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Sample records for abyssal plain sediments

  1. Mineralogical and rock magnetic provenance variation in Alaskan Abyssal Plain sediments, Gulf of Alaska

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    The interplay between regional tectonic activity and climate is a fundamental issue in ocean and earth sciences. These interactions are greatest in areas of high topographic relief coupled with aggressive erosional agents. Focused erosion in uplifting glaciated regions generates a positive feedback loop, accelerating uplift (Tompkin, 2007) and depositing erosional products into adjacent basins. Gulf of Alaska (GoA) strata offer insight into erosional responses to shifts in climate, such as the intensification of Cordilleran glaciation at 2.6 Ma. This coincides with increased accumulation of terrigenous sediment and appearance of ice rafted debris in the adjacent mud-rich Surveyor Fan (SF). It is hypothesized that this change in sediment accumulation and lithology at 2.6 Ma between the Lower Fan Sequence (LFS) and Upper Fan Sequence (UFS) may represent intensification of glacial erosion along the windward side of coastal mountains in southern Alaska. Establishing a provenance record of the UFS and LFS would provide insight into the history of glaciation and subsequent erosion of this region. Determining provenance of fine-grained sediments of the SF requires tracers that not only uniquely differentiate the adjacent Chugach and Yakutat geologic terranes, but are also preserved in offshore muds. Preliminary quantitative powder XRD mineralogy suggests that muds from onshore terranes and UFS sediments can be largely characterized by their distribution as resolved clusters on cross-plots of quartz, feldspar, clinochlore, and muscovite abundance. Within these plots, UFS sediments predominantly occupy the same region as Yakutat-derived samples, suggesting the mineralogy of UFS fine-grained sediments reflects that of the Yakutat Terrane. Distinctive groupings of on- and offshore sediments can also be observed on a Day plot of coercivity of remnance (Hcr/Hc) versus magnetic grain size (Mr/Ms), where Chugach and Yakutat samples group into separate clusters in the multi-domain and pseudo-single-domain (PSD) regions, respectively. UFS sediments also form a cluster in the center of the PSD region. Magnetic data are consistent with previous provenance work in which Mr/Ms, Hcr/Hc, and mass susceptibility of the sand-sized fraction were used to distinguish between the Chugach and Yakutat terranes (Cowan et al., 2006). These preliminary data suggest that mineralogic and magnetic tracers exist in the mud fraction of onshore fluvial sediments and can be used to develop a provenance history of fine-grained marine muds on the Surveyor Fan.

  2. 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).

  3. System requirements report for Abyssal Plains waste isolation project

    SciTech Connect

    Marcy, A.L.; Richards, W.R.; Hightower, J.M.

    1994-09-26

    The Department of Defense`s Naval Research Laboratory (NRL) has been tasked by the Strategic Environmental Research and Development Program (SERDP) to study environmental viability of the storage of dredged materials, sewage sludge, and municipal incinerator fly ash in the abyssal plains of the ocean floor. Abyssal Plains Waste Isolation (APWI) is the term given by this project to the storage of waste in the abyssal plains. Oceaneering Technologies (OTECH) has been tasked by the NRL to assess waste handling technologies regarding engineering feasibility and reliability. The first step in assessing waste handling technologies as to engineering feasibility and reliability is to identify top level or system level requirements that will have to be met by any APWI technology considered. Sources of APWI system level requirements are environmental regulations, physical and chemical characteristics of the waste streams (dredged materials, sewage sludge, and municipal incinerator fly ash), weather/site conditions, and standard references for ocean going vessels. A literature search of each of these sources was performed. The information extracted from these various sources was placed into the categories of handling, transportation, and emplacement. System level requirements were then derived from the information contained in the sources mentioned above.

  4. 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.

  5. 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.

  6. 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.

  7. Deep-sea sipunculans from the Kuril-Kamchatka Trench and adjacent abyssal plain

    NASA Astrophysics Data System (ADS)

    Maiorova, Anastassya S.; Adrianov, Andrey V.

    2015-01-01

    Deep-sea sipunculans collected during the expedition to the Kuril-Kamchatka Trench and adjacent abyssal plain are described and illustrated using differential interference contrast microscopy (DIC) and scanning electron microscopy (SEM). Specimens were sorted from brown silt collected by giant boxcorer (GKG), epibenthic sledge (EBS) and Agassiz trawl (AGT) from the depths 4830-5780 m. Within about 150 valid species of sipunculans only 15 have been known to be abyssal and six of them were found and identified in this KURAMBIO expedition. Eight species of sipunculans have been previously recorded from the Kuril-Kamchatka region but all of them were described based on preserved museum's material collected by bottom dredge and these descriptions are far from to be complete and comparable with other samplings. All KURAMBIO species are described according to a unified protocol to illustrate the most important taxonomic characters. This is the first description and illustrating of abyssal sipunculans in live condition with natural coloration of non-preserved specimens. Abyssal species were for a first time described with SEM facilities and according to a standardized protocol. For a first time for abyssal sipunculans, species accounts also include quantitative characteristics, distribution and specific biotope data. Nephasoma abyssorum is reported for the Kuril-Kamchatka Trench and adjacent abyssal plain for a first time.

  8. 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.

  9. 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.

  10. 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.; Galéron, 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.

  11. 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.

  12. 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.

  13. 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...

  14. 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.

  15. 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 (μg 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.

  16. Export of organic carbon and biominerals derived from 234Th and 210Po at the Porcupine Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Le Moigne, F. A. C.; Villa-Alfageme, M.; Sanders, R. J.; Marsay, C.; Henson, S.; García-Tenorio, R.

    2013-02-01

    The simultaneous estimation of particulate organic carbon (POC), particulate inorganic carbon (PIC) and biogenic silica (BSi) export fluxes is key to the study of carbon export due to the hypothesized role of biominerals in the sinking of organic particles. This paper presents of the first attempts to measure downward fluxes of POC, PIC and BSi from the surface ocean using both the 234Th-238U and the 210Po-210Pb disequilibria and drifting sediments trap synchronously at the Porcupine Abyssal Plain in summer 2009. The combined use of the three techniques allowed us to analyze their suitability not only for POC flux estimates, but also as tracers of PIC and BSi fluxes. POC and biomineral/radionuclide ratios were measured in two size fractions to better understand differences between 234Th derived export and 210Po derived export. 210Po derived POC and biomineral fluxes were unexpectedly closer to POC and biomineral fluxes recorded by sediment traps than 234Th derived POC and biomineral fluxes which were higher than obtained from the other two approaches. We suggest that 210Po, because of its biogeochemical behavior, is a better proxy for POC and mineral fluxes than is 234Th in post bloom conditions. The contribution of smaller (1-53 μm) particles to flux is also considered in order to explain the differences in derived fluxes.

  17. Late Quaternary paleoenvironmental changes revealed by multi-proxy records from the Chukchi Abyssal Plain, western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Wang, Rujian; Xiao, Wenshen; März, Christian; Li, Qianyu

    2013-09-01

    Late Quaternary paleoenvironmental changes in the western Arctic Ocean are revealed by multi-proxy records of core 03M03 from the Chukchi Abyssal Plain (CAP). Proxy parameters include lithology, grain size fractions, and mineralogy and petrology of ice-rafted detritus (IRD), element contents, biogenic components, δ18O, δ13C and Mg/Ca of planktonic foraminifera Neogloboquadrina pachyderma (sin.) (Nps). Seven IRD (> 250 μm) peaks are interpreted as marking detrital input by rafting sea ice or icebergs during MIS 3 interstadials and early MIS 1. High MnO, CaO and MgO contents and high Ca/Al and Mg/Al ratios during MIS 3 and MIS 1 correspond to increases in ice-rafted detrital carbonates and the synchronous declines in siliciclastic elements (e.g., Al2O3, Fe2O3). Therefore, these warmer periods were characterized by a high detrital carbonate input entrained in icebergs from the Canadian Arctic Archipelago coeval with an increased input of Mn through rivers and/or coastal erosion. Relatively stable contents of siliciclastic elements and their ratios in the grayish sediment units are interpreted from turbid surface water plumes or nepheloid flows delivered by meltwater and/or brine rejection from ice-sheet margins at the Arctic Ocean periphery. Relatively stable clay- and silt-sized fractions were attributed mainly to sea ice entrainment over glacial-interglacial cycles. High foraminiferal abundances in the brown units during MIS 3 and 1 are related to enhanced calcareous plankton productivity under more open water conditions and/or the incremental input of Atlantic water masses. Relatively high TOC and opal contents in the grayish units of MIS 3 appear to have accumulated by lateral transport of organic matter from the Chukchi shelf to the deep abyssal plain. Lower contents of biogenic material in the brown units probably result from increased dilution by rapid IRD deposition, and from early diagenetic degradation. Depletions in Nps-δ18O and -δ13C concurrent with high foraminiferal abundances and IRD peaks within the brown units of MIS 3 and 1 are indicative of meltwater pulses, as previously documented across the Arctic Ocean. However, several Nps-δ18O and -δ13C depletions between the brown units B3 and B2 in MIS 3 could have resulted from enhanced sea ice formation. The Nps-Mg/Ca has the potential to record paleotemperature changes in the Arctic region, but still awaits a better calibration of the Nps-Mg/Ca-temperature relationship with results from core-tops, sediment traps, and plankton tows.

  18. 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.

  19. 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.

  20. The influence of oxic degradation on the sedimentary biomarker record I: evidence from Madeira Abyssal Plain turbidites

    NASA Astrophysics Data System (ADS)

    Hoefs, Marcel J. L.; Rijpstra, W. Irene C.; Sinninghe Damsté, Jaap S.

    2002-09-01

    Free and ester-bound lipid biomarkers were analysed in oxidised and unoxidised parts of four distinct turbidites from the Madeira Abyssal Plain (MAP), which contained 1 to 2% organic carbon homogeneously distributed throughout the turbidites at the time they were deposited. These turbidites are well suited to study the effects of oxic degradation on lipid biomarkers without the complicating influence of varying organic matter sources, sedimentation rates, or bioturbation. One sample from the oxidised turbidite was compared with two samples from the unoxidised part of each turbidite. Postdepositional oxic degradation decreased concentrations of biomarkers by several orders of magnitude. The ester-bound lipids were degraded to a far lesser extent than their free counterparts were. The extent of degradation of different compounds differed substantially. Within a specific class of biomarkers, degradation also took place to a different extent, altering their distributions. This study shows that oxic degradation of the organic matter may have a profound effect on the biomarker fingerprint and may result in a severe bias in, for example, the interpretation of organic matter sources and the estimation of the palaeoproductivity of specific groups of phytoplankton.

  1. Vertical electric field fluctuations at the floor of the Tasman Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Bindoff, N. L.; Filloux, J. H.; Mulhearn, P. J.; Lilley, F. E. M.; Ferguson, I. J.

    1986-05-01

    A record of vertical electric field fluctuations occuring naturally in the ocean has been obtained at a site (36°14'S, 152°15'E) off the coast of easter Australia, on the floor of the Tasman Abyssal Plain in water of depth 4836 m. The free-fall and self-contained sea-floor instrument measured ambient voltage fluctuations between two low-noise silver-silver chloride electrodes connected by a vertical insulated wire 160 m long. The record returned is 107 days in duration, with readings taken every 28 1/8 s. The data obtained are interpreted in terms of east-west fluid current motion past the wire, causing electromagnetic induction with the horizontal north component of the earth's steady magnetic field. These motional fields are observed on a wide range of time scales. Spectral analysis of the data shows inertial oscillations and shorter period internal waves, with good agreement between observation and the theory of CHAVE (1984, Journal of Geophysical Research, 89, 10519-10528). There is also a peak in the power spectrum at the frequency of the semi-diurnal tides. The shortest period signals occurring are interpreted as due to some form of turbulence. Aperiodic motions on time scales of days are attributed to mesoscale activity in the East Australian Current system.

  2. 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 10°W to 11°W, and 35°50'N to 36°10'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.

  3. Temporal changes (1989-1999) in deep-sea metazoan meiofaunal assemblages on the Porcupine Abyssal Plain, NE Atlantic

    NASA Astrophysics Data System (ADS)

    Kalogeropoulou, V.; Bett, B. J.; Gooday, A. J.; Lampadariou, N.; Martinez Arbizu, P.; Vanreusel, A.

    2010-08-01

    Trends among major metazoan meiofaunal taxa were investigated based on 56 deployments of a multicorer at 10 time points over a period of 11 years (1989-1999) at the Porcupine Abyssal Plain Sustained Observatory site (PAP-SO: 48°50'N 16°30'W, 4850 m depth). This area is characterised by a strong seasonality in the deposition of organic matter to the seafloor and by the massive increase in the density of holothurian species since 1996, the so-called ' Amperima event'. Total meiofaunal densities ranged from 346 to 1074 ind.×10 cm -2 and showed a significant increase with time when time was represented by cruises, years and the ' Amperima period' (1996-1999) vs. the pre- Amperima period (1989-1994). This pattern was driven mainly by the nematodes, which were the dominant taxon (˜90% of total abundance). The third most abundant group, the polychaetes, also increased significantly in abundance over the time series, while the ostracods showed a significant decrease. Most other taxa, including the second-ranked group, the copepods (harpacticoids and nauplii), did not exhibit significant temporal changes in abundance. Ordination of taxon composition showed a shift from the pre- Amperima to the Amperima periods, a trend supported by the significant correlation between the x-ordinate and time. The majority (52-75%) of meiofaunal animals inhabited the top 2 cm of the 5 cm sediment cores analysed. There were significant increases in the proportion of total meiofauna, nematodes and copepods (but not polychaetes) inhabiting the 0-1 cm layer over time (represented by cruises) and between the pre- Amperima and Amperima periods in the case of copepods and polychaetes. During the intensively sampled period (1996-1997), there were indications of seasonal changes in the vertical distribution patterns of total meiofauna and nematodes within the sediment. We discuss the potential link between temporal variations in organic matter flux to the seafloor and meiofaunal populations, considering both qualitative and quantitative changes in fluxes and how they may be linked to climate variations.

  4. 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

  5. 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

  6. 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.

  7. 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.; Gaytán-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.

  8. 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.

  9. 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.

  10. Early India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies in the Perth Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Williams, Simon E.; Whittaker, Joanne M.; Granot, Roi; Müller, Dietmar R.

    2013-07-01

    seafloor within the Perth Abyssal Plain (PAP), offshore Western Australia, is the only section of crust that directly records the early spreading history between India and Australia during the Mesozoic breakup of Gondwana. However, this early spreading has been poorly constrained due to an absence of data, including marine magnetic anomalies and data constraining the crustal nature of key tectonic features. Here, we present new magnetic anomaly data from the PAP that shows that the crust in the western part of the basin was part of the Indian Plate—the conjugate flank to the oceanic crust immediately offshore the Perth margin, Australia. We identify a sequence of M2 and older anomalies in the west PAP within crust that initially moved with the Indian Plate, formed at intermediate half-spreading rates (35 mm/yr) consistent with the conjugate sequence on the Australian Plate. More speculatively, we reinterpret the youngest anomalies in the east PAP, finding that the M0-age crust initially formed on the Indian Plate was transferred to the Australian Plate by a westward jump or propagation of the spreading ridge shortly after M0 time. Samples dredged from the Gulden Draak and Batavia Knolls (at the western edge of the PAP) reveal that these bathymetric features are continental fragments rather than igneous plateaus related to Broken Ridge. These microcontinents rifted away from Australia with Greater India during initial breakup at ~130 Ma, then rifted from India following the cessation of spreading in the PAP (~101-103 Ma).

  11. 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.

  12. Interelement relationship in abyssal Pacific ferromanganese nodules and associated pelagic sediments

    NASA Astrophysics Data System (ADS)

    Li, Yuan-Hui

    1982-06-01

    By R-mode factor analysis and enrichment factor calculations, most of the elements in abyssal ferromanganese nodules and associated pelagic sediments (excluding common authigenic minerals like apatite, barite, opal and carbonates) are found to be preferentially concentrated in one of the following three major phases: aluminosilicates ( e.g., Al, Si, Sc, Ga, Cr, Be, Na, K, Rb and Cs), Fe-oxides ( e.g., Fe, P, S, V, Se, Te, As, B, Sn, U, Hg, Pb, Ti, Ge, Y, Zr, Nb, Pd, In, rare-earths, Hf, Th, Pa, Pu, Am, Ru and Bi), and Mn-oxides ( e.g., Mn, Tl, Ag, Cd, Mg, Ca, Ba, Ra, Co, Ni, Cu, Zn, Mo, Sb and probably W). The specific association of elements with these three phases can be explained by the difference in chemical forms of elements in seawater and by fundamental differences in physicochemical properties ( e.g., the pH of zero point of charge and dieletric constant) of these three phases.

  13. 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.

  14. 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.

  15. 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.

  16. Insights on the Deep Structure of the Iberia Abyssal Plain and Galicia Bank Southern Edge From new MCS and Wide Angle Data

    NASA Astrophysics Data System (ADS)

    Lourenco, N.; Afilhado, A.; Pimentel, F.; Matias, L.; Abreu, M.; Miranda, M.

    2007-12-01

    In the scope of the Portuguese Continental Shelf Extension Program, 1600 km of 2D MCS reflection lines were acquired over the Iberia Abyssal Plain and the southern edge of the Galicia Bank. The survey ties in with other academic and industry surveys. It comprised four E-W lines, crossing from continental to oceanic crust along the Zone of Exhumed Continental Mantle, and two N-S lines crossing the Iberia abyssal plain from the Galicia Bank to the Tore seamount and the Tagus Abyssal plain. Additionally nine OBSs were deployed along the MCS IB02 profile (roughly at 41°N). The MCS acquisition layout consisted in a streamer 8 km long and an array of bolt long- life air guns (5720 cu.in.). In order to record deep reflections the record length was set to 18 s. The E-W lines were Kirchoff pre-stack time (PSTM) and depth migrated (PSDM). Velocity model for the depth migration was obtained on the sedimentary cover by using a grid based tomography algorithm from Paradigm's Geodepth software, and constrained, from the basement to deeper sections, using IB02 wide angle results and other published refraction studies on the area. Results show a clear improvement of the PSDM lines with respect to the original time migrated lines, especially in the deeper sections. A good agreement is verified between the wide-angle IB02 velocity model and the coincident depth migrated MCS line. The basement topography is highly variable across the studied lines and suggests that the tectonic segmentation pattern of the margin is complex in this sector. Mid to High amplitude intra-basement reflectors are often observed: i) forming wedges internally defined by sets of sub-parallel reflectors, sometimes disrupted by high angle faults (pre-rift sequences?); ii) Consisting on several low angle intra-basement reflectors, interpretable as detachments faults, dipping both westward and eastward and reaching, in some cases, at least a depth of 20 km. We discuss the implications of our interpretations, from these enhanced PSDM images, to the existing tectonic models for this segment of the West Iberian Margin.

  17. 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.

  18. 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...

  19. 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.

  20. 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.

  1. 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 Stüven, 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Seasonal and inter-annual biogeochemical variations in the Porcupine Abyssal Plain 2003-2005 associated with winter mixing and surface circulation

    NASA Astrophysics Data System (ADS)

    Hartman, S. E.; Larkin, K. E.; Lampitt, R. S.; Lankhorst, M.; Hydes, D. J.

    2010-08-01

    We present a 3-year multidisciplinary biogeochemical data set taken in situ at the Porcupine Abyssal Plain (PAP) time-series observatory in the Northeast Atlantic (49°N, 16.5°W; water depth ˜4850 m) for the period 2003 to 2005. The high-resolution year-round autonomous measurements include temperature, salinity, chlorophyll-a (derived from in situ chlorophyll-fluorescence) and inorganic nitrate, all at a nominal depth of 30 m on an Eulerian observatory mooring. This study compares these in situ time-series data with satellite chlorophyll-a data, regional data from a ship of opportunity, mixed-layer depth measurements from profiling Argo floats and lateral advection estimates from altimetry. This combined and substantial data set is used to analyse seasonal and inter-annual variability in hydrography and nitrate concentrations in relation to convective mixing and lateral advection. The PAP observatory site is in the inter-gyre region of the North Atlantic where convective mixing ranges from 25 m in the summer to over 400 m in winter when nutrients are supplied to the surface. Small inter-annual changes in the winter mixed layer can result in large changes in nitrate supply and productivity. However the decrease in maximum winter nitrate over the three-year period, from 10 to 7 mmol m -3, cannot be fully explained by convective mixing. Trajectories leading to the PAP site, computed from altimetry-derived geostrophic velocities, confirm that lateral advection cannot be ignored at this site and may be an important process along with convective mixing. Over the three years, there is an associated decrease in new production calculated from nitrate assimilation from 85.4 to 40.3±4.3 gCm -2 a -1. This confirms year-to-year variability in primary production seen in model estimates for the region. The continuous in situ dataset also shows inter-annual variation in the timing of the spring bloom due to variations in heat flux; the 2005 bloom occurred earlier than in 2004.

