Sample records for abyssal plain sediments

  1. Miocene sedimentation in the Sigsbee Abyssal Plain, Gulf of Mexico

    E-print Network

    Kuzela, Robert Christian

    1971-01-01

    ~ 10 , :0. , 3 70 3 3i c Jl 3 75 3 2 71 v. " O~ 4 5 C7 r+ 2 2-7 9 '12 ~ 4 2( 7 ? 11 12-1 7 14-3 3 51 4-ray sample 4. ) An interpretation of this depositional environment and the changes that occurred in the basin from Miocene... MIOCENE SEDIMENTATION IN THE SIGSBEE ABYSSAL PLAIN, GULF OF MEXICO A Thesis by ROBERT CHRISTIAN XUZELA Submitted to the Graduate College of Texas A&M University in pa, rtia. l ulfillment of the r quirement for the degree of MASTER...

  2. Hydrolysable amino acids in sediments from the Porcupine Abyssal Plain, northeast Atlantic Ocean

    Microsoft Academic Search

    Ian M. Horsfall; George A. Wolff

    1997-01-01

    The distributions of hydrolysable amino acids have been examined in replicate sediment cores from the Porcupine Abyssal Plain in the northeastern Atlantic Ocean. The amino acid concentrations in surficial sediments ranged from 11.4 to 12.6 ?mol g?1 dry sediment, with a mean of 11.8 ?mol g?1 dry sediment, and decreased with increasing sediment depth, but showed a marked maximum between

  3. Selective preservation of soil organic matter in oxidized marine sediments (Madeira Abyssal Plain)

    Microsoft Academic Search

    Carme Huguet; Gert J. de Lange; Örjan Gustafsson; Jack J. Middelburg; Jaap S. Sinninghe Damsté; Stefan Schouten

    2008-01-01

    In ocean margin sediments both marine and terrestrial organic matter (OM) are buried but the factors governing their relative preservation and degradation are not well understood. In this study, we analysed the degree of preservation of marine isoprenoidal and soil-derived branched glycerol dialkyl glycerol tetraethers (GDGTs) upon long-term oxygen exposure in OM-rich turbidites from the Madeira Abyssal Plain by analyzing

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

    SciTech Connect

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

    1987-05-01

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

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

    Microsoft Academic Search

    Arthur Grantz; R. L. Phillips; M. W. Mullen; S. W. Starratt; G. A. Jones; A. Sathy Naidu; B. P. Finney

    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 clastic 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

  6. The benthic response to the seasonal deposition of phytopigments at the Porcupine Abyssal Plain in the North East Atlantic

    Microsoft Academic Search

    R. Witbaard; G. C. A. Duineveld; J. A. Van der Weele; E. M. Berghuis; J. P. Reyss

    2000-01-01

    We have assessed the impact of seasonal pulses of phyto-detritus towards the bottom of the Porcupine Abyssal Plain (PAP) in the NE Atlantic. Phytopigments were determined (HPLC) in sediment, near-bottom suspended matter and sediment trap samples to obtain an impression of the quantity and quality of the organic material reaching the bottom. Its supposed effect on the benthic community was

  7. 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.

  8. Food web structure of the benthic community at the Porcupine Abyssal Plain (NE Atlantic): a stable isotope analysis

    Microsoft Academic Search

    K. Iken; T. Brey; U. Wand; J. Voigt; P. Junghans

    2001-01-01

    The deep-sea benthic community at the Porcupine Abyssal Plain (NE Atlantic) is a highly food limited system. The annual input of sedimenting phytodetritus, which reaches the sea floor around May\\/June, is the major input of energy. The relative trophic position of the most abundant components of the benthos (90 species or higher taxonomic groups), including meiofaunal, macrofaunal, and megafaunal organisms,

  9. Heavy mineral dispersal patterns of the abyssal plain and Louisiana inner shelf of the Gulf of Mexico

    E-print Network

    Moore, Walter Richard

    1969-01-01

    . , Colorado School of Mines Directed by: Dr. William R. Bryant The Mississippi River system acted as the major source of detrital sediment to the Gulf of. Mexico during both Pleistocene and Holocene times. Sands, silts, and clays from the Mississippi were... provinces are the Sigsbee abyssal plain and the con- tinental shelf of Texas and Louisiana, Because of their proximity to, or available access from, the Mississippi River, both areas derive a considerable amount of sediment from this input source. One...

  10. Heavy mineral dispersal patterns of the abyssal plain and Louisiana inner shelf of the Gulf of Mexico 

    E-print Network

    Moore, Walter Richard

    1969-01-01

    . , Colorado School of Mines Directed by: Dr. William R. Bryant The Mississippi River system acted as the major source of detrital sediment to the Gulf of. Mexico during both Pleistocene and Holocene times. Sands, silts, and clays from the Mississippi were... transported along two main paths; 1) south to southwest into the abyssal plain via the Mississippi F'an, and 2) west along the Louisiana continental shelf. Sediment dispersal, in each direction, is performed by distinctly diff'erent transport mechanisms...

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

    Microsoft Academic Search

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

    2001-01-01

    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

  12. 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.

  13. 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.

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

    Microsoft Academic Search

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

    2001-01-01

    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

  15. 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.

  16. 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...

  17. Changes in kerogen composition across an oxidation front in Madeira Abyssal Plain turbidites as revealed by pyrolysis-GC-MS

    Microsoft Academic Search

    J. S. Sinninghe Damsté; M. J. L. Hoefs; J. W. de Leeuw; G. J. de Lange

    1998-01-01

    Isolated kerogens from Madeira Abyssal Plain turbidite samples were qualitatively and semiquantitatively studied by means of analytical pyrolysis for the effect of oxygen exposure on organic matter preservation. The initial organic matter in the turbidite is very homogeneous and relatively high and offers an ideal case for the study of oxygen effects on organic matter preservation without the usual complications

  18. 34. EXTENTS AND IMPLICATIONS OF ORGANIC MATTER ALTERATION AT OXIDATION FRONTS IN TURBIDITES FROM THE MADEIRA ABYSSAL PLAIN 1

    Microsoft Academic Search

    Gregory Cowie; Stephen Calvert; Gert De Lange; Richard Keil; John Hedges

    Organic geochemical, stable N isotope, and mineral surface area analyses were made on samples spanning oxidation fronts at the tops of organic matter-rich turbidites from Sites 951 and 952 on the Madeira Abyssal Plain (MAP), off northwest Africa. These oxidation fronts permit the isolation of the effects of oxygen exposure on sedimentary organic matter preservation. Organic matter contents of the

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

    E-print Network

    Granot, Roi

    Early India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies 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

  20. Hydrocarbon potential, organic matter diagenesis, sedimentology, and paleoenvironment of upper Mesozoic dark shales, northern Himalayas and Argo abyssal plain

    SciTech Connect

    Thurow, J.; Gibling, M.

    1989-03-01

    The Late Jurassic was a time favorable for the deposition of black shale-type sediments in shallow environments as known from circum-North Atlantic basins, North Sea, and Himalayan Tethys regions. Locally these shales have excellent hydrocarbon source potential. The site of the Spiti shales in the Thakkola region of north-central Nepal provides the opportunity to study a long-term (Oxfordian-Tithonian) stable, shallow, and oxygen-depleted environment. Strata with calcareous benthic communities show that the environment was not anoxic. Organic geochemical and sedimentological analyses on the Spiti shales (Oxfordian-Valanginian) were done to understand the hydrocarbon potential, organic matter diagenesis, sedimentology, and paleoenvironment of this sequence. The depositional environment changed, driven by tectono-eustatic and climatic events, from an open shelf (approximately 250 m) with low amounts of detrital input and rich macrofossil communities to an extremely shallow, partly continental environment with intercalations of quartzose channel fill, silty shales, rare lumachelle layers, and coal seams. Paleocurrents suggest a north-facing continental margin bordering the Tethys Sea. The organic matter changed from marine (Jurassic) to terrestrial in the Cretaceous. Analysis of coeval strata, deposited in the deep-marine environment off the northern Indian shelf (contiguous with the present-day Argo abyssal plain), demonstrates the changing shallow to deep-water hydrocarbon potential. It reflects the more advanced organic matter maturation of the onshore material due to Himalayan tectonics and allows tracing the transport of the organic matter.

  1. The Ionian Abyssal Plain - closure of a remnant Mesozoic oceanic domain: subbottom structures, deep deformation and the Calabrian subduction zone

    NASA Astrophysics Data System (ADS)

    Gallais, F.; Gutscher, M.; Graindorge, D.; Klaeschen, D.

    2010-12-01

    The Ionian Abyssal Plain (IAP), located in the Central Mediterranean area is a deep triangular shaped basin, surrounded by the Calabrian subduction zone to the NW, the Mediterranean Ridge to the NE and the Medina Ridges to the South. Available heat flow measurements show very low values under the Ionian Abyssal plain, suggesing a very old age of 180-200 Ma for the basin. The Bouguer gravity anomaly map shows only a strong positive anomaly in this region and the depth of the Moho is around 16 to 18 km corresponding to high refraction velocities of 8.1-8.2 km/s. The Ionian basin is interpreted as one of the oldest basins in the Mediterranean area, and is thought to represent a remnant part of the Mesozoic Tethyan ocean. Due to the complex relative motions of microplates and blocks, currently, the oceanic lithosphere of the Ionian basin is being simultaneously consumed by subduction to the NE beneath the Hellenic system and to the NW beneath Calabria. We present the most relevant lines of the Archimede multi-channel seismic cruise (1997, R/V Le Nadir) crossing the Ionian Abyssal Plain and the Calabrian subduction zone. Interpretation of this seismic dataset is based on correlation with published seismic data and with ESP results. Beneath the IAP, we identify a thick sedimentary cover (> 5km) from the Jurassic to the Plio-Quaternary in age, which overlies the oceanic basement. The Pre-Messinian sequences are affected by a set of NE/SW striking compressional faults with some syn-tectonic basins NW of these faults. These features are interpreted as a re-activated set of normal faults, possibly formed during rifting and/or subsequent accretion of oceanic crust. The orientation of the subbottom structures and the thickness of the Messinian deposits in the south-eastern part of the IAP may be linked with the presence of these faults and their activity through time. On the Calabrian side of the IAP, the Post-Messinian sequences are accreted to the Calabrian wedge. The weak rheology of the Messinian salts acts as the décollement level in the frontal part of the wedge. Repeated imbricate thrusting within in the Calabrian wedge allows the thickening of the Messinian sediments from 1200 m beneath the IAP to 2400 m 30 km away from the deformation front. A major tectonic structure is imaged east of the Malta Escarpment by the Archimede profiles, it offsets the top Pre-Messinian deposits by 0.5 - 1 sTWT increasing from S to N. This N150°E oriented lithospheric fault is interpreted as a tear fault (“STEP” fault) which has allowed the roll-back of the Ionian slab. The activity of these faults and the Calabrian and Mediterranean subduction zones have been reconstructed through time to reach the present-day physiology of the remnant Ionian basin. The analysis of their activity will allow a better understanding of the closure of the Ionian domain.

  2. Study of abyssal seafloor isolation of contaminated sediments concluded

    SciTech Connect

    Valent, P.

    1998-12-31

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

  3. Temporal variability of near-bottom particle resuspension and dynamics at the Porcupine Abyssal Plain, Northeast Atlantic

    Microsoft Academic Search

    A. Vangriesheim; B Springer; P Crassous

    2001-01-01

    In order to study particle behaviour and its time-variability in the near-bottom layer on the Porcupine Abyssal Plain (48°50?N, 16°30?W, 4850 m), long-term measurements were made of currents, and nephelometry and particle samples were collected using an autonomous lander between mid-1996 and mid-1998. Water samples, collected in the Bottom Nepheloid Layer within 1000 m of the bottom, were filtered for

  4. Food web structure of the benthic community at the Porcupine Abyssal Plain (NE Atlantic): a stable isotope analysis

    NASA Astrophysics Data System (ADS)

    Iken, K.; Brey, T.; Wand, U.; Voigt, J.; Junghans, P.

    The deep-sea benthic community at the Porcupine Abyssal Plain (NE Atlantic) is a highly food limited system. The annual input of sedimenting phytodetritus, which reaches the sea floor around May/June, is the major input of energy. The relative trophic position of the most abundant components of the benthos (90 species or higher taxonomic groups), including meiofaunal, macrofaunal, and megafaunal organisms, was evaluated by stable isotope analysis. The majority of the macro- and megafaunal organisms investigated were deposit feeders ( N=35), less numerous were suspension feeders ( N=17) and predators/scavengers ( N=29). Stable nitrogen values overlap and cover a large range within feeding types, indicating a strong overlap in food sources and a high degree of competition for food. Suspension feeders, mainly cnidarians, have a broad trophic spectrum through feeding on resuspended material as well as capturing pelagic prey; thus during the greater part of the year they can compensate for any shortage in sedimenting fresh POM. Benthic deposit feeders use a variety of feeding strategies to exploit their common food resource. The holothurians, the dominant megabenthic group at PAP, included some highly mobile species, which seem to be quite efficient in tracing and exploiting localised patches of nutritious phytodetritus. Other holothurian species, however, forage successfully on more refractory material, possibly assisted by enteric bacteria. Predators/scavengers fall into two groups, representing two major trophic pathways. Firstly, several of the invertebrate predators prey on deposit-feeding organisms and so are the end consumers of an exclusively benthic food web. Secondly, there are highly mobile benthopelagic predators/scavengers, which are a major link with the benthopelagic food web through their feeding on pelagic prey. Generally, within the benthic community at PAP competition for food is reduced by two alternative evolutionary adaptations: (1) specialization on slightly different food sources and (2) vertical expansion of the trophic spectrum. This leads to a rather complex food web, covering a total ? 15N range of at least 10‰.

  5. Miocene sedimentation in the Sigsbee Abyssal Plain, Gulf of Mexico 

    E-print Network

    Kuzela, Robert Christian

    1971-01-01

    K 7 c1 4-78A Z 4. gaA q 3. 6A g0-10-4 30 25 20 D=grees 15 48 The laminites and pelagites have assemblages of benthonic and planktonic foraminifera from the outer shelf and slope areas. Pyritizied burrows, carbonate hash, and glauconite... was described as a fine grained volcanic rock consisting of predominantly acicular calcic plagio- clase and pyroxene with minor amounts of olivine and quartz. Andesite has a larger crystal size groundmass with sodic plagioclase, a porphyritic texture...

  6. Fate of corrosion products released from stainless steel in marine sediments and seawater. Part 4: Hatteras abyssal red clay

    SciTech Connect

    Schmidt, R.L.

    1982-07-01

    A study in which neutron-activated 347 stainless steel was exposed to surficial sediment from a site in the Hatteras Abyssal Plain of the Northwest Atlantic Ocean is described. This sediment consists of approx. 20% CaCO/sub 3/, which could lead to the formation of calcareous scale on the metal surface and reduce the corrosion rate. The distribution of indigenous metals among different chemical fractions shows that extractable Cr, Mn, Fe, Co, and Zn were associated with amorphous Mn and Fe oxides. Most of the remaining extractable Cr, and about a third of the extractable Cu appear to have been weakly complexed. Major fractions (25 to 36%) of extractable Mn, Co and Ni were present as adsorbed cations. Organic complexation appears to account for a large amount of extractable Fe, Ni, Cu and Zn. Neutron-activated 347 stainless steel specimens were exposed to sediment slurry under aerobic and non-oxygenated conditions for a period of 94 days. The redox potential measurements for air-sparged and N/sub 2/, CO/sub 2/-sparged sediment slurries were +410 and +60 mv, respectively. The presence of 0/sub 2/ produced increased amounts of corrosion products. Chemical extraction showed that relatively labile substances constituted about 84% of the /sup 60/Co activity released in aerated sediment. Relatively labile substances constitute about 82% of the total /sup 60/Co activity released under non-oxygenated conditions. A large fraction of /sup 60/Co which was in the soluble or easily dissolved forms under non-oxygenated conditions appears to have been more strongly adsorbed to the sediment under aerated conditions.

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

    Microsoft Academic Search

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

    2009-01-01

    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

  9. Seismic interpretation of pelagic sedimentation regimes in the 18-53 Ma eastern equatorial Pacific: Basin-scale sedimentation and infilling of abyssal valleys

    NASA Astrophysics Data System (ADS)

    Tominaga, Masako; Lyle, Mitchell; Mitchell, Neil C.

    2011-03-01

    Understanding how pelagic sediment has been eroded, transported, and deposited is critical to evaluating pelagic sediment records for paleoceanography. We use digital seismic reflection data from an Integrated Ocean Drilling Program site survey (AMAT03) to investigate pelagic sedimentation across the eastern-central equatorial Pacific, which represents the first comprehensive record published covering the 18-53 Ma eastern equatorial Pacific. Our goals are to quantify (1) basin-hill-scale primary deposition regimes and (2) the extent to which seafloor topography has been subdued by abyssal valley-filling sediments. The eastern Pacific seafloor consists of a series of abyssal hills and basins, with minor late stage faulting in the basement. Ocean crust rarely outcrops at the seafloor away from the rise crest; both hills and basins are sediment covered. The carbonate compensation depth is identified at 4440 m by the appearance of acoustically transparent clay intervals in the seismic data. Overall, we recognized three different sedimentation regimes: depositional (high sedimentation rate), transitional, and minimal sedimentation (low sedimentation rate) regimes. In all areas, the sedimented seafloor mimics the underlying basement topography, although the degree to which topography becomes subdued varies. Depositional regimes result in symmetric sedimentation within basins and subdued topography, whereas minimal sedimentation regimes have more asymmetric distribution of sediments within topographic lows and higher seafloor relief. Regardless of sedimentation regime, enhanced sediment deposition occurs within basins. However, we observe that basin infill is rarely more than twice as thick as sediment cover over abyssal hills. If this variation is due to sediment focusing, the focusing factor in the basins, as measured by 230Th, is no more than a factor of ˜1.3 of the total vertical particulate rain.

  10. Variability of Total Organic Carbon and Nitrogen in Abyssal Sediments in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Garcia, F. J.; Escobar Briones, E.

    2007-05-01

    Marine sediments represent the largest reservoir of carbon on Earth and an important factor in climate change and allow us to understand the role of the deep sea sediments as a reservoir for the organic carbon and the chemical balance of nitrogen in the basin. This study determined the precision (CV < 3%) and accuracy (CV < 3%) of the elemental analysis carried out that described the variability of total organic carbon (TOC) and nitrogen from samples collected at 115 locations during several cruises in a depth interval of 1025 and 3725 m. The average values recorded for abyssal sediment samples in the SW Gulf of Mexico were 0.95% +/- 0.135% for TOC and 0.12% +/- 0.025% for N with a C/N ratio of 7.96 +/- 1.406. Only samples from chemosynthetic locations (i.e. Chapopote asphalt volcano) recorded S in 3.35% +/- 1.503%. The elemental composition of TOC and N is controlled by depth and follows a polynomial pattern; the C/N followed a sigmoid pattern and together with TOC varies with the distance to the coast and depth. The presence of topographic features in the seafloor influence the distribution of TOC and N.

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

    Microsoft Academic Search

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

    2002-01-01

    The depth-related distribution of seastar (Echinodermata: Asteroidea) species between 150 and 4950m 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

  12. Characterizing the Galicia Bank-Southern Iberia Abyssal Plain rifted margin segment boundary using multichannel seismic and ocean bottom seismometer data

    Microsoft Academic Search

    Stephen A. Clark; Dale S. Sawyer; James A. Austin Jr; Gail L. Christeson; Yosio Nakamura

    2007-01-01

    We present multichannel seismic reflection and ocean bottom seismometer reflection\\/refraction data from ISE-9, a margin-parallel, north–south oriented profile ?200 km west of the Portuguese coast. ISE-9 images the boundary between two distinct segments of the Iberia nonvolcanic rifted margin: Galicia Bank (GB) and the Southern Iberia Abyssal Plain (SIAP). The bathymetric contrast between GB (2 km depth) and SIAP (4–5

  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. ?alitholus (?) 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. 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.

  15. INDEX TO VOLUME 204 abyssal plains, age constraints, B3:45

    E-print Network

    :61; A5:28; A6:39; A7:36; A8:48; A9:46; A10:52; A11:35 anaerobic methane oxidation carbon cycling, A7 fault, sediments, B4:13 ammonium organic matter decomposition, A3:17; A10:14­15 vs. depth, A3:59; A4

  16. 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.

  17. SUBJECT INDEX abyssal plains

    E-print Network

    ­194 clasts, A:282­283 folds, A:143­144 photograph, A:188 tonalite gneiss, A:131 albitization, meta-anorthosite­189 breccia clasts and matrix, A:193­194 clasts, A:282­283 meta-anorthosite, A:131 metagabbro clasts, A:191

  18. 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.

  19. 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...

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

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

  2. 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.

  3. 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.

  4. 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.

  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. Iodine diagenesis in pelagic deep-sea sediments

    Microsoft Academic Search

    H. A. Kennedy; H. Elderfield

    1987-01-01

    Nineteen sediment cores from the Madeira, Seine, Tagus and Nares Abyssal Plains and the Alboran Sea have been used to evaluate the speciation, fluxes and diagenesis of iodine in the deep sea. The sediments have surficial molar I\\/C ratios of 10-30 × 10 -4 in excess of previous reported values for planktonic material (~1 × 10 -4 ). Solid phase

  7. Paleoceanographic interpretations of late Pleistocene to Holocene sedimentological and geochemical proxy-data from SE-Atlantic abyssal plains (Cape, Angola and Guinea Basin)

    NASA Astrophysics Data System (ADS)

    Piller, W. E.; Müllegger, S.

    2009-04-01

    Sediments of the deep abyssal regions of the Southeast Atlantic (Cape Basin, Angola Basin and Guinea Basin) were studied to reconstruct changes in surface and deep water circulation, bioproductivity, and terrigenous sediment flux. To gain these results various sedimentological and geochemical proxies were imposed, including grain size data, foraminiferal fragmentation, carbonate and organic carbon content, as well as stable oxygen and carbon isotope contents of foraminiferal tests. Samples were gained with a multicorer device during Meteor cruise 63/2 (2005) in water depths between ~5,100 and ~5,600 m. The superficial 30 cm of sediment, sampled in 1/2, 1 and 5 cm steps, were processed for this study. The record covers parts of the Pleistocene and Holocene. Even if the sedimentation conditions seem to be similar in the deep-sea regions of the SE-Atlantic there are clear differences between the three sampled locations. This is caused by major changes in deep water corrosiveness leading to fluctuations in the sedimentation rate and carbonate preservation. Cape Basin localities show a pattern of enhanced carbonate preservation around 12 ka BP possibly indicating a delayed Last Glacial Maximum signal. This pattern, which is typical for Indo-Pacific records, clearly points to an influence of Antarctic Bottom Water (AABW) at water depths below 5000 m in the Northern Cape Basin. The non-correlation between carbonate content and grain size distribution is owing to a coccoliths' dominated carbonate production possibly caused by low nutrient availability in surface waters and the higher dissolution susceptibility of foraminiferal tests. Angola Basin samples delivered highest sand contents, a carbonate peak and low organic carbon values around 8.2 ka BP which indicate a reduced bioproduction and nutrient supply in superficial waters. A connection of the 8.2 ka cold event in the northern hemisphere and central African precipitation, equatorial East Atlantic (EEA) upwelling intensity and bioproduction is likely. Thus we expect the observed peak to be a response to the mentioned cold event at about 8.2 ka. The overall sedimentological record indicates that the Northern Angola Basin sedimentation may not be triggered by changes in the influence of North Atlantic Deep Water (NADW) and AABW as observed in the Northern Cape Basin. Therefore, the Walvis Ridge is expected to be an effective barrier for AABW. Studied Guinea Basin sediments (>5000 m) show quite uniform spatial bioproduction caused by the EEA divergence zone overlying the sample sites. Concerning the Holocene, temporal variations are mirrored in the grain size distribution which can possibly be correlated to changes in the thermocline depth. The trend to higher sand contents, especially in the uppermost sediment layers hints to increasing bioproductivity (foraminifers) and thus upwelling intensity during the Holocene. Dissolution, even in the deepest parts of the Guinea Basin, is minimal during the sampled timespan (low foraminferal fragmentation) owing to a predominant influence of NADW north of the Guinea Rise. Differences in the carbonate content are therefore expected to be caused by dilution by terrigenous material delivered by fluvial (Niger River) and eolian (Trade Winds) transport in combination with a change in bioproductivity.

  8. Riverine sediment inflow to Louisiana Chenier Plain in the Northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Rosen, Timothy; Xu, Y. Jun

    2011-12-01

    The Louisiana Chenier Plain is a geomorphologic extension of the Mississippi Deltaic Plain, highly influenced by sediments originating from the Mississippi River. With the Mississippi River unable to avulse closer to the Plain local riverine sediment resources are integral to maintaining the physical and ecological integrity of the estuaries and marshlands. To gain insight into the sediment resources, this study assessed two decades (1990-2009) of discharge and total suspended solids (TSS) of four rivers, Sabine River, Calcasieu River, Mermentau River, and Vermilion River that flow into the Chenier Plain. The study quantified long-term sediment delivery, analyzed seasonal and inter-annual trends of sediment transport, and investigated the effect of hydrometeorological conditions on sediment yields. Total sediment delivery from the rivers over the 20-year period was 6.86 × 10 6 tonnes, with the Sabine River contributing 62% of the sediment load. The Sabine River also showed a significant decreasing trend ( p = 0.03) in annual sediment yield. Long-term trends of sediment loads in all the rivers were influenced by their discharge, not their TSS concentrations. Annual mean sediment load was 342,950 tonnes with higher sediment loading during the winter and spring months and lower during the summer and fall months. Annual sediment inflow has the capacity to create 2.3 × 10 7 m 2 of land to the depth of 1 cm, but most of this sediment is unable to reach the coastline. The greatest asset that these rivers provide for the Chenier Plain is sediment and freshwater for restoration of marsh lost to salinization or inundation.

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

    SciTech Connect

    Stephenson, D.E. [Westinghouse Savannah River Co., Aiken, SC (United States); Coruh, C.; Costain, J.K. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences

    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.

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

    Microsoft Academic Search

    Francis H. Chapelle; Joseph L. Zelibor; D. Jay Grimes; LeRoy L. Knobel

    1987-01-01

    Nineteen cores of unconsolidated Coastal Plain sediments obtained from depths of 14 to 182 m below land surface near Waldorf, Maryland, were collected and examined for metabolically active bacteria. The age of the sediments cored range from Miocene to Early Cretaceous. Acridine orange direct counts of total (viable and nonviable) bacteria in core subsamples ranged from 108 to 104 bacteria\\/g

  11. 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.

  12. Episodic sediment accumulation on Amazonian flood plains influenced by El Niño\\/Southern Oscillation

    Microsoft Academic Search

    Rolf Aalto; Laurence Maurice-Bourgoin; Thomas Dunne; David R. Montgomery; Charles A. Nittrouer; Jean-Loup Guyot

    2003-01-01

    Continental-scale rivers with a sandy bed sequester a significant proportion of their sediment load in flood plains. The spatial extent and depths of such deposits have been described, and flood-plain accumulation has been determined at decadal timescales, but it has not been possible to identify discrete events or to resolve deposition on near-annual timescales. Here we analyse 210Pb activity profiles

  13. Episodic sediment accumulation on Amazonian flood plains influenced by El Niño/Southern Oscillation.

    PubMed

    Aalto, Rolf; Maurice-Bourgoin, Laurence; Dunne, Thomas; Montgomery, David R; Nittrouer, Charles A; Guyot, Jean-Loup

    2003-10-01

    Continental-scale rivers with a sandy bed sequester a significant proportion of their sediment load in flood plains. The spatial extent and depths of such deposits have been described, and flood-plain accumulation has been determined at decadal timescales, but it has not been possible to identify discrete events or to resolve deposition on near-annual timescales. Here we analyse (210)Pb activity profiles from sediment cores taken in the pristine Beni and Mamore river basins, which together comprise 720,000 km2 of the Amazon basin, to investigate sediment accumulation patterns in the Andean-Amazonian foreland. We find that in most locations, sediment stratigraphy is dominated by discrete packages of sediments of uniform age, which are typically 20-80 cm thick, with system-wide recurrence intervals of about 8 yr, indicating relatively rare episodic deposition events. Ocean temperature and stream flow records link these episodic events to rapidly rising floods associated with La Niña events, which debouch extraordinary volumes of sediments from the Andes. We conclude that transient processes driven by the El Niño/Southern Oscillation cycle control the formation of the Bolivian flood plains and modulate downstream delivery of sediments as well as associated carbon, nutrients and pollutants to the Amazon main stem. PMID:14523442

  14. Episodic sediment accumulation on Amazonian flood plains influenced by El Niño/Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Aalto, Rolf; Maurice-Bourgoin, Laurence; Dunne, Thomas; Montgomery, David R.; Nittrouer, Charles A.; Guyot, Jean-Loup

    2003-10-01

    Continental-scale rivers with a sandy bed sequester a significant proportion of their sediment load in flood plains. The spatial extent and depths of such deposits have been described, and flood-plain accumulation has been determined at decadal timescales, but it has not been possible to identify discrete events or to resolve deposition on near-annual timescales. Here we analyse 210Pb activity profiles from sediment cores taken in the pristine Beni and Mamore river basins, which together comprise 720,000km2 of the Amazon basin, to investigate sediment accumulation patterns in the Andean-Amazonian foreland. We find that in most locations, sediment stratigraphy is dominated by discrete packages of sediments of uniform age, which are typically 20-80cm thick, with system-wide recurrence intervals of about 8yr, indicating relatively rare episodic deposition events. Ocean temperature and stream flow records link these episodic events to rapidly rising floods associated with La Niña events, which debouch extraordinary volumes of sediments from the Andes. We conclude that transient processes driven by the El Niño/Southern Oscillation cycle control the formation of the Bolivian flood plains and modulate downstream delivery of sediments as well as associated carbon, nutrients and pollutants to the Amazon main stem.

  15. Early organic diagenesis: The significance of progressive subsurface oxidation fronts in pelagic sediments

    Microsoft Academic Search

    T. R. S. Wilson; J. Thomson; S. Colley; D. J. Hydes; N. C. Higgs; J. Sørensen

    1985-01-01

    Porewater and solid phase geochemical data at two contrasting NE Atlantic stations are reported. Station 10552, on the Cape Verde abyssal plain, is a site of slow pelagic accumulation ( ca . 0.4 cm kyr -1 ). Molecular oxygen is present in the sediment column to at least 2 m, and probably much deeper, labile organic-carbon is almost totally consumed

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

    Microsoft Academic Search

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

    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 10 3 - and 10 4 -fold dilutions

  17. 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

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

    NASA Astrophysics Data System (ADS)

    Fuller, Elizabeth R.; Head, James W.

    2002-10-01

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

  19. Seismic interpretation of pelagic sedimentation regimes in the 18–53 Ma eastern equatorial Pacific: Basin-scale sedimentation and infilling of abyssal valleys

    Microsoft Academic Search

    Masako Tominaga; Mitchell Lyle; Neil C. Mitchell

    2011-01-01

    Understanding how pelagic sediment has been eroded, transported, and deposited is critical to evaluating pelagic sediment records for paleoceanography. We use digital seismic reflection data from an Integrated Ocean Drilling Program site survey (AMAT03) to investigate pelagic sedimentation across the eastern-central equatorial Pacific, which represents the first comprehensive record published covering the 18–53 Ma eastern equatorial Pacific. Our goals are

  20. Abyssal basins and the polar seas

    Microsoft Academic Search

    Philippe Blondel

    \\u000a Abyssal plains and basins are traditionally defined as areas of the deep-ocean floor in which the seabed is flat, with a slope\\u000a of less than 1°, and deeper than 4,500 meters. They were not recognized as distinct physiographic features until the late\\u000a 1940s, and there have been very few systematic investigations of limited areas. As a result, they are among

  1. 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 ?m). 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.

  2. 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

  3. Sediments in Marsh Ponds of the Gulf Coast Chenier Plain: Effects of Structural Marsh Management and Salinity

    Microsoft Academic Search

    François Bolduc; Alan D. Afton

    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;

  4. Vertical distribution of bacterial communities in high arsenic sediments of Hetao Plain, Inner Mongolia.

    PubMed

    Wang, Yanhong; Li, Ping; Jiang, Dawei; Li, Bing; Dai, Xinyue; Jiang, Zhou; Wang, Yanxin

    2014-12-01

    Vertical distribution of bacterial communities was detected in high arsenic (As) sediments in a representative high As area in Inner Mongolia. Nineteen sediment samples were collected from a 30 m borehole and detected by geochemistry and molecular ecological approaches including polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), 16S rRNA gene clone library and 454 pyrosequencing. As contents ranged from 42.1 to 111.3 mg kg(-1) which fluctuated with different depth and significantly high in clay and mild clay sediment samples at depth of 8, 20, 25 and 28 m respectively. The ratios of As(III) to total As generally increased with depth but As(V) dominated in all sediment samples. High concentrations of total As, sulfur, iron and total organic carbon were generally found in clay and low in sand samples. Both DGGE patterns and 454 pyrosequencing results indicated that bacterial communities dynamically diversified with increasing depth and were dominated by Firmicutes, Bacteroidetes, Proteobacteria and Chloroflexi. Most of the sediment samples were dominated by populations including Sporosarcina, Acinetobacter, Pseudomonas, Halomonas, Polaromonas, Paenibacillus and Flavobacterium. These populations were found with high similarities with those microbes capable of denitrification, sulfur oxidation, organic matter degradation and As resistance and reduction. These results implied that microbes might play an important role in As mobilization in the shallow aquifers of Hetao Plain, Inner Mongolia. PMID:25154458

  5. 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.

  6. 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.

  7. Crystallization of abyssal tholeiites

    Microsoft Academic Search

    Fumiko Shido; Akiho Miyashiro; Maurice Ewing

    1971-01-01

    In some abyssal tholeiite magmas having a relatively high content of olivine component, olivine is the first mineral to crystallize. In others having a relatively high content of plagioclase component, plagioclase is the first mineral to crystallize. The rooks of these two groups are called OL- and PL-tholeiites respectively. Continued crystallization drives the residual liquids to the cotectic curve between

  8. Clay minerals from Weichselian glaciolimnic sediments of the S?popolska Plain (NE Poland)

    NASA Astrophysics Data System (ADS)

    Dlugosz, Jacek; Orzechowski, Miroslaw; Kobierski, Miroslaw; Smolczynski, Slawomir; Zamorski, Ryszard

    2009-06-01

    Glaciolimnic deposits sampled from three sedimentation reservoirs located on the S?popolska Plain (northeastern Poland) were investigated. The material under study was deposited in the recession phase of the Pomeranian phase of Vistula (Weichselian) glaciation. The clay fraction was separated by centrifugation after preparation according to Jackson. Mineralogical investigations were done by X-ray diffraction. The analysed deposits had a similar complex composition of clay minerals. The main components were illites mixed with the illite/smectite mineral with percentages < 10 % S. Another part were minerals of the illite/smectite type which had differentiated content of smectite layers (mainly 80-90 % S). There were also chlorite minerals, probably as mixed layer minerals of the chlorite/vermiculite type or HIV with a negligible amount of chlorite layers. The results indicated that all the deposits were of the same age as well as similar deposited material and the samples are different from typical Pomeranian till and typical limnic material of the same age. Small differences observed among the deposits of specific sedimentation reservoirs were probably the result of later processes.

  9. Is long-term change in the abyssal Northeast Atlantic driven by qualitative changes in export flux? Evidence from selective feeding in deep-sea holothurians

    NASA Astrophysics Data System (ADS)

    Wigham, in deep-sea holothurians [review article] B. D.; Hudson, I. R.; Billett, D. S. M.; Wolff, G. A.

    2003-12-01

    The Porcupine Abyssal Plain (NE Atlantic) time-series has shown large, wide-scale, changes in the composition of the benthic community at 4800 m depth (48°50?N, 16°30?W). The abundance of holothurians has increased significantly since 1996 and one species in particular, Amperimarosea, has increased in abundance by three orders of magnitude. Environmental forcing in the form of phytodetrital food supply to the benthos is believed to be driving these changes. Chlorophyll and carotenoid pigments were determined from the gut sediments of seven species of abyssal holothurian, sampled from the Porcupine Abyssal Plain during Autumn 2000 and Spring 2002. These two samples fell either side of the main phytoplankton bloom in the NE Atlantic, providing an opportunity for seasonal comparisons. Significant inter-species differences in pigment profiles were observed among the seven species. Seasonal differences were noted among four species sampled in both time periods. All seven species were collected from the same geographical area and depth. As algal pigments cannot be synthesised by the holothurians, they provide good biomarkers for the composition of the phytodetritus. Differences in pigments from gut sediment profiles are indicative of selective feeding among the holothurians. A.rosea had a gut profile dominated by the pigments zeaxanthin, chlorophyll a/echineone and ?-carotene; these pigments were all present in significantly smaller quantities in the other species. The high quantities of these pigments are indicative of a diet rich in cyanobacteria. The gut sediments of A. rosea also lacked many chloropigments characteristic of other phytoplankton groups, which were observed in the guts of other holothurian species. Ovarian tissue for the five species taken in the pre-spring bloom 2002 sample were examined. All species showed similar carotenoid profiles, dominated by zeaxanthin, echinenone and ?-carotene, all of which are important compounds for reproductive success in echinoderms. The differences in gut pigment profiles highlight the potential for several species of deposit-feeding holothurians to partition the same phytodetrital food source, possibly providing a mechanism for maintaining the high diversity of deposit feeders at abyssal depths. The dominance of reproductively important carotenoids in the guts and gonads of A. rosea may highlight the ability of this species to rapidly utilise any change in the composition of the phytodetrital flux and translate that advantage into a successful reproductive and recruitment event. The results are discussed in relation to work on bathyal holothurians and the potential for food-driven regime shifts in both the abyssal and bathyal Northeast Atlantic.

  10. Organochlorine pesticide concentrations in sediment and amphibian tissue in playa wetlands in the southern high plains, USA.

    PubMed

    Venne, Louise S; Anderson, Todd A; Zhang, Baohong; Smith, Loren M; McMurry, Scott T

    2008-06-01

    Playa wetlands are critical habitat for wildlife in the Southern High Plains (SHP), a region dominated by agriculture. Little information on pesticide levels exists for playas, and thus we measured organochlorine pesticide concentrations in sediment and amphibians collected from playas in cropland and grassland watersheds. Heptachlor, alpha- and beta-BHC, gamma-chlordane, and dieldrin were detected in sediment and/or tissue samples, typically at or below 1 ng/g, dry weight. However, mean DDT and DDE reached 19.7 and 4.1 ng/g in sediments and 6.3 and 2.4 ng/g in tissues, respectively. Land use did not influence pesticide levels in sediment or amphibians. PMID:18498007

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

    PubMed Central

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

    2010-01-01

    Blackwater streams are found throughout the Coastal Plain of the southeastern United States and are characterized by a series of instream floodplain swamps that play a critical role in determining the water quality of these systems. Within the state of Georgia, many of these streams are listed in violation of the 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

  12. Tracing young faults in the Atlantic Coastal Plain sediments: Use of composite refraction-reflection stack sections

    SciTech Connect

    Stephenson, D.E. (Westinghouse Savannah River Co., Aiken, SC (United States)); Coruh, C.; Costain, J.K.; Domoracki, W.J. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States))

    1994-03-01

    Study of the basement faults that penetrate upward into the Atlantic Coastal Plain sediments might constrain the timing of deformation in the form of folding and faulting. Composite refraction-reflection stack sections are produced by reprocessing available seismic data to investigate basement faults that penetrate upward into Atlantic coastal Plain sediments near Aiken, South Carolina. The purpose of the refraction stack was to recover events as shallow as possible while reprocessing of the reflected arrivals was designed to image reflections from depths as deep as the Moho. Seismic data processing for refracted head wave arrivals produced refraction stack sections that constrain the upward penetration depth of the faults image and interpreted in crystalline basement and Triassic sediments. The faulting, in general, is not limited to the Triassic Dunbarton basin, which is interpreted to be bounded by reverse (at the NW) faults. Other faults are also imaged in the sediments and extend upward. Displacement imaged along faults decreases rapidly upward from the basement. The composite refraction-reflection stack sections exhibit that the depth of upward penetration of the faults varies: most of them are associated with deformation at times as small as 50 ms two-way time (about 25 m), while two faults (the Atta and Steel Creek) penetrate to depths that include a shallow refracted horizon. Imbricated upper crustal structures, the buried Triassic Dunbarton basin, and reverse and normal faults suggest that the subsurface is overprinted by compression followed by extension and later by compression.

  13. Quaternary deposits and sediment fluxes at the toe of the Barbados Accretionary Prism

    NASA Astrophysics Data System (ADS)

    Massé, L.; Faugères, J. C.; Gonthier, E.

    1995-06-01

    Sedimentologic and stratigraphic investigations on four cores collected close to the front of the Barbados accretionary prism provided information about the Quaternary depositional processes and sediment fluxes in the region. The morphology of the prism is marked by N—Soriented anticlinal ridges separated by troughs. The deposits are hemipelagic on top of the ridges and in the abyssal plain, with a mean global flux of 1.35 1.40 g cm-2 10-3 yr. The carbonate flux decreases from the prism to the abyssal plain (0.49 and 0.3 g cm-2 10-3 yr, respectively). Terrigenous material is provided by distal turbiditic plumes. It decreases slightly from the abyssal plain to the prism (1.06 and 0.9 g cm-2 10-3 yr, respectively). During cold climatic stages, it is up to 1.4 g cm-2 10-3 yr. The global flux is much higher (7.1 g cm-2 10-3 yr) in the interridge troughs, which act as sediment traps for distal turbidity currents.

  14. 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.

  15. GEOSTAR: a GEophysical and Oceanographic STation for Abyssal Research

    NASA Astrophysics Data System (ADS)

    Beranzoli, L.; De Santis, A.; Etiope, G.; Favali, P.; Frugoni, F.; Smriglio, G.; Gasparoni, F.; Marigo, A.

    1998-06-01

    The GEOSTAR is a technological and scientific project aimed at the realisation of an autonomous benthic observatory able to perform long-term, continuous and integrated geophysical and environmental measurements in deep seafloors. The observatory is conceived to be a node of existing and future geophysical monitoring networks, making possible their extension offshore. The GEOSTAR observatory prototype hosts sensors for seismic, geomagnetic, gravimetric, geochemical and oceanographic researches up to abyssal depths (4000 m). The first 1-year scientific mission is foreseen within the end of the millennium in the abyssal plain (3400 m) of the Southern Tyrrhenian Sea, where key information about the geodynamics and oceanography of the whole Mediterranean basin can be acquired.

  16. Late Hesperian plains formation and degradation in a low sedimentation zone of the northern lowlands of Mars

    USGS Publications Warehouse

    Rodriguez, J.A.P.; Tanaka, K.L.; Berman, D.C.; Kargel, J.S.

    2010-01-01

    The plains materials that form the martian northern lowlands suggest large-scale sedimentation in this part of the planet. The general view is that these sedimentary materials were transported from zones of highland erosion via outflow channels and other fluvial systems. The study region, the northern circum-polar plains south of Gemini Scopuli on Planum Boreum, comprises the only extensive zone in the martian northern lowlands that does not include sub-basin floors nor is downstream from outflow channel systems. Therefore, within this zone, the ponding of fluids and fluidized sediments associated with outflow channel discharges is less likely to have taken place relative to sub-basin areas that form the other northern circum-polar plains surrounding Planum Boreum. Our findings indicate that during the Late Hesperian sedimentary deposits produced by the erosion of an ancient cratered landscape, as well as via sedimentary volcanism, were regionally emplaced to form extensive plains materials within the study region. The distribution and magnitude of surface degradation suggest that groundwater emergence from an aquifer that extended from the Arabia Terra cratered highlands to the northern lowlands took place non-catastrophically and regionally within the study region through faulted upper crustal materials. In our model the margin of the Utopia basin adjacent to the study region may have acted as a boundary to this aquifer. Partial destruction and dehydration of these Late Hesperian plains, perhaps induced by high thermal anomalies resulting from the low thermal conductivity of these materials, led to the formation of extensive knobby fields and pedestal craters. During the Early Amazonian, the rates of regional resurfacing within the study region decreased significantly; perhaps because the knobby ridges forming the eroded impact crater rims and contractional ridges consisted of thermally conductive indurated materials, thereby inducing freezing of the tectonically controlled waterways associated with these features. This hypothesis would explain why these features were not completely destroyed. During the Late Amazonian, high-obliquity conditions may have led to the removal of large volumes of volatiles and sediments being eroded from Planum Boreum, which then may have been re-deposited as thick, circum-polar plains. Transition into low obliquity ~5. myr ago may have led to progressive destabilization of these materials leading to collapse and pedestal crater formation. Our model does not contraindicate possible large-scale ponding of fluids in the northern lowlands, such as for example the formation of water and/or mud oceans. In fact, it provides a complementary mechanism involving large-scale groundwater discharges within the northern lowlands for the emplacement of fluids and sediments, which could have potentially contributed to the formation of these bodies. Nevertheless, our model would spatially restrict to surrounding parts of the northern plain either the distribution of the oceans or the zones within these where significant sedimentary accumulation would have taken place. ?? 2010 Elsevier Inc.

  17. 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. [Univ. of Texas, Austin, TX (United States). Texas Archeological Research Lab.; Holliday, V.T. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Geography

    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.

  18. 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.

  19. Polychlorinated dibenzo-p-dioxin and dibenzofuran concentration profiles in sediments and flood-plain soils of the Tittabawassee River, Michigan.

