extensive, low-relief flood plains occupied interaxial areas. The model proposed for the Realitos and Mathis fluvial systems may aid in recognition of analogous ancient depositional systems. In addition, since facies characteristics exercise broad controls on Goliad uranium mineralization, the proposed depositional models aid in defining target zones for Goliad uranium exploration.

  12. Alluvial plain dynamics in the southern Amazonian foreland basin

    NASA Astrophysics Data System (ADS)

    Lombardo, U.

    2015-10-01

    Alluvial plains are formed with sediments that rivers deposit on the adjacent flood-basin, mainly through crevasse splays and avulsions. These result from a combination of processes, some of which push the river towards the crevasse threshold, while others act as triggers. Based on the floodplain sedimentation patterns of large rivers in the southern Amazonian foreland basin, it has been suggested that alluvial plain sediment accumulation is primarily the result of river crevasse splays triggered by above normal precipitation events due to La Nia. However, more than 90 % of the Amazonian river network is made of small rivers and it is unknown whether small river floodplain sedimentation is influenced by the ENSO cycle as well. Using Landsat images from 1984 to 2014, here I analyse the behaviour of all the twelve tributaries of the Ro Mamor with a catchment in the Andes. I show that these are very active rivers and that the frequency of crevasses is not linked to ENSO activity. I found that most of the sediments eroded from the Andes by the tributaries of the Mamor are deposited in the alluvial plains, before reaching the parent river. The mid- to late Holocene paleo-channels of these rivers are located tens of kilometres further away from the Andes than the modern crevasses. I conclude that the frequency of crevasses is controlled by intrabasinal processes that act on a year to decade time scale, while the average location of the crevasses is controlled by climatic or neo-tectonic events that act on a millennial scale. Finally, I discuss the implications of river dynamics on rural livelihoods and biodiversity in the Llanos de Moxos, a seasonally flooded savannah covering most of the southern Amazonian foreland basin and the world's largest RAMSAR site.

  13. Investigating the effects of abyssal peridotite alteration on Si, Mg and Zn isotopes

    NASA Astrophysics Data System (ADS)

    Savage, P. S.; Wimpenny, J.; Harvey, J.; Yin, Q.; Moynier, F.

    2013-12-01

    Around 1/3 of Earth's divergent ridge system is now classified as "slow" spreading [1], exposing ultramafic rocks (abyssal peridotites) at the seafloor. Such material is often highly altered by serpentinisation and steatisation (talc formation). It is crucial to understand such processes in order to access the original composition of the mantle, and to quantify any impact on ocean composition. Here we examine the effect of both serpentinisation and steatisation on Si, Mg and Zn isotopes. Hydrothermal alteration and seafloor weathering are both sources of oceanic Si [2] and weathering of abyssal peridotites is a source of oceanic Mg [3]; hence isotopic fractionation as a result of seafloor alteration could affect oceanic Si and Mg isotope composition. Zinc isotopes can provide complimentary information; the magnitude and direction of fractionation is highly dependent on complexing ligand [4] and can provide compositional information on the fluids driving metasomatism. For this study, two cores from the well-characterised abyssal peridotites recovered on ODP Leg 209 were examined [5]. Hole 1274a peridotites exhibit variable serpentinisation at ~200C, whereas samples from Hole 1268a have been comprehensively serpentinised and then subsequently steatised to talc facies at ~350C, by a low Mg/Si, low pH fluid. The Si, Mg and Zn isotope compositions of 1274a samples are extremely homogeneous, identical to that of pristine mantle rocks (BSE) i.e., serpentinisation at this locality was predominantly isochemical [5]. In contrast, samples from 1268a show greater isotopic variability. In all samples, Mg is enriched in the heavier isotopes relative to BSE, consistent with formation of isotopically heavy secondary phases [6]. For Si, serpentinised samples are slightly enriched in the lighter isotopes compared to BSE, again consistent with the behaviour of Si during formation of secondary phases [7]. Within the steatised samples, some exhibit enrichments in the lighter Si isotopes (similar to the serpentinites), however, some are isotopically heavy, relative to BSE. Such samples were found to have abundant chlorite, whose formation requires fluid with high Al activity, likely sourced from late-emplaced gabbroic dykes. The Zn of all 1268a samples are enriched in the lighter isotopes, implying the involvement of isotopically light sulfide precipitation during metasomatism [4]. The consistently heavy Mg isotope data suggest that seafloor alteration of peridotites can input an isotopically light Mg-bearing fluid to the ocean. Fluid composition is less easy to determine from the more complex behaviour observed in Si isotopes, although it is unlikely to substantially deviate from BSE, consistent with previous observations [8]. Finally, the strong enrichment in the lighter isotopes of Zn confirms that this isotope system could be used as a tracer of recycled serpentinised material at arc settings, as suggested in [4]. [1] Dick et al. (2003) Nature 426, 405-412; [2] Treguer and De La Rocha (2013) Ann. Rev. Mar. Sci. 5, 477-501; [3] Snow & Dick (1995) GCA, 59, 4219-4235; [4] Pons et al. (2011) PNAS 108(43) 17639-17643; [5] Bach et al., (2004) G3 5; [6] Tipper et al. (2006) EPSL 247, 267-279; [7] Opfergelt et al. (2012) Chem. Geol. 326, 113-122; [8] De La Rocha et al. (2000) GCA 64, 2467-2477.

  14. Abyssal intimacies and temporalities of care: How (not) to care about deformed leaf bugs in the aftermath of Chernobyl.

    PubMed

    Schrader, Astrid

    2015-10-01

    Prompted by a classroom discussion on knowledge politics in the aftermath of the Chernobyl disaster, this article offers a reading of Hugh Raffles' Insectopedia entry on Chernobyl. In that entry, Raffles describes how Swiss science-artist and environmental activist Cornelia Hesse-Honegger collects, studies, and paints morphologically deformed leaf bugs that she finds in the proximity of nuclear power plants. In exploring how to begin to care about beings, such as leaf bugs, this article proposes a notion of care that combines an intimate knowledge practice with an ethical relationship to more-than-human others. Jacques Derrida's notion of 'abyssal intimacy' is central to such a combination. Hesse-Honegger's research practices enact and her paintings depict an 'abyssal intimacy' that deconstructs the oppositions between concerns about human suffering and compassion for seemingly irrelevant insects and between knowledge politics and ethics. At the heart of such a careful knowledge production is a fundamental passivity, based on a shared vulnerability. An abyssal intimacy is not something we ought to recognize; rather, it issues from particular practices of care that do not identify their subjects of care in advance. Caring or becoming affected thus entails the dissociation of affection not only from the humanist subject, but also from movements in time: from direct helping action and from the assumption that advocacy necessarily means speaking for an other, usually assumed to be inferior. PMID:26630816

  15. Flood plain and channel dynamics of the Quinault and Queets Rivers, Washington, USA

    USGS Publications Warehouse

    O'Connor, J. E.; Jones, M.A.; Haluska, T.L.

    2003-01-01

    Comparison of historic channel migration rates, modern planform conditions, and overall sediment, wood, and flow conditions and interactions for the Quinault River and Queets River in the western Olympic Peninsula, Washington, reveals decadal- to century-scale interactions between gravel-bed channels and forested flood plains in temperate maritime environments. The downstream alluvial portions of these two rivers can be divided into three reaches of different slope, flow, sediment, and wood regimes: (i) the upper Quinault River is aggrading behind Lake Quinault, a natural lake that traps most sediment and wood transported from the Olympic Mountain headwaters. (ii) The lower Quinault River, downstream of Lake Quinault, transports only sediment and wood derived from reworking of flood-plain deposits and contributed from valley margins. (iii) The Queets River has unimpeded movement of sediment and water from the mountainous headwaters to the Pacific Ocean. Measurements of channel planform characteristics and historic migration rates and patterns show that these three reaches have correspondingly distinct channel and flood-plain morphologies and dynamics. The aggrading and sediment-rich upper Quinault River has the widest flood plain, widest active channel, greatest number of low-flow channels and flanking gravel bars, and an average channel migration rate of 12.7??3.3 m/year between 1900 and 1994. The comparatively sediment-poor lower Quinault River has the narrowest flood plain, narrowest active channel, and lowest channel migration rate (4.0??1.2 m/year); and most flow is through a single channel with few adjacent gravel bars. The Queets River has attributes intermediate between the lower and upper Quinault Rivers, including an average channel migration rate of 7.5??2.9 m/year. Flood-plain turnover rates are similar for all three reaches, with channels eroding the flood plain at the rate of about 0.2% of the flood-plain area per year, and with corresponding flood-plain half-lives of 300 to 500 years. Observations from this study and previous studies on the Queets River show that channel and flood-plain dynamics and morphology are affected by interactions between flow, sediment, and standing and entrained wood, some of which likely involve time frames similar to 200-500-year flood-plain half-lives. On the upper Quinault River and Queets River, log jams promote bar growth and consequent channel shifting, short-distance avulsions, and meander cutoffs, resulting in mobile and wide active channels. On the lower Quinault River, large portions of the channel are stable and flow within vegetated flood plains. However, locally, channel-spanning log jams have caused channel avulsions within reaches that have been subsequently mobile for several decades. In all three reaches, log jams appear to be areas of conifer germination and growth that may later further influence channel and flood-plain conditions on long time scales by forming flood-plain areas resistant to channel migration and by providing key members of future log jams. Appreciation of these processes and dynamics and associated temporal and spatial scales is necessary to formulate effective long-term approaches to managing fluvial ecosystems in forested environments. Published by Elsevier Science B.V.

  16. The Interior Lowland Plains Unit of Mars: Evidence for a Possible Mud Ocean and Induced Tectonic Deformation

    NASA Technical Reports Server (NTRS)

    Tanaka, K. L.; Banerdt, W. B.

    2000-01-01

    We conclude from MOC and MOLA data that the northern plains of Mars were infilled by a sediment-rich, mud ocean. Evidence for subsidence within the north polar basin and reversed channel-floor gradients are consistent with tectonic deformation due to the sediment load.

  17. Suspended particulate loads and transports in the nepheloid layer of the abyssal Atlantic Ocean

    USGS Publications Warehouse

    Biscaye, P.E.; Eittreim, S.L.

    1977-01-01

    Vertical profiles of light scattering from over 1000 L-DGO nephelometer stations in the Atlantic Ocean have been used to calculate mass concentrations of suspended particles based on a calibration from the western North American Basin. From these data are plotted the distributions of particulate concentrations at clear water and in the more turbid near-bottom water. Clear water is the broad minimum in concentration and light scattering that occurs at varying mid-depths in the water column. Concentrations at clear water are as much as one-to-two orders of magnitude lower than those in surface water but still reflect a similar geographic distribution: relatively higher concentrations at ocean margins, especially underneath upwelling areas, and the lowest concentrations underneath central gyre areas. These distributions within the clear water reflect surface-water biogenic productivity, lateral injection of particles from shelf areas and surface circulation patterns and require that the combination of downward vertical and horizontal transport processes of particles retain this pattern throughout the upper water column. Below clear water, the distribution of standing crops of suspended particulate concentrations in the lower water column are presented. The integration of mass of all particles per unit area (gross particulate standing crop) reflects a relative distribution similar to that at the surface and at clear water levels, superimposed on which is the strong imprint of boundary currents along the western margins of the Atlantic. Reducing the gross particulate standing crop by the integral of the concentration of clear water yields a net particulate standing crop. The distribution of this reflects primarily the interaction of circulating abyssal waters with the ocean bottom, i.e. a strong nepheloid layer which is coincident with western boundary currents and which diminishes in intensity equatorward. The resuspended particulate loads in the nepheloid layer of the basins west of the Mid-Atlantic Ridge, resulting from interaction of abyssal currents with the bottom, range from ??? 2 ?? 106 tons in the equatorial Guyana Basin to ??? 50 ?? 106 tons in the North American Basin. The total resuspended particulate load in the western basins (111 ?? 106 tons) is almost an order of magnitude greater than that in the basins east of the Mid-Atlantic Ridge (13 ?? 106 tons). The net northward flux of resuspended particles carried in the AABW drops from ??? 8 ?? 106 tons/year between the southern and northern ends of the Brazil Basin and remains ??? 1 ?? 106 tons/year across the Guyana Basin. ?? 1977.

  18. The Horoman Peridotite Massif: an Example of Ancient Ultraslow-Spreading Ridge Abyssal Peridotites?

    NASA Astrophysics Data System (ADS)

    Shimizu, N.; Warren, J. M.; Frey, F. A.; Takazawa, E.

    2006-12-01

    Ultraslow-spreading ridges (full spreading rate less than 20 mm per year) comprise about one third (lengthwise) of the global ridge system today, and might also have been important in the geologic past, particularly after breakup of large continents. Geochemical studies of abyssal peridotites show that large local- scale (single-dredge to hand specimen scales) variations in isotopic composition, modal abundance of clinopyroxene (CPX), and trace element abundance in CPX are distinct characteristics of ultraslow-spreading ridge peridotites. It is suggested that these local-scale variabilities are produced by melt-rock reaction during melt migration in the mantle (e.g., Warren et al., 2006). We explored using these geochemical characteristics to identify ancient ultraslow-spreading ridge peridotites among "orogenic lherzolite massifs". The Horoman peridotite massif in Hokkaido, Japan, possesses DMM-like initial Nd and Sr isotopic characteristics at the time of melt extraction, and displays large variations in modal CPX (13.2 - 5.2%, only for lherzolites and plagioclase lherzolites) and in trace elements in CPX (e.g., Nd ranges from 0.3 to 10 times C1 chondrite) over a sampling scale length of 150 m. Additionally, there is ample evidence for chromatographic melt-rock reaction in the presence of garnet (Takazawa et al., 1996; Yoshikawa and Nakamura, 2000). These geochemical characteristics are very similar to those observed for the present-day ultraslow-spreading ridge peridotites such as those from the SWIR and Gakkel ridge. A whole-rock Sm-Nd isochron age for the plagioclase lherzolites of 830+/-78 Ma (Yoshikawa and Nakamura, 2000) and a suggestion by Saal et al. (2001) that refertilization of depleted peridotites by a MORB-like magma occurred around 900 Ma, based on the Re-Os systematics, indicate that melt extraction and melt-rock reaction formed the Horoman peridotite massif at 800 to 900 Ma. This time is similar to that, 750 Ma, estimated for formation of the Paleopacific ocean by rifting of the Rodinia supercontinent (e.g., Torsvik, 2003). We suggeset that the Horoman massif could represent abyssal peridotite beneath the Paleopacific ridge when its spreading rate was ultraslow. Saal et al. (2001) J. Petrol., 42, 25-37; Takazawa et al. (1996) Chem. Geol., 134, 3-26; Torsvik (2003) Science, 300, 1379-1381; Yoshikawa and Nakamura (2000) JGR, 105, 2879-2901; Warren et al. (2006) Goldschmidt Conf. Abstract.

  19. Geologic map of the northern plains of Mars

    USGS Publications Warehouse

    Tanaka, Kenneth L.; Skinner, James A.; Hare, Trent M.

    2005-01-01

    The northern plains of Mars cover nearly a third of the planet and constitute the planet's broadest region of lowlands. Apparently formed early in Mars' history, the northern lowlands served as a repository both for sediments shed from the adjacent ancient highlands and for volcanic flows and deposits from sources within and near the lowlands. Geomorphic evidence for extensive tectonic deformation and reworking of surface materials through release of volatiles occurs throughout the northern plains. In the polar region, Planum Boreum contains evidence for the accumulation of ice and dust, and surrounding dune fields suggest widespread aeolian transport and erosion. The most recent regional- and global-scale maps describing the geology of the northern plains are largely based on Viking Orbiter image data (Dial, 1984; Witbeck and Underwood, 1984; Scott and Tanaka, 1986; Greeley and Guest, 1987; Tanaka and Scott, 1987; Tanaka and others, 1992a; Rotto and Tanaka, 1995; Crumpler and others, 2001; McGill, 2002). These maps reveal highland, plains, volcanic, and polar units based on morphologic character, albedo, and relative ages using local stratigraphic relations and crater counts. This geologic map of the northern plains is the first published map that covers a significant part of Mars using topography and image data from both the Mars Global Surveyor and Mars Odyssey missions. The new data provide a fresh perspective on the geology of the region that reveals many previously unrecognizable units, features, and temporal relations. In addition, we adapted and instituted terrestrial mapping methods and stratigraphic conventions that we think result in a clearer and more objective map. We focus on mapping with the intent of reconstructing the history of geologic activity within the northern plains, including deposition, volcanism, erosion, tectonism, impact cratering, and other processes with the aid of comprehensive crater-density determinations. Mapped areas include all plains regions within the northern hemisphere of Mars, as well as an approximately 300-km-wide strip of cratered highland and volcanic regions, which border the plains. Note that not all of the contiguous northern plains are mapped, because some minor parts of Elysium and Amazonis Planitiae lie south of the equator.

  20. Origin of lunar light plains

    NASA Technical Reports Server (NTRS)

    Chao, E. C. T.; Hodges, C. A.; Boyce, J. M.; Soderblom, L. A.

    1975-01-01

    In order to determine the origin of Cayley-type lunar light plains, their physical properties, distribution, and relative ages are examined from Apollo orbital and Lunar Orbiter photographs. The distribution and apparent age of the plains deposits and data on highly feldspathic breccias indicate that these superficial materials are neither locally derived nor part of the Imbrium ejecta. The existence of a planar facies of continuous ejecta at Orientale and in the ejecta blankets of small craters is demonstrated. The data and interpretation presented support the hypothesis that the surface and near-surface materials of some light plains, including those at the Apollo 16 site, are at least partly composed of ejecta from the Orientale basin and that the materials of many rugged areas, such as the Descartes highlands, are overlain by similar material. The possibility that some Cayley-type plains may have a different origin is not excluded.

  1. Rocky Martian Plain

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The rocky Martian plain surrounding Viking 2 is seen in high resolution in this 85-degree panorama sweeping from north at the left to east at right during the Martian afternoon on September 5. Large blocks litter the surface. Some are porous, sponge-like rocks like the one at the left edge (size estimate: 1 1/2 to 2 feet); others are dense and fine-grained, such as the very bright rounded block (1 to 1 1/2 feet across) toward lower right. Pebbled surface between the rocks is covered in places by small drifts of very fine material similar to drifts seen at the Viking 1 landing site some 4600 miles to the southwest. The fine-grained material is banked up behind some rocks, but wind tails seen by Viking 1 are not well-developed here. On the right horizon, flat-topped ridges or hills are illuminated by the afternoon sun. Slope of the horizon is due to the 8-degree tilt of the spacecraft.

  2. Fluid migration pathways, sediment subduction, and the source of fluids escaping along the forearc seafloor revealed offshore Nicaragua with marine electromagnetic data

    NASA Astrophysics Data System (ADS)

    Naif, S.; Key, K.; Constable, S.; Evans, R. L.

    2014-12-01

    The subduction of sediments and hydrated oceanic plates transports the primary flux of water into the interior of the Earth. As an oceanic plate sinks, water is progressively released by compaction and chemical dehydration reactions, a significant fraction of which is released during the initial stages of subduction. In order to map the flux of fluids at the Middle America Trench, we collected marine magnetotelluric and controlled-source electromagnetic data along a 280-km profile that spans the offshore component of the Nicaraguan margin. Fluids and volatiles present in the crust and mantle can decrease the bulk electrical resistivity by up to several orders of magnitude, making electromagnetic methods an ideal exploration tool for quantifying fluids along convergent margins. Our joint two-dimensional electrical resistivity model provides new constraints on the cycling of fluids at crustal depths. We image a variety of conductive channels that are indicative of: (1) crustal hydration along bending-induced normal faults at the outer rise, (2) the complete subduction of water-rich sediments, and (3) the vertical migration of fluids from the plate interface to the forearc seafloor. We estimate porosity from electrical resistivity using Archie's law to show that the porosity of the lower crust is increased by 115% at the outer rise compared with the abyssal plain, suggesting that more pore water is being subducted than previously thought. At the margin toe, we observe the porosity of the underthrust sediment layer to decay exponentially with increasing depth of burial to 10-km inland of the trench, which agrees well with laboratory studies of compaction driven porosity loss. At 23-km into the forearc, our data reveal an anomalous conductor that extends from the plate interface into the overlying forearc crust, terminating 1-2-km below a high density region of active fluid seeps and mud mounds that have previously been mapped. The temperature and pressure regime in the vicinity of the anomalous conductor suggests it arises from diagenetic dewatering of subducted sediment and/or upper crust material, providing a flux of additional water that may be the source of fluids escaping on the forearc seafloor.

  3. Quantifying variable rainfall intensity events on runoff and sediment losses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Coastal Plain soils in Georgia are susceptible to runoff, sediment, and chemical losses from short duration-high intensity, runoff producing storms at critical times during the growing season. We quantified runoff and sediment losses from a Tifton loamy sand managed under conventional- (CT) and stri...

  4. Photo-real rendering of bioluminescence and iridescence in creatures from the abyss

    NASA Astrophysics Data System (ADS)

    Prusten, Mark

    2008-08-01

    The generation of photo-real renderings of bioluminescence is developed for creatures from the abyss. Bioluminescence results from a chemical reaction with examples found in deep-sea marine environments including: algae, copepods, jellyfish, squid, and fish. In bioluminescence, the excitation energy is supplied by a chemical reaction, not by a source of light. The greatest transparency window in seawater is in the blue region of the visible spectrum. From small creatures like single-cell algae, to large species of siphonophore Praya dubia (40m), luminescent phenomena can be produced by mechanical excitement from disturbances of objects passing by. Deep sea fish, like the Pacific Black Dragonfish are covered with photophores along the upper and lower surfaces which emits light when disturbed. Other animals like small squids have several different types of light organs oscillating at different rates. Custom shaders and material phenomena incorporate indirect lighting like: global illumination, final gathering, ambient occlusion and subsurface scattering to provide photo real images. Species like the Hydomedusae jellyfish, produce colors that are also generated by iridescence of thin tissues. The modeling and rendering of these tissues requires thin film multilayer stacks. These phenomena are simulated by semi-rigid body dynamics in a procedural animation environment. These techniques have been applied to develop spectral rendering of scenes outside the normal visible window in typical computer animation render engines.

  5. Mineralogy of the mid-ocean-ridge basalt source from neodymium isotopic composition of abyssal peridotites.

    PubMed

    Salters, Vincent J M; Dick, Henry J B

    2002-07-01

    Inferring the melting process at mid-ocean ridges, and the physical conditions under which melting takes place, usually relies on the assumption of compositional similarity between all mid-ocean-ridge basalt sources. Models of mantle melting therefore tend to be restricted to those that consider the presence of only one lithology in the mantle, peridotite. Evidence from xenoliths and peridotite massifs show that after peridotite, pyroxenite and eclogite are the most abundant rock types in the mantle. But at mid-ocean ridges, where most of the melting takes place, and in ophiolites, pyroxenite is rarely found. Here we present neodymium isotopic compositions of abyssal peridotites to investigate whether peridotite can indeed be the sole source for mid-ocean-ridge basalts. By comparing the isotopic compositions of basalts and peridotites at two segments of the southwest Indian ridge, we show that a component other than peridotite is required to explain the low end of the (143)Nd/(144)Nd variations of the basalts. This component is likely to have a lower melting temperature than peridotite, such as pyroxenite or eclogite, which could explain why it is not observed at mid-ocean ridges. PMID:12097907

  6. Diversity and distribution of Porifera in the bathyal and abyssal Weddell Sea and adjacent areas

    NASA Astrophysics Data System (ADS)

    Janussen, Dorte; Tendal, Ole Secher

    2007-08-01

    During the ANDEEP I-III expeditions, we obtained a rich and highly diverse sponge collection from the deep Weddell Sea. All the three Poriferan classes, Calcarea, Demospongiae and Hexactinellida, were well represented. Among this material, we have identified a total of 76 species from 47 genera and 30 families. Of these, 17 species (22%) are new to science and 37 (49%) new for the Southern Ocean. Particularly remarkable is the considerable depth of the boundary between bathyal and abyssal sponge faunas. Both Demospongiae and Hexactinellida show a strong shift in their taxonomic composition from a typical shelf assemblage to a more cosmopolitan deep-sea fauna at around 2500 m. Within the Demospongiae, the families Polymastiidae and Cladorhizidae (carnivorous sponges) are particularly abundant and very diverse. The Calcarea are recorded for the first time from the Antarctic deep sea. The type of sampling gear used, especially the epibenthic sledge, was an important factor for the successful collection of deep-sea sponges during the ANDEEP campaigns.

  7. Surprises in abyssal peridotites: implications for melt migration beneath ocean ridges

    NASA Astrophysics Data System (ADS)

    Niu, Y.