  8. Deep structure of the ocean-continent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect

    NASA Astrophysics Data System (ADS)

    Chian, Deping; Louden, Keith E.; Minshull, Tim A.; Whitmarsh, Robert B.

    1999-04-01

    We present a wide-angle seismic refraction study of an 80×40 km region of the southern Iberia Abyssal Plain, south of Galicia Bank. An intersecting grid of two E-W and four N-S wide-angle reflection/refraction profiles is used to define variations of the basement velocity structure within this unusually wide ocean-continent transition (OCT). These structures can be systematically linked to variations in acoustic basement morphology and to results from Ocean Drilling Program (ODP) boreholes. Lateral changes in the velocity structure of the basement occur abruptly over distances of ˜20 km where complex variations may be found. Thinned upper continental crust, 2-5 km thick with velocities of 5.0-6.6 km/s, is limited to a series of N-S fault blocks immediately south of Galicia Bank. This crust is underlain by a high-velocity layer (7.3-7.9 km/s) of weakly serpentinized (i.e., 0-25%) peridotite, which exists throughout the eastern part of the survey area. Basement within the OCT appears to consist dominantly of a broad region of exposed upper mantle that has been serpentinized heterogeneously both vertically and horizontally. In the southeast sector of our survey where basement topography deepens and becomes subdued, continental fault blocks are absent; instead, basement contains an upper layer of more pervasively serpentinized (i.e., 25-45%) peridotite that is ˜2 km thick. This layer is characterized by low velocity at the top of basement (4.2 km/s) that increases rapidly with depth, and it probably corresponds to a seismically unreflective layer, previously identified in reflection profiles to the south of our survey. In the western section of our survey, beneath a series of elevated basement ridges, velocities are reduced within both the upper basement layer (3.5-6.0 km/s) and lower layer (6.4-7.5 km/s). These changes suggest that both upper and lower layers have become more highly serpentinized (with values of 60-100% in the upper layer and 25-45% in the lower layer) probably during the last stages of rifting and immediately before formation of oceanic crust. A normal or slow spreading oceanic crustal structure is not found within the survey region. Thus it appears that the onset of seafloor spreading occurs in the region west of the peridotite ridge sampled at ODP Site 897 and east of the J magnetic anomaly.

  9. 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.

  10. 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,...

  11. 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...

  12. 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.

  13. 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.

  14. 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.

  15. Patterns of Late Pleistocene proglacial fluvial sedimentation in the SE Lithuanian Plain

    NASA Astrophysics Data System (ADS)

    Blažauskas, Nerijus; Jurgaitis, Algirdas; Šinkūnas, Petras

    2007-01-01

    We investigated proglacial fluvial sedimentation processes in the SE Lithuanian Plain by means of lithofacies analysis. The main parameters on which interpretations were based, were depositional structures of sandy sediments, paleohydraulic parameters and grain-size distribution. The development of the SE Lithuanian Plain illustrates the phenomenal shift of proglacial fluvial sedimentation from outwash plain to ice-marginal river during the ice retreat of the last glaciation. Three facies assemblages of braidplain deposits and two facies assemblages of palaeovalley deposits were distinguished in the sandy plain by means of qualitative and quantitative sedimentological research. This raises the question how the commonly accepted development of a SE orientated outwash plain could turn into an almost perpendicular (SW running) ice-marginal river. The vertical and lateral transitions of outwash plain facies present a classical example of braidplain evolution on slightly inclined lowlands, with well expressed proximal, middle and distal parts. Mid- and side-channel (point-bar) deposits of the proglacial valley point, however, which is unusual for proglacial fluvial systems, to a meandering character of the ice-marginal river. River types of various scale show a change from braided into meandering in the proglacial subenvironment. Lithofacies analysis and paleohydraulic parameters show distinct differences of the hydrodynamic regime during the first stage of the sandy plain development: from sedimentation on an outwash plain in a proglacial valley to sedimentation on a braidplain in a wide ice-marginal valley. The outwash system is characterized by a distinct downstream decrease in energy, whereas the ice-marginal river maintained most of its power and velocity.

  16. 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.

  17. 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.

  18. 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 (31°6.1'N, 21°10.9'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.

  19. 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.

  20. 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.

  1. Geostatistical Modeling of the Spatial Distribution of Sediment Oxygen Demand Within a Coastal Plain Blackwater Watershed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Blackwater streams of the Georgia Coastal Plain are often listed as impaired due to chronically low DO levels. Previous research has shown that high sediment oxygen demand (SOD) values, a hypothesized cause of lowered DO within these waters, are significantly positively correlated with TOC within th...

  2. Epifaunal and shallow infaunal foraminiferal communities at three abyssal NE Atlantic sites subject to differing phytodetritus input regimes

    NASA Astrophysics Data System (ADS)

    Gooday, Andrew J.

    1996-09-01

    Multiple corer samples (0-1 cm sediment layer and overlying phytodetritus) obtained at three northeast Atlantic sites were analysed for Rose Bengal stained benthic foraminifera ( > 63 μm). Strong phytodetrital pulses have been documented at the northern site on the Porcupine Abyssal Plain (PAP; 48°50'N, 16°30'W) but not at the southern sites on the Madeira Abyssal Plain (MAP; 31°N, 20°W) and Cape Verde Abyssal Plain (CVAP; 21°N, 31°W). Foraminiferal densities reflected surface primary productivity estimates fairly closely, being higher at the PAP (mean: 800 per 25.5 cm 2 sample area= 314 per 10 cm z) than at the southern sites (mean: 502 per sample =197 per 10 cm Z). In part, this difference was attributable to the presence of a substantial phytodetrital deposit in two of the PAP samples. The phytodetrital aggregates provided organically-enriched microenvironments exploited by dense foraminiferal populations, which accounted for up to 22.4% of the entire foraminiferal fauna. They were of low diversity with a few dominant species (notably the rotaliid Epistominella exigua), a population structure typical of organically enriched systems. Most of the phytodetrital species were much less common in the sediments. The total (i.e. sediment + phytodetritus) populations were highly diverse (123-167 species); but southern site populations were somewhat more diverse than PAP populations, and the two PAP phytodetritus-rich cores had higher dominance values than other samples. Total species assemblages were broadly similar. However, in addition to the phytodetritus-dwelling species, some species of Reophax, Leptohalysis, Lagenammina and "Hyperammina" were more abundant at the PAP site, perhaps benefiting from degraded phytodetritus or from the associated bacterial populations. A few species, e.g. Subreophax aduncus and Lagenammina tubulata, were more abundant at the southern sites.

  3. 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

  4. Large-scale patterns in biodiversity of microbial eukaryotes from the abyssal sea floor

    PubMed Central

    Scheckenbach, Frank; Hausmann, Klaus; Wylezich, Claudia; Weitere, Markus; Arndt, Hartmut

    2009-01-01

    Eukaryotic microbial life at abyssal depths remains “uncharted territory” in eukaryotic microbiology. No phylogenetic surveys have focused on the largest benthic environment on this planet, the abyssal plains. Moreover, knowledge of the spatial patterns of deep-sea community structure is scanty, and what little is known originates primarily from morphology-based studies of foraminiferans. Here we report on the great phylogenetic diversity of microbial eukaryotic communities of all 3 abyssal plains of the southeastern Atlantic Ocean---the Angola, Cape, and Guinea Abyssal Plains---from depths of 5,000 m. A high percentage of retrieved clones had no close representatives in genetic databases. Many clones were affiliated with parasitic species. Furthermore, differences between the communities of the Cape Abyssal Plain and the other 2 abyssal plains point to environmental gradients apparently shaping community structure at the landscape level. On a regional scale, local species diversity showed much less variation. Our study provides insight into the community composition of microbial eukaryotes on larger scales from the wide abyssal sea floor realm and marks a direction for more detailed future studies aimed at improving our understanding of deep-sea microbes at the community and ecosystem levels, as well as the ecological principles at play. PMID:20007768

  5. Sediment thickness beneath the Indo-Gangetic Plain and Siwalik Himalaya inferred from receiver function modelling

    NASA Astrophysics Data System (ADS)

    Borah, Kajaljyoti; Kanna, Nagaraju; Rai, S. S.; Prakasam, K. S.

    2015-03-01

    The Indo-Gangetic Plain and the adjoining Siwalik Himalaya are the seismically most vulnerable regions due to high density of human population and presence of thick sediments that amplify the seismic waves due to an earthquake in the region. We investigate the sedimentary structure and crustal thickness of the region through joint inversion of the receiver function time series at 14 broadband seismograph locations and the available Rayleigh velocity data for the region. Results show significant variability of sedimentary layer thicknesses from 1.0 to 2.0 km beneath the Delhi region to 2.0-5.0 km beneath the Indo-Gangetic Plain and the Siwalik Himalaya. As we progress from the Delhi to the Indo-Gangetic Plain, we observe a decrease in the shear velocity in sedimentary layer from ∼2.0 km/s to ∼1.3 km/s while the layer thickness increases progressively from ∼1.0 km in south to 2.0-5.0 km in the north. Average S-velocity in the sedimentary layer beneath the Siwalik Himalaya is ∼2.1 km/s. Crustal thicknesses varies from ∼42 in the Delhi region, ∼48 km in the Indo-Gangetic Plain, ∼50 km in the western part of Siwalik Himalaya to ∼60 km in the Kumaon region of Siwalik Himalaya.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Environmental magnetism in fluvial and loessic Holocene sediments and paleosols from the Chacopampean plain (Argentina)

    NASA Astrophysics Data System (ADS)

    Orgeira, M. J.; Walther, A. M.; Tófalo, R. O.; Vásquez, C.; Berquó, T.; Favier Dobois, C.; Bohnel, H.

    2003-08-01

    The magnetic signals of fluvial and loessic sediments and paleosol sequences developed in the Chacopampean plain (Buenos Aires province, Argentina) are described and interpreted. To provide an analysis of the rock magnetism, sedimentological studies were performed, which led to a stratigraphic framework of so-called 'post-Pampean' sediments deposited in different paleoenvironments. The Luján formation, composed of fine sand and pelitic sediments, is fluvial and includes floodplain facies, whereas the La Postrera Formations is eolian but particularly loessic. Variations in the magnetic signals observed in paleosols in the units were ascribed to pedogenic processes that occurred at different stages of soil development. An extensive process of dissolution of detrital ferrimagnetic minerals was recognized. In one paleosol, dissolution was accompanied by the appearance of a superparamagnetic (SP) fraction, which may indicate that the loss is connected to subsequent formation of ferrimagnetic minerals in the same paleosol. Both processes did not act simultaneously. The abundant rainfall and absence of CO 3Ca in the parent material could be necessary conditions for a defensible scenario for SP genesis. In the loessic sediments (Tapalqué locality), dissolution could be associated with the genesis of a high coercive fraction. The presence of high coercivity minerals may indicate a climate with a distinctly dry season, though their lack does not necessarily imply the absence of a dry season.

  12. 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.

  13. 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.

  14. Sediment-Basalt Architecture, Pliocene and Pleistocene Eastern and Central Snake River Plain

    NASA Astrophysics Data System (ADS)

    Helm-Clark, C. M.; Link, P. K.

    2006-12-01

    This presentation is a synthesis of known stratigraphic studies of the Pliocene, Pleistocene and Holocene basalts and interbedded sedimentary beds on the Eastern Snake River Plain (ESRP). This information is important for understanding the post-caldera tectonic evolution of the ESRP, especially for tracking patterns of volcanic eruption and changes in topography. Geophysical surveys and existing well logs indicate the depth of the basalt sequence is usually 2 km or less, even near the axis of the Plain. An alteration horizon, the product of high heat-flow in the wake of the Yellowstone hot spot, moderated by cold-water recharge in the thick and highly-transmissive Snake River Aquifer, has variable depth. The surface and near-surface of the lava fields are mainly basalts less than a half a million years old, from Island Park to Twin Falls/Shoshone. Near the junction of the Eastern and Western Snake River Plains, these youngest late Pleistocene basalts, many less than 100,000 years old, overlie early Pleistocene basalts more than a million and a half years old. Most basalt flows have been erupted from NW-trending volcanic rift zones like the Great Rift of Idaho or from the Axial Volcanic High (AVH). The AVH is a constructional axial ridge formed by multiple volcanic vents, small shield volcanoes and rhyolitic domes which run the length of the ESRP. A combination of previous and new stratigraphic and geochronology studies, including U-Pb detrital-zircon geochronology on sediments, reveals several lake sequences, formed by the damming of rivers. These tend to be thickest in upstream, valley-mouth, and Plain-marginal locations where the rivers were trapped. The lake beds generally pinch out toward the AVH. The most notable of these are the Mid-Pleistocene Raft Formation, the Late Pleistocene American Falls Lake Beds, at least two mid-Pleistocene sequences of ponded sediment from the Big Lost River at its egress onto the ESRP, and a 2.5 to 1.6 Ma sequence in the Big Lost Trough (BLT). Argon-argon dating of intercalated basalts demonstrates that the Big Lost River was trapped in the BLT starting about ~2Ma. Egress was blocked by the AVH to the southeast and by constructional volcanic rift zones to the southwest. Channel deposits of the ancestral Big Lost River are present in well logs, with one 20 m thick sequence traceable to the southwest under the Craters of the Moon National Monument (COM) between 1430 and 1380 m MSL. Other lake sequences in the ESRP subsurface include two mid-Pleistocene 30 to 50m thick sequences of clayey sediments in the BLT, near the southeast corner of the Idaho National Laboratory at ~250 to ~300 m depths. Two other fine-grained sediment sequences of unknown age are found at similar depths south of COM. Lake Terreton and its predecessors can be traced from Howe to Menan in the northeastern ESRP. Fluvial sediments here are coarse-grained gravels and sands of the Snake River, exposed near Blackfoot and logged in many well logs. Other notable fluvial sediments include the southwest-trending channel deposits and the two previously-mentioned clay sequences south of COM may prove to be parts of a paleo-Big Lost River that flowed to the southwest before 2 Ma.

  15. 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.

  16. 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.

  17. 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...

  18. 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/).

  19. 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

  20. High resolution study of the spatial distributions of abyssal fishes by autonomous underwater vehicle

    PubMed Central

    Milligan, R. J.; Morris, K. J.; Bett, B. J.; Durden, J. M.; Jones, D. O. B.; Robert, K.; Ruhl, H. A.; Bailey, D. M.

    2016-01-01

    On abyssal plains, demersal fish are believed to play an important role in transferring energy across the seafloor and between the pelagic and benthic realms. However, little is known about their spatial distributions, making it difficult to quantify their ecological significance. To address this, we employed an autonomous underwater vehicle to conduct an exceptionally large photographic survey of fish distributions on the Porcupine Abyssal Plain (NE Atlantic, 4850 m water depth) encompassing two spatial scales (1–10 km2) on and adjacent to a small abyssal hill (240 m elevation). The spatial distributions of the total fish fauna and that of the two dominant morphotypes (Coryphaenoides sp. 1 and C. profundicolus) appeared to be random, a result contrary to common expectation but consistent with previous predictions for these fishes. We estimated total fish density on the abyssal plain to be 723 individuals km−2 (95% CI: 601–844). This estimate is higher, and likely more precise, than prior estimates from trawl catch and baited camera techniques (152 and 188 individuals km−2 respectively). We detected no significant difference in fish density between abyssal hill and plain, nor did we detect any evidence for the existence of fish aggregations at any spatial scale assessed. PMID:27180728

  1. High resolution study of the spatial distributions of abyssal fishes by autonomous underwater vehicle.

    PubMed

    Milligan, R J; Morris, K J; Bett, B J; Durden, J M; Jones, D O B; Robert, K; Ruhl, H A; Bailey, D M

    2016-01-01

    On abyssal plains, demersal fish are believed to play an important role in transferring energy across the seafloor and between the pelagic and benthic realms. However, little is known about their spatial distributions, making it difficult to quantify their ecological significance. To address this, we employed an autonomous underwater vehicle to conduct an exceptionally large photographic survey of fish distributions on the Porcupine Abyssal Plain (NE Atlantic, 4850 m water depth) encompassing two spatial scales (1-10 km(2)) on and adjacent to a small abyssal hill (240 m elevation). The spatial distributions of the total fish fauna and that of the two dominant morphotypes (Coryphaenoides sp. 1 and C. profundicolus) appeared to be random, a result contrary to common expectation but consistent with previous predictions for these fishes. We estimated total fish density on the abyssal plain to be 723 individuals km(-2) (95% CI: 601-844). This estimate is higher, and likely more precise, than prior estimates from trawl catch and baited camera techniques (152 and 188 individuals km(-2) respectively). We detected no significant difference in fish density between abyssal hill and plain, nor did we detect any evidence for the existence of fish aggregations at any spatial scale assessed. PMID:27180728

  2. [Relationship between organic carbon and water content in four type wetland sediments in Sanjiang Plain].

    PubMed

    Tong, Cheng-li; Zhang, Wen-ju; Wang, Hong-qing; Tang, Guo-yong; Yang, Gai-ren; Wu, Jin-shui

    2005-11-01

    Characteristic and relationship were analyzed between organic carbon and water content in four types of wetlands (one cultivated wetland and three typical natural wetlands including fen, marsh and marshy meadow) in Sanjiang Plain of Northeastern China. Results show that there are distinct differences in the depths of organic carbon deposition, the organic carbon and water content in sediment profiles of these four type wetlands. There are significant positive correlations between organic carbon and water content in sediment profiles of the same type wetland (p < 0.01; R2 = 0.8276, 0.9917, 0.9916 and 0.9782 for cultivated wetland, fen, marsh and marshy meadow, respectively). The trend for evolution of ecological and environmental functions of wetland ecosystems is discussed based on the analysis of the relationship between soil organic carbon and water content. The results further illustrate the viewpoint that the protection and restoration of wetlands could lessen the global climate change caused by the increase in atmospheric CO2 concentration. PMID:16447426

  3. 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.

  4. 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

  5. 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.

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

    PubMed

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

    2010-10-15

    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 state's 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

  7. 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.

  8. 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.

  9. 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.

  10. Recent sedimentation and surface-water flow patterns on the flood plain of the North Fork Forked Deer River, Dyer County, Tennessee

    USGS Publications Warehouse

    Wolfe, W.J.; Diehl, T.H.

    1993-01-01

    Sedimentation in the 19th and 20th centuries has had a major effect on surface-water drainage conditions along a 7-mile section of the North, Fork Forked Deer River flood plain, Dyer County, Tenn. During the century prior to 1930, 5 to 12 feet of sediment were deposited over much of the flood plain, resulting in channel obstruction and widespread flooding. The estimated bankfull capacity of the natural channel before it was channelized in 19 16 was comparable to the base flow of the river during the 1980's. Ditching of the river between 191i6 and 1;9,21 was followed by reductions in sedimentation rates over parts of the flood plain. However, the effects of sedimentation have persisted. Occlusions along the natural channel of the river have divided this stream reach into a series of sloughs. These sloughs continue to fill with sediment and are surrounded by ponds that have expanded since 1941. Degradation of the North Fork Forked Deer ditch may eventually reduce ponding over much of the flood plain. Active incision of headcuts in both banks of the ditch is enhancing the drainage of widespread ponded areas. These headcuts likely will have limited effect on drainage of most tributaries. The highest recent sedimentation rates, in places more than 0.2 foot per year, are concentrated near the flood-plain margin along tributary streams. In conjunction with beaver dams and debris, ongoing sedimentation has blocked flow in several tributaries, posing a flood hazard to agricultural land near the flood-plain margin. The occluded tributaries likely will continue to overflow unless they are periodically dredged or their sediment loads are reduced.

  11. 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...

  12. 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 ...

  13. 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 (15–25 mg/kg), and groundwater discharging to the streams contains elevated levels of arsenic (>80 μg/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 process—natural or anthropogenic—that 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.

  14. 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...

  15. 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...

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Productivity of ephemeral headwater riparian forests impacted by sedimentation in the southeastern United States coastal plain.

