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Sample records for distributary deep-water deposits

  1. Distribution of palaeosols and deposits in the temporal evolution of a semiarid fluvial distributary system (Bauru Group, Upper Cretaceous, SE Brazil)

    NASA Astrophysics Data System (ADS)

    Basilici, Giorgio; Bo, Patrick Führ Dal'; de Oliveira, Emerson Ferreira

    2016-07-01

    The stratigraphic and sedimentological knowledge of the Bauru Group (Upper Cretaceous, SE Brazil) is still generally insufficient and controversial. A sedimentological and palaeopedological study allowed to interpret the south-eastern portion of the Bauru Group according to the model of a fluvial distributary system. This work has two objectives: (1) to include palaeosols in the interpretation of a fluvial distributary system and (2) to give detailed information on the sedimentological and stratigraphic features of the SE portion of the Bauru Group in order to support biostratigraphical, taphonomic and palaeoecological studies. In the south-eastern portion of the Bauru Group, three genetic stratigraphic units were described and interpreted, here informally called lower, intermediate and upper units. The lower unit is constituted of muddy sandstone salt flat deposits and sandstone sheet deltas deposits and is interpreted as a basinal part of a fluvial distributary system. The intermediate unit is formed of very fine to fine-grained sandstone-filled ribbon channel and sandy sheet-shaped beds, suggesting a distal or medial portion of a fluvial distributary system. The upper unit does not match with the present models of the fluvial distributary system because mostly constituted of moderately developed, well-drained, medium- to fine-grained sandstone palaeosols, which testify pauses of sedimentation to the order of 104 years. Preserved features of sedimentary structures suggest that the parent material was formed by occasional catastrophic unconfined flows. This unit may represent the most distal portion of a fluvial distributary system generated by retrogradation of the alluvial system due to aridification of the climate. The upper unit may be interpreted also as proximal portion of fluvial distributary system if considering the coarser-grained and the well-drained palaeosols. However, the absence of channel deposits makes this interpretation unconvincing.

  2. Depositional conditions in the Dead Sea and reinterpretations of ancient deep-water evaporites

    SciTech Connect

    Kendall, A.C. )

    1991-03-01

    Published work on post-1979 changes affecting the Dead Sea brine body imply that alternative explanations for some ancient deep-water evaporites are possible. Seasonally variable thermohaline stratification in the Dead Sea brine body allows gypsum-supersaturated brines to be transported to the basin floor, permitting growth of gypsum crusts, as long as the basin floor lies above the thermocline (20-25 m). Below this, only laminated gypsum and carbonates are likely to form in appreciable amounts. Complete brine overturns are ephemeral events, unlikely to cause significant growth of bottom-grown gypsum. The occurrence of numerous basin-wide layers of former gypsum crusts (now nodular anhydrite layers) in such deep-water evaporites as the Castile, Elk Point, and Zechstein suggests that these evaporite layers were deposited in brine depths less than that of the local thermocline, i.e. at depths of only a few tens of meters. Abrupt brine-deepening events caused laminated sediments to be deposited above former gypsum crusts. The continuation of calcium sulfate precipitation in these laminated sediments from the Castile and Zechstein evaporites indicates brine deepening was not accompanied by brine dilutions sufficient to cause gypsum undersaturation. This imposes limits upon the amount of brine deepening and implies that even the deepest of the laminated sulfate sediments were deposited from brines only tens of meters deep. Where crusts are overlain by laminated carbonates (Elk Point and some Zechstein evaporites), greater amounts of brine deepening and dilution are suggested.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  4. Highstand fans in the California borderland: the overlooked deep-water depositional systems

    USGS Publications Warehouse

    Covault, Jacob A.; Normark, William R.; Romans, Brian W.; Graham, Stephan A.

    2007-01-01

    Contrary to widely used sequence-stratigraphic models, lowstand fans are only part of the turbidite depositional record; our analysis reveals that a comparable volume of coarse-grained sediment has been deposited in California borderland deep-water basins regardless of sea level. Sedimentation rates and periods of active sediment transport have been determined for deep-water canyon-channel systems contributing to the southeastern Gulf of Santa Catalina and San Diego Trough since 40 ka using an extensive grid of high-resolution and deep-penetration seismic-reflection data. A regional seismic-reflection horizon (40 ka) has been correlated across the study area using radiocarbon age dates from the Mohole borehole and U.S. Geological Survey piston cores. This study focused on the submarine fans fed by the Oceanside, Carlsbad, and La Jolla Canyons, all of which head within the length of the Ocean-side littoral cell. The Oceanside Canyon–channel system was active from 45 to 13 ka, and the Carlsbad system was active from 50 (or earlier) to 10 ka. The La Jolla system was active over two periods, from 50 (or earlier) to 40 ka, and from 13 ka to the present. One or more of these canyon-channel systems have been active regardless of sea level. During sea-level fluctuation, shelf width between the canyon head and the littoral zone is the primary control on canyon-channel system activity. Highstand fan deposition occurs when a majority of the sediment within the Oceanside littoral cell is intercepted by one of the canyon heads, currently La Jolla Canyon. Since 40 ka, the sedimentation rate on the La Jolla highstand fan has been >2 times the combined rates on the Oceanside and Carlsbad lowstand fans.

  5. Evidence for deep-water evaporite deposition in the Miocene Kareem Formation, Gemsa basin, eastern Egypt

    SciTech Connect

    May, J.A.; Stonecipher, S.A.; Steinmetz, J.C. ); Dyess, J.N. )

    1991-03-01

    The correct interpretation of intercalated Miocene siliciclastics and evaporites of Gemsa basin is crucial for understanding early rift tectonics of the Gulf of Suez, pinpointing the timing of isolation of the Gulf from the Mediterranean, and developing exploration plays. Evaporites of the Kareem Formation comprise celestites and massive, 'chicken-wire,' and laminated anhydrites. Although previously interpreted as sabkha deposits; sedimentologic, petrographic, and paleontologic analyses indicate these evaporites more likely formed in a submarine setting. Marls that encase the evaporites contain a diverse and abundant assemblage of nannoplankton, planktonic foraminifera, diatoms, pteropods, and fish scales indicative of basinal deposition. Associated turbidites also denote deep-water sedimentation. The paucity of benthic diatoms and foraminifera, plus the presence of unburrowed shales, phosphate nodules, early ferroan carbonate cements, and authigenic pyrite, suggest periodic anoxic, or at least disaerobic, bottom waters. These sequences probably represent partial isolation of the Gulf of Suez by middle Miocene, producing periodic basin restriction and evaporative drawdown. Episodes of increasing salinity likely caused the progressive decreases in foram abundance and diversity in marls beneath the anhydrites, culminating in subaqueous evaporite formation. Diverse, indigenous nannoplankton assemblages from shale seams within the anhydrites suggest Gemsa basin was stratified; shallow open-marine conditions coexisted with anhydrite crystallization from deeper hypersaline waters.

  6. North Atlantic Ocean deep-water processes and depositional environments: A study of the Cenozoic Norway Basin

    NASA Astrophysics Data System (ADS)

    Oline Hjelstuen, Berit; Andreassen, Elin V.

    2015-04-01

    Despite the enormous areas deep-water basins occupy in modern oceans, our knowledge about them remains poor. At depths of greater than 2000 m, the Cenozoic Norway Basin in the northernmost part of the Atlantic Ocean, is one such basin. Interpretation of 2D multichannel seismic data suggests a three-stage evolution for the Norway Basin. (1) Eocene-Pliocene. This time period is characterised by deposition of ooze-rich sediments in a widening and deepening basin. (2) Early-Middle Pleistocene. A significant shift in sedimentary processes and depositional environments took place in the Early Pleistocene. Mass failures initiated on the Norwegian continental slope, and three Early and Middle Pleistocene slide debrites, with maximum thicknesses of 600 m and sediment volumes of up to 25000 km3, were deposited. With ages estimated at c. 2.7-1.7 Ma, 1.7-1.1 Ma and 0.5 Ma, these slide deposits are among the largest identified worldwide, and among the oldest mapped along the entire NE Atlantic continental margin. (3) Late Pleistocene-Present. Since c. 0.5 Ma the Norway Basin has been effected by glacigenic debris flows, the Storegga Slide and hemipelagic-glacimarine sedimentation. These sedimentary processes were active during a time of repeated shelf-edge ice advances along the NE Atlantic continental margin. This study shows that deep-water basins represent dynamic depositional environments reflecting regional tectonic and climatic changes trough time.

  7. Dynamic depositional and early diagenetic processes in a deep-water shelf setting, upper cretaceous Austin Chalk, North Texas

    SciTech Connect

    Hovorka, S.D.; Nance, H.S.

    1994-12-31

    The Austin Chalk of north Texas was deposited on a deep-water shelf north of the Sea Marcos Platform during a worldwide Coniacian and Santonian sea-level highstand. Transgressive (lowermost lower Austin Chalk), highstand (uppermost lower Austin Chalk), and regressive (middle and upper Austin Chalk) phases of cyclic chalk and marl sedimentation are recognized in excavations and tunnels created in Ellis County for the Superconducting Super Collider provide new evidence of sediment transport during Austin Chalk deposition. During transgression, bottom currents syndepositionally reworked nannoplankton oozes, incising channels as much as 120 ft across and 8 ft deep. Weakly burrowed channel fills having preservation of fine lamination document rapid infilling. Channel fills are composed of pyritized and carbonized wood and Inoceramus lag deposits, pellets, echinoderm fragments, and globigerinid grainstones, and coccolith ooze. During maximum highstand, bottom reworking was suppressed. Detrital content of highstand marls is low (>20 percent); organic content is high (1.4 to 3.5 percent). Coccolith preservation is excellent because of minimal diagenetic alteration. Regression is marked by resumed channel cutting and storm-bed winnowing in the middle and upper Austin Chalk. Suppressed resistivity log response and recessive weathering characteristics of the middle Austin Chalk are not primarily related to depositional environment but rather to increased input of volcanic ash during the accumulation of this interval. Early stabilization of ash produced clay-coated microfabrics in sediments that are otherwise similar to the transgressive deposits.

  8. Role of sea-level change in deep water deposition along a carbonate shelf margin, Early and Middle Permian, Delaware Basin: implications for reservoir characterization

    NASA Astrophysics Data System (ADS)

    Li, Shunli; Yu, Xinghe; Li, Shengli; Giles, Katherine A.

    2015-04-01

    The architecture and sedimentary characteristics of deep water deposition can reflect influences of sea-level change on depositional processes on the shelf edge, slope, and basin floor. Outcrops of the northern slope and basin floor of the Delaware Basin in west Texas are progressively exposed due to canyon incision and road cutting. The outcrops in the Delaware Basin were measured to characterize gravity flow deposits in deep water of the basin. Subsurface data from the East Ford and Red Tank fields in the central and northeastern Delaware Basin were used to study reservoir architectures and properties. Depositional models of deep water gravity flows at different stages of sea-level change were constructed on the basis of outcrop and subsurface data. In the falling-stage system tracts, sandy debris with collapses of reef carbonates are deposited on the slope, and high-density turbidites on the slope toe and basin floor. In the low-stand system tracts, deep water fans that consist of mixed sand/mud facies on the basin floor are comprised of high- to low-density turbidites. In the transgression and high-stand system tracts, channel-levee systems and elongate lobes of mud-rich calciturbidite deposits formed as a result of sea level rise and scarcity of sandy sediment supply. For the reservoir architecture, the fan-like debris and high-density turbidites show high net-to-gross ratio of 62 %, which indicates the sandiest reservoirs for hydrocarbon accumulation. Lobe-like deep water fans with net-to-gross ratio of 57 % facilitate the formation of high quality sandy reservoirs. The channel-levee systems with muddy calciturbidites have low net-to-gross ratio of 30 %.

  9. Origin and architecture of deep-water levee deposits: Insight from the ancient rock record and experiments

    NASA Astrophysics Data System (ADS)

    Khan, Zishann

    Although levee deposits make up a significant part of modern and ancient deep-marine slope systems, details of their internal lithological composition and stratal architecture remain poorly documented. At the Castle Creek study area, strata of the Neoproterozoic Isaac Formation (Windermere Supergroup) crop out superbly in a kilometre-scale section through a sinuous deep-water channel-levee system (ICC3). Levee deposits near the outer bend of the channel consist of sandstone-rich (sandstone-to-mudstone ratio of 68:42), medium- to thick-bedded turbidites interstratified with thinly-bedded turbidites. Structureless sandstone (T a), planar laminated sandstone (Tb), non-climbing ripple cross-stratified sandstone (Tc) and massive and laminated siltstone (Td) are common. Thick beds generally thicken and then thin and fine laterally over about 300 m. Thin-bedded strata, in contrast, thin and fine negligibly over similar distances. In the distal part of the outer-bend levee (up to 700 m laterally away from the channel) strata consist predominantly of thin-bedded Tcd turbidites with a much lower sandstone-to-mudstone ratio (35:65). On the opposite side of the channel, inner-bend levee deposits are mudstone-rich, locally as low as 15:85, and consist mostly of thin-bedded, Tcd turbidites, although thicker-bedded, Ta-d turbidites are more common in the lower part of the section. Lateral thinning and fining of beds is more rapid than their outer-bend counterpart. Levee deposits of ICC3 comprise three stacked decametre-scale upward-thinning and -fining successions. Each is interpreted to record a depositional history consisting of lateral channel migration, levee deposition, channel filling, and distal levee deposition. During the early stage of increasing levee relief it is proposed that the termini of individual beds progressively backstep towards the channel margin resulting in an overall lateral thinning of the stratal profile. This interpretation notably contrasts the common

  10. Deep-water environments for the putative Early Archean life: Chert units depositional facies, Warrawoona Group, Western Australia

    NASA Astrophysics Data System (ADS)

    Dromart, G.; Coltice, N.; Flament, N.; Olivier, N.; Rey, P.

    2008-12-01

    The principal objective of this work is to find and interpret evidence for the depositional conditions of the greenstone-belt facies that possibly hosted primitive life forms. That information is critical to any attempt to assess the habitability of Early Earth's environments, as well as their potential for fossil preservation. Chert members of the Duffer Fm and the Apex chert, which bears fossil-like filaments (3.465 Ga), are exposed in the vicinity of Marble Bar. The Marble Bar Chert is made up of dm-scale sequences of interbedded red, white and black finely crystalline silica. Sticky beds consist of flow-oriented clasts (i.e., large, angular, elongated, light-colored clasts showing load-structures, and regularly-inclined and vertically- oriented imbrications) interpreted here as gravity flows of early-lithified sediments. The Chinaman Pool Chert Mb is incised by a deep scour upon which sandstone beds with chert interlayers onlap. This unit includes coarse mafic sands, and conglomerates with chert lithoclasts and felsic pebbles. Locally, m-scale growth faults localize sand-filled channels. The depositional architectures and facies of this upper unit are indicative of a deep-water fan depositional system. This interpretation conflicts with the current view that chert units derived from hydrothermalism overprint of original shallow deposits, and that hydrothermalism hampered microfossil preservation. Alternatively, we suggest that deep-water environments and early lithification of siliceous sediments may have favored life preservation. Earth's oldest stromatolites (3.49-3.47 Ga) of the Dresser Fm are exposed in the North Pole Dome area. Autochtonous stromatolites consist of banded microstructures with iron-rich, wavy and wrinkle laminae, and form regular domes. The stromatolite layers cap a sandstone bed at the top of which asymmetric ripples show steeply-inclined sets of laminae that typically represent overturned ripples at uppermost turbiditic flow deposits. The

  11. Shallow to deep-water deposition in a Cratonic basin: an example from the Proterozoic Penganga Group, Pranhita Godavari Valley, India

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Joydip; Chaudhuri, Asru K.

    2003-03-01

    The unmetamorphosed Proterozoic succession dominated by deep-water lithographic limestone and shale in the western flank of the Pranhita-Godavari Valley is designated as the Penganga Group. The succession in different parts of the Valley includes the Pranhita Sandstone (25-400 m), the Chanda Limestone (300 m), and the Sat Nala Shale (>2000 m) in ascending order. The Pranhita Sandstone and the Chanda Limestone reveal considerable variations in the character of the stratal packages and depositional settings from Mancherial in the south to Adilabad in the north. The Sat Nala Shale in both southern and northern outcrop belts is completely devoid of sand. It is brown to purple in colour and resembles present-day deep-water mud deposits. In the Mancherial area, the Pranhita Sandstone consists of 25-400 m thick conglomerate, pebbly red arkose and quartzose sandstone succession of coastal alluvial fan to shallow shelf origin. The Chanda Limestone is micritic and locally includes interbedded lenses of cross-stratified quartzose sandstone in the lower part. The depositional milieu varies from shallow shelf to below wave base outer ramp carbonate platform. Around Adilabad, the Pranhita Sandstone (25 m) lacks the conglomerate-pebbly arkose association at the base and comprises only quartzose sandstone and shale of shoreface to muddy shelf settings. The Chanda Limestone is essentially micritic but, in contrast to the Mancherial area, includes several interbedded intervals of slope-related, autoclastic debris flow limestone conglomerates and calciturbidites, and represents deep, outer ramp to slope and basinal settings. A predominantly deep-water micritic limestone and deep-water shale succession suggests that the Penganga basin evolved to a vast, deep epicratonic sea connected to an open ocean. The absence of a coastal alluvial fan association at the lower part of the Pranhita Sandstone and presence of a slope to basinal association in the Chanda Limestone in the northern

  12. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2016-04-30

    OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics-043016 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics...understanding of the impact of the ocean and seafloor environmental variability on deep- water (long-range) ocean acoustic propagation and to...improve our understanding. During the past few years, the physics effects studied have been three-dimensional propagation on global scales, deep water

  13. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2015-10-19

    OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics-093015 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics...number. 1. REPORT DATE OCT 2015 2. REPORT TYPE 3. DATES COVERED 01-07-2015 to 30-09-2015 4. TITLE AND SUBTITLE Deep Water Ocean Acoustics...understanding of the impact of the ocean and seafloor environmental variability on deep- water (long-range) ocean acoustic propagation and to develop

  14. Cambrian–Ordovician of the central Appalachians:Correlations and event stratigraphy of carbonate platform andadjacent deep-water deposits

    USGS Publications Warehouse

    Brezinski, David K.; Taylor, John F.; Repetski, John E.; Loch, James D.

    2015-01-01

    deposited within the Pennsylvania and Maryland portion of the Great American Carbonate Bank. From the Early Cambrian (Dyeran) through Late Ordovician (Turinan), the Laurentian paleocontinent was rimmed by an extensive carbonate platform. During this protracted period of time, a succession of carbonate rock, more than two miles thick, was deposited in Maryland and Pennsylvania. These strata are now exposed in the Nittany arch of central Pennsylvania; the Great Valley of Pennsylvania, Maryland, and Virginia; and the Conestoga and Frederick Valleys of eastern Pennsylvania and Maryland. This fi eld trip will visit key outcrops that illustrate the varied depositional styles and environmental settings that prevailed at different times within the Pennsylvania reentrant portion of the Great American Carbonate Bank. In particular, we will contrast the timing and pattern of sedimentation in off-shelf (Frederick Valley), outer-shelf (Great Valley), and inner-shelf (Nittany arch) deposits. The deposition was controlled primarily by eustasy through the Cambrian and Early Ordovician (within the Sauk megasequence), but was strongly infl uenced later by the onset of Taconic orogenesis during deposition of the Tippecanoe megasequence.

  15. Impact of structural and autocyclic basin-floor topography on the depositional evolution of the deep-water Valparaiso forearc basin, central Chile

    USGS Publications Warehouse

    Laursen, J.; Normark, W.R.

    2003-01-01

    The Valparaiso Basin constitutes a unique and prominent deep-water forearc basin underlying a 40-km by 60-km mid-slope terrace at 2.5-km water depth on the central Chile margin. Seismic-reflection data, collected as part of the CONDOR investigation, image a 3-3.5-km thick sediment succession that fills a smoothly sagged, margin-parallel, elongated trough at the base of the upper slope. In response to underthrusting of the Juan Ferna??ndez Ridge on the Nazca plate, the basin fill is increasingly deformed in the seaward direction above seaward-vergent outer forearc compressional highs. Syn-depositional growth of a large, margin-parallel monoclinal high in conjunction with sagging of the inner trough of the basin created stratal geometries similar to those observed in forearc basins bordered by large accretionary prisms. Margin-parallel compressional ridges diverted turbidity currents along the basin axis and exerted a direct control on sediment depositional processes. As structural depressions became buried, transverse input from point sources on the adjacent upper slope formed complex fan systems with sediment waves characterising the overbank environment, common on many Pleistocene turbidite systems. Mass failure as a result of local topographic inversion formed a prominent mass-flow deposit, and ultimately resulted in canyon formation and hence a new focused point source feeding the basin. The Valparaiso Basin is presently filled to the spill point of the outer forearc highs, causing headward erosion of incipient canyons into the basin fill and allowing bypass of sediment to the Chile Trench. Age estimates that are constrained by subduction-related syn-depositional deformation of the upper 700-800m of the basin fill suggest that glacio-eustatic sea-level lowstands, in conjunction with accelerated denudation rates, within the past 350 ka may have contributed to the increase in simultaneously active point sources along the upper slope as well as an increased

  16. The Porcupine Bank Canyon coral mounds: oceanographic and topographic steering of deep-water carbonate mound development and associated phosphatic deposition

    NASA Astrophysics Data System (ADS)

    Mazzini, A.; Akhmetzhanov, A.; Monteys, X.; Ivanov, M.

    2012-06-01

    . Evidently, slope breaks such as escarpments and deep-water canyon headwalls are important structural elements in the development of mature carbonate mounds induced by deep-water coral growth. Stable isotope data show no evidence of methane-derived carbon in the carbonates and lithified sediments of the Porcupine Bank Canyon mounds.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    The west Iberian margin is indented by a network of submarine canyons that create rugged seafloor morphology and act as major pathways for the transport of sediment from land to the abyssal plains. The Setúbal and Nazaré Canyons are part of this complex environment and strongly influence sediment distribution, capturing sediments from the Tagus River and the littoral cell transport respectively. Deep submarine sedimentary sequences thus reflect changes in sediment input and depositional environments. The high-resolution sedimentological study here presented was applied in four cores of the deep water levees of Nazaré and Setúbal Canyons in order to explore how sediment input to the canyons changed during the last glacial - interglacial transition, and how this reflects changing environmental conditions on land. By means of non-destructive corelogger measurements and analyses of spectral signatures, geochemical compositions and colour variations, it was possible to identify ice-rafted debris (IRD) deposits, to characterize hemipelagic and turbidite layers and to investigate terrestrial-derived sediments input variation during the last 26 ka. Preliminary results from the sedimentological and turbidite frequency analyses show that highest turbidite occurrence is recorded during the glacial stage, confirming that the generation of turbidity flows in submarine canyons is tightly related to low sea-level stands. We found that major peaks in frequency and thickness of turbidite deposits in the deep Portuguese margin are mainly coeval with abrupt climatic (H2 and 1) and sea-level changes (~ 19 and ~ 23 ka BP), as a consequence of which a major amount of continentally-derived material was transported into the deep sea. During the Holocene, the inception of sea-level rises, independent of their magnitude, has been found to be sufficient to generate turbidity currents, particularly in the Nazaré system. Moreover, a multiple regression analysis was attempted in order to

  18. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2015-07-17

    under-ice scattering , bathymetric diffraction and the application of the ocean acoustic Parabolic Equation to infrasound. 2. Tasks a. Task 1...QSR-14C0172-Ocean Acoustics -063015 Figure 10. Estimated reflection coefficient as a function of frequency by taking the difference of downgoing and...OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics -063015 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics

  19. Deep Water Formation

    NASA Technical Reports Server (NTRS)

    Killworth, P. D.

    1984-01-01

    Some simple arguments on plumes of dense water and filling boxes were given. What determines the time for a large-scale environment to be modified by the injection of dense water at its edge is the mass flux, not the buoyancy flux. However, it is the denser buoyancy flux, when there are several competing plumes (e.g., the Mediterranean outflow versus the Denmark Strait outflow) that determines which plume will provide the bottom water for that ocean basin. It was noted that the obvious laboratory experiment (rotate a pie-shaped annulus, and heat/cool it on the surface) had never been performed. Thus, to some extent our belief that deep convection is somehow automatic at high latitudes to close off some ill-defined meridional circulation has never been tested. A summary of deep convection was given. The two fundamental formation mechanisms were shown. Of the two, it is open-ocean convection which forms the water which supplies the Denmark Strait overflow -- in all likelihood, as formation in the Greenland Sea remains stubbornly unobserved. But it is the slope convection which finally creates North Atlantic deep water, following the Denmark Strait overspill.

  20. Integrated biostratigraphy of foraminifers, radiolarians and conodonts in shallow and deep water Middle Permian (Capitanian) deposits of the "Rader slide", Guadalupe Mountains, West Texas

    USGS Publications Warehouse

    Nestell, M.K.; Nestell, G.P.; Wardlaw, B.R.; Sweatt, M.J.

    2006-01-01

    A diverse assemblage of microfossils is present in a 6m thick sequence of three debris flow deposits interbedded with thin turbidite limestone beds and fine grained siliciclastics exposed above the megaconglomerate in a section (known as the "Rader Slide" in numerous guidebook stops) of the Rader Limestone Member of the Bell Canyon Formation of Capitanian age (Middle Permian) in the Guadalupe Mountains of West Texas. Each debris flow, derived from nearby Capitan Reef shelf-margin and slope deposits, contains a distinct microfossil assemblage. Small foraminifers and fusulinaceans, conodonts, radiolarians, sponge spicules, fish dermal plates and teeth, and other fragmental fossils are present in this sequence. Conodonts are relatively scarce in the first (or lowest) debris flow, except in its upper part, but they are common to abundant in the other two debris flows, and very abundant in several of the thin turbidite limestone beds. All of the conodonts present appear to be morphotypes of one population of the species Jinogondolella postserrata, except for one new conodont species, and the Jinogondolella postserrata Zone is clearly documented in this sequence. The debris flows contain the fusulinaceans Rauserella, rare Codonofusiella, Polydiexodina, Leella? and various species of the small foraminifers Globivalvulina, Hemigordius, Baisalina, Abadehella, Deckerella, Neoendothyranella, Vachardella, Geinitzina, and Polarisella. Some of the thin turbidite limestone beds contain a foraminiferal assemblage similar to that found in the debris flows, but with lower diversity. Many small foraminiferal species appear to be endemic, although a few are closely related to species known in Permian age strata in Italy, Greenland, the Russian Far East, northeastern part of Russia (Omolon massif), and the Zechstein of Germany and the Baltic area. Two thin limestone beds above the second debris flow contain primarily radiolarian species known from the Follicucullus japonicus Zone of

  1. Surface water-groundwater connectivity in deltaic distributary channel networks

    NASA Astrophysics Data System (ADS)

    Sawyer, Audrey H.; Edmonds, Douglas A.; Knights, Deon

    2015-12-01

    Delta distributary channel networks increase river water contact with sediments and provide the final opportunity to process nutrients and other solutes before river water discharges to the ocean. In order to understand surface water-groundwater interactions at the scale of the distributary channel network, we created three numerical deltas that ranged in composition from silt to sand using Delft3D, a morphodynamic flow and sediment transport model. We then linked models of mean annual river discharge to steady groundwater flow in MODFLOW. Under mean annual discharge, exchange rates through the numerical deltas are enhanced relative to a single-threaded river. We calculate that exchange rates across a <10 km2 network are equivalent to exchange through ~10-100 km of single-threaded river channel. Exchange rates are greatest in the coarse-grained delta due to its permeability and morphology. Groundwater residence times range from hours to centuries and have fractal tails. Deltas are vanishing due to relative sea level rise. River diversion projects aimed at creating new deltaic land should also aim to restore surface water-groundwater connectivity, which is critical for biogeochemical processing in wetlands. We recommend designing diversions to capture more sand and thus maximize surface water-groundwater connectivity.

  2. Deep water recycling through time

    PubMed Central

    Magni, Valentina; Bouilhol, Pierre; van Hunen, Jeroen

    2014-01-01

    We investigate the dehydration processes in subduction zones and their implications for the water cycle throughout Earth's history. We use a numerical tool that combines thermo-mechanical models with a thermodynamic database to examine slab dehydration for present-day and early Earth settings and its consequences for the deep water recycling. We investigate the reactions responsible for releasing water from the crust and the hydrated lithospheric mantle and how they change with subduction velocity (vs), slab age (a) and mantle temperature (Tm). Our results show that faster slabs dehydrate over a wide area: they start dehydrating shallower and they carry water deeper into the mantle. We parameterize the amount of water that can be carried deep into the mantle, W (×105 kg/m2), as a function of vs (cm/yr), a (Myrs), and Tm (°C):. We generally observe that a 1) 100°C increase in the mantle temperature, or 2) ∼15 Myr decrease of plate age, or 3) decrease in subduction velocity of ∼2 cm/yr all have the same effect on the amount of water retained in the slab at depth, corresponding to a decrease of ∼2.2×105 kg/m2 of H2O. We estimate that for present-day conditions ∼26% of the global influx water, or 7×108 Tg/Myr of H2O, is recycled into the mantle. Using a realistic distribution of subduction parameters, we illustrate that deep water recycling might still be possible in early Earth conditions, although its efficiency would generally decrease. Indeed, 0.5–3.7 × 108 Tg/Myr of H2O could still be recycled in the mantle at 2.8 Ga. Key Points Deep water recycling might be possible even in early Earth conditions We provide a scaling law to estimate the amount of H2O flux deep into the mantle Subduction velocity has a a major control on the crustal dehydration pattern PMID:26321881

  3. Deep water recycling through time.

    PubMed

    Magni, Valentina; Bouilhol, Pierre; van Hunen, Jeroen

    2014-11-01

    We investigate the dehydration processes in subduction zones and their implications for the water cycle throughout Earth's history. We use a numerical tool that combines thermo-mechanical models with a thermodynamic database to examine slab dehydration for present-day and early Earth settings and its consequences for the deep water recycling. We investigate the reactions responsible for releasing water from the crust and the hydrated lithospheric mantle and how they change with subduction velocity (vs ), slab age (a) and mantle temperature (Tm). Our results show that faster slabs dehydrate over a wide area: they start dehydrating shallower and they carry water deeper into the mantle. We parameterize the amount of water that can be carried deep into the mantle, W (×10(5) kg/m(2)), as a function of vs (cm/yr), a (Myrs), and Tm (°C):[Formula: see text]. We generally observe that a 1) 100°C increase in the mantle temperature, or 2) ∼15 Myr decrease of plate age, or 3) decrease in subduction velocity of ∼2 cm/yr all have the same effect on the amount of water retained in the slab at depth, corresponding to a decrease of ∼2.2×10(5) kg/m(2) of H2O. We estimate that for present-day conditions ∼26% of the global influx water, or 7×10(8) Tg/Myr of H2O, is recycled into the mantle. Using a realistic distribution of subduction parameters, we illustrate that deep water recycling might still be possible in early Earth conditions, although its efficiency would generally decrease. Indeed, 0.5-3.7 × 10(8) Tg/Myr of H2O could still be recycled in the mantle at 2.8 Ga.

  4. Potential flood hazards and hydraulic characteristics of distributary-flow areas in Maricopa County, Arizona

    USGS Publications Warehouse

    Hjalmarson, H.W.

    1994-01-01

    Flood hazards of distributary-flow areas in Maricopa County, Arizona, can be distinguished on the basis of morphological features. Five distributary-flow areas represent the range of flood-hazard degree in the study area. Descriptive factors, including the presence of desert varnish and the absence of saguaro cactus, are more useful than traditional hydraulic-based methods in defining hazards. The width, depth, and velocity exponents of the hydraulic-geometry relations at the primary diffluences of the sites are similar to theoretical exponents for streams with cohesive bank material and the average exponents of stream channels in other areas in the United States. Because of the unexplained scatter of the values of the exponent of channel width, however, the use of average hydraulic-geometry relations is con- sidered inappropriate for characterizing flood hazards for specific distributary-flow in Maricopa County. No evidence has been found that supports the use of stochastic modeling of flows or flood hazards of many distributary-flow areas. The surface of many distributary-flow areas is stable with many distributary channels eroded in the calcreted surface material. Many distributary- flow areas do not appear to be actively aggrading today, and the paths of flow are not changing.

  5. Early Oligocene initiation of North Atlantic Deep Water formation.

    PubMed

    Davies, R; Cartwright, J; Pike, J; Line, C

    2001-04-19

    Dating the onset of deep-water flow between the Arctic and North Atlantic oceans is critical for modelling climate change in the Northern Hemisphere and for explaining changes in global ocean circulation throughout the Cenozoic era (from about 65 million years ago to the present). In the early Cenozoic era, exchange between these two ocean basins was inhibited by the Greenland-Scotland ridge, but a gateway through the Faeroe-Shetland basin has been hypothesized. Previous estimates of the date marking the onset of deep-water circulation through this basin-on the basis of circumstantial evidence from neighbouring basins-have been contradictory, ranging from about 35 to 15 million years ago. Here we describe the newly discovered Southeast Faeroes drift, which extends for 120 km parallel to the basin axis. The onset of deposition in this drift has been dated to the early Oligocene epoch ( approximately 35 million years ago) from a petroleum exploration borehole. We show that the drift was deposited under a southerly flow regime, and conclude that the initiation of deep-water circulation from the Norwegian Sea into the North Atlantic Ocean took place much earlier than is currently assumed in most numerical models of ancient ocean circulation.

  6. Deep Water Ambient Noise and Mode Processing

    DTIC Science & Technology

    2014-09-30

    Deep Water Ambient Noise and Mode Processing Kathleen E. Wage George Mason University Electrical and Computer Engineering Department 4400...specific objectives of the project are: 1) to characterize the ambient noise in the PhilSea data set using spectral analysis and to compare the results...to those for other deep water data sets; 2) to analyze the acoustic modes in the ambient noise and moored source data sets acquired in the PhilSea

  7. Hydraulic and sediment transport properties of autogenic avulsion cycles on submarine fans with supercritical distributaries

    NASA Astrophysics Data System (ADS)

    Hamilton, Paul B.; Strom, Kyle B.; Hoyal, David C. J. D.

    2015-07-01

    Submarine fans, like other distributive systems, are built by repeated avulsion cycles. However, relative to deltas and alluvial fans, much less is known about avulsions in subaqueous settings. In this study, we ran a set of subaqueous fan experiments to investigate the mechanics associated with autogenic avulsion cycles of self-formed channels and lobe deposits on steep slopes. The experiments used saline density currents with crushed plastic to emulate sustained turbidity currents and bed load transport. We collected detailed hydraulic and bathymetric measurements and made use of a 1-D laterally expanding density current model to better understand different aspects of the avulsion cycle. Our results reveal three major components of the avulsion cycles: (1) distributary channel incision, extension, and stagnation; (2) mouth bar aggradation and hydraulic jump initiation; and (3) hydraulic jump sedimentation and upstream retreat. Interestingly, in all but one experiment, the avulsion cycles led to fans that remained perched above the basin slope break. Experimental data and hydraulic theory were used to unravel actual mechanics associated with cycles. We found that channels stopped extending into the basin due to a decay in sediment transport capacity relative to sediment supply and that the reduction in capacity was primarily an outcome of expansion-driven velocity reduction; dilution played a secondary role. Once channel extension ceased, mouth bar deposits aggraded to a thickness approximately equal to the critical step height needed to create a choked flow condition. The choke then initiated a hydraulic jump on the upstream side of the bar. Once formed, the jump detained a majority of the incoming sediment and forced the channel-to-lobe transition upstream, filling the channel with steep backset bedding and capping the entire channel with a mounded lobate deposit. These intrinsic processes repeated through multiple avulsion cycles to build the fan.

  8. Biology of deep-water chondrichthyans: Introduction

    NASA Astrophysics Data System (ADS)

    Cotton, C. F.; Grubbs, R. D.

    2015-05-01

    Approximately half of the known chondrichthyans (sharks, skates, rays, and chimaeras), 575 of 1207 species (47.6%, Table 1), live in the deep ocean (below 200 m), yet little is known of the biology or life histories of most of these fishes (Kyne and Simpfendorfer, 2007). The limited information available for deep-water chondrichthyans is compounded by their rarity, as well as the prevalent uncertainty in the alpha taxonomy of deep-water species. Many species are known only from the type materials, which are generally limited to nondestructive sampling, e.g., morphometrics, imaging (X-ray, MRI, CT scanning). Thus, research has been hindered by a lack of specimens available for investigation that requires destructive sampling or live specimens (e.g., life history, diet, telemetry). The need for more research and dissemination of information about deep-water chondrichthyans has become imperative as fisheries worldwide continue to expand into deeper waters and exploit deep-water stocks, usually in the absence of data required for appropriate management (Morato et al., 2006; Kyne and Simpfendorfer, 2010).

