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1

Ocean-Bottom Topography: The Divide between the Sohm and Hatteras Abyssal Plains.  

PubMed

A compilation of precision echo soundings has delineated the complex topography between the Sohm and Hatteras abyssal plains off the Atlantic coast of the United States. At present the divide between the two plains is a broad, flat area about 4950 meters deep; however, the configuration of channels and depressions suggests spillage of turbidity currents from the Sohm Plain into the Hatteras Plain and a shifting of the divide toward the northeast. Hudson Canyon terminates in the divide area and has probably fed sediment into both plains. PMID:17769918

Pratt, R M

1965-06-18

2

Geotechnical properties of fine-grained turbidite sequences: observations from the Nares Abyssal Plain  

Microsoft Academic Search

Variations in the geotechnical properties of fine-grained turbidite sequences located in the Nares Abyssal Plain appear directly related to the dominant processes controlling sediment deposition. Changes in the index properties are gradational from the turbidite bases, often containing silt beds or laminae, upwards through the chemically laminated possibly turbiditic clays and into the nonturbiditic pelagic and hemipelagic clays. The depth

L. E. Shephard; A. K. Rutledge; W. R. Bryant; K. M. Moran

1986-01-01

3

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

SciTech Connect

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.

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

4

Geotechnical properties of fine-grained turbidite sequences: observations from the Nares Abyssal Plain  

SciTech Connect

Variations in the geotechnical properties of fine-grained turbidite sequences located in the Nares Abyssal Plain appear directly related to the dominant processes controlling sediment deposition. Changes in the index properties are gradational from the turbidite bases, often containing silt beds or laminae, upwards through the chemically laminated possibly turbiditic clays and into the nonturbiditic pelagic and hemipelagic clays. The depth at which consolidation processes begin to control the distribution of geotechnical properties is unclear; however, it is apparent that depositional processes predominate to depths of 3 to 4 meters. Consolidation test results indicate that abyssal plain sediments appear normally to overconsolidated using standard soil mechanics terminology and methods. Clay fabric analyses using transmission electron microscopy show significant variations in grain size, grain type, and orientation between the turbiditic and nonturbiditic clays.

Shephard, L.E.; Rutledge, A.K.; Bryant, W.R.; Moran, K.M.

1986-01-15

5

Comparative geoscience studies of the Madeira and Southern Nares Abyssal Plains: NEA/SWG preference location document  

SciTech Connect

This document summarizes the status of geoscience investigations in the two primary North Atlantic study locations Great Meteor East (GME) in the Madeira Abyssal Plain, and the Southern Nares Abyssal Plain (SNAP), and assesses the characteristics of these locations relative to the guidelines considered desirable and necessary for a potential subseabed high-level waste repository. These characteristics will be continually reevaluated as additional data become available and as our understanding of deep-sea sediment processes within abyssal plain environments improves. Initially, a number of areas of minimum size were identified in the ocean basins that appeared to comply with most of the stability and barrier guidelines. However, detailed studies in both GME and SNAP demonstrate that as our level of knowledge improves, and the degree of resolution increases, the number of 100 km/sup 2/ areas complying with these guidelines becomes much more limited. This observation may be characteristic of abyssal plain and abyssal hill environments in both the North Atlantic and North Pacific basins. Marked differences in geoscience characteristics exist between the Great Meteor East and the Southern Nares Abyssal Plain study locations. The significance of these differences, as they impact the selection of a single preferred site for a potential subseabed repository, can only be determined by using an integrated systems risk assessment modeling approach. The known geoscience characteristics can, however, be used in conjunction with the site assessment guidelines to draw conclusions concerning the geoscience suitability of these two locations. These conclusions will be modified as specific types of data from future expeditions become available.

Auffret, G.A.; Buckley, D.E.; Schuttenhelm, R.T.E.; Searle, R.C.; Shephard, L.E.; Cranston, R.E.

1986-01-01

6

New magnetic survey in the Tagus Abyssal Plain (TECTAP Project)  

NASA Astrophysics Data System (ADS)

The southern segment of the West Iberia Margin (WIM), the Tagus Abyssal Plain (TAP), and its conjugate margin, the southeast Grand Banks in Newfoundland, have not been drilled and geophysical data are sparse. On the contrary, the central and northern segments of the WIM are well-studied and the deep structure of the crust is well established. Nevertheless, a geological transect of the crust and upper mantle structure in the Tagus Abyssal Plain (TAP) was published in 2006, extending from the un-thinned continental crust in the East to the typical oceanic crust in the West (Afilhado, 2006; Afilhado et al., 2008). The results of the interpretation and modelling of seismic data, which includes refraction and wide-angle reflection and near vertical reflection, along IAM-5 multi-channel (MCS) profile are distinct to the one already available in the Iberia Abyssal Plain. These results on the deep structure indicate that nearly the entire TAP is underlain by oceanic crust. Both seismic, magnetic and free-air anomaly data modelling concur to the identification of a major rock property contrast at 10.5°W, which is interpreted as the eastern limit of the oceanic crust. A 40 km wide domain, to the east of 10.5°W, with high velocity gradient and seismic velocity in the range 6.0 km/s to 7.2 km/s (Afilhado, 2006; Afilhado et al., 2008) was recognized. Numerical modeling favours a serpentinized mantle composition in this domain, instead of continental crust affinity rocks (Neves et al., 2008), i.e. similar to the domain of exhumed serpentinized mantle recognized in the Iberia Abyssal Plain, to the north. However, this exhumed serpentinized mantle domain in the TAP is rather narrower than in the Iberia Abyssal Plain. This interpretation has important consequences to explain the nature of the crust in the transitional domain and for kinematics reconstructions. Moreover, the TAP is characterized, eastward of the J anomaly, by a set of low amplitude magnetic anomalies, suggesting a near N-S alignment. The origin of these anomalies and consequently the nature and age of the crust in the area, are matters of scientific dispute, unsolved till today. In order to confirm the interpretation of Afilhado et al., 2008 and to determine if low amplitude magnetic anomalies are really formed by seafloor spreading, we have acquired a new survey of the magnetic profiles in the TAP. These data and other available data on magnetics, geology and geophysics, from the TAP and its conjugate margin, will be used to update the plate kinematic evolution model for Iberia. The amount of stretching thus computed will put additional constrains on the model to explain the formation of this margin.

Moulin, M.

2009-04-01

7

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

NASA Astrophysics Data System (ADS)

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

Carney, Robert S.; Carey, Andrew G.

1982-05-01

8

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

E-print Network

HEAVY MINERAL DISPERSAL PATTERNS OF THE ABYSSAL PLAIN AND LOUISIANA INNER SHELF OF THE GULF OF MEXICO A Thesis WALTER RICHARD MOORE Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE January 1969 Major Subject: Geological Oceanography HEAVY MINERAL DISPERSAL PATTERNS OF THE ABYSSAL PLAIN AND LOUISIANA INNER SHELF OF THE GULF OF MEXICO A Thesis by WALTER RICHARD MOORE Approved as to style...

Moore, Walter Richard

2012-06-07

9

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

10

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...

11

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

SciTech Connect

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.

Thurow, J.; Gibling, M.

1989-03-01

12

Study of abyssal seafloor isolation of contaminated sediments concluded  

SciTech Connect

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.

Valent, P.

1998-12-31

13

Miocene sedimentation in the Sigsbee Abyssal Plain, Gulf of Mexico  

E-print Network

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.... ) Andesite with rectangular plagioclase cryst- als and a porphyritic texture, 91-25-4-3 x30 3. ) Andesite illustrating feldspar laths and fin- er crystal size groundmass. 91-25-4-c/c x35 4. ) Rasalt with plagioclas and pyroxene the dom- inant, consti...

Kuzela, Robert Christian

2012-06-07

14

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

15

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

PubMed

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

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

2008-11-01

16

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

NASA Astrophysics Data System (ADS)

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

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

17

Response of a multi-domain continental margin to compression: Study from seismic reflection-refraction and numerical modelling in the Tagus Abyssal Plain  

NASA Astrophysics Data System (ADS)

The effects of the Miocene through Present compression in the Tagus Abyssal Plain are mapped using the most up to date available to scientific community multi-channel seismic reflection and refraction data. Correlation of the rift basin fault pattern with the deep crustal structure is presented along seismic line IAM-5. Four structural domains were recognized. In the oceanic realm mild deformation concentrates in Domain 1 adjacent to the Tore-Madeira Rise. Domain 2 is characterized by the absence of shortening structures, except near the ocean-continent transition (OCT), implying that Miocene deformation did not propagate into the Abyssal Plain. In Domain 3 we distinguish three sub-domains: Sub-domain 3A which coincides with the OCT, Sub-domain 3B which is a highly deformed adjacent continental segment, and Sub-domain 3C. The Miocene tectonic inversion is mainly accommodated in Domain 3 by oceanwards directed thrusting at the ocean-continent transition and continentwards on the continental slope. Domain 4 corresponds to the non-rifted continental margin where only minor extensional and shortening deformation structures are observed. Finite element numerical models address the response of the various domains to the Miocene compression, emphasizing the long-wavelength differential vertical movements and the role of possible rheologic contrasts. The concentration of the Miocene deformation in the transitional zone (TC), which is the addition of Sub-domain 3A and part of 3B, is a result of two main factors: (1) focusing of compression in an already stressed region due to plate curvature and sediment loading; and (2) rheological weakening. We estimate that the frictional strength in the TC is reduced in 30% relative to the surrounding regions. A model of compressive deformation propagation by means of horizontal impingement of the middle continental crust rift wedge and horizontal shearing on serpentinized mantle in the oceanic realm is presented. This model is consistent with both the geological interpretation of seismic data and the results of numerical modelling.

Neves, M. C.; Terrinha, P.; Afilhado, A.; Moulin, M.; Matias, L.; Rosas, F.

2009-04-01

18

Seismotectonics of the Gulf of Cadiz and Horseshoe Abyssal Plain - active faulting in continental and oceanic mantle  

NASA Astrophysics Data System (ADS)

In the area to the west of the Gibraltar Arc the plate boundary between Africa and Iberia is poorly defined. The deformation in the area is forced by the slow NW-SE convergence of 4 mm/yr between the oceanic domains of Iberia/Eurasia and Africa and is accommodated over a 200 km broad tectonically-active deformation zone. The region, however, is also characterized by large earthquakes and tsunamis, such as the 1969 Mw=7.9 Horseshoe Abyssal Plain earthquake and the November 1, 1755 Great Lisbon earthquake with an estimated magnitude of Mw~8.5. The exact location of the source of the 1755 Lisbon earthquake is still unknown. Recent work, however, may suggest that the event occurred in the vicinity of the Horseshoe fault, an oblique thrust fault. Further, the area is marked by the presence of compressive structures with a roughly NE-SW orientation and E-W trending, segmented, crustal-scale, strike slip faults that extend from the Gorringe Bank to the Gibraltar arc in the eastern Gulf of Cadiz, which were called "South West Iberian Margin" or SWIM faults. The fault system may mark a developing Eurasia-Africa plate boundary. Two local seismic networks were operated in the area. First, within the framework of TOPOE-EUROPE, a network of 24 ocean bottom seismometers (OBS) monitored the seismicity between January and July 2010 in the northern Gulf of Cadiz to the north of 36°N between 9°30'W and ~7 °W. The second network operated between April and October 2012 14OBS in the vicinity of the Horseshoe fault between 10°W to 11°W, and 35°50'N to 36°10'N. Recordings from the both deployments were supplemented by land stations operated in Portugal and the Gibraltar Arc. The networks provided in the order of 100 locale earthquakes occurring with the networks. In the Gulf of Cadiz, the two largest events of Mw~3.6 where thrust faulting events occurring in the vicinity of the Portimao Bank. With a depth of 40-50 km these events, among others, occurred within the continental mantle. Earthquakes in the Horseshoe occurred at even greater depth, at 40-60 km, either in oceanic or unroofed continental mantle. The large source depth observed in the Horseshoe Abyssal plain supports the interpretation that large catastrophic earthquakes, like the Great Lisbon earthquake of 1755, may indeed occur in the area.

Grevemeyer, Ingo; Matias, Luis

2013-04-01

19

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

20

The Kefalonia Transform Zone (offshore Western Greece) with special emphasis to its prolongation towards the Ionian Abyssal Plain  

NASA Astrophysics Data System (ADS)

Information concerning two seismic lines, the first located northwest of the Lefkada Island and the second from the deep Ionian basin to the gulf of Patras, is used to trace the Kefalonia Transform Zone (KTZ) and to explore its relation with the sedimentary sequences and the deeper geologic structures in the study area. In addition, sea bottom topography and fault plane solutions are combined in order to explore the prolongation of the KTZ into the Ionian Abyssal Plain (IoAP) and to describe its properties. The boundary between the subduction of the eastern Mediterranean oceanic crust under the overriding continental crust and the KTZ is well constrained by the seismic data in association with seismicity and regional stress field. The southern prolongation of the KTZ is located in the IoAP towards the direction between Kefalonia and Zakynthos Islands at depth greater than 15 km. The southern part of the KTZ exhibits a strike slip motion with a thrust component according to fault plane solutions of moderate and strong earthquakes. The seismic section mostly confirms the existence of the thrust component and gives information about the tectonic status east and west of the KTZ.

Kokinou, E.; Papadimitriou, E.; Karakostas, V.; Kamberis, E.; Vallianatos, F.

2006-12-01

21

Interelement relationship in abyssal Pacific ferromanganese nodules and associated pelagic sediments  

NASA Astrophysics Data System (ADS)

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

Li, Yuan-Hui

1982-06-01

22

South-directed mass wasting from the Galicia Bank: How might it affect interpretations of seismic and drilling results in the Iberia Abyssal Plain?  

NASA Astrophysics Data System (ADS)

Recently, we have interpreted seismic profiles ISE-1 and ISE-9 crossing the west and south sides of the Galicia Bank, west of Spain in the Atlantic Ocean, to show evidence of very large mass wasting events presumed to have occurred late in the process of continental breakup and the initiation of seafloor spreading. The events are driven by large topographic relief created at the boundary between the half-thickness, extended, continental crust of the Galicia Bank and crust composed of mantle rocks exhumed to the seafloor (Zone of exhumed continental mantle; ZECM) after the continental crust has separated and before normal seafloor spreading is established. The slide material is interpreted to consist of blocks of Galicia Bank extended continental crust and pre-sliding sediment. A portion of this slide material was emplaced over the ZECM. We examine possible consequences of this controversial hypothesis for the well-known and widely interpreted ODP Legs 149 and 173 drilling in the Iberia Abyssal Plain and nearby seismic profiles Lusigal 12 and IAM-9. We interpret that profile Lusigal 12 crosses the foot of the proposed south-directed landslide. We argue that the several low-angle faults (including H, HD, and HDD) observed in profile Lusigal 12 were formed within and at the base of the foot of the slide covering ZECM. We interpret that profile IAM-9 crosses the region of ZECM just to the south of the toe of the landslide. However, because the landslide moved continental crustal blocks to the south of their original position, we interpret that the pre-slide boundary between extended crust of the Galicia Bank and ZECM lies tens of km north of its presently mapped position. Specifically, we map this boundary north of both profile Lusigal 12 and the ODP drilling transect. This suggests that the eastern part of the drilling transect overlies mantle rocks that were exhumed at the seafloor and existed at the seafloor for some time before the continental rocks and pre-rift sediments were placed on top by southward sliding off the Galicia Bank. If true, this contrasts with the now commonly accepted model in which the eastern part of the drilling transect lies over mantle that was continuously covered by continental crust and pre-rift sediment, and where all movements of continental crust were to the west in detachment-bounded slivers.

Sawyer, D. S.; Clark, S. A.

2006-12-01

23

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

24

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

25

North Atlantic Deep Water and Antarctic Bottom Water variability during the last 200 ka recorded in an abyssal sediment core off South Africa  

Microsoft Academic Search

Benthic ?13C values (F. wuellerstorfi), kaolinite\\/chlorite ratios and sortable silt median grain sizes in sediments of a core from the abyssal Agulhas Basin record the varying impact of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) during the last 200ka. The data indicate that NADW influence decreased during glacials and increased during interglacials, in concert with the global

S. Krueger; D. C. Leuschner; W. Ehrmann; G. Schmiedl; A. Mackensen

26

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

USGS Publications Warehouse

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

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

1987-01-01

27

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

NASA Astrophysics Data System (ADS)

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

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

2002-10-01

28

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...

29

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

USGS Publications Warehouse

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.

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

1980-01-01

30

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)

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.

Piller, W. E.; Müllegger, S.

2009-04-01

31

Sediment deformation and plate tectonics in the Gulf of Oman  

Microsoft Academic Search

The continental margin off the Makran coast of Iran and Pakistan is an excellent example of active deformation of sediments at a compressive plate boundary. Seismic reflection profiles across the margin suggest that relatively flat-lying sediments from the Oman abyssal plain are being scraped off the Arabian plate and accreted onto the Eurasian plate in a series of tightly folded

R. S. White; K. Klitgord

1976-01-01

32

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

33

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

USGS Publications Warehouse

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

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

1998-01-01

34

Residence Time of Sediments in Alluvial Plains from U-Th Isotope Analyses: The Ganges River System. (Invited)  

Microsoft Academic Search

As illustrated in recent studies (Granet et al., 2007 ; 2010), the analysis of U-Th disequilibria in sediments collected along rivers allows the estimation of sediment transfer time in alluvial plains. Such an approach requires understanding the secondary processes which modify the U and Th isotopes of the sediments during their transfer within the plain. It also assumes a negligible

F. J. Chabaux; E. Blaes; M. Granet; A. Dosseto; P. Stille; M. Lupker

2010-01-01

35

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

Microsoft Academic Search

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

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

1987-01-01

36

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

37

Late Pleistocene alluvial plain sedimentation in Lower Narmada Valley, Western India: Palaeoenvironmental implications  

NASA Astrophysics Data System (ADS)

Late Pleistocene fluvial sediments that were deposited in a slowly sinking basin are now exposed as 30-50 m high incised vertical cliffs all along the Lower Narmada Valley in western India. The exposed fluvial deposits have been classified into two sediment packages, alluvial fan sediments overlain by alluvial plain sediments. The alluvial plain sequence has not been studied previously. It consists mainly of sands and silts and is dominated by overbank deposits. Occurrence of large scale bedforms in the alluvial plain sequence points to the existence of a large sand bed river in an alluvial plain setting. The major sedimentary facies in stratigraphic order include large channel fills, giant epsilon cross bedded strata, overbank fines occurring in horizontal, massive and undulatory stratified forms associated with crevasse splay and backswamp deposits, and a reddish brown palaeosol overlain by thinly stratified sands and silts at the top of the exposed sediment succession. Large sized channel fills occur at two stratigraphic levels, which are morphologically similar and are indicative of high rates of deposition and avulsion. The large channel fill structures and the giant epsilon cross bedded strata indicate a large single channel river that was consistently 10-15 m deep and about 70-80 m wide even during the dry seasons. These dimensions are larger than those of the present day Narmada River at low discharge levels. The overbank sediments indicate rapid deposition through frequent overbank floods and floodplain aggradation by a laterally shifting river. Available chronologic data suggests that the reddish brown palaeosol correlates with a regional phase of pedogenesis in the alluvial plain of Gujarat prior to the Last Glacial Maximum (LGM). The thinly stratified sands and silts overlying the palaeosol were deposited by a considerably depleted but perennial river during the arid phase of the Last Glacial Maximum. Overall, the alluvial plain sediments of the Lower Narmada valley, particularly those below the palaeosol, have been attributed to a hyper-avulsive large river with low sinuosity whose high discharge levels were determined primarily by a large catchment area further to the east and not by the semiarid climate prevailing in the Gujarat alluvial plain during the upper part of the Late Pleistocene. The study concludes that the Narmada River has maintained a large catchment at least since the last 100 ka, however, the river was characterised by a much bigger channel during much of the Late Pleistocene with discharge levels higher than the present day.

Bhandari, S.; Maurya, D. M.; Chamyal, L. S.

2005-01-01

38

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

PubMed

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

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

2014-10-01

39

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

Microsoft Academic Search

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

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

2000-01-01

40

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

Microsoft Academic Search

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

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

1985-01-01

41

Sediments in marsh ponds of the Gulf Coast Chenier Plain: effects of structural marsh management and salinity  

E-print Network

Sediments in marsh ponds of the Gulf Coast Chenier Plain: effects of structural marsh management: impoundments, marsh sediments, ponds, salinity Abstract Physical characteristics of sediments in coastal marsh ponds (flooded zones of marsh associated with little vegetation) have important ecological consequences

Afton, Alan D.

42

Sediment compaction rates and subsidence in deltaic plains: Numerical constraints and stratigraphic influences  

USGS Publications Warehouse

Natural sediment compaction in deltaic plains influences subsidence rates and the evolution of deltaic morphology. Determining compaction rates requires detailed knowledge of subsurface geotechnical properties and depositional history, neither of which is often readily available. To overcome this lack of knowledge, we numerically forward model the incremental sedimentation and compaction of stochastically generated stratigraphies with geotechnical properties typical of modern depositional environments in the Mississippi River delta plain. Using a Monte Carlo approach, the range of probable compaction rates for stratigraphies with compacted thicknesses ?1. The fastest compacting stratigraphies are composed primarily of peat and bar sand, whereas the slowest compacting stratigraphies are composed of prodelta mud and natural levee deposits. These results suggest that compaction rates can significantly influence vertical and lateral stratigraphic trends during deltaic evolution.

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

2007-01-01

43

Microbial acetogenesis as a source of organic acids in ancient Atlantic Coastal Plain sediments  

USGS Publications Warehouse

Field and laboratory evidence shows that deeply buried (90-888 m) fine-grained sediments of the Atlantic Coastal Plain contain viable acetogenic microorganisms, and that these microorganisms actively produce organic acids. Concentrations of formate, acetate, and propionate in pore waters extracted from fine-grained sediments ranged from 50 ??M to 5 mM and were much higher than in adjacent pore waters associated with sandy sediments (<2 ??M). Laboratory studies showed that asceptically cored fine-grained sediments incubated under a H2 atmosphere produced formate and acetate, and that H14CO-3 was converted to 14C-acetate and 14C-formate over time. An enrichment culture of these acetogenic microorganisms was recovered from one long-term incubation that showed the presence of several morphologically distinct gram-positive, rod-shaped bacteria. These microorganisms were capable of growth under autotrophic (H2 + CO2), heterotrophic (syringate), and mixotrophic (H2 + CO2 + syringate) conditions. These results suggest that microbial acetogenesis, rather than abiotic processes, is the most important organic acid-producing mechanism during low-temperature (???30 ??C) diagenesis of Atlantic Coastal Plain sediments.

Chapelle, F.H.; Bradley, P.M.

1996-01-01

44

Sediment storage and movement on the Southern High Plains of Texas as indicated by beryllium-ten  

Microsoft Academic Search

The Southern High Plains is an area in which most runoff and water-entrained sediment collects and is stored in ephemeral-lake basins, or playas. Ponded playa water recharges the High Plains aquifer. Measured thicknesses and carbon-isotope analyses of playa sediment lead to calculated rates of net playa deposition up to 0.48 meter per 1,000 years, of which 0.09 meter per 1000

W. R. Osterkamp

45

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

PubMed Central

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

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

2009-01-01

46

Abyssal undular vortices in the Eastern Mediterranean basin.  

PubMed

Abyssal temperature and velocity observations performed within the framework of the Neutrino Mediterranean Observatory, a project devoted to constructing a km(3)-scale underwater telescope for the detection of high-energy cosmic neutrinos, demonstrate cross-fertilization between subnuclear physics and experimental oceanography. Here we use data collected south of Sicily in the Ionian abyssal plain of the Eastern Mediterranean (EM) basin to show for the first time that abyssal vortices exist in the EM, at depths exceeding 2,500 m. The eddies consist of chains of near-inertially pulsating mesoscale cyclones/anticyclones. They are embedded in an abyssal current flowing towards North-Northwest. The paucity of existing data does not allow for an unambiguous determination of the vortex origin. A local generation mechanism seems probable, but a remote genesis cannot be excluded a priori. The presence of such eddies adds further complexity to the discussion of structure and evolution of water masses in the EM. PMID:22588296

Rubino, A; Falcini, F; Zanchettin, D; Bouche, V; Salusti, E; Bensi, M; Riccobene, G; De Bonis, G; Masullo, R; Simeone, F; Piattelli, P; Sapienza, P; Russo, S; Platania, G; Sedita, M; Reina, P; Avolio, R; Randazzo, N; Hainbucher, D; Capone, A

2012-01-01

47

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

Microsoft Academic Search

A study of organic carbon mineralization from the Congo continental shelf to the abyssal plain through the Congo submarine channel and Angola Margin was undertaken using in situ measurements of sediment oxygen demand as a tracer of benthic carbon recycling. Two measurement techniques were coupled on a single autonomous platform: in situ benthic chambers and microelectrodes, which provided total and

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

2009-01-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

49

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

50

Residence Time of Sediments in Alluvial Plains from U-Th Isotope Analyses: The Ganges River System. (Invited)  

NASA Astrophysics Data System (ADS)

As illustrated in recent studies (Granet et al., 2007 ; 2010), the analysis of U-Th disequilibria in sediments collected along rivers allows the estimation of sediment transfer time in alluvial plains. Such an approach requires understanding the secondary processes which modify the U and Th isotopes of the sediments during their transfer within the plain. It also assumes a negligible contribution of new and fresh sediments coming from the erosion of the plain substratum during the sedimentary transfer. In order to specify these first results on the Ganges Basin river system, the main Himalayan tributaries of the Ganges were sampled at the exit of the Himalayan range and at the outlet of their watershed just before their confluence with the Ganges. In addition, at several sampling locations, suspended sedimentary load was collected at different depths of the water column. Our new data along with previously published data in (Granet et al., 2007 ; 2010) show that a wide range of variation in Th activity ratios in bedload and suspended sediments for several of these rivers. Such differences probably point to contrasting (geographical, geological, lithological, pedological..) origins of these two types of sediments. Furthermore, bedload and suspended load exhibit very different covariations of U and Th isotope ratios from upstream to downstream. These different trends of variations highlight the occurrence of different transfer histories within the plain for the coarse-grained and fine-grained sediments: 100 ky or more for the bedload sediments from the Himalayan range to the confluence with the Ganges, but much less for the suspended sediments. Variations in the U-Th isotope ratios of suspended sediments recorded for the same sampling location but at different seasons suggest that their transfer time could be as fast as one year. These data therefore confirm the real potential of U and Th isotopes in river sediments to constrain their transfer time within alluvial plain but also their origin. M. Granet et al. (2007) time-scales of sedimentary transfer and weathering processes from U-series nuclides: Clues from the Himalayan rivers, Earth and Planet. Sc. Let., 261, 389-406. Granet M et al. (2010) U-series disequilibria in suspended river sediments and implication for sediment transfer time in alluvial plains : the case of the Himalayan rivers Geochim. Cosmochim. Acta, 74, 2851-2865

Chabaux, F. J.; Blaes, E.; Granet, M.; Dosseto, A.; Stille, P.; France-Lanord, C.; Lupker, M.

2010-12-01

51

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

52

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

NASA Astrophysics Data System (ADS)

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

Hamilton, W. B.

2009-05-01

53

Metasomatism of Abyssal Peridotite  

Microsoft Academic Search

On Leg 153 of the Ocean Drilling Program, cores of typical serpentinized abyssal peridotite were recovered from the western wall of the median valley of the Mid-Atlantic Ridge south of the Kane F.Z. In a sample from this suite, we have found evidence for extensive metasomatism, resulting in large changes in mineral compositions, with only minor changes in modal mineralogy.

K. Ross; D. Elthon

2001-01-01

54

Organochlorine Pesticide Concentrations in Sediment and Amphibian Tissue in Playa Wetlands in the Southern High Plains, USA  

Microsoft Academic Search

Playa wetlands are critical habitat for wildlife in the Southern High Plains (SHP), a region dominated by agriculture. Little\\u000a information on pesticide levels exists for playas, and thus we measured organochlorine pesticide concentrations in sediment\\u000a and amphibians collected from playas in cropland and grassland watersheds. Heptachlor, ?- and ?-BHC, ?-chlordane, and dieldrin\\u000a were detected in sediment and\\/or tissue samples, typically

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

2008-01-01

55

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

56

Assessment of pollution of bottom sediments of water sources of Kuban low plain, Russia  

SciTech Connect

The levels of pollution of bottom sediments (BS) of various water sources (water reservoirs, rivers, rice irrigation system, the Asov and the Black sea bays) of Kuban low plain in Krasnodar region, Russia have been assessed. The content of various pollutants, both widespreading (DDT and its metabolites (DDD, DDE), PCBs, benz(a)pyrenes) and localizing (3,4-dicholaniline (DChA), the main metabolite of herbicide propanide used in rice production) has been analyzed. It has been found chromato-mass spectrometrically that the total content of DDT and its metabolites in BS of various water sources was deviated in limits of 4--41 mkg/kg being on 1--2 order less in comparison with industrial originated pollutants -- PCBs whose content was 51--1,978 mkg/kg and predominantly consisted of tetra-, penta- and hexachlorobiphenyls (> 90%). Benz(a)pyrenes as typical carcinogenic compounds have been founded in limits of 2--16 mkg/kg. The main interest during the monitoring has been connected with an assessment of distribution of propanide and its metabolite DChA in BS of irrigation channels -- Asov sea bay system. It is well known that DChA can be immobilized and conserved long-term in soil. During pre-harvested water removal from rice fields, the runoff of fine dispersed soil particles with sorbed pesticide residues, the transportation by drainage waters and final sedimentation take place. It has been determined that the content of immobilized DChA in BS mas 1,700--3,400 mkg/kg with transit pattern of DChA accumulation in drainage net: the relative part of this metabolite in BS of irrigation channels was 31 % and in BS of the Asov sea bay 69%. The results obtained testify on the presence of heavy pollution by PCBs and DChA in the irrigated agrolandscapes of Kuban low plain.