    PubMed

    Jolley, Rachel L; Lockaby, B Graeme; Cavalcanti, Guadalupe G

    2009-01-01

    Riparian forests serve an essential function in improving water quality through the filtering of sediments and nutrients from surface runoff. However, little is known about the impact of sediment deposition on productivity of riparian forests. Sediment inputs may act as a subsidy to forest productivity by providing additional nutrients for plant uptake or may act as a stress by creating anoxic soil conditions. This study determined how sediment deposition affected riparian forests along ephemeral headwater streams at Ft. Benning, Georgia, USA. Above- and belowground productivity, leaf-area index (LAI), and standing crop biomass for fine roots, shrubs, and trees were compared along a gradient of present sedimentation rates in 17 riparian forests. Annual litterfall production was determined from monthly collections using 0.25- m(2) traps; woody biomass was determined from annual diameter at breast height (DBH) measurements using species-specific allometric equations; fine root productivity was determined using sequential coring; LAI was measured by expanding specific leaf area by annual litterfall production; and shrub biomass was determined using species-specific biomass equations based on height and root collar diameter. Significant declines in litterfall, woody biomass production, fine root production, LAI, and shrub biomass were found with as little as 0.1 to 0.4 cm yr(-2) sedimentation. We conclude that the levels of sedimentation in this study do not subsidize growth in ephemeral headwater riparian forests but instead create a stress similar to that found under flooded conditions. PMID:19329685

  1. Geophysical Evidence for Large Scale Fluid Vent Structure in the Abyssal Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Dohmen, T. E.

    2005-05-01

    This talk examines geophysical evidence for the appearance of a large-scale fissure or fluid vent structure in the abyssal Gulf of Mexico, located in Lund Area. We notice a near vertical fissure 20,000 ft tall and about 100km long, which directly underlies the thickest portion of the Mississippi River Fan. Disruption of the sedimentary layers below the fan resembles fluid vent structures normally seen as localized chimneys on seismic from deep water. In this case, the feature has developed into a long, linear structure, the upper portion of which appears to contain hydrates. We expect a relationship between the formation of the fissure and the rapid deposition of the Mississippi Fan during Pleistocene and Holocene glacial lowstands. The expanding fan would have led to uneven loading of the pre-existing, layered sediments of the abyssal plain. This may have caused a zone of low effective stress to develop at the leading edge of the levee, reaching deep into the subsurface due to the large spatial wavelength of the load, and bringing pore pressures close to the fracture gradient in much the same manner as envisioned by Dugan & Flemings, 2000 for formation of the box canyons off the New Jersey coast. Geophysically, we can document: 1) A long, linear time structure appearing at all levels underlying the Mississippi Fan and above the known source rock section (i.e., Top K through Pliocene). 2) Isopachs show no thinning implying a late, catastrophic event. 3) Banded, high amplitude reflections crowded into the top of the vent may be hydrates or alternating layers of hydrates and free gas trapped under the fan sediments. 4) Low impedance, low frequency, chaotic seismic "halo" 20-25miles wide surrounds the vent. 5) Near and far offset stacks of seismic data resemble one another enough to prove the feature is not just a shallow velocity anomaly. Far offset raypaths would undershoot a near surface feature causing deep reflectors from a far offset record to differ from a near offset record if it were simply a shallow velocity anomaly. 6) Congruence of the subsurface feature with the bathymetric maximum thickness of the Mississippi Fan combined with the apparent late-stage deformation suggests a causal relationship. Understanding the formation of this vent feature may provide insight into large-scale petroleum migration routes, the origins of overpressure in the shallow sedimentary section, effects on the distribution of hydrates, and possibly rates of petroleum sourcing.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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...

  8. Sediment loading and controls in the grasslands of the Great Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, the effects of upstream conservation measures on sediment delivery to and half-life of the Fort Cobb Reservoir in West-Central Oklahoma are investigated. Few conservation practices were implemented on the Fort Cobb Reservoir watershed before the 1950s. In the second half of the 20th ...

  9. 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

  10. Comparison and correlation of physical properties from the plain and slope sediments in the Ulleung Basin, East Sea (Sea of Japan)

    NASA Astrophysics Data System (ADS)

    Kim, G. Y.; Kim, D. C.

    2001-08-01

    High-resolution profiles (chirp sonar, 2-7 kHz) acquired from the Ulleung Basin, East Sea (Sea of Japan) revealed several discrete echo types, suggesting deposits formed mainly by mass flow processes. The Ulleung Basin plain sediments are characterized by turbidite/hemipelagic deposits, while slide, slump, and debrite deposits are mainly found in the slope area. Rock fall deposits also appear near the Ulleung Island. The core sediments show distinctive downslope variations in most physical properties studied. Over the plain and the slope, mass physical properties (water content, porosity, wet bulk density, shear strength, and velocity) show considerably different values in spite of the nearly constant sediment texture. However, the relationships among the physical properties have relatively good correlations, although the absolute values are different. Grain density in the plain is relatively lower than the slope, probably because of a tephra and calcite compensation depth (CCD). Therefore, we suggest that the slope sediments may be affected by sedimentological changes resulting from diagenesis such as a certain degree of compaction and/or consolidation.

  11. 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.

  12. 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.

  13. 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.

  14. 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 51°S; 12°W and 50°S; 39°W) 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.

  15. Submarine ridges do not prevent large-scale dispersal of abyssal fauna: A case study of Mesocletodes (Crustacea, Copepoda, Harpacticoida)

    NASA Astrophysics Data System (ADS)

    Menzel, Lena; George, Kai Horst; Arbizu, Pedro Martínez

    2011-08-01

    We examined the large-scale distribution of deep-sea harpacticoid copepods at the species level, in order to clarify the underlying processes of copepod dispersal. The study was based on samples collected from 12 regions and a total of 113 stations: 57 stations at depths between 1107 and 5655 m on abyssal plains in the South and North Atlantic, Southern Ocean, southern Indian Ocean, and the Pacific Ocean, and 56 stations above 900 m in the North Atlantic and eastern Mediterranean Sea. We chose the genus Mesocletodes Sars, 1909 as an ideal group to study the large-scale distribution of harpacticoid copepods in the deep oceans. Clear apomorphies and a comparatively large body size of about 1 mm allow rapid recognition of allied species in meiofauna samples. In addition, Mesocletodes represents more than 50% of the family Argestidae Por, 1986, one of the most abundant harpacticoid families in the deep sea. The geographical distributions of 793 adult females of Mesocletodes belonging to 61 species throughout the South and North Atlantic, Southern Ocean, southern Indian Ocean, Pacific Ocean, and eastern Mediterranean Sea indicated that most species are cosmopolitan. Neither the topography of the sea bottom nor long distances seem to prevent species from dispersing. Passive transport by bottom currents after resuspension is likely the propulsive factor for the dispersal of Harpacticoida, while plate tectonics and movement of individuals in the sediment may play relatively minor roles.

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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).

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Quantitative characterization of abyssal seafloor with transit multibeam backscatter data

    NASA Astrophysics Data System (ADS)

    Pockalny, R. A.; Ferrini, V. L.

    2014-12-01

    The expanding volume of deep-water multibeam echosounder data provides emerging opportunities for the improved characterization of the abyssal seafloor. Nearly 500 cruises criss-cross the oceans with modern wide-swath multibeam systems, and these cruise tracks have imaged a variety of morphologic, tectonic and magmatic environments. The qualitative analysis of the seafloor backscatter data strongly suggests a local and regional variability that correlates with sediment thickness, sediment type and/or depositional environment. We present our initial attempts to develop a method that quantifies this observed seafloor backscatter variability and to explore the causes and potential implications of this variability. Our approach is rooted in the Angular Range Analysis methodology, which utilizes changes in backscatter amplitude observed as a function of grazing angle, to characterize the seafloor. The primary difference in our approach is that we do not invert for geo-acoustical parameters, but rather explores empirical relationships between geological observations and stacked slope and y-intercept values. In addition, we also include the mean and the variance of detrended backscatter measurements. Our initial results indicate intriguing relationships between backscatter parameters and the CaCO3 content of surface sediments. Seafloor regions reported to have high manganese nodule concentrations also tend to have characteristic trends in backscatter parameters. We will present these regional correlations as well as some preliminary statistical analyses of the backscatter parameters and key environmental factors.

  8. 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.

  9. 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.

  10. 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.

  11. Iunconsistencies in Accumulation Rates of Black Sea Sediments Inferred from Records of Laminae and 210Pb

    NASA Astrophysics Data System (ADS)

    Crusius, J.; Anderson, R. F.

    1992-04-01

    Recently-published estimates for the age of the unit 1-unit 2 contact in Black Sea sediments based on accelerator mass spectrometry (AMS) 14C measurements [Jones, 1990; Calvert et al., 1991] appear to be older than those based on the previously published chronology based on lamina couplets [Degens et al., 1980; Hay, 1988] by a factor of 2 to 3. To help reconcile the differences, we compare sediment accumulation rates based on the 210Pb method with estimates based on lamina counts for two cores from the Black Sea abyssal plain. Accumulation rates estimated using the 210Pb technique have varied little over the last 150 years from the averages of 55 and 50 g m-2 yr-1 at stations in the western and eastern basins, respectively. These values are about a factor of 2 lower than accumulation rates derived by counting lamina couplets over the dated intervals. Close examination of the laminae suggests that the discrepancy exists both because it is difficult to count the very fine laminae and because a complete couplet is not deposited every year. In order to provide a useful stratigraphic horizon for future investigators studying sedimentary records of the Black Sea, we estimate the age of a distinct black marker horizon which can be easily identified across the entire abyssal plain to be 150±8 years (deposited in 1838±8 A.D.).

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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

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

    PubMed Central

    Pawlowski, Jan; Christen, Richard; Lecroq, Béatrice; 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

  18. Sorption kinetics of Hg and HgCl[sub 2] on Kirkwood-Cohansey aquifer sediments from the New Jersey Coastal Plain

    SciTech Connect

    MacLeod, C.; Peterson, J. . Dept. of Geological and Geophysical Sciences)

    1992-01-01

    Anomalously high Hg concentrations have been detected from domestic wells in the Kirkwood-Cohansey Aquifer System, New Jersey Coastal Plain. Mercury concentrations ranging from 0.2--83.0 [mu]g/l in relatively shallow wells ([lt] 100 feet) have been detected. Concentrations in excess of 2.0 [mu]g/l, (the USEPA Drinking Water Standard) have been detected in wells where the Cohansey Sand is overlain by the Bridgeton Formation; a fluvial iron-rich sand with some gravelly channel deposits containing goethite and gibbsite nodules. In this study, Bridgeton Fm. sediments were used to determine the sorption kinetics for solutions containing HgCl[sub 2] and for solutions containing dissolved elemental Hg in order to assess the potential for the Bridgeton sediments to act as a conduit for Hg mobilized from the surface. Results of batch equilibrium experiments suggest that dissolved elemental Hg sorbs to Bridgeton sediments by a risk-order kinetic process. Sorption of the Hg proceeded exponentially and equilibrium was reached within 14 hours. The sorption kinetics for the HgCl[sub 2] solutions, however, appear to be of a second or higher order. For this compound sorption to the sediments begins exponentially, but after 6 hours desorption into the water begins to predominate followed by a slower exponential sorption step that requires nearly 36 hours to reach equilibrium. These experiments illustrate the necessity of determining the distribution coefficients of possible source compounds when attempting to evaluate mobilization potential of a contaminant in the unsaturated zone. Moreover, these data also suggest that HgCl[sub 2], a seed dressing for corn, medial bacteriacide, and embalming fluid ingredient, is more mobile in the environment than dissolved elemental Hg. Consequently, the ground water contamination potential appears to be greater for HgCl[sub 2] than for elemental Hg.

  19. 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

  20. 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

  1. 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...

  2. Convective circulation in mesoscale abyssal basins

    NASA Astrophysics Data System (ADS)

    Whitehead, J. A.; Korotaev, G. K.; Bulgakov, S. N.

    Deep circulation in natural water basins that are smaller than the large global abyssal ocean, but bigger than a Rossby radius of deformation is both scantily documented and poorly understood. For buoyancy driving alone, angular momentum balance dictates that currents of both cyclonic and anticyclonic sense of circulation must exist, although both senses need not be of the same magnitude in the interior. Three laboratory experiments performed on a rotating turntable have been found with interior velocities that demonstrate layers with alternating cyclonic and anticyclonic azimuthal circulation. In one example an internal thermocline implies there is a set of two stacked meriodonal cells of opposite sign. Numerical results and laboratory data display qualitative agreement over a wide range of parameters. Quantitative comparison is within roughly two in the worst cases, but somewhat better for other cases. An argument based upon energetics is advanced which produces a velocity scale in rough agreement with some of the laboratory and numerical results.

  3. 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.; Dühnforth, 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.

  4. 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}).

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. Plumbing the abyss: black ring microstates

    NASA Astrophysics Data System (ADS)

    Bena, Iosif; Wang, Chih-Wei; Warner, Nicholas P.

    2008-07-01

    We construct the first smooth, horizonless ``microstate geometries'' that have the same charges, dipole charges and angular momenta as a BPS black ring whose horizon is macroscopic. These solutions have exactly the same geometry as black rings, except that the usual infinite throat is smoothly capped off at a very large depth. If the solutions preserve a U(1) × U(1) isometry, then this depth is limited by flux quantization but if this symmetry is broken then the throat can be made arbitrarily deep by tuning classical, geometric moduli. Interpreting these ``abysses'' (smooth microstate geometries of arbitrary depth) from the point of view of the AdS-CFT correspondence suggests two remarkable alternatives: either stringy effects can eliminate very large regions of a smooth low-curvature supergravity solution, or the D1-D5-P CFT has quantum critical points. The existence of solutions whose depth depends on moduli also enables us to define ``entropy elevators,'' and these provide a new tool for studying the entropy of BPS and near-BPS black holes.

  13. 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

  14. Geochemistry of sediments from the Huaibei Plain (east China): Implications for provenance, weathering, and invasion of the Yellow River into the Huaihe River

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Qin, Xiaoguang; Liu, Jiaqi; Sun, Chunqing; Mu, Yan; Gao, Jinliang; Guo, Wenfeng; An, Shikai; Lu, Chunhui

    2016-05-01

    The sediments of the Huaibei Plain in semi-humid mid-eastern China represent valuable geological records with respect to eolian-fluvial interactions, depositional environments, and climate change in this region. Provenance and weathering conditions are often reconstructed using sedimentary geochemistry methods. In this study, an 8-m core from Huainan and a set of loess samples from northern and southern China were analyzed for major, trace, and rare earth elements (REEs). Results were compared to determine the samples' provenance. The major, trace, rare earth elements contents, and grain size distribution were found to fluctuate widely in the 2-8 m section of the Huainan core and more narrowly closer to the surface (0-2 m). This suggests a provenance shift at a depth of 2 m. The TiO2/Al2O3, SiO2/Al2O3, Th/Nb, La/Nb values and REE patterns in the upper core (0-2 m) are similar to those found in samples from the Chinese Loess Plateau (CLP). These results suggest that the CLP in northern China is likely to be the primary origin of the upper part (0-2 m) of the Huainan core. Compared with CLP samples, the upper part of the Huainan core exhibits lower K2O/Al2O3 values and higher chemical alteration indices. This is indicative of the material's substantial weathering during transportation and re-deposition and implies that these sediments could reasonably be classified as typical recycled loess. The sediments may have been transported from the CLP to Huainan as Yellow River flood events, probably during the last deglaciation (∼13.2 ka) as a result of increased precipitation, along with glacier and snow melt in the upper reaches of the Yellow River catchment during this period. This suggests that the Yellow River may have migrated into the Huaihe River catchment much earlier than the earliest historical records (361 BCE) suggest. The implications of this would be profound with respect to Chinese history.

  15. 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.

  16. A late Quaternary loess-paleosol pedosedimentary sequence at Monte Netto (northern Italy): loess sedimentation, soil formation and tectonics in the central Po Plain.

    NASA Astrophysics Data System (ADS)

    Trombino, Luca; Zerboni, Andrea; Livio, Franz; Berlusconi, Andrea; Michetti, Alessandro M.; Spötl, Christoph; Rodnight, Helena

    2013-04-01

    In the area of the Po Plain south of Brescia several isolated hills are present (Castenedolo hill, Ciliverghe hill, and Monte Netto), corresponding to the top of Late Quaternary anticlines. The Castenedolo and Ciliverghe area was widely explored in the last decades and thick sequences of pedosediments furnished detailed archives for the evolution of this part of the Po Plain. A new thick and complex loess-paleosol sequence, resting upon fluvial and fluvioglacial deposits exposed in a clay pit at the top of the Monte Netto hill is being studied in great detail. The Monte Netto is a large flat hill, gently undulated at its top, and the clay pit was opened close to the centre of the anticline, where fluvial and fluvioglacial deposits are deformed. This succession, probably of middle Pleistocene age, is buried by a loess-paleosol sequence 2 to 7 m thick; the depth of the loess is related to its physiographic position, i.e. it becomes thicker going away from the top of the anticline. Furthermore, the upper pedosediments are faulted by bending-moment structures, developed during fold amplification and allow to date some of the latest movements of the anticline. A geopedological, sedimentological and micropedological investigation of the whole extension of the quarry shows a distinctive difference between the loess-paleosol sequence at the top of the anticline and the one placed at its southern fringe (150 m away). On the top of the anticline a deeply weathered red paleosols developed in loess underneath a weakly weathered loess. In this soil also a small lithic assemblage dating to the Middle Palaeolithic was found. The pedosedimentary sequence at the southern fringe of the anticline consists of several loess layers showing different degrees of weathering. According to OSL dating, the upper part of the sequence was formed in the Upper Pleistocene, when most of the loess at the margins of the Po Plain was deposited. A tentative model of the exposed profiles involves the burial of the anticline by loess layers since the Middle Pleistocene and their successive weathering (and probably truncation) during subsequent interglacials and interstadials. These events probably correspond to the number of loess-paleosol couplets identified in the outer part of the anticline. In this sense the light weathered horizons could represent buried paleosols. Furthermore, the highly rubfied paleosols at the top of the anticline should be regarded as a polygenetic soil or as a vetusol, developed near the surface for a long time since the Middle Pleistocene. The on-going geopedological, geoarchaeological and seismic analyses will permit to define the time and steps of development of the Monte Netto hill and help to clarify the climatic and tectonic context during which these sediments where deposited, deformed, and weathered.

  17. 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).

  18. 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.

  19. 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.

  20. 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.

  1. Ontogeny of a flood plain

    USGS Publications Warehouse

    Moody, J.A.; Pizzuto, J.E.; Meade, R.H.

    1999-01-01

    The ontogeny of five flood-plain segments is described for a period of 18 yr following a major flood in 1978 on the Powder River in southeastern Montana. The flood plains developed on relatively elevated sand and gravel deposits left within the channel by the 1978 flood. In cross section, the flood plains resemble benches with well-developed natural levees. Flood-plain growth occurred as sediment was draped onto preexisting surfaces in layers of sand and mud a few centimeters to decimeters thick, resulting in some lateral, but mostly vertical accretion. Annual and biannual measurements indicated that, as the flood-plain segments grew upward, the annual rate of vertical accretion decreased as the partial duration recurrence interval for the threshold or bankfull discharge increased from 0.16 to 1.3 yr. It is clear that a constant recurrence interval for overbank flow cannot be meaningfully assigned to this type of flood-plain ontogeny. These flood plains did not grow on migrating point bars, and vertical accretion at least initially occurred within the channel, rather than across the valley flat during extensive overbank flows. Sediments of these flood plains define narrow, elongated stratigraphic units that border the active channel and onlap older flood-plain deposits. These characteristics are considerably different from those of many facies models for meandering river deposits. Facies similar to those described in this paper are likely to be preserved, thereby providing important evidence in the geologic record for episodes of periodic channel expansion by ancient rivers.

  2. 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.

  3. Sediment transport and fan deposition in the Gulf of Alaska: Effects of transform motion on deep sea sedimentation

    SciTech Connect

    Stevenson, A.J.; Bruns, T.R.; Carlson, P.R. ); Dobson, M.R. )

    1990-06-01

    GLORIA side-scan sonar images and two channel seismic profiles recently collected in the Gulf of Alaska reveal a major site of late Miocene to Recent terrigenous sediment accumulation on the oceanic plate adjacent to the Fairweather-Queen Charlotte transform and the Yakutat Terrane. Sediment moving across this margin has formed several large channel dominated fan systems that blanket the entire gulf and spill westward onto the Tufts Abyssal Plain. The Surveyor Fan, fed by the glaciers of the Yakutat Terrane and insulated from transform sediment source offset by the Terrane, has maintained a single channel course over the entire life of the fan. The Chirikov and Baranof fans receive their sediment supply from glaciofluvial point sources along the SE Alaska margin, separated from the fans by an active transform. The fans show a southward younging of channel ages consistent with the sense of plate motion. Early (late Miocene) deposition within the gulf was limited to the structural basin between the continental margin and the Kodiak-Bowie seamount chain. The geometry of these early depositional systems is poorly known, but available data suggest their channels were oriented NW-SE. Subsequent establishment of a depositional slope between the margin and the seamount chain, coupled with the filling of the basin, led to a reorganization into SW-NE channel systems. The fan bodies of the Gulf of Alaska are members of a distinct class of fans that are characterized by long distributary channels which persist to near the fan limits. This type of fan morphology is most often attributed to a predominantly fine-grained sediment supply. This is difficult to reconcile with the obvious proximal glacial source for much of the sediment supplied to these fans.