  9. Hawaii Deep Water Cable Program: Executive Summary

    SciTech Connect

    1990-09-01

    The Hawaii Deep Water Cable Program has succeeded unequivocally in determining the feasibility of deploying a submarine power cable system between the islands of Hawaii and Oahu. Major accomplishments of the program include designing, fabricating and testing an appropriate power cable, developing an integrated system to control all aspects of the cable laying operation, and testing all deployment systems at sea in the most challenging sections of the route.

  10. Long Range Acoustic Communication in Deep Water

    DTIC Science & Technology

    2013-09-30

    ocean is challenging due to the substantial propagation loss, multipath delay spread , and channel variability. Analysis of deep-water data collected...were exploited. In addition, a robust algorithm (double differentially coded spread spectrum) was demonstrated recently using the LRAC10 data [10...Spray gliders with a commercial acoustic modem for data retrieval from subsurface moorings and seafloor systems installed with a similar modem in deep

  11. Recharge mixing in a complex distributary spring system in the Missouri Ozarks, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Toronto Springs is a complex distributary karst spring system with 11 perennial springs in the central Missouri Ozarks, USA. Carroll Cave (CC) and Wet Glaize Creek (WG) were previously identified as principal recharge sources. This study 1) characterized physical and chemical properties of the sprin...

  12. Suspended sediment transport in distributary channel networks and its implication on the evolution of delta

    NASA Astrophysics Data System (ADS)

    Suying, Ou; hao, Yang

    2016-04-01

    Suspended sediment (SS) transport in distributary channels play an important role on the evolution of deltas and estuaries. Under the interactions between river discharge, tide, and bathymetry of Pearl River delta (PRD) in south China, the spatial and temporal characteristics of suspended sediment transport are investigated by using the field data of July 16 to 25, 1999 and February 7 to 15, 2001. The PRD, as one of the most complex tributary system in the world and composed of 324 transversal and longitudinal tributaries, with eight outlets to the three sub-estuaries, has higher suspended sediment load in middle delta including six outlets than in right and left tidal dominant channels of PRD, that is Humen channel and Yamen channel system. Under large river discharge of one flood in summer, the tidal averaged SS transport from channel to the estuaries, the SS concentration of middle delta is 10~20 times and the transport rate is 100~500 times of dry season. But the transport rate changes little between flood season and dry season in the upper channel system of Yamen and Humen, and in dry season the tidal averaged transport change direction from estuary to these channel systems. About 70~85% of total Pearl River SS load transport along the main channel of West River, then transport about 45~55% into the lower West river delta, about 30% of total SS load flushed into the Modaomen outlets. Under the bathymetry of branched channels, SS load which advected from the Pearl River and resuspended from bed, redistributed 4~8 times in the PRD and then cause the different changes of channels. It found that in flood season, the suspended sediment load from Pearl River including East, West, North River and Tanjiang, Liuxi River into the PRD is less than that discharged into the estuaries through eight outlets, which indicated the erosion in the channels of PRD especially in the lower part of PRD. Suspended sediment budget in dry season during neap-spring cycle indicated that

  13. Distributary-mouth bar development and role of submarine landslides in delta growth, South Pass, Mississippi delta

    SciTech Connect

    Lindsay, J.F.; Coleman, J.M.; Prior, D.B.

    1984-11-01

    Submarine landslides play a major role in the development of distributary-mouth bars and are of major importance in transporting sediment from the bar front to deeper water along the Mississippi delta front. Historic maps of the South Pass of the Mississippi delta show that the bar advanced seaward more than 1 mi (1.6 km) between 1867 and 1953. Details of the growth of the bar have been elucidated using an elaborate computer modeling program to analyze these historic maps. The analysis has shown that the geometry of the bar was controlled by the dynamics of the freshwater plume of river water as it mixed with saline Gulf water. Approximately half the sediment deposited on the bar was moved into deeper water by submarine landslides. The underlying causes of bar failure were established during major floods with the deposition of thick blankets of unstable, watersaturated sediments on the bar front. Failure occurred one to four years later in response to a variety of triggering mechanisms, which either changed the shear strength of the sediment or modified local bottom slope. The triggering mechanisms include: major storms and hurricanes, mudlump activity, and possibly, increased pore pressures resulting from generation of biogenic gas. Bar growth and basinward movement of sediment thus represent a multilvariate problem that can be approached by means of a computer analysis of bathymetric data.

  14. Deep-water Circulation: Processes & Products (16-18 June 2010, Baiona): introduction and future challenges

    NASA Astrophysics Data System (ADS)

    Hernández-Molina, Francisco Javier; Stow, Dorrik A. V.; Llave, Estefanía; Rebesco, Michele; Ercilla, Gemma; van Rooij, David; Mena, Anxo; Vázquez, Juan-Tomás; Voelker, Antje H. L.

    2011-12-01

    Deep-water circulation is a critical part of the global conveyor belt that regulates Earth's climate. The bottom (contour)-current component of this circulation is of key significance in shaping the deep seafloor through erosion, transport, and deposition. As a result, there exists a high variety of large-scale erosional and depositional features (drifts) that together form more complex contourite depositional systems on continental slopes and rises as well as in ocean basins, generated by different water masses flowing at different depths and at different speeds either in the same or in opposite directions. Yet, the nature of these deep-water processes and the deposited contourites is still poorly understood in detail. Their ultimate decoding will undoubtedly yield information of fundamental importance to the earth and ocean sciences. The international congress Deep-water Circulation: Processes & Products was held from 16-18 June 2010 in Baiona, Spain, hosted by the University of Vigo. Volume 31(5/6) of Geo-Marine Letters is a special double issue containing 17 selected contributions from the congress, guest edited by F.J. Hernández-Molina, D.A.V. Stow, E. Llave, M. Rebesco, G. Ercilla, D. Van Rooij, A. Mena, J.-T. Vázquez and A.H.L. Voelker. The papers and discussions at the congress and the articles in this special issue provide a truly multidisciplinary perspective of interest to both academic and industrial participants, contributing to the advancement of knowledge on deep-water bottom circulation and related processes, as well as contourite sedimentation. The multidisciplinary contributions (including geomorphology, tectonics, stratigraphy, sedimentology, paleoceanography, physical oceanography, and deep-water ecology) have demonstrated that advances in paleoceanographic reconstructions and our understanding of the ocean's role in the global climate system depend largely on the feedbacks among disciplines. New insights into the link between the biota of

  15. Breaking of waves in deep water

    NASA Astrophysics Data System (ADS)

    Ruiz-Chavarria, Gerardo

    2013-11-01

    The breaking of waves is a nonlinear phenomenon during which a fraction of the energy is dissipated. In the previous stage the wave undergoes a growth of its amplitude and the wave pattern is modified in the sense that the crests become more pronounced than the troughs. The breaking has been extensively studied in the case of waves approaching the shore. However, the wave breaking in deep water remains an open problem in fluid dynamics. In this work we study the wave breaking due to focusing of an initially parabolic wave front. To this end the evolution of wave is numerically investigated using a meshless code (Smoothed Particle Hydrodynamics). We present some results about the evolution of waves excited by a parabolic wave maker, among others, the growth induced by the focusing, the behavior around the Huygens' cusp and the process of wave breaking. Then, we compare the numerical results with the criteria given in the literature about the onset of breaking and we discuss how the energy dissipates, for example by the rise of short waves. In addition we compare the numerical results with data obtained in two different experiments made by our team. Author acknowledges DGAPA-UNAM by support under project IN116312, ``Vorticidad y ondas no lineales en fluidos.''

  16. Non-Fickian diffusion and the accumulation of methane bubbles in deep-water sediments.

    PubMed

    Goldobin, D S; Brilliantov, N V; Levesley, J; Lovell, M A; Rochelle, C A; Jackson, P D; Haywood, A M; Hunter, S J; Rees, J G

    2014-05-01

    In the absence of fractures, methane bubbles in deep-water sediments can be immovably trapped within a porous matrix by surface tension. The dominant mechanism of transfer of gas mass therefore becomes the diffusion of gas molecules through porewater. The accurate description of this process requires non-Fickian diffusion to be accounted for, including both thermal diffusion and gravitational action. We evaluate the diffusive flux of aqueous methane considering non-Fickian diffusion and predict the existence of extensive bubble mass accumulation zones within deep-water sediments. The limitation on the hydrate deposit capacity is revealed; too weak deposits cannot reach the base of the hydrate stability zone and form any bubbly horizon.

  17. Characterizing Natural Gas Hydrates in the Deep Water Gulf of Mexico: Applications for Safe Exploration and Production Activities

    SciTech Connect

    Bent, Jimmy

    2014-05-31

    In 2000 Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deep water portion of the Gulf of Mexico (GOM). Chevron is an active explorer and operator in the Gulf of Mexico and is aware that natural gas hydrates need to be understood to operate safely in deep water. In August 2000 Chevron worked closely with the National Energy Technology Laboratory (NETL) of the United States Department of Energy (DOE) and held a workshop in Houston, Texas to define issues concerning the characterization of natural gas hydrate deposits. Specifically, the workshop was meant to clearly show where research, the development of new technologies, and new information sources would be of benefit to the DOE and to the oil and gas industry in defining issues and solving gas hydrate problems in deep water.

  18. Patterns in life history traits of deep-water chondrichthyans

    NASA Astrophysics Data System (ADS)

    Rigby, Cassandra; Simpfendorfer, Colin A.

    2015-05-01

    Life history traits are important indicators of the productivity of species, and their ability to tolerate fishing pressure. Using a variety of life history traits (maximum size, size and age at maturity, longevity, growth rate, litter and birth size) we demonstrated differences in chondrichthyan life histories between shelf, pelagic and deep-water habitats and within the deep habitat down the continental slope and across geographic regions. Deep-water species had lower growth rates, later age at maturity, and higher longevity than both shelf and pelagic species. In the deep habitat, with increasing depth, species matured later, lived longer, had smaller litters and bred less frequently; regional differences in traits were also apparent. Deep-water species also had a smaller body size and the invariants of relative size and age at maturity were higher in deep water. The visual interaction hypothesis offers a potential explanation for these findings and it is apparent habitat influences the trade-offs in allocation of energy for survival and reproduction. Body size is not appropriate as a predictor of vulnerability in deep-water chondrichthyans and regional trait differences are possibly due to a fishing pressure response. Deep-water chondrichthyans are more vulnerable to exploitation than shelf and pelagic species and this vulnerability markedly increases with increasing depth. The life history traits of deep-water chondrichthyans are unique and reflect adaptations driven by both mortality and resource limitations of their habitat.

  19. Deep water dissolution in Marine Isotope Stage 3 from the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Huang, B.

    2015-12-01

    The production, transport, deposition, and dissolution of carbonate profoundly implicate the global carbon cycle affect the inventory and distribution of dissolved organic carbon (DIC) and alkalinity (ALK), which drive atmospheric CO2 change on glacial-interglacial timescale. the process may provide significant clues for improved understanding of the mechanisms that control the global climate system. In this study, we calculate and analyze the foraminiferal dissolution index (FDX) and the fragmentation ratios of planktonic foraminifera over 60-25 ka based on samples from 17924 and ODP 1144 in the northeastern South China Sea (SCS) to reconstruct the deep water carbonate dissolution during Marine Isotope Stage 3 (MIS 3). Result shows that the dissolution of carbonate increases gradually at 17924 but keeps stable at ODP 1144. The changes of FDX coincidence with that of fragmentation ratios at 17924 and ODP 1144 suggest both indexes can be used as reliable dissolving proxies of planktonic foraminifera. Comparing FDX and fragmentation ratios at both sites, we find the FDX and fragmentation ratios at 17924 are higher than those at 1144, indicating that carbonate dissolution is intenser in 17924 core during MIS 3. The increasing total percentage of both N. dutertrei and G. bulloides during MIS 3 reveals the rising primary productivity that may lead to deep water [CO32-] decrease. The slow down of thermohaline circulation may increase deep water residence time and accelerate carbonate dissolution. In addition, the covering of ice caps, iron supply and increased surface-water stratification also contribute to atmosphere CO2 depletion and [CO32-] decrease in deep water. In the meanwhile, regression result from colder temperature increases the input of ALK and DIC to the deep ocean and deepens the carbonate saturation depth, which makes the deep water [CO32-] rise. In ODP Site 1144, the decrease in [CO32-] caused by more CO2 restored in deep water is equal to the increase in

  20. Recharge mixing in a complex distributary spring system in the Missouri Ozarks, USA

    NASA Astrophysics Data System (ADS)

    Miller, Benjamin V.; Lerch, Robert N.; Groves, Christopher G.; Polk, Jason S.

    2015-05-01

    Toronto Springs is a complex distributary karst spring system with 11 perennial springs in the Missouri Ozarks, USA. Carroll Cave (CC) and Wet Glaize Creek (WG) were previously identified as principal recharge sources. This study (1) characterized physical and chemical properties of springs and recharge sources; (2) developed end-member mixing models to estimate contributing proportions of CC and WG; and (3) created a conceptual model for the system. Samples analyzed for major ions and specific conductivity, in conjunction with a rotating continuous monitoring program to identify statistically comparable baseflow conditions, were used to assess differences among the sites. Monitoring data showed that the springs differed depending upon recharge proportions. Cluster analysis of average ion concentrations supported the choice of CC and WG as mixing model end members. Results showed a range in the proportions of the recharge sources, from surface-water to groundwater dominated. A conceptual model suggests that a system of distinct conduits beneath the WG flood plain transmits water to the individual springs. These conduits controlled the end-member recharge contributions and water chemistry of the springs. Interpretation of relative proportions of recharge contributions extends existing knowledge of karst hydrologic geometry beyond that of point-to-point connections to revealing complex surface-water/groundwater mixing in heterogeneous distributary spring systems.

  1. SEISMIC EVALUATION OF HYDROCARBON SATURATION IN DEEP-WATER RESERVOIRS

    SciTech Connect

    Michael Batzle; D-h Han; R. Gibson; Huw James

    2005-08-12

    We are now entering the final stages of our ''Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs'' project (Grant/Cooperative Agreement DE-FC26-02NT15342). We have now developed several techniques to help distinguish economic hydrocarbon deposits from false ''Fizz'' gas signatures. These methods include using the proper in situ rock and fluid properties, evaluating interference effects on data, and doing better constrained inversions for saturations. We are testing these techniques now on seismic data from several locations in the Gulf of Mexico. In addition, we are examining the use of seismic attenuation as indicated by frequency shifts below potential reservoirs. During this quarter we have: Began our evaluation of our latest data set over the Neptune Field; Developed software for computing composite reflection coefficients; Designed and implemented stochastic turbidite reservoir models; Produced software & work flow to improve frequency-dependent AVO analysis; Developed improved AVO analysis for data with low signal-to-noise ratio; and Examined feasibility of detecting fizz gas using frequency attenuation. Our focus on technology transfer continues, both by generating numerous presentations for the upcoming SEG annual meeting, and by beginning our planning for our next DHI minisymposium next spring.

  2. Buried Distributaries as a Conduit for Groundwater Flow in Barataria Bay, Louisiana

    NASA Astrophysics Data System (ADS)

    Breaux, A.; Schneider, A.; Kolker, A.; Telfeyan, K.; Kim, J.; Johannesson, K. H.; Cable, J. E.; Coleman, D.

    2013-12-01

    Many studies have focused on hydrological and geochemical fluxes to the ocean from land to the ocean via submarine groundwater discharge (SGD), however few have assessed these contributions of SGD in deltaic settings. The Mississippi River delta is the largest delta in North America, and the magnitude of groundwater that discharges from the River into its delta is relatively unknown. Hydrological budgets have indicated that there is a large magnitude of water lost in the Mississippi's Delta. Recent evidence in our study indicates that paleochannels, or semi-permeable buried sandy channels that were former distributaries of the River, allow for water to discharge out of the Mississippi's main channel and into its Delta. Our study uses geophysical data, including CHIRP and resistivity methods, to detect the location of these paleochannels in Barataria Bay, a coastal bay located in the Mississippi Delta. CHIRP data shows that these paleochannel features are ubiquitous in the Mississippi Delta, while resistivity data indicates that lower salinity water is found during high river flow in bays proximate to the River. Sediment core analysis is also used to characterize the area of study, as well as further understand the regional geology of the Mississippi Delta. The geophysical and sediment core data will be used to contextualize geochemical data collected in the field, which includes an assessment of major cations and anions, as well as in situ Rn-222 activities, a method that has been proven to be useful as a tracer of groundwater movement. The results may be useful in understanding potential global magnitude of hydrological and geochemical fluxes of other large rivers with abandoned distributaries.

  3. Deep-water anoxygenic photosythesis in a ferruginous chemocline.

    PubMed

    Crowe, S A; Maresca, J A; Jones, C; Sturm, A; Henny, C; Fowle, D A; Cox, R P; Delong, E F; Canfield, D E

    2014-07-01

    Ferruginous Lake Matano, Indonesia hosts one of the deepest anoxygenic photosynthetic communities on Earth. This community is dominated by low-light adapted, BChl e-synthesizing green sulfur bacteria (GSB), which comprise ~25% of the microbial community immediately below the oxic-anoxic boundary (OAB; 115-120 m in 2010). The size of this community is dependent on the mixing regime within the lake and the depth of the OAB-at ~117 m, the GSB live near their low-light limit. Slow growth and C-fixation rates suggest that the Lake Matano GSB can be supported by sulfide even though it only accumulates to scarcely detectable (low μm to nm) concentrations. A model laboratory strain (Chlorobaculum tepidum) is indeed able to access HS- for oxidation at nm concentrations. Furthermore, the GSB in Lake Matano possess a full complement of S-oxidizing genes. Together, this physiological and genetic information suggests that deep-water GSB can be supported by a S-cycle, even under ferruginous conditions. The constraints we place on the metabolic capacity and physiology of GSB have important geobiological implications. Biomarkers diagnostic of GSB would be a good proxy for anoxic conditions but could not discriminate between euxinic and ferruginous states, and though GSB biomarkers could indicate a substantial GSB community, such a community may exist with very little metabolic activity. The light requirements of GSB indicate that at light levels comparable to those in the OAB of Lake Matano or the Black Sea, GSB would have contributed little to global ocean primary production, nutrient cycling, and banded iron formation (BIF) deposition in the Precambrian. Before the proliferation of oxygenic photosynthesis, shallower OABs and lower light absorption in the ocean's surface waters would have permitted greater light availability to GSB, potentially leading to a greater role for GSB in global biogeochemical cycles.

  4. Detailed anatomy of a deep-water carbonate breccia lobe (Upper Jurassic, French subalpine basin)

    NASA Astrophysics Data System (ADS)

    Courjault, Thomas; Grosheny, Danièle; Ferry, Serge; Sausse, Judith

    2011-06-01

    Detailed correlations across Tithonian carbonate breccia deposits in the Drôme River area (northern part of the so-called "Vocontian Through") suggest the depositional system was that of an elongated deep-water lobe, up to 70 km long and 20 to 30 km wide, for a thickness reaching 200 m. The Drôme lobe, as it is now called, is mainly made of slope to basinal mudstones breccias with minor platform components, interpreted as debris flow and mud flow deposits, associated with slump deposits. It is basically a base-of-slope system, whose elongated depositional area implies it was a "point-sourced" gravity system, thus perhaps connected to a small canyon cut onto the western slope of the basin. But the mostly mudstone material of the breccias also suggests that the walls of this inferred canyon were the main supplier of the lobe, not the carbonate platform proper. The updip part of the lobe has a complex internal geometry as the deposition of breccia bed packages is interrupted by scourings locally 50 m-deep, indicating maybe a canyon mouth environment. The middle part of the lobe is dominated by pure vertical aggradation of breccia beds with minor intervening erosion. In the downdip part of the system a morphological compensation mechanism occurs as breccia beds tend to spread laterally. A huge slump carrying large mudstone olistoliths ends the breccia deposition at the beginning of the Berriasian. This megaslump deposit was mostly emplaced on the right side of the breccia lobe supporting the idea of a depositional relief. Our observations thus show that previous interpretations as a submarine canyon infilling or as shallow-water breccias formed in-situ by cyclic loading under attenuating hurricane waves approaching the platform are not consistent with our observations. The internal geometry of the system studied brings new data about a poorly-studied kind of "turbidite" systems that of deep-water carbonate breccias.

  5. Geology of Sarawak deep water and its surroundings

    SciTech Connect

    Ismail, M.I.; Mohamad, A.M.; Ganesan, M.S.; Aziz, S.A. )

    1994-07-01

    A geological and geophysical investigation based primarily on seismic data indicates that four tectonostratigraphic zonations are recognizable in the Sarawak deep water and its surroundings. Zone A is a 7-8-km-thick Tertiary sedimentary basin in Sarawak deep water characterized by north-south-trending buried hills, extensional fault-bounded features, and local occurrences of compressional structures, and is separated from the northwest Sabah platform (zone B) by a major north-south-trending basin margin fault. This margin fault is distinct from the northwest-southeast transform fault known as Baram-Tinjar Line. The northwest Sabah platform, an attenuated continental crust that underwent late Mesozoic-Tertiary crystal stretching and rifting, is characterized by northeast-southwest-tending rift systems and generally up to 4 km-thick sedimentary cover. The leading edge of the northwest Sabah platform that was subducted beneath the northwest Borneo crust is marked by the Sabah trough (zone C). The western Sarawak deep water is occupied by a 13-km-thick, north-south-trending basin, the west Luconia delta province (zone D), demonstrating post mid-Miocene deltaic growth faults and toe-thrusts. Crustal offsets of the South China Sea Basin, north-south-trending basin margin fault between zones A and B, and extensional and compressional structures in zone A are evidence for north-south-directed transform motions leading to the development of the Sarawak deep-water Tertiary basin. Four main sedimentation phases describe the sedimentation history in Sarawak deep water and its surroundings. Oligocene-Miocene coastal plain sediments form the main hydrocarbon plays in the Sarawak deep water, and the numerous occurrences of amplitude anomalies clearly suggest a working hydrocarbon charge system.

  6. Three new records of deep-water goniasterids (Echinodermata: Asteroidea: Goniasteridae) from China seas

    NASA Astrophysics Data System (ADS)

    Xiao, Ning; Liao, Yulin

    2013-09-01

    In this paper, three deep-water species of the family Goniasteridae, Ceramaster misakiensis (Goto, 1914), Nymphaster arthrocnemis Fisher, 1913 and Pontioceramus grandis Fisher, 1911, are recorded for the first time from Chinese waters based on collections deposited in the Marine Biological Museum, Chinese Academy of Sciences. The specimens examined were collected during the period 1956 to 1978 from the East China and South China Seas at depths of 184 to 472 m. Diagnosis, detailed figures, and the geographic distributions are provided. A revised list of Goniasteridae recorded from Chinese waters is proposed.

  7. Early colonization of metazoans in the deep-water: Evidences from the lowermost Cambrian black shales of South China

    NASA Astrophysics Data System (ADS)

    Zhu, M.-Y.; Yang, A.-H.; Zhang, J.-M.; Li, G.-X.; Yang, X.-L.

    2003-04-01

    Diversity of metazoans is high in the deep-water of the present ocean. But it is unknown that when the metazoans began to colonize in the deep-water and what kinds of metazoans first colonized in the deep-water since origin and radiation of metazoans during the Precambrian-Cambrian transition interval. Up to the present, colonization of the deep-sea began in the Ordovician. Although it is suggested that animals were penetrated into the intermediate water depth during the Precambrian, evidences support such suggestion are based on the problematic Ediacaran-grade fossils. However, almost fossil materials that support the Cambrian Explosion hypothesis were discovered from the lowermost Cambrian shallow-water deposits. The abundant earliest Cambrian mineralized small shelly fossils (SSF) are globally from the shallow-water deposits, and the well-known Chengjiang fauna that may records most complete features of metazoans in the ocean after the Cambrian Explosion, occurs as well in the shallow basin near an old land on the Yangtze Platform. In order to understand ecology of the Cambrian Explosion time interval and how happened of the onshore-offshore trends of metazoans, we focused our attention on collecting fossils in the lowermost Cambrian deposits under the varied facies on the Yangtze Platformm during recent years. Investigations of the shallow-water carbonate facies and the oxygen-depleted deep-water black shale facies revealed additional biological and ecological information that are not recorded in the Chengjiang fauna in the siliclastic shallow-water facies. Here we report our discovery of a particular fossil association from more than 10 sections in the deep-water black shales (Qiongzhusian) in the out shelf and slope area of the Yangtze Platform. The fossil association is composed of pelagic and sessile organisms, including abundant sponges, 3 types of bivalved arthropods, 3 types of tubular animals and few problematic organisms. The fossils have either

  8. GCM studies of intermediate and deep waters in the Mediterranean

    NASA Astrophysics Data System (ADS)

    Haines, Keith; Wu, Peili

    1998-12-01

    Results from GCM simulations of the Mediterranean thermohaline circulation are presented under repeating year wind and surface buoyancy forcings and the reproduction of important physical processes is discussed. It is shown that baroclinic eddies are critical to the effective dispersal of Levantine intermediate water (LIW) throughout the eastern Mediterranean basin. These develop rapidly even in a 1/4 degree model which does not resolve the deformation radius, provided horizontal friction is small enough. It is shown that LIW enters the Adriatic basin and pre-conditions deep water formation which would not otherwise occur due to low surface salinity in winter. The dispersal of Adriatic deep waters is modelled, and it is shown that the introduction of the Gent and McWilliams advective scheme greatly improves the distribution of deep waters in the eastern basin by permitting the formation of dense overflow waters from the Otranto straits. This is achieved with very small parametrised advection that still permits the formation of baroclinic eddies unlike most applications which use the scheme to replace eddies. Results from a 100-year climate simulation are then presented in which the thermohaline circulation has reached equilibrium conditions. Dense water formation in both eastern and western basin still occur after 100 years. While the eastern basin water masses are reasonably realistic, the western basin is a little too cold and fresh, suggesting that insufficient LIW is reaching the deep water formation site in the northwest basin. Further work is needed in this area.

  9. SEISMIC EVALUATION OF HYDROCARBON SATURATION IN DEEP-WATER RESERVOIRS

    SciTech Connect

    Michael Batzle; D-h Han; R. Gibson; Huw James

    2005-01-22

    During this last quarter of the ''Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs'' project (Grant/Cooperative Agreement DE-FC26-02NT15342), we have moved forward on several fronts, including data acquisition as well as analysis and application. During this quarter we have: (1) Completed our site selection (finally); (2) Measured fluid effects in Troika deep water sand sample; (3) Applied the result to Ursa ''fizz gas'' zone; (4) Compared thin layer property averaging on AVO response; (5) Developed target oriented NMO stretch correction; (6) Examined thin bed effects on A-B crossplots; and (7) Begun incorporating outcrop descriptive models in seismic forward models. Several factors can contribute to limit our ability to extract accurate hydrocarbon saturations in deep water environments. Rock and fluid properties are one factor, since, for example, hydrocarbon properties will be considerably different with great depths (high pressure) when compared to shallow properties. Significant over pressure, on the other hand will make the rocks behave as if they were shallower. In addition to the physical properties, the scale and tuning will alter our hydrocarbon indicators. Reservoirs composed of thin bed effects will broaden the reflection amplitude distribution with incident angle. Normal move out (NMO) stretch corrections based on frequency shifts can be applied to offset this effect. Tuning will also disturb the location of extracted amplitudes on AVO intercept and gradient (A-B) plots. Many deep water reservoirs fall this tuning thickness range. Our goal for the remaining project period is to systematically combine and document these various effects for use in deep water exploration.

  10. Seismic Evaluation of Hydorcarbon Saturation in Deep-Water Reservoirs

    SciTech Connect

    Michael Batzle; D-h Han; R. Gibson; Huw James

    2005-10-31

    During this last quarter of the ''Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs'' project (Grant/Cooperative Agreement DE-FC26-02NT15342), we have moved forward on several fronts, including data acquisition as well as analysis and application. During this quarter we have: (1) Completed our site selection (finally); (2) Measured fluid effects in Troika deep water sand sample; (3) Applied the result to Ursa ''fizz gas'' zone; (4) Compared thin layer property averaging on AVO response; (5) Developed target oriented NMO stretch correction; (6) Examined thin bed effects on A-B crossplots; and (7) Begun incorporating outcrop descriptive models in seismic forward models. Several factors can contribute to limit our ability to extract accurate hydrocarbon saturations in deep water environments. Rock and fluid properties are one factor, since, for example, hydrocarbon properties will be considerably different with great depths (high pressure) when compared to shallow properties. Significant over pressure, on the other hand will make the rocks behave as if they were shallower. In addition to the physical properties, the scale and tuning will alter our hydrocarbon indicators. Reservoirs composed of thin bed effects will broaden the reflection amplitude distribution with incident angle. Normal move out (NMO) stretch corrections based on frequency shifts can be applied to offset this effect. Tuning will also disturb the location of extracted amplitudes on AVO intercept and gradient (A-B) plots. Many deep water reservoirs fall this tuning thickness range. Our goal for the remaining project period is to systematically combine and document these various effects for use in deep water exploration.

  11. Modulational instabilities of periodic traveling waves in deep water

    NASA Astrophysics Data System (ADS)

    Akers, Benjamin F.

    2015-04-01

    The spectrum of periodic traveling waves in deep water is discussed. A multi-scale method is used, expanding the spectral data and the Bloch parameter in wave amplitude, to compute the size and location of modulated instabilities. The role of these instabilities in limiting the spectrum's analyticity is explained. Both two-dimensional and three-dimensional instabilities are calculated. The asymptotic predictions are compared to numerical simulations.

  12. Pressure induced breather overturning on deep water: Exact solution

    NASA Astrophysics Data System (ADS)

    Abrashkin, A. A.; Oshmarina, O. E.

    2014-08-01

    A vortical model of breather overturning on deep water is proposed. The action of wind is simulated by nonuniform pressure on the free surface. The fluid motion is described by an exact solution of 2D hydrodynamic equations for an inviscid fluid in Lagrangian variables. Fluid particles rotate in circles of different radii. Formation of contraflexure points on the breather profile is studied. The mechanism of wave breaking and the role of flow vorticity are discussed.

  13. Ocean Ambient Noise Studies for Shallow and Deep Water Environments

    DTIC Science & Technology

    2014-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Ocean Ambient Noise Studies for Shallow and Deep Water...Siderius.php LONG-TERM GOALS The objective of this research is to study the ocean ambient noise field by means of new physics-based processing... ambient -noise field using a vertical line array has been developed by Harrison and Simons [Harrison, 2002]. The advantages of passive bottom-survey

  14. The Circulation of Newly Formed Deep Water in the Atlantic

    NASA Astrophysics Data System (ADS)

    Rhein, M.; Kieke, D.; Steinfeldt, R.

    2012-04-01

    The circulation of newly formed deep water masses (Labrador Sea Water, LSW, and Denmark Strait Overflow Water, DSOW) is examined by discussing the distribution of two parameters (age τ and fraction F of young water) calculated from the chlorofluorocarbon data measured between 1980 and 2005 in the Atlantic. Compared to previous studies, a much larger data set was used with an improved gridding procedure, allowing to resolve the distributions in more detail.

  15. Deep-sea channel/submarine-yazoo system of the Labrador Sea: A new deep-water facies model

    SciTech Connect

    Hesse, R.; Rakofsky, A. )

    1992-05-01

    The deep-sea channel/submarine-yazoo system is a newly recognized deep-water depositional environment that is significantly different from previously documented turbidite environments. The new system is in many ways the antithesis of classical deep-sea fans. The purpose of this paper is to present the characteristics and elements of the system, develop a facies model for it, establish the system variables, and discuss its possible significance in the geologic record and in subsurface exploration. Previous investigators of deepwater turbidite sediments often faced difficulties in trying to fit their sequences into traditional single-source, deep-sea fan models. The present model fills part of an obvious gap in interpretation schemes for deep-water clastic sediments.

  16. Is Centrophorus squamosus a highly migratory deep-water shark?

    NASA Astrophysics Data System (ADS)

    Rodríguez-Cabello, Cristina; Sánchez, Francisco

    2014-10-01

    Deep-water sharks are considered highly vulnerable species due to their life characteristics and very low recovery capacity against overfishing. However, there is still limited information on the ecology or population connectivity of these species. The aim of this study was to investigate if the species Centrophorus squamosus could make long displacements and thus confirm the existence of connectivity between different deep-water areas. In addition, the study was the first attempt to use tagging techniques on deep-water sharks, since it has never been undertaken before. Five C. squamosus were tagged with satellite tags (PAT) in the El Cachucho Marine Protected Area (Le Danois Bank) located in waters of the North of Spain, Cantabrian Sea (NE Atlantic). Data from four of these tags were recovered. One of the sharks travelled approximately 287 nm toward the north east (French continental shelf) hypothetically following the continental slope at a mean depth of 901±109 m for 45 days. Two other sharks spent almost 4 months traveling, in which time they moved 143 and 168 nm, respectively, to the west (Galician coast). Finally, another leafscale gulper shark travelled to the NW (Porcupine Bank) during a period of 3 months at a mean depth of 940±132 m. Depth and temperature preferences for all the sharks are discussed. Minimum and maximum depths recorded were 496 and 1848 m, respectively. The temperature range was between 6.2 and 11.4 °C, but the mean temperature was approximately 9.9±0.7 °C. The sharks made large vertical displacements throughout the water column with a mean daily depth range of 345±27 m. These preliminary results support the suggestion of a whole population in the NE Atlantic and confirm the capacity of this species to travel long distances.

  17. Chronobiology of deep-water decapod crustaceans on continental margins.

    PubMed

    Aguzzi, Jacopo; Company, Joan B

    2010-01-01

    Species have evolved biological rhythms in behaviour and physiology with a 24-h periodicity in order to increase their fitness, anticipating the onset of unfavourable habitat conditions. In marine organisms inhabiting deep-water continental margins (i.e. the submerged outer edges of continents), day-night activity rhythms are often referred to in three ways: vertical water column migrations (i.e. pelagic), horizontal displacements within benthic boundary layer of the continental margin, along bathymetric gradients (i.e. nektobenthic), and endobenthic movements (i.e. rhythmic emergence from the substrate). Many studies have been conducted on crustacean decapods that migrate vertically in the water column, but much less information is available for other endobenthic and nektobenthic species. Also, the types of displacement and major life habits of most marine species are still largely unknown, especially in deep-water continental margins, where steep clines in habitat factors (i.e. light intensity and its spectral quality, sediment characteristics, and hydrography) take place. This is the result of technical difficulties in performing temporally scheduled sampling and laboratory testing on living specimens. According to this scenario, there are several major issues that still need extensive research in deep-water crustacean decapods. First, the regulation of their behaviour and physiology by a biological clock is almost unknown compared to data for coastal species that are easily accessible to direct observation and sampling. Second, biological rhythms may change at different life stages (i.e. size-related variations) or at different moments of the reproductive cycle (e.g. at egg-bearing) based on different intra- and interspecific interactions. Third, there is still a major lack of knowledge on the links that exist among the observed bathymetric distributions of species and selected autoecological traits that are controlled by their biological clock, such as the

  18. Fluvial ecosystem services in the Rhine delta distributaries between 1995 and 2035

    NASA Astrophysics Data System (ADS)

    Straatsma, Menno; Kleinhans, Maarten

    2016-04-01

    Mapping of ecosystem services (ES) and documenting their change over time provides important information for the societal debate and decision making on river management. Large and Gilvear (2014) showed how to score fluvial ES using imagery and tools available through Google Earth, linking observable features, or landcover to ES through inferred fluvial processes, and natural ecosystem functions. While the use of Google Earth enables application anywhere on the globe, their method is labor intensive, and involves subjective judgement as not all parameters are easily observable in spectral data, e.g. the location of embankments. In addition, the method does not take advantage of readily available spatial databases, and existing hydrodynamic model parameterizations, nor can it be used in scenario studies of future fluvial landscapes. Therefore, we aimed at the development of a generic GIS routine to extract the ecosystem services from existing spatial and hydrodynamic model data, and its application to historic and future fluvial landscapes in the Rhine delta. Here, we consider the Rhine distributaries, sized 400 km2, where river restoration measures were carried out between 1995 and 2015 to reduce flood risk reduction and simultaneously improve the ecological status. We computed ES scores for provisioning ES (fisheries, agriculture, timber, water supply), regulating ES (flood mitigation, carbon sequestration, water quality), and supporting ES (biodiversity). Historic ES were derived for the years 1997, 2005, and 2012, based on ecotope maps for these respective years, combined with a water levels and flow velocities derived from a calibrated 2D hydrodynamic model (WAQUA). Ecotopes are defined as 'spatial landscape units that are homogeneous as to vegetation structure, succession stage, and the main abiotic factors that are relevant to plant growth'. ES for 2035 were based on scenarios of landscaping measures. Suitable locations for the measures were determined

  19. High resolution sequence stratigraphy of Miocene deep-water clastic outcrops, Taranaki coast, New Zealand

    SciTech Connect

    King, P.R.; Browne, G.H.; Slatt, R.M.