    2003-04-01

    Since Mike's two classic papers [1,2], the last 35 years have seen much progress on MORB petrogenesis because of improved experimental/theoretical approaches and because of rapid growth of geochemical database on MORB samples from the global ocean ridge system. Our current understanding of MORB genesis also owes a great deal to the studies [3-5] of abyssal peridotites - interpreted as mantle melting residues for MORB. Recent studies [6,7] have confirmed the complementary relationship between MORB and abyssal peridotites, but also revealed the hidden complexities in these peridotites such as olivine addition [6-8] and melt refertilization [7-9]. These same studies [6,7] have simultaneously excited serious debates on the petrogenesis of abyssal peridotites [10-14]. These debates are actually different views on the same observations: modes and major element compositions of residual minerals, and trace element data on residual clinopyroxene (Cpx) [3-5]. I report here whole-rock ICP-MS trace element data on abyssal peridotites including samples previously studied for Cpx trace elements [5]. Residual Cpx shows highly depleted light rare earth elements (LREEs) with flat-to-elevated middle-heavy REEs (e.g., [Ce]_N = 0.250.51 [mean1?]; [Yb]_N = 6.092.59; [Nd/Sm]_N = 0.290.14; [Nd/Dy]_N = 0.140.11), which is consistent with varying extents of melt depletion [5]. In contrast, whole-rock data of the same samples [15] show elevated abundances of LREEs with flat to enriched LREE patterns (e.g., [Ce]_N = 0.570.74; [Yb]_N, 0.720.41; [Nd/Sm]_N = 1.180.41; [Nd/Dy]_N = 0.700.38). If the constituent Cpx records the melting process, the whole-rock data would suggest post-melting LREE addition. The significant correlations of LREEs with high-field strength elements (HFSEs) (e.g., RCe-Zr = 0.730, RNd-Zr = 0.789, RCe-Nb = 0.836, RNd-Nb = 0.900) suggest that this LREE addition is magmatic refertilization (vs. serpentinization). The observation that this magmatic refertilization did not affect Cpx composition is informative. There are two possibilities: (A) The refertilization took place in the "cold" thermal boundary layer atop the mantle through which the ascending melts cooled and crystallized olivine out accompanied by some melt entrapment, giving rise to excess olivine and elevated LREE abundances in the bulk tock [6-8]. (B) The ascending melts, when percolating along grain boundaries, could only affect Cpx crystal "rims", which together with the rest of the rock had been serpentinized; the Cpx trace elements were determined from unaffected Cpx "cores" [5]. In either scenario, the following statements are true: (1) the ascending melts will interact with the advanced residues, seen on petrographic scales; (2) the interaction is not chemically reactive; and (3) porous flow is significant even at the "cold" shallow depths. These statements are supported by unexpectedly large, yet correlated variations of HFSEs (Nb = 0.5-1840; Ta = 0.1-71; Zr = 9-18605; Hf = 1-590; Nb/Ta = 0.8-200; Zr/Hf = 2.4-336) exhibited by the entire data set [16]. References: [1] O'Hara, Earth Sci. Rev., 4, 69-133, 1968; [2] O'Hara, Nature, 220, 683-686, 1968; [3] Dick et al., Earth Planet. Sci. Lett., 69, 88-106, 1984; [4] Dick, Geol. Soc. Lon. Spec. Pub., 42, 71-105, 1989; [5] Johnson et al., J. Geophys. Res., 95, 2661-2678, 1990; [6] Niu et al., Earth Planet. Sci. Lett., 152, 251-265, 1997; [7] Niu, J. Petrol., 38, 1047-1074, 1997; [8] Niu & Hkinian, Earth Planet. Sci. Lett., 146, 243-258, 1997; [9] Elthon, J. Geophys. Res., 97, 9015-9025, 1992; [10] Walter, J. Petrol., 40, 1187-1193, 1999; [11] Niu, J. Petrol., 40, 1195-1203, 1999; [12] Baker & Beckett, Earth Planet. Sci. Lett., 171, 49-61, 1999; [13] Asimow, Earth Planet. Sci. Lett., 169, 303-319, 1999; [14] Lundstrom, Nature, 403, 527-530, 2000; [15] Fisher et al., Ofioliti, 11, 147-178, 1987; [16] Niu & Greig, Eos Trans. AGU, Suppl., 81 (48), F1282, 2000.

  8. Evaluation of abyssal meiobenthos in the eastern central Pacific (Clarion-Clipperton fracture zone)

    NASA Astrophysics Data System (ADS)

    Renaud-Mornant, Jeanne; Gourbault, Nicole

    Meiobenthos were sampled from 17 stations in the abyssal deep-sea system of the central Pacific centered around 14N, 130W at depths 4960-5154m, during the Nixo 47 R/V Jean Charcot cruise. Meiofaunal density range from 45-89 ind. 10cm 2. Predominant taxa are nematodes (84-100%) and copepods (0-10%). Rotifera, Polychaeta, and Acarina also occur. Nematodes are uniformly distributed spatially with 45 species or so; Monhysteridae is the dominant taxon, and Syringolaimus sp. (Ironidae) co-occurs faithfully. Low biomass (0.4-70.6?g 10cm 2) are attributed to supposed dwarfism of metazoan meiofauna and very high proportion (60-80%) of juveniles and pre-adult forms. The majority of protozoans and metazoans are detritus- or deposit-feeders; in addition symbiotic associations, coprophagy and gardening activities are frequent. In such an oligotrophic environment, low food supply may limit meiofaunal abundance, biomass and maturation, and to a lesser extent species richness.

  9. Evidence for enhanced mixing over rough topography in the abyssal ocean

    PubMed

    Ledwell; Montgomery; Polzin; St. Laurent LC; Schmitt; Toole

    2000-01-13

    The overturning circulation of the ocean plays an important role in modulating the Earth's climate. But whereas the mechanisms for the vertical transport of water into the deep ocean--deep water formation at high latitudes--and horizontal transport in ocean currents have been largely identified, it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished. Turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise. However, measurements of the internal wave field, the main source of energy for mixing, and of turbulent dissipation rates, have typically implied diffusivities across surfaces of equal density of only approximately 0.1 cm2 s(-1), too small to account for the return flow. Here we report measurements of tracer dispersion and turbulent energy dissipation in the Brazil basin that reveal diffusivities of 2-4 cm2 s(-1) at a depth of 500 m above abyssal hills on the flank of the Mid-Atlantic Ridge, and approximately 10 cm2 s(-1) nearer the bottom. This amount of mixing, probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry, may be large enough to close the buoyancy budget for the Brazil basin and suggests a mechanism for closing the global overturning circulation. PMID:10646599

  10. Supra-subduction and abyssal mantle peridotites of the Coast Range ophiolite, California

    NASA Astrophysics Data System (ADS)

    Choi, Sung Hi; Shervais, John W.; Mukasa, Samuel B.

    2008-11-01

    The Coast Range ophiolite (CRO) of California is one of the most extensive tracts of oceanic crust preserved in the North American Cordillera, but its origin has long remained controversial. We present here new data on mineral compositions in mantle peridotites that underlie crustal sections of the ophiolite, and show that these are dominantly refractory harzburgites related to high apparent melting in a supra-subduction zone (SSZ) setting. Abyssal peridotite (characterized by high-Al spinels and relatively high Ti, Na, Nd, Sm, Lu, and Hf in pyroxene) occurs at one location where it is associated with SSZ mantle peridotite and volcanic rocks with both oceanic and arc-like geochemistry. SSZ mantle peridotites (characterized by intermediate-Cr/Al or high-Cr spinels, and by extremely low Ti, Na, Nd, Sm, Lu, and Hf in pyroxenes) are associated with crustal sections containing arc-related volcanic rocks, including boninites. This convergence between conclusions based on crustal lithologies and their underlying mantle sections confirms previous proposals that link the CRO to SSZ processes, and seriously undermines hypotheses that invoke formation of the ophiolite at a mid-ocean ridge spreading center.

  11. Genetic and Morphological Divergences in the Cosmopolitan Deep-Sea Amphipod Eurythenes gryllus Reveal a Diverse Abyss and a Bipolar Species

    PubMed Central

    Havermans, Charlotte; Sonet, Gontran; dUdekem dAcoz, Cdric; Nagy, Zoltn T.; Martin, Patrick; Brix, Saskia; Riehl, Torben; Agrawal, Shobhit; Held, Christoph

    2013-01-01

    Eurythenes gryllus is one of the most widespread amphipod species, occurring in every ocean with a depth range covering the bathyal, abyssal and hadal zones. Previous studies, however, indicated the existence of several genetically and morphologically divergent lineages, questioning the assumption of its cosmopolitan and eurybathic distribution. For the first time, its genetic diversity was explored at the global scale (Arctic, Atlantic, Pacific and Southern oceans) by analyzing nuclear (28S rDNA) and mitochondrial (COI, 16S rDNA) sequence data using various species delimitation methods in a phylogeographic context. Nine putative species-level clades were identified within E. gryllus. A clear distinction was observed between samples collected at bathyal versus abyssal depths, with a genetic break occurring around 3,000 m. Two bathyal and two abyssal lineages showed a widespread distribution, while five other abyssal lineages each seemed to be restricted to a single ocean basin. The observed higher diversity in the abyss compared to the bathyal zone stands in contrast to the depth-differentiation hypothesis. Our results indicate that, despite the more uniform environment of the abyss and its presumed lack of obvious isolating barriers, abyssal populations might be more likely to show population differentiation and undergo speciation events than previously assumed. Potential factors influencing species origins and distributions, such as hydrostatic pressure, are discussed. In addition, morphological findings coincided with the molecular clades. Of all specimens available for examination, those of the bipolar bathyal clade seemed the most similar to the true E. gryllus. We present the first molecular evidence for a bipolar distribution in a macro-benthic deep-sea organism. PMID:24086322

  12. Genetic and morphological divergences in the cosmopolitan deep-sea amphipod Eurythenes gryllus reveal a diverse abyss and a bipolar species.

    PubMed

    Havermans, Charlotte; Sonet, Gontran; d'Udekem d'Acoz, Cdric; Nagy, Zoltn T; Martin, Patrick; Brix, Saskia; Riehl, Torben; Agrawal, Shobhit; Held, Christoph

    2013-01-01

    Eurythenes gryllus is one of the most widespread amphipod species, occurring in every ocean with a depth range covering the bathyal, abyssal and hadal zones. Previous studies, however, indicated the existence of several genetically and morphologically divergent lineages, questioning the assumption of its cosmopolitan and eurybathic distribution. For the first time, its genetic diversity was explored at the global scale (Arctic, Atlantic, Pacific and Southern oceans) by analyzing nuclear (28S rDNA) and mitochondrial (COI, 16S rDNA) sequence data using various species delimitation methods in a phylogeographic context. Nine putative species-level clades were identified within E. gryllus. A clear distinction was observed between samples collected at bathyal versus abyssal depths, with a genetic break occurring around 3,000 m. Two bathyal and two abyssal lineages showed a widespread distribution, while five other abyssal lineages each seemed to be restricted to a single ocean basin. The observed higher diversity in the abyss compared to the bathyal zone stands in contrast to the depth-differentiation hypothesis. Our results indicate that, despite the more uniform environment of the abyss and its presumed lack of obvious isolating barriers, abyssal populations might be more likely to show population differentiation and undergo speciation events than previously assumed. Potential factors influencing species' origins and distributions, such as hydrostatic pressure, are discussed. In addition, morphological findings coincided with the molecular clades. Of all specimens available for examination, those of the bipolar bathyal clade seemed the most similar to the 'true' E. gryllus. We present the first molecular evidence for a bipolar distribution in a macro-benthic deep-sea organism. PMID:24086322

  13. Neogene paleogeography of western Snake River plain, Idaho and Oregon

    SciTech Connect

    Porter, M.L.; Middleton, L.T.

    1984-04-01

    Analysis of Miocene through Pleistocene siliciclastic and volcaniclastic sequences in the western Snake River Plain of Idaho and Oregon allows detailed paleogeographic reconstruction of sedimentation associated with the development of a rapidly subsiding continental basin. Extensional tectonism was accompanied by voluminous outpourings of basaltic and silicic volcanic material. These in turn were reworked basinward by marginal alluvial fan-braided stream networks into basin-center fluviolacustrine systems. Episodic influxes of both felsic and basaltic tephra are recorded in fossiliferous lacustrine silt and claystones of the Poison Creek and Chalk Hills Formations, radiometrically bracketed between 12.5 to 5 m.y.B.P. Basinward-fining facies indicate deposition in the large lacustrine complex fed by at least 2 major fluvial systems. Complex interfingering of coarse-grained strandline deposits with offshore fine-grained sediments suggests repeated expansion and contraction of the lake system and record the dynamic interplay between basin tectonism and sedimentation.

  14. Interval velocity and attenuation measurements in sediments from marine seismic reflection data

    SciTech Connect

    Wrolstad, K.

    1980-11-01

    Deterministic source signature deconvolution has been applied to the processing of marine airgun wide angle and vertical profiler data. The resulting improvement in reflection event timing accuracy allowed the computation of more reliable interval velocities for upper sedimentary layers by the T/sup 2/-X/sup 2/ method, provided that the layer thickness limitation of the method was not exceeded. Computations of frequency dependent attenuation were also made from the data by a procedure using frequency domain univariate least-squares regression. Estimates of maximum attenuation were made for an abyssal plain and a turbidite sedimentary environment off the coast of Oregon. The interval velocity and attenuation in the upper layers of the turbidite environment correlate well with the average material type found in the core of nearby DSDP site 174 (sandy silt with greater than 60% sand). The maximum estimated attenuation at about 100 Hz in the abyssal plain environment (silts and clays) was found to be greater than that for the sea fan environment.

  15. Nutrient yield of the Apalachicola River flood plain, Florida; water-quality assessment plan

    USGS Publications Warehouse

    Mattraw, H.C., Jr.; Elder, John F.

    1980-01-01

    The Apalachicola River in northwestern Florida is the location of one of four current U.S. Geological Survey National River Quality Assessments. The investigation of the Apalachicola River and flood plain is designed to quantify the organic detritus and nutrient yield to the productive, estuarine Apalachicola Bay. The extensive riverine flood plain is subject to seasonal flooding which transports large quantities of accumulated, decaying leaf litter from the flood plain into the river and ultimately into Apalachicola Bay. The Apalachicola River Quality Assessment has four major objectives; (1) Determine the accumulation of organic substances and trace elements in benthic organisms and fine-grained sediments; (2) Define the distribution of the major tree communities on the flood plain; (3) Assess the role of leaf fall and decomposition on nutrient yield; and (4) Identify and quantify major sources and pathways of nutrients to the river. Extensive emphasis is given to investigation approaches and techniques to facilitate technology transfer to similar wetland ecosystems. (USGS)

  16. Impact of dredging on dissolved phosphorus transport in agricultural drainage ditches of the Atlantic Coastal Plain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Drainage ditches can be a key conduit of phosphorus (P) between agricultural soils of the Atlantic coastal plain and local surface waters, including the Chesapeake Bay. This study sought to quantify the effect of a common ditch management practice, sediment dredging, on fate of P in drainage ditches...

  17. Relationship of structural development and Cenozoic sedimentation, northern Gulf of Mexico

    SciTech Connect

    Humphris, C.C. Jr.

    1985-02-01

    Development of structure in the northern Gulf of Mexico, mainly listric faulting and salt features, is directly related to Cenozoic sedimentation. Essentially all oil and gas production in this region occurs in structural features resulting from faulting and/or salt movement. A thick section of continental shallow-water sediments rimming the entire Gulf of Mexico was deposited during overall Gulf subsidence in Mesozoic time. Very little sedimentation took place in the central Gulf, so that, at the close of the Mesozoic the central Gulf probably was of abyssal depths. Cenozoic sedimentation surpassed the rate of subsidence causing sediments to prograde across the Mesozoic shelf margin, with greatest deposition occurring gulfward of this margin. These depocenters or areas of thickest sedimentation prograded gulfward throughout time (in response to sediment supply) and migrated northeastward from south Texas to south Louisiana. Listric or growth faults that formed contemporaneously with deposition are a common structural feature developed during Cenozoic sedimentation. These features are apparently caused by differential loading of higher density sandstones on prodelta shales near the shelf margin. In those areas underlain by thicker salt, such as the Miocene and younger depocenters, there is greater involvement of salt in growth-fault development. Salt features, the other major type of producing structure, are developed by salt movement as a direct response to Cenozoic sediment loading. Initiation of salt movement is believed to be due to differential loading of prograding sediments. Further salt movement and structural development are completely dependent on continued sedimentation.

  18. Moored observation of abyssal flow and temperature near a hydrothermal vent on the Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Liao, Guanghong; Zhou, Beifeng; Liang, Chujin; Zhou, Huaiyang; Ding, Tao; Wang, Yuan; Dong, Changming

    2016-01-01

    Four moorings were deployed near "Dragon Flag," an active hydrothermal vent in the valley of the Southwest Indian Ridge. The goal was to examine the variability of currents and temperature, which will guide the trajectory of spreading plumes. The mean current was cross-isobath, and the circulation was characterized by a submesoscale circulation. Observed currents also showed fluctuations with periods of 1-15 days. The inferred phase speed and wavelength for the wave with a period of 4.4 day are 10.4 km d-1 and 45.8km, respectively, which are consistent with the topographic Rossby wave theory. The persistent warming tendency with corresponding variation of salinity based on background θ-S properties may be caused by background circulation and divergence of the water column. The warming or cooling episodes were most likely as signatures of isopycnal surface depression or uplifting induced by the moving of mesoscale eddies. Well-resolved rotary spectra exhibited important nonlinear interactions between inertial and semidiurnal tide in the velocity and temperature records. Amplification of near-inertial currents in the near bottom is also exposed. These discoveries provided new evidence for the nonlinear interaction and trapped near-inertial waves by the ridge, which occurred in the deep ocean of the Southern Hemisphere. Such nonlinear interaction may represent a significant energy loss pathway for the internal waves, and part of the decay of such motion would likely result in increased mixing to maintain the abyssal stratification. Enhanced near-inertial motions can play a major role for the local advection of hydrothermal plumes.

  19. A reverse taxonomic approach to assess macrofaunal distribution patterns in abyssal Pacific polymetallic nodule fields.

    PubMed

    Janssen, Annika; Kaiser, Stefanie; Meiner, Karin; Brenke, Nils; Menot, Lenaick; Martnez Arbizu, Pedro

    2015-01-01

    Heightened interest in the exploitation of deep seafloor minerals is raising questions on the consequences for the resident fauna. Assessing species ranges and determination of processes underlying current species distributions are prerequisites to conservation planning and predicting faunal responses to changing environmental conditions. The abyssal central Pacific nodule belt, located between the Clarion and Clipperton Fracture Zones (CCZ), is an area prospected for mining of polymetallic nodules. We examined variations in genetic diversity and broad-scale connectivity of isopods and polychaetes across the CCZ. Faunal assemblages were studied from two mining claims (the eastern German and French license areas) located 1300 km apart and influenced by different productivity regimes. Using a reverse taxonomy approach based on DNA barcoding, we tested to what extent distance and large-scale changes in environmental parameters lead to differentiation in two macrofaunal taxa exhibiting different functions and life-history patterns. A fragment of the mitochondrial gene Cytochrome Oxidase Subunit 1 (COI) was analyzed. At a 97% threshold the molecular operational taxonomic units (MOTUs) corresponded well to morphological species. Molecular analyses indicated high local and regional diversity mostly because of large numbers of singletons in the samples. Consequently, variation in composition of genotypic clusters between sites was exceedingly large partly due to paucity of deep-sea sampling and faunal patchiness. A higher proportion of wide-ranging species in polychaetes was contrasted with mostly restricted distributions in isopods. Remarkably, several cryptic lineages appeared to be sympatric and occurred in taxa with putatively good dispersal abilities, whereas some brooding lineages revealed broad distributions across the CCZ. Geographic distance could explain variation in faunal connectivity between regions and sites to some extent, while assumed dispersal capabilities were not as important. PMID:25671322

  20. Population genetic structure of the abyssal grenadier (Coryphaenoides armatus) around the mid-Atlantic ridge

    NASA Astrophysics Data System (ADS)

    Ritchie, H.; Cousins, N. J.; Cregeen, S. J.; Piertney, S. B.

    2013-12-01

    Understanding the factors that affect the levels and distribution of genetic diversity in oceanic and deep sea environments is a central focus in marine population genetics. Whilst it has been considered that the oceans represent a homogenous environment that would facilitate dispersal and minimise population structure, it is now clear that topographical features and current patterns can influence the extent of spatial gene flow and promote significant population genetic divergence even at local scales. Here we examine patterns of population genetic structure among N. Atlantic populations of the cosmopolitan abyssal grenadier Coryphaenoides armatus in relation to two hypothesised barriers to gene flow-the mid-Atlantic Ridge and the Charlie-Gibbs Fracture Zone/Sub-Polar Front. A suite of microsatellite markers were developed to examine the spatial pattern of allelic variation among 210 individuals from ten sampling locations encompassing sites east and west of the MAR and north and south of the CGFZ, plus a geographically distinct sample of individuals from the Crozet Islands in the Indian Ocean. Considerable genetic diversity was detected among individuals (na=5-13 and HO=0.46-0.69 across populations) but with an overall lack of genetic divergence between populations. Pairwise estimates of divergence among NE Atlantic samples were small and non-significant (max FST=0.04) and Structure-based Bayesian analysis of genetic clusters returned no distinct population structure. The only indication of genetic structure was between the Atlantic and Indian Oceans, with FST estimates of ca. 0.05. Patterns of genetic diversity and divergence are discussed in relation to what has been resolved in Coryphaenoides congeners, and what is known about the life history and ecology of C. armatus.

  1. A Reverse Taxonomic Approach to Assess Macrofaunal Distribution Patterns in Abyssal Pacific Polymetallic Nodule Fields

    PubMed Central

    Janssen, Annika; Kaiser, Stefanie; Meißner, Karin; Brenke, Nils; Menot, Lenaick; Martínez Arbizu, Pedro

    2015-01-01

    Heightened interest in the exploitation of deep seafloor minerals is raising questions on the consequences for the resident fauna. Assessing species ranges and determination of processes underlying current species distributions are prerequisites to conservation planning and predicting faunal responses to changing environmental conditions. The abyssal central Pacific nodule belt, located between the Clarion and Clipperton Fracture Zones (CCZ), is an area prospected for mining of polymetallic nodules. We examined variations in genetic diversity and broad-scale connectivity of isopods and polychaetes across the CCZ. Faunal assemblages were studied from two mining claims (the eastern German and French license areas) located 1300 km apart and influenced by different productivity regimes. Using a reverse taxonomy approach based on DNA barcoding, we tested to what extent distance and large-scale changes in environmental parameters lead to differentiation in two macrofaunal taxa exhibiting different functions and life-history patterns. A fragment of the mitochondrial gene Cytochrome Oxidase Subunit 1 (COI) was analyzed. At a 97% threshold the molecular operational taxonomic units (MOTUs) corresponded well to morphological species. Molecular analyses indicated high local and regional diversity mostly because of large numbers of singletons in the samples. Consequently, variation in composition of genotypic clusters between sites was exceedingly large partly due to paucity of deep-sea sampling and faunal patchiness. A higher proportion of wide-ranging species in polychaetes was contrasted with mostly restricted distributions in isopods. Remarkably, several cryptic lineages appeared to be sympatric and occurred in taxa with putatively good dispersal abilities, whereas some brooding lineages revealed broad distributions across the CCZ. Geographic distance could explain variation in faunal connectivity between regions and sites to some extent, while assumed dispersal capabilities were not as important. PMID:25671322

  2. Inter-annual species-level variations in an abyssal polychaete assemblage (Sta. M, NE Pacific, 4000 m)

    NASA Astrophysics Data System (ADS)

    Laguionie-Marchais, Claire; Paterson, Gordon L. J.; Bett, Brian J.; Smith, Kenneth L.; Ruhl, Henry A.

    2016-01-01

    Understanding the dynamics of abyssal community structure and function has become increasingly important as deep-sea resource exploitation and climate change pressures are expected to ramp up. This time-series study investigates macrofaunal polychaete dynamics at a station in the North East Pacific (Sta. M; 35° N 123° W, 4000 m, 1991-2011). Infaunal polychaete species were identified and their proxy biomass and proxy energy use rate estimated. The assemblage comprised 167 species, having a composition consistent with other abyssal areas globally. Significant changes in univariate and multivariate parameters (rank abundance distribution, Simpson's diversity index, and species and functional group composition) were detected across 1991-2011. However, no change in biomass or energy use rate was apparent through the time-series. The largest changes in the polychaete assemblage coincided with both an increase in sinking particulate organic carbon flux to the seafloor in 2007, and a 40 km relocation of the sampling location to a site 100 m shallower, preventing a conclusive assessment of which might drive the observed variation. Analyses prior to the change of sampling location showed that the polychaete assemblage composition dynamics were primary driven by food supply variation. Changes in several species were also lagged to changes in POC flux by 4-10 months. The polychaete fauna exhibited a significant positive relationship between total density and total energy use rate, suggesting population-level tracking of a common resource (e.g. POC flux food supply). Neither compensatory nor energetic zero-sum dynamics were detected among the polychaete assemblage, but the results suggest that the latter occur in the macrofaunal community as a whole. The results do indicate (a) potential control of species composition, and the density of individual key species, by food supply, when the time-series prior to the sampling location was analysed separately, and (b) generally sensitive detection of environmental change by species-level analysis of the abyssal polychaete assemblage.

  3. Late Quaternary geology of the Lower Central Plain, Thailand

    NASA Astrophysics Data System (ADS)

    Sinsakul, Sin

    2000-08-01

    The Lower Central Plain or Chao Phraya Plain, located in the upper Gulf of Thailand, has an average elevation of 2 m above the present mean sea level. It is a fault bounded basin developed in the Plio-Pleistocene epoch. Consequently, the basin has been filled with Quaternary sediment reaching a thickness of almost 2000 m, of which only the upper 300 m is known. The Pleistocene deposits of the Lower Central Plain represent a complex interplay of alluvial, fluvial and deltaic environments of the Chao Phraya River and its tributaries. The upper sequence of sand and stiff clay with iron-oxide concretions on the surface was deposited in a fluviatile environment subjected to a regressive period in the late Pleistocene. The term "Chao Phraya delta" is used to define the landform where the Chao Phraya River interacted with marine processes as the sea level changed during the Holocene transgression. These strata indicated that the Holocene sea reached its maximum height of 4 m above the present mean sea level around 6000 years B.P.; from then on sea level fluctuated until it reached its present level around 1500 years B.P. This complex sea level history has caused the progradation of tidal flat, and tide-dominated delta deposits, consisting of soft marine clay, that covered the Lower Central Plain to an average depth of 15 m in the Bangkok area. The soft marine clay or Bangkok clay is the most important unit in the stratigraphic sequence in terms of land subsidence in the Lower Central Plain. Evidence of coastal erosion is also considerable in the low tidal flat area on the west bank of the Chao Phraya River mouth and adjacent coast.