    PubMed

    Hilscherova, Klara; Kannan, Kurunthachalam; Nakata, Haruhiko; Hanari, Nobuyasu; Yamashita, Nobuyoshi; Bradley, Patrick W; McCabe, John M; Taylor, Allan B; Giesy, John P

    2003-02-01

    Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in sediments and flood-plain soils collected along the Tittabawassee River in Michigan ranged from 102 to 53,600 pg/g, dry wt. Mean PCDD/PCDF concentrations in downstream sediment and soil were from 10- to 20-fold greater than those found at locations upstream of Midland, Michigan. Concentrations of PCDD/PCDF in sediments and flood-plain soils from the Tittabawassee watershed were comparable to those found in industrialized areas such as the Housatonic and lower Passaic Rivers in the U.S. Concentrations of PCDDs/PCDFs in soil and sediment were not correlated with total organic carbon (TOC) in sediments or soils. OCDD and 2,3,7,8-TeCDF were the predominant congeners in sediment/soil collected from locations downstream of Midland, Michigan. Principal component analysis of the PCDD/PCDF congener profile suggested the presence of sources originating from a mixture of chlorophenol and other chlorinated compound production. Mass balance analysis of TCDD equivalents (TCDD-EQs) derived from H4IIE-luc bioassay of sediment extracts and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) estimated from instrumental analysis suggested that PCDDs/PCDFs were the major dioxin-like compounds present in sediments. A significant correlation existed between bioassay-derived TCDD-EQs and instrumentally measured TEQs (r2 = 0.94). PMID:12630460

  20. Authigenic uranium in Atlantic sediments of the last glacial stage — a diagenetic phenomenon

    NASA Astrophysics Data System (ADS)

    Thomson, J.; Wallace, H. E.; Colley, S.; Toole, J.

    1990-05-01

    Cores from three different Atlantic localities (equatorial, Cape Verde Rise and Porcupine Abyssal Plain) are shown to have anomalous high U contents (5-8 ppm total) in sediments laid down during the last glacial stage (12-24 ky BP). Radiocarbon data demonstrate that the sediments hosting the peak U levels were accumulated at rates similar to those immediately above and below. All the cores exhibit maximum Mn levels, characteristic colour changes, and maximum U levels in the same sequence with increasing depth in core. On the evidence of the similarities between the cores, and pore water U data from a Porcupine Abyssal Plain site, it is proposed that the authigenic U enrichments are syndiagenetic and possibly active. No correlation is observed between sediment authigenic U and C org contents. The source of enrichment is bottom water U which has diffused downwards into the sediments to be sorbed at a particular redox level, located 10-30 cm below the oxic/post-oxic boundary marked by the colour change. The magnitude of the enrichments is caused by the persistence of this boundary at a particular level as a result of the decrease in mean sediment accumulation rate between the last glacial stage (5.2 up to at least 19.1 cm ky -1) and the Holocene (2.2-4.1 cm ky -1). Similar accumulation rate contrasts are expected to be widespread in the Atlantic, and the implications for previous reported work, particularly from the Mid-Atlantic Ridge, are discussed.

  1. 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.

  2. Assessing the accuracy of thermoluminescence for dating baked sediments beneath late Quaternary lava flows, Snake River Plain, Idaho

    SciTech Connect

    Forman, S.L.; Pierson, J. [Ohio State Univ., Columbus, OH (United States)] [Ohio State Univ., Columbus, OH (United States); Valentine, G. [Los Alamos National Lab., NM (United States)] [and others] [Los Alamos National Lab., NM (United States); and others

    1994-08-10

    Baked sediments beneath lava flows on the Snake River Plain, Idaho, with independent age control by either {sup 14}C or K/Ar dating were analyzed to evaluate the accuracy of the thermoluminescence (TL) technique. The age of flows ranges from {approximately}2 to 100 ka and multiple TL analyses by the total bleach method yielded ages that overlap at one sigma with independent chronologic control. The TL signal of one sample of baked sediment beneath a lava flow with an inferred age of at least 641 {plus_minus} 54 ka was near saturation, perhaps reflecting a relatively high environmental dose rate, and is not datable by TL. This study underscores several major limitations of luminescence geochronology, the natural spatial and temporal variability in environmental radioactivity and the susceptibility of silicate minerals to the growth and retention of a luminescence signal. Despite these limitations, the results demonstrate the utility of luminescence geochronology to date volcanic eruptive events during the Quaternary. 39 refs., 7 figs., 4 tabs.

  3. Infaunal density, biomass and bioturbation in the sediments of the Arctic Ocean

    Microsoft Academic Search

    Lisa M. Clough; William G. Ambrose; J. Kirk Cochran; Christina Barnes; Paul E. Renaud; Robert C. Aller

    1997-01-01

    Little is known about the benthic communities of the Arctic Ocean's slope and abyssal plains. Here we report on benthic data collected from box cores along a transect from Alaska to the Barents Abyssal Plain during the Arctic Ocean Section of 1994. We determined: (1) density and biomass of the polychaetes, foraminifera and total infauna; (2) concentrations of potential sources

  4. 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

  5. Numerical constraints of current rates of subsidence due to compaction of shallow sediments in the Louisiana coastal plain

    NASA Astrophysics Data System (ADS)

    Meckel, T. A.; ten Brink, U.; Williams, S. J.

    2005-12-01

    The conversion of wetlands to open water occurs at alarming rates in coastal Louisiana, where relative sea level rise is ~1cm/yr. The value of wetlands for buffering storm surge and providing habitat has prompted efforts to identify and mitigate subsidence (and other) processes that cause wetland loss. Quantitative estimates of the relative contributions of geologic and anthropogenic processes to subsidence of coastal Louisiana are largely unknown. Such information is critical for ongoing regional wetland restoration. We use a stochastic methodology (see related abstract) to estimate the probable contribution of shallow (<200 m) natural compaction to present subsidence rates in the Louisiana coastal plain. Knowledge of present stratigraphic thickness and accumulation time at a location allows the cumulative distribution and probable maximum and minimum rates of surface elevation change due to compaction to be predicted. We then convert present thickness data above the late Wisconsin unconformity in coastal Louisiana to probable ranges of present rates of surface displacement due to compaction, assuming a constant accumulation rate. If regional average accumulation rates have been ~10 mm/yr, 90% of our calculated rates of land surface elevation change due to compaction of post late-Wisconsin sediments are <~2 mm/yr. If regional average accumulation rates have been closer to 40 mm/yr, 90% of compaction rates are likely <~4 mm/yr. We provide graphic solutions for assessing maximum probable surface-displacement rates due to compaction at any site of interest, provided fundamental stratigraphic characteristics are moderately well known. Our methods enable the identification of locations where observed subsidence rates are unlikely to result from post late-Wisconsin unconformity sediment compaction alone for further investigation. Observed subsidence rates greater than the 90th percentile of the calculated compaction rate distributions likely reflect processes in addition to compaction of post-late Wisconsin sediments.

  6. 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.

  7. 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.

  8. 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...

  9. 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 ...

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

    NASA Astrophysics Data System (ADS)

    Deville, E.

    2011-12-01

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

  11. 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.

  12. Importance of geomorphology and sedimentation processes for metal dispersion in sediments and soils of the Ganga Plain: identification of geochemical domains

    Microsoft Academic Search

    A. A. Ansari; I. B. Singh; H. J. Tobschall

    2000-01-01

    The Ganga Plain, one of the largest alluvial plains of the earth is under severe environmental stress due to rapid industrial and urban development and exploding population growth. Disposal of industrial and urban wastes and the ignorance of their management have resulted severe environmental problems, especially metal pollution. In the present study, an attempt is made to understand the transport

  13. 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).

  14. 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.

  15. 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.

  16. Census of Marine Life: Census of the Diversity of Abyssal Marine Life

    NSDL National Science Digital Library

    A field project of the multi-national Census of Marine Life, the Census of the Diversity of Abyssal Marine Life (CeDAMar) was created to document "actual species diversity of abyssal plains as a basis for global change research and for a better understanding of historical causes and actual ecological factors regulating biodiversity." This site provides Deep-Sea researchers with a forum for discussion and information-sharing. Specifically, this forum allows "researchers to exchange experiences and results from the Projects united under the umbrella of CeDAMar." Additionally, this site links to relevant Projects, Articles, News, FAQ, and Web links, and provides a search engine for locating specific information about CeDAMar.

  17. 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.).

  18. 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.

  19. 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.

  20. Estimates of historic, present, and future rates of surface displacement due to hydrodynamic autocompaction of Holocene sediments in the Louisiana delta plain

    NASA Astrophysics Data System (ADS)

    Meckel, T. A.; ten Brink, U.; Williams, S.

    2005-05-01

    Subsidence and resulting rapid relative sea level rise and wetland loss in Louisiana have been attributed to natural geologic (isostatic sediment loading, faulting, sediment compaction, dewatering) and human (subsurface fluid withdrawal, salt mining) processes, but we lack quantitative estimates of the relative contributions of each factor, and their role in future subsidence is largely unknown. Such information is critical for ongoing regional-scale wetland restoration plans. We attempt to isolate the component of subsidence attributable to compaction (gravity-driven reduction in porosity and resulting surface displacement) of sediments deposited above the Lower Wisconsin unconformity (<~18 k.y.) in the delta region. One-dimensional, multi-lithology compaction models based on Darcy flow and Terzaghi effective stress principles are solved using a finite difference technique, allowing calculations of cumulative sedimentation and surface displacement, as well as historic, present, and future (in the absence of further loading) rates of vertical surface displacement. Detailed modeling of the USGS/LGS P-1-90 boring (47 m recovered, 13 radiocarbon dates), at the LUMCON facility in Cocodrie, revealed relationships among sediment type, geotechnical parameters, depositional rate, time, and compaction rate. Results indicate that, regardless of variations in depositional history, present rates of surface displacement can be constrained by two end-member stratigraphic models: 100% sand and 100% mud. Shallow (0-200 m) borehole data from the U.S. Army Corps of Engineers have been used to interpolate a regional isopach of Holocene sediments for the Mississippi River alluvial valley and adjacent delta plain and to extend lithologic generalizations (topstratum/substratum) and suitable geotechnical parameters from the USGS boring. Regional-scale analysis allows comprehensive testing of the hypothesis that higher subsidence rates in the alluvial valley can be attributed to compaction of thicker Holocene deposits.

  1. 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.

  2. 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.

  3. 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.

  4. Surface sediments in the marsh-sandy land transitional area: sandification in the western Songnen Plain, China.

    PubMed

    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

  5. Early organic diagenesis: The significance of progressive subsurface oxidation fronts in pelagic sediments

    NASA Astrophysics Data System (ADS)

    Wilson, T. R. S.; Thomson, J.; Colley, S.; Hydes, D. J.; Higgs, N. C.; Sørensen, J.

    1985-03-01

    Porewater and solid phase geochemical data at two contrasting NE Atlantic stations are reported. Station 10552, on the Cape Verde abyssal plain, is a site of slow pelagic accumulation ( ca. 0.4 cm kyr -1). Molecular oxygen is present in the sediment column to at least 2 m, and probably much deeper, labile organic-carbon is almost totally consumed in the upper few centimetres of the sediment. By contrast, at station 10554 on the Madeira abyssal plain, the pelagic sequence has been interrupted by the occasional deposition of organic-rich turbidites. Porewater oxygen and nitrate profiles show that subsurface organic metabolism of the organic-carbon associated with the uppermost turbidite layer is a significant fraction of the overall metabolism in the sediment column. This metabolism occurs at a relatively thin reaction front which progresses deeper into the turbidite with time. This phenomenon exerts a controlling influence on the present nutrient profile and redox succession. In a less extreme form, substrate distributions of this latter type are not uncommon in Atlantic sediments. A model has been developed which is controlled by both oxygen and nitrate data. This model permits a vertical profile of metabolic activity to be derived, and also gives estimates of the reaction rate constants and solid phase mixing rates at these two contrasting stations. About 30% of the total activity at station 10554 is located within the turbidite at the deepening reaction front; this is a non-steady-state condition. In fact, it is found that the integrated metabolic activity at the two stations is not dissimilar ( ca. 1-2 × 10 -13moles cm -2 sec -1). The striking differences in redox profile are therefore primarily attributable to differences in the distribution of metabolic activity within the column.

  6. 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...

  7. Abyssal food limitation, ecosystem structure and climate change

    Microsoft Academic Search

    Craig R. Smith; Fabio C. De Leo; Angelo F. Bernardino; Andrew K. Sweetman; Pedro Martinez Arbizu

    2008-01-01

    The abyssal seafloor covers more than 50% of the Earth and is postulated to be both a reservoir of biodiversity and a source of important ecosystem services. We show that ecosystem structure and function in the abyss are strongly modulated by the quantity and quality of detri- tal food material sinking from the surface ocean. Climate change and human activities

  8. Manifestations of hydrothermal discharge from young abyssal hills on the fast-spreading East Pacific Rise flank

    NASA Astrophysics Data System (ADS)

    Haymon, Rachel M.; MacDonald, Ken C.; Benjamin, Sara B.; Ehrhardt, Christopher J.

    2005-02-01

    Spectacular black smokers along the mid-ocean-ridge crest represent a small fraction of total hydrothermal heat loss from ocean lithosphere. Previous models of measured heat flow suggest that 40% 50% of oceanic hydrothermal heat and fluid flux is from young seafloor (0.1 5 Ma) on mid-ocean-ridge flanks. Despite evidence that ridge-flank hydrothermal flux affects crustal properties, ocean chemistry, and the deep-sea biosphere, few ridge-flank vent sites have been discovered. We describe the first known seafloor expressions of hydrothermal discharge from tectonically formed abyssal hills flanking a fast-spreading ridge. Seafloor manifestations of fluid venting from two young East Pacific Rise abyssal hills (0.1 Ma at 10°20?N, 103°33.2?W; 0.5 Ma at 9°27?N, 104°32.3?W) include fault-scarp hydrothermal mineralization and macrofauna; fault-scarp flocculations containing hyperthermophilic microbes; and hilltop sediment mounds and craters possibly created by fluid expulsion. These visible features can be exploited for hydrothermal exploration of the vast abyssal hill terrain flanking the mid-ocean ridge and for access to the subseafloor biosphere. Petrologic evidence suggests that abyssal hills undergo repeated episodes of transitory fluid discharge, possibly linked to seismic events, and that fluid exit temperatures can be briefly high enough to transport copper (?250 °C).

  9. Extreme 2002: Mission to the Abyss

    NSDL National Science Digital Library

    This is the expedition page of the 2002 Mission to the Abyss. Developed by the University of Delaware Graduate College of Marine Studies, the site highlights the mission and crew, seafloor geology, creature features, and high-tech tools used in the study. This interactive website allows students to explore the submersible Alvin, find out how hydrothermal vents form, define the deep ocean, study plate tectonics, and meet hydrothermal vent organisms. The site includes extreme experiments, including: compression of a fluid vs. a gas, rising under pressure, my cup shrinks, soda squeeze, and plant pressure.

  10. Modern alluvial fan and deltaic sedimentation in a foreland tectonic setting: the Lower Mesopotamian Plain and the Arabian Gulf

    NASA Astrophysics Data System (ADS)

    Baltzer, Frédéric; Purser, Bruce H.

    1990-05-01

    The Arabo-Persian Gulf, generally considered as a classical carbonate basin, in fact also includes important terrigenous systems whose nature and geometry are related closely to the tectonic framework. The Gulf is bordered along its northeastern periphery by an active alpine system which constitutes a major source of both siliceous and calcareous detritus. There are four types of terrigenous discharge which are classified according to their structural relationships. Numerous alluvial fans terminate ephemeral consequent streams draining the flanks of anticlines forming the external parts of the Zagros Mountain belt. Alluvial-fan deltas studied in detail in southeastern Iran terminate semi-permanent streams which flow along major synclinal axis. They are composed mainly of fine carbonate detritus, part of which accumulates as spectacular marine mud banks. Two major types of delta occur. Relatively small marine deltas, associated with permanent antecedent streams which cross the Zagros fold system, are scattered along the Persian shoreline. The other is the a major deltaic complex which is associated with the Tigris-Euphrates Rivers. This system has prograded along the main axis of the Gulf, the resulting Mesopotamian Plain filling at least half of the original basin which, in early Quaternary times, extended from Hormuz to Syria.

  11. Analysis of the community structure of abyssal kinetoplastids revealed similar communities at larger spatial scales

    PubMed Central

    Salani, Faezeh Shah; Arndt, Hartmut; Hausmann, Klaus; Nitsche, Frank; Scheckenbach, Frank

    2012-01-01

    Knowledge of the spatial scales of diversity is necessary to evaluate the mechanisms driving biodiversity and biogeography in the vast but poorly understood deep sea. The community structure of kinetoplastids, an important group of microbial eukaryotes belonging to the Euglenozoa, from all abyssal plains of the South Atlantic and two areas of the eastern Mediterranean was studied using partial small subunit ribosomal DNA gene clone libraries. A total of 1364 clones from 10 different regions were retrieved. The analysis revealed statistically not distinguishable communities from both the South-East Atlantic (Angola and Guinea Basin) and the South-West Atlantic (Angola and Brazil Basin) at spatial scales of 1000–3000?km, whereas all other communities were significantly differentiated from one another. It seems likely that multiple processes operate at the same time to shape communities of deep-sea kinetoplastids. Nevertheless, constant and homogenous environmental conditions over large spatial scales at abyssal depths, together with high dispersal capabilities of microbial eukaryotes, maintain best the results of statistically indistinguishable communities at larger spatial scales. PMID:22071346

  12. Abyssal Hill Deflections at Pacific-Antarctic Ridge Transform Intersections

    NASA Astrophysics Data System (ADS)

    Croon, M. B.; Cande, S. C.; Stock, J. M.

    2009-05-01

    Almost complete shipboard multibeam bathymetry coverage at the Menard and Pitman Fracture Zones allowed us to map abyssal hill deviations along their traces. We compared the mapped abyssal hill deflections to a detailed plate motion model for the Pacific-Antarctic Ridge to test how abyssal hill curvature correlates to changes in plate motion direction, which leads to periods of transtension or transpression. To better understand the range of curvatures, we compared our observations with a model for curved cracks [Pollard and Aydin, 1984]. Spreading centers can be considered as giant cracks. The propagation path of a crack under combined loading can be predicted as a function of the stress ratio between the relative stresses required for spreading at the spreading axis (Mode I loading) and stresses resisting sliding along the transform (Mode II loading). We mapped 124 abyssal hill deflections at Menard Fracture Zone and 113 at Pitman Fracture Zone, respectively. The observations show that the amount of curvature can change rapidly over short periods of time. A high abundance of deflected abyssal hills is expected when a significant adjustment in plate motion direction occurs, which puts stress on the transform fault. This is observed, in particular, at the Pitman Fracture Zone, which experienced significant transtension since chron C5y (9.8 Ma) in response to a 17° clockwise rotation of the spreading direction azimuth. In contrast to the abyssal hill tips, which were deflected in response to the changing stress field when approaching a ridge transform intersection, we also mapped several anomalously curved abyssal hill structures. Such anomalous deflections are expected in oceanic crust formed near ridge transform intersections during periods of transpression [Sonder and Pockalny, 1999]. We mapped 19 anomalous abyssal hill deflections at Menard Fracture Zone between chrons C15o and C7 (34.9 to 24.8 Ma) and 15 at Pitman Fracture Zone between chrons C11y and C6B (30.1 to 23.1 Ma), respectively. These anomalously curved abyssal hills are related to block rotation about a vertical axis, in response to the transpression, and typically occurs in seafloor less than 2 Ma old when the oceanic lithosphere is thin. References Pollard, D. D., and A. Aydin (1984), Propagation and Linkage of Oceanic Ridge Segments, Journal of Geophysical Research, 89(Nb12), 17-28. Sonder, L. J., and R. A. Pockalny (1999), Anomalously rotated abyssal hills along active transforms: Distributed deformation of oceanic lithosphere, Geology, 27(11), 1003- 1006.

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

    NASA Astrophysics Data System (ADS)

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

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

  14. 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.

  15. 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.

  16. Abyssal ostracods from the South and Equatorial Atlantic Ocean: Biological and paleoceanographic implications

    USGS Publications Warehouse

    Yasuhara, Moriaki; Cronin, T. M.; Martinez, Arbizu P.

    2008-01-01

    We report the distribution of ostracods from ???5000 m depth from the Southeast and Equatorial Atlantic Ocean recovered from the uppermost 10 cm of minimally disturbed sediments taken by multiple-corer during the R/V Meteor DIVA2 expedition M63.2. Five cores yielded the following major deep-sea genera: Krithe, Henryhowella, Poseidonamicus, Legitimocythere, Pseudobosquetina, and Pennyella. All genera are widely distributed in abyssal depths in the world's oceans and common in Cenozoic deep-sea sediments. The total number of ostracod specimens is higher and ostracod shell preservation is better near the sediment-water interface, especially at the 0-1 cm core depths. Core slices from ???5 to 10 cm were barren or yielded a few poorly preserved specimens. The DIVA2 cores show that deep-sea ostracod species inhabit corrosive bottom water near the carbonate compensation depth (CCD) even though their calcareous valves are rarely preserved as fossils in sediment cores due to postmortem dissolution. Their occurrence at great water depths may partially explain the well-known global distributions of major deep-sea taxa in the world's oceans, although further expeditions using minimal-disturbance sampling devices are needed to fill geographic gaps. ?? 2008 Elsevier Ltd. All rights reserved.

  17. Abyssal ostracods from the South and Equatorial Atlantic Ocean: Biological and paleoceanographic implications

    NASA Astrophysics Data System (ADS)

    Yasuhara, Moriaki; Cronin, Thomas M.; Martínez Arbizu, Pedro

    2008-04-01

    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.

  18. Sedimental Reasons

    NSDL National Science Digital Library

    Visitors to this site can view satellite imagery and read an account of how remote sensing was employed to evaluate the extent of flooding and sediment load in rivers on the coastal plain of North Carolina as a result of Hurricane Floyd in September, 1999. This feature is part of NASA's Earth Observatory, a publication that focuses on Earth's climate and environmental change.

  19. Quantifying trace element disequilibria in mantle xenoliths and abyssal peridotites

    E-print Network

    Lee, Cin-Ty Aeolus

    distribution between orthopyroxene and clinopyroxene for quantifying rare earth element (REE) disequilibria in ultramafic rocks in the subsolidus state. We present case studies of the REE contents of mineral cores are known to be light REE-contaminated from the host lava. In the case of the abyssal peridotites, 13 out

  20. ORIGINAL PAPER Supra-subduction and abyssal mantle peridotites

    E-print Network

    Shervais, John W.

    ORIGINAL PAPER Supra-subduction and abyssal mantle peridotites of the Coast Range ophiolite 2008 / Published online: 16 April 2008 Ó Springer-Verlag 2008 Abstract The Coast Range ophiolite (CRO compositions in mantle peridotites that underlie crustal sections of the ophiolite, and show

  1. Abyssal circulation of the southeastern Pacific and some geological implications

    Microsoft Academic Search

    Peter Lonsdale

    1976-01-01

    The abyssal circulation of the Pacific Ocean east of the East Pacific Rise is deduced from hydrographic data, supported by a few direct current measurements. Two main flow paths are recognized: across the Chile Rise into the Chile Basin, and thence northward into the Peru Basin and Panama Basin: and eastward across the East Pacific Rise into the Guatemala Basin

  2. 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.

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

    USGS Publications Warehouse

    Crusius, John; Thomson, John

    2003-01-01

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

  4. 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

  5. Abyssal Ocean Warming Around Antarctica Strengthens the Atlantic Overturning Circulation

    NASA Astrophysics Data System (ADS)

    Boning, C. W.; Patara, L.

    2014-12-01

    The abyssal warming around Antarctica is one of the most prominent multi-decadal signals of change in the global ocean. Here we investigate its dynamical impacts on the large-scale circulation and heat transport in the Atlantic Ocean by performing a set of experiments with a global ocean-sea ice model. The simulations suggest that the ongoing warming of AABW, already affecting much of the Southern Hemisphere with a rate of up to 0.05 °C per decade, has important implications for the Atlantic Meridional Overturning Circulation (AMOC). While the abyssal northward flow of AABW is weakening, we find the upper cell of the AMOC 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.

  6. 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.

  7. Abyssal recipes II: energetics of tidal and wind mixing

    Microsoft Academic Search

    Walter Munk; Carl Wunsch

    1998-01-01

    Without deep mixing, the ocean would turn, within a few thousand years, into a stagnant pool of cold salty water with equilibrium maintained locally by near-surface mixing and with very weak convectively driven surface-intensified circulation. (This result follows from Sandström’s theorem for a fluid heated and cooled at the surface.) In this context we revisit the 1966 “Abyssal Recipes”, which

  8. Active diagenetic formation of metal-rich layers in N. E. Atlantic sediments

    NASA Astrophysics Data System (ADS)

    Wallace, H. E.; Thomson, J.; Wilson, T. R. S.; Weaver, P. P. E.; Higgs, N. C.; Hydes, D. J.

    1988-06-01

    Sediment cores from the Porcupine Abyssal Plain exhibit an indurated layer 0.5-3 cm thick at depths of approximately 50 cm. This is some 15-20 cm below the glacial/Holocene transition as interpreted by radiocarbon dating and the palaeontological criteria of RUDDIMAN and MCINTYRE (1981). The layer is forming currently at the oxic/post-oxic boundary in the sediments, as revealed by pore water data: O 2 and NO -3 are present in solution above the layer, while Fe 2+, Mn 2+, PO 3-4 and NH +4 are present in solution below, and all these species show concentration gradients indicating fluxes into the layer. These data are consistent with the hypothesis for the initiation and sustained formation of such layers proposed by WILSONet al. (1986a,b). The elements Mn, Ni, Co, Fe, P, V, Cu, Zn and U are all enriched to varying degrees in the vicinity of the layer. Some differential stratification of these elements in the vertical, consistent with a redox control, is observed at one site with a 0.5 cm layer, with Mn, Ni and Co above, Fe, P, V and Cu in the layer, and U below. At another site the metal-rich layer has higher Fe and P concentrations and is more indurated. Here all enrichments except Co are contained within a single layer sample, 3 cm thick.

  9. 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

  10. Patterns of bathymetric zonation of bivalves in the Porcupine Seabight and adjacent Abyssal plain, NE Atlantic

    Microsoft Academic Search

    Celia Olabarria

    2005-01-01

    Although the organization patterns of fauna in the deep sea have been broadly documented, most studies have focused on the megafauna. Bivalves represent about 10% of the deep-sea macrobenthic fauna, being the third taxon in abundance after polychaetes and peracarid crustaceans. This study, based on a large data set, examined the bathymetric distribution, patterns of zonation and diversity–depth trends of

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  12. 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.

  13. Spatial and Temporal Variations of Sediment Input to the Cascadia Subduction Zone

    NASA Astrophysics Data System (ADS)

    Underwood, M. B.

    2003-12-01

    The abundance of expandable clay (smectite) in subducting sediments is an important parameter to consider during studies of plate-boundary seismogenic zones because the mineral has an unusually low coefficient of internal friction. Furthermore, interlayer water is released during smectite-to-illite diagenesis, which increases the likelihood of excess pore pressure and low effective stress. In theory, the up-dip limit of a seismogenic zones might coincide with the down-dip dissipation of excess pore pressure. In the specific case of Cascadia Basin, the amount and types of clay on the abyssal floor change considerably in both time and space. Those variations probably influence the strength of the plate-boundary fault, the vergence of imbricate thrusts within the frontal accretionary prism, and the fluid budget in 3-D. New data from more than 200 gravity-piston cores show that distal parts of Cascadia Basin contain 4% to 70% smectite in the clay fraction (Biscaye weighting factors). Smectite is more abundant within a plume of discharge that emanates from the Columbia River, but spatial variations are not clear-cut, even within the upper meter of Holocene mud. This complexity is a product of interplay among autocyclic factors (e.g., channel switching, migration of surface currents), allocyclic variables (e.g., continental glaciation, volcanism, balance of chemical to mechanical weathering, earthquake trigger of turbidity currents), and eustatic forcing (e.g., attachment-detachment of river-canyon connections). In addition, new data from ODP Site 888 (Nitinat Fan) and DSDP Site 174 (Astoria Fan) show substantial changes in clay composition with depth. Smectite at Site 888 varies erratically from 13% to 55%. Smectite content is 11% to 64% at Site 174, with a marked increase from the younger submarine-fan facies (average 22%) to the underlying abyssal-plain facies (average 42%). Models of fault-zone mechanics and accretionary-prism hydrogeology should take this compositional variability into account.

  14. Moored observations of episodic abyssal flow and mixing at station ALOHA

    E-print Network

    Frandsen, Jannette B.

    Moored observations of episodic abyssal flow and mixing at station ALOHA M. H. Alford,1 Roger Lukas at station ALOHA (22.75°N, 158°W). Three major cold events were observed in our 2.5year record, of which we observations of episodic abyssal flow and mixing at station ALOHA, Geophys. Res. Lett., 38, L15606, doi:10

  15. Exploring the Abyssal Ocean at Station ALOHA: Early results from the ALOHA Cabled

    E-print Network

    Frandsen, Jannette B.

    the design of a global-scale abyssal observing system for climate. Other early observations will be shown scales of variability in the deep and abyssal ocean. Since 2008, autonomous moorings deployed at ALOHA motions. These discoveries have implications for the design of other deep-sea infrastructure, including

  16. 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.

  17. 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.

  18. 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 [National Research Centre - Kurchatov Institute, 1 Kurchatov Sq. (Russian Federation)] [National Research Centre - Kurchatov Institute, 1 Kurchatov Sq. (Russian Federation)

    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)

  19. 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.

  20. 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-

  1. Laboratory-Measured and Property-Transfer Modeled Saturated Hydraulic Conductivity of Snake River Plain

    E-print Network

    Laboratory-Measured and Property-Transfer Modeled Saturated Hydraulic Conductivity of Snake River Conductivity of Snake River Plain Aquifer Sediments at the Idaho National Laboratory, Idaho By Kim S. Perkins saturated hydraulic conductivity of Snake River Plain aquifer sediments at the Idaho National Laboratory

  2. Inter-annual dynamics of abyssal polychaete communities in the North East Pacific and North East Atlantic—A 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.

  3. 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 0.025°C, 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.

  4. Use of OSL dating to establish the stratigraphic framework of Quaternary eolian sediments, Anton scarp upper trench, Northeastern Colorado High Plains, USA

    USGS Publications Warehouse

    Mahan, S.A.; Noe, D.C.; McCalpin, J.P.

    2009-01-01

    This paper contains the results of the optically stimulated luminescence (OSL) dating used to establish stratigraphic ages and relationships of eolian sediments in a trench in northeastern Colorado, USA. This trench was located in the upper face of the Anton scarp, a major topographic lineament trending NW-SE for a distance of 135 km, in anticipation of intersecting near-surface faulting. The trench was 180 m long, 4.5-6.0 m deep, and exposed 22 m of stratigraphic section, most of which dipped gently west and was truncated by gulley channeling at the face of the scarp. No direct evidence of faulting was found in the upper trench. The stratigraphy from the trench was described, mapped and dated using OSL on quartz and potassium feldspar, and 14C obtained from woody material. OSL dating identified two upper loess units as Peoria Loess and Gilman Canyon Loess, deposited between 16 and 30 ka ago. The bottom layers of the trench were substantially older, giving OSL ages in excess of 100 ka. These older ages are interpreted as underestimates, owing to saturation of the fast component of OSL. Using OSL and 14C dating, we can constrain the erosion and down cutting of the scarp face as occurring between 16 and 5.7 ka. As the trenching investigation continues in other parts of the scarp face, the results of this preliminary study will be of importance in relating the ages of the strata that underlie different parts of the scarp, and in determining whether Quaternary faulting was a mechanism that contributed to the formation of this regional geomorphic feature.

  5. 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.

  6. Saturation of the Internal Tides and Induced Mixing in the Abyssal Ocean

    E-print Network

    Bu?hler, Oliver

    As part of an ongoing effort to develop a parameterization of wave-induced abyssal mixing, the authors derive an heuristic model for nonlinear wave breaking and energy dissipation associated with internal tides. Then the ...

  7. Isotopic evidence for the source of lead in the North Pacific abyssal water

    E-print Network

    Wu, Jingfeng

    The absence of accurate measurements of lead (Pb) isotopic composition in the pristine North Pacific abyssal water has made it difficult to assess the relative importance of what are believed to be the two major Pb sources: ...

  8. 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.

  9. A comparison of bistatic scattering from two geologically distinct abyssal hills

    PubMed

    Chia; Makris; Fialkowski

    2000-11-01

    The bistatic scattering characteristics of two geologically distinct abyssal hills located on the western flank of the Mid-Atlantic Ridge, known as B' and C', are experimentally compared using data acquired with low-frequency towed-array systems at 1/2 convergence zone (approximately 33 km) stand-off. The comparison is significant because the abyssal hills span the two classes of elevated seafloor crust that cover the Mid-Atlantic Ridge. The highly lineated B' feature is representative of abyssal hills composed of outside corner crust, the most commonly occurring category, whereas the domed C' promontory is representative of the rougher, low-aspect-ratio abyssal hills composed of inside corner crust. The latter are less common and usually restricted to segment valley margins. The mean biazimuthal scattering distributions of the two abyssal hills each exhibit Lambertian behavior with comparable albedos, suggesting that the distinction between abyssal hills composed of differing crust is not significant in modeling long-range reverberation. The adverse effect of using bathymetry that undersamples seafloor projected area in scattering strength analysis is also quantified with data from the B' ridge. Specifically, the use of undersampled bathymetry can lead to significant overestimates in the strength of seafloor scattering. PMID:11108343

  10. Holocene and late glacial palaeoceanography and palaeolimnology of the Black Sea: Changing sediment provenance and basin hydrography over the past 20,000 years

    Microsoft Academic Search

    D. Z. Piper; S. E. Calvert

    2011-01-01

    The elemental geochemistry of Late Pleistocene and Holocene sediments of the Black Sea, recovered in box cores from the basin margins and a 5-m gravity core from the central abyssal region of the basin, identifies two terrigenous sediment sources over the last 20 kyrs. One source region includes Anatolia and the southern Caucasus; the second region is the area drained

  11. Holocene and late glacial palaeoceanography and palaeolimnology of the Black Sea: Changing sediment provenance and basin hydrography over the past 20,000 years

    Microsoft Academic Search

    D. Z. Piper; S. E. Calvert

    2011-01-01

    The elemental geochemistry of Late Pleistocene and Holocene sediments of the Black Sea, recovered in box cores from the basin margins and a 5-m gravity core from the central abyssal region of the basin, identifies two terrigenous sediment sources over the last 20kyrs. One source region includes Anatolia and the southern Caucasus; the second region is the area drained by

  12. 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.

  13. Holocene flood plain soil formation in the lower Mississippi River Valley: Implications for the interpretation of alluvial paleosols

    Microsoft Academic Search

    A. Aslan; W. J. Autin

    1992-01-01

    Holocene Mississippi River flood soils representing different depositional environments and ages were sampled along three east-west transects between Vicksburg, MS and Baton Rouge, LA. Flood plain soil development is primarily controlled by episodic flood plain sedimentation and ground water table fluctuations as evidenced by relatively thick cumulative soil profiles with abundant mottles, nodules, and slickensides. Within flood plain deposits of

  14. 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...

  15. 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.

  16. Clay mineral distribution in surface sediments of the South Atlantic: sources, transport, and relation to oceanography

    Microsoft Academic Search

    Rainer Petschick; Gerhard Kuhn; Franz Gingele

    1996-01-01

    Surface samples, mostly from abyssal sediments of the South Atlantic, from parts of the equatorial Atlantic, and of the Antarctic Ocean, were investigated for clay content and clay mineral composition. Maps of relative clay mineral content were compiled, which improve previous maps by showing more details, especially at high latitudes. Large-scale relations regarding the origin and transport paths of detrital

  17. Hydrogeologic framework of the Virginia coastal plain

    USGS Publications Warehouse

    Meng, Andrew A., III; Harsh, John F.

    1988-01-01

    This report defines the hydrogeologic framework of the Virginia Coastal Plain and is a product of a comprehensive regional study to define the geology, hydrology, and geochemistry of the northern Atlantic Coastal Plain aquifer system extending from North Carolina to Long Island, New York. The Virginia Coastal Plain consists of an eastward-thickening wedge of generally unconsolidated, interbedded sands and clays, ranging in age from Early Cretaceous to Holocene. These sediments range in thickness from more than 6,000 feet beneath the northeastern part of the Eastern Shore Peninsula to nearly 0 feet along the Fall Line. Eight confined aquifers, eight confining units, and an uppermost water table aquifer are delineated as the hydrogeologic framework of the Coastal Plain sediments in Virginia. The nine regional aquifers, from oldest to youngest, are lower, middle, and upper Potomac, Brightseat, Aquia, Chickahominy-Piney Point, St. Marys-Choptank, Yorktown-Eastover, and Columbia. The Brightseat is a newly identified and correlated aquifer of early Paleoceneage. This study is one of other, similar studies of the Coastal Plain areas in North Carolina, Maryland-Delaware, New Jersey, and Long Island, New York. These combined studies provide a system of hydrogeologic units that can be identified and correlated throughout the northern Atlantic Coastal Plain. Data for this study were collected and analyzed from October 1979 to May 1983. The nine aquifers and eight confining units are identified and delineated by use of geophysical logs, drillers' information, and stratigraphic and paleontologic data. By correlating geophysical logs with hydrologic, stratigraphic, and paleontologic data throughout the Coastal Plain, a comprehensive multilayered framework of aquifers and confining units, each with distinct lithologic properties, was developed. Cross sections show the stratigraphic relationships of aquifers and confining units in the hydrogeologic framework of the Virginia Coastal Plain. Maps show confining-unit thicknesses and altitudes of aquifer tops, provide the basis for assigning aquifers to screened intervals of observation and production wells, and are used for the development of a comprehensive observation-well network in the Virginia Coastal Plain.

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

    PubMed

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

    2011-06-01

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

  19. Sensitivity of abyssal water masses to overflow parameterisations

    NASA Astrophysics Data System (ADS)

    Snow, Kate; Hogg, Andrew McC.; Downes, Stephanie M.; Sloyan, Bernadette M.; Bates, Michael L.; Griffies, Stephen M.

    2015-05-01

    Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW) control the abyssal limb of the global overturning circulation and play a major role in oceanic heat uptake and carbon storage. However, current general circulation models are unable to resolve the observed AABW and NADW formation and transport processes. One key process, that of overflows, motivates the application of overflow parameterisations. We present a sensitivity study of both AABW and NADW properties to three current parameterisations using a z? -coordinate ocean-sea ice model within a realistic-topography sector of the Atlantic Ocean. Overflow parameterisations that affect only tracer equations are compared to a fully dynamical Lagrangian point particle method. An overflow parameterisation involving partial convective mixing of tracers is most efficient at transporting dense NADW water downslope. This parameterisation leads to a maximum mean increase in density in the north of 0.027 kg m-3 and a decrease in age of 525 years (53%). The relative change in density and age in the south is less than 30% of that in the north for all overflow parameterisations. The reduced response in the south may result from the differing dense water formation and overflow characteristics of AABW compared to NADW. Alternative approaches may be necessary to improve AABW representation in z? -coordinate ocean climate models.

  20. 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.

  1. 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...

  2. 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.

  3. Sediment chemistry and magnetic properties in an anomalously reducing core from the eastern Mediterranean Sea

    Microsoft Academic Search

    Hilde F. Passier; Mark J. Dekkers; Gert J. de Lange

    1998-01-01

    In Core KC19C (19.6 m long), recovered in the abyssal plain between Crete and Cyprus in the eastern Mediterranean, a large number of organic-rich layers (sapropels) occur, which correlate to maxima in the insolation curve. In contrast to other sites in the eastern Mediterranean, porewaters contain sulfide below a few meters below seafloor (mbsf). Geochemical analyses were performed on the

  4. Phytodetritus entering the benthic boundary layer and aggregated on the sea floor in the abyssal NE Pacific

    Microsoft Academic Search

    Stace E. Beaulieu; Kenneth L. Smith Jr.

    1998-01-01

    Phytodetritus, which can originate in surface waters following seasonal phytoplankton blooms, is considered to be an important food resource for abyssal fauna. We analyzed the composition of phytodetritus sampled discretely in situ at an abyssal station in the NE Pacific. The phytodetritus was collected during two time periods straddling a seasonal maximum in the flux of particulate matter into a

  5. 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.

  6. River sediments.

    PubMed

    Williams, Martin

    2012-05-13

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

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

    NASA Astrophysics Data System (ADS)

    Dygert, Nick; Liang, Yan

    2015-06-01

    Mantle peridotites from ophiolites are commonly interpreted as having mid-ocean ridge (MOR) or supra-subduction zone (SSZ) affinity. Recently, an REE-in-two-pyroxene thermometer was developed (Liang et al., 2013) that has higher closure temperatures (designated as TREE) than major element based two-pyroxene thermometers for mafic and ultramafic rocks that experienced cooling. The REE-in-two-pyroxene thermometer has the potential to extract meaningful cooling rates from ophiolitic peridotites and thus shed new light on the thermal history of the different tectonic regimes. We calculated TREE for available literature data from abyssal peridotites, subcontinental (SC) peridotites, and ophiolites around the world (Alps, Coast Range, Corsica, New Caledonia, Oman, Othris, Puerto Rico, Russia, and Turkey), and augmented the data with new measurements for peridotites from the Trinity and Josephine ophiolites and the Mariana trench. TREE are compared to major element based thermometers, including the two-pyroxene thermometer of Brey and 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.

  8. Heat flow in the Piedmont and Atlantic Coastal Plain of the southeastern United States

    Microsoft Academic Search

    J. K. Costain; J. A. Speer; L. Glover; L. Perry; S. Dashevsky; M. McKinney

    1986-01-01

    Seventy-four new heat flow values have been determined at sites from New Jersey to Georgia, mostly in the Piedmont and Atlantic Coastal Plain provinces. Relatively high heat flows are characteristic of premetamorphic and postmetamorphic granites exposed in the Piedmont and occurring in the basement beneath the sediments of the Atlantic Coastal Plain. The Piedmont heat flow and heat generation values,

  9. An association between komokiacean foraminifers (Protozoa) and paludicelline ctenostomes (Bryozoa) from the abyssal Northeast Atlantic

    Microsoft Academic Search

    A. J. Gooday; P. L. Cook

    1984-01-01

    Large collections of komokiacean foraminifers have been obtained from epibenthic sledge samples taken at bathyal and abyssal depths in the north-east Atlantic. Eight of the 32 species so far recognized have been found to form an association with paludicelline bryozoans. Approximately 4% of the > 12000 komokiaceans studied were involved in the association. The bryozoan colonies intergrow as networks with

  10. Crystallization and differentiation in abyssal tholeiites and gabbros from mid-oceanic ridges

    Microsoft Academic Search

    Akiho Miyashiro; Fumiko Shido; Maurice Ewing

    1970-01-01

    Tholeiitic gabbros from the Mid-Atlantic Ridge near 24°N were found to show remarkable differentiation, producing high-iron, high-titanium gabbros and aplite in later stages. Crystallization of olivine and plagioclase from abyssal tholeiite magma approximately follows cotectic relation in the system olivine-plagioclase-pyroxene.

  11. 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…

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

    Microsoft Academic Search

    Mark Prusten

    2008-01-01

    The generation of photo-real renderings of bioluminescence is developed for creatures from the abyss. Bioluminescence results from a chemical reaction with examples found in deep-sea marine environments including: algae, copepods, jellyfish, squid, and fish. In bioluminescence, the excitation energy is supplied by a chemical reaction, not by a source of light. The greatest transparency window in seawater is in the

  13. Research paper Behavior of fluid-mobile elements in serpentines from abyssal to subduction

    E-print Network

    Research paper Behavior of fluid-mobile elements in serpentines from abyssal to subduction. In order to constrain geochemical behavior of fluid-mobile elements hosted by serpentine phases during indicating extensive fluid­rock interaction. In situ analyses allow distinction of three types of serpentines

  14. Salt Plains Microbial Observatory

    NSDL National Science Digital Library

    Mark Buchheim

    This site is home of the Salt Plains Microbial Observatory, located in the Salt Plains National Wildlife Refuge in northern Oklahoma. This area has permitted the first extensive study of a non-marine, terrestrial, hypersaline environment. The web site offers information about the extreme environment, images and video clips of its microbial inhabitants, an image-rich summary of research activities, information about summer courses and research opportunities, a list of publications, and links to other informative resources pertaining to hypersaline environments.

  15. 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 ...

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    Mooring observations were conducted from July 16, 2011 to March 30, 2012 east of Mindanao, Philippines (127°2.8'E, 8°0.3'N) to observe the abyssal current at about 5 600 m deep and 500 m above the ocean bottom. Several features were revealed: 1) the observed abyssal current was highly variable with standard deviations of 57.3 mm/s and 34.0 mm/s, larger than the mean values of -31.9 and 16.6 mm/s for the zonal and meridional components, respectively; 2) low-frequency current longer than 6 days exhibited strong seasonal variation, flowing southeastward (mean flow direction of 119.0° clockwise from north) before about October 1, 2011 and northwestward (mean flow direction of 60.5° counter-clockwise from north) thereafter; 3) the high-frequency flow bands were dominated by tidal currents O1, K1, M2, and S2, and near-inertial currents, whose frequencies were higher than the local inertial frequency. The two diurnal tidal constituents were much stronger than the two semidiurnal ones. This study provides for the first time an observational insight into the abyssal western boundary current east of Mindanao based on long-term observations at one site. It is meaningful for further research into the deep and abyssal circulation over the whole Philippine Sea and the 3D structure of the western boundary current system in this region. More observational and high-resolution model studies are needed to examine the spatial structure and temporal variation of the abyssal current over a much larger space and longer period, their relation to the upper-layer circulation, and the underlying dynamics.

  17. 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 725×375 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.