    1995-08-01

    Approximately 700m of deep water clastic deposits of Mt. Messenger Formation are superbly exposed along the Taranaki coast of North Island, New Zealand. Biostratigraphy indicates the interval was deposited during the time span 10.5-9.2m.y. in water depths grading upward from lower bathyal to middle-upper bathyal. This interval is considered part of a 3rd order depositional sequence deposited under conditions of fluctuating relative sea-level, concomitant with high sedimentation rates. Several 4th order depositional sequences, reflecting successive sea-level falls, are recognized within the interval. Sequence boundaries display a range of erosive morphologies from metre-wide canyons to scours several hundred metres across. All components of a generic lowstand systems tract--basin floor fan, channel-levee complex and progading complex--are present in logical and temporal order. They are repetitive through the interval, with the relatively shallower-water components becoming more prevalent upward. Basin floor fan lithologies are mainly m-thick, massive and convolute-bedded sandstones that alternate with cm- and dm-thick massive, horizontally-stratified and ripple-laminated sandstones and bioturbated mudstones. Channel-levee deposits consist of interleaving packages of thin-bedded, climbing-rippled and parallel-laminated sandstones and millstones; infrequent channels are filled with sandstones and mudstones, and sometimes lined with conglomerate. Thin beds of parallel to convoluted mudstone comprise prograding complex deposits. Similar lowstand systems tracts can be recognized and correlated on subsurface seismic reflection profiles and wireline logs. Such correlation has been aided by a continuous outcrop gamma-ray fog obtained over most of the measured interval. In the adjacent Taranaki peninsula, basin floor fan and channel-levee deposits comprise hydrocarbon reservoir intervals. Outcrop and subsurface reservior sandstones exhibit similar permeabilities.

  20. Piping coarse-grained sediment to a deep water fan through a shelf-edge delta bypass channel: Tank experiments

    NASA Astrophysics Data System (ADS)

    Kim, Yuri; Kim, Wonsuck; Cheong, Daekyo; Muto, Tetsuji; Pyles, David R.

    2013-12-01

    is now generally accepted that deltas that prograde to the shelf edge are able to transport coarse sediment to deep water either with or without sea level changes. However, it is still unclear how feeder rivers behave differently in the shelf-edge delta case to rivers found in a delta that progrades over the shelf. A series of nine shelf-edge delta experiments are presented to investigate the lateral mobility of the feeder channel at the shelf edge and the associated deep water depositional system under a range of sediment supply rates and shelf-front depths. In the experiments, constant sediment supply from an upstream point source under static sea level led the fluviodeltaic system to prograde over the shallow shelf surface and advance beyond the shelf edge into deep water. The feeder river of the fluviodeltaic system became a bypass system once the toe of the delta front reached the shelf edge. After the delta front was perched at the shelf edge, a submarine fan developed in deep water although remaining disconnected from the delta. In this bypass stage, no regional avulsion or lateral migration of the feeder river occurred and all sediment from the upstream source bypassed the river, delta front, and shelf-front slope. The duration of the bypass stage is proportional to shelf-front depth and inversely proportional to sediment discharge. The combined duration of the shelf-transit phase of the fluviodeltaic system and the bypass phase is the characteristic time scale for the continental margin to "anneal" transgression-inducing perturbation due to high-frequency and/or high-amplitude relative sea level rise. The sequential evolution in the experiment compares favorably to the Eocene Sobrarbe Formation, a shelf-edge delta in Spain, although natural variations are noted. This comparison justifies the application of concepts proposed herein to natural systems and provides insight into interpreting processes from ancient shelf-edge delta systems.

  1. Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs

    SciTech Connect

    Michael Batzle

    2006-04-30

    During this last period of the ''Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs'' project (Grant/Cooperative Agreement DE-FC26-02NT15342), we finalized integration of rock physics, well log analysis, seismic processing, and forward modeling techniques. Most of the last quarter was spent combining the results from the principal investigators and come to some final conclusions about the project. Also much of the effort was directed towards technology transfer through the Direct Hydrocarbon Indicators mini-symposium at UH and through publications. As a result we have: (1) Tested a new method to directly invert reservoir properties, water saturation, Sw, and porosity from seismic AVO attributes; (2) Constrained the seismic response based on fluid and rock property correlations; (3) Reprocessed seismic data from Ursa field; (4) Compared thin layer property distributions and averaging on AVO response; (5) Related pressures and sorting effects on porosity and their influence on DHI's; (6) Examined and compared gas saturation effects for deep and shallow reservoirs; (7) Performed forward modeling using geobodies from deepwater outcrops; (8) Documented velocities for deepwater sediments; (9) Continued incorporating outcrop descriptive models in seismic forward models; (10) Held an open DHI symposium to present the final results of the project; (11) Relations between Sw, porosity, and AVO attributes; (12) Models of Complex, Layered Reservoirs; and (14) Technology transfer Several factors can contribute to limit our ability to extract accurate hydrocarbon saturations in deep water environments. Rock and fluid properties are one factor, since, for example, hydrocarbon properties will be considerably different with great depths (high pressure) when compared to shallow properties. Significant over pressure, on the other hand will make the rocks behave as if they were shallower. In addition to the physical properties, the scale and tuning will alter our

  2. Deep-water antipatharians: Proxies of environmental change

    USGS Publications Warehouse

    Williams, B.; Risk, Michael J.; Ross, S.W.; Sulak, K.J.

    2006-01-01

    Deep-water (307-697 m) antipatharian (black coral) specimens were collected from the southeastern continental slope of the United States and the north-central Gulf of Mexico. The sclerochronology of the specimens indicates that skeletal growth takes place by formation of concentric coeval layers. We used 210Pb to estimate radial growth rate of two specimens, and to establish that they were several centuries old. Bands were delaminated in KOH and analyzed for carbon and nitrogen stable isotopes. Carbon values ranged from -16.4??? to -15.7???; oldest specimen displayed the largest range in values. Nitrogen values ranged from 7.7??? to 8.6???. Two specimens from the same location and depth had similar 15N signatures, indicating good reproducibility between specimens. ?? 2006 Geological Society of America.

  3. Deep-water fisheries at the Atlantic Frontier

    NASA Astrophysics Data System (ADS)

    Gordon, J. D. M.

    2001-05-01

    The deep sea is often thought of as a cold, dark and uniform environment with a low-fish biomass, much of which is highly adapted for life in a food-poor environment. While this might be true of the pelagic fish living in the water column, it is certainly not true of the demersal fish which live on or close to the bottom on the continental slopes around the British Isles (the Atlantic Frontier). These fish are currently being commercially exploited. There is growing evidence to support the view that success of the demersal fish assemblages depends on the pelagic or benthopelagic food sources that impinge both vertically and horizontally onto the slope. There are several quite separate and distinct deep-water fisheries on the Atlantic Frontier. It is a physical barrier, the Wyville-Thomson Ridge, which results in the most significant division of the fisheries. The Ridge, which has a minimum depth of about 500 m, separates the warmer deep Atlantic waters from the much colder Norwegian Sea water and as a result, the deep-water fisheries to the west of the Hebrides and around the offshore banks are quite different from those of the Faroe-Shetland Channel (West of Shetland). The fisheries to the West of the Hebrides can be further divided by the fishing method used into bottom trawl, semipelagic trawl and longline. The bottom-trawl fisheries extend from the shelf-slope break down to about 1700 m and the target species varies with depth. The smallest vessels in the fleet fish on the upper slope, where an important target species is the anglerfish or monkfish ( Lophius spp.). On the mid-slope the main target species are blue ling ( Molva dypterygia) and roundnose grenadier ( Coryphaenoides rupestris), with bycatches of black scabbardfish ( Aphanopus carbo) and deep-water sharks. On the lower slope orange roughy ( Hoplostethus atlanticus) is an important target species. The major semipelagic trawl fishery is a seasonal fishery on spawning aggregations of blue whiting

  4. North Atlantic Deep Water Production during the Last Glacial Maximum.

    PubMed

    Howe, Jacob N W; Piotrowski, Alexander M; Noble, Taryn L; Mulitza, Stefan; Chiessi, Cristiano M; Bayon, Germain

    2016-06-03

    Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial-interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ(13)C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters.

  5. North Atlantic Deep Water Production during the Last Glacial Maximum

    PubMed Central

    Howe, Jacob N. W.; Piotrowski, Alexander M.; Noble, Taryn L.; Mulitza, Stefan; Chiessi, Cristiano M.; Bayon, Germain

    2016-01-01

    Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial–interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ13C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters. PMID:27256826

  6. Deep-water antipatharians: Proxies of environmental change

    NASA Astrophysics Data System (ADS)

    Williams, B.; Risk, M. J.; Ross, S. W.; Sulak, K. J.

    2006-09-01

    Deep-water (307 697 m) antipatharian (black coral) specimens were collected from the southeastern continental slope of the United States and the north-central Gulf of Mexico. The sclerochronology of the specimens indicates that skeletal growth takes place by formation of concentric coeval layers. We used 210Pb to estimate radial growth rate of two specimens, and to establish that they were several centuries old. Bands were delaminated in KOH and analyzed for carbon and nitrogen stable isotopes. Carbon values ranged from -16.4‰ to -15.7‰; the oldest specimen displayed the largest range in values. Nitrogen values ranged from 7.7‰ to 8.6‰. Two specimens from the same location and depth had similar 15N signatures, indicating good reproducibility between specimens.

  7. Precession resonance mechanism in deep-water gravity surface waves

    NASA Astrophysics Data System (ADS)

    Bustamante, Miguel; Lucas, Dan

    2016-11-01

    Discovered by Bustamante et al. in 2014 and published in Phys. Rev. Lett. in the same year, precession resonance is a mechanism whereby strong nonlinear energy transfers occur between modes of oscillations whose frequencies are detuned: the amplitude-dependent precession frequencies of the phases help restore the resonance, hence the name "precession resonance". After explaining how this mechanism works and how robust it is, we will discuss new applications of this effect in systems of technological interest, focusing on deep-water gravity surface waves. We report transfer efficiencies of up to 40%, depending on the numerical-experimental setup. All evidence gathered so far points to the conclusion that, to leading order, this effect is dominated by triad interactions at small (but finite) amplitudes. Joint work with Dan Lucas (DAMTP, Cambridge). Financially supported by Science Foundation Ireland (SFI) under research Grant No. 12/IP/1491.

  8. The hydrography of the mid-latitude northeast Atlantic Ocean. I: The deep water masses

    NASA Astrophysics Data System (ADS)

    van Aken, Hendrik M.

    2000-05-01

    The circulation of the deep water masses in the mid-latitude northeast Atlantic Ocean was studied by analysis of the distributions of potential temperature, salinity, dissolved oxygen, phosphate, nitrate, and silicate. Pre-formed nutrients were used to allow a quantitative description of the deep water masses, especially the Northeast Atlantic Deep Water, in terms of four local source water types: Iceland-Scotland Overflow Water, Lower Deep Water, Labrador Sea Water, and Mediterranean Sea Water. Over the Porcupine Abyssal Plain between 2500 and 2900 dbar Northeast Atlantic Deep Water appears to be a mixture of mainly Iceland-Scotland Overflow Water and Labrador Sea Water (˜80%), with minor contributions of Lower Deep Water and Mediterranean Sea Water. When the Northeast Atlantic Deep Water re-circulates in the north-eastern Atlantic and flows southwards towards the Madeira Abyssal Plain, contributions of the former two water types of northern origin diminish to about 50% due to diapycnal mixing with the overlying and underlying water masses. The observed meridional and zonal trends of dissolved oxygen and nutrients in the Northeast Atlantic Deep Water appear to be caused both by diapycnal mixing with the underlying Lower Deep Water and by mineralization of organic matter. The eastward decrease of oxygen and increase of nutrients especially require considerable mineralization of organic matter near the European continental margin. At deeper levels (˜4100 dbar), where the nutrient rich Lower Deep Water is found near the bottom, the meridional gradients of oxygen and nutrients are opposite to those found between 2500 and 2900 dbar. Diapycnal mixing cannot explain this change in gradients, which is therefore considered to be a qualitative indication of ageing of the Lower Deep Water when it flows northwards. A considerable part of the Iceland-Scotland Overflow Water and the Lower Deep Water that enter the northeast Atlantic may be removed by deep upwelling in the Bay

  9. North Pacific Acoustic Laboratory: Deep Water Acoustic Propagation in the Philippine Sea

    DTIC Science & Technology

    2016-06-21

    Acoustic Laboratory: Deep Water Acoustic Propagation in the Philippine Sea 5b. GRANT NUMBER NOOO 14-12-1 -0226 5c. PROGRAM ELEMENT NUMBER 6...the "Special Issue on Deep- water Ocean Acoustics" in the Journal of the Acoustical Society of America (Vol. 134, No . 4, Pt. 2 of 2 , October20 13...15. SUBJECT TERMS ocean acoustics, deep water acousti c propagati on 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF a. REPORT b. ABSTRACT c

  10. Laboratory Studies of Steep and Breaking Deep Water Waves in a Convergent Channel

    DTIC Science & Technology

    2015-05-28

    TASK NO RR023- 11 TITLE (Include Security Classification) Laboratory Studies of Steep and Breaking Deep Water Waves in a Convergent Channel...These include the relative motion between the water and, say, a ship in the seaway or a cylindrical obstacle in a wavefield; wind blowing over the water ...in deep water . The present experiments were conducted to study the evolution of steep and breaking deep water waves. The waves were made to steepen

  11. Cestodes from deep-water squaliform sharks in the Azores

    NASA Astrophysics Data System (ADS)

    Caira, Janine N.; Pickering, Maria

    2013-12-01

    The majority of our knowledge on marine tapeworms (cestodes) is limited to taxa that are relatively easy to obtain (i.e., those that parasitize shallower-water species). The invitation to participate in a deep-water research survey off the Condor seamount in the Azores offered the opportunity to gain information regarding parasites of the less often studied sharks of the mesopelagic and bathypelagic zone. All tapeworms (Platyhelminthes: Cestoda) found parasitizing the spiral intestine of squaliform shark species (Elasmobranchii: Squaliformes) encountered as part of this survey, as well as some additional Azorean sampling from previous years obtained from local fishermen are reported. In total, 112 shark specimens of 12 species of squaliform sharks representing 4 different families from depths ranging between 400 and 1290 m were examined. Cestodes were found in the spiral intestines from 11 of the 12 squaliform species examined: Deania calcea, D. cf. profundorum, D. profundorum, Etmopterus princeps, E. pusillus, E. spinax, Centroscyllium fabricii, Centroscymnus coelolepis, C. cryptacanthus, C. crepidater, and Dalatias licha. No cestodes were found in the spiral intestines of Centrophorus squamosus. Light microscopy and scanning electron microscopy revealed several potentially novel trypanorhynch and biloculated tetraphyllidean species. Aporhynchid and gilquiniid trypanorhynchs dominated the adult cestode fauna of Etmopterus and Deania host species, respectively, while larval phyllobothriids were found across several host genera, including, Deania, Centroscyllium, and Centroscymnus. These results corroborate previous findings that deep-water cestode faunas are relatively depauperate and consist primarily of trypanorhynchs of the families Gilquiniidae and Aporhynchidae and larval tetraphyllideans. A subset of specimens of most cestode species was preserved in ethanol for future molecular analysis to allow more definitive determinations of the identification of the

  12. Implementation and testing of a Deep Water Correlation Velocity Sonar

    SciTech Connect

    Dickey, F.R.; Bookheimer, W.C.; Rhoades, K.W.

    1983-05-01

    The paper describes a new sonar designated the Magnavox MX 810 Deep Water Correlation Sonar which is under development by the General Electric Company and the Magnavox Advanced Products and Systems Company. The sonar measures ship's velocity relative to the bottom but instead of using the conventional doppler effect, it uses the correlation method described by Dickey and Edward in 1978. In this method, the narrow beams required for doppler are not needed and a low frequency that penetrates to the bottom in deep water is used. The sonar was designed with the constraint that it use a transducer that mounts through a single 12 inch gate valve. Most offshore geophysical surveys at present make use of an integrated navigation system with bottom referenced velocity input from a doppler sonar which, because of limitations on the sonar bottomtracking range, has difficulty in areas where the water depth is greater than about 500 meters. The MX 810 provides bottom tracking in regions of much greater water depth. It also may be applied as an aid in continuous positioning of a vessel over a fixed location. It also should prove useful as a more general navigation aid. The sonar is undergoing a series of tests using Magnavox's facilities for the purpose of verifying the performance and obtaining data to support and quantify planned improvements in both software and hardware. A prototype transducer of only 5 watts power output was used, but in spite of this low power, successful operation to depths of 1900 meters was obtained. Extrapolation to system parameters to be implemented in production models predicts operation to depths of 5000 meters.

  13. Implications of Subduction Rehydration for Earth's Deep Water Cycle

    NASA Astrophysics Data System (ADS)

    Ruepke, L. H.; Phipps Morgan, J.; Dixon, J.

    2006-12-01

    The presence of liquid water is the principle difference between our Earth and other planets in the solar system. The global ocean is the obvious surface expression of this. The 'standard model' for the genesis of the oceans is that they are exhalations from Earth's deep interior continually rinsed through surface rocks by the global hydrologic cycle. The question of how much water resides within the Earth's deep interior remains unresolved and is a matter of vigorous ongoing scientific debate. We have addressed the question of water distribution between the exosphere and the mantle throughout Earth's history with simple mass balance considerations. In our model, water is outgassed from the mantle into the exosphere (atmosphere + continental crust) during pressure-release melting at mid-ocean ridges and hotspots. Plate subduction may transport water back from the surface into the deeper mantle thereby 'closing' the global geologic water cycle. In series of some 5000 model runs we have thoroughly explored the mutual effect of model parameters. All models correctly predict the formation of the present-day oceans but differ in their predicted sea-level changes through time and in the amount of water in the present-day mantle. To distinguish which model runs are the most realistic we use geochemical constraints and observed sealevel changes during the Phanerozoic. Recently Dixon et al. [2002] estimated water concentrations for some of the major mantle components and concluded that the most primitive (FOZO) are significantly wetter than the recycling associated EM or HIMU mantle components and the even drier depleted mantle source that melts to form MORB. Sealevel changes over hundreds of million of years are notoriously bad constrained. But a maximum drop in sealevel of 400-600m appears to be an upper bound. We find that only those model runs are consistent with these constraints in which deep water subduction is limited and in which the present-day mantle is

  14. Dunes versus ripples in deep-water, fine-grained sediments

    NASA Astrophysics Data System (ADS)

    Masalimova, L.; Lowe, D. R.

    2012-12-01

    The Lower Mount Messenger Formation (LMMF) is characterized by fine- to very fine-grained sediments. While the grain size doesn't change much within the formation, the sedimentary structures do. Perhaps the most striking difference between the channels in the upper part of the LMMF and the lobes in the lower part of the LMMF is the abundance of large-scale, climbing-dune cross-stratification in the lobes and of small-scale, climbing-ripple cross-lamination within channels. The sole presence of climbing dunes in fine-grained sandstones in deep-water lobe complex is surprising. Firstly, dunes are characteristic features largely in fluvial environments. Cross-stratification is not a widespread sedimentary structure in deep-water, part of the reason might be the difficulty in recognizing subtle stratification in weathered outcrop. The absence can be also explained by the fact that the flows might be insufficiently deep or there is never sufficient time for dune formation. Secondly, the hydraulics of the cross-stratification requires sand coarser than 0.2 mm (middle fine sand) to form dunes based on flume experiments. The cross-stratification mostly was documented in deep-water in coarse-grained sediments such as pebbles and gravels in southern Chile and in Quebec, medium to granule-grade sands in Oceanographer Canyon, and medium to coarse-grained sands in the Eocene Hecho Group, etc. Nevertheless, the dunes are documented in fine-grained systems such as Brushy Canyon Formation (the authors use "plow-and-fill" term instead of "dunes"). Thirdly, the cross-stratification is generally documented in confined setting such as channels and scours. But this study shows that the cross-stratification can be present in largely unconfined depositional setting of the LMMF. We postulate that the dunes found in the LMMF can be unusually high ripples from the hydrodynamic point of view. Considering the facts that (1) ripples are different from dunes in outcrop by size and the size of

  15. High archaeal diversity in Antarctic circumpolar deep waters.

    PubMed

    Alonso-Sáez, Laura; Andersson, Anders; Heinrich, Friederike; Bertilsson, Stefan

    2011-12-01

    Archaea are abundant in polar oceans but important ecological aspects of this group remain enigmatic, such as patterns of diversity and biogeography. Here, we provide the first high-throughput sequencing population study of Antarctic archaea based on 198 bp fragments of the 16S rRNA gene, targeting different water masses across the Amundsen and Ross Seas. Our results suggest that archaeal community composition is strongly shaped by hydrography and significantly influenced by environmental parameters. Archaeal communities from cold continental shelf waters (SW) of the Ross Sea were similar over depth with a single thaumarchaeal phylotype dominating Antarctic surface waters (AASW) and deeper SW (contributing up to 80% of reads). However, this phylotype contributed less than 8% of reads in circumpolar deep waters (CDW). A related thaumarchaeon (98% identity) was almost absent in AASW, but contributed up to 30% of reads in CDW, suggesting ecological differentiation of closely related phylotypes. Significantly higher archaeal richness and evenness were observed in CDW, with Shannon indices (c. 2.5) twice as high as for AASW, and high contributions of Group II Euryarchaeota. Based on these results, we suggest that CDW is a hotspot of archaeal diversity and may play an important role in the dispersal of archaeal phylotypes to other oceanic water masses.

  16. SEISMIC EVALUATION OF HYDROCARBON SATURATION IN DEEP-WATER RESERVOIRS

    SciTech Connect

    M. Batzle; D-h Han; R. Gibson; O. Djordjevic

    2003-03-20

    The ''Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs'' (Grant/Cooperative Agreement DE-FC26-02NT15342) began September 1, 2002. During this second quarter: A Direct Hydrocarbon Indicator (DHI) symposium was held at UH; Current DHI methods were presented and forecasts made on future techniques; Dr. Han moved his laboratory from HARC to the University of Houston; Subcontracts were re-initiated with UH and TAMU; Theoretical and numerical modeling work began at TAMU; Geophysical Development Corp. agreed to provide petrophysical data; Negotiations were begun with Veritas GDC to obtain limited seismic data; Software licensing and training schedules were arranged with Paradigm; and Data selection and acquisition continues. The broad industry symposium on Direct Hydrocarbon Indicators was held at the University of Houston as part of this project. This meeting was well attended and well received. A large amount of information was presented, not only on application of the current state of the art, but also on expected future trends. Although acquisition of appropriate seismic data was expected to be a significant problem, progress has been made. A 3-D seismic data set from the shelf has been installed at Texas A&M University and analysis begun. Veritas GDC has expressed a willingness to provide data in the deep Gulf of Mexico. Data may also be available from TGS.

  17. Ireland's deep-water coral carbonate mounds: multidisciplinary research results

    NASA Astrophysics Data System (ADS)

    Kozachenko, M.; Wheeler, A.; Beyer, A.; Blamart, D.; Masson, D.; Olu-Le Roy, K.

    2003-04-01

    Recent international research activity, involving a strong Irish collaboration, has shown that coral reefs are not exclusively associated with warm tropical waters but are also present in the deeper and colder Northeast Atlantic. In the Porcupine Seabight west of Ireland, coral-colonised carbonate mounds (up to 350m high) are present at 600-900m water depth. The corals Lophelia pertusa L. and Madrepora oculata L. contribute to this diverse ecosystem that may also play a significant role in expanding deep-water fisheries. New side-scan sonar, multibeam echosounder, sub-bottom profiler and underwater video imagery supplemented with sedimentological sample material were used to map the seabed in the environs of the Belgica Carbonate Mound province, eastern Porcupine Seabight. The data were integrated in a GIS and provides information on sediment pathways and benthic current patterns within the study area. A facies map of the study area highlights differing sedimentary processes showing evidences for strong northward bottom currents whose interaction has an influence on mounds growth and morphology. This survey revealed mound flanks dominated by sediment waves that give way to coral banks towards the mound summits. A form of coral accumulation was also documented. Detailed analyses of sediment properties from long cores through sediment drifts have generated a high-resolution palaeoclimate record revealing temporal patterns in bottom current strength variations. An accurate assessment of this influence on mound through a comparison with coral growth rates is ongoing.

  18. Turbidite systems in deep-water basin margins classified by grain size and feeder system

    SciTech Connect

    Reading, H.G. ); Richards, M. )

    1994-05-01

    Depositional system in deep-water basin margins can be classified on the basis of grain size and feeder system into 12 classes: mud-rich, mud/sand-rich, sand-rich, and gravel-rich [open quotes]point-source submarine fans,[close quotes] mud-rich, mud/sand-rich, sand-rich, and gravel-rich [open quotes]multiple-source submarine ramps;[close quotes] and mud-rich, mud/sand-rich, sand-rich, and gravel-rich [open quotes]linear-source slope aprons.[close quotes] The size and stability of channels and the organization of the depositional sequences decreases toward a linear source as does the length:width ratio of the system. As grain size increases, so does slope gradient, impersistence of channel systems, and tendency for channels to migrate. As grain size diminishes, there is an increase in the size of the source area, the size of the depositional system, the downcurrent length, the persistence and size of flows, fan channels, channel-levee systems, and in the tendency to meander and for major slumps and sheet sands to reach the lower fan and basin plan. The exact positioning of any one depositional system within the scheme cannot always be precise and the position may be altered by changes in tectonic, climate, supply, and sea level. The models derived from each system are sufficiently different to significantly affect the nature of petroleum prospectivity and reservoir pattern. Understanding and recognizing this variability is crucial to all elements of the exploration-production chain. In exploration, initial evaluations of prospectivity and commerciality rely on the accurate stratigraphic prediction of reservoir facies, architecture, and trapping styles. For field appraisal and reservoir development, a similar appreciation of variability aids reservoir description by capturing the distribution and architecture of reservoir and nonreservoir facies and their impact on reservoir delineation, reservoir behavior, and production performance. 161 refs., 19 figs., 4 tabs.

  19. Mechanical stratigraphy of deep-water sandstones: insights from a multisciplinary field and laboratory study

    NASA Astrophysics Data System (ADS)

    Agosta, Fabrizio; di Celma, Claudio; Tondi, Emanuele; Corradetti, Amerigo; Cantalamessa, Gino

    2010-05-01

    -perpendicular joint spacing/bed thickness (S/T) relationships on sandstone bodies that experienced similar diagenetic and tectonic histories. The field area is located in the Periadriatic foreland basin, eastern central Italy, which show late Pliocene slope turbidites in excellent 3d views. The Periadriatic foreland basin is an elongated, roughly N-S oriented trough located immediately east of the Apennines fold-thrust belt. The basin fill mostly consists of deepwater Plio-Pleistocene sediments partially incorporated into the frontal part of the orogenic wedge. During the late Pliocene, gravel and sand originated from the uplifting Apennines were abundantly supplied to the deep-water basin through a series of erosional conduits that, in the rock record, appear as a series of N-S oriented slope submarine canyon systems deeply incised into the hemipelagic mudstones of the adjacent slope. The studied exposure allows direct observation of spatial and temporal relationships among the various depositional elements comprising the canyon system and related lithofacies, as well as the bed-perpendicular joint density within each lithofacies. We performed a multidisciplinary work involving the following tasks: (i) 3D stratigraphic model of the depositional architecture of the Castignano and Ascensione canyon systems (Marche region, Italy); (ii) 2D scanline survey of several outcrops displaying bed-perpendicular joints; (iii) digital image analysis of selected thin-section obtained from oriented hand samples to characterize the 3D intergranualr porosity; (iv) Stiffness analysis of representative sandstone bodies by mean of Schmidt hammer tests. The first results of this ongoing study on the mechanical stratigraphy of the two Late Pliocene canyon systems are consistent with the joint density being effected by both geometrical (i.e., bed thickness) and mechanical properties. This data set will help field and experimental geologists to better define common strategies to assess the controlling

  20. Stability of steep gravity capillary solitary waves in deep water

    NASA Astrophysics Data System (ADS)

    Calvo, David C.; Akylas, T. R.

    2002-02-01

    The stability of steep gravity capillary solitary waves in deep water is numerically investigated using the full nonlinear water-wave equations with surface tension. Out of the two solution branches that bifurcate at the minimum gravity capillary phase speed, solitary waves of depression are found to be stable both in the small-amplitude limit when they are in the form of wavepackets and at finite steepness when they consist of a single trough, consistent with observations. The elevation-wave solution branch, on the other hand, is unstable close to the bifurcation point but becomes stable at finite steepness as a limit point is passed and the wave profile features two well-separated troughs. Motivated by the experiments of Longuet-Higgins & Zhang (1997), we also consider the forced problem of a localized pressure distribution applied to the free surface of a stream with speed below the minimum gravity capillary phase speed. We find that the finite-amplitude forced solitary-wave solution branch computed by Vanden-Broeck & Dias (1992) is unstable but the branch corresponding to Rayleigh’s linearized solution is stable, in agreement also with a weakly nonlinear analysis based on a forced nonlinear Schrödinger equation. The significance of viscous effects is assessed using the approach proposed by Longuet-Higgins (1997): while for free elevation waves the instability predicted on the basis of potential-flow theory is relatively weak compared with viscous damping, the opposite turns out to be the case in the forced problem when the forcing is strong. In this régime, which is relevant to the experiments of Longuet-Higgins & Zhang (1997), the effects of instability can easily dominate viscous effects, and the results of the stability analysis are used to propose a theoretical explanation for the persistent unsteadiness of the forced wave profiles observed in the experiments.

  1. Experimental study on plunging breaking waves in deep water

    NASA Astrophysics Data System (ADS)

    Lim, Ho-Joon; Chang, Kuang-An; Huang, Zhi-Cheng; Na, Byoungjoon

    2015-03-01

    This study presents a unique data set that combines measurements of velocities and void fraction under an unsteady deep water plunging breaker in a laboratory. Flow properties in the aerated crest region of the breaking wave were measured using modified particle image velocimetry (PIV) and bubble image velocimetry (BIV). Results show that the maximum velocity in the plunging breaker reached 1.68C at the first impingement of the overturning water jet with C being the phase speed of the primary breaking wave, while the maximum velocity reached 2.14C at the beginning of the first splash-up. A similarity profile of void fraction was found in the successive impinging and splash-up rollers. In the highly foamy splashing roller, the increase of turbulent level and vorticity level were strongly correlated with the increase of void fraction when the range of void fraction was between 0 and 0.4 (from the trough level to approximately the center of the roller). The levels became constant when void fraction was greater than 0.5. The mass flux, momentum flux, kinetic energy, potential energy, and total energy were computed and compared with and without the void fraction being accounted for. The results show that all the mean and turbulence properties related to the air-water mixture are considerably overestimated unless void fraction is considered. When including the density variation due to the air bubbles, the wave energy dissipated exponentially a short distance after breaking; about 54% and 85% of the total energy dissipated within one and two wavelengths beyond the breaking wave impingement point, respectively.

  2. A Possible Role for Agglutinated Foraminifers in the Growth of Deep-Water Coral Bioherms

    NASA Astrophysics Data System (ADS)

    Messing, C. G.; Reed, J. K.; Brooke, S. D.

    2008-05-01

    Exploration of deep-water bioherms dominated by the scleractinian corals Lophelia pertusa and Enallopsammia profunda along the east coast of Florida in ~400-800 m depth reveals an often dense and rich assemblage of small (~1-30 mm) epifauna on dead coral branches, which is often dominated by agglutinated astrorhizacean foraminifers accompanied by thecate and athecate hydroids, sponges, stylasterids, anemones and barnacles. The dominant agglutinated foraminifer is an arborescent form up to 15 mm tall, consisting of a basal tube that gives rise to branchlets of successively decreasing diameter and thickly coated with fine-grained material including coccoliths and diatom frustules. The large numbers of foraminifers generate an enormous adhesive, sediment-trapping surface area and may represent an important accelerated route for sediment deposition and bioherm growth relative to baffling of suspended sediment particles by the coral branches themselves. These foraminifers also occur on still living coral, suggesting that they may either contribute to coral death or invade stressed colonies. They may thus be responsible for or contribute to the small percent of living corals observed in many of these habitats. Other epifauna appear to colonize after the coral has died.

  3. Detailed subsurface descriptions drive record breaking wells in the deep water Gulf of Mexico

    SciTech Connect

    Guderjahn, C.; Hill, P.; Blankenship, C.; Epps, D.

    1996-12-31

    Increased well productivity is motivating development teams to successfully complete record breaking wells. Advances in subsurface description are leveraging with breakthroughs in drilling and completion technology to achieve new levels of financial performance. Gulf of Mexico industry and company records have recently been set in extended reach drilling, horizontal drilling, curvilinear completions, and frac-packed high angle completions. These advanced well designs are establishing new production records in the deep water Gulf of Mexico. Improvements in 3D seismic imaging, geologic depositional models, and reservoir pressure predictions are enhancing the subsurface model such that significant productivity benefits are achieved by targeting completions in specific geometries. Advances in directional drilling accuracy and the utilization of synthetic oil-base muds are assuring that wells are placed precisely on target. In the BP operated Pompano Field horizontal wells have been placed down turbidite channel axes, high angle wells are used to connect separate reservoir compartments, extended reach wells have been steered away from over-pressured sections identified from seismic, and a multi-lateral completion is next on the drilling schedule. Multi-disciplinary innovation and focused teamwork is also changing behavioral working styles. It is now accepted that the {open_quote}teams{close_quotes} consist of geoscientists, engineers, and offshore drilling hands. Well planning takes place both on the rig floor and in the office. The payoff for further integration is higher profits, lower risk, and a safer working environment.

  4. Detailed subsurface descriptions drive record breaking wells in the deep water Gulf of Mexico

    SciTech Connect

    Guderjahn, C.; Hill, P.; Blankenship, C.; Epps, D. )

    1996-01-01

    Increased well productivity is motivating development teams to successfully complete record breaking wells. Advances in subsurface description are leveraging with breakthroughs in drilling and completion technology to achieve new levels of financial performance. Gulf of Mexico industry and company records have recently been set in extended reach drilling, horizontal drilling, curvilinear completions, and frac-packed high angle completions. These advanced well designs are establishing new production records in the deep water Gulf of Mexico. Improvements in 3D seismic imaging, geologic depositional models, and reservoir pressure predictions are enhancing the subsurface model such that significant productivity benefits are achieved by targeting completions in specific geometries. Advances in directional drilling accuracy and the utilization of synthetic oil-base muds are assuring that wells are placed precisely on target. In the BP operated Pompano Field horizontal wells have been placed down turbidite channel axes, high angle wells are used to connect separate reservoir compartments, extended reach wells have been steered away from over-pressured sections identified from seismic, and a multi-lateral completion is next on the drilling schedule. Multi-disciplinary innovation and focused teamwork is also changing behavioral working styles. It is now accepted that the [open quote]teams[close quotes] consist of geoscientists, engineers, and offshore drilling hands. Well planning takes place both on the rig floor and in the office. The payoff for further integration is higher profits, lower risk, and a safer working environment.

  5. 78 FR 30242 - Fisheries of the Economic Exclusive Zone Off Alaska; Deep-Water Species Fishery by Vessels Using...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-22

    ... Exclusive Zone Off Alaska; Deep-Water Species Fishery by Vessels Using Trawl Gear in the Gulf of Alaska... comprise the deep-water species fishery by vessels using trawl gear in the Gulf of Alaska (GOA). This... specified for the deep-water species fishery in the GOA has been reached. DATES: Effective 1200...