  4. Mercury in waters, soils, and sediments of the New Jersey Coastal Plain: A comparison of regional distribution and mobility with the mercury contamination at the William J. Hughes Technical Center, Atlantic County, New Jersey

    USGS Publications Warehouse

    Barringer, Julia L.; Szabo, Zoltan; Reilly, Pamela A.

    2012-01-01

    Mercury in soils, surface water, and groundwater at the William J. Hughes Technical Center , Atlantic County, New Jersey, has been found at levels that exceed established background concentrations in Coastal Plain waters, and, in some cases, New Jersey State standards for mercury in various media. As of 2012, it is not known whether this mercury is part of regional mercury contamination or whether it is related to former military activities. Regionally, groundwater supplying about 700 domestic wells in the New Jersey Coastal Plain is contaminated with mercury that appears to be derived from anthropogenic inputs, such as agricultural pesticide use and atmospheric deposition. High levels of mercury occasionally are found in Coastal Plain soils, but disturbance during residential development on former agricultural land is thought to have mobilized any mercury applied during farming, a hypothesis borne out by experiments leaching mercury from soils. In the unsewered residential areas with mercury-contaminated groundwater, septic-system effluent is believed to create reducing conditions in which mercury sorbed to subsoils is mobilized to groundwater. In comparing the levels of mercury found in soils, sediments, streamwater, and groundwater at the William J. Hughes Technical Center site with those found regionally, mercury concentrations in groundwater in the region are, in some cases, substantially higher than those found in groundwater at the William J. Hughes Technical Center site. Nevertheless, concentrations of mercury in streamwater at the site are, in some instances, higher than most found regionally. The mercury contents in soils and sediment at the William J. Hughes Technical Center site are substantially higher than those found to date (2012) in the region, indicating that a source other than regional sources may be present at the site.

  5. 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.

  6. 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

  7. Do laminated sediment-gravity-flow deposits on the Antarctic Peninsula continental shelf record ice shelf grounding events?

    NASA Astrophysics Data System (ADS)

    Adams, V.; Bart, P.

    2007-12-01

    Drifts on the continental rise of the Antarctic Peninsula may contain a high-resolution record of ice-sheet expansion on the adjacent continental shelf (Baker and Carmerlenghi, 1999). During major ice-sheet grounding events, sediment is delivered to the outer continental shelf and upper slope. Associated slope instabilities trigger additional mass transport to the continental rise and abyssal plain. Therefore, major glacial periods should be recorded on the continental rise by laminated sediment-gravity-flow deposits within the drifts. When grounded ice retreats during interglacials, sedimentation rates would decline and the tops of laminated sections should be bioturbated. In this ongoing study, we compile the laminated-bioturbated couplets from ODP Leg 178 Sites 1095, 1096, and 1101. We are in the process of evaluating whether the timing and frequency of the sediment cycles on the drift are possibly related to orbital forcing as opposed to an uneven distribution of sediment input from the outer continental shelf and/or bioturbation on the drift.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. The Ocean's Abyssal Mass Flux Sustained Primarily By the Wind: Vector Correlation of Time Series in Upper and Abyssal Layers

    NASA Astrophysics Data System (ADS)

    Hancock, L. O.

    2003-12-01

    As Wunsch has recently noted (2002), use of the term "thermohaline circulation" is muddled. The term is used with at least seven inconsistent meanings, among them abyssal circulation, the circulation driven by density and pressure differences in the deep ocean, the global conveyor, and at least four others. The use of a single term for all these concepts can create an impression that an understanding exists whereby in various combinations the seven meanings have been demonstrated to mean the same thing. But that is not the case. A particularly important consequence of the muddle is the way in which abyssal circulation is sometimes taken to be driven mostly or entirely by temperature and density differences, and equivalent to the global conveyor. But in fact the distinction between abyssal and upper-layer circulation has not been measured. To find out whether available data justifies a distinction between the upper-layer and abyssal circulations, this study surveyed velocity time series obtained by deep current meter moorings. Altogether, 114 moorings were identified, drawn from about three dozen experiments worldwide over the period 1973-1996, each of which deployed current meters in both the upper (200abyssal (z>3750) layers. For each pair of current meters, the Kundu and Crosby measures of vector correlation were estimated, as well as coherences for periods from 10 to 60 days. In the North Atlantic, for example, Kundu vector correlation (50-day window): 0.48 +/- .03 Crosby vector correlation (absolute value, 50 day window): 0.46 +/- .07 Coherence at 60 days: .36 +/- .07 - at 30 days: 0.40 +/- .06 - at 10 days: 0.22 +/- .05 Most figures for the South Atlantic, Pacific and Southern Oceans are similar. Those obtained in the Indian Ocean or near the Equator are somewhat different. The statistics obtained here are consistent with the work of Wunsch (1997), and tend to confirm Wunsch's result that current velocities at depth are linked with those in the upper layers. Energetics of the circulation that do not take this into account are making an unjustifiable approximation of the physics. These results do not tell us whether time averaged flow on longer time scales might permit distinction of upper layer and abyssal flow components. Some intriguing corollaries do follow. First, the abyssal circulation is not identically the same thing as a global conveyor belt driven by temperature and density differences. Rather, as Wunsch noted (2002), the ocean's mass flux is sustained primarily by the wind. We may add that these wind patterns are about as robust as the temperature differences between equator and pole; this major driver of circulation is not a frail phenomenon. Second, the classical notion of a level of no motion that is also a constant-density surface, an LNM, is inconsistent with the results presented here. Such an LNM would wall off the upper layer circulation from the lower, and as they are not walled off, there can be no such LNM. Third, wind stress is being transmitted down column, presumably to the sea floor.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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; Røy, Hans; Evans, Thomas W; Lever, Mark A; Jørgensen, 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 < 10 μM in oligotrophic abyssal plain sediments near the South Atlantic Gyre compared with ammonium concentrations of > 700 μM 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

  20. 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.

  1. 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).

  2. Depth Transects of Sediment Age, Reflectance, and Aquifer Arsenic in the Bac Bo Plain, Vietnam: Implications for Groundwater Arsenic Heterogeneity in the Red River Delta

    NASA Astrophysics Data System (ADS)

    Weinman, B.; Goodbred, S. L.; Radloff, K.; Aziz, Z.; Jung, H.; Frei, F.; Berg, M.; Trang, P. K.; Singhvi, A.; van Geen, A.

    2007-12-01

    Shallow aquifer groundwater arsenic heterogeneity is well documented in many of the fluvial regions of Asia. To this day, the cause for the heterogeneity remains poorly understood in part because of the heterogeneity of sediment properties inherent to a young floodplain depositional environment. In April 2006, a needle-sampler device was used to obtain depth transects of both sediment and porewater samples as the first step towards understanding the heterogeneous subsurface environment. Depth transects were taken between sites with opposing trends in tube-well arsenic, e.g. low As cluster to high As cluster, in a stable, fault controlled river bend in Van Phuc, Vietnam, to determine how sediment properties such as grainsize and reflectance relate to dissolved arsenic. Luminescence dating of aquifer sands and He3/H3 dating of the groundwater was conducted to investigate how aquifer redox conditions and groundwater arsenic evolve in Van Phuc's river-bend over time. Results indicate that localized zones of sediments enriched in leachable arsenic exist at depth within the aquifer and provide a mostly local source of arsenic. It also appears that groundwater flow encountering sediments of different ages can account for some of the observed spatial patterns of groundwater heterogeneity. Compiled with observations that reducing groundwaters with both low dissolved and extractable arsenic exist in the upper deltaic region, it appears that heterogeneities in shallow floodplain arsenic can be driven by magnitude differences in sediment-labile arsenic. Finally, given that these localized packages of arsenic enrichment correspond to a particular in-filling type of facies, it appears that fluvial cycling along the delta is the underlying cause of arsenic heterogeneity in the shallow floodplain.

  3. 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

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

    NASA Astrophysics Data System (ADS)

    Patara, Lavinia; Böning, 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 ½° 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 0.05°C 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

    Guimarães, 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 (Tapajós, Negro and Amazon rivers), the Pantanal floodplain (Paraguay river basin), freshwater coastal lagoons in Rio de Janeiro and oxbow lakes in the Mogi-Guaçú river, São 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 Tapajós 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 Cuiabá 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

  9. Abyssal foraminifers, including two new genera, encrusting the interior of Bathysiphon rusticus tubes

    NASA Astrophysics Data System (ADS)

    Gooday, A. J.; Haynes, J. R.

    1983-06-01

    Empty or sediment-filled tubes of the large agglutinated foraminifer Bathysiphon rusticus de Folin, 1886 occur abundantly in an abyssal epibenthic sledge sample taken in the northeast Atlantic. More than half of the tubes are coated inside and outside with a variably developed deposit rich in iron and manganese. They also bear on their inner surfaces an unusual assemblage of encrusting Foraminifera or Foraminifera-like rhizopods. Most of the 26 forms present are restricted to this habitat and other potential substrates carry only a sparse fauna of attached foraminifers. The majority of the forms are agglutinated and many contain protoplasm suggesting that they were alive when captured. Two are described as new species and genera, 14 are identified to species or genus, the remainder are left unidentified. Minute (<100 μm) calcareous foraminifers, including microforaminifers, are an important element in the assemblage. The foraminifers probably encrust the tube interiors because they provide a smooth and sheltered substrate. Some species, for example, the microforaminifers, may also be obtaining food, presumably bacteria, from the surfaces. There is some evidence that the protozoans are attracted by the presence of an iron-manganese coating. A comparison of the Bathysiphon tube foraminifers with previously described encrusting assemblages from deep-sea iron-manganese nodules reveals some interesting similarities. However, there are also some notable discrepancies for which explanations are offered.

  10. A Spatial Analysis of the Relationship Between Mangrove ( Avicennia marinavar. australasica) Physiognomy and Sediment Accretion in the Hauraki Plains, New Zealand

    NASA Astrophysics Data System (ADS)

    Young, Brodie M.; Harvey, Edward L.

    1996-02-01

    The relationship between mangrove ( Avicennia marinavar. australasica) physiognomy and forest bed accretion was quantified using experimental and field measurements at the Piako river mouth, Firth of Thames, New Zealand. Sediment accretion under six densities of artificial pneumatophores was monitored for 13 weeks in an experimental plot, while accretion was simultaneously monitored for 5 months at 102 locations along two parallel 500-m transects. Experimental results demonstrated that accretion increases with pneumatophore density. This was supported by bivariate analyses of cumulative accretion and Avicennia marinastem density, basal area and pneumatophore density along the transects. Only the latter is significantly correlated with accretion. Geostatistical analyses showed that variation in sediment accretion occurs at the same spatial scale as pneumatophore density. Accretion and pneumatophore density are spatially autocorrelated over distances <70 m and have fractal dimensions of 1·5-1·6. It is proposed that Avicennia marinagrow pneumatophores at a density that balances the benefits of aeration with the drawbacks of sediment accretion. These results are compared with the concept of positive-feedback switches in plant communities.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  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. 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)

  20. Sedimentation in Canada Basin, Western Arctic

    NASA Astrophysics Data System (ADS)

    Mosher, D. C.; Shimeld, J.; Jackson, R.; Hutchinson, D. R.; Chapman, B.; Chian, D.; Childs, J. R.; Mayer, L. A.; Edwards, B. D.; Verhoef, J.

    2010-12-01

    The Canada Basin of the western Arctic Ocean is the least studied ocean basin on Earth. Marine seismic field programs were conducted during the past 5 years in order to study the geology, sedimentary history and geomorphology of the region. As part of this program, five annual icebreaker expeditions acquired bathymetric, seismic reflection and seismic refraction data on a regional scale. More than 12,000 km of multi-channel seismic reflection data and 120 sonobuoy seismic refraction records over abyssal plain and continental rise regions of Canada Basin, Northwind Ridge and Alpha Ridge were acquired. The success of these programs was achieved through novel technical modifications to equipment to permit towing in heavy ice conditions and through collaboration between multiple Canadian and US agencies and institutions, enabling utilization of two ice breakers during seismic and multibeam data acquisition in heavy ice. The seafloor of the Canada Basin is remarkably flat-lying in its central region, with little bathymetric change over most of its extent. The sedimentary succession is generally flat lying with reflections extending over hundreds of km. These reflections onlap bathymetric highs, such as Alpha and Northwind ridges. The sedimentary succession is thickest in the Beaufort Sea region, reaching more than 6.5 km, and generally thins to the north and west. Reflection characteristics suggest that sediment volume input to the Arctic Ocean has been high and dominated by turbidity current deposition, similar to Amundsen and Nansen Basins of the eastern Arctic. These turbidites originate from the eastern and southern continental margins. There is no evidence of contemporaneous or post-depositional reworking by bottom currents. Additionally, there is little evidence of tectonic deformation after primary basin-forming events except in the NE quadrant, nearer Alpha Ridge. In this area, there is significant normal faulting propagating from basement through much of the sedimentary succession. Basement graben stuctures in combination with these faults imply possible crustal extension contemporaneous with deposition.

  1. Evidence for Pulsed Hydrothermal Venting from Young Abyssal Hills on the EPR Flank Suggests Frequent Seismic Pumping of Ridge Flank Fluid Flow

    NASA Astrophysics Data System (ADS)

    Haymon, R. M.; MacDonald, K. C.; Benjamin, S. B.; Ehrhardt, C. J.

    2004-12-01

    Although measured heat flow suggests that 40-50% of oceanic hydrothermal heat and fluid flux is from young (0.1-5 Ma) abyssal hill terrain on MOR flanks, hydrothermal vents in this setting rarely have been found. On the EPR flanks, seafloor evidence of venting from abyssal hills has been discovered recently at two sites: on ˜0.1 Ma seafloor at 10° 20'N, 103° 33.2'W ("Tevnia Site") and on ˜0.5 Ma seafloor at 9° 27'N, 104° 32.3'W ("Macrobes Site"). Manifestations of venting at these sites include: fault scarp hydrothermal mineralization and macrofauna; fault scarp flocculations containing hyperthermophilic microbes; and hilltop sediment mounds and craters possibly created by fluid "blow-outs." Hydrothermal deposits recovered at the ˜0.1 Ma "Tevnia Site" are fault breccias that record many episodes of brecciation followed by hydrothermal cementation (Benjamin et al., this session). Tubeworm casings, live crabs, and "dandelions" observed at this site indicate that the most recent episode of venting was active during, or shortly before, this site was visited with Alvin in 1994. To create the 200 m-high axis-facing fault scarp at Tevnia Site in 100,000 years, an average uplift rate of at least 2 cm/y is required. Since off-axis earthquakes located on abyssal hill fault scarps typically are abyssal hills are uplifted on ridge flanks. Hyperthermophiles identified in microbial floc on the axis-facing fault scarp at the ˜0.5 Ma "Macrobes Site" are associated with chalcopyrite particles (Ehrhardt et al., this session). These observations indicate recent, transient venting of high-T (at least 250° C), Cu-rich fluids from the fault scarp. The hilltop here has many meter-scale sediment mounds and craters (macs). These appear to be small mud volcanoes that have formed at different times from fluids expelled episodically through the thin sediments blanketing the hilltop. Formation of macs may be triggered by frequent (decadal) seismic events that also produce transient bursts of high T fluid flow from the adjacent fault scarp. Hyperthermophiles in the subsurface may flush out and bloom on the fault scarp during these events, and then remain dormant until the next event. The combined evidence from the two EPR ridge flank sites points to seismic pumping of EPR abyssal hill hydrothermal pulses every few years-to-decades. These frequent hydrothermal pulses may be important in sustaining ridge flank biota. Monitoring of EPR abyssal hill fault scarps is needed to test these ideas.

  2. 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.

  3. 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.

  4. Stratigraphy of the Martian northern plains

    NASA Technical Reports Server (NTRS)

    Tanaka, K. L.

    1993-01-01

    The northern plains of Mars are roughly defined as the large continuous region of lowlands that lies below Martian datum, plus higher areas within the region that were built up by volcanism, sedimentation, tectonism, and impacts. These northern lowlands span about 50 x 10(exp 6) km(sup 2) or 35 percent of the planet's surface. The age and origin of the lowlands continue to be debated by proponents of impact and tectonic explanations. Geologic mapping and topical studies indicate that volcanic, fluvial, and eolian deposition have played major roles in the infilling of this vast depression. Periglacial, glacial, fluvial, eolian, tectonic, and impact processes have locally modified the surface. Because of the northern plains' complex history of sedimentation and modification, much of their stratigraphy was obscured. Thus the stratigraphy developed is necessarily vague and provisional: it is based on various clues from within the lowlands as well as from highland areas within and bordering the plains. The results are summarized.

  5. High mixing rates in the abyssal Southern Ocean.

    PubMed

    Heywood, Karen J; Naveira Garabato, Alberto C; Stevens, David P

    2002-02-28

    Mixing of water masses from the deep ocean to the layers above can be estimated from considerations of continuity in the global ocean overturning circulation. But averaged over ocean basins, diffusivity has been observed to be too small to account for the global upward flux of water, and high mixing intensities have only been found in the restricted areas close to sills and narrow gaps. Here we present observations from the Scotia Sea, a deep ocean basin between the Antarctic peninsula and the tip of South America, showing a high intensity of mixing that is unprecedented over such a large area. Using a budget calculation over the whole basin, we find a diffusivity of (39 plus minus 10) x 104[?]m2[?]s-1, averaged over an area of 7 x 105[?]km2. The Scotia Sea is a basin with a rough topography, situated just east of the Drake passage where the strong flow of the Antarctic Circumpolar Current is constricted in width. The high basin-wide mixing intensity in this area of the Southern Ocean may help resolve the question of where the abyssal water masses are mixed towards the surface. PMID:11875565

  6. The Efficiency of Deep and Abyssal Ocean Turbulent Mixing

    NASA Astrophysics Data System (ADS)

    Mashayek, Ali; Caulfield, Colm; Ferrari, Raffaele; Nikurashin, Maxim; Peltier, Richard

    2015-11-01

    Turbulent mixing produced by breaking of internal waves in the deep ocean plays a primary role in the climate through exerting a control upon the upwelling of deep dense waters formed at high latitudes, thereby driving the global ocean overturning circulation. A key parameter used to characterize turbulent mixing in observations, climate models, and global energy budgets, is the `efficiency' of mixing, here defined as the ratio of the portion of the tide and wind energy input into the deep ocean that is invested in mixing, to the portion viscously dissipated into heat. Efficiency is conventionally assumed to be a constant of approximately twenty percent. Here we show that it varies significantly in the abyssal ocean, and that mixing is predicted to be most efficient, reaching values as high as fifty percent near topographic features which host vigorous wave generation and breaking. This result suggests a more accurate closure of the bulk ocean energy budget, a goal lying at the heart of understanding the role of the ocean circulation in climate and one towards which the oceanographic community has been striving for decades.

  7. Abyssal echinoid and asteroid fauna of the North Pacific

    NASA Astrophysics Data System (ADS)

    Mironov, A. N.; Minin, K. V.; Dilman, A. B.

    2015-01-01

    Echinoidea and Asteroidea collected in the Kuril-Kamchatka Trench area by the KuramBio Expedition were examined. Altogether 20 species belonging to 16 genera were found, among them six species and two genera were recorded in the North Pacific for the first time. Morphological variability of Abyssaster tara suggests that this species is congeneric with Styracaster transitivus and Styracaster paucispinus. Complete age series of the echinoid Echinosigra amphora and the asteroid Eremicaster crassus are described. The juveniles of E. amphora (>0.5 mm in length) are characterized by unique ophicephalous pedicellaria in the centre of aboral side of the test. The abyssal echinoid and asteroid fauna of the North Pacific (north of 30°N and deeper than 3000 m) comprises 62 species of 36 genera; 22 species (35%) and 3 genera are endemic to this region. Global distribution patterns of genera support the hypothesis that there were two stages of dispersal from the Antarctic to the North Pacific: at earlier stage the dispersal occurred via the East Pacific and at the later stage - via the West Pacific. The genera that had dispersed at earlier stage are represented only in the North and East Pacific and Antarctic. Distribution ranges of these genera in the East Pacific are limited to the narrow zone extending meridionally along the base of the American continental slope. Genera with such distribution pattern are likely adapted to highly eutrophic conditions.

  8. 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.; Mühlenhardt-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.

  9. 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.