  4. Aquatic Sediments.

    ERIC Educational Resources Information Center

    Sanville, W. D.; And Others

    1978-01-01

    Presents a literature review of aquatic sediments and its effect upon water quality, covering publications of 1976-77. This review includes: (1) sediment water interchange; (2) chemical and physical characterization; and (3) heavy water in sediments. A list of 129 references is also presented. (HM)

  5. AQUATIC SEDIMENTS

    EPA Science Inventory

    One hundred seventeen literature references in the area of freshwater sediments were abstracted and synthesized to produce a review of sediment-related research for the period November, 1975 through October, 1976. Research areas covered included sediment-water interchange, sampli...

  6. Development of benthic biological monitoring criteria for disposal of low-level radioactive waste in the abyssal deep sea. Final report

    SciTech Connect

    Smith, C.R.; Present, T.M.C.; Jumars, P.A.

    1988-09-01

    In order to develop recommendations for monitoring low-level radioactive waste dumpsites in the abyss, the report attempts a synthesis of information from three overlapping topical areas. First, U.S. Regulations governing the dumping and monitoring of wastes in the ocean are interpreted in a deep-sea context. Second, significant attention is given to experiences obtained from past dumping of low-level radioactive wastes in marine environments, both shallow-water and deep-sea. Third, the report attempts to apply the monitoring Requirements and conceptual approaches selected to the abyssal seafloor, based on present understandings of the deep-sea ecosystem.

  7. Lava Flows on Coastal Plain

    USGS Multimedia Gallery

    The lava flows on the coastal plain, which show up as the light colored flows in the foreground, are erupted into the TEB tube system from the D fissure which first opened up in July 2007. This vent is faintly visible as a fuming source in the background near the upper left corner of the photo. Smal...

  8. Lava Flow on Coastal Plain

    USGS Multimedia Gallery

    Lava flows remain active within the Royal Gardens subdivision and onto the coastal plain below. The number of surface flows has decreased however, due in part to a probable decrease in activity related to the ongoing deflation of Pu`u `? `?, and because the new lava tube branch...

  9. 'Endurance' Goal Across the Plains

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This mosaic image from the Mars Exploration Rover Opportunity's panoramic camera provides an overview of the rover's drive direction toward 'Endurance Crater,' which is in the upper right corner of image.

    The plains appear to be uniform in character from the rovers current position all the way to Endurance Crater. Granules of various sizes blanket the plains. Spherical granules fancifully called blueberries are present some intact and some broken. Larger granules pave the surface, while smaller grains, including broken blueberries, form small dunes. Randomly distributed 1-centimeter (0.4 inch) sized pebbles (as seen just left of center in the foreground of the image) make up a third type of feature on the plains. The pebbles' composition remains to be determined. Scientists plan to examine these in the coming sols.

    Examination of this part of Mars by NASA's Mars Global Surveyor orbiter revealed the presence of hematite, which led NASA to choose Meridiani Planum as Opportunity's landing site. The rover science conducted on the plains of Meridiani Planum serves to integrate what the rovers are seeing on the ground with what orbital data have shown.

    Opportunity will make stop at a small crater called 'Fram' (seen in the upper left, with relatively large rocks nearby) before heading to the rim of Endurance Crater.

  10. Ages of Lunar Light Plains

    NASA Astrophysics Data System (ADS)

    Hiesinger, Harald; Howes van der Bogert, Carolyn; Thiessen, Fiona; Robinson, Mark

    2013-04-01

    Light plains are characterized by their relative smoothness and lower crater densities (compared to the highlands), and their occurrence as crater fills. They also exhibit highland-like characteristics, such as high albedos (in comparison to mare basalts) and their geological and stratigraphic setting. Despite the long history of investigating light plains, there are still numerous open questions concerning their mode of emplacement, their mineralogical composition, their ages, and their origin. We dated 16 light plains with crater size-frequency distribution (CSFD) measurements. All dated regions were previously identified as light plains in the geologic maps [1-5] and either mapped as smooth light plains (Ip) or light plains with undulatory surfaces (INp). The studied light plains occur both inside and outside the South Pole-Aitken (SPA) basin within a latitudinal band between ~-36° and ~-75°. In particular, we investigated the following smooth light plains: Janssen (40.82°E, -44.96°; Ip [1]), Nishina (-170.8°E, -44.57°; Ip [2]), South of Nishina (Ip [2]), Obruchev (162.43°E, -38.67°; Ip [2]), Oresme (169.22°E, -42.61°, Ip [2]), Schrödinger (132.93°E, -74.73°; Ip [3]), Nearch (39.01°E, -58.58°; Ip [3]), Nasmyth (-56.39°E, -50.49°; Ip [3]), Manzinus (26.37°E, -67.51°; Ip [3]), Klaproth (-26.26°E, -69.85°; Ip [3]), Phocylides (-57.31°E, -52.79°, Ip [3]), Buffon (-133.53°E, -40.64°; Ip [4]), Roche (136.54°E, -42.37°; Ip [5]). We also dated the following light plains with undulatory surfaces: Koch (150.33°E, -42.13°; INp [2]), Garavito (156.78°E, -47.21°; INp [2]), Eötvös (134.43°E, -35.61°; INp [5]). Our CSFD measurements resulted in absolute model ages of 3.71 to 4.02 Ga for all investigated light plains, thus confirming the Imbrian and/or Nectarian ages of the geologic maps [1-5]. We only dated three INp light plains, but they appear to have ages that are close to the upper limit, i.e., 3.96-4.02 Ga. However, further CSFDs of INp light plains are necessary to corroborate this preliminary observation. In general, our new absolute model ages are similar to model ages derived for light plains north of Mare Frigoris (3.65-4.0 Ga) [6], light plains within the SPA basin (3.43-3.81 Ga) [7], and light plains in the surroundings of the Orientale and Imbrium basins (3.8-4.3 Ga) [8]. The ages are not only similar, but also show similar ranges. While our model ages vary by about 300 Ma, model ages of [6,7] exhibit ranges of ~350 Ma and ~380 Ma, respectively. Ages of [8] show a somewhat wider range of ~500 Ma. From this wide range in ages it has been concluded that a formation of the light plains by a single event (i.e., Orientale or Imbrium) is unlikely [6-8]. References: [1] Wilhelms and McCauley (1971), USGS I-703; [2] Stuart-Alexander (1978), USGS I-1047; [3] Wilhelms et al. (1979), USGS I-1162; [4] Scott et al. (1977), USGS I-1034; [5] Wilhelms and El-Baz (1977), USGS I-948; [6] Köhler et al. (2000), LPSC 31, #1822; [7] Thiessen et al. (2012), LPSC 43, #2060; [8] Neukum (1977b), Moon 17, 383-393.

  11. A sediment budget for Town Creek watershed: Suspended sediment transport analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Town Creek watershed is located in the Southeastern Plains Ecoregion in Mississippi. Its total area covers 1,769 km2 and represents approximately 50% of the upper Tombigbee River basin area contributing to the Aberdeen Pool on the Tennessee-Tombigbee Waterway. The sediment yield from the watersh...

  12. Direct connectivity between upstream and downstream promotes rapid response of lower coastal-plain rivers to land-use change

    NASA Astrophysics Data System (ADS)

    Mattheus, Christopher R.; Rodriguez, Antonio B.; McKee, Brent A.

    2009-10-01

    Low-relief fluvial systems that originate in the lower coastal plain and discharge into estuaries are common along passive margins. These watersheds are thought to be disconnected from their termini by floodplains, which buffer the sediment-routing system by sequestration. Here, we present a detailed study of the Newport River, a typical lower coastal-plain system, which reveals high connectivity between watershed and delta. Connectivity is measured as the time lag between initiation of a silviculture operation, which increased landscape erosion, and when the sediment appeared at the bay-head delta. The time lag, measured from aerial photographs and sedimentation rates calculated from 210Pb- and 137Cs-activities in cores from the watershed and delta, is <3 years. Most lower coastal-plain rivers are steeper and have less floodplain accommodation available for storage than their larger counterparts that originate landward of the fall line, which promotes higher connectivity between upstream and downstream.

  13. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Plain bearings. 229.64 Section 229.64 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....64 Plain bearings. A plain bearing box shall contain visible free oil and may not be cracked to...

  14. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Plain bearings. 229.64 Section 229.64 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....64 Plain bearings. A plain bearing box shall contain visible free oil and may not be cracked to...

  15. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Plain bearings. 229.64 Section 229.64 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....64 Plain bearings. A plain bearing box shall contain visible free oil and may not be cracked to...

  16. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Plain bearings. 229.64 Section 229.64 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....64 Plain bearings. A plain bearing box shall contain visible free oil and may not be cracked to...

  17. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Plain bearings. 229.64 Section 229.64 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....64 Plain bearings. A plain bearing box shall contain visible free oil and may not be cracked to...

  18. The Texas High Plains Evapotranspiration (TXHPET) network

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The newly developed Texas High Plains Evapotranspiration (TXHPET) network is comprised of the North Plains and South Plains evapotranspiration (ET) networks. The TXHPET network currently entails the operation of 18 meteorological stations located in 15 Texas counties and regional coverage is estima...

  19. Morphological and ontogenetic stratification of abyssal and hadal Eurythenes gryllus sensu lato (Amphipoda: Lysianassoidea) from the Peru-Chile Trench

    NASA Astrophysics Data System (ADS)

    Eustace, Ryan M.; Ritchie, Heather; Kilgallen, Niamh M.; Piertney, Stuart B.; Jamieson, Alan J.

    2016-03-01

    The globally ubiquitous lysianassoid amphipod, Eurythenes gryllus, has been shown to consist of multiple genetically distinct cryptic taxa, with depth considered a major driver of speciation and morphological divergence. Here we examine morphological variation of E. gryllus sensu lato through a continuous depth distribution that spans from abyssal (3000-6000 m) into hadal depths (>6000 m) in the Peru-Chile Trench (SE Pacific Ocean). Three distinct morphospecies were identified: one was confirmed as being E. magellanicus (4602-5329 m) based on DNA sequence and morphological similarity. The other two morphologically distinct species were named based upon depth of occurrence; Abyssal (4602-6173 m) and Hadal (6173-8074 m). The three Eurythenes morphospecies showed vertical ontogenetic stratification across their bathymetric range, where juveniles were found shallower in their depth range and mature females deeper. Potential ecological and evolutionary drivers that explain the observed patterns of intra and inter-specific structure, such as hydrostatic pressure and topographical isolation, are discussed.

  20. Intensity of pelagic-benthic coupling in different regions along the Antarctic Polar Front - Clues from abyssal megafauna

    NASA Astrophysics Data System (ADS)

    Würzberg, Laura; Zinkann, Ann-Christine; Brandt, Angelika; Janussen, Dorte; Bohn, Jens M.; Schwabe, Enrico

    2014-10-01

    The zone surrounding the Antarctic Polar Front is a region characterized by elevated seasonal primary production. Studies on the implications for the fauna inhabiting the underlying deep-sea floor, however, are rare. The present study focuses on the abundance of megafaunal organisms caught by means of an Agassiz Trawl during the SYSTem COupling in the Southern Ocean II (SYSTCO II) expedition (RV Polarstern cruise ANT XXVIII/3). Biomass estimates in terms of volume as well as species richness of echinoderms were additionally taken into account. Abyssal stations (ca. 4000 m depth) located in three different regions along the Antarctic Polar Front characterized by different primary production regimes and oceanographic features were sampled. One shallower station (337 m depth) was used as reference station. Highest megafaunal abundances were found at the shallow station (147 individuals per 1000 m2). Megafaunal abundances were low to moderate at the abyssal stations (7.2-23.5 individuals per 1000 m2) with the exception of the region northwest of South Georgia, where distinctly higher abundances were found (up to 119.7 individuals per 1000 m2). The same pattern was observed for biomass estimates. At the other regions, magnitude of megafaunal abundances and echinoderm biomasses were found not to be linked to the surface levels of primary production. This indicates that strong pelagic-benthic coupling likely occurs only downstream of South Georgia. Echinoderm species richness does not appear to be directly related to the environmental conditions as it does not differ statistically between the considered areas.

  1. Lead and osmium isotopic constraints on the oceanic mantle from single abyssal peridotite sulfides

    NASA Astrophysics Data System (ADS)

    Warren, J. M.; Shirey, S. B.

    2012-12-01

    Single sulfides from abyssal peridotites have been analyzed for Pb and Re-Os to constrain the evolution of oceanic mantle composition. These represent the first analyses of Pb and Os isotopic compositions in the same sulfide grain. The sulfides are from Gakkel and Southwest Indian ridge peridotites, occur at <0.1% modal abundances, and contain 0.001-0.4 ppm Re, 0.003-5 ppm Os, and 0.12-12 ppm Pb. Sulfide Pb isotopic compositions extend from depleted (e.g., 206Pb/204Pb=17.0) to enriched (19.6), covering a larger range than associated basalts. The Os isotopic range of sulfides is more restricted, but extends from depleted (187Os/188Os=0.116) to enriched (0.150). Pb and Os concentrations and isotopic compositions co-vary, with correlation coefficients of 0.76-0.94. Both Pb and Re-Os isotopic data follow ?2 Ga isochrons, with isotopic compositions varying down to small (?1 km) length-scales and some sulfides containing supra-chondritic 187Re/188Os and 187Os/188Os. These observations are best explained by long-term recycling of oceanic lithosphere combined with melt extraction and refertilization at ancient ocean ridges, rather than a specific event at 2 Ga. The concentration of Pb in sulfides indicates that they host <4% of the mantle Pb budget. A re-evaluation of the mass balance of Pb in peridotites indicates that most mantle Pb is stored in silicate phases. The Pb partition coefficient between sulfide melt and silicate melt is estimated to be ?3, based on the correlation of Pb-Os concentrations in this study and measured Os partition coefficients from the literature. These observations indicate that sulfides do not exert a strong control on the fractionation of Pb during mantle melting, but they can be used to constrain mantle Pb isotopic composition. Sulfides in this study, combined with literature data for Pb isotopes in peridotite whole rocks and pyroxene separates, provide evidence for ultra-depleted mantle, as 24% of peridotites are unradiogenic (i.e., 207Pb/204Pb <15.440 and 206Pb/204Pb <17.726), compared to only 3% of ridge basalts. This suggests that the mantle contains volumetrically significant reservoirs of ultra-depleted material, probably derived from recycled oceanic lithospheric mantle. These depleted reservoirs contribute in only small amounts to oceanic crust generation, both due to a limited ability to melt and to the dilution of any melt by more enriched melts during crust formation.

  2. Relation of sediment yield to climatic and physical characteristics in the Missouri River basin

    USGS Publications Warehouse

    Jordan, P.R.

    1979-01-01

    Data from 64 stream-sediment stations and reservoirs in the plains area and from 15 stream-sediment stations in the mountainous area of the Missouri River basin were analyzed to determine the relation of sediment yield to basin characteristics. Data from each sediment station and reservoir represented at least 7 years of sediment discharge in the plains area or 4 years of sediment discharge in the mountainous area. Results of the analysis show the approximate relations of sediment yield to basin characteristics in the plains area, but data for the mountainous area are insufficient to show any significant relation. In the plains area the sediment yield was most closely related to contributing drainage area, mean streamflow, average thickness of loess, and average land slope. A regression equation, using these characteristics, estimates sediment yields with a standard error of +142 percent and -59 percent. The relation of sediment yield to size of drainage area was consistent with the relation found earlier for the upper Mississippi River basin. (Woodard-USGS)

  3. Exploring the temporal change in provenance encoded in the late Quaternary deposits of the Ganga Plain

    NASA Astrophysics Data System (ADS)

    Agrawal, Shailesh; Sanyal, Prasanta; Balakrishnan, Srinivasan; Dash, Jitendra K.

    2013-07-01

    Temporal analysis of Sr isotopes in soil carbonates and Sr and Nd isotopes in silicate fractions has been carried out in a sedimentary core (Kalpi core; 50 m long) raised from the southern bank of the Yamuna river, Ganga Plain, India. The aim of the study is to constrain sediment provenance through comparison with the modern Himalayan and peninsular river systems' water and bank sediments. Sr isotopic data in soil carbonates (0.71874 to 0.71410) and Srsbnd Nd isotopic data in silicate (0.72865 to 0.74544 and - 13.9 to - 17.2, respectively) vary significantly with depth and are indicative of both Himalayan and peninsular sources for sediments in the southern Ganga Plain. The positive correlation between 87Sr/86Sr ratio and 1/Sr in soil carbonate and the negative correlation between 87Sr/86Sr and ɛNd in silicate confirm mixing of sediments from these sources. Variations of 87Sr/86Sr ratios in soil carbonates show that at ~ 80 and 45 ka the Himalaya acted as the major source of sediments in the southern part of the Ganga Plain. The gradual decrease in 87Sr/86Sr ratios after 80 and 45 ka indicates change in source to peninsular India which is also supported by limited Sr and Nd isotope data in silicates. The change in sediment provenance corresponds well with the available climatic record and is suggestive of strong climatic control in sediment supply with high supply from the Himalaya during the interglacial period and peninsular sediments during glacial period.

  4. Geochemistry and mineralogy of shallow alluvial aquifers in Daudkandi upazila in the Meghna flood plain, Bangladesh

    NASA Astrophysics Data System (ADS)

    Hasan, M. Aziz; von Brmssen, Mattias; Bhattacharya, Prosun; Ahmed, Kazi Matin; Sikder, Arif Mohiuddin; Jacks, Gunnar; Sracek, Ondra

    2009-04-01

    The shallow alluvial aquifers of the delta plains and flood plains of Bangladesh, comprises about 70% of total land area are mostly affected by elevated concentrations of arsenic (As) in groundwater exposing a population of more than 35 million to As toxicity. Geochemical studies of shallow alluvial aquifer in the Meghna flood plain show that the uppermost yellowish grey sediment is low in As (1.03 mg/kg) compared to the lower dark grey to black sediment (5.24 mg/kg) rich in mica and organic matter. Sequential extraction data show that solid phase As bound to poorly crystalline and amorphous metal (Fe, Mn, Al)-oxyhydroxides is dominant in the grey to dark grey sediment and reaches its maximum level (3.05 mg/kg) in the mica rich layers. Amount of As bound to sulphides and organic matter also peaks in the dark grey to black sediment. Vertical distributions of major elements determined by X-ray fluorescence (XRF) show that iron (Fe2O3), aluminum (Al2O3) and manganese (MnO) follow the general trend of distribution of As in the sediments. Concentrations of As, Mn, Fe, HCO3 -, SO4 2- and NO3 - in groundwater reflect the redox status of the aquifer and are consistent with solid phase geochemistry. Mineralogical analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) fitted with energy dispersive X-ray spectrometer (EDS) revealed dominance of crystalline iron oxides and hydroxides like magnetite, hematite and goethite in the oxidised yellowish grey sediment. Amorphous Fe-oxyhydroxides identified as grain coating in the mica and organic matter rich sediment suggests weathering of biotite is playing a critical role as the source of Fe(III)-oxyhydroxides which in turn act as sink for As. Presence of authigenic pyrite in the dark grey sediment indicates active reduction in the aquifer.

  5. Hydrogeologic setting and potential for denitrification in ground water, coastal plain of southern Maryland

    USGS Publications Warehouse

    Krantz, David E.; Powars, David S.

    2000-01-01

    The types and distribution of Coastal Plain sediments in the Patuxent River Basin may contribute to relatively low concentrations of nitrate (typically less than 1 milligram per liter) in stream base flow because of the chemical reduction of dissolved nitrate (denitrification) in ground water. Water chemistry data from synoptic stream base-flow surveys in the Patuxent River Basin show higher dissolved nitrate concentrations in the Piedmont than in the Coastal Plain section of the watershed. Stream base flow reflects closely the chemistry of ground water discharging from the surficial (unconfined) aquifer to the stream. Because land use in the sampled subbasins is virtually the same in each section, differences in the physical and geochemical characteristics of the surficial aquifer may explain the observed differences in water chemistry. One possible cause of lower nitrate concentrations in the Coastal Plain is denitrification within marine sediments that contain chemically reduced compounds. During denitrification, the oxygen atoms on the nitrate (N03-) molecule are transferred to a reduced compound and N gas is produced. Organic carbon and ferrous iron (Fe2+), derived from the dissolution of minerals such as pyrite (FeS2) and glauconite (an iron aluminosilicate clay), can act as reducing substrates; these reduced chemical species are common in the marine and estuarine deposits in Southern Maryland. The spatial distribution of geologic units and their lithology (sediment type) has been used to create a map of the potential for denitrification of ground water in the surficial aquifer of the Coastal Plain in Southern Maryland.

  6. High Plains Aquifer Hydrologic Observatory

    NASA Astrophysics Data System (ADS)

    Steward, D. R.

    2004-12-01

    The High Plains Aquifer encompasses 174,000 square miles in eight states and provides the primary source of potable water to the region. The hydrologic cycle exhibits great diversity across this geological basin, with significant expanses experiencing sustained declines in groundwater elevation (e.g., portions of the southern and central basins in Kansas, New Mexico, Oklahoma, and Texas) while other areas are experiencing rises (e.g., portions of the northern basin in central Nebraska). The proposed High Plains Aquifer Hydrologic Observatory would promote significant scientific advancement in hydrology related to: (1) Recharge and evapotranspiration, (2) Surface water-groundwater exchange in dynamic riparian corridors, (3) Ecological role of vegetation in the hydrologic cycle, (4) Human systems and the hydrologic cycle, (5) Multi-scale monitoring, modeling & analysis, (6) Climate change studies, and (7) Utilization of remote sensing technology

  7. Tuffaceous ephemeral lake deposits on an alluvial plain, Middle Tertiary of central California

    USGS Publications Warehouse

    Bartow, J.A.

    1994-01-01

    The Oligocene and Miocene Valley Springs Formation represents a large fluvial depositional system that extended westward from sediment-filled palaeovalleys in the high Sierra Nevada to a piedmont alluvial plain under the present Central Valley. The Valley Springs Formation consists largely of tuffaceous mudrocks, tuffaceous sandstone, polymict conglomerate and rhyodacitic tuff. The tuffaceous mudrock lithofacies probably represents a complex of ephemeral lake and marsh environments on a low gradient alluvial plain. The inferred abundance of shallow lakes, ponds and marshes implies a climate that was wetter than the semi-arid climate of the region today. -from Author

  8. Southern Great Plains Safety Orientation

    SciTech Connect

    Schatz, John

    2014-05-01

    Welcome to the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ARM) Southern Great Plains (SGP) site. This U.S. Department of Energy (DOE) site is managed by Argonne National Laboratory (ANL). It is very important that all visitors comply with all DOE and ANL safety requirements, as well as those of the Occupational Safety and Health Administration (OSHA), the National Fire Protection Association, and the U.S. Environmental Protection Agency, and with other requirements as applicable.

  9. Influence of seasonal phytodetritus deposition on biogenic silica dissolution in marine sedimentsPotential effects on preservation

    NASA Astrophysics Data System (ADS)

    Gallinari, M.; Ragueneau, O.; DeMaster, D. J.; Hartnett, H.; Rickert, D.; Thomas, C.

    2008-11-01

    The deposition of fresh phytoplankton detritus (phytodetritus) following phytoplankton blooms may influence biogenic silica (BSi) dissolution in marine sediments. We studied BSi dissolution properties before, during, and after periods of phytodetritus deposition during time-series field programs in the abyssal North Atlantic (the BENGAL project), and on the West Antarctic Peninsula Shelf (the FOODBANCS project). Dissolution experiments, performed by means of flow-through reactors, showed temporal variations in the dissolution properties of BSi in the sediment column after phytodetritus deposition. This non-steady-state character of benthic silica dynamics is an important aspect of pelagic-benthic coupling. The last FOODBANCS cruise occurred after a phytodetritus deposition event, and yielded high pore-water dissolved silica (DSi) concentrations and DSi effluxes in the upper centimetres of the sediment column, suggesting a rapid turnover of recently deposited siliceous material. Higher dissolution rates were measured in the phytodetritus-rich sediments relative to surface sediments collected during previous seasons on earlier FOODBANCS cruises. During the BENGAL project, high dissolution rates were measured at depth in the sediment column only after a summer phytodetritus deposition event. In the highly detrital sediment matrix of the abyssal North Atlantic Ocean, resolution of increased dissolution rates and experimental artefacts of the flow-through reactors can be difficult because of the low abundance of BSi. Depending on the sediment matrix, bioturbation can play a crucial role in transporting fresh BSi particles to depth, where DSi concentrations are close to experimentally determined BSi solubilities. The potential impacts of such processes on BSi preservation are discussed. We suggest that future models of BSi early diagenesis should include the rapid mixing of freshly deposited particles if we want to describe further the preservation of BSi in marine sediments.