  6. 75 FR 38939 - Fisheries of the Economic Exclusive Zone Off Alaska; Deep-Water Species Fishery by Catcher...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-07

    ... Exclusive Zone Off Alaska; Deep-Water Species Fishery by Catcher/Processor Rockfish Cooperatives in the Gulf... for species that comprise the deep-water species fishery by catcher/processor rockfish cooperatives... limit specified for the deep-water species fishery by catcher/processor rockfish cooperatives subject...

  7. 75 FR 38937 - Fisheries of the Economic Exclusive Zone Off Alaska; Deep-Water Species Fishery by Catcher...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-07

    ... Exclusive Zone Off Alaska; Deep-Water Species Fishery by Catcher Vessels in the Gulf of Alaska AGENCY... the deep-water species fishery for catcher vessels subject to sideboard limits established under the... Pacific halibut prohibited species catch (PSC) sideboard limit specified for the deep-water...

  8. 76 FR 39790 - Fisheries of the Economic Exclusive Zone Off Alaska; Deep-Water Species Fishery by Catcher...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-07

    ... Exclusive Zone Off Alaska; Deep-Water Species Fishery by Catcher Vessels in the Gulf of Alaska AGENCY... the deep-water species fishery for catcher vessels subject to sideboard limits established under the... Pacific halibut prohibited species catch (PSC) sideboard limit specified for the deep-water...

  9. 75 FR 23189 - Fisheries of the Economic Exclusive Zone Off Alaska; Deep-Water Species Fishery by Vessels Using...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-03

    ... Exclusive Zone Off Alaska; Deep-Water Species Fishery by Vessels Using Trawl Gear in the Gulf of Alaska... comprise the deep-water species fishery by vessels using trawl gear in the Gulf of Alaska (GOA). This... prohibiting directed fishing for the deep-water species fishery by vessels using trawl gear in the GOA....

  10. 77 FR 46338 - Fisheries of the Economic Exclusive Zone Off Alaska; Deep-Water Species Fishery by Vessels Using...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-03

    ... Exclusive Zone Off Alaska; Deep-Water Species Fishery by Vessels Using Trawl Gear in the Gulf of Alaska... comprise the deep-water species fishery by vessels using trawl gear in the Gulf of Alaska (GOA). This..., NMFS is prohibiting directed fishing for the deep-water species fishery by vessels using trawl gear...

  11. 76 FR 23511 - Fisheries of the Economic Exclusive Zone Off Alaska; Deep-Water Species Fishery by Vessels Using...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-27

    ... Exclusive Zone Off Alaska; Deep-Water Species Fishery by Vessels Using Trawl Gear in the Gulf of Alaska... comprise the deep-water species fishery by vessels using trawl gear in the Gulf of Alaska (GOA). This... prohibiting directed fishing for the deep-water species fishery by vessels using trawl gear in the GOA....

  12. Deep water masses and sediments are main compartments for polychlorinated biphenyls in the Arctic Ocean.

    PubMed

    Sobek, Anna; Gustafsson, Örjan

    2014-06-17

    There is a wealth of studies of polychlorinated biphenyls (PCB) in surface water and biota of the Arctic Ocean. Still, there are no observation-based assessments of PCB distribution and inventories in and between the major Arctic Ocean compartments. Here, the first water column distribution of PCBs in the central Arctic Ocean basins (Nansen, Amundsen, and Makarov) is presented, demonstrating nutrient-like vertical profiles with 5-10 times higher concentrations in the intermediate and deep water masses than in surface waters. The consistent vertical profiles in all three Arctic Ocean basins likely reflect buildup of PCBs transported from the shelf seas and from dissolution and/or mineralization of settling particles. Combined with measurement data on PCBs in other Arctic Ocean compartments collected over the past decade, the total Arctic Ocean inventory of ∑7PCB was estimated to 182 ± 40 t (±1 standard error of the mean), with sediments (144 ± 40 t), intermediate (5 ± 1 t) and deep water masses (30 ± 2 t) storing 98% of the PCBs in the Arctic Ocean. Further, we used hydrographic and carbon cycle parametrizations to assess the main pathways of PCBs into and out of the Arctic Ocean during the 20th century. River discharge appeared to be the major pathway for PCBs into the Arctic Ocean with 115 ± 11 t, followed by ocean currents (52 ± 17 t) and net atmospheric deposition (30 ± 28 t). Ocean currents provided the only important pathway out of the Arctic Ocean, with an estimated cumulative flux of 22 ± 10 t. The observation-based inventory of ∑7PCB of 182 ± 40 t is consistent with the contemporary inventory based on cumulative fluxes for ∑7PCB of 173 ± 36 t. Information on the concentration and distribution of PCBs in the deeper compartments of the Arctic Ocean improves our understanding of the large-scale fate of POPs in the Arctic and may also provide a means to test and improve models used to assess the fate of organic pollutants in the Arctic.

  13. New records of Primnoidae (Cnidaria: Octocorallia) in Brazilian deep waters

    NASA Astrophysics Data System (ADS)

    Arantes, Renata C. M.; Loiola, Livia L.

    2014-01-01

    The knowledge of octocorals occurring in Brazilian deep waters is still lacking, with only a few studies conducted so far, most of which focused on large-scale marine habitats characterization. Primnoidae are common and characteristic of seamounts and deepwater coral banks, often providing habitat for other marine species. Although primnoids occur in all ocean basins, only Primnoella and Plumarella species were recorded along the Brazilian coast before this study. Primnoid specimens were obtained through dredging and remotely operated vehicles (ROV) sampling, collected by research projects conducted off the Brazilian coast, between 15 and 34°S. Taxonomic assessment resulted in 5 new records of Primnoidae genera in Brazil: Calyptrophora, Candidella, Dasystenella, Narella and Thouarella. The occurrences of Narella-off Salvador and Vitória, and in Campos Basin (935-1700 m), and Calyptrophora-in Campos Basin (1059-1152 m), are herein reported for the first time in the South Atlantic. Calyptrophora microdentata was previously known in Lesser Antilles, New England and Corner Rise Seamounts, between 686 and 2310 m. Candidella imbricata geographical distribution includes Western and Eastern Atlantic (514-2063 m and 815-2139 m, respectively), being registered herein in Campos Basin, between 1059 and 1605 m. Dasystenella acanthina collected off Rio Grande do Sul state (810 m) and occurs also off Argentina and Southern Ocean, between 150 and 5087 m. Plumarella diadema, which type locality is off São Sebastião, Brazil, has its geographical range extended northwards, occurring in Campos Basin (650 m). Thouarella koellikeri previously known for Patagonia and Antartic Peninsula, is registered for the off Brazil for the first time, in Campos Basin and off São Sebastião (609-659 m). There is a lot of work yet to be done in terms of taxonomic knowledge of Brazilian deep-sea octocorals. Research projects focusing on the investigations, including ROV sampling, of other

  14. The elusive character of discontinuous deep-water channels: New insights from Lucia Chica channel system, offshore California

    USGS Publications Warehouse

    Maier, K.L.; Fildani, A.; Paull, C.K.; Graham, S.A.; McHargue, T.R.; Caress, D.W.; McGann, M.

    2011-01-01

    New high-resolution autonomous underwater vehicle (AUV) seafloor images, with 1 m lateral resolution and 0.3 m vertical resolution, reveal unexpected seafloor rugosity and low-relief (<10 m), discontinuous conduits over ~70 km2. Continuous channel thalwegs were interpreted originally from lower-resolution images, but newly acquired AUV data indicate that a single sinuous channel fed a series of discontinuous lower-relief channels. These discontinuous channels were created by at least four avulsion events. Channel relief, defined as the height from the thalweg to the levee crest, controls avulsions and overall stratigraphic architecture of the depositional area. Flowstripped turbidity currents separated into and reactivated multiple channels to create a distributary pattern and developed discontinuous trains of cyclic scours and megaflutes, which may be erosional precursors to continuous channels. The diverse features now imaged in the Lucia Chica channel system (offshore California) are likely common in modern and ancient systems with similar overall morphologies, but have not been previously mapped with lower-resolution detection methods in any of these systems. ?? 2011 Geological Society of America.

  15. Biogeochemical malfunctioning in sediments beneath a deep-water fish farm.

    PubMed

    Valdemarsen, Thomas; Bannister, Raymond J; Hansen, Pia K; Holmer, Marianne; Ervik, Arne

    2012-11-01

    We investigated the environmental impact of a deep water fish farm (190 m). Despite deep water and low water currents, sediments underneath the farm were heavily enriched with organic matter, resulting in stimulated biogeochemical cycling. During the first 7 months of the production cycle benthic fluxes were stimulated >29 times for CO(2) and O(2) and >2000 times for NH(4)(+), when compared to the reference site. During the final 11 months, however, benthic fluxes decreased despite increasing sedimentation. Investigations of microbial mineralization revealed that the sediment metabolic capacity was exceeded, which resulted in inhibited microbial mineralization due to negative feed-backs from accumulation of various solutes in pore water. Conclusions are that (1) deep water sediments at 8 °C can metabolize fish farm waste corresponding to 407 and 29 mmol m(-2) d(-1) POC and TN, respectively, and (2) siting fish farms at deep water sites is not a universal solution for reducing benthic impacts.

  16. A new pathway for Deep water exchange between the Natal Valley and Mozambique Basin?

    NASA Astrophysics Data System (ADS)

    Wiles, Errol; Green, Andrew; Watkeys, Mike; Jokat, Wilfried; Krocker, Ralf

    2014-12-01

    Although global thermohaline circulation pathways are fairly well known, the same cannot be said for local circulation pathways. Within the southwest Indian Ocean specifically there is little consensus regarding the finer point of thermohaline circulation. We present recently collected multibeam bathymetry and PARASOUND data from the northern Natal Valley and Mozambique Ridge, southwest Indian Ocean. These data show the Ariel Graben, a prominent feature in this region, creates a deep saddle across the Mozambique Ridge at ca. 28°S connecting the northern Natal Valley with the Mozambique Basin. Results show a west to east change in bathymetric and echo character across the northern flank of the Ariel Graben. Whereby eroded plastered sediment drifts in the west give way to aggrading plastered sediment drift in the midgraben, terminating in a field of seafloor undulations in the east. In contrast, the southern flank of the Ariel Graben exhibits an overall rugged character with sediments ponding in bathymetric depressions in between rugged sub/outcrop. It is postulated that this change in sea-floor character is the manifestation of deep water flow through the Ariel Graben. Current flow stripping, due to increased curvature of the graben axis, results in preferential deposition of suspended load in an area of limited accommodation space consequently developing an over-steepened plastered drift. These deposited sediments overcome the necessary shear stresses, resulting in soft sediment deformation in the form of down-slope growth faulting (creep) and generation of undulating sea-floor morphology. Contrary to previous views, our works suggests that water flows from west to east across the Mozambique Ridge via the Ariel Graben.

  17. North Pacific Acoustic Laboratory: Deep Water Acoustic Propagation in the Philippine Sea

    DTIC Science & Technology

    2012-09-30

    high power, rubidium oscillator that is turned on once a day to check the frequency of a less precise, but low power, Q-Tech Microcomputer...understanding of (i) the basic physics of low- frequency , broadband propagation in deep water, including the effects of oceanographic variability on signal...stability and coherence, (ii) the structure of the ambient noise field in deep water at low frequencies , and (iii) the extent to which acoustic

  18. Morphological divergence between three Arctic charr morphs – the significance of the deep-water environment

    PubMed Central

    Skoglund, Sigrid; Siwertsson, Anna; Amundsen, Per-Arne; Knudsen, Rune

    2015-01-01

    Morphological divergence was evident among three sympatric morphs of Arctic charr (Salvelinus alpinus (L.)) that are ecologically diverged along the shallow-, deep-water resource axis in a subarctic postglacial lake (Norway). The two deep-water (profundal) spawning morphs, a benthivore (PB-morph) and a piscivore (PP-morph), have evolved under identical abiotic conditions with constant low light and temperature levels in their deep-water habitat, and were morphologically most similar. However, they differed in important head traits (e.g., eye and mouth size) related to their different diet specializations. The small-sized PB-morph had a paedomorphic appearance with a blunt head shape, large eyes, and a deep body shape adapted to their profundal lifestyle feeding on submerged benthos from soft, deep-water sediments. The PP-morph had a robust head, large mouth with numerous teeth, and an elongated body shape strongly related to their piscivorous behavior. The littoral spawning omnivore morph (LO-morph) predominantly utilizes the shallow benthic–pelagic habitat and food resources. Compared to the deep-water morphs, the LO-morph had smaller head relative to body size. The LO-morph exhibited traits typical for both shallow-water benthic feeding (e.g., large body depths and small eyes) and planktivorous feeding in the pelagic habitat (e.g., streamlined body shape and small mouth). The development of morphological differences within the same deep-water habitat for the PB- and PP-morphs highlights the potential of biotic factors and ecological interactions to promote further divergence in the evolution of polymorphism in a tentative incipient speciation process. The diversity of deep-water charr in this study represents a novelty in the Arctic charr polymorphism as a truly deep-water piscivore morph has to our knowledge not been described elsewhere. PMID:26357540

  19. Changes in the deep-water benthos of eastern Lake Erie between 1979 and 1993

    SciTech Connect

    Dermott, R.; Kerec, D.

    1995-06-01

    In order to examine changes of the benthic community and benthic biomass as a result of mussel colonization, a survey of the deep-water benthic fauna in eastern Lake Erie was repeated in 1993 using the same sites and methods as in a 1979 survey. During 1979, the community beyond 30 m was dominated by oligochaete worms and the burrowing amphipod Diporeia, which represented 50 and 40% of the total benthic biomass respectively. By 1993, quagga mussels (Dreissena bugensis) formed over 90% of the benthic biomass. Mussels were present at all 13 sites. Densities of individuals >2 mm in length averaged 3,241 mussels m{sup -2}. Of these mussels, 97% were quagga mussels. Total density of all sizes retained on a 180 {mu}m sieve averaged 34,800 mussels m{sup -2} but total biomass decreased from 1.58 to 0.98 g m{sup -2}. The density of the amphipod Diporeia was reduced from 1,844 in 1979 to 218 m{sup -2} in 1993. While present at all sites during 1979, Diporeia remained common only at two sites and were absent at 8 of the 13 sites in 1993. The native fingernail clams, Pisidium spp., were reduced from 327 to 82 m{sup -2}. No significant reduction occurred in the worm and chironomid populations, however the dry biomass of the chironomids was reduced from 0.07 to 0.0008 g m{sup -2}. These reductions may be due to competition with the mussels for freshly settling algae. The meiofauna, which included small nematodes, ostracods, and harpacticoids retained on a 180 {mu}m sieve, all increased in density. Perhaps they benefited from an increase in the detritus deposited as pseudofeces around the mussels.

  20. Source rock in the lower Tertiary and Cretaceous, deep-water Gulf of Mexico

    SciTech Connect

    Wagner, B.E.; Sofer, Z.; Claxton, B.L.

    1994-12-31

    The MC-84 (King) well was drilled in the deep-water Gulf of Mexico in 1993, in Mississippi Canyon Block 84 in a water depth of 5,149 ft. This well drilled an anticlinal feature. The well penetrated an Upper Cretaceous section and crossed Middle Cretaceous Unconformity with final total depth in the Lower Cenomanian. Numerous sidewall cores were taken throughout the Lower Tertiary and Cretaceous. Six of the sidewall cores (from 14,230 to 15,170 ft subsea) are organic rich and contain Type II oil-prone kerogen (TOC values from 2.6 to 5.2% and hydrogen indices from 360 to 543 ppm). The Lower Tertiary through Lower Cenomianian section is thermally immature for oil generation, on the basis of biomarker ratios and vitrinite reflectance measurements. Organic extracts from cores in the Cretaceous section had biomarker characteristics similar to oil recovered from the Miocene in the MC-84 well. The oil was generated from a similar but more mature source rock, probably of Early Cretaceous age. Results of thermal modeling indicate that the only section thermally mature for oil generation is in the lower portion of the Lower Cretaceous, below the total depth of the well. The model also indicates that the organic-rich section equivalent to that penetrated by the MC-84 well could be mature farther to the north, where water depths are shallower, overburden thickness is greater, and heat flow is higher. Late Tertiary sediment loading in this area, primarily during the Miocene, is probably the driving mechanism for hydrocarbon generation from the Cretaceous (and possibly the Lower Tertiary) potential source rocks. This offers a favorable geological setting for capturing hydrocarbons because reservoirs and traps associated with Miocene deposition and subsequent loading-induced salt movement had formed prior to the onset of oil generation and migration.

  1. Seismic blanking zones in the deep-water Ullung Basin, East Sea of Korea.

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae; Riedel, Michael; Yoo, Dong-Geun

    2015-04-01

    A total 12366.395 L.km of 2D multichannel seismic data were acquired by the Korea Institute of Geoscience and Mineral Resources (KIGAM) for detecting and mapping seismic indicators for the presence of gas hydrate in the deep-water Ulleung Basin, East Sea of Korea. The seismic data were acquired using Trilogy System of Geco-Prakla, Bolt Air-gun System onboard the R/V TAMHAE II of KIGAM during the years of 2000 to 2004. The seismic faices of shallow sediments were also analyzed to understand the sedimentary strata developed in the basin. Seismic data were processed to define gas hydrate indicators such as bottom simulating reflectors (BSRs) and seismic blank zones. The BSR was identified by (a) its polarity opposite to the seafloor, (b) its seafloor-parallel reflection behavior, and (c) its occurrence at a sub-bottom depth corresponding to the expected base of gas hydrate stability zone, on heat flow and other thermal data for the region and on seismic velocity data. The seismic velocity analysis was also conducted for determining the velocity deviation effect of high-velocity gas hydrate and underlying low-velocity free gas. The BSRs occur mainly in the southern part of the basin where mass transport deposits are widely occurring. A number of vertical to sub-vertical seismic blanking zones were identified in the basin. The blanking zones are near-vertical broad chimney-like structures of reduced seismic reflectivity. They may be formed by gas and/or fluid upwelling through fractures and faults. Many of the blanking zones show apparent velocity pull-up effects of sediment layering structures that are interpreted to be a result of higher velocity gas hydrate. The presence of substantial amounts of gas hydrate in the blank zones were first found by piston coring in 2007, and subsequently confirmed by two deep-drilling expeditions in 2007 and 2010. Most of the blanking zones occur in well-bedded turbidite/hemi-pelagic sediments in the northern deep basin. The

  2. The distribution of anthropogenic REE in the Dutch distributaries of the Rhine: the role of suspended matter

    NASA Astrophysics Data System (ADS)

    Roskam, Gerlinde; Verheul, Marc; Klaver, Gerard; Bakker, Ingrid

    2014-05-01

    In nature rare earth elements (REE) occur in fixed ratios; contamination with a single rare earth element causes a clear deviation from the natural NASC normalized REE-patterns: an anomaly. REE are progressively used in many high technology products and processes. For example, gadolinium-containing chelates have been used since the '80s as contrasting agent in MRI-imaging. The pertaining anomaly is currently used as a tracer for distinguishing waste water from water unaffected by anthropogenic contamination. In the Dutch monitoring program in the Rhine-Meuse distributaries, total (10% HNO3 digested) and dissolved (< 0.45 µm) fractions in surface water are routinely analysed, and with two-week intervals suspended matter samples are collected with a centrifuge. Since 2008, the set of analysed elements was extended with REE, enabling this study. Lobith, the entry point of the River Rhine in The Netherlands, shows an annual oscillation in the magnitude of the lanthanum (La) anomaly. This positive La-anomaly was reported by Kulaksiz and Bau in 2011; they identified the point source as a production plant for catalysts used in petroleum refining in the German city of Worms. Since the spring of 2011, samarium (Sm) is used in the same process, resulting in matching La- and Sm-anomalies. The anthropogenic La and Sm concentrations are predominantly present in the total fraction, which suggests that the anthropogenic La and Sm concentrations are associated with suspended matter. The anthropogenic La and Sm concentrations are lower in the suspended matter samples collected with the centrifuge, suggesting a bias of these La and Sm concentrations in the finer fraction of the suspended matter. The anthropogenic La en Sm concentrations remain relatively constant throughout the rivers, but close to Lake IJsselmeer and the North Sea, sedimentation causes a sharp decrease in the anthropogenic concentrations. Detailed sampling of sediments, suspended matter and water could give a

  3. Deep-water riser fatigue monitoring systems based on acoustic telemetry

    NASA Astrophysics Data System (ADS)

    Li, Baojun; Wang, Haiyan; Shen, Xiaohong; Yan, Yongsheng; Yang, Fuzhou; Hua, Fei

    2014-12-01

    Marine risers play a key role in the deep and ultra-deep water oil and gas production. The vortex-induced vibration (VIV) of marine risers constitutes an important problem in deep water oil exploration and production. VIV will result in high rates of structural failure of marine riser due to fatigue damage accumulation and diminishes the riser fatigue life. In-service monitoring or full scale testing is essential to improve our understanding of VIV response and enhance our ability to predict fatigue damage. One marine riser fatigue acoustic telemetry scheme is proposed and an engineering prototype machine has been developed to monitor deep and ultra-deep water risers' fatigue and failure that can diminish the riser fatigue life and lead to economic losses and eco-catastrophe. Many breakthroughs and innovation have been achieved in the process of developing an engineering prototype machine. Sea trials were done on the 6th generation deep-water drilling platform HYSY-981 in the South China Sea. The inclination monitoring results show that the marine riser fatigue acoustic telemetry scheme is feasible and reliable and the engineering prototype machine meets the design criterion and can match the requirements of deep and ultra-deep water riser fatigue monitoring. The rich experience and field data gained in the sea trial which provide much technical support for optimization in the engineering prototype machine in the future.

  4. Upwelling at the ice edge - A mechanism for deep water formation?

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa

    1987-01-01

    This study sets forward a hypothesis which anticipates deep water formation due to ice edge upwelling. The upwelling can raise thermocline waters (the lower Arctic Intermediate Water) to the surface or near it, where the water is exposed to cooling, evaporation, mixing, and oxygenation. Thus, upwelling can act as a preconditioning mechanism for deep convection. The conjecture would also explain the salinity range of the Greenland Sea Deep Water if the upper and lower Arctic Intermediate Water masses are mixed so that the latter has at least an 80-percent contribution. It is also anticipated that the convection events induced by ice edge upwelling during winter season could give rise to a new deep water annual production rate consistent with observations.

  5. Deep water exchanges between the South China Sea and the Pacific since the last glacial period

    NASA Astrophysics Data System (ADS)

    Wan, Sui; Jian, Zhimin

    2014-12-01

    Deep ocean circulation is widely considered as one of the important factors for increasing CO2 concentration and decreasing radiocarbon activity (Δ14C) of the atmosphere during the last deglaciation. The AMS 14C ages of benthic and planktonic foraminifers from 18 samples of Core MD05-2904 (water depth of 2066 m) in the northern South China Sea (SCS) and 15 samples of Core MD05-2896 (water depth of 1657 m) in the southern SCS were analyzed in this study for reconstructing the intrabasin deep oceanic processes and hence exploring the deep water exchanges between the SCS and the Pacific since the last glacial period. The results show that during the Holocene the average apparent ventilation age of deep water was younger in the southern SCS (~1350 years) than in the northern SCS (~1850 years) due to relatively strong vertical mixing and advection, consistent with modern observations. However, during the last glacial period and deglaciation the deep water was older in the southern SCS (~2050 years and ~1800 to 1200 years, respectively) than in the northern SCS (~1600 years and ~670 years, respectively), indicating reduced deep mixing and advection. Moreover, the northern SCS deep water was significantly younger during the last deglaciation than during the Holocene and the last glacial period, implying the existence of northern sourced newly formed and relatively young North Pacific deep water. Our records do not support the intrusion of anomalously 14C-depleted deep water to the middepth of the low-latitude western Pacific and the SCS during the "Mystery Interval" (17.5-14.5 kyr B.P.).

  6. Tidal inlet processes and deposits along a low energy coastline: easter Barataria Bight, Louisiana

    SciTech Connect

    Moslow, T.F.; Levin, D.R.

    1985-01-01

    Historical, seismic and vibracore data were used to determine the geologic framework of sand deposits along the predominantly muddy coastline of eastern Barataria Bight, Louisiana. Three inlet types with distinct sand body geometries and morphologies were identified and are found 1) at flanking barrier island systems spread laterally across the front of interdistributary bays; 2) in old distributary channels; 3) at overwash breaches; or 4) combination of these. Barataria Bight, a sheltered barrier island shoreline embayment with limited sand supply, minimal tidal range (36 cm) and low wave energies (30 cm) can be used to show examples of each inlet type. Barataria Pass and Quatre Bayou Pass are inlets located in old distributary channels. However, Barataria Pass has also been affected by construction between barrier islands. Pass Ronquille is located where the coastline has transgressed a low area in the delta plain. This breach is situated in a hydraulically efficient avenue between the Gulf and Bay Long behind it. Pass Abel is a combination of a low-profile barrier breach and the reoccupation of an old distributary channel. Shelf and shoreline sands are reworked from abandoned deltaic distributaries and headlands. Inner shelf sands are concentrated in thick (10 m) shore-normal relict distributary channels with fine grained cross-bedded and ripple laminated sand overlain by burrowed shelf muds. Shoreface sand deposits occur as 2-3 m thick, fine-grained, coarsening upward and burrowed ebb-tidal delta sequences and shore-parallel relict tidal inlet channels filled through lateral accretion.

  7. Changes in deep-water epibenthic megafaunal assemblages in relation to seabed slope on the Nigerian margin

    NASA Astrophysics Data System (ADS)

    Jones, Daniel O. B.; Mrabure, Charles O.; Gates, Andrew R.

    2013-08-01

    Local-scale habitat heterogeneity associated with changes in slope is a ubiquitous feature of bathyal continental margins. The response of deep-sea species to high habitat heterogeneity is poorly known and slope can be used as a proxy for many important ecological variables, such as current flow, sedimentation and substratum type. This study determines how slope angle effects megafaunal species density and diversity at the Usan field, offshore Nigeria, between 740 and 760 m depth. This deep-water area is increasingly exploited for hydrocarbons, yet lacking in baseline biological information. Replicated remotely operated vehicle video transect surveys were carried out using industry infrastructure (through the SERPENT Project) at a representative range of slopes (1°, 3°, 11° and 29°). Twenty-four species of benthic megafaunal invertebrate were found, numerically dominated by the echinoid Phormosoma placenta, and nine species of fish were observed. Megafaunal invertebrate deposit feeder density decreased significantly with increasing slope (density range 0.503-0.081 individuals m-2). Densities of megafaunal suspension feeders were very low except at the highest slope site (mean density 0.17 m-2). Overall species richness was greater on steeper slopes, although the richness of deposit feeders was not affected. Reduced labile organic matter in sediments on steeper slopes likely reduced deposit feeder densities, but increased current flow at higher slopes allowed both increased richness and density of suspension feeders.

  8. Are high p-wave velocity sediments on thin Tethyan crust, deep-water carbonates?

    NASA Astrophysics Data System (ADS)

    Gutscher, Marc-Andre; Graindorge, David; Klingelhoefer, Frauke; Dellong, David; Kopp, Heidrun; Sallares, Valenti; Bartolome, Rafael; Gallais, Flora

    2016-04-01

    Seismic reflection profiles from the Central Mediterranean and Gulf of Cadiz regions indicate the widespread presence of a seismic unit, marked by strong continuous reflectors, directly overlying the basement. Seismic velocity analysis from seismic reflection and refraction studies indicate high p-wave velocities of 3.5 - 4.5 km/s in this layer. These same seismic studies image a thin crust, typically 6-9 km thick, in most cases thought to be oceanic in nature and related to the Tethys oceanic domain separating Africa (Gondwana) from Laurussia. We interpret this 2-3 km thick reflective layer to be carbonates, deposited in the late Triassic, Jurassic and early Cretaceous in the Tethys Ocean, in deep marine basins. Few drilling studies have penetrated into this layer. In one case (DSDP site 135, drilled at 4152 m water depth on Coral Patch Ridge in the western Gulf of Cadiz), Aptian (early Cretaceous) marls and limestone were drilled (560-689 m sub-seafloor depth). The Calcite compensation depth during the Jurassic to Early Cretaceous was about 4000 m to 3500 m according to compilations from the Atlantic and Indian Oceans and is consistent with deposition of deep-water carbonates. For the NW Moroccan margin (Mazagan transect near El Jadida) there is a 2 km thick sedimentary layer with p-wave velocities of 4.0 - 4.5 km/s at the base of a 4 - 6 km thick sedimentary section. This layer extends from seafloor thought to be oceanic crust (west of the West African Coast magnetic anomaly) across a domain of thin/transitional crust with abundant Triassic salt diapirs to the foot of the margin. This reflective basal layer is also observed in reflection and refraction profiles from the Seine abyssal plain, below the toe of the Cadiz accretionary wedge (S. Algarve margin), in the Ionian abyssal plain and below the toe of the Calabrian accretionary wedge, all regions floored by this thin Tethyan crust. Work is in progress to determine the exact nature of this crust.

  9. Understanding how gravity flows shape deep-water channels. The Rhone delta canyon (Lake Geneva, Switzerland/France)

    NASA Astrophysics Data System (ADS)

    Corella, Juan Pablo; Loizeau, Jean Luc; Hilbe, Michael; le Dantec, Nicolas; Sastre, Vincent; Girardclos, Stéphanie

    2014-05-01

    Deep-water marine channels are highly dynamic environments due to the erosive power of sediment-laden currents that are continuously reshaping the morphology of these major sediment conduits. Proximal levees are prone to scarp failures generating gravity flows that can be transported thousands of kilometres from the original landslide. Nevertheless, the evolution of these underflows is still poorly understood because of the spatial scale of the processes and their difficult monitoring. For this reason, the smaller size, well-known boundary conditions and detailed bathymetric data makes Lake Geneva's sub-aquatic canyon in the Rhone delta an excellent analogue to understand these types of sedimentary processes that usually occur in deep-water channels in the marine realm. A multidisciplinary research strategy including innovative coring via MIR submersibles, in-situ geotechnical tests, geophysical and sedimentological analyses, as well as acquisition of different multibeam bathymetric data sets, were applied to understand the triggering processes, transport mechanisms and deposit features of gravity flows throughout the Rhone delta active canyon. The difference between two bathymetric surveys in 1986 and 2000 revealed an inversion in the topography of the distal active canyon, as a former distal canyon was transformed into a mound-like structure. A 12 m-thick layer was deposited in the canyon and modified the sediment transfer conduit. Sediment cores from this deposit were retrieved in-situ in 2002 and 2011 via the "F.-A. Forel" and Russian MIR submersibles, respectively. These cores contained a homogeneous, sandy material. Its sediment texture, grain-size, high density and shear strength, and low water content suggests that it corresponds to a debris-flow deposit that possibly took place after the initiation of a mass movement due to a scarp failure in proximal areas of the canyon. In addition, in-situ geotechnical tests on the modern canyon floor have shown a soft

  10. Eastern-Mediterranean ventilation variability during sapropel S1 formation, evaluated at two sites influenced by deep-water formation from Adriatic and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Filippidi, A.; Triantaphyllou, M. V.; De Lange, G. J.

    2016-07-01

    Present-day bottom-water ventilation in the Eastern Mediterranean basin occurs through deep-water convection originating from the two marginal basins, i.e. Adriatic and Aegean Seas. In the paleo record, long periods of enhanced deep-water formation have been alternating with shorter periods of reduced deep-water formation. The latter is related mainly to low-latitude humid climate conditions and the enhanced deposition and preservation of organic-rich sediment units (sapropels). This study focuses on sedimentary archives of the most-recent sapropel S1, retrieved from two sites under the direct influence of the two deep-water formation areas. Restricted oxygen conditions have developed rapidly at the beginning of S1 deposition in the Adriatic site, but bottom-water conditions have not persistently remained anoxic during the full interval of sapropel deposition. In fact, the variability in intensity and persistence of sedimentary redox conditions at the two deep-water formation sites is shown to be related to brief episodes of climate cooling. In the Adriatic site, sapropel deposition appears to have been interrupted twice. The 8.2 ka event, only recovered at the Adria site, is characterized by gradually increasing suboxic to possibly intermittently oxic conditions and decreasing Corg fluxes, followed by an abrupt re-establishment of anoxic conditions. Another important event that disrupted sapropel S1 formation, has taken place at ca. 7.4 cal ka BP. The latter event has been recovered at both sites. In the Adriatic site it is followed by a period of sedimentary conditions that gradually change from suboxic to more permanently oxic, as deduced from the Mn/Al pattern. Using the same proxy for suboxic/oxic sedimentary redox conditions, we observe that conditions in the Aegean Sea site shift to more permanently oxic from the 7.4 ka event onwards. However, at both sites the accumulation and preservation of enhanced amounts of organic matter have continued under these

  11. Deep-Water Waves: on the Nonlinear Schrödinger Equation and its Solutions

    NASA Astrophysics Data System (ADS)

    Vitanov, Nikolay K.; Chabchoub, Amin; Hoffmann, Norbert

    2013-06-01

    We present a brief discussion on the nonlinear Schrödinger equation for modelling the propagation of the deep-water wavetrains and a discussion on its doubly-localized breather solutions, that can be connected to the sudden formation of extreme waves, also known as rogue waves or freak waves.

  12. The contribution of the Greenland and Barents Seas to the deep water of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Swift, James H.; Takahashi, Taro; Livingston, Hugh D.

    1983-07-01

    The deep waters of the Arctic Ocean are traditionally held to be fed by an influx of Norwegian Sea Deep Water (NSDW) via the northward flowing West Spitsbergen Current. Discrete sample and CTD observations obtained from the Greenland-Spitsbergen Passage in August 1981 during the Transient Tracers in the Ocean (TTO) North Atlantic expedition showed a ≈ 100-m-thick layer of modified Greenland Sea Deep Water (GSDW: colder and fresher than NSDW) at 2500 m, spreading northward along the bottom of a deep, unimpeded channel, underneath the NSDW. Since the available data indicate that Arctic Ocean Deep Water (AODW) has a higher salinity than NSDW, mixing of NSDW and GSDW can not produce AODW. Therefore, other sources, such as the peripheral arctic shelf seas, must contribute dense saline water to the Arctic Ocean. Concentrations of 137Cs and 90Sr observed in AODW are greater than those observed in GSDW and NSDW. The concentrations of these radionuclides on the Barents Sea shelf are sufficiently high and in the correct relative proportions to support this proposition.

  13. 75 FR 34929 - Safety Zones: Neptune Deep Water Port, Atlantic Ocean, Boston, MA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-21

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zones: Neptune Deep Water Port, Atlantic Ocean... turret loading (STL) buoys and accompanying systems that are part of GDF Suez Energy's Neptune Deepwater... of a final regulatory action, which will be proposed in a separate rulemaking docket titled:...

  14. Deep-water kelp refugia as potential hotspots of tropical marine diversity and productivity.

    PubMed

    Graham, Michael H; Kinlan, Brian P; Druehl, Louis D; Garske, Lauren E; Banks, Stuart

    2007-10-16

    Classic marine ecological paradigms view kelp forests as inherently temperate-boreal phenomena replaced by coral reefs in tropical waters. These paradigms hinge on the notion that tropical surface waters are too warm and nutrient-depleted to support kelp productivity and survival. We present a synthetic oceanographic and ecophysiological model that accurately identifies all known kelp populations and, by using the same criteria, predicts the existence of >23,500 km(2) unexplored submerged (30- to 200-m depth) tropical kelp habitats. Predicted tropical kelp habitats were most probable in regions where bathymetry and upwelling resulted in mixed-layer shoaling above the depth of minimum annual irradiance dose for kelp survival. Using model predictions, we discovered extensive new deep-water Eisenia galapagensis populations in the Galápagos that increased in abundance with increasing depth to >60 m, complete with cold-water flora and fauna of temperate affinities. The predictability of deep-water kelp habitat and the discovery of expansive deep-water Galápagos kelp forests validate the extent of deep-water tropical kelp refugia, with potential implications for regional productivity and biodiversity, tropical food web ecology, and understanding of the resilience of tropical marine systems to climate change.