  18. Arsenic Levels in Groundwater from Quaternary Alluvium in the Ganga Plain and the Bengal Basin, Indian Subcontinent: Insights into Influence of Stratigraphy

    Microsoft Academic Search

    S. K. Acharyya

    2005-01-01

    Late Quaternary stratigraphy and sedimentation in the Ganga Alluvial Plain and the Bengal Basin have influenced arsenic contamination of groundwater. Arsenic contaminated aquifers are pervasive within lowland organic rich, clayey deltaic sediments in the Bengal Basin and locally within similar facies in narrow, entrenched river valleys within the Ganga Alluvial Plain. These were mainly deposited during early-mid Holocene sea level

  19. Diversity and origin of abyssal tholeiite from the Mid-Atlantic Ridge near 24° and 30° North latitude

    Microsoft Academic Search

    Akiho Miyashiro; Fumiko Shido; Maurice Ewing

    1969-01-01

    On cursory examination of hand specimens and thin sections, the abyssal tholeiite in a dredge haul may appear to be uniform in composition. Chemical analyses of a considerable number of fragments, however, have always revealed the existence of regular compositional variation in them. The MgO content decreases with increasing SiO2. In abyssal tholeiites with relatively low Al2O3 contents, the SiO2,

  20. Status of anthropogenically induced metal pollution in the Kanpur-Unnao industrial region of the Ganga Plain, India

    Microsoft Academic Search

    A. A. Ansari; I. B. Singh; H. J. Tobschall

    1999-01-01

    The Ganga Plain is one of the most densely populated regions and one of the largest groundwater repositories of the Earth.\\u000a For several decades, the drainage basin of the Ganga Plain has been used for the disposal of domestic and industrial wastes\\u000a which has adversely affected the quality of water, sediments and agricultural soils of the plain. The concentrations of

  1. The Abyss and the Circle: A Cyclo-Analysis of Being and Time

    E-print Network

    Martinot, Steve

    The Abyss and the Circle: A Cyclo-Analysis of Being and Time STEVE MARTINOT University of Colorado Charles Guignon, in his recent critique of Heidegger,1 argues that Heidegger deflates the skeptical attitude by showing that it has concerned... structure of Heidegger's "quantum numbers," will be the terrain we will traverse. He warns that, as we approach the dry of understanding, and enter its gates, we will find a veritable inferno of drcles, a complex textile of terms...

  2. A model that reconciles major- and trace-element data from abyssal peridotites

    Microsoft Academic Search

    Paul D. Asimow

    1999-01-01

    Abyssal peridotite samples from slow-spreading oceanic ridges have been interpreted as residues of near-fractional melting processes on the basis of trace-element data, whereas major-element compositions and modes of the same samples require interactions between migrating melts and residual solids, either by equilibrium porous flow, refertilization, or olivine crystallization. Modeling of major- and trace-element data shows that these peridotite samples are

  3. 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 ?-taxonomic data across oceans basins and especially of biogeographic transition zones between oceans. The Antarctic Polar Frontal Zone has been discussed as major biogeographic barrier hindering faunal exchange between Subantarctic and Antarctic provinces and conserving high rates of endemism in the Southern Ocean benthos. In the present study we report first, exploratory ?-taxonomy on the malacofauna sampled by means of an epibenthic sledge from four bathyal respectively abyssal stations (2732-4327 m depth) in the vicinity of the Antarctic Polar Front during the SYSTCO II expedition (SYSTem COupling in the Southern Ocean, RV Polarstern cruise ANT XXVIII/3). We identified 58 distinct molluscan taxa based on external morphology ('morphospecies'); of the 33 taxa successfully assigned to described species 94% were previously reported from the Southern Ocean, but 24% exhibit distribution ranges crossing the Polar Front. One North Atlantic scaphopod is reported for the first time in Antarctic waters. Our study supports that the Antarctic Polar Front does not serve as effective barrier preventing gene flow in deep-sea molluscs. The present dataset shows the general characteristics of deep-sea sampling: patchiness in distribution and a high degree of singletons. Overall molluscan abundances were generally low ranging between 3.60 and 24.65 ind./1000 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.

  4. ROLE OF LAND USE AND BMPS IN REDUCING THE EFFECT OF EXTREME MAGNITUDE EVENTS ON SEDIMENT AND POLLUTANT TRANSPORT IN THE SE US COASTAL PLAIN AND MISSISSIPPI ALLUVIAL VALLEY

    EPA Science Inventory

    Suspended sediment is a major non-point source pollutant of surface waters. Best management practices (BMPs) and current landuse decisions may not be sufficient to protect water quality in a changing climate, as a result of a loss of efficiency at reducing suspended sedimen...

  5. 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.

  6. 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.

  7. Coastal Plain Near Kalapana

    USGS Multimedia Gallery

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

  8. Flood Plain Management. 

    E-print Network

    McNeely, John G.; Lacewell, Ronald D.

    1976-01-01

    characteristics fairly representative for the en- tire length of each reach. Flood frequency data for the various streams in the study are developed from dis- charge-frequency relationships based on regionalized hydrologic analyses. Using the peak discharges... Contents Introduction.. .................................... 4 Agricultural Flood Plain Management ............... Flood Hazard Studies ............................. Federal Flood Insurance .......................... 11 Flood Insurance...

  9. 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).

  10. SEDIMENT REMOVAL

    EPA Science Inventory

    When properly conducted, sediment removal is an effective lake management technique. This chapter describes: (1) purposes of sediment removal, (2) environmental concerns, (3) appropriate depth of sediment removal, (4) sediment removal techniques, (5) suitable lake conditions, (6)...

  11. 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.

  12. New data from the eastern flank of the Mid-Atlantic Ridge (~2527N) show that slow-spreading abyssal hill faults maintain maxi-

    E-print Network

    Bohnenstiehl, Delwayne

    -spreading abyssal hill faults maintain maxi- mum displacement-length ratios that are systematically greater than-spreading environment may reflect the importance of fault linkage (rather than lateral propagation) in deter- mining the lengths of abyssal hill faults and the limited ability of fault systems that evolve within an extremely

  13. High Plains Regional Climate Center

    NSDL National Science Digital Library

    School of Natural Resources

    The mission of the High Plains Regional Climate Center is to increase the use and availability of climate data in the High Plains region. This site contains a variety of climatic and hydrologic data from High Plains research projects. Data types include automated weather data, interactive climate summary maps, historical weather data, and an interactive climate atlas. Research projects include Nebraska soil moisture, crop phenology, and wind energy on the High Plains. This website also features relevant publications and a variety of weather and climate links.

  14. Distinctive upper mantle anisotropy beneath the High Lava Plains and Eastern Snake River Plain,

    E-print Network

    Distinctive upper mantle anisotropy beneath the High Lava Plains and Eastern Snake River Plain and continuing with the still- ongoing volcanism in the High Lava Plains (HLP) and eastern Snake River Plain (SRP waves; shear wave splitting; high lava plains; Snake River Plain; Yellowstone. Index Terms: 8137

  15. Abyssal Peridotites From Ultra-Slow Spreading Ridges: Mantle Heterogeneities Versus Melting Processes

    NASA Astrophysics Data System (ADS)

    Sakaguchi, C.; Warren, J. M.; Shimizu, N.; Dick, H. J.; Nakamura, E.

    2005-12-01

    Abyssal peridotite geochemistry can provide important constraints on mantle convection, mid-ocean ridge processes, and earth composition. However, separating the chemical signatures of melt extraction processes at mid-ocean ridges from underlying source heterogeneity is not entirely straightforward. Ultra-slow spreading ridges are an ideal location to distinguish the effects of source versus process in abyssal peridotites, due to reduced crustal production resulting from low upwelling rates and on-axis conductive cooling. We present data on abyssal peridotites from ultra-slow spreading portions of the Southwest Indian Ridge (SWIR). At ultra-slow spreading rates, peridotites have a wide range in modal mineralogy and trace element composition, due to (i) variable degrees of melting, (ii) melt addition, and (iii) underlying mantle heterogeneity. In contrast, peridotites from fast spreading ridges have a narrow compositional range, reflecting high degrees of melting. SWIR peridotites from the Atlantis II Fracture Zone and the Oblique Segment are heterogeneous on all scales, from the >100 km ridge scale down to the hand specimen scale and in some cases, on the grain scale. Heterogeneity is observed in a variety of forms, including (i) veins, (ii) ranges in modal clinopyroxene content, (iii) variations in trace elements by up to three orders of magnitude, and (iv) isotopic variations. Some of this heterogeneity is clearly related to shallow level melt processes. For example, pervasive gabbroic veining and matrix plagioclase within one peridotite dredge indicates the freezing of melts in situ in the shallow mantle. However, the pyroxene veins in another dredge, which may be similar to compositional layering observed in orogenic lherzolites and ophiolites, are not as clearly related to melting processes. The isotopic composition of peridotite clinopyroxenes in this dredge extends to an enriched 143Nd/144Nd value of 0.512937. Pb isotopes in the clinopyroxenes are similarly enriched relative to depleted MORB mantle, with 206Pb/204Pb =19.6057, 207Pb/204Pb =15.5816 and 208Pb/204Pb =39.1233. Overall, the isotopic composition of the SWIR peridotites is variable, some of which may reflect underlying mantle compositional heterogeneity unrelated to the recent melt extraction events. Through detailed isotopic analysis on multiple samples from single dredges with well-defined characteristics, we attempt to distinguish between source and process in the SWIR abyssal peridotites.

  16. Plenty on the Plains

    NSDL National Science Digital Library

    2014-04-30

    In this activity, learners compare the ways of life of Plains Native Americans who hunted and moved frequently to follow the buffalo herds, and Native Americans who farmed and lived in more permanent villages along the river valleys. As they learn about different ways of life, learners also explore the benefits of trading. Learners act out a trading scenario, in which they make and trade goods including wristbands and popcorn snacks. This activity is featured on pp.23-24 of the "One With the Earth: Native Americans and the Natural World" multidisciplinary unit of study for kindergarten through third grade.

  17. Devil-Streaked Plain

    NASA Technical Reports Server (NTRS)

    2006-01-01

    19 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark streaks on a plain south of the giant impact basin, Hellas Planitia. The streaks map the routes traveled by dozens of individual southern spring and early summer dust devils.

    Location near: 68.4oS, 296.1oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  18. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 2013-10-01 2013-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

  19. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 2011-10-01 2011-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

  20. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 2012-10-01 2012-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

  1. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 2010-10-01 2010-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

  2. 49 CFR 229.64 - Plain bearings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 2014-10-01 2014-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

  3. Aerosols Over Yellow Sea Sediments

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This SeaWiFS image shows complex phytoplankton distribution patterns in the Bohai and Yellow seas. A wide band of brownish water along the coast north and south of the mouth of the Yangtze River indicates a heavy load of suspended sediment. The air over eastern central China and the Yellow Sea is thick with aerosols. Farther north over the Manchurian Plain and Greater Khingan Range, the air is much clearer.

  4. The Kansas Plains

    E-print Network

    Zimmerman, Karen P.

    1973-01-01

    The Kansas Plains An Exhibit from the Kansas Collection UNIVERSITY OF KANSAS LIBRARIES T R A V E L L I N G ACROSS KANSAS f r o m e a s t to west , one is a w a r e of a t rans i t ion f r o m the ta l l g r a s s P r a i r i e P l a i n... s with wooded val leys to the f lat , t r e e l e s s , ar id High P l a i n s of w e s t e r n K a n s a s . Wal ter P r e s c o t t Webb in The G r e a t P l a i n s explains the c h a r a c t e r i s t i c s of the plains environment and the f l o r a l...

  5. Dunes on Plains

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03047 Dunes on Plains

    These dunes are located on the plains around Doanus Vallis.

    Image information: VIS instrument. Latitude 62.3S, Longitude 335.3E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  6. ACTUAL AND REFERENCE SEDIMENT YIELDS FOR THE JAMES CREEK WATERSHED - MISSISSIPPI

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study determined "actual" sediment-transport rates and rates for similar, but stable or unimpaired ("reference") streams that could be used to develop water-quality targets for sediment. "Reference" rates were obtained from historical stream flow and sediment load data in the Southeastern Plain...

  7. "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

  8. “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

  9. 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

    Microsoft Academic Search

    C. G. Ramatchandirane; A. Kolker; A. D. Ameen; K. Williams; J. P. Donnelly; L. Giosan

    2010-01-01

    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

  10. 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.

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

    PubMed

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

    2013-12-01

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

  12. 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...

  13. Geology and Wine 11. Terroir of the Western Snake River Plain, Idaho, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This article explores unique factors that shape the terroir of Idaho’s principal wine grape-growing district. Most Idaho wine grape vineyards are located in the Western Snake River Plain (WSRP) rift basin (~43°N, ~114°W) on soils derived from lake, river, or wind-blown sediments, volcanic events, a...

  14. The crustacean scavenger guild in Antarctic shelf, bathyal and abyssal communities

    NASA Astrophysics Data System (ADS)

    De Broyer, Claude; Nyssen, Fabienne; Dauby, Patrick

    2004-07-01

    Peracarid crustaceans form a significant part of the macrobenthic community that is responsible for scavenging on large food falls onto the sea floor. Although several studies are available about scavengers from tropical and temperate seas, very little information has been published about such species living in Antarctic waters, particularly at greater depths. The present paper is based on a collection of 31 baited trap sets deployed in the Weddell Sea, Scotia Sea, and off the South Shetland Islands, and presents results on the geographical and bathymetric distribution of the different taxa and on the eco-functional role of scavengers. Some 68,000 peracarid crustaceans from 62 species were collected. About 98% of individuals belonged to the amphipod superfamily Lysianassoidea, and 2% to the isopod family Cirolanidae. Of these species, 31, including 26 lysianassoids (1400 individuals), were collected deeper than 1000 m. High species richness was discerned for the eastern Weddell Sea shelf compared with other Antarctic areas. The Antarctic slope also seems to be richer in species than other areas investigated in the world, while in the abyss, scavenger species richness appears to be lower in Antarctica. A richness gradient was thus observed from the shelf to the deep. For amphipods, a number of species extend their distribution from the shelf to the slope and only one to the abyssal zone. Amphipod species showed degrees of adaptation to necrophagy. The functional adaptations of the mandible and the storage function of the gut are discussed. Feeding experiments conducted on lysianassoid species collected at great depths and maintained in aquaria showed a mean feeding rate of about 1.4-4.1% dry body weight day -1, which is consistent with data obtained from other species.

  15. 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...

  16. The bounty channel system: A 55-million-year-old sediment conduit to the deep sea, Southwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Carter, Robert M.; Carter, Lionel

    1987-12-01

    The Bounty Channel system is located within the Bounty Trough, a Cretaceous rift on the eastern edge of the New Zealand microcontinent. Today, the system is fed with sediment from the eastern South Island shelf, through the Otago Fan complex. The main Bounty Channel is about 800 km long and forms a sediment transport link between the continental margin and the distal Bounty Fan, located at the mouth of the Bounty Trough and onlapping onto abyssal oceanic crust. The Bounty Channel system has existed in its present setting since the inception of the Alpine Fault plate boundary in the mid-Cenozoic, while ancestral marine channel systems occur back to the Paleocene.

  17. Dimethylsulfide (DMS) production from dimethylsulfoniopropionate by freshwater river sediments: phylogeny of Gram-positive DMS-producing isolates

    Microsoft Academic Search

    Duane C Yoch; Robin H Carraway; Robert Friedman; Nitin Kulkarni

    2001-01-01

    Freshwater river sediments from both the Coastal Plain and Piedmont regions of South Carolina showed high rates of dimethylsulfide (DMS) production from added dimethylsulfoniopropionate (DMSP). These rates were considered to be high as they were ca. 1% of rates in salt marsh sediments. Most probable number enumeration of DMS producers in river water and sediments were also about 1% of

  18. Suspended-sediment and fresh-water discharges in the Ob and Yenisey rivers, 1960-1988

    Microsoft Academic Search

    R. H. Meade; N. N. Bobrovitskaya; V. I. Babkin

    2000-01-01

    Of the world's great rivers, the Ob and Yenisey rank among the largest suppliers of fresh water and among the smallest suppliers of suspended sediment to the coastal ocean. Sediment in the middle reaches of the rivers is mobilized from bordering terraces and exchanged between channels and flood plains. Sediment in the lower reaches of these great rivers is deposited

  19. Chapter 19 Evolution of Quaternary to Modern Fluvial Network in the Mid-Hungarian Plain, Indicated by Heavy Mineral Distributions and Statistical Analysis of Heavy Mineral Data

    Microsoft Academic Search

    Lajos Ó. Kovács

    2007-01-01

    Heavy mineral data of 590 samples from ten cored boreholes, penetrated into Quaternary fluvial successions in the central part of the Hungarian Plain, and complemented by data from modern river sediments, have been evaluated using numerical methods. Cluster analysis and principal component analysis (PCA) have revealed appreciable similarities between the heavy mineral composition of modern river sediments and those from

  20. Geochemistry and mineralogy of shallow alluvial aquifers in Daudkandi upazila in the Meghna flood plain, Bangladesh

    NASA Astrophysics Data System (ADS)

    Hasan, M. Aziz; von Brömssen, Mattias; Bhattacharya, Prosun; Ahmed, Kazi Matin; Sikder, Arif Mohiuddin; Jacks, Gunnar; Sracek, Ondra

    2009-04-01

    The shallow alluvial aquifers of the delta plains and flood plains of Bangladesh, comprises about 70% of total land area are mostly affected by elevated concentrations of arsenic (As) in groundwater exposing a population of more than 35 million to As toxicity. Geochemical studies of shallow alluvial aquifer in the Meghna flood plain show that the uppermost yellowish grey sediment is low in As (1.03 mg/kg) compared to the lower dark grey to black sediment (5.24 mg/kg) rich in mica and organic matter. Sequential extraction data show that solid phase As bound to poorly crystalline and amorphous metal (Fe, Mn, Al)-oxyhydroxides is dominant in the grey to dark grey sediment and reaches its maximum level (3.05 mg/kg) in the mica rich layers. Amount of As bound to sulphides and organic matter also peaks in the dark grey to black sediment. Vertical distributions of major elements determined by X-ray fluorescence (XRF) show that iron (Fe2O3), aluminum (Al2O3) and manganese (MnO) follow the general trend of distribution of As in the sediments. Concentrations of As, Mn, Fe, HCO3 -, SO4 2- and NO3 - in groundwater reflect the redox status of the aquifer and are consistent with solid phase geochemistry. Mineralogical analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) fitted with energy dispersive X-ray spectrometer (EDS) revealed dominance of crystalline iron oxides and hydroxides like magnetite, hematite and goethite in the oxidised yellowish grey sediment. Amorphous Fe-oxyhydroxides identified as grain coating in the mica and organic matter rich sediment suggests weathering of biotite is playing a critical role as the source of Fe(III)-oxyhydroxides which in turn act as sink for As. Presence of authigenic pyrite in the dark grey sediment indicates active reduction in the aquifer.

  1. 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.

  2. 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

  3. Plain Talk about Lupus and Key Words

    MedlinePLUS

    ... Words to Ask About Word Meaning in Plain English ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ ___________ ________________________ 46 Places To Call For More Information YOUR ...

  4. Floods, floodplains, delta plains — A satellite imaging approach

    NASA Astrophysics Data System (ADS)

    Syvitski, James P. M.; Overeem, Irina; Brakenridge, G. Robert; Hannon, Mark

    2012-08-01

    Thirty-three lowland floodplains and their associated delta plains are characterized with data from three remote sensing systems (AMSR-E, SRTM and MODIS). These data provide new quantitative information to characterize Late Quaternary floodplain landscapes and their penchant for flooding over the last decade. Daily proxy records for discharge since 2002 and for each of the 33 river systems can be derived with novel Advanced Microwave Scanning Radiometer (AMSR-E) methods. A descriptive framework based on analysis of Shuttle Radar Topography Mission (SRTM) data is used to capture the major landscape-scale floodplain elements or zones: 1) container valleys with their long and narrow pathways of largely sediment transit and bypass, 2) floodplain depressions that act as loci for frequent flooding and sediment storage, 3) zones of nodal avulsions common to many continental scale rivers, and often located seaward of container valleys, and 4) coastal floodplains and delta plains that offer both sediment bypass and storage but under the influence of marine processes. The SRTM data allow mapping of smaller-scale architectural elements in unprecedented systematic manner. Floodplain depressions were found to play a major role, which may largely be overlooked in conceptual floodplain models. Lastly, MODIS data (independently and combined with AMSR-E) allows the tracking of flood hydrographs and pathways and sedimentation patterns on a near-daily timescale worldwide. These remote-sensing data show that 85% of the studied major river systems experienced extensive flooding in the last decade. A new quantitative paradigm of floodplain processes, honoring the frequency and extent of floods, can be develop by careful analysis of these new remotely sensed data.

  5. Cretaceous sedimentation along the Betic-Maghrebidian Alboran margin (Gibraltar arch area, southern Spain, northern Morocco)

    SciTech Connect

    Olivier, P.; Thurow, J.; Kuhnt, W. (Univ. of Toulouse (France))

    1988-08-01

    Cretaceous sediments of the Alboran margin are now outcropping within four structural units (Malaguides, Dorsale, Predorsalina, Mauretanian) in the Gibraltar arch area. Sediments from carbonate platform, slope, proximal fan, distal fan, and pelagic deep-water environments were observed. Four evolutionary stages were discriminated: (1) buildup of a carbonate platform, formation of half-graben structures (rifting), breakup, and local oceanization (Late Triassic and Jurassic); pelagic sediments in the shelf-to-slope environment; (2) continuing pelagic sedimentation with local uplift (preflysch phase of Tithonian to Early Cretaceous; calciturbidites with ophiolite debris); (3) local deposition of thick clastic wedges (Barremian to late Albian), and (4) decreasing sedimentation rates and ceasing terrigenous input (late Albian), resulting in an overall pelagic environment (Cenomanian to Paleocene). Two supra-regional black shale events are documented in the sedimentary sequences: (1) late Liassic, during the rifting stage, and (2) Cenomanian-Turonian, during a juvenile oceanic stage. Total organic carbon content is up to 30% in Liassic and 15% in Cenomanian-Turonian. In both cases, organic-rich deposits may reach 10 m thick. Attention is focused on sedimentation patterns on shelf-to-abyssal paleobathymetric settings during Cenomanian-Turonian. Within shelf sequences (Malaguides and Dorsale), condensation and stratigraphic gaps are common. Sediments include pelagic limestone and marlstone. The deeper sequences (Predorsalian and Maurentanian) exhibit organic-rich siliceous sedimentation intercalated in a calciturbidite sequence. Sedimentological, biostratigraphic, and geochemical characteristics of this sedimentation are briefly discussed.

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

    USGS Publications Warehouse

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

    2015-01-01

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

  7. Expanded Plain TEX Steven Smith

    E-print Network

    Mintmire, John W.

    Expanded Plain TEX Sept 2004 2.8.4 Karl Berry Steven Smith #12;This manual documents the Eplain Berry. Steven Smith wrote the documentation for the commutative diagram macros. (He also wrote the macros.) Some additions/corrections by Adam Lewenberg. Permission is granted to make and distribute

  8. White Plains MetARs

    NSDL National Science Digital Library

    Steve Kluge

    In this activity, students use METeorological Aerodome Reports (METARs) to view changes in temperature, dew point, air pressure, sky condition, wind, and visibility at White Plains, New York. After studying the reports, they answer a series of questions related to radiation and insolation, radiative balance, and meteorological processes.

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

    NASA Astrophysics Data System (ADS)

    Niu, Y.

    2003-04-01

    Since Mike's two classic papers [1,2], the last 35 years have seen much progress on MORB petrogenesis because of improved experimental/theoretical approaches and because of rapid growth of geochemical database on MORB samples from the global ocean ridge system. Our current understanding of MORB genesis also owes a great deal to the studies [3-5] of abyssal peridotites - interpreted as mantle melting residues for MORB. Recent studies [6,7] have confirmed the complementary relationship between MORB and abyssal peridotites, but also revealed the hidden complexities in these peridotites such as olivine addition [6-8] and melt refertilization [7-9]. These same studies [6,7] have simultaneously excited serious debates on the petrogenesis of abyssal peridotites [10-14]. These debates are actually different views on the same observations: modes and major element compositions of residual minerals, and trace element data on residual clinopyroxene (Cpx) [3-5]. I report here whole-rock ICP-MS trace element data on abyssal peridotites including samples previously studied for Cpx trace elements [5]. Residual Cpx shows highly depleted light rare earth elements (LREEs) with flat-to-elevated middle-heavy REEs (e.g., [Ce]_N = 0.25±0.51 [mean±1?]; [Yb]_N = 6.09±2.59; [Nd/Sm]_N = 0.29±0.14; [Nd/Dy]_N = 0.14±0.11), which is consistent with varying extents of melt depletion [5]. In contrast, whole-rock data of the same samples [15] show elevated abundances of LREEs with flat to enriched LREE patterns (e.g., [Ce]_N = 0.57±0.74; [Yb]_N, 0.72±0.41; [Nd/Sm]_N = 1.18±0.41; [Nd/Dy]_N = 0.70±0.38). If the constituent Cpx records the melting process, the whole-rock data would suggest post-melting LREE addition. The significant correlations of LREEs with high-field strength elements (HFSEs) (e.g., RCe-Zr = 0.730, RNd-Zr = 0.789, RCe-Nb = 0.836, RNd-Nb = 0.900) suggest that this LREE addition is magmatic refertilization (vs. serpentinization). The observation that this magmatic refertilization did not affect Cpx composition is informative. There are two possibilities: (A) The refertilization took place in the "cold" thermal boundary layer atop the mantle through which the ascending melts cooled and crystallized olivine out accompanied by some melt entrapment, giving rise to excess olivine and elevated LREE abundances in the bulk tock [6-8]. (B) The ascending melts, when percolating along grain boundaries, could only affect Cpx crystal "rims", which together with the rest of the rock had been serpentinized; the Cpx trace elements were determined from unaffected Cpx "cores" [5]. In either scenario, the following statements are true: (1) the ascending melts will interact with the advanced residues, seen on petrographic scales; (2) the interaction is not chemically reactive; and (3) porous flow is significant even at the "cold" shallow depths. These statements are supported by unexpectedly large, yet correlated variations of HFSEs (Nb = 0.5-1840; Ta = 0.1-71; Zr = 9-18605; Hf = 1-590; Nb/Ta = 0.8-200; Zr/Hf = 2.4-336) exhibited by the entire data set [16]. References: [1] O'Hara, Earth Sci. Rev., 4, 69-133, 1968; [2] O'Hara, Nature, 220, 683-686, 1968; [3] Dick et al., Earth Planet. Sci. Lett., 69, 88-106, 1984; [4] Dick, Geol. Soc. Lon. Spec. Pub., 42, 71-105, 1989; [5] Johnson et al., J. Geophys. Res., 95, 2661-2678, 1990; [6] Niu et al., Earth Planet. Sci. Lett., 152, 251-265, 1997; [7] Niu, J. Petrol., 38, 1047-1074, 1997; [8] Niu & Hékinian, Earth Planet. Sci. Lett., 146, 243-258, 1997; [9] Elthon, J. Geophys. Res., 97, 9015-9025, 1992; [10] Walter, J. Petrol., 40, 1187-1193, 1999; [11] Niu, J. Petrol., 40, 1195-1203, 1999; [12] Baker & Beckett, Earth Planet. Sci. Lett., 171, 49-61, 1999; [13] Asimow, Earth Planet. Sci. Lett., 169, 303-319, 1999; [14] Lundstrom, Nature, 403, 527-530, 2000; [15] Fisher et al., Ofioliti, 11, 147-178, 1987; [16] Niu & Greig, Eos Trans. AGU, Suppl., 81 (48), F1282, 2000.

  10. Abyssal water mass exchange between the Japan and Yamato Basins in the Japan Sea

    NASA Astrophysics Data System (ADS)

    Senjyu, Tomoharu; Aramaki, Takafumi; Tanaka, Shinichi S.; Zhang, Jin; Isoda, Yutaka; Kumamoto, Yuichiro; Hibino, Sho; Nakano, Toshiya

    2013-10-01

    Bottom water exchange between the Japan and Yamato Basins in the abyssal Japan Sea is investigated based on data from two research cruises in June 2010 and June 2011. Distributions of water properties and velocity profiles from CTD/LADCP observations revealed a two-layer water mass exchange in a rotating system. The cold Japan Basin Bottom Water (JBBW) with high dissolved oxygen (DO) concentrations flowed into the Yamato Basin along the northern boundary of the channel connecting the basins, while the warmer, lower-DO Yamato Basin Bottom Water (YBBW) extended over the JBBW along the southern periphery of the channel. A benthic front between the JBBW and YBBW was observed in both cruises, though the front shifted to the northeast in 2011 compared with its 2010 location. Further, the bottom flows in the channel were not unidirectional in 2011, though consistent southwestward flows were observed in 2010. The JBBW transport into the Yamato Basin was also larger in 2010 than in 2011. Analysis of historical hydrographic data showed that the benthic front exists mostly in the narrowest region of the channel, though it fluctuates temporarily to the northeast or southwest. The fluctuation of the benthic front appears to be associated with the JBBW transport because the observations in June 2010 and June 2011 were carried out during periods of southwestward extension of cold water and northeast protrusion of warm water, respectively. A relationship between benthic front displacements and mesoscale warm eddy migrations is suggested.

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

    NASA Astrophysics Data System (ADS)

    Prusten, Mark

    2008-08-01

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

  12. Aquatic sediments

    SciTech Connect

    DePinto, J.V.; Young, T.C.; Booty, W.G.

    1984-06-01

    This literature review includes conference proceedings on the interactions of PCBs. Papers range from the adsorption/desorption behavior of PCBs to the influence of suspended and benthic sediments on fate and transport modeling of PCBs in the Great Lakes. Other papers are included in the review which involve analytical and sampling methods, paleolimnology, and modeling and sediment transport. Two papers presented the results of using radionuclides (Pb-210, Ru-106, Cs-137) in the study of lake-sediment dynamics. 111 references.

  13. Aquatic sediments

    SciTech Connect

    Bonner, J.S.; Autenrieth, R.L.; Schreiber, L. (Texas A and M Univ., College Station (United States))

    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.

  14. Middle and upper jurassic depositional environments at outer shelf and slope of Baltimore Canyon Trough

    Microsoft Academic Search

    L. A. Gamboa; P. L. Stoffa; M. Truchan

    1985-01-01

    New CDP data acquired in the Baltimore Canyon Trough during project LASE made it possible to map a continuous Jurassic sedimentary sequence from the continental margin to the abyssal plain without interruption by basement structures. Intense carbonate sedimentation is inferred at the outer shelf during the Middle and Late Jurassic. Carbonate sedimentation probably started during the Middle Jurassic with a

  15. 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.

  16. 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.

  17. 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.

  18. High Plains Aquifer Hydrologic Observatory

    NASA Astrophysics Data System (ADS)

    Steward, D. R.

    2004-12-01

    The High Plains Aquifer encompasses 174,000 square miles in eight states and provides the primary source of potable water to the region. The hydrologic cycle exhibits great diversity across this geological basin, with significant expanses experiencing sustained declines in groundwater elevation (e.g., portions of the southern and central basins in Kansas, New Mexico, Oklahoma, and Texas) while other areas are experiencing rises (e.g., portions of the northern basin in central Nebraska). The proposed High Plains Aquifer Hydrologic Observatory would promote significant scientific advancement in hydrology related to: (1) Recharge and evapotranspiration, (2) Surface water-groundwater exchange in dynamic riparian corridors, (3) Ecological role of vegetation in the hydrologic cycle, (4) Human systems and the hydrologic cycle, (5) Multi-scale monitoring, modeling & analysis, (6) Climate change studies, and (7) Utilization of remote sensing technology

  19. Ion exchange and soil attenuation of Gulf Coast and Great Plains soils. Quarterly report, April 1June 30, 1986

    Microsoft Academic Search

    D. J. Hassett; A. Larson; D. Daly

    1986-01-01

    The overall objective of this project is to study the trace element attenuation characteristics of various overburden sediments from Texas and the Northern Great Plains. Soil trace element attenuation was measured using batch experiments. These batch attenuation experiments are being carried out on carefully selected soils which have been characterized with respect to both chemical and mineralogical properties. The key

  20. Disequilibria in the uranium decay series in sedimentary deposits at Allen's cave, nullarbor plain, Australia: Implications for dose rate determinations

    Microsoft Academic Search

    Jon M. Olley; Richard G. Roberts; Andrew S. Murray

    1997-01-01

    Disequilibrium in the uranium decay series can cause a time-dependent variation in the radiation dose received by deposited sediments. In luminescence and ESR dating studies, the observation of disequilibrium usually requires modelling of the variation in dose rate as a function of burial time. In this paper, we report on radionuclide data collected from Allen's Cave on the Nullarbor Plain,

  1. 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

  2. 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 ( ?) and quantity of littoral transport ( Mtotal) are the most important factors controlling inlet stability. Greater discharge and/or tidal prism increase the ability of river and estuarine systems to interrupt longshore sediment transport, maintain and naturally stabilize tidal entrances, and promote updrift deposition. Thus, prior to human modification and stabilization efforts, the Mermentau River entrance would be classified as wave-dominated, Sabine Pass as tide-dominated, and Calcasieu Pass as tide-dominated to occasionally mixed. Hoyt [Hoyt, J.H., 1969. Chenier versus barrier, genetic and stratigraphic distinction. Am. Assoc. Petrol. Geol. Bull., 53: 299-306] presented the first detailed depositional model for chenier genesis and mudflat progradation, which he attributed to changes in Mississippi River flow direction (i.e., delta switching) caused by upstream channel avulsion. However, Hoyt's model oversimplifies Chenier-Plain evolution because it omits ridges created by other means. Thus, the geologic evolution of the Chenier Plain is more complicated than channel avulsions of the Mississippi River, and it involved not only chenier ridges (i.e., transgressive), but also ridges that are genetically tied to regression (beach ridges) and lateral accretion (recurved spits). A six-stage geomorphic process-response model was developed to describe Chenier-Plain evolution primarily as a function of: (i) the balance between sediment supply and energy dissipation associated with Mississippi River channel avulsions, (ii) local sediment reworking and lateral transport, (iii) tidal-entrance dynamics, and (iv) possibly higher-than-present stands of Holocene sea level. Consequently, the geneses of three different ridge types (transgressive, reg

  3. Coastal Mudflat Accretion under Energetic Conditions, Louisiana Chenier-Plain Coast, USA

    NASA Technical Reports Server (NTRS)

    Draut, Amy E.; Kineke, Gail C.; Huh, Oscar K.; Grymes, John M., III; Westphal, Karen A.; Moeller, Christopher C.

    2005-01-01

    Mudflat accretion on the chenier-plain coast of Louisiana, northern Gulf of Mexico, is anomalous in an area that otherwise experiences widespread land loss due to rapid relative sea level rise. Accretion is shown to be related to energetic events (Winta cold fronts and occasional tropical-dcprrssion srmms) using a 17-year record of meteorological conditions and aerial surveys The results indicate substantial differences between the behavior of sand- and mud-dominated coastal systems under energetic conditions. Comparison of the Louisiana chenier plain to other mud-rich coasts indicates that certain conditions are necessary for mudflat accretion to occur during energetic atmospheric activity. These include an abundant supply of fine-grained fluvial sediment and resuspension events that maintain an unconsolidated sea floor, dominant onshore wind direction during energetic conditions, particularly when onshore winds coincide with high fluvial sediment input to the coastal ocean, and a low tidal range.

  4. Stratigraphic evolution of the late Holocene Ganges–Brahmaputra lower delta plain

    Microsoft Academic Search

    M. A. Allison; S. R. Khan; S. L. Goodbred; S. A. Kuehl

    2003-01-01

    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

  5. 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.

  6. Sediment Transport

    NSDL National Science Digital Library

    Karen Williams

    Each student reviews a recent USGS publication detailing sediment transport data collection and reduction on the Yellowstone River. Using that report, they answer a series of questions about sediment transport and make some basic hydrologic and hydraulic calculations using data in the report. They also use USGS software to analyze cross-sections on the Yellowstone in a real world application. Designed for a geomorphology course

  7. Environmental perceptions in Great Plains novels 

    E-print Network

    Pardee, Celeste Frances

    1976-01-01

    encompasses a wide range of topics, including explorers', settlers', and surveyors' images of the Plains, as well as perceptions of natural resources and climatic hazards. However, no one appear s to have studied novelists' depic- tions of the Plains... wind. Characters in novels perceive and react to the non-climatic Plains hazards--prairie fires and locust plagues- ? in almost the same way that histories and diaries reveal that actual settlers reacted. Yet significant divergence also exists...

  8. Montagne et plaines: adversaires ou partenaires?

    E-print Network

    Stoffel, Markus

    Montagne et plaines: adversaires ou partenaires? Exemple du Haut Atlas, Maroc #12;Adresse de? Exemple du Haut Atlas, Maroc Préface OSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Haut Atlas, colonne vertébrale du Maroc

  9. Contrasting lithofacies architecture in ring-plain deposits related to edifice construction and destruction, the Quaternary Stratford and Opunake Formations, Egmont Volcano, New Zealand

    NASA Astrophysics Data System (ADS)

    Palmer, Beth A.; Neall, Vincent E.

    1991-11-01

    The early constructional and destructional history of ancestral Egmont Volcano is recorded by variations in lithofacies assemblages and architecture in volcaniclastic deposits making up the southern ring plain. Eruptive periods and edifice construction are recorded by aggradational sequences of debris-flow deposits on the ring plain and numerous tephra deposits preserved on the lower flanks of the volcano. The aggradational sequences represent fairly long-term periods of accumulation when a succession of lahars delivered coarse-grained sediment to the ring plain. Edifice destruction is recorded on the ring plain by deposits of debris-avalanches and associated debris flows. Individual deposits represent rapid (as much as 2.6 km 3), but episodic, sedimentation over large areas (up to 500 km 2) of the ring plain. Sedimentation following these events was slow, with reworked tephra and lignite accumulating over most of the ring plain. Episodes of edifice destruction usually marked the beginning of long-term quiescent intervals or periods of low-frequency eruptive activity. Tephra deposits on the flanks of the volcano are not as abundant as in stratigraphic intervals representing periods of edifice construction.

  10. 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

  11. Structure along the northwest edge of the Snake River Plain interpreted from seismic refraction

    NASA Astrophysics Data System (ADS)

    Pankratz, Leroy W.; Ackermann, Hans D.

    1982-04-01

    The results of a seismic refraction survey at the Idaho National Engineering Laboratory along the northwest boundary of the Snake River Plain show that velocities of the volcanic rocks beneath the Plain increase from 1.5 km/s at the surface to 5.2-5.5 km/s at depths between approximately 2200 and 2500 m. An exploration well in the area (INEL-1) encountered Cenozoic volcanic rock with some interbedded sediments to a depth of 2460 m underlain by 700 m of a rhyodacite porphyry. The refraction data demonstrate a nearly vertical faultlike discontinuity of about 1000-m displacement beneath the plain, about 1.8 km from the southeast flank of the Arco Hills (Lost River Range). Whether this discontinuity represents the northwest flank of the Snake River Plain graben, the east flank of the Lost River Range fault, Or a caldera wall is not known. The results further indicate that Paleozoic rocks may extend beneath the plain as far as 5.6 km southeastward from the Arco Hills.

  12. 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.

  13. 2010 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide

    E-print Network

    Mukhtar, Saqib

    and seed. Cotton producers in the Texas High Plains face difficult decisions at harvest time that have2010 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide Dr. Randy Boman, Extension Agronomist-Cotton, Dr. Mark Kelley, Extension Program Specialist-Cotton, Texas AgriLife Extension Service; Dr

  14. 2009 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide

    E-print Network

    Behmer, Spencer T.

    and seed. Cotton producers in the Texas High Plains face difficult decisions at harvest time that have2009 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide Dr. Randy Boman, Extension Agronomist-Cotton, Dr. Mark Kelley, Extension Program Specialist-Cotton, Texas AgriLife Extension Service; Dr

  15. Hydrologic Controls On Methylmercury Availability In Coastal Plain Rivers

    NASA Astrophysics Data System (ADS)

    Bradley, P. M.; Brigham, M. E.; Burns, D. A.; Button, D. T.; Lutz, M. A.; Marvin-DiPasquale, M. C.; Riva-Murray, K.; Journey, C.

    2011-12-01

    Methylmercury (MeHg) in streams is often attributed to methylation in up-gradient wetland areas, with episodic flood events maximizing wetland-stream hydrologic connectivity and dominating MeHg supply to the stream habitat. A number of studies have demonstrated that Coastal Plain streams in the southeastern United States are particularly vulnerable to high MeHg bioaccumulation and have attributed this vulnerability to wetland abundance and strong hydrologic connectivity between wetland areas and adjacent stream aquatic habitat. Because characteristically coarse-grained Coastal Plain sediments favor vertical infiltration with little surface runoff, flood events attributable to Coastal Plain precipitation are driven by rising groundwater, promoting efficient transport of MeHg from wetland/floodplain source areas to the stream habitat and increasing in-stream availability. Several observations at McTier Creek, South Carolina, however, suggest that good hydrologic connectivity and efficient MeHg transport in Coastal Plain systems are not limited to flood conditions. Close correspondence between stream and shallow-groundwater water levels at McTier indicate good hydrologic connectivity exists prior to flood conditions. Dissolved MeHg concentrations do not increase under flood conditions. Thus, we assessed the flux of water and dissolved mercury (Hg) species (FMeHg and total Hg (FTHg)) from surface water and groundwater sources in a short reach at McTier Creek during separate events in April and July 2009, to determine the importance of shallow groundwater Hg transport from floodplain areas to the stream under non-flood conditions. Mass balance assessments indicated that, under non-flood conditions, the primary supply of water, FMeHg, and FTHg within the reach (excluding upstream surface-water influx) was groundwater discharge, rather than tributary transport from wetlands, in-stream MeHg production, or atmospheric deposition. The results indicate efficient transport of MeHg from out-of-channel (wetland and riparian floodplain) areas to the stream aquatic habitat in Coastal Plain streams of the southeastern United States, even under non-flood conditions.

  16. Lipid, sterols and fatty acid composition of abyssal holothurians and ophiuroids from the North-East Pacific Ocean: Food web implications

    Microsoft Academic Search

    Jeffrey C. Drazen; Charles F. Phleger; Michaela A. Guest; Peter D. Nichols

    2008-01-01

    The lipid, fatty acid (FA), and sterol composition of two ophiuroids and four holothurians from the abyssal eastern North Pacific were analysed to assess their feeding habits and to ascertain their composition for use in a larger study to examine food web dynamics and trophic ecology. Holothurians were rich in phytosterols and algal derived FA such as docosahexaenoic acid and

  17. Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions to Global Heat and Sea Level Rise Budgets*

    E-print Network

    Johnson, Gregory C.

    Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions of recent warming of these regions in global heat and sea level budgets. The authors 1) compute warming produces a 0.053 (60.017) mm yr21 increase in global average sea level and the deep warming south

  18. Relative paleointensity of geomagnetic field recorded by glaciomarine sediments in Prydz Bay as a potential time-marker

    NASA Astrophysics Data System (ADS)

    Ge, Shulan; Wu, Li; Chen, Zhihua; Wang, Rujian; Liu, Helin; Huang, Yuanhui; Tang, Zheng

    2015-04-01

    Glaciomarine sediments in Antarctica are notoriously known to be poorly dated in glacial-interglacial scales because of scarcity of calcareous foraminifera and variable old carbon input to the bulk sediment both of which hinder the use of AMS dating. Therefore relative paleointensity of geomagnetic field (RPI) from these cores are obtained to produce this inference. The results show that the abyssal (>2000 m) cores present comparative features of RPIs with PISO1500, the global geomagnetic field variation for the last 1500 ka, while conditions are much more complicated for the cores from the continental shelf and slope. Overall an average sedimentation rate ~1-2 cm/ka is deduced from this comparison, which agrees well with nearby ODP cores. Further work of a pilot core among them support our RPI comparison, in which grain size changes through Weibull decomposition, biogenic Ba flux calculation are included. Therefore, continuous deposition in abyssal Prydz Bay can be expected and RPI method could serve as an important tool for determination of the Quaternary age framework.

  19. HIGH PLAINS INTEGRATED PEST MANAGEMENT GUIDE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many diseases affect crops grown in the High Plains region. This guide is intended to provide current effective management options for plant diseases affecting all major field crops grown in the High Plains region. Chemical and non-chemical control practices, when available, are described in detai...

  20. Life on the Great Plains. [Lesson Plan].

    ERIC Educational Resources Information Center

    2000

    In this four-part lesson, students examine the concept of geographic region by exploring the history of the United States Great Plains. In Part I, students gather information about the location and environment of the Great Plains in order to produce a map outlining the region in formal terms. In Part II, students examine how the region has been…

  1. Second chance for the plains bison

    Microsoft Academic Search

    Curtis H. Freese; Keith E. Aune; Delaney P. Boyd; James N. Derr; Steve C. Forrest; C. Cormack Gates; Peter J. P. Gogan; Shaun M. Grassel; Natalie D. Halbert; Kyran Kunkel; Kent H. Redford

    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

  2. Mountain-Plains Curriculum Package. Teacher Guide.

    ERIC Educational Resources Information Center

    England, Robert G.

    Designed to give the teacher a capsule explanation of how the system works, this guide introduces the Mountain-Plains instructor to specific curriculum materials and provides examples of the basic instruments used in the Mountain-Plains program, a residential, family-based education program developed to improve the economic potential and lifestyle…

  3. 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 Louisiana’s high rates of wetland loss, this study points to evidence of wetland accretion in SW Louisiana as a result of the Atchafalaya River diversion.

  4. Sedimentation and depositional environments of the Barremian-Cenomanian Debre Libanose Sandstone, Blue Nile (Abay) Basin, Ethiopia

    Microsoft Academic Search

    A. Wolela

    2009-01-01

    Exploration of oil and gas deposits in the Blue Nile Basin targeted the Debre Libanose Sandstone as a reservoir objective. The unit was deposited in broad alluvial plains, and shows some elements of the Platte type braided river sedimentation in the lower and middle succession. The braided river sedimentation is dominated by single storey and multistorey amalgamated sandstone bodies, and

  5. FLUVIAL CONDITIONS DURING THE HOLOCENE AS EVIDENCED BY ALLUVIAL SEDIMENTS FROM ABOVE HOWISON'S POORT, NEAR GRAHAMSTOWN, SOUTH AFRICA

    Microsoft Academic Search

    C. A. Lewis; P. M. Illgner

    1998-01-01

    Mapping and analyses of alluvial sediments in the Berg River valley, near Grahamstown, has resulted in the identification of over 5 000 years of environmental stability in the early Holocene, in which flood plain sediments accumulated. Subsequent to 4390±90 BP environmental instability, probably due to climatic fluctuations, resulted in the formation of river terraces. Further research is needed to establish

  6. 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.