  10. Relationship between the parent material and the soil, in plain and mountainous areas

    NASA Astrophysics Data System (ADS)

    Kerek, Barbara; Kuti, Laszlo; Dobos, Timea; Vatai, Jozsef; Szentpetery, Ildiko

    2013-04-01

    One of the most important tasks of the soil is the nutrition of plants. This function is determinated by those parts of the geological media on what is the soil situated and from what the soil was formed (those two can be different). Soil can be formed definitely just from sediment, so it is more proper to speak about parent material than parent rock. Soil forming sediment is defined as the loose sediment on the surface, which is the upper layer of near-surface rocks in flat and hilly regions, and it is the upper layer of the sediment-ensemble situated on the undisturbed bedrock in mountainous areas. Considering its origin, these sediments could be autochthon or allochton. Soil forming is determinated, besides other factors (climate, elevation, vegetation, etc.), by the parent material, which has a crucial influence on the type, quality and fertility of soils through its mineral composition, physical and chemical characteristics. Agrogeological processes happen in the superficial loose sediments in mountainous areas, but the underlying solid rock (where on the surface or close to it, there is solid rock), has an effect on them. The plain and hilly regions covered by thick loose sediment and the areas build up by solid rock and covered with thinner loose sediment in mountainous areas should be searched separately. In plain areas the near-surface formations have to be studied as a whole down to the saturated zone, but at least to 10 m. In regions of mountain and mountain fronts, the thickness, the composition and genetics of the young unconsolidated sediments situated above the older solid rocks have a vital importance, and also the relations among the soils, soil forming sediments and the base rocks have to be understood.

  11. The Abyssal Ocean's Contributions to the Global Energy and Sea Level Budgets Between the 1990s and 2000s

    NASA Astrophysics Data System (ADS)

    Purkey, Sarah Michelle Goldstein

    Over the past three decades, Antarctic Bottom Water (AABW), a cold, dense water-mass produced around Antarctica that feeds the bottom limb of the Meridional Overturning Circulation (MOC), has warmed, freshened, and declined in volume. We quantify water-property changes in the deep Southern Ocean and the abyssal global ocean and evaluate the relative contribution of these abyssal changes to the global energy and sea level rise budgets. We find a strong warming trend throughout the deep (greater than 1000 m) Southern Ocean and abyssal (greater than 4000 m) global oceans, equivalent to a heat flux of 0.095 (+/- 0.062) W m -2 applied over the entire surface area of the Earth, a statistically significant fraction of the present global energy budget. The observed warming pattern is also consistent with a global-scale contraction of AABW, suggesting a slowdown of the bottom limb of the MOC. In addition, freshening of 0.02 PSS-78 per decade is observed in the AABW directly downstream from formation sites along the Antarctic continent, with freshening rates roughly a tenth of this in the deep interior of basins adjacent to Antarctica in the Indian and Pacific sectors of the Southern Ocean. The fresh water flux required to account for the observed freshening of AABW in these two basins is 73 (+/- 26) GT yr -1. Finally, the full-depth steric contributions to SLR calculated along the repeated hydrographic sections are used to assess regional and global rates of SLR owing to mass addition through a full depth SLR budget and compared to mass addition estimated directly using data from the Gravity Recovery And Climate Experiment (GRACE) from 2003--2013. These two independent methods both find a global mean rate of mass addition of 1.5 (+/- 0.4) mm yr -1 over their respective periods with large regional variability with higher rates of mass addition in the North Pacific, South Atlantic, and Indo-Atlantic sector of the Southern Ocean, possibly associated with recent changes in the gravity field from ice loss in these two regions.

  12. Hurricane-induced sediment deposition in a gulf coast marsh

    NASA Astrophysics Data System (ADS)

    Rejmnek, Marcel; Sasser, Charles E.; Peterson, Gary W.

    1988-08-01

    Rates of sediment accumulation in four coastal marsh communities in the Mississippi River deltaic plain, Louisiana, were studied using feldspar clay marker horizons. The results indicate that normal riverine flooding contributes relatively little (<01 cm year -1) to marsh accretion in the studied area. In contrast, even a minor hurricane can resuspend sediments from shallow bays and deposit more than 22 cm of sediments in Phragmites australis dominated communities adjacent to the bayous as far as 7 km inland from the bay shore. Hurricane-induced sedimentation represents at least a partial compensation to prevailing subsidence of marshes in abandoned delta lobes.

  13. History of plains resurfacing in the Scandia region of Mars

    USGS Publications Warehouse

    Tanaka, Kenneth L.; Fortezzo, Corey M.; Hayward, Rosalyn K.; Rodriguez, J. Alexis P.; Skinner, James A.

    2011-01-01

    We present a preliminary photogeologic map of the Scandia region of Mars with the objective of reconstructing its resurfacing history. The Scandia region includes the lower section of the regional lowland slope of Vastitas Borealis extending about 500–1800 km away from Alba Mons into the Scandia sub-basin below −4800 m elevation. Twenty mapped geologic units express the diverse stratigraphy of the region. We particularly focus on the materials making up the Vastitas Borealis plains and its Scandia sub-region, where erosional processes have obscured stratigraphic relations and made the reconstruction of the resurfacing history particularly challenging. Geologic mapping implicates the deposition, erosion, and deformation/degradation of geologic units predominantly during Late Hesperian and Early Amazonian time (~3.6–3.3 Ga). During this time, Alba Mons was active, outflow channels were debouching sediments into the northern plains, and basal ice layers of the north polar plateau were accumulating. We identify zones of regional tectonic contraction and extension as well as gradation and mantling. Depressions and scarps within these zones indicate collapse and gradation of Scandia outcrops and surfaces at scales of meters to hundreds of meters. We find that Scandia Tholi display concentric ridges, rugged peaks, irregular depressions, and moats that suggest uplift and tilting of layered plains material by diapirs and extrusion, erosion, and deflation of viscous, sedimentary slurries as previously suggested. These appear to be long-lived features that both pre-date and post-date impact craters. Mesa-forming features may have similar origins and occur along the southern margin of the Scandia region, including near the Phoenix Mars Lander site. Distinctive lobate materials associated with local impact craters suggest impact-induced mobilization of surface materials. We suggest that the formation of the Scandia region features potentially resulted from crustal heating related to Alba Mons volcanism, which acted upon a sequence of lavas, outflow channel sediments, and polar ice deposits centered within the Scandia region. These volatile-enriched sediments may have been in a state of partial volatile melt, resulting in the mobilization of deeply buried ancient materials and their ascent and emergence as sediment and mud breccia diapirs to form tholi features. Similar subsurface instabilities proximal to Alba Mons may have led to surface disruption, as suggested by local and regional scarps, mesas, moats, and knob fields.

  14. History of plains resurfacing in the Scandia region of Mars

    NASA Astrophysics Data System (ADS)

    Tanaka, Kenneth L.; Fortezzo, Corey M.; Hayward, Rosalyn K.; Rodriguez, J. Alexis P.; Skinner, James A.

    2011-09-01

    We present a preliminary photogeologic map of the Scandia region of Mars with the objective of reconstructing its resurfacing history. The Scandia region includes the lower section of the regional lowland slope of Vastitas Borealis extending about 500-1800 km away from Alba Mons into the Scandia sub-basin below -4800 m elevation. Twenty mapped geologic units express the diverse stratigraphy of the region. We particularly focus on the materials making up the Vastitas Borealis plains and its Scandia sub-region, where erosional processes have obscured stratigraphic relations and made the reconstruction of the resurfacing history particularly challenging. Geologic mapping implicates the deposition, erosion, and deformation/degradation of geologic units predominantly during Late Hesperian and Early Amazonian time (˜3.6-3.3 Ga). During this time, Alba Mons was active, outflow channels were debouching sediments into the northern plains, and basal ice layers of the north polar plateau were accumulating. We identify zones of regional tectonic contraction and extension as well as gradation and mantling. Depressions and scarps within these zones indicate collapse and gradation of Scandia outcrops and surfaces at scales of meters to hundreds of meters. We find that Scandia Tholi display concentric ridges, rugged peaks, irregular depressions, and moats that suggest uplift and tilting of layered plains material by diapirs and extrusion, erosion, and deflation of viscous, sedimentary slurries as previously suggested. These appear to be long-lived features that both pre-date and post-date impact craters. Mesa-forming features may have similar origins and occur along the southern margin of the Scandia region, including near the Phoenix Mars Lander site. Distinctive lobate materials associated with local impact craters suggest impact-induced mobilization of surface materials. We suggest that the formation of the Scandia region features potentially resulted from crustal heating related to Alba Mons volcanism, which acted upon a sequence of lavas, outflow channel sediments, and polar ice deposits centered within the Scandia region. These volatile-enriched sediments may have been in a state of partial volatile melt, resulting in the mobilization of deeply buried ancient materials and their ascent and emergence as sediment and mud breccia diapirs to form tholi features. Similar subsurface instabilities proximal to Alba Mons may have led to surface disruption, as suggested by local and regional scarps, mesas, moats, and knob fields.

  15. Yellowstone-Snake River Plain seismic profilling experiment: Crustal structure of the eastern Snake River Plain

    SciTech Connect

    Braile, L.W.; Smith, R.B.; Ansorge, J.; Baker, M.R.; Sparlin, M.A.; Prodehl, C.; Schilly, M.M.; Healy, J.H.; Mueller, S.; Olsen, K.H.

    1982-04-10

    Seismic refraction profiles recorded along the eastern Snake River Plain (ESRP) in southeastern Idaho during the 1978 Yellowstone-Snake River Plain cooperative seismic profiling experiment are interpreted to infer the crustal velocity and attenuation (Q-1) structure of the ESRP. Travel-time and synthetic seismogram modeling of a 250 km reversed refraction profile as well as a 100 km detailed profile indicate that the crust of the ESRP is highly anomalous. Approximately 3 to 6 km of volcanic rocks (with some interbedded sediments) overlie an upper-crustal layer (compressional velocity approx. =6.1 km/s) which thins southwestward along the ESRP from a thickness of 10 km near Island Park Caldera to 2 to 3 km beneath the central and southwestern portions of the ESRP. An intermediate-velocity (approx. =6.5 km/s) layer extends from approx. =10 to approx. =20 km depth. a thick (approx. =22 km) lower crust of compressional velocity 6.8 km/s, a total crustall thickness of approx. =42 km, and a P/sub n/ velocity of approx. =7.9 km/s is observed in the ESRP, similar to the western Snake River Plain and the Rocky Mountains Provinces. High attenuation is evident on the amplitude corrected seismic data due to low-Q values in the volcanic rocks (Q/sub p/ = 20 to 200) and throughout the crust (Q/sub p/ = 160 to 300). Based on these characteristics of the crustal structure and volcanic-age progression data, it is suggested that the ESRP has resulted from an intensitive period of intrusion of mantle-derived basaltic magma into the upper crust generating explosive silicic volcanism and associated regional uplift and caldera collapse. This activity began about 15 m.y. ago in southwestern Idaho and has migrated northeast to its present position at Yellowstone. Subsequent cooling of the intruded upper crust results in the 6.5 km/s velocity intermediate layer. Crustal subsidence and periodic basaltic volcanism as represented by the ESRP complete the sequence of crustal evolution.

  16. Planetary stations and Abyssal Benthic Laboratories: An overview of parallel approaches for long-term investigation in extreme environments

    NASA Technical Reports Server (NTRS)

    Dipippo, S.; Prendin, W.; Gasparoni, F.

    1994-01-01

    In spite of the apparent great differences between deep ocean and space environment, significant similarities can be recognized when considering the possible solutions and technologies enabling the development of remote automatic stations supporting the execution of scientific activities. In this sense it is believed that mutual benefits shall be derived from the exchange of experiences and results between people and organizations involved in research and engineering activities for hostile environments, such as space, deep sea, and polar areas. A significant example of possible technology transfer and common systematic approach is given, which describes in some detail how the solutions and the enabling technologies identified for an Abyssal Benthic Laboratory can be applied for the case of a lunar or planetary station.

  17. Petrological, magnetic and chemical properties of basalt dredged from an abyssal hill in the North-east pacific

    USGS Publications Warehouse

    Luyendyk, B.P.; Engel, C.G.

    1969-01-01

    OVER the years, samples of basalt from the oceanic crust have been taken mainly from seamounts, fracture zones and ridge and rise crests1-6, and rarely from the vast fields of abyssal hills which cover a large part of the deep-sea floor. The basalt sampled from the deeper regions of the oceanic crust (for example, on fault scarps) is a distinct variety of tholeiitic basalt, while alkali basalt is restricted to the volcanic edifices4. Oceanic tholeiitic basalt differs from alkali basalt and continental tholeiite chiefly in having a relatively low percentage of K2O (0.2 weight per cent)4. Some authors have speculated that this type of tholeiitic basalt is the major extrusion from the upper mantle and constitutes the predominant rock type in the upper oceanic crust. ?? 1969 Nature Publishing Group.

  18. Influence of the Atchafalaya River on recent evolution of the chenier-plain inner continental shelf, northern Gulf of Mexico

    USGS Publications Warehouse

    Draut, A.E.; Kineke, G.C.; Velasco, D.W.; Allison, M.A.; Prime, R.J.

    2005-01-01

    This study examines the influence of the Atchafalaya River, a major distributary of the Mississippi River, on stratigraphic evolution of the inner continental shelf in the northern Gulf of Mexico. Sedimentary, geochemical, and shallow acoustic data are used to identify the western limit of the distal Atchafalaya subaqueous delta, and to estimate the proportion of the Atchafalaya River's sediment load that accumulates on the inner shelf seaward of Louisiana's chenier-plain coast. The results demonstrate a link between sedimentary facies distribution on the inner shelf and patterns of shoreline accretion and retreat on the chenier plain. Mudflat progradation on the eastern chenier-plain coast corresponds to the location of deltaic mud accumulation on the inner shelf. On the central chenier-plain shelf, west of the subaqueous delta, relict sediment is exposed that was originally deposited between ???1200 and 600 years BP during activity of the Lafourche lobe of the Mississippi Delta complex. Mass-balance calculations indicate that the eastern chenier-plain inner shelf and coastal zone form a sink for 7??2% of the sediment load carried by the Atchafalaya River. ?? 2004 Elsevier Ltd. All rights reserved.

  19. Petrological significance of the abyssal peridotites from the ophiolite belt of Indo-Myanmar Range, northeastern India

    NASA Astrophysics Data System (ADS)

    Maibam, B.; Foley, S.

    2009-04-01

    The ophiolite belt of the Indo-Myanmar Range of northeastern India is regarded as the continental extension of the Indonesia island arc. The ophiolite sequence forms a belt extending about 200 km from Pukhpur (Nagaland state) in the north to Moreh (Manipur state) in the south. Here we report preliminary mineralogical and phase geochemical data of peridotites collected from the ophiolite sequences of the Ukhrul district in Manipur. Primary minerals are clinopyroxene, orthopyroxene and spinel with scarce relicts of olivine. Andraditic garnet present in a few samples is of secondary origin. The clinopyroxene and orthopyroxene show limited compositional range. Well's (1977) single clinopyroxene thermometry yielded variable equilibrium temperature between 780-1250oC. The lower temperature value suggests post-crystallisation re-equilibration. Equilibrium pressure estimates based on Nimis and Ulmer's single clinopyroxene (1998) and Köhler and Brey's (1990) olivine-spinel geobarometries range from 19 to 25 kbars. Oxygen fugacity expressed in terms of quartz-fayalite-magnetite (Delta QFM) value is calculated as -1.32. Spinel Cr# (Cr/(Cr+Al)) of the peridotites reflects mantle residues after low degree of melting (F = 0.5 - 11%) if derived from primitive mantle. Mineral composition tectonomagmatic discrimination diagrams confirm the studied samples to be abyssal peridotites. Laser Ablation ICPMS analyses of the rare earth element patterns of clinopyroxene in the peridotites show depleted light rare earth element with flat middle and heavy rare earth element patterns, similar to the reported abyssal peridotites. References Wells P.R.A. (1977) CMP, 62, 129-139. Nimis P., Ulmer P. (1998) CMP, 133, 122-135. Köhler T., Brey G.P. (1990) GCA, 54, 2375-2388.

  20. Flocculated sediments can reduce the size of sediment basin at construction sites.

    PubMed

    Kang, Jihoon; King, Scott E; McLaughlin, Richard A

    2016-01-15

    Due to stringent water quality regulations on stormwater discharges, there is increasing interest in chemically-assisted settling of suspended sediments at construction sites. This study investigated settling characteristics of flocculated sediment by polyacrylamide (PAM) in a top-loading settling tube. Studied sediment materials were obtained from construction sites in North Carolina, USA: Coastal Plain loamy sand (CPLS), Piedmont sandy clay loam (PSCL), Piedmont silt loam (PSL), and Mountain clay loam (MCL). The four different sediment suspensions mixed with and without dissolved PAM were introduced to the top of the column individually. During a 1-h settling period, samples were taken at 1-m depth from surface at various times and analyzed for total suspended solids (TSS). Flocculated sediment by PAM greatly increased its settled TSS fraction up to 95-97% only in 1-min settling period compared to those of unflocculated sediment (16-72%). The settling improvement by PAM was profound in the finer-textured soils (PSL and MCL) by increasing their median particle settling velocity (>2cms(-1)) compared to unflocculated counterparts (<1.1cms(-1)). Estimated surface area requirement of sediment basin suggested that the basins receiving flocculated sediment could be reduced in size (surface area) by 2- to 4-times compared to those receiving unflocculated sediment. Our results suggests that current sediment basin design could be modified when chemically-assisted settling is implemented, taking up less space and cost in construction sites. PMID:26555101

  1. Braid-plain dynamics and bank erosion along the Matanuska River, Alaska

    NASA Astrophysics Data System (ADS)

    Curran, J. H.

    2009-12-01

    Braid-plain activity and geomorphic features in the Matanuska River in southcentral Alaska between 1949 and 2006 were examined to support a bank erosion hazard assessment. The glacial Matanuska River drains 6,500 km2 and is braided for 85 percent of its 150 km course, which parallels a major highway and flows through the towns of Sutton and Palmer, Alaska. The historical braid plain was defined as the envelope of areas with active channels, unvegetated bars, or vegetated bars with evidence of channels since 1949 and delineated in a GIS from 1949, 1962, and 2006 aerial orthoimagery. We created a strip map of bank height and composition (primarily bedrock and unconsolidated sediment) at braid-plain margins and outlined valley bottom features (terraces and tributary fans) adjacent to the braid plain to assess erodibility. Braid-plain dynamism has created a mosaic of extensive lightly vegetated bars interspersed with forested bars in strips along the banks and in small mid-channel positions. Abandoned channels filled with groundwater or tributary streamflow have created clearwater side channels within these bars that serve as the primary spawning location for chum, sockeye, and coho salmon in the Matanuska River basin. Erosion magnitudes for the periods 1949-1962 and 1962-2006 were computed as braid-plain expansion at transects across the historical braid-plain boundaries. Episodic, spatially distributed erosion and the antiquity of some eroded surfaces suggests that average annual erosion rates at a location are not adequate for assessing future erosion at that location in a braid plain. Lateral expansion caused bank erosion of 100 -275 m at 20 locations over the full period, about half at tributary fans and most occurring in a single time period. Minor growth of tributary fans constricted the braid plain, and emerging terraces have the potential to shrink the braid plain. Eroded banks included undated but pre-historic fluvial terraces and tributary fans. Where bedrock bluffs defining the valley wall flank the braid plain, they form an obviously resistant braid-plain margin, but erosion resistance appears to have also been provided by previously unmapped intermittent bedrock 0-2 m above river level, locally exposed and elsewhere mantled by glacial or riverine sediment in bluffs up to 75 m high. Braid-plain process changes since 1949 include incision that created a terrace 2-3 m high within the braid plain in the lower river near Palmer and at a mid-river location, and channel narrowing and conversion from braided to single-thread within 5 km downstream of the Matanuska Glacier, likely as a result of changes to locations or amounts of glacier drainage. Constraining estimates of future erosion in braided rivers is more likely to be successful by considering bank erodibility, the process of local, episodic braid-plain expansion, and process changes such as incision or channel planform conversion, rather than restricting analysis to strictly historical erosion rate studies.

  2. A conceptual model to facilitate amphibian conservation in the northern Great Plains

    USGS Publications Warehouse

    Mushnet, David M.; Euliss, Ned H.; Stockwell, Craig A.

    2012-01-01

    As pressures on agricultural landscapes to meet worldwide resource needs increase, amphibian populations face numerous threats including habitat destruction, chemical contaminants, disease outbreaks, wetland sedimentation, and synergistic effects of these perturbations. To facilitate conservation planning, we developed a conceptual model depicting elements critical for amphibian conservation in the northern Great Plains. First, we linked upland, wetland, and landscape features to specific ecological attributes. Ecological attributes included adult survival; reproduction and survival to metamorphosis; and successful dispersal and recolonization. Second, we linked ecosystem drivers, ecosystem stressors, and ecological effects of the region to each ecological attribute. Lastly, we summarized information on these ecological attributes and the drivers, stressors, and effects that work in concert to influence the maintenance of viable and genetically diverse amphibian populations in the northern Great Plains. While our focus was on the northern Great Plains, our conceptual model can be tailored to other geographic regions and taxa.

  3. Origin and nature of intercrater plains in northwestern rim of Hellas Basin

    NASA Astrophysics Data System (ADS)

    Salese, F.; Mangold, N.; Ansan, V.; Carter, J.; Ody, A.; Poulet, F.; Ori, G. G.

    2015-10-01

    The nature and origin of intercrater plains within the martian cratered highlands is a major unresolved and controversial issue that have been somewhat enigmatic, receiving little attention since the Mariner era [1,2,3,4,5]. Are flat-lying smooth plains sedimentary or volcanic or both ? Whether these plains are mainly constituted of volcanic material or sediments is a crucial difference for understanding the surface environment of the Noachian period. In order to answer to previous question, we focus our study on the NW rim of Hellas basin defining first the relative stratigraphy and absolute age, throughout crater counting method,of the different units by a precise mapping and correlating then these units with mineralogy and texture.

  4. A qualitative assessment of the influence of bioturbation in Lake Baikal sediments

    NASA Astrophysics Data System (ADS)

    Martin, Patrick; Boes, Xavier; Goddeeris, Boudewijn; Fagel, Nathalie

    2005-04-01

    The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing, was assessed by studying the actual vertical distribution of benthic animals in continuous accumulation zones selected by seismic survey (Vydrino Shoulder, Posolskoe Bank, Continent Ridge). To assess the influence of the bioturbation, animals were extracted from short cores and identified at the relevant taxonomic level. The faunal distribution is examined in parallel with the bioturbation tracks observed in thin section. Oligochaeta, Nematoda, Ostracoda, Copepoda, Gammaridae, Chironomidae and Hydrachnidia were found inhabiting the sediment. Among them, only oligochaete worms were assumed to have a significant impact on sediment mixing because of their "conveyor belt" feeding. The other two most abundantly sampled groups, nematods and copepods, belong to the interstitial fauna that has no significant impact on the vertical displacement of sediment particles and do not ingest the sediment. The presence of a benthic fauna as deep as 15 cm in the sediment indicates that the possibility of sediment disturbance by invertebrate activity cannot be dismissed in Lake Baikal. The effect of biological mixing is more limited in the deepest stations because the number of potential bioturbators is reduced, qualitatively as well as quantitatively. Located in the abyssal zone, Continent and Vydrino (but outside turbidites) deep stations appear to be most promising sediment records for tracking climate signal at high resolution.

  5. Late Pleistocene braided rivers of the Atlantic Coastal Plain, USA

    NASA Astrophysics Data System (ADS)

    Leigh, David S.; Srivastava, Pradeep; Brook, George A.

    2004-01-01

    Infrared Landsat imagery (band 4) clearly reveals braided river patterns on late Pleistocene terraces of unglaciated rivers in the Atlantic Coastal Plain of the southeastern United States, a region that presently exhibits meandering patterns that have existed throughout the Holocene. These Pleistocene braided patterns provide a unique global example of river responses to late Quaternary climate changes in an unglaciated humid subtropical region at 30-35 north latitude. Detailed morphological and chronological results are given for the Oconee-Altamaha River valley in Georgia and for the Pee Dee River valley in South Carolina, including 15 optically stimulated luminescence (OSL) dates and four radiocarbon dates. Correlative examples are drawn from additional small to large rivers in South- and North Carolina. OSL and radiocarbon ( 14C) dates indicate distinct braiding at 17-30 ka, within oxygen isotope stage 2 (OIS 2), and braiding probably existed at least during parts of OIS 3 and possibly OIS 4 back to ca 70 ka. The chronology suggests that braiding is the more common pattern for the late Quaternary in the southeastern United States. Braided terraces appear to have been graded to lower sea-levels and are onlapped by Holocene floodplain deposits up to 10-60 km from the coast. The braiding probably reflects the response of discharge and sediment yield to generally cooler and drier paleoclimates, which may have had a pronounced runoff season. Sedimentation of eolian dunes on the braid plains is coeval with braiding and supports the conclusion of dry soils and thin vegetation cover during the late Pleistocene. Our chronological data contribute to a body of literature indicating that reliable OSL age estimates can be obtained from quartz-rich bed load sand from braided rivers, based on good correlations with both radiocarbon dates from braided fluvial sediment and OSL dates from stratigraphically correlative eolian sand.

  6. Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge

    USGS Publications Warehouse

    Colby, B.R.