  15. Insight into the microbial community structure of a Norwegian deep-water coral reef environment

    NASA Astrophysics Data System (ADS)

    Jensen, Sigmund; Neufeld, Josh D.; Birkeland, Nils-Kåre; Hovland, Martin; Murrell, J. Colin

    2008-11-01

    Deep-water coral reefs support rich biological communities below the photic zone of fjords and continental shelves around the world. In this environment, life is enclosed within cold permanent darkness, in stark contrast to life in tropical coral reefs. We collected samples of water, sediment and a Desmacidon sp. sponge from a deep-water coral reef off the coast of Norway, and characterised bacterial communities with focus on primary producers in the dark. Following DNA extraction, PCR amplification and 16S rRNA gene library sequencing, bioinformatic analyses demonstrated significant differences between bacterial communities associated with the three samples. The finding that 50% of the clones showed <90% identity to cultured bacteria reflects the novel and uncharacterised diversity associated with these deep-water coral reefs. A total of 13 bacterial phyla were identified. Acidobacteria dominated the sponge library and Proteobacteria dominated the bacterioplankton and sediment libraries. Phylogenetic analysis revealed a possible new clade of sponge-associated Acidobacteria, which includes representatives from the Desmacidon sp. (Norway), Rhopaloeides odorabile (Australia) and Discodermia dissoluta (Curacao). Furthermore, the targeted recovery of a particulate methane monooxygenase ( pmoA) gene from the Desmacidon sp. DNA extract suggests that as yet uncultivated type I methanotrophs may mediate methane oxidation in this deep-water coral reef. Methanotrophs were not identified in the 16S rRNA gene libraries, but the presence of a high number (8%) of clones related to sulfide-, nitrite- and iodide-oxidising bacteria suggests chemosynthesis to be involved with maintenance of the deep-water coral reef ecosystem.

  16. Flood frequency matters: Why climate change degrades deep-water quality of peri-alpine lakes

    NASA Astrophysics Data System (ADS)

    Fink, Gabriel; Wessels, Martin; Wüest, Alfred

    2016-09-01

    Sediment-laden riverine floods transport large quantities of dissolved oxygen into the receiving deep layers of lakes. Hence, the water quality of deep lakes is strongly influenced by the frequency of riverine floods. Although flood frequency reflects climate conditions, the effects of climate variability on the water quality of deep lakes is largely unknown. We quantified the effects of climate variability on the potential shifts in the flood regime of the Alpine Rhine, the main catchment of Lake Constance, and determined the intrusion depths of riverine density-driven underflows and the subsequent effects on water exchange rates in the lake. A simplified hydrodynamic underflow model was developed and validated with observed river inflow and underflow events. The model was implemented to estimate underflow statistics for different river inflow scenarios. Using this approach, we integrated present and possible future flood frequencies to underflow occurrences and intrusion depths in Lake Constance. The results indicate that more floods will increase the number of underflows and the intensity of deep-water renewal - and consequently will cause higher deep-water dissolved oxygen concentrations. Vice versa, fewer floods weaken deep-water renewal and lead to lower deep-water dissolved oxygen concentrations. Meanwhile, a change from glacial nival regime (present) to a nival pluvial regime (future) is expected to decrease deep-water renewal. While flood frequencies are not expected to change noticeably for the next decades, it is most likely that increased winter discharge and decreased summer discharge will reduce the number of deep density-driven underflows by 10% and favour shallower riverine interflows in the upper hypolimnion. The renewal in the deepest layers is expected to be reduced by nearly 27%. This study underlines potential consequences of climate change on the occurrence of deep river underflows and water residence times in deep lakes.

  17. Gas hydrates in the deep water Ulleung Basin, East Sea, Korea.

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae

    2016-04-01

    Studies on gas hydrates in the deep-water Ulleung Basin, East Sea, Korea was initiated by the Korea Institute of Geoscience and Mineral Resources (KIGAM) to secure the future energy resources in 1996. Bottom simulating reflectors (BSRs) were first identified on seismic data collected in the southwestern part of the basin from 1998 to 1999. Regional geophysical surveys and geological studies of gas hydrates in the basin have been carried out by KIGAM from 2000 to 2004. The work included 12,367 km of 2D multi-channel seismic reflection lines and 38 piston cores 5 to 8 m long. As a part of the Korean National Gas Hydrate Program that has been performed since 2005, 6690 km of 2D multi-channel reflection seismic lines, 900 km2 of 3D seismic data, 69 piston cores and three PROD cores were additionally collected. In addition, two gas hydrate drilling expeditions were performed in 2007 and 2010. Cracks generally parallel to beddings caused by the dissociation of gas hydrate were often observed in cores. The lack of higher hydrocarbons and the carbon isotope ratios indicate that the methane is primarily biogenic. The seismic data showed clear and wide-spread bottom-simulating reflectors (BSRs). The BSR was identified by (a) its polarity opposite to the seafloor, (b) its seafloor-parallel reflection behavior, and (c) its occurrence at a sub-bottom depth corresponding to the expected base of gas hydrate stability zone. Several vertical to sub-vertical chimney-like blank zones up to several kilometers in diameter were also identified in the study area. They are often associated with velocity pull-up structures that are interpreted due to higher velocity in gas hydrate-bearing deposits. Seismic velocity analysis also showed a high velocity anomaly within the pull-up structure. Gas hydrate samples were collected from the shallow sedimentary section of blanking zone by piston coring in 2007. BSRs mainly occur in the southern part of the basin. They also locally observed in the

  18. Habitat, Fauna, and Conservation of Florida's Deep-Water Coral Reefs

    NASA Astrophysics Data System (ADS)

    Reed, J. K.; Pomponi, S. A.; Messing, C. G.; Brooke, S.

    2008-05-01

    Various types of deep-water coral habitats are common off the southeastern United States from the Blake Plateau through the Straits of Florida to the eastern Gulf of Mexico. Expeditions in the past decade with the Johnson-Sea- Link manned submersibles, ROVs, and AUVs have discovered, mapped and compiled data on the status, distribution, habitat, and biodiversity for many of these relatively unknown deep-sea coral ecosystems. We have discovered over three hundred, high relief (15-152-m tall) coral mounds (depth 700-800 m) along the length of eastern Florida (700 km). The north Florida sites are rocky lithoherms, whereas the southern sites are primarily classic coral bioherms, capped with dense 1-2 m tall thickets of Lophelia pertusa and Enallopsammia profunda. Off southeastern Florida, the Miami Terrace escarpment (depth 300-600 m) extends nearly 150 km as a steep, rocky slope of Miocene-age phosphoritic limestone, which provides habitat for a rich biodiversity of fish and benthic invertebrates. Off the Florida Keys, the Pourtalès Terrace (depth 200- 460 m) has extensive high-relief bioherms and numerous deep-water sinkholes to depths of 250-610 m and diameters up to 800 m. The dominant, deep-water, colonial scleractinian corals in this region include Oculina varicosa, L. pertusa, E. profunda, Madrepora oculata, and Solenosmilia variabilis. Other coral species include hydrozoans (Stylasteridae), bamboo octocorals (Isididae), numerous other gorgonians, and black corals (Antipatharia). These structure-forming taxa provide habitat and living space for a relatively unknown but biologically rich and diverse community of crustaceans, mollusks, echinoderms, polychaete and sipunculan worms, and associated fishes. We have identified 142 taxa of benthic macro-invertebrates, including 66 Porifera and 57 Cnidaria. Nearly 100 species of fish have been identified to date in association with these deep-water coral habitats. Paull et al. (2000) estimated that over 40

  19. Deep water formation in the North Pacific and deglacial CO2 rise

    NASA Astrophysics Data System (ADS)

    Rae, James W. B.; Sarnthein, Michael; Foster, Gavin L.; Ridgwell, Andy; Grootes, Pieter M.; Elliott, Tim

    2014-06-01

    Deep water formation in the North Atlantic and Southern Ocean is widely thought to influence deglacial CO2 rise and climate change; here we suggest that deep water formation in the North Pacific may also play an important role. We present paired radiocarbon and boron isotope data from foraminifera from sediment core MD02-2489 at 3640 m in the North East Pacific. These show a pronounced excursion during Heinrich Stadial 1, with benthic-planktic radiocarbon offsets dropping to ~350 years, accompanied by a decrease in benthic δ11B. We suggest that this is driven by the onset of deep convection in the North Pacific, which mixes young shallow waters to depth, old deep waters to the surface, and low-pH water from intermediate depths into the deep ocean. This deep water formation event was likely driven by an increase in surface salinity, due to subdued atmospheric/monsoonal freshwater flux during Heinrich Stadial 1. The ability of North Pacific Deep Water (NPDW) formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity Earth system model. These experiments also show that breakdown of stratification in the North Pacific leads to a rapid ~30 ppm increase in atmospheric CO2, along with decreases in atmospheric δ13C and Δ14C, consistent with observations of the early deglaciation. Our inference of deep water formation is based mainly on results from a single sediment core, and our boron isotope data are unavoidably sparse in the key HS1 interval, so this hypothesis merits further testing. However, we note that there is independent support for breakdown of stratification in shallower waters during this period, including a minimum in δ15N, younging in intermediate water 14C, and regional warming. We also re-evaluate deglacial changes in North Pacific productivity and carbonate preservation in light of our new data and suggest that the regional pulse of export production observed during the B

  20. Geochemical evidence for anoxic deep water in the Arabian Sea during the last glaciation

    SciTech Connect

    Sarkar, A.; Bhattacharya, S.K.; Sarin, M.M. )

    1993-03-01

    Various paleoceanographic studies have indicated that the deep ocean was probably depleted in dissolved oxygen during the last glacial period ([approximately]18 kyr B.P.; [delta][sup 18]O, stage 2) compared to present time. However, direct evidence of low oxygen content in the deep waters has been lacking. Here, the authors report geochemical evidence of near anoxic conditions in the deep Arabian Sea during the entire last glacial cycle ([delta][sup 18]O; stages 2, 3, and 4). Anoxia is inferred from the concomitant enrichment of organic carbon and authigenic uranium in the glacial sections of a core from the deep eastern Arabian Sea. The anoxic conditions during the last glacial period, probably caused by a change in deep water circulation, evidently enhanced preservation of organic matter and simultaneous removal of uranium from seawater. 57 refs., 3 figs., 2 tabs.

  1. Deep-water octocorals (Cnidaria: Octocorallia) from Brazil: Family Chrysogorgiidae Verrill, 1883.

    PubMed

    Cordeiro, Ralf T S; Castro, Clovis B; Pérez, Carlos D

    2015-12-15

    Current knowledge about the Brazilian deep-water octocoral fauna remains scarce, fragmented, and mostly based on unpublished, regional scale surveys. The present work provides the first comprehensive study of the family Chrysogorgidae Verrill, 1883 in Brazil, based on morphological analysis of specimens collected in the last decade and those currently placed in museums. Members of this family are common mainly at great depths and remarkable for the iridescent aspect of their colonies. In Brazil, to the present, only four species were reported: Chrysogorgia elegans (Verrill, 1883), Chrysogorgia multiflora Deichmann, 1936, Stephanogorgia rattoi Castro, Medeiros & Loiola, 2010 and Trichogorgia brasiliensis Castro, Medeiros & Loiola, 2010-the last two are shallow-water species. In this study, three new deep-water species are described, Chrysogorgia tuberculata, Chrysogorgia upsilonia and Radicipes kopelatos, and a new record to Brazil is reported, Chrysogorgia fewkesii Verrill, 1883, as well as latitudinal expansions in distributions of Chrysogorgia elegans and Chrysogorgia multiflora are presented.

  2. Effects of two deep water training programs on cardiorespiratory and muscular strength responses in older adults.

    PubMed

    Kanitz, Ana Carolina; Delevatti, Rodrigo Sudatti; Reichert, Thais; Liedtke, Giane Veiga; Ferrari, Rodrigo; Almada, Bruna Pereira; Pinto, Stephanie Santana; Alberton, Cristine Lima; Kruel, Luiz Fernando Martins

    2015-04-01

    This study aimed to investigate the effects of two deep water training programs on cardiorespiratory and muscular strength responses in older adults. Thirty-four older adults men were placed into two groups: deep water endurance training (ET; n = 16; 66 ± 4 years) and deep water strength prior to endurance training (concurrent training: CT; n = 18; 64 ± 4 years). The training period lasted 12 weeks, with three sessions a week. The resting heart rate and the oxygen uptake at peak (VO2peak) and at the second ventilatory threshold (VO2VT2) were evaluated during a maximal incremental test on a cycle ergometer before and after training. In addition, maximal dynamic strength (one repetition maximum test--1RM) and local muscular resistance (maximum repetitions at 60% 1RM) of the knee extensors and flexors were evaluated. After the training period, the heart rate at rest decreased significantly, while the VO2peak and VO2VT2 showed significant increases in both groups (p<0.05). Only the VO2VT2 resulted in significantly greater values for the ET compared to the CT group after the training (p<0.05). In addition, after training, there was a significant increase in the maximal dynamic strength of the knee extensors and the local muscular endurance of the knee extensors and flexors, with no difference between the groups (p > 0.05). In summary, the two training programs were effective at producing significant improvements in cardiorespiratory and muscular strength responses in older adult men. However, deep water endurance training at high intensities provides increased cardiorespiratory responses compared to CT and results in similar muscular strength responses.

  3. First description of deep-water elasmobranch assemblages in the Exuma Sound, The Bahamas

    NASA Astrophysics Data System (ADS)

    Brooks, Edward J.; Brooks, Annabelle M. L.; Williams, Sean; Jordan, Lance K. B.; Abercrombie, Debra; Chapman, Demian D.; Howey-Jordan, Lucy A.; Grubbs, R. Dean

    2015-05-01

    Deep-sea chondrichthyans, like many deep-water fishes, are very poorly understood at the most fundamental biological, ecological and taxonomic levels. Our study represents the first ecological investigation of deep-water elasmobranch assemblages in The Bahamas, and the first assessment of species-specific resilience to capture for all of the species captured. Standardised deep-water longline surveys (n=69) were conducted September to December 2010 and 2011 between 472 m and 1024 m deep, resulting in the capture of 144 sharks from 8 different species. These included the Cuban dogfish, Squalus cubensis, the bigeye sixgill shark, Hexanchus nakamurai, the bluntnose sixgill shark, Hexanchus griseus, the smooth dogfish, Mustelus canis insularis, the roughskin dogfish, Centroscymnus owstoni, Springer's sawtail catshark, Galeus springeri and the false catshark, Pseudotriakis microdon. Preliminary genetic analysis indicated two or more species of gulper sharks, Centrophorus spp.; however, for the present study they were treated as a single species complex. Water depth and distance from the rocky structure of the Exuma Sound wall were inversely correlated with species richness, whereas seabed temperature was directly correlated with species richness. These variables also had a significant influence on the abundance and distribution of many species. Expanded depth ranges were established for S. cubensis and H. nakamurai, which, in the case of S. cubensis, is thought to be driven by thermal preferences. At-vessel mortality rates increased significantly with depth, and post-release mortality was thought to be high for some species, in part due to high post-release predation. This study highlights the importance of utilising strategic geographic locations that provide easy access to deep water, in combination with traditional expedition-based deep-ocean science, to accelerate the acquisition of fundamental ecological and biological insights into deep-sea elasmobranchs.

  4. The Mediterranean deep-water kelp Laminaria rodriguezii is an endangered species in the Adriatic Sea.

    PubMed

    Žuljević, Ante; Peters, Akira F; Nikolić, Vedran; Antolić, Boris; Despalatović, Marija; Cvitković, Ivan; Isajlović, Igor; Mihanović, Hrvoje; Matijević, Slavica; Shewring, Dawn M; Canese, Simonepietro; Katsaros, Christos; Küpper, Frithjof C

    Deep-water kelps are little-known large brown algae occurring close to the lower limit of photosynthetic life in the sea. This study compares historical and recent records of the deep-water Mediterranean kelp Laminaria rodriguezii in the Adriatic Sea. Historical records include data from herbarium collections and trawling fishery expeditions in the mid-twentieth century, while recent data comprise records of the last 17 years from MEDITS expeditions, ROV surveys of historical kelp locations, benthic surveys and records by fishermen. Altogether, these findings demonstrate that the Adriatic population of L. rodriguezii has suffered a decline of more than 85 % of its historical range and is now present only around the small offshore island of Palagruža. Bottom trawling activities are presumably responsible for the disappearance elsewhere. We propose to classify L. rodriguezii as "Endangered" in the Adriatic Sea under IUCN criteria B1ab(i,iii,iv), ver 3.1. Oceanographic characteristics of the habitat suggest that besides high water transparency, presence of North Adriatic Dense Water with both strong currents and stable low temperatures of around 14 °C are essential oceanographic factors for the development of L. rodriguezii in the Central Adriatic. The origin of cold water thus differs from that at upwelling sites permitting populations of tropical deep-water kelps. The phylogenetic position of L. rodriguezii is so far unknown. DNA sequences from nuclear and cytoplasmic markers of two thalli from Croatia and the western Mediterranean confirmed that L. rodriguezii is a member of the Laminariaceae and most closely related to L. ochroleuca, L. pallida and the Brazilian deep-water kelp L. abyssalis.

  5. Possible deep-water gas hydrate accumulations in the Bering Sea

    USGS Publications Warehouse

    Barth, Ginger A.; Scholl, David W.; Childs, Jonathan R.

    2006-01-01

    Seismic reflection images from the deep-water Aleutian and Bowers Basins of the Bering Sea contain many hundreds of acoustic Velocity-AMPlitude (VAMP) anomalies, each of which may represent a large accumulation of natural gas hydrate. Against a backdrop of essentially horizontal sedimentary reflections, the VAMP anomalies stand out as both high-amplitude bright spots and zones of vertically aligned horizon distortions. The VAMPs are interpreted as natural gas chimneys overlain by concentrated hydrate caps.

  6. Spatial correlation of the high intensity zone in deep-water acoustic field

    NASA Astrophysics Data System (ADS)

    Li, Jun; Li, Zheng-Lin; Ren, Yun

    2016-12-01

    The spatial correlations of acoustic field have important implications for underwater target detection and other applications in deep water. In this paper, the spatial correlations of the high intensity zone in the deep-water acoustic field are investigated by using the experimental data obtained in the South China Sea. The experimental results show that the structures of the spatial correlation coefficient at different ranges and depths are similar to the transmission loss structure in deep water. The main reason for this phenomenon is analyzed by combining the normal mode theory with the ray theory. It is shown that the received signals in the high intensity zone mainly include one or two main pulses which are contributed by the interference of a group of waterborne modes with similar phases. The horizontal-longitudinal correlations at the same receiver depth but in different high intensity zones are analyzed. At some positions, more pulses are received in the arrival structure of the signal due to bottom reflection and the horizontal-longitudinal correlation coefficient decreases accordingly. The multi-path arrival structure of receiving signal becomes more complex with increasing receiver depth. Project supported by the National Natural Science Foundation of China (Grant Nos. 11434012 and 41561144006).

  7. Rapid vertical mixing rates in deep waters of the Andaman Basin.

    PubMed

    Dutta, Koushik; Bhushan, Ravi; Somayajulu, B L K

    2007-10-01

    The Andaman Basin is an enclosed region in the northeastern Indian Ocean with its deep water below approximately 1800 m almost isolated with respect to horizontal ventilation by the Andaman-Nicobar Islands separating it from the Bay of Bengal. The physical and chemical properties including radiocarbon ((14)C) measured at two stations of the Andaman Basin show negligible variation with depth in the waters below 1300 m, indicating a well-mixed water mass. This study attempts to derive the mixing rates for deep waters of the Andaman Basin. Model calculations based on (14)C profile measurements indicate rapid vertical mixing (vertical advection velocity, w>200 m year(-1)) in waters deeper than 1800 m of the basin. For a basin with deep water thickness of 1000 m below 1800 m, deduced mixing rate of >200 m year(-1) translates to mixing time of <5 years. As shown for other regions, the possible mechanism responsible for such high vertical mixing rates could be the internal waves generated from tidal currents flowing through rough topography. In addition, Andaman Basin is underlain with a young crust and is known for its high heat flow, which also could contribute to the high vertical mixing.

  8. Depositional architecture and evolution of inner shelf to shelf edge delta systems since the Late Oliocene and their respone to the tectonic and sea level change, Pear River Mouth Basin, northern South China Sea

    NASA Astrophysics Data System (ADS)

    Lin, Changsong; Zhang, Zhongtao; liu, Jingyan; Jiang, Jing

    2016-04-01

    The Pear River Mouth Basin is located in the northern continent margin of the South China Sea. Since the Late Oligocene, the long-term active fluvial systems (Paleo-Zhujiang) from the western basin margin bebouched into the northern continental margin of the South China Sea and formed widespread deltaic deposits in various depositional geomorphologies and tectonic settings. Based of integral analysys of abundant seismic, well logging and drilling core data, Depositional architecture and evolution of these delta systems and their respone to the tectonic and sea level change are documented in the study. There are two basic types of the delta systems which have been recognized: inner shelf delta deposited in shallow water enviroments and the outer shelf or shelf-edge delta systems occurred in deep water settings. The paleowater depths of these delta systems are around 30 to 80m (inner shelf delta) and 400-1000m (shelf-edge delta) estimated from the thickness (decompaction) of the delta front sequences. The study shows that the inner shelf delta systems are characterized by relatively thin delta forests (20-40m), numereous stacked distributary channel fills, relative coarse river mouth bar deposits and thin distal delta front or distal bar and prodelta deposits. In contrast, the outer shelf or shelf edge delta systems are characteristic of thick (300-800m) and steep (4-60) of deltaic clinoforms, which commonly display in 3D seismic profiles as "S" shape reflection. Large scale soft-sediment deformation structures, slump or debris flow deposits consisting mainly of soft-sediment deformed beds, blocks of sandstones and siltstones or mudstones widely developed in the delta front deposits. The shelf edge delta systems are typically associated with sandy turbidite fan deposits along the prodelta slopes, which may shift basinwards as the progradation of the delta systems. The delta systems underwent several regional cycles of evolution from inner shelf deltas to shelf edge

  9. CHARACTERIZING NATURAL GAS HYDRATES IN THE DEEP WATER GULF OF MEXICO: APPLICATIONS FOR SAFE EXPLORATION AND PRODUCTION ACTIVITIES

    SciTech Connect

    Steve Holditch; Emrys Jones

    2003-01-01

    In 2000, Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deepwater portions of the Gulf of Mexico. A Joint Industry Participation (JIP) group was formed in 2001, and a project partially funded by the U.S. Department of Energy (DOE) began in October 2001. The primary objective of this project is to develop technology and data to assist in the characterization of naturally occurring gas hydrates in the deep water Gulf of Mexico (GOM). These naturally occurring gas hydrates can cause problems relating to drilling and production of oil and gas, as well as building and operating pipelines. Other objectives of this project are to better understand how natural gas hydrates can affect seafloor stability, to gather data that can be used to study climate change, and to determine how the results of this project can be used to assess if and how gas hydrates act as a trapping mechanism for shallow oil or gas reservoirs. During the first six months of operation, the primary activities of the JIP were to conduct and plan Workshops, which were as follows: (1) Data Collection Workshop--March 2002 (2) Drilling, Coring and Core Analyses Workshop--May 2002 (3) Modeling, Measurement and Sensors Workshop--May 2002.

  10. Transport of sludge-derived organic pollutants to deep-sea sediments at deep water dump site 106

    USGS Publications Warehouse

    Takada, H.; Farrington, J.W.; Bothner, Michael H.; Johnson, C.G.; Tripp, B.W.

    1994-01-01

    Linear alkylbenzenes (LABs), coprostanol and epi-coprostanol, were detected in sediment trap and bottom sediment samples at the Deep Water Dump Site 106 located 185 km off the coast of New Jersey, in water depths from 2400 to 2900 m. These findings clearly indicate that organic pollutants derived from dumped sludge are transported through the water column and have accumulated on the deep-sea floor. No significant difference in LABs isomeric composition was observed among sludge and samples, indicating little environmental biodegradation of these compounds. LABs and coprostanol have penetrated down to a depth of 6 cm in sediment, indicating the mixing of these compounds by biological and physical processes. Also, in artificially resuspended surface sediments, high concentrations of LABs and coprostanols were detected, implying that sewage-derived organic pollutants initially deposited on the deep-sea floor can be further dispersed by resuspension and transport processes. Small but significant amounts of coprostanol were detected in the sediment from a control site at which no LABs were detected. The coprostanol is probably derived from feces of marine mammals and sea birds and/or from microbial or geochemical transformations of cholesterol. Polcyclic aromatic hydrocarbons (PAHs) in sediment trap samples from the dump site were largely from the sewage sludge and had a mixed petroleum and pyrogenic composition. In contrast, PAHs in sediments in the dump site were mainly pyrogenic; contributed either from sewage sludge or from atmospheric transport to the overlying waters. & 1994 American Chemical Society.

  11. CHARACTERIZING NATURAL GAS HYDRATES IN THE DEEP WATER GULF OF MEXICO: APPLICATIONS FOR SAFE EXPLORATION AND PRODUCTION ACTIVITIES

    SciTech Connect

    Steve Holditch; Emrys Jones

    2003-01-01

    In 2000, Chevron began a project to learn how to characterize the natural gas hydrate deposits in the deepwater portions of the Gulf of Mexico. A Joint Industry Participation (JIP) group was formed in 2001, and a project partially funded by the U.S. Department of Energy (DOE) began in October 2001. The primary objective of this project is to develop technology and data to assist in the characterization of naturally occurring gas hydrates in the deep water Gulf of Mexico (GOM). These naturally occurring gas hydrates can cause problems relating to drilling and production of oil and gas, as well as building and operating pipelines. Other objectives of this project are to better understand how natural gas hydrates can affect seafloor stability, to gather data that can be used to study climate change, and to determine how the results of this project can be used to assess if and how gas hydrates act as a trapping mechanism for shallow oil or gas reservoirs. During April-September 2002, the JIP concentrated on: Reviewing the tasks and subtasks on the basis of the information generated during the three workshops held in March and May 2002; Writing Requests for Proposals (RFPs) and Cost, Time and Resource (CTRs) estimates to accomplish the tasks and subtasks; Reviewing proposals sent in by prospective contractors; Selecting four contractors; Selecting six sites for detailed review; and Talking to drill ship owners and operators about potential work with the JIP.

  12. Stratigraphic hierarchy of organic carbon rich siltstones in deep-water facies, Brushy Canyon Formation (Guadalupian), Delaware Basin, West Texas

    NASA Astrophysics Data System (ADS)

    Sageman, Bradley B.; Gardner, Michael H.; Armentrout, John M.; Murphy, Adam E.

    1998-05-01

    The first systematic test for a predictive relationship between organic carbon content and stratigraphic hierarchy in a deep-water slope to basin-floor deposit was performed. The studied section includes the Pipeline Shale, the Brushy Canyon Formation, and the lower part of the Cherry Canyon Formation of the Delaware Mountain Group, West Texas. This interval represents one large-scale, 3rd-order genetic sequence within which 4th- and 5th-order stratigraphic cycles are recognized. Samples of fine-grained facies throughout the section were collected from outcrop and analyzed for organic carbon content and hydrogen index. Degree of pyritization was also determined for a subset of the samples. The results indicate that organic enrichment is closely correlated to the stratigraphic hierarchy at the 3rd-, 4th-, and 5th-order levels. The data suggest that quantity and quality of preserved organic matter are controlled by changes in bulk sedimentation rate (dilution vs. condensation), which affect organic matter inputs to the sediment, as well as the balance between (1) burial and preservation of organic matter and (2) its degradation on the sea floor during times of sediment starvation.

  13. Inter-annual variability and potential for selectivity in the diets of deep-water Antarctic echinoderms

    NASA Astrophysics Data System (ADS)

    Wigham, B. D.; Galley, E. A.; Smith, C. R.; Tyler, P. A.

    2008-11-01

    The continental shelf of the West Antarctic Peninsula (WAP) is a highly productive region but also unusually deep as a result of isostatic depression by the polar ice cap. The close coupling of surface processes with those of the benthos would be expected in such a seasonally variable environment; however, the cold, deep conditions of the WAP shelf may allow for the persistence of organic material in the sediments as a "food bank". Chlorophyll and carotenoid pigments were determined from the gut contents of seven species of echinoderm and from the surficial sediment on the bathyal continental shelf. Samples were collected as part of the FOODBANCS programme during successive cruises in austral spring (October 2000) and austral autumn (March 2001). Pigments were identified and quantified using reverse-phase high-performance liquid chromatography (HPLC). A lack of qualitative selectivity was observed among species, compared to that observed for deep-water assemblages at temperate latitudes, supporting the theory of a persistent "food bank". However, significant quantitative differences were observed among species and between years and sampling location on the shelf. Species differences were marked between those we classified as "true" deposit feeders and those species whose diet also may be supplemented by scavenging and/or grazing.

  14. Detection and Characterization of Deep Water Wave Breaking Using Moderate Incidence Angle Microwave Backscatter from the Sea Surface

    DTIC Science & Technology

    1990-06-01

    with the detected events. (A discussion of the distribution of Fmax follows in the next section.) These plots confirm that very few non-breaking waves ...8217 and 0 Oceanographic Engineering 1930 DOCTORAL DISSERTATION Detection and Characterization of Deep Water Wave Breaking Using Moderate Incidence...Characterization of Deep Water Wave Breaking Using Moderate Incidence Angle Microwave Backscatter from the Sea Surface by -- Andrew Thomas Jessup ,. D, Woods

  15. 240Pu/239Pu isotopic ratios and 239 + 240Pu total measurements in surface and deep waters around Mururoa and Fangataufa atolls compared with Rangiroa atoll (French Polynesia).

    PubMed

    Chiappini, R; Pointurier, F; Millies-Lacroix, J C; Lepetit, G; Hemet, P

    1999-09-30

    The average values of 240Pu/239Pu mass isotopic ratios of plutonium deposited in Mururoa and Fangataufa atoll sediments by French atmospheric nuclear tests range from 3.5 to 5%. In order to assess the near field and far field influence of those deposits in the open ocean, two water profiles were measured for 239 + 240Pu and 240Pu/239Pu using, for the first time, an Inductively Coupled Plasma Mass Spectrometer which was developed to achieve femtogram detection limits. One site was located at the limit of the French territorial waters, which is 22 km distant from Mururoa. The second site was located close to Rangiroa atoll, at a distance of approximately 1200-km from French nuclear test sites. The sample volumes were approximately 500 litres and plutonium was purified prior to mass spectrometry and alpha spectrometry measurements. In Rangiroa, the 239 + 240Pu profile is comparable with those already determined in world open oceans but the maximum detected activity, 9 mBq/m3 at 500-600 m is a lot lower than those measured in the northern hemisphere. 240Pu/239Pu ratios were measured between 500 and 1000 m and were not statistically different from the typical 0.18 +/- 0.01 ratio which characterises the global fallout. Consequently, any influence of plutonium from the tests in Mururoa and Fangataufa is not apparent at Rangiroa. The vertical distribution of 239 + 240Pu near Mururoa shows similar changes with depth but with a slight increase in concentration. 240Pu/239Pu mass ratios vary with depth, from 7 to 10% in the upper 500 m and in the deep waters (below 1000 m) to 15-16% between 600 and 1000 m. A contribution from plutonium deposited in the sediments at Mururoa and Fangataufa is observed at the limit of territorial waters, especially in surface and deep waters.

  16. Bearing splitting and near-surface source ranging in the direct zone of deep water

    NASA Astrophysics Data System (ADS)

    Wu, Jun-Nan; Zhou, Shi-Hong; Peng, Zhao-Hui; Zhang, Yan; Zhang, Ren-He

    2016-12-01

    Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a bearing-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz-360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The bearing-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations. Project supported by the Program of One Hundred Talented People of the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant Nos. 11434012 and 41561144006).

  17. Response of South Atlantic deep waters to deglacial warming during Terminations V and I

    NASA Astrophysics Data System (ADS)

    Vázquez Riveiros, Natalia; Waelbroeck, Claire; Skinner, Luke; Roche, Didier M.; Duplessy, Jean-Claude; Michel, Elisabeth

    2010-10-01

    New deep-sea core data from the Atlantic sector of the Southern Ocean, covering MIS12 to MIS10 and the last deglaciation, show a clear lag of the changes in deep water properties with respect to changes in surface conditions. The development of a chronology based on the correlation of Southern Ocean sea surface temperature with air temperature over Antarctica allows the quantification and comparison of phase lags within the marine records during Termination V (TV) and Termination I (TI). Deglacial changes in the South Atlantic are interpreted as the response to changes in the state of the Atlantic meridional ocean circulation (AMOC). The warming of South Atlantic surface waters and air temperature over Antarctica at the beginning of both TV and TI is attributable to a reduction in interhemispheric heat transport due to the weakening of the AMOC. Comparison of our results with CLIMBER-2 simulations indicates that the response of bottom waters seen in the benthic isotopic records, delayed with respect to South Atlantic surface warming, can be explained by the increased inflow of North Atlantic Deep Water (NADW) to the South Atlantic site at the time of the AMOC recovery. Reconstructed sea surface temperature at our South Atlantic site exhibits a cold spell at the end of TV, resembling the Antarctic Cold Reversal of the last deglaciation. The presence of cold spells during TV and TI may be explained by the fact that the recovery of the AMOC took place early during the termination in both cases. The sequence of events is similar during both terminations; however, the magnitude of the phase shifts between South Atlantic surface and deep waters conditions differs from one termination to the other, suggesting variations in the magnitude and duration of the AMOC perturbation.

  18. Asymmetric oceanic response to a hurricane: Deep water observations during Hurricane Isaac

    NASA Astrophysics Data System (ADS)

    Spencer, Laura J.; DiMarco, Steven F.; Wang, Zhankun; Kuehl, Joseph J.; Brooks, David A.

    2016-10-01

    The eye of Hurricane Isaac passed through the center of an array of six deep water water-column current meter moorings deployed in the northern Gulf of Mexico. The trajectory of the hurricane provided for a unique opportunity to quantify differences in the full water-column oceanic response to a hurricane to the left and right of the hurricane trajectory. Prior to the storm passage, relative vorticity on the right side of the hurricane was strongly negative, while on the left, relative vorticity was positive. This resulted in an asymmetry in the near-inertial frequencies oceanic response at depth and horizontally. A shift in the response to a slightly larger inertial frequencies ˜1.11f was observed and verified by theory. Additionally, the storm passage coincided with an asymmetric change in relative vorticity in the upper 1000 m, which persisted for ˜15 inertial periods. Vertical propagation of inertial energy was estimated at 29 m/d, while horizontal propagation at this frequency was approximately 5.7 km/d. Wavelet analysis showed two distinct subinertial responses, one with a period of 2-5 days and another with a period of 5-12 days. Analysis of the subinertial bands reveals that the spatial and temporal scales are shorter and less persistent than the near-inertial variance. As the array is geographically located near the site of the Deep Water Horizon oil spill, the spatial and temporal scales of response have significant implications for the fate, transport, and distribution of hydrocarbons following a deep water spill event.

  19. Lepidapedon sereti n. sp. (Digenea: Lepidapedidae) in Coelorinchus sereti (Gadiformes: Macrouridae) from deep waters off Vanuatu.

    PubMed

    Bray, Rodney A; Faliex, Elisabeth; Allienne, Jean François; Mouahid, Gabriel

    2013-12-01

    Lepidapedon sereti n. sp. is described from the macrourid Coelorinchus sereti from the deep water off Vanuatu. It is placed in the Elongatum group and Elongatum subgroup. It differs from the other species described in this subgroup by the distinctly dorsally subterminal excretory pore. It also differs from other species in combinations of size, excretory vesicle length, proportions of forebody, post-testicular region and other metric features. This constitutes the first record of a Lepidapedon (sensu stricto) from the Central Western Pacific Ocean.

  20. Dissolved inorganic carbon isotopic composition of the Gulf of Mexico deep-water masses.

    NASA Astrophysics Data System (ADS)

    Quintanilla-Terminel, J. G.; Herguera, J. C.; Ferreira-Bartrina, V.; Hernández-Ayón, J. M.; Camacho-Ibar, V.