  7. Trend analyses of sediment data for the DEC project

    USGS Publications Warehouse

    Rebich, Richard Allen

    1995-01-01

    Daily stream discharge, suspended-sediment concentration, and suspended-sediment discharge data were collected at eight sites in six watersheds of the Demonstration Erosion Control project in the Yazoo River Basin in north-central Mississippi during the period July 1985 through September 1991. The project is part of an ongoing interagency program of planning, design, construction, monitoring, and evaluation to alleviate flooding, erosion, sedimentation, and water-quality problems for watersheds located in the bluff hills upstream of the Mississippi River alluvial plain. This paper presents preliminary results of trend analyses for stream discharge and sediment data for the eight project sites. More than 550 stream discharge measurements and 20,000 suspended-sediment samples have been collected at the eight sites since 1985.

  8. Tidal drawdown: A mechanism for producing cyclic sediment laminations in glaciomarine deltas

    NASA Astrophysics Data System (ADS)

    Smith, Norman D.; Phillips, Andrew C.; Powell, Ross D.

    1990-01-01

    A process for generating sediment laminations by tide-controlled storage and release of delta-plain sediment is described, using data from two glacier-fed deltas in Glacier Bay, Alaska. Intertidal mudflats and lower channel reaches store fluvial bed load and suspended load when the lower delta plain is flooded, which occurs periodically during spring intervals and continuously during neap intervals. Spring lower low tides expose the channel mouths at the delta lip and the entire delta plain, which causes abrupt transport pulses of stored sediment into the basin. Each pulse and ensuing flood tide forms a coarse and fine laminated couplet in the fjord-head basin. Neap-generated deposits are either structureless or faintly laminated.

  9. 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.

  10. 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.

  11. 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.

  12. Suspended-sediment and fresh-water discharges in the Ob and Yenisey rivers, 1960-1988

    USGS Publications Warehouse

    Meade, R.H.; Bobrovitskaya, N.N.; Babkin, V.I.

    2000-01-01

    Of the world's great rivers, the Ob and Yenisey rank among the largest suppliers of fresh water and among the smallest suppliers of suspended sediment to the coastal ocean. Sediment in the middle reaches of the rivers is mobilized from bordering terraces and exchanged between channels and flood plains. Sediment in the lower reaches of these great rivers is deposited and stored (permanently, on a millennial time scale) in flood plains. Sediment discharges, already small under natural conditions, are diminished further by large manmade reservoirs that trap significant proportions of the moving solids. The long winter freeze and sudden spring breakup impose a peakedness in seasonal water runoff and sediment discharge that contrasts markedly with that in rivers of the tropics and more temperate climates. Very little sediment from the Ob and Yenisey rivers is being transported to the open waters of the Arctic Ocean under present conditions.

  13. CORN BELT PLAIN RIVER AND STREAMS PROJECT - 3 BIOCRITERIA PRODUCTS

    EPA Science Inventory

    This effort resulted in eight products, as follows: 1) Development of Index of Biotic Integrity Expectations for the Ecoregions of Indiana I. Central Corn Belt Plain; 2) Ibid. II. Huron-Erie Lake Plain; 3) Ibid III. Northern Indiana Till Plain; 4) Ibid .IV.Eastern Corn Belt Plain...

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 2005 Texas High Plains Cotton Variety Ratings

    E-print Network

    Mukhtar, Saqib

    2005 Texas High Plains Cotton Variety Ratings for Verticillium Wilt Dr. Terry Wheeler Research ($) (Loan value x yield) ­ seed + tech fees/acre % Plants with wilt on Aug. 25 (rank) Paymaster 2167RR 909

  20. Plain Language Thesauruses | accrualnet.cancer.gov

    Cancer.gov

    These resources offer plain language equivalents to medical terms, phrases, and references frequently used in clinical trials. They are helpful when developing informed consent forms and other patient information text.

  1. Sorghum Tillage in the Texas High Plains 

    E-print Network

    Bean, Brent W.; Jones, Ordie; Unger, Paul; Baumhardt, Louis

    2003-05-12

    of planters or drills. A mulch treader with ground-driven, rotating fingers (similar to a sand- M ATER IS ALL we sell in agriculture.? Whether the enter- prise is corn, cattle, cauliflower, cotton, or grain sorghum water is essential for its pro- duction... and the R North Texas (Rolling Plains, South Plains and Panhandle regions) is produced on dryland or with limited irrigation. Consequently, water manage- ment, both precipitation and supplemental irriga- tion water, is the most important factor in sorghum...

  2. Holocene Coastal Stratigraphy and the Sedimentary Development of the Hai Phong Area of the Bac Bo Plain (Red River Delta), Vietnam

    Microsoft Academic Search

    DOAN DINH LAM; William E Boyd

    2003-01-01

    We report a study of the Holocene coastal sediments of the Hai Phong area of the Bac Bo Plain (also known as the Red River Delta) in northern Vietnam. This is the first attempt to interpret the region's coastal depositional environments in the light of a geological model of Holocene environmental change recognising the interacting roles of Holocene sea-level change,

  3. Preliminary geological interpretation and lithologic log of the exploratory geothermal test well (INEL-1), Idaho National Enginering Laboratory, eastern Snake River Plain, Idaho

    Microsoft Academic Search

    D. J. Doherty; L. A. McBroome; M. A. Kuntz

    1979-01-01

    A 10,365 ft (3159 m) geothermal test well was drilled in the spring of 1979 at the Idaho National Engineering Laboratory, eastern Snake River Plain, Idaho. The majority of rock types encountered in the borehole are of volcanic origin. An upper section above 2445 ft (745 m) consists of basaltic lava flows and interbedded sediments of alluvial, lacustrine, and volcanic

  4. Eddy-driven sediment transport in the Argentine Basin: Is the height of the Zapiola Rise hydrodynamically controlled?

    NASA Astrophysics Data System (ADS)

    Weijer, Wilbert; Maltrud, Mathew E.; Homoky, William B.; Polzin, Kurt L.; Maas, Leo R. M.

    2015-03-01

    In this study, we address the question whether eddy-driven transports in the Argentine Basin can be held responsible for enhanced sediment accumulation over the Zapiola Rise, hence accounting for the existence and growth of this sediment drift. To address this question, we perform a 6 year simulation with a strongly eddying ocean model. We release two passive tracers, with settling velocities that are consistent with silt and clay size particles. Our experiments show contrasting behavior between the silt fraction and the lighter clay. Due to its larger settling velocity, the silt fraction reaches a quasisteady state within a few years, with abyssal sedimentation rates that match net input. In contrast, clay settles only slowly, and its distribution is heavily stratified, being transported mainly along isopycnals. Yet, both size classes display a significant and persistent concentration minimum over the Zapiola Rise. We show that the Zapiola Anticyclone, a strong eddy-driven vortex that circulates around the Zapiola Rise, is a barrier to sediment transport, and hence prevents significant accumulation of sediments on the Rise. We conclude that sediment transport by the turbulent circulation in the Argentine Basin alone cannot account for the preferred sediment accumulation over the Rise. We speculate that resuspension is a critical process in the formation and maintenance of the Zapiola Rise.

  5. Great Plains Synfuels` hidden treasures

    SciTech Connect

    Kuhn, A.K.; Duncan, D.H. [Dakota Gasification Co., Beulah, ND (United States)

    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.

  6. Interpretation of sea-floor processes in Gulf of Mexico using GLORIA side-scan sonar system

    Microsoft Academic Search

    B. A. McGregor; N. H. Kenyon; R. G. Rothwell; D. C. Twichell; L. M. Parson

    1986-01-01

    The extensive deformation of the continental slope seaward of Texas and Louisiana by salt tectonics has resulted in a complex pattern of basins and salt-dome highs. One continuous meandering channel was identified in this part of the gulf, extending from the shelf edge to the Sigsbee abyssal plain. Bottom currents have reworked the sediments in this channel's levees seaward of

  7. Geochemistry of abyssal peridotites (Mid-Atlantic Ridge, 15°20?N, ODP Leg 209): Implications for fluid\\/rock interaction in slow spreading environments

    Microsoft Academic Search

    H. Paulick; W. Bach; M. Godard; J. C. M. De Hoog; G. Suhr; J. Harvey

    2006-01-01

    Abyssal peridotite from the 15°20?N area of the Mid-Atlantic Ridge show complex geochemical variations among the different sites drilled during ODP Leg 209. Major element compositions indicate variable degrees of melt depletion and refertilization as well as local hydrothermal metasomatism. Strongest evidence for melt–rock interactions are correlated Light Rare Earth Element (LREE) and High Field Strength Element (HFSE) additions at

  8. New Mineral and Microbial Evidence of High Temperature Hydrothermal Venting Along Off-Axis Abyssal Hill Fault Scarp on the East Pacific Rise Flank at 9° 27'N

    Microsoft Academic Search

    C. Ehrhardt; R. Haymon; T. Holden

    2004-01-01

    During Alvin dives in May 2002, orange-brown filamentous flocculations were sampled from an axis-facing abyssal hill fault scarp located on ˜0.5 Ma seafloor west of the EPR at 9° 27'N. Many sedimentary structures thought to be products of episodic fluid expulsion were found on the top of this hill (see Haymon et al., this session). Recovered samples of flocculations from

  9. Satellite-Based Assessment of Sediment Transport, Distribution and Resuspension Associated with the Atchafalaya River Discharge Plume

    NASA Technical Reports Server (NTRS)

    Walker, Nan; Roberts, Harry; Stone, Gregory; Bentley, Samuel; Huh, Oscar; Sheremet, Alexandru; Rouse, Larry; Inoue, Masamichi; Welsh, Susan; Hsu, S. A.

    2002-01-01

    Tbe Atchafalaya River discharges over 80 x 10(exp 6) tons of sediment annually onto the broad shallow continental shelf of central and western Louisiana. Satellite imagery from the NOAA AVHRR and Terra MODIS are used in this paper to quantify suspended sediment concentrations and to assess sediment transport processes along the Louisiana shelf under varying conditions of river discharge and wind forcing. The image data reveal the maim sources of sediment, direction of transport amd regional extent of wind-wave resuspension. The prevailing easterly winds transport much of the suspended sediments westward toward the Chernier Plain in a well-defined mud stream. Westerly flow rates of 25-50 cm/s (21-43 km per day) have been measured, yielding a transit time of about 1.5-2.5 days from the mouth of Atchafalaya Bay to the Chernier Plain. Progradation rates along the Chernier Plain coast reach 50 m per year. The westward-flowing Atchafalaya "mud stream" is rapidly disrupted by westerly winds and northerly winds, which accompany frequent winter storms and less frequent tropical storms or hurricanes. During these events, the coastal current reverses and sediments are rapidly transported out of Atchafalaya Bay and offshore where substantial sedimentary deposits can also be found. Offshore sediment fluxes during storm events, in combination with wind-wave resuspension, can result in surface sediment "plumes" extending 70 km offshore and 150 km alongshore. Field measurements of suspended sediment concentrations, current and wind velocities, and directions are used to assess sediment transport processes on the shelf. These combined processes are extending the pro-delta deposits of the Atchafalaya-Wax Lake delta complex far onto the continental shelf and supplying sediments for a renewal era of progradation along tbe downdrift Chernier Plain coast.

  10. Holocene flood plain soil formation in the lower Mississippi River Valley: Implications for the interpretation of alluvial paleosols

    SciTech Connect

    Aslan, A. (Univ. of Colorado, Boulder, CO (United States). Dept. of Geological Sciences); Autin, W.J. (Louisiana Geological Survey, Baton Rouge, LA (United States))

    1992-01-01

    Holocene Mississippi River flood soils representing different depositional environments and ages were sampled along three east-west transects between Vicksburg, MS and Baton Rouge, LA. Flood plain soil development is primarily controlled by episodic flood plain sedimentation and ground water table fluctuations as evidenced by relatively thick cumulative soil profiles with abundant mottles, nodules, and slickensides. Within flood plain deposits of similar age, profile, development is best expressed in moderately-drained silty and sandy soils in natural levee and point bar ridge environmental that occur within and adjacent to meander belts. Soils in natural levee and point bar ridge environments greater than 3 ka generally are acidic and have better-developed Bt horizons and brighter mottles than their younger counterparts. In addition to being acidic and brightly mottled, older back swamp soils have larger and more abundant slickensides and iron nodules. This study suggests that alluvial paleosols formed in aggradational settings may be better suited for interpreting flood plain depositional histories and paleohydrology than climate. Parameters such as solum thickness and clay and carbonate accumulations, routinely used to estimate relative time and climatic effects on soil development in Quaternary studies of stable geomorphic surfaces, may not be applicable to ancient alluvial deposits that reflect continuous sediment aggradation.

  11. Evolution of radioactive dose rates in fresh sediment deposits along coastal rivers draining Fukushima contamination plume

    PubMed Central

    Evrard, Olivier; Chartin, Caroline; Onda, Yuichi; Patin, Jeremy; Lepage, Hugo; Lefèvre, Irène; Ayrault, Sophie; Ottlé, Catherine; Bonté, Philippe

    2013-01-01

    Measurement of radioactive dose rates in fine sediment that has recently deposited on channel bed-sand provides a solution to address the lack of continuous river monitoring in Fukushima Prefecture after Fukushima Dai-ichi nuclear power plant (FDNPP) accident. We show that coastal rivers of Eastern Fukushima Prefecture were rapidly supplied with sediment contaminated by radionuclides originating from inland mountain ranges, and that this contaminated material was partly exported by typhoons to the coastal plains as soon as by November 2011. This export was amplified during snowmelt and typhoons in 2012. In 2013, contamination levels measured in sediment found in the upper parts of the catchments were almost systematically lower than the ones measured in nearby soils, whereas their contamination was higher in the coastal plains. We thereby suggest that storage of contaminated sediment in reservoirs and in coastal sections of the river channels now represents the most crucial issue. PMID:24165695

  12. 2011 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide

    E-print Network

    Behmer, Spencer T.

    harvest timings can have adverse effects on both yield and quality of lint and seed. Cotton producers2011 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide Dr. Mark Kelley, Extension Program Specialist-Cotton, Texas AgriLife Extension Service; Dr. Wayne Keeling, Systems Agronomist, Texas

  13. 2007 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide

    E-print Network

    Mukhtar, Saqib

    have adverse effects on both yield and quality of lint and seed. Cotton producers on the Texas High2007 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide Dr. Randy Boman, Extension Agronomist-Cotton, Texas Cooperative Extension; Dr. Mark Kelley, Extension Program Specialist-Cotton, Texas

  14. Cenozoic global sea level, sequences, and the New Jersey transect: Results from coastal plain and continental slope drilling

    Microsoft Academic Search

    Kenneth G. Miller; James V. Browning; Michelle Kominz; Peter J. Sugarman; Nicholas Christie-Blick; Miriam E. Katz; James D. Wright

    1998-01-01

    The New Jersey Sea Level Transect was designed to evaluate the relationships among global sea level (eustatic) change, unconformity-bounded sequences, and variations in subsidence, sediment supply, and climate on a passive continental margin. By sampling and dating Cenozoic strata from coastal plain and continental slope locations, we show that sequence boundaries correlate (within +\\/-0.5 myr) regionally (onshore-offshore) and interregionally (New

  15. The Holocene warm-humid phases in the North China Plain as recorded by multi-proxy records

    Microsoft Academic Search

    Jianxin Cui; Shangzhe Zhou; Hong Chang

    2009-01-01

    The grain size and palinology of sediment and the frequency of 14C dada provide an integrated reconstruction of the Holocene warm-humid phases of the North China Plain. Two clear intense\\u000a and long-lasting warm-humid phases were identified by comprehensive research in this region. The first phase was dated back\\u000a to the early Holocene (9 000–7 000 a BP), and the second

  16. Influence of the Atchafalaya River on recent evolution of the chenier-plain inner continental shelf, northern Gulf of

    E-print Network

    -plain inner shelf and coastal zone form a sink for 7±2% of the sediment load carried by the Atchafalaya River, northern Gulf of Mexico A.E. Draut, G.C. Kineke, D.W. Velasco, M.A. Allison, R.J. Prime Abstract This study, on stratigraphic evolution of the inner continental shelf in the northern Gulf of Mexico. Sedimentary, geochemical

  17. 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.

  18. Influence of lignite mining and utilization on organic matter budget in the Alfeios River Plain, Peloponnese (South Greece)

    SciTech Connect

    G. Siavalas; S. Kalaitzidis; G. Cornelissen; A. Chatziapostolou; K. Christanis [University of Patras, Rio-Patras (Greece). Department of Geology

    2007-09-15

    The Megalopolis Lignite Centre (MLC) is a lignite mining and power generation complex located in Southern Greece. In the present study, we investigate the influence of mining and combustion activities on the organic matter (OM) budget of the adjacent Alfeios River plain sediments. A total of 28 plain-sediment samples along with 13 lignite and ash samples from the MLC were collected. The sediment samples were collected from sites upstream and downstream, as well as from the vicinity of the MLC. Their OM and total organic carbon contents range from 0.9 to 43.4 and 0.2 to 24.0 wt %, respectively. The particulate OM was classified in coal-derived, carbonized particles and fresh tissues according to its origin. The different OM phases were quantified using maceral analysis on the sediments' light fraction obtained after heavy media separations. Approximately 75 vol % of the OM was of anthropogenic origin (coal and char particles) related to mining, transport, and combustion processes at the MLC, revealing a high contamination degree. The most contaminated sites were those in the vicinity of the MLC, but upstream and downstream sites also proved to contain high concentrations of anthropogenic OM. The polycyclic aromatic hydrocarbons content of the same sediments was very low, similar to pristine areas indicating that there is no contamination from such compounds in the area. 82 refs., 7 figs., 6 tabs.

  19. Predicting reservoir sedimentation

    E-print Network

    Wooten, Stephanie

    1997-01-01

    Sediments accumulate in reservoirs and significantly decrease storage capacity. Predicting sedimentation is an important consideration in the design of new reservoir projects and in the management of existing reservoirs. Sedimentation rates may vary...

  20. Chromian spinel as a petrogenetic indicator in abyssal and alpine-type peridotites and spatially associated lavas

    NASA Astrophysics Data System (ADS)

    Dick, Henry J. B.; Bullen, Thomas

    1984-04-01

    The composition of chromian spinel in alpine-type peridotites has a large reciprocal range of Cr and Al, with increasing Cr# (Cr/(Cr+Al)) reflecting increasing degrees of partial melting in the mantle. Using spinel compositions, alpine-type peridotites can be divided into three groups. Type I peridotites and associated volcanic rocks contain spinels with Cr#<0.60; Type III peridotites and associated volcanics contain spinels with Cr#>0.60, and Type II peridotites and volcanics are a transitional group and contain spinels spanning the full range of spinel compositions in Type I and Type II peridotites. Spinels in abyssal peridotites lie entirely within the Type I spinel field, making ophiolites with Type I alpine-type peridotites the most likely candidates for sections of ocean lithosphere formed at a midocean ridge. The only modern analogs for Type III peridotites and associated volcanic rocks are found in arc-related volcanic and intrusive rocks, continental intrusive assemblages, and oceanic plateau basalts. We infer a sub-volcanic arc petrogenesis for most Type III alpine-type peridotites. Type II alpine-type peridotites apparently reflect composite origins, such as the formation of an island-arc on ocean crust, resulting in large variations in the degree and provenance of melting over relatively short distances. The essential difference between Type I and Type III peridotites appears to be the presence or absence of diopside in the residue at the end of melting. Based on an examination of co-existing rock and spinel compositions in lavas, it appears that spinel is a sensitive indicator of melt composition and pressure of crystallization. The close similarity of spinel composition fields in genetically related basalts, dunites and peridotites at localities in the oceans and in ophiolite complexes indicates that its composition reflects the degree of melting in the mantle source region. Accordingly, we infer from the restricted range of spinel compositions in abyssal basalts that the degree of mantle melting beneath mid-ocean ridges is generally limited to that found in Type I alpine-type peridotites. It is apparent, therefore, that the phase boundary OL-EN-DI-SP +melt?OL-EN-SP+melt has limited the degree of melting of the mantle beneath mid-ocean ridges. This was clearly not the case for many alpine-type peridotites, implying very different melting conditions in the mantle, probably involving the presence of water.

  1. SEDIMENTATION PATTERNS AND DEPOSITION IN THE PROGRADING WAX LAKE DELTA

    NASA Astrophysics Data System (ADS)

    Bailey, C. H.; Holm, G. O.

    2009-12-01

    The Mississippi River has been dammed and levied since the 1950s to control the river from flooding and support navigation and commerce. Sediments delivered to the Louisiana delta plain have decreased by half since the major projects of the 1950’s. Despite significant reductions in sediment load, the Wax Lake Delta is forming at the mouth of a man made dredged channel that flows off of the Atchafalaya River, which is the principal distributary of the Mississippi River. The remaining sediments carried by the Mississippi River are essential in the building of delta wetlands and helping to reverse coastal wetland loss. This study analyzes pre- and post-elevation data from 2008 and 2009 to understand the amount of elevation gain and sediment deposition associated with large river floods. Mean wetland elevation gain during the floods of 2008 and 2009 was 3.9 cm and 2.2 cm, respectively. Using soil bulk properties and mean elevation gain, I estimated that 2.3x106 Mt and 1.2x106Mt of sediment was deposited in the Wax Lake Delta wetlands for 2008 and 2009, respectively. If the total annual load of sediments in the Atchafalaya River is approximately 50Mt yr-1, we can estimate that <10% of the total available sediment load is deposited in the wetlands, just during spring flood events. This study provides good first order estimates of sediment deposition that can contribute to future research and understanding of the Wax Lake Delta formation and maintenance.

  2. 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.

  3. Aeolian Processes and Landforms in River Valleys of Central Russian Plain in MIS 2

    NASA Astrophysics Data System (ADS)

    Matlakhova, Ekaterina

    2015-04-01

    Late Pleistocene terraces in river valleys of Central Russian Plain were subject to aeolian reworking after the alluvial sedimentation had finished. Severe natural conditions of LGM (cold and dry climate, scarce vegetation) contributed activation of aeolian processes. Ground water lowering because of deep pre-LGM incision of rivers made deep aeolian reworking possible at low hypsometric levels of valley bottom. We studied lithological structure of terraces in river valleys of Central Russian Plain. The key sites were located in Seim (the middle Dnieper catchment) and Khoper (the middle Don catchment) river valleys. Field data was combined with quartz grains morphoscopy technique (study of texture of sediment particles using scanning electron microscope). Wide participation of aeolian sediments in terrace deposits was detected. During this study a new technique of the distinguishing of short-term aeolian reworking of alluvial deposits using quartz grains morphoscopy technique was developed. The main problem of interpretation the results of quartz grains morphoscopy is that aeolian signals are sometimes not clear due to short duration of wind action over alluvial sands. However, detailed studies of the quartz grains surfaces under scanning electron microscope helped to solve this problem. We used scanning electron microscope JEOL JSM-661 LV and worked with magnification from ×160 to ×400 for whole grains and up to ×1800 for some parts of grains. Deep aeolian reworking of Late Pleistocene terrace alluvium in river valleys of Central Russian Plain during LGM led to the formation of aeolian covers on the terrace surfaces. Also there are many relict dunes on Late Pleistocene river terrace surfaces. Sometimes the development of aeolian processes could led to more significant changes in the shape of the valley and formation of aeolian aprons. The thickness of aeolian covers can reach 3-5 m or more. Due to this reason morphology and topography of river terraces could have been changed considerably during LGM.

  4. Rethinking the Mississippi River diversion for effective capture of riverine sediments

    NASA Astrophysics Data System (ADS)

    Xu, Y. Jun

    2015-03-01

    Many river deltas in the world are vibrant economic regions, serving as transportation hubs, population centres, and commercial hotspots. However, today, many of these deltaic areas face a tremendous challenge with land loss due to a number of factors, such as reduced riverine sediment supply, coastal land erosion, subsidence, and sea level rise. The development of the Mississippi River Deltaic Plain (MRDP) in southeast Louisiana, USA, over the past century is a good example. Since 1932, approximately 4877 km2 of the coastal land of MRDP has become submerged. The lower Mississippi River main channel entering the Gulf of Mexico has become an isolated waterway with both sides losing land. In contrast, large open water areas in the Mississippi River's distributary basin, the Atchafalaya River basin, have been silted up over the past century, and the river mouth has developed a prograding delta feature at its two outlets to the Gulf of Mexico. The retrospective analysis of this paper makes it clear that the main cause of the land loss in the MRDP is not the decline of riverine sediment, but the disconnection of the sediment sources from the natural flood plains. Future sediment management efforts in the MRDP should focus on restoring the natural connection of riverine sediment supplies with flood plains, rather than solely using channelized river diversion. This could be achieved through controlled overbank flooding (COF) and artificial floods in conjunction with the use of a hydrograph-based sediment availability assessment.

  5. SEDIMENT FACIES CHANGE AND DELTA EVOLUTION DURING HOLOCENE IN THE MEKONG RIVER DELTA, VIETNAM

    Microsoft Academic Search

    TA Thi; Kim Oanh; NGUYEN Van Lap; Masaaki TATEISHI

    The Mekong River Delta (MRD) in southern Vietnam with a wide delta plain formed during the last 6 to 8 ky is a typical mixed tide- and wave- dominated delta. The late Pleistocene- Holocene sequence since the last sea- level lowstand is composed of an incised- valley fill, comprising late Pleistocene to early Holocene fluvial to estuarine sediments, and Holocene

  6. Responses of Hyalella azteca to chronic exposure of Mississippi Delta sediments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hyalella azteca was used to assess biological impairment in sediments from nine water bodies in the Mississippi alluvial plain. Water bodies were categorized according to land use and implementation of agricultural best management practices (BMPs). Three reference oxbow lakes were located in the Whi...

  7. Impact of suburbanization on ground water quality and denitrification in coastal aquifer sediments

    Microsoft Academic Search

    C. Marjorie Aelion; J. N. Shaw; M. Wahl

    1997-01-01

    The South Carolina coastal plain is currently facing rapid population growth and suburbanization. Suburbanization brings the potential for surface- and ground water contamination from the use of nitrogen-based fertilizers, which can render water toxic to humans and fish, and lead to eutrophication. Additionally, nitrate is highly mobile in sediments and poses the potential for contamination of receiving waters, downstream areas,

  8. Water Management Studies in the Rolling Plains

    E-print Network

    Gerard, C.J.; Bordovsky, D.G.; Clark, L.E.

    1980-01-01

    in the Red River Basin could further improve and increase the potential for irrigation along the rivers in this section of Texas. It is important, therefore, that the response of different crops to irrigation and rainfall in the Rolling Plains be better... patterns at Chillicothe and Iowa Park showed that irrigation often is not needed for production of 30 to 50 bushels of wheat per acre. Water Management Studies In the Rolling Plains C. J. GERARD, D. G. BORDOVSKY, AND L. E. CLARK* Crop production...

  9. Cotton and Manpower - Texas High Plains

    E-print Network

    Ducoff, Louis J.; Metzler, William H.; Motheral, Joe R.

    1953-01-01

    -size groups. The tenure status of an operator often affects labor utili- zation. It determines the incidence of labor costs or, if ma- chinery is substituted, of labor savings. (See "Economics of Mechanical Harvesting in the High Plains Cotton Area of Tex... harvesting as a means of reducing the risk of labor shortages and high labor costs. Competition with Other Areas Despite the increased use of machine harvesters, most farmers on the High Plains still prefer to "snap" their cotton by hand the first time...

  10. Sedimentation patterns in floodplains of the Mekong Delta - Vietnam

    NASA Astrophysics Data System (ADS)

    Van Manh, Nguyen; Merz, Bruno; Viet Dung, Nguyen; Apel, Heiko

    2013-04-01

    Quantification of floodplain sedimentation during the flood season in the Mekong Delta (MD) plays a very important role in the assessment of flood deposits for a sustainable agro-economic development. Recent studies on floodplain sedimentation in the region are restricted to small pilot sites because of the large extend of the Delta, and the complex channel. This research aims at a quantification of the sediment deposition in floodplains of the whole Mekong Delta, and to access the impacts of the upstream basin development on the sedimentation in the Delta quantitatively. To achieve this, a suspended sediment transport model is developed based on the quasi-2D hydrodynamic model of the whole Mekong Delta developed by Dung et al. (2011). The model is calibrated and validated using observed data derived from several sediment measurement campaigns in channel networks and floodplains. Measured sediment data and hydrodynamic model quantify the spatio-temporal variability of sediment depositions in different spatial units: individual dyke compartments, and the sub-regions Plain of Reeds, Long Xuyen Quadrangle and the area between Tien River and Hau River. It is shown that the distribution of sediment deposition over the delta is highly depended on the flood magnitude, that in turn drives the operation policy of flood control systems in floodplains of the Mekong Delta. Thus, the sedimentation distribution is influenced by the protection level of the dyke systems in place and the distance to the Tien River and Hau River, the main branches of the Mekong in the Delta. This corroborates the main findings derived from data analysis obtained from a small scale test site by Hung et al, (2011, 2012a). Moreover, the results obtained here underlines the importance of the main channels for the sediment transport into the floodplains, and the deposition rate in floodplains is strongly driven by the intake locations and the distance from these to the main channels as well.

  11. 18 CFR 801.8 - Flood plain management and protection.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...interest. A balanced flood plain management and protection...needed to reduce the flood hazard to a minimum...safeguard public health, welfare, safety...To foster sound flood plain controls...water resources management, the...

  12. 18 CFR 801.8 - Flood plain management and protection.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Flood plain management and protection. 801...COMMISSION GENERAL POLICIES § 801.8 Flood plain management and protection. ...waterways has not discouraged development of flood hazards areas. Major floods cause...

  13. 18 CFR 801.8 - Flood plain management and protection.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2012-04-01 true Flood plain management and protection. 801...COMMISSION GENERAL POLICIES § 801.8 Flood plain management and protection. ...waterways has not discouraged development of flood hazards areas. Major floods cause...

  14. Ancient DNA complements microfossil record in deep-sea subsurface sediments.

    PubMed

    Lejzerowicz, Franck; Esling, Philippe; Majewski, Wojciech; Szczuci?ski, Witold; Decelle, Johan; Obadia, Cyril; Arbizu, Pedro Martinez; Pawlowski, Jan

    2013-08-23

    Deep-sea subsurface sediments are the most important archives of marine biodiversity. Until now, these archives were studied mainly using the microfossil record, disregarding large amounts of DNA accumulated on the deep-sea floor. Accessing ancient DNA (aDNA) molecules preserved down-core would offer unique insights into the history of marine biodiversity, including both fossilized and non-fossilized taxa. Here, we recover aDNA of eukaryotic origin across four cores collected at abyssal depths in the South Atlantic, in up to 32.5 thousand-year-old sediment layers. Our study focuses on Foraminifera and Radiolaria, two major groups of marine microfossils also comprising diverse non-fossilized taxa. We describe their assemblages in down-core sediment layers applying both micropalaeontological and environmental DNA sequencing approaches. Short fragments of the foraminiferal and radiolarian small subunit rRNA gene recovered from sedimentary DNA extracts provide evidence that eukaryotic aDNA is preserved in deep-sea sediments encompassing the last glacial maximum. Most aDNA were assigned to non-fossilized taxa that also dominate in molecular studies of modern environments. Our study reveals the potential of aDNA to better document the evolution of past marine ecosystems and opens new horizons for the development of deep-sea palaeogenomics. PMID:23658006

  15. Intermittent Elevated Radium Concentrations in Coastal Plain Groundwater of South Carolina, U.S.A.

    SciTech Connect

    Denham, Miles; Millings, Margaret; Noonkester, Jay

    2005-09-22

    To learn the cause of intermittent radium concentrations in groundwater of Coastal Plain aquifers, 31 groundwater wells in South Carolina, U.S.A. were sampled for radium and other geochemical parameters. Sediments cored from near the well screens were also sampled to examine any relationship between sediment properties and radium concentration in the groundwater. Elevated radium concentrations only occurred in groundwater with low electrical conductivity and pH values below 6.3. The adsorption edge for radium on hematite--a major surface active mineral in these aquifers--is at a pH value of about 6. Near this value, small changes in pH can result in significant adsorption or desorption of radium. In groundwater with initially low alkalinity, small intermittent decreases in partial pressure of carbon dioxide in groundwater cause decreases in pH and desorption of radium. The result is intermittent elevated radium concentrations.

  16. Distribution and altitude of the top of saline ground water in the southeastern coastal plain

    USGS Publications Warehouse

    Lee, Roger W.; DeJarnette, Sydney S.; Barker, Rene A.

    1986-01-01

    A map prepared by the U.S. Geological Survey shows the approximate distribution of saline water (greater than 10,000 mg/L as NaCl) in the Southeastern Coastal Plain. The primary distribution of saline water is in Cretaceous sediments and may be characterized as an extensive body of fluid whose upper surface generally slopes upward from inland toward coastal areas. Some freshwater appears to occupy parts of the deeper water-bearing zones in Georgia. A small amount of saline water appears to occupy a narrow upper zone of limited extent in lower Tertiary sediments in Georgia and parts of South Carolina. The freshwater-saline water interface for the lower zone lies offshore, east of the South Carolina coast. Consequently, the saline water distribution is inferred offshore. (USGS)

  17. Provenance, areal distribution, and contemporary sedimentation of quartz sand and silt types on the mid-atlantic continental shelf

    E-print Network

    Prusak, Deanne

    1985-01-01

    ; the distribution pattern of the coastal plain sand overlies the coastal plain river systems and exposed cuestas. The coincidence of these paleogeographic features with the sediment types indicates that modern processes on the shelf have not been intense enough... of the major rivers of the eastern United States (Table 1), in which ebb and flood channels and shoals are present. In general, fine-grained, moderate- to poorly-sorted sediment is. confined to the estuaries and nearshore areas (Schlee, 1973; Demars et al...

  18. 49 CFR 215.107 - Defective plain bearing box: General.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Defective plain bearing box: General. 215.107 Section...System § 215.107 Defective plain bearing box: General. A railroad may not place...car, if the car has— (a) A plain bearing box that does not contain visible...

  19. 49 CFR 215.111 - Defective plain bearing.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Defective plain bearing. 215.111 Section 215.111 Transportation...System § 215.111 Defective plain bearing. A railroad may not place or continue in service a car, if the car has a plain bearing— (a) That is missing,...

  20. 49 CFR 215.113 - Defective plain bearing wedge.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Defective plain bearing wedge. 215.113 Section 215...System § 215.113 Defective plain bearing wedge. A railroad may not place...continue in service a car, if a plain bearing wedge on that car is— (a)...

  1. 49 CFR 215.111 - Defective plain bearing.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Defective plain bearing. 215.111 Section 215.111 Transportation...System § 215.111 Defective plain bearing. A railroad may not place or continue in service a car, if the car has a plain bearing— (a) That is missing,...

  2. 49 CFR 215.111 - Defective plain bearing.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Defective plain bearing. 215.111 Section 215.111 Transportation...System § 215.111 Defective plain bearing. A railroad may not place or continue in service a car, if the car has a plain bearing— (a) That is missing,...

  3. 49 CFR 215.107 - Defective plain bearing box: General.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Defective plain bearing box: General. 215.107 Section...System § 215.107 Defective plain bearing box: General. A railroad may not place...car, if the car has— (a) A plain bearing box that does not contain visible...

  4. 49 CFR 215.107 - Defective plain bearing box: General.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Defective plain bearing box: General. 215.107 Section...System § 215.107 Defective plain bearing box: General. A railroad may not place...car, if the car has— (a) A plain bearing box that does not contain visible...

  5. 49 CFR 215.107 - Defective plain bearing box: General.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Defective plain bearing box: General. 215.107 Section...System § 215.107 Defective plain bearing box: General. A railroad may not place...car, if the car has— (a) A plain bearing box that does not contain visible...

  6. 49 CFR 215.113 - Defective plain bearing wedge.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Defective plain bearing wedge. 215.113 Section 215...System § 215.113 Defective plain bearing wedge. A railroad may not place...continue in service a car, if a plain bearing wedge on that car is— (a)...

  7. 49 CFR 215.113 - Defective plain bearing wedge.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Defective plain bearing wedge. 215.113 Section 215...System § 215.113 Defective plain bearing wedge. A railroad may not place...continue in service a car, if a plain bearing wedge on that car is— (a)...

  8. 49 CFR 215.107 - Defective plain bearing box: General.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Defective plain bearing box: General. 215.107 Section...System § 215.107 Defective plain bearing box: General. A railroad may not place...car, if the car has— (a) A plain bearing box that does not contain visible...

  9. 49 CFR 215.111 - Defective plain bearing.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Defective plain bearing. 215.111 Section 215.111 Transportation...System § 215.111 Defective plain bearing. A railroad may not place or continue in service a car, if the car has a plain bearing— (a) That is missing,...

  10. 49 CFR 215.113 - Defective plain bearing wedge.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Defective plain bearing wedge. 215.113 Section 215...System § 215.113 Defective plain bearing wedge. A railroad may not place...continue in service a car, if a plain bearing wedge on that car is— (a)...

  11. 49 CFR 215.113 - Defective plain bearing wedge.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Defective plain bearing wedge. 215.113 Section 215...System § 215.113 Defective plain bearing wedge. A railroad may not place...continue in service a car, if a plain bearing wedge on that car is— (a)...

  12. 49 CFR 215.111 - Defective plain bearing.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Defective plain bearing. 215.111 Section 215.111 Transportation...System § 215.111 Defective plain bearing. A railroad may not place or continue in service a car, if the car has a plain bearing— (a) That is missing,...

  13. Writing Government Policies and Procedures in Plain Language

    ERIC Educational Resources Information Center

    Byrne, Don

    2008-01-01

    Plain language involves more than just a few simple techniques, such as using everyday words, short sentences, and active voice. Although there is no single definition, "plain language" basically stands for several dozen well-established principles of clear communication. In this article, the author discusses the significance of plain language…

  14. 44 CFR 10.14 - Flood plains and wetlands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Flood plains and wetlands. 10.14 Section 10.14 Emergency...Procedures § 10.14 Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions of this part...

  15. 44 CFR 10.14 - Flood plains and wetlands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Flood plains and wetlands. 10.14 Section 10.14 Emergency...Procedures § 10.14 Flood plains and wetlands. For any action taken by FEMA in a flood plain or wetland, the provisions of this part...

  16. NITROGEN EXPORT FROM COASTAL PLAIN FIELD DITCHES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Successfully mitigating the adverse impact of agricultural N and P applications will depend on a sound understanding of transport mechanisms and flow pathways (from fields). The objective of this study was to evaluate N losses from ditches for a Coastal Plain landscape on the Maryland Eastern Shore,...

  17. Flood Plain and Higher Ground Habitats

    NSDL National Science Digital Library

    SCETV

    2008-08-29

    This video segment from NatureScene features the area of the Congaree Swamp where the high ground and the flood plain meet. Learn how a few feet of difference in elevation on a floodplain can yield drastic changes in what you’ll find living there.

  18. Corrosion of plain bearings in diesel engines

    Microsoft Academic Search

    B. M. Bunakov; G. P. Belyanchikov; A. L. Chudinovskikh; M. A. Grigorev

    1983-01-01

    The serviceability of plain bearings depends on many factors, in particular the engine operating temperatures and loads, the bearing design and conditions of assembly, the type of antifriction layer and break-in coating, the design features of the engine lubrication system, and the quality of the engine oil. Demonstrates that the corrosivity of modern oils for high-performance diesel engines depends on

  19. Recent Breakout On The Coastal Plain

    USGS Multimedia Gallery

    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...

  20. Nitrogen Deposition in the Southern High Plains 

    E-print Network

    Upadhyay, Jeetendra; Auvermann, Brent W.; Bush, K. Jack; Mukhtar, Saqib

    2008-02-11

    Nitrogen, the most abundant element in the atmosphere, is necessary for life. But too much of this vital element can have negative effects on the environment. This publication can help landowners in the Southern High Plains region of Texas learn how...

  1. 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...

  2. Nitrogen Deposition in the Southern High Plains

    E-print Network

    Upadhyay, Jeetendra; Auvermann, Brent W.; Bush, K. Jack; Mukhtar, Saqib

    2008-02-11

    Nitrogen, the most abundant element in the atmosphere, is necessary for life. But too much of this vital element can have negative effects on the environment. This publication can help landowners in the Southern High Plains region of Texas learn how...

  3. A river is reborn--Use Attainability Analysis for the Lower Des Plaines River, Illinois.

    PubMed

    Novotny, Vladimir; O'Reilly, Neal; Ehlinger, Timothy; Frevert, Toby; Twait, Scott

    2007-01-01

    The goal of the Use Attainability Analysis (UAA) of the Lower Des Plaines River was to upgrade the designated "Secondary Contact Recreation and Indigenous Aquatic Life Use" to a higher use that would be commensurate with the goals of the Clean Water Act (CWA). In Illinois, the water body use in compliance with the goals of the CWA is named "General Use". The river has been extensively modified and receives most point-source and urban runoff discharges from the Chicago metropolitan area (9.5 million inhabitants). The study included an extensive assessment of the physical, chemical, biological, and bacteriological integrity status of the water body and sediments. The UAA found that the water quality situation of the river has improved significantly since the 1970s, when the Illinois Pollution Control Board defined and assigned the Secondary Contact Recreation and Indigenous Aquatic Life Use designation to the Lower Des Plaines River. The study defined and suggested a "Modified Impounded Use" for one highly modified reach, with adjusted standards for dissolved oxygen and recreation. The study also recommended adoption of the General Use standards, some of them in a modified form, for other water quality parameters. Standards for limited recreation were also developed. The UAA also outlines a suggested action plan that will bring UAA segments of the Lower Des Plaines River in compliance with UAA goals. PMID:17290974

  4. Hydrology of Salt Wells Creek : a plains stream in southwestern Wyoming

    USGS Publications Warehouse

    Lowham, H.W.; DeLong, L.L.; Collier, K.R.; Zimmerman, E.A.

    1982-01-01

    Development of energy minerals in plains areas of Wyoming is expanding rapidly. Such development may affect water resources and hydrologic relations of the plains; however, little information exists concerning hydrologic processes for these areas. This report summarizes results of a hydrologic study made during 1975-78 of Salt Wells creek, a drainage area of about 500 square miles located southeast of Rock Springs, Wyoming. The area is typical of arid and semiarid plains areas in southwestern Wyoming where mineral development is occurring. Salt Wells Creek is predominately an intermittent stream. Numerous springs in the headwaters cause small perennial flows in some upstream tributaries, but evaporation, freezeup, and seepage deplete these flows so that the middle and lower reaches of the main channel have only intermittent flows. The intermittent nature of streamflow affects water quality. It was observed that a flushing of dissolved solids and suspended sediment occurs during the first flows of a runoff event. A striking feature of the stream is its deeply incised channel. The downcutting is attributed to the cummulative effects of: (1) a change in the relative climate, amounts of annual precipitation occurring as rain and snow, (2) change in base level due to downstream channelization, and (3) changes in land use. Because of the incision, erosion is now expanding to include intervening tributaries. (USGS)

  5. Tidal inlet variability in Mississippi River delta plain

    SciTech Connect

    Levin, D.; Nummedal, D.; Penland, S.

    1983-09-01

    Stratigraphic sequences of deltaic and shallow marine origin commonly contain sand bodies transgressively overlying lower delta-plain and delta-front deposits. Although generally ascribed to barriers formed during the destructive phase of the delta cycle, most of this sand is probably of tidal-inlet origin because of the high preservation potential for sediment deposited below the base of the retreating shoreface in deep migratory tidal channels and their associated tidal deltas. To facilitate the identification of such units, this paper reviews the temporal evolution of the inlet sand bodies found along the rapidly transgressive shoreline of the abandoned Holocene Mississippi River deltas. This study also reveals that tide dominance of a coastline is not simply a function of tide range and wave height; it depends largely on the tidal prism, an inlet parameter which, in Louisiana, changes rapidly over time. Three distinct stages can be identified in the evolutionary sequence for Louisiana tidal inlets: (1) wave-dominated inlets with flood-tidal deltas, (2) tide-dominated inlets with large ebb deltas, and (3) wide, transitional inlets with sand bodies confined to the throat section. As the inlets migrate during the transgression, they will leave behind on the continental shelf, tidal sand bodies with a landward succession of facies changing from those characteristic of wave dominance, into tide dominance, and back again to transitional or wave-dominated inlets.

  6. 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.

  7. Supra-subduction and abyssal mantle peridotites of the Coast Range ophiolite, California: Initiation of Franciscan subduction along a large-offset fracture zone

    NASA Astrophysics Data System (ADS)

    Choi, S. H.; Shervais, J. W.; Mukasa, S. B.

    2009-04-01

    The Coast Range ophiolite (CRO) of California is one of the most extensive tracts of oceanic crust preserved in the Cordillera, but its origin has long remained controversial. We present here new data on mineral compositions in mantle peridotites that underlie crustal sections of ophiolite, and show that these are dominantly refractory harzburgites related to high apparent melting in a supra-subduction zone (SSZ) setting. Abyssal peridotite occurs at one location, Stonyford, in the CRO where it is associated with SSZ mantle peridotite and volcanic rocks with both oceanic and arc-like geochemistry. SSZ mantle peridotites are associated with crustal sections containing arc-related volcanics, including boninites. This convergence between conclusions based on crustal lithologies and their underlying mantle sections confirms previous proposals that link the CRO to SSZ processes, and seriously undermines hypotheses that call on formation of the ophiolite at a mid-ocean ridge spreading center. We also report on the radiogenic isotope characteristics of peridotite clinopyroxenes. Based on the Sr-Nd-Pb-Hf isotopic compositions and estimated temperatures, we suggest that the abyssal peridotite block represents a remnant of large-offset transform oceanic lithosphere at >172 Ma. East-dipping, proto-Franciscan subduction is likely to have been initiated along this fault zone, which produced the supra-subduction zone (SSZ) peridotites in the CRO. We propose that the remnant abyssal peridotites represent a snapshot of the mantle wedge composition prior to overprinting of large sectors by hydrous melting during the subsequent subduction-controlled SSZ processes.

  8. Flood plain stability of the Peace River, southwestern Florida, since the last glacial lowstand of sea level

    SciTech Connect

    Guccione, M.J. (Univ. of Arkansas, Fayetteville, AR (United States). Geology Dept.)