Galiulin, R.; Bashkin, V. [Russian Academy of Sciences, Puschino (Russian Federation). Inst. Soil Science and Photosynthesis

1995-12-31

57

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

58

U-series disequilibria in suspended river sediments and implication for sediment transfer time in alluvial plains: The case of the Himalayan rivers  

NASA Astrophysics Data System (ADS)

238U- 234U- 230Th radioactive disequilibria were analyzed in suspended sediments (collected at different depths) from the Ganges River and one of its main tributaries: the Narayani-Gandak River. Results associated with bedload sediment data suggest that uranium-series (U-series) disequilibria in river sediments of the Ganges basin vary with grain size and sampling location. The range of observed U-series disequilibria is explained by a mixing model between a coarse-grained sediment end-member, represented by bedload and bank sediments, and a fine-grained end-member that both originate from Himalaya but undergo different transfer histories within the plain. The coarse-grained sediment end-member transits slowly (i.e. >several 100's ky) in the plain whereas the fine-grained sediment end-member is transferred much faster (<20-25 ky), as indicated by the absence of significant variations in Th isotope composition of the fine-grained sediment end-members. These results show that U-series isotopes can be used to quantify the various transfer times of river sediments of different sizes and infer that there can be an order of magnitude of difference, or more, between the transfer time of suspended and bedload sediments. This underlines that a good knowledge of the proportion of suspended vs. bedload sediments transported in the river is required to accurately assess how fast erosion products are transferred in a catchment and how fast a catchment is likely to respond to external forcing factors.

Granet, M.; Chabaux, F.; Stille, P.; Dosseto, A.; France-Lanord, C.; Blaes, E.

2010-05-01

59

Sedimentation model of gravel-dominated alluvial piedmont fan, Ganga Plain, India  

NASA Astrophysics Data System (ADS)

The Piedmont Zone of the Indo-Gangetic Plain contains numerous, laterally coalescing small alluvial fans. The Latest Pleistocene-Holocene 30 km long Gaula Fan can be divided into gravelly proximal fan (0-14 km down-stream), gravel-sand rich mid fan (14-22 km) and sand-mud dominated distal fan (22-30 km). The fan succession is composed of two fan expansion cycles A and B. Separated by an undulatory erosional contact of regional extent, cycle A is characterized by river borne clast-supported gravelly deposits, and the overlying fan expansion cycle B by matrix-supported gravely debris flows. The main process behind fan development has been lateral migration of channels over the fan surface probably due to rapid sedimentation caused by increased sediment supply, and the fluctuating water budget in response to changing climate. The water laid expansion cycle A represents a humid phase. The debris flow deposits of expansion cycle B suggest a dry phase. Approximately between 8 and 3 Ka, cycle B also indicates a phase of tectonic instability in the Siwalik Hills forming the mountain front. The tectonic activity caused incision of rivers into the fan surface, and in turn resulted in reduced fan-building activity. At present the fan surface is accreting by sheet flow processes.

Shukla, U. K.

2009-03-01

60

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)

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.

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

2003-12-01

61

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

PubMed

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

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

2014-02-01

62

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

SciTech Connect

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

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

1980-01-01

63

Heavy Metals in Freshly Deposited Stream Sediments of Rivers Associated with Urbanisation of the Ganga Plain, India  

Microsoft Academic Search

Freshly deposited stream sediments from six urban centres of the Ganga Plain were collected and analysed for heavy metals\\u000a to obtain a general scenery of sediment quality. The concentrations of heavy metals varied within a wide range for Cr (115–817),\\u000a Mn (440–1 750), Fe (28 700–61 100), Co (11.7–29.0), Ni (35–538), Cu (33–1 204), Zn (90–1 974), Pb (14–856) and

Munendra Singh; German Müller; I. B. Singh

2002-01-01

64

Ocean floor sediment as a repository barrier: comparative diffusion data for selected radionuclides in sediments from the Atlantic and Pacific Oceans  

SciTech Connect

Effective diffusion coefficients for selected radionuclides have been measured in ocean floor sediments to provide data for the assessment of barrier effectiveness in subseabed repositories for nuclear waste. The sediments tested include illite-rich and smectite-rich red clays from the mid plate gyre region of the Pacific Ocean, reducing sediment from the continental shelf of the northwest coast of North America, and Atlantic Ocean sediments from the Southern Nares Abyssal Plain and the Great Meteor East region. Results show extremely small effective diffusion coefficients with values less than 10/sup -14/ m/sup 2/s/sup -1/ for plutonium, americium, curium, thorium, and tin. Radionuclides with high diffusion coefficients of approximately 10/sup -10/ m/sup 2/s/sup -/ include the anionic species pertechnetate, TcO/sub 4//sup -/, iodide, I/sup -/, and selenite, SO/sub 3//sup -2/. Uranyl(VI) and neptunyl(V) ions, which are stable in solution, have diffusion coefficients around 10/sup -12/m/sup 2/s/sup -1/. The diffusion behavior of most radionuclides is similar in the oxygenated Pacific sediments and in the anoxic sediments from the Atlantic. An exception is neptunium, which is immobilized by Great Meteor East sediment, but has high mobility in Southern Nares Abyssal Plain sediment. Under stagnant conditions a 30 m thick sediment layer forms an effective geologic barrier isolating radionuclides in a subseabed repository from the biosphere.

Schreiner, F.; Sabau, C.; Friedman, A.; Fried, S.

1986-01-01

65

The influence of vegetation and organic debris on flood-plain sediment dynamics: case study of a low-order stream in the New Forest, England  

NASA Astrophysics Data System (ADS)

The presence of large woody debris (LWD) has important implications for the physical and ecological behaviour of rivers, and these aspects have been researched extensively in recent years. However, this research has so far focused primarily on interactions between LWD and in-channel processes, and the role of LWD in flood-plain genesis is still poorly understood. Established conceptual models of flood-plain evolution are, therefore, lacking because they neglect the complex interaction between water, sediment, and vegetation in systems with accumulations of LWD. This study examines the effect of LWD on patterns of sediment deposition within a small area of forest flood plain along the Highland Water, S. England. In-channel debris dams locally increase the frequency and extent of overbank flows, and the impact of such dam on flood-plain sedimentation was observed. Nine separate flood events were monitored through the exceptionally wet winter of 2000-2001. During each of these, water and sediment fluxes were quantified and correlated with general rates of overbank sedimentation. Flood-plain topography, vegetation, and LWD were surveyed and related to micro- and mesoscale patterns of sediment accretion. The amount of overbank sediment deposition was correlated most closely with flood hydrology and sediment input. The amounts (0-28 kg m -2) and patterns of sediment deposition were both greater and more variable than have been observed on nonforest flood plains. The highly variable pattern of accretion can be explained by the combined effects of topography and organic material present on the surface of the flood plain.

Jeffries, Richard; Darby, Stephen E.; Sear, David A.

2003-03-01

66

Quaternary evolution of ephemeral playa lakes on the Southern High Plains of Texas, USA: cyclic variation in lake level recorded in sediments  

Microsoft Academic Search

Ephemeral playa lakes on the Southern High Plains northeast of Amarillo, Texas, are underlain by more than 10 m of Quaternary lake deposits. Sediments beneath 12 lakes were examined in 76 hollow-stem auger cores and in excavations. Stacked depositional cycles recognized in lake sediments record repeated phases of (1) initial highstand, (2) ephemeral lake, and (3) lake shrinkage and prolonged

Susan D. Hovorka

1997-01-01

67

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

NASA Astrophysics Data System (ADS)

SummaryOld World Bluestems, such as yellow bluestem (Bothriochloa ischaemum), have been seeded extensively in the Southern Great Plains because they are responsive to nitrogen fertilization and allow for higher stocking rates. From 1991 to 2005, we measured the effects of moderately grazing prairie species and heavily grazing fertilized yellow bluestem on runoff, sediment yield, leaf litter cover, and aboveground plant biomass for four adjacent watersheds located at the USDA-ARS Southern Plains Range Research Station in the sub-humid Rolling Red Plains of western Oklahoma. Here we show that factors other than leaf litter cover and biomass determine variation in runoff when leaf litter exceeds 70%. Runoff was related to grazing rate and storm size and inversely related to storm duration. Rainfall thresholds were similar between the moderately grazed prairie watersheds (15 mm) and the heavily grazed yellow bluestem watersheds (18 mm); however, the slope of the rainfall-runoff curve from heavily grazed yellow bluestem (0.242) was steeper than that of moderately grazed prairie (0.087). Slightly higher runoff from heavily grazed yellow bluestem relative to moderately grazed prairie may occur due to compaction of both the leaf litter and topsoil. Sediment yield was low from moderately grazed native prairie and heavily grazed yellow bluestem. Our findings indicate that both treatments assessed appear hydrologically sustainable.

Wine, Michael L.; Zou, Chris B.; Bradford, James A.; Gunter, Stacey A.

2012-07-01

68

GEOSTAR: a GEophysical and Oceanographic STation for Abyssal Research  

NASA Astrophysics Data System (ADS)

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.

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

1998-06-01

69

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

EPA Science Inventory

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

70

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

USGS Publications Warehouse

The Cretaceous and Tertiary sediments that underlie the Inner Coastal Plain of New Jersey contain the arsenic-rich mineral glauconite. Streambed sediments in two Inner Coastal Plain streams (Crosswicks and Raccoon Creeks) that traverse these glauconitic deposits are enriched in arsenic (15–25 mg/kg), and groundwater discharging to the streams contains elevated levels of arsenic (>80 ?g/L at a site on Crosswicks Creek) with arsenite generally the dominant species. Low dissolved oxygen, low or undetectable levels of nitrate and sulfate, detectable sulfide concentrations, and high concentrations of iron and dissolved organic carbon (DOC) in the groundwater indicate that reducing environments are present beneath the streambeds and that microbial activity, fueled by the DOC, is involved in releasing arsenic and iron from the geologic materials. In groundwater with the highest arsenic concentrations at Crosswicks Creek, arsenic respiratory reductase gene (arrA) indicated the presence of arsenic-reducing microbes. From extracted DNA, 16s rRNA gene sequences indicate the microbial community may include arsenic-reducing bacteria that have not yet been described. Once in the stream, iron is oxidized and precipitates as hydroxide coatings on the sediments. Arsenite also is oxidized and co-precipitates with or is sorbed to the iron hydroxides. Consequently, dissolved arsenic concentrations are lower in streamwater than in the groundwater, but the arsenic contributed by groundwater becomes part of the arsenic load in the stream when sediments are suspended during high flow. A strong positive relation between concentrations of arsenic and DOC in the groundwater samples indicates that any process—natural or anthropogenic—that increases the organic carbon concentration in the groundwater could stimulate microbial activity and thus increase the amount of arsenic that is released from the geologic materials.

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

2010-01-01

71

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

72

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

USGS Publications Warehouse

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

Speiran, Gary K.; Aucott, Walter R.

1994-01-01

73

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

74

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

E-print Network

between rivers and lakes. Greater water reten- tion time in reservoirs provides conditions for cycling in the Great Plains (Kansas, USA), an area where little is known about these dominant hydrologic features. We . Multipurpose reservoirs . Nutrient removal . Solids retention Introduction Reservoirs dominate most river

Dodds, Walter

75

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

76

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

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.

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

77

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

NASA Astrophysics Data System (ADS)

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.

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

1990-05-01

78

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

NASA Astrophysics Data System (ADS)

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

Amorosi, Alessandro

2012-12-01

79

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

SciTech Connect

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.

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

80

Long-term change in the abyssal NE Atlantic: The ‘Amperima Event’ revisited  

NASA Astrophysics Data System (ADS)

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.

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

2010-08-01

81

Determination of transfer time for sediments in alluvial plains using 238U-234U-230Th disequilibria: The case of the Ganges river system  

NASA Astrophysics Data System (ADS)

An approach to deriving the transfer time of sediments within alluvial plains by using the variation of the U-series nuclides in sediments collected along rivers is presented in this article and discussed in the light of new data from samples from different locations within the Ganges watershed and its outlet. These data indicate that the upstream-downstream variation of 238U-234U-230Th disequilibria in the sediments, with different variation trends for suspended and coarse-grained sediments, is probably a general feature of all Himalayan rivers flowing across the Indo-Gangetic plain. The data therefore confirm the occurrence of very different transfer times within the plain, depending on the sediments granulometry, with much shorter transfer time for the fine-grained (a few ky or less) than for the coarse-grained sediments (100 ky or more). A new solving approach, using a parallel stochastic Quantum-behaved Particle Swarm Optimization (p-QPSO), has been developed for identifying the unknown parameters of the model necessary for the determination of the transfer time. The data of sediments collected at the Ganges outlet show significant variations of the 234U/230Th activity ratios for the fine-grained sediment end-member collected in 2004 and 2008. Such variations indicate that the fine-grained sediments transit quickly (a year or less) within the plain. The highly variable activity ratios might be the result of quickly changing weathering intensities. Conversely, the U-Th variations observed for the 2004 and 2008 bedload from the Ganges basin cannot result from a short sedimentary transfer time. They probably result from the dredge sampling procedure, which might be influenced by local placer effects controlling the abundance of U and Th carrying minerals. Dredging may not allow the sampling of a representative bedload, hence it may cause an artificial mineralogical and, therefore, an U-Th variability for bedload sediments collected at different periods. At this stage, the transfer time uncertainty induced by this variability is difficult to assess.

Chabaux, François; Blaes, Estelle; Granet, Mathieu; Roupert, Raphaël di Chiara; Stille, Peter

2012-11-01

82

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

NASA Astrophysics Data System (ADS)

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

Hori, Kazuaki; Usami, Shogo; Ueda, Hiroki

2011-05-01

83

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

USGS Publications Warehouse

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

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

2010-01-01

84

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

E-print Network

. One problem with piston cores of soft sediments is that, after recovery, the core dries out and contracts. Generally, the sedi mentary s+ructures in the core are relatively undis+urbed; however, the outer edge of the core is often distorted due... performed on the samples of Core 12 was determination o+ +he percent coarse fraction (percent of the sample of at least very fine sand size), organic and inorganic, of each sample. This was accomplished by drying and weighing each sample prior...

Pollard, Richard Mark

1979-01-01

85

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

Microsoft Academic Search

We analysed the reproductive biology of the asteroid species Styracaster elongatus based on time-series samples from a 5000-m-deep site on the Porcupine Abyssal Plain (N.E. Atlantic). The ratio of males to females, the gonadosomatic index (GI), and pyloric caecum index (PCI) were determined and the results were corroborated by histological examination of the gonads. Fecundity and oocyte-size distribution were determined

Francisco Benítez-Villalobos; Julia P. Díaz-Martínez

2010-01-01

86

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

Microsoft Academic Search

High-resolution profiles (chirp sonar, 2–7kHz) acquired from the Ulleung Basin, East Sea (Sea of Japan) revealed several discrete echo types, suggesting deposits formed mainly by mass flow processes. The Ulleung Basin plain sediments are characterized by turbidite\\/hemipelagic deposits, while slide, slump, and debrite deposits are mainly found in the slope area. Rock fall deposits also appear near the Ulleung Island.

G. Y Kim; D. C Kim

2001-01-01

87

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

SciTech Connect

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

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

1981-02-01

88

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

USGS Publications Warehouse

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

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

2013-01-01

89

Black carbon's long trip to the abyssal plain  

NASA Astrophysics Data System (ADS)

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

Schultz, Colin

2014-08-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

91

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

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).

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

2008-01-01

92

Algal pigments in Southern Ocean abyssal foraminiferans indicate pelagobenthic coupling  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

93

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.

94

Quantifying trace element disequilibria in mantle xenoliths and abyssal peridotites  

E-print Network

Quantifying trace element disequilibria in mantle xenoliths and abyssal peridotites Arnaud Agranier in mantle xenoliths and abyssal peridotites using in situ analytical tools. Even when only mineral cores in mantle xenoliths are closer to equilibrium than those in abyssal peridotites even though mantle xenoliths

Lee, Cin-Ty Aeolus

95

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

NASA Astrophysics Data System (ADS)

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

Rich, J.; Stokes, S.

2011-03-01

96

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

USGS Publications Warehouse

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

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

1999-01-01

97

Comparison of bioturbation rates determined by lead-210 and plutonium in abyssal cores  

E-print Network

are mixed only to 10 or 15 centimeters. Goldberg and Koide (1962) first introduced a model to account for bio- turbation observed in thorium profiles from abyssal cores. Guinasso and Schink (1975) suggested a means to make quantitative estimates... of bioturbation rates by use of tracers such as microtektites and plutonium. Thorium-234, silicon-32, and lead-210 have also been used to determine mixing rates in marine sediments. In this work, bioturbation rates evaluated by lead-210 will be compared...

Stordal, Mary Christine

1981-01-01

98

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

PubMed Central

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

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

2000-01-01

99

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

USGS Publications Warehouse

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

Perkins, Kim S.

2008-01-01

100

U-series disequilibria in suspended river sediments and implication for sediment transfer time in alluvial plains: The case of the Himalayan rivers  

Microsoft Academic Search

238U–234U–230Th radioactive disequilibria were analyzed in suspended sediments (collected at different depths) from the Ganges River and one of its main tributaries: the Narayani–Gandak River. Results associated with bedload sediment data suggest that uranium-series (U-series) disequilibria in river sediments of the Ganges basin vary with grain size and sampling location. The range of observed U-series disequilibria is explained by a

M. Granet; F. Chabaux; P. Stille; A. Dosseto; E. Blaes

2010-01-01

101

Sediment Distribution and Volcanic Activities in the Northern South China Sea Continental Margin  

NASA Astrophysics Data System (ADS)

Multi-channel seismic reflection data and magnetic anomaly data have been used to probe the distribution of slope sediments and igneous bodies in the northern South China Sea (SCS) continental margin and deep sea basin south of the Dongsha Island. We have identified faults, volcanic bodies and basement structures in the study area. Most of the normal faults are distributed in the continental slope and abyssal plain; they were formed in the syn-rift crust when seafloor spreading of the South China Sea was active. From the compiled isopach map, the thicknesses of the continental margin sediments vary between 250~3400 m, and the sediment distribution is largely affected by the development of small basins formed due to normal faulting and volcanic activities. Three areas in the study area where thick sediments are present: the South China Sea abyssal plain; the Pearl River Mouth Basin; and a series of slope basins developed on the continental slope south of the Dongsha Island. Many igneous bodies have been identified from the seismic reflection profiles. We utilize borehole data from ODP Leg 184 to provide age constraints of the sedimentary layers. Then the ages of various igneous activities are proposed based on the contact relationships of igneous bodies with their surrounding sediment layers, respectively. We suggest that the continental margin of the northern South China Sea is a "volcanic rifted margin", the high velocity materials in the lower crust reported from seismic refraction studies were formed during the South China Sea expansion period through underplating processes, and distributed beneath the continent slope along the whole northern South China Sea continental margin. After the seafloor spreading ceased, another magmatic event occurred in the eastern portion of the continental margin that thickened high velocity material of the lower crust south of the Dongsha Island.

Liu, C.; Chuang, S.; Tsai, Y.; Hsu, H.

2011-12-01

102

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)

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.

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

1977-01-01

103

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

PubMed

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

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

2014-01-01

104

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

PubMed Central

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

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

2014-01-01

105

Cooling and ventilating the Abyssal Ocean  

NASA Astrophysics Data System (ADS)

The abyssal ocean is filled with cold, dense waters that sink along the Antarctic continental slope and overflow sills that lie south of the Nordic Seas. Recent integrations of chlorofluorocarbon-11 (CFC) measurements are similar in Antarctic Bottom Water (AABW) and in lower North Atlantic Deep Water (NADW), but Antarctic inputs are ? 2°C colder than their northern counterparts. This indicates comparable ventilation rates from both polar regions, and accounts for the Southern Ocean dominance over abyssal cooling. The decadal CFC-based estimates of recent ventilation are consistent with other hydrographic observations and with longer-term radiocarbon data, but not with hypotheses of a 20th-century slowdown in the rate of AABW formation. Significant variability is not precluded by the available ocean measurements, however, and interannual to decadal changes are increasingly evident at high latitudes.

Orsi, Alejandro H.; Jacobs, Stanley S.; Gordon, Arnold L.; Visbeck, Martin

106

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

107

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...

108

Paleogene Submarine Fan Depocenters of the Abyssal Gulf of Mexico: Paleogeography, Provenance, and Tectonic Implications  

NASA Astrophysics Data System (ADS)

In the abyssal Gulf of Mexico (AGOM) seven major Paleogene submarine fan depocenters are identified on regional 2D and local 3D seismic data tied to wells on adjacent structural belts. Source directions are inferred from (1) location of isopach maxima relative to paleo-margins; (2) seismic facies; (3) channel orientations on 3D seismic; and (4) sandstone composition, particularly that of lithic grains. Paleogene fan depocenters in the southwestern and southeastern AGOM are associated with relatively narrow and high-gradient (several degrees), high-bypass continental margins adjacent to orogenic belts. The (1) Chicontepec Fan (Paleocene, syn-Laramide) and (2) Post-Chicontepec Fan (Eocene-Oligocene) had westerly sources in east-central Mexico. Sandstone lithic modes are predominantly carbonate in the Chicontepec and mixed volcanic-carbonate in the Post-Chicontepec. The Laramide-age (3) Straits of Florida depocenter (Paleocene-Eocene?) was sourced from Cuba to the southeast; sandstone composition is unknown. In contrast, Paleogene fan depocenters in the northwestern AGOM are associated with large deltaic depocenters, low- to moderate-bypass margins, and very low-gradient (1 degree or less) continental slopes. The Wilcox fans (Upper Paleocene-Lower Eocene, syn-Laramide) had a dominant source direction to the northwest, but can be separated into (4) Lower Wilcox (northerly source), (5) Middle Wilcox (westerly source in NE Mexico), and (6) Upper Wilcox (westerly to northwesterly source). Like the Upper Wilcox, the (7) Frio fan depocenter (Middle Oligocene) had a westerly source associated with a large deltaic depocenter. Sandstone lithic modes of Wilcox fans range from metamorphic to mixed metamorphic-volcanic, clays are predominantly illite, and polygonal faulting is absent. Sandstones of the overlying Post-Chicontepec and Frio fans are mixed volcanic-carbonate, clays are smectite-rich, and polygonal faulting is abundant. Six of these depocenters attain maximum thicknesses of less than 1 km and can be related either to Laramide- age orogenesis (Chicontepec, Wilcox, Straits of Florida) or mid-Cenozoic arc volcanism (Frio). The Post- Chicontepec depocenter is anomalously thick, locally exceeding 3 km, and represents one of the major sediment influxes of AGOM history, attributed here to post-orogenic uplift of a large region extending possibly from the Mexican coastal plain to the Sierra Madre Occidental.

Winker, C. D.

2008-05-01

109

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.

110

‘Live’ benthic foraminifera at an abyssal site in the equatorial Pacific nodule province: Abundance, diversity and taxonomic composition  

Microsoft Academic Search

Replicate sediment samples were obtained from 3 closely spaced stations in the Kaplan East (KE) area of the abyssal eastern Equatorial Pacific (?15°N, 119°W; ?4100m water depth), just below the carbonate compensation depth. At each site, 2 (Stns 827, 838) or 3 (Stn 824) complete cores (57mm i.d.) were subsampled using 2–3 cut-off syringes of 6.6cm3 cross-sectional area. The 0–1cm

Fusae Nozawa; Hiroshi Kitazato; Masashi Tsuchiya; Andrew J. Gooday

2006-01-01

111

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

NASA Astrophysics Data System (ADS)

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.

Baltzer, Frédéric; Purser, Bruce H.

1990-05-01

112

Comparison of velocity--depth characteristics in western North Atlantic and Norwegian Sea sediments  

SciTech Connect

The western North Atlantic was divided into 17 sediment provinces, and sonobuoy sound velocities were compiled from each region. The regions were analyzed statistically to develop least-squares regressions of the form V=V/sub 0/+Kt, where t is one-way vertical travel time. Eight regions provided velocity functions, four were inadequately sampled, and five provided mean values from single-layer solutions in sediment bodies < 1 km thick. The eight values of K are grouped very closely about a mean of 1.14 +- 0.17 km/s/sup 2/. By contrast, 12 regions from the Norwegian Sea yield 10 values of K that range from 0.6 to 2.5 km/s/sup 2/. The three highest values (>2.1 km/s/sup 2/) were measured in regions uniquely floored by thick Mesozoic epicontinental sediments that predate the breakup of the Norwegian Sea. These older sediment bodies account for most of the regional heterogeneity in the velocity functions of the Norwegian Sea. About one fifth the surface area of the North Atlantic is floored by sediments thinner than 200 m. Within these vast areas, the sound velocity of acoustic basement is a crucial factor in developing low-frequency propagation models. A contour map of basement refraction velocities in the North Atlantic shows a rough increase from 3.5 km/s near the mid-Atlantic ridge to 5.0 km/s at variable distance from the ridge. The region in which geoacoustic models are most sensitive to basement velocity is between 15/sup 0/ and 30/sup 0/N, where sediment cover thinner than 200 m accounts for about half the surface area. Interval velocities from the thinner deposits of pelagic sediment seaward of the abyssal plains, are greater by about 200 m/s than those from the continental rise and abyssal plains at comparable depths of overburden. The difference suggests that sound velocities in the predominantly pelagic sediments increase more rapidly with depth than they do in the silty hemipelagic clays and turbidites nearer the continents.

Houtz, R.E.

1980-11-01

113

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

PubMed Central

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

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

2012-01-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

115

Internal tide generation by abyssal hills using analytical theory  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

117

Plumbing the abyss: black ring microstates  

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

118

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

SciTech Connect

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

Stevenson, A.J.; Bruns, T.R.; Carlson, P.R. (Geological Survey, Palo Alto, CA (USA)); Dobson, M.R. (Univ. of College of Wales, Aberystwyth (Wales))

1990-06-01

119

Ontogeny of a flood plain  

USGS Publications Warehouse

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

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

1999-01-01

120

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

NASA Astrophysics Data System (ADS)

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.

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

121

2005 Nature Publishing Group In situ Os isotopes in abyssal peridotites bridge the  

E-print Network

© 2005 Nature Publishing Group In situ Os isotopes in abyssal peridotites bridge the isotopic gap Abyssal peridotites are assumed to represent the mantle residue of mid-ocean-ridge basalts (MORBs). However, the osmium isotopic compositions of abyssal peridotites and MORB do not appear

Demouchy, Sylvie

122

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

NASA Astrophysics Data System (ADS)

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

Hegewald, A.; Jokat, W.

2011-12-01

123

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

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.

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

2012-01-01

124

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

USGS Publications Warehouse

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.

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

2008-01-01

125

Abyssal Canyons and Mixing by Low-Frequency Flow  

Microsoft Academic Search

The role canyons play in abyssal mixing is discussed, with a focus on the issue of low-frequency flow over sills and associated overturning instability as opposed to tidally generated mixing. Flow through several deep canyons on the mid-ocean ridge is reviewed and some global consequences are discussed.

K. G. Speer; A. M. Thurnherr

126

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.

127

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

USGS Publications Warehouse

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

Nelson, C.H.

1990-01-01

128

Plain Language  

Cancer.gov

The Plain Writing Act of 2010 requires federal agencies to write "clear Government communication that the public can understand and use." President Obama also emphasized the importance of establishing "a system of transparency, public participation, and collaboration" in his January 21, 2009, Memorandum on Transparency and Open Government.

129

Feasibility of disposal of high-level radioactive wastes into the seabed: Review of laboratory investigations of radionuclide migration through deep-sea sediments  

SciTech Connect

The Sediment Barrier Task Group (SBTG) coordinated laboratory studies of radionuclide migration through deep-sea sediments by investigators in six countries over a period of 12 years. The objectives of these studies were to evaluate the barrier properties of a variety of deep- sea sediments from study locations characterized by the Site Assessment Task Group (SATG), and to obtain site-specific data for use by the Radiological Assessment Task Group (RATG) in models of radionuclide transport through the sediments at the Great Meteor East (GME) and Southern Nares Abyssal Plain (SNAP) study locations in the North Atlantic Ocean. This volume presents a review of these laboratory investigations and the results obtained from them. Although the SBTG also participated in numerous geochemical investigations at the study locations characterized by the SATG, these field studies are not discussed here. For the convenience of the reader, however, this volume contains a brief description of the sediments from GME and SNAP, and the Mid-Plate Mid-Gyre I (MPG I) study location in the North Pacific Ocean. 130 refs., 48 figs., 11 tabs.

Brush, L.H.

1988-08-01

130

Holocene Climate in the Northern Great Plains Inferred from Sediment Stratigraphy, Stable Isotopes, Carbonate Geochemistry, Diatoms, and Pollen at Moon Lake, North Dakota  

Microsoft Academic Search

Seismic stratigraphy, sedimentary facies, pollen stratigraphy, diatom-inferred salinity, stable isotope (?18O and ?13C), and chemical composition (Sr\\/Ca and Mg\\/Ca) of authigenic carbonates from Moon Lake cores provide a congruent Holocene record of effective moisture for the eastern Northern Great Plains. Between 11,700 and 950014C yr B.P., the climate was cool and moist. A gradual decrease in effective moisture occurred between

Blas L. Valero-Garcés; Kathleen R. Laird; Sherilyn C. Fritz; Kerry Kelts; Emi Ito; Eric C. Grimm

1997-01-01

131

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

NASA Astrophysics Data System (ADS)

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

Kalm, Volli; Gorlach, Aleksandr

2014-02-01

132

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

PubMed

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

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

1993-12-17

133

Abyssal recipes II: energetics of tidal and wind mixing  

Microsoft Academic Search

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

Walter Munk; Carl Wunsch

1998-01-01

134

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

USGS Publications Warehouse

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.

Crusius, John; Thomson, John

2003-01-01

135

Sexual biochemistry in the deep sea – the link between phytoplankton and abyssal holothurians.  

E-print Network

??Holothurians play an important role in carbon cycling. They dominate the abyssal oceanic megabenthos, reworking large amounts of organic matter. Holothurians require essential organic nutrients,… (more)

Smith, Tania

2008-01-01

136

Meiofauna communities along an abyssal depth gradient in the Drake Passage  

NASA Astrophysics Data System (ADS)

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

Gutzmann, E.; Martínez Arbizu, P.; Rose, A.; Veit-Köhler, G.