    2014-12-01

    This study provides new data for the establishment of a carbon biogeochemical dynamics baseline in the deep Gulf of Mexico (GM) based on carbon isotopes in dissolved inorganic carbon. Water samples from 40 deep-water stations south of 25˚N were collected during XIXIMI-2 cruise, July 2011, aboard BO/Justo Sierra. Vertical profiles of temperature, salinity and dissolved oxygen (DO) were further measured in each station. In the Stable Isotopes Laboratory at CICESE we determined the carbon isotopic composition of the dissolved inorganic carbon (DIC) (δ13CDIC). Remarkably, density, DO and δ13CCID profiles showed a clear difference between the Loop current and the deep-waters of the GM south of 25˚N. We found the following average δ13CCID values in the Loop current and in the deep-waters of the Gulf: subtropical underwater (SUW): 0.73±0.06‰ and 0.86±0.04‰; 18 degree water (18W): 0.76 ± 0.08‰ and 0.58± 0.06‰; North Atlantic central water (NACW): 0.77 ± 0.05‰ and 0.71 ± 0.09‰; South Atlantic central water (SACW): 0.80 ± 0.08‰ and 0.77 ± 0.07‰; Antartic intermediate water (AAIW): 1.00 ± 0.06‰ and 0.90 ± 0.08‰; North Atlantic deep water (NADW): 1.03 ± 0.06‰ and 1.01 ± 0.10‰. We will discuss how the biological component, δ13CCID-BIO, of subsurface water masses match very closely the apparent oxygen utilization relation described by Kroopnick, 1985, with the exception of SUW, and as a consequence the 18W is probably the water mass most affected by organic carbon remineralization processes in the GM south of 25˚N. We further show how these waters seem to store a larger proportion of anthropogenic carbon than the deeper water masses.

  1. AUV Reveals Deep-Water Coral Mound Distribution, Morphology and Oceanography in the Florida Straits

    NASA Astrophysics Data System (ADS)

    Grasmueck, M.; Eberli, G. P.; Viggiano, D. A.; Correa, T.; Rathwell, G.; Luo, J.

    2006-12-01

    Since the 1960's dredge sampling and submersible dives have discovered numerous mound-forming deep- water corals in water depths of 400-800 m in the Straits of Florida. This extensive collection of samples and observations however can not be put into a geomorphologic context as existing bathymetric charts do not resolve coral mounds. To make progress in understanding the distribution and genesis of coral mounds, maps of morphology and oceanographic conditions resolving features at the 1-10 m scale are needed. On 11-18 December 2005 the C-Surveyor II(TM) mapped five sites ranging from 14-48 km2 in 590-875 m water acquiring 1-3 m resolution bathymetry and acoustic backscatter together with subbottom profiles, current vectors, salinity, and temperature. The areas mapped with the AUV contain hundreds of coral mounds with heights of 1-120 m. Mound distribution, morphology and currents are different for each survey site. Coral mounds develop on off-bank transported sediment ridges and slump features at the toe-of-slope of Great Bahama bank, while chevron pattern ridges and sinusoidal ridges are found further east in the Straits. Currents range from 0.1-0.5 m/s. At two sites currents reversed every 6 hours indicating tidal control. The AUV surveys and subsequent ground truthing with a drop camera and a submersible revealed a surprising abundance and diversity of deep-water coral habitats. The boundaries between mound fields and the barren muddy or sandy seafloor are sharp. Hull- mounted multi-beam reconnaissance mapping helped us select the most promising coral mound areas to optimize the use of valuable AUV time. Such combined use of hull-mounted and AUV-based mapping enables efficient environmental characterization of large deep-water regions such as the Florida Straits. The synoptic high-resolution datasets acquired by the multiple sensors on board the AUV enable for the first time a comprehensive assessment of deep-water coral mound ecosystems. Utilization of such

  2. Gulf Coast Deep Water Port Facilities Study. Appendix C. Eastern Gulf Hydrobiological Zones.

    DTIC Science & Technology

    1973-04-01

    namely, activities regarding deep water ports including those for oil tankers). However, there are local populations, particularly in coastal zones...to eutrophication , pesticides. and petrochemical loads present in sediments. The Pensacola-Escamnbia-East BaY stsem has been gnrel ’re damaged. About...River 671 646.4 Palm River 62 45.2 Alatia River 384 418.2 Additional Area -92.6 Lower Tampa Bay 2.0- 2.3 Little Manatee River 186 205.2 Manatee River

  3. Seismic characterization of deep-water pipe structures in the Levant Basin, SE Mediterranean

    NASA Astrophysics Data System (ADS)

    Eruteya, Ovie Emmanuel; Waldmann, Nicolas; Schalev, Dagan; Makovsky, Yizhaq; Ben-Avraham, Zvi

    2015-04-01

    Analysis of a new deep-water (1100 m - 1500 m) high resolution 3D seismic dataset covering part of the central Levant Basin, offshore Israel reveals previously undocumented evidences for subsurface fluid flow in the post-Messinian overburden manifested as pipe structures. Interestingly, these pipe structures are genetically and spatially contextualized east and west of the study area, all emanating from the Messinian evaporite substratum. Pipes in the western group accounts for 83% of the pipe population, are crudely cylindrical, oval to elliptical in planform, with diameter and height ranging ca. 350 m - 2000 m and 320 m - 420 m, respectively. Internal configuration within this group varies from chaotic to concave upward reflections diagnostic of fluid induced collapse. Pipes in the eastern group are seepage pipes appearing conical in shape, with height of ~350 m - 510 m and diameter of 320 m - 420 m. The western group indicates an episode of fluid flow till the mid-Pliocene, compared to late Pliocene in the eastern group where successive mass wasting events during the late Pliocene plugged piping. A conceptual model for the pipes in the western group is proposed to have occurred from subjacent dissolution of the Messinian evaporite under deep-water marine conditions during the Pliocene by vertically focused fluid flow from intra-Messinian realm dissolving the top evaporites and inducing systematic collapse in the overburden. The onset of which may have been triggered by seismicity. Conversely, pipes in the eastern group are proposed to develop from breaching the top evaporite by pressurized fluids that developed from lateral pressure transfer due to differential loading of the overburden and salt tectonics. Most likely, these fluids are biogenic gas since the major gas fields in deep-waters offshore Israel and close to the study area are of this composition. The pipe structures identified in the study area extend the current understanding of fluid flow subsequent

  4. Cathodic protection survey of deep-water structures and subsea installations

    SciTech Connect

    Leask, L.J. )

    1989-11-01

    The successful and efficient cathodic protection (CP) survey of a deep water structure using a remotely operated vehicle (ROV) has remained an enigma to many corrosion engineers in oil companies. The location of the corrosion group within the company structure often plays a major role in the success of the project. Operators locate their corrosion departments in different groups, some in the offshore/onshore operations and others in the design group. This location often has a bearing on the financial and operational approach to the project. The author discusses how a successful CP survey is both an achievable and exciting project with experienced preplanning and selection of the correct equipment.

  5. CP survey of deep water structures and subsea installations using an ROV

    SciTech Connect

    Leask, L.J. )

    1989-01-01

    The successful and efficient CP survey of a deep water structure using a remotely operated vehicle (ROV) has remained an enigma to many corrosion engineers in oil companies. The location of the corrosion group within the company structure often plays a major role in the success of the project. Operators locate their corrosion departments in different groups, some in the offshore/onshore operations and others in the design group. This location often has a bearing on the financial and operational approach to the project. This paper discusses how a successful CP survey is both an achievable and exciting project with experienced pre- planning and selection of the correct equipment.

  6. Lower Paleozoic deep-water facies of the Medfra area, central Alaska: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1997

    USGS Publications Warehouse

    Dumoulin, Julie A.; Bradley, Dwight C.; Harris, Anita G.; Repetski, John E.

    1999-01-01

    Deep-water facies, chiefly hemipelagic deposits and turbidites, of Cambrian through Devonian age are widely exposed in the Medfra and Mt. McKinley quadrangles. These strata include the upper part of the Telsitna Formation (Middle-Upper Ordovician) and the Paradise Fork Formation (Lower Silurian-Lower Devonian) in the Nixon Fork terrane, the East Fork Hills Formation (Upper Cambrian-Lower Devonian) in the East Fork subterrane of the Minchumina terrane, and the chert and argillite unit (Ordovician) and the argillite and quartzite unit (Silurian- Devonian? and possibly older) in the Telida subterrane of the Minchumina terrane.In the western part of the study area (Medfra quadrangle), both hemipelagic deposits and turbidites are largely calcareous and were derived from the Nixon Fork carbonate platform. East- ern exposures (Mt. McKinley quadrangle; eastern part of the Telida subterrane) contain much less carbonate; hemipelagic strata are mostly chert, and turbidites contain abundant rounded quartz and lesser plagioclase and potassium feldspar. Deep-water facies in the Medfra quadrangle correlate well with rocks of the Dillinger terrane exposed to the south (McGrath quadrangle), but coeval strata in the Mt. McKinley quadrangle are compositionally similar to rocks to the northeast (Livengood quadrangle). Petrographic data thus suggest that the Telida subterranes presently defined is an artificial construct made up of two distinct sequences of disparate provenance.Restoration of 90 and 150 km of dextral strike-slip on the Iditarod and Farewell faults, respectively, aligns the deep-water strata of the Minchumina and Dillinger terranes in a position east of the Nixon Fork carbonate platform. This restoration supports the interpretation that lower Paleozoic rocks in the Nixon Fork and Dillinger terranes, and in the western part of the Minchumina terrane (East Fork subterrane and western part of the Telida subterrane), formed along a single continental margin. Rocks in the

  7. The tectono-stratigraphic evolution of basement highs in hyper extended deep-water rifted margins : the example of the Briançonnais domain in the Alps and comparisons with modern analogues

    NASA Astrophysics Data System (ADS)

    Haupert, Isabelle; Manatschal, Gianreto; Unternehr, Patrick; Decarlis, Alessandro

    2013-04-01

    The discovery of hydrocarbon systems in hyper-extended deep-water rifted margins, in conjunction with technical developments, expanded the hydrocarbon exploration into domains that are yet little investigated. The increasing number of high-quality reflection and refraction seismic surveys and drill hole data show that deep-water rifted margins are very different from proximal rifted margins. The new data show evidence for a polyphase rift evolution resulting in complex rift architectures with variable amounts of magmatic addition and local mantle exhumation that cannot be predicted by classical rift models. Thus, understanding the thermal structure, subsidence history, depositional environment and sedimentary architecture is a prerequisite to apply the "play elements" in these yet little investigated domains, which is essential to evaluate the survivability of syn- to post-rift petroleum systems. Although a big progress was made in the understanding of deep water rifted margins in the last 5 years, there are still many fundamental questions that remain open and ask for further research on this topic. One open scientific question is related to the tectono-sedimentary evolution and subsidence history of basement highs in deep water rifted margins. Péron-Pinvidic and Manatschal (2010) showed that different types of basement highs can be distinguished in rifted margins. These highs include micro-continents, continental ribbons, H-blocks and extensional allochthons. Mapping these highs and properly define their stratigraphic and tectonic evolution provide important insights into the tectonic evolution of rifted margins. However, these blocks are often at deep-water and sealed by thick post-rift sediments. Therefore access to direct observations requires expensive drillings. An alternative way to study these blocks is to use field analogues. One of which is the Briançonnais domain in the Alps. To achieve our goal we propose to review the existing structural

  8. Deep-water running: a practical review of the literature with an emphasis on biomechanics.

    PubMed

    Killgore, Garry L

    2012-02-01

    Deep-water running (DWR) is used as an adjunct to training and conditioning, and as an injury-rehabilitation technique. It is important for the physician or sports medicine practitioner to focus on the underlying physics and biomechanics of running in water in order to better produce the desired physiological, metabolic, and psychological outcomes. Deep-water running maximal heart rate and oxygen consumption values have been consistently shown to be lower than those found during treadmill running. However, recent evidence reveals that there is less of a difference between these maximal values relative to treadmill running and DWR with increased DWR experience. Submaximal values have been shown to be strikingly similar. The skill level of DWR technique, psychological comfort, perception of work, muscular recruitment patterns, and running kinematics are all affected by the physics (ie, temperature, buoyancy, hydrostatic pressure, specific gravity, and drag) of running in water. Therefore, the relationship between the biomechanics and the corollary practical physiological indicators of workload found in DWR must be factored into the appropriate prescription of training and conditioning workloads and rehabilitation protocols.

  9. Synchronous deglacial thermocline and deep-water ventilation in the eastern equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Umling, Natalie E.; Thunell, Robert C.

    2017-01-01

    The deep ocean is most likely the primary source of the radiocarbon-depleted CO2 released to the atmosphere during the last deglaciation. While there are well-documented millennial scale Δ14C changes during the most recent deglaciation, most marine records lack the resolution needed to identify more rapid ventilation events. Furthermore, potential age model problems with marine Δ14C records may obscure our understanding of the phase relationship between inter-ocean ventilation changes. Here we reconstruct changes in deep water and thermocline radiocarbon content over the last deglaciation in the eastern equatorial Pacific (EEP) using benthic and planktonic foraminiferal 14C. Our records demonstrate that ventilation of EEP thermocline and deep waters occurred synchronously during the last deglaciation. In addition, both gradual and rapid deglacial radiocarbon changes in these Pacific records are coeval with changes in the Atlantic records. This in-phase behaviour suggests that the Southern Ocean overturning was the dominant driver of changes in the Atlantic and Pacific ventilation during deglaciation.

  10. A new deep-water goatfish of the genus Upeneus (Mullidae) from Vanuatu, South Pacific.

    PubMed

    Uiblein, Franz; Causse, Romain

    2013-01-01

    A new goatfish, Upeneus vanuatu (Mullidae), is described based on five specimens collected off two islands of Vanuatu (South Pacific), at depths of 191-321 m, and compared with five closely related species: Upeneus davidaroni (Red Sea), U. mascareinsis (Western Indian Ocean), U. stenopsis (northern Australia, Philippines, 127-275 m), and the more shallow-occurring Indo-West Pacific species U. subvittatus (26-120 m) and U. vittatus (deep-water Upeneus species, the so-called "stenopsis" species group can be distinguished from four other species groups that were established in earlier studies in order to facilitate intrageneric comparisons. The ecological and evolutionary significance of deep-water goatfishes is briefly discussed.

  11. Use of deep water lagoons for reducing sewage toxicity prior to wastewater treatment

    SciTech Connect

    Shaw, J.R.; Zuiderveen, J.A.; Belcher, B.; McGinley, P.; Birge, W.J.

    1994-12-31

    Investigations were conducted to determine the effectiveness of deep lagoons as a means of wastewater pretreatment. A lagoon system associated with a wastewater treatment plant (WWTP) was selected for study and parameters identified for monitoring included toxicity, metals, total suspended solids (TSS) and ammonia. This system included two lagoons, with 7--15 day hydraulic retention times, fed sequentially with untreated water. Toxicity and other parameters were measured for raw influent water, the two lagoon outfalls, and the final WWTP effluent. In seven-day chronic tests with Ceriodaphnia dubia, the NOEC of influent water was as low as 20%, and 100% mortality occurred at 40%. Outfall from the first deep water lagoon showed reduced toxicity. The NOEC was > 50% but complete mortality occurred in undiluted effluent. Further reduction in toxicity occurred in the second lagoon. Its undiluted effluent had no effect on survival, but did markedly reduce fecundity. The final effluent discharged from the treatment plant affected neither survival nor fecundity. Results of this investigation support the use of deep water lagoons as an effective and economical means of pretreating wastewater. This approach offers promise for municipal waters, industrial effluents and stormwater runoff.

  12. Vertical distribution of a deep-water moss and associated epiphytes in Crater Lake, Oregon

    USGS Publications Warehouse

    McIntire, C.D.; Phinney, H.K.; Larson, Gary L.; Buktenica, M.W.

    1994-01-01

    A one-person submersible was used to examine the vertical distribution of the deep-water moss Drepanocladus aduncus (Hedw.) Warnst in Crater Lake (Oregon). Living specimens were found attached to sediment and rocks at depths between 25 m and 140 m. Dense beds of the moss were observed at depths between 30 m and 80 m, a region that corresponded roughly to the zone of maximum primary production by phytoplankton. The moss population supported a diverse assemblage of epiphytic algae, of which the most abundant genera included Cladophora,Oedogonium, Rhizoclonium, Tribonema, Vaucheria, and the diatoms Cocconeis, Cymbella, Epithemia, Fragilaria, Gomphonema, Melosira, Navicula, and Synedra. Chemical and physical data supported the hypothesis that the lower limit of distribution of the moss is determined by light limitation, whereas the upper limit is related to the availability of nutrients, particularly nitrate-nitrogen and trace elements. Deep-water videotapes of the moss population indicated that D. aduncus with its epiphytic algae was abundant enough in regions associated with the metalimnion and upper hypolimnion to have a potential influence on the nutrient dynamics of the Crater Lake ecosystem. Although the maximum depth at which living bryophytes occur in Crater Lake is similar to that found for Lake Tahoe, conditions in Lake Tahoe allow the growth and survival of a much more diverse assemblage of bryophytes and charophytes than is present in Crater Lake.

  13. Atlantic Deep-water Response to the Early Pliocene Shoaling of the Central American Seaway.

    PubMed

    Bell, David B; Jung, Simon J A; Kroon, Dick; Hodell, David A; Lourens, Lucas J; Raymo, Maureen E

    2015-07-20

    The early Pliocene shoaling of the Central American Seaway (CAS), ~4.7-4.2 million years ago (mega annum-Ma), is thought to have strengthened Atlantic Meridional Overturning Circulation (AMOC). The associated increase in northward flux of heat and moisture may have significantly influenced the evolution of Pliocene climate. While some evidence for the predicted increase in North Atlantic Deep Water (NADW) formation exists in the Caribbean and Western Atlantic, similar evidence is missing in the wider Atlantic. Here, we present stable carbon (δ(13)C) and oxygen (δ(18)O) isotope records from the Southeast Atlantic-a key region for monitoring the southern extent of NADW. Using these data, together with other δ(13)C and δ(18)O records from the Atlantic, we assess the impact of the early Pliocene CAS shoaling phase on deep-water circulation. We find that NADW formation was vigorous prior to 4.7 Ma and showed limited subsequent change. Hence, the overall structure of the deep Atlantic was largely unaffected by the early Pliocene CAS shoaling, corroborating other evidence that indicates larger changes in NADW resulted from earlier and deeper shoaling phases. This finding implies that the early Pliocene shoaling of the CAS had no profound impact on the evolution of climate.

  14. Synchronous deglacial thermocline and deep-water ventilation in the eastern equatorial Pacific

    PubMed Central

    Umling, Natalie E.; Thunell, Robert C.

    2017-01-01

    The deep ocean is most likely the primary source of the radiocarbon-depleted CO2 released to the atmosphere during the last deglaciation. While there are well-documented millennial scale Δ14C changes during the most recent deglaciation, most marine records lack the resolution needed to identify more rapid ventilation events. Furthermore, potential age model problems with marine Δ14C records may obscure our understanding of the phase relationship between inter-ocean ventilation changes. Here we reconstruct changes in deep water and thermocline radiocarbon content over the last deglaciation in the eastern equatorial Pacific (EEP) using benthic and planktonic foraminiferal 14C. Our records demonstrate that ventilation of EEP thermocline and deep waters occurred synchronously during the last deglaciation. In addition, both gradual and rapid deglacial radiocarbon changes in these Pacific records are coeval with changes in the Atlantic records. This in-phase behaviour suggests that the Southern Ocean overturning was the dominant driver of changes in the Atlantic and Pacific ventilation during deglaciation. PMID:28112161

  15. Study on dynamic characteristics of coupled model for deep-water lifting system

    NASA Astrophysics Data System (ADS)

    Wu, Yunxia; Lu, Jianhui; Zhang, Chunlei

    2016-10-01

    The underwater installation of marine equipment in deep-water development requires safe lifting and accurate positioning. The heave compensation system is an important technology to ensure normal operation and improve work accuracy. To provide a theoretical basis for the heave compensation system, in this paper, the continuous modeling method is employed to build up a coupled model of deep-water lifting systems in vertical direction. The response characteristics of dynamic movement are investigated. The simulation results show that the resonance problem appears in the process of the whole releasing load, the lifting system generates resonance and the displacement response of the lifting load is maximal when the sinking depth is about 2000 m. This paper also analyzes the main influencing factors on the dynamic response of load including cable stiffness, damping coefficient of the lifting system, mass and added mass of lifting load, among which cable stiffness and damping coefficient of the lifting system have the greatest influence on dynamic response of lifting load when installation load is determined. So the vertical dynamic movement response of the load is reduced by installing a damper on the lifting cable and selecting the appropriate cable stiffness.

  16. Impact of deep-water fish farms on benthic macrofauna communities under different hydrodynamic conditions.

    PubMed

    Valdemarsen, Thomas; Hansen, Pia Kupka; Ervik, Arne; Bannister, Raymond J

    2015-12-30

    In this study the environmental impacts of two fish farms located over deep water (180-190 m) were compared. MC-Farm was located at a site with slightly higher water currents (mean current speed 3-5 cms(-1)) than LC-farm (<2 cms(-1)). Macrofauna composition, bioirrigation and benthic fluxes (CO2 and NH4(+)) were quantified at different stages of the production cycle, revealing very different impact of the two farms. Macrofauna abundance and bioirrigation were stimulated compared to a non-impacted reference site at MC-farm, while macrofauna diversity was only moderately reduced. In contrast, macrofauna communities and related parameters were severely impoverished at LC-Farm. This study suggests that deep-water fish farms should not be sited in low current areas (<2 cms(-1)), since this will hamper waste dispersal and aggravate environmental impacts. On the other hand, fish farming at slightly more dynamic sites can lead to stimulated benthic macrofauna communities and only moderate environmental impacts.

  17. Atlantic Deep-water Response to the Early Pliocene Shoaling of the Central American Seaway

    PubMed Central

    Bell, David B.; Jung, Simon J. A.; Kroon, Dick; Hodell, David A.; Lourens, Lucas J.; Raymo, Maureen E.

    2015-01-01

    The early Pliocene shoaling of the Central American Seaway (CAS), ~4.7–4.2 million years ago (mega annum-Ma), is thought to have strengthened Atlantic Meridional Overturning Circulation (AMOC). The associated increase in northward flux of heat and moisture may have significantly influenced the evolution of Pliocene climate. While some evidence for the predicted increase in North Atlantic Deep Water (NADW) formation exists in the Caribbean and Western Atlantic, similar evidence is missing in the wider Atlantic. Here, we present stable carbon (δ13C) and oxygen (δ18O) isotope records from the Southeast Atlantic-a key region for monitoring the southern extent of NADW. Using these data, together with other δ13C and δ18O records from the Atlantic, we assess the impact of the early Pliocene CAS shoaling phase on deep-water circulation. We find that NADW formation was vigorous prior to 4.7 Ma and showed limited subsequent change. Hence, the overall structure of the deep Atlantic was largely unaffected by the early Pliocene CAS shoaling, corroborating other evidence that indicates larger changes in NADW resulted from earlier and deeper shoaling phases. This finding implies that the early Pliocene shoaling of the CAS had no profound impact on the evolution of climate. PMID:26193070

  18. Abrupt changes in the southern extent of North Atlantic Deep Water during Dansgaard-Oeschger events

    NASA Astrophysics Data System (ADS)

    Gottschalk, Julia; Skinner, Luke C.; Misra, Sambuddha; Waelbroeck, Claire; Menviel, Laurie; Timmermann, Axel

    2015-12-01

    The glacial climate system transitioned rapidly between cold (stadial) and warm (interstadial) conditions in the Northern Hemisphere. This variability, referred to as Dansgaard-Oeschger variability, is widely believed to arise from perturbations of the Atlantic Meridional Overturning Circulation. Evidence for such changes during the longer Heinrich stadials has been identified, but direct evidence for overturning circulation changes during Dansgaard-Oeschger events has proven elusive. Here we reconstruct bottom water [CO32-] variability from B/Ca ratios of benthic foraminifera and indicators of sedimentary dissolution, and use these reconstructions to infer the flow of northern-sourced deep water to the deep central sub-Antarctic Atlantic Ocean. We find that nearly every Dansgaard-Oeschger interstadial is accompanied by a rapid incursion of North Atlantic Deep Water into the deep South Atlantic. Based on these results and transient climate model simulations, we conclude that North Atlantic stadial-interstadial climate variability was associated with significant Atlantic overturning circulation changes that were rapidly transmitted across the Atlantic. However, by demonstrating the persistent role of Atlantic overturning circulation changes in past abrupt climate variability, our reconstructions of carbonate chemistry further indicate that the carbon cycle response to abrupt climate change was not a simple function of North Atlantic overturning.

  19. Environmental risk management and preparations for the first deep water well in Nigeria

    SciTech Connect

    Berger, F.

    1996-12-31

    Statoil is among the leaders in protecting health, environment and safety in all aspects of the business. The evaluations of business opportunities and development of blocks opened by authorities for petroleum exploration, are assessed in accordance with the goals for environmental protection. Progressive improvement of environmental performance is secured through proper environmental risk management. In 1995, Statoil, the technical operator on Block 210 off the Nigerian coast, was the first company to drill in deep waters in this area. An exploration well was drilled in a water depth of about 320 meters. The drilling preparations included environmental assessment, drillers Hazop, oil spill drift calculations, oil spill response plans and environmental risk analysis. In the environmental preparations for the well, Statoil adhered to local and national government legislation, as well as to international guidelines and company standards. Special attention was paid to the environmental sensitivity of potentially affected areas. Statoil co-operated with experienced local companies, with the authorities and other international and national oil companies. This being the first deep water well offshore Nigeria, it was a challenge to co-operate with other operators in the area. The preparations that were carried out, will set the standard for future environmental work in the area. Co-operation difficulties in the beginning were turned positively into a attitude to the environmental challenge.

  20. Deep-water fossorial shrimps from the Oligocene Kiscell Clay of Hungary: Taxonomy and palaeoecology

    PubMed Central

    HYŽNÝ, MATÚŠ; DULAI, ALFRÉD

    2015-01-01

    We describe deep-water ghost shrimp assemblages from the otherwise well known Oligocene Kiscell Clay in Hungary. The described fossorial shrimps (Decapoda: Callianassidae and Ctenochelidae) include: Ctenocheles rupeliensis (younger synonym Callianassa nuda) and Lepidophthalmus crateriferus (younger synonym Callianassa brevimanus). The fossil material of the former species is assigned to Ctenocheles based on the morphology of the major cheliped, particularly the pectinate fingers, bulbous propodus, cup-shaped carpus and elongated merus. Lepidophthalmus crateriferus from the Oligocene of Hungary is the first unequivocal fossil record of the genus, which is distinguished in the fossil record on the basis of the presence of a meral blade and meral hook on the major cheliped. Lepidophthalmus is today known exclusively from shallow-water environments. The finding of a deep-water fossil representative of Lepidophthalmus therefore appears to be a reverse of the common pattern of groups shifting environments from onshore to offshore over geological time, as seen in many taxa. The presence of Lepidophthalmus crateriferus comb. nov. in the Kiscell Clay therefore suggests different ecological requirements for at least some populations of this genus in the geological past. PMID:25908897

  1. High Biodiversity on a Deep-Water Reef in the Eastern Fram Strait

    PubMed Central

    Meyer, Kirstin S.; Soltwedel, Thomas; Bergmann, Melanie

    2014-01-01

    We report on the distribution and abundance of megafauna on a deep-water rocky reef (1796–2373 m) in the Fram Strait, west of Svalbard. Biodiversity and population density are high, with a maximum average of 26.7±0.9 species m−2 and 418.1±49.6 individuals m−2 on the east side of the reef summit. These figures contrast with the surrounding abyssal plain fauna, with an average of only 18.1±1.4 species and 29.4±4.3 individuals m−2 (mean ± standard error). The east side of the reef summit, where the highest richness and density of fauna are found, faces into the predominant bottom current, which likely increases in speed to the summit and serves as a source of particulate food for the numerous suspension feeders present there. We conclude that the observed faunal distribution patterns could be the result of hydrodynamic patterns and food availability above and around the reef. To our knowledge, this study is the first to describe the distribution and diversity of benthic fauna on a rocky reef in deep water. PMID:25153985

  2. Changes in the South Pacific deep water Nd isotope composition over the last 140 ka

    NASA Astrophysics Data System (ADS)

    Fröllje, Henning; Basak, Chandranath; Lamy, Frank; Gersonde, Rainer; Ullermann, Johannes; Pahnke, Katharina

    2015-04-01

    The Southern Ocean plays a central role in the global overturning circulation of the ocean through the formation of intermediate and bottom waters and the import and redistribution of deep waters from all major ocean basins that make up Circumpolar Deep Water (CDW). The South Pacific is an ideal location to study the evolution of CDW over the last glacial-interglacial cycles with little direct overprint by fluctuating North Atlantic Deep Water (NADW) input. Here were present a 140ky-long record of neodymium isotope ratios (143Nd/144Nd, expressed as ɛNd) analyzed on fossil fish teeth and debris from sediment core PS75/056-1 (55° 09.74 S, 114° 47.31 W, 3581 m water depth) in the open South Pacific that is bathed today by Lower Circumpolar Deep Water (LCDW) with a small contribution from Pacific Deep Water. The Late Holocene and Marine Isotope Stage (MIS) 5 ɛNd values of -7.5 to -7.7 are close to the modern seawater isotopic composition near the core site [1]. Glacial ɛNd of about -6 is observed during MIS 2 and 6. The decrease in the ɛNd record during the penultimate deglaciation is more gradual compared to that during the last deglaciation and the most negative values of the last interglacial are reached during MIS 5c. The transition from MIS 5 into MIS 4 is characterized by a shift towards more negative ɛNd (-6.5) but full glacial values are not reached. The change to more positive ɛNd at the MIS 4/3 transition is followed by a long-term increase to maximum values reached during the last glacial maximum. The timing of the observed transitions is comparable to a nearby δ13C record (core E11-2) [2] and to published ɛNd records from the deep South Atlantic and Indian Oceans [3, 4]. We observe consistently more positive absolute ɛNd values in the South Pacific compared to the Atlantic. The offset is around one ɛNd unit during cold periods (MIS 2, 4, 6) and 1.5 ɛNd units during the interglacials. During MIS 3, on the other hand, there is little difference

  3. Deep-water carbonate slope failure events in a newly discovered Silurian basin, Blue Ridge province, southern Appalachians, Tennessee

    SciTech Connect

    Unrug, R. )

    1991-03-01

    Siliciclastic deep-water turbidites of the Walden Creek Group, Ocoee Supergroup, underlying the foothills of the Great Smoky Mountains, contain olistolith blocks and olistostromal debris-flow breccia beds. Paleozoic fossils discovered recently in the olistoliths indicate Silurian age of the carbonates. The Walden Creek Group is therefore Silurian or younger, not late Proterozoic in age, as believed previously. The carbonate olistoliths and breccias formed by collapse of post-Taconic Silurian carbonate-dominated basin present in the Blue Ridge province of the Southern Appalachians into the younger basin of the Walden Creek Group. Two modes of occurrence of the olistoliths are present: (1) discrete horizons in which olistoliths are sitting spaced ten to hundreds of meters apart underneath a widespread conglomerate bed and (2) accumulations of olistoliths in localized stacked horizons in the vertical sequence of the enclosing siliciclastic rocks. Both modes can be related to failure of active fault scarps. Rocks of the olistolith are lithologically varied and record an older event of slope failure within the Silurian carbonate-dominated basin. Three facies assemblages representing two sedimentary environments are present in the olistoliths. Facies assemblage A includes oolitic limestone, stromatolite, carbonate breccia encrusted by stromatolite, and massive sandy limestone. It represents a high-energy, shallow-water, carbonate platform environment. Facies assemblage B consists of bedded dark limestone, alternating with black shale, and represents sediments of the carbonate platform slope. Facies assemblage C includes carbonate breccias intercalated in the bedded limestones and shales and is interpreted as deposits of the lower slope formed by failure of the carbonate platform margin.

  4. Evidence for deep-water production in the North Pacific Ocean during the early Cenozoic warm interval.

    PubMed

    Thomas, Deborah J

    2004-07-01

    The deep-ocean circulation is responsible for a significant component of global heat transport. In the present mode of circulation, deep waters form in the North Atlantic and Southern oceans where surface water becomes sufficiently cold and dense to sink. Polar temperatures during the warmest climatic interval of the Cenozoic era (approximately 65 to 40 million years (Myr) ago) were significantly warmer than today, and this may have been a consequence of enhanced oceanic heat transport. However, understanding the relationship between deep-ocean circulation and ancient climate is complicated by differences in oceanic gateways, which affect where deep waters form and how they circulate. Here I report records of neodymium isotopes from two cores in the Pacific Ocean that indicate a shift in deep-water production from the Southern Ocean to the North Pacific approximately 65 Myr ago. The source of deep waters reverted back to the Southern Ocean 40 Myr ago. The relative timing of changes in the neodymium and oxygen isotope records indicates that changes in Cenozoic deep-water circulation patterns were the consequence, not the cause, of extreme Cenozoic warmth.

  5. Increasing presence of Arctic Ocean deep waters in the Greenland Sea

    NASA Astrophysics Data System (ADS)

    Somavilla Cabrillo, Raquel; Schauer, Ursula; Budeus, Gedeon

    2013-04-01

    Deep convection has been known to provide the coldest and freshest waters to the deep Greenland Sea, whose properties are balanced with the advection of warmer and saltier waters from the deep Arctic Ocean. However, during the last three decades, deep convection has come to a halt in the Greenland Sea. As previously reported and updated in this work through the analysis of the free available hydrographic data in the central Greenland Sea and in the Arctic Ocean from 1950 to 2010 (Pangaea and ICES data bases), as a consequence of this, two major hydrographic changes are observed: (1) the appearance and deepening of an intermediate temperature maximum and (2) a continuous warming and saltening of the deep Greenland Sea. The origin of both findings is found in the advection of Arctic Ocean deep waters from the Amerasian and Eurasian basins, respectively, into the central Greenland Sea. Associated to the first, a temperature increase of 0.35° C from 1993 to 2009 is observed at 1700 m. Below 2000 m, the temperature and salinity have increased at a mean rate of 0.136° C/decade and 0.01decade-1 in the last three decades. Overall, the stop of deep convection and the advection of Arctic Ocean deep waters result among the highest deep warming and saltening trends of the World Ocean in the Greenland Sea. In addition to the described update of the state of these changes, two new accomplishments are fulfilled in this study. First, in absence of deep convection, the continuous changing of the thermohaline properties of the deep Greenland Sea requires exchanges with adjacent ocean basins. This scenario enables us the estimation of the necessary transports from the deep Arctic to explain the observed changes. A transport of Eurasian Basin Deep Water of 0.31±0.04 Sv is obtained. Secondly, the warming and saltening of the deep Greenland Sea contributes, as any other ocean basin, to the World Ocean heat content and sea level rise. The estimation of these contributions shows larger

  6. Reconstructing late Quaternary deep-water masses in the eastern Arctic Ocean using benthonic Ostracoda

    USGS Publications Warehouse

    Jones, R. Ll; Whatley, R.C.; Cronin, T. M.; Dowsett, H.J.

    1999-01-01

    The distribution of Ostracoda in three long cores from the deep eastern Arctic Ocean was studied to determine the palaeoceanographical history of the Eurasian Basin during the late Quaternary. The samples for this study were obtained from the Lomonosov Ridge, Morris Jesup Rise and Yermak Plateau during the Arctic 91 expedition. Ostracoda previously studied in coretops at the same sites as the present study have shown that individual species have a strong association with different water masses and bathymetry. Throughout the late Quaternary, cores exhibit ostracod-rich layers separated by barren intervals. On the basis of biostratigraphical, isotopic and palaeomagnetic data the fossiliferous levels are interpreted as representing interglacial stages. The twenty most significant species were selected for subsequent quantitative investigation using Cluster and Factor analyses, in order to determine similarity and variance between the assemblages. An additional statistical method employing Modern Analogues and the Squared Chord Distance dissimilarity coefficient was utilized to compare the present late Quaternary fossil samples with a modern Arctic database. The results reveal a major faunal division within the Arctic Ocean Deep Water (AODW). Highly abundant and diverse assemblages within the cores were found to group and have good analogues with the Recent bathyal depth (1000-2500 m) upper AODW assemblages. Conversely, assemblages with low abundance and diversity correlate well with abyssal depth (> 3000 m) lower AODW assemblages. The palaeoceanographical history is complicated by the influence of adjacent water masses such as Canada Basin Deep Water (CBDW), Greenland Sea Deep Water (GSDW) and most importantly, Arctic Intermediate Water (AIW), which all had an influence on the ostracod assemblages during the late Quaternary. An enhanced flow of warm saline AIW into the Eurasian Basin results in species-rich upper AODW assemblages having good analogues down to 2750 m

  7. Deciduous and Evergreen Trees Rely on Deep Water Throughout the Year in a Subtropical Seasonal Forest

    NASA Astrophysics Data System (ADS)

    Ellsworth, P.