    1993-03-01

    The 186 km long Peace River heads in the Central Highlands, dissects marine terraces of the Coastal Lowlands, and flows into the Gulf of Mexico. Between river kms 80 and 137 the gradient is low (0.1 to 0.3 m/km), sinuosity is moderate (1.2 to 1.8), and the flood plain is wide (0.6 to 2.5 km). The flood plain is underlain by a well-sorted fine/very fine-grained quartz sand overbank deposit. This overlies crossbedded and rippled, medium/coarse-grained quartz and phosphatic sand channel deposits, organic-rich loamy sand channel-fill deposits, and/or non-fluvial strata. Radiocarbon dates of organics in channel deposits at two sites 57 km apart indicate that aggradation of the flood plain was in progress by 24,760 [plus minus] 920 (Wauchula) and 21,870 [plus minus] 130 (Arcadia) years B.P. during a lowstand of sea level. Well-developed soils in the overlying fine sand have accumulated 12% and 9% clay respectively, indicating that the flood-plain surface has been stable for a considerable portion of the 22,000 years since deposition began. Between dated sites, soils are developed in nearly identical parent material with less, but varying degrees of development and clay accumulation, suggesting that other portions of the flood plain surface are younger. Because of the very low river gradient, both during lowstands and highstands of sea level, the Peace River cannot easily aggrade or degrade. It slowly reworks its flood-plain sediment resulting in a variety of soil development and surface ages on a single geomorphic surface.

  9. 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.

  10. Optical dating of palaeochannel deposits in the Riverine Plain, southeastern Australia: testing the reliability of existing thermoluminescence dates.

    PubMed

    Banerjee, D; Page, K; Lepper, K

    2002-01-01

    We present the first quartz optically stimulated luminescence (OSL) ages for palaeochannel sediments from the Riverine Plain in southeastern Australia. For young fluvial sediments, we agree with the notion that analysis of the leading edge of a dose distribution curve provides an objective method for determining the OSL age. For a modern flood deposit (less than 200 years old), the OSL ages estimated using the leading edge method (250 +/- 50 years) and by using the lowest 5% of the measured dose in single aliquots (230 +/- 50 years) agree within experimental errors. For older sediments, we suggest that the mean estimate of the dose distribution is likely to provide a reliable estimate of the OSL age. The luminescence ages suggest that the Coleambally and Kerarbury palaeochannel systems were active between 105 and 80 ky and 55 and 35 thousand years ago; the Yanco palaeochannel system could have been active as recently as 9000 years ago. PMID:12382761

  11. Evolution of playa basins on the Texas High Plains--Evidence from playa-basin fills

    SciTech Connect

    Hovorka, S.D. (Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology)

    1993-02-01

    Heterogeneous sediments in playa basins document the evolution of shallow depressions on the Texas High Plains surface through the late Quaternary. The suite of sediments encountered in playa-lake basins differs from the typical lithologies of the Blackwater Draw Formation in upland areas. The upland Blackwater Draw Formation has red-brown clayey silt containing root casts, well-developed soil fabrics, and abundant pedogenic carbonate nodules. Cores drilled in playa basins encountered a repetitive suite of gray clay, well-sorted fine to medium sand, and laminated sand and silt associated with clay drapes and beds of pedogenic calcite pebbles. The gray clay was deposited in ephemeral lakes similar to modern playa lakes. Small clams and drab colors extending downward from these deposits demonstrate ponding. Soil fabrics, soil slickensides, deep clay-filled cracks, and root tubules within the clayey beds indicate desiccation and exposure of the lake floor. Well-sorted sand layers represent episodic migration of sand sheets across the playa. Laminated sand and silt beds are interpreted as delta deposits that formed at the mouths of draws. Minimal soil formation indicates relatively rapid deposition during delta progradation. The suite of playa sediments interfingers with upland Blackwater Draw facies, documenting the temporal equivalence of playa and upland deposition and expansion and contraction of the lake within the playa basin. Complex patterns of oxidation, reduction, and precipitation and dissolution of calcite document the interaction between ground water and sediments.

  12. Sediment discharge into a subsiding Louisiana deltaic estuary through a Mississippi River diversion

    NASA Astrophysics Data System (ADS)

    Snedden, Gregg A.; Cable, Jaye E.; Swarzenski, Christopher; Swenson, Erick

    2007-01-01

    Wetlands of the Mississippi River deltaic plain in southeast Louisiana have been hydrologically isolated from the Mississippi River by containment levees for nearly a century. The ensuing lack of fluvial sediment inputs, combined with natural submergence processes, has contributed to high coastal land loss rates. Controlled river diversions have since been constructed to reconnect the marshes of the deltaic plain with the river. This study examines the impact of a pulsed diversion management plan on sediment discharge into the Breton Sound estuary, in which duplicate 185 m 3 s -1-diversions lasting two weeks each were conducted in the spring of 2002 and 2003. Sediment delivery during each pulse was highly variable (11,300-43,800 metric tons), and was greatest during rising limbs of Mississippi River flood events. Overland flow, a necessary transport mechanism for river sediments to reach the subsiding backmarsh regions, was induced only when diversion discharge exceeded 100 m 3 s -1. These results indicate that timing and magnitude of diversion events are both important factors governing marsh sediment deposition in the receiving basins of river diversions. Though the diversion serves as the primary source of river sediments to the estuary, the inputs observed here were several orders of magnitude less than historical sediment discharge through crevasses and uncontrolled diversions in the region, and are insufficient to offset present rates of relative sea level rise.

  13. Evolution of the Gulf of Alaska coastal plain: Cape Suckling to Icy Point

    SciTech Connect

    Molnia, B.F.

    1985-01-01

    The Gulf of Alaska coastline, coastal plain, and adjacent continental margin between Cape Suckling and Icy Point is located on the leading edge of the northwestward moving Pacific Plate. Although dominated by intensive wind and wave erosion, this coastal region is accretionary. This apparent contradiction results from the ongoing combination of aperiodic seismic uplift and long-term tectonic uplift raising new shoreline areas which are immediately attacked by erosion. If the hiatus between episodes of successive uplift is short, then a segment of the uplifted area is preserved as a coastal plain ridge. About one-half of the almost 500 km long coastal area has a ridge cover. Near the Alsek River and west of Cape Yakataga, as many as 20 distinct parallel ridges exist. All are younger than 3000 radiocarbon years old. Approximately 4000 years ago, as eustatic sea level reached present level, there was no coastal plain. Rather, the Pacific Ocean covered a deep, glacially-scoured bedrock shelf and reached directly to the foot of the coast mountains. Rivers draining onto the continental shelf had to fill fiords and shelf basins before a continental shelf sediment wedge developed. Only in the past 2000-3000 years has the wedge projected above sea level. Once this occurred, the combination of seismicity and tectonics began the ridge building process. This combination of processes has produced an extremely young, very dynamic, changing coastline and coastal plain. As evidence of its youthfulness, the two largest ridge complexes adjacent to the coastline were too young to date by radiocarbon methods.

  14. The effect of sea level rise on coastal plain estuaries, with examples from Chesapeake Bay

    SciTech Connect

    Colman, S.M. (Geological Survey, Woods Hole, MA (USA))

    1990-05-01

    Estuaries are geologically transitory features whose evolution depends on a delicate balance among relative sea level basin geometry, shoreline erosion, fluvial sediment discharge, littoral drift, and tidal exchange. Models of modern estuarine development require specific sea level scenarios; almost all assume a continuation of the decelerating sea level rise of the last few thousand years. However, under constant external conditions, estuaries are ephemeral because they rapidly fill with fluvial and marine sediment. The rate of filling changes with time, but only a few thousand years are required to fill most estuaries. The persistence of estuaries, therefore, requires that relative sea level rises at a rate sufficient to compensate for the inherent tendency of estuaries to fill with sediment. Coastal plain estuaries, of which Chesapeake Bay is a prime example, are often referred to as drowned river valleys. Although this description is appropriate for the first-order morphology of Chesapeake Bay, the implied passivity can be misleading, especially in the high-tidal-energy area of the bay mouth where dramatic spit progradation and channel migration have occurred in the last few thousand years. Holocene sediment accumulation rates are more irregular along the length of the estuary than most models would predict; but in general, sediment accumulation has been greater at the mouth and at the head of the bay and less along the middle reaches. If relative sea level were to stabilize, the estuary would fill with sediment from both ends within a few thousand years. Evidence for two previous generations of the bay is preserved as the estuarine fill of major fluvial valleys, demonstrating that estuarine episodes have been closely tied to cyclic sea level changes.

  15. A budget of marine and terrigenous sediments, Hanalei Bay, Kauai, Hawaiian Islands

    NASA Astrophysics Data System (ADS)

    Calhoun, R. Scott; Fletcher, Charles H.; Harney, Jodi N.

    2002-06-01

    The sediment budget of Hanalei Bay on the north shore of Kauai was calculated using sedimentological and geophysical methods. The calculations of the budget subsequently allowed an interpretation of the Holocene history of the bay. The bay sediments are easily separated into marine (carbonate) and terrigenous (siliciclastic) grains. Surficial sediments are dominated by carbonate grains (˜70%) of coralline algae, coral, and mollusc fragments as well as foraminifera, Halimeda, bryozoa, and echinoderm tests. However, siliciclastic grains (e.g. olivine, plagioclase, volcanic lithics) from the Hanalei River watershed draining shield volcanic highlands are the most common individual grain type (˜27%) and form a zone of high concentration from the mouth of the Hanalei River into the center of the bay. Flooding in the bay by the post-glacial sea-level rise began soon after 11.7 kyears. The resulting marine environment caused the net deposition of 45.5±1.5×10 6 m 3 of sediment in the bay and approximately 33.7±11.2×10 6 m 3 of sediment on the Hanalei coastal plain. The total volume of carbonate sediment stored in the bay and coastal plain is greater than the volume likely to have been produced exclusively within the bay during the same time. Calculations indicate that approximately 2490 m 3 year -1 have been imported into the bay or coastal plain and deposited since 11,700 years ago. The majority of this sediment influx is likely delivered from the east by the strong tradewind-driven littoral currents that characterize Kauai's north shore. Net carbonate sediment deposition in Hanalei Bay peaked at a rate of 15,500 m 3 year -1 between 5000 and 3000 years ago (when sea level may have been 2 m above present) diminishing to 3890 m 3 year -1 from 1000 years ago to the present. This influx is likely to have played a significant role in the mid to late Holocene progradation of the Hanalei shoreline.

  16. Candidate Mud Volcanoes in the Northern Plains of Mars

    NASA Astrophysics Data System (ADS)

    Kite, E. S.; Hovius, N.; Hillier, J. K.; Besserer, J.

    2007-12-01

    Domes in the the `Borealis back-basin' (centre 76N 160W) on Mars resemble products of mud volcanism (MV) on Earth. Description of domes: Our mapping shows ~30 Early Amazonian domes in the back-basin (~50 x 40 km, height ~300 m). Many have marginal and central peaks (~7 x 5 km, height ~400 m), and moats ~2.5 km wide. Domes are rough at km-scale; some have central depressions; some have annular ridges. Mean rise/run is (0.93±0.22)%. Dome orientations, and alignments of multiple domes, run parallel to the continuation of grabens associated with Alba Patera diking [1]. Distributary channels are found in association with one dome. Aspect-frequency plots for the domes region show significant deviations from randomness. (Detrended) slopes facing S or N are more common than other aspects; local maxima are (S±5°) and (N±5°). N-facing slopes are more abundant than S-facing slopes, so mean S- facing slope must be steeper. A control region at the same latitude shows no comparable anomaly. Interpretation: Many worlds show igneous volcanism, but only Earth has confirmed MV. So, when assessing an extraterrestrial construct, one should assign a high prior probability to igneous volcanism. However, (1) Dome morphologies can be matched with MV in the Caspian Basin and Cadiz Gulf [2], though Martian domes have diameters ~5 times greater. (2) Moat morphometry excludes flexural origin and suggests a collapse origin. Collapse moats are often associated with MV on Earth. (3) Aspect anomalies suggest that near-surface dome material was subject to insolation-driven processing, requiring dome near-surface material to have been partially volatile [3]. (4) Volcanic constructs are rare closer to Alba Patera, inferred to have triggered dome construction. So there must be a major increase in the fusibility of materials in our basin. In the absence of Martian granites, volatile-rich deposits satisfy this requirement. (5) Mars' thick sediment piles permit MV. Crater fill studies suggest that the Scandia and Borealis back- basins contain the greatest thickness of cover in the Northern Plains, making these preferred MV locations [4]. We infer that domes may well result from MV. Outstanding puzzles: We currently lack a compelling mechanism for expulsion in the extensional tectonic setting required for dyking. One possibility is direct triggering of MV through intersection of dyke fluids with a volatile-rich sediment column. OMEGA spectra of domes show no significant differences between dome and non-dome terrain. Band depth methods and linear unmixing models [5] yield compositions uniformly dominated by ferric oxides and pyroxenes. This may be due to recent mantling, or MV may tap a source layer of similar composition to adjacent plains. Implications: Post-Hesperian cover in our study area is too thin for MV; older sediments are probably the source. These may record catastrophic flooding or oceans. Our results have implications for the ease of future drill-rig access to these ancient deposits. There is also a tempting geographic link with young evaporates [6]. [1] K.L.Tanaka (2006), 4th Mars Polar Sci., Abs. #8024. [2]L.Somoza et al. (2003), Mar. Geol. 195, doi:10.1016/S0025-3227(02)00686-2. [3] M.A.Kreslavsky and J.W.Head (2003),GRL 30, doi:10.1029/2003GL017795. [4] D.Buczkowski(2007),JGR-E, doi:10.1029/2006JE002836. [5] J.- P.Combe(2005),PhD thesis, U. Nantes. [6] K.E.Fishbaugh et al.(2007),JGR-E 112, doi:10.1029/2006JE00286.

  17. The peatlands developing history in the Sanjiang Plain, NE China, and its response to East Asian monsoon variation.

    PubMed

    Zhang, Zhenqing; Xing, Wei; Wang, Guoping; Tong, Shouzheng; Lv, Xianguo; Sun, Jimin

    2015-01-01

    Studying the peatlands accumulation and carbon (C) storage in monsoonal areas could provide useful insights into the response of C dynamics to climate variation in the geological past. Here, we integrated 40 well-dated peat/lake sediment cores to reveal the peatlands evolution history in the Sanjiang Plain and examine its links to East Asian monsoon variations during the Holocene. The results show that 80% peatlands in the Sanjiang Plain initiated after 4.7?ka (1 ka?=?1000 cal yr BP), with the largest initiating frequency around 4.5?ka. The mean C accumulation rate of peatlands in the Sanjiang Plain exhibits a synchronous increase with the peatlands expansion during the Holocene. Such a peatlands expanding and C accumulating pattern corresponds well to the remarkable drying event subsequent to the Holocene monsoon maximum. We suggest that in addition to the locally topographic conditions, Holocene variations of East Asian summer monsoon (especially its associated precipitation) have played a critical role in driving the peatlands initiation and expansion in the Sanjiang Plain. PMID:26076653

  18. The peatlands developing history in the Sanjiang Plain, NE China, and its response to East Asian monsoon variation

    PubMed Central

    Zhang, Zhenqing; Xing, Wei; Wang, Guoping; Tong, Shouzheng; Lv, Xianguo; Sun, Jimin

    2015-01-01

    Studying the peatlands accumulation and carbon (C) storage in monsoonal areas could provide useful insights into the response of C dynamics to climate variation in the geological past. Here, we integrated 40 well-dated peat/lake sediment cores to reveal the peatlands evolution history in the Sanjiang Plain and examine its links to East Asian monsoon variations during the Holocene. The results show that 80% peatlands in the Sanjiang Plain initiated after 4.7?ka (1 ka?=?1000 cal yr BP), with the largest initiating frequency around 4.5?ka. The mean C accumulation rate of peatlands in the Sanjiang Plain exhibits a synchronous increase with the peatlands expansion during the Holocene. Such a peatlands expanding and C accumulating pattern corresponds well to the remarkable drying event subsequent to the Holocene monsoon maximum. We suggest that in addition to the locally topographic conditions, Holocene variations of East Asian summer monsoon (especially its associated precipitation) have played a critical role in driving the peatlands initiation and expansion in the Sanjiang Plain. PMID:26076653

  19. Microbial transformations of arsenic: mobilization from glauconitic sediments to water.

    PubMed

    Mumford, Adam C; Barringer, Julia L; Benzel, William M; Reilly, Pamela A; Young, L Y

    2012-06-01

    In the Inner Coastal Plain of New Jersey, arsenic (As) is released from glauconitic sediment to carbon- and nutrient-rich shallow groundwater. This As-rich groundwater discharges to a major area stream. We hypothesize that microbes play an active role in the mobilization of As from glauconitic subsurface sediments into groundwater in the Inner Coastal Plain of New Jersey. We have examined the potential impact of microbial activity on the mobilization of arsenic from subsurface sediments into the groundwater at a site on Crosswicks Creek in southern New Jersey. The As contents of sediments 33-90 cm below the streambed were found to range from 15 to 26.4 mg/kg, with siderite forming at depth. Groundwater beneath the streambed contains As at concentrations up to 89 ?g/L. Microcosms developed from site sediments released 23 ?g/L of As, and active microbial reduction of As(V) was observed in microcosms developed from site groundwater. DNA extracted from site sediments was amplified with primers for the 16S rRNA gene and the arsenate respiratory reductase gene, arrA, and indicated the presence of a diverse anaerobic microbial community, as well as the presence of potential arsenic-reducing bacteria. In addition, high iron (Fe) concentrations in groundwater and the presence of iron-reducing microbial genera suggests that Fe reduction in minerals may provide an additional mechanism for release of associated As, while arsenic-reducing microorganisms may serve to enhance the mobility of As in groundwater at this site. PMID:22494492

  20. Evidence for natural gas hydrate occurrences in Colombia Basin

    SciTech Connect

    Finley, P.D.; Krason, J.; Dominic, K.

    1987-05-01

    Multichannel and selected single-channel seismic lines of the continental margin sediments of the Colombia basin display compelling evidence for large accumulations of natural gas hydrate. Seismic bottom simulating reflectors (BSRs), interpreted to mark the base of the hydrate stability zone, are pronounced and very widespread along the entire Panama-Colombia lower continental slope. BSRs have also been identified at two locations on the abyssal plain. Water depths for these suspected hydrate occurrences range from 900 to 4000 m. Although no gas hydrate samples have been recovered from this area, biogenic methane is abundant in Pliocene turbidites underlying the abyssal plain. More deeply buried rocks beneath the abyssal plain are thermally mature. Thermogenic gas from these rocks may migrate upward along structural pathways into the hydrate stability zone and form hydrate. Impermeable hydrate layers may form caps over large accumulations of free gas, accounting for the very well-defined BSRs in the area. The abyssal plain and the deformed continental margin hold the highest potential for major economic accumulations of gas hydrate in the basin. The extensive continuity of BSRs, relatively shallow water depths, and promixity to onshore production facilities render the marginal deformed belt sediments the most favorable target for future economic development of the gas hydrate resource within the Colombia basin. The widespread evidence of gas hydrates in the Colombia basin suggests a high potential for conventional hydrocarbon deposits offshore of Panama and Colombia.

  1. Patterns of sediment deposition in subsiding coastal salt marshes, Terrebonne Bay, Louisiana: The role of winter storms

    Microsoft Academic Search

    Denise J. Reed

    1989-01-01

    High rates of wetland loss in the Mississippi deltaic plain have been attributed to a combination of insufficient marsh sedimentation\\u000a and relative sea-level rise rates of over 1.2 cm yr?1. This study examines contemporary patterns of sediment delivery to the marsh surface by evaluating the contribution of individual\\u000a marsh flooding events. Strong meteorological effects on water level in Terrebonne Bay

  2. Predicting reservoir sedimentation 

    E-print Network

    Wooten, Stephanie

    1997-01-01

    Assessment Tool (SWAT) watershed model for developing relationships between streamflow discharge and sediment load, (2) use of historical sediment accumulation amounts determined from hydrographic surveys to adjust parameters in the watershed model, (3...

  3. Hydrothermal sediments record changes in deep water oxygen content in the SE Pacific

    NASA Astrophysics Data System (ADS)

    Mills, Rachel A.; Taylor, Sarah L.; Pälike, Heiko; Thomson, John

    2010-12-01

    The distribution of redox-sensitive metals in sediments is potentially a proxy for past ocean ventilation and productivity, but deconvolving these two major controls has proved difficult to date. Here we present a 740 kyr long record of trace element concentrations from an archived sediment core collected at ˜15°S on the western flank of the East Pacific Rise (EPR) on 1.1 Myr old crust and underlying the largest known hydrothermal plume in the world ocean. The downcore trace element distribution is controlled by a variable diagenetic overprint of the inferred primary hydrothermal plume input. Two main diagenetic processes are operating at this site: redox cycling of transition metals and ferrihydrite to goethite transition during aging. The depth of oxidation in these sediments is controlled by fluctuations in the relative balance of bottom water oxygen and electron donor input (organic matter and hydrothermal sulfides). These fluctuations induce apparent variations in the accumulation of redox-sensitive species with time. Subsurface U and P peaks in glacial age sediments, in this and other published data sets along the southern EPR, indicate that basin-wide changes in deep ocean ventilation, in particular at glacial-interglacial terminations II, III, IV, and V, alter the depth of the oxidation front in the sediments. These basin-wide changes in the deep Pacific have significant implications for carbon partitioning in the ocean-atmosphere system, and the distribution of redox-sensitive metals in ridge crest sediment can be used to reconstruct past ocean conditions at abyssal depths in the absence of alternative proxy records.

  4. Indian Peoples of the Northern Great Plains

    NSDL National Science Digital Library

    Created with grant support from the Institute of Museum and Library Services National Leadership Grant Program, this online database highlights the photographic and visual record of current and former Indian groups from the Northern Great Plains. Housed at Montana State University, this particular online collection was designed to provide students, researchers, and the general public with direct access to valuable primary source material on Plains Indian cultures. The general organization of the site's archival materials is by tribe, but there are several themed collections, including one of Blackfeet tipis. The search options are quite impressive, as users can search by subject, date, location, tribe, and artist or photographer, along with further refining each search by looking by the geographical location of where the item is currently held.

  5. Hiding in plain sight: criminal network analysis

    Microsoft Academic Search

    Christopher E. Hutchins; Marge M. Benham-Hutchins

    2010-01-01

    The United States is faced with an increasingly complex criminal enterprise. Advances in technology, communications, transport,\\u000a and economies enable a highly adaptive criminal element to hide in plain site. These advances provide criminal organizations\\u000a with the same global boundaries and opportunities as legitimate organizations.\\u000a \\u000a \\u000a As boundaries expand the data to be analyzed by law enforcement mounts at a geometrically astounding

  6. PIPING PLOVER SURVIVAL IN THE GREAT PLAINS

    Microsoft Academic Search

    BRIAN G. ROOT; MARK R. RYAN; PAUL M. MAYER

    Survival was estimated for the Great Plains population of the threatened\\/en- dangered Piping Plover (Charadrius melodus) from resightings of 352 (214 adult, 138 juvenile) uniquely color-banded individuals in 1984-1990. One hundred one (47.2%) adults and 19 (13.8%) juveniles returned to the North Dakota study site in years after banding. Low return rates of juveniles precluded estimation of survival for that

  7. Sediment yield estimation in a small watershed on the northern Loess Plateau, China

    NASA Astrophysics Data System (ADS)

    Zhao, Guangju; Klik, Andreas; Mu, Xingmin; Wang, Fei; Gao, Peng; Sun, Wenyi

    2015-07-01

    Soil erosion is a major form of land degradation throughout the world and the key environmental problem that threatens the ecosystem of the Chinese Loess Plateau. In this study, we determined the sediment yield from a small dam-controlled watershed in the Huangfuchuan watershed, northern Loess Plateau, with a drainage area of 0.64 km2. The dam infill sediment provided evidence of at least 31 flood couplets, which corresponded to rain storms during 1958-1972. In total, 1.65 × 105 t sediment was accumulated within the whole check dams in this period. The annual sediment yield ranged from null in 1965 to 59,990 t in 1959. We used the modified WATEM/SEDEM model to simulate soil erosion and the sediment yield in the watershed and the sedimentation records were used for model verification. The model produced satisfactory results; the total soil erosion and sediment delivery ratio were estimated to be 1.97 × 105 t and 83.6%, respectively. Bare weathered stone in the steep gullies contributed > 90% of the sediment yield, while the remainder was derived mainly from bare loess slopes and the alluvial plain. This study suggests that analyzing sedimentation behind check dams and applying the WATEM/SEDEM model are useful for the quantitative analysis of sediment dynamics in ungauged basins on the Loess Plateau.

  8. Lipid, sterols and fatty acid composition of abyssal holothurians and ophiuroids from the North-East Pacific Ocean: food web implications.

    PubMed

    Drazen, Jeffrey C; Phleger, Charles F; Guest, Michaela A; Nichols, Peter D

    2008-09-01

    The lipid, fatty acid (FA), and sterol composition of two ophiuroids and four holothurians from the abyssal eastern North Pacific were analysed to assess their feeding habits and to ascertain their composition for use in a larger study to examine food web dynamics and trophic ecology. Holothurians were rich in phytosterols and algal derived FA such as docosahexaenoic acid and eicosapentaenoic suggesting tight trophic coupling to phytodetritus. Large proportions of stanols were found, probably a result of enteric bacteria but they may come from sterol metabolism in the holothurians themselves. Oneirophanta mutabilis was distinct with much higher levels of stanols and bacterially derived FA suggesting specific selection of bacteria rich detrital particles or the activity of enteric and integumental bacteria. The ophiuroids sterol and FA compositions differed greatly from the holothurians and reflected consumption of animal material in addition to phytodetritus. Large proportions of energy storage lipids suggested a sporadic food supply. Several unusual fatty acids were found in these abyssal echinoderms. Tetracosahexaenoic acid, 24:6omega3, in ophiuroids and 23:1 in holothurians may be good biomarkers for food web studies. We report the first occurrence of alphaOH 24:1 in holothurians with none detected in ophiuroids. Its function is presently unknown. PMID:18577461

  9. Establishing Catchment Sediment Budgets

    NASA Astrophysics Data System (ADS)

    Walling, D. E.; Collins, A. L.

    2005-12-01

    The sediment budget concept, first introduced more than 40 years ago, is of fundamental importance to an understanding of the interaction between sediment mobilization, delivery, storage and yield within a catchment, and such understanding is a key requirement for designing effective sediment control and management strategies. However, despite its importance as a concept, from both a scientific and management perspective, there have to date been few successful attempts to establish detailed sediment budgets for individual catchments. Arguably, therefore, the sediment budget concept has yet to be fully exploited as a practical or operational tool within a management context. Recent advances in monitoring sediment loads, establishing sediment sources, documenting sediment mobilisation and storage on the slopes of a catchment and quantifying storage on river floodplains, in river channels and in other sediment sinks have, however, greatly advanced the potential for establishing reliable sediment budgets for small and intermediate sized catchments. In particular, the use of environmental or fallout radionuclides to trace sediment mobilization and transfer within a drainage basin has provided important new opportunities for obtaining spatially distributed and temporally integrated data on sediment mobilization, delivery and storage. Several examples of the application of these and related techniques to the establishment of sediment budgets for small and intermediate sized agricultural catchments in both the UK and overseas (e.g. Africa) will be presented. Despite such advances, significant problems still remain. These include the need to reconcile the different levels of temporal resolution associated with different techniques, and the inability to effect a rigorous budget closure in most investigations. The need for further work in developing techniques for establishing sediment budgets and in facilitating the application of the sediment budget concept as an operational tool will be reviewed.

  10. Holocene and late glacial palaeoceanography and palaeolimnology of the Black Sea: Changing sediment provenance and basin hydrography over the past 20,000years

    USGS Publications Warehouse

    Piper, D.Z.; Calvert, S.E.

    2011-01-01

    The elemental geochemistry of Late Pleistocene and Holocene sediments of the Black Sea, recovered in box cores from the basin margins and a 5-m gravity core from the central abyssal region of the basin, identifies two terrigenous sediment sources over the last 20. kyrs. One source region includes Anatolia and the southern Caucasus; the second region is the area drained by rivers entering the Black Sea from Eastern Europe. Alkali metal:Al and heavy:light rare-earth element ratios reveal that the relative contribution of the two sources shifted abruptly every few thousand years during the late glacial and early Holocene lacustrine phase of the basin. The shifts in source were coeval with changes in the lake level as determined from the distribution of quartz and the heavy mineral-hosted trace elements Ti and Zr. The geochemistry of the abyssal sediments further recorded a sequence of changes to the geochemistry of the water column following the lacustrine phase, when high salinity Mediterranean water entered the basin beginning 9.3. kyrs BP. Bottom water that had been oxic throughout the lake phase became anoxic at approximately 8.4. kyrs BP, as recorded by the accumulation from the water column of several redox-sensitive trace metals (Mo, Re, U). The accumulation of organic carbon and several trace nutrients (Cd, Cu, Ni, Zn) increased sharply ca. 0.4. kyrs later, at 8.0. kyrs BP, reflecting an increase of primary productivity. Its increase was coeval with a shift in the dinoflagellate ecology from stenohaline to euryhaline assemblages. During this profound environmental change from the lacustrine to the marine phase, the accumulation rate of the lithogenous sediment fraction decreased as much as 10-fold in response to the rise of the water level in the basin from a low stand ca. 9.3. ka to its current level. ?? 2011.

  11. Sedimentology, weathering, age and geomorphological significance of Tertiary sediments on the far south coast of New South Wales

    Microsoft Academic Search

    J. F. Nott; R. W. Young; M. Idnurm

    1991-01-01

    The age of the NSW coastal lowland from Tuross to the Victorian border can now be shown to be at least mid?Tertiary. By this time the coastal plain had twice been partially blanketed by terrestrial sediments. Palaeomagnetic determinations on the more recent of these sedimentary accumulations, the Long Beach Formation, reveal a minimum depositional age of Early Miocene. Eustatic influences

  12. Surface Water, Ground Water and Sediment Quality in Three Oxbow Lake Watersheds in the Mississippi Delta Agricultural Region: Pesticides

    Microsoft Academic Search

    CHARLES COOPER; SAMMIE SMITH; MATT MOORE

    We measured residual and current use pesticides in shallow groundwater, surface water, and lake sediment in three oxbow lakes and their watersheds in the intensively cultivated alluvial plain of the Mississippi River, USA. The three-year study focussed on providing knowledge of pesticide movement and concentrations from intensive agricultural production into aquatic ecosystems and evaluating the degree of contaminant deposition and

  13. Let's Bet on Sediments

    NSDL National Science Digital Library

    In their investigation of Hudson Canyon sediments, students will discover how sediment size is related to the amount of time the sediment is suspended in water. During this activity, students will investigate and analyze the patterns of sedimentation in the Hudson Canyon off the Atlantic coast of North America. They will observe how heavier particles sink faster than finer particles, learn that submarine landslides (trench slope failures) are sediment "avalanches" that occur in deep-ocean canyons, and infer that the passive side of a continental margin is not as geologically static as scientists previously believed. Students will also discover that when sediments such as sand, dirt, silt, and other fine particles become suspended in water by currents, the water becomes murky, or turbid and then may become a turbidity current, which is a down-slope movements of sediment-laden water that continuously erodes many submarine canyons such as the Hudson Canyon.

  14. Rates of intrastratal solution of heavy minerals in southeast Atlantic coastal plain and their potential for dating sedimentary events

    SciTech Connect

    Carver, R.E.

    1986-05-01

    The heavy mineral content of sedimentary deposits depends on provenance, the effect of chemical and mechanical weathering during transport, grain size of the host sediments, and postdepositional intrastratal solution that selectively removes, over time, the less table minerals. Giles and Pilkey pointed out that two types of sand-sized sediment arrive at the southeast Atlantic Coast: sediments originating in the Piedmont with immature heavy mineral assemblages, and sediments derived from older coastal plain sediments with mature heavy mineral assemblages. Most of the coastal sands are mixtures of these two types, and the heavy mineral suites of well-mixed coastal sands are reasonably predictable, as are the suites of Piedmont sands. For sands from similar sources and with similar transport histories, the mineralogy of fine-grained sand samples differs from that of coarse-grained samples. For example, fine-grained samples invariably have more zircon. Examination of a single size fraction of the samples eliminates the size effect. For well-mixed coastal sands, postdepositional intrastratal solution is the only variable producing significant differences in heavy mineral suites. Of the common heavy minerals in southeast Atlantic coastal and Piedmont suites, hornblende and epidote appear to be the most susceptible to intrastratal solution, hornblende more so than epidote. The rate of intrastratal solution is progressive, but because of variation in vertical and horizontal permeability and other factors, the rate is rarely, if ever, linear with time. However, under certain circumstances, heavy mineral suites indicate relative areas of coastal plain sand units and rough estimates of absolute ages.

  15. Carbon, nitrogen, and phosphorus accumulation in floodplains of Atlantic Coastal Plain rivers, USA

    USGS Publications Warehouse

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

    2005-01-01

    Net nutrient accumulation rates were measured in riverine floodplains of the Atlantic Coastal Plain in Virginia, Maryland, and Delaware, USA. The floodplains were located in watersheds with different land use and included two sites on the Chickahominy River (urban), one site on the Mattaponi River (forested), and five sites on the Pocomoke River (agricultural). The Pocomoke River floodplains lie along reaches with natural hydrogeomorphology and on reaches with restricted flooding due to channelization and levees. A network of feldspar clay marker horizons was placed on the sediment surface of each floodplain site 3-6 years prior to sampling. Sediment cores were collected from the material deposited over the feldspar clay pads. This overlying sediment was separated from the clay layer and then dried, weighed, and analyzed for its total carbon (C), nitrogen (N), and phosphorus (P) content. Mean C accumulation rates ranged from 61 to 212 g??m-2??yr-1, N accumulation rates ranged from 3.5 to 13.4 g??m -2??yr-1, and P accumulation rates ranged from 0.2 to 4.1 g??m-2??yr-1 among the eight floodplains. Patterns of intersite variation in mineral sediment and P accumulation rates were similar to each other, as was variation in organic sediment and C and N accumulation rates. The greatest sediment and C, N, and P accumulation rates were observed on Chickahominy River floodplains downstream from the growing metropolitan area of Richmond, Virginia. Nutrient accumulation rates were lowest on Pocomoke River floodplains that have been hydraulically disconnected from the main channel by channelization and levees. Sediment P concentrations and P accumulation rates were much greater on the hydraulically connected floodplain immediately downstream of the limit of channelization and dense chicken agriculture of the upper Pocomoke River watershed. These findings indicate that (1) watershed land use has a large effect on sediment and nutrient retention in floodplains, and (2) limiting the hydraulic connectivity between river channels and floodplains minimizes material retention by floodplains in fluvial hydroscapes. ?? 2005 by the Ecological Society of America.

  16. Stratigraphic and sedimentologic response to Late Quaternary climate change and glacio-eustasy, Colorado River, Gulf Coastal Plain of Texas

    SciTech Connect

    Blum, M.D. (Southern Illinois Univ., Carbondale, IL (United States). Dept. of Geology)

    1992-01-01

    This paper summarizes results of investigations of the Colorado River, Gulf Coastal Plain of Texas, which provides a detailed record of fluvial response to late Quaternary climatic change and glacio-eustatic sea level rise. Four allostratigraphic units of late Pleistocene through modern age are differentiated in the bedrock-confined lower Colorado valley on the Inner Coastal Plain. Here up to 10 meters of late Pleistocene sediments underlie a terrace at 17--20 meters above the present-day channel. Two distinct allostratigraphic units underlie an extensive Holocene terrace at 12--14 meters above the present-day channel. Allostratigraphic units and bounding disconformities correlate with climatic changes that have been identified from paleobiological data, and represent stratigraphic response to changes in the relationship between discharge and sediment supply. In addition, changes in sedimentary facies through time represents a response to changes in climate coupled with a protracted degradation of upland soil mantles. This degradation of soils altered the rate at which precipitation inputs were transferred to stream channels as runoff, which led to increases in the peakedness of flood hydrographs and changes in the relative importance of channel versus floodplain depositional environments. Increased flood stages during the late Holocene promoted the increasing importance of floodplain construction by vertical accretion, and late Holocene to modern allostratigraphic units contain thick vertical accretion facies. These same allostratigraphic units and component facies persist downvalley to the Outer Coastal Plain, but stratigraphic architecture changes as a result of the last glacio-eustatic cycle. Here late Holocene and modern sediments onlap and bury late Pleistocene and early to middle Holocene stratigraphic units that were emplaced during the last sea level lowstand and the transgression that followed.

  17. Paonia Reservoir Sediment Management

    NASA Astrophysics Data System (ADS)

    Kimbrel, S.; Collins, K.; Williams, C.

    2014-12-01

    Paonia Dam and Reservoir are located on Muddy Creek, a tributary of the North Fork Gunnison River in western Colorado. Since dam closure in 1962, the 2002 survey estimates an annual sedimentation rate of 153,000 m3/y, resulting in a 25% loss of total reservoir capacity. Long before sediment levels completely fill the reservoir, the outlet works have recently plugged with sediment and debris, adversely impacting operations, and emphasizing the urgency of formulating an effective sediment management plan. Starting in 2010-2011, operations were changed to lower the reservoir and flush sediment through the outlet works in early spring before filling the pool for irrigation. Even though the flushing strategy through the long, narrow reservoir (~5 km long and 0.3 km wide) has prevented outlet works plugging, a long term plan is needed to manage inflowing and deposited sediment more efficiently. Reclamation's Sedimentation and River Hydraulics Group is leading an effort to study the past and current sediment issues at Paonia Dam and Reservoir, evaluate feasible sediment management alternatives, and formulate a plan for future operations and monitoring. The study is building on previously collected data and the existing knowledge base to develop a comprehensive, sustainable sediment management plan. The study is being executed in three phases: Phase 1 consisted of an initial site visit to map and sample existing reservoir bottom sediments, a preliminary site evaluation upstream and downstream of the dam, and establishment of time-lapse photo sites and taking initial ground-based photos. Phase 2 includes a bathymetric survey of entire reservoir and 11 km of the river downstream of the dam, continuous suspended sediment monitoring upstream and downstream of the reservoir, and collection of additional core samples of reservoir bottom sediments. Phase 3 involves the evaluation of current and past operations and sediment management practices, evaluate feasible sediment management methods, and providing recommendations for future monitoring and sediment management operations. Data collected during Phases 1 and 2 are used in a one-dimensional numerical sediment transport model for evaluating past, current, and potential future sediment management options.

  18. Channel narrowing and vegetation development following a great plains flood

    USGS Publications Warehouse

    Friedman, J.M.; Osterkamp, W.R.; Lewis, W.M., Jr.

    1996-01-01

    Streams in the plains of eastern Colorado are prone to intense floods following summer thunderstorms. Here, and in other semiarid and arid regions, channel recovery after a flood may take several decades. As a result, flood history strongly influences spatial and temporal variability in bottomland vegetation. Interpretation of these patterns must be based on understanding the long-term response of bottomland morphology and vegetation to specific floods. A major flood in 1965 on Plum Creek, a perennial sandbed stream, removed most of the bottomland vegetatiqn and transformed the single-thread stream into a wider, braided channel. Channel narrowing began in 1973 and continues today. In 1991, we determined occurrences of 150 vascular plant species in 341 plots (0.5 m2) along a 7-km reach of Plum Creek near Louviers, Colorado. We related patterns of vegetation to elevation, litter cover, vegetative cover, sediment particle size, shade, and year of formation of the underlying surface (based on age of the excavated root flare of the oldest woody plants). Geomorphic investigation determined that Plum Creek fluvial surfaces sort into five groups by year of formation: terraces of fine sand formed before 1965; terraces of coarse sand deposited by the 1965 flood; stable bars formed by channel narrowing during periods of relatively high bed level (1973-1986); stable bars similarly formed during a recent period of low bed level (1987-1990); and the present channel bed (1991). Canonical correspondence analysis indicates a strong influence of elevation and litter cover, and lesser effects of vegetative cover, shade, and sediment particle size. However, the sum of all canonical eigenvalues explained by these factors is less than that explained by an analysis including only the dummy variables that define the five geomorphically determined age groups. The effect of age group is significant even when all five other environmental variables are specified as covariables. Therefore, the process of postflood channel narrowing has a dominant influence on vegetation pattern. Channel narrowing at Plum Creek includes a successional process: annual and perennial plants become established on the channel bed, sediment accretes around the vegetation, and increasing litter cover, shade, and scarcity of water eliminate species that are not rhizomatous perennials. However, successional trajectories of individual surfaces are modified by flow-related fluctuations of the bed level; surfaces deposited by the 1965 flood have had distinct sediment and vegetation since their formation. Species richness is highest on surfaces dating to 1987-1990; the many species restricted to this transitory assemblage are perpetuated by flood-related fluctuations in channel width. Since the 1965 flood, seedling establishment of the dominant trees (genus Populus) has occurred only on low surfaces formed during channel narrowing. Thus, the flood has indirectly promoted Populus establishment over a 26-yr period.

  19. Golfingicola abyssalis gen. et sp. nov., a new endoparasitic copepod (Crustacea) in a sipunculan from abyssal depths of the Northwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Schwabe, Enrico; Maiorova, Anastassya

    2015-01-01

    Marine copepods, which inhabit the entire water column down to the seafloor, are key contributors to the food web, mainly providing a food source for many organisms in the form of zooplankton. Furthermore, they also play an important ecological role as associates or even parasites with various degrees of harm to their hosts. Copepods are found in almost all habitats and can be associated with virtually every metazoan group. A female and four males of a new endoparasitic copepod genus and species (Golfingicola abyssalis) are described from the trunk celom of the sipunculan Golfingia muricaudata (Southern, 1913), collected from the abyssal depths of the Northwest Pacific Ocean near the Kuril-Kamchatka Trench. This sipunculan species is a typical deep sea representative of the northwestern Pacific region, occurring in the Bering Sea and the abyssal regions east of the Kuril Island chain. Despite numerous records of this species, a copepod association has not been reported prior to this paper. The new parasitic copepod species is tentatively placed in the Akessonia group given its endoparasitic behavior in Sipuncula, the elongated shape, the enlarged egg strings, and the presence of subchelate antenna, as well as lateral processes in males. Golfingicola abyssalis, however, shows some peculiarities that clearly differentiate it from the remaining endoparasites in Sipuncula. As the first abyssal endoparasite in Sipuncula, the species is characterized by the complete lack of any processes in females, the presence of a mandible in females, a weakly defined prosome-urosome boundary in females, the presence of a mouth in males, the free living behavior of males, a distinctly reduced number of trunk processes in males, as well as a more modified male antenna, displaying an endopodite and a highly modified setal element. A detailed review on the morphological characters of the four species currently grouped in the Akessonia group, and systematic and biogeographic information of their relevant host taxa is provided. On the basis of morphological and ecological similarities, the new species seems to be more closely related to the northern Atlantic Akessonia occulta Bresciani and Luetzen, 1962 than to Siphonobius gephyreicola Augener, 1903 and Coelotrophus nudus Ho et al., 1981.

  20. Impact crater degradation on venusian plains

    NASA Astrophysics Data System (ADS)

    Izenberg, N. R.; Arvidson, R. E.; Phillips, R. J.

    1994-02-01

    In venusian plains, impact craters without extensive low backscatter ejecta deposits are more likely to have low backscatter floors, be embayed by volcanic deposits, and exhibit fractures as compared to craters with extensive low backscatter ejecta. We interpret these trends as evidence of ongoing degradation of low backscatter ejecta by aeolian activity, weathering, and volcanism. Using a crater age sequence based on extent of preservation of low backscatter ejecta, together with Monte Carlo simulations, we find that tectonic activity has extended over a longer time period than volcanism.

  1. Medicine Wheels of the Great Plains

    NASA Astrophysics Data System (ADS)

    Vogt, David

    Medicine Wheels are unexplained aboriginal boulder configurations found primarily on hilltops and river valley vistas across the northwest Great Plains of North America. Their varied, complex designs have inspired diverse hypotheses concerning their meaning and purpose, including astronomical ones. While initial "observatory" speculations were unfounded, and quests to "decode" these structures remain unfulfilled and possibly misguided, the Medicine Wheels nevertheless represent a uniquely worthwhile case study in archaeoastronomical theory and method. In addition, emerging technologies for data acquisition and analysis pertinent to Medicine Wheels offer prospectively important new sight lines for the future of archaeoastronomy.

  2. Avalanches, Barkhausen noise, and plain old criticality

    SciTech Connect

    Perkovic, O.; Dahmen, K.; Sethna, J.P. [Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501 (United States)

    1995-12-01

    We explain Barkhausen noise in magnetic systems in terms of avalanches of domains near a plain old critical point in the hysteretic zero-temperature random-field Ising model. The avalanche size distribution has a universal scaling function, making nontrivial predictions of the shape of the distribution up to 50{percent} above the critical point, where two decades of scaling are still observed. We simulate systems with up to 1000{sup 3} domains, extract critical exponents in 2, 3, 4, and 5 dimensions, compare with our 2D and 6{minus}{epsilon} predictions, and compare to a variety of experiments. {copyright} {ital 1995 The American Physical Society.}

  3. Cotton and Manpower - Texas High Plains.

    E-print Network

    Ducoff, Louis J.; Metzler, William H.; Motheral, Joe R.

    1953-01-01

    large stream of migratory farm workers originating mainly in South Texas. Labor-saving machinery, including mechanical cotton har- vesters, are in wide use and make the High Plains an excel- lent laboratory for anallyzing the probable effects of high...- level mechanization in the rest of the Cotton South. The find- ings point up the role of regular hired workers and of the op- erator and his family in mechanized cotton production. They also show the need for worker training programs, more ade- quate...

  4. Old Basin Filled by Smooth Plains

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Old basin, 190 km in diameter, filled by smooth plains at 43 degrees S, 55 degrees W. The basin's hummocky rim is partly degraded and cratered by later events. Mariner 10 frame 166607.