  10. 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.

  11. Strontium, neodymium, and lead isotopic and trace-element signatures of the East indonesian sediments: provenance and implications for banda arc magma genesis

    NASA Astrophysics Data System (ADS)

    Vroon, P. Z.; van Bergen, M. J.; Klaver, G. J.; White, W. M.

    1995-06-01

    We present new trace-element and Sr-Nd-Pb isotope data for 127 surface sediments and five sediments from DSDP Site 262, distributed along and across the arc-continent collision region of the Banda Arc, East Indonesia. The results are used to evaluate the role of subducted continental material (SCM) in the genesis of the Banda Arc magmas and to assess the extent to which geochemical and isotopic signatures of SCM are controlled by sediment provenance. In the surface sediments lead and neodymium isotope ratios are variable: 206Pb/ 204Pb = 18.65-19.57; 143Nd/ 144Nd = 0.51230-0.51190, with an increase in lead isotope ratios and a decrease in the 143Nd/ 144Nd ratio from northeast to southwest along the Banda Arc. DSDP Site 262 sediments, farthest to the west in the Timor Trough, overlap with the surface sediments and have 206Pb/ 204Pb = 18.89-19.23 and 143Nd/ 144Nd = 0.51200-0.51220. In contrast, the trace-element ratios and REE patterns of the sediments do not show systematic along-arc variations and largely overlap with estimated values for Upper Continental Crust, Post Archean Australian Shale (PAAS), and ODP Site 765 sediments from the Argo Abyssal Plain. From the combined isotopic and trace-element ratios in the terrigenous fraction of the sediments four major provenance areas can be distinguished: North New Guinea + Seram, South New Guinea, Timor, and northern Australia. The lead isotopic variations in the shelf and wedge sediments along the Banda Arc are parallel to similar variations in the volcanics; this is considered to be strong evidence for the incorporation of subducted continental material in the arc magmas. The trace-element characteristics of both the volcanics and the sediments are also consistent with the involvement of sediments in the Banda Arc magma genesis. The hinterland of the sediments is responsible for isotopic signatures created in the Banda Arc mantle through recent subduction. This suggests that some of the mantle heterogeneities that are inferred from oceanic basalts can be explained by differences in the provenance of (ancient) subducted sediment.

  12. 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.

  13. 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.

  14. 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.

  15. 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 Köhler (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.

  16. 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.

  17. 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.

  18. Modern accumulation rates and a budget of sediment off the Gaoping (Kaoping) River, SW Taiwan: A tidal and flood dominated depositional environment around a submarine canyon

    NASA Astrophysics Data System (ADS)

    Huh, Chih-An; Lin, Hui-Ling; Lin, Saulwood; Huang, Ya-Wen

    2009-03-01

    Ninety-two box cores collected during 2004-2006 from an area of ~ 3000 km 2 off the Gaoping (formerly spelled Kaoping) River, SW Taiwan, were analyzed for fallout radionuclides ( 210Pb, 137Cs and 7Be) to elucidate sedimentation rates and processes, and for the calculation of a sediment budget. The study area is located at an active collision margin with a narrow shelf and a submarine canyon extending essentially into the river's mouth. The results indicate fairly constant hemipelagic sedimentation in much of the open margin and for most of the time except in the inner shelf and along the axis of the canyon where sediment transport is more dynamic and is controlled by tidal current and wave activities constantly, and by fluvial floods or gravity-driven flows episodically. Sedimentation rates in the study area derived from 210Pb and constrained by 137Cs vary from 0.04 to 1.5 cm/yr, with the highest rates (> 1 cm/yr) flanking the Gaoping canyon over the upper slope (200-600 m) and the lowest rates (< 0.1 cm/yr) in the distal basin beyond the continental slope. The depocenter delineated from 210Pb-based sedimentation rates overlaps with the area covered by a flood layer resulting from super-typhoon Haitang in July 2005. Such correspondence supports the notion that the processes operating on event timescale have bearing on the formation of the sediment strata over centennial or longer timescales. From the distribution of sedimentation rates, sediment deposited in the study area annually is estimated to be 6.6 Mton/yr, accounting for less than 20% of Gaoping River's sediment load. The calculated budget, coupled with the presence of the short-lived 7Be and non-steady-state distribution of low levels of 210Pb in sediments along the canyon floor, suggests rapid transport of sediment from Gaoping River's mountainous watershed (the source) via the Gaoping (Kaoping) Submarine Canyon and adjacent channels (as the conduit and temporary sink) to the abyssal plain and the Manila Trench in the South China Sea (the ultimate sink).

  19. 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.

  20. 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…

  1. Constraining the stable isotope budget for Antarctic Bottom Water: New results from the abyssal southwestern Atlantic

    NASA Astrophysics Data System (ADS)

    Hoffman, J. L.; Lund, D. C.

    2010-12-01

    The circulation of Antarctic Bottom Water (AABW) is a primary unknown in our understanding of the climate state of the Last Glacial Maximum (LGM). Stable isotope tracer budgets suggest the transport to vertical diffusivity ratio for AABW in the Atlantic was higher at the LGM. Reduced mixing across the upper 'lid' of AABW is consistent with movement of this surface away from the zone of intense mixing near the seafloor, and may be an important factor in sequestering atmospheric CO2 in the abyssal ocean. A key parameter for the tracer budget approach is the stable isotope value for AABW as it enters the southwest Atlantic. Due to a lack of core material below 3000 m water depth at Brazil Margin, it has been necessary to extrapolate the trends from shallower cores to estimate AABW δ18O and δ13C values at the LGM. For the modern, δ18O and δ13C for AABW had been determined using water column data. Here we present new benthic foraminiferal stable isotope records from four cores between 3000 and 4000 m water depth at the Brazil Margin. Radiocarbon dates were acquired where possible in order to accurately and consistently select LGM and Holocene horizons. Sedimentation rates ranged between 11 and 18 cm/kyr during the LGM and 2 and 5 cm/kyr during the Holocene. The vertical profile of δ18O at the LGM increases monotonically with water depth to a maximum of 4.8±0.1‰ at 4000 m. To our knowledge, this is the highest δ18O for the deep western Atlantic in the published literature and therefore the best available approximation of an AABW 'endmember' δ18O value. LGM δ13C values decrease monotonically below 3000 m water depth, reaching a minimum of -0.4±0.4‰ at 4000 m. Overall our results from the deep cores verify initial estimates of LGM endmember δ18O and δ13C based on extrapolation from shallower cores. For the Holocene, the maximum vertical gradient in δ18O occurs below 3000 m water depth, consistent with the location of the upper 'lid' for AABW indicated by modern hydrographic data. Holocene δ13C values decrease with water depth reaching 0.4±0.4‰ at 4000 m, similar to the δ13C of dissolved inorganic carbon in the modern southwest Atlantic. The new foraminiferal isotopic data will allow for the use of core tops to constrain the late Holocene tracer budget for AABW, as opposed to relying solely on δ18O and δ13C estimates from water column data.

  2. Martian lake basins and lacustrine plains

    NASA Astrophysics Data System (ADS)

    de Hon, R. A.

    1992-02-01

    A classification of Martian lake basins based on the location of the basin in respect to water sources is proposed. The classes are type 1: valley-head basins; type 2: intravalley basins; type 3: valley-terminal basins; and type 4: isolated basins. Martian lakes are ephemeral features. Many craters and irregular depressions impounded water only until the basins filled and overflowed. Water escaping by spillover rapidly cut crevasses in the downstream side of basins and drained the ponds. Clastic lacustrine sediments collected in the lakes as flowing water lost velocity and turbulence. Evaporitic deposits may be significant in those basins that were not rapidly drained. Sediments deposited in lake basins form smooth, featureless plains. Lacustrine plains are potentially candidate sites for Mars landings and for the search for evidence of ancient life.

  3. 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.

  4. 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…

  5. 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

  6. 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...

  7. 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...

  8. 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.

  9. 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.

  10. Species composition and distribution of bivalves in bathyal and abyssal depths of the Sea of Japan

    NASA Astrophysics Data System (ADS)

    Kamenev, Gennady M.

    2013-02-01

    Twenty-six bivalve species collected by four Russian (1972, 1976, 1985, 2005) and Russian-German (2010) expeditions in the bathyal and abyssal depths of the Sea of Japan (465-3435 m) are listed with the material examined and illustrated. Taxonomic decisions herein: Robaia habei Scarlato, 1981 is synonymized with Nuculana (Robaia) robai (Kuroda, 1929); following Scarlato (1981) and Coan et al. (2000)Dacrydium nipponicum Okutani, 1975 and Dacrydium minimum Okutani and Izumidate, 1992 are synonymized with Dacrydium vitreum (Möller, 1842); Maorithyas yamatotaensis Okutani and Izumidate, 1992 is synonymized with Adontorhina cyclia Berry, 1947; Axinopsida rubiginosa Okutani and Izumidate, 1992 is synonymized with Mendicula ferruginosa (Forbes, 1844); Cardiomya lindbergi batialis Scarlato, 1972 is synonymized with Cardiomya tosaensis (Kuroda, 1948); Cuspidaria sadoensis Okutani and Ito, 1983 is synonymized with Cuspidaria ascoldica Scarlato, 1972; Cyclocardia rjabininae (Scarlato, 1955) recognized as valid and distinct from Cyclocardia ovata (Rjabinina, 1952). The deep-water bivalve fauna of the Sea of Japan is characterized by an impoverished shelf fauna and consists of eurybathic species that extend from the shelf to the bathyal and abyssal zones. Most of them have a wide geographic distribution and inhabit cold water regions of the Northern Atlantic, Northern Pacific, and Arctic Ocean. Only five species are endemic to the Sea of Japan. With increase in depth, the species richness of bivalves decreases. In the depth range from 200 to 1600 m, all species (26) found in the deep Sea of Japan were recorded, while only 10 species were recorded in the lower bathyal slope (1700-3000 m). At depths below 3000 m, only D. vitreum, Delectopecten vancouverensis (Whiteaves, 1893), and Thyasira (Parathyasira) sp. were found. The lack of typical abyssal species of bivalves in the deep Sea of Japan is probably connected with the isolation of this body of water from the Pacific abyssal depths.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Jörger, K. M.; Schrödl, M.; Schwabe, E.; Würzberg, 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 α-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 α-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 m², 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.

  13. Depositional environments of late glacial to Holocene sediments on the deep water levees of Setúbal and Nazaré 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 Setúbal and Nazaré 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 Nazaré and Setúbal 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 Nazaré 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.

  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. 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.

  16. 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.

  17. 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.

  18. 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 μm 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.

  19. Phosphorus in drainage waters of the Atlantic Coastal Plain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Atlantic Coastal Plain region has had a long history of experimental and applied efforts to exclude phosphorus (P) from drainage waters. Early research focusing upon the chemical controls of soil and sediment P has given way to field studies aimed at refining our understanding of hydrologic path...

  20. 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 ...

  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

    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. 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

  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. 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.

  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. 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.

  8. Formation of Mercury's smooth plains

    SciTech Connect

    Kiefer, W.S.; Murray, B.C.

    1987-12-01

    Indirect evidence is presented for a volcanic origin in the case of two smooth plains on Mercury, the Borealis Planitia and the Hilly and Lineated Terrain. These results, in conjunction with those previously obtained for the circum-Caloris plains and the Tolstoj basin, indicate that smooth plains volcanism was a global process on Mercury. It is further suggested that the smooth and intercrater plains may have resulted from two separate volcanic episodes, with smooth plains volcanism being a consequence of Caloris impact-triggering. 45 references.

  9. 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

  10. 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.

  11. Major Elements Budget Between Abyssal Peridotite And Seawater During The Serpentinization

    NASA Astrophysics Data System (ADS)

    Yu, X.; Dong, Y.; Li, X.; Chu, F.

    2012-12-01

    Water-Rock Interaction is one of the most hot-debated issues among geologists, geophysicists, as well as geochemists. Abyssal peridotites recovered from the seafloor are often greatly affected or alterated by seawater in the form of serpentinization. The alteration to the peridotites makes it difficult to do the straightforward analysis for its primary composition as it was settled in the upper mantle, which confine the usage of these rare direct samples from the mantle in the scientific study, such as mantle dynamics, mantle composition and crust-mantle interaction. Besides, It was revealed recently that the serpentinization of abyssal peridotites may give birth to the hydrothermal activity. The elements migration during the serpentinization may perform a great role on the chemical composition of the hydrothermal fluid, which can support a hidden chemosynthetic ecosystem in the abyssal seabed. The research work focused on the major elements behavior during the serpentinization by studying the partially serpentinized samples of abyssal peridotite from Southwest Indian Ridge. The primary mineral assemblage of peridotite is olivine (Mg2SiO4), orthopyroxene (Mg2Si2O6), clinopyroxene (CaMgSi2O6) and spinel ((Mg,Fe)(Al,Cr)2O4). The major chemical composition are usually as SiO2 (30~45wt.%), MgO (20~45 wt.%), FeO and Fe2O3 (total 5~15 wt.%). Besides there are very few MnO, CaO, Al2O3, Cr2O3, NiO, Na2O, K2O and H2O. While on the other hand the serpentinized peridotite shows a more complicated mineral assemblage, besides the primary minerals there are more alteration minerals, such as serpentine (Mg3[Si2O5](OH)4), magnetite (Fe3O4), talc (Mg3[Si4O10](OH)2), brucite (Mg(OH)2), tremolite (Ca2Mg5[Si8O22](OH)2), chromite (FeCr2O4), chlorite ((Mg,Fe)6[(Si,Al)4O10](OH)8), and other accessary minerals like native metals, sulfides, clay minerals and hornblende. According to the EMPA analysis, the serpentinized sample shows the chemical composition as SiO2(~40 wt.%), MgO(~30 wt.%), total FeO(~7 wt.%), Al2O3(~1 wt.%), MnO(~0.4 wt.%), Cr2O3(~0.3 wt.%), NiO(~0.2 wt.%), CaO(~0.2 wt.%), and very few TiO2, Na2O and K2O. The overall percentages for all the elements mentioned above are usually around 80wt.%, about 20% less than full percent, which indicates the volatile matters in the altered samples. Based on the preliminary study, we get the general picture for the major elements behavior during the alteration. Taking the abyssal peridotite for example, it gains large quantities of H and O in the form of H2O, and other volatile elements like F, Cl, B from the seawater during serpentinization. It may also get additional Na, K, Mg from the seawater as shown from the standardized concentration in primary minerals as well as altered minerals. It loses Fe, Al, Ca, Si during the serpentinization seen from the EMPA mapping results. The element Mn, Cr and Ni are relatively immobile during the alteration. To get more precise deduction as to the element budget during the alteration process, much more sensitive analytical instruments like LA-ICP-MS are needed. And more work need to be done to get the quantitive estimation for transferring rate of each element.

  12. On the morphodynamics of a channel on a small proglacial braid plain (Fagge River, Ötztal 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).

  13. Soils and landscape evolution of eolian plains: the Southern High Plains of Texas and New Mexico

    NASA Astrophysics Data System (ADS)

    Holliday, Vance T.

    1990-09-01

    Sheets of eolian sediment cover many areas of the earth's surface, sand seas, dune fields, and loess sheets being the best known examples of such features. Less well known are deposits of sandy, eolian sediment forming extensive plains. An excellent example of such a region is the semi-arid Southern High Plains (northwest Texas and eastern New Mexico). The level landscape of the area was created by deposition of multiple, extensive (≈ 80,000 km 2) sheets of eolian sediment (Blackwater Draw Formation) over the past 1.4+ Ma. This deposit grades from sandy (southwest) to silty and clayey (northeast) and is up to 27 m thick. Surface soils (at least 30,000 and possibly 120,000 years old) are well developed (5YR hues, agrillic horizons, 1-2m thick with prismatic structure, Stage II-III calcic horizons) and are generally Paleustolls and Paleustalfs, with some Paleargids and Haplargids. Morphologic variation is due mainly to textural variation of the eolian parent material, although locally thickness of the parent material and wind erosion and cumulization are important factors, and locally slight variation in effective precipitation may be significant. The Blackwater Draw Formation contains as many as six well-developed buried soils, each formed in individual layers of eolian sediment, similar to or more strongly expressed (2.5YR hues, higher illuvial clay content) than the regional surface soils. The presence of the buried soils indicates that sedimentation was episodic and separated by long periods of relative landscape stability. Eolian processes also appear to have been important during the periods of stability and pedoenesis by providing clayey, calcareous dust that was added to the soil, promoting formation of the argillic and calcic horizons. The sedimentologic and pedologic uniformity of the deposit suggests that the regional environment has not varied significantly during the Quaternary except for periods of increased sedimentation or wind deflation. Underlying the Blackwater Draw Formation is an Upper Tertiary deposit (up to 36 m thick) of eolian sand, silt, and clay (Ogallala Formation). This deposit contains buried soils very similar to those in the Blackwater Draw Formation, suggesting that the geomorphic processes that created the Quaternary landscape of the Southern High Plains began to operate in the late Tertiary, perhaps as much as 11 million years ago.

  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 (63.5°E, 28.0°S, 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. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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)

  20. 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

  1. 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...

  2. 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.

  3. Playa basin development, southern High Plains, Texas and New Mexico

    SciTech Connect

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

    1992-01-01

    More than 20,000 playa basins have formed on fine-grained eolian sediments of the Quaternary Blackwater Draw and Tertiary Ogallala Formations on the High Plains of TX and NM. Numerous hypotheses have been proposed for the development of playa basins: (1) subsidence due to dissolution of underlying Permian bedded salt, (2) dissolution of soil carbonate and piping of clastic sediment into the subsurface, (3) animal activity, and (4) deflation. Evidence of eolian processes includes lee dunes and straightened shorelines on the eastern and southern margins of many playas. Lee dunes, which occur on the eastern side of ca 15% of playa basins and contain sediment deflated from adjacent playas, are cresentic to oval in plain view and typically account for 15--40% of the volume of the playa basin. Quaternary fossil biotas and buried calcic soils indicate that grasslands and semi-arid to aid climatic conditions prevailed as these basins formed. Evidence of fluviolacustrine processes in playa basins includes centripetal drainage leading to fan deltas at playa margins and preserved deltaic and lacustrine sediments. Playa basins expanded as fluvial processes eroded basin slopes and carried sediment to the basin floor where, during periods of minimal vegetation cover, loose sediment was removed by deflation. Other processes that played secondary roles in the development of certain playa basins include subsidence induced by dissolution of deeply buried Permian salt, dissolution of soil carbonate and piping, and animal activity. Two small lake basins in Gray County, TX, occur above strata affected by dissolution-induced subsidence. Dissolution of soil carbonate was observed in exposures and cores of strata underlying playa basins. Cattle, and in the past vast numbers of migrating buffalo, destroy soil crusts in dry playas, making these sediments more susceptible to deflation, and carry sediment out of flooded playas on their hooves.

  4. 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.

  5. 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.

  6. Alluvial plain dynamics in the southern Amazonian foreland basin

    NASA Astrophysics Data System (ADS)

    Lombardo, Umberto

    2016-05-01

    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 and sheet sands triggered by above-normal precipitation events due to La Niña. 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 12 tributaries of the Río Mamoré 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. The data suggest that most of the sediments eroded from the Andes by the tributaries of the Mamoré 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 yearly to decadal timescale, 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.

  7. 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 Niña. 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 Río Mamoré 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 Mamoré 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.

  8. 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 ~200°C, whereas samples from Hole 1268a have been comprehensively serpentinised and then subsequently steatised to talc facies at ~350°C, 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Characterization of Lunar Farside Plains

    NASA Technical Reports Server (NTRS)

    Mest, S.C.; Garry, W. B.; Ostrach, L. R.; Han, S.-C.; Staid, M. I.

    2016-01-01

    The Moon contains broad and isolated areas of plains that have been recognized as mare, cryptomare, impact ejecta, or impact melt. These deposits have been extensively studied on the lunar nearside by remote sensing via telescopes and numerous spacecraft, and in some cases, in situ robotically and by astronauts. Only recently have the deposits on the entire farside been able to be observed and evaluated to the same degree. There are spatially extensive plains deposits located throughout the lunar farside highlands whose formation has remained ambiguous. Many of the plains deposits in the lunar farside highlands display higher albedos than mare materials. Some deposits are located in close proximity to relatively younger impact craters suggesting that plains could be composed of cryptomare or ejecta materials. Some deposits are within the range in which ejecta from large basin-forming events (e.g., SPA and Orientale) likely distributed large amounts of ejecta across the surface. Here we are conducting a series of observations and models in order to resolve the nature and origin of lunar farside plains deposits. Understanding these plains is important for understanding the volcanic and impact histories of the lunar farside, and is important for future mapping and thermal modeling studies.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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 14°N, 130°W 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 (0.4-70.6μg 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.