    2010-12-01

    In subtropical and tropical seasonal forests, trees have adapted to low shallow soil water availability during the dry season by modifying root density, rooting depth, and leaf phenology. Here we test the well known hypothesis that water uptake in deciduous trees is restricted to the shallow soil layer, which prevents them from sustaining transpiring leaves during the dry season. Evergreens, on the other hand, access perennially available deep water sources, allowing them to maintain their transpiring leaves during the dry season. To determine where in the soil profile deciduous and evergreen trees take up water, we used stable isotope analysis to measure water source use of two deciduous and three evergreen species for a period of 13 months. In addition, to test the possibility that leaflessness could alter the isotopic composition of stem water, we measured the isotopic variation in stem water caused by artificial defoliation of an evergreen species. Deciduous and evergreen trees took up water from the same depths in both the wet and dry seasons. Deciduous and evergreen trees used approximately 51% deep water (50-150cm) throughout the year, while soil from 0-20cm was the least important water source with 24 and 6% of water uptake for wet and dry seasons, respectively. Low use of shallow water (0-20cm) in the wet season was due to inconstant water availability. Though the top 20cm of soil is the location of most nutrients, the soil’s limited water availability requires plants to have access to a more reliable deep water source to meet both their dry and wet season transpirational demands. This apparent spatial uncoupling in water and nutrient uptake denotes separate resource allocation for nutrient and water acquisition. Deciduous trees showed isotopic enrichment of stem water compared to evergreen plants only during the period that deciduous trees were leafless. We explain this as isotopic enrichment of fixed pool of stem water by evaporation as our defoliation

  8. Modeling the dispersal of Levantine Intermediate Water and its role in Mediterranean deep water formation

    NASA Astrophysics Data System (ADS)

    Wu, Peili; Haines, Keith

    1996-03-01

    This paper demonstrates the importance of Levantine Intermediate Water (LIW) in the deep water formation process in the Mediterranean using the modular ocean general circulation model at 0.25° resolution, 19 vertical levels, over the entire Mediterranean with an open Gibraltar strait. LIW formation is strongly prescribed in the Rhodes Gyre region by Haney [1971] relaxation, while in other regions, surface salinity relaxation is much reduced by applying the `mixed' thermohaline surface boundary conditions. Isopycnal diagnostics are used to trace water mass movements, and volume fluxes are monitored at straits. Low viscosity and diffusion are used to permit baroclinic eddies to play a role in water mass dispersal. The overall water budget is measured by an average flux at Gibraltar of 0.8 Sv, of which 0.7 Sv is exchanged with the eastern basin at Sicily. LIW (density around 28.95) spreads rapidly after formation throughout the entire Levantine due to baroclinic eddies. Toward the west, LIW accumulates in the northern and central Ionian, with some entering the Adriatic through Otranto and some mixing southward in eddies and exiting to the western Mediterranean through Sicily. LIW is converted to deep water in the south Adriatic at an average rate of 0.4 Sv. Water exchange through the Otranto strait appears to be buoyancy driven, with a strong bias to the end of winter (March-April), while at Sicily the exchange has a strong symmetric seasonal cycle, with maximum transport of 1.1 Sv in December indicating the effects of wind driving. LIW pathways in the west are complex and variable. In the Tyrrhenian, intermediate water becomes uniform on isopycnal surfaces due to eddy stirring. West of Sardinia, two LIW boundary currents are formed in the Balearic basin; one flows northward up the west coast of Sardinia and Corsica, and one westward along the northern African coast. The northward current is consistent with observations, while the westward current is intermittent for

  9. Simulation of Deep Water Renewal in Crater Lake, Oregon, USA under Current and Future Climate Conditions

    NASA Astrophysics Data System (ADS)

    Piccolroaz, S.; Wood, T. M.; Wherry, S.; Girdner, S.

    2015-12-01

    We applied a 1-dimensional lake model developed to simulate deep mixing related to thermobaric instabilities in temperate lakes to Crater Lake, a 590-m deep caldera lake in Oregon's Cascade Range known for its stunning deep blue color and extremely clear water, in order to determine the frequency of deep water renewal in future climate conditions. The lake model was calibrated with 6 years of water temperature profiles, and then simulated 10 years of validation data with an RMSE ranging from 0.81°C at 50 m depth to 0.04°C at 350-460 m depth. The simulated time series of heat content in the deep lake accurately captured extreme years characterized by weak and strong deep water renewal. The lake model uses wind speed and lake surface temperature (LST) as boundary conditions. LST projections under six climate scenarios from the CMIP5 intermodel comparison project (2 representative concentration pathways X 3 general circulation models) were evaluated with air2water, a simple lumped model that only requires daily values of downscaled air temperature. air2water was calibrated with data from 1993-2011, resulting in a RMSE between simulated and observed daily LST values of 0.68°C. All future climate scenarios project increased water temperature throughout the water column and a substantive reduction in the frequency of deepwater renewal events. The least extreme scenario (CNRM-CM5, RCP4.5) projects the frequency of deepwater renewal events to decrease from about 1 in 2 years in the present to about 1 in 3 years by 2100. The most extreme scenario (HadGEM2-ES, RCP8.5) projects the frequency of deepwater renewal events to be less than 1 in 7 years by 2100 and lake surface temperatures never cooling to less than 4°C after 2050. In all RCP4.5 simulations the temperature of the entire water column is greater than 4°C for increasing periods of time. In the RCP8.5 simulations, the temperature of the entire water column is greater than 4°C year round by the year 2060 (HadGEM2

  10. Interpretation of depositional systems in lower Silurian Medina group of western New York

    SciTech Connect

    Davis, R.J.; Johnson, C.A.; Gilreath, J.A. )

    1988-08-01

    Depositional systems in the Medina Group (Lower Silurian) of western New York have been studied using stratigraphic dipmeter data. Results of this study indicate a nearshore-deltaic-interdeltaic depositional environment. Only minor deltaic episodes are preserved in the study area. This fits the generally arid climate with seasonal wet periods suggested by C.D. Laughrey. Facies recognized include: longshore-current sand waves in a shoreface environment, distributary mouth bars, distributary channels, tidal inlets, flood deltas, beaches, sandy tidal flats on which beach ridges were formed, and possible upper delta-plain sediments. Once the depositional sequences are recognized, paleocurrents within key sand units can be interpreted to determine favorable directions for successfully locating offset wells.

  11. Plastic debris ingested by deep-water fish of the Ionian Sea (Eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Anastasopoulou, Aikaterini; Mytilineou, Chryssi; Smith, Christopher J.; Papadopoulou, Konstantia N.

    2013-04-01

    Debris has been recognized as a global environmental problem including within deep habitats. From 26 fish species (1504 specimens) caught in the Eastern Ionian Sea during deep-water long-line surveys, plastic debris was found in 24 individuals of Galeus melastomus (3.2%) and single individuals of Pteroplatytrygon violacea, Squalus blainville, Etmopterus spinax, and Pagellus bogaraveo. The occurrence of debris among their food was infrequent. Ingested debris included primarily plastics (86.5%) and to a lesser extent pieces of metal and wood. Among ingested plastics, fragments of hard plastic material constituted the highest proportion (56.0%), followed by plastic bag fragments (22.0%), fragments of fishing gears (19.0%) and textile fibers (3.0%). Among the species with ingested debris, G. melastomus swallowed all debris categories; P. violacea and S. blainville ingested plastic bag fragments, whereas pieces of hard plastics were found in E. spinax and P. bogaraveo.

  12. Rapid reductions in North Atlantic Deep Water during the peak of the last interglacial period.

    PubMed

    Galaasen, Eirik Vinje; Ninnemann, Ulysses S; Irvalı, Nil; Kleiven, Helga Kikki F; Rosenthal, Yair; Kissel, Catherine; Hodell, David A

    2014-03-07

    Deep ocean circulation has been considered relatively stable during interglacial periods, yet little is known about its behavior on submillennial time scales. Using a subcentennially resolved epibenthic foraminiferal δ(13)C record, we show that the influence of North Atlantic Deep Water (NADW) was strong at the onset of the last interglacial period and was then interrupted by several prominent centennial-scale reductions. These NADW transients occurred during periods of increased ice rafting and southward expansions of polar water influence, suggesting that a buoyancy threshold for convective instability was triggered by freshwater and circum-Arctic cryosphere changes. The deep Atlantic chemical changes were similar in magnitude to those associated with glaciations, implying that the canonical view of a relatively stable interglacial circulation may not hold for conditions warmer and fresher than at present.

  13. Preparation and assessment of a candidate reference sample of Lake Baikal deep water

    NASA Astrophysics Data System (ADS)

    Suturin, A. N.; Paradina, L. F.; Epov, V. N.; Semenov, A. R.; Lozhkin, V. I.; Petrov, L. L.

    2003-02-01

    The possibility of the creation of a multi-element reference sample of Lake Baikal deep-water composition is justified. This is a new type of reference sample composed of natural water with a wide range of macro- and microelements. This candidate reference sample has a matrix composition consisting of hydrocarbonate and calcium water, a composition that is typical of many rivers and lakes of the world, as well as rain water. The creation of a candidate reference sample of Lake Baikal water is possible due to the stable water composition at a depth of 500 m, and to the use of water sampling technology which results in the preservation of the initial composition of water and its absolute sterility. Trial batches of Baikal water collected annually and stored in special polyethylenetereftalate bottles for a period of 9 years remained stable and homogenous for most elements. Preliminary data for a range of elements and compounds are presented.

  14. Contributions of the Siberian shelf polynyas to the Arctic Ocean intermediate and deep water

    NASA Technical Reports Server (NTRS)

    Martin, Seelye; Cavalieri, Donald J.

    1989-01-01

    To investigate the role of Siberian Shelf polynyas in water mass formation, and that of Whalers Bay in the cooling of the West Spitsbergen Current, satellite observations from the Nimbus 7 scanning multichannel microwave radiometer are used to determine the size and location of polynyas for November-March, 1978-1982. If salt contributes only to the Arctic Intermediate Water, the results show that the continental shelves can produce 20-60 percent of this water. Alternatively, if the salt contributes only to the deep water of the Eurasian Basin, then without consideration of the mixing of the bottom water with the Greenland and Norwegian Sea water, the contribution from the shelves yields a renewal time of about 100 years. These results imply that there is insufficient water produced in the shelf polynyas to perform all of the roles that have historically been assigned to it.

  15. Increased reservoir ages and poorly ventilated deep waters inferred in the glacial Eastern Equatorial Pacific

    PubMed Central

    de la Fuente, Maria; Skinner, Luke; Calvo, Eva; Pelejero, Carles; Cacho, Isabel

    2015-01-01

    Consistent evidence for a poorly ventilated deep Pacific Ocean that could have released its radiocarbon-depleted carbon stock to the atmosphere during the last deglaciation has long been sought. Such evidence remains lacking, in part due to a paucity of surface reservoir age reconstructions required for accurate deep-ocean ventilation age estimates. Here we combine new radiocarbon data from the Eastern Equatorial Pacific (EEP) with chronostratigraphic calendar age constraints to estimate shallow sub-surface reservoir age variability, and thus provide estimates of deep-ocean ventilation ages. Both shallow- and deep-water ventilation ages drop across the last deglaciation, consistent with similar reconstructions from the South Pacific and Southern Ocean. The observed regional fingerprint linking the Southern Ocean and the EEP is consistent with a dominant southern source for EEP thermocline waters and suggests relatively invariant ocean interior transport pathways but significantly reduced air–sea gas exchange in the glacial southern high latitudes. PMID:26137976

  16. Pockmark formation and evolution in deep water Nigeria: Rapid hydrate growth versus slow hydrate dissolution

    NASA Astrophysics Data System (ADS)

    Sultan, N.; Bohrmann, G.; Ruffine, L.; Pape, T.; Riboulot, V.; Colliat, J.-L.; De Prunelé, A.; Dennielou, B.; Garziglia, S.; Himmler, T.; Marsset, T.; Peters, C. A.; Rabiu, A.; Wei, J.

    2014-04-01

    In previous works, it has been suggested that dissolution of gas hydrate can be responsible for pockmark formation and evolution in deep water Nigeria. It was shown that those pockmarks which are at different stages of maturation are characterized by a common internal architecture associated to gas hydrate dynamics. New results obtained by drilling into gas hydrate-bearing sediments with the MeBo seafloor drill rig in concert with geotechnical in situ measurements and pore water analyses indicate that pockmark formation and evolution in the study area are mainly controlled by rapid hydrate growth opposed to slow hydrate dissolution. On one hand, positive temperature anomalies, free gas trapped in shallow microfractures near the seafloor and coexistence of free gas and gas hydrate indicate rapid hydrate growth. On the other hand, slow hydrate dissolution is evident by low methane concentrations and almost constant sulfate values 2 m above the Gas Hydrate Occurrence Zone.

  17. In situ growth rates of deep-water octocorals determined from 3D photogrammetric reconstructions

    NASA Astrophysics Data System (ADS)

    Bennecke, Swaantje; Kwasnitschka, Tom; Metaxas, Anna; Dullo, Wolf-Christian

    2016-12-01

    Growth rates of deep-water corals provide important information on the recovery potential of these ecosystems, for example from fisheries-induced impacts. Here, we present in situ growth dynamics that are currently largely unknown for deep-water octocorals, calculated by applying a non-destructive method. Videos of a boulder harbouring multiple colonies of Paragorgia arborea and Primnoa resedaeformis in the Northeast Channel Coral Conservation Area at the entrance to the Gulf of Maine at 863 m depth were collected in 2006, 2010 and 2014. Photogrammetric reconstructions of the boulder and the fauna yielded georeferenced 3D models for all sampling years. Repeated measurements of total length and cross-sectional area of the same colonies allowed the observation of growth dynamics. Growth rates of total length of Paragorgia arborea decreased over time with higher rates between 2006 and 2010 than between 2010 and 2014, while growth rates of cross-sectional area remained comparatively constant. A general trend of decreasing growth rates of total length with size of the coral colony was documented. While no growth was observed for the largest colony (165 cm in length) between 2010 and 2014, a colony 50-65 cm in length grew 3.7 cm yr-1 between 2006 and 2010. Minimum growth rates of 1.6-2.7 cm yr-1 were estimated for two recruits (<23 cm in 2014) of Primnoa resedaeformis. We successfully extracted biologically meaningful data from photogrammetric models and present the first in situ growth rates for these coral species in the Northwest Atlantic.

  18. Benthic foraminiferal B/Ca ratios reflect deep water carbonate saturation state

    NASA Astrophysics Data System (ADS)

    Yu, Jimin; Elderfield, Henry

    2007-06-01

    Boron/calcium ratios were measured in four benthic foraminiferal species (three calcitic: Cibicidoides wuellerstorfi, Cibicidoides mundulus, and Uvigerina spp., and one aragonitic: Hoeglundina elegans) from 108 core-top samples located globally. Comparison of coexisting species shows: B/Ca of C. wuellerstorfi > C. mundulus > H. elegans > Uvigerina spp., suggestive of strong "vital effects" on benthic foraminiferal B/Ca. A dissolution effect on benthic B/Ca is not observed. Core-top data show large intra-species variations (50-130 μmol/mol) in B/Ca. Within a single species, benthic foraminiferal B/Ca show a simple linear correlation with deep water Δ[CO 32-], providing a proxy for past deep water [CO 32-] reconstructions. Empirical sensitivities of Δ[CO 32-] on B/Ca have been established to be 1.14 ± 0.048 and 0.69 ± 0.072 μmol/mol per μmol/kg for C. wuellerstorfi and C. mundulus, respectively. The uncertainties associated with reconstructing bottom water Δ[CO 32-] using B/Ca in C. wuellerstorfi and C. mundulus are about ± 10 μmol/kg. A preliminary application shows that the Last Glacial Maximum (LGM) B/Ca ratios were increased by 12% at 1-2 km and decreased by 12% at 3.5-4.0 km relative to Holocene values in the North Atlantic Ocean. This implies that the LGM [CO 32-] was higher by ˜ 25-30 μmol/kg at intermediate depths and lower by ˜ 20 μmol/kg in deeper waters, consistent with glacial water mass reorganization in the North Atlantic Ocean inferred from other paleochemical proxies.

  19. A lower-extremities kinematic comparison of deep-water running styles and treadmill running.

    PubMed

    Killgore, Garry L; Wilcox, Anthony R; Caster, Brian L; Wood, Terry M

    2006-11-01

    The purpose of this investigation was to identify a deep-water running (DWR) style that most closely approximates terrestrial running, particularly relative to the lower extremities. Twenty intercollegiate distance runners (women, N = 12; men, N = 8) were videotaped from the right sagittal view while running on a treadmill (TR) and in deep water at 55-60% of their TR VO(2)max using 2 DWR styles: cross-country (CC) and high-knee (HK). Variables of interest were horizontal (X) and vertical (Y) displacement of the knee and ankle, stride rate (SR), VO(2), heart rate (HR), and rating of perceived exertion (RPE). Multivariate omnibus tests revealed statistically significant differences for RPE (p < 0.001). The post hoc pairwise comparisons revealed significant differences between TR and both DWR styles (p < 0.001). The kinematic variables multivariate omnibus tests were found to be statistically significant (p < 0.001 to p < 0.019). The post hoc pairwise comparisons revealed significant differences in SR (p < 0.001) between TR (1.25 +/- 0.08 Hz) and both DWR styles and also between the CC (0.81 +/- 0.08 Hz) and HK (1.14 +/- 0.10 Hz) styles of DWR. The CC style of DWR was found to be similar to TR with respect to linear ankle displacement, whereas the HK style was significantly different from TR in all comparisons made for ankle and knee displacement. The CC style of DWR is recommended as an adjunct to distance running training if the goal is to mimic the specificity of the ankle linear horizontal displacement of land-based running, but the SR will be slower at a comparable percentage of VO(2)max.

  20. Impact of water mass mixing on the biogeochemistry and microbiology of the Northeast Atlantic Deep Water

    PubMed Central

    Reinthaler, Thomas; Salgado, Xosé Antón Álvarez; Álvarez, Marta; van Aken, Hendrik M.; Herndl, Gerhard J.

    2014-01-01

    The extent to which water mass mixing contributes to the biological activity of the dark ocean is essentially unknown. Using a multiparameter water mass analysis, we examined the impact of water mass mixing on the nutrient distribution and microbial activity of the Northeast Atlantic Deep Water (NEADW) along an 8000 km long transect extending from 62°N to 5°S. Mixing of four water types (WT) and basin scale mineralization from the site where the WT where defined to the study area explained up to 95% of the variability in the distribution of inorganic nutrients and apparent oxygen utilization. Mixing-corrected average O2:N:P mineralization ratios of 127(±11):13.0(±0.7):1 in the core of the NEADW suggested preferential utilization of phosphorus compounds while dissolved organic carbon mineralization contributed a maximum of 20% to the oxygen demand of the NEADW. In conjunction with the calculated average mineralization ratios, our results indicate a major contribution of particulate organic matter to the biological activity in the NEADW. The variability in prokaryotic abundance, high nucleic acid containing cells, and prokaryotic heterotrophic production in the NEADW was explained by large scale (64–79%) and local mineralization processes (21–36%), consistent with the idea that deep-water prokaryotic communities are controlled by substrate supply. Overall, our results suggest a major impact of mixing on the distribution of inorganic nutrients and a weaker influence on the dissolved organic matter pool supporting prokaryotic activity in the NEADW. PMID:24683294

  1. Use of deep water lagoons for reducing sewage toxicity prior to wastewater treatment

    SciTech Connect

    Shaw, J.R.; Zuiderveen, J.A.; Belcher, B.; McGinley, P.; Birge, W.J.

    1995-12-31

    Investigations were conducted to determine the effectiveness of deep lagoons as a means of minimizing toxicity and reducing wastewater parameters. A lagoon system associated with a wastewater treatment plant (WWTP) was selected for study and parameters identified for monitoring included toxicity, metal concentrations, total suspended solids (TSS) and ammonia. This system included two lagoons, with 7--15 day hydraulic retention times, which received municipal waste. Toxicity and other parameters were measured for raw influent water, the two lagoon outfalls, and the final WWTP effluent. In a definitive seven-day chronic test with Ceriodaphnia dubia, the NOEC of influent water was 20%, and the IC{sub 50} for reproduction was 22.3%. Outfall from the first deep water lagoon showed reduced toxicity. The NOEC and IC{sub 50} were 80 and 71.8%, respectively. Further reduction in toxicity occurred in the second lagoon. The NOEC was 80% and the IC{sub 50} was 75.9. The final effluent discharged from the treatment plant affected neither survival nor fecundity. A 7-day embryo larval test conducted with Pimephales promelas yielded similar results. NOEC values increased through the lagoon system and were 2.5, 40.0, 40.0 and 100%, respectively. Acute TIE procedures implicated both metals and ammonia as primary toxicants. In all tests a sequential reduction in toxicity was observed through the lagoons. Results of this investigation support the use of deep water lagoons as an effective and economical means of pretreating wastewater. This approach offers promise for municipal waters, industrial effluents and stormwater runoff.

  2. Neodymium isotopic composition of intermediate and deep waters in the glacial southwest Pacific

    NASA Astrophysics Data System (ADS)

    Noble, Taryn L.; Piotrowski, Alexander M.; McCave, I. Nick

    2013-12-01

    Neodymium (Nd) isotopes, tracers of deep water mass source and mixing, were measured on sedimentary planktic foraminifera with authigenic coatings from a depth-transect of cores (1400-4800 m) from Chatham Rise in the southwest Pacific, over the past 30 ka. We observe deglacial variations in the Nd isotopic composition, which showed an average glacial composition of ɛNd=-5.0 (1σ; ±0.3n=4) for cores sites below 3200 mbsl. No significant deglacial variation was observed in the Nd isotopic composition of intermediate depth waters (1400 mbsl), in contrast with benthic foraminifera δC13 data. The deglacial ɛNd shift of CDW in the southwest Pacific is consistent with changes observed in the deep South Atlantic and Equatorial Indian Ocean, but ɛNd values are offset by ˜1ɛNd-unit to more radiogenic values throughout the deglacial records, likely due to admixture of a Nd isotope signal which was modified in the Southern Ocean or Pacific, perhaps by boundary exchange. However, this modification did not overprint the deglacial Nd isotope change. The consistent deglacial evolution of ɛNd in the South Atlantic, Equatorial Indian and southwest Pacific CDW, is evidence for the connection of CDW during the glacial, and propagation of diminished North Atlantic Deep Water export to the glacial Southern Ocean. In contrast, spatial heterogeneities in the benthic foraminifera δC13 of CDW have been observed in the Atlantic, Indian and Pacific basins of the deep glacial Southern Ocean. The Nd isotope data implies a well-connected deep Southern Ocean, which transported waters from the Atlantic to the Indian and Pacific oceans, during the glacial. This suggests that basin-scale variability in the glacial δC13 composition of CDW was unrelated to circulation changes.

  3. Deep water renewal in Lake Baikal: A model for long-term analyses

    NASA Astrophysics Data System (ADS)

    Piccolroaz, Sebastiano; Toffolon, Marco

    2013-12-01

    The phenomenon of deep water renewal in the South Basin of Lake Baikal is investigated by means of a simplified one-dimensional model. The downwelling process, whereby large volumes of superficial, cold, and oxygenated water periodically sink to the lake bottom (>1400m) due to thermobaric instability, is simulated by means of three main submodules: a reaction-diffusion equation for temperature and other tracers, and two Lagrangian algorithms, the first for the vertical stabilization of unstable density regions (including thermobaric effects) and the second handling the downwelling mechanism. A self-consistent procedure for the dynamical reconstruction of the diapycnal diffusivity profile is included to account for the effect of the variability of external conditions. The model has been developed aimed at providing a detailed description of deep-ventilation and a quantification of its consequences at the basin scale; the core algorithms have been designed suitably to perform long-term simulations (hundreds of years) and to deal with a limited amount of information about boundary conditions, which are expressed in terms of wind forcing and surface water temperature. The main parameters have been calibrated using measured profiles of temperature and chlorofluorocarbons (CFC-12) concentration over a 40 year historical period. A long-term simulation (one millennium), in which the current meteorological conditions have been kept statistically unchanged, has been used to determine the asymptotic dynamics. The results are consistent with previous measurements and estimates, suggesting that the model is suitable to qualitatively and quantitatively simulate deep water renewal in deep, temperate lakes, capturing the relative contribution and interaction of the different processes involved.

  4. The petroleum potential of deep-water northwestPalawan Block GSEC 66

    NASA Astrophysics Data System (ADS)

    Sales, Alessandro O.; Jacobsen, Eric C.; Morado, Arturo A.; Benavidez, Jeciel J.; Navarro, F. A.; Lim, Antonette E.

    This paper presents the results of the evaluation of the petroleum, potential of thedeep-water acreage of Philodrill, GSEC 66, or what the authors call the "Northwest Malampaya Block". All the elements necessary for a major hydrocarbon accumulation are believed to be present in the block. Probable source rocks are the deep-water Nido Limestone, the pre-Nido Early Tertiary syn-rift section, and pre-Tertiary sediments. Potential reservoirs include the Nido reefal buildups, Nido and pre-Nido detrital and/or fractured carbonates, Early Miocene Galoc elastic equivalent turbidites and pre-Nido sediments. The principal play-types recognized in the area are the Late Oligocene to Early Miocene reefs and the erosional/karsted carbonate highs. After evaluation of available pre-1982 seismic data, an acquisition program of 1625 km was undertaken. Eleven leads/prospects were delineated in the area after the interpretation of this new seismic data. Two prospects were upgraded to drillable status (the Santa Monica Prospect and the Ipil Prospect). The Santa Monica Prospect is a well-defined four-way dip closure on the Nido Limestone with a vertical closure of over 1500 feet and an areal closure of over 20,500 acres. The Ipil Prospect is a gently closed feature developed at the Nido Limestone platform level with an areal closure of over 11,600 acres and a vertical relief of 400 feet. The technical merits of the delineated huge prospects, combined with the very favorable deep-water exploration terms of the Philippines and their proximity to the soon-to-be-developed Malampaya-Camago Field, make this block a very promising area for further exploration work.

  5. Advection of North Atlantic Deep Water from the Labrador Sea to the southern hemisphere

    NASA Astrophysics Data System (ADS)

    Rhein, Monika; Kieke, Dagmar; Steinfeldt, Reiner

    2015-04-01

    Recently formed Labrador Seawater (LSW) and overflow water from Denmark Strait (DSOW) are main components of the Atlantic Meridional Overturning Circulation. Both exhibit a distinct chlorofluorocarbon (CFC) maximum. Here we use 25 years of CFC observations in the Atlantic to study the main features of the circulation of LSW and DSOW. From the CFC data, the age and fraction of young deep water are inferred. Due to the superior spatial data resolution compared to former attempts, regional differences in the spreading velocity and pathways of young deep water become evident, dependent on the regional circulation. The observed distributions of young LSW and DSOW showed that the DWBC is the fastest pathway to reach the southern hemisphere. The downstream decrease of the fractions of young LSW in the DWBC is slower compared to model studies. From 47°N to 42°N, DWBC transports of young LSW and DSOW decrease by 44% and 49%, respectively. At 26°N, the DWBC transport of young water is still 39% of the LSW formation rate and 44% of the DSOW overflow transport. Interior pathways also exist, especially in the subpolar North Atlantic and in the transition zone between the subpolar and subtropical gyre. Compared to DSOW, the distributions indicate a higher tendency for LSW to follow additional interior pathways. North of 45°N the major part of LSW is younger than 20 years. The general weakening of new LSW formation since the 1990s worked toward a homogenization between the LSW in the western and the eastern subpolar North Atlantic.

  6. Early life history of deep-water gorgonian corals may limit their abundance.

    PubMed

    Lacharité, Myriam; Metaxas, Anna

    2013-01-01

    Deep-water gorgonian corals are long-lived organisms found worldwide off continental margins and seamounts, usually occurring at depths of ∼200-1,000 m. Most corals undergo sexual reproduction by releasing a planktonic larval stage that disperses; however, recruitment rates and the environmental and biological factors influencing recruitment in deep-sea species are poorly known. Here, we present results from a 4-year field experiment conducted in the Gulf of Maine (northwest Atlantic) at depths >650 m that document recruitment for 2 species of deep-water gorgonian corals, Primnoa resedaeformis and Paragorgia arborea. The abundance of P. resedaeformis recruits was high, and influenced by the structural complexity of the recipient habitat, but very few recruits of P. arborea were found. We suggest that divergent reproductive modes (P. resedaeformis as a broadcast spawner and P. arborea as a brooder) may explain this pattern. Despite the high recruitment of P. resedaeformis, severe mortality early on in the benthic stage of this species may limit the abundance of adult colonies. Most recruits of this species (∼80%) were at the primary polyp stage, and less than 1% of recruits were at stage of 4 polyps or more. We propose that biological disturbance, possibly by the presence of suspension-feeding brittle stars, and limited food supply in the deep sea may cause this mortality. Our findings reinforce the vulnerability of these corals to anthropogenic disturbances, such as trawling with mobile gear, and the importance of incorporating knowledge on processes during the early life history stages in conservation decisions.

  7. Early Life History of Deep-Water Gorgonian Corals May Limit Their Abundance

    PubMed Central

    Lacharité, Myriam; Metaxas, Anna

    2013-01-01

    Deep-water gorgonian corals are long-lived organisms found worldwide off continental margins and seamounts, usually occurring at depths of ∼200–1,000 m. Most corals undergo sexual reproduction by releasing a planktonic larval stage that disperses; however, recruitment rates and the environmental and biological factors influencing recruitment in deep-sea species are poorly known. Here, we present results from a 4-year field experiment conducted in the Gulf of Maine (northwest Atlantic) at depths >650 m that document recruitment for 2 species of deep-water gorgonian corals, Primnoa resedaeformis and Paragorgia arborea. The abundance of P. resedaeformis recruits was high, and influenced by the structural complexity of the recipient habitat, but very few recruits of P. arborea were found. We suggest that divergent reproductive modes (P. resedaeformis as a broadcast spawner and P. arborea as a brooder) may explain this pattern. Despite the high recruitment of P. resedaeformis, severe mortality early on in the benthic stage of this species may limit the abundance of adult colonies. Most recruits of this species (∼80%) were at the primary polyp stage, and less than 1% of recruits were at stage of 4 polyps or more. We propose that biological disturbance, possibly by the presence of suspension-feeding brittle stars, and limited food supply in the deep sea may cause this mortality. Our findings reinforce the vulnerability of these corals to anthropogenic disturbances, such as trawling with mobile gear, and the importance of incorporating knowledge on processes during the early life history stages in conservation decisions. PMID:23762358

  8. Deep-water facies, processes and models: a review and classification scheme for modern and ancient sediments

    NASA Astrophysics Data System (ADS)

    Pickering, Kevin; Stow, Dorrik; Watson, Mike; Hiscott, Richard

    1986-03-01

    A review of previous work on modern and ancient deep-water facies, processes and models is presented with a new classification scheme involving 40 distinct facies related to 15 conceptually distinct facies groups. These facies are fixed points in a spectrum of facies generated in a process continuum from resedimentation processes, through semi-permanent bottom-currents, to pelagic settling. In essence, the scheme is descriptive of the sedimentary attributes of sediments, although it is designed to aid interpretation of possible sediment transport/deposition processes. The classification scheme is three-tier with facies classes, groups and constituent facies, and is hierarchical to allow flexibility in its use. There are seven facies classes, with Classes A-E defined largely on the basis of grain-size differences, Class F on the basis of internal organization, and Class G on composition. The facies classes are: Class A, gravels, muddy gravels, gravelly muds, and pebbly sands, with ⩾ 5% gravel grade; Class B, sands, with ⩾ 80% sand grade and < 5% pebble grade; Class C, sand-mud couplets and muddy sands, with 20-80% sand grade and < 80% mud grade (mostly silt); Class D, silts, silty muds and silt-mud couplets, with > 80% mud, ⩾ 40% silt and 0-20% sand; Class E, muds and clays, with ⩾ 95% mud grade, < 40% silt grade and < 5% sand and coarser grade; Class F, chaotic deposits, with variable grain or clast sizes, and Class G, biogenic oozes, hemipelagites and chemogenic sediments, with < 5% terrigenous sand and gravel. The second-order classification into facies groups (A1, A2 etc.) is based mainly on organized versus disorganized sediments, the latter lacking marked stratification or grading and the former having clearly-defined primary sedimentary structures. At the level of facies, the criteria used to distinguish different types is more complex and more flexible. For the purpose of large-scale mapping or reconnaissance fieldwork, either the level of facies

  9. Deep water circulation in the eastern Mediterranean Sea for the last 95 kyr: new insights from stable isotopes and benthic foraminiferal assemblages

    NASA Astrophysics Data System (ADS)

    Cornuault, Marine; Vidal, Laurence; Tachikawa, Kazuyo; Licari, Laetitia; Rouaud, Guillaume; Sonzogni, Corinne; Revel, Marie

    2016-04-01

    The response of the Eastern Mediterranean Sea circulation to climate forcing over the last 95 kyr BP was studied using core MD04-2722 collected at 1780m water depth in the Levantine Sea. Foraminiferal stable isotopes and benthic foraminiferal assemblages were combined to reconstruct deep water ventilation and oxygenation in relation to surface water freshening. Over the last deglaciation, benthic foraminiferal δ13C values and benthic foraminiferal oxygen index decreased while δ18O gradient between benthic and planktonic foraminifera increased. These results testify respectively of slower ventilation, bottom water oxygen depletion and stronger stratification prior to S1 sapropel deposition. Similar conditions were deduced for S3 sapropel. Combination of deglacial sea level rise and fresher North Atlantic surface water contribution were evaluated to be a precondition of S1 formation in the Levantine Sea. Local Nile freshwater supply during the African Humid Period further strengthened the water column stratification. For the last glacial period, three events at around 53, 46 and 37 ka BP were marked by benthic δ13C decrease demonstrating deep water circulation reduction at the core location. Bottom water oxygenation was only slightly lowered. Considering the effect of North Atlantic surface water salinity to the Mediterranean Sea circulation, we propose the 46 and 37 ka BP events as responses to the Heinrich Events 4 and 5 that supplied fresher surface water to the Mediterranean Sea. Since the '53 ka event' is characterized by the appearance of an anoxic benthic foraminiferal species observed for S1 and S3 layers, we tentatively attributed it to the 'missing' sapropel S2. Our results indicate that intense stagnation in the Eastern Mediterranean Sea could occur when both local freshwater supply and fresher North Atlantic surface water contributed. The influence of North Atlantic condition was significant on the eastern Mediterranean circulation under warm and cold

  10. Reproductive biology of the deep-water coral Acanella arbuscula (Phylum Cnidaria: Class Anthozoa: Order Alcyonacea), northwest Atlantic

    NASA Astrophysics Data System (ADS)

    Beazley, Lindsay I.; Kenchington, Ellen L.

    2012-10-01

    Knowledge of the reproductive life-history of deep-water corals is important for assessing their vulnerability to anthropogenic impacts. Yet, the reproductive biology of many deep-water corals, especially members of the subclass Octocorallia, has not been examined. We used histological techniques to describe the reproductive biology of the deep-water gorgonian coral Acanella arbuscula from the northwest Atlantic. All colonies examined were gonochoric, and no embryos or planula larvae were observed in the polyps. Mean polyp-level fecundity (females: 21.0±17.5 oocytes polyp-1, and males: 13.9±13.5 sperm sacs polyp-1) is high compared to other deep-water gorgonians, and polyps closer to the branch tips had the highest fecundities in both females and males. The presence of large oocytes (maximum diameter 717.8 μm) suggests that A. arbuscula produces lecithotrophic larvae. Despite the potentially high fecundity and small size at first reproduction, the paucity of information on dispersal and recruitment, combined with its longevity, vulnerability to bottom fishing gear, and ecological role as a structure-forming species, still warrants the classification of A. arbuscula as a vulnerable marine ecosystem indicator.

  11. Deep-Water Benthic Foraminifers from the Paleocene and Eocene of the North Pacific Region: Paleontology, Biostratigraphy, and Paleoceanological Reconstructions

    NASA Astrophysics Data System (ADS)

    Olshanetskiy, D. M.