2004-07-01

137

Plains Traveler  

NASA Technical Reports Server (NTRS)

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

2006-01-01

138

Streaked Plain  

NASA Technical Reports Server (NTRS)

4 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark streaks created by dust devils on a plain southwest of Hellas Planitia. Based on the width and the length of individual streaks in this scene, it is clear that not all dust devils are created equally.

Location near: 55.8oS, 317.5oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

2006-01-01

139

The Late Pliocene Eltanin Impact: Documentation From Sediment Core Analyses  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

140

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

PubMed

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

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

2000-10-16

141

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

NASA Astrophysics Data System (ADS)

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.

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

1988-06-01

142

PhD position in igneous petrology Marie-Curie Initial Training Network ABYSS (ESR3)  

E-print Network

no later than November 1, 2014. It is funded by ABYSS, an EU Framework 7 Marie Curie Integrated Training the private sector; it proposes 12 PhDs (ESR) positions and 3 postdoctoral fellowships (ER). Recruitment) and Benoit Ildefonse (ildefonse@um2.fr) 1 ABYSS has received funding from the People programme (Marie Curie

Demouchy, Sylvie

143

PhD position in Experimental Geochemistry MarieCurie Initial Training Network ABYSS (ESR10)  

E-print Network

, 2014. It is funded by ABYSS, an EU Framework 7 Marie Curie Integrated Training Network1 starting; it proposes 12 PhDs (ESR) positions and 3 postdoctoral fellowships (ER). Recruitment.garrido@csic.es) 1 ABYSS has received funding from the People programme (Marie Curie Actions) of the European Union

Demouchy, Sylvie

144

Minor and trace element abundance of Cr-spinel from forearc mantle and abyssal peridotites  

E-print Network

Minor and trace element abundance of Cr-spinel from forearc mantle and abyssal peridotites 1 1 2. Geological Survey of Canada, Ottawa. Introduction We studied chemical compositions of Cr-spinel). To characterize the spinel compositions from forearc mantle peridotites, spinel in abyssal peridotites from

145

Tectonic types of oceanic abyssal basins and related potentially economic fields of ferromanganese nodules  

Microsoft Academic Search

Tectonic typification of the abyssal basins of the Atlantic, Indian, and Pacific oceans is proposed. Six types of basins are recognized: perispreading, pericontinental, central thalassogenic, intermontane abyssal, interfault, and thalassosyneclise. The tectonic diversity of the basins and their systems reflects significant regional tectono-geodynamic features of the oceanic lithosphere. Basins of the first type are inherent to the Atlantic Ocean; of

Yu. M. Pushcharovsky

2008-01-01

146

A Deep Cabled Observatory: Biology and Physics in the Abyss  

NASA Astrophysics Data System (ADS)

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

Howe, Bruce M.

2014-11-01

147

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

USGS Publications Warehouse

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

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

1987-01-01

148

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

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)

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

149

Sedimentation in Canada Basin, Western Arctic  

NASA Astrophysics Data System (ADS)

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.

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

150

Stratigraphy of the Martian northern plains  

NASA Technical Reports Server (NTRS)

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

Tanaka, K. L.

1993-01-01

151

Morphology and Late Quaternary sedimentation in the Gulf of Oman Basin  

NASA Astrophysics Data System (ADS)

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

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

152

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

153

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

154

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

E-print Network

The results presented in this paper demonstrate that the geothermal heat flux (GHF) from the solid Earth into the ocean plays a non-negligible role in determining both abyssal stratification and circulation strength. Based ...

Mashayek, A.

155

190Pt– 186Os and 187Re– 187Os systematics of abyssal peridotites  

Microsoft Academic Search

Abyssal peridotites are normally thought to be residues of melting of the mid-ocean ridge basalt (MORB) source and are presumably a record of processes affecting the upper mantle. Samples from a single section of abyssal peridotite from the Kane Transform area in the Atlantic Ocean were examined for 190Pt–186Os and 187Re–187Os systematics. They have uniform 186Os\\/188Os ratios with a mean

Alan D Brandon; Jonathan E Snow; Richard J Walker; John W Morgan; Timothy D Mock

2000-01-01

156

Tectonic types of oceanic abyssal basins and related potentially economic fields of ferromanganese nodules  

Microsoft Academic Search

Tectonic typification of the abyssal basins of the Atlantic, Indian, and Pacific oceans is proposed. Six types of basins are\\u000a recognized: perispreading, pericontinental, central thalassogenic, intermontane abyssal, interfault, and thalassosyneclise.\\u000a The tectonic diversity of the basins and their systems reflects significant regional tectono-geodynamic features of the oceanic\\u000a lithosphere. Basins of the first type are inherent to the Atlantic Ocean; of

Yu. M. Pushcharovsky

2008-01-01

157

Elemental and major biochemical changes across oxidation fronts in N. E. Atlantic sediments  

SciTech Connect

Fine-grained turbidites from the Madeira Abyssal Plain often contain surficial oxidation fronts in which molecular oxygen has burned down through sediments containing organic substances that previously coexisted with porewater sulfate for thousands of years. These deposits provide an opportunity to establish the extent and selectivity of slow oxic degradation without the need for conditions of long-term steady state deposition without mixing. The authors analyzed the elemental and major biochemical compositions of oxidized and unreacted sediments from f-turbidite sequences recovered at depths of 7--9 m from two separate MAP cores. In both turbidites, one sample from the reddish upper layer was compared to two deeper unreacted sediments. The unoxidized deeper sequences of both turbidites contained 0.93--1.02 wt% organic carbon and 0.05--0.07 wt% total nitrogen, with C/N ratios near 20. The oxidized upper horizons of both sequences contained approximately 1/5th the organic carbon and total nitrogen with C/N ratios of about 10. All samples gave extremely low yields of lignin phenols and comparable yields of total aldoses and total amino acids, indicated little land-derived organic matter and nonselective oxic degradation of these major biochemical classes. Reactivity differences among individual aldoses and protein amino acids were also relatively subtle and in non instance clearly indicated in situ formation. The most outstanding compositional differences were that the oxidized horizons yielded decreased percentages of total aldose and amino acid carbon, decreased percentages of amino acid nitrogen and elevated percentages of nonprotein amino acids. Comparison of these compositional trends to those observed in other marine environments suggests that the three previous parameters broadly reflect the diagenetic state of sedimentary organic mixtures.

Cowie, G.L. (Univ. de Nantes (France). Lab. Biologie Marine); Hedges, J.I. (Univ. of Washington, Seattle, WA (United States). School of Oceanography); Prahl, F.G. (Oregon State Univ., Corvallis, OR (United States). Coll. of Oceanography); Lange, G.J. de (Univ. of Utrecht (Netherlands). Dept. of Geochemistry)

1992-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

159

Z .Earth and Planetary Science Letters 152 1997 251265 The origin of abyssal peridotites: a new perspective  

E-print Network

Z .Earth and Planetary Science Letters 152 1997 251­265 The origin of abyssal peridotites: a new peridotites have been interpreted to be residues of mantle melting beneath ocean ridges. Recent experimental that abyssal peridotites are not purely melting residues. Their modal proportions and whole-rock compositions

Langmuir, Charles H.

160

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...

161

Postdoctoral fellowship in ore-deposit geology/igneous geochemistry Marie-Curie Initial Training Network ABYSS (ER1)  

E-print Network

Postdoctoral fellowship in ore-deposit geology/igneous geochemistry Marie-Curie Initial Training Network ABYSS (ER1) Training network on reactive geological systems from the mantle to the abyssal sub-Cu-PGE deposits Requirements: Candidates must hold PhD in geology/geochemistry This fellowship is for a period

Demouchy, Sylvie

162

Phylogenetic identification of marine bacteria isolated from deep-sea sediments of the eastern South Atlantic Ocean.  

PubMed

The deep-sea environments of the South Atlantic Ocean are less studied in comparison to the North Atlantic and Pacific Oceans. With the aim of identifying the deep-sea bacteria in this less known ocean, 70 strains were isolated from eight sediment samples (depth range between 1905 to 5560 m) collected in the eastern part of the South Atlantic, from the equatorial region to the Cape Abyssal Plain, using three different culture media. The strains were classified into three phylogenetic groups, Gammaproteobacteria, Firmicutes and Actinobacteria, by the analysis of 16s rRNA gene sequences. Gammaproteobacteria and Firmicutes were the most frequently identified groups, with Halomonas the most frequent genus among the strains. Microorganisms belonging to Firmicutes were the only ones observed in all samples. Sixteen of the 41 identified operational taxonomic units probably represent new species. The presence of potentially new species reinforces the need for new studies in the deep-sea environments of the South Atlantic. PMID:23565357

da Silva, Marcus Adonai Castro; Cavalett, Angélica; Spinner, Ananda; Rosa, Daniele Cristina; Jasper, Regina Beltrame; Quecine, Maria Carolina; Bonatelli, Maria Letícia; Pizzirani-Kleiner, Aline; Corção, Gertrudes; Lima, André Oliveira de Souza

2013-12-01

163

The Plains City Story  

ERIC Educational Resources Information Center

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

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

2006-01-01

164

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

USGS Publications Warehouse

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.

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

1996-01-01

165

Depositional environments of late glacial to Holocene sediments on the deep water levees of Setúbal and Nazaré Canyons, offshore Portugal: preliminary results  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

166

PhD position in Experimental Geosciences MarieCurie Initial Training Network ABYSS (ESR8)  

E-print Network

starting no later than November 1, 2014. It is funded by ABYSS, an EU Framework 7 Marie Curie Integrated partners from the private sector; it proposes 12 PhDs (ESR) positions and 3 postdoctoral fellowships (ER funding from the People programme (Marie Curie Actions) of the European Union's Seventh Framework

Demouchy, Sylvie

167

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

Microsoft Academic Search

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.

Akiho Miyashiro; Fumiko Shido; Maurice Ewing

1970-01-01

168

Internal tide generation by abyssal hills using analytical theory Angelique Melet,1  

E-print Network

Internal tide generation by abyssal hills using analytical theory Angelique Melet,1 Maxim 2013. [1] Internal tide driven mixing plays a key role in sustaining the deep ocean stratification and meridional overturning circulation. Internal tides can be generated by topographic horizontal scales ranging

Nycander, Jonas

169

Os isotopic systematics of the MORB mantle: results from altered abyssal peridotites  

Microsoft Academic Search

Abyssal peridotites are fragments of the oceanic upper mantle. Previous studies have indicated that their Os isotopic compositions span a wide range, including values more radiogenic than most estimates of the average bulk Earth 187Os188Os ratio. This is difficult to reconcile with their derivation as residues of MORB partial melting. We present results that suggest that some of this variation,

Jonathan E. Snow; Laurie Reisberg

1995-01-01

170

Eddy-induced variability in Southern Ocean abyssal mixing on climatic timescales  

NASA Astrophysics Data System (ADS)

The Southern Ocean plays a pivotal role in the global ocean circulation and climate. There, the deep water masses of the world ocean upwell to the surface and subsequently sink to intermediate and abyssal depths, forming two overturning cells that exchange substantial quantities of heat and carbon with the atmosphere. The sensitivity of the upper cell to climatic changes in forcing is relatively well established. However, little is known about how the lower cell responds, and in particular whether small-scale mixing in the abyssal Southern Ocean, an important controlling process of the lower cell, is influenced by atmospheric forcing. Here, we present observational evidence that relates changes in abyssal mixing to oceanic eddy variability on timescales of months to decades. Observational estimates of mixing rates, obtained along a repeat hydrographic transect across Drake Passage, are shown to be dependent on local oceanic eddy energy, derived from moored current meter and altimetric measurements. As the intensity of the regional eddy field is regulated by the Southern Hemisphere westerly winds, our findings suggest that Southern Ocean abyssal mixing and overturning are sensitive to climatic perturbations in wind forcing.

Sheen, K. L.; Naveira Garabato, A. C.; Brearley, J. A.; Meredith, M. P.; Polzin, K. L.; Smeed, D. A.; Forryan, A.; King, B. A.; Sallée, J.-B.; St. Laurent, L.; Thurnherr, A. M.; Toole, J. M.; Waterman, S. N.; Watson, A. J.

2014-08-01

171

Adaptation to the rarefied air of abysses and caves.A laboratory study  

Microsoft Academic Search

Introduction and aims: The atmosphere in the abysses of the mountains of Garraf (Barcelona) have lower oxygen levels and higher CO2 concentrations with respect to normality. To evaluate the risk of speleological exploration in this area, we studied 19 cavers (14 men and 5 women) while performing controlled exercise in a hypercapnic, hypoxic and normobaric atmosphere (15.2 ± 0.8% of

Ignasi De Yzaguirre i Maura; Jaume Escoda i Mora; Joan Bosch Cornet; Jose Antonio Gutiérrez Rincón; Diego Dulanto Zabala; Ramón Segura Cardona

2008-01-01

172

The origin of abyssal peridotites: a reinterpretation of constraints based on primary bulk compositions  

Microsoft Academic Search

We calculated primary bulk compositions for a global suite of abyssal peridotites using primary mineral modes and either analyzed or calculated phase compositions. The latter were obtained through correlations between reported mineral compositions and modal olivine contents. Both the modal data and the mineral compositions were averaged by dredge site, drill hole, or fracture zone (FZ) depending on the amount

Michael B. Baker; John R. Beckett

1999-01-01

173

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

Microsoft Academic Search

The oceanic abyss (depths greater than 3000 m), one of the largest environments on the planet, is characterized by absence of solar light, high pressures and remoteness from surface food supply necessitating special molecular, physiological, behavioural and ecological adaptations of organisms that live there. Sampling by trawl, baited hooks and cameras we show that the Chondrichthyes (sharks, rays and chimaeras)

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

2006-01-01

174

Warming and Freshening in the Abyssal Southeastern Indian Ocean* GREGORY C. JOHNSON  

E-print Network

Warming and Freshening in the Abyssal Southeastern Indian Ocean* GREGORY C. JOHNSON NOAA. Johnson, NOAA/ Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Bldg. 3, Seattle, WA 98115. E-mail: gregory.c.johnson@noaa.gov 15 OCTOBER 2008 J O H N S O N E T A L . 5351 DOI: 10

Johnson, Gregory C.

175

Salt Plains Microbial Observatory  

NSDL National Science Digital Library

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.

Buchheim, Mark; University Of Tulsa, Biological S.

176

The Plains of Venus  

NASA Astrophysics Data System (ADS)

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.

Sharpton, V. L.

2013-12-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

178

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

E-print Network

region of preserved seafloor that directly records the history of Early Cretaceous seafloor spreading between India and Australia. However, despite the clear importance of the seafloor spreading historyEarly India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies

Granot, Roi

179

Phosphorus in drainage waters of the Atlantic Coastal Plain  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

180

Hummocky and Smooth Plains  

NASA Technical Reports Server (NTRS)

This image (FDS 108), acquired during the spacecraft's first encounter with Mercury, is located about 500 km east of the Caloris basin. The image shows hummocky plains interpreted as Caloris ejecta in the upper half of the picture and smooth plains in the lower half. Elongated hummocks and troughs aligned concentrically to the rim of the Caloris are well developed in the upper right part of the picture. A part of the pre-Caloris basin (240-km in diameter) seen in the lower part of the picture is filled with smooth plains. At the western margin of this basin is a west facing scarp that forms the boundary between hummocky plains (west) and smooth plains (east).

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

1974-01-01

181

Smooth Volcanic Plains  

NASA Technical Reports Server (NTRS)

The plains filling this 440 kilometer basin centered at 15 degrees S, 149 degrees W (partially shown in the lower right of the picture) are uniformly brighter and slightly redder than the surrounding cratered terrain [Hapke et al., 1975]. Also, notice the flooded craters on the floor of the basin and that the terrain exterior to the basin is much more heavily cratered than the plains on the interior. These relationships indicate the smooth plains filling this basin are volcanic.

This image (FDS 125) was taken during the spacecraft's first encounter with Mercury.

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

1974-01-01

182

Petrological review of the oceanic lithospheric mantle: implications from mantle xenoliths and abyssal peridotite  

NASA Astrophysics Data System (ADS)

Peridotite xenoliths included in oceanic volcanoes show wide variation of the degree of melting. Lherzolite is the dominant rock type of mantle xenoliths from oceanic setting, while some samples are harzburgite with low concentration of the rare earth elements (HREE) with comparable degree to that of the forearc peridotite as well as some abyssal peridotite. Compositional variation of the mantle xenoliths in the ocean settings is wider than that of the abyssal peridotite sampled by dredge, dive or ocean drilling. Resent studies of such samples show complex processes in the upper mantle beneath mid-ocean ridges and in the oceanic lithosphere. Some peridotite xenoliths show dehydration texture of serpentinite. The samples show geotherms and melting conditions in the oceanic lithosphere when it was trapped or exhumed on the seafloor. The compilation data of recent studies on such peridotite samples from the oceanic lithosphere show the evolution history of the different depths in the oceanic lithosphere.

Abe, N.

2012-12-01

183

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

NASA Astrophysics Data System (ADS)

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.

Jörger, K. M.; Schrödl, M.; Schwabe, E.; Würzberg, L.

2014-10-01

184

Orbit Accuracy Requirement for ABYSS: The Space Station Radar Altimeter to Map Global Bathymetry  

Microsoft Academic Search

The Altimetric Bathymetry from Surface Slopes (ABYSS), which is the proposed science payload on the International Space Station (ISS), is a Johns Hopkins University Applied Physics Laboratory-developed flight-proved delay-Doppler phase-monopulse radar altimeter capable of measuring ocean surface slope in the 6-200-km half-wavelength frequency band range with an accuracy of 0.5 mu rad , with autonomous gimbal control to compensate for

C. K. Shum; P. A. M. Abusali; Chung-Yen Kuo; Hyongki Lee; James Ogle; R. Keith Raney; John C. Ries; Walter H. F. Smith; Drazen Svehla; Changyin Zhao

2009-01-01

185

Plains Tectonics on Venus  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

186

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...

187

From winds to eddies to diapycnal mixing of the deep ocean: the abyssal meridional overturning circulation driven by the surface wind-stress.  

E-print Network

??Previous numerical and theoretical results based on constant diapycnal diffusivity suggested the abyssal meridional overturning circulation (MOC) should weaken as winds over the Southern Ocean… (more)

Stanley, Geoffrey John

2013-01-01

188

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)...

189

Geohydrologic framework of the coastal plain aquifers of South Carolina  

USGS Publications Warehouse

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

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

1987-01-01

190

Wet coastal plain tundra  

SciTech Connect

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

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

1980-01-01

191

Devil-Streaked Plain  

NASA Technical Reports Server (NTRS)

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

2006-01-01

192

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

193

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

NASA Astrophysics Data System (ADS)

A study of organic carbon mineralization from the Congo continental shelf to the abyssal plain through the Congo submarine channel and Angola Margin was undertaken using in situ measurements of sediment oxygen demand as a tracer of benthic carbon recycling. Two measurement techniques were coupled on a single autonomous platform: in situ benthic chambers and microelectrodes, which provided total and diffusive oxygen uptake as well as oxygen microdistributions in porewaters. In addition, sediment trap fluxes, sediment composition (Org-C, Tot-N, CaCO 3, porosity) and radionuclide profiles provided measurements of, respectively input fluxes and burial rate of organic and inorganic compounds. The in situ results show that the oxygen consumption on this margin close to the Congo River is high with values of total oxygen uptake (TOU) of 4±0.6, 3.6±0.5 mmol m -2 d -1 at 1300 and 3100 m depth, respectively, and between 1.9±0.3 and 2.4±0.2 mmol m -2 d -1 at 4000 m depth. Diffusive oxygen uptakes (DOU) were 2.8±1.1, 2.3±0.8, 0.8±0.3 and 1.2±0.1 mmol m -2 d -1, respectively at the same depths. The magnitude of the oxygen demands on the slope is correlated with water depth but is not correlated with the proximity of the submarine channel-levee system, which indicates that cross-slope transport processes are active over the entire margin. Comparison of the vertical flux of organic carbon with its mineralization and burial reveal that this lateral input is very important since the sum of recycling and burial in the sediments is 5-8 times larger than the vertical flux recorded in traps. Transfer of material from the Congo River occurs through turbidity currents channelled in the Congo valley, which are subsequently deposited in the Lobe zone in the Congo fan below 4800 m. Ship board measurements of oxygen profiles indicate large mineralization rates of organic carbon in this zone, which agrees with the high organic carbon content (3%) and the large sedimentation rate (19 mm y -1) found on this site. The Lobe region could receive as high as 19 mol C m -2 y -1, 1/3 being mineralized and 2/3 being buried and could constitute the largest depocenter of organic carbon in the South Atlantic.

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

2009-12-01

194

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

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

195

Calcareous sponges from abyssal and bathyal depths in the Weddell Sea, Antarctica  

NASA Astrophysics Data System (ADS)

Calcareous sponges have traditionally been regarded as shallow-water organisms, a persistent myth created by Hentschel (1925), partly supported by the problematic question of calcareous skeletal secretion under high partial CO 2-pressure below the CCD in the abyss. Up to now, only few species world-wide of the sponge class Calcarea have been described from depths below 2000 m. By far, the largest number of records of Antarctic Calcarea is known from shelf areas between 50 and 400 m depth. They have only been sporadically recorded on the lower shelf and the upper slope from depths between 570 and 850 m. From abyssal depths in the Antarctic there are no previous records of calcareous sponges. It was therefore a big surprise when the first true deep-sea Calcarea from the Antarctic were collected at depths between 1120 and 4400 m during the ANDEEP I, II and III expeditions ( Janussen et al., 2006). To date, five calcareous sponge species have been found, including three species new to science. The three new species belong to the genera Ascaltis, Clathrina and Leucetta. Although calcareous sponges are rare in the Antarctic deep sea, they seem to constitute a constant component of the fauna. Antarctic Calcarea shows all the characteristics of need for revision and further collection and investigation. Still, many new species are likely to be discovered in the Antarctic deep-sea.

Rapp, Hans Tore; Janussen, Dorte; Tendal, Ole S.

2011-03-01

196

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

PubMed

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

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

2006-06-01

197

Causes and Consequences of Mantle Heterogeneity From Observations of Abyssal Peridotites (Invited)  

NASA Astrophysics Data System (ADS)

Melting at mid-ocean ridges is often assumed to occur in asthenospheric mantle of homogeneous composition and result in depleted lithospheric mantle (e.g., Johnson et al., 1990). However, recent observations suggest that areas of the oceanic upper mantle are heterogeneous chemically and/or lithologically. We present a global compilation of abyssal peridotite data that reveals much larger variations in peridotite composition than predicted for the residue of near-fractional melting. We suggest that abyssal peridotite compositions reflect a combination of long-term mantle heterogeneity and recent melt-rock interaction during melting and melt extraction. This heterogeneous mantle is eventually subducted back into the convecting mantle, generating further heterogeneities. Our dataset consists of a global compilation of abyssal peridotite modal, major and trace element compositions, consisting of ~300 samples from all major mid-ocean ridges. The distribution of peridotite compositions as a function of spreading rate is compared to the peridotite compositions predicted using a simple fractional melting model. After filtering the dataset for veined samples, we observe considerable variation among nominally residual peridotites. For example, concentrations of light rare earth elements in peridotite clinopyroxene vary by 4 orders of magnitude at length-scales ranging from the grain-scale to the ridge segment-scale. As a function of spreading rate, peridotites at slow (<40 mm/yr full spreading rate) and ultra-slow (<20 mm/yr) ridges extend to both more depleted and more enriched compositions than predicted by the melting model. The observation of large variations in peridotite composition at the sub-kilometer length-scale indicates that other processes, in addition to melting, influence peridotite composition. We suggest that variations in peridotite compositions at small length-scales reflect melt-rock reaction processes during melt extraction. In some peridotites, evidence for melt-rock reaction is obvious, as it occurs in the form of pyroxenite or gabbroic veins or interstitial plagioclase. In other peridotites, evidence for refertilization is more cryptic and can take the form of metasomatic mineral inclusions (e.g., Seyler et al., 2004), small enrichments in light rare earth elements (e.g., Brunelli et al., 2006), or localized zones of highly enriched trace elements (Warren and Shimizu, submitted). The role of mantle source heterogeneity on abyssal peridotite compositions is best constrained from long-lived radiogenic isotopes. Using a compilation of all published data for abyssal peridotite mineral separates (70 samples), we find that the average 143Nd/144Nd isotopic composition of peridotite Cpx (0.513167) is similar to average MORB (0.51313), but that peridotites extend to more depleted compositions than MORB (Warren et al., JGR in press). While the isotopic composition of peridotites clearly indicate source heterogeneity, the lack of a correlation between concentration and isotopic composition indicates the role of recent melt-rock reaction in modifying peridotite compositions. On this basis, we suggest that some or many peridotites are the product of melt re-fertilization of initially depleted mantle.

Warren, J. M.; Shimizu, N.; Dick, H. J.

2009-12-01

198

Major Elements Budget Between Abyssal Peridotite And Seawater During The Serpentinization  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

199

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

200

Hidden in Plain Sight  

NSDL National Science Digital Library

Steganography is the science and art of hiding messages in plain sight so only the sender and intended recipient know the existence of a message. Steganography can be characterized as security through obscurity. Through this lesson, students experience a portion of the engineering design process as they research steganography and steganographic methods; identify problems, criteria and constraints; brainstorm possible solutions; and generate ideas. These are the critical first steps in the engineering design process, often overlooked by students who want to get to the "doing" phasesâdesigning, building and testing. In computer science, a thorough design phase makes program implementation much easier and more effective. Students obtain practice with a portion of the design process that may be less exciting, but is just as important as the other steps in the process.

IMPART RET Program, College of Information Science & Technology,

201

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

PubMed Central

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

Allcock, Louise; Schwabe, Enrico

2013-01-01

202

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

PubMed

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

Allcock, Louise; Schwabe, Enrico

2013-01-01

203

A comment on "Bathymetry gradients of lineated abyssal hills: Inferring seafloor spreading vectors and a new model for hills formed  

E-print Network

Discussion A comment on "Bathymetry gradients of lineated abyssal hills: Inferring seafloor spreading vectors and a new model for hills formed at ultra-fast spreading rates" by K.A. Kriner et al- and outward-facing slopes de- creases as a function spreading rate, with the sense of asymmetry reversing

Bohnenstiehl, Delwayne

204

Process recognition in multi-element soil and stream-sediment geochemical data  

USGS Publications Warehouse

Stream-sediment and soil geochemical data from the Upper and Lower Coastal Plains of South Carolina (USA) were studied to determine relationships between soils and stream sediments. From multi-element associations, characteristic compositions were determined for both media. Primary associations of elements reflect mineralogy, including heavy minerals, carbonates and clays, and the effects of groundwater. The effects of groundwater on element concentrations are more evident in soils than stream sediments. A "winnowing index" was created using ratios of Th to Al that revealed differing erosional and depositional environments. Both soils and stream sediments from the Upper and Lower Coastal Plains show derivation from similar materials and subsequent similar multi-element relationships, but have some distinct differences. In the Lower Coastal Plain, soils have high values of elements concentrated in heavy minerals (Ce, Y, Th) that grade into high values of elements concentrated into finer-grain-size, lower-density materials, primarily comprised of carbonates and feldspar minerals (Mg, Ca, Na, K, Al). These gradational trends in mineralogy and geochemistry are inferred to reflect reworking of materials during marine transgressions and regressions. Upper Coastal Plain stream-sediment geochemistry shows a higher winnowing index relative to soil geochemistry. A comparison of the 4 media (Upper Coastal Plain soils and stream sediments and Lower Coastal Plain soils and stream sediments) shows that Upper Coastal Plain stream sediments have a higher winnowing index and a higher concentration of elements contained within heavy minerals, whereas Lower Coastal Plain stream sediments show a strong correlation between elements typically contained within clays. It is not possible to calculate a functional relationship between stream sediment-soil compositions for all elements due to the complex history of weathering, deposition, reworking and re-deposition. However, depending on the spatial separation of the stream-sediment and soil samples, some elements are more highly correlated than others. Crown Copyright ?? 2009.

Grunsky, E.C.; Drew, L.J.; Sutphin, D.M.

2009-01-01

205

The Nd-isotopic composition of late Cretaceous bathyal-abyssal seawater from fossil fish skeletal debris  

NASA Astrophysics Data System (ADS)

There is currently very little proxy data available for determining the inter-ocean mixing of deep-water masses during the Cretaceous, and thus uncertainty remains as to the importance of deep-water circulation in latitudinal heat transport and bottom-water oxygenation for that time. A solution lies in exploiting a geochemical water-mass tracer, such as the neodymium (Nd) isotopic composition of seawater. It has been shown that the distinct differences in the Nd-isotopic composition observed in modern deep and intermediate waters have persisted since the early Cenozoic, but currently our knowledge of the Cretaceous oceans is poor. Most of the existing Nd-isotope data for the Cretaceous are from shallow-water masses on the continental shelves of the Tethyan and Atlantic Oceans. It has previously been shown that biogenic apatites record the Nd-isotopic composition of bottom-waters during an early diagenetic reaction at the sediment-water interface. We present Nd-isotope data from fish-teeth and skeletal debris picked from deep-ocean sediments recovered by DSDP and ODP drilling in the North and South Atlantic, Indian and Pacific Oceans. The sites chosen for this study were all deposited at bathyal-abyssal water depths. In conjunction with other recent studies, our data establish that the Pacific Ocean has likely maintained a constant range of Nd-isotopic values between ~-5 and -3 since at least 135 Ma. The data from the North Atlantic, South Atlantic and proto-Indian Ocean show that bottom-waters in these basins had relatively radiogenic Nd-isotopic compositions for much of the mid-Cretaceous (~-8 to ~-5), before shifting to less radiogenic values (<-9) between 85 and 75 Ma. A recently published study from Demerara Rise (MacLeod et al. 2008) revealed the existence there of a large positive Nd-isotope excursion during OAE2, which we see no evidence for elsewhere suggesting that the excursion most likely resulted from mixing of locally-sourced bottom-waters with bottom-waters from the rest of the deep North Atlantic. We interpret the Late Cretaceous shift in our data as reflecting either a decrease in the influence of Pacific waters via circum-equatorial surface currents, or as an increase in the contribution of a deep-water mass with a highly radiogenic value. The values attained by this shift suggest a Late Cretaceous age for the establishment of the Cenozoic Nd-isotope pattern. However, this shift did not occur at the transition in the Turonian to more oxygenated sedimentation in the North Atlantic, thereby leaving unanswered the question of whether ocean circulation changes and shifting tectonic gateways were responsible for the oxygenation event. MacLeod, K.G., et al., 2008, Nd isotopic excursion across Cretaceous ocean anoxic event 2 (Cenomanian-Turonian) in the tropical North Atlantic, Geology, 36, 811-814.