    The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

    Image Credit: NASA/JPL/Northwestern University

  5. The internal strength of rivers: autogenic processes in control of the sediment load (Tana River, Kenya)

    NASA Astrophysics Data System (ADS)

    Geeraert, Naomi; Ochieng Omengo, Fred; Tamooh, Fredrick; Paron, Paolo; Bouillon, Steven; Govers, Gerard

    2014-05-01

    The construction of sediment rating curves for monitoring stations is a widely used technique to budget sediment fluxes. Changes in the relationship between discharge and sediment concentrations over time are often attributed to human-induced changes in catchment characteristics, such as land use change, dam construction or soil conservation measures and many models have been developed to quantitatively link catchment characteristics and river sediment load. Conversely, changes in river sediment fluxes are often interpreted as indications of major changes in the catchment. By doing so, autogenic processes, taking place within the river channel, are overlooked despite the increasing awareness of their importance. We assessed the role of autogenic processes on the sediment load of Tana River (Kenya). The Tana river was impacted by major dam construction between 1968 and 1988, effectively blocking at least 80% of the sediment transfer from the highlands to the lower river reaches. However, a comparison of pre-dam sediment fluxes at Garissa (located 250 km downstream of the dams) with recent measurements shows that sediment fluxes have not changed significantly. This suggests that most of the sediment in the post-dam period has to originate from inside the alluvial plain of the river, as tributaries downstream of the dams are scarce and intermittent. Several observations are consistent with this hypothesis. We observed that, during the wet season, sediment concentrations rapidly increased below the dams and are not controlled by inputs from tributaries. Also, sediment concentrations were high at the beginning of the wet season, which can be attributed to channel adjustment to the higher discharges. The river sediment does not contain significant amounts of 137Cs or 210Pbxs, suggesting that sediments are not derived from topsoil erosion. Furthermore, we observed a counter clockwise hysteresis during individual events which can be explained by the fact that sediment mobilised within the river during a given event travels slower than the water. The highly dynamic behaviour of the river is further demonstrated by the rapid changes in river cross-section at Garissa and meander migration rates of several m y-1. In order to estimate a time frame for which changes in sediment inputs will be reflected in the sediment concentration at Garissa a single box model was developed. Results indicate that the effects of sediment blockage by the dams will only be visible after several hundreds to perhaps thousands of years. This clearly shows that autogenic processes are dominant in the lower Tana River and that, therefore, changes in sediment delivery cannot be detected in the sediment discharge record. More generally, understanding and interpreting the dynamics of such river systems requires that autogenic processes are correctly accounted for.

  6. 40 CFR 81.152 - Southern Coastal Plain Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 2010-07-01 false Southern Coastal Plain Intrastate Air Quality Control...Control Regions § 81.152 Southern Coastal Plain Intrastate Air Quality Control Region. The Southern Coastal Plain Intrastate Air Quality...

  7. Abyssal soil investigation equipment

    SciTech Connect

    Smits, F.P.; Maggioni, W.; Mainardi, U. [ISMES, Bergamo (Italy)

    1994-12-31

    The present paper deals with the development of a testing device for quick offshore geotechnical investigations. The equipment, at present, consists of a penetrometer, mounted on a sea bed platform, a handling frame and a control cabin; a further development includes a drill rig and a geotechnical laboratory. All this is designed so as to be an autonomous unit that can be handled by various types of non-specialized ships which have the necessary deck space. The sea bed platform can operate in 2,000 m of waterdepth and is provided with a hydraulic penetrometer, with a thrust capacity of 400 kN, able to carry out cone penetration type testing until a depth of more than 100 m, as well as shallow depth continuous sampling. The penetrometer can be equipped with a series of probes (piezocone, pressiocone, total radial pressure transducer, seismic cone) allowing the execution of the wide range of direct geotechnical measurements normally performed during on-land penetration tests.

  8. Northern Plains Textures Visible Near the Terminator

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Each day, Mars Global Surveyor makes 12 orbits around the red planet. On each orbit at the present time (April 1999), the spacecraft passes from daylight into night somewhere over the northern plains of Mars, and re-emerges into daylight over the southern cratered highlands. The illumination conditions near the martian terminator--the line between night and day--are perfect for observing surface texture and topography. This picture shows a common, rough and bumpy texture that MOC has revealed on the northern plains of Mars. Note the eroded impact crater at the bottom right--small black dots along its rim are interpreted to be boulders. This image covers an area 3 kilometers (1.9 miles) wide by 8 kilometers (5 miles) long and is illuminated by the sun shining low from the northeastern horizon (from the upper right).

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  9. Agricultural Field in the Great Plains Region of Montana

    USGS Multimedia Gallery

    Agricultural fields and an abandoned farmstead in eastern Montana in the Great Plains region. The Great Plains region of the United States has experienced significant land-use change since European settlement, with vast swaths of grasslands converted to agricultural lands. Access to water, technolog...

  10. IRRIGATION WASTEWATER DISPOSAL WELL STUDIES--SNAKE PLAIN AQUIFER

    EPA Science Inventory

    An investigation was conducted to evaluate the impact of irrigation disposal well practices on the water quality of the Snake Plain aquifer. A study site was selected where the geology was determined to be characteristic of areas in the Snake River Plain where irrigation disposal...

  11. Texas High Plains Vegetable & Weed Control Research Program

    E-print Network

    Mukhtar, Saqib

    Texas High Plains Vegetable & Weed Control Research Program Research Summary Reports 2008 Texas W. Wallace, Ph.D. Extension Vegetable & Weed Specialist Alisa K. Petty Research Technician #12 RESULTS OF HIGH PLAINS TRIALS 8 Herbicides and Weed Control Herbicide screen for mustard and collard

  12. Texas High Plains Vegetable & Weed Control Research Program

    E-print Network

    Mukhtar, Saqib

    Texas High Plains Vegetable & Weed Control Research Program Research Summary Reports 2006 Texas Experiment Station Russell W. Wallace Extension Vegetable & Weed Specialist Alisa K. Petty Research ................................................... 7 RESULTS OF HIGH PLAINS TRIALS 8 Herbicides and Weed Control Evaluation of Firestorm Applied

  13. High Plains Regional Ground-water Study web site

    USGS Publications Warehouse

    Qi, Sharon L.

    2000-01-01

    Now available on the Internet is a web site for the U.S. Geological Survey's (USGS) National Water-Quality Assessment (NAWQA) Program- High Plains Regional Ground-Water Study. The purpose of the web site is to provide public access to a wide variety of information on the USGS investigation of the ground-water resources within the High Plains aquifer system. Typical pages on the web site include the following: descriptions of the High Plains NAWQA, the National NAWQA Program, the study-area setting, current and past activities, significant findings, chemical and ancillary data (which can be downloaded), listing and access to publications, links to other sites about the High Plains area, and links to other web sites studying High Plains ground-water resources. The High Plains aquifer is a regional aquifer system that underlies 174,000 square miles in parts of eight States (Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming). Because the study area is so large, the Internet is an ideal way to provide project data and information on a near real-time basis. The web site will be a collection of living documents where project data and information are updated as it becomes available throughout the life of the project. If you have an interest in the High Plains area, you can check this site periodically to learn how the High Plains NAWQA activities are progressing over time and access new data and publications as they become available.

  14. High-resolution correlation of coastal plain strata for definition of reservoir attributes

    SciTech Connect

    Navarre, J.C.; Cross, T.A. [Colorado School of Mines, Golden, CO (United States)

    1995-08-01

    Three type of stratigraphic cycles are recognized in coastal-plain strata of the MesaVerde Group (Cretaceous) San Juan Basin, Colorado. The cycle types change as a function of accommodation and geographic position. The cycles record oscillations of base level and concomitant oscillations of increasing and decreasing accommodation. Coastal-plain strata were traced physically into shoreface strata to establish temporal equivalency of strata within the two environments, and thus ensure correct recognition of base-level rise and fall hemicycles in coastal-plain strata. Potential reservoir units are channel belt sandstones and backbarrier and bay sandstones which occur in two of the cycle types. These sandstones change geometry, connectivity, and volumes within cycles, reflecting changes in accommodation, the types of original geomorphic elements within environments, and sediment preservation during base-level cycles. The occurrence of different facies successions in the different types of cycles establishes the empirical basis for recognizing such cycles with well-log inversion techniques. One type of stratigraphic cycle, which occurs in the lowest accommodation condition of the Mesa Verde Group, is an alternation between laterally amalgamated channels and either crevasse splay/crevasse channel complexes or floodplain vertical accretion deposits and soils. Laterally amalgamated channel sandstones accumulated during base-level rise hemicycles. The third type of stratigraphic cycle also occurs in the maximum accommodation conditions, but in a more seaward position than the previous type. Like the first, this type of stratigraphic cycle comprises an alternation of two types of facies associations. This type is an alternation between tidally dominated estuarine and bay sandstones and mudstones which accumulated during base-level rise, and shallowing-up and bed-thickening up hummocky cross stratified back-barrier and bay sandstones which accumulated during base-level fall.

  15. Evidence of Late-Holocene floods in the central Great Plains

    SciTech Connect

    May, D.W. (Univ. of Northern Iowa, Cedar Falls, IA (United States). Dept. of Geography)

    1992-01-01

    From southwestern Kansas to northeastern Nebraska alluvial studies are revealing stratigraphic and morphological evidence of two brief periods of large-magnitude floods in the central Great Plains during the past 2,500 years. Evidence for these floods consists of deeply-scoured paleochannels, coarse-textured point-bar deposits overlying fine-grained deposits, soils on former floodplains that are buried by alluvium, and fluvial terraces. Wood and bone collagen in several deeply-scoured paleochannels date to about 2,300--2,000 yr B.P. Modest incision and floodplain reconstruction at this time is evident from both maps of fluvial landforms and C-14-dated stratigraphic sections in both large and small basins. Sediments near the base and top of inset gully fills in both trenched and untrenched tributary valleys to Great Plains rivers date to about 2,000 yr B.P. A second episode of large floods in the central Great Plains occurred about 1,300--850 yr B.P. Throughout most valleys a buried soil that developed in alluvium occurs from 50 cm to 1.0 m below terraces. Recently, stratified point-bar deposits beneath a low terrace in a small (9.6 km[sup 2]) basin in east-central Nebraska were exposed and studied. Crossbedded, gravelly sand strata alternative with massive, dark, silty strata. The C-14-dated section indicates that multiple floods occurred between 1,250 and 850 yr B.P. Such widespread evidence of flooding about 2,300--2,000 yr B.P. and again 1,250--850 yr B.P. attests to regional, and probably, global climate changes at these times. Discontinuities in the alluvial record have previously been recognized at 2,000 and 1,200 yr B.P. Furthermore, a discontinuity in the pollen record at 850 yr B.P. has long been recognized.

  16. Considerations over the distribution of the organic matter in the soil cover of Transylvania Plain (Romania)

    NASA Astrophysics Data System (ADS)

    Cacovean, Horia; Man, Titus; Rusu, Teodor

    2010-05-01

    Considerations over the distribution of the organic matter in the soil cover of Transylvania Plain (Romania) Horea Cacovean*, Titus Man**, Teodor Rusu*** *OSPA-Cluj- 1Faglui street, Cluj Napoca, RO-40048, Romania- turda75@yahoo.com ** Faculty of Geographie, University of Babes-Bolyai, 5-7 Clinicilor street, Cluj Napoca, RO-400006, Romania *** Faculty of Agriculture, USAMV, 3-5 Calea Manastur street,Cluj Napoca, RO-400372, Romania Soil degradation has become a major concern in the Transylvania Plain. Erosion, landslides, salinization, gleysation, and loss of humus are the main forms of soil deterioration in that region. This factsheet deals with the role of organic matter in soil productivity and the effects of various management practices and abandonment of the lands on soil organic matter. Soils in Transylvania Plain are analyzed concerning the amount of humus they contain. The influence of soil texture, climatic variables, and soil management on the qualitative soil humus content was studied in the top 20 cm of different managed loess soils of more then 100 profiles along a climosequence in that region. Taken together, soil, landform, land use and vegetation data suggest: (1) summit positions are relatively stable with immobilizing humus environments; (2) the content of humus increase progressively down steep at the contact with the floodplains; 3) without the influx of organic materials, erodible backslopes may become humus depleted as it happen the poor inputs of grassland and forest litter are mixed with surface soil horizon; 4) influx of mixed sediment and organic materials from backslopes maintains concentrations of humus on footslopes and toeslopes. This influence was more pronounced in the heavy clayey soils, suggesting that the accumulation of humus was enhanced by organo-mineral interactions. Entrenchment of drainage ways can circumvent these translocation processes. The results underscore the importance of functional connectivity between upland hillslopes and alluvial soils.

  17. The Seismotectonics of the Po Plain (Northern Italy): Tectonic Diversity in a Blind Faulting Domain

    NASA Astrophysics Data System (ADS)

    Vannoli, Paola; Burrato, Pierfrancesco; Valensise, Gianluca

    2015-05-01

    We present a systematic and updated overview of a seismotectonic model for the Po Plain (northern Italy). This flat and apparently quiet tectonic domain is, in fact, rather active as it comprises the shortened foreland and foredeep of both the Southern Alps and the Northern Apennines. Assessing its seismic hazard is crucial due to the concentration of population, industrial activities, and critical infrastructures, but it is also complicated because (a) the region is geologically very diverse, and (b) nearly all potential seismogenic faults are buried beneath a thick blanket of Pliocene-Pleistocene sediments, and thus can be investigated only indirectly. Identifying and parameterizing the potential seismogenic faults of the Po Plain requires proper consideration of their depth, geometry, kinematics, earthquake potential and location with respect to the two confronting orogens. To this end, we subdivided them into four main, homogeneous groups. Over the past 15 years we developed new strategies for coping with this diversity, resorting to different data and modeling approaches as required by each individual fault group. The most significant faults occur beneath the thrust fronts of the Ferrara-Romagna and Emilia arcs, which correspond to the most advanced and buried portions of the Northern Apennines and were the locus of the destructive May 2012 earthquake sequence. The largest known Po Plain earthquake, however, occurred on an elusive reactivated fault cutting the Alpine foreland south of Verona. Significant earthquakes are expected to be generated also by a set of transverse structures segmenting the thrust system, and by the deeper ramps of the Apennines thrusts. The new dataset is intended to be included in the next version of the Database of Individual Seismogenic Sources (DISS; http://diss.rm.ingv.it/diss/, version 3.2.0, developed and maintained by INGV) to improve completeness of potential sources for seismic hazard assessment.

  18. Deep-sea scavenging amphipod assemblages from the submarine canyons of the Western Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Duffy, G. A.; Horton, T.; Billett, D. S. M.

    2012-11-01

    Submarine canyons have often been identified as hotspots of secondary production with the potential to house distinct faunal assemblages and idiosyncratic ecosystems. Within these deep-sea habitats, assemblages of scavenging fauna play a vital role in reintroducing organic matter from large food falls into the wider deep-sea food chain. Free-fall baited traps were set at different depths within three submarine canyons on the Iberian Margin. Amphipods from the traps were identified to species level and counted. Scavenging amphipod assemblages were compared at different depths within each canyon and between individual canyon systems. Using data from literature, abyssal plain assemblages were compared to submarine canyon assemblages. Samples from canyons were found to contain common abyssal plain species but in greater than expected abundances. It is proposed that this is a result of the high organic carbon input into canyon systems owing to their interception of sediment from the continental shelf and input from associated estuarine systems. Community composition differed significantly between the submarine canyons and abyssal plains. The cause of this difference cannot be attributed to one environmental variable due to the numerous inherent differences between canyons and abyssal plains.

  19. Controls on phosphorous mobility in the Potomac River near the Blue Plains wastewater treatment plant

    USGS Publications Warehouse

    Hearn, Paul P.

    1985-01-01

    The Blue Plains wastewater treatment plant is the largest point source of phosphorus in the Potomac River basin, discharging an average of 2 metric tons of phosphorus into the river each day in 1980. An intensive study of the water and sediments in the vicinity of the treatment plant was conducted in 1979-80 in order to characterize the major factors controlling the mobility of effluent-derived phosphorus in the area. The transport of phosphorus near the treatment plant was found to be affected by the circulation regime, by inorganic adsorption reactions with sediments, and by metabolic uptake and release by phytoplankton. The effect of river discharge on the convective transport of phosphorus near the outfall is significantly reduced by a mid-river shoal area, which confines the flow path of the effluent to an embayment on the eastern side of the river for a distance of 4 kilometers below the outfall. This embayment appears to serve as a sediment trap, where protection from bottom scour during high-flow events has permitted fine-grained sediments to accumulate. Measurements of mean residence time indicate that the effluent leaves the embayment area 21? days after being discharged from the outfall. Measurements of the linear decay constant for the removal of dissolved phosphorus from the water column reveal a diurnal cycle corresponding to the metabolic utilization of phosphorus by phytoplankton. This cyclic removal is superimposed on a constant and noncyclic adsorption of phosphorus by inorganic phases. Forty-eight hour average values of the linear decay constant for dissolved phosphorus in the area range from 0.4 to 1.1 per day. Analyses of bottom sediments indicate that approximately 13 percent of the phosphorus discharged between September 1977 and August 1980 has been retained in the embayment. The primary inorganic phase responsible for phosphorus adsorption is amorphous iron (ferric oxy-hydroxides); amorphous aluminum and clay minerals appear to play secondary roles. The accumulation of sorbed phosphorus in the embayment has been promoted by the deposition of fine-grained sediments enriched in ferric oxy-hydroxides. Conversely, the absence of ferric oxy-hydroxides in coarse-grained sediments near the outfall has facilitated the precipitation of the ferrous phosphate mineral vivianite.

  20. SOUTHEASTERN PLAINS NUTRIENT RESPONSE (SPNR) PROJECT

    EPA Science Inventory

    This study is part of a multi-year effort to examine nutrient biological responses and to develop accurate tools for measuring and assessing those responses. For 2007, this work involves developing a methodology for sampling and analysis of periphyton from sand and sediment. We...

  1. Salt-dome locations in the Gulf Coastal Plain, South-Central United States

    USGS Publications Warehouse

    Beckman, J.D.; Williamson, A.K.

    1990-01-01

    Information on salt domes in Gulf of Mexico Coastal Plain, south-central United States and the adjacent Continental Shelf were compiled from major published sources, 1973-84. The location of 624 salt domes is shown on a map at a scale of 1:1 ,500,000. A color-coding system was used to show that the occurrence, size, shape, and location of these domes varies among sources. Two tables of additional data accompany the map and include other available information such as: identifying sources, depth to salt and caprock, diameter, volume, name, and uppermost zone of surrounding sediment that is penetrated, as well as the number of matches between sources. The locations of salt domes that penetrate specific zones within the gulf coast regional aquifer system are shown on maps. (USGS)

  2. Harvesting energy from the marine sediment-water interface II. Kinetic activity of anode materials.

    PubMed

    Lowy, Daniel A; Tender, Leonard M; Zeikus, J Gregory; Park, Doo Hyun; Lovley, Derek R

    2006-05-15

    Here, we report a comparative study on the kinetic activity of various anodes of a recently described microbial fuel cell consisting of an anode imbedded in marine sediment and a cathode in overlying seawater. Using plain graphite anodes, it was demonstrated that a significant portion of the anodic current results from oxidation of sediment organic matter catalyzed by microorganisms colonizing the anode and capable of directly reducing the anode without added exogenous electron-transfer mediators. Here, graphite anodes incorporating microbial oxidants are evaluated in the laboratory relative to plain graphite with the goal of increasing power density by increasing current density. Anodes evaluated include graphite modified by adsorption of anthraquinone-1,6-disulfonic acid (AQDS) or 1,4-naphthoquinone (NQ), a graphite-ceramic composite containing Mn2+ and Ni2+, and graphite modified with a graphite paste containing Fe3O4 or Fe3O4 and Ni2+. It was found that these anodes possess between 1.5- and 2.2-fold greater kinetic activity than plain graphite. Fuel cells were deployed in a coastal site near Tuckerton, NJ (USA) that utilized two of these anodes. These fuel cells generated ca. 5-fold greater current density than a previously characterized fuel cell equipped with a plain graphite anode, and operated at the same site. PMID:16574400

  3. Vegetation change, erosion risk and land management on the Nullarbor Plain, Australia

    NASA Astrophysics Data System (ADS)

    Gillieson, D.; Wallbrink, P.; Cochrane, A.

    1996-10-01

    Arid karst landscapes that have been degraded by human activities provide a challenge for rehabilitation and an opportunity to test ideas about the stability and resilience of limestone ecosystems. The Nullarbor Plain is the largest arid karst area in Australia (220 000 km2) and is divided into extensive closed karstic depressions separated by low rocky ridges, while the dominant vegetation is chenopod shrubland. Since European settlement there has been considerable change in the vegetation, with significant reduction in shrub and grass cover over large areas of the plain. These changes are related to a state and transition model of vegetation dynamics which incorporates climatic variability, fire history and grazing pressure from sheep, kangaroos and rabbits. A partial sediment budget using 137Cs inventories reveals local and regional patterns of soil redistribution within this arid karst landscape. Rehabilitation of eroded soil in pastoral lands has been accomplished at several sites but is labour intensive and vulnerable to climatic fluctuations. Given the low stock numbers, limited number of people involved, and poor economic returns, it would be sensible to make pastoral activities on the Nullarbor secondary to conservation priorities. This would necessitate a change in land ethic to stewardship, with emphasis on rehabilitation and control of feral animals. Management of increased numbers of visitors to the caves and karst also requires that resource inventories and management plans for each area be drawn up and used.

  4. Paleolimnological reconstruction of Holocene environments in wetland ponds of the Upper Atlantic Coastal Plain

    SciTech Connect

    Gaiser, E.E.; Taylor, B.E. [Univ. of Georgia, Athens, GA (United States)

    1995-06-01

    The paleohydrology and paleoecology of Carolina bays and upland wetland ponds on the Savannah River Site (SRS), Aiken, South Carolina are being investigated to reconstruct environmental changes brought about by long-term variation in the climate of the Upper Atlantic Coastal Plain. Cores were taken in transacts through Flamingo Bay, a temporary pond on the SRS, to determine the vertical and horizontal sediment particle size and diatom, plant phytolith and sponge spicule microfossils. Stratigraphic data were used to construct a 3-dimensional map of the basin. In conjunction with archaeological data from the rim of the pond, physical stratigraphic data indicate a decrease in pond size and depth during the past 10,000 years. In order to infer past ecological settings from the fossil record, a survey to determine microhabitat requirements of regional diatom flora was undertaken in 43 temporary ponds throughout the coastal plain of South Carolina. The relationships between diatom assemblages and environmental variables were assessed using canonical correspondence analysis. Variables contributing significantly to the diatom-environment relationship included surface core location (near shore or pelagic), water depth, hydroperiod, microhabitat substrate, and sampling date, in order of decreasing influence. Strong relationships of diatom assemblages to drought frequency within and among basins provides a reliable basis for water level reconstruction in upland temporary ponds.

  5. Longitudinal variability in hydraulic geometry and substrate characteristics of a Great Plains sand-bed river

    NASA Astrophysics Data System (ADS)

    Costigan, Katie H.; Daniels, Melinda D.; Perkin, Joshuah S.; Gido, Keith B.

    2014-04-01

    Downstream trends in hydraulic geometry and substrate characteristics were investigated along a 200 km reach of the Ninnescah River in south central Kansas, USA. The Ninnescah River is a large sand-bed, perennial, braided river located in the Central Plains physiographic province and is a tributary of the Arkansas River. Hydraulic geometry characteristics were measured at eleven reaches and included slope, sinuosity, bankfull channel width, and bankfull channel depth. Results indicated that the Ninnescah River followed a predicted trend of decreasing slope and increasing depth and width downstream. There were localized divergences in the central tendency, most notability downstream of a substantial tributary that is impounded and at the end of the surveying reach where the Ninnescah River approaches the Arkansas River. Surface grain-size samples were taken from the top 10 cm of the bed at five points across the wetted cross-section within each of the 11 reaches. Sediment analyses demonstrated a significant trend in downstream fining of surface grain-sizes (D90 and D50) but unlike previous studies of sand-bedded rivers we observed coarsening of substrates downstream of the major tributary confluence. We propose that the overall low discharge from the tributary was the primary reason for coarsening of the bed downstream of the tributary. Results of this study provide valuable baseline information that can provide insight in to how Great Plains sand-bed systems may be conserved, managed, and restored in the future.

  6. The Magilligan beach ridge plain (Northern Ireland, UK): A detailed sedimentary approach

    NASA Astrophysics Data System (ADS)

    Tillmann, Tanja; Surmann, Kirstin; Cooper, Andrew

    2015-04-01

    Beach ridges are a common geological feature on prograded sandy coasts . Beach ridges and their subsurface deposits record past coastal processes and are indicators of previous shoreline position, shape and sea level. This work presents preliminary results and provides new information about the late Holocene development of the Magilligan Foreland in Northern Ireland (UK). The triangular beach-ridge plain of Magilligan was formed in the early and mid-Holocene as a consequence of land and sea level change and sediment abundance. The focus of the investigations is a detailed grain size analysis of beach ridge deposits using the settling tube method. The main aim is to distinguish the beach ridge deposits from the aeolian dune sand cover and to draw conclusions about the development and sedimentary formation of the beach ridges. A semi-continuous outcrop of the upper units of the beachridge plain is preserved along the coastline. The geological descriptions in the field show significant differences between adjacent outcrops and grain size analysis was undertaken to distinguish aeolian and swash-lain sediemnts. Buried soil layers and unconformities helped to define the palaeotopography which consist of a sequence of beach ridge crests and inter-ridge depressions. The beach ridges of the subsurface are independent of the modern dune topography. There are more beach ridges than previously thought.

  7. Correlation of Miocene sequences and hydrogeologic units, New Jersey Coastal Plain

    USGS Publications Warehouse

    Sugarman, P.J.; Miller, K.G.

    1997-01-01

    We have developed a Miocene sequence stratigraphic framework using data from recently drilled boreholes in the New Jersey Coastal Plain. Sequences are shallowing upward, unconformity-bounded units; fine-grained shelf and prodelta sediments grade upward to delta front and shallow-marine sands, corresponding to confining bed-aquifer couplets. By dating Miocene sequences using Sr-isotope stratigraphy, and mapping with borehole data and geophysical logs, we can predict the continuity and effectiveness of the confining beds and aquifers. The following are illustrated on a 90-km basinward dip section: (1) the composite confining bed is comprised of the KwO and lower Kw1a (ca. 23.8-20.5 Ma) sequences downdip at Atlantic City, and the Kw1b, Kw1a and older sequences updip (ca. 69.3-20.6 Ma), and is continuous throughout most of the coastal plain; (2) the major confined aquifer, the Atlantic City 800-foot sand, is comprised of the upper Kw1a and Kw1b sequences (ca. 20.5-20.2 Ma) and is an areally continuous sand that is interconnected with the Kirkwood-Cohansey aquifer system updip of Mays Landing; (3) the confining bed above the Atlantic City 800-foot sand is comprised of the Kw2a, Kw2b, and Kw3 sequences (18.1-13.3 Ma) and is an extensive confining bed that pinches out updip. These sequences and aquifer-confining bed couplets are linked to global sea-level changes evinced by the ??18O record. We conclude that sequence stratigraphy is a powerful tool when applied to regional hydrogeologic problems, although basinal tectonic differences and localized variations in sediment supply can affect aquifer thickness and permeability.

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

    PubMed

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

    2007-04-01

    Analysis of site geomorphology and sedimentation rates as an indicator of long-term bed stability is central to the evaluation of remedial alternatives for depositional aquatic environments. In conjunction with various investigations of contaminant distribution, sediment dynamics, and bed stability in the Passaic River Estuary, 121 sediment cores were collected in the early 1990s from the lower 9.7 km of the Passaic River and analyzed for lead-210 (210Pb), cesium-137 (137Cs), and other analytes. This paper opportunistically uses the extensive radiochemical dataset to examine the spatial patterns of long-term sedimentation rates in, and associated geomorphic aspects of, this area of the river. For the purposes of computing sedimentation rates, the utility of the 210Pb and 137Cs depositional profiles was assessed to inform appropriate interpretation. Sedimentation rates were computed for 90 datable cores by 3 different methods, depending on profile utility. A sedimentation rate of 0 was assigned to 17 additional cores that were not datable and for which evidence of no deposition exists. Sedimentation patterns were assessed by grouping results within similar geomorphic areas, delineated through inspection of bathymetric data. On the basis of channel morphology, results reflect expected patterns, with the highest sedimentation rates observed along point bars and channel margins. The lowest rates of sedimentation (and the largest percentage of undatable cores) were observed in the areas along the outer banks of channel bends. Increasing sedimentation rates from upstream to downstream were noted. Average and median sedimentation rates were estimated to be 3.8 and 3.7 cm/y, respectively, reflecting the highly depositional nature of the Passaic River estuary. This finding is consistent with published descriptions of long-term geomorphology for Atlantic Coastal Plain estuaries. PMID:17477286

  9. Late Cenozoic fluvial development within the Sea of Azov and Black Sea coastal plains

    NASA Astrophysics Data System (ADS)

    Matoshko, A.; Gozhik, P.; Semenenko, V.

    2009-09-01

    Late Cenozoic terrestrial deposits are widespread across the northern coastal regions of the Black Sea and the Sea of Azov and represent diverse fluvial, estuarine and deltaic environments. The dating and correlation of these deposits rely on stratigraphically-associated marine index beds, mammalian and molluscan faunas and magnetostratigraphy. In detail the geometries of these sediment bodies are extremely complex, typically varying between localities and representing many cycles of incision and aggradation. However, the overall disposition of the sediments reflects the transition from the uplifting sediment source region to the north and the subsiding depocentre in the interior of the Black Sea to the south. Since the Middle Miocene the area of the Paratethys/Black Sea depocentre has decreased significantly, but since the Middle Pliocene the hinge zone between uplift and subsidence has been located close to the modern coastline. A combination of regional and local differential crustal movements has given rise to the great variety of fluvial sediment bodies, to the erosion-aggradation cycles, different phases and river activity and to the various fluvial landforms that have all been important in landscape development in this region during the past 12 Ma. The fluvial erosion-accumulation cycles (during the upper Serravillian-Messinian, the Zanclean-late Gelasian, and the Pleistocene) and corresponding cycles of relief dissection and planation are reconstructed against a background of local sea-level changes and climatic variations determined from palaeobotanical data. The maximum fluvial incision occurred in the early Zanclean time with alluvial coastal plains, unique in this area, developing in the Gelasian. Increased climatic aridity during the Pleistocene caused a reduction of fluvial activity in comparison with the Late Miocene and Pliocene. The sea-level oscillations and Pleistocene glaciations affected fluvial processes in different ways. The most remarkable events were the substantial reduction of fluvial activity during the Messinian dessication in the Black Sea and drainage of the shelf, with intensive dissection, coeval with the Last Glaciation.

  10. Indications for algae-degrading benthic microbial communities in deep-sea sediments along the Antarctic Polar Front

    NASA Astrophysics Data System (ADS)

    Emil Ruff, S.; Probandt, David; Zinkann, Ann-Christine; Iversen, Morten H.; Klaas, Christine; Würzberg, Laura; Krombholz, Nicole; Wolf-Gladrow, Dieter; Amann, Rudolf; Knittel, Katrin

    2014-10-01

    Phytoplankton blooms in surface waters of the oceans are known to influence the food web and impact microbial as well as zooplankton communities. Numerous studies have investigated the fate of phytoplankton-derived organic matter in surface waters and shelf sediments, however, little is known about the effect of sinking algal biomass on microbial communities in deep-sea sediments. Here, we analyzed sediments of four regions in the Southern Atlantic Ocean along the Antarctic Polar Front that had different exposures to phytoplankton bloom derived organic matter. We investigated the microbial communities in these sediments using high-throughput sequencing of 16S rRNA molecules to determine microorganisms that were active and catalyzed reporter deposition fluorescence in situ hybridization to infer their abundance and distribution. The sediments along the Antarctic Polar Front harbored microbial communities that were highly diverse and contained microbial clades that seem to preferably occur in regions of high primary productivity. We showed that organisms affiliated with the gammaproteobacterial clade NOR5/OM60, which is known from surface waters and coastal sediments, thrive in the deep-sea. Benthic deep-sea NOR5 were abundant, diverse, distinct from pelagic NOR5 and likely specialized on the degradation of phytoplankton-derived organic matter, occupying a similar niche as their pelagic relatives. Algal detritus seemed to not only fuel the benthic microbial communities of large areas in the deep-sea, but also to influence communities locally, as we found a peak in Flavobacteriaceae-related clades that also include degraders of algal biomass. The results strongly suggest that phytoplankton-derived organic matter was rapidly exported to the deep-sea, nourished distinct benthic microbial communities and seemed to be the main energy source for microbial life in the seafloor of vast abyssal regions along the Antarctic Polar Front.

  11. The effect of sediment on survival, growth, reproductive success and bioaccumulation in Neanthes: Summary report

    SciTech Connect

    Gerlinger, T.V.; Fanizzi, M.; Soong, K.; Armstrong, J. [Sanitation Districts of Orange County, Fountain Valley, CA (United States); Reish, D.J. [California State Univ., Long Beach, CA (United States)

    1995-12-31

    Sediments taken from the vicinity of the County Sanitation Districts of Orange County ocean outfall were tested for survival, growth, reproduction and bioaccumulation of toxicants on the polychaete, Neanthes arenaceodentata. The end points were survival, growth (dry weight), reproductive success (as number of emerged larvae) and bioaccumulation (metals, DDT, PCBs). Ten experiments have been conducted over a 2 year period of which 2 measured reproductive success. The experiments for survival and growth utilized 2--3 week old post-emergence juvenile worms and subjected them to different test sediments including an inert sediment and plain sea water control. Worms were fed during the experiments. Experiments for reproductive success and bioaccumulation consisted of placing 100 juvenile worms each in 10 gallon aquaria together with test sediment for a 35--40 day period. After which, 10--15 pairs were made and each pair was placed in a separate 1 liter beaker together with sediment for the reproductive experiment. The remaining worms in each aquarium were used for chemical analysis. No toxic responses, as measured by survival, growth and reproductive success, were noted at any station during the 2 year study. Growth was generally lower in the inert sediment and sea water controls compared to test sediments indicating that worms were obtaining some nutrients from the sediment. No difference was noted in the number of emerged juveniles in any test container. While worms accumulated metals and organics in their tissue, there was neither a relationship to the station location nor to survival, growth or reproduction.

  12. Mass sedimentation of the swimming crab Charybdis smithii (Crustacea: Decapoda) in the deep Arabian Sea

    NASA Astrophysics Data System (ADS)

    Christiansen, Bernd; Boetius, Antje

    During cruise Meteor 33/1 in the northern Arabian Sea in September/October 1995, large numbers of the portunid crab Charybdis smithii were observed swimming in the open ocean. In a photographic survey at three abyssal stations in the northern Arabian Sea (NAST, WAST, CAST), even higher densities of Charybdis smithii - up to 1 crab m -2 - were found dead on the sea floor. Average sizes of the crabs were around 34-44 mm carapace width, indicating that the animals died prematurely, before returning to the breeding grounds presumable on the shelves of India or Oman. The average weight of the crabs was 10-14 g wet weight. From the photographic quantification it can be deduced that these large food falls represent a significant carbon input of at least 10-30% of the annual flux of POC as measured in sediment traps in this region. The exceptionally high microbial chitinase activity in the surface sediment layers detected at the same stations indicates that this energy is utilized and channelled into the deep-sea benthic food web of the deep Arabian Sea. There are frequent observations of dense Charybdis smithii swarms in the Arabian Sea from different years; however, it is not certain whether such large food falls as observed during M 33/1 are regular seasonal events that repeat each year.

  13. Re-Wilding the Great Plains

    NSDL National Science Digital Library

    A new paper published in the journal Nature has proposed re-wilding North America by introducing populations of large animals from Africa related to ones that roamed the Great Plains during the Pleistocene era. This radio broadcast features discussion with one of the architects of this idea about the ecology of America 13,000 years ago; how large mammals interacted with the environment in ways important to biodiversity; how they are thought to have been driven to extinction by humans; and whether re-introduced large animals would fill their ancient niches or become invasive species. There is also discussion about the feasibility of using biotechnology to produce Woolly Mammoths from bone-extracted DNA. The broadcast is 21 minutes in length.

  14. Contributions of suspended sediment from highway construction and other land uses to the Olentangy River, Columbus, Ohio

    USGS Publications Warehouse

    Helsel, D.R.

    1985-01-01

    Highway construction within the Olentangy River flood plain in Columbus, Ohio, was projected to be a large source of suspended sediment to the river system. A monitoring program was begun by the U.S. Geological Survey in 1978 to quantify the implacts of construction process. Sediment information was collected daily at six gaging stations located above, below, and within the construction area. Yields of suspended sediment from the active construction area ranged from 9,580 to 15,700 tons per square mile per year. Surrounding suburban terrain yielded 428 to754 tons per square mile per year. However, the size of the construction project was small in comparison to the surrounding suburbs contributing sediment. No more than 4 percent of the yearly downstream suspended-sediment loads were produced by high-way construction during the monitoring periods.

  15. Tobacco plain packaging: Evidence based policy or public health advocacy?

    PubMed

    McKeganey, Neil; Russell, Christopher

    2015-06-01

    In December 2012, Australia became the first country to require all tobacco products be sold solely in standardised or 'plain' packaging, bereft of the manufacturers' trademarked branding and colours, although retaining large graphic and text health warnings. Following the publication of Sir Cyril Chantler's review of the evidence on the effects of plain tobacco packaging, the Ministers of the United Kingdom Parliament voted in March 2015 to implement similar legislation. Support for plain packaging derives from the belief that tobacco products sold in plain packs have reduced appeal and so are more likely to deter young people and non-smokers from starting tobacco use, and more likely to motivate smokers to quit and stay quit. This article considers why support for the plain packaging policy has grown among tobacco control researchers, public health advocates and government ministers, and reviews Australian survey data that speak to the possible introductory effect of plain packaging on smoking prevalence within Australia. The article concludes by emphasising the need for more detailed research to be undertaken before judging the capacity of the plain packaging policy to deliver the multitude of positive effects that have been claimed by its most ardent supporters. PMID:26041731

  16. CALCULATING SEDIMENT COMPACTION FOR RADIOCARBON DATING OF INTERTIDAL SEDIMENTS

    Microsoft Academic Search

    M I Bird; L K Fifield; S Chua; B Goh

    2004-01-01

    This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holocene mangrove sediments in Singapore, in order to correct apparent sediment accretion rates for the effects of sediment compres- sion due to autocompaction. Relationships developed for a suite of modern (surface) sediment samples between bulk density, particle-size distribution, and organic matter content were used to estimate the initial

  17. EXTERNAL EFFECTS OF IRRIGATORS' PUMPING DECISIONS, HIGH PLAINS AQUIFER.

    USGS Publications Warehouse

    Alley, William M.; Schefter, John E.

    1987-01-01

    The High Plains aquifer, which underlies about 174,000 square miles (1 square mile equals 2. 59 km**2) in the Great Plains, is the principal source of water in one of the nation's major agricultural areas. This paper examines relationships between the scale of management areas and physical factors, resulting from the lateral movement of groundwater, that limit the ability of irrigators in the High Plains to reduce their own future pumping lifts. At the scale of individual farms, irrigators have very limited ability to 'bank' water in order to obtain reduced future pumping lifts.

  18. Dissolved and solid-phase arsenic fate in an arsenic-enriched aquifer in the river Brahmaputra alluvial plain.

    PubMed

    Baviskar, Shirishkumar; Choudhury, Runti; Mahanta, Chandan

    2015-03-01

    Dissolved arsenic mobility in the environment is controlled by its associations with solid-phase As and other minerals by chemodynamics of adsorptions and co-precipitation. Arsenic mobilization potential and mechanisms in the groundwater of a part of the river Brahmaputra alluvial plain in India were inferred from aqueous and solid-phase geochemical analyses of groundwater samples and sediment cores from various depths. Sediments were analyzed for key parameters, e.g., total and sequentially extracted Fe, As, and Mn; organic carbon content; carbonate phases; and specific surface area, while groundwater samples collected from close proximity of the drilled bore well were analyzed for major and trace element hydrogeochemistry. Result shows Mn- and Fe-oxyhydroxides as the major leachable As solid phases. Median total leachable solid-phase As was found to be ~9.50 mg/kg, while groundwater As ranged between 0.05 and 0.44 mg/L from adjoining water wells. Morphological and mineralogical studies of the aquifer sediments conducted using scanning electronic microscope energy-dispersive X-ray (SEM-EDX) and X-ray diffraction (XRD) analysis indicate the major presence of Fe- and Mn-oxyhydroxides. Sequential leaching experiments along with the mineralogical studies suggest that bacterially mediated, reductive dissolution of MnOOH and FeOOH is probably an important mechanism for releasing As into the groundwater from the sediments. PMID:25663398

  19. Comparison of Plains Volcanism in the Tempe Terra Region of Mars to the Eastern Snake River Plains, Idaho with Implications for Geochemical Constraints

    NASA Technical Reports Server (NTRS)

    Weren, S. L.; Sakimoto, S. E. H.; Hughes, S. S.; Gregg, T. K. P.

    2004-01-01

    The Eastern Snake River Plains (ESRP) in Idaho have long been considered a terrestrial analog for the plains volcanism like that evident in Syria Planum and Tempe Terra, Mars. Both the ESRP and Tempe Terra are sediment-blanketed volcanic fields in areas with significant extensional faulting. Similar volcanic features can be observed throughout both study areas using field analysis and DEMs of the ESRP and the Mars Global Surveyor (MGS) data from Mars. These features include flow fields, low shields, shields with steep summits, and fissure eruptions. A few other volcanic features, such as cinder cones, which suggest variable compositions, volatile interactions, and multiple volcanic events can be seen in both areas. The eruptions in both the ESRP and Tempe Terra generally originate from the fissures creating elongate, multi-vent shields as well as isolated or aligned single vent shields. Many of these show evidence of radial flow patterns from summit craters as well as lava tube fed flows. The volcanoes of Tempe Terra display some of the global latitudinal parameter trends of small volcanoes on Mars. Some of these trends may be explained by the variation of volatile content and compositional variation across Mars. However, within Tempe Terra no significant local latitudinal trends can be seen in edifice attributes and not all variations are explained by global trends. This study builds upon previous studies of the Tempe Terra region and the ESRP in order to develop a more detailed representation of features and topographic data. Using these data we attempt to help constrain the composition and eruptive style of the Tempe Terra volcanoes by correlating them with the similar and quantified ESRP variations.

  20. Depositional environments of lacustrine-deltaic sediments, southeast Hungary

    SciTech Connect

    Phillips, R.L.; Berczi, I.; Mattick, R.E.; Rumpler, J.

    1986-05-01

    More than 6000 m of Neogene lacustrine, deltaic, and fluvial sediments fill the Mako-Hodmezoevasahely graben in southeast Hungary. Studies of geophysical profiles, well logs, and cores define the facies and basin-fill processes. Five facies are recognized and include in ascending order (1) basal facies (392 m of interbedded marls and graded beds of sandstone and conglomerate), (2) deep basin facies (1165 m of laminated calcareous to silty marls), (3) prodelta facies (1035 m of parallel beds of marl and graded sandstone changing vertically to inclined and deformed strata), (4) delta-front facies (733 m of inclined strata of marl and sandstone containing abundant soft-sediment deformation features), and (5) delta-plain facies (2500 m of horizontal bedded marl, sandstone, lignite, and red beds). The five facies record the filling of a deep stratified lacustrine basin. Identification of the depositional environments and facies will aid in locating possible depositional petroleum traps, define possible petroleum migration pathways, document the facies where the petroleum has accumulated (delta-front and delta-plain), and record the history of lacustrine basin fill.

  1. Ligand extraction of rare earth elements from aquifer sediments: Implications for rare earth element complexation with organic matter in natural waters

    Microsoft Academic Search

    Jianwu Tang; Karen H. Johannesson

    2010-01-01

    The ability of organic matter as well as carbonate ions to extract rare earth elements (REEs) from sandy sediments of a Coastal Plain aquifer was investigated for unpurified organic matter from different sources (i.e., Mississippi River natural organic matter, Aldrich humic acid, Nordic aquatic fulvic acid, Suwannee River fulvic acid, and Suwannee River natural organic matter) and for extraction solutions

  2. Lacustrin magnetic parameters reveal the last 3,000 years environmental variation of the Ilan Plain, northeastern Taiwan

    NASA Astrophysics Data System (ADS)

    Huang, Yin-Sheng; Lee, Teh-Quei

    2015-04-01

    We discuss the paleo-environmental variation of the Ilan Plain in northeastern Taiwan for the last 3,000 years by using lacustrine magnetic records obtained from Meihua Lake (the MHL-5A core; 24° 38.58' N, 121° 43.96' E) and Longtan Lake (the LTL-9C core; 24° 47.70' N, 121° 44.40' E). The magnetic parameters analyzed in the study include magnetic susceptibility (?), SIRM (saturated isothermal remnant magnetization), ARM (anhysteretic remnant magnetization), ARM/?, and ARM/SIRM. The most notable feature in the magnetic records of both cores is an anomaly appeared at ~1,800 years. In the MHL-5A core, the parameters representing magnetic abundance variation (?, SIRM, and ARM) are relatively higher before ~1,800 years and become lower after the time. On the contrary, the magnetic abundance parameters are lower before ~1,800 years but become higher after the time in the LTL-9C core. Besides, for the last ~700 years, the magnetic parameters in the MHL-5A core show a clear period variation. Also in the LTL-9C core, this period variation could be observed though the period is relatively ambiguous. Moreover, the magnetic grain size parameter ARM/SIRM shows that the grain size of magnetic minerals in both cores became finer gradually for the last ~3,000 years. The reason could be preliminary deduced: The Ilan Plain is a flooding plain and the main river in the plain is a braided river, the Lanyang River. Before ~1,800 years, the channel of the Lanyang River should be in the south of the plain (closer to the Meihua Lake). More sediment was brought into the lake by the flooding of the Lanyang River. After ~1,800 years, the channel of the Lanyang River shifted northward (closer to the Longtan Lake), and therefore the input to the Longtan Lake from the flooding might increase. The period variation after ~700 years could be roughly attributed to the rainfall effect. That is, precipitation variation resulting from the influence of the monsoon system might become significant for the last ~700 years in the Ilan Plain.