    1963-01-01

    This paper presents a broad but undetailed picture of fluvial sediments in streams, reservoirs, and lakes and includes a discussion of the processes involved in the movement of sediment by flowing water. Sediment is fragmental material that originates from the chemical or physical disintegration of rocks. The disintegration products may have many different shapes and may range in size from large boulders to colloidal particles. In general, they retain about the same mineral composition as the parent rocks. Rock fragments become fluvial sediment when they are entrained in a stream of water. The entrainment may occur as sheet erosion from land surfaces, particularly for the fine particles, or as channel erosion after the surface runoff has accumulated in streams. Fluvial sediments move in streams as bedload (particles moving within a few particle diameters of the streambed) or as suspended sediment in the turbulent flow. The discharge of bedload varies with several factors, which may include particle size and a type of effective shear on the surface of the streambed. The discharge of suspended sediment depends partly on concentration of moving sediment near the streambed and hence on discharge of bedload. However, the concentration of fine sediment near the streambed varies widely, even for equal flows, and, therefore, the discharge of fine sediment normally cannot be computed theoretically. The discharge of suspended sediment also depends on velocity, turbulence, depth of flow, and fall velocity of the particles. In general, the coarse sediment transported by a stream moves intermittently and is discharged at a rate that depends on properties of the flow and of the sediment. If an ample supply of coarse sediment is available at the surface of the streambed, the discharge of the coarse sediment, such as sand, can be roughly computed from properties of the available sediment and of the flow. On the other hand, much of the fine sediment in a stream usually moves nearly continuously at about the velocity of the flow, and even low flows can transport large amounts of fine sediment. Hence, the discharge of fine sediments, being largely dependent on the availability of fine sediment upstream rather than on the properties of the sediment and of the flow at a cross section, can seldom be computed from properties, other than concentrations based directly on samples, that can be observed at the cross section. Sediment particles continually change their positions in the flow; some fall to the streambed, and others are removed from the bed. Sediment deposits form locally or over large areas if the volume rate at which particles settle to the bed exceeds the volume rate at which particles are removed from the bed. In general, large particles are deposited more readily than small particles, whether the point of deposition is behind a rock, on a flood plain, within a stream channel, or at the entrance to a reservoir, a lake, or the ocean. Most samplers used for sediment observations collect a water-sediment mixture from the water surface to within a few tenths of a foot of the streambed. They thus sample most of the suspended sediment, especially if the flow is deep or if the sediment is mostly fine; but they exclude the bedload and some of the suspended sediment in a layer near the streambed where the suspended-sediment concentrations are highest. Measured sediment discharges are usually based on concentrations that are averages of several individual sediment samples for a cross section. If enough average concentrations for a cross section have been determined, the measured sediment discharge can be computed by interpolating sediment concentrations between sampling times. If only occasional samples were collected, an average relation between sediment discharge and flow can be used with a flow-duration curve to compute roughly the average or the total sediment discharges for any periods of time for which the flow-duration c

  7. Wet coastal plain tundra III

    SciTech Connect

    Myers, J.P.; Gellman, S.T.; Pitelka, F.A.

    1980-01-01

    This year's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSE of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 38'W; Barrow Quadrangle, USGS reflect a decrease in the total number of species breeding. However, total breeding density rose by 82%. Lapland Longspurs (up 105%) accounted for half of this increase while the rest was spread among many species. There was a total of 8 species; 40.5 territorial males or females (162/km/sup 2/, 66/100 acres).

  8. A decade of investigations on groundwater arsenic contamination in Middle Ganga Plain, India.

    PubMed

    Saha, Dipankar; Sahu, Sudarsan

    2016-04-01

    Groundwater arsenic (As) load in excess of drinking limit (50 µg L(-1)) in the Gangetic Plains was first detected in 2002. Though the menace was known since about two decades from the downstream part of the plains in the Bengal Basin, comprising of Lower Ganga Plain and deltaic plains of Ganga-Brahmaputra-Meghna River system, little thought was given to its possible threat in the upstream parts in the Gangetic Plains beyond Garo-Rajmahal Hills. The contamination in Bengal Basin has become one of the extensively studied issues in the world and regarded as the severest case of health hazard in the history of mankind. The researches and investigations in the Gangetic Plains during the last decade (2003-2013) revealed that the eastern half of the plains, also referred as Middle Ganga Plain (MGP), is particularly affected by contamination, jeopardising the shallow aquifer-based drinking water supply. The present paper reviews researches and investigations carried out so far in MGP by various research institutes and government departments on wide array of issues of groundwater As such as its spatio-temporal variation, mobilisation paths, water level behaviour and flow regime, configuration of contaminated and safe aquifers and their recharge mechanism. Elevated conc. of groundwater As has been observed in grey and dark grey sediments of Holocene age (Newer Alluvium) deposited in a fluvio-lacustrine environment in the floodplain of the Ganga and most of its northern tributaries from Himalayas. Older Alluvium, comprising Pleistocene brownish yellow sediment, extending as deeper aquifers in Newer Alluvium areas, is low in groundwater As. Similarities and differences on issues between the MGP and the Bengal Basin have been discussed. The researches point towards the mobilisation process as reductive dissolution of iron hydroxide coating, rich in adsorbed As, mediated by microbial processes. The area is marked with shallow water level (<8.0 m below ground) with ample monsoonal recharge. The infiltrated rainwater and percolating water from surface water bodies carry organic carbon from sediments (particularly from the clay plugs in abandoned channels), abetting microbial processes, spread of anoxic front and release of As. PMID:26116052

  9. Coastal morphodynamics and Chenier-Plain evolution in southwestern Louisiana, USA: A geomorphic model

    NASA Astrophysics Data System (ADS)

    McBride, Randolph A.; Taylor, Matthew J.; Byrnes, Mark R.

    2007-08-01

    Using 28 topographic profiles, air-photo interpretation, and historical shoreline-change data, coastal processes were evaluated along the Chenier Plain to explain the occurrence, distribution, and geomorphic hierarchy of primary landforms, and existing hypotheses regarding Chenier-Plain evolution were reconsidered. The Chenier Plain of SW Louisiana, classified as a low-profile, microtidal, storm-dominated coast, is located west and downdrift of the Mississippi River deltaic plain. This Late-Holocene, marginal-deltaic environment is 200 km long and up to 30 km wide, and is composed primarily of mud deposits capped by marsh interspersed with thin sand- and shell-rich ridges ("cheniers") that have elevations of up to 4 m. In this study, the term "ridge" is used as a morphologic term for a narrow, linear or curvilinear topographic high that consists of sand and shelly material accumulated by waves and other physical coastal processes. Thus, most ridges in the Chenier Plain represent relict open-Gulf shorelines. On the basis of past movement trends of individual shorelines, ridges may be further classified as transgressive, regressive, or laterally accreted. Geomorphic zones that contain two or more regressive, transgressive, or laterally accreted ridges are termed complexes. Consequently, we further refine the Chenier-Plain definition by Otvos and Price [Otvos, E.G. and Price, W.A., 1979. Problems of chenier genesis and terminologyan overview. Marine Geology, 31: 251-263] and define Chenier Plain as containing at least two or more chenier complexes. Based on these definitions, a geomorphic hierarchy of landforms was refined relative to dominant process for the Louisiana Chenier Plain. The Chenier Plain is defined as a first-order feature (5000 km 2) composed of three second-order features (30 to 300 km 2): chenier complex, beach-ridge complex, and spit complex. Individual ridges of each complex type were further separated into third-order features: chenier, beach ridge, and spit. To understand the long-term evolution of a coastal depositional system, primary process-response mechanisms and patterns found along the modern Chenier-Plain coast were first identified, especially tidal-inlet processes associated with the Sabine, Calcasieu, and Mermentau Rivers. Tidal prism ( ?) and quantity of littoral transport ( Mtotal) are the most important factors controlling inlet stability. Greater discharge and/or tidal prism increase the ability of river and estuarine systems to interrupt longshore sediment transport, maintain and naturally stabilize tidal entrances, and promote updrift deposition. Thus, prior to human modification and stabilization efforts, the Mermentau River entrance would be classified as wave-dominated, Sabine Pass as tide-dominated, and Calcasieu Pass as tide-dominated to occasionally mixed. Hoyt [Hoyt, J.H., 1969. Chenier versus barrier, genetic and stratigraphic distinction. Am. Assoc. Petrol. Geol. Bull., 53: 299-306] presented the first detailed depositional model for chenier genesis and mudflat progradation, which he attributed to changes in Mississippi River flow direction (i.e., delta switching) caused by upstream channel avulsion. However, Hoyt's model oversimplifies Chenier-Plain evolution because it omits ridges created by other means. Thus, the geologic evolution of the Chenier Plain is more complicated than channel avulsions of the Mississippi River, and it involved not only chenier ridges (i.e., transgressive), but also ridges that are genetically tied to regression (beach ridges) and lateral accretion (recurved spits). A six-stage geomorphic process-response model was developed to describe Chenier-Plain evolution primarily as a function of: (i) the balance between sediment supply and energy dissipation associated with Mississippi River channel avulsions, (ii) local sediment reworking and lateral transport, (iii) tidal-entrance dynamics, and (iv) possibly higher-than-present stands of Holocene sea level. Consequently, the geneses of three different ridge types (transgressive, reg

  10. Coastal Mudflat Accretion under Energetic Conditions, Louisiana Chenier-Plain Coast, USA

    NASA Technical Reports Server (NTRS)

    Draut, Amy E.; Kineke, Gail C.; Huh, Oscar K.; Grymes, John M., III; Westphal, Karen A.; Moeller, Christopher C.

    2005-01-01

    Mudflat accretion on the chenier-plain coast of Louisiana, northern Gulf of Mexico, is anomalous in an area that otherwise experiences widespread land loss due to rapid relative sea level rise. Accretion is shown to be related to energetic events (Winta cold fronts and occasional tropical-dcprrssion srmms) using a 17-year record of meteorological conditions and aerial surveys The results indicate substantial differences between the behavior of sand- and mud-dominated coastal systems under energetic conditions. Comparison of the Louisiana chenier plain to other mud-rich coasts indicates that certain conditions are necessary for mudflat accretion to occur during energetic atmospheric activity. These include an abundant supply of fine-grained fluvial sediment and resuspension events that maintain an unconsolidated sea floor, dominant onshore wind direction during energetic conditions, particularly when onshore winds coincide with high fluvial sediment input to the coastal ocean, and a low tidal range.

  11. Hydrogeologic Framework of the New Jersey Coastal Plain

    USGS Publications Warehouse

    Zapecza, Otto S.

    1989-01-01

    This report presents the results of a water-resources, oriented subsurface mapping program within the Coastal Plain of New Jersey. The occurrence and configuration of 15 regional hydrogeologic units have been defined, primarily on the basis of an interpretation of borehole geophysical data. The nine aquifers and six confining beds are composed of unconsolidated clay, silt, sand, and gravel and range in age from Cretaceous to Quaternary. Electric and gamma-ray logs from more than 1,000 Coastal Plain wells were examined. Of these, interpretive data for 302 sites were selected, on the basis of logged depth, quality of data, and data distribution, to prepare structure contour and thickness maps for each aquifer and a thickness map for each confining bed. These maps, together with 14 hydrogeologic sections, show the geometry, lateral extent, and vertical and horizontal relationships among the 15 hydrogeologic units. The hydrogeologic maps and sections show that distinct lower, middle, and upper aquifers are present within the Potomac, Raritan-Magothy aquifer system near the Delaware River from Burlington County to Salem County. Although the lower aquifer is recognized only in this area, the middle aquifer extends into the northeastern Coastal Plain of New Jersey, where it is stratigraphically equivalent to the Farrington aquifer. The upper aquifer extends throughout most of the New Jersey Coastal Plain and is stratigraphically equivalent to the Old Bridge aquifer in the northeastern Coastal Plain. The overlying Merchantville-Woodbury confining bed is the most regionally extensive confining bed within the New Jersey Coastal Plain. Its thickness ranges from less than 100 feet near the outcrop to more than 450 feet along the coast. The Englishtown aquifer system acts as a single aquifer throughout most of its subsurface extent, but it contains two water-bearing sands in pars of Monmouth and Ocean Counties. The overlying Marshalltown-Wenonah confining bed is a thin, leaky unit ranging in thickness from approximately 20 to 80 feet. The Wenonah-Mount Laurel aquifer is identified in the subsurface throughout the New Jersey Coastal Plain southeast of its outcrop area. Sediments that overlie the Wenonah-Mount Lauren aquifer and that are subjacent to the major aquifers within the Kirkwood Formation and the Cohansey Sand are described hydrologically as a composite confining bed. These include the Navesink Formation, Red Bank Sand, Tinton Sand, Hornerstown Sand, Vincentown Formation, Manasquan Formation, Shark River Formation, and Piney Point Formation and the basal clay of the Kirkwood Formation.. The Vincentown Formation functions as n aquifer within 3 to 10 miles downdip of its outcrop area. In areas farther downdip the Vincentown Formation functions as a confining bed. The Piney Point aquifer is laterally persistent from the southern New Jersey Coastal Plain northward into parts of Burlington and Ocean Counties. The Atlantic City 800-foot sand of the Kirkwood Formation can be recognized in the subsurface along coastal areas of Cape May, Atlantic, and southern Ocean Counties, but inland only as far west as the extent of the overlying confining bed. In areas west of the extent of the overlying confining bed, the Kirkwood Formation is in hydraulic connection with the overlying Cohansey Sand and younger surficial deposits and functions as an unconfined aquifer.

  12. Rates of microbial metabolism in deep coastal plain aquifers

    USGS Publications Warehouse

    Chapelle, F.H.; Lovley, D.R.

    1990-01-01

    Rates of microbial metabolism in deep anaerobic aquifers of the Atlantic coastal plain of South Carolina were investigated by both microbiological and geochemical techniques. Rates of [2-14C]acetate and [U-14C]glucose oxidation as well as geochemical evidence indicated that metabolic rates were faster in the sandy sediments composing the aquifers than in the clayey sediments of the confining layers. In the sandy aquifer sediments, estimates of the rates of CO2 production (millimoles of CO2 per liter per year) based on the oxidation of [2-14C]acetate were 9.4 x 10-3 to 2.4 x 10-1 for the Black Creek aquifer, 1.1 x 10-2 for the Middendorf aquifer, and <7 x 10-5 for the Cape Fear aquifer. These estimates were at least 2 orders of magnitude lower than previously published estimates that were based on the accumulation of CO2 in laboratory incubations of similar deep subsurface sediments. In contrast, geochemical modeling of groundwater chemistry changes along aquifer flowpaths gave rate estimates that ranged from 10-4 to 10-6 mmol of CO2 per liter per year. The age of these sediments (ca. 80 million years) and their organic carbon content suggest that average rates of CO2 production could have been no more than 10-4 mmol per liter per year. Thus, laboratory incubations may greatly overestimate the in situ rates of microbial metabolism in deep subsurface environments. This has important implications for the use of laboratory incubations in attempts to estimate biorestoration capacities of deep aquifers. The rate estimates from geochemical modeling indicate that deep aquifers are among the most oligotrophic aquatic environments in which there is ongoing microbial metabolism.

  13. What can we learn about the history of oceanic shield volcanoes from deep marine sediments? Example from La Reunion volcanoes.

    NASA Astrophysics Data System (ADS)

    Bachelery, Patrick; Babonneau, Nathalie; Jorry, Stephan; Mazuel, Aude

    2014-05-01

    The discovery in 2006, during the oceanographic survey FOREVER, of large volcaniclastic sedimentary systems off La Runion Island (western Indian ocean) revealed a new image of the evolution of oceanic shield volcanoes and their dismantling. Marine data obtained from 2006 to 2011 during the oceanographic surveys ERODER 1 to ERODER 4 included bathymetry, acoustic imagery, echosounding profiles, dredging and coring. Six major turbidite systems were mapped and described on the submarine flanks of La Reunion volcanic edifice and the surrounding oceanic plate. The interpretation of sediment cores enable us to characterise the processes of gravity-driven sediment transfer from land to deep sea and also to revisit the history of the volcanoes of La Runion Island. Turbidite systems constitute a major component of the transfer of volcanic materials to the abyssal plain (Saint-Ange et al., 2011; 2013; Sisavath et al., 2011; 2012; Babonneau et al., 2013). These systems are superimposed on other dismantling processes (slow deformation such as gravity sliding or spreading, and huge landslides causing debris avalanches). Turbidite systems mainly develop in connection with the hydrographic network of the island, and especially at the mouths of large rivers. They show varying degrees of maturity, with canyons incising the submarine slope of the island and feeding depositional areas, channels and lobes extending over 150 km from the coast. The cores collected in turbidite systems show successions of thin and thick turbidites alternating with hemipelagic sedimentation. Sedimentological and stratigraphic analysis of sediment cores yielded a chronology of submarine gravity events. First-order information was obtained on the explosive activity of these volcanoes by identifying tephra layers in the cores (glass shards and pumice). In addition, major events of the volcanic and tectonic history of the island can be identified and dated. In this contribution, we focus most attention on the southernmost turbidite system (St-Joseph system). Sedimentary records allow us to establish a link between two major landslides affecting the flanks of Piton de la Fournaise volcano and the triggering of major turbidity currents. Thus, the age of these events could be obtained; their chronology being far too difficult to establish otherwise. In short: a beautiful example of the contribution of sedimentology to the study of the structural evolution of the volcanoes. References Babonneau N., Delacourt C., Cancouet R., Sisavath E., Bachelery P., Deschamps A., Mazuel A., Ammann J., Jorry S.J., Villeneuve N., 2013, Marine Geology, 346, 47-57. Saint-Ange F., Bachlery P., Babonneau N., Michon, L., Jorry S.J., 2013, Marine Geology. 337, 35-52. Saint-Ange, F., Savoye, B., Michon, L., Bachelery, P., Deplus, C., De Voogd, B., Dyment, J., Le Drezen, E., Voisset, M., Le Friant, A., and Boudon, G., 2011. Geology, 39, 271-274, doi: 10.1130/G31478.1. Sisavath, E., Mazuel, A., Jorry, S., Babonneau, N., Bachlery P., De Voogd, B., Salpin, M., Emmanuel, L., Beaufort, L., Toucanne, S., 2012, Sedimentary Geology, 281, p. 180-193, doi :10.1016/j.sedgeo.2012.09.010. Sisavath, E., Babonneau N., Saint-Ange F., Bachlery P., Jorry S., Deplus C., De Voogd B., Savoye B., 2011, Marine Geology, v. 288, p. 1-17, doi:10.1016/j.margeo.2011.06.011.

  14. JAPANESE BROME IMPACTS NORTHERN GREAT PLAINS RANGELAND

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Japanese brome (Bromus japonicus Thunb.) is an annual grass that has invaded thousands of hectares of Northern Great Plains rangelands. We studied the effect of Japanese brome on the current year's increase in biomass in a plant community in the Northern Great Plains dominated by western wheatgrass...

  15. Geomorphic evidence for an eolian contribution to the formation of the Martian northern plains

    NASA Technical Reports Server (NTRS)

    Zimbelman, J. R.

    1993-01-01

    The northern plains of Mars have many morphologic characteristics that are uncommon or absent on the rest of the planet. Mariner 9 and Viking images obtained north of latitude 30 deg N revealed 'smooth' and 'mottled' plains of an uncertain origin. Some or all of the northern plains were interpreted to consist of lava plains intermixed with eolian and volcanic materials thick eolian mantles that buried portions of the mid latitudes periglacial deposits resulting from the presence of ground ice and as water-transported sediments derived from fluvial runoff, lacustrine deposition in standing bodies of water, or glacial runoff. The highest-resolution Viking images show many intriguing details that may provide clues to the origin of this complex and distinctive terrain. Some of the informative features present in the best Viking images, comparing the observations to what may be expected from various hypotheses of formation, are reviewed. While the results are not conclusive for any single hypothesis, eolian processes have played a major role in the erosion (and possibly deposition) of the materials that make up the surface exposures in the Martian northern plains.

  16. Spatial genetic sequences of soil horizons and soil profiles on the Russian and West Siberian plains

    NASA Astrophysics Data System (ADS)

    Tonkonogov, V. D.

    2008-06-01

    The analysis of spatial sequences of genetic horizons as elementary constituents of soil profiles in relation to the factors of soil formation makes it possible to draw several new conclusions about the geneses and geography of soils in the north of the Russian and West Siberian plains. An important role in the spatial diversity of automorphic soils of these territories belongs to the texture of the parent materials and to the stratification of the latter within the soil profiles. The study of spatial soil sequences with due respect for the character of the parent materials suggests that the popular notion about the ideal bioclimatic zonality of the soils within these vast plains should be refined. It is shown that this notion is grounded in the phenomenon of good agreement between the bioclimatic zonality and the sedimentation zonality (or, according to I.A. Sokolov, the striated pattern of different types of sediments) in the studied territory. In turn, the sedimentation zonality was shaped by the directed movements of Quaternary glaciers over the plains from the north, northwest, or northeast.

  17. Mid-ocean ridge bathymetry records past variations in sea level: evidence from spectral analysis of abyssal hills and implications for 100 ky glacial cycles.

    NASA Astrophysics Data System (ADS)

    Huybers, P. J.; Carbotte, S. M.; Katz, R. F.; Langmuir, C. H.

    2014-12-01

    Evidence has accumulated from continental tephra, marine tephra, and abyssal hill topography that deglaciation drives volcanism. Additional analysis of abyssal topography flanking mid-ocean ridges is presented indicating the presence of excess energy near periods corresponding to precession, obliquity, and 100 ky variations. Wavelength is transformed into period using independently estimated spreading rates. This topographic structure is consistent with the expected response of mid-ocean ridge productivity and evolved crustal thickness to changes in pressure associated with variations in sea level. If ridge CO2 emissions track these indications of ridge productivity, decreased emissions as a result of deglaciation are implied, constituting a negative feedback. CO2 emissions would be delayed, however, because of transit times from the base of the melt zone, and a simple delayed oscillator is presented for how delayed negative feedbacks could be important for setting the 100 ky glacial cycle period.

  18. PLAINS CO2 REDUCTION PARTNERSHIP

    SciTech Connect

    Edward N. Steadman

    2004-07-01

    The Plains Co{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) activities have focused on developing information on deployment issues to support Task 5 activities by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) activities have focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) has included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 (Modeling and Phase II Action Plans) activities have focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

  19. PLAINS CO2 REDUCTION PARTNERSHIP

    SciTech Connect

    Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

    2005-01-01

    The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

  20. PLAINS CO2 REDUCTION PARTNERSHIP

    SciTech Connect

    Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

    2004-10-01

    The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

  1. Behaviour of fluid mobile elements during subduction and exhumation of abyssal peridotites: Example of serpentinites from Cuba and Dominican Republic

    NASA Astrophysics Data System (ADS)

    Deschamps, F.; Guillot, S.; Godard, M.; Chauvel, C.; Andreani, M.

    2009-04-01

    Seawater interaction with abyssal peridotites at the sea floor is an important process for chemical exchange between lithosperic mantle and ocean at slow-spreading ridge. Serpentinites from oceanic lithosphere are known to represent an important sink for fluid mobile element, notably boron. In parallel we know extreme enrichment in fluid mobile element (As, Sb, B, U, Li) in high-pressure serpentine minerals (antigorite) coming from part of mantle wedge hydrated by slab's fluids released (Himalaya, Deschamps et al., in prep.). In order to constrain geochemical behaviour of fluid mobile element hosted by serpentine during subduction processes, we examined abyssal serpentinites coming from the accretionary wedge of Greater Carribean (Cuba and Dominican Republic). They represent subducted Atlantic oceanic lithosphere, which have experienced low to high- metamorphism (greenschist to eclogite facies), before being exhumed. These rocks are an opportunity to understand the chemical mobility of fluid mobile element during prograde metamorphism occurring along subduction surface. Here we present bulk-rock and in-situ composition of serpentinites and their primary and alteration-related phase obtained on (LA-)HR-ICP-MS. Except for a few cumulates, serpentinites have depleted compositions in agreement with a refractory mantle, but also strong enrichment in U, Pb, Th, Sr, and other fluid mobile element (e.g., U up to 10xPM) indicating extensive fluid-rock intercation. In-situ composition allows the distinction of two groups of serpentine. Group 1 is characterized by relatively flat and depleted REE patterns (Yb ? 0.5xChondrite) reflecting formation after olivine, while group 2 formed after pyroxene is characterized by slightly higher HREE content (Yb ? 1xChondrite) but light LREE depleted patterns and displays higher content in Sc, V, Ti and Co. Both groups are strongly enriched in B (up to 120 ppm), and reach values already observed in serpentinites from mantle wedge (Himalaya, Deschamps et al., in prep.). Other fluid mobile elements such As (up to 6.85 ppm), Sb (up to 0.84 ppm), Li (up to 2 ppm) or U (up to 0.62 ppm) present strong enrichment in serpentine from both groups (0.1 up to 50 times primitive mantle values). The occurrence of amphibole having REE signature close to oceanic amphiboles, in cumulates, are in favour of an hydration event, leading to the observed strong mobile element enrichment, at the ridge. Compositions of the oceanic derived samples - especially in fluid mobile elements - are relatively close to the abyssal peridotites from MARK Zone (Andreani et al., 2008), without evidence of mobility for trace element during prograde and retrograde metamorphism. It confirms that the observed enrichment result from sea-water/peridotites interactions at the ridge. Also it suggests that mobile element stored into serpentine minerals become immobile during subduction processes. Major consequence of this observation is that serpentine minerals (chrysotile and lizardite) are a good sink for mobile element (As, Sb and B) into subduction zones, until their dehydration.

  2. Bait-attending fauna of the Kermadec Trench, SW Pacific Ocean: Evidence for an ecotone across the abyssal-hadal transition zone

    NASA Astrophysics Data System (ADS)

    Jamieson, A. J.; Kilgallen, N. M.; Rowden, A. A.; Fujii, T.; Horton, T.; Lrz, A.-N.; Kitazawa, K.; Priede, I. G.