Robinson, S. A.; Vance, D.

2009-04-01

206

Aerosols Over Yellow Sea Sediments  

NASA Technical Reports Server (NTRS)

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.

2002-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

208

Plain English on Plant Floor.  

ERIC Educational Resources Information Center

Illustrates how Allen-Bradley Company identified problems with manual writing, scheduling, and graphics and how the company solved those problems by using plain English and clear document design. (DF)

Jereb, Barry

1986-01-01

209

Ages of Lunar Light Plains  

NASA Astrophysics Data System (ADS)

Light plains are characterized by their relative smoothness and lower crater densities (compared to the highlands), and their occurrence as crater fills. They also exhibit highland-like characteristics, such as high albedos (in comparison to mare basalts) and their geological and stratigraphic setting. Despite the long history of investigating light plains, there are still numerous open questions concerning their mode of emplacement, their mineralogical composition, their ages, and their origin. We dated 16 light plains with crater size-frequency distribution (CSFD) measurements. All dated regions were previously identified as light plains in the geologic maps [1-5] and either mapped as smooth light plains (Ip) or light plains with undulatory surfaces (INp). The studied light plains occur both inside and outside the South Pole-Aitken (SPA) basin within a latitudinal band between ~-36° and ~-75°. In particular, we investigated the following smooth light plains: Janssen (40.82°E, -44.96°; Ip [1]), Nishina (-170.8°E, -44.57°; Ip [2]), South of Nishina (Ip [2]), Obruchev (162.43°E, -38.67°; Ip [2]), Oresme (169.22°E, -42.61°, Ip [2]), Schrödinger (132.93°E, -74.73°; Ip [3]), Nearch (39.01°E, -58.58°; Ip [3]), Nasmyth (-56.39°E, -50.49°; Ip [3]), Manzinus (26.37°E, -67.51°; Ip [3]), Klaproth (-26.26°E, -69.85°; Ip [3]), Phocylides (-57.31°E, -52.79°, Ip [3]), Buffon (-133.53°E, -40.64°; Ip [4]), Roche (136.54°E, -42.37°; Ip [5]). We also dated the following light plains with undulatory surfaces: Koch (150.33°E, -42.13°; INp [2]), Garavito (156.78°E, -47.21°; INp [2]), Eötvös (134.43°E, -35.61°; INp [5]). Our CSFD measurements resulted in absolute model ages of 3.71 to 4.02 Ga for all investigated light plains, thus confirming the Imbrian and/or Nectarian ages of the geologic maps [1-5]. We only dated three INp light plains, but they appear to have ages that are close to the upper limit, i.e., 3.96-4.02 Ga. However, further CSFDs of INp light plains are necessary to corroborate this preliminary observation. In general, our new absolute model ages are similar to model ages derived for light plains north of Mare Frigoris (3.65-4.0 Ga) [6], light plains within the SPA basin (3.43-3.81 Ga) [7], and light plains in the surroundings of the Orientale and Imbrium basins (3.8-4.3 Ga) [8]. The ages are not only similar, but also show similar ranges. While our model ages vary by about 300 Ma, model ages of [6,7] exhibit ranges of ~350 Ma and ~380 Ma, respectively. Ages of [8] show a somewhat wider range of ~500 Ma. From this wide range in ages it has been concluded that a formation of the light plains by a single event (i.e., Orientale or Imbrium) is unlikely [6-8]. References: [1] Wilhelms and McCauley (1971), USGS I-703; [2] Stuart-Alexander (1978), USGS I-1047; [3] Wilhelms et al. (1979), USGS I-1162; [4] Scott et al. (1977), USGS I-1034; [5] Wilhelms and El-Baz (1977), USGS I-948; [6] Köhler et al. (2000), LPSC 31, #1822; [7] Thiessen et al. (2012), LPSC 43, #2060; [8] Neukum (1977b), Moon 17, 383-393.

Hiesinger, Harald; Howes van der Bogert, Carolyn; Thiessen, Fiona; Robinson, Mark

2013-04-01

210

Seismic character of the BSR in the Ulleung Basin plain, East Sea (Japan Sea)  

Microsoft Academic Search

A bottom simulating reflector (BSR) was identified in multichannel seismic reflection profiles collected in the Ulleung Basin\\u000a plain, East Sea (Japan Sea). The BSR, occurring in densely stratified sediments, is observed very close to the boundary between\\u000a two sequences interpreted as low-energy turbidites\\/hemipelagic sediments and mass-transport deposits. The essential characteristics\\u000a of the BSR include its cross-cutting relationship to strata at

Han-Joon Kim; Gwang Hoon Lee; Hyeong-Tae Jou; Sang Hoon Lee; Dong-Geun Yoo; Nam-Hyung Koo; Gap-Sik Jeong; Bong-Chool Suk

2010-01-01

211

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

PubMed Central

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

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

2013-01-01

212

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

PubMed

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

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

2013-12-01

213

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

E-print Network

river Sand-bed Channel characteristics Great Plains Hydraulic geometry Downstream trends in hydraulic 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

Gido, Keith B.

214

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...

215

Spatial and temporal variations in the grain-size characteristics of historical flood plain deposits, Blue River, Wisconsin, USA  

Microsoft Academic Search

This study examined vertical, lateral, and downstream variations in the grain-size characteristics of historical (post-1830) overbank deposits in a watershed that has experienced high rates of accelerated flood plain sedimentation. More than 800 samples were collected from 53 cores along nine flood plain transects. Overbank deposits exhibit a coarsening-upward sequence attributed to historical changes in the sand content of source

Scott A. Lecce; Robert T. Pavlowsky

2004-01-01

216

Northern Plains Of Mars  

NASA Technical Reports Server (NTRS)

This rocky panoramic scene is the second picture of the Martian surface that was taken by Viking Lander 2 shortly after touchdown on September 3 at 3:58 PM PDT (Earth received time). The site is on a northern plain of Mars, at about 48 N. Lat., 226 W. Long., known as Utopia Planitia. The picture sweeps around 330 degrees in azimuth, starting from northwest at the left through north (above the sampler arm housing) past east, where the sky is bright at the center, and southeast toward the right above the radioisotope thermoelectric generator cover. The surface is strewn with rocks out to the horizon, ranging in size up to several meters across. Some pitted rocks resemble fragments of porous volcanic lava. Other rocks have grooves that may have been eroded by windblown sand and dust. Although fine-grained material is seen between the boulders, no sand dunes are evident. The dip in the eastern horizon at the center is an illusion caused by an 8-degree tilt of the Lander toward the west. Actually, the terrain is more level than that at the Viking 1 site. The horizon toward the left of the panorama (northwest) appears featureless, indicating that it may be several kilometers distant. The sky at the center (east) is bright because the sun was above but out of the picture at 10 AM Mars time. Toward the right (southeast), the rocks that are silhouetted against the skyline indicate that the horizon is much nearer, probably because of a slight rise in that area of the terrain. The circular high-gain antenna at the right has clots of fine-grained material adhering to the lower half, some of which appeared to have been sliding downward while the camera was scanning the area. At the extreme right, the banded appearance resulted because the camera continued to scan while it was no longer moving in azimuth. Any motion or other variation in the scene would show up as a change in successive lines.

1976-01-01

217

Ventilation of the abyssal Southern Ocean during the late Neogene: A new perspective from the subantarctic Pacific  

Microsoft Academic Search

Benthic foraminiferal stable carbon isotope records from the South Atlantic show significant declines toward more “Pacific-like” values at ?7 and ?2.7 Ma, and it has been posited that these shifts may mark steps toward increased CO2 sequestration in the deep Southern Ocean as climate cooled over the late Neogene. We generated new stable isotope records from abyssal subantarctic Pacific cores

Lindsey M. Waddell; Ingrid L. Hendy; Theodore C. Moore; Mitchell W. Lyle

2009-01-01

218

A sediment budget for Town Creek watershed: Suspended sediment transport analysis  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Town Creek watershed is located in the Southeastern Plains Ecoregion in Mississippi. Its total area covers 1,769 km2 and represents approximately 50% of the upper Tombigbee River basin area contributing to the Aberdeen Pool on the Tennessee-Tombigbee Waterway. The sediment yield from the watersh...

219

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

220

Structure and evolution of the abyssal jet in the Vema Channel of the South Atlantic  

NASA Astrophysics Data System (ADS)

The Vema Channel represents the only major conduit through which the deepest and coldest (<0.2 °C potential temperature) Antarctic Bottom Water (AABW) flows from the Argentine into the Brazil Basin. From 2003 to 2007 two current meter moorings were present on each side of the Vema Sill, close to the narrowest spot of the Vema Channel. The data from the moorings are compared with earlier current and temperature observations. On average the maximum current core lies ˜100 m above the bottom of the sill with a mean northward speed of 0.3 m s-1. Farther up in the water column where Lower Circumpolar Deep Water and North Atlantic Deep Water prevail, one finds a level of sluggish currents with a southward tendency in the sub-centimeter-per-second range. The lower boundary of a layer of 'no' motion was observed at ˜3700 m depth where the mean potential temperature amounts to 1.5 °C. The evolution of the abyssal warming phenomenon over the last decades with notable fluctuations at the choke point between the Argentine and the Brazil Basin differs from the more stable attitude of deep horizontal currents. Starting with CTD observations in 1972 we find a steady increase of temperatures of the coldest AABW in the Vema Channel. This general trend of rising abyssal potential temperatures of almost 2 mKelvin per year is based on mostly annual CTD observations. The overall warming trend is fully compatible with our three-year moored temperature series in agreement with earlier records with high temporal resolution. Distinct frequently fluctuating horizontal current shear between the western and eastern sides of the Vema Sill may be explained by two different catchment areas for AABW at the mouth of the Vema Channel. One pathway originates at the American continental rise and advects bottom water in form of the deep western boundary current. A second pathway is supplied by an eastern boundary current along the Mid Atlantic Ridge in the Argentine Basin. Both source waters merge at the channel entrance, mix, and their respective strengths can alternate within the sill area.

Zenk, Walter; Visbeck, Martin

2013-01-01

221

Helium in Abyssal Peridotites: New Results From the Southwest Indian Ridge  

NASA Astrophysics Data System (ADS)

Dredged peridotites provide important insights into mantle melting processes, but have not been extensively studied for noble gases. We present new helium concentrations and isotopic abundances in a suite of dredged abyssal peridotites from the Southwest Indian Ridge. In an effort to determine the helium distribution in the peridotites, the experimental protocol included coupled in vacuo crushing and melting of whole rocks and mineral separates. Most of the helium was released by melting (of previously crushed powders), suggesting that helium within abyssal peridotites is associated with the mineral matrices rather than fluid or melt inclusions. Several mylonites and ultramylonites have relatively high helium concentrations, up to 4.4 x 10 7 cc STP/gram, suggesting a relationship between metamorphic texture and noble gas abundance, and that mylonitization can introduce mantle helium into mineral matrices. The most likely mechanism is trapping within defects at pressure in the mantle. Measurement of associated serpentinite and peridotite shows that serpentinite has low but measurable helium concentrations, but with mantle 3He/4He, suggesting that serpentinization does not involve atmospheric helium and is not necessarily a source of contamination. Orthopyroxene mineral separates from a suite of samples within a single dredge near the Shaka Fracture Zone reveal no relationship between helium abundance, degree of melt/rock interaction, or proximity to veined mineralogy; this suggests that melt rock interaction and mantle veins are not necessarily dominant controls on helium within peridotites. The 3He/4He ratios in the peridotites are similar to the associated basalts, suggesting that peridotite helium data can be used to infer the source mantle isotopic compositions. Samples from the eastern wall of the Shaka fracture zone have 3He/4He ratios up to 9.1 time atmospheric (Ra) whereas samples to the east of the fracture zone have 3He/4He less than 7 Ra, demonstrating that this fracture zone is an important boundary, with influence of the Bouvet hotspot to the west. The relationships between texture and helium abundances in peridotites show that these samples cannot be viewed as simple residua of partial melting, and that deformation and metamorphism are important controls on noble gases.

Kurz, M. D.; Curtice, J.; Warren, J. M.; Shimizu, N.; Dick, H.

2006-12-01

222

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

PubMed Central

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

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

223

White Plains MetARs  

NSDL National Science Digital Library

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.

Kluge, Steve

224

'Endurance' Goal Across the Plains  

NASA Technical Reports Server (NTRS)

This mosaic image from the Mars Exploration Rover Opportunity's panoramic camera provides an overview of the rover's drive direction toward 'Endurance Crater,' which is in the upper right corner of image.

The plains appear to be uniform in character from the rovers current position all the way to Endurance Crater. Granules of various sizes blanket the plains. Spherical granules fancifully called blueberries are present some intact and some broken. Larger granules pave the surface, while smaller grains, including broken blueberries, form small dunes. Randomly distributed 1-centimeter (0.4 inch) sized pebbles (as seen just left of center in the foreground of the image) make up a third type of feature on the plains. The pebbles' composition remains to be determined. Scientists plan to examine these in the coming sols.

Examination of this part of Mars by NASA's Mars Global Surveyor orbiter revealed the presence of hematite, which led NASA to choose Meridiani Planum as Opportunity's landing site. The rover science conducted on the plains of Meridiani Planum serves to integrate what the rovers are seeing on the ground with what orbital data have shown.

Opportunity will make stop at a small crater called 'Fram' (seen in the upper left, with relatively large rocks nearby) before heading to the rim of Endurance Crater.

2004-01-01

225

Lava Flow on Coastal Plain  

USGS Multimedia Gallery

Lava flows remain active within the Royal Gardens subdivision and onto the coastal plain below. The number of surface flows has decreased however, due in part to a probable decrease in activity related to the ongoing deflation of Pu`u `? `?, and because the new lava tube branch...

226

Expanded Plain TEX Steven Smith  

E-print Network

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

Mintmire, John W.

227

Lava Flows on Coastal Plain  

USGS Multimedia Gallery

The lava flows on the coastal plain, which show up as the light colored flows in the foreground, are erupted into the TEB tube system from the D fissure which first opened up in July 2007. This vent is faintly visible as a fuming source in the background near the upper left corner of the photo. Smal...

2010-06-18

228

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

Microsoft Academic Search

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

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

2000-01-01

229

Hydrogeologic setting and potential for denitrification in ground water, coastal plain of southern Maryland  

USGS Publications Warehouse

The types and distribution of Coastal Plain sediments in the Patuxent River Basin may contribute to relatively low concentrations of nitrate (typically less than 1 milligram per liter) in stream base flow because of the chemical reduction of dissolved nitrate (denitrification) in ground water. Water chemistry data from synoptic stream base-flow surveys in the Patuxent River Basin show higher dissolved nitrate concentrations in the Piedmont than in the Coastal Plain section of the watershed. Stream base flow reflects closely the chemistry of ground water discharging from the surficial (unconfined) aquifer to the stream. Because land use in the sampled subbasins is virtually the same in each section, differences in the physical and geochemical characteristics of the surficial aquifer may explain the observed differences in water chemistry. One possible cause of lower nitrate concentrations in the Coastal Plain is denitrification within marine sediments that contain chemically reduced compounds. During denitrification, the oxygen atoms on the nitrate (N03-) molecule are transferred to a reduced compound and N gas is produced. Organic carbon and ferrous iron (Fe2+), derived from the dissolution of minerals such as pyrite (FeS2) and glauconite (an iron aluminosilicate clay), can act as reducing substrates; these reduced chemical species are common in the marine and estuarine deposits in Southern Maryland. The spatial distribution of geologic units and their lithology (sediment type) has been used to create a map of the potential for denitrification of ground water in the surficial aquifer of the Coastal Plain in Southern Maryland.

Krantz, David E.; Powars, David S.

2000-01-01

230

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

PubMed

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

Salters, Vincent J M; Dick, Henry J B

2002-07-01

231

Early Holocene Landscape evolution of Thessaloniki Plain, Northern Greece  

NASA Astrophysics Data System (ADS)

Seven cores from the western part of the Thessaloniki plain have been drilled and analysed for palaeoenvironmental studies. This paper aims to detail the links between the landscape changes and the human occupation of the actual largest deltaic plain of Greece during Neolithic Times. During the maximum of the last post glacial marine transgression, this large alluvial plain was occupied by a wide bay, subsequently affected by a marine regression running from the west to the east. Facies identification, geochemical analyses, radiocarbon dating and magnetic susceptibility measurements revealed different sediment environments and helped to redefine the precise position of the different Neolithic settlements from 6000 BC and 3000 BC. The results highlight the presence of large marine bay at 6000 years cal.BC and gradually a lagoon stage and an important peat stage developped in context of deceleration of the sea level rise. Archaeological studies (Bintliff, 1976; Rodden & Wardle, 1996) were incorporated into the work and the interpretation must be reconsidered with the help of the new data presented here. Moreover, the previous geoarchaeological studies (Ghilardi, 2007) must be completed for the early holocene.

Ghilardi, Matthieu

2010-05-01

232

Sediment Setback  

E-print Network

. Ultraviolet light, or sunlight, naturally kills bacteria; therefore, suspended sediment in the area's water is particularly problematic because of its ability to diminish the water's light absorption. Sediment can also spread absorbed hazardous chemicals... Sediment SetbackStory by Amanda Crawford Since 1942, Fort Hood has been home to theU.S. Army's III Mobile Armored Corps. It is the only U.S. military post able to station and train two armored divisions at once. At this base, troops execute...

Crawford, Amanda

2005-01-01

233

Deep sea benthic bioluminescence at artificial food falls, 1,000–4,800 m depth, in the Porcupine Seabight and Abyssal Plain, North East Atlantic Ocean  

Microsoft Academic Search

Natural bioluminescence (that not mechanically stimulated by human intervention) produced by organisms on the seafloor of\\u000a the northeast Atlantic ocean between 970 and 4,800 m depth was examined using an image intensifying (ISIT) camera mounted\\u000a on an autonomous lander system. In the absence of bait little or no luminescence was observed but with bait present there\\u000a was a significant inverse relationship

E. J. V. Gillibrand; P. Bagley; A. Jamieson; P. J. Herring; J. C. Partridge; M. A. Collins; R. Milne; I. G. Priede

2007-01-01

234

Young Craters on Smooth Plains  

NASA Technical Reports Server (NTRS)

Young craters (the largest of which is about 100 kilometers in diameter) superposed on smooth plains. Larger young craters have central peaks, flat floors, terraced walls, radial ejecta deposits, and surrounding fields of secondary craters. Smooth plains have well-developed ridges extending NW and NE. This image (FDS 167), acquired during the spacecraft's first encounter with Mercury, is located approximately 60 degrees N, 175 degrees W.

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

1974-01-01

235

The Arctic Coastal Plain, Alaska  

NSDL National Science Digital Library

This tutorial is about the Arctic tundra biome; the plants and animals found there; and the amount of sunlight, temperatures, seasons and permafrost. Examples of Arctic ecosystem interactions, food chains, and biological adaptations to the Arctic Coastal Plain are given. There are photographs of wolves, caribou, arctic hares, minks, lemmings, arctic foxes, polar bears, seals, walruses, ptarmigans, hawks, and owls. Definitions of ecosystem terms can be found by clicking on the term within the tutorial.

236

Scales and Causes of Chemical Heterogeneity in the Oceanic Mantle: Abyssal Peridotites from Gakkel Ridge  

NASA Astrophysics Data System (ADS)

We have obtained major and trace element mineral data on 80 residual abyssal peridotites from 19 dredge hauls, collected along Gakkel Ridge (spreading rate W to E: 13-10 mm/yr full). This data set allows us to address the extent and causes of along-ridge chemical variation as well as small- to local-scale heterogeneities. Gakkel Ridge can be divided into 3 regions: (1) the western region (west of 3^oE), characterized by normal-fault ridge morphology and complete basaltic crust; (2) a magma-poor region (3-19^oE), consisting mainly of abyssal peridotites and some basalts; and (3) the eastern region (east of 19^oE), dominated by basalts and subordinate peridotites. A giant point-source volcano at 20^oE divides the magma-poor from the eastern region. The magma-poor region can be divided into 4 domains from W to E. Domains A and B are devoid of basalts. Spinel Cr# in lhz varies between 0.14 and 0.21 (5 dr., n=23, 60 km along axis). In the easternmost B dredge haul, dunites were sampled (spinel Cr# 0.41-0.43), as yet the only evidence for local heterogeneity. Cpx are homogeneous on a dredge scale, but there is a clear distinction between the 3 western (A) and 2 eastern (B) dredges. In domain A, Na_2O is higher (˜0.9 vs ˜0.4 wt%) and REE patterns are less fractionated ((La/Nd)N: ˜1 vs ˜0.02). Domain C is basalt-dominated. Peridotites display large compositional variation (lhz, hzb, dun; Cr#: 0.15-0.53; LREE-depleted and -enriched within 1 dredge). The lowest Cr# in each dredge haul, which is relevant for estimating the regional degree of melting, varies from 0.16 to 0.21 and is therefore similar to domains A and B. Domain D consists exclusively of virtually cpx-free hzb and dun (4 dr., n=11, 40 km). The change from C to D is abrupt (<20 km). Cr#s between 0.53 and 0.60 are among the most depleted on the ocean floor, and not at all consistent with a spreading-rate dependent degree of melting. Most cpx REE patterns are LREE-enriched, 1 dunite is LREE-depleted, 2 hzb have hump-shaped patterns. East of 20^oE, Cr# quickly drop to ˜0.2, with large local and regional heterogeneity. The easternmost peridotite dredge has the largest chemical variation along Gakkel Ridge (n=14, Cr#: 0.12-0.43; cpx Na2O: 0.5-1.3; (La/Nd)N: 0.005-1.2 ). These results suggest low degrees of regional partial melting in domains A and B, as well as limited reactive melt percolation. The extreme depletion of domain D may be the result of a large-scale reaction with percolating melts. This is not consistent with scarcity of basalts at the surface, or even off-axis, unless there was highly asymmetrical along-axis melt focussing. Alternatively, depletion may be inherited.

Hellebrand, E.; Snow, J. E.; Dick, H.; von der Handt, A.; Michael, P.

2003-04-01

237

Noble gas behavior during deformation and serpentinization of abyssal peridotites: St. Peter-St. Paul massif  

NASA Astrophysics Data System (ADS)

We present new noble gas (He, Ne, Ar), Sr and Pb isotopic analyses of St. Peter-St. Paul (SPSP) abyssal peridotites sampled in 1998-1999 using the Nautile submersible (IFREMER). The goals of the study were to geochemically characterize both granular and mylonitized peridotites, and to evaluate the effects of mylonitization and serpentinization on rare gas concentrations and isotopic compositions. Samples included whole rocks for mylonitic peridotites, and mineral separates (serpentine and olivine+pyroxene) from massive peridotites. The abyssal peridotites exhibit strong enrichment in light rare earths and other incompatible elements, and positive Ce anomalies are found in several non-mylonitic samples. Mylonitic samples are characterized by lower loss on ignition, and higher SiO2 and MgO, and unradiogenic 87Sr/86Sr isotopic composition (~0.7034) and extremely radiogenic 206Pb/204Pb (up to 20), which is more radiogenic than previous measurements from SPSP. Rare gas analyses were made by paired in vacuo crushing and melting of whole rocks and mineral separates. Most SPSP peridotites contain high concentrations of He, Ne, and Ar that are air-like demonstrating atmospheric contamination. The group of samples plots along a He-Ne mixing line between air and typical mantle values, where the mylonitic samples are characterized by higher fractions of mantle Ne (20Ne/22Ne>10) and 3He/4He (R/Ra~7). The binary mixing behavior is also supported by Ar-Ne isotopes. For the mylonites, melting released high concentrations of He (1.4x10-5ccSTP/g) and the most radiogenic argon (40Ar/36Ar = 2810), demonstrating that noble gases are stored in the crystal structure of the minerals. In contrast, the undeformed peridotites had much lower total helium concentrations for both serpentine (2x10-8ccSTP/g) and olivine+pyroxene (6.9x10-8ccSTP/g) separates. The serpentine mineral separate showed low 3He/4He (R/Ra~1) that was similar in both crushed and melting methods and low air-like 40Ar/36Ar (~355), although they released the highest argon concentration (3.2x10-5cc/g). The low He concentrations suggest that serpentine is not a determining mineral phase in He fractionation. The olivine+pyroxene mineral separates yield lower 3He/4He through the melting method and similar to whole rock values and lower 40Ar/36Ar (~383). Because melt inclusions are not found in the mylonites, the large fraction of 4He released during melting suggests that a significant mantle component may be retained in the recrystallized neoblasts during the deformation processes. It is hypothesized that recrystallization and grain growth in the mylonitization process may have favored gas retention (i.e. supporting a relationship between deformation and gas contents), or is related to metasomatism in a gas-rich (CO2 and rare gas) environment.

Angel Amaya, J.; Kurz, M. D.; Sichel, S. E.; Blusztajn, J.

2010-12-01

238

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

239

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

PubMed Central

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

Janssen, Annika; Kaiser, Stefanie; Meißner, Karin; Brenke, Nils; Menot, Lenaick; Martínez Arbizu, Pedro

2015-01-01

240

History of plains resurfacing in the Scandia region of Mars  

NASA Astrophysics Data System (ADS)

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.

Tanaka, Kenneth L.; Fortezzo, Corey M.; Hayward, Rosalyn K.; Rodriguez, J. Alexis P.; Skinner, James A.

2011-09-01

241

History of plains resurfacing in the Scandia region of Mars  

USGS Publications Warehouse

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.

Tanaka, Kenneth L.; Fortezzo, Corey M.; Hayward, Rosalyn K.; Rodriguez, J. Alexis P.; Skinner, James A.

2011-01-01

242

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

USGS Publications Warehouse

This study examines the influence of the Atchafalaya River, a major distributary of the Mississippi River, on stratigraphic evolution of the inner continental shelf in the northern Gulf of Mexico. Sedimentary, geochemical, and shallow acoustic data are used to identify the western limit of the distal Atchafalaya subaqueous delta, and to estimate the proportion of the Atchafalaya River's sediment load that accumulates on the inner shelf seaward of Louisiana's chenier-plain coast. The results demonstrate a link between sedimentary facies distribution on the inner shelf and patterns of shoreline accretion and retreat on the chenier plain. Mudflat progradation on the eastern chenier-plain coast corresponds to the location of deltaic mud accumulation on the inner shelf. On the central chenier-plain shelf, west of the subaqueous delta, relict sediment is exposed that was originally deposited between ???1200 and 600 years BP during activity of the Lafourche lobe of the Mississippi Delta complex. Mass-balance calculations indicate that the eastern chenier-plain inner shelf and coastal zone form a sink for 7??2% of the sediment load carried by the Atchafalaya River. ?? 2004 Elsevier Ltd. All rights reserved.

Draut, A.E.; Kineke, G.C.; Velasco, D.W.; Allison, M.A.; Prime, R.J.

2005-01-01

243

Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge  

USGS Publications Warehouse

This paper presents a broad but undetailed picture of fluvial sediments in streams, reservoirs, and lakes and includes a discussion of the processes involved in the movement of sediment by flowing water. Sediment is fragmental material that originates from the chemical or physical disintegration of rocks. The disintegration products may have many different shapes and may range in size from large boulders to colloidal particles. In general, they retain about the same mineral composition as the parent rocks. Rock fragments become fluvial sediment when they are entrained in a stream of water. The entrainment may occur as sheet erosion from land surfaces, particularly for the fine particles, or as channel erosion after the surface runoff has accumulated in streams. Fluvial sediments move in streams as bedload (particles moving within a few particle diameters of the streambed) or as suspended sediment in the turbulent flow. The discharge of bedload varies with several factors, which may include particle size and a type of effective shear on the surface of the streambed. The discharge of suspended sediment depends partly on concentration of moving sediment near the streambed and hence on discharge of bedload. However, the concentration of fine sediment near the streambed varies widely, even for equal flows, and, therefore, the discharge of fine sediment normally cannot be computed theoretically. The discharge of suspended sediment also depends on velocity, turbulence, depth of flow, and fall velocity of the particles. In general, the coarse sediment transported by a stream moves intermittently and is discharged at a rate that depends on properties of the flow and of the sediment. If an ample supply of coarse sediment is available at the surface of the streambed, the discharge of the coarse sediment, such as sand, can be roughly computed from properties of the available sediment and of the flow. On the other hand, much of the fine sediment in a stream usually moves nearly continuously at about the velocity of the flow, and even low flows can transport large amounts of fine sediment. Hence, the discharge of fine sediments, being largely dependent on the availability of fine sediment upstream rather than on the properties of the sediment and of the flow at a cross section, can seldom be computed from properties, other than concentrations based directly on samples, that can be observed at the cross section. Sediment particles continually change their positions in the flow; some fall to the streambed, and others are removed from the bed. Sediment deposits form locally or over large areas if the volume rate at which particles settle to the bed exceeds the volume rate at which particles are removed from the bed. In general, large particles are deposited more readily than small particles, whether the point of deposition is behind a rock, on a flood plain, within a stream channel, or at the entrance to a reservoir, a lake, or the ocean. Most samplers used for sediment observations collect a water-sediment mixture from the water surface to within a few tenths of a foot of the streambed. They thus sample most of the suspended sediment, especially if the flow is deep or if the sediment is mostly fine; but they exclude the bedload and some of the suspended sediment in a layer near the streambed where the suspended-sediment concentrations are highest. Measured sediment discharges are usually based on concentrations that are averages of several individual sediment samples for a cross section. If enough average concentrations for a cross section have been determined, the measured sediment discharge can be computed by interpolating sediment concentrations between sampling times. If only occasional samples were collected, an average relation between sediment discharge and flow can be used with a flow-duration curve to compute roughly the average or the total sediment discharges for any periods of time for which the flow-duration c

Colby, B.R.

1963-01-01

244

Aquatic sediments  

SciTech Connect

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.