  3. Paleoenvironments and sedimentation

    SciTech Connect

    Roehler, H.W.

    1987-01-01

    The Vermillion Creek coal bed and associated rocks in the Niland Tongue of the Wasatch Formation in the Vermillion Creek basin were deposited in mountain front, upland flood-plain, lowland flood-plain, paludal, pond, peat bog, onshore lacustrine, and offshore lacustrine environments. The environments have characteristic lithofacies and biofacies. The origin, composition, stratigraphic location, paleontology, and paleogeographic distribution of the environments are described and illustrated by photographs, diagrams, maps, and sections. The data indicate that the early Eocene climate in the area of the Vermillion Creek basin was warm and temperate. The landscape was forested between areas of grass-like and shrub-like vegetation. Terrestrial and aquatic animal life was abundant and diverse.

  4. Biostratigraphic interpretation for the cyclic sedimentation in northwestern Libya

    SciTech Connect

    Tekbali, A.O.; Cornell, W.C. (Univ. of Texas at El Paso, (United States) Dept. of Geological Sciences)

    1993-02-01

    Mesozoic sediments in western Libya are best exposed along the Jabal Nafusah escarpment. This northeast-southwest trending structure overlooks the Al Jifarah plain and extends more than 300 km westward to connect with a T-shaped anticlinorium in Algeria and Tunisia. The Al Aziziyan fault (normal, north side down) parallels the northern edge of the escarpment and marks its initial position. Alternate deposition of marine and continental sediments began in the Triassic before the formation of a major monocline in the Late Jurassic-Early Cretaceous time. Subsequent epiorogenic movements and isostatic adjustments initiated a westward sloping shelf along the southern edge of the Tethys. As a result, the eastern and central regions of western Libya were subjected to severe erosion and coalescing of unconformities towards the topographic highs, prior to the deposition of the overstepping Kiklah Formation. Geometrical and physical interpretation of the Mesozoic sediments in the region, combined with paleogeographic reconstruction indicate that the post-Hercynian epiorogenic adjustments and fluctuations of the Tethys resulted in local cyclic sedimentation. Accurate age assessment of the boundaries between the Jurassic-Early Cretaceous facies in northwestern Libya can be carried out on the basis of microfloral and faunal distribution and makes possible correlation of aquifers and probable oil-bearing sequences in western Libya.

  5. Fluvial sedimentation following Quaternary eruptions of Mount St. Helens, Washington

    SciTech Connect

    Janda, R.J.; Meyer, D.F

    1985-01-01

    Depositional records of convulsive volcanic events at Mount St. Helens are in many places obscured by rapid fluvial erosion and deposition close to the volcano. Some major eruptions are recorded primarily by lahars and alluvium deposited tens of kilometers away. About 35 percent of the distinctive hummocky topography of the 1980 North Fork Toutle debris avalanche deposit now resembles an alluvial fan or a braided glacial outwash plain covered with 10 m or more of alluvium. Deposits of small (20 x 10/sup 6/m/sup 3/) but damaging lahars, such as those generated in the afternoon of 18 May 1980 and on 19 March 1982, have been largely eroded away. Rivers draining rapidly eroding areas surrounding Mount St. Helens presently have sediment yields that are among the highest in the world for nonglaciated streams of comparable size. These sediment loads are capable of causing aggradation-induced flooding in populated areas along the lower Toutle and Cowlitz Rivers. Sediment retention structures and dredging have prevented such flooding. Immediately following prehistoric eruptions, however, coarse-grained volcanic alluvium was deposited in the Cowlitz River to levels more than 1 m above the 1980 mud flow inundation level. Post-1980 rapid landscape modifications and high sediment yields are noteworthy because the eruption-impact area has not yet had a major regional storm and potentially catastrophic breachings of avalanche-impounded lakes have been prevented through engineering measures.

  6. Guide for selecting Manning's roughness coefficients for natural channels and flood plains

    USGS Publications Warehouse

    Arcement, George J.; Schneider, Verne R.

    1989-01-01

    Although much research has been done on Manning's roughness coefficient, n, for stream channels, very little has been done concerning the roughness values for densely vegetated flood plains. The n value is determined from the values of the factors that affect the roughness of channels and flood plains. In densely vegetated flood plains, the major roughness is caused by trees, vines, and brush. The n value for this type of flood plain can be determined by measuring the vegetation density of the flood plain. Photographs of flood-plain segments where n values have been verified can be used as a comparison standard to aid in assigning n values to similar flood plains.

  7. Assessing morphological, climatic and structural factors controlling water discharge and sediment load of rivers flowing from the Sierra Madre de Chiapas to the Pacific Coast (Southern Mexico)

    NASA Astrophysics Data System (ADS)

    Munoz-Salinas, E.; Castillo, M.

    2014-12-01

    The Sierra Madre de Chiapas (SMC) is a steep mountain range located in the south-western part of Mexico with elevations higher than 2000 m. The SMC is ~30 km off the Pacific Coast and it is oriented parallel to the coast. The annual rainfall exceeds 6 m and most of this takes place during summer season when low-pressure systems and cyclones are frequent. The rivers in SMC incise into the granite and transport large volumes of sediment. Even though rivers can be regarded as bedrock bedrock channels these suddenly change to alluvial-type rivers when these flow in the coastal plain which is ~10 km from the headwater of rivers. There are not data available of the sediment yield of rivers, however, the well-broad coastal plain and the wide continental shelf suggest that the sediment transport from the mountain area to the lowlands is significantly high. Here we assess the main morphological, climatic and structural factors controlling water discharge and sediment load of the rivers flowing from the SMC to the Pacific Coast by means of (1) topographical analysis on a high-resolution DEM, (2) grain-size and OSL analysis on sediment extracted from the riverbed of the main rivers and (3) time-series analysis from the available data of sediment discharge and sediment load. Our results indicate that the river incision and sediment transport is particularly high at the southern sector of the SMC where the topographic and climatic factors promote higher erosion rates.

  8. AMBIENT WATER, POREWATER, AND SEDIMENT

    EPA Science Inventory

    Sediment assessments may be performed for a variety of purposes; these include: dredging and dredged sediment disposal, for evaluations of sediments as a capping material, to determine sediment quality, to assess biological impairment and to assess the status of environment monit...

  9. Distribution and preservation of pteropod tests in sediments of the Sigsbee Plain, Gulf of Mexico

    E-print Network

    Pollard, Richard Mark

    1979-01-01

    subula Clio pyramidata Cavolinia gibbosa Cavolinia inflexa 2. Tropical Province Limacina trochiformis Ryalocylis striata cavolinia uncinata Clio convexa (Indo-Pacific only) Cavolinia globulosa (Indo-pacific only) 3. Harv-Water Cosmopo...

  10. Fe(III)-reducing bacteria in deeply buried sediments of the Atlantic Coastal Plain

    USGS Publications Warehouse

    Lovley, D.R.; Chapelle, F.H.; Phillips, E.J.P.

    1990-01-01

    The enzymatic reduction of Fe(III) by microorganisms reported here is the first mechanism of any kind actually shown to have the potential to couple the oxidation of organic matter to carbon dioxide with the reduction of Fe(III) under the environmental conditions typically found in deep aquifers. -from Authors

  11. Distribution and preservation of pteropod tests in sediments of the Sigsbee Plain, Gulf of Mexico 

    E-print Network

    Pollard, Richard Mark

    1979-01-01

    particles. dos studies indicate, however, that pteropods are important constituents of plankton tous (Be et al. , 1971; murray and Renard, 1891; Berger, 1976); and pteropods have been recorded as being nearly equal in abundance to foraminifera in some... shown when larger-south nets were used, with the low diversity indicated to be due to avoidance of the smallez-mouth net by the highly motile pteropods. The mesh size of the net has also proved to have an influence on the density and species...

  12. Chemical composition of sediments from White Sea, Russian Arctic

    NASA Astrophysics Data System (ADS)

    Gamza, Olga; Shevchenko, Vladimir; Novigatsky, Aleksandr

    2010-05-01

    The White Sea, the only Russian inland sea, is located on the north of outlying districts of the European part of Russia, belongs to Arctic Ocean. Area of water of sea occupies about 90 tousend square kilometers. The sea can be divided into some general parts: neck, funnel, basin and 4 Bays: Dvina Bay, Kandalaksha Bay, Mezen Bay and Onega Bay. The purpose of this work was geochemical mapping of the surface sediments of this area. The main tasks were: compilation data base of element composition of the surface sediments, geochemical mapping of each element, research of the anormal concentration of elements on the surface. To detect the content of chemical elements several methods were used: atomic absorption spectrometry (P.P. Shirshov Institute of Oceanology); neutron activation analysis (Vernadsky Institute of Geochemistry and Analytical Chemistry), total and organic carbon analysis, photometric method to detection Si, Al, P (P.P. Shirshov Institute of Oceanology). Bulk composition is one of the fundamental characteristics of sediments and bottom deposites of modern basins. Coarse-grained sediments with portion of pelitic component <50% is spread on the shallow area (Kandalaksha Bay), in areas with high hydrodynamic activity of near-bottom water. Under the conditions of their low activity, fine-grained facies are common(>80%). Character of elements distribution correlates with facial distribution of sediments from White Sea. According to litologic description, bottom surface of Dvina Bay is practically everywhere covered by layer of fine-grained sand. In the border area between Dvina Bay and White Sea basin on terraced subwater slope aleurite politic silts are abundant. They tend to exhange down the slope to clay silts. In Onega Bay fractions of non-deposition are observed. They are characterized by wide spread of thin blanket poorgraded sediments, which are likely to be relic. Relief of Kandalakscha Bay bottom is presented as alternation of abyssal fosses (near 300 m) with silles and elevations (<20 m), and also numerous islands. Thus variety of sediment composition is observed here - from rules and gravels to fine-grained clay silts [1]. The map of distribution of chemical elements was created by using bulk composition data with the help of program ArcView. Mn distribution in sedimentation mass is largely determed by influence of redox diagenesis. Reactive form of Mn dominates over less moving, litogenic form in sedimation mass of White Sea. Litogenic form remains in sediment, reactive form moves into silt near-bottom water, resulting Mn migration both in sediment and near-bottom layer of marine water. Mn oxidizes on the contact with oxygen of marine water and alters into insoluble form MnO2, causing Mn enrichment of surface layer of sediments. Highly movable silt deposit MnO2 and enriched by Mn suspension are moved by underflow and accumulate in bottom depressions and in central part of the sea, which is quite wide from both places of original sedimentation and run off sources [2]. Thus, the interrelation between granulometric composition of sediment and materials concentration can be shown by the example of Mn. Local conditions, leading to accumulation of clastic components, are: 1. Rise of content in sand owning to separation of heavy minerals 2. Rise of content in surface, mainly sandy clay sediments owning to presence of concretions 3. Rise of content in lower bunches roof owning to diagenetic contraction. Authors thank academic Lisitsyn for encourage, Andrey Apletalin for valuable help, and everybody, who helped in field and laboratory research of the White sea sediments. Work was being done under the auspices of Russian foundation of basic research (grants 09-05-10081, 09-05-00658 and 08-05-00860), RSA presidiums program of 17 fundamental researches (project 17.1). References: 1.Kuzmina T., Lein A., Lutchsheva L., Murdmaa I., Novigatsky A., Shevchenko V. Chemical composition of White Sea's sediments // Litology and mineral deposits . 2009. - ? 2. - P 115-132. 2.Nevessky E., Medvedev V. , Kalin

  13. Natural factors and human modifications contributing to marsh loss in Louisiana's Mississippi River Deltaic Plain

    NASA Astrophysics Data System (ADS)

    Deegan, Linda A.; Kennedy, Helen M.; Neill, Christopher

    1984-11-01

    Natural factors and human modifications contribute to the estimated annual loss of 10,200 ha of coastal land in the Mississippi River Deltaic Plain Region of south Louisiana. This paper combines information on regional geology and human-induced habitat alterations to evaluate the relative importance of human and natural factors to marsh loss. Data on marsh area and habitat type for 139 7.5-min quadrangles were calculated from maps based on aerial photographs from 1955/56 and 1978, and data on regional geology obtained from published maps were used to construct multivariate model relating initial marsh area, change in urban and agricultural area, change in canal and spoil area, canal area in 1978, depth of sediment overlying the Prairie terrace, and subdelta age to marsh loss. The model indicated that between 25.0% and 39.0% of the marsh loss that occurred during the 23-year period was related to canal and spoil construction, and between 9.5% and 12.7% was related to urban and agricultural development. These are minimal estimates of loss because they do not include many secondary effects (for example, canal orientation, saltwater intrusion, and eutrophication) that can also result in indirect loss. Depth of sediment, initial marsh area, delta lobe age by 1978 canal and spoil area interaction, and indirect effects not included in the model accounted for remaining marsh loss.

  14. Ius Chasma Tributary Valleys and Adjacent Plains

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image covers valley tributaries of Ius Chasma, as well as the plains adjacent to the valleys. Ius Chasma is one of several canyons that make up the Valles Marineris canyon system. Valles Marineris likely formed by extension associated with the growth of the large volcanoes and topographic high of Tharsis to the northwest. As the ground was pulled apart, large and deep gaps resulted in the valleys seen in the top and bottom of this HiRISE image. Ice that was once in the ground could have also melted to create additional removal of material in the formation of the valleys. HiRISE is able to see the rocks along the walls of both these valleys and also impact craters in the image. Rock layers that appear lower down in elevation appear rougher and are shedding boulders. Near the top of the walls and also seen in patches along the smooth plains are brighter layers. These brighter layers are not shedding boulders so they must represent a different kind of rock formed in a different kind of environment than those further down the walls. Because they are highest in elevation, the bright layers are youngest in age. HiRISE is able to see dozens of the bright layers, which are perhaps only a meter in thickness. Darker sand dunes and ripples cover most of the plains and fill the floors of impact craters.

    Image PSP_001351_1715 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 9, 2006. The complete image is centered at -8.3 degrees latitude, 275.4 degrees East longitude. The range to the target site was 254.3 km (158.9 miles). At this distance the image scale ranges from 25.4 cm/pixel (with 1 x 1 binning) to 101.8 cm/pixel (with 4 x 4 binning). The image shown here has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 3:32 PM and the scene is illuminated from the west with a solar incidence angle of 59 degrees, thus the sun was about 31 degrees above the horizon. At a solar longitude of 133.0 degrees, the season on Mars is Northern Summer.

    NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo.

  15. San Andreas Fault in the Carrizo Plain

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The 1,200-kilometer (800-mile)San Andreas is the longest fault in California and one of the longest in North America. This perspective view of a portion of the fault was generated using data from the Shuttle Radar Topography Mission (SRTM), which flew on NASA's Space Shuttle last February, and an enhanced, true-color Landsat satellite image. The view shown looks southeast along the San Andreas where it cuts along the base of the mountains in the Temblor Range near Bakersfield. The fault is the distinctively linear feature to the right of the mountains. To the left of the range is a portion of the agriculturally rich San Joaquin Valley. In the background is the snow-capped peak of Mt. Pinos at an elevation of 2,692 meters (8,831 feet). The complex topography in the area is some of the most spectacular along the course of the fault. To the right of the fault is the famous Carrizo Plain. Dry conditions on the plain have helped preserve the surface trace of the fault, which is scrutinized by both amateur and professional geologists. In 1857, one of the largest earthquakes ever recorded in the United States occurred just north of the Carrizo Plain. With an estimated magnitude of 8.0, the quake severely shook buildings in Los Angeles, caused significant surface rupture along a 350-kilometer (220-mile) segment of the fault, and was felt as far away as Las Vegas, Nev. This portion of the San Andreas is an important area of study for seismologists. For visualization purposes, topographic heights displayed in this image are exaggerated two times.

    The elevation data used in this image was acquired by SRTM aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of Earth's land surface. To collect the 3-D SRTM data, engineers added a mast 60 meters (about 200 feet) long, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense, and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif, for NASA's Earth Science Enterprise, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena.

    Distance to Horizon: 73 kilometers (45.3 miles) Location: 35.42 deg. North lat., 119.5 deg. West lon. View: Toward the Southeast Date Acquired: February 16, 2000 SRTM, December 14, 1984 Landsat Image: NASA/JPL/NIMA

  16. Application form (on plain paper) AttachmentA)

    E-print Network

    Abbondandolo, Alberto

    Application form (on plain paper) AttachmentA) President Scuola Normale Superiore Piazza dei/social security number) REQUESTS participation in the public selection based on the curriculum vitae, work to date ............................................... postal code .................. tel. ...................................mobile

  17. Larger Black Flour Beetle in Southern High Plains Homes 

    E-print Network

    Porter, Patrick; McIntyre, Nancy E.

    2007-04-09

    Larger black flour beetles have invaded homes and other buildings in some Southern High Plains counties in Texas. This publication explains how to identify the beetles, find and eliminate the source, and exclude the insects from the house....

  18. Larger Black Flour Beetle in Southern High Plains Homes

    E-print Network

    Porter, Patrick; McIntyre, Nancy E.

    2007-04-09

    Larger black flour beetles have invaded homes and other buildings in some Southern High Plains counties in Texas. This publication explains how to identify the beetles, find and eliminate the source, and exclude the insects from the house....

  19. North-Polar Lunar Light Plains: Ages and Compositional Observations

    NASA Astrophysics Data System (ADS)

    Koehler, U.; Head, J. W., III; Neukum, G.; Wolf, U.

    1999-01-01

    Varying surface ages of lunar light plains in northern-nearside latitudes indicate an origin of these smooth terrae units not exclusively related to Imbrium and/or Orientale impact ejecta. and subsequent processes. Multispectral data seem to support a more diversified history for many of these plains. The nature, ages, stratigraphic position, composition, and mode of emplacement of lunar light plains have been discussed with controversy for more than three decades. Covering about 5% of the lunar terra surface, the relatively low albedo plains are the most distinctive terra landforms after the more crater-like ejecta of the fresh basins. Morphological properties, like their smoothness, lower crater densities, their superposition on the "Imbrian Sculpture," and frequent occurence as crater fill, are mare-like. Other features, such as relative (compared to mare basalts) high-albedo and geological/stratigraphical setting, are more highland-like. Not surprisingly, light plains were seen as both volcanic and impact related deposits. The Cayley Plains, a type locality in the central-nearside highlands, has been chosen as the landing site of the Apollo XVI mission partly to help resolve these interpretations. The astronauts collected samples - highly brecciated rocks - and concluded that the Cayley was indeed of impact origin. These findings have been extrapolated to stratigraphically similar plains units on the nearside, focusing on the Imbrium and Orientale impacts as responsible events for resurfacing terrae environment to form light plains. In addition, theoretical modeling mechanisms have been provided that could explain how basin and crater ejecta were able to make up for the smoothness of light plains by stirring up local material through secondary-impact related processes, or mega impact induced seismic shaking. However, subsequent age determinations showed that some light plains cannot be correlated to the Imbrium or Orientale event, the last two basin-forming impacts to occur on the Moon that had the ability to resurface areas thousands of kilometers away from their target site. An unknown form of highland volcanism was proposed as a contributing process in light-plains formation. The question remained unanswered whether processes other than impact-related processes were responsible for the formation of these enigmatic geological units, and how these processes might have worked. Focusing on light plains in the northern-nearside highlands, a chronological approach has been chosen to address these questions, and compositional information from multispectral data has been included to support our investigations. Mapping the northern-nearside light plains, earlier workers have recognized the stratigraphically and morphologically obvious bimodal distribution of smooth terrae units north and northeast of Mare Frigoris. The older of these plains (IP-1; based on stratigraphic relations and surface-crater densities) show gradual transition into (Imbrium-impact) Fra Mauro Formation units, whereas the younger unit (IP-2) cannot be related to this relatively nearby impact event. Instead, it was proposed that the impact of Orientale, despite the fact it is several thousand kilometers away, could have smoothed these terrae units with its ejecta stirring up local highland material, an interpretation that seems to be not very compelling, as these younger plains show quite homogeneous surfaces over extended areas. Determining precise surface ages of smooth surface units should help with getting a chronology of plains emplacement in these latitudes. Based on the principle of crater-frequency distribution measurements and adjusting the cumulative crater-frequency distributions to a lunar standard distribution, and "fixing" the Orientale and Imbrium event with the absolute ages obtained by radiometric measurements of Apollo samples to this distribution, one is able to determine reliable absolute-age data for surfaces after measuring the crater-frequency distribution on it. As the decline in impact frequency is rather ste

  20. SECOND FLOOR, VIEW OF THE NORTH PLAIN OF THE 1772 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    SECOND FLOOR, VIEW OF THE NORTH PLAIN OF THE 1772 ROOF TO SHOW ROUND-BUTT WOOD SHINGLES; THIS ROOF IS PROTECTED BY THE 1784 SHED ADDITION - Murray-Dick-Fawcett House, 517 Prince Street, Alexandria, Independent City, VA

  1. 18. PLAIN OFFICE; SHOWS WOODWORK AND WALL TREATMENT. ROOM 2662, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. PLAIN OFFICE; SHOWS WOODWORK AND WALL TREATMENT. ROOM 2662, SECOND FLOOR, SOUTH SIDE. - Hughes Aircraft Company, Processing & Electronics Building, 6775 Centinela Avenue, Los Angeles, Los Angeles County, CA

  2. From technical jargon to plain English for application.

    PubMed Central

    Lindsley, O R

    1991-01-01

    These examples of translating technical jargon into plain English application words, acronyms, letter codes, and simple tests were necessary as we developed Precision Teaching. I hope our experience is useful to others facing the problems of applying technology in practical settings. At the least, our experience should give you an idea of the work and time involved in making your own translations. Above all, be patient. Accurate plain English translations do not come easily. They cannot be made at your desk. A search often takes years to produce one new accurate plain English translation. Rapid publication pressures, journal editorial policies, and investments in materials, books, and computer programs all combine to hamper these translations. It's possible that you will find some of our plain English equivalents useful in your own applied behavior analysis applications. PMID:1752836

  3. INTRODUCTION Mesopotamia is the broad, flat alluvial plain

    E-print Network

    deMenocal, Peter B.

    INTRODUCTION Mesopotamia is the broad, flat alluvial plain between the Tigris and Euphrates Rivers to the headwaters of the Tigris and Euphrates Rivers from ca. 4300 to 4200 B.P. Particularly important

  4. 27 CFR 9.144 - Texas High Plains.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...Big Spring, Texas” 1954, revised 1975. (c) Boundary. The Texas High Plains viticultural area is located in Armstrong, Bailey, Borden, Briscoe, Castro, Cochran, Crosby, Dawson, Deaf Smith, Dickens, Floyd, Gaines, Garza,...

  5. Plain Packaging Laws Might Spur Smokers to Quit

    MedlinePLUS

    ... gov/medlineplus/news/fullstory_151566.html Plain Packaging Laws Might Spur Smokers to Quit Legislation would also ... 2012 and 2013. During that time, an Australian law was implemented requiring that all tobacco packaging be ...

  6. Effects of Great Plains Irrigation on Regional Climate

    E-print Network

    Huber, David B.

    2011-08-31

    Irrigation provides a much needed source of water in regions of low precipitation such as the western Great Plains. However, adding water to a region that would otherwise see little natural precipitation has ramifications for the partitioning...

  7. Tribal Training -- Sediment Devices

    USGS Multimedia Gallery

    USGS Research Hydrologist Art Horowitz and USGS Oklahoma Water Science Center Hydrologic Technician Ernie Smith describe streambed sediment collection devices for a Tribal training class at the Canadian River, Norman, Oklahoma....

  8. Great Plains Wind Energy Transmission Development Project

    SciTech Connect

    Brad G. Stevens, P.E.; Troy K. Simonsen; Kerryanne M. Leroux

    2012-06-09

    In fiscal year 2005, the Energy & Environmental Research Center (EERC) received funding from the U.S. Department of Energy (DOE) to undertake a broad array of tasks to either directly or indirectly address the barriers that faced much of the Great Plains states and their efforts to produce and transmit wind energy at the time. This program, entitled Great Plains Wind Energy Transmission Development Project, was focused on the central goal of stimulating wind energy development through expansion of new transmission capacity or development of new wind energy capacity through alternative market development. The original task structure was as follows: Task 1 - Regional Renewable Credit Tracking System (later rescoped to Small Wind Turbine Training Center); Task 2 - Multistate Transmission Collaborative; Task 3 - Wind Energy Forecasting System; and Task 4 - Analysis of the Long-Term Role of Hydrogen in the Region. As carried out, Task 1 involved the creation of the Small Wind Turbine Training Center (SWTTC). The SWTTC, located Grand Forks, North Dakota, consists of a single wind turbine, the Endurance S-250, on a 105-foot tilt-up guyed tower. The S-250 is connected to the electrical grid on the 'load side' of the electric meter, and the power produced by the wind turbine is consumed locally on the property. Establishment of the SWTTC will allow EERC personnel to provide educational opportunities to a wide range of participants, including grade school through college-level students and the general public. In addition, the facility will allow the EERC to provide technical training workshops related to the installation, operation, and maintenance of small wind turbines. In addition, under Task 1, the EERC hosted two small wind turbine workshops on May 18, 2010, and March 8, 2011, at the EERC in Grand Forks, North Dakota. Task 2 involved the EERC cosponsoring and aiding in the planning of three transmission workshops in the midwest and western regions. Under Task 3, the EERC, in collaboration with Meridian Environmental Services, developed and demonstrated the efficacy of a wind energy forecasting system for use in scheduling energy output from wind farms for a regional electrical generation and transmission utility. With the increased interest at the time of project award in the production of hydrogen as a critical future energy source, many viewed hydrogen produced from wind-generated electricity as an attractive option. In addition, many of the hydrogen production-related concepts involve utilization of energy resources without the need for additional electrical transmission. For this reason, under Task 4, the EERC provided a summary of end uses for hydrogen in the region and focused on one end product in particular (fertilizer), including several process options and related economic analyses.

  9. Notes 04. Static load performance of plain journal bearings 

    E-print Network

    San Andres, Luis

    2010-01-01

    X Y W e ? Simple lumped parameter thermal analysis for predicting the exit temperature and effective viscosity in a short length journal bearing Appendix to Notes 4 : Static load performance of journal bearing Luis San Andres ? Fall2009 (NUS) All...NOTES 4. STATIC LOAD PERFORMANCE OF PLAIN JOURNAL BEARINGS. Dr. Luis San Andr?s ? 2010 1 NOTES 4 STATIC LOAD PERFORMANCE OF PLAIN JOURNAL BEARINGS Lecture 4 introduces the fundaments of journal bearing analysis. The long and short length...

  10. Water Conservation in Southern Great Plains Wheat Production.

    E-print Network

    Finnell, H. H. (Henry Howard)

    1944-01-01

    A. B. CONNER, DIRECTOR, College Station, Texas BULLETIN NO. 655 WATER CONSERVATION IN GREAT PLAINS WHEAT PRODUCTION H. H. FINNELL Division of Agronomy in coope;ation with Soil Conservation Service U. S. Department of Agriculture AGRICULTURAL... and wind erosion damage was reduced. Zievc use 01 areas -.!-P-l ticabili rnethw ertheless, water conservation alone is not enough to make the best F current soil and water resources available in the winter wheat of the Texas high plains. The amount...

  11. Great Plains ASPEN model development: Phosam section. Final topical report

    Microsoft Academic Search

    S. S. Stern; J. J. Kirman

    1985-01-01

    An ASPEN model has been developed of the PHOSAM Section, Section 4600, of the Great Plains Gasification Plant. The bases for this model are the process description given in Section 6.18 of the Great Plains Project Management Plan and the Lummus Phosam Schematic Process Flow Diagram, Dwg. No. SKD-7102-IM-O. The ASPEN model that has been developed contains the complete set

  12. Critical Mach Numbers of Thin Airfoil Sections with Plain Flaps

    NASA Technical Reports Server (NTRS)

    Pardee, Otway O'm.; Heaslet, Max A.

    1946-01-01

    Critical Mach number as function of lift coefficient is determined for certain moderately thick NACA low-drag airfoils. Results, given graphically, included calculations on same airfoil sections with plain flaps for small flap deflections. Curves indicate optimum critical conditions for airfoils with flaps in such form that they can be compared with corresponding results for zero flap deflections. Plain flaps increase life-coefficient range for which critical Mach number is in region of high values characteristic of low-drag airfoils.

  13. Multiple distal basin plains reveal a common distribution for large volume turbidity current recurrence intervals

    NASA Astrophysics Data System (ADS)

    Clare, M. A.; Talling, P. J.; Hunt, J.; Challenor, P. G.

    2013-12-01

    Remarkably large volume (>>1 km3) deposits emplaced by turbidity currents in distal basin plains result from large submarine landslides. Such landslides may generate tsunamis, and the turbidity currents pose threats to seafloor structures as well as being one of the most important processes for sediment transport across our planet. It is therefore important to understand the recurrence intervals and timing of landslides and the turbidity currents they generate. An understanding of their frequency provides information to assist in forward-looking geohazard analyses, including probabilistic modelling of potential damage. Analysis of their frequency distribution may also help to unravel links to triggering and conditioning mechanisms. We present long term records (up to 17 Ma) of landslide-triggered turbidity current recurrence intervals. We document the distribution of recurrence intervals for large volume turbidites in four basin-plains in disparate locations worldwide, including two recent systems and two outcrop studies. The recurrence times of turbidity currents is inferred from intervals of hemipelagic mud that form by fallout of background sediment between turbidity currents, and the average accumulation rate of hemipelagic mud between dated horizons. There is very little erosion below turbidite beds in the study locations; hence they represent an almost continuous sedimentary record. This method has the advantage of providing information on the timing of many different events from a small number of cores, with such large numbers (N> 100) of beds needed for robust statistical analysis. A common frequency distribution of turbidite recurrence intervals is observed, despite their variable ages and disparate locations, suggesting similar underlying controls on triggering mechanism and frequency. This common distribution closely approximates a temporally-random Poisson distribution, such that the probability of an event occurring along the basin margin is independent of the time since the last. Surprisingly, this frequency distribution suggests that non-random processes such as sea level change are not a dominant control on slide frequency. This conclusion is validated by the results of a suite of various statistical analyses including: regression analysis, Generalised Linear Model, rescaled range analysis and Cox proportional hazards model. Finally, we show that the same statistical analyses indicate that there does appear to be a strong relationship between sea level and event magnitude (and hence deposit volume). This is the first study to show that turbidity currents triggered by large submarine landslides may have a common frequency distribution on a basin scale, and that this distribution is temporally random; however, sea level may exert a control on the magnitude of events that travel to distal basinal settings. These findings have important implications for understanding global sediment flux, sequence stratigraphic modelling, and assessment of geohazards posed by submarine landslides and turbidity currents.

  14. Factors Shaping Macrofaunal Polychaete Communities in the Gulf of Mexico

    E-print Network

    Carvalho, Russell G

    2013-04-23

    proboscides and S; eversible pharynges which are sac- like feeding structures. 2.3.3 Data analysis Polychaete samples were sorted and separated to their lowest taxonomic unit. Volumetric dimensions of specimens were measured from selected stations (MT1...M but was exclusively comprised of the lower-slope and deep Mississippi Sediment Fan (~2000 to 3300 m) sites in the Northeast GoM. Group 3 consisted of a majority of sites from the abyssal plain region (p structure...

  15. La sedimentazione nell’ambiente anossico del Bacino Bannock (Mediterraneo orientale): Caratterizzazione chimica, fisica e biologica dei sedimenti

    Microsoft Academic Search

    Silvia di Montagnana; Maria Carla Sala

    1993-01-01

    \\u000a Abstract  Seven cores containing anoxic sediments recovered in the Bannock Basin were analysed in their chemical, physical and biological\\u000a characters. Bannock Basin is a large deep subcircular depression near the deformation front of the Mediterranean Ridge facing\\u000a the Sirte Abyssal Plain. The basin is divided into several sub-basins aligned along a rim-syncline surrounding a central domelike\\u000a area. High-density brines, deriving from

  16. Hurricane Katrina sediment slowed elevation loss in subsiding brackish marshes of the Mississippi River delta

    USGS Publications Warehouse

    McKee, K.L.; Cherry, J.A.

    2009-01-01

    Although hurricanes can damage or destroy coastal wetlands, they may play a beneficial role in reinvigorating marshes by delivering sediments that raise soil elevations and stimulate organic matter production. Hurricane Katrina altered elevation dynamics of two subsiding brackish marshes in the Mississippi River deltaic plain by adding 3 to 8 cm of sediment to the soil surface in August 2005. Soil elevations at both sites subsequently declined due to continued subsidence, but net elevation gain was still positive at both Pearl River (+1.7 cm) and Big Branch (+0.7 cm) marshes two years after the hurricane. At Big Branch where storm sediments had higher organic matter and water contents, post-storm elevation loss was more rapid due to initial compaction of the storm layer in combination with root-zone collapse. In contrast, elevation loss was slower at Pearl River where the storm deposit (high sand content) did not compact and the root zone did not collapse. Vegetation at both sites fully recovered within one year, and accumulation of root matter at Big Branch increased 10-fold from 2005 to 2006, suggesting that the hurricane stimulated belowground productivity. Results of this study imply that hurricane sediment may benefit subsiding marshes by slowing elevation loss. However, long-term effects of hurricane sediment on elevation dynamics will depend not only on the amount of sediment deposited, but on sediment texture and resistance to compaction as well as on changes in organic matter accumulation in the years following the hurricane.

  17. Tracking sedimentation from the historic A.D. 2011 Mississippi River flood in the deltaic wetlands of Louisiana, USA

    USGS Publications Warehouse

    Khan, Nicole S.; Horton, Benjamin P.; McKee, Karen L.; Jerolmack, Douglas; Falcini, Federico; Enache, Mihaela D.; Vane, Christopher H.

    2013-01-01

    Management and restoration of the Mississippi River deltaic plain (southern United States) and associated wetlands require a quantitative understanding of sediment delivery during large flood events, past and present. Here, we investigate the sedimentary fingerprint of the 2011 Mississippi River flood across the Louisiana coast (Atchafalaya Delta, Terrebonne, Barataria, and Mississippi River Delta basins) to assess spatial patterns of sedimentation and to identify key indicators of sediment provenance. The sediment deposited in wetlands during the 2011 flood was distinguished from earlier deposits based on biological characteristics, primarily absence of plant roots and increased presence of centric (planktonic) diatoms indicative of riverine origin. By comparison, the lithological (bulk density, organic matter content, and grain size) and chemical (stable carbon isotopes of bulk organic matter) properties of flood sediments were nearly identical to the underlying deposit. Flood sediment deposition was greatest in wetlands near the Atchafalaya and Mississippi Rivers and accounted for a substantial portion (37% to 85%) of the annual accretion measured at nearby monitoring stations. The amount of sediment delivered to those basins (1.1–1.6 g cm?2) was comparable to that reported previously for hurricane sedimentation along the Louisiana coast (0.8–2.1 g cm?2). Our findings not only provide insight into how large-scale river floods influence wetland sedimentation, they lay the groundwork for identifying previous flood events in the stratigraphic record.

  18. Preliminary report on mercury geochemistry of placer gold dredge tailings, sediments, bedrock, and waters in the Clear Creek restoration area, Shasta County, California

    USGS Publications Warehouse

    Ashley, Roger P.; Rytuba, James J.; Rogers, Ronald; Kotlyar, Boris B.; Lawler, David

    2002-01-01

    Clear Creek, one of the major tributaries of the upper Sacramento River, drains the eastern Trinity Mountains. Alluvial plain and terrace gravels of lower Clear Creek, at the northwest edge of the Sacramento Valley, contain placer gold that has been mined since the Gold Rush by various methods including dredging. In addition, from the 1950s to the 1980s aggregate-mining operations removed gravel from the lower Clear Creek flood plain. Since Clear Creek is an important stream for salmon production, a habitat restoration program is underway to repair damage from mining and improve conditions for spawning. This program includes using dredge tailings to fill in gravel pits in the flood plain, raising the concern that mercury lost to these tailings in the gold recovery process may be released and become available to biota. The purposes of our study are to determine concentrations and speciation of mercury in sediments, tailings, and water in the lower Clear Creek area, and to determine its mobility. Mercury concentrations in bedrock and unmined gravels both within and above the mined area are low, and are taken to represent background concentrations. Bulk mercury values in flood-plain sediments and dry tailings are elevated to several times these background concentrations. Mercury in sediments and tailings is associated with fine size fractions. Although methylmercury levels are generally low in sediments, shallow ponds in the flood plain may have above-normal methylation potential. Stream waters in the area show low mercury and methylmercury levels. Ponds with elevated methylmercury in sediments have more methylmercury in their waters as well. One seep in the area is highly saline, and enriched in mercury, lithium, and boron, similar to connate waters that are expelled along thrust faults to the south on the west side of the Sacramento Valley. This occurrence suggests that mercury in waters may at least in part be from sources other than placer mining.

  19. Microbial activities of methanogenesis and methane oxidation in terrestrial subsurface environment of the Kanto Plain in Japan

    NASA Astrophysics Data System (ADS)

    Yoshioka, H.; Takeuchi, M.; Tanabe, S.; Takahashi, H. A.; Tamaki, H.; Sakata, S.

    2012-12-01

    Methane is a relatively potent greenhouse gas compared with carbon dioxide. Although the concentration is low in the atmosphere, recent rise in concentration makes it an important issue to understand methane flux in the surface environments and restriction of methane emission to the atmosphere. Methane is mainly produced by thermal degradation of organic matter in deep region or by methanogens in anaerobic condition of subsurface area. In marine environments, methane is mostly consumed by anaerobic methanotrophic archaea (ANME) and/or aerobic methane-oxidizing bacteria before it diffuses to the atmosphere. On the other hand, there were only a few reports of anaerobic methane-oxidizing activities in terrestrial region. In previous study, we found biogenic methane was accumulated in terrestrial sediments in the Kanto Plain in Japan and freshwater-adapted anaerobic methane-oxidizing archaea subgroup (ANME-1) dominates in the sediments (Takeuchi et al. 2011). To make it clear whether the biogenic methane is produced or consumed, we analyzed stable carbon isotopic compositions of methane and dissolved inorganic carbon (DIC) in the sediments and measured microbial activities of methane production by radiotracer experiments and methane oxidation by tracer experiment using 13C-labeled methane. Methane was mainly detected in the Holocene mud layer and the stable carbon isotopic compositions increased from -84 ‰ at the top (depth of 4 m) of the mud layer to -75 ‰ at depth of 10 m and showed almost constant value in the lower part. Carbon isotopic compositions of DIC showed a similar trend: increasing from -13‰ at the top of the mud layer to -5 ‰ at depth of 10 m and showing almost constant value in the lower part. The constant value of difference between the two isotopic compositions indicated that the biogenic methane was produced by microbial methanogenesis through carbonate reduction pathway and there was no obvious evidence of methane oxidation. Results of activity experiments showed both methane oxidation and production activities occurred in the sediments. The apparent contradiction between results of geochemical study and microbial study may imply that the methane accumulated in the present sediments has been produced through geological time or during sedimentation period, and ANME present in the sediments has grown after interstitial water in the sediments has exchanged with fresh water relatively recently. Sulfate concentration in the interstitial water was mostly lower than 10 micromole per liter. Therefore, methane oxidation in the sediments might have been controlled by amount of sulfate in the interstitial water.

  20. Reproduction of radiologic images on plain paper.

    PubMed

    Ibbott, G S; Zhang, Y; Mohiuddin, M; Adams, E

    1998-01-01

    Skyrocketing health care costs and pressures from managed care have combined to promote cost-cutting strategies in radiology and radiation oncology departments. A study was conducted to evaluate the use of a high-resolution laser printer for printing plain-paper images as substitutes for both original and duplicate radiologic film images. A variety of radiologic images were used to evaluate the image reproduction capabilities of the printer in terms of linearity, detail, and contrast. In many cases, printed images had a quality comparable to that of the original images. Six computed tomographic (CT) scans and six radiation therapy simulator radiographs were compared with printed reproductions by each of seven board-certified radiation oncologists, who rated the reproductions as acceptable for documentation, acceptable for diagnostic purposes (CT scans only), or unacceptable. Ninety-five percent of printed CT images and 90% of printed simulation images were rated acceptable for documentation. The quality of printed images of radiation therapy port films was not quantitatively measured but was improved by adjusting image contrast and brightness and using various image enhancement techniques. The use of printed images is less expensive than that of processed film and eliminates the environmental, time, storage, and delivery problems associated with film. Technologic advances in imaging, networking, and printing have made possible the inexpensive duplication of medical images. PMID:9599396

  1. DNAPL migration in a coastal plain aquifer

    SciTech Connect

    DiGuiseppi, W.H.; Jung, A.D. [Consoer Townsend Envirodyne Engineers, Inc., Fairfax, VA (United States)

    1995-12-31

    Soil and ground water at the Dover Gas Light Superfund Site, a former manufactured gas plant (1859 to 1948), are contaminated with polynuclear aromatic hydrocarbons and volatile organic compounds. Contaminants of concern include light aromatics, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), and heavy aromatics, including naphthalene, acenaphthylene, phenanthrene, and benzo(a)pyrene. Although ground-water contaminant levels are elevated near the site, only naphthalene and acenaphthylene are present within an order of magnitude of their solubility limits, indicating the possibility of dense non-aqueous phase liquids (DNAPL) in the subsurface. The unconfined Columbia Aquifer, which is characterized by interfingering and discontinuous sand, silt, and clay Coastal Plain deposits, overlies a clay aquitard at a depth of 60 feet. The ground water beneath the intermediate clay horizon exhibited little or no contamination, even immediately downgradient from the site. The relationship between the more permeable granular sand horizons and the less permeable interfingering clay zones controls the migration of both the aqueous-phase contamination and the DNAPL. A detailed horizontal and vertical characterization of the subsurface stratigraphy was critical to the accurate interpretation of the extent and magnitude of contamination and the identification and delineation of DNAPL zones.

  2. The Yellowstone-Snake River Plain seismic profilling experiment: Crustal structure of the eastern Snake River Plain

    Microsoft Academic Search

    L. W. Braile; R. B. Smith; J. Ansorge; M. R. Baker; M. A. Sparlin; C. Prodehl; M. M. Schilly; J. H. Healy; St. Mueller; K. H. Olsen

    1982-01-01

    Seismic refraction profiles recorded along the eastern Snake River Plain (ESRP) in southeastern Idaho during the 1978 Yellowstone-Snake River Plain cooperative seismic profiling experiment are interpreted to infer the crustal velocity and attenuation (Q-1) structure of the ESRP. Travel-time and synthetic seismogram modeling of a 250 km reversed refraction profile as well as a 100 km detailed profile indicate that

  3. Field and laboratory data describing physical and chemical characteristics of metal-contaminated flood-plain deposits downstream from Lead, west-central South Dakota

    USGS Publications Warehouse

    Marron, D.C.

    1988-01-01

    Samples from metal-contaminated flood-plain sediments at 9 sites downstream from Lead, in west-central South Dakota, were collected during the summers of 1985-87 to characterize aspects of the sedimentology, chemistry, and geometry of a deposit that resulted from the discharge of a large volume of mining wastes into a river system. Field and laboratory data include stratigraphic descriptions, chemical contents and grain-size distributions of samples, and surveyed flood-plain positions of samples. This report describes sampling-site locations, and methods of sample collection and preservation, and subsequent laboratory analysis. Field and laboratory data are presented in 4 figures and 11 tables in the ' Supplemental Data ' section at the back of the report. (USGS)

  4. Anticipated sediment delivery to the lower Elwha River during and following dam removal: Chapter 2 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

    USGS Publications Warehouse

    Czuba, Christiana R.; Randle, Timothy J.; Bountry, Jennifer A.; Magirl, Christopher S.; Czuba, Jonathan A.; Curran, Christopher A.; Konrad, Christopher P.

    2011-01-01

    During and after the planned incremental removal of two large, century-old concrete dams between 2011 and 2014, the sediment-transport regime in the lower Elwha River of western Washington will initially spike above background levels and then return to pre-dam conditions some years after complete dam removal. Measurements indicate the upper reaches of the steep-gradient Elwha River, draining the northeast section of the Olympic Mountains, carries between an estimated 120,000 and 290,000 cubic meters of sediment annually. This large load has deposited an estimated 19 million cubic meters of sediment within the two reservoirs formed by the Elwha and Glines Canyon Dams. It is anticipated that from 7 to 8 million cubic meters of this trapped sediment will mobilize and transport downstream during and after dam decommissioning, restoring the downstream sections of the sediment-starved river and nearshore marine environments. Downstream transport of sediment from the dam sites will have significant effects on channel morphology, water quality, and aquatic habitat during and after dam removal. Sediment concentrations are expected to be between 200 and 1,000 milligrams per liter during and just after dam removal and could rise to as much as 50,000 milligrams per liter during high flows. Downstream sedimentation in the river channel and flood plain will be potentially large, particularly in the lower Elwha River, an alluvial reach with a wide flood plain. Overall aggradation could be as much as one to several meters. Not all reservoir sediment, however, will be released to the river. Some material will remain on hill slopes and flood plains within the drained reservoirs in quantities that will depend on the hydrology, precipitation, and mechanics of the incising channel. Eventually, vegetation will stabilize this remaining reservoir sediment, and the overall sediment load in the restored river will return to pre-dam levels.

  5. Influenza-Sediment Interactions

    NASA Astrophysics Data System (ADS)

    Trusiak, A.; Block, K. A.; Katz, A.; Gottlieb, P.; Alimova, A.; Galarza, J.; Wei, H.; Steiner, J. C.

    2013-12-01

    A typical water fowl can secrete 1012 influenza virions per day. Therefore it is not unexpected that influenza virions interact with sediments in the water column. The influence of sediments on avian influenza virions is not known. With the threat of avian influenza emerging into the human population, it is crucial to understand virus survivability and residence time in a body of water. Influenza and clay sediments are colloidal particles and thus aggregate as explained by DLVO (Derjaguin & Landau, Verwey & Overbeek) theory. Of great importance is an understanding of the types of particulate or macromolecular components that bind the virus particles, and whether the virus remains biologically active. We present results of hetero-aggregation and transmission electron microscopy experiments performed with influenza A/PR8/38. Influenza particles are suspended with sediment and minimal nutrients for several days, after which the components are evaluated to determine influenza concentration and survivability. Transmission electron microscopy results are reported on the influenza-sediment aggregates to elucidate structure and morphology of the components.