    2011-01-01

    The bait-attending fauna of the abyssal-hadal transition zone of the Kermadec Trench, SW Pacific Ocean (4329-7966 m), was investigated using a baited camera and a trap lander. The abyssal stations (4329-6007 m) revealed a typical scavenging fish community comprising macrourids and synaphobranchid eels, as well as natantian decapods. At the hadal depths of 7199 and 7561 m, the endemic liparid Notoliparis kermadecensis was observed aggregating at the bait reaching surprisingly high numbers of 5 and 13, respectively. A total of 3183 invertebrate samples were collected (mean deployment time=16 h) of which 97.8% were of the order Amphipoda (nine families, 16 species). Ten of the amphipod species represent new distributional records for the Kermadec Trench and the New Zealand Exclusive Economic Zone; this includes the shallowest known record of the endemic hadal amphipod Hirondellea dubia (6000, 6007 m). Using amphipods to statistically examine the compositional change across the abyssal-hadal boundary, an ecotone between depths <6007 and >6890 m was found, indicating that there is an ecologically distinct bait-attending fauna in this trench.

  3. Simple models for disequilibrium fractional melting and batch melting with application to REE fractionation in abyssal peridotites

    NASA Astrophysics Data System (ADS)

    Liang, Yan; Liu, Boda

    2016-01-01

    Disequilibrium melting arises when the kinetics of chemical exchange between a residual mineral and partial melt is sluggish compare to the rate of melting. To better understand the role of a finite crystal-melt exchange rate on trace element fractionation during mantle melting, we have developed a disequilibrium melting model for partial melting in an upwelling steady-state column. We use linear kinetics to approximate crystal-melt mass exchange rate and obtain simple analytical solutions for cases of perfect fractional melting and batch melting. A key parameter determining the extent of chemical disequilibrium during partial melting is an element specific dimensionless ratio (ε) defined as the melting rate relative to the solid-melt chemical exchange rate for the trace element of interest. In the case of diffusion in mineral limited chemical exchange, ε is inversely proportional to diffusivity of the element of interest. Disequilibrium melting is important for the trace element when ε is comparable to or greater than the bulk solid-melt partition coefficient for the trace element (k). The disequilibrium fractional melting model is reduced to the equilibrium perfect fractional melting model when ε is much smaller than k. Hence highly incompatible trace elements with smaller mobilities in minerals are more susceptible to disequilibrium melting than moderately incompatible and compatible trace elements. Effect of chemical disequilibrium is to hinder the extent of fractionation between residual solid and partial melt, making the residual solid less depleted and the accumulated melt more depleted in incompatible trace element abundances relative the case of equilibrium melting. Application of the disequilibrium fractional melting model to REE and Y abundances in clinopyroxene in abyssal peridotites from the Central Indian Ridge and the Vema Lithospheric Section, Mid-Atlantic Ridge revealed a positive correlation between the disequilibrium parameter ε and the degree of melting, which can be explained by an increase in melting rate and a decrease in REE diffusion rate in the upper part of the melting column. Small extent of disequilibrium melting for LREE and equilibrium melting for HREE in the upper part of the melting column can explain the elevated LREE abundances or spoon-shaped REE patterns in clinopyroxene in more refractory abyssal peridotites. The latter has often been attributed to melt refertilization.

  4. Geobotanical assessment in the Great Plains, Rocky Mountains and Himalaya

    NASA Astrophysics Data System (ADS)

    Shroder, John F.; Bishop, Michael P.

    1995-09-01

    Vegetation patterns and dendrochronology were used to study landforms and processes in three unique geographic areas. Specifically, we report on geobotanical associations related to forest fires, slope failures, rivers, and glaciers. The work was conducted in the Niobrara valley of the Great Plains of Nebraska, Tensleep Canyon of the Bighorn Mountains, Yellowstone Teton fire areas of the Snake River drainage in Wyoming, and the Nanga Parbat and Batura areas of the western Himalaya. Results indicate that geobotanical associations can be used to provide additional information to study landforms, natural hazards, and sediment yields. In addition, geobotany can be used to detect processes responsible for environmental change. Remote sensing technology can play an important role in detecting vegetation distributions and green biomass variations.

  5. Flood Plain Lakes Along the Elbe River - a Forgotten Risk

    NASA Astrophysics Data System (ADS)

    Heise, Susanne

    2014-05-01

    Flood Plain Lakes Along the Elbe River - a Forgotten Risk Introduction: Along the German part of the Elbe River, more than 1000 "side structures" form potential sinks of contaminated sediment. They are mostly remains of previous river courses which have been cut off by natural causes or anthropogenic alterations of the river (oxbow lakes), or are floodplain lakes that were formed during high water conditions. These water bodies sometimes have a small opening towards the Elbe, or are hydrodynamically connected only in situations of high discharges. High discharges in the Elbe River, however, are mainly responsible for transporting historic contaminants along with suspended matter from former historic sources in the middle Elbe downstream. As these may settle when the current dies down at the end of a high discharge period, side structures have been under suspicion to have accumulated contaminated material over the last decades. Until this study was conducted, nothing was known about erodibility and contamination of sediment in these lakes even though they could have a large impact on the Elbe River itself: A preliminary investigation showed that the total surface of side structures in the Elbe floodplain adds up to about 50 km2. In case that deposited sediment is contaminated and only the upper 20 cm are prone to resuspension and transport during flooding, 10 Mio m3 of contaminated sediment could potentially be added to the contaminant load during a high water event. This study was carried out to evaluate the risk from these side structures for the environmental quality of the Elbe River. Methods: 15 side structures were investigated. Sediment cores were taken on 1 to 3 locations per water body in order to obtain the following information: • Depth of sediment layer • Erodibility of surface sediment, measured immediately after sampling - using the "Gust Microcosm", • Eroded mass at over-critical shear stress, measured in the lab by eroding a sediment core for one hour and collecting the suspended sediment matter. • Chemical contamination • Ecotoxicological effects Results and Discussion All side structures that were sampled exceeded the national quality guidelines for sediments which have been set by the International Commission for the Protection of the Elbe. In some cases very high concentrations were reached such as 1300 µg/kg dw for p,p-DDD, up to 61 mg/kg for Hg and 39 mg/kg for Cd. Erodibility varied a lot with critical shear stresses of less than 1 cm/s to more than 2 cm/s. Ecotoxicological data were also very different between side structures and sampling locations, but partly indicating very high inhibitions. Methanol extracts of sediments on all locations were screened using the luminescence bacteria test with Vibrio fischeri. Selected sediemt samples were tested applying the sediment contact test with Arthrobacter globiformes and the algae growth inhibition test with Pseudokirchneriella subcapitata. An integrated evaluation of all information led to a classification of 7 sites out of 15 to be of high risk, 7 to be of medium risk and only one site to be of low risk for the environmental quality of the Elbe River.

  6. Anomalous heat flow in the Northwest Atlantic: A case for continued hydrothermal circulation in 80-m. y. crust

    SciTech Connect

    Embley, R.W.; Hobart, M.A.; Anderson, R.N.; Abbott, D.

    1983-02-10

    A study of a 60 x 150 km area at 60 /sup 0/W.24/sup 0/N at the eastern end of the Nares Abyssal Plain indicates that hydrothermal circulation is still active in the 80 m.y. B.P. oceanic crust. The 58 heat flow measurements made at five stations in the area have revealed (1) constant heat flow over the abyssal plain (56 mW m/sup -2/), (2) a cycle heat flow over the abyssal hills (mean of 77 mW m/sup -2/), and (3) a large anomaly of 710 mW m/sup -2/ over one of several small domes which protrude from the abyssal plain. The domes are 0.5-1.0 km in diameter near the top and rise 50 m above the level of the abyssal plain. They are recognized from surface echo sounders by an abrupt disappearance in the abyssal plain subbottom reflectors, but on near-bottom pinger records they appear as steep-walled structures which are covered by approx.10 m of sediment (compared to approx.75 m on the surrounding abyssal hills). From analogy with active ridge crests, these features are probably small volcanoes. The heat flow anomaly over one of the domes is matched well by a finite element convection model with the following characteristics: (1) recharge at one basement outcrop and discharge at another, (2) 300 m of sediment fill between outcrops, and (3) permeabilities of 10/sup -10/ cm/sup 2/ for basalt and 10/sup -13/ cm/sup 2/ for sediment. We believe that there is very effective convective heat transfer within the crust and out of the relatively permeable, thinly sedimented basement dome, resulting in the local high heat flow. The results from the Nares survey vividly show the age independent muting effect of sediment on the surface manifestation of crustal convection. The mode of heat transfer varies from purely conductive in the more thickly sedimented abyssal plain areas to moderate amplitude convection pattern beneath the abyssal hills to a very large thermal anomaly over the small dome or 'chimneylike' structure.

  7. Does Reactivation of Louisiana's Chenier Plain Lead to the Development of Interior Coastal Wetlands? Assessing the Relative Roles of Storm Impacts and Riverine Deposits

    NASA Astrophysics Data System (ADS)

    Ramatchandirane, C. G.; Kolker, A.; Ameen, A. D.; Williams, K.; Donnelly, J. P.; Giosan, L.

    2010-12-01

    At the beginning of the 20th century, increased flow into the Atchafalaya River from the Mississippi River reactivated sediment dynamics along the Chenier Plain. The Chenier Plain is a microtidal, storm-dominated coastal environment situated west and downdrift of the Mississippi River Delta. Composed of alternating mudflats, marsh, and elevated chenier (oak) ridges, this coastal system provides an ideal case study to both investigate the success of the Atchafalaya River diversion in building wetlands, and to construct a chronology of storm impacts on the Louisiana Gulf coast. To examine whether and how the reactivation of the Chenier Plain has impacted sediment dynamics in coastal wetlands, sediment cores from Miller Lake in the Chenier Plain were analyzed. Historic photos and maps of Miller Lake show open water in an area now dominated by marsh. The recent filling in of Miller Lake suggests new deposition by a possible combination of storm impacts and riverine deposits. In this study, carbonate deposition is used as a proxy for marine-dominated sedimentation, which reflects the shelly marine-dominated coastal environment of the Chenier Plain. Grain size analysis data was collected to distinguish sand layers from possible overwash deposits of storm impacts. Rates of sediment accretion and mineral deposition were determined using the naturally occurring radioisotope 210Pb. The collected sediment cores indicate new marsh developing over muddy sediments. In contrast to SE Louisianas high rates of wetland loss, this study points to evidence of wetland accretion in SW Louisiana as a result of the Atchafalaya River diversion.

  8. Observations of polarized seismoacoustic T waves at and beneath the seafloor in the abyssal Pacific ocean.

    PubMed

    Butler, Rhett

    2006-12-01

    Combined seismic and hydrophone observations show that the traditional T wave propagates as a seismoacoustic polarized interface wave (Ti) coupled to the seafloor. Seismoacoustic Ti waves propagating at the sound speed of water are routinely observed over megameter distances at the deep (4979 m) seafloor Hawaii-2 Observatory (H2O) between Hawaii and California, even though the seafloor site is within a shadow zone for acoustic wave propagation. Ti has also been observed on seismometers 225 km SSW of Oahu at the OSN1 site at the seafloor and within an ODP borehole into the basalt basement. Analyses of timing, apparent velocity, energy, and polarization of these interface waves are presented. At low frequency (< approximately 5 Hz) Ti propagates dominantly in the sediments and is consistent with higher-mode Rayleigh waves. At higher frequencies the observed Ti waves dominantly propagate acoustically with characteristics suggesting local scattering. The observation of Ti from an earthquake in Guatemala at OSN1, whose path is blocked by the Island of Hawaii, is consistent with scattering from the vicinity of the Cross Seamount. PMID:17225389

  9. Ice-walled-lake plains: Implications for the origin of hummocky glacial topography in middle North America

    USGS Publications Warehouse

    Clayton, L.; Attig, J.W.; Ham, N.R.; Johnson, M.D.; Jennings, C.E.; Syverson, K.M.

    2008-01-01

    Ice-walled-lake plains are prominent in many areas of hummocky-till topography left behind as the Laurentide Ice Sheet melted from middle North America. The formation of the hummocky-till topography has been explained by: (1) erosion by subglacial floods; (2) squeezing of subglacial till up into holes in stagnant glacial ice; or (3) slumping of supraglacial till. The geomorphology and stratigraphy of ice-walled-lake plains provide evidence that neither the lake plains nor the adjacent hummocks are of subglacial origin. These flat lake plains, up to a few kilometers in diameter, are perched as much as a few tens of meters above surrounding depressions. They typically are underlain by laminated, fine-grained suspended-load lake sediment. Many ice-walled-lake plains are surrounded by a low rim ridge of coarser-grained shore sediment or by a steeper rim ridge of debris that slumped off the surrounding ice slopes. The ice-walled lakes persisted for hundreds to thousands of years following glacial stagnation. Shells of aquatic molluscs from several deposits of ice-walled-lake sediment in south-central North Dakota have been dated from about 13 500 to 10 500??B.P. (calibrated radiocarbon ages), indicating a climate only slightly cooler than present. This is confirmed by recent palaeoecological studies in nearby non-glacial sites. To survive so long, the stagnant glacial ice had to be well-insulated by a thick cover of supraglacial sediment, and the associated till hummocks must be composed primarily of collapsed supraglacial till. ?? 2007 Elsevier B.V. All rights reserved.

  10. CORN BELT PLAIN RIVER AND STREAMS PROJECT - 3 BIOCRITERIA PRODUCTS

    EPA Science Inventory

    This effort resulted in eight products, as follows: 1) Development of Index of Biotic Integrity Expectations for the Ecoregions of Indiana I. Central Corn Belt Plain; 2) Ibid. II. Huron-Erie Lake Plain; 3) Ibid III. Northern Indiana Till Plain; 4) Ibid .IV.Eastern Corn Belt Plain...

  11. 44 CFR 10.14 - Flood plains and wetlands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Executive Order 11988, Flood Plain Management, and Executive Order 11990, Protection of Wetlands (44 CFR... 44 Emergency Management and Assistance 1 2013-10-01 2013-10-01 false Flood plains and wetlands. 10... Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions...

  12. 44 CFR 10.14 - Flood plains and wetlands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Executive Order 11988, Flood Plain Management, and Executive Order 11990, Protection of Wetlands (44 CFR... 44 Emergency Management and Assistance 1 2014-10-01 2014-10-01 false Flood plains and wetlands. 10... Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions...

  13. 44 CFR 10.14 - Flood plains and wetlands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Executive Order 11988, Flood Plain Management, and Executive Order 11990, Protection of Wetlands (44 CFR... 44 Emergency Management and Assistance 1 2010-10-01 2010-10-01 false Flood plains and wetlands. 10... Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions...

  14. 44 CFR 10.14 - Flood plains and wetlands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Executive Order 11988, Flood Plain Management, and Executive Order 11990, Protection of Wetlands (44 CFR... 44 Emergency Management and Assistance 1 2011-10-01 2011-10-01 false Flood plains and wetlands. 10... Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions...

  15. 44 CFR 10.14 - Flood plains and wetlands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Executive Order 11988, Flood Plain Management, and Executive Order 11990, Protection of Wetlands (44 CFR... 44 Emergency Management and Assistance 1 2012-10-01 2011-10-01 true Flood plains and wetlands. 10... Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions...

  16. Continental sediments in South Africa

    NASA Astrophysics Data System (ADS)

    Turner, B. R.

    In the central part of the Karoo Basin, South Africa, the Triassic fluviatile Molteno Formation forms a northerly thinning braided clastic wedge. In the eastern Karoo Basin it forms part of a thick sequence of upper Karoo sediments (Triassic-Jurassic) assigned to a meanderbelt facies, a fluvio-lacustrine facies and an aeolian facies. Two braided classic wedges occur within the succession, one in the meanderbelt facies, and the other (the Molteno) between the meanderbelt and fluvio-lacustrine facies. An upward-fining sequence of uranium-bearing Permian sandstones and mudstones in the southwesternn Karoo Basin has been dividedt into three facies associations, representing deposition in the parximal, intermidiate and distal parts of an extensive alluvial plain. Coal-bearing Permian Karoo sediments in the Nongoma graben, north of the main Karoo Basin comprise low and high sinuosity channel deposits, with the latter containing the best coals. The early Palaeozoic Cape Peninsula Basin contains a prograding sequence of arenites with subordinate interbedded shales and siltstones deposited on the proximal and distal parts of a marine influenced braidplain. Younger (Triassic-Jurassic) upper Karoo sediments in northeast Swaziland contain diamonds near the base of a fluvio-lacustrine 'red bed' sequence, overlain by aeolian deposite similar to those in the main Karoo Basin.

  17. High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth

    NASA Astrophysics Data System (ADS)

    Glud, Ronnie N.; Wenzhöfer, Frank; Middelboe, Mathias; Oguri, Kazumasa; Turnewitsch, Robert; Canfield, Donald E.; Kitazato, Hiroshi

    2013-04-01

    Microbes control the decomposition of organic matter inmarine sediments. Decomposition, in turn, contributes to oceanic nutrient regeneration and influences the preservation of organic carbon. Generally, rates of benthic decomposition decline with increasing water depth, although given the vast extent of the abyss, deep-sea sediments are quantitatively important for the global carbon cycle. However, the deepest regions of the ocean have remained virtually unexplored. Here, we present observations of microbial activity in sediments at Challenger Deep in the Mariana Trench in the central west Pacific, which at almost 11,000m depth represents the deepest oceanic site on Earth. We used an autonomous micro-profiling system to assess benthic oxygen consumption rates. We show that although the presence of macrofauna is restricted at Challenger Deep, rates of biological consumption of oxygen are high, exceeding rates at a nearby 6,000-m-deep site by a factor of two. Consistently, analyses of sediments collected from the two sites reveal higher concentrations of microbial cells at Challenger Deep. Furthermore, analyses of sediment 210Pb profiles reveal relatively high sediment deposition in the trench. We conclude that the elevated deposition of organic matter at Challenger Deep maintains intensified microbial activity at the extreme pressures that characterize this environment.

  18. Roughness coefficients for densely vegetated flood plains

    USGS Publications Warehouse

    Arcement, G.J.; Schneider, V.R.

    1987-01-01

    Although much research has been done on Manning 's roughness coefficients for stream channels, very little has been done on the selection of roughness values for densely vegetated flood plains. In this report four method for determining roughness coefficients for flood plains are examined and evaluated. Field data were collected at 13 sites on wide, densely vegetated flood plains where verified n values were known. The ' vegetation density ' of representative sample areas was measured at each site for use in determining roughness coefficients. The vegetation density method, proved to be useful in determining n values for wide, densely wooded plains. By measuring the area occupied by tree trunks and vegetation in a representative sample area, the vegetation density can be determined. Using the vegetation density in an equation developed from Manning 's formula, the Manning 's n can be determined for the representative sample area. (USGS)

  19. The High Plains: Land of Extremes.

    ERIC Educational Resources Information Center

    Capron, Ranel Stephenson; And Others

    1996-01-01

    Provides rich background information about unique High Plains ecosystems. Focuses on water, plant, animal, and energy resources. Describes hands-on activities related to ground water movement and energy resources. Contains 18 references. (DDR)

  20. Low sea-level stand emplacement of megaturbidites in the western and eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Rothwell, R. G.; Reeder, M. S.; Anastasakis, G.; Stow, D. A. V.; Thomson, J.; Kähler, G.

    2000-09-01

    Piston cores from the Balearic and Herodotus Abyssal Plains in the Mediterranean Sea show that the Late Pleistocene to Holocene sedimentary sequence is dominated by turbidite muds. On each plain, one turbidite bed is conspicuous by its thickness, and this bed can be correlated basinwide on the basis of geochemical compositional analysis and its apparent correspondence with a distinct acoustically transparent layer on high-resolution seismic records. These megabeds on the two plains represent megaturbidites of very large volume (300-600 km 3 each) and are shown by AMS radiocarbon dating to have been emplaced during the last low stand of sea-level at the height of the last glacial maximum. The megabed on the Balearic Abyssal Plain is derived from the southern European margin and is the main sedimentation event over the last 120 ka. It emplaced as much material as was deposited by smaller flows during the previous 25 ka. Sedimentation rate curves for the Balearic Abyssal Plain show that falling sea-level correlates with increased terrigenous deposition, and that gross sedimentation rates in the basin increased as sea level fell from 120-18 ka due to more frequent emplacement of distal turbidites. The Herodotus Abyssal Plain megabed is derived from the Libyan-Egyptian continental shelf west of the Nile Delta and was the dominant sedimentation event in this basin during the past 60 kyr. High-resolution seismic profiles from the Ionian and Sirte Abyssal Plains in the central Mediterranean also suggest possible low sea-level emplacement of megabeds in these regions. Available evidence suggests widespread emplacement of megaturbidites throughout the Mediterranean at the last glacial maximum. Although the triggering mechanisms for these events remain speculative, catastrophic destabilisation of the margin after a long period of accumulation with an increased rate of sediment supply is suggested.

  1. PLAINS CO2 REDUCTION PARTNERSHIP

    SciTech Connect

    Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Lisa S. Botnen

    2005-07-01

    The Plains CO{sub 2} Reduction (PCOR) Partnership characterization work is nearing completion, and most remaining efforts are related to finalizing work products. Task 2 (Technology Deployment) has developed a Topical Report entitled ''Deployment Issues Related to Geologic CO{sub 2} Sequestration in the PCOR Partnership Region''. Task 3 (Public Outreach) has developed an informational Public Television program entitled ''Nature in the Balance'', about CO{sub 2} sequestration. The program was completed and aired on Prairie Public Television in this quarter. Task 4 (Sources, Sinks, and Infrastructure) efforts are nearing completion, and data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation are being incorporated into a series of topical reports. The expansion of the Decision Support System Geographic Information System database has continued with the development of a ''save bookmark'' feature that allows users to save a map from the system easily. A feature that allows users to develop a report that summarizes CO{sub 2} sequestration parameters was also developed. Task 5 (Modeling and Phase II Action Plans) focused on screening and qualitatively assessing sequestration options and developing economic estimates for important regional CO{sub 2} sequestration strategies.

  2. PLAINS CO2 REDUCTION PARTNERSHIP

    SciTech Connect

    Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

    2005-04-01

    The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) and provided information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 2 efforts also included preparation of a draft topical report entitled ''Deployment Issues Related to Geologic CO{sub 2} Sequestration in the PCOR Partnership Region'', which is nearing completion. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. The video will be completed and aired on Prairie Public Television in the next quarter. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. The addition of the Canadian province of Alberta to the PCOR Partnership region expanded the decision support system (DSS) geographic information system database. Task 5 screened and qualitatively assessed sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

  3. Groundwater resources in the North China Plain

    SciTech Connect

    Fei Jin )

    1988-08-01

    Shallow groundwater is a major object of exploitation in the North China Plain. About 20 billion m{sup 3}/yr of fresh groundwater and about 20 billion m{sup 3}/yr of surface water are available. Present water demand is about equal to or exceeds the utilizable water resources in the North China Plain. Strict economy of water use is needed along with strengthened water control, a restructured development plan, and artificial recharge.

  4. Mapping Titans Undifferentiated Plains (Blandlands) to infer their origin

    NASA Astrophysics Data System (ADS)

    Lopes, Rosaly M.; Malaska, Michael J.; Schoenfeld, Ashley M.; LeGall, Alice; Hayes, Alexander G.; Birch, Samuel P.; Solomonidou, Anezina

    2014-11-01

    The undifferentiated plains first mapped by Lopes et al. (2010, Icarus, 205) are vast expanses of terrains that appear bland in Cassini RADAR Synthetic Aperture Radar images, hence the designation blandlands. While the interpretation of several other geologic units on Titan, such as dunes and well-preserved impact craters, has been relatively straightforward, the origin of the blandlands has remained mysterious. SAR images show that the blandlands are mostly found at mid-latitudes and appear relatively featureless at radar wavelengths, with no significant topographic variations. Their gradational boundaries and paucity of features in SAR data make geologic interpretation particularly challenging. We have mapped the distribution of these terrains using SAR swaths up to T92 (July 2013), which cover > 50% of Titans surface. We compared SAR images with their de-noised counterparts, the topography using the SARTopo method (Stiles et al., 2009, Icarus 202) and, where possible, the response from radiometry. We examined and evaluated different formation mechanisms. Plains may be sedimentary in origin, resulting from fluvial or lacustrine deposition or accumulation of photolysis products created in the upper atmosphere. Alternatively, the plains may be cryovolcanic, consisting of overlapping flows of low relief, obscured by accumulation of sediments. In this paper, we use SAR, radiometry, and SARTopo data to examine the characteristics of the plains and compare them with other geologic units. The results from our analysis suggest that the sedimentary origin is the most likely, and that plain materials are similar or the same as dune materials. Plains occur mostly at mid-latitudes, while dunes occur mostly at low latitudes. This may be a result of wind patterns, decrease in sand supply, or changes in properties of sand, perhaps moisture content, all of which would inhibit the formation of large dunes.

  5. Soil and geomorphic evolution within the rolling red plains using pleistocene volcanic ash deposits

    NASA Astrophysics Data System (ADS)

    Carter, Brian J.; Ward, Phil A.; Shannon, Jean T.