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

1990-06-01

245

MOVEMENT OF TRACTIVE SEDIMENT FROM DISTURBED LANDS.  

USGS Publications Warehouse

The Smoky Creek basin of the coal area of northeastern Tennessee shows extensive evidence of tractive movement of coarse sediment from mined tributary basins into the main channel. Coal-rich gravel bars and flood-plain debris are common below tributaries. Using a combination of techniques including channel-geometry and bar measurements, sediment sampling for rock-debris and coal size distributions, and botanical dating of flood events and geomorphic features, an average annual yield of 65 metric tons per square kilometer (187 tons per square mile) for tractively moved sediment has been calculated for the period 1977 to 1982. This value, 8 percent of the total sediment load, is probably an underestimate owing to the method of calculation. Slightly more than half of the traction load is coal, which moves through the basin within a few years. Rock debris, however, appears to require years to decades to move similar distances.

Osterkamp, W.R.; Carey, W.P.; Hupp, C.R.; Bryan, B.A.

1984-01-01

246

A conceptual model to facilitate amphibian conservation in the northern Great Plains  

USGS Publications Warehouse

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.

Mushnet, David M.; Euliss, Ned H.; Stockwell, Craig A.

2012-01-01

247

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

Microsoft Academic Search

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

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

1985-01-01

248

Progressive deformation of an evaporite-bearing accretionary complex: SeaMARC I, SeaBeam and piston-core observations from the Mediterranean Ridge  

Microsoft Academic Search

The Mediterranean Ridge is an arcuate ridge of deformed sediment caught up in the convergent plate margin between the African plate and the Aegean. An intensive campaign of SeaMARC I and SeaBeam surveys followed by piston coring has been conducted along the contact between undeformed turbidites of the Sirte Abyssal Plain and folded and faulted sediments of the Mediterranean Ridge.

Kim A. Kastens; Nancy A. Breen; Maria B. Cita

1992-01-01

249

Lacustrine carbonates of the northern Great Plains of Canada  

NASA Astrophysics Data System (ADS)

The northern Great Plains of western Canada, a vast region stretching from the Precambrian Shield east of Winnipeg, Manitoba, westward for some 1600 km to the foothills of the Rocky Mountains, contains literally millions of lakes and wetlands. Although often characterized as a saline, Na-SO4 system, in fact the wide range of water chemistries exhibited by the lakes results in an unusually large diversity of sediment composition. Despite a long history of limnogeological study, it is only recently that the spectrum of carbonate minerals and sedimentological processes in these lakes has been realized. About 30 species of carbonate minerals have been reported from the modern and Holocene sediment of about 50 basins in the region. The ubiquity of detrital calcite and dolomite is a legacy of the carbonate bedrock and carbonate-rich glacial sediments. Elevated salinities of the lakes, together with high alkalinities, productivity, and pH values, act in concert to create thermodynamically saturated or supersaturated conditions with respect to many carbonate minerals. The most common non-detrital components are Mg-calcite, aragonite and non-stoichiometric dolomite. Many of the basins whose brines have very high Mg/Ca ratios also contain hydromagnesite, magnesite, and nesquehonite. Although not common, sodium carbonates, including trona, natron and nahcolite, also occur in some of the hypersaline lakes. Because of their great range of formative conditions, carbonates have been the workhorse for much of the physical and geochemical paleolimnology in the Canadian Great Plains. However, the often-difficult task of distinguishing endogenic lacustrine carbonates from allogenic and authigenic minerals has limited the use of carbonate stratigraphy in the region. Despite this problem, the carbonates have been useful in deciphering (i) past changes in hydrology and drainage basin characteristics, (ii) lake level and water column stratification fluctuations, and (iii) water chemistry and salinity variations.

Last, Fawn M.; Last, William M.

2012-11-01

250

Spatial and temporal variations in the grain-size characteristics of historical flood plain deposits, Blue River, Wisconsin, USA  

E-print Network

deposits, Blue River, Wisconsin, USA Scott A. Leccea,*, Robert T. Pavlowskyb a Tobacco Road Research Team 2004 Abstract This study examined vertical, lateral, and downstream variations in the grain of accelerated flood plain sedimentation. More than 800 samples were collected from 53 cores along nine flood

Lecce, Scott A.

251

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

Microsoft Academic Search

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,

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

1997-01-01

252

A qualitative assessment of the influence of bioturbation in Lake Baikal sediments  

NASA Astrophysics Data System (ADS)

The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing, was assessed by studying the actual vertical distribution of benthic animals in continuous accumulation zones selected by seismic survey (Vydrino Shoulder, Posolskoe Bank, Continent Ridge). To assess the influence of the bioturbation, animals were extracted from short cores and identified at the relevant taxonomic level. The faunal distribution is examined in parallel with the bioturbation tracks observed in thin section. Oligochaeta, Nematoda, Ostracoda, Copepoda, Gammaridae, Chironomidae and Hydrachnidia were found inhabiting the sediment. Among them, only oligochaete worms were assumed to have a significant impact on sediment mixing because of their "conveyor belt" feeding. The other two most abundantly sampled groups, nematods and copepods, belong to the interstitial fauna that has no significant impact on the vertical displacement of sediment particles and do not ingest the sediment. The presence of a benthic fauna as deep as 15 cm in the sediment indicates that the possibility of sediment disturbance by invertebrate activity cannot be dismissed in Lake Baikal. The effect of biological mixing is more limited in the deepest stations because the number of potential bioturbators is reduced, qualitatively as well as quantitatively. Located in the abyssal zone, Continent and Vydrino (but outside turbidites) deep stations appear to be most promising sediment records for tracking climate signal at high resolution.

Martin, Patrick; Boes, Xavier; Goddeeris, Boudewijn; Fagel, Nathalie

2005-04-01

253

Early chromite mining and agricultural clearance: Opportunities for the investigation of agricultural sediment dynamics in the Eastern Piedmont (USA)  

USGS Publications Warehouse

Many flood plains in the Eastern Piedmont (USA) are buried under deposits of sediment resulting from European agricultural clearance. Classic radioisotopic dating techniques cover temporal periods too short (137Cs, 210Pb) or too long (14C) to reliably date sediments deposited during periods of local European activity (1660-1900). Moreover, many potential biomarkers, such as pollen, degrade in oxic flood plain sediments. In the Baltimore, Maryland (USA) region, early chromite mining (1820 - 1880) occurred during periods of rapid agricultural clearance. Use of chromium (Cr) chemostratigraphic profiles in flood plain sediments tied to historical mining activity can provide improved precision in overbank accumulation rates and timing. Sediment cores were collected from the Red Run basin, which is part of the Baltimore Ecosystem Study, an urban Long-Term Ecological Research site. Trace metal chemostratigraphic profiles were measured and peaks in Cr concentration tied to historic mining activity. Dates from Cr chemostratigraphic profiles were combined with 137Cs dating to reconstruct flood plain sedimentation rates. Red Run early sedimentation rates (1820 - 1880) were higher (0.45 - 1.19 cm/yr) than more recent (1880 - 1963) rates (0.08 - 0.46 cm/yr). This indicates that Piedmont flood plain vertical sediment accumulation might have peaked before the peak in agricultural clearance, earlier than assumed by regional models. The Cr chemostratigraphy is applicable to a wider region including much of the Maryland and Pennsylvania (USA) Piedmont.

Bain, D.J.; Brush, G.S.

2005-01-01

254

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

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

255

Wet coastal plain tundra III  

SciTech Connect

This year's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSE of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 38'W; Barrow Quadrangle, USGS reflect a decrease in the total number of species breeding. However, total breeding density rose by 82%. Lapland Longspurs (up 105%) accounted for half of this increase while the rest was spread among many species. There was a total of 8 species; 40.5 territorial males or females (162/km/sup 2/, 66/100 acres).

Myers, J.P.; Gellman, S.T.; Pitelka, F.A.

1980-01-01

256

Martian Plain in Late Summer  

NASA Technical Reports Server (NTRS)

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

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

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

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

2008-01-01

257

Rates of microbial metabolism in deep coastal plain aquifers  

USGS Publications Warehouse

Rates of microbial metabolism in deep anaerobic aquifers of the Atlantic coastal plain of South Carolina were investigated by both microbiological and geochemical techniques. Rates of [2-14C]acetate and [U-14C]glucose oxidation as well as geochemical evidence indicated that metabolic rates were faster in the sandy sediments composing the aquifers than in the clayey sediments of the confining layers. In the sandy aquifer sediments, estimates of the rates of CO2 production (millimoles of CO2 per liter per year) based on the oxidation of [2-14C]acetate were 9.4 x 10-3 to 2.4 x 10-1 for the Black Creek aquifer, 1.1 x 10-2 for the Middendorf aquifer, and <7 x 10-5 for the Cape Fear aquifer. These estimates were at least 2 orders of magnitude lower than previously published estimates that were based on the accumulation of CO2 in laboratory incubations of similar deep subsurface sediments. In contrast, geochemical modeling of groundwater chemistry changes along aquifer flowpaths gave rate estimates that ranged from 10-4 to 10-6 mmol of CO2 per liter per year. The age of these sediments (ca. 80 million years) and their organic carbon content suggest that average rates of CO2 production could have been no more than 10-4 mmol per liter per year. Thus, laboratory incubations may greatly overestimate the in situ rates of microbial metabolism in deep subsurface environments. This has important implications for the use of laboratory incubations in attempts to estimate biorestoration capacities of deep aquifers. The rate estimates from geochemical modeling indicate that deep aquifers are among the most oligotrophic aquatic environments in which there is ongoing microbial metabolism.

Chapelle, F.H.; Lovley, D.R.

1990-01-01

258

Sediment Transport  

NSDL National Science Digital Library

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

Karen Williams

259

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)

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.

Bachelery, Patrick; Babonneau, Nathalie; Jorry, Stephan; Mazuel, Aude

2014-05-01

260

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

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

Johnson, Gregory C.

261

12 CFR 611.1217 - Plain language requirements.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Plain language requirements. 611.1217 Section 611...System Institution Status § 611.1217 Plain language requirements. (a) Plain language presentation. All communications to...

2011-01-01

262

12 CFR 611.1217 - Plain language requirements.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Plain language requirements. 611.1217 Section 611...System Institution Status § 611.1217 Plain language requirements. (a) Plain language presentation. All communications to...

2010-01-01

263

7 CFR 650.25 - Flood-plain management.  

Code of Federal Regulations, 2010 CFR

...25 Flood-plain management. Through...sound flood-plain management decisions by land users...General. NRCS provides leadership and takes action...assistance. NRCS provides leadership, through consultation...addressing flood-plain management in...

2010-01-01

264

Life on the Great Plains. [Lesson Plan].  

ERIC Educational Resources Information Center

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…

2000

265

Ohio Conservation Plan: Plains gartersnake, Thamnophis radix  

Microsoft Academic Search

This plan outlines strategies and methods used in an ongoing study initiated in 1999 to restore a selfsustaining population of the Plains gartersnake (Thamnophis radix) in Ohio. Restoring a self-sustaining population would require increases in the current population to where the ratios of T. radix to T. sirtalis are approximately 1:1 in multiple locations in Killdeer Plains Wildlife Area (KPWA).

Norman Reichenbach; M. Barrie; K. Becka; G. Burghardt; S. Butterworth; C. Caldwell; F. Dierkes; P. Johantgen; K. Stanford; D. Wynn

2010-01-01

266

Second chance for the plains bison  

Microsoft Academic Search

Before European settlement the plains bison (Bison bison bison) numbered in the tens of mil- lions across most of the temperate region of North America. Within the span of a few dec- ades 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

Curtis H. Freesea; Keith E. Auneb; Delaney P. Boydc; James N. Derrd; Steve C. Forresta; C. Cormack Gatese; Peter J. P. Goganf; Shaun M. Grasselg; Natalie D. Halbertd; Kyran Kunkelh; Kent H. Redfordi

267

JAPANESE BROME IMPACTS NORTHERN GREAT PLAINS RANGELAND  

Technology Transfer Automated Retrieval System (TEKTRAN)

Japanese brome (Bromus japonicus Thunb.) is an annual grass that has invaded thousands of hectares of Northern Great Plains rangelands. We studied the effect of Japanese brome on the current year's increase in biomass in a plant community in the Northern Great Plains dominated by western wheatgrass...

268

Texas South Plains Spring-Planted Oats  

E-print Network

Texas South Plains Spring-Planted Oats Suggestions for Late-Season Small Forage Production When.746.6101, ctrostle@ag.tamu.edu #12;Past Several Years Oats planted in late winter for "catch up" small grains forage expected Up to 50,000 acres per year in TX High Plains Oat forage yields look very good, but seldom grazed

Mukhtar, Saqib

269

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains Co{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) activities have focused on developing information on deployment issues to support Task 5 activities by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) activities have focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) has included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 (Modeling and Phase II Action Plans) activities have focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman

2004-07-01

270

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

2005-01-01

271

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)

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.

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

2010-12-01

272

Sediment fingerprinting to determine the source of suspended sediment in a southern Piedmont stream.  

PubMed

Thousands of stream miles in the southern Piedmont region are impaired because of high levels of suspended sediment. It is unclear if the source is upland erosion from agricultural sources or bank erosion of historic sediment deposited in the flood plains between 1830 and 1930 when cotton farming was extensive. The objective of this study was to determine the source of high stream suspended sediment concentrations in a typical southern Piedmont watershed using sediment fingerprinting techniques. Twenty-one potential tracers were tested for their ability to discriminate between sources, conservative behavior, and lack of redundancy. Tracer concentrations were determined in potential sediment sources (forests, pastures, row crop fields, stream banks, and unpaved roads and construction sites), and suspended sediment samples collected from the stream and analyzed using mixing models. Results indicated that 137Cs and 15N were the best tracers to discriminate potential sediment sources in this watershed. The delta15N values showed distinct signatures in all the potential suspended sediment sources, and delta15N was a unique tracer to differentiate stream bank soil from upland subsurface soils, such as soil from construction sites, unpaved roads, ditches, and field gullies. Mixing models showed that about 60% of the stream suspended sediment originated from eroding stream banks, 23 to 30% from upland subsoil sources (e.g., construction sites and unpaved roads), and about 10 to 15% from pastures. The results may be applicable to other watersheds in the Piedmont depending on the extent of urbanization occurring in these watersheds. Better understanding of the sources of fine sediment has practical implications on the type of sediment control measures to be adopted. Investment of resources in improving water quality should consider the factors causing stream bank erosion and erosion from unpaved roads and construction sites to water quality impairment. PMID:20830921

Mukundan, R; Radcliffe, D E; Ritchie, J C; Risse, L M; McKinley, R A

2010-01-01

273

Characterization of suspended-sediment transport conditions for stable, “Reference” streams in selected Ecoregions of EPA Region 8  

Technology Transfer Automated Retrieval System (TEKTRAN)

Historic flow and sediment transport data from about 350 sites across the Mountains and Plains region of the United States were analyzed for the purpose of developing ‘background’ or ‘reference’ rates of suspended-sediment transport by Level III ecoregion. Rapid Geomorphic Assessments (RGAs) were c...

274

A reconnaissance study of the effect of irrigated agriculture on water quality in the Ogallala Formation, Central High Plains Aquifer  

USGS Publications Warehouse

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.

McMahon, Peter B.

2000-01-01

275

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...

276

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.

277

The High Plains: Land of Extremes.  

ERIC Educational Resources Information Center

Provides rich background information about unique High Plains ecosystems. Focuses on water, plant, animal, and energy resources. Describes hands-on activities related to ground water movement and energy resources. Contains 18 references. (DDR)

Capron, Ranel Stephenson; And Others

1996-01-01

278

Sorghum Tillage in the Texas High Plains  

E-print Network

Sorghum Tillage in the Texas High Plains Ordie R. Jones, Paul W. Unger, R. Louis Baumhardt and Brent Bean* Tillage Management Tools Producers can manage sorghum crops by differ- ent types of tilling ? no-tillage, stubblemulch till- age, reduced...

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

2003-05-12

279

Sweetened Plain and Flavored Carbonated Yogurt Beverages  

Microsoft Academic Search

Sweetened plain and strawberry- flavored carbonated yogurt beverages without free whey were developed. Yogurts, after blending with a 12% suc- rose solution and additionally with flavor extract, were carbonated under .5 kg\\/cm 2 at 4°C. Sweetened flavored yogurt bever- ages contained 15.5% total solids, 2.8% protein, 1.5% fat, .5% ash, and 10.7% carbohydrates. Carbonation of chilled sweetened plain yogurt beverages

H. S. Choi; F. V. Kosikowski

1985-01-01

280

Assessment of the effects of farming and conservation programs on pesticide deposition in high plains wetlands.  

PubMed

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

Belden, Jason B; Hanson, Brittany Rae; McMurry, Scott T; Smith, Loren M; Haukos, David A

2012-03-20

281

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) and provided information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 2 efforts also included preparation of a draft topical report entitled ''Deployment Issues Related to Geologic CO{sub 2} Sequestration in the PCOR Partnership Region'', which is nearing completion. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. The video will be completed and aired on Prairie Public Television in the next quarter. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. The addition of the Canadian province of Alberta to the PCOR Partnership region expanded the decision support system (DSS) geographic information system database. Task 5 screened and qualitatively assessed sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

2005-04-01

282

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership characterization work is nearing completion, and most remaining efforts are related to finalizing work products. Task 2 (Technology Deployment) has developed a Topical Report entitled ''Deployment Issues Related to Geologic CO{sub 2} Sequestration in the PCOR Partnership Region''. Task 3 (Public Outreach) has developed an informational Public Television program entitled ''Nature in the Balance'', about CO{sub 2} sequestration. The program was completed and aired on Prairie Public Television in this quarter. Task 4 (Sources, Sinks, and Infrastructure) efforts are nearing completion, and data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation are being incorporated into a series of topical reports. The expansion of the Decision Support System Geographic Information System database has continued with the development of a ''save bookmark'' feature that allows users to save a map from the system easily. A feature that allows users to develop a report that summarizes CO{sub 2} sequestration parameters was also developed. Task 5 (Modeling and Phase II Action Plans) focused on screening and qualitatively assessing sequestration options and developing economic estimates for important regional CO{sub 2} sequestration strategies.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Lisa S. Botnen

2005-07-01

283

A Long-term Perspective on Drought in the Great Plains Sherilyn C. Fritz, Department of Geosciences and School of Biological Sciences,  

E-print Network

years or so, provides a snapshot of the contemporary history of drought and its impacts, but this record of human impacts. A variety of so-called paleoclimatic records - such as tree rings, lake sedimentsA Long-term Perspective on Drought in the Great Plains and West Sherilyn C. Fritz, Department

Nebraska-Lincoln, University of

284

Mineral resources of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona  

SciTech Connect

This paper reports on geologic, geochemical, and geophysical studies in the Cactus Plain and East Cactus Plain Wilderness Study Areas outlined in areas with moderate to high potential for gold, silver, copper, lead, zinc, barite, fluorite, manganese, and sand suitable for foundry, fracturing, and abrasive uses and low resource potential for beryllium, uranium and bentonitic clays.

Tosdal, R.M.; Eppinger, R.G.; Erdman, J.A.; Hanna, W.F.; Pitkin, J.A.; Blank, H.R. Jr.; O'Leary, R.M.; Watterson, J.R. (US Geological Survey (US)); Kreidler, T.J. (US Bureau of Mines (US))

1990-01-01

285

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)

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.

Deschamps, F.; Guillot, S.; Godard, M.; Chauvel, C.; Andreani, M.

2009-04-01

286

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

287

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

PubMed Central

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

Last, William M; Ginn, Fawn M

2005-01-01

288

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

PubMed

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

Last, William M; Ginn, Fawn M

2005-01-01

289

Fire Cycles on the Northern Great Plains and Their Relation to Prairie Drought  

NASA Astrophysics Data System (ADS)

Drought is a naturally occurring, recurrent phenomenon that has historically gripped large regions of the United States, often with catastrophic consequences. Human insight into the duration, frequency, and dynamics of drought is largely limited to short-term observation. For example, the "Dust Bowl" of the 1930's in the central plains is one of the most vivid cases of prolonged drought in the USA and yet it persisted for less than a decade. To circumnavigate this limited perspective, we employed a paleoenvironmental approach to better characterize landscape response to prairie droughts and specifically document fire response to droughts. Two long sediment cores were collected from Kettle and Brush lakes in the Northern Great Plains (NGP) and age-depth models were developed for the cores by fitting locally weighted loess curves to AMS radiocarbon dates. The cores were continuously sub-sampled at high resolution (1 cm) for particulate charcoal, pollen, sediment mineralogy, and loss-on-ignition. In contrast to recent human observation, spectral and wavelet analyses reveal that multi-decadal to centennial drought cycles have persisted on the northern plains for much of the last ca. 10,000 years, though there were intervals where the cycles were muted, further compounding the dynamics of climate on the plains. In the latest Holocene interval, 160-year fire and drought cycles are clearly denoted. Fires are more common during the wet phases of the drought cycles because moist conditions foster increased grass productivity, resulting in greater fuel loads. In contrast, forbs expanded during the drier periods, limiting fuel loads which resulted in less fire. The charcoal data reveal three general Holocene fire intervals on the NGP associated with millennial-scale changes in climate. In general, the incidence of fire was greater in the early- and late-Holocene with less fire during the warm dry mid-Holocene.

Brown, K. J.; Clark, J. S.; Grimm, E. C.; Donovan, J. J.; Mueller, P.

2004-12-01

290

Activity and growth of microbial populations in pressurized deep-sea sediment and animal gut samples.  

PubMed Central

Benthic animals and sediment samples were collected at deep-sea stations in the northwest (3,600-m depth) and southeast (4,300- and 5200-m depths) Atlantic Ocean. Utilization rates of [14C]glutamate (0.67 to 0.74 nmol) in sediment suspensions incubated at in situ temperatures and pressures (3 to 5 degrees C and 360, 430, or 520 atmospheres) were relatively slow, ranging from 0.09 to 0.39 nmol g-1 day-1, whereas rates for pressurized samples of gut suspensions varied widely, ranging from no detectable activity to a rapid rate of 986 nmol g-1 day-1. Gut flora from a holothurian specimen and a fish demonstrated rapid, barophilic substrate utilization, based on relative rates calculated for pressurized samples and samples held at 1 atm (101.325 kPa). Substrate utilization by microbial populations in several sediment samples was not inhibited by in situ pressure. Deep-sea pressures did not restrict growth, measured as doubling time, of culturable bacteria present in a northwest Atlantic sediment sample and in a gut suspension prepared from an abyssal scavenging amphipod. From the results of this study, it was concluded that microbial populations in benthic environments can demonstrate significant metabolic activity under deep-ocean conditions of temperature and pressure. Furthermore, rates of microbial activity in the guts of benthic macrofauna are potentially more rapid than in surrounding deep-sea sediments. PMID:6127054

Tabor, P S; Deming, J W; Ohwada, K; Colwell, R R

1982-01-01

291

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

USGS Publications Warehouse

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

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

1990-01-01

292

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

SciTech Connect

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.

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

2007-09-15

293

Environmental changes in the central Po Plain (northern Italy) due to fluvial modifications and anthropogenic activities  

NASA Astrophysics Data System (ADS)

The fluvial environment of the central Po Plain, the largest plain in Italy, is discussed in this paper. Bounded by the mountain chains of the Alps and the Apennines, this plain is a link between the Mediterranean environment and the cultural and continental influences of both western and eastern Europe. In the past decades, economic development has been responsible for many changes in the fluvial environment of the area. This paper discusses the changes in fluvial dynamics that started from Late Pleistocene and Early Holocene due to distinct climatic changes. The discussion is based on geomorphological, pedological, and archaeological evidences and radiocarbon dating. In the northern foothills, Late Pleistocene palaeochannels indicate several cases of underfit streams among the northern tributaries of the River Po. On the other hand, on the southern side of the Po Plain, no geomorphological evidence of similar discharge reduction has been found. Here, stratigraphic sections, together with archaeological remains buried under the fluvial deposits, show a reduction in the size of fluvial sediments after the 10th millennium BC. During the Holocene, fluvial sedimentation became finer, and was characterised by minor fluctuations in the rate of deposition, probably related to short and less intense climatic fluctuations. Given the high rate of population growth and the development of human activities since the Neolithic Age, human influence on fluvial dynamics, especially since the Roman Age, prevailed over other factors (i.e., climate, tectonics, vegetation, etc.). During the Holocene, the most important changes in the Po Plain were not modifications in water discharge but in sediment. From the 1st to 3rd Century AD, land grants to war veterans caused almost complete deforestation, generalised soil erosion, and maximum progradation of the River Po delta. At present, land abandonment in the mountainous region has led to reafforestation. Artificial channel control in the mountain sector of the basins and in-channel gravel extraction (now illegal but very intense in the 1960s and 1970s) are causing erosion along the rivers and along large sectors of the Adriatic coast. These changes are comparable with those occurring in basins of other Mediterranean rivers.

Marchetti, Mauro

2002-05-01

294

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

295

Solute geochemistry of the Snake River plain regional aquifer system, Idaho and eastern Oregon  

USGS Publications Warehouse

Three geochemical methods were used to determine chemical reactions that control solute concentrations in the Snake River Plain regional aquifer system: (1) calculation of a regional solute balance within the aquifer and of mineralogy in the aquifer framework to identify solute reactions, (2) comparison of thermodynamic mineral saturation indices with plausible solute reactions, and (3) comparison of stable isotope ratios of the groundwater with those in the aquifer framework. The geothermal groundwater system underlying the main aquifer system was examined by calculating thermodynamic mineral saturation indices, stable isotope ratios of geothermal water, geothermometry, and radiocarbon dating. Water budgets, hydrologic arguments, and isotopic analyses for the eastern Snake River Plain aquifer system demonstrate that most, if not all, water is of local meteoric and not juvenile or formation origin. Solute balance, isotopic, mineralogic, and thermodynamic arguments suggest that about 20% of the solutes are derived from reactions with rocks forming the aquifer framework. Solute reactions indicate that calcite and silica are precipitated in the aquifer. Large amounts of sodium and chloride, relative to their concentration in the igneous rock, are being removed from the aquifer. Release of fluids from inclusions in the igneous rocks, and initial flushing of grain boundaries and pores of detrital marine sediments in interbeds are believed to be the source of the sodium chloride. Identification and quantification of reactions controlling solute concentrations in groundwater in the eastern plain indicate that the aquifer is not a large mixing vessel that simply stores and transmits water and solutes but is undergoing diagenesis and is both a source and sink for solutes. Reactions controlling solutes in the western Snake River basin are believed to be similar to those in the eastern basin but the regional geothermal system that underlies the Snake River Plain contains total dissolved solids similar to those in the overlying Snake River Plain aquifer system but contains higher concentrations of sodium, bicarbonate, silica, fluoride, sulfate, chloride, arsenic, boron, and lithium, and lower concentrations of calcium, magnesium, and hydrogen. (Lantz-PTT)

Wood, W.W.; Low, W.H.

1987-01-01

296

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

297

Contaminated Sediments in Water  

MedlinePLUS

... Contact Us Water: Contaminated Sediments You are here: Water Pollution Prevention & Control Sediments Contaminated Sediments in Water Contaminated ... Water Education & Training Grants & Funding Laws & Regulations Our Waters Pollution Prevention & Control Applications & Databases Low Impact Development Impaired ...

298

Late Middle Pleistocene deposits at Norton Farm on the West Sussex coastal plain, southern England  

NASA Astrophysics Data System (ADS)

The coastal plain of West Sussex, southern England, is internationally important because of the sequence of discrete high-sea-level events preserved at various elevations across it. New evidence is presented from a site at Norton Farm, near Chichester, on the Lower Coastal Plain, where Pleistocene marine sands, fining upwards into silts, occur between 5.3 m and 9.1 m OD. The sequence reflects a regressive tendency at the transition from an interglacial to a cold stage. The marine sands have yielded foraminifera, ostracods and molluscs that indicate a declining marine influence through the sequence, culminating in a tidal mudflat, strongly weathered in places. Cool-climate foraminifera (including Elphidium clavatum, Cassidulina reniformis and Elphidium albiumbilicatum) and ostracods have been recovered from the marine sands. Some species with an apparent preference for warmer water conditions, however, are also present. Freshwater taxa washed into the terminal marine sediments include some cold climate indicators, such as Pisidium stewarti and P. obtusale lapponicum. Additional evidence for cool climatic conditions during the deposition of the upper part of the marine sequence is provided by the lack of tree taxa in the pollen record and by features of the micromorphology. The marine sediments probably began accumulating during OIS 7, a conclusion based on their elevation, on amino acid ratios from shells, but especially on vertebrate evidence, particularly the presence of a small form of horse, together with a large, distinctive, form of northern vole (Microtus oeconomus). The occurrence of cool climate indicators in these marine sediments may demonstrate a lag between the climatic deterioration and the expected glacio-eustatic fall in relative sea-level. This evidence appears to support the conclusions drawn from the study of coral terraces in Barbados. Such a scenario would provide the conditions necessary for the emplacement of the large erratic boulders reported from the Lower Coastal Plain of West Sussex.

Bates, Martin R.; Bates, C. Richard; Gibbard, Philip L.; MacPhail, Richard I.; Owen, Frederick J.; Parfitt, Simon A.; Preece, Richard C.; Roberts, Mark B.; Robinson, J. Eric; Whittaker, John E.; Wilkinson, Keith N.