  6. Metal concentrations and trace metal Al and Fe ratios in soil of the Chenier Plain, southwest Louisiana coastal zone.

    PubMed

    DeLaune, R D; Jugsujinda, A; Gambrell, R P; Miao, S

    2008-02-15

    Soil baseline metal concentrations were determined in 220 surface soil samples collected from the Chenier Plain area of southwest coastal Louisiana. Regression relationships between Al, Fe, and various metals were calculated from the data set. The use of these relationships to identify enhanced metal contents in the Chenier Plain soils is presented. Statistical analyses showed an average Al concentration of 1.6% with a maximum concentration of 4.8% and a minimum concentration of 1.3 mg kg(-1). Al concentration in the sediments was positively correlated at the 1% significance level to Cu (r = 0.577**), Pb (r = 0.936**), Cr (r = 0.969**), Ni (r = 0.830**), Cd (r = 0.617**), and Zn (r = 0.506**), but only a 5% significance correlation was found with Mn (r = 0.148*). Average Fe concentration was 1.2% with a maximum value of 3.4% and a minimum concentration of 9.3 mg kg(-1). Fe concentration in the sediments was positively correlated at the 1% significance level to Cu (r = 0.586**), Pb (r = 0.847**), Cr (r = 0.875**), Ni (r = 0.932**), Cd (r = 0.803**), Zn (r = 0.551**), and Mn (r = 0.479**). These relationships were used to evaluate sites for metal contamination. Data from two known contaminated sites, Capitol Lake (Baton Rouge, LA) and Bayou Trepagnier (LA), fell well outside the prediction limits developed with the Chenier Plain Al and Fe metal regression lines for Cr and Zn. Pb and Cd at Capitol Lake were also elevated beyond the metal/Al prediction developed for the Chenier Plain, but the prediction was not out of range when using the metal/Fe regression. Samples from additional sites with no known metal contamination fell within the predictive limits of the regression equations except for Cd and Pb at some sites. Data presented showed that metal/Al and metal/Fe regression relationships can be used as a tool for identifying areas of potential metal contamination in the coastal zone, but must be regionally correlated. PMID:18205062

  7. Strontium Distribution Coefficients of Basalt and Sediment Infill Samples from the Idaho National Engineering and Environmental Laboratory, Idaho

    SciTech Connect

    M. N. Pace; R. C. Bartholomay (USGS); J. J. Rosentreter (ISU)

    1999-07-01

    The U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy, are conducting a study to determine and evaluate strontium distribution coefficients (Kds) of subsurface materials at the Idaho National Engineering and Environmental Laboratory (INEEL). The purpose of this study is to aid in assessing the variability of strontium Kds at the INEEL as part of an ongoing investigation of chemical transport of strontium-90 in the Snake River Plain aquifer. Batch experimental techniques were used to determine Kds of six basalt core samples, five samples of sediment infill of vesicles and fractures, and six standard material samples. Analyses of data from these experiments indicate that the Kds of the sediment infill samples are significantly larger than those of the basalt samples. Quantification of such information is essential of furthering the understanding of transport processes of strontium-90 in the Snake River Plain aquifer and in similar environments.

  8. Tectonic and sediment supply control of deep rift lake turbidite systems: Lake Baikal, Russia

    USGS Publications Warehouse

    Nelson, C.H.; Karabanov, E.B.; Colman, Steven M.; Escutia, C.

    1999-01-01

    Tectonically influenced half-graben morphology controls the amount and type of sediment supply and consequent type of late Quaternary turbidite systems developed in the active rift basins of Lake Baikal, Russia. Steep border fault slopes (footwall) on the northwest sides of half-graben basins provide a limited supply of coarser grained clastic material to multiple small fan deltas. These multiple sediment sources in turn laterally feed small (65 km) axially fed elongate mud-rich fans sourced by regional exterior drainage of the Selenga River that supplies large quantities of silt. Basin plain turbidites in the center of the linear basins and axial channels that are controlled by rift-parallel faults are fed from, and interfinger with, aprons and fans. The predictability of the turbidite systems in Lake Baikal provides the best example yet studied of how tectonics and sediment supply interact to control the development of a wide variety of coeval turbidite systems on a single basin floor.

  9. PLAINS CO2 REDUCTION (PCOR) PARTNERSHIP

    SciTech Connect

    Edward N. Steadman; Daniel J. Daly; Lynette L. de Silva; John A. Harju; Melanie D. Jensen; Erin M. O'Leary; Wesley D. Peck; Steven A. Smith; James A. Sorensen

    2006-01-01

    During the period of October 1, 2003, through September 30, 2005, the Plains CO2 Reduction (PCOR) Partnership, identified geologic and terrestrial candidates for near-term practical and environmentally sound carbon dioxide (CO2) sequestration demonstrations in the heartland of North America. The PCOR Partnership region covered nine states and three Canadian provinces. The validation test candidates were further vetted to ensure that they represented projects with (1) commercial potential and (2) a mix that would support future projects both dependent and independent of CO2 monetization. This report uses the findings contained in the PCOR Partnership's two dozen topical reports and half-dozen fact sheets as well as the capabilities of its geographic information system-based Decision Support System to provide a concise picture of the sequestration potential for both terrestrial and geologic sequestration in the PCOR Partnership region based on assessments of sources, sinks, regulations, deployment issues, transportation, and capture and separation. The report also includes concise action plans for deployment and public education and outreach as well as a brief overview of the structure, development, and capabilities of the PCOR Partnership. The PCOR Partnership is one of seven regional partnerships under Phase I of the U.S. Department of Energy National Energy Technology Laboratory's Regional Carbon Sequestration Partnership program. The PCOR Partnership, comprising 49 public and private sector members, is led by the Energy & Environmental Research Center at the University of North Dakota. The international PCOR Partnership region includes the Canadian provinces of Alberta, Saskatchewan, and Manitoba and the states of Montana (part), Wyoming (part), North Dakota, South Dakota, Nebraska, Missouri, Iowa, Minnesota, and Wisconsin.

  10. Chinese Tallow: Invading the Southeastern Coastal Plain

    USGS Publications Warehouse

    U.S. Geological Survey

    2000-01-01

    Chinese tallow is an ornamental tree with colorful autumn foliage that can survive full sunlight and shade, flooding, drought, and in some cases fire. To horticulturists this kind of tree sounds like a dream, but to ecologists, land managers, and land owners this kind of tree can be a nightmare, especially when it invades an area and takes over native vegetation. Chinese tallow (Triadica sebifera), a nonnative tree from China, is currently transforming the southeastern Coastal Plain. Over the last 30 years, Chinese tallow has become a common tree in old fields and bottomland swamps of coastal Louisiana. Several studies at the U.S. Geological Survey's National Wetlands Research Center (NWRC), Lafayette, Louisiana, are aimed at understanding the factors that contribute to Chinese tallow growth, spread, and management. When tallow invades, it eventually monopolizes an area, creating a forest without native animal or plant species. This tree exhibits classic traits of most nonnative invaders: it is attractive so people want to distribute it, it has incredible resiliency, it grows quickly and in a variety of soils, and it is resistant to pests. In the coastal prairie of Louisiana and Texas, Chinese tallow can grow up to 30 feet and shade out native sun-loving prairie species. The disappearing of prairie species is troublesome because less than 1% of original coastal prairie remains, and in Louisiana, less than 500 of the original 2.2 million acres still exist. Tallow reproduces and grows quickly and can cause large-scale ecosystem modification (fig. 1). For example, when it completely replaces native vegetation, it has a negative effect on birds by degrading the habitat. Besides shading out grasses that cattle like to eat, it can also be potentially harmful to humans and animals because of its berries (fig. 2) and plant sap that contain toxins. There is some concern its leaves may shed toxins that change the soil chemistry and make it difficult for other plants to grow.

  11. 11. MOVABLE BED SEDIMENTATION MODELS. AUTOMATIC SEDIMENT FEEDER DESIGNED AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. MOVABLE BED SEDIMENTATION MODELS. AUTOMATIC SEDIMENT FEEDER DESIGNED AND BUILT BY WES. - Waterways Experiment Station, Hydraulics Laboratory, Halls Ferry Road, 2 miles south of I-20, Vicksburg, Warren County, MS

  12. 9. SEDIMENTATION CHAMBER, VIEW DOWNSTREAM. AFTER SEDIMENTATION, WATER FLOWS INTO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. SEDIMENTATION CHAMBER, VIEW DOWNSTREAM. AFTER SEDIMENTATION, WATER FLOWS INTO ONE 8" CAST-IRON PIPELINE. - Kalaupapa Water Supply System, Waikolu Valley to Kalaupapa Settlement, Island of Molokai, Kalaupapa, Kalawao County, HI

  13. Early mid-Holocene sea-level change and coastal environmental response on the southern Yangtze delta plain, China: implications for the rise of Neolithic culture

    NASA Astrophysics Data System (ADS)

    Wang, Zhanghua; Zhuang, Chencheng; Saito, Yoshiki; Chen, Jie; Zhan, Qing; Wang, Xiaodan

    2012-03-01

    We used a series of Holocene sediment cores with AMS 14C dated basal saltmarsh peat and supratidal sediment to reconstruct early mid-Holocene sea-level change on the southern Yangtze delta plain. We also synthesized results for ca 150 late Quaternary cores, as well as archeological data to reveal the unique interplay between coastal evolution and Neolithic cultural response. Relative sea level was ca -16.5 to -14.5 m from 8600 to 8500 cal BP and ca -6 to -4 m from 7400 to 7200 cal BP, reflecting the rate of eustatic sea-level rise but being ca 10 m higher possibly because of the effect of hydro-istostasy. Three late Pleistocene interfluve terraces, T3 to T1, were revealed at burial depths of <5 m, 5-15 m, and 20-30 m, respectively, lying between the paleo-incised mega-valleys of the Yangtze River in the north and the Qiantang River in the south, during the last glacial maximum. During the early mid-Holocene, the combined effect of rapid sea-level rise and the huge sediment accommodation space of the mouths of the two mega-rivers resulted in widespread inundation by brackish water and the shoreline retreated onto the highest terrace (T3). Although seaward migration of the Yangtze delta probably began at ca 7300 cal BP, saltmarsh and tidal flats dominated on the southern Yangtze delta plain until ca 6500 to 6000 cal BP when sea level became relatively stable and the shoreline prograded rapidly from T3 to the seaward boundary of T2. The concurrent formation of the freshwater-dominated Taihu Plain allowed Neolithic settlement and development of agriculture.

  14. Characterizing mercury concentrations and fluxes in a Coastal Plain watershed: Insights from dynamic modeling and data

    NASA Astrophysics Data System (ADS)

    Golden, H. E.; Knightes, C. D.; Conrads, P. A.; Davis, G. M.; Feaster, T. D.; Journey, C. A.; Benedict, S. T.; Brigham, M. E.; Bradley, P. M.

    2012-03-01

    Mercury (Hg) is one of the leading water quality concerns in surface waters of the United States. Although watershed-scale Hg cycling research has increased in the past two decades, advances in modeling watershed Hg processes in diverse physiographic regions, spatial scales, and land cover types are needed. The goal of this study was to assess Hg cycling in a Coastal Plain system using concentrations and fluxes estimated by multiple watershed-scale models with distinct mathematical frameworks reflecting different system dynamics. We simulated total mercury (HgT, the sum of filtered and particulate forms) concentrations and fluxes from a Coastal Plain watershed (McTier Creek) using three watershed Hg models and an empirical load model. Model output was compared with observed in-stream HgT. We found that shallow subsurface flow is a potentially important transport mechanism of particulate HgTduring periods when connectivity between the uplands and surface waters is maximized. Other processes (e.g., stream bank erosion, sediment re-suspension) may increase particulate HgT in the water column. Simulations and data suggest that variable source area (VSA) flow and lack of rainfall interactions with surface soil horizons result in increased dissolved HgTconcentrations unrelated to DOC mobilization following precipitation events. Although flushing of DOC-HgTcomplexes from surface soils can also occur during this period, DOC-complexed HgT becomes more important during base flow conditions. TOPLOAD simulations highlight saturated subsurface flow as a primary driver of daily HgT loadings, but shallow subsurface flow is important for HgTloads during high-flow events. Results suggest limited seasonal trends in HgT dynamics.

  15. Effects of infiltration chemistry on the mobilization potential of mercury (Hg) in soils from the New Jersey Coastal Plain

    SciTech Connect

    MacLeod, C.; Taylor, E. (Princeton Univ., NJ (United States). Dept. of Geological and Geophysical Sciences)

    1992-01-01

    Mercury concentrations in ground water exceeding the USEPA maximum contaminant level of 2 [mu]g/l have been found in wells 60 to 100 feet deep in the Kirkwood-Cohansey Aquifer System of the New Jersey Coastal Plain. The aquifer is a sand and gravel aquifer consisting primarily of quartz with minor amounts of biotite, plagioclase feldspars and ilmenite. This is the shallowest aquifer system in the NJ Coastal Plain and is unconfined over much of central and southern NJ. Soils on these aquifer sediments are quartz-rich with poorly developed A[sub 0] and B horizons. These are weakly-buffered acid soils with a pH ranging from 4.0 to 5.5, and little or no capacity for metal retention. Mercury contaminated soils from Gloucester County, NJ were used to determine the mobilization potential of Hg by run-off solutions containing 0.02M NaCl and 0.02M CaCl[sub 2] salt solutions that approximate diluted highway de-icing salts; and by a simulated acid rain solution of pH 4.0. These experimental data are in agreement with previous studies suggesting that chlorides from de-icing salts are capable of mobilizing Hg. However, the mobilization potential of Hg in coastal plain soils attributable to acid rain is much greater (approx. 1 to 2 orders of magnitude) than that estimated for de-icing salts. These data also indicate that in NJ Coastal Plain soils Hg mobilization may be controlled by colloidal movement during an infiltration event. Mobilization of Hg by the simulated acid rain solution was found to coincide with the resuspension of Fe and Al colloids, while no colloidal movement was found with either of the salt solutions. Thus Hg sorbed to Fe and Al colloids in NJ Coastal Plain soils is more likely to be mobilized by infiltration of acidic rain water or fluctuating acidic ground water than by highway de-icing salts.

  16. Wheat Evolution: Sedimentation Testing

    NSDL National Science Digital Library

    Biotechnology and Biological Sciences Research Council

    2012-01-01

    In this activity (p.8-9 of PDF), learners investigate the evolution of wheat by conducting sedimentation tests on different flours. The evolution of wheat from wild grasses demonstrates the dramatic effect of both natural and directed evolution on the structure of a crop plant and the chemical makeup of the product harvested from it. These activities illustrate the changes to both the structure and the chemistry of the wheat plant. Note: Sedimentation test can also be done using SDS detergent and lactic acid instead of soap and vinegar.

  17. Experimental sediment transport research at the USDA National Sedimentation Laboratory

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research on sediment transport under controlled conditions in laboratory flume channels has been an important part of the program of the National Sedimentation Laboratory (NSL) since its beginning in 1958. Studies over the years have included topics such as the initiation of motion of sediment, susp...

  18. Suspended sediment structure: implications for sediment and contaminant transport modelling

    Microsoft Academic Search

    I. G. DROPPO; D. E. WALLING; E. D. ONGLEY

    This paper examines the influence of sediment (floe) structure (size, shape, porosity and density) on the physical behaviour (e.g. settling and transport) of suspended sediment (floes) and its implications for sediment and contaminant transport models. Results demonstrate that as floe size increases, the settling velocity increases in a linear fashion. The rate of settling is, however, substantially below that predicted

  19. Air pollution history elucidated from anthropogenic spherules and their magnetic signatures in marine sediments offshore of Southwestern Taiwan

    Microsoft Academic Search

    Chorng-Shern Horng; Chih-An Huh; Kuo-Hang Chen; Pin-Ru Huang; Kan-Hsi Hsiung; Hui-Ling Lin

    2009-01-01

    Kaohsiung City and its neighborhood in the southwestern coastal plain of Taiwan have suffered serious air pollution since the region became the largest center for heavy-industry on the island. In order to unravel the air pollution history of the region, four 210Pb- and 137Cs-dated sediment box cores recovered in 2006 from offshore of this area were chosen for magnetic and

  20. Feasibility of using near-infrared reflectance spectroscopy for the analysis of C, N, P, and diatoms in lake sediments

    Microsoft Academic Search

    D. F. Malley; H. Rönicke; D. L. Findlay; Forename Surname

    1999-01-01

    The present study explored whether rapid, non-destructive near-infrared reflectance spectroscopy (NIRS) could complement conventional paleolimnological and chemical analyses of sediment cores for greater efficiency and cost-effectiveness. The study used a 47-cm long freeze-core from the deepest point in Lake Arendsee, Mecklenburg Plain in northern Germany taken in 1993 to elucidate eutrophication history and to identify the pre-impact algal communities in

  1. Impact of Irrigated Agroecosystems on Groundwater Resources in the US High Plains and North China Plain

    NASA Astrophysics Data System (ADS)

    Scanlon, B. R.; Longuevergne, L.; Cao, G.; Shen, Y.; Gates, J. B.; Reedy, R. W.; Zheng, C.

    2010-12-01

    Overabstraction of groundwater for irrigation in semiarid regions is depleting the worlds’ largest aquifers at much greater rates than these aquifers are being replenished by recharge. This study evaluates groundwater sustainability in the US High Plains (US HP) and North China Plain (NCP) where intensive irrigation has resulted in large water table declines. A variety of approaches were used to evaluate impacts of irrigation on groundwater resources, including GRACE satellite data, unsaturated zone profiling, and groundwater quantity and quality data. Cultivation (40% of area) and irrigation (12%) are less intensive in the US HP than in the NCP (80% cultivated, 50% irrigated). Irrigation is estimated to consume ~97% of groundwater resources in the US HP and ~70% in the NCP. Although only ~10% of groundwater resources has been consumed in the US HP (330 km3 out of 3,900 km3), the problem lies in the uneven spatial distribution. Groundwater depletion is greatest in the Central High Plains (CHP) where water table declines of up to 1.5 m/yr have been recorded in individual wells and regional declines of up to 30 m have been found over a 7,000 km2 area since irrigation began in the 1950s to 1960s. This depletion indicates an irrigation deficit of ~75 mm/yr over 60 yr (specific yield 15%). Recharge rates in the CHP are extremely low (median ~10 mm/yr) with reductions in groundwater storage exceeding recharge by ~10 times. High correlations between GRACE and measured water storage changes (R = 0.7 - 0.8) show that the satellite can accurately track regional changes in water storage. Groundwater in the NCP has declined from a depth of ~1 m in the 1960s to 20 to 40 m in the Piedmont region since expansion of irrigation beginning in the 1970s. Groundwater level declines in individual hydrographs range from 0.5 to 1.0 m/yr, indicating irrigation deficits ranging from 100 to 200 mm/yr (specific yield 20%). Lower groundwater storage changes from GRACE satellites relative to the monitoring well network are attributed to regional overestimation of groundwater level declines from monitoring wells in urban regions. Many strategies are being evaluated to move towards more sustainable water resource management. Transfer of water from the Yangste River to the NCP should relieve some of the water stress in the region. Other proposed approaches include more efficient irrigation, deficit irrigation, mulching, crop rotation, and no irrigation. Future system management needs to consider tradeoffs between water consumption, crop yield, and lifespan of these aquifers.

  2. Determination of sedimentary transfer time from U-series nuclides:implications from the study of the Gandak river sediments

    NASA Astrophysics Data System (ADS)

    Bosia, Clio; Chabaux, Francois; France-Lanord, Christian; Deloule, Etienne; Pelt, Eric

    2014-05-01

    In previous studies, it was proposed to constrain sediments transfer time in alluvial plains by analyzing the variations of the U-series disequilibria in river sediments along the stream. This approach was illustrated in the case of the Ganges-Brahmaputra basin and it allowed defining a sediment transfer scenario that includes significantly different transfer times within the alluvial plain. These studies suggest that the transfer times depend on the sediment grain size: short transfer times for fine-grained sediments (a few ky or less) and much longer ones for coarse-grained sediments (100 ky or more - [1-4]). However, those estimations can be questioned in the light of recent studies based on the analysis of cosmonuclides [5] and Sr et Nd isotopes [6] , that suggest shorter transfer times (respectively 1-2 ky and less for the second study) for coarse-grained sediments in Himalayan streams. In order to better constrain the origin of the U-series disequilibria variations in river sediments, we performed a detailed study of the U-series nuclides in the sediments of the Gandak River, one of the main Ganges tributaries. This study involves the sampling during monsoon period of suspended sediments, collected at different depths of the water column in the downstream and upstream river sections. At the same time, a regular upstream-downstream sampling of riverbank sediments during non-monsoon period was conducted, with sediments collection on both riversides of a same sampling station. U-Th data obtained on whole rock samples outline the occurrence of significant 238U-230Th-226Ra disequilibria in river sediments, with however no simple upstream-downstream variation. The correlations observed between (238U/232Th) activity ratios and Ti/Th ratios as well as between (230Th/238U) ratios and (Nd, Ce, La, Sm)/Th ratios suggest that minor mineral phases, such as Ti-bearing minerals, monazite, zircon or xenotime, are likely to control a significant part of the U-Th-Ra budget in the Gandak sediments. U-isotopes fractionation could therefore not only depend on the chemical evolution of the sediments during its transfer within the plain and on the time evolution, but also on the mechanical transformation of the sediments mineralogical composition. This last aspect can be significantly influenced by local hydraulic conditions, inducing important sorting effects in river sediments. These results illustrate the interest to investigate separated mineral phases of river sediments. Indeed, we need to clarify the role of the mineral composition in the control of U-Th-Ra isotopic fractionation in river sediments. This is a key point to achieve more reliable transfer times, avoiding problems linked to environmental bias. [1] Chabaux et al., 2012, C. R. Geoscience, 344 (11-12): 688-703; [2] Chabaux et al., 2006, J. Geochem. Exploration, 88: 373-375 ; [3] Granet et al., 2010, Geochim. et Cosmoch. Acta, 74 (10): 2851-2865 ; [4] Granet et al., 2007, Earth and Planet. Sci. Lett., 261 (3-4): 389-406 ; [5] Lupker et al., 2012, Earth and Planet. Sci. Lett., 333-334: 146-156; [6] Rahaman et al., 2009, Geology, 37 (6): 559-562.

  3. Radiocarbon studies of latest Pleistocene and Holocene lava flows of the Snake River Plain, Idaho: Data, lessons, interpretations

    NASA Astrophysics Data System (ADS)

    Kuntz, Mel A.; Spiker, Elliott C.; Rubin, Meyer; Champion, Duane E.; Lefebvre, Richard H.

    1986-03-01

    Latest Pleistocene-Holocene basaltic lava fields of the Snake River Plain, Idaho, have been dated by the radiocarbon method. Backhoe excavations beneath lava flows typically yielded carbon-bearing, charred eolian sediment. This material provided most of the samples for this study; the sediment typically contains less than 0.2% carbon. Charcoal fragments were obtained from tree molds but only from a few backhoe excavations. Contamination of the charred sediments and charcoal by younger carbon components is extensive; the effects of contamination were mitigated but appropriate pretreatment of samples using acid and alkali leaches. Twenty of the more than 60 lava flows of the Craters of the Moon lava field have been dated; their ages range from about 15,000 to about 2000 yr B.P. The ages permit assignment of the flows to eight distinct eruptive periods with an average recurrence interval of about 2000 yr. The seven other latest Pleistocene-Holocene lava fields were all emplaced in short eruptive bursts. Their 14C ages (yr B.P.) are: Kings Bowl (2222± 100), Wapi (2270 ± 50), Hells Half Acre (5200 ± 150), Shoshone (10,130 ± 350), North Robbers and South Robbers (11.980 ± 300), and Cerro Grande (13,380 ± 350).

  4. Radiocarbon studies of latest Pleistocene and Holocene lava flows of the Snake River Plain, Idaho: Data, lessons, interpretations

    USGS Publications Warehouse

    Kuntz, M.A.; Spiker, E. C.; Rubin, M.; Champion, D.E.; Lefebvre, R.H.

    1986-01-01

    Latest Pleistocene-Holocene basaltic lava fields of the Snake River Plain, Idaho, have been dated by the radiocarbon method. Backhoe excavations beneath lava flows typically yielded carbon-bearing, charred eolian sediment. This material provided most of the samples for this study; the sediment typically contains less than 0.2% carbon. Charcoal fragments were obtained from tree molds but only from a few backhoe excavations. Contamination of the charred sediments and charcoal by younger carbon components is extensive; the effects of contamination were mitigated but appropriate pretreatment of samples using acid and alkali leaches. Twenty of the more than 60 lava flows of the Craters of the Moon lava field have been dated; their ages range from about 15,000 to about 2000 yr B.P. The ages permit assignment of the flows to eight distinct eruptive periods with an average recurrence interval of about 2000 yr. The seven other latest Pleistocene-Holocene lava fields were all emplaced in short eruptive bursts. Their 14C ages (yr B.P.) are: Kings Bowl (2222?? 100), Wapi (2270 ?? 50), Hells Half Acre (5200 ?? 150), Shoshone (10,130 ?? 350), North Robbers and South Robbers (11.980 ?? 300), and Cerro Grande (13,380 ?? 350). ?? 1986.

  5. Decreased oxygen concentration in the glacial abyssal subarctic Pacific - evidence for enhanced oceanic carbon sequestration during cold periods?

    NASA Astrophysics Data System (ADS)

    Jaccard, S. L.; Galbraith, E. D.; Sigman, D. M.; Haug, G. H.; Francois, R.; Pedersen, T. F.

    2008-12-01

    Measurements of benthic foraminiferal Cd/Ca have indicated that the glacial-interglacial change in deep North Pacific PO4 concentration was minimal, which has been taken by some workers as a sign that the biological pump did not store more carbon in the deep glacial ocean. Here we present sedimentary redox- sensitive trace metal (Mn, Mo, U) records from ODP Site 882 (NW subarctic Pacific, water depth 3,244 m) to make inferences about changes in deep North Pacific oxygenation - and thus respired carbon storage - across glacial Terminations I and II. These observations are complemented with 230Th-normalized biogenic barium and opal measurements as indicators for past organic carbon export to separate the influences of deep-water oxygen concentration and sedimentary organic carbon respiration on the redox state of the sediment. Our results suggest that the deep subarctic Pacific water mass was depleted in oxygen during glacial maxima, though it was not anoxic. We reconcile our results with the existing benthic foraminiferal Cd/Ca by invoking a decrease in the fraction of the deep ocean nutrient inventory that was preformed, rather than remineralized. This change would have corresponded to an increase in the deep Pacific storage of respired carbon, which would have lowered atmospheric carbon dioxide (CO2) by sequestering CO2 away from the atmosphere and by increasing ocean alkalinity through a transient dissolution event in the deep sea. Preliminary calculations show that the magnitude of change in preformed nutrients suggested by the North Pacific data would have accounted for a substantial portion of the observed decrease in glacial atmospheric pCO2.

  6. High-precision provenance determination using detrital-zircon ages and petrography of Quaternary sands on the eastern Snake River Plain, Idaho

    SciTech Connect

    Geslin, J.K.; Link, P.K. [Idaho State Univ., Pocatello, ID (United States). Dept. of Geology] [Idaho State Univ., Pocatello, ID (United States). Dept. of Geology; Fanning, C.M. [Australian National Univ., Canberra (Australia). Research School of Earth Sciences] [Australian National Univ., Canberra (Australia). Research School of Earth Sciences

    1999-04-01

    The Big Lost trough is an upper Pliocene to Holocene sedimentary basin containing volcanic sills in the northeastern Snake River Plain, Idaho. The basin receives sediment primarily from Basin and Range fluvial systems of the Big Lost River, Little Lost River, and Birch Creek. The Big Lost trough contains a >200-m-thick succession of lacustrine, fluvial, eolian, and playa sediments, recording high-frequency Quaternary climatic fluctuations interbedded with basalt flows. Alternating deposition of clay-rich lacustrine sediments and sandy fluvial and eolian sediments in the central part of the basin was in response to the interaction of fluvial and eolian systems with Pleistocene Lake Terreton. The source areas for modern sands from the fluvial systems can be differentiated by using both petrography and U/Pb age spectra from detrital-zircon populations. Provenance data from subsurface sands indicate that the Big Lost trough was supplied with sand largely deposited by the Big Lost River, with local redeposition by eolian processes, similar to the modern depositional system. Provenance and stratigraphic data suggest that during Pleistocene wet climate cycles, the center of the basin was dominated by lacustrine sedimentation; during dry climate cycles, the base level dropped, the Big Lost River prograded across the basin, and the eolian system became active. At least seven climate oscillations are recorded in strata deposited between {approximately}140 and {approximately}1250 ka.

  7. Soft-sediment mullions

    NASA Astrophysics Data System (ADS)

    Ortner, Hugo

    2015-04-01

    In this contribution I describe the appearance, formation and significance of soft-sediment mullions. I use several examples from synorogenic turbidites of the Alps and the Pyrenees to show their appearance in the field. Soft-sediment mullions are elongate, slightly irregular bulges at the base of coarse-grained clastic beds (sand to conglomerate), separated by narrow, elongate flames of fine-grained material (mud) protruding into the coarse-grained bed. Various processes may lead to the formation of such structures: (1) longitudinal furrows parallel to the sediment transport direction may form by spiral motion in flow rolls during sediment transport (Dzulinski, 1966; Dzulinski & Simpson, 1966). (2) Loading combined with downslope movement can produce elongate structures parallelling the dowslope direction (Anketell et al., 1970). (3) Soft-sediment mullions are oriented perpendicular or oblique to the downslope direction, and show evidence of bedding-parallel shortening. Thus, they resemble cuspate-lobate folds or mullions, which are well-known in ductile structural geology (e.g. Urai et al., 2001). Soft-sediment mullions have been observed in two cases: Either bedding-parallel shortening can be achieved by slump processes, or by active tectonic shortening. Slumping is characterized by an alternation of stretching and shortening (e.g. Ortner, 2007; Alsop & Marco 2014), and therefore mullions do overprint or are overprinted by normal faults. In active depositional systems that are subject to tectonic shortening growth strata will form, but sediments already deposited will be shortened during lithification. In some cases, the formation of soft-sediment mullions predates folding, but the most widespread expression of syn-lithification shortening seems to be soft-sediment mullions, that form in the inner arcs of fold hinges. In the examples documented so far, the size of soft-sediment mullions is dependent on the grain-size of the coarse-grained layer, in which the mullions form. In coarse conglomerates, meter-scale mullions were observed, in sandstones centimeter-scale mullions. There does not seem to exist a relationship to the rate of shortening, as the size of mullions is independent of their position in larger scale folds, or in slump complexes or tectonic folds. Anketell, J.M., Cegla, J. & Dzulynsky, S. (1970): On the deformational structures in systems with reversed density gradients. Ann. Soc. Geol. Pol., 40(1): 3-30. Alsop, G.I., Marco, S., 2014. Fold and fabric relationships in temporally and spatially evolving slump systems: A multi-cell flow model. Jour. Struct. Geol., 63(0): 27-49. Dzulynsky, S. (1966): Sedimentary structures resulting from convection-like pattern of motion. Ann. Soc. Geol. Pol., 36(1): 3-21. Dzulinsky, S. & Simpson, F. (1966): Experiments on interfacial current markings. Geol. Rom., 5: 197 - 214. Ortner, H. (2007): Styles of soft-sediment deformation on top of a growing fold system in the Gosau Group at Muttekopf, Northern Calcareous Alps, Austria: Slumping versus tectonic deformation. Sed. Geol., 196: 99-118. Urai, J.L., Spaeth, G., Van der Zee, W. & Hilger, C. (2001): Evolution of mullion (boudin) structures in the Variscan of the Ardennes and Eifel. Jour. Virt. Expl., 3: 1-16.

  8. Radar and Geomorphic Evidence Regarding the Occurrence of Massive Ground Ice in the Martian Northern Plains

    NASA Astrophysics Data System (ADS)

    Clifford, S. M.; PetitJean, M.; Costard, F.; Mouginot, J.; Parker, T. J.

    2013-12-01

    The possibility that an ocean once occupied the Martian northern plains has been proposed based on the identification of various landforms - most notably of possible paleoshorelines by Parker et al., who identified evidence of a series of nested levels located along the dichotomy boundary. Subsequent burial by fluvial, eolian and volcanic deposits may have preserved a frozen relic of such an ocean to the present day. Late Hesperian (LH) and Early Amazonian (EA) outflow channel activity, may have contributed to the complex volatile stratigraphy of the northern plains. The Vastitas Borealis Formation (VBF), widely interpreted to be a 100+ m-thick deposit of fluvial sediment left by the LH/EA outflow channels, is the most extensive geologic unit in the northern plains. It is characterized by an unexpectedly weak radar surface reflectivity - as determined by the MARSIS orbital radar sounder on Mars Express. This low reflectivity is consistent with a surface permittivity of ~4.6×0.5, indicative of either a high-porosity (~35%) or ice-rich (~60%) sedimentary layer - values which are believed to be representative of the subsurface to a depth of one MARSIS wavelength (~60-80 m in the subsurface). To discriminate between a high-porosity or ice-rich origin for the low permittivity of the VBF, we compared the geographic correlation of low surface permittivities with the distribution of ground ice inferred from the occurrence of Martian fluidized ejecta craters. We find that the distribution of fluidized ejecta craters with the smallest onset diameters (<2 km) coincides with the regions of lowest surface permittivity. Similarly, there is a strong correlation between low surface permittivity and craters exhibiting the highest fluidized ejecta mobility (ejecta diameter/crater diameter, interpreted as a measure of their volatile content). These findings provide persuasive evidence of that the low surface permittivity of the VBF is attributable to the presence of massive ground ice, most plausibly related to a surviving frozen remnant of a former ocean and/or the discharge of the outflow channels.

  9. Sediment Deposition into a Valley-Margin Lake in a Managed Floodplain, Catahoula Lake, Louisiana, USA

    NASA Astrophysics Data System (ADS)

    Keim, R.; Latuso, K.; DeLaune, R. D.; Weindorf, D. C.

    2014-12-01

    Sediment sources to valley-margin lakes vary spatially and temporally depending on relative dominance of the main or tributary rivers. Catahoula Lake is the largest valley-margin lake in the lower Mississippi River Alluvial Valley and is hydrologically influenced by backwaters of the Mississippi and Red rivers and headwaters of the Little River. Our objective was to understand effects of hydrological management of the floodplain and the lake itself on lake sediments and recent changes in vegetation. Comparison of 137Cs profiles with prior 210Pb and 14C profiles indicates the recent deposition rate has been low (0.3 cm/yr) but triple that prior to settlement. Sediment chemistry profiles indicate dominance of acidic coastal-plain sediments from the tributary Little River in the past ~60 yr, but spatially mixed influence of acidic and neutral, Mississippi-Red sediments prior to that. We conclude that a century of increasing hydrologic management of the Mississippi and Red rivers has disconnected Catahoula Lake from their sedimentary influence and that the consequent change in chemical composition of surficial sediments may be contributing to ecologic changes in the lake.

  10. Fractures/Pits in Northern Plains (Utopia Plains: 44.9 N, 274.7 W)

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Although northern plains are often called 'flat' or 'featureless' by people who study altimetry data, clearly this isn't true. This area has an indurated (strong or cemented) crust that has been subjected to directional stress (that's why the beaded-pitted fractures are almost all aligned the same direction) and that has been undermined (hence the pitting at both the small scale--the beaded fractures--and the large scale--the large irregular depressions.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  11. Inferring tidal wetland stability from channel sediment fluxes: observations and a conceptual model

    USGS Publications Warehouse

    Ganju, Neil K.; Nidzieko, Nicholas J.; Kirwan, Matthew L.

    2013-01-01

    Anthropogenic and climatic forces have modified the geomorphology of tidal wetlands over a range of timescales. Changes in land use, sediment supply, river flow, storminess, and sea level alter the layout of tidal channels, intertidal flats, and marsh plains; these elements define wetland complexes. Diagnostically, measurements of net sediment fluxes through tidal channels are high-temporal resolution, spatially integrated quantities that indicate (1) whether a complex is stable over seasonal timescales and (2) what mechanisms are leading to that state. We estimated sediment fluxes through tidal channels draining wetland complexes on the Blackwater and Transquaking Rivers, Maryland, USA. While the Blackwater complex has experienced decades of degradation and been largely converted to open water, the Transquaking complex has persisted as an expansive, vegetated marsh. The measured net export at the Blackwater complex (1.0?kg/s or 0.56?kg/m2/yr over the landward marsh area) was caused by northwesterly winds, which exported water and sediment on the subtidal timescale; tidally forced net fluxes were weak and precluded landward transport of suspended sediment from potential seaward sources. Though wind forcing also exported sediment at the Transquaking complex, strong tidal forcing and proximity to a turbidity maximum led to an import of sediment (0.031?kg/s or 0.70?kg/m2/yr). This resulted in a spatially averaged accretion of 3.9?mm/yr, equaling the regional relative sea level rise. Our results suggest that in areas where seaward sediment supply is dominant, seaward wetlands may be more capable of withstanding sea level rise over the short term than landward wetlands. We propose a conceptual model to determine a complex's tendency toward stability or instability based on sediment source, wetland channel location, and transport mechanisms. Wetlands with a reliable portfolio of sources and transport mechanisms appear better suited to offset natural and anthropogenic loss.

  12. Regional variation of As concentration in alluvial plain: An insight obtained from Mankyeong River plain, Korea

    NASA Astrophysics Data System (ADS)

    Kim, K.; Kim, S.; Kim, B.; Zhu, W.; Lee, E.; Ko, K.; Lee, K.

    2010-12-01

    The arsenic (As) concentrations in the groundwater of alluvial plains generally show high spatial variability. We geochemically explored the regional variation of As concentration from Mankyeong River floodplain. Even though its watershed is very small, it shows a close similarity to the Ganger-Megna-Bramaputra Plain of Bengal Basin in the occurrence of As-rich groundwater. Therefore, a precise investigation of the study area can provide important clues for the mechanisms causing the spatial variation of As concentrations in Bangladesh. We collected 163 groundwater samples from 122 shallow wells placed into the alluvial aquifer and analyzed for pH, Eh, alkalinity, DOC, As, Fe, Mn, Cl, SO4, NO3, NH4, PO4-P. 42 wells out of the investigated wells show As concentrations exceeding the drinking water limit (10 ug/L) and they are mostly distributed as a zone apart from the coast likely to those in Bangladesh. The As-rich groundwaters show high alkalinity, Fe, Mn, PO4, NH4, and DOC levels and very low NO3 and SO4 levels, indicating that the reductive dissolution of iron oxide is the main mechanism mobilizing As. In contrast, groundwater generally shows very low As and Fe concentrations in the coastal zone even though the waters are under much stronger reducing condition. Our results show that the limited supply of SO4 caused the high As concentration in the inland. But As concentrations were low in the coastal zone due to SO4 supplied by seawater intrusion. Very high alkalinity was observed in the coastal zone due to sulfate reduction, and which also plays a role decreasing As concentration by precipitating carbonate minerals such as siderite and rhodocrosite.

  13. Age of organic carbon of sediments flowing through an intermittent Mediterranean river basin

    NASA Astrophysics Data System (ADS)

    Boix-Fayos, Carolina; de Vente, Joris; Martínez-Mena, María; Almagro, María; Nadeu, Elisabet

    2015-04-01

    Fluvial sediments have the potential to bury large amounts of organic carbon (OC) annually, contributing to the terrestrial carbon sink. The temporal significance of this sink will strongly depend on the attributes of the sediment sources, that partially determine the characteristics of OC in sediments, and on the depositional environment, which influences the stability of sediments upon deposition. Knowledge of the age of the redistributed organic carbon could give us an indication of its origin and potential stability, however, little is known about the characteristics and age of organic carbon (OC) flowing through Mediterranean intermittent rivers. Several studies undertaken in an intermittent medium sized catchment (111 km2) in SE Spain showed how sediments flowing through the catchment, that were sampled during transport (suspended sediments) and at different depositional settings (sediment wedges, alluvial bars, delta, reservoir sediments), showed an OC content of approximately half of that in the soils of the drainage area (9.42±9.01 g kg-1 versus 20.45±7.71 g kg-1, respectively), with important variation between the explored sediment deposits. Selective sorting of mineral and organic material during transport and deposition increased from upstream towards downstream. A characterization of carbon ages from radiocarbon analysis showed much younger organic carbon in soils related directly to the vegetation cover (547±380 years BP with large variations between forest and agricultural soils) than in fluvial sediments. The sediments transported in suspension showed the oldest average age (7396±1640 years BP) coming probably from bedrock sources and petrogenic origin, compared to the sediments deposited in the delta-alluvial plain (3999±365 years BP) and compared to the relatively young carbon found in the reservoir-lake at the outlet of the catchment (1838±2000 BP with large variations depending on the sediment depth). Variation of organic carbon age with sediment depth in the reservoir can possibly be related to different hydrological events and to the in-situ formation of organic carbon by lake ecological processes. Complementary information on stable isotopes (?13C, ?15N) could possibly give more insight in the processes concerning the redistribution of organic carbon by fluvial processes in intermittent rivers.

  14. Intermediate sulfur oxidation state compounds in the euxinic surface sediments of the Dvurechenskii mud volcano (Black Sea)

    NASA Astrophysics Data System (ADS)

    Lichtschlag, Anna; Kamyshny, Alexey; Ferdelman, Timothy G.; deBeer, Dirk

    2013-03-01

    The deep Black Sea is known to be depleted in electron-acceptors for sulfide oxidation. This study on depth distributions of sulfur species (S(II), S(0), Sn2-, SO32-, SO32-, SO42-) in the Dvurechenskii mud volcano, a cold seep situated in the permanently anoxic eastern Black Sea basin (Sorokin Trough, 2060 m water depth), showed remarkable concentrations of sulfide oxidation products. Sulfite concentrations of up to 11 ?mol L-1, thiosulfate concentrations of up to 22 ?mol L-1, zero-valent sulfur concentrations of up to 150 ?mol L-1 and up to five polysulfide species were measured in the upper 20 cm of the sediment. Electron-acceptors found to be available in the Dvurechenskii mud volcano (DMV) for the oxidation of hydrogen sulfide to sulfide oxidation intermediates are iron-minerals, and probably also reactive manganese phases. Up to 60 ?mol g-1 of reactive iron-minerals and up to 170 ?mol L-1 dissolved iron was present in the central summit with the highest fluid upflow and fresh mud outflow. Thus, the source for the oxidative power in the DMV are reactive iron phases extruded with the mud from an ancient source in the deeply buried sediments, leading to the formation of various sulfur intermediates in comparably high concentrations. Another possible source of sulfide oxidation intermediates in DMV sediments could be the formation of zero-valent sulfur by sulfate dependent anaerobic microbial oxidation of methane followed by disproportionation of zero-valent sulfur. Sulfide oxidation intermediates, which are produced by these processes, do not reach thermodynamic equilibrium with rhombic sulfur, especially close to the active center of the DMV due to a short equilibration time. Thus, mud volcano sediments, such as in the DMV, can provide oxidizing niches even in a highly reduced environment like the abyssal part of the Black Sea.

  15. COLLECTION OF UNDISTURBED SURFACE SEDIMENTS

    EPA Science Inventory

    The National Resource Council identified the need for a capability to collect undisturbed surface sediments. Surface sediments are an important source for most exposure of fish to polychlorinated biphenyls via direct uptake from water in contact with sediments. An innovative sedi...

  16. Sediment bioassays with oyster larvae

    SciTech Connect

    Chapman, P.M.; Morgan, J.D.

    1983-10-01

    Tests with naturally-occurring sediments are rare and sediment testing methodology is not standardized. The authors present a simple methodology for undertaking sediment bioassays with oyster larvae, and present data from a recent study to prove the utility of this method.

  17. Re-Assessing Plains-style Volcanism on Mars

    NASA Technical Reports Server (NTRS)

    Sakimoto, S. E. H.; Gregg, T. K. P.; Hughes, S. S.; Chadwick, J.

    2003-01-01

    The volcanic plains of Mars have long been thought to be analogous to the Snake River Plains (SRP), Idaho, on Earth, primarily in terms of the range of low shields, fissure eruptions, and flows that coalesce to resurface large tracts of plains regions. The Tempe region of Mars was usually the most frequently cited analog prior to the Mars Global Surveyor (MGS) and Mars Odyssey (MO) missions. Since the (MGS) Mission and the availability of Mars Orbiter Laser Altimeter (MOLA) topography, it has become clear that the number of shields and vents is far greater than that estimated on the basis of prior image data alone, and that in many cases, the previously identified shields were actually only the steeper summits of far more extensive edifices with shallow lower flanks.

  18. A two-dimensional dam-break flood plain model

    USGS Publications Warehouse

    Hromadka, T.V., II; Berenbrock, C.E.; Freckleton, J.R.; Guymon, G.L.

    1985-01-01

    A simple two-dimensional dam-break model is developed for flood plain study purposes. Both a finite difference grid and an irregular triangle element integrated finite difference formulation are presented. The governing flow equations are approximately solved as a diffusion model coupled to the equation of continuity. Application of the model to a hypothetical dam-break study indicates that the approach can be used to predict a two-dimensional dam-break flood plain over a broad, flat plain more accurately than a one-dimensional model, especially when the flow can break-out of the main channel and then return to the channel at other downstream reaches. ?? 1985.

  19. PHYTOASSESSMENT OF ESTUARINE SEDIMENTS

    EPA Science Inventory

    Most sediment quality assessments and quality guidelines are based on the laboratory response of single animal species and benthic animal community composition. The role of plants in this hazard assessment process is poorly understood despite the fact that plant-dominated habitat...

  20. Sedimentation of Prairie Wetlands

    NSDL National Science Digital Library

    In keeping with its high standards, the Northern Prairie Wildlife Research Center (NPWRC, discussed in the October 15, 1997 Scout Report for Science & Engineering) has released more wetland resources. Sedimentation of Prairie Wetlands by Robert Gleason and Ned Euliss, Jr. was first released in 1998.