  3. A data brief on the Smithsonian Abyssal Volcanic Glass Data File

    NASA Astrophysics Data System (ADS)

    Melson, William G.; O'Hearn, Timothy; Jarosewich, Eugene

    2002-04-01

    It is well known that the compositions of glasses quenched by contact with seawater are a good guide to unmodified erupted liquid compositions. We present here an updated version of the Smithsonian Abyssal Volcanic Glass Data File (AVGDF) of the major and minor element compositions of such glasses mainly from seafloor spreading centers determined by electron microprobe analyses. These data help define the major and minor element compositions of the most abundant terrestrial volcanic rock. The AVGDF contains 9050 individual glass analyses along with the sample donor, latitude, longitude, depth, tectonic setting, ship-cruise-dredge, and the major and minor elements SiO2, Al2O3, FeO*, MgO, CaO, Na2O, K2O, TiO2, P2O5, and MnO (for some samples). The samples are from 664 Atlantic, 28 Caribbean, 89 Indian, and 1304 Pacific localities. These include dredge, submersible, DSDP and ODP sites. The data serve to (1) map out and model processes associated with magma generation and fractionation in the asthenosphere and lithosphere beneath seafloor spreading centers and (2) as an educational aide for exercises in the use of such data at the graduate and undergraduate levels in geochemistry, geophysics, and igneous petrology. The extensive polished sample collection is available on loan for additional petrographic (in reflected light) or microbeam analyses.

  4. Sediment flux and the Anthropocene.

    PubMed

    Syvitski, James P M; Kettner, Albert

    2011-03-13

    Data and computer simulations are reviewed to help better define the timing and magnitude of human influence on sediment flux--the Anthropocene epoch. Impacts on the Earth surface processes are not spatially or temporally homogeneous. Human influences on this sediment flux have a secondary effect on floodplain and delta-plain functions and sediment dispersal into the coastal ocean. Human impact on sediment production began 3000 years ago but accelerated more widely 1000 years ago. By the sixteenth century, societies were already engineering their environment. Early twentieth century mechanization has led to global signals of increased sediment flux in most large rivers. By the 1950s, this sediment disturbance signal reversed for many rivers owing to the proliferation of dams, and sediment load reduction below pristine conditions is the dominant signal today. A delta subsidence signal began in the 1930s and is now a dominant signal in terms of sea level for many coastal environments, overwhelming even the global warming imprint on sea level. Humans have engineered how most water and sediment are discharged into the coastal ocean. Hyperpycnal flow events have become more common for some rivers, and less common for other rivers. Bottom trawling is now widespread, suggesting that even continental shelves have received a significant but as yet quantified Anthropocene impact. The Anthropocene attains the level of a geological climate event, such as that seen in the transition between the Pleistocene and the Holocene. PMID:21282156

  5. 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; d’Udekem d’Acoz, Cédric; Nagy, Zoltán 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

  6. 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...

  7. 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)

  8. 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...

  9. 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

  10. 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.

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

    PubMed

    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

  12. 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.

  13. 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.

  14. 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.

  15. Serratotantulus chertoprudae gen. et sp. n. (Crustacea, Tantulocarida, Basipodellidae): A new tantulocaridan from the abyssal depths of the Indian Ocean.

    PubMed

    Savchenko, Alexandra S; Kolbasov, Gregory A

    2009-08-01

    A single tantulus larva was found at the abyssal depth of the Indian Ocean attached to a harpacticoid host of the family Cletodidae. It represents a new genus and species of Tantulocarida, family Basipodellidae. Its ultrastructure was studied with SEM. This genus can be easily distinguished from the other genera of Basipodellidae by the pore pattern, bilobed oral disk with strong longitudinal ridges and the posterior projection of the cephalic shield. A morphological analysis of two related families Basipodellidae and Deothertridae shows that they represent polyphyletic taxa and need further revision. PMID:21669851

  16. Lava Flow on Coastal Plain

    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...

  17. '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.

  18. Lava Flows on Coastal Plain

    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...

  19. 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.

  20. A Seminar in "Plain Doctoring."

    ERIC Educational Resources Information Center

    Billings, J. Andrew; And Others

    1985-01-01

    Plain Doctoring, an elective, preclinical seminar on the phenomenology of the patient and the physician at Harvard Medical School, is described. Home visits serve as the major text for examining the patient's experience of illness and treatment. Readings in the humanities complement the house calls. (Author/MLW)

  1. 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.

  2. 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)

  3. 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...

  4. 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.

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  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. 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.

  13. 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.

  14. 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.

  15. 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.

  16. “First” abyssal record of Stenosemus exaratus (G.O. Sars, 1878) (Mollusca, Polyplacophora) in the North-Atlantic Ocean

    PubMed Central

    Allcock, Louise; Schwabe, Enrico

    2013-01-01

    Abstract 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

  17. "First" abyssal record of Stenosemus exaratus (G.O. Sars, 1878) (Mollusca, Polyplacophora) in the North-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

  18. 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.

  19. Conceptual Hydrogeologic Models for the Eastern Snake River Plain, Idaho

    NASA Astrophysics Data System (ADS)

    Johnson, E. G.; McLing, T. L.; Holt, R. M.

    2001-12-01

    We develop two alternative conceptual hydrogeologic models of the Eastern Snake River Plain (ESRP) aquifer to explain the spatial distribution of strontium and uranium isotope data. The ESRP aquifer flows southwesterly within a northeastern trending structural basin 200 miles long and 50 to 70 miles wide. The basin is composed of 3000 to 10000 feet of Late Cenozoic basalt, eolian sand and loess, and alluvial and lacustrine sediments. Up to 85 percent of the deposit is basalt from hundreds of flows where individual flow areas range from 2 to 900 square miles. The bulk of the recharge for the basin is derived from the Yellowstone Plateau, but other recharge waters with high (>.71100) 87Sr/86Sr ratios enter the basin from a series of alluvial valleys north of the ESRP. The first conceptual model includes regional-scale preferential flowpaths to explain the 87Sr/86Sr distribution, whereas groundwater mixing is the primary process in the second. Common factors in the conceptual model such as faulting, discontinuity of basalt flows, rift zones and sedimentary interbeds in the basin strongly affect groundwater flow. Additionally, a high geothermal gradient in the basin with associated upwelling waters may also influence the distribution of isotope ratios. Other factors also include local sediment sources for high 87Sr/86Sr ratios in the basin itself in addition to that entering form the valleys north of the plain. Estimates of critical time and length scales for each hydrologic process are compared.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Aquatic sediments

    SciTech Connect

    Bonner, J.S.; Autenrieth, R.L.; Schreiber, L. )

    1990-06-01

    The authors present a literature review concerning sediment properties, interactions, and conditions. Topics of discussion include the following: biological activity and toxicity; nutrients; metals; organic compounds; dredging; radionuclides; oxygen demand and organic carbon; mathematical modeling; sediment transport and suspension; and paleolimnology.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Lunar Smooth Plains Identification and Classification

    NASA Astrophysics Data System (ADS)

    Boyd, A. K.; Robinson, M. S.; Mahanti, P.; Lawrence, S. J.; Spudis, P.; Jolliff, B. L.

    2012-12-01

    Smooth plains are widespread on the Moon and have diverse origins. The maria comprise the majority of the smooth plains and are volcanic in origin. Highland smooth plains are patchy, and tend to fill large craters and basins; their origins have eluded unambiguous classification. Prior to the Apollo 16 mission, many workers thought that highland plains were volcanic, possibly more silicic than the maria. However, as the Apollo 16 samples are mostly impact breccias, the highland smooth plains were re-interpreted basin impact ejecta, most likely from the Imbrium and possibly Orientale basins. Conversely, some known non-mare volcanic units, such as the Apennine Bench Formation, contain light plains. These interpretations do not rule out alternate origins for a subset of highland smooth plains, including impact melt or volcanic origins (effusive or pyroclastic). We developed an algorithm to identify smooth plains using topographic parameters from the WAC Global Lunar Digital Terrain Model (DTM) (GLD100), sampled at 333 m/pixel. We classify the smooth plains using the Clementine UVVIS FeO map and photometrically corrected Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) images. Terrain with slopes less than 2° (1 km baseline) and standard deviation of slope less than 0.75° (1 km x 1 km box, n=9) are defined as smooth plains. Highland smooth plains are distinguished from basaltic smooth plains using the following criteria: LROC WAC 643 nm normalized reflectance > 0.056, LROC WAC 321 nm / 415 nm ratio < 0.74, and Clementine FeO < 12 wt.% (excluding Clementine non-coverage areas). The remaining smooth plains are classified as maria and are subdivided into two classes: LROC WAC 321 nm / 415 nm ratio > 0.77 is termed blue maria and a ratio ≤ 0.77 is termed red maria. The automatic classification was limited to the 87% of the Moon covered by photometrically normalized WAC data (60°S to 60°N). The differences between the maria and highland smooth plains deposits were more ambiguous in regions where the Clementine data had gores and albedo of the maria was elevated (i.e. Mare Frigoris and eastern Imbrium basin). For example, Schickard crater hosts a mare deposit that was covered by Orientale basin ejecta. However the cryptomare in Schickard crater were successfully classified and cratering after basin ejecta emplacement can be seen to have excavated the mare material. Known impact melt deposits, such as the melt pool adjacent to King crater, are resolved as highlands smooth plains. Classified Smooth Plains Distribution;

  14. Martian Plain in Late Summer

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Surface Stereo Imager on NASA's Mars Phoenix Lander acquired this view of the textured plain near the lander at about 11 a.m. local Mars solar time during the mission's 124th Martian day, or sol (Sept. 29, 2008).

    The image was taken through an infrared filter. The brighter patches are dustier than darker areas of the surface.

    The last signal from the lander came on Nov. 2, 2008.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  15. 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

  16. 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 (>2 cm s(-1)) compared to unflocculated counterparts (<1.1 cm s(-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

  17. 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 terminology—an 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 ( Ω) 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, regressive, and laterally accreted) typically occur contemporaneously along the same shoreline at different locations.

  18. 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.

  19. 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

  20. SOURCES AND TRANSPORT OF NUTRIENTS IN COASTAL PLAIN WATERSHEDS AND THE EFFECTS OF THESE NUTRIENTS ON ESTUARINE ECOSYSTEMS

    EPA Science Inventory

    Poster for the EPA Science Forum.

    This collaborative research effort assessed how changing coastal plain watershed land-uses influence the delivery of nutrients and sediments to estuaries and subsequently how estauries respond to increasing loads of pollutants.

  1. 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.

  2. Rates of microbial metabolism in deep coastal plain aquifers.

    PubMed

    Chapelle, F H; Lovley, D R

    1990-06-01

    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-C]acetate and [U-C]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 CO(2) production (millimoles of CO(2) per liter per year) based on the oxidation of [2-C] acetate were 9.4 x 10 to 2.4 x 10 for the Black Creek aquifer, 1.1 x 10 for the Middendorf aquifer, and <7 x 10 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 CO(2) 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 to 10 mmol of CO(2) per liter per year. The age of these sediments (ca. 80 million years) and their organic carbon content suggest that average rates of CO(2) production could have been no more than 10 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. PMID:16348227

  3. Rates of Microbial Metabolism in Deep Coastal Plain Aquifers

    PubMed Central

    Chapelle, Francis H.; Lovley, Derek 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 × 10−3 to 2.4 × 10−1 for the Black Creek aquifer, 1.1 × 10−2 for the Middendorf aquifer, and <7 × 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. PMID:16348227

  4. 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...

  5. 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.

  6. 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 Réunion 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 Réunion 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., Bachèlery 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., Bachèlery 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., Bachèlery 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.

  7. Lunar Smooth Plains Identification and Classification

    NASA Astrophysics Data System (ADS)

    Boyd, A. K.; Mahanti, P.; Robinson, M. S.; Lawrence, S. J.; Spudis, P. D.; Jolliff, B. L.

    2012-09-01

    Smooth plains are widespread on the Moon and appear to have diverse origins. The maria comprise the majority of the smooth plains on the Moon and are volcanic in origin. Highland smooth plains are patchy and tend to fill large craters and basins; their origins have eluded unambiguous classification. Prior to the Apollo 16 mission, many workers thought that smooth highland plains were volcanic, possibly more silicic than the basaltic maria [e.g., 1]. However, as the Apollo 16 samples are mostly impact breccias, the highland smooth plains were re-interpreted as being deposits generated by impact events, most likely ejecta from the youngest and largest multi-ring basins, e.g., Imbrium and Orientale [1]. Spectral interpretations by Pieters [2] showed that the highland light plains are not mare basalt, but are composed of significantly more feldspathic, nonmare material [2]. Conversely, some known non-mare volcanic units, such as the Apennine Bench Formation (a deposit of post-Imbrium KREEP basalt [3,4]), contain light plains. These interpretations do not rule out alternate origins for a subset of highland smooth plains, including impact melt or volcanic origins (effusive or pyroclastic). We have developed an algorithm to identify smooth plains using topographic parameters from the WAC Global Lunar Digital Terrain Model (DTM) (GLD100) [5], sampled at 333 m/pixel. We classify the identified smooth plains using the Clementine UVVIS FeO map and photometrically corrected Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) images [6]. In this abstract, we do not address formation mechanisms for the nonmare deposits.

  8. 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.

  9. 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.

  10. 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.

  11. Long-term cycling of mantle Pb: A trace element study of the major mantle mineral phases in abyssal peridotites

    NASA Astrophysics Data System (ADS)

    D'Errico, M. E.; Warren, J. M.; Godard, M.; Ildefonse, B.

    2012-12-01

    Peridotites from ultraslow-spreading ridges preserve signatures of the depleted mantle, while also reflecting the fine scale compositional variability present in the mantle. Traditional analyses of these depleted rocks have focused on clinopyroxene, the main trace element host in spinel peridotites. However, key isotopic systems, such as lead and osmium, are hosted in other phases at low but significant concentration levels. The amount of lead contained within mantle mineral phases is of critical importance to understanding the long-term evolution of the Earth, because the radiogenic isotopes of lead are sensitive to past material cycling and melt-rock interaction. Sulfides have long been suggested as the main host for lead (Pb) in the mantle, but recent studies have demonstrated that Pb is not exclusively hosted in this trace phase. Therefore, the Pb contents of the major peridotite mineral phases (olivine, orthopyroxene, and clinopyroxene) need to be reassessed. Lead concentration data is available for orogenic and xenolith peridotite samples, which are typically more enriched than abyssal peridotites, but these do not provide direct information on the oceanic upper mantle. Direct measurement of Pb in abyssal peridotites has so far been limited because of its extremely low concentration (often <1 ppm). We report Pb and other trace element concentration data for peridotite phases determined by in-situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The LA-ICP-MS technique achieves high spatial resolution combined with detection of low elemental abundances. External precision varied from 6% to 17%, with a precision of 6% for Pb, based on 14 repeat analyses of BIR-1G standard basalt glass. Laser spot size varied from 102-163 microns, which produced a detection limit of 0.42-0.81 ppb for Pb. This study focused on abyssal peridotites from the ultra-slow spreading Gakkel and Southwest Indian Ridges (SWIR), with samples coming from segments with full spreading rates <13 mm/yr. Both Gakkel and SWIR samples are relatively unaltered (<50%) and include some completely fresh samples from Gakkel. A total of five Gakkel and six SWIR peridotites were analyzed by LA-ICP-MS, with a subset of samples also analyzed for bulk rock trace elements by solution ICP-MS. Combined with mineral modal data, this study provides a direct comparison of measured and calculated bulk rock Pb concentrations to determine a comprehensive assessment of the distribution of Pb among upper mantle phases Results indicate that all three of the main mantle mineral phases have similar Pb concentrations, ranging from 2-20 ppb, which corresponds to 0.1-0.01 times the primitive mantle composition. Preliminary calculations suggest that olivine, orthopyroxene and clinopyroxene combined contain enough Pb to match measured bulk rock concentrations. Clinopyroxene typically exhibits a negative Pb anomaly relative to Ce and Nd. In comparison, orthopyroxene, olivine, and bulk rock powders show positive Pb anomalies. Therefore, relative concentrations suggest that orthopyroxene (and to a lesser extent olivine) may host the majority of Pb in the mantle and therefore control the long-term cycling of this important isotopic tracer.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Coastal Evolution of the Mississippi River Chenier Plain: A Geomorphic Process-Response Model

    NASA Astrophysics Data System (ADS)

    McBride, R. A.; Taylor, M. J.; Byrnes, M. R.

    2007-12-01

    Using 28 topographic profiles, air-photo interpretation, and historical shoreline-change data, coastal processes were evaluated along the Mississippi River Chenier Plain to explain the occurrence, distribution, and geomorphic hierarchy of primary landforms. The Louisiana Chenier Plain, 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, less than 30 km wide, and composed of mud deposits capped by marsh interspersed with thin sand- and shell-rich ridges ("cheniers") that are less than 4 m in elevation. Most Chenier-Plain ridges represent open-Gulf paleoshorelines. Past shoreline morphodynamics allow ridges to be classified as transgressive (cheniers), regressive (beach ridges), or laterally accreted (spits). 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 (1979, Marine Geology) and define Chenier Plain as containing at least two or more chenier complexes. As such, a geomorphic hierarchy of landforms is devised relative to dominant coastal process. The Chenier Plain is defined as a first-order feature (5000 km2) composed of three second-order features (30 to 300 km2): 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 long-term evolution of the Chenier Plain, modern tidal-inlet processes operating at Sabine, Calcasieu, and Mermentau river entrances were also examined relative to the inlet-stability ratio. Prior to human modification and stabilization efforts, the Mermentau River entrance is classified as wave-dominated, Sabine Pass as tide-dominated, and Calcasieu Pass as tide-dominated to mixed. Hoyt (1969, American Association of Petroleum Geologists Bulletin) presented the first depositional model for chenier genesis and mudflat progradation. However, Hoyt's model oversimplifies Chenier-Plain evolution because it omits ridges created by non-transgressive processes. Thus, the geologic evolution of the Chenier Plain is more complicated than Mississippi River channel avulsions, and it involved not only chenier ridges (transgressive), but also beach ridges (regressive) and spits (lateral accreted). A six-stage geomorphic process-response model is presented to describe Chenier-Plain evolution primarily as a function of: 1) the balance between sediment supply and energy dissipation associated with Mississippi River channel avulsions, 2) local sediment reworking and lateral transport, 3) tidal-entrance dynamics and sediment trapping, and 4) possibly higher-than-present stands of Holocene sea level. Hence, the development of transgressive, regressive, and laterally-accreted ridges typically occurred contemporaneously along the same shoreline at different locations.

  17. 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

  18. 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.

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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.

  5. 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.

  6. 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)

  7. Targeting the Plains of Venus from Orbit

    NASA Astrophysics Data System (ADS)

    Sharpton, V. L.

    2014-05-01

    Lowland plains house a spectacular array of poorly understood volcanic, tectonic, and impact features that are key to settling the continuing global stratigraphy debate and resolving how the only other accessible Earth-sized planet has evolved.

  8. Great Plains Synfuels` hidden treasures

    SciTech Connect

    Kuhn, A.K.; Duncan, D.H.

    1996-12-31

    The Great Plains Synfuels Project was commissioned 12 years ago. While demonstrating success regarding SNG production, DGC quietly started development of chemical products derived from the liquid by-product streams of Lurgi moving bed gasifiers. Naphtha, crude phenol, and tar oil are the primary by-products, and these contain valuable compounds such as phenol, cresylic acid, catechols, naphthols, fluorene, and BTX. Process technologies have been developed for (1) separation of various impurities from cresylic acid distillate fractions or from whole cresylic acid; (2) extracting cresylic acid from tar oil; (3) conversion of tar pitch to a blend stock used in making anode binder pitch; and (4) separating high purity catechol and methyl catechols. As a result of this work, DGC built a phenol/cresylic acid facility. The cresylic acid side supplies over 10 percent of the world market. The achievement with the catechols is presently leading to bench scale routes for synthesis of chemical intermediates which ultimately may include compounds such as vanillin, pyrogallol, sesamol, homoveratrylamine, and many others, penetrating the fields of flavors and fragrances, pharmaceuticals, pesticides, photographic chemicals, dyes, etc. These efforts stimulate DGC`s growth and will provide an economic uplift. By-products already contribute more than 10% of revenues and are destined to rival natural gas in importance.

  9. 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.

  10. 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.