    1990-09-01

    Pleistocene volcanic ash deposits are found within alluvium from the Arkansas river south to the Brazos river. This drainage area includes tributaries originating in the High Plains, the Raton volcanic field and the Rocky Mountain Front Range within the states of Colorado, New Mexico, Kansas, Texas, and Oklahoma. Thirteen ash deposits are dated from within the High Plains of Kansas and Texas eastward into central Oklahoma to understand the geomorphic history and improve soil and geologic mapping. Within the study area unsolidated Tertiary and Quaternary sediments deposited in a west to east direction overlie Triassic, Permian, and Pennsylvanian bedrock. Volcanic ash deposits are predominantly Early to Middle Pleistocene age. Volcanic ash deposits were dated by the fission track method on shards. The ash deposits are contained within four land resource regions, the Southern and Central High Plains, the High Plains Breaks, the Rolling Red Plains, and the Reddish Prairies. Extensive Middle Pleistocene constructional stream terrace surfaces occur within the Rolling Red Plains. Multiple stream terrace surfaces were recognized across the study area with the highest level being dated Early Pleistocene to Pliocene and the lowest bordering the Holocene floodplains. Topographic cross-sections (100 km long at 1:24,000 scale) transecting dated ash deposits and perpendicular to major river systems were used to distinguish terrace levels. Constructional terrace surfaces dated by ash deposits range from 21 to 100 m above and 1 to 16 km distance from present river channels. Soil orders formed in Quaternary alluvium are Entisols, Inceptisols, Mollisols, Alfisols and Vertisols. Ustic and udic soil moisture regimes and a thermic (15 to 22C mean annual temperature) soil temperature regime dominate the study area. The same soil series is often mapped on terrace surfaces spanning Early to Middle Pleistocene age because current classification does not recognize differences in deeply weathered soils (greater than 2 m) and lacks recognition of loess. Soil great groups found on Early and Middle Pleistocene surfaces were Paleustolls and Argiustolls.

  6. A reconnaissance study of the effect of irrigated agriculture on water quality in the Ogallala Formation, Central High Plains Aquifer

    USGS Publications Warehouse

    McMahon, Peter B.

    2000-01-01

    In 1998, the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program began a regional study of water quality in the High Plains aquifer. The High Plains aquifer underlies an area of about 174,000 square miles in parts of eight States. Because of its large size, the High Plains aquifer has been divided into three regions: the Southern High Plains, Central High Plains, and Northern High Plains (fig. 1A). Although an assessment of water quality in each of the three regions is planned, the initial focus will be the Central High Plains aquifer. Anyone who has flown over the Central High Plains in the summer and has seen the large green circles associated with center pivot sprinklers (fig. 2) knows that irrigated agriculture is a widespread land use. Pesticides and fertilizers applied on those irrigated fields will not degrade ground-water quality if they remain in or above the root zone (fig. 3). However, if those chemicals move downward through the unsaturated zone to the water table, they may degrade the quality of the ground water. Water is the principal agent for transporting chemicals from land surface to the water table, and in the semiarid Central High Plains, irrigation often represents the most abundant source of water during the growing season. One objective of NAWQA's High Plains Regional Ground-Water study is to evaluate the effect of irrigated agriculture on the quality of recently recharged water in the Ogallala Formation of the Central High Plains aquifer (figs. 1A and 1B). The Ogallala Formation is the principal geologic unit in the Central High Plains aquifer, and it consists of poorly sorted clay, silt, sand, and gravel that generally is unconsolidated (Gutentag and others, 1984). Approximately 23 percent of the cropland overlying the Ogallala Formation is irrigated (U.S. Department of Agriculture, 1999). The NAWQA Program generally defines recently recharged ground water to be water recharged in the last 50 years. The water table in the Ogallala Formation is separated from overlying land-use practices by as much as 400 feet of unsaturated sediments. Consequently, one may hypothesize that recently recharged water is not present in the formation. The U.S. Geological Survey conducted a reconnaissance study in 1999 to establish (a) if recently recharged water was present in the Ogallala Formation underlying irrigated cropland and (b) if agricultural land-use practices affect water quality. Results from the reconnaissance study will be used to determine whether a full-scale land-use study is warranted.

  7. Visual sedimentation.

    PubMed

    Huron, Samuel; Vuillemot, Romain; Fekete, Jean-Daniel

    2013-12-01

    We introduce Visual Sedimentation, a novel design metaphor for visualizing data streams directly inspired by the physical process of sedimentation. Visualizing data streams (e. g., Tweets, RSS, Emails) is challenging as incoming data arrive at unpredictable rates and have to remain readable. For data streams, clearly expressing chronological order while avoiding clutter, and keeping aging data visible, are important. The metaphor is drawn from the real-world sedimentation processes: objects fall due to gravity, and aggregate into strata over time. Inspired by this metaphor, data is visually depicted as falling objects using a force model to land on a surface, aggregating into strata over time. In this paper, we discuss how this metaphor addresses the specific challenge of smoothing the transition between incoming and aging data. We describe the metaphor's design space, a toolkit developed to facilitate its implementation, and example applications to a range of case studies. We then explore the generative capabilities of the design space through our toolkit. We finally illustrate creative extensions of the metaphor when applied to real streams of data. PMID:24051811

  8. Salt dissolution features in saline lakes of the northern Great Plains, western Canada

    NASA Astrophysics Data System (ADS)

    Last, William M.

    1993-12-01

    Large-scale salt dissolution is an important process affecting the sediments of many of the saline lakes in the northern Great Plains region of western Canada. The most easily recognized features of this salt karst are water-filled chimneys, vertical shafts, and collapse structures. The largest individual chimneys can be up to 20 m deep and 50 m in diameter, with volumes exceeding 25,000 m 3. Large, mud-filled chimneys and cavities, and salt-filled chimneys have also been identified in both the modern lakes and in the Quaternary sediments of the basins, which can adversely affect the salt mining potential of the basins. Because these salt karst features can affect large vertical sections of the sediment fill in the lakes, their recognition is of fundamental importance in attempting to use the stratigraphic records of the basins for paleoenvironmental research.

  9. Characterization of suspended-sediment transport conditions for stable, Reference streams in selected Ecoregions of EPA Region 8

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Historic flow and sediment transport data from about 350 sites across the Mountains and Plains region of the United States were analyzed for the purpose of developing background or reference rates of suspended-sediment transport by Level III ecoregion. Rapid Geomorphic Assessments (RGAs) were c...

  10. Effects of hydrology, watershed size, and agricultural practices on sediment yields in two river basins in Iowa and Mississippi

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The specific sediment yield (SSY) from watersheds is the result of the balance between natural, scale-dependent erosion, and deposition processes, but can be greatly altered by human activities. In general, the SSY decreases along the course of a river as sediments are trapped in alluvial plains and...

  11. Evolution of Ganges-Brahmaputra western delta plain: Clues from sedimentology and carbon isotopes

    NASA Astrophysics Data System (ADS)

    Sarkar, A.; Sengupta, S.; McArthur, J. M.; Ravenscroft, P.; Bera, M. K.; Bhushan, Ravi; Samanta, A.; Agrawal, S.

    2009-12-01

    Sedimentology, carbon isotope and sequence stratigraphic analysis of subsurface sediments from western part of Ganges-Brahmaputra (GB) delta plain shows that a Late Quaternary marine clay and fluvial channel-overbank sediments of MIS 5 and 3 highstands are traceable below the Holocene strata. During the Last Glacial Maximum (LGM) sea-level lowering of >100 m produced a regional unconformity (type 1), represented by palaeosols and incised valley. C4 vegetation expanded on exposed lowstand surface in an ambient dry glacial climate. At 9 ka transgression inundated the lowstand surface pushing the coastline and mangrove front 100 km inland. Simultaneous intensification of monsoon and very high sediment discharge (4-8 times than modern) caused a rapid aggradation of both floodplain and estuarine valley fill deposits between 8 and 7 ka. The Hoogli River remaining along its present drainage possibly acted as the main conduit for transgression and sediment discharge that was subsequently abandoned. C3 vegetation dominated the delta plain during this time. From 7 ka onward progradation of delta plain started and continued till recent. This period experienced a mixed C3-C4 vegetation with localized mangroves in the mid-Holocene to dominant return of C4 vegetation in the late Holocene period. The study indicates that while the initiation of western part of GB delta occurred at least 1 ka earlier than the global mean delta formation age, the progradation started at 7 ka, at least 2 ka earlier than thought before. The terrestrial vegetation change was modulated by changes in depositional environment, specific ecological niches and climate rather than pCO 2.

  12. Hiding video in plain sight

    NASA Astrophysics Data System (ADS)

    Rosiene, Carolyn P.; Rosiene, Joel A.

    2000-05-01

    With the increasing number of digital transmissions, there is an opportunity to utilize existing broadcast channels to send hidden video transmissions. This presentation outlines and demonstrates a technique to insert a hidden video channel within a larger standard video feed, or 'hide in plain sight.' The approach outlined consists of three parts: data (or video) insertion, data security, and data recovery. These three components are essential to complete a secured digital transmission. To insert the data, knowledge of the standard (for example, MPEG 1, 2, or 4) is used to place the information to be hidden into the compressed data stream post quantization. Since the encoder has perfect knowledge of the receiver's model, it is possible to place the data in the compressed data in a manner that is visually un-intrusive. The technique to hide the data will be presented and an example given. Since, the data (or video) to be inserted may be of a sensitive nature, it is necessary to provide a level of security, which will render the video stream useless if its presence is detected. Both, spatial and temporal dispersion are used to reduce the likelihood of detection with the addition of a modulation of the signal to reduce the image to noise unless the key is known. The intended viewer of the embedded data (or video stream), with knowledge of the key recovers the data by encoding the incoming video stream with the appropriate standard, and extracting the data prior to quantization. While the work in this paper focuses on the insertion of hidden video into a broadcast signal, the same technique serves to prevent tampering to the broadcast signal, since modification of the image data will corrupt the hidden signal. In this way, this provides a level of tamper protection/detection for video, which may be used in legal proceedings.

  13. Assessment of the effects of farming and conservation programs on pesticide deposition in high plains wetlands.

    PubMed

    Belden, Jason B; Hanson, Brittany Rae; McMurry, Scott T; Smith, Loren M; Haukos, David A

    2012-03-20

    We examined pesticide contamination in sediments from depressional playa wetlands embedded in the three dominant land-use types in the western High Plains and Rainwater Basin of the United States including cropland, perennial grassland enrolled in conservation programs (e.g., Conservation Reserve Program [CRP]), and native grassland or reference condition. Two hundred and sixty four playas, selected from the three land-use types, were sampled from Nebraska and Colorado in the north to Texas and New Mexico in the south. Sediments were examined for most of the commonly used agricultural pesticides. Atrazine, acetochlor, metolachlor, and trifluralin were the most commonly detected pesticides in the northern High Plains and Rainwater Basin. Atrazine, metolachlor, trifluralin, and pendimethalin were the most commonly detected pesticides in the southern High Plains. The top 5-10% of playas contained herbicide concentrations that are high enough to pose a hazard for plants. However, insecticides and fungicides were rarely detected. Pesticide occurrence and concentrations were higher in wetlands surrounded by cropland as compared to native grassland and CRP perennial grasses. The CRP, which is the largest conservation program in the U.S., was protective and had lower pesticide concentrations compared to cropland. PMID:22356096

  14. Stratigraphic evolution of the late Holocene Ganges Brahmaputra lower delta plain

    NASA Astrophysics Data System (ADS)

    Allison, M. A.; Khan, S. R.; Goodbred, S. L.; Kuehl, S. A.

    2003-02-01

    Sediment cores from the Ganges-Brahmaputra delta in Bangladesh were examined for sedimentological character, clay mineralogy, elemental trends (C, N, S), and 14C geochronology to develop a model for the sedimentary sequence resulting from lower delta plain progradation in the late Holocene. A widespread facies succession from Muddy Sand to Interbedded Mud records progradation of shoal-island complexes and the transition from subtidal to intertidal conditions. Mangrove-vegetated islands and peninsulas represent the final phase of progradation; a Mottled Mud that is deposited by penetration of turbid coastal water into the mangroves during high water events. Organic matter preservation is generally low (<1% TOC) in most of these well-drained deposits that are characterized by a permeable, silt-dominated granulometry. Clay mineralogy in the cores records the relative influence of smectite and kaolinite-rich Ganges sediments and illite and chlorite-rich Brahmaputra material. The lower delta plain west of the modern river mouths was deposited as a Ganges-dominated delta in three phases since 5000 cal years BP, with Brahmaputra influence confined to the Meghna estuary area and to the supratidal section of western delta deposits. Evolution of the lower delta plain in the late Holocene was influenced by regional subsidence patterns in the tectonically active Bengal Basin, which controlled distributary channel avulsion and migration, and the creation of accommodation space.

  15. Cenozoic ice sheet history from East Antarctic Wilkes Land continental margin sediments

    USGS Publications Warehouse

    Escutia, C.; De Santis, L.; Donda, F.; Dunbar, R.B.; Cooper, A. K.; Brancolini, Giuliano; Eittreim, S.L.

    2005-01-01

    The long-term history of glaciation along the East Antarctic Wilkes Land margin, from the time of the first arrival of the ice sheet to the margin, through the significant periods of Cenozoic climate change is inferred using an integrated geophysical and geological approach. We postulate that the first arrival of the ice sheet to the Wilkes Land margin resulted in the development of a large unconformity (WL-U3) between 33.42 and 30 Ma during the early Oligocene cooling climate trend. Above WL-U3, substantial margin progradation takes place with early glacial strata (e.g., outwash deposits) deposited as low-angle prograding foresets by temperate glaciers. The change in geometry of the prograding wedge across unconformity WL-U8 is interpreted to represent the transition, at the end of the middle Miocene "climatic optimum" (14-10 Ma), from a subpolar regime with dynamic ice sheets (i.e., ice sheets come and go) to a regime with persistent but oscillatory ice sheets. The steep foresets above WL-U8 likely consist of ice proximal sediments (i.e., water-lain till and debris flows) deposited when grounded ice-sheets extended into the shelf. On the continental rise, shelf progradation above WL-U3 results in an up-section increase in the energy of the depositional environment (i.e., seismic facies indicative of more proximal turbidite and of bottom contour current deposition from the deposition of the lower WL-S5 sequence to WL-S7). Maximum rates of sediment delivery to the rise occur during the development of sequences WL-S6 and WL-S7, which we infer to be of middle Miocene age. During deposition of the two uppermost sequences, WL-S8 and WL-S9, there is a marked decrease in the sediment supply to the lower continental rise and a shift in the depocenters to more proximal areas of the margin. We believe WL-S8 records sedimentation during the final transition from a dynamic to a persistent but oscillatory ice sheet in this margin (14-10 Ma). Sequence WL-S9 forms under a polar regime during the Pliocene-Pleistocene, when most sediment delivered to the margin is trapped in the outer shelf and slope-forming steep prograding wedges. During the warmer but still polar, Holocene, biogenic sediment accumulates quickly in deep inner-shelf basins during the high-stand intervals. These sediments contain an ultrahigh resolution (annual to millennial) record of climate variability. Validation of our inferences about the nature and timing of Wilkes Land glacial sequences can be achieved by deep sampling (i.e., using IODP-type techniques). The most complete record of the long-term history of glaciation in this margin can be obtained by sampling both (1) the shelf, which contains the direct (presence or no presence of ice) but low-resolution record of glaciation, and (2) the rise, which contains the distal (cold vs. warm) but more complete record of glaciation. The Wilkes Land margin is the only known Antarctic margin where the presumed "onset" of glaciation unconformity (WL-U3) can be traced from shelf to the abyssal plain, allowing links between the proximal and the distal records of glaciation to be established. Additionally, the eastern segment of the Wilkes Land margin may be more sensitive to climate change because the East Antarctic Ice Sheet (EAIS) is grounded below sea level. Therefore, the Wilkes Land margin is not only an ideal location to obtain the long-term EAIS history but also to obtain the shorter-term record of ice sheet fluctuations at times that the East Antarctic Ice Sheet is thought to have been more stable (after 15 Ma-recent). ?? 2004 Elsevier B.V. All rights reserved.

  16. Thermal and tectonic implications of heat flow in the Eastern Snake River Plain, Idaho

    NASA Astrophysics Data System (ADS)

    Brott, Charles A.; Blackwell, David D.; Ziagos, John P.

    1981-12-01

    Geothermal data from 248 wells and drill holes, a thermal model for the effects of the Snake Plain aquifer on observed heat flow, an estimate of the regional heat flow in the eastern Snake River Plain, a detailed moving source, regional thermal model, and a discussion of the origin and the relationship of the eastern and western halves of the Snake River Plain are included in this paper. In order to determine the thermal structure of the eastern Snake River Plain, an extensive geothermal gradient and heat flow survey was carried out. Data from 248 holes show high heat flow values along the margins but low values along the center because of effects of the extensive Snake Plain aquifer. Based on a thermal model of the aquifer, a heat budget was derived from which a mean heat flow for the eastern Snake River Plain of 190 m W m-2 was calculated. This value can be compared to observed values along the margins of 120 mW m-2 and two values in deep holes along the northeastern margin of 110 and 109 mW m-2. The areas of highest expected values, in the Island Park caldera region, have not been sampled by heat flow measurements, however. Based on the heat flow results from the eastern and the western Snake River Plain and other geophysical and geological data, a finite-width moving-source-plane thermal model is developed for the Snake River Plain. Even though the geological and geophysical characteristics of the eastern and western Snake River Plain are somewhat different, they are attributed to the same moving heat source, and the spatial geological and geophysical differences are explained by different stages in a time-related sequence of thermally driven geological and tectonic events. The Snake River Plain is due to a strong thermal source interacting with the crust with the resulting complete chemical reorganization of the crust. The major immediate driving mechanism is a thick mafic intrusive emplaced in the midlevels of the crust. Associated with this thermal event are regional uplift of a kilometer or so as the heating occurs, associated melting of the upper crust, and subsequent rapid subsidence of approximately 1/2 to 1 km because of the change in density of the crust and upper mantle section associated with the emplacement of the basic intrusive and the disruption of the granitic upper crust. After the heat source moves eastward, continued subsidence occurs due to cooling of the lithospheric section (similar to that seen for oceanic regions). Along with the subsidence and soon after completion of the extensive silicic volcanism, basalts began to be extruded. Thermal contraction also generates faulting on the sides and perhaps in the center of the hot spot track. The subsidence causes reversal of the dips of the silicic ash flows from their initial away-from-the-source configuration, to the toward-the-source configuration observed in the Snake River Plain. Continued subsidence and cooling cause the formation of the basin which is then filled by sediments, causing additional subsidence due to isostatic adjustment (the western Snake River basin). Thus all aspects of the Snake River Plain-Yellowstone region are consequences of a single thermal event, and all stages in the future history of the Yellowstone region and the past history of the western Snake River basin are represented by westward or eastward traverses (respectively) along the Snake River Plain.

  17. Light Plains in the South-Pole Aitken Basin: Surface Ages and Mineralogical Composition

    NASA Astrophysics Data System (ADS)

    Thiessen, F.; Hiesinger, H.; van der Bogert, C. H.; Pasckert, J. H.; Robinson, M. S.

    2012-04-01

    We studied light plains in the north-eastern South-Pole Aitken basin to investigate their origin, ages, and mineralogical composition. Light plains, also known as the Cayley Formation, occur on the near- and farside of the Moon. Due to their smooth texture, lower crater densities, and occurrence as crater fills, they were thought to be of volcanic origin [e.g., 1]. However, Apollo 16 samples of light plains deposits were in fact highly brecciated rocks [2]. Therefore, the Imbrium and Orientale impacts were thought to have formed light plains because they reshaped the surface thousands of kilometers from their impact sites. Subsequent studies revealed varying surface ages of light plains [e.g., 3] and different mineralogical compositions, which are in some cases more highland-like and in others more mare-like. Hence, an origin solely from the Imbrium and/or Orientale impacts is unlikely. Thus, the question whether light plains formed due to large impacts or regional cratering, or through endogenic processes remains open. We performed crater size-frequency measurements [e.g., 4] on Lunar Reconnaissance Orbiter Wide Angle Camera images and obtained absolute model ages between 3.43 and 3.81 Ga. We observed neither a distinctive peak of light plains ages nor clustering of similar ages in any specific regions of the studied area. Due to the fact that the derived ages vary as much as 380 Ma, an origin by a single event seems unlikely. Moreover, some ages even post-date the Imbrium and Orientale impacts, and thus an origin related to those impacts is not likely. Examination of multispectral data from Clementine [5] shows that the Ti abundances vary between 0.2 and 3 wt % and Fe abundances between 12.5 and 19 wt %. We observed a regional difference in distribution: light plains units within the Apollo basin have lower Fe and Ti values and are more highland-like, whereas light plains outside the Apollo basin show higher Fe and Ti values and are more mare-like. Furthermore, M3 spectra from small impact craters on light plains show characteristic absorption bands for pyroxene. We conclude that light plains are unlikely to have formed by the Imbrium and Orientale impacts due to the range of surface ages and the compositional differences. Nevertheless, these impacts together with secondary cratering and sedimentation from regional and local impacts may have played an important role in forming these plains. An endogenic origin can still not be excluded due to the mare-like composition of some light plains. [1] Wilhelms D.E. (1970) Astrogeol. Stud. Ann. Prog. Report, 13-28. [2] Young J.W. (1972) NASA Apollo 16 Prelim. Sci. Rep., 5-1-5-6. [3] Neukum, G. (1977) The Moon 17, 383-393. [4] Neukum G. et al. (1975) The Moon 12, 201-229. [5] Lucey P.G. et al. (2000) J. Geophys. Res. 105, 20,297-20,305.

  18. Human Responses to Middle Holocene (Altithermal) Climates on the North American Great Plains

    NASA Astrophysics Data System (ADS)

    Meltzer, David J.

    1999-11-01

    The climate of the Great Plains during the middle Holocene varied considerably, but overall it was marked by a north-south gradient of increasingly warmer and drier conditions, with a reduction in effective moisture, surface water, and resource abundance, and an increase in resource patchiness, sediment weathering, erosion, and aeolian activity. Pronounced drought conditions were most evident on the Southern High Plains. Understanding the human responses to middle Holocene climates is complicated by a lack of archaeological data, which is partly a result of geomorphic processes that removed or deeply buried sites of this age, and by the varying adaptive responses of hunter-gatherers during this period. On the Southern High Plains, where drought was most severe, surface and groundwater sources dried and bison populations were diminished, prompting substantial adaptive changes, including local abandonment, well-digging to tap underground water, and a widening of the diet breadth to incorporate higher-cost, lower-return seed and plant resources. Sites of this age on the Central and Northern Plains also show a possible increase in diet breadth (with the incorporation of plant foods in the diet), and perhaps changes in settlement mobility (including possible shift into higher elevation areas, or mapping-on to extant rivers and springs). But linking those changes to middle Holocene drought is less straightforward.

  19. Age determinations and Earth-based multispectral observations of lunar light plains

    NASA Technical Reports Server (NTRS)

    Koehler, U.; Jaumann, R.; Neukum, G.

    1993-01-01

    The history of light plains still remains doubtful, but there are good arguments - mainly obtained by age determinations and supported by multispectral observations - for an endogenic (magmatic) instead of an (exclusively) impact related origin. Light plains are characterized by smooth areas with an albedo lower than the surrounding highlands (12 - 13 percent), but significantly higher than maria (5 - 6 percent). Before Apollo 16 a volcanic source has been supposed, but analysis of returned samples (highly brecciated and metamorphosed rocks) favored an impact ejecta related origin. Among the currently discussed models are formation by ejecta sedimentation from multi-ringed basins, formation by secondary and tertiary cratering action of ballistically ejected material during the formation of multi-ringed basins, in situ formation by impact melt of large events, and premare (crypto-) volcanism basalts covered by a thin ejecta cover; younger impacts penetrated the ejecta surface to create the dark haloed craters. To find arguments in favor or against these ideas the chronology of light plains is of major importance. Obviously a genetic relationship between the evolution of light plains and the basin forming impacts can be possible only if the events of emplacement features happened simultaneously.

  20. Mineral resources of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona

    SciTech Connect

    Tosdal, R.M.; Eppinger, R.G.; Erdman, J.A.; Hanna, W.F.; Pitkin, J.A.; Blank, H.R. Jr.; O'Leary, R.M.; Watterson, J.R. ); Kreidler, T.J. )

    1990-01-01

    This paper reports on geologic, geochemical, and geophysical studies in the Cactus Plain and East Cactus Plain Wilderness Study Areas outlined in areas with moderate to high potential for gold, silver, copper, lead, zinc, barite, fluorite, manganese, and sand suitable for foundry, fracturing, and abrasive uses and low resource potential for beryllium, uranium and bentonitic clays.

  1. Do abyssal scavengers use phytodetritus as a food resource? Video and biochemical evidence from the Atlantic and Mediterranean

    NASA Astrophysics Data System (ADS)

    Jeffreys, Rachel M.; Lavaleye, Marc S. S.; Bergman, Magda J. N.; Duineveld, Gerard C. A.; Witbaard, Rob

    2011-04-01

    Deep-sea benthic communities derive their energetic requirements from overlying surface water production, which is deposited at the seafloor as phytodetritus. Benthic invertebrates are the primary consumers of this food source, with deep-sea fish at the top of the trophic hierarchy. Recently, we demonstrated with the use of baited cameras that macrourid fish rapidly respond to and feed vigorously on large plant food falls mimicked by spinach ( Jeffreys et al., 2010). Since higher plant remains are scarce in the deep-sea, with the exception of canyons, where terrestrial material has been observed, these results led us to ask if a more commonly documented plant material i.e. phytodetritus might form a food source for deep-sea fish and mobile scavenging megafauna. We simulated a phytodetritus dump at the seafloor in two contrasting environments (1) the NE Atlantic where carpets of phytodetritus have been previously observed and (2) the oligotrophic western Mediterranean, where the deposition of phytodetritus at the seafloor is a rare occurrence. We recorded the response of the scavenging fauna using an in situ benthic lander equipped with baited time-lapse cameras. In the NE Atlantic at 3000 m, abyssal macrourids and cusk-eels were observed ingesting the phytodetritus. The phytodetrital patch was significantly diminished within 2 h. Abundance estimates calculated from first arrival times of macrourids at the phytodetrital patch in the Atlantic corresponded with abundance estimates from video-transect indicating that fish were attracted to the scent of phytodetrital bait. In contrast to this, in the western Mediterranean at 2800 m a single macrourid was observed investigating the phytodetrital patch but did not feed from it. The phytodetrital patch was significantly diminished within 6.5 h as a result of mainly invertebrate activity. At 1900 m, Lepidion lepidion was observed near the lander and the bait, but did not feed. The phytodetrital patch remained intact until the end of the experiment. In the deployments in the Mediterranean abundance estimates from first arrival times at the bait, corrected for their body size, were lower than estimates obtained from video-transects and trawl catches. This suggests that the Mediterranean fish were not readily attracted to this food source. In contrast, invertebrates in the Balearic Sea were observed ingesting the phytodetritus bait despite the rare occurrence of phytodetritus dumps in the Mediterranean. Stable isotope values of the fish at both study sites, set within the context of the benthic food web, did not demonstrate a strong trophic link to phytodetritus. Fatty acid profiles of these fish indicated a strong link between their lipid pool and primary producers i.e. phytoplankton, which may be attributed to trophic transfer. The usefulness of fatty acid biomarkers in ascertaining deep-sea fish diets is discussed. Our study suggests that the abyssal grenadier C. armatus on the Atlantic Iberian margin is attracted to phytodetritus. However the exact contribution of this food source to the diet of macrourids in this area remains unresolved.