2000-01-01

299

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

PubMed Central

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

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

2013-01-01

300

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

301

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

PubMed

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

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

2013-01-01

302

Iron and manganese diagenesis in deep sea volcanogenic sediments and the origins of pore water colloids  

NASA Astrophysics Data System (ADS)

Volcanogenic sediments are typically rich in Fe and Mn-bearing minerals that undergo substantial alteration during early marine diagenesis, however their impact on the global biogeochemical cycling of Fe and Mn has not been widely addressed. This study compares the near surface (0-20 cm below sea floor [cmbsf]) aqueous (<0.02 ?m) and aqueous + colloidal here in after 'dissolved' (<0.2 ?m) pore water Fe and Mn distributions, and ancillary O 2(aq), NO3- and solid-phase reactive Fe distributions, between two volcanogenic sediment settings: [1] a deep sea tephra-rich deposit neighbouring the volcanically active island of Montserrat and [2] mixed biosiliceous-volcanogenic sediments from abyssal depths near the volcanically inactive Crozet Islands archipelago. Shallow penetration of O 2(aq) into Montserrat sediments was observed (<1 cmbsf), and inferred to partially reflect oxidation of fine grained Fe(II) minerals, whereas penetration of O 2(aq) into abyssal Crozet sediments was >5 cmbsf and largely controlled by the oxidation of organic matter. Dissolved Fe and Mn distributions in Montserrat pore waters were lowest in the surface oxic-layer (0.3 ?M Fe; 32 ?M Mn), with maxima (20 ?M Fe; 200 ?M Mn) in the upper 1-15 cmbsf. Unlike Montserrat, Fe and Mn in Crozet pore waters were ubiquitously partitioned between 0.2 ?m and 0.02 ?m filtrations, indicating that the pore water distributions of Fe and Mn in the (traditionally termed) 'dissolved' size fraction are dominated by colloids, with respective mean abundances of 80% and 61%. Plausible mechanisms for the origin and composition of pore water colloids are discussed, and include prolonged exposure of Crozet surface sediments to early diagenesis compared to Montserrat, favouring nano-particulate goethite formation, and the elevated dissolved Si concentrations, which are shown to encourage fine-grained smectite formation. In addition, organic matter may stabilise authigenic Fe and Mn in the Crozet pore waters. We conclude that volcanogenic sediment diagenesis leads to a flux of colloidal material to the overlying bottom water, which may impact significantly on deep ocean biogeochemistry. Diffusive flux estimates from Montserrat suggest that diagenesis within tephra deposits of active island volcanism may also be an important source of dissolved Mn to the bottom waters, and therefore a source for the widespread hydrogenous MnO x deposits found in the Caribbean region.

Homoky, W. B.; Hembury, D. J.; Hepburn, L. E.; Mills, R. A.; Statham, P. J.; Fones, G. R.; Palmer, M. R.

2011-09-01

303

Carbon isotopic changes in benthic foraminifera from the western South Atlantic: Reconstruction of glacial abyssal circulation patterns  

NASA Astrophysics Data System (ADS)

Oxygen- and carbon-isotopic analyses have been performed on the benthic foraminifer Planulina wuellerstorfi in seven Late Quaternary cores from the Vema Channel-Rio Grande Rise region. The cores are distributed over the water-depth interval of 2340 to 3939 m, which includes the present transition from North Atlantic Deep Water (NADW) to Antarctic Bottom Water (AABW). The carbon-isotopic records in the cores vary as a function of water depth. The shallowest and deepest cores show no significant glacial-interglacial difference in ? 13C. Four of the five cores presently located in the NADW have benthic foraminiferal ? 13C that is lower during glacial isotopic stages. Based on bathymetric gradients in ? 13C, we conclude that, like today, there were two water masses present in the Vema Channel during glacial intervals: a water mass enriched in 13C overlying another water mass depleted in 13C. The largest gradient of change of ? 13C with depth, however, occurred at 2.7 km, ˜ 1 km shallower than the present position of this gradient. On the basis of paleontologic and sedimentologic evidence, we consider it unlikely that the NADW:AABW transition shallowed to this level. Reduced carbon-isotopic gradients between the deep basins of the North Atlantic and Pacific Oceans during the last glaciation suggest that production of NADW was reduced. Lower production of NADW may have modified the local abyssal circulation pattern in the Vema Channel region.

Curry, W. B.; Lohmann, G. P.

1982-09-01

304

Hydrogeochemical analysis for Tasuj plain aquifer, Iran  

NASA Astrophysics Data System (ADS)

This study investigated the hydrogeochemical processes of groundwater in the Tasuj plain, Iran. The Tasuj plain is one of the 12 marginal plains around Urmia Lake which is currently under a critical ecological condition. In the last decades, the Tasuj plain aquifer suffered from severe groundwater level declination and caused degradation of groundwater quality. To better understand hydrogeochemical processes in the Tasuj plain, this study adopted graphical methods and multivariate statistical techniques to analyze groundwater samples. A total of 504 groundwater samples was obtained from 34 different locations (qanats, wells, and springs) over 12 years (1997-2009) and analyzed for 15 water quality parameters. From the results, the Piper diagram indicated four groundwater types and the Stiff diagram showed eight different sources of groundwater samples. The Durov diagram identified five major hydrogeochemical processes in the aquifer. However, hierarchical cluster analysis (HCA) identified five water types in the groundwater samples because HCA was able to analyze more chemical and physical data than graphical methods. The HCA result was checked by discriminant analysis and found consistency in all samples that were classified into correct groups. Using factor analysis, we identified three factors that accounted for 81.6% of the total variance of the dataset. Based on the high factor loadings of the variables, factors 1 and 2 reflected the natural hydrogeochemical processes and factor 3 explained the effect of agricultural fertilizers and human activities in the Tasuj plain. Dendrograms from 2000 to 2009 were studied to understand the temporal variation of groundwater quality. Comparing the distributions of groundwater types in 2000 and 2009, we found that the mixing zone was expanded. This may be due to artificial groundwater recharge in the recharge area and the effect of inverse ion exchange in the discharge area.

Nadiri, Ata Allah; Moghaddam, Asghar Asghari; Tsai, Frank T.-C.; Fijani, Elham

2013-08-01

305

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

USGS Publications Warehouse

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

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

1980-01-01

306

Coastal geomorphology of the Martian northern plains  

NASA Astrophysics Data System (ADS)

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

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

1993-06-01

307

Detrital carbonate-rich sediments, northwestern Labrador Sea: Implications for ice-sheet dynamics and iceberg rafting (Heinrich) events in the North Atlantic  

Microsoft Academic Search

Much of the bed of the central and eastern sectors of the Laurentide Ice Sheet was underlain by Paleozoic carbonates. We propose that pulses of detrital carbonate-rich sediments in two cores from the northwestern Labrador Sea reflect episodes when an ice stream from the Hudson Strait extended to the shelf break and delivered sediment onto the slope and deep-sea plain.

J. T. Andrews; K. Tedesco

1992-01-01

308

Suspended sediment dynamics in the Amazon River of Peru  

NASA Astrophysics Data System (ADS)

The erosion and transport of sediments allow us to understand many activities of significance, such as crust evolution, climate change, uplift rates, continental processes, the biogeochemical cycling of pollutants and nutrients. The Amazon basin of Peru has contrasting physiographic and climatic characteristics between the Andean piedmont and the plains and between the north and south of the basin which is why there are 8 gauging stations located along the principal rivers of the Andean piedmont (Marañón, Huallaga, Ucayali) and the plain (Marañón, Tigre, Napo, Ucayali and Amazon rivers). Since 2003, the ORE-Hybam (IRD-SENAMHI-UNALM) observatory has performed out regular measurements at strategic points of the Amazon basin to understand and model the systems, behavior and long-term dynamics. On the Andean piedmont, the suspended yields are governed by a simple model with a relationship between the river discharge and the sediment concentration. In the plain, the dilution effect of the concentrations can create hysteresis in this relationship on a monthly basis. The Amazon basin of Peru has a sediment yield of 541 *106 t year-1, 70% comes from the southern basin.

Armijos, Elisa; Crave, Alain; Vauchel, Philippe; Fraizy, Pascal; Santini, William; Moquet, Jean-Sèbastien; Arevalo, Nore; Carranza, Jorge; Guyot, Jean-Loup

2013-07-01

309

Land use and conservation reserve program effects on the persistence of playa wetlands in the High Plains.  

PubMed

Watershed cultivation and subsequent soil erosion remains the greatest threat to the service provisioning of playa wetlands in the High Plains. The U.S. Department of Agriculture's (USDA) Conservation Reserve Program (CRP) plants perennial vegetation cover on cultivated lands including playa watersheds, and therefore, the program influences sediment deposition and accumulation in playas. Our objective was to measure the effects of the CRP on sediment deposition by comparing sediment depth and present/historic size characteristics in 258 playas among three High-Plains subregions (northern, central, and southern) and the three dominant watershed types: cropland, CRP, and native grassland. Sediment depth and resultant volume loss for CRP playas were 40% and 57% lower than cropland playas, but 68% and 76% greater than playas in native grassland. Playas in CRP had remaining volumes exceeding those of cropland playas. Grassland playas had nearly three times more original playa volume and 122% greater wetland area than CRP playas. Overall, playas were larger in the south than other subregions. Sediment depth was also three times greater in the south than the north, which resulted in southern playas losing twice as much total volume as northern playas. However, the larger southern playas provide more remaining volume per playa than those in other subregions. The results of this study demonstrate the importance of proper watershed management in preserving playa wetland ecosystem service provisioning in the High Plains. Furthermore, we identify regional differences in playas that may influence management decisions and provide valuable insight to conservation practitioners trying to maximize wetland services with limited resources. PMID:24635683

Daniel, Dale W; Smith, Loren M; Haukos, David A; Johnson, Lacrecia A; McMurry, Scott T

2014-04-15

310

Gulf coastal plain evolution in West Louisiana: Heavy mineral provenance and Pleistocene alluvial chronology  

NASA Astrophysics Data System (ADS)

High Resolution Heavy Mineral Analysis (HRHMA) of late Pleistocene terrace samples, their Tertiary source rocks, and modern river sediments provided an effective tool for reconstructing sediment provenance and mapping heavy mineral provinces in southwest Louisiana. Each province, linked to a discrete source region, represents Pleistocene fluvial channel belts within which depositional activity was controlled by periods of climate, sediment supply, and sea level changes. Four coastal heavy mineral provinces have been identified. The Northern Province (NP), drained by the lower reaches of the Sabine and Calcasieu Rivers underlies level mid- and late Pleistocene coastal terrace surfaces and is distinguished by high-grade metamorphic assemblages (kyanite, staurolite, sillimanite) and abundant zircon, probably of Ouachita Mts. derivation. Transporting eroded Cretaceous, Tertiary, and Pleistocene coastal plain deposits, the modern Calcasieu and Sabine River sands in west-central and southwest Louisiana and east Texas, display identical heavy mineral composition to that of the NP. Level Late Pleistocene coastal terrace areas in the east represent the Red River Province (RRP) with dominant epidote, tourmaline, garnet, and zircon. Its mineralogy is influenced significantly by Paleozoic-Mesozoic sedimentary units that frame the drainage basin upstream. Modern Red River sands differ in their spectra both from Red River Pleistocene coastal terrace and valley terrace deposits, interpreted by temporal fluctuations in sediment supply initiating a variable contribution of detritus from different sources. Tributaries that drain formations with high concentrations of high-grade metamorphic minerals also affected Red River valley Pleistocene terrace deposits in west-central Louisiana, enriching them in kyanite and staurolite. The Mississippi Province (MP) occupies the eastern-southeastern area of the low, flat, gently seaward-sloping Prairie coastal terrace. Whereas modern Mississippi alluvium is dominated by hornblende, pyroxenes, and epidote, as the result of post-depositional dissolution, pyroxenes are rare in the MP. The Mixed Suite Province (MSP) reflects MP, RRP, and to a lesser degree, NP signatures and forms the Prairie fluvial coastal plain surface closer to the Texas state line. Raw data of the principal heavy minerals were used for statistical analysis. Statistical parameters proved consistent with mineralogy-derived reconstruction of sediment provenance and provinciality of heavy mineral suites, thus providing an independent and objective support to data interpretation. Optical and thermal luminescence dating at other Gulf locations [Otvos, E.G. (2005). Numerical chronology of Pleistocene coastal plain and valley development; extensive aggradation during glacial low sea levels. Quaternary Internat., 135 91-113.] supports the pre-Sangamon ages of the Intermediate Pleistocene terraces in the NP area. Sangamon (135-116 ka), Eowisconsin (114-76 ka), and Wisconsin (74-36 ka) dates characterize the four provinces in the low, level northern Gulf Prairie coastal plain. Refuting earlier assumptions that coastal plain aggradation occurred only during marine highstand phases, thermal and optical luminescence dates indicated that, despite the low Eowisconsin and Wisconsin eustatic sea levels of several preglacial and glacial stages and substages, coastal plain alluviation, paradoxically, recurred between 106 and 35 ka BP. An interesting outcome of our heavy mineral study is the recognition and dating of a previously undocumented, rare ash-fall event that originated in Caribbean andesitic volcanoes. It was identified by the presence of a volcanogenic heavy mineral suite, composed of pristine euhedral clinopyroxene, sphene, zircon, apatite, and hexagonal biotite. Unaffected by fluvial reworking, this suite was recovered from a MP sample, dated ca. 86 ka BP.

Mange, Maria A.; Otvos, Ervin G.

2005-12-01

311

FLOOD-PLAIN DELINEATION IN ICE JAM PRONE REGIONS  

E-print Network

FLOOD-PLAIN DELINEATION IN ICE JAM PRONE REGIONS By Richard M. Vogel,1 S. M. ASCE and Jery R. Stedinger,2 A. M. ASCE ABSTRACT:Flood-plain delineation in ice jam prone regions is in its infancy .A-plain boundaries. These results document the need to consider the probability of ice jam flood events

Vogel, Richard M.

312

Property Rights and Groundwater Management in the High Plains Aquifer  

E-print Network

of the High Plains Aquifer system, located in the Midwestern plains of the United States, began in the lateProperty Rights and Groundwater Management in the High Plains Aquifer Lisa Pfeiffer 7600 Sand Point. The authors would like to acknowledge Jeffrey Peterson, Bill Golden, and Nathan Hendricks for their assistance

Lin, C.-Y. Cynthia

313

44 CFR 10.14 - Flood plains and wetlands.  

Code of Federal Regulations, 2010 CFR

...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...

2010-10-01

314

44 CFR 10.14 - Flood plains and wetlands.  

Code of Federal Regulations, 2012 CFR

...2011-10-01 true 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...

2012-10-01

315

44 CFR 10.14 - Flood plains and wetlands.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 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...

2013-10-01

316

44 CFR 10.14 - Flood plains and wetlands.  

Code of Federal Regulations, 2011 CFR

...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...

2011-10-01

317

44 CFR 10.14 - Flood plains and wetlands.  

...2014-10-01 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...

2014-10-01

318

Great plains regional climate assessment technical report  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

319

Flood routing in channels with flood plains  

NASA Astrophysics Data System (ADS)

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

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

1995-09-01

320

Plains Culture Area. Native American Curriculum Series.  

ERIC Educational Resources Information Center

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

Ross, Cathy; Fernandes, Roger

321

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...

322

Geomorphology of the Eastern Snake River Plain  

NSDL National Science Digital Library

This two-week long laboratory exercise examines the linkages between the endogenic (tectonic and isostatic) and exogenic processes that created the Eastern Snake River Plain (ESRP) landscape. The landform analysis portion of the exercise focuses upon recent basaltic volcanism and the Menan Buttes, the St. Anthony dunes and the fluvial drainage patterns that developed in the region.

David Franzi

323

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

USGS Publications Warehouse

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)

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

1986-01-01

324

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

SciTech Connect

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.

Denham, Miles; Millings, Margaret; Noonkester, Jay

2005-09-22

325

Ancient DNA complements microfossil record in deep-sea subsurface sediments  

PubMed Central

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

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

2013-01-01

326

Precise Dating of Flood-Plain Stratigraphy Using Changes in Tree-Ring Anatomy Following Burial  

NASA Astrophysics Data System (ADS)

Determination of sediment deposition rates from stratigraphy is typically limited by a scarcity of chronological information. We present a method for precise dating of sedimentary beds based on the change in anatomy of tree rings upon burial. When stems of tamarisk (Tamarix ramosissima)and sandbar willow (Salix exigua) are buried, subsequent annual rings in the buried portions become narrower and vessels within the rings become larger. Observation of these changes can be combined with tree ring counts to determine the year of deposition of sedimentary beds that are at least 10 cm thick. Using a backhoe we dug trenches across the flood plain at three locations along the arroyo of the Rio Puerco, New Mexico. At each cross section we prepared a detailed stratigraphic description and excavated several tamarisks to depths as great as 5 meters. From each excavated tree we cut and sanded 10-50 slabs for tree-ring analysis. We cross-dated slabs within and between plants and used the burial signature in the tree rings to date all sedimentary beds in the stratigraphic profile near each plant. We then used the trench stratigraphy to convert depths of sediment deposition around individual trees to areas of deposition in the cross section. In the lower Rio Puerco introduction of tamarisk in 1926 occurred just prior to the beginning of channel narrowing and arroyo filling. Thus the tamarisks record a process of channel change to which they may have contributed. Aggradation has not been synchronous along the lower arroyo. For example, near Highway 6 and Belen, the flood plain has aggraded more than 2 m since 1970, while there has been little aggradation downstream at Bernardo. Much of the sediment deposition in levies at Highway 6 occurred during a flood in 1988. Future work will document longitudinal variation in the arroyo so that we can convert areas of sediment deposition in cross sections to volumes in the arroyo.

Friedman, J. M.; Shafroth, P. B.; Vincent, K. R.; Scott, M. L.; Auble, G. T.

2001-12-01

327

In the Balance: Natural v. Embanked Landscapes in the Ganges-Brahmaputra Tidal Delta Plain  

NASA Astrophysics Data System (ADS)

Natural river deltas are defined by a balance of net aggradational processes that construct the delta platform, and marine processes that redistribute sediments and facilitate platform evolution. The future of deltas worldwide will be determined by this balance of sedimentation, subsidence and sea-level rise, in addition to human-caused perturbations. Among the world's delta systems the Ganges-Brahmaputra is perceived to be at great risk to degradation and submergence under multiple climate and sea-level rise (SLR) scenarios. In particular, the lower delta plain in southwest Bangladesh is isolated from fluvial processes, yet still receives up to 1 cm of sediment accretion annually as sediments discharged at the river mouth are reworked by tides and deposited onto the lower delta plain. In the Sundarbans, a 10,000 km2 block of pristine mangrove forest in the region, this tidally supported sedimentation has been effective in maintaining a dynamic equilibrium with SLR that is augmented by local subsidence and shallow compaction. Adjacent to the Sundarbans, however, human modification has significantly impacted the landscape through embankment construction that occurred in the 1960s to increase arable land for rice production and famine relief. As a consequence, the embankments have locally inhibited sediment delivery to the landscape, decoupling these interacting systems. In the ensuing five decades the land has continued to subside and compact, and in the absence of sediment accretion has experienced a net elevation loss of more than 1 m since embankment construction. The acute effects of this elevation offset were felt in 2009 when the embankments of several large islands breached during Cyclone Aila. We are studying Polder 32, a 60 km2 island that was land tidally inundated for two years until its embankments were repaired. Despite sustained human suffering during this time, the newly reconnected landscape rebounded with tens of centimeters of tidally deposited sediment, accounting for decades-worth of normal sedimentation, but only partly restoring the elevation lost over the previous five decades. This work implements field measurements and a conceptual model of the lower delta plain to establish a budget for observed elevation differences among local, relative water levels and the natural and human-altered landscapes. We demonstrate that embanked regions of the lower delta are more vulnerable than pristine areas to changes in sea level caused by impeded sediment delivery as a result of decoupling the tidal channel-landscape system. The elevation disparity that has developed in the past 50 years is equivalent to ~2 cm/yr of RSL rise. This rate is more than twice the upper end of Intergovernmental Panel on Climate Change projections for future sea-level rise, making these poldered landscapes a very useful, albeit troubling, analog for studying the impact of increased SLR in coming decades.

Wallace Auerbach, L.; Goodbred, S. L.; Mondal, D. R.; Wilson, C.; Ahmed, K.; Roy, K.; Steckler, M. S.; Gilligan, J. M.; Nooner, S. L.

2013-12-01

328

Sedimentation patterns in floodplains of the Mekong Delta - Vietnam  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

329

North-south compression, active uplift, and abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean  

NASA Astrophysics Data System (ADS)

This article presents near N-S compression, active uplift tectonism, and the consequent abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean. The mantle peridotite ridge is about 80 km long, 25 km wide, 3800 m high, and of near E-W direction. The ridge flanks are extremely steep with sub-vertical scarps of about 2000 m of relative height. The Flandrian wave-cut and the 14C datings for the carbonaceous algae of the Saint Peter and Saint Paul Rock indicate active uplift of 1.5 mm/year. The tectonic factures shows conjugated system of N-S compression tending slightly to NW-ES. Close to the peridotite ridge, the earthquakes with near N-S compression focal mechanism take place. The southern half of the peridotite ridge is constituted by undeformed peridotite. The existence of corrugation morphology indicates that the mantle rocks are originated from old megamullion. On the other hand, the northern half is composed of strongly deformed mylonitic peridotite suggesting that the ultramafic rocks are possibly originated from sub-crustal abyssal mantle of old transform fault. The mylonite structure is intensely perturbed indicating the tectonic events which disturbed the original parallel structure. The Saint Paul transform fault zone is characterized by E-W trend right lateral movement and the near N-S compression is unlikely. Therefore, an unusual local geotectonic process is expected. This tectonism was originated from the plate boundary jump at about 8 Ma, caused by the emergence of a new ridge segment, and the new transform fault is oblique to the relative plate movement. This angular discrepancy causes the compression perpendicular to the oblique transform fault, of near N-S direction, which squeeze out the sub-crustal abyssal mantle up to sea level. Therefore, the peridotite Ridge is considered to be a pressure ridge of the strike-slip movement of the Saint Paul transform fault.

Motoki, A.; Sichel, S. E.; Campos, T. F.; Motoki, K. F.; Szatmari, P.; Poseidon-Colmeia

2013-05-01

330

Geomicrobiology of Archaeal Communities Isolated from an Off-axis Abyssal Hill Fault Scarp on the East Pacific Rise Flank at 9° 27'N  

NASA Astrophysics Data System (ADS)

Although heat flow studies suggest that ~70% of the hydrothermal heat loss in the oceans occurs in the abyssal hill terrain on the flanks of mid-ocean ridges, very few off-axis hydrothermal sites have been discovered. In May 2002, sedimentary blowout structures of probable hydrothermal origin were discovered along East Pacific Rise at 9° 27'N on an off-axis abyssal hill bounded by a fault scarp covered with orange-brown microbial flocculations. Recovered samples of these flocculations have presented an opportunity to study the unknown nature and role of thermophilic and hyperthermophilic microbial communities on the ridge flanks. Furthermore, the archaeal communities that we have identified in the samples are useful "microbial tracers" which can be used to locate off-axis areas of moderate-to-high temperature fluid flow (>50° C). In this study, we used molecular techniques to isolate, amplify, and sequence community archaeal RNA sequences from fault scarp flocculations collected with a slurp pump system mounted in the Alvin basket. Molecular phylogenies based on 16S rRNA were constructed. Phylogenetic relationships of isolated clones were used to infer temperature preferences of archaeal communities. We identified 12 clones that clustered within thermophilic or hyperthermophilic clades within Archaea suggesting that moderately high temperature fluid (>50° C) exited the seafloor along this abyssal hill fault scarp. Our studies also suggest that these communities mediate the formation of Fe-sulfide mineral phases. Analysis of the samples with an Environmental Scanning Electron Microscope (ESEM) and X-ray energy dispersive analysis (EDS) revealed unique iron sulfide mineral phases with anomalously low Fe/S ratios in direct association with microbial communities.

Ehrhardt, C. J.; Haymon, R.; Holden, P.; Lamontagne, M.

2003-12-01

331

Serpentinization of abyssal peridotites from the MARK area, Mid-Atlantic Ridge: Sulfur geochemistry and reaction modeling  

USGS Publications Warehouse

The opaque mineralogy and the contents and isotope compositions of sulfur in serpentinized peridotites from the MARK (Mid-Atlantic Ridge, Kane Fracture Zone) area were examined to understand the conditions of serpentinization and evaluate this process as a sink for seawater sulfur. The serpentinites contain a sulfur-rich secondary mineral assemblage and have high sulfur contents (up to 1 wt.%) and elevated ??34Ssulfide (3.7 to 12.7???). Geochemical reaction modeling indicates that seawater-peridotite interaction at 300 to 400??C alone cannot account for both the high sulfur contents and high ??34Ssulfide. These require a multistage reaction with leaching of sulfide from subjacent gabbro during higher temperature (???400??C) reactions with seawater and subsequent deposition of sulfide during serpentinization of peridotite at ???300??C. Serpentinization produces highly reducing conditions and significant amounts of H2 and results in the partial reduction of seawater carbonate to methane. The latter is documented by formation of carbonate veins enriched in 13C (up to 4.5???) at temperatures above 250??C. Although different processes produce variable sulfur isotope effects in other oceanic serpentinites, sulfur is consistently added to abyssal peridotites during serpentinization. Data for serpentinites drilled and dredged from oceanic crust and from ophiolites indicate that oceanic peridotites are a sink for up to 0.4 to 6.0 ?? 1012 g seawater S yr-1. This is comparable to sulfur exchange that occurs in hydrothermal systems in mafic oceanic crust at midocean ridges and on ridge flanks and amounts to 2 to 30% of the riverine sulfate source and sedimentary sulfide sink in the oceans. The high concentrations and modified isotope compositions of sulfur in serpentinites could be important for mantle metasomatism during subduction of crust generated at slow spreading rates. ?? 2003 Elsevier Science Ltd.

Alt, J.C.; Shanks, W. C., III

2003-01-01

332

Spatial and Temporal Variability of Temperature and Salinity in the Deep and Abyssal Layers of the Subpolar North Atlantic  

NASA Astrophysics Data System (ADS)

The dense water overflows crossing the Denmark Strait and Faroe-Shetland Channel form the Denmark Strait Overflow Water (DSOW) and Northeast Atlantic Deep Water, respectively. Collectively with the convectively-formed Labrador Sea Water (LSW), these water masses form the deep limb of the Atlantic Meridional Overturning Circulation and hence are important components of the global climate system. Recent variability in the properties of the intermediate and deep water masses will be described by using hydrographic, moored, profiling float, altimeter and tracer data from several programs. We will show that the variability of intermediate-depth water is strongly influenced by the strength and duration of winter convection in the Labrador Sea on the western side, and the advection of warmer more saline intermediate waters from the lower latitudes on the eastern side. Four variations of LSW produced in different years were identified in the 2010 annual survey of the Labrador Sea. While gradually transforming in time, these waters have been preserved in different ranges of density and depth because of gradual weakening of winter convection since 2008, and are still distinguishable by their unique signatures in temperature, salinity and chemical tracers. The fate of each individual LSW class can now be followed by combining profiles from Argo floats and hydrographic data from several institutes. We will show how an international array of hydrographic and tracer sections supported by moored, profiling float and satellite measurements has resolved the downstream propagation of some interesting events formed in the subpolar or Arctic seas. In particular, we document strong fresh and cold anomalies in DSOW, first observed in the Irminger Sea in 1999, 2004 and 2009, and then with a year delay in the abyssal Labrador Sea.

Yashayaev, I.; Bacon, S.; de Jong, F.; Dye, S.; Fischer, J.; Holliday, N. P.; Kieke, D.; Quadfasel, D. R.; Rhein, M.; Sarafanov, A.; Valdimarsson, H.; van Aken, H. M.

2010-12-01

333

Tidal inlet variability in Mississippi River delta plain  

SciTech Connect

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.

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

1983-09-01

334

Sources of suspended-sediment flux in streams of the chesapeake bay watershed: A regional application of the sparrow model  

USGS Publications Warehouse

We describe the sources and transport of fluvial suspended sediment in nontidal streams of the Chesapeake Bay watershed and vicinity. We applied SPAtially Referenced Regressions on Watershed attributes, which spatially correlates estimated mean annual flux of suspended sediment in nontidal streams with sources of suspended sediment and transport factors. According to our model, urban development generates on average the greatest amount of suspended sediment per unit area (3,928 Mg/km2/year), although agriculture is much more widespread and is the greatest overall source of suspended sediment (57 Mg/km2/year). Factors affecting sediment transport from uplands to streams include mean basin slope, reservoirs, physiography, and soil permeability. On average, 59% of upland suspended sediment generated is temporarily stored along large rivers draining the Coastal Plain or in reservoirs throughout the watershed. Applying erosion and sediment controls from agriculture and urban development in areas of the northern Piedmont close to the upper Bay, where the combined effects of watershed characteristics on sediment transport have the greatest influence may be most helpful in mitigating sedimentation in the bay and its tributaries. Stream restoration efforts addressing floodplain and bank stabilization and incision may be more effective in smaller, headwater streams outside of the Coastal Plain. ?? 2010 American Water Resources Association. No claim to original U.S. government works.

Brakebill, J.W.; Ator, S.W.; Schwarz, G.E.

2010-01-01

335

Fate of sediments delivered to the sea by Asian large rivers: Long-distance transport and formation of remote alongshore clinothems  

Microsoft Academic Search

Recent studies show that the global flux of river-derived sediment reaching the coasts and oceans is about 15-19 x 109 tons per year. New sediment budgets for the major Asian river systems (e.g.,Yellow, Yangtze, Mekong, Ganges-Brahmaputra, etc.) suggest that 30-50% of their sediment load has been retained in the lower channel reaches to form an extensive subaerial delta plain, while

J. P. Liu; Z. Xue; K. Ross; Z. S. Yang; S. Gao

2009-01-01

336

Development of sediment drifts approaching an active plate margin under the SW Pacific Deep Western Boundary Current  

NASA Astrophysics Data System (ADS)

The abyssal Pacific Ocean is fed by a 1000 km wide, deep western boundary current (DWBC) that flows northward along the continental margin, east of New Zealand. Between the passive margin of Chatham Rise and the subduction zone of Kermadec Trench, a distance of 1200 km, the DWBC has formed a suite of sediment drifts over a depth range of 2200-5700 m. Airgun and 3.5-kHz profiles record a variety of drift types that reflect regional variations in bathymetry, sediment supply, and the tectonic/volcanic framework. On Chatham Rise the DWBC has deposited a sinuous, linear body along the south flank (3000 m), an extensive apronlike drift on the north flank (2200-4500 m), and a ridgelike drift about the rise base (4500-5200 m). The flow has also deposited a body of sediment over 400 km long within a moat at the base of the nearby Louisville Seamount Chain. Further downcurrent, the 250 km long Rekohu Drift (3600-4190 m) has developed northward to 39°S. South of this latitude, drifts comprise mainly reworked pelagic/hemipelagic material and sediment transported from distant southerly sources. In contrast, drifts north of 39°S have received a major injection of terrigenous sediment from Hikurangi Channel which runs 1400 km from New Zealand, eastward across the Hikurangi Plateau to disgorge on to the abyssal floor at the plateau edge. En route, turbidity current overspill from the channel has moved north under the influence of the shallow DWBC to contribute to a series of small ridge and patch drifts among the numerous seamounts on the plateau at 3500-4200 m. Off Hikurangi Channel mouth, a large fan has accumulated. The DWBC has extended the fan into a drift running over 250 km along the base of Hikurangi Plateau (5150-5770 m) toward Kermadec Trench. Here drift sediment becomes increasingly disrupted by mass wasting associated with the active subduction in this area. The seismic stratigraphy reveals the drifts to rest mainly on a widespread erosional surface that is interpreted to mark the inception of the DWBC in the region with the late Oligocene opening of the Australian-Antarctic seaway. Drift construction commenced during the Miocene but was punctuated in the late Miocene by another period of erosion that coincided with increased bottom water production in Antarctica. Deposition resumed in Plio-Pleistocene times when large quantities of sediment from the rapidly rising landmass of New Zealand were injected into the boundary current. The modern flow continues to affect drift deposition as manifest by an active boundary channel along the foot of Hikurangi Plateau and widespread scour zones and sediment wave fields.