  11. 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 22°C 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Multisensor characterization of subsurface structures in a desert plain area in Egypt with implications for groundwater exploration

    NASA Astrophysics Data System (ADS)

    Koch, Magaly; Gaber, Ahmed; Geriesh, Mohamed H.; Zaghloul, El-Sayed; Arafat, Sayed M.; AbuBakr, Mostafa

    2013-10-01

    A desert plain in Egypt is being investigated to develop new techniques of multisensor data integration for groundwater exploration. A combination of multispectral, thermal and microwave data (ASTER and PALSAR) and supported by ground measurements (GPR, field spectroradiometry and magnetometry) were used to investigate surface sediment characteristics of the El-Gallaba Plain area, NW of Aswan. This desert plain once hosted an ancestral river system long before the Nile even existed. Nowadays the fluvial deposits are largely covered by Aeolian and gravelly sands and thus only detectible with radar and thermal images. Results show two broad strips of thermal cooling anomalies arranged in a linear fashion and diagonally crossing the alluvial basin. Spectral signatures collected along the linear land surface temperature (LST) anomalies show generally higher reflectance values (higher albedo) than the surrounding sediments. Both, the cooler LST and higher albedo, suggest that the surface sediments within the anomaly strips have lower emissivity values (low heat storage capacity). Furthermore, the homogeneity of these sediments was measured with a ground penetrating radar (GPR) using 250 and 100 MHz shielded antenna. The 12 GPR profiles across the LST anomalies confirmed that the near-surface sediments (up to 10 m depth) consist of thin horizontal layers of sandstone with very low gravel content. They show very different textural and compositional characteristics with respect to the surrounding areas suggesting a different depositional environment. Thus 12 magnetic profiles with 1.5 km average length were acquired across the LST anomalies to investigate deep seated structures. The results confirmed the existence of graben-like structures with a maximum depth to the basement of 150 m and shallower depths toward the edges of the LST anomalies. Consequently, these structurally controlled basins could be promising areas for ground water accumulation and exploration in the El-Gallaba Plain of the Western Desert in Egypt.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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...

  3. 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...

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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).

  11. 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 32°50'N, 124°W, 4400 m deep in the vicinity of the California current and Sta. CNP 31°N, 159°W, 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 = α 0/x(1 - c -xf) t ⩽ β α 0/x c -xt(c βx - 1) t > β where Nt is number of fish present at time t min after bait reaches the sea floor, α0 is initial arrival rate of fish, β is mean fish staying time and x is the bait decay constant. In accordance with optimal foraging theory staying time (β) is longer at Sta. CNP.

  12. 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.

  13. 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.

  14. 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.

  15. Global calcite cycling constrained by sediment preservation controls

    NASA Astrophysics Data System (ADS)

    Dunne, John P.; Hales, Burke; Toggweiler, J. R.

    2012-09-01

    We assess the global balance of calcite export through the water column and burial in sediments as it varies regionally. We first drive a comprehensive 1-D model for sediment calcite preservation with globally gridded field observations and satellite-based syntheses. We then reformulate this model into a simpler five-parameter box model, and combine it with algorithms for surface calcite export and water column dissolution for a single expression for the vertical calcite balance. The resulting metamodel is optimized to fit the observed distributions of calcite burial flux. We quantify the degree to which calcite export, saturation state, organic carbon respiration, and lithogenic sedimentation modulate the burial of calcite. We find that 46% of burial and 88% of dissolution occurs in sediments overlain by undersaturated bottom water with sediment calcite burial strongly modulated by surface export. Relative to organic carbon export, we find surface calcite export skewed geographically toward relatively warm, oligotrophic areas dominated by small, prokaryotic phytoplankton. We assess century-scale projected impacts of warming and acidification on calcite export, finding high sensitive to inferred saturation state controls. With respect to long-term glacial cycling, our analysis supports the hypothesis that strong glacial abyssal stratification drives the lysocline toward much closer correspondence with the saturation horizon. Our analysis suggests that, over the transition from interglacial to glacial ocean, a resulting ˜0.029 PgC a-1decrease in deep Atlantic, Indian and Southern Ocean calcite burial leads to slow increase in ocean alkalinity until Pacific mid-depth calcite burial increases to compensate.

  16. 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.

  17. The Geologic Story of the Great Plains

    USGS Publications Warehouse

    Trimble, Donald E.

    1980-01-01

    The Great Plains! The words alone create a sense of space and a feeling of destiny - a challenge. But what exactly is this special part of Western America that contains so much of our history? How did it come to be? Why is it different? Geographically, the Great Plains is an immense sweep of country; it reaches from Mexico far north into Canada and spreads out east of the Rocky Mountains like a huge welcome mat. So often maligned as a drab, featureless area, the Great Plains is in fact a land of marked contrasts and limitless variety: canyons carved into solid rock of an arid land by the waters of the Pecos and the Rio Grande; the seemingly endless grainfields of Kansas; the desolation of the Badlands; the beauty of the Black Hills. Before it was broken by the plow, most of the Great Plains from the Texas panhandle northward was treeless grassland. Trees grew only along the floodplains of streams and on the few mountain masses of the northern Great Plains. These lush prairies once were the grazing ground for immense herds of bison, and the land provided a bountiful life for those Indians who followed the herds. South of the grasslands, in Texas, shrubs mixed with the grasses: creosote bush along the valley of the Pecos River; mesquite, oak, and juniper to the east. The general lack of trees suggests that this is a land of little moisture, as indeed it is. Nearly all of the Great Plains receives less than 24 inches of rainfall a year, and most of it receives less than 16 inches. This dryness and the strength of sunshine in this area, which lies mostly between 2,000 and 6,000 feet above sea level, create the semiarid environment that typifies the Great Plains. But it was not always so. When the last continental glacier stood near its maximum extent, some 12,000-14,000 years ago, spruce forest reached southward as far as Kansas, and the Great Plains farther south was covered by deciduous forest. The trees retreated northward as the ice front receded, and the Great Plains has been a treeless grassland for the last 8,000-10,000 years. For more than half a century after Lewis and Clark crossed the country in 1805-6, the Great Plains was the testing ground of frontier America - here America grew to maturity (fig. 1). In 1805-7, explorer Zebulon Pike crossed the southcentral Great Plains, following the Arkansas River from near Great Bend, Kans., to the Rocky Mountains. In later years, Santa Fe traders, lured by the wealth of New Mexican trade, followed Pike's path as far as Bents Fort, Colo., where they turned southwestward away from the river route. Those pioneers who later crossed the plains on the Oregon Trail reached the Platte River near the place that would become Kearney, Nebr., by a nearly direct route from Independence, Mo., and followed the Platte across the central part of the Great Plains.

  18. Configuration and hydrology of the Pre-Cretaceous rocks underlying the southeastern Coastal Plain aquifer system

    USGS Publications Warehouse

    Wait, Robert L.; Davis, Marvin E.

    1986-01-01

    An investigation was conduced to define the configuration and hydrology of the rock surface upon which the sand aquifers and confining beds of the Southeastern Coastal Plain aquifer system were deposited. The base of the Southeastern Coastal Plain aquifer system consists of crystalline rocks, saprolite, Paleozoic rocks, Triassic sedimentary rocks (some of which are intruded by basalt), and Jurassic sedimentary rocks. The permeability of these rocks is extremely low and little exchange of water occurs upward to the overlying Cretaceous aquifers. Porosity values are in the range of 10% or less in some of the rocks, indicating little water is stored in them. The transmissivity values are extremely low, indicating very slow movement of water in these rocks. The small volume of water moving at a very slow rate has a long residence time and is usually mineralized to a greater degree than water in the more permeable overlying sediments. (Peters-PTT)

  19. 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.

  20. 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

  1. 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.

  2. Contrasting soils and landscapes of the Piedmont and Coastal Plain, eastern United States

    USGS Publications Warehouse

    Markewich, H.W.; Pavich, M.J.; Buell, G.R.

    1990-01-01

    The Piedmont and Coastal Plain physiographic provinces comprise 80 percent of the Atlantic Coastal states from New Jersey to Georgia. The provinces are climatically similar. The soil moisture regime is udic. The soil temperature regime is typically thermic from Virginia through Georgia, although it is mesic at altitudes above 400 m in Georgia and above 320 m in Virginia. The soil temperature regime is mesic for the Piedmont and Coastal Plain from Maryland through New Jersey. The tightly folded, structurally complex crystalline rocks of the Piedmont and the gently dipping "layer-cake" clastic sedimentary rocks and sediments of the Coastal Plain respond differently to weathering, pedogenesis, and erosion. The different responses result in two physiographically contrasting terrains; each has distinctive near-surface hydrology, regolith, drainage morphology, and morphometry. The Piedmont is predominantly an erosional terrain. Interfluves are as narrow as 0.5 to 2 km, and are convex upward. Valleys are as narrow as 0.1 to 0.5 km and generally V-shaped in cross section. Alluvial terraces are rare and discontinuous. Soils in the Piedmont are typically less than 1 m thick, have less sand and more clay than Coastal Plain soils, and generally have not developed sandy epipedons. Infiltration rates for Piedmont soils are low at 6-15 cm/h. The soil/saprolite, soil/rock, and saprolite/rock boundaries are distinct (can be placed within 10 cm) and are characterized by ponding and/or lateral movement of water. Water movement through soil into saprolite, and from saprolite into rock, is along joints, foliation, bedding planes and faults. Soils and isotopic data indicate residence times consistent with a Pleistocene age for most Piedmont soils. The Coastal Plain is both an erosional and a constructional terrain. Interfluves commonly are broader than 2 km and are flat. Valleys are commonly as wide as 1 km to greater than 10 km, and contain numerous alluvial and estuarine terrace sequences that can be correlated along valleys for tens of kilometers. Coastal Plain soils are typically as thick as 2 to 8 m, have high sand content throughout, and have sandy epipedons. These epipedons consist of both A and E horizons and are 1 to 4 m thick. In Coastal Plain soils, the boundaries are transitional between the solum and the underlying parent material and between weathered and unweathered parent material. Infiltration rates for Coastal Plain soils are typically higher at 13-28 cm/h, than are those for Piedmont soils. Indeed, for unconsolidated quartz sand, rates may exceed 50 cm/h. Water moves directly from the soil into the parent material through intergranularpores with only minor channelization along macropores, joints, and fractures. The comparatively high infiltration capacity results in relatively low surface runoff, and correspondingly less erosion than on the Piedmont uplands. Due to differences in Piedmont and Coastal Plain erosion rates, topographic inversion is common along the Fall Zone; surfaces on Cenozoic sedimentary deposits of the Coastal Plain are higher than erosional surfaces on regolith weathered from late Precambrian to early Paleozoic crystalline rocks of the Piedmont. Isotopic, paleontologic, and soil data indicate that Coastal Plain surficial deposits are post-middle Miocene to Holocene in age, but most are from 5 to 2 Ma. Thus, the relatively uneroded surfaces comprise a Pliocene landscape. In the eastern third of the Coastal Plain, deposits that are less than 3.5 Ma include alluvial terraces, marine terraces and barrier/back-barrier complexes as morphostratigraphic units that cover thousands of square kilometers. Isotopic and soil data indicate that eastern Piedmont soils range from late Pliocene to Pleistocene in age, but are predominantly less than 2 Ma old. Thus, the eroded uplands of the Piedmont "peneplain" comprise a Pleistocene landscape. ?? 1990.

  3. Saline systems of the Great Plains of western Canada: an overview of the limnogeology and paleolimnology

    PubMed Central

    Last, William M; Ginn, Fawn M

    2005-01-01

    In much of the northern Great Plains, saline and hypersaline lacustrine brines are the only surface waters present. As a group, the lakes of this region are unique: there is no other area in the world that can match the concentration and diversity of saline lake environments exhibited in the prairie region of Canada and northern United States. The immense number of individual salt lakes and saline wetlands in this region of North America is staggering. Estimates vary from about one million to greater than 10 million, with densities in some areas being as high as 120 lakes/km2. Despite over a century of scientific investigation of these salt lakes, we have only in the last twenty years advanced far enough to appreciate the wide spectrum of lake types, water chemistries, and limnological processes that are operating in the modern settings. Hydrochemical data are available for about 800 of the lake brines in the region. Composition, textural, and geochemical information on the modern bottom sediments has been collected for just over 150 of these lakes. Characterization of the biological and ecological features of these lakes is based on even fewer investigations, and the stratigraphic records of only twenty basins have been examined. The lake waters show a considerable range in ionic composition and concentration. Early investigators, concentrating on the most saline brines, emphasized a strong predominance of Na+ and SO4-2 in the lakes. It is now realized, however, that not only is there a complete spectrum of salinities from less than 1 ppt TDS to nearly 400 ppt, but also virtually every water chemistry type is represented in lakes of the region. With such a vast array of compositions, it is difficult to generalize. Nonetheless, the paucity of Cl-rich lakes makes the northern Great Plains basins somewhat unusual compared with salt lakes in many other areas of the world (e.g., Australia, western United States). Compilations of the lake water chemistries show distinct spatial trends and regional variations controlled by groundwater input, climate, and geomorphology. Short-term temporal variations in the brine composition, which can have significant effects on the composition of the modern sediments, have also been well documented in several individual basins. From a sedimentological and mineralogical perspective, the wide range of water chemistries exhibited by the lakes leads to an unusually large diversity of modern sediment composition. Over 40 species of endogenic precipitates and authigenic minerals have been identified in the lacustrine sediments. The most common non-detrital components of the modern sediments include: calcium and calcium-magnesium carbonates (magnesian calcite, aragonite, dolomite), and sodium, magnesium, and sodium-magnesium sulfates (mirabilite, thenardite, bloedite, epsomite). Many of the basins whose brines have very high Mg/Ca ratios also have hydromagnesite, magnesite, and nesquehonite. Unlike salt lakes in many other areas of the world, halite, gypsum, and calcite are relatively rare endogenic precipitates in the Great Plains lakes. The detrital fraction of the lacustrine sediments is normally dominated by clay minerals, carbonate minerals, quartz, and feldspars. Sediment accumulation in these salt lakes is controlled and modified by a wide variety of physical, chemical, and biological processes. Although the details of these modern sedimentary processes can be exceedingly complex and difficult to discuss in isolation, in broad terms, the processes operating in the salt lakes of the Great Plains are ultimately controlled by three basic factors or conditions of the basin: (a) basin morphology; (b) basin hydrology; and (c) water salinity and composition. Combinations of these parameters interact to control nearly all aspects of modern sedimentation in these salt lakes and give rise to four 'end member' types of modern saline lacustrine settings in the Great Plains: (a) clastics-dominated playas; (b) salt-dominated playas; (c) deep water, non-stratified lakes; and (d) deep water, "permanently" stratified lakes. PMID:16297237

  4. Hydrogeology and geochemistry of the Ogallala aquifer, Southern High Plains

    NASA Astrophysics Data System (ADS)

    Nativ, Ronit; Smith, D. Anderson

    1987-06-01

    The Ogallala aquifer, which underlies the Southern High Plains, consists of saturated sediments of the Ogallala Formation (Neogene) that are deposited mainly as a set of humid-type alluvial fans derived from the Rocky Mountains. The Ogallala aquifer, the main source of water for the High Plains of Texas and New Mexico, has been severely depleted by extensive pumpage. The hydrology and geochemistry of the aquifer are controlled by the surface topography of the underlying formations and by the thickness and permeability of the alluvial-fan deposits. Axes of three major alluvial fans trend from northwest to southeast; the fans have increased thickness and permeability compared with interfan areas. Flow lines follow the orientation of the alluvial fans. Along these major axes, the saturated section is thick and the chemical composition is relatively constant (CaHCO 3 to mixed-cationHCO 3 water, depleted in δ 18O, δD and tritium). External effects on the chemical composition are less pronounced. The aquifer is thinner and less permeable in areas between major fan axes and along the Caprock Escarpment. In these areas, groundwater can discharge from aquifers in the Cretaceous, Triassic and Permian formations into the Ogallala Formation. Cross-formational movement of water and low permeabilities in the Ogallala Formation result in varying hydrochemical facies and in isotopic compositions that differ from those of the major depositional areas. Areas where upward cross-formational flow occurs are evident by the presence of permeable contacts between the Ogallala and the underlying formations, water-level head differences and chemical and isotopic similarities. Secondary factors that locally affect the chemical composition of Ogallala Formation groundwater include contamination from evaporating saline lakes, agricultural chemicals and fertilizers and oil field brines. Impact of chemicals and brines may increase in the future because much of these contaminants may still be moving through the unsaturated zone toward the water table.

  5. Glaciation of the Coastal Plain of Northern Alaska

    NASA Astrophysics Data System (ADS)

    Jorgenson, M. T.; Shur, Y.

    2008-12-01

    Our 15 years of studies of permafrost soils on the coastal plain of northern Alaska show that it was affected by a continental ice sheet during the last glacial maximum. Evidence for this includes: occurrence of buried glacial basal ice at Barter Island; widespread sandy diamicton from Demarcation Bay to Barrow of late Pleistocene age; orientation of surficial deposits; poorly integrated drainage and gentle ridge and swale topography; the continuity of glacial-related deposits from the coast to the Brooks Foothills; and perennially frozen sediments unlike those of unglaciated Arctic regions. We documented a 10-m-high exposure ~1 km long at Barter Island that had abundant basal glacier ice with large-scale deformation structures, complex ice-contact deposits, and highly deformed bedded silt, sand, and gravel inclusions within the basal ice. Similar ice structures were observed at Prudhoe Bay and Cape Halkett. The glacial till is highly unusual in that it is comprised of massive, non-fossiliferous, brackish, slightly pebbly loamy sand with occasional gravel to cobble-sized clasts. In most areas the till is only 2-5 m thick, although at Barter Island the till was up to 10- m thick. Gravel particles, which comprise 1-5% of the deposits, usually are 0.5-2 cm long, mostly durable chert, highly polished, and frequently cracked off at one end, with the broken face faceted and polished. We believe the material mostly originated from marine deposits on the continental shelf, although rocks of Canadian provenance also occur. Prevalent, large (1-5 m) deformation features of discontinuous yellow oxidized and gray reduced sediment suggest deformation of sediment during collapse of the ice sheet. The sandy till is found along most of the Beaufort coast with the exception of deltas and lagoons and is found inland as much as 80 km. The sandy till is easily eroded, causing the morainal margin to be indistinct and the topography subdued. Previous thermoluminescence dating by Rawlinson (1993) of the sediment indicates it was deposited 20-30 ka BP, and our radiocarbon dating of organic matter at the surface of the sediment indicates that deglaciation and surface stabilization occurred 10-17 ka BP. The glacial deposit is synchronous with the extensive late Pleistocene sand sea in the western Beaufort coastal plain that dates to 9.6-11.4 ka BP (Carter 1981) and the large loess belt along the lower Brooks Foothills that was deposited 20-30 ka BP. The sand sea and loess belt probably were deposited in unglaciated areas by catabatic winds associated with the ice sheet. The presence of an ice sheet that covered the Beaufort Sea and adjacent coast helps explain the lack of typical ice-rich Pleistocene permafrost (yedoma) along the Beaufort coast, the reported lack of permafrost on the outer continental shelf of the Beaufort Sea, and the lack of thaw-lake depressions on the continental shelf. In contrast, these features are abundant on unglaciated portions of the continental shelf in the Russian Arctic and northern Seward Peninsula and adjacent Chukchi Sea. This evidence from terrestrial deposits is consistent with recent evidence of glacial scouring at depths up to 700 m along the continental margin of the Beaufort Sea documented by Engels et al. (2007). We name this glaciation the Kuukpik Glaciation and the deposit the Kuukpik member of the Gubik Formation.

  6. Coastal geomorphology of the Martian northern plains

    NASA Astrophysics Data System (ADS)

    Parker, T. J.; Gorsline, D. S.; Saunders, R. S.; Pieri, D. C.; Schneeberger, D. M.

    1993-06-01

    The paper considers the question of the formation of the outflow channels and valley networks discovered on the Martian northern plains during the Mariner 9 mission. Parker and Saunders (1987) and Parker et al. (1987, 1989) data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains. It is suggested, that of the geological processes capable of producing similar morphologies on earth, lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on Mars.

  7. Coastal geomorphology of the Martian northern plains

    NASA Technical Reports Server (NTRS)

    Parker, Timothy J.; Gorsline, Donn S.; Saunders, Stephen R.; Pieri, David C.; Schneeberger, Dale M.

    1993-01-01

    The paper considers the question of the formation of the outflow channels and valley networks discovered on the Martian northern plains during the Mariner 9 mission. Parker and Saunders (1987) and Parker et al. (1987, 1989) data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains. It is suggested, that of the geological processes capable of producing similar morphologies on earth, lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on Mars.

  8. Soils, plants and climate of the eemian interglacial local landscapes of the Russian plain on base of biogenic silica analysis

    NASA Astrophysics Data System (ADS)

    Golyeva, A.; Sycheva, S.