  2. Water in orthopyroxene from abyssal spinel peridotites of the East Pacific Rise (ODP Leg 147: Hess Deep)

    NASA Astrophysics Data System (ADS)

    Hesse, Kirsten T.; Gose, Jürgen; Stalder, Roland; Schmädicke, Esther

    2015-09-01

    Abyssal spinel peridotites from Hess Deep, East Pacific Rise (ODP Leg 147) were investigated concerning their major, minor, and trace element mineral chemistry and the incorporation of structural water in orthopyroxene. The rocks are partially serpentinized harzburgites containing primary minerals of olivine, orthopyroxene, clinopyroxene, and spinel. Orthopyroxene is enstatitic with Mg# (Mg/(Mg + Fe)) between 0.90 and 0.92 and Al2O3 from 0.5 to 2.9 wt.%. The residual harzburgite experienced high degrees of melt removal in the spinel peridotite stability field. The average degree of partial melting was calculated to be 17.5% (range: 16.4-17.8%). Trace element data of ortho- and clinopyroxenes reflect this strong depletion, characteristic for the restitic nature of abyssal peridotites. Mantle re-equilibration temperatures around 1000 °C indicate that, after melt extraction and before exhumation to the ocean floor, the rocks experienced significant cooling in the spinel peridotite facies. Water contents of orthopyroxene range from 86 to 233 wt. ppm H2O with an average concentration of 142 wt. ppm H2O. These results represent the first data on water contents in the sub-pacific mantle obtained by direct measurements of sub-oceanic peridotite. The water contents are not related to mineral chemistry, stratigraphy, melting degree, mantle equilibrium conditions or oxidation state. Calculated post-melt peridotite water contents vary between 40 and 100 wt. ppm H2O. Compared to Mid-Atlantic Ridge peridotites, the East Pacific Rise samples of Leg 147 contain somewhat lower water concentrations than samples from Leg 153 and considerably higher contents than those of Leg 209 (Gose et al., 2009; Schmädicke et al., 2011). In Leg 147, the strongest OH absorbtion band occurs at 3420 cm- 1, wheras orthopyroxene from MAR peridotite (Legs 153 and 209) has its strongest absorbtion band at 3566 and 3522 cm- 1. The mantle equilibrium temperature of Leg 147 peridotites is lower than that of Leg 209 (~ 1250 °C) but close to that of Leg 153 samples (950-1000 °C). The high degree of partial melting of Leg 147 peridotite samples overlaps with the Leg 209 samples. In accordance to this data we conclude that in order to obtain relatively high water contents of up to 233 wt. ppm in depleted peridotite, after melt removal water must have re-entered the orthopyroxene structure. We suggest that re-equilibration of water contents took place under spinel-facies conditions before exhumation of the tectonite, since elevated temperatures enhance diffusion and elevated pressures facilitate hydrogen uptake. The extended time span between melt removal and uplift inferred from significant isobaric cooling of at least 200 K at spinel-facies depth facilitates re-equilibration of water contents and may explain the high concentrations. Exhumation from spinel-facies depth was fast and accompanied by further cooling such that re-equilibration to lower pressure assemblages and decompression-induced water loss were prevented.

  3. Silicate weathering in the Ganges alluvial plain

    NASA Astrophysics Data System (ADS)

    Frings, Patrick J.; Clymans, Wim; Fontorbe, Guillaume; Gray, William; Chakrapani, Govind J.; Conley, Daniel J.; De La Rocha, Christina

    2015-10-01

    The Ganges is one of the world's largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny, weathering and global climate change. Three regions can be recognised in the Ganges basin, with the Himalayan orogeny to the north and the plateaus of peninsular India to the south together delimiting the Ganges alluvial plain. Despite constituting approximately 80% of the basin, weathering processes in the peninsula and alluvial plain have received little attention. Here we present an analysis of 51 water samples along a transect of the alluvial plain, including all major tributaries. We focus on the geochemistry of silicon and its isotopes. Area normalised dissolved Si yields are approximately twice as high in rivers of Himalaya origin than the plain and peninsular tributaries (82, 51 and 32 kmol SiO2 km-2 yr-1, respectively). Such dissolved Si fluxes are not widely used as weathering rate indicators because a large but variable fraction of the DSi mobilised during the initial weathering process is retained in secondary clay minerals. However, the silicon isotopic composition of dissolved Si (expressed as δ30Si) varies from + 0.8 ‰ in the Ganges mainstem at the Himalaya front to + 3.0 ‰ in alluvial plain streams and appears to be controlled by weathering congruency, i.e. by the degree of incorporation of Si into secondary phases. The higher δ30Si values therefore reflect decreasing weathering congruency in the lowland river catchments. This is exploited to quantify the degree of removal using a Rayleigh isotope mass balance model, and consequently derive initial silica mobilisation rates of 200, 150 and 107 kmol SiO2 km-2 yr-1, for the Himalaya, peninsular India and the alluvial plain, respectively. Because the non-Himalayan regions dominate the catchment area, the majority of initial silica mobilisation from primary minerals occurs in the alluvial plain and peninsular catchment (41% and 34%, respectively).

  4. Foraging behavior of abyssal grenadier fish: inferences from acoustic tagging and tracking in the North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Priede, Imants G.; Smith, Kenneth L.; Armstrong, John D.

    1990-01-01

    Abyssal grenadier fish Coryphaenoides yaquinae were Coryphaenoides armatus and observed arriving at baits deployed within view of a free-fall video vehicle (FVV) camera on the sea floor at two stations in the North Pacific, Sta. F 3250'N, 124W, 4400 m deep in the vicinity of the California current and Sta. CNP 31N, 159W, a 5900 m deep oligotrophic station. Included within each bait deployment were one or two ingestible acoustic transmitters. A total of 23 fish at Sta. F and 13 fish at Sta. CNP ingested transmitters and were tracked using an acoustic tracking system (ATEX). The number of fish within view of the camera increased to a mean maximum of 4.7 at 60 min at Sta. F and 11.8 by 400 min at Sta. CNP, a paradox in view of presumed lower fish population density at Sta. CNP. Fish that ingested transmitters moved away at radial velocities between 1 and 15 cm s -1, reaching a mean radius of 233 m by 370 min at Sta. F and 622 min at Sta. CNP. Fish appear to be active foragers with no evidence for a "sit and wait" foraging strategy. Grenadiers generally remained near the sea floor as they dispersed. Only one vertical movement to an altitude of ca 25 m was recorded and this comprised less than 0.2% of tracking time. The number of fish present at the bait was found to correspond to the following relationship: N t = ? 0/x(1 - c -xf) t ? ? ? 0/x c -xt(c ?x - 1) t > ? where Nt is number of fish present at time t min after bait reaches the sea floor, ?0 is initial arrival rate of fish, ? is mean fish staying time and x is the bait decay constant. In accordance with optimal foraging theory staying time (?) is longer at Sta. CNP.

  5. Serpentinization of abyssal peridotites from the MARK area, Mid-Atlantic Ridge: Sulfur geochemistry and reaction modeling

    USGS Publications Warehouse

    Alt, J.C.; Shanks, Wayne C., III

    2003-01-01

    The opaque mineralogy and the contents and isotope compositions of sulfur in serpentinized peridotites from the MARK (Mid-Atlantic Ridge, Kane Fracture Zone) area were examined to understand the conditions of serpentinization and evaluate this process as a sink for seawater sulfur. The serpentinites contain a sulfur-rich secondary mineral assemblage and have high sulfur contents (up to 1 wt.%) and elevated ??34Ssulfide (3.7 to 12.7???). Geochemical reaction modeling indicates that seawater-peridotite interaction at 300 to 400??C alone cannot account for both the high sulfur contents and high ??34Ssulfide. These require a multistage reaction with leaching of sulfide from subjacent gabbro during higher temperature (???400??C) reactions with seawater and subsequent deposition of sulfide during serpentinization of peridotite at ???300??C. Serpentinization produces highly reducing conditions and significant amounts of H2 and results in the partial reduction of seawater carbonate to methane. The latter is documented by formation of carbonate veins enriched in 13C (up to 4.5???) at temperatures above 250??C. Although different processes produce variable sulfur isotope effects in other oceanic serpentinites, sulfur is consistently added to abyssal peridotites during serpentinization. Data for serpentinites drilled and dredged from oceanic crust and from ophiolites indicate that oceanic peridotites are a sink for up to 0.4 to 6.0 ?? 1012 g seawater S yr-1. This is comparable to sulfur exchange that occurs in hydrothermal systems in mafic oceanic crust at midocean ridges and on ridge flanks and amounts to 2 to 30% of the riverine sulfate source and sedimentary sulfide sink in the oceans. The high concentrations and modified isotope compositions of sulfur in serpentinites could be important for mantle metasomatism during subduction of crust generated at slow spreading rates. ?? 2003 Elsevier Science Ltd.

  6. Prior Tectonic Brecciation Favors Carbonation of Abyssal Serpentinites : a Petrographic and Stable Isotope Study of Southwest Indian Ridge Dredged Samples.

    NASA Astrophysics Data System (ADS)

    Cannat, M.; Payré, V.; Martinez, I.

    2014-12-01

    Partial carbonation of the uppermost oceanic lithosphere represents a significant natural reservoir for long term carbon storage. About 25% of the oceanic basement formed at slow spreading ridges is made of tectonically exhumed and variably serpentinized abyssal peridotites in which carbonates veins have been documented. Previous studies indicate formation of these veins at temperatures between ~180°C and <10°C, at the seafloor or in shallow levels of the exhumation faults, and from fluids ranging from pure seawater to seawater-hydrothermal fluids mixtures. In this presentation we show that partial carbonation of serpentinites dredged at and near the easternmost Southwest Indian Ridge (SWIR) similarly occurred in two settings: dolomite formed at temperatures ~50°C presumably in shallow fluid-rich domains of the exhumation fault(s), while aragonite formed at yet lower temperatures within a few meters of the seafloor. We also present a detailed petrographic study of carbonation textures showing that while carbonate veining is prevalent in the seafloor-type carbonation, it is superseeded by serpentine dissolution and replacement in our samples of the fault zone-type carbonation. In these samples, dolomite preferably replaces the matrix of a tectonic breccia, that comprises angular clasts of serpentinite. TEM observations and diffraction patterns identify this matrix as microcrystalline to amorphous serpentine and document the contacts between this material and the dolomite. A comparison with textures reported for carbonated serpentine breccia from the Alps, and the Galicia margin suggests that prior tectonic brecciation enhances the potential for pervasive carbonation of serpentinites in the oceanic lithosphere at both mid-ocean ridges and the ocean-continent transition of divergent continental margins.

  7. Effects of Late Cretaceous and Cenozoic faulting on the geology and hydrology of the coastal plain near the Savannah River, Georgia and South Carolina

    USGS Publications Warehouse

    Faye, R.E.; Prowell, D.C.

    1982-01-01

    Geologic and hydrologic investigations by the U.S. Geological Survey have defined stratigraphic and hydraulic anomalies suggestive of faulting within Coastal Plain sediments between the Ogeechee River in east-central Georgia and the Edisto River in west-central South Carolina. Examination of borehole cuttings, cores, and geophysical logs from test wells indicate that Triassic rocks and Upper Cretaceous and lower Tertiary Coastal Plain sediments near the Barnwell-Allendale County line near Millett, South Carolina, are offset by a northeast-trending fault downthrown to the northwest. The location of this suspected Coastal Plain fault generally coincides with the location of an inferred fault in basement rocks as interpreted from aeromagnetic surveys. Apparent vertical offsets range from about 700 feet at the base of Upper Cretaceous sediments to about 20 feet in strata of Late Eocene age. As a result, the Upper Cretaceous Middendorf Formation which directly overlies crystalline and Triassic rocks updip (northwest) of this fault, is absent immediately downdip of the fault. The thickness of Tipper Cretaceous sediments is also sharply reduced from about 700 feet to about 180 feet across the fault. Sediments of the basal Coastal Plain aquifer are largely truncated by uplifted Triassic rocks at the fault near Millett, South Carolina. Lateral ground-water flow near the Savannah River Is consequently disrupted updip of the fault and ground water is transferred vertically into overlying sediments and possibly into the Savannah River. At several locations, abrupt changes in potentiometric head occur across this fault. Computed transmissivity of the basal Coastal Plain aquifer is also radically reduced downdip of the fault, sharply reversing a downdip trend of rapidly increasing aquifer transmissivity. Other anomalous potentiometric data along a northeast-trending line between Statesboro, Georgia, and Fairfax, South Carolina, suggest the possibility of similar faulting in correlative geologic units. The location of the suspected fault near Statesboro, Georgia, generally coincides with the eastward extension of the Gulf Trough, a regional potentiometric anomaly in central Georgia.

  8. Reproduction among protobranch bivalves of the family Nuculidae from sublittoral, bathyal, and abyssal depths off the New England coast of North America

    NASA Astrophysics Data System (ADS)

    Scheltema, Rudolf S.; Williams, Isabelle P.

    2009-09-01

    Protobranch bivalve species of the family Nuculidae pass through either a planktonic lecithotrophic larval stage or a direct non-planktonic development. Oogenesis of the three sublittoral species examined is synchronous. Deposition of egg masses by Nucula delphinodonta and spawning by Nucula annulata and Nucula proxima occur only during summer months. Among the four bathyal and abyssal species, Ennucula similis, Ennucula granulosa, Deminucula atacellana, and Brevinucula verrilli, oogenesis is asynchronous and there is no discernable pattern of periodicity of spawning. Absence of periodicity in reproduction in these deep-sea species is confirmed by examination of individuals from dredge samples taken at different times of the year. The median apparent fecundity among both sublittoral and deep-sea species is directly related to size (i.e. shell length) and age. Among the Nuculidae the median apparent fecundity is greater among sublittoral than bathyal and abyssal species. The geographic distribution of a species depends on its capacity to disperse. The dispersal of the planktonic lecithotrophic larvae of the sublittoral species N. annulata and N. proxima is limited to the continental shelf of the northwestern Atlantic by inshore bottom circulation and because these very small planktonic larvae (<2.5 mm) lack the capacity to move vertically upward through the water column into the offshore currents. On the other hand, the bathyal and abyssal species having lecithotrophic larvae have a very wide amphi-Atlantic distribution extending from 60N to 40S latitude along the North and South American coasts and from 55N to ca. 19S from off Europe southwards to the coast of West Africa as a consequence of dispersal by planktonic lecithotrophic larvae along the seafloor. The amphi-Atlantic dispersal must occur stepwise between deep-sea populations (e.g., off Greenland). Such a geographic distribution indicates a widespread dispersal and is supported by the genetic similarity that has been described between North American and western European populations of D. atacellana.

  9. North-south compression, active uplift, and abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Motoki, A.; Sichel, S. E.; Campos, T. F.; Motoki, K. F.; Szatmari, P.; Poseidon-Colmeia

    2013-05-01

    This article presents near N-S compression, active uplift tectonism, and the consequent abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean. The mantle peridotite ridge is about 80 km long, 25 km wide, 3800 m high, and of near E-W direction. The ridge flanks are extremely steep with sub-vertical scarps of about 2000 m of relative height. The Flandrian wave-cut and the 14C datings for the carbonaceous algae of the Saint Peter and Saint Paul Rock indicate active uplift of 1.5 mm/year. The tectonic factures shows conjugated system of N-S compression tending slightly to NW-ES. Close to the peridotite ridge, the earthquakes with near N-S compression focal mechanism take place. The southern half of the peridotite ridge is constituted by undeformed peridotite. The existence of corrugation morphology indicates that the mantle rocks are originated from old megamullion. On the other hand, the northern half is composed of strongly deformed mylonitic peridotite suggesting that the ultramafic rocks are possibly originated from sub-crustal abyssal mantle of old transform fault. The mylonite structure is intensely perturbed indicating the tectonic events which disturbed the original parallel structure. The Saint Paul transform fault zone is characterized by E-W trend right lateral movement and the near N-S compression is unlikely. Therefore, an unusual local geotectonic process is expected. This tectonism was originated from the plate boundary jump at about 8 Ma, caused by the emergence of a new ridge segment, and the new transform fault is oblique to the relative plate movement. This angular discrepancy causes the compression perpendicular to the oblique transform fault, of near N-S direction, which squeeze out the sub-crustal abyssal mantle up to sea level. Therefore, the peridotite Ridge is considered to be a pressure ridge of the strike-slip movement of the Saint Paul transform fault.

  10. Supra-subduction and abyssal mantle peridotites of the Coast Range ophiolite, California: Initiation of Franciscan subduction along a large-offset fracture zone

    NASA Astrophysics Data System (ADS)

    Choi, S. H.; Shervais, J. W.; Mukasa, S. B.

    2009-04-01

    The Coast Range ophiolite (CRO) of California is one of the most extensive tracts of oceanic crust preserved in the Cordillera, but its origin has long remained controversial. We present here new data on mineral compositions in mantle peridotites that underlie crustal sections of ophiolite, and show that these are dominantly refractory harzburgites related to high apparent melting in a supra-subduction zone (SSZ) setting. Abyssal peridotite occurs at one location, Stonyford, in the CRO where it is associated with SSZ mantle peridotite and volcanic rocks with both oceanic and arc-like geochemistry. SSZ mantle peridotites are associated with crustal sections containing arc-related volcanics, including boninites. This convergence between conclusions based on crustal lithologies and their underlying mantle sections confirms previous proposals that link the CRO to SSZ processes, and seriously undermines hypotheses that call on formation of the ophiolite at a mid-ocean ridge spreading center. We also report on the radiogenic isotope characteristics of peridotite clinopyroxenes. Based on the Sr-Nd-Pb-Hf isotopic compositions and estimated temperatures, we suggest that the abyssal peridotite block represents a remnant of large-offset transform oceanic lithosphere at >172 Ma. East-dipping, proto-Franciscan subduction is likely to have been initiated along this fault zone, which produced the supra-subduction zone (SSZ) peridotites in the CRO. We propose that the remnant abyssal peridotites represent a snapshot of the mantle wedge composition prior to overprinting of large sectors by hydrous melting during the subsequent subduction-controlled SSZ processes.

  11. Sediment Sources and Storage in the Chesapeake Bay Watershed

    NASA Astrophysics Data System (ADS)

    Gellis, A. C.; Landwehr, J. M.; Pavich, M.; Hupp, C. R.; Ritchie, J. C.

    2006-05-01

    Physically and chemically, sediment is a pollutant of concern in many waterbodies. In the Chesapeake Bay, sediment is having an adverse effect on the living resources and habitat of the Chesapeake Bay and its watershed. Identifying significant sources of watershed sediment is important in reducing sediment loads. In the Chesapeake Bay, several approaches were used to understand the sources, transport, and storage of watershed-derived sediment. From 1985 through 2001, the U.S. Geological Survey collected suspended sediment at 35 stations draining portions of the 103,000 km2 Chesapeake Bay. Of the 35 sites, 4 of the 6 highest sediment yields were in the Conestoga River Basin, Pennsylvania, which drains to the Susquehanna River. In the Susquehanna River Basin (43,600 km2), erosion rates were determined using atmospheric 10Be at 92 river outlets and confirmed that the highest rates of erosion were in the Conestoga River Basin. In three small watersheds draining to the Chesapeake Bay -- the Pocomoke River (157 km2), Little Conestoga Creek (68.1 km2), and Mattawoman Creek (92.8 km2) -- sediment sources were identified using a sediment-source identification approach. In this approach, the sources of fine-grained suspended sediment in transport can be established by comparing physical and chemical properties of the suspended sediment to potential sources. In this study, suspended sediment (< 0.062 mm) collected during storm runoff was compared to upland sediment sources (cropland, construction sites, and forest) and channel corridor sources (channel banks and bed) using radionuclides (210Pb, 137Cs), stable isotopes (13C, 15N), and total C, N, and P. Preliminary results are available for two of the three watersheds. In the Pocomoke River watershed, which drains the Coastal Plain physiographic province, ditch beds which were dug to drain cropland were a significant source of sediment. In the Little Conestoga Creek watershed, which drains the Piedmont physiographic province, river banks and cropland were significant sources.

  12. Eddy-driven sediment transport in the Argentine Basin: Is the height of the Zapiola Rise hydrodynamically controlled?

    DOE PAGESBeta

    Weijer, Wilbert; Maltrud, Mathew E.; Homoky, William B.; Polzin, Kurt L.; Maas, Leo R. M.

    2015-03-27

    In this study, we address the question whether eddy-driven transports in the Argentine Basin can be held responsible for enhanced sediment accumulation over the Zapiola Rise, hence accounting for the existence and growth of this sediment drift. To address this question, we perform a 6 year simulation with a strongly eddying ocean model. We release two passive tracers, with settling velocities that are consistent with silt and clay size particles. Our experiments show contrasting behavior between the silt fraction and the lighter clay. Due to its larger settling velocity, the silt fraction reaches a quasisteady state within a few years,more » with abyssal sedimentation rates that match net input. In contrast, clay settles only slowly, and its distribution is heavily stratified, being transported mainly along isopycnals. Yet, both size classes display a significant and persistent concentration minimum over the Zapiola Rise. We show that the Zapiola Anticyclone, a strong eddy-driven vortex that circulates around the Zapiola Rise, is a barrier to sediment transport, and hence prevents significant accumulation of sediments on the Rise. We conclude that sediment transport by the turbulent circulation in the Argentine Basin alone cannot account for the preferred sediment accumulation over the Rise. We speculate that resuspension is a critical process in the formation and maintenance of the Zapiola Rise.« less

  13. Eddy-driven sediment transport in the Argentine Basin: Is the height of the Zapiola Rise hydrodynamically controlled?

    SciTech Connect

    Weijer, Wilbert; Maltrud, Mathew E.; Homoky, William B.; Polzin, Kurt L.; Maas, Leo R. M.

    2015-03-27

    In this study, we address the question whether eddy-driven transports in the Argentine Basin can be held responsible for enhanced sediment accumulation over the Zapiola Rise, hence accounting for the existence and growth of this sediment drift. To address this question, we perform a 6 year simulation with a strongly eddying ocean model. We release two passive tracers, with settling velocities that are consistent with silt and clay size particles. Our experiments show contrasting behavior between the silt fraction and the lighter clay. Due to its larger settling velocity, the silt fraction reaches a quasisteady state within a few years, with abyssal sedimentation rates that match net input. In contrast, clay settles only slowly, and its distribution is heavily stratified, being transported mainly along isopycnals. Yet, both size classes display a significant and persistent concentration minimum over the Zapiola Rise. We show that the Zapiola Anticyclone, a strong eddy-driven vortex that circulates around the Zapiola Rise, is a barrier to sediment transport, and hence prevents significant accumulation of sediments on the Rise. We conclude that sediment transport by the turbulent circulation in the Argentine Basin alone cannot account for the preferred sediment accumulation over the Rise. We speculate that resuspension is a critical process in the formation and maintenance of the Zapiola Rise.

  14. Eddy-driven sediment transport in the Argentine Basin: Is the height of the Zapiola Rise hydrodynamically controlled?

    NASA Astrophysics Data System (ADS)

    Weijer, Wilbert; Maltrud, Mathew E.; Homoky, William B.; Polzin, Kurt L.; Maas, Leo R. M.

    2015-03-01

    In this study, we address the question whether eddy-driven transports in the Argentine Basin can be held responsible for enhanced sediment accumulation over the Zapiola Rise, hence accounting for the existence and growth of this sediment drift. To address this question, we perform a 6 year simulation with a strongly eddying ocean model. We release two passive tracers, with settling velocities that are consistent with silt and clay size particles. Our experiments show contrasting behavior between the silt fraction and the lighter clay. Due to its larger settling velocity, the silt fraction reaches a quasisteady state within a few years, with abyssal sedimentation rates that match net input. In contrast, clay settles only slowly, and its distribution is heavily stratified, being transported mainly along isopycnals. Yet, both size classes display a significant and persistent concentration minimum over the Zapiola Rise. We show that the Zapiola Anticyclone, a strong eddy-driven vortex that circulates around the Zapiola Rise, is a barrier to sediment transport, and hence prevents significant accumulation of sediments on the Rise. We conclude that sediment transport by the turbulent circulation in the Argentine Basin alone cannot account for the preferred sediment accumulation over the Rise. We speculate that resuspension is a critical process in the formation and maintenance of the Zapiola Rise.