Carter, L.; McCave, I. N.

1994-12-01

337

Chemical osmosis test and numerical modeling of the clay samples in the North China Plain  

NASA Astrophysics Data System (ADS)

Sediments with high clay content can act as semipermeable membranes, leading to osmotic flow and osmotic hydraulic pressure. The semipermeable membrane ability is usually quantified in terms of a reflection coefficient, ?, or chemico-osmotic efficiency, ?. In the previous studies, the osmotic transport was never taken into account in salt-rich region of the North China Plain. In a rigid wall permeameter, an undisturbed soil core sample drilled in this region and a remolded soil sample with the same clay content and porosity were subjected to a certain chemical potential gradient to estimate the reflection coefficient, ?, by measuring the osmotic flow and the induced pressure. Meanwhile, the constant-head tests for determining the hydraulic conductivity of soil samples were conducted before and after the osmotic test. It is indicated that the permeability of the remolded sample is smaller than the undisturbed sample in both periods. Also, the chemical osmosis was observed in both samples, and the measured value of ? for in-situ sampling (0.074) is much smaller than that value for remolded sampling (0.350). Moreover, a chemical osmosis continuum model presented by Garavito et al. (2006) was used to fit the evolution of the osmotically driven hydraulic pressure in the clay samples where more intrinsic parameters of the samples were calibrated. The results demonstrated in our tests can provide the reliable basis for the further study of clay sediments in the North China Plain.

sun, X.; Wu, J.

2013-12-01

338

[Profile nutrient distribution and sedimentary characteristics in typical marshes of Sanjiang Plain].  

PubMed

Profile distribution characteristics of organic carbon (C), total nitrogen (N), total phosphorus (P) and total sulfur (S) were studied in two typical marshes including Carex lasiocarpa marsh and Phragmites australis marsh in the Sanjiang Plain. Sedimentary characteristics of typical mashes were analyzed. The results showed that vertically these soil chemical elements also varied, showing obvious stratification and enrichment. In a soil profile, soil organic C under both vegetation communities gradually decreased; soil total N first increased and then decreased under both; total P under Carex lasiocarpa first decreased and then increased, whereas it decreased with the increasing depth under Carex lasiocarpa; total S was reduced with increasing depth under both marshes. Total N, total P and total S were all strongly correlated with soil organic C (P < 0.01); soil organic C was strongly correlated with bulk density (P < 0.01). Our study also illustrated that the vegetation types had different influences for organic C, total N, total P and total S of the marsh profiles. Environmental 137Cs and 210Pb dating techniques were applied to determine recent sedimentation rates, and the constant rate of supply (CRS) was applied to deduce the age of sediment core, and the results showed that the mean sedimentation rate was 0.33 cm x a(-1), and the sedimentation fluxes ranged 0.03-0.48 g x (cm2 x a)(-1) [Mean = 0.29 g x (cm2 x a) -1]. PMID:25338362

Li, Rui-Li; Chai, Min-Wei; Qiu, Guo-Yu; Shi, Fu-Chen; Sasa, Kaichiro

2014-08-01

339

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.

340

Small Craters Engulfed by Smooth Plains  

NASA Technical Reports Server (NTRS)

This double ring basin (top center of image), 220 km in diameter centered at 18 degrees S, 52 degrees W, was photographed on the second encounter and shows two craters about 30 km in diameter which have been engulfed by smooth plains on the floor of the inner ring. This stratigraphic relationship is common in the lunar maria and suggests that the plains within the inner ring were emplaced by volcanic processes after basin formation (FDS 166649).

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

1975-01-01

341

Intercrater Plains and Heavily Cratered Terrain  

NASA Technical Reports Server (NTRS)

Intercrater plains and heavily cratered terrain typical of much of Mercury outside the area affected by the formation of the Caloris basin are shown in this image (FDS 166738) taken during the spacecraft's second encounter with Mercury. Abundant shallow elongate craters and crater chains are present on the intercrater plains. North is to the top of this image, centered at 56 degrees S, 128 degrees W and 400 kilometers across.

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

1975-01-01

342

Characteristics and origin of Earth-mounds on the Eastern Snake River Plain, Idaho  

SciTech Connect

Earth-mounds are common features on the Eastern Snake River Plain, Idaho. The mounds are typically round or oval in plan view, <0.5 m in height, and from 8 to 14 m in diameter. They are found on flat and sloped surfaces, and appear less frequently in lowland areas. The mounds have formed on deposits of multiple sedimentary environments. Those studied included alluvial gravel terraces along the Big Lost River (late Pleistocene/early Holocene age), alluvial fan segments on the flanks of the Lost River Range (Bull Lake and Pinedale age equivalents), and loess/slopewash sediments overlying basalt flows. Backhoe trenches were dug to allow characterization of stratigraphy and soil development. Each mound has features unique to the depositional and pedogenic history of the site; however, there are common elements to all mounds that are linked to the history of mound formation. Each mound has a {open_quotes}floor{close_quotes} of a sediment or basement rock of significantly different hydraulic conductivity than the overlying sediment. These paleosurfaces are overlain by finer-grained sediments, typically loess or flood-overbank deposits. Mounds formed in environments where a sufficient thickness of fine-grained sediment held pore water in a system open to the migration to a freezing front. Heaving of the sediment occurred by the growth of ice lenses. Mound formation occurred at the end of the Late Pleistocene or early in the Holocene, and was followed by pedogenesis. Soils in the mounds were subsequently altered by bioturbation, buried by eolian deposition, and eroded by slopewash runoff. These secondary processes played a significant role in maintaining or increasing the mound/intermound relief.

Tullis, J.A.

1995-09-01

343

Water Management Studies in the Rolling Plains.  

E-print Network

CROP WATER REQUIREMENT 4 COTION 9 GRAIN SORGHUM 12 SMALL GRAINS 14 POTATOES 16 SWB6TCORN 19 LITKRATURE CITED SUMMARY Water management studies were conducted with cotton, grain sorghum, wheat, potatoes, and sweet com from 1976 through 1978.... These studies demonstrated that water is the dominant factor influencing yields in the Rolling Plains. Yields of cotton, grain sorghum, potatoes, and sweet corn were a linear function of applied water and water use. Moisture need and average rainfall...

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

1980-01-01

344

The First Plains Geologic Transect on Mars: Spirit Rover Traverse of the Plains in Gusev Crater  

NASA Astrophysics Data System (ADS)

The location and near-field geologic setting of Spirit were mapped on regional image and remote sensing data during the approximately 2.3 km traverse from the landing site within the Gusev Crater floor plains to the Columbia Hills. Differences in surficial geology together with boundaries between geologic units identified from ground observation were recorded and mapped along a 40 m-wide corridor along the traverse. The observations yield the first systematic geologic transect of a plains surface and multiple impact crater ejecta sheets on another planet. Several concepts were examined or tested: (1) the regional morphologic variability of an Hesperian plains surface, (2) the distribution of small craters on the plains, (3) the relative degree of chemical weathering and importance of impact gardening in modifying basaltic plains, (4) surface characteristics in regions of differing themophysical properties, (5) the systematic structure of crater ejecta, and (6) the ability to locate and identify contacts defined from orbital and remote sensing data during surface traverse. The resulting geologic transect map also provides a base for the systematic measurements made by Athena science instruments. Geologic contacts crossed included ejecta blanket boundaries, crater rims, a two-fold geologic and topographic division of inner and outer ejecta, and the regional contact between the lava plains and the Columbia Hills. A comparison of contacts in geologic maps prepared from orbital data sets prior to the traverse and contacts observed at the surface along the transect confirm that surface traverses on Mars can identify the contact relations defined from orbital image data. Maps prepared from surface traverse and remote sensing differ mainly in the precision of location of boundaries, such as the outer edge of ejecta sheets, and distribution of surficial materials. Apparent vesicularity (ratio of summed vesicle volume from area over rock unit volume) of rocks in the plains lava surface decreased with increasing host rock size and angularity. It is interpreted that this population of vesicular clasts is a result of (1) impact gardening of an upper vesicular zone, and (2) that the vesicular zone is thin compared with that predicted for lava flows on Earth. If supported by additional on-going analysis, the presence of a thin upper vesicular zone in the Gusev plains lavas could be indirect evidence for atmospheric pressure close to current values at the time of Gusev plains basalt emplacement during the Hesperian.

Crumpler, L. S.

2004-12-01

345

Simplified Micromechanics of Plain Weave Composites  

NASA Technical Reports Server (NTRS)

A micromechanics based methodology to simulate the complete hygro-thermomechanical behavior of plain weave composites is developed. This methodology is based on micromechanics and the classical laminate theory. The methodology predicts a complete set of thermal, hygral and mechanical properties of plain woven composites, generates necessary data for use in a finite element structural analysis, and predicts stresses all the way from the laminate to the constituent level. This methodology is used in conjunction with a composite mechanics code to analyze and predict the properties/response of a generic graphite/epoxy woven textile composite and a plain weave ceramic composite. The fiber architecture, including the fiber waviness and fiber end distributions through the thickness, is properly accounted for. Predicted results compare reasonably well with those from detailed three-dimensional finite element analyses as well as available experimental data. However, the main advantage of the proposed methodology is its high computational efficiency as compared with three-dimensional finite element analyses.

Mital, Subodh K.; Murthy, Pappu L. N.; Chamis, Christos C.

1996-01-01

346

Venus Ovda Regio Stratigraphy and Tectonics: Highlands-Plains Relationships  

NASA Astrophysics Data System (ADS)

The global plains materials of the Venusian lowlands, generally interpreted to be composed of flood basalts, lap onto the equatorial highlands of Western Aphrodite Regio. Systematic geologic mapping of the Ovda region using the Magellan global data (radar images, altimetry and gravity) has revealed that the contacts between highlands and plains have been tilted up toward the highlands after the plains emplacement. Analysis of the western part of Ovda Regio shows that the northern contact occurs at an average radius of 6053.8 km and the mean plains elevation 500 km to the north of the contact is at a radius of 6052.0 km, indicating that the boundary position has changed by nearly 2 km. Volcanic rilles are superposed on the tilted plains surfaces along both the northern and southern boundaries of the Ovda highlands. The local volcanicity that cut the rilles indicates that some local volcanic activity occurred subsequent to the marginal uplift. Models under study include post plains-emplacement uplift of the highlands or relative sinking of the plains. Isostatic mechanisms are likely in either case. Although complex structural models for the plains-highland margin are possible, simple structural models in which plains were emplaced as a nearly level geoidal surface and subsequently the highlands of Ovda were uplifted relative to the plains. Initial mapping is focused on 1:5,000,000 scale and is integrating observations of surface characteristics and geophysical inferences drawn from topography and gravity.

Saunders, R. S.

1996-03-01

347

Quantitative palaeodrainage analysis in the Pleistocene of the Po Plain (Italy)  

NASA Astrophysics Data System (ADS)

During the Pleistocene, Po Plain deposits recorded repeated waxing and waning of Alpine ice caps, and thus provide an excellent opportunity to investigate the interactions between pronounced climatic fluctuations and background tectonic activity (Scardia et al., 2006), resulting in frequent changes of drainage patterns. A high-resolution Pleistocene stratigraphy, with a complete sedimentological, paleontological, petrographic-mineralogical, magneto-stratigraphic, and seismic data base, was recently obtained from eleven continuous cores drilled in the Lombardy Po Plain north of the Po River (ENI and Regione Lombardia, 2002). In the present study we focus on two cores in the proximal (Cilavegna) and distal plain (Pianengo), which best exemplify the drastic change in sedimentary systems and drainage patterns associated with the onset of major Pleistocene glaciations in the Alps (˜870ky; Muttoni et al., 2003). This climatic event is recorded by a regional unconformity (named R-unconformity by Muttoni et al., 2003), traced all across the Po Basin and encountered at -81 m depth in the Pianengo Core and at -98 m depth in the Cilavegna Core. The Cilavegna Core consists of metamorphiclastic floodplain sediments, capped by the R-unconformity and overlain by quartzofeldspathic braidplain deposits. The Pianengo Core consists of metamorphiclastic deltaic to floodpain sediments, capped by the R-unconformity and overlain by alluvial-fan gravels rich in carbonate pebbles; another unconformity at -39 m depth is overlain by metamorphiclastic braidplain deposits. Our quantitative approach to paleodrainage analysis is based on comprehensive information obtained from modern settings (Garzanti et al., 2004; 2006). End-member modelling and similarity analysis allows us to objectively compare detrital modes from modern and ancient deposits, and to reconstruct the evolution of sediment pathways through geologic time (Vezzoli and Garzanti 2009). The Cilavegna Core documents stepwise south-westward shifts of major tributaries draining the axial belt. The Pianengo Core records the rapid southward progradation of transverse alluvial fans fed locally from the Southern Alps, followed by progressive establishment of the modern Adda river system. Evolving drainage patterns and river avulsions represent a major cause of compositional change in foreland-basin deposits. Lateral shifts of river courses, commonly associated with unconformities and favoured by an increase in the ratio between sediment fluxes and subsidence, provide crucial information on tectonic or climatic events, and should be given full consideration in provenance studies. ENI and Regione Lombardia. 2002. Geologia degli acquiferi padani della Regione Lombardia. Firenze, Società Elaborazioni Cartografiche s.r.l., 130 p. Muttoni G., Carcano C., Garzanti E., Ghielmi M., Piccin A., Pini R., Rogledi S., and Sciunnach D. 2003. Onset of major Pleistocene glaciations in the Alps. Geology, 31, 989-992. Scardia G., Muttoni G., and Sciunnach D. 2006. Subsurface magnetostratigraphy of Pleistocene sediments from the Po Plain (Italy): constraints on rates of sedimentation and rock uplift. Geological Society of America Bulletin, 118, 1299-1312. Vezzoli G. and Garzanti E. 2009. Tracking paleodrainage in foreland-basin sequences. Journal of Geology, In press.

Vezzoli, G.; Garzanti, E.; Sciunnach, D.

2009-04-01

348

Silicon flux and distribution of biogenic silica in deep-sea sediments in the western North Pacific Ocean  

NASA Astrophysics Data System (ADS)

We investigated biogenic silica, several biological components, and silicate in pore-water in the abyssal sediment to determine silicon flux of western North Pacific during several cruises. The surficial sediment biogenic silica content was high at high latitudes with the boundary running along the Kuroshio Extension, and maximum values (exceeding 20%) were found in the Oyashio region. In the subtropical region to the south, most stations showed less than 5% biogenic silica content. This distribution pattern reflected primary production and ocean currents in the surface layer very well. Pore-water samples were collected from 4 stations along the east coast of Japan. The highest asymptotic silicic acid concentration (670 ?mol L -1) in pore-water was observed at the junction of Kuroshio and Oyashio, followed by samples from the Oyashio region. It is at the southern station that the lowest value (450 ?mol L -1) was observed, and the primary production is low under the influence of Kuroshio there. The diffusive flux followed the same geographic trend as the asymptotic silicic acid concentrations did, ranging 77-389 mmol m -2 yr -1. Multiple sampling of pore-water was conducted throughout the year at one station at high latitude. The average annual biogenic silica rain flux observed using sediment traps was 373 mmol m -2 yr -1; the diffusive flux and burial flux at the sediment-water interface were 305 and 9 mmol m -2 yr -1, respectively. We concluded that most of the settling silica particles dissolved and diffused at the sediment-water interface and approximately 3% only were preserved in this area. In addition, the obvious time lag observed between the peak rain flux and the maximum diffusive flux suggested that primary production in the surface layer has a great influence on the sedimentation environment of abyssal western North Pacific. These transitions of Si flux at the sediment-water interface were considerably greater in northwestern North Pacific than in southwestern North Pacific. In addition, a station in the Philippine Sea indicated high biogenic silica content because of Ethmodiscus ooze, which are scattered randomly on the sea floor in the subtropical region.

Shibamoto, Yoko; Harada, Koh

2010-02-01

349

Late Cretaceous to early Tertiary deltaic to marine sedimentation, North Slope, Alaska  

SciTech Connect

Along the lower Colville River near Ocean Point, Alaska, Late Cretaceous to early Tertiary sediments (Colville Group and the Sagavanirktok Formation) record depositional environments from delta plain to prograding delta to shallow marine shelf. The unit hosts the northernmost known dinosaur remains and is less than 100 m thick with numerous tephra deposits in its lower sections. Furthermore, it is characterized by cyclic, relatively fine-grained sediments indicating mostly depositional and few erosional events. The major depositional elements of the delta plain are 3.5 to 5.45-m thick tabular fining-upward cycles that are cut by sand-filled fluvial channels (up to 10 m thick). The cyclic sediments contain abundant roots and grade upward from small-scale cross-beds to laminated and then structureless silt and clay terminating in organic-rich layers. The channel-fill sequences fine upward and change vertically from large to small-scale cross-beds. Over-bank flooding as well as lateral migration of small meandering fluvial channels formed the cyclically interbedded deposits, meandering rivers deposited the thick cross-bedded sands, and soil development or marsh deposits formed the organic-rich horizons that cap each cycle. Plant debris, nonmarine invertebrates, and vertebrate fossils are locally concentrated in the delta plain sediments. Subsidence related to compaction of the deltaic sediments along with possible delta lobe switching resulted in repeated progradation of the delta front over the delta plain. Delta front sediments are 3 to 10-m thick tabular deposits of large and small-scale cross-bedded sands and silt bounded by organic-rich beds. Also, there are abundant roots, rare channels and invertebrate fossils that suggest a transitional environment from sand-flats to estuarine or bay.

Phillips, R.L.

1987-05-01

350

Sediment patches, sediment supply, and channel morphology  

Microsoft Academic Search

Bed surface particle size patchiness may play a central role in bedload and morphologic re- sponse to changes in sediment supply in gravel-bed rivers. Here we test a 1-D model (from Parker ebook) of bedload transport, surface grain size, and channel profile with two previously published flume studies that documented bed surface response, and specifically patch development, to reduced sediment

W. E. Dietrich; P. A. Nelson; E. Yager; J. G. Venditti; M. P. Lamb; L. Collins

351

Microbial transformations of arsenic: Mobilization from glauconitic sediments to water  

USGS Publications Warehouse

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.

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

2012-01-01

352

Distribution and origin of shallow gas in deep-sea sediments of the Ulleung Basin, East Sea (Sea of Japan)  

Microsoft Academic Search

A synthesis of high-resolution (Chirp, 2–7 kHz) subbottom profiles in the Ulleung Basin reveals patchy distribution of shallow\\u000a (<90 m subbottom depth) gassy sediments in the eastern basin plain below 1,800-m water depth. The shallow gases in the sediments\\u000a are associated with acoustic turbidities, columnar acoustic blankings, enhanced reflectors, dome structures, and pockmarks.\\u000a Analyses of gas samples collected from a

S. H. Lee; S. K. Chough

2002-01-01

353

Environmental magnetic record of the fluvial sediments from the Tianzhu borehole in Beijing for the last 800 ka  

Microsoft Academic Search

A high-resolution environmental magnetic investigation has been carried out on a 186.3-m-thick sequence of fluvial sediments from the Tianzhu borehole in the Beijing Plain. Magnetic stratigraphic analysis revealed that the sediment sequence spans the last 800 ka without significant hiatuses. Comparison of the magnetic susceptibility (k) with pollen records suggests that the magnetic susceptibility serves as a good proxy for

L. Shi; Z. Yang; L. Zheng; S. Jia; Y. Tong; S. Zhang; D. Xu; G. Guo

2010-01-01

354

Occurrence of nitrous oxide in the central High Plains aquifer, 1999  

USGS Publications Warehouse

Nitrogen-enriched groundwater has been proposed as an important anthropogenic source of atmospheric nitrous oxide (N2O), yet few measurements of N2O in large aquifer systems have been made. Concentrations of N2O in water samples collected from the 124 000 km2 central High Plains aquifer in 1999 ranged from < 1 to 940 nM, with a median concentration of 29 nM (n = 123). Eighty percent of the N20 concentrations exceeded the aqueous concentration expected from equilibration with atmospheric N2O. Measurements of N2O, NO3-, and 3H in unsaturated-zone sediments, recently recharged groundwater, and older groundwater indicate that concentrations of N2O in groundwater increased over time and will likely continue to increase in the future as N-enriched water recharges the aquifer. Large concentrations of O2 and NO3- and small concentrations of NH4+ and dissolved organic carbon in the aquifer indicate that N2O in the central High Plains aquifer was produced primarily by nitrification. Calculations indicate that the flux of N2O from the central High Plains aquifer to the atmosphere from well pumping and groundwater discharge to streams was not a significant source of atmospheric N2O.Nitrogen-enriched groundwater has been proposed as an important anthropogenic source of atmospheric nitrous oxide (N2O), yet few measurements of N2O in large aquifer systems have been made. Concentrations of N2O in water samples collected from the 124000 km2 central High Plains aquifer in 1999 ranged from < 1 to 940 nM, with a median concentration of 29 nM (n = 123). Eighty percent of the N2O concentrations exceeded the aqueous concentration expected from equilibration with atmospheric N2O. Measurements of N2O, NO3-, and 3H in unsaturated-zone sediments, recently recharged groundwater, and older groundwater indicate that concentrations of N2O in groundwater increased over time and will likely continue to increase in the future as N-enriched water recharges the aquifer. Large concentrations of O2 and NO3- and small concentrations of NH4+ and dissolved organic carbon in the aquifer indicate that N2O in the central High Plains aquifer was produced primarily by nitrification. Calculations indicate that the flux of N2O from the central High Plains aquifer to the atmosphere from well pumping and groundwater discharge to streams was not a significant source of atmospheric N2O.Water samples were collected from 92 domestic wells, 16 monitoring wells and 15 public-supply wells in the High Plains Aquifer in 1999, and concentrations of nitrous oxide were measured. The groundwater concentrations ranged from less than 1 to 940 nM. Concentrations expressed as a percent of saturation in water ranged from less than 10 to 9690%. A significant decrease was noted in N2O concentrations with increasing depth of the well screen below the water table, and a significant positive correlation was found between the concentrations of N2O and nitrate. The small area-averaged N2O emission rate for the aquifer indicated that it was not an important component of the atmospheric N2O budget, but the importance could increase as groundwater N2O concentrations increase.

McMahon, P.B.; Bruch, B.W.; Becker, M.F.; Pope, L.M.; Dennehy, K.F.

2000-01-01

355

RADIOCARBON, Vol 52, Nr 1, 2010, p 1324 2010 by the Arizona Board of Regents on behalf of the University of Arizona DATING HUMAN OCCUPATION ON DIATOM-PHYTOLITH-RICH SEDIMENT: CASE  

E-print Network

, 1985). A com- mon difficulty in 14C dating sediment is the presence of carbon from different sources of the University of Arizona 13 DATING HUMAN OCCUPATION ON DIATOM-PHYTOLITH-RICH SEDIMENT: CASE STUDIES OF MUSTANG and ecology. Chronometric dating of archaeo- logical sites in many areas of the Great Plains, however

Holliday, Vance T.

356

Fossil mollusc-faunas: Their bearing on the Holocene evolution of the Lower Central Plain of Bangkok (Thailand)  

NASA Astrophysics Data System (ADS)

In this work, fossil molluscan assemblages are analyzed in order to reconstruct the evolution of the Northern Gulf of Thailand during the Holocene. The marine sediments (Bangkok Clay Formation) of the Lower Central Plain of Bangkok and the coastal plain of Phetchaburi were sampled at 16 localities, obtaining fossil shells and mangrove peat whose 14C ages range from 9000 to 2000 CYBP. A statistical treatment of abundance data returned four major groups, namely the Dendostrea rosacea association (intertidal mud), the Corbula fortisulcata- Mactra luzonica association (shallow infralittoral sandy mud), the Nuculana mauritiana- Timoclea scabra association (infralittoral sand spit) and the Timoclea scabra- Arcopagia pudica association (infralittoral mud). The data allowed both a stratigraphic correlation along two transects covering all of the Holocene basin and the creation of digitalized maps showing the presumable extension of the Thai paleogulf around the apex of Flandrian transgression event (about 5500 CYBP).

Negri, Mauro Pietro

2009-08-01

357

Sulfur isotope and porewater geochemistry of Florida escarpment seep sediments  

USGS Publications Warehouse

Distributions of porewater constituents, SO4=, NH4+, Cl-, ???CO2, and H2S, solid phase iron, and sulfur concentrations, and the sulfur isotopic composition of dissolved and solid phases were investigated in sediments from abyssal seeps at the base of the Florida escarpment. Despite the apparent similarity of seep sediment porewater chemistry to that of typical marine sediments undergoing early diagenesis, relationships between chemical distributions and isotopic measurements revealed that the distribution of pore fluid constituents was dominated by processes occurring within the platform rather than by in situ microbial processes. Ammonium and sulfate concentrations were linearly correlated with chloride concentrations, indicating that variations in porewater chemistry were controlled by the admixture of seawater and a sulfate depleted brine with a chlorinity of 27.5 ?? 1.9%. and 2.2 ?? 1.3 mM ammonium concentration. At sites dominated by seepage, dissolved sulfate isotopic composition remained near seawater values despite depletion in porewater concentrations. Porewater ???CO2 concentrations were found to be elevated relative to seawater, but not to the extent predicted from the observed sulfate depletion. Sediment solid phase sulfur was predominantly pyrite, at concentrations as high as 20% S by weight. In contrast to typical marine deposits, pyrite concentrations were not related to the quantity of sedimentary organic matter. Pyrite ??34S values ranged from -29%. to + 21%. (CDT). However, only positive ??34S values were observed at sites associated with high pyrite concentrations. Isotopically heavy pyrite was observed at sites with porewater sulfate of seawater-like isotopic composition. Isotopically light pyrite was associated with sites where porewater sulfate exhibited ??34S values greater than those in seawater, indicating the activity of in situ microbial sulfate reduction. Thus, dual sulfide sources are suggested to explain the range in sediment pyrite isotopic composition: a ??34S enriched (+10 to +20%.) source adverted from within the Florida platform, and a lighter 34S depleted component generated in situ from microbial reduction of seawater sulfate. The degree of pyritization of seep sediments was as high as 0.9 and was controlled by pyrite concentrations, which varied over a wider range than did the non-pyrite solid phase iron concentrations. The highest non-sulfide solid phase iron concentrations were observed in sediments that are believed to be at the "front" of the advancing seep fluids (i.e., hemipelagic sediments newly exposed to the seep fluids), indicating that dissolution of hemipelagic background sediment may be the source of at least half of the iron to the highly pyritized seep sediments. Porewater sulfide concentrations were variable, reaching a maximum of 5.7 mM, and were not correlated with the degree of pyritization of the sediments, suggesting that iron was not particularly limiting to pyrite formation. ?? 1993.

Chanton, J.P.; Martens, C.S.; Paull, C.K.; Coston, J.A.

1993-01-01

358

Ground-water conditions in the Plaine de Moustiques, Haiti  

USGS Publications Warehouse

The Plaine des Moustiques lies on the north coast of Haiti about 12 kilometers west-southwest of Port-de-Paix. During January 1949 the writers made a brief geologic study to determine the availability of ground water in the plain for irrigation. At present irrigation is practiced by diversions from the Rivière des Moustiques. However, the dry-season flow of this stream is generally inadequate for irrigation or is sufficient to cover only a small part of the Irrigable area of the plain. According to Lieurance1 there is a total of about 1,120 hectares of irrigable land in the plain.

Taylor, George C., Jr.; Lemoine, Rémy C.

1949-01-01

359

Impact crater degradation on venusian plains  

NASA Astrophysics Data System (ADS)

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.

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

1994-02-01

360

Medicine Wheels of the Great Plains  

NASA Astrophysics Data System (ADS)

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.

Vogt, David

361

Avalanches, Barkhausen noise, and plain old criticality  

SciTech Connect

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.}

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

362

Environmental perceptions in Great Plains novels  

E-print Network

. Their recorded impressions indicate that some per- ceived it as uniformly level while others observed endless- ly rolling hills; some saw a barren desert while others visualized it as a potential agricultural cornucopia; some felt it friendly to settlement... conditions, tall-grass to desert-like vegetation, and flat to hilly terrain--all of which are typical of the region (Hammond, 1971, 189-91). The time period of the novels selected roughly spans the decades of Plains settlement, from the 1850's through...

Pardee, Celeste Frances

1976-01-01

363

A Sustainable Agro-ecological Solution to Water Shortage in the North China Plain (Huabei Plain)  

Microsoft Academic Search

A highly seasonal rainfall pattern in the agriculturally productive region of Huabei Plain has been widely considered in China as a handicap to maximizing agricultural production. Enhancing this perception is the traditional policy of achieving provincial or regional self-sufficiency in grain production, which underlies China's production quotas. The Chinese government has decided to overcome this perceived handicap in order to

Shu Geng; Yixing Zhou; Minghua Zhang; K. Shawn Smallwood

2001-01-01

364

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.