    2010-12-01

    The Late Pleistocene sediments and soils are exposed in the paleogully (or buried balka) in the Aleksandrov quarry (central part of the European Plain and Middle Russian Upland) The previous Mikulino-Valdai climatic and erosional cycles are illustrated using silica biomorphic analysis. The distributions of sponge spicules and phytoliths have shown dynamic and stable changes during the formation of interglacial pedosediments (OIS 5e). Such changes in alluvial, deluvial and pedological processes formed local landscapes of the European Russia.

  9. Depth-dependent mechanisms that drive land subsidence in Beijing plain, China

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Gong, H.; Wang, R.; Liu, H.; Gu, Z.; Li, X.

    2014-12-01

    The Beijing city, located in the north of North China Plain, China, has undergone severe land subsidence for the last several decades. An integrated subsidence-monitoring program, including leveling survey, borehole extensometer and and Satellite radar interferometry (InSAR) time series analysis, has been designed to meet the needs of mapping and monitoring land subsidence in this region. The monitoring data reveal that the subsidence rates of plain area exhibit significant spatial variability, ranging from 1cm to 15cm/yr. The purpose of this article is to identify and analyze the natural and anthropogenic mechanisms that drive the land subsidence. The movement sources are described and classified by their depth of occurrence. We attribute effects of displacement of the Beijing plain to three major components: (1) shallow components, (2) mediate component, and (3) deep component. Deep components are recognized as tectonic movement of the pre-Tertiary basement. Medium component act at depths generally range of 50 to 450m, and include groundwater exploitation; geochemical compaction, due to the high salt concentration in the deep lacustrine sendiments. Shallow components are related to the settlement of building; natural consolidation, due to the compaction of the loose sediments occurred mainly in the clayey layers of the uppermost 26-m Holocene deposits and organic soil subsidence occurs mainly with drainage and development of peat by land reclamation. The latter factor primarily involve the southeast area of the Beijing plain. The loads of new buildings may also cause short-live compaction of shallow deposits. Groundwater exploitation is thought to be the major factor that contributes to the present land subsidence in the Beijing plain. Settlement caused by buildings loads cannot be omitted in newly developed area, but such phenomenon might be localized.

  10. Project HOTSPOT: Borehole geophysics log interpretation from the Snake River Plain, Idaho

    NASA Astrophysics Data System (ADS)

    Lee, M. D.; Schmitt, D. R.; Chen, X.; Shervais, J. W.; Liberty, L. M.; Potter, K. E.; Kessler, J. A.

    2013-12-01

    The Snake River Plain (SRP), Idaho, hosts potential geothermal resources due to elevated groundwater temperatures associated with the thermal anomaly Yellowstone-Snake River hotspot. Project HOTSPOT has coordinated international institutions and organizations to understand subsurface stratigraphy and assess geothermal potential. Over 5.9km of core were drilled from three boreholes within the SRP in an attempt to acquire continuous core documenting the volcanic and sedimentary record of the hotspot: (1) Kimama, (2) Kimberely, and (3) Mountain Home. The most eastern drill hole is Kimama located along the central volcanic axis of the SRP and documents basaltic volcanism. The Kimberely drill hole was selected to document continuous volcanism when analysed in conjunction with the Kimama drill hole and is located near the margin of the plain. The Mountain Home drill hole is located along the western plain and documents older basalts overlain by sediment. A suite of ground and borehole geophysical surveys were carried out within the SRP between 2010 and 2012. The borehole geophysics logs included gamma ray (spectral and natural), neutron hydrogen index, electrical resistivity, magnetic susceptibility, ultrasonic borehole televiewer imaging, full waveform sonic, and vertical seismic profile. The borehole geophysics logs were qualitatively assessed through visual interpretation of lithological horizons and quantitatively through physical property specialized software and digital signal processing automated filtering process to identify step functions and high frequency anomalies. Preliminary results were published by Schmitt et al. (2012), Potter et al. (2012), and Shervais et al. (2013). The results are continuously being enhanced as more information is qualitatively and quantitatively delineated from the borehole geophysics logs. Each drill hole encounters three principal units: massive basalt flows, rhyolite, and sediments. Basalt has a low to moderate porosity and is low in the natural gamma ray isotopes uranium, thorium, and potassium, while rhyolites produce high total gamma ray responses. Sediment interbeds become apparent as the radioactivity associated with fine grained minerals is significantly higher than that of the host rock (e.g. basalt) due to high hydrogen concentration within the crystal structure of clays. Basalt lacks conductive minerals and results in high resistivity but moderate magnetic susceptibility. The sediments on the other hand are highly conductive and have a low magnetic susceptibility. The basalt and rhyolite units are relatively massive except for fractures which become apparent in the ultrasonic borehole televiewer. Signal is lost in soft sediments resulting in dark regions when full amplitude is displayed for the ultrasonic borehole televiewer. The massive basalt shows short P- and S-wave travel times and therefore a high sonic velocity, while the sediments display only P-wave first arrivals.

  11. Geochemistry of abyssal peridotites from the super slow-spreading Southwest Indian Ridge near 65E: Implications for magma source and seawater alteration

    NASA Astrophysics Data System (ADS)

    Zeng, Zhigang; Wang, Qiaoyun; Wang, Xiaomei; Chen, Shuai; Yin, Xuebo; Li, Zhaoxue

    2012-10-01

    The geochemical characteristics of abyssal peridotite samples from one dredge station (2749.74'S, 6502.14'E, water depth 4473 m) on the super slow-spreading Southwest Indian Ridge (SWIR) near 65E were investigated. Abyssal peridotites recovered from this site were comprised mainly of lizardite, chlorite, carbonate and magnetite with minor amounts of talc, pyroxene phenocrysts and sparse olivines. Serpentinites exhibit talc veins and major serpentine derived from serpentinization with relict olivine granuloblasts. Olivine grains in serpentinites display exsolution lamellae, indicating the occurrence of talc reduction or decompression during seawater-rock interaction. Pyroxene shows clear cleavage in two directions, with clinopyroxene or orthopyroxene exsolution lamellae. By contrast, bulk rock trace element patterns of serpentinites reveal depletion in most incompatible elements, similarly to the depleted mid-ocean ridge basalt mantle composition, indicating that the SWIR peridotites originated from a depleted mantle source magma and have experienced partial melting. Meanwhile, Rb, Ba, U, Pb, Sr, Li anomalies and the Ce/Pb ratio suggest that these serpentinites have been strongly altered by seawater.

  12. 49 CFR 230.102 - Tender plain bearing journal boxes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Locomotives and Tenders Running Gear § 230.102 Tender plain bearing journal boxes. Plain bearing journal boxes... not contain visible free oil; (b) A box lid that is missing, broken, or open except to...

  13. 49 CFR 230.102 - Tender plain bearing journal boxes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Locomotives and Tenders Running Gear § 230.102 Tender plain bearing journal boxes. Plain bearing journal boxes... not contain visible free oil; (b) A box lid that is missing, broken, or open except to...

  14. Geochemical investigations of the oldest (greater than 3800 Ma) abyssal peridotites: implications for early differentiation Earth processes

    NASA Astrophysics Data System (ADS)

    Bennett, V.; Nutman, A.; Friend, C.; Norman, M.

    2003-04-01

    Peridotites from southern West Greenland are currently the best characterised "sample" of the early Archean upper mantle. As such they are the focus of integrated geochemical, geochronological, field investigations and are providing unique insights into early earth processes including the role of impacts, early Earth environments, mantle evolution and mechanisms of crust formation. These rocks are located in the northern part of the early Archean Itsaq Gneiss Complex and occur as <500m long enclaves of variably altered ultramafics containing rare relics of unaltered dunite-harzburgite. The ultramafic enclaves are associated with mafic supracrustal and plutonic rocks, and siliceous metasediments. SHRIMP U/Pb geochronology on igneous zircons from components of the surrounding and intruding orthogneisses, indicate an age for the ultramafic rocks of >3800 Ma (1). The diverse ultramafic and mafic rocks are interpreted as first being tectonically intercalated, and then enclosed in much more voluminous tonalitic rocks during the development of a 3790-3810 Ma composite magmatic arc early in the evolution of the Itsaq Gneiss Complex. Although these samples represent early Archean lithospheric mantle that was trapped within ancient sialic crust during its formation, their chemical affinities (e.g. Si-Al-Mg proportions, ol/opx ratio and mineral compositions) are much closer to modern abyssal peridotites than to cratonic Archean lithospheric mantle as sampled by peridotite xenoliths from southern Africa and Siberia. These samples provide the first direct constraints on mantle redox conditions in the pre-3800 mantle. Their V, MgO, and Ni systematics in comparison with younger mantle suites argue for a mantle environment equal to or even more oxidising than the present upper mantle. The antiquity and chemical integrity of some of these samples is demonstrated by preservation of extremely unradiogenic 187Os/188Os isotopic compositions (2). The age of the peridotites overlaps with estimates for the timing of the lunar terminal cataclysm (3.8-4.0 Ga). The similarity of the highly siderophile element characteristics of these c.3800 Ma samples to modern mantle peridotites, argues for a limited contribution from late impacts, such as those that formed the major lunar basins, to the siderophile element inventory of the Earth's upper mantle. This suggests a benign environment for the development of early terrestrial life. References: 1. Friend C, Bennett V., and Nutman A. (2002) Contrib. Min. Petrol., 143: 71-92. 2. Bennett V., Nutman A., and Esat T. (2002) Geochim. Cosmochim. Acta 66: 2615-2630.

  15. Geomorphology and flood-plain vegetation of the Sprague and lower Sycan Rivers, Klamath Basin, Oregon

    USGS Publications Warehouse

    O'Connor, James E.; McDowell, Patricia F.; Lind, Pollyanna; Rasmussen, Christine G.; Keith, Mackenzie K.

    2015-01-01

    Despite these effects of human disturbances, many of the fundamental physical processes forming the Sprague River fluvial systems over the last several thousand years still function. In particular, flows are unregulated, sediment transport processes are active, and overbank flooding allows for floodplain deposition and erosion. Therefore, restoration of many of the native physical conditions and processes is possible without substantial physical manipulation of current conditions for much of the Sprague River study area. An exception is the South Fork Sprague River, where historical trends are not likely to reverse until it attains a more natural channel and flood-plain geometry and the channel aggrades to the extent that overbank flow becomes common.

  16. Potentiometric surface map for the Cretaceous Aquifer, Virginia Coastal Plain, 1978

    USGS Publications Warehouse

    Hopkins, Herbert T.; Bower, R.F.; Abe, J.M.; Harsh, J.F.

    1980-01-01

    The Atlantic Coastal Plain of Virginia includes 9,600 square miles--all or part of 40 counties east of the Fall Line. The undifferentiated Cretaceous sediments underlying this area are the most productive and extensive source of ground water, from which large withdrawals have been made over the past 40 years. In 1978, withdrawals exceeded 100 million gallons per day. To determine the effect of continued withdrawals, annual synoptic water levels for 1978 were used to prepare a map showing the approximate configuration of the potentiometric surface. (USGS)

  17. Climate vulnerabilities in the southern plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The value of agricultural production in the Southern Plains exceeded $59 bil (2012 Agricultural Census) with livestock accounting for 58% of total agricultural sales. Crop and livestock commodities exceeding $1 bil include wheat, corn, horticultural crops, cotton, hay and forages, sorghum, soybean, ...

  18. Plains Culture Area. Native American Curriculum Series.

    ERIC Educational Resources Information Center

    Ross, Cathy; Fernandes, Roger

    One in a series of Native American instructional materials, this booklet introduces elementary students to the tribes of the plains culture area, extending from the Rocky Mountains to the Mississippi River and from Texas to Canada. Written in simple language, the booklet begins with a brief description of the region--its extreme climate and the…

  19. THE WHITE PLAINS RACIAL BALANCE PLAN.

    ERIC Educational Resources Information Center

    White Plains Public Schools, NY.

    WHITE PLAINS'S SCHOOL RACIAL BALANCE PLAN, IMPLEMENTED IN 1964 IN A CITY DISTRICT OF 8700 PUPILS, 17 PERCENT OF WHOM ARE NEGRO, IS STATISTICALLY ANALYZED AND EVALUATED IN THIS REPORT. TO ASSESS CHILDREN'S ACADEMIC ACHIEVEMENT, STANDARDIZED TEST SCORES FROM WHITE FIFTH GRADE STUDENTS WHO WERE IN THE THIRD GRADE OF THE INTEGRATED RECEIVING SCHOOLS…

  20. Plains Culture Area. Native American Curriculum Series.

    ERIC Educational Resources Information Center

    Ross, Cathy; Fernandes, Roger

    One in a series of Native American instructional materials, this booklet introduces elementary students to the tribes of the plains culture area, extending from the Rocky Mountains to the Mississippi River and from Texas to Canada. Written in simple language, the booklet begins with a brief description of the region--its extreme climate and the

  1. Recent Breakout On The Coastal Plain

    The most recent breakout on the coastal plain, which began on October 15, is still active in several places along its southern margin. The lighter grey lava flows in the middle of the photograph are the extent of the latest activity. The flow is 550 m (1800 ft) long and runs parallel with the tr...

  2. Great plains regional climate assessment technical report

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Great Plains region (GP) plays important role in providing food and energy to the economy of the United States. Multiple climatic and non-climatic stressors put multiple sectors, livelihoods and communities at risk, including agriculture, water, ecosystems and rural and tribal communities. The G...

  3. Guayule production on the southern high plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    New production areas need to be identified for guayule in order to meet the expected world-wide shortage of natural rubber by 2020. One promising area is the Texas High Plains region. For guayule to be grown in this region, more cold tolerant lines need to be identified. The objective of our study w...

  4. Calibrating northern Texas High Plains groundwater model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the Northern High Plains of Texas, irrigated crop production accounts for a major portion of groundwater withdrawals from the Ogallala aquifer. The concern is that diminishing groundwater supplies will severely reduce regional crop and animal production, which in turn would impact the regional ec...

  5. Water Production Functions For High Plains Crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Declining water supplies is the critical resource issue for irrigated agriculture in the High Plains and much of the western U.S. Farmers need to maximize production per unit water consumed to remain economically viable and sustain irrigated agriculture. The Agricultural Research Service (ARS) Wat...

  6. Flood routing in channels with flood plains

    NASA Astrophysics Data System (ADS)

    Mizanur Rashid, R. S. M.; Hanif Chaudhry, M.

    1995-09-01

    Experimental data on unsteady flows in a channel with flood plains obtained in a laboratory test facility are presented. Flood flow at the upstream end of the channel was produced by an electrically actuated butterfly valve in the supply pipe. Water level variations were recorded at nine stations along the channel using capacitance probes and a computerized data acquisition system. Tests were conducted for various initial conditions, and duration and peak of the flood wave. Complete data for two tests are presented which may be used to verify numerical models. A one-dimensional numerical model was developed to simulate flood flow. The model solves the St. Venant equations by using the Preissmann four-point implicit finite-difference scheme. The suitability of two procedures for approximating the channel cross-section is investigated: (1) the flow velocity over the flood plains is negligible, the flood plain acts as storage only and does not contribute to the momentum (the flood plains and the main channel are separated by a vertical line at their interface and the division line is not included in the wetted perimeter); (2) the entire channel section contributes to momentum flux, the entire channel section has uniform average flow velocity and the non-uniform velocity is taken into consideration by a momentum coefficient. Although comparisons between the computed and experimental results are satisfactory in both cases, Approximation (1) gives better results than Approximation (2).

  7. Reading for Young People: The Great Plains.

    ERIC Educational Resources Information Center

    Laughlin, Mildred

    One of five annotated bibliographies that describe books about certain regions of the United States, this compilation focuses on books about the Great Plains. The stated purposes of these regional bibliographies are: (1) to introduce young people living in the subject region to books dealing with their cultural heritage, (2) to help young people…

  8. Second chance for the plains bison

    USGS Publications Warehouse

    Freese, Curtis H.; Aune, K.; Boyd, D.; Derr, James N.; Forrest, Steven C.; Gates, C. Cormack; Gogan, Peter J.; Grassel, Shaun M.; Halbert, Natalie D.; Kunkel, Kyran; Redford, K.

    2007-01-01

    Before European settlement the plains bison (Bison bison bison) numbered in the tens of millions across most of the temperate region of North America. Within the span of a few decades during the mid- to late-1800s its numbers were reduced by hunting and other factors to a few hundred. The plight of the plains bison led to one of the first major movements in North America to save an endangered species. A few individuals and the American Bison Society rescued the remaining animals. Attempts to hybridize cattle and bison when bison numbers were low resulted in extensive cattle gene introgression in bison. Today, though approximately 500,000 plains bison exist in North America, few are free of cattle gene introgression, 96% are subject to anthropogenic selection for commodity production, and only 4% are in herds managed primarily for conservation purposes. Small herd size, artificial selection, cattle-gene introgression, and other factors threaten the diversity and integrity of the bison genome. In addition, the bison is for all practical purposes ecologically extinct across its former range, with multiple consequences for grassland biodiversity. Urgent measures are needed to conserve the wild bison genome and to restore the ecological role of bison in grassland ecosystems. Socioeconomic trends in the Great Plains, combined with new information about bison conservation needs and new conservation initiatives by both the public and public sectors, have set the stage for significant progress in bison conservation over the next few years.

  9. JAPANESE BROME IN THE NORTHERN GREAT PLAINS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Japanese brome (Bromus japonicus) and downy brome (B. tectorum), both introduced annual weedy grasses have invaded thousands of hectares of Northern Great Plains rangeland. Presented is a summary of information derived from a series of studies conducted at the USDA-Agricultural Research Service, Fo...

  10. Venus: Crater distribution and plains resurfacing models

    NASA Astrophysics Data System (ADS)

    Hauck, Steven A.; Phillips, Roger J.; Price, Maribeth H.

    1998-06-01

    Detailed analysis of the distribution of craters on Venus using Mth nearest neighbor analysis, coupled with models based upon surface morphology constraints, indicates that the hypothesis of complete spatial randomness (CSR) cannot be rejected, but is not a unique model of the observed crater distribution. Based on morphologic mapping, the extensive volcanic plains can be divided into four units that have a spread in age of the order of 0.5T (the mean surface age of the planet). This four-unit plains model, along with its derivatives, produce test statistics that indicate such models also cannot be rejected. Further, the probability of obtaining a result at least as extreme as the observed test statistic given that the null hypothesis (model corresponds to Venus) is true is lowest for the CSR model. There is no particular reason to pick a CSR model (along with its implications for catastrophic resurfacing) as a constraint on the evolution of Venus, and there are geological reasons to choose the multiage models. We find that we cannot distinguish statistically among models that have two, three, or four distinct production ages within the plains. However, the hypothesis that the variation in crater density within all of the plains is due to a single random process can be rejected for two reasons. First, the binomial probability that such a process could exist within each of the plains units is <=0.05 except the smallest and youngest unit, PLI. Second, using a chi-squared statistic to test the hypothesis that four plains units have the same age gives a p value of 10-4, indicating confident rejection of the hypothesis. Thus CSR cannot be used as a constraint on models of resurfacing or planetary evolution of Venus because of the non-uniqueness in matching such a model to the observed crater distribution and the strong indication of distinct ages within the plains with a significant spread in age. Geological and geophysical constraints provide our best clues for understanding Venus.

  11. 12 CFR 611.1217 - Plain language requirements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Plain language requirements. 611.1217 Section 611.1217 Banks and Banking FARM CREDIT ADMINISTRATION FARM CREDIT SYSTEM ORGANIZATION Termination of System Institution Status § 611.1217 Plain language requirements. (a) Plain language presentation....

  12. 7 CFR 650.25 - Flood-plain management.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 6 2011-01-01 2011-01-01 false Flood-plain management. 650.25 Section 650.25 Agriculture Regulations of the Department of Agriculture (Continued) NATURAL RESOURCES CONSERVATION SERVICE... Flood-plain management. Through proper planning, flood plains can be managed to reduce the threat...

  13. 12 CFR 611.1217 - Plain language requirements.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 12 Banks and Banking 7 2014-01-01 2014-01-01 false Plain language requirements. 611.1217 Section 611.1217 Banks and Banking FARM CREDIT ADMINISTRATION FARM CREDIT SYSTEM ORGANIZATION Termination of System Institution Status § 611.1217 Plain language requirements. (a) Plain language presentation....

  14. 12 CFR 611.1217 - Plain language requirements.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 6 2011-01-01 2011-01-01 false Plain language requirements. 611.1217 Section 611.1217 Banks and Banking FARM CREDIT ADMINISTRATION FARM CREDIT SYSTEM ORGANIZATION Termination of System Institution Status § 611.1217 Plain language requirements. (a) Plain language presentation....