365

Sediment Retention Dynamics and Vegetation Along Three Tributaries of the Chesapeake Bay  

NASA Astrophysics Data System (ADS)

Coastal Plain riparian wetlands in the Mid-Atlantic United States are the last place for sediment and contaminant storage before reaching critical estuarine and marine environments. The deteriorating health of the Chesapeake Bay has been attributed in part to elevated sediment loads. The purpose of this study is to investigate the effects of channelization and urbanization on sediment deposition and geomorphic processes along the Pocomoke and Chickahominy Rivers and Dragon Run, three Coastal Plain tributaries. Floodplain microtopography was surveyed in 100 x 100 m grids at three characteristic reaches along each river and woody vegetation analyses were conducted. Floodplain suspended sediment concentrations and short and long-term sedimentation rates were estimated at each reach using single stage sediment sampler arrays, clay pads and dendrogeomorphic techniques, respectively. Site hydroperiod and flow characteristics were determined from USGS gaging station records, floodplain water level recorders, and field observations. Channelized floodplain reaches along the Pocomoke River are flooded less frequently, have lower mineral sedimentation rates (2 mm/yr to 6 mm/yr) and woody species diversity than the unchannelized reaches. Along the Chickahominy River, floodplain wetlands close to urban centers are flooded more frequently, but have shorter hydroperiods (3.5 days/yr compared to more than 45 days/yr), lower sedimentation rates (1.8 mm/yr to 6.8 mm/yr), and lower woody species diversity (0.51 to 1.95 on the Shannon-Weiner diversity index) than floodplains further downstream. Suspended sediment delivery and deposition rates are significantly influenced by floodplain hydroperiod duration and channel-floodplain connectivity. These results suggest that understanding floodplain sediment dynamics and geomorphic processes with respect to dominant watershed landuse patterns is critical for effective water quality management and restoration efforts.

Ross, K.; Ross, K.; Hupp, C.; Alexander, L.; Alexander, L.

2001-12-01

366

Heavy metal geochemistry and dispersion pattern in coastal sediments, soil, and water of Kedron Brook floodplain area, Brisbane, Australia  

Microsoft Academic Search

Hydrochemical monitoring and heavy metal speciation by sequential extraction techniques indicate direct relationships among enrichment of the heavy metals (copper, lead, zinc, iron, manganese, and cadmium), soil acidification, and salinization in Kedron Brook floodplain area of Brisbane, Australia. Assessment of modes of occurrence and distribution pattern of the heavy metals in soil, sediment, and water environments of this coastal plain

A. V. Arakel; T. Hongjun

2009-01-01

367

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

Microsoft Academic Search

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

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

1991-01-01

368

Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA  

USGS Publications Warehouse

Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the B??lling-Aller??d episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial of both the Brady Soil and the Leonard Paleosol by renewed loess influx probably represents eolian system response that occurred when gradual change toward a drier climate eventually crossed the threshold for eolian activity. Overall, the loess-paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture across the late Pleistocene to Holocene boundary, rather than well-defined climatic episodes corresponding to the B??lling-Aller??d and Younger Dryas episodes in the North Atlantic region. ?? 2008 Elsevier Ltd. All rights reserved.

Mason, J.A.; Miao, X.; Hanson, P.R.; Johnson, W.C.; Jacobs, P.M.; Goble, R.J.

2008-01-01

369

The distribution and origin of smooth plains on Mercury  

NASA Astrophysics Data System (ADS)

Orbital images from the MESSENGER spacecraft show that ~27% of Mercury's surface is covered by smooth plains, the majority (>65%) of which are interpreted to be volcanic in origin. Most smooth plains share the spectral characteristics of Mercury's northern smooth plains, suggesting they also share their magnesian alkali-basalt-like composition. A smaller fraction of smooth plains interpreted to be volcanic in nature have a lower reflectance and shallower spectral slope, suggesting more ultramafic compositions, an inference that implies high temperatures and high degrees of partial melting in magma source regions persisted through most of the duration of smooth plains formation. The knobby and hummocky plains surrounding the Caloris basin, known as Odin-type plains, occupy an additional 2% of Mercury's surface. The morphology of these plains and their color and stratigraphic relationships suggest that they formed as Caloris ejecta, although such an origin is in conflict with a straightforward interpretation of crater size-frequency distributions. If some fraction is volcanic, this added area would substantially increase the abundance of relatively young effusive deposits inferred to have more mafic compositions. Smooth plains are widespread on Mercury, but they are more heavily concentrated in the north and in the hemisphere surrounding Caloris. No simple relationship between plains distribution and crustal thickness or radioactive element distribution is observed. A likely volcanic origin for some older terrain on Mercury suggests that the uneven distribution of smooth plains may indicate differences in the emplacement age of large-scale volcanic deposits rather than differences in crustal formational process.

Denevi, Brett W.; Ernst, Carolyn M.; Meyer, Heather M.; Robinson, Mark S.; Murchie, Scott L.; Whitten, Jennifer L.; Head, James W.; Watters, Thomas R.; Solomon, Sean C.; Ostrach, Lillian R.; Chapman, Clark R.; Byrne, Paul K.; Klimczak, Christian; Peplowski, Patrick N.

2013-05-01

370

Characterization of geomorphic units in the alluvial valleys and channels of Gulf Coastal Plain rivers in Texas, with examples from the Brazos, Sabine, and Trinity Rivers, 2010  

USGS Publications Warehouse

The U.S. Geological Survey, in cooperation with the Texas Water Development Board, described and characterized examples of geomorphic units within the channels and alluvial valleys of Texas Gulf Coastal Plain rivers using a geomorphic unit classification scale that differentiates geomorphic units on the basis of their location either outside or inside the river channel. The geomorphic properties of a river system determine the distribution and type of potential habitat both within and adjacent to the channel. This report characterizes the geomorphic units contained in the river channels and alluvial valleys of Texas Gulf Coastal Plain rivers in the context of the River Styles framework. This report is intended to help Texas Instream Flow Program practitioners, river managers, ecologists and biologists, and others interested in the geomorphology and the physical processes of the rivers of the Texas Gulf Coastal Plain (1) gain insights into how geomorphic units develop and adjust spatially and temporally, and (2) be able to recognize common geomorphic units from the examples cataloged in this report. Recent aerial imagery (high-resolution digital orthoimagery) collected in 2008 and 2009 were inspected by using geographic information system software to identify representative examples of the types of geomorphic units that occurred in the study area. Geomorphic units outside the channels of Texas Gulf Coastal Plain rivers are called \\"valley geomorphic units\\" in this report. Valley geomorphic units for the Texas Gulf Coastal Plain rivers described in this report are terraces, flood plains, crevasses and crevasse splays, flood-plain depressions, tie channels, tributaries, paleochannels, anabranches, distributaries, natural levees, neck cutoffs, oxbow lakes, and constructed channels. Channel geomorphic units occur in the river channel and are subject to frequent stresses associated with flowing water and sediment transport; they adjust (change) relatively quickly in response to short-term variations in flow. Channel geomorphic units described in this report are channel banks, benches and ledges, bank failures, point bars, cross-bar channels, channel bars, exposed bedrock, pools, runs, and crossovers.

Coffman, David K.; Malstaff, Greg; Heitmuller, Franklin T.

2011-01-01

371

Messages from the Abyss  

NASA Astrophysics Data System (ADS)

VLT Observes Infrared Flares from Black Hole at Galactic Centre [1] Summary An international team of astronomers led by researchers at the Max-Planck Institute for Extraterrestrial Physics (MPE) in Garching (Germany) [2] has discovered powerful infrared flares from the supermassive black hole at the heart of the Milky Way . The signals, rapidly flickering on a scale of minutes, must come from hot gas falling into the black hole, just before it disappears below the "event horizon" of the monster. The new observations strongly suggest that the Galactic Centre black hole rotates rapidly . Never before have scientists been able to study phenomena in the immediate neighbourhood of a black hole in such a detail. The new result is based on observations obtained with the NACO Adaptive Optics instrument on the 8.2-m VLT YEPUN telescope and is published in this week's edition of the research journal Nature. PR Photo 29a/03 : A powerful flare from the black hole at the galactic centre. PR Photo 29b/03 : Light curve of the flare . PR Video 01/03 : A powerful flare from the black hole at the galactic centre . Flashes of light from disappearing matter ESO PR Photo 29a/03 ESO PR Photo 29a/03 [Preview - JPEG: 650 x 400 pix - 118k [Normal - JPEG: 1300 x 800 pix - 370k] ESO PR Video Clip 01/03 [MPEG] ESO PR Video Clip 01/03 [MPEG Video; 29X k] Captions : PR Photo 29a/03 and PR Video Clip 01/03 show the detection of a powerful flare from the centre of the Milky Way galaxy. These and other adaptive optics (AO) images (with resolution 0.040 arcsec in the near-infrared H-band at wavelength 1.65 µm) of the central region of the Milky Way were obtained with the NACO imager on the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory on May 9, 2003. The image covers a sky area of about 1 x 1 arcsec, corresponding to about 45 light-days at the distance of the Galactic Centre. The time (in minutes from the beginning of the data set at 6h59m24s (UT) on May 9, 2003) is shown at the upper right of each image. North is up and East to the left. The position of the 15-year orbiting star S2 (cf. ESO Press Release 17/02 ) is marked by a cross and the astrometric location of the black hole is indicated by a circle. The scene was the usual one in the VLT Control Room at the Paranal Observatory in the early morning of May 9, 2003. Groups of astronomers from different nations were sitting in front of the computer screens, pointing the four giant telescopes in different directions and recording the sparse photons from the remotest corners of the Universe. There were the usual brief exchanges of information, numbers, wavelengths, strange acronyms, but then suddenly something happened at the YEPUN desk.... " What is that star doing there? " exclaimed Rainer Schödel , one of the MPE scientists in the team working with the NACO Adaptive Optics instrument [3] that delivers razor-sharp images. He and Reinhard Genzel, leader of the team and MPE Director, were observing the Milky Way Centre, when they saw the "new" object on the screen in front of them. The astronomers were puzzled and then became excited - something unusual must be going on, there at the centre of our galaxy! And then, a few minutes later, the "star" disappeared from view. Now the scientists had little doubt - they had just witnessed, for the first time, a powerful near-infrared flare from exactly the direction of the supermassive black hole at the heart of the Milky Way , cf. PR Photo 29a/03 and PR Video Clip 01/03 . " We had been looking for infrared emission from that black hole for more than a decade " recalls another team member, Andreas Eckart of the Cologne University. " We were certain that the black hole must be accreting matter from time to time. As this matter falls towards the surface of the black hole, it gets hotter and hotter and starts emitting infrared radiation ". But no such infrared radiation had been seen until that night at the VLT. This was the wonderful moment of breakthrough. Never before had anybody witnessed t

2003-10-01

372

Into the Abyss  

NSDL National Science Digital Library

Designed for use with small groups in an introductory geology class, this case study allows students to determine the relationship between sinkhole development and groundwater levels in Orlando, Florida. Students then apply the relationship to a lawsuit f

David L. Ozsvath

2000-09-01

373

Floodplain geomorphic processes and environmental impacts of human alteration along coastal plain rivers, USA  

USGS Publications Warehouse

Human alterations along stream channels and within catchments have affected fluvial geomorphic processes worldwide. Typically these alterations reduce the ecosystem services that functioning floodplains provide; in this paper we are concerned with the sediment and associated material trapping service. Similarly, these alterations may negatively impact the natural ecology of floodplains through reductions in suitable habitats, biodiversity, and nutrient cycling. Dams, stream channelization, and levee/canal construction are common human alterations along Coastal Plain fluvial systems. We use three case studies to illustrate these alterations and their impacts on floodplain geomorphic and ecological processes. They include: 1) dams along the lower Roanoke River, North Carolina, 2) stream channelization in west Tennessee, and 3) multiple impacts including canal and artificial levee construction in the central Atchafalaya Basin, Louisiana. Human alterations typically shift affected streams away from natural dynamic equilibrium where net sediment deposition is, approximately, in balance with net erosion. Identification and understanding of critical fluvial parameters (e.g., stream gradient, grain-size, and hydrography) and spatial and temporal sediment deposition/erosion process trajectories should facilitate management efforts to retain and/or regain important ecosystem services. ?? 2009, The Society of Wetland Scientists.

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

2009-01-01

374

Flood risk of natural and embanked landscapes on the Ganges-Brahmaputra tidal delta plain  

NASA Astrophysics Data System (ADS)

The Ganges-Brahmaputra river delta, with 170 million people and a vast, low-lying coastal plain, is perceived to be at great risk of increased flooding and submergence from sea-level rise. However, human alteration of the landscape can create similar risks to sea-level rise. Here, we report that islands in southwest Bangladesh, enclosed by embankments in the 1960s, have lost 1.0-1.5 m of elevation, whereas the neighbouring Sundarban mangrove forest has remained comparatively stable. We attribute this elevation loss to interruption of sedimentation inside the embankments, combined with accelerated compaction, removal of forest biomass, and a regionally increased tidal range. One major consequence of this elevation loss occurred in 2009 when the embankments of several large islands failed during Cyclone Aila, leaving large areas of land tidally inundated for up to two years until embankments were repaired. Despite sustained human suffering during this time, the newly reconnected landscape received tens of centimetres of tidally deposited sediment, equivalent to decades’ worth of normal sedimentation. Although many areas still lie well below mean high water and remain at risk of severe flooding, we conclude that elevation recovery may be possible through controlled embankment breaches.

Auerbach, L. W.; Goodbred, S. L., Jr.; Mondal, D. R.; Wilson, C. A.; Ahmed, K. R.; Roy, K.; Steckler, M. S.; Small, C.; Gilligan, J. M.; Ackerly, B. A.

2015-02-01

375

High-K alkali basalts of the Western Snake River Plain: Abrupt transition from tholeiitic to mildly alkaline plume-derived basalts, Western Snake River Plain, Idaho  

E-print Network

High-K alkali basalts of the Western Snake River Plain: Abrupt transition from tholeiitic to mildly alkaline plume-derived basalts, Western Snake River Plain, Idaho John W. Shervais a, , Scott K. Vetter b Snake River Plain SRP Yellowstone plume hotspots Basaltic volcanism in the western Snake River Plain

Shervais, John W.

376

Heavily Cratered Terrain and Smooth Plain  

NASA Technical Reports Server (NTRS)

This photograph of Mercury was taken by the Mariner 10 spacecraft from a range of 34,860 miles (55,340 kilometers) during the first Mercury encounter on March 29, 1974. It shows an area in the northern hemisphere in the general area of photography to be obtained during the third encounter, Sunday, March 16, 1975. Seen in the photograph is a transition from heavily cratered terrain to a smooth plain. These smooth plains areas on Mercury are thought to be volcanic in origin with lava flows filling in heavily cratered areas. The photograph area is about 308 miles (490 kilometers) wide. (FDS 156)

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

1975-01-01

377

DOE receives title to Great Plains plant  

SciTech Connect

On June 30, 1986 the Great Plains Coal Gasification Project was sold at a foreclosure sale at the Mercer County courthouse in North Dakota. The US Department of Energy was the only bidder at the sale. DOE's bid for the plant was $1 billion DOE-secured loan that the five sponsor companies defaulted on when they withdrew from the project in August 1985. DOE did not receive title to the plant until a lawsuit filed by American Natural Resources (ANR) was settled on July 14, 1986. DOE has vowed to keep the plant running as long as it does not cost the taxpayers any money. Eventually DOE wishes to dispose of the plant. Therefore, in February 1986 DOE requested that interested organizations submit expressions of interest in the Great Plains plant. This paper, after discussing the lawsuit, summarizes the nine responses received by DOE. Some companies were willing for it to remain a coal gasification facility; other submitted plans for modifications to produce methanol.

Not Available

1986-09-01

378

Trace Element Systematics in Bulk-Rock Abyssal Peridotites and Constituent Minerals: Evidence for Porous Melt Migration Beneath Ocean Ridges  

NASA Astrophysics Data System (ADS)

Trace element studies of residual clinopyroxene (cpx) in abyssal peridotites (AP) [1,2] confirmed the earlier notion that AP are mantle melting residues for MORB [3-5], and also argued that near-perfect fractional melting best explains the cpx trace element data, e.g., progressively more depleted in the lighter rare earth elements (REEs). However, a recent study [6] showed that light REEs in bulk-rock AP samples are more enriched, not more depleted, than in the constituent cpx of the same sample suites previously studied. If the cpx light REEs record sub-ridge mantle melting processes, then the bulk-rock light REEs must reflect post-melting refertilization [6]. The significant correlations of light REEs (e.g., La, Ce, Pr, Nd) with immobile high field strength elements (HFSEs, e.g., Nb and Zr) in bulk-rock AP samples suggest that enrichments of both light REEs and HFSEs resulted from a common magmatic process [6]. The post-melting magmatic refertilization has been suggested previously [7-10] to be important, and is interpreted to take place in the "cold" thermal boundary layer beneath ridges where the ascending melts migrate through and interact with the advanced residues [6]. The apparent problem, however, is why such magmatic refertilization did not affect cpx analyzed for trace elements. Niu [6] interpreted that the ascending melts may not be thermally "reactive", and thus may have only affected "rims" of cpx. These affected rims were later serpentinized together with the rest of the rock, and the analyzed portions of cpx are only "cores" that were unaffected by the ascending melts and also survived subsequent serpentinization. I report here a preliminary LA-ICP-MS study that supports the above interpretation. That is, in some AP samples, while relics of cpx and orthopyroxene (opx) are depleted in light REEs, serpentines (ser) adjacent to cpx and opx relics are less depleted or enriched in light REEs. Below are representative data from three samples. Sample YN1: [La/Sm]N = 0.009 (cpx), 0.014 (opx), 10.0 (ser); [Sm/Yb]N = 0.403 (cpx), 0.081 (opx), 0.741 (ser); [Yb]N = 5.36 (cpx), 1.32 (opx), 0.13 (ser). Sample YN9: [La/Sm]N = 0.007 (cpx), 0.013 (opx), 0.395 (ser); [Sm/Yb]N = 0.648 (cpx), 0.255 (opx), 0.110 (ser); [Yb]N = 7.35 (cpx), 2.15 (opx), 0.09 (ser). Sample YN14: [La/Sm]N = 0.595 (cpx), 1.630 (opx), 4.19 (ser); [Sm/Yb]N = 0.032 (cpx), 0.044 (opx), 0.212 (ser); [Yb]N = 2.62 (cpx), 0.82 (opx), 0.09 (ser). Note also that trace element distributions are quite heterogeneous on various fine scales for all samples (thin sections) studied. These new data and existing observations [6,8-10] point to the significance of grain-boundary porous melt migration in the "cold" thermal boundary layer beneath ocean ridges. References: [1] Johnson et al., J. Geophys. Res., 95, 2661-2678, 1990; [2] Johnson &Dick, J. Geophys. Res., 97, 9219-9241, 1992; [3] Dick et al., Earth Planet. Sci. Lett., 69, 88 -106, 1984; [4] Dick &Fisher, In International Kimberlite Conference vol. 2., 295-308, 1984; [5] Dick, Geol. Soc. Spec. Publ., 42, 71-105, 1989; [6] Niu, J. Petrol., 40, 2423-2458, 2004; [7] Elthon, J. Geophys. Res., 97, 9015 9025, 1992; [8] Niu & Hékinian, Earth Planet. Sci. Lett., 146, 243-258, 1997; [9] Niu, J. Petrol., 38, 1047-1074, 1997; [10] Niu et al., Earth Planet. Sci. Lett., 152, 251-265, 1997.

Niu, Y.

2006-12-01

379

40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Southwestern Mountains-Augustine Plains Intrastate...Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air...Control Region. The Southwestern Mountains-Augustine Plains...

2012-07-01

380

40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Southwestern Mountains-Augustine Plains Intrastate...Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air...Control Region. The Southwestern Mountains-Augustine Plains...

2011-07-01

381

40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Southwestern Mountains-Augustine Plains Intrastate...Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air...Control Region. The Southwestern Mountains-Augustine Plains...

2010-07-01

382

40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Southwestern Mountains-Augustine Plains Intrastate...Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air...Control Region. The Southwestern Mountains-Augustine Plains...

2013-07-01

383

40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.  

...2014-07-01 false Southwestern Mountains-Augustine Plains Intrastate...Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air...Control Region. The Southwestern Mountains-Augustine Plains...

2014-07-01

384

Economic Effect on Agricultural Production of Alternative Energy Input Prices: Texas High Plains  

E-print Network

Extension subregions of High Plains II, High Plains III, and High Plains IV. The crops chosen for study were cotton, grain sorghum, wheat, corn, and soybeans. The energy and energy-related inputs under investigation were diesel, herbicide, natural gas...

Adams, B. M.; Lacewell, R. D.; Condra, G. D.

385

Creep of plain weave polymer matrix composites  

NASA Astrophysics Data System (ADS)

Polymer matrix composites are increasingly used in various industrial sectors to reduce structural weight and improve performance. Woven (also known as textile) composites are one class of polymer matrix composites with increasing market share mostly due to their lightweight, their flexibility to form into desired shape, their mechanical properties and toughness. Due to the viscoelasticity of the polymer matrix, time-dependent degradation in modulus (creep) and strength (creep rupture) are two of the major mechanical properties required by engineers to design a structure reliably when using these materials. Unfortunately, creep and creep rupture of woven composites have received little attention by the research community and thus, there is a dire need to generate additional knowledge and prediction models, given the increasing market share of woven composites in load bearing structural applications. Currently, available creep models are limited in scope and have not been validated for any loading orientation and time period beyond the experimental time window. In this thesis, an analytical creep model, namely the Modified Equivalent Laminate Model (MELM), was developed to predict tensile creep of plain weave composites for any orientation of the load with respect to the orientation of the fill and warp fibers, using creep of unidirectional composites. The ability of the model to predict creep for any orientation of the load is a "first" in this area. The model was validated using an extensive experimental involving the tensile creep of plain weave composites under varying loading orientation and service conditions. Plain weave epoxy (F263)/ carbon fiber (T300) composite, currently used in aerospace applications, was procured as fabrics from Hexcel Corporation. Creep tests were conducted under two loading conditions: on-axis loading (0°) and off-axis loading (45°). Constant load creep, in the temperature range of 80-240°C and stress range of 1-70% UTS of the composites, was experimentally evaluated for time periods ranging from 1--120 hours under both loading conditions. The composite showed increase in creep with increase in temperature and stress. Creep of composite increased with increase in angle of loading, from 1% under on-axis loading to 31% under off-axis loading, within the tested time window. The experimental creep data for plain weave composites were superposed using TTSP (Time Temperature Superposition Principle) to obtain a master curve of experimental data extending to several years and was compared with model predictions to validate the model. The experimental and model results were found in good agreement within an error range of +/-1-3% under both loading conditions. A parametric study was also conducted to understand the effect of microstructure of plain weave composites on its on-axis and off-axis creep. Generation of knowledge in this area is also "first". Additionally, this thesis generated knowledge on time-dependent damage m woven composites and its effect on creep and tensile properties and their prediction.

Gupta, Abhishek

386

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...

387

Isolation, transmission and purification of the High Plains virus.  

PubMed

The wheat curl mite (Aceria tosichella Keifer) often simultaneously transmits the High Plains virus and Wheat streak mosaic virus under field conditions, resulting in doubly infected plants. In this study, a pure culture of the High Plains virus (isolate HPV95ID), which was infected with both High Plains virus and Wheat streak mosaic virus, was mechanically transmitted from barley (Hordeum vulgáre L.) to maize (Zea mays L.) by vascular puncture inoculation. Different water temperatures and durations for soaking kernels at pre-inoculation and different incubation temperatures and durations at post-inoculation on transmission of High Plains virus were studied. Transmissions of the High Plains virus were significantly different for post-inoculation incubations at 11, 21, or 30 degrees C after a 2 h pre-inoculation soaking at 30 degrees C and post-inoculation incubations of kernels for 1 day versus 2 days. Use of Cs2SO4 in a partial purification protocol resulted in infectious final fractions. Bioassays, serological assays, analyses by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and examinations by electron microscopy confirmed isolation of a pure culture of High Plains virus from infectious final partially purified fractions. We demonstrate infectivity of the final fractions and associate it with the High Plains disease symptoms, the 32 kDa protein and double membrane bodies and discuss this evidence to support the viral nature of High Plains virus. PMID:16672165

Louie, Raymond; Seifers, Dallas L; Bradfute, Oscar E

2006-08-01

388

Design for Field Testing of Mountain-Plains Curriculum.  

ERIC Educational Resources Information Center

The field test design information packet was devised for use by persons representing institutions using the Mountain-Plains curriculum products. The primary purpose of field testing the curriculum is to get third party profession and student reaction to what has proved to be successful with students and instructors at Mountain-Plains. The…

England, Robert G.; Pollack, Robert M.

389

History of the Central Great Plains Research Station  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Central Great Plains Research Station was established in 1907 as one of several Agricultural Fact Finding Institutions located in the Great Plains of the United States by the Bureau of Plant Industry. This document summarizes the circumstances surrounding the creation of the station and changes ...

390

High Plains Regional Ground-water Study web site  

USGS Publications Warehouse

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.

Qi, Sharon L.

2000-01-01

391

Spatial and temporal variations in landscape evolution: historic and longer-term sediment flux through global catchments  

USGS Publications Warehouse

Sediment generation and transport through terrestrial catchments influence soil distribution, geochemical cycling of particulate and dissolved loads, and the character of the stratigraphic record of Earth history. To assess the spatiotemporal variation in landscape evolution, we compare global compilations of stream gauge–derived () and cosmogenic radionuclide (CRN)–derived (predominantly 10Be; ) denudation of catchments (mm/yr) and sediment load of rivers (Mt/yr). Stream gauges measure suspended sediment loads of rivers during several to tens of years, whereas CRNs provide catchment-integrated denudation rates at 102–105-yr time scales. Stream gauge–derived and CRN-derived sediment loads in close proximity to one another (<500 km) exhibit broad similarity ( stream gauge samples; CRN samples). Nearly two-thirds of CRN-derived sediment loads exceed historic loads measured at the same locations (). Excessive longer-term sediment loads likely are a result of longer-term recurrence of large-magnitude sediment-transport events. Nearly 80% of sediment loads measured at approximately the same locations exhibit stream gauge loads that are within an order of magnitude of CRN loads, likely as a result of the buffering capacity of large flood plains. Catchments in which space for deposition exceeds sediment supply have greater buffering capacity. Superior locations in which to evaluate anthropogenic influences on landscape evolution might be buffered catchments, in which temporary storage of sediment in flood plains can provide stream gauge–based sediment loads and denudation rates that are applicable over longer periods than the durations of gauge measurements. The buffering capacity of catchments also has implications for interpreting the stratigraphic record; delayed sediment transfer might complicate the stratigraphic record of external forcings and catchment modification.

Covault, Jacob A.; Craddock, William H.; Romans, Brian W.; Fildani, Andrea; Gosai, Mayur

2013-01-01

392

Linking the historic 2011 Mississippi River flood to coastal wetland sedimentation  

USGS Publications Warehouse

Wetlands in the Mississippi River deltaic plain are deteriorating in part because levees and control structures starve them of sediment. In Spring of 2011 a record-breaking flood brought discharge on the lower Mississippi River to dangerous levels, forcing managers to divert up to 3500 m3/s-1 of water to the Atchafalaya River Basin. Here we quantify differences between the Mississippi and Atchafalaya River inundation and sediment-plume patterns using field-calibrated satellite data, and assess the impact these outflows had on wetland sedimentation. We characterize hydrodynamics and suspended sediment patterns of the Mississippi River plume using in-situ data collected during the historic flood. We show that the focused, high-momentum jet from the leveed Mississippi delivered sediment far offshore. In contrast, the plume from the Atchafalaya was more diffuse; diverted water inundated a large area; and sediment was trapped within the coastal current. Maximum sedimentation (up to several centimetres) occurred in the Atchafalaya Basin despite the larger sediment load carried by the Mississippi. Minimum accumulation occurred along the shoreline between these river sources. Our findings provide a mechanistic link between river-mouth dynamics and wetland sedimentation patterns that is relevant for plans to restore deltaic wetlands using artificial diversions.

Falcini, Federico; Khan, Nicole S.; Macelloni, Leonardo; Horton, Benjamin P.; Lutken, Carol B.; McKee, Karen L.; Santoleri, Rosalia; Colella, Simone; Li, Chunyan; Volpe, Gianluca; D’Emidio, Marco; Salusti, Alessandro; Jerolmack, Douglas J.

2012-01-01

393

Precipitation Event Size Controls on Long-Term Abundance of Opuntia Polyacantha (Plains Prickly-Pear) in Great Plains Grasslands  

Microsoft Academic Search

Opuntia polyacantha Haw. (plains prickly-pear) is a common cactus in the Great Plains of North America. We used two data sets, from Montana and Colorado, to test the hypothesis that there is a range of precipitation event sizes upon which O. polyacantha specializes. Events smaller than this range (>2 to ?6 mm) do not moisten sufficient soil to be utilized,

William K. Lauenroth; R. L. Dougherty; J. S. Singh

2009-01-01

394

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

USGS Publications Warehouse

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.

Hearn, Paul P.

1985-01-01

395

Nomenclature of regional hydrogeologic units of the Southeastern Coastal Plain aquifer system  

USGS Publications Warehouse

Clastic sediments of the Southeastern Coastal Plain aquifer system can be divided into four regional aquifers separated by three regional confining units. The four regional aquifers have been named for major rivers that cut across their outcrop areas and expose the aquifer materials. From youngest to oldest, the aquifers are called the Chickasawhay River, Pearl River, Chattahoochee River, and Black Warrior River aquifers, and the regional confining units separating them are given the same name as the aquifer they overlie. Most of the regional hydrogeologic units are subdivided within each of the four States that comprise the study area. Correlation of regional units is good with hydrogeologic units delineated by a similar regional study to the west and southwest. Because of complexity created by a major geologic structure to the northeast of the study area and dramatic facies change from clastic to carbonate strata to the southeast, correlation of regional hydrogeologic units is poor in these directions. (Author 's abstract)

Miller, J.A.; Renken, R.A.

1988-01-01

396

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

NASA Astrophysics Data System (ADS)

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