    2015-12-01

    A zonal scheme for the Lower Paleogene of the northern Pacific Ocean is proposed on the basis of the stratigraphic distribution of benthic foraminifers in the lower bathyal-abyssal beds studied in boreholes in the North and South Pacific regions. This scheme includes eight subdivisions (six zones and two subzones). The boundaries of the benthic zonal subdivisions are defined by bioevents (appearance or disappearance of stratigraphically important taxa) and are linked to the zonal scales based on planktonic foraminifers and calcareous nannoplankton. It is established that most of these bioevents are recognized subglobally. Apart from the evolutionary events, changes in the deep-water benthic foraminiferal assemblages were caused by changes in the paleooceanological environment. This allowed detailed characterization of a global mass extinction of assemblages of deep-water benthic foraminifers in the region studied. It is also established that changes in the assemblages of deep-water benthic foraminifers, observed in either change in their taxonomic composition or changes in abundance and diversity, resulted from the presence of different deep-water masses in the region.

  12. Reduced admixture of North Atlantic Deep Water to the deep central South Pacific during the last two glacial periods

    NASA Astrophysics Data System (ADS)

    Molina-Kescher, Mario; Frank, Martin; Tapia, Raúl; Ronge, Thomas A.; Nürnberg, Dirk; Tiedemann, Ralf

    2016-06-01

    The South Pacific is a sensitive location for the variability of the global oceanic thermohaline circulation given that deep waters from the Atlantic Ocean, the Southern Ocean, and the Pacific Basin are exchanged. Here we reconstruct the deep water circulation of the central South Pacific for the last two glacial cycles (from 240,000 years ago to the Holocene) based on radiogenic neodymium (Nd) and lead (Pb) isotope records complemented by benthic stable carbon data obtained from two sediment cores located on the flanks of the East Pacific Rise. The records show small but consistent glacial/interglacial changes in all three isotopic systems with interglacial average values of -5.8 and 18.757 for ɛNd and 206Pb/204Pb, respectively, whereas glacial averages are -5.3 and 18.744. Comparison of this variability of Circumpolar Deep Water (CDW) to previously published records along the pathway of the global thermohaline circulation is consistent with reduced admixture of North Atlantic Deep Water to CDW during cold stages. The absolute values and amplitudes of the benthic δ13C variations are essentially indistinguishable from other records of the Southern Hemisphere and confirm that the low central South Pacific sedimentation rates did not result in a significant reduction of the amplitude of any of the measured proxies. In addition, the combined detrital Nd and strontium (87Sr/86Sr) isotope signatures imply that Australian and New Zealand dust has remained the principal contributor of lithogenic material to the central South Pacific.

  13. The Search for Eight Glacial Cycles of Deep-Water Temperatures and Global ice Volume From the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Ferretti, P.; Elderfield, H.; Greaves, M.; McCave, N.

    2007-12-01

    It has been recently suggested "a substantial portion of the marine 100-ky cycle that has been object of so much attention over the past quarter of a century is, in reality, a deep-water temperature signal and not an ice volume signal" (Shackleton, 2000). There are currently few records available of deep-water temperature variations during the Pleistocene and most of our understanding is inferred from the oxygen isotopic composition (δ18O) of benthic foraminifera from deep-sea sediments. However, variations in benthic δ18O reflect some combination of local to regional changes in water mass properties (largely deep- water temperature) as well as global changes in seawater δ18O (δ18Osw) resulting from the growth and decay of continental ice. Recent studies suggest that benthic foraminiferal Mg/Ca may be useful in reconstructing deep-water temperature changes, but the application of this method to benthic species has been hampered by a number of unresolved issues, such as uncertainties related to the calibration for benthic Mg at the coldest temperatures. Here we present deep-sea Mg/Ca and δ18O records for the past eight glacial cycles in benthic foraminiferal ( Uvigerina spp.) calcite from a marine sediment core recovered in the mid Southern latitudes. Ocean Drilling Program Site 1123 was retrieved from Chatham Rise, east of New Zealand in the Southwest Pacific Ocean (3290 m water depth). This site lies under the Deep Western Boundary Current (DWBC) that flows into the Pacific Ocean, and is responsible for most of the deep water in that ocean; DWBC strength is directly related to processes occurring around Antarctica. Temperatures derived via pore fluid modeling of the last glacial maximum are available from Site 1123 and represent an important tool to constrain deep-water temperatures estimates using Mg/Ca. In selected time slices, we measured B/Ca ratios in Uvigerina in order to gain information on the deep-water carbonate saturation state and have data of Mg

  14. Occurrence and biogeography of hydroids (Cnidaria: Hydrozoa) from deep-water coral habitats off the southeastern United States

    NASA Astrophysics Data System (ADS)

    Henry, Lea-Anne; Nizinski, Martha S.; Ross, Steve W.

    2008-06-01

    Deep-water coral habitats off the southeastern USA (SEUS) support diverse fish and invertebrate assemblages, but are poorly explored. This study is the first to report on the hydroids collected from these habitats in this area. Thirty-five species, including two species that are likely new to science, were identified from samples collected primarily by manned submersible during 2001-2005 from deep-water coral habitats off North Carolina to east-central Florida. Eleven of the species had not been reported since the 19th to mid-20th century. Ten species, and one family, the Rosalindidae, are documented for the first time in the SEUS. Latitudinal ranges of 15 species are extended, and the deepest records in the western North Atlantic for 10 species are reported. A species accumulation curve illustrated that we continue to add to our knowledge of hydroid diversity in these habitats. Sexually mature individuals were collected for 19 species during the summer to early autumn months. Most of the observed species (89%) liberate planula larvae as part of their life cycles, suggesting that these species exhibit a reproductive strategy that reduces the risk of dispersal to sub-optimal habitats. Hydroids occurred across various substrata including coral rubble, live corals, rock and other animal hosts including hydroids themselves. All observed species were regionally widespread with typically deep-neritic to bathyal sub-tropical/tropical distributions. Hydroid assemblages from deep-water SEUS coral habitats were most similar to those from adjacent deep-water habitats off the SEUS (17 shared species), and those in the Straits of Florida/Bahamas and Caribbean/West Indian regions (14 and 8 shared species, respectively). The similarity to sub-tropical and tropical assemblages and the richness of plumularioids in the SEUS deep-water coral habitats support the idea of a Pleistocene intrusion of tropical species northwards following an intensification of the Gulf Stream from the

  15. Glacial/Interglacial changes of southwest Pacific intermediate- and deep-water circulation over the last 350,000 years

    NASA Astrophysics Data System (ADS)

    Ronge, Thomas; Tiedemann, Ralf; Prange, Matthias; Merkel, Ute; Kuhn, Gerhard; Lamy, Frank

    2015-04-01

    On glacial/interglacial timescales, Southern Ocean air-sea gas exchange is considered to be an important factor, driving the variability of atmospheric CO2 concentrations. To understand the role of oceanic variability in the global carbon cycle, it is necessary to reconstruct changes in deep- and intermediate-water circulation and chemistry of Southern Ocean water masses. In this context, our study aims on the reconstruction of glacial/interglacial changes in the vertical expansion of southwest Pacific Antarctic Intermediate Water. For our study, we compared isotope records (δ13C and δ18O) measured on the epibenthic foraminifera Cibicidoides wuellerstorfi from the Antarctic Intermediate Water and the Upper Circumpolar Deep Water (943 - 2066 m water depth) off New Zealand. We used two sediment cores from the Tasman Sea (MD06-2990 and MD06-2986), retrieved during R/V Marion Dufresne cruise MD152, and three sediment cores from the Bounty Trough east of New Zealand (MD97-2120, SO 213-82-1 and SO 213-84-1). Comparing these records, we can monitor changes in southwest Pacific water mass circulation over the past 350,000 years. Over this time period, we record a significant shoaling of the boundary between Antarctic Intermediate Water and Upper Circumpolar Deep Water during all glacial stages. We propose that freshwater input by melting sea ice into the glacial intermediate-water increased the buoyancy difference to underlying deep-waters, thus hampering the downward expansion of southwest Pacific Antarctic Intermediate Water during glacials. This interpretation is consistent with our modeling results, based on the Community Climate System model version 3, which also indicate a shoaling of glacial intermediate waters due to the input of meltwater. The glacial upward displacement of the water mass boundary significantly increased the vertical extent of circumpolar deep-waters, consequently extending the volume of the proposed glacial deep-water carbon pool.

  16. Stochastic Plume Simulations for the Fukushima Accident and the Deep Water Horizon Oil Spill

    NASA Astrophysics Data System (ADS)

    Coelho, E.; Peggion, G.; Rowley, C.; Hogan, P.

    2012-04-01

    The Fukushima Dai-ichi power plant suffered damage leading to radioactive contamination of coastal waters. Major issues in characterizing the extent of the affected waters were a poor knowledge of the radiation released to the coastal waters and the rather complex coastal dynamics of the region, not deterministically captured by the available prediction systems. Equivalently, during the Gulf of Mexico Deep Water Horizon oil platform accident in April 2010, significant amounts of oil and gas were released from the ocean floor. For this case, issues in mapping and predicting the extent of the affected waters in real-time were a poor knowledge of the actual amounts of oil reaching the surface and the fact that coastal dynamics over the region were not deterministically captured by the available prediction systems. To assess the ocean regions and times that were most likely affected by these accidents while capturing the above sources of uncertainty, ensembles of the Navy Coastal Ocean Model (NCOM) were configured over the two regions (NE Japan and Northern Gulf of Mexico). For the Fukushima case tracers were released on each ensemble member; their locations at each instant provided reference positions of water volumes where the signature of water released from the plant could be found. For the Deep Water Horizon oil spill case each ensemble member was coupled with a diffusion-advection solution to estimate possible scenarios of oil concentrations using perturbed estimates of the released amounts as the source terms at the surface. Stochastic plumes were then defined using a Risk Assessment Code (RAC) analysis that associates a number from 1 to 5 to each grid point, determined by the likelihood of having tracer particle within short ranges (for the Fukushima case), hence defining the high risk areas and those recommended for monitoring. For the Oil Spill case the RAC codes were determined by the likelihood of reaching oil concentrations as defined in the Bonn Agreement

  17. Geochemistry of the Deep Water Bamboo Coral Isidella; Intermediate Depth and Surface Ocean Chemical Recorder

    NASA Astrophysics Data System (ADS)

    Spero, H. J.; Jang, N. A.; Adkins, J. F.

    2003-12-01

    Geochemical analyses of deep water corals have provided a wealth of data on past ocean circulation and chemical changes. Information obtained from these carbonate precipitating organisms generally reflects ambient conditions at the depth of growth. The bamboo coral, Isidella sp., belongs to a group of deep water Octocorals that live at intermediate ocean depths ( ˜200-1500m) and produce a calcite skeleton that is divided by proteinaceous gorgonin internodes. Because, the calcite and organic regions of the skeleton are precipitated simultaneously, their chemistries are temporally coupled. Stable isotope, radiocarbon and 210Pb data were obtained from several specimens of Isidella sp. that were collected in fishing dredges from the outer continental shelf near Pt. Reyes, CA (38° N 123.4° W ˜220 m). 210Pb analyses on one of the specimens suggests the coral was ~15-80 years old. δ 13C and δ 18O data from the calcite skeleton display the typical nonequilibrium covariation that has been described previously, thereby limiting the use of these data in reconstructing environmental temperatures. Although δ 13C analyses of the organic internodes produced typical marine values of -16.9+/-0.1‰ (n=17), δ 15N values were unusually high, 13.8+/-0.4‰ . Because the internode geochemistry records the organic chemistry of sinking particulate matter ingested by the coral, the enriched δ 15N data reflect the chemistry of local upwelled NO3 that was strongly influenced by subsurface denitrification. AMS analyses of the center and outer edge of the skeleton (branch diameter = 2.2 cm) and adjacent organic internodes (growth proceeds from center outwards) yield 14C ages of 2065 and 2000+/-35 years for the calcite (Δ 14C = -226.4 and -220.3‰ ) and 785 and 765+/-35 years for the organic node (Δ 14C = -93.1 and -90.7‰ ) respectively. The calcite AMS ages record the 14C reservoir age of upper N. Pacific thermocline waters whereas the organic data record the surface ocean

  18. North Atlantic Surface and Deep-Water Hydrography during the Early Pliocene Warm Period

    NASA Astrophysics Data System (ADS)

    Voelker, A. H. L.; Evans, H. F.; Naafs, B. D.; Cavaleiro, C. D.; Rebotim, A.; Ventura, C.; Stein, R. H.; Channell, J. E. T.

    2014-12-01

    The early Pliocene, with atmospheric carbon dioxide concentrations at levels similar to today, is seen as a case study for Earth's future climate evolution. During this period the progressive closing of the Central American Seaway led to increased poleward heat and salt transport within the Atlantic with North Atlantic Deep Water (NADW) becoming warmer and saltier and resulting in an enhanced Atlantic Meridional Overturning Circulation (AMOC). In order to understand how stable the AMOC really was we produced millennial-scale (1-2 kyr) surface and deep-water records for IODP Site U1313 (41°N, 33°W, 3412m) for the interval from 3.4 to 4.1 Ma. This site is ideally located to monitor past AMOC changes with North Atlantic Drift waters at the surface and NADW in the deep. Although interglacial/glacial cycles are visible, the higher frequency oscillations recorded in both the planktonic G. ruber (white) and benthic Cibicidoides sp. δ18O records impede tuning to the LR04 stack (Lisiecki and Raymo, 2005). We therefore exploit a different approach: using the magnetic polarity chrons (Gilbert, Cochiti) as recorded at Site U1313 as framework, we tune our benthic δ18O record to that of ODP Site 1085 (on LR04 ages). The benthic δ13C record shows millennial-scale oscillations, and the values indicate nearly continuous NADW presence and confirm a strong AMOC, also during most of the glacial periods. Varying surface water conditions, especially during the younger interglacial periods, are reflected in the G. ruber isotope data and appear to be linked to salinity changes since they are not recorded in the alkenone sea-surface temperature data. Although glacial stages Gi 2 and Gi 4 show the expected higher benthic δ18O values, Gi 6 was the glacial period with the strongest impact on the AMOC as revealed by cooler, less ventilated surface waters and a less ventilated NADW. Overall, the AMOC was strong throughout, but experienced high frequency oscillations at a level similar to

  19. Can Plume-Forming Asteroid Airbursts Generate Meteotsunami in Deep Water?

    NASA Astrophysics Data System (ADS)

    Boslough, M.

    2015-12-01

    Hydrocode simulations suggest that the 1908 Tunguska explosion was a plume-forming airburst analogous to those caused by Comet Shoemaker-Levy 9 (SL9) collisions with Jupiter in 1994. A noctilucent cloud that appeared over Europe following the Tunguska event is similar to post-impact features on Jupiter, consistent with a collapsed plume containing condensation from the vaporized asteroid. Previous workers treated Tunguska as a point explosion and used seismic records, barograms, and extent of fallen trees to determine explosive yield. Estimates were based on scaling laws derived from nuclear weapons data, neglecting directionality, mass, and momentum of the asteroid. This point-source assumption, with other simplifications, led to a significant overestimate. Tunguska seismic data were consistent with ground motion from a vertical point impulse of 7×1018dyn sec caused by the downward blast wave of a 12.5-megaton nuclear explosion at an altitude of 8.5 km for an effective momentum multiplication factor (β) of ~80. However, simulations of a 3-megaton collisional airburst reveal that the upward-directed momentum contained in a ballistic plume can reach this level within the first minute after the explosion (β≈300). The reaction impulse from such an airburst is therefore similar to a much larger non-plume-forming nuclear explosion. Momentum is coupled through the atmosphere to the surface, generating disproportionately large seismic signatures. This result suggests that coupling from an over-water plume-forming airburst could be a more efficient tsunami source mechanism than a collapsing impact cavity or direct air blast because the characteristic time of the plume is closer to that of a long-period wave in deep water. As the plume accelerates upward, it creates a slowly-rising and sustained overpressure with a ramp wave that propagates outward at the speed of sound, generating a tsunami in deep ocean by the same mechanism that yields slower meteotsunami in shallow

  20. AN EARLY MIOCENE DEEP-WATER DECAPOD CRUSTACEAN FAUNULE FROM THE SLOVENIAN PART OF THE STYRIAN BASIN, AND ITS PALAEOENVIRONMENTAL AND PALAEOBIOGEOGRAPHICAL SIGNIFICANCE

    PubMed Central

    GAŠPARIČ, ROK; HYŽNÝ, MATÚŠ

    2015-01-01

    A new decapod crustacean faunule is described from the early Miocene of the Slovenian part of the Styrian Basin. The Ivnik Beds exposed at the Činžat locality contain seven species: Calliax michelottii (Axiidea: Callianassidae), Lepidophthalmus paratethyensis sp. nov. (Axiidea: Callianassidae), Jaxea kuemeli (Gebiidea: Laomediidae), Styrioplax exiguus (Brachyura: Chasmocarcinidae), Goneplax gulderi (Brachyura: Goneplacidae), Neopilumnoplax pohorjensis sp. nov. (Brachyura: Mathildellidae) and Retropluma slovenica sp. nov. (Brachyura: Retroplumidae). Numerous specimens of well-preserved Styrioplax exiguus permitted its redescription and re-assignment of its familial placement to Chasmocarcinidae. Neopilumnoplax pohorjensis sp. nov. constitutes the first fossil occurrence of the genus known to date. The decapod association, as well as other faunal elements, suggests low-energy deep-water depositional environment with epibathyal water depth of more than 125 m. The studied locality is situated in the Ribnica–Selnica graben filled with sediments once deposited in the Central Paratethys sea. Based on the affinities of decapod genera of the Central Paratethys and the Proto-Mediterranean, we conclude that the exchange of decapod faunas between these regions was probably regulated by an anti-estuarine circulation permitting an easier incursion of species from the Proto-Mediterranean into the Paratethys and simultaneous hindering the Paratethyan endemics (Styrioplax) from entering the Mediterranean. PMID:26689949

  1. Diversity and taphonomic gradients from shoreface to deep water: Case studies based on sea urchin assemblages from the Miocene of Sardinia

    NASA Astrophysics Data System (ADS)

    Nebelsick, James; Mancosu, Andrea

    2016-04-01

    Echinoid faunas from Miocene sediments from Sardinia allow diversity to be correlated to variations in depositional environments as well as taphonomic pathways. Taxonomic richness and preservation potentials vary among both carbonate and siliciclastic dominated shelf environments. Studies include detailed investigation of stratigraphy, sedimentology, palaeontology and taphonomy in both the field and in the laboratory. Environmental Interpretations are based on composition and diversity of taxa, functional morphological interpretation of life habits as well as taphonomic signatures. These investigations have revealed: 1) various mass accumulations of clypeasteroid echinoids ranging from autochthonous assemblages to multiple in situ reworked accumulations in shore face environments, 2) the distribution of morphotypes of the common genus Clypeaster, 3) echinoid assemblages dominated by both irregular and regular echinoids in siliciclastic and carbonate shelf environments, 4) spatangoid assemblages in heavily bioturbated coarse sands, and 5) monotypic shell beds of well-preserved regular echinoids and spatangoid from deeper siliciclastic environments. Variations in the diversity of echinoid taxa are correlated to biotic and abiotic ecological factors in specific depositional environments. Preservation potentials vary highly as determined by ambient environmental conditions and skeletal architectures. A synthesis of faunal diversities and preservation potentials along shelf gradient ranging from shoreface to deep water is presented.

  2. On the Impacts of Different Surface Forcing Regimes for Deep Water Formation in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Josey, S.; Tsimplis, M.; Gomis, D.; Ruiz, S.; Marcos, M.; Somot, S.

    2009-04-01

    Deep water formation is known to occur at 3 major sites (the Gulf of Lions, Adriatic and Aegean Seas) in the Mediterranean basin. However, the role played by air-sea interaction in setting the frequency and strength of formation events (including major transient episodes such as that experienced in the Aegean sea in the early 1990s) is not well understood. We will explore this relationship using air-sea heat, freshwater and density flux fields, including output from downscaled versions (HIPOCAS and ARPERA) of the NCEP/NCAR and ECMWF reanalyses. The downscaled fields reveal small scale forcing features (including jet-like structures over the dense water formation sites) that are not present in the coarser resolution reanalysis datasets. They also show greater variability in the forcing of the Aegean and the Gulf of Lions than the Adriatic Sea. The differences between the forcing distributions of the Aegean and Adriatic will be discussed in detail and will be advanced as a potential cause for variations in frequency of dense water formation in these two regions.

  3. Footprint of Deepwater Horizon blowout impact to deep-water coral communities.

    PubMed

    Fisher, Charles R; Hsing, Pen-Yuan; Kaiser, Carl L; Yoerger, Dana R; Roberts, Harry H; Shedd, William W; Cordes, Erik E; Shank, Timothy M; Berlet, Samantha P; Saunders, Miles G; Larcom, Elizabeth A; Brooks, James M

    2014-08-12

    On April 20, 2010, the Deepwater Horizon (DWH) blowout occurred, releasing more oil than any accidental spill in history. Oil release continued for 87 d and much of the oil and gas remained in, or returned to, the deep sea. A coral community significantly impacted by the spill was discovered in late 2010 at 1,370 m depth. Here we describe the discovery of five previously unknown coral communities near the Macondo wellhead and show that at least two additional coral communities were impacted by the spill. Although the oil-containing flocullent material that was present on corals when the first impacted community was discovered was largely gone, a characteristic patchy covering of hydrozoans on dead portions of the skeleton allowed recognition of impacted colonies at the more recently discovered sites. One of these communities was 6 km south of the Macondo wellhead and over 90% of the corals present showed the characteristic signs of recent impact. The other community, 22 km southeast of the wellhead between 1,850 and 1,950 m depth, was more lightly impacted. However, the discovery of this site considerably extends the distance from Macondo and depth range of significant impact to benthic macrofaunal communities. We also show that most known deep-water coral communities in the Gulf of Mexico do not appear to have been acutely impacted by the spill, although two of the newly discovered communities near the wellhead apparently not impacted by the spill have been impacted by deep-sea fishing operations.

  4. Climatic Impact of a Change in North Atlantic Deep Water Formation

    NASA Technical Reports Server (NTRS)

    Rind, D.

    1984-01-01

    The response of the ocean to climate changes is one of the most uncertain questions regarding the impact of increasing CO2 on climate and society. North Atlantic deep water (NADW) formation apparently depends on a complex confluence of different water masses originating in different areas, all of which will presumably be affected by changes in wind, evaporation, etc., as the atmosphere warms. To analyze from first principles what the effect will be on NADW formation is a task which requires an ocean modeling capability not yet available. As a substitute, past climates can be investigated to see if there is any evidence for alterations in NADW formation. In addition, the possible impact of such changes on climate can be explored. An estimate of NADW sensitivity (at least in the past) and of the climate consequences can be studied. The North Atlantic surface water temperatures can be reconstructed to indicate a substantial cooling between 11,000 and 10,000 years B.P. Were NADW formation to have ceased, it would have resulted in cooler surface waters; whether the reconstructed temperatures were due to this or some other effect cannot be determined at this time. Nevertheless, it was decided that it would be useful to see what the effect these colder temperatures would have had on the climate.

  5. Organic matter fluxes and the sites of oxygen consumption in deep water

    NASA Astrophysics Data System (ADS)

    Tsunogai, Shizuo; Noriki, Shinichiro

    1987-06-01

    Sediment trap experiments at various stations in the Pacific and Antarctic Ocean compare observed particulate organic carbon fluxes with those obtained indirectly from vertical profiles of dissolved oxygen in the Pacific deep water. The observed carbon fluxes are characterized by large spatial variation and small vertical variation. The organic carbon fluxes at the 1000 m level ranged from 2 mg C m -2 d -1 in the subtropical ocean to more than 100 mg C m -2 d -1 in the highly productive subpolar sea, and decreased by 25 ± 10% at intervals 1000 m in depth. These results suggest that much particulate matter is transferred rapidly to the bottom of comparatively small areas of the polar, subpolar, hemipelagic and coastal seas and degraded there, and that the bottom water imprint resulting from the effects of degradation of particulate matter is transported fairly quickly to the pelagic ocean by isopycnal mixing and advection. Many unsolved phenomena occurring in the deep ocean can be explained by this suggestion.

  6. Stability of Steep Gravity--Capillary Solitary Waves in Deep Water

    NASA Astrophysics Data System (ADS)

    Akylas, T. R.; Calvo, D. C.

    2000-11-01

    The stability of steep gravity--capillary solitary waves in deep water is numerically investigated using the full nonlinear water-wave equations with surface tension. As was found in prior work based on model equations for small-amplitude solitary waves in shallow water, out of the two solution branches that bifurcate at the minimum gravity--capillary phase speed, solitary waves of depression again turn out to be stable while those of elevation are unstable to small disturbances. Motivated by the experiments of Longuet-Higgins & Zhang (Phys. Fluids 9:1963--1968, 1997), we also consider the forced problem of a localised pressure distribution applied to the free surface of a stream with speed below the minimum gravity--capillary phase speed. We find that the finite-amplitude forced solitary-wave solution branch computed by Vanden-Broeck & Dias (J. Fluid Mech. 240:549--557, 1992) is unstable but the branch corresponding to Rayleigh's linearised solution is stable. The significance of viscous effects is assessed; the effects of instability in steep waves generally are comparable to, and in some cases greater than, those of dissipation. These findings are discussed in connection with the experimental observations of Longuet-Higgins & Zhang.

  7. Deep water pipeline intervention work with an acoustically controlled power module

    SciTech Connect

    Conter, A.; Launaro, F.; Bigoni, G.

    1995-12-31

    The stabilisation of submarine pipeline free spans along uneven sea bottoms is conventionally performed using technologies such as gravel dumping, post trenching, matresses installation etc.. A new technology has been developed to support free spans along the 26 inches Transmed Gas Pipelines crossing the Sicily Channel in water depths ranging from 50m to 510m. This technology is based on the pipeline mechanical supports {open_quotes}Atlantis{close_quotes} and their installation module {open_quotes}Pegaso{close_quotes} and was developed having in mind requirements such as short installation time, system redundancy, operational flexibility and simple interface with the support vessel. The installation time reduction is achieved by automatic operational procedures which are acoustically controlled from surface. Power is stored inside two dedicated battery packs placed onboard Pegaso; no umbilical cable is necessary so that a vessel equipped with a normal crane is enough to launch and operate the system. Marine operations carried out in 1993 showed that a support can be installed in about one hour; in good weather conditions three Atlantis were installed in 24 hours including deck operations for recharging the battery packs; as a total sixteen supports were installed along the 4th and 5th Transmed Gas Pipelines. The system has proved to be a cost effective and flexible alternative to conventional technologies for free span support, especially in deep waters. A cost/benefit analysis also shows the breakeven point of the new technology versus gravel dumping.

  8. The virial theorem for water waves and its application to deep-water wave breaking

    NASA Astrophysics Data System (ADS)

    Pizzo, Nicholas; Melville, W. Ken

    2014-11-01

    The connection between the geometry, kinematics and dynamics of steep and breaking waves is crucial for an improved understanding of air-sea interaction processes. In this study, we present a virial theorem for deep-water surface gravity waves, related to a conserved integral quantity originally derived by Benjamin and Olver (1982), and we apply this theorem to the study of properties of steep and breaking waves. Specifically, we relate the geometry and dynamics of these wave scenarios in an attempt to better understand the breakdown of equipartition between the kinetic and potential energy. The virial theorem will be studied both analytically and numerically, where in the latter case we make use of a variational description of water waves in a conformally mapped reference frame (Balk 1996) that we have developed for use in a numerical model. Particular attention will be given to the application of these findings to recent theoretical and laboratory studies in which it has been shown that the potential energy available to breaking waves plays a crucial role in setting the scales of post-breaking phenomena; for example, the breaking induced energy dissipation rate (Drazen et al. 2008) and the circulation generated by breaking (Pizzo and Melville 2013).

  9. A trophic ecology of two grenadier species (Macrouridae, Pisces) in deep waters of the Southwest Atlantic

    NASA Astrophysics Data System (ADS)

    Laptikhovsky, V. V.

    2005-08-01

    The feeding habits of slope-dwelling macrourid fishes from the southern Southwest Atlantic is unknown. In this study the feeding ecology of the two most abundant species, Macrourus carinatus and M. holotrachys, was investigated. Both these grenadiers fed on a variety of prey, including gelatinous plankton, crustaceans, mesopelagic and benthic fish and cephalopods, echinoderms, as well as fishery discards. M. carinatus forage mostly in depths shallower than 900 m and its feeding spectrum and hunting strategy display important seasonal variability. It consumes more pelagic fish, squid and crustaceans than M. holotrachys, which probably indicates occasional feeding in the water column and higher availability of pelagic prey. M. holotrachys forages mostly in depths deeper than 1100 m and is a specialised bottom feeder. Macrourids are able to switch their feeding strategy from browsing on abundant food sources in summer and autumn (a narrow niche breadth and high number of prey per stomach) to hunting occasional prey in winter and spring (a wide niche breadth, low number of prey per stomach). Both species are of similar size and hard to distinguish morphologically, but in deep water M. holotrachys males are smaller than, and females larger than, those of M. carinatus. A probable reason for such energy re-distribution within a population in M. holotrachys is to achieve a higher reproductive output in a food-poor and harsh deep-sea environment.

  10. On the interaction of gravity-capillary lumps in deep water

    NASA Astrophysics Data System (ADS)

    Masnadi, Naeem; Duncan, James

    2016-11-01

    The nonlinear response of a water surface to a pressure source moving at a speed just below the minimum phase speed of linear gravity-capillary waves in deep water (cmin = 23 . 1 cm/s) consists of periodic generation of pairs of three-dimensional solitary waves (lumps) in a V-shaped pattern downstream of the source. In the reference frame of the laboratory, these unsteady lumps propagate in a direction oblique to the motion of the source and are damped by viscosity. In the current study, the interaction of lumps generated by two equal strength pressure sources moving side by side in parallel straight lines is investigated experimentally via photography-based techniques. The first lump generated by each source, collides with the lump from the other source in the center-plane of the two sources. It is observed that a steep depression is formed during the collision. Soon after the collision, this depression radiates energy in the form of small-amplitude radial waves. After the radiation, a quasi-stable pattern is formed with several rows of localized depressions that are qualitatively similar to lumps but exhibit periodic oscillations in depth, similar to a "breather". The shape of the wave pattern and the period of oscillations depend strongly on the distance between the soures.

  11. Endemic Lake Baikal sponges from deep water. 2: Taxonomy and Bathymetric Distribution.

    PubMed

    Itskovich, Valeria B; Kaluzhnaya, Oxana V; Veynberg, Elena; Erpenbeck, Dirk

    2017-02-22

    Unique samples of deep-water sponges of Lake Baikal were collected between 120 and 1450 m depth and their taxonomy and bathymetric distribution were studied. Based on morphological studies with scanning electron microscopy (SEM) and molecular analyses (CO1, ITS) we describe a new species, Baikalospongia abyssalis sp. nov. Spicule morphology of this new species is similar to Palaeoephydatia sp., a species previously known only from fossils in Late Pliocene (3.2-2.8 mya) sediments. Other sponge samples collected were identified as Baikalospongia intermedia intermedia, B. intermedia profundalis, B. bacillifera, B. fungiformis, B. martinsoni and Swartschewskia papyracea, all from the family Lubomirskiidae. Sponge specimens with giant spicules, identified as B. fungiformis, were found at great depths. B.i. intermedia and B. i. profundalis are dominating species at great depth. Light is a limiting factor for distribution of Lubomirskia baicalensis, possibly due to its symbiosis with photosynthetic protists. The current study extends our knowledge on the distribution boundaries of Lubomirskiidae at great depths.

  12. About transformation of the deep-water methane bubbles into hydrate powder and hydrate foam

    NASA Astrophysics Data System (ADS)

    Egorov, A. V.; Nigmatulin, R. I.; Rozhkov, A. N.; Sagalevich, A. M.; Chernyaev, E. S.

    2012-04-01

    During the Russian Academy of Sciences "MIRI na Baikale, 2008-2010" expedition, deep-water experiments with the bubbles of methane seeping from the bottom at depths 405, 860 and 1400 meters were carried out. These depths correspond to gas hydrate stability zone. Bubbles were caught by the trap which was looked like an inverted glass. It was found that the behavior of bubbles in a trap depends on the depth. At depth of 405 meters formation of hydrates was not observed. Having got to a trap at the depth of 860 meters, bubbles became covered by solid hydrate envelope, kept the initial form, and after a time period collapsed in a number of hydrate fragments which showed all properties of a granular matter. No visible changes in the hydrate granular matter were observed in the course of lifting it to a depth of 380 meters. Shallower, the decomposition of the hydrate granular matter into methane gas was observed. In the experiments at depth of 1400 meters the caught bubbles, becoming covered by hydrate envelope formed solid hydrate foam in the trap. At lifting this foam structure was deformed slightly but simultaneously a free gas left the foam and filled the trap. The volume of free gas in the trap at lifting varied according to the Boyle-Mariotte law.

  13. Benthic foraminiferal biogeography: controls on global distribution patterns in deep-water settings.

    PubMed

    Gooday, Andrew J; Jorissen, Frans J

    2012-01-01

    Benthic foraminifera, shell-bearing protists, are familiar from geological studies. Although many species are well known, undescribed single-chambered forms are common in the deep sea. Coastal and sublittoral species often have restricted distributions, but wide ranges are more frequent among deep-water species, particularly at abyssal depths. This probably reflects the transport of tiny propagules by currents across ocean basins that present few insurmountable barriers to dispersal, combined with slow rates of evolution. Undersampling of the vast deep-sea habitat, however, makes it very difficult to establish the ranges of less common foraminiferal species, and endemism may be more prevalent than currently realized. On continental slopes, some species have restricted distributions, but wide-ranging bathyal species that exhibit considerable morphological variation are more common. This may be linked to the greater heterogeneity of continental slopes compared with oceans basins. Improved knowledge of deep-sea foraminiferal biogeography requires sound morphology-based taxonomy combined with molecular genetic studies.

  14. On the difficulty of modeling Circumpolar Deep Water intrusions onto the Amundsen Sea continental shelf

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Timmermann, R.; Schröder, M.; Hellmer, H. H.

    2014-12-01

    In the Amundsen Sea, warm Circumpolar Deep Water (CDW) intrudes onto the continental shelf and flows into the ice shelf cavities of the West Antarctic Ice Sheet, resulting in high basal melt rates. However, none of the high resolution global models resolving all the small ice shelves around Antarctica can reproduce a realistic CDW flow onto the Amundsen Sea continental shelf, and previous studies show simulated bottom potential temperature at the Pine Island Ice Shelf front of about -1.8 °C. In this study, using the Finite-Element Sea ice-ice shelf-Ocean Model (FESOM), we reproduce warm CDW intrusions onto the Amundsen Sea continental shelf and realistic melt rates of the ice shelves in West Antarctica. To investigate the importance of horizontal resolution, forcing, horizontal diffusivity, and the effect of grounded icebergs, eight sensitivity experiments are conducted. To simulate the CDW intrusion realistically, a horizontal resolution of about 5 km or smaller is required. The choice of forcing is also important and the cold bias in the NCEP/NCAR reanalysis over the eastern Amundsen Sea prevents warm CDW from intruding onto the continental shelf. On the other hand, the CDW intrusion is not highly sensitive to the strength of horizontal diffusion. The effect of grounded icebergs located off Bear Peninsula is minor, but may act as a buffer to an anomalously cold year.

  15. Petroleum geology of Campos Basin, Brazil: A successful case history of deep water exploration

    SciTech Connect

    Franke, M.R.; Lugon, H.A.F.; Beraldo, W.L. )

    1990-05-01

    Campos Basin, the most prolific Brazilian basin, produces almost 400,000 bbl of oil per day and contains 70% of the national reserves. The basin is located on the southeastern coast of Brazil, covering a prospectable area of 100,000 km{sup 2} Campos is a passive continental margin basin originated by the breakup of Pangea and the rifting of the South American and African plates in the Early Cretaceous. The basin's sedimentary section encompasses three megasequences: nonmarine, transitional, and marine, ranging in age from Neocomian to Holocene. Hydrocarbon generation is related to nonmarine organic-rich shales and marls, and hydrocarbon entrapment assumes ascendent migration along fault planes and through salt gaps toward reservoirs ranging in age from Neocomian to Tertiary (mainly turbiditic sandstones). The first onshore stratigraphic well was drilled based on gravity surveys in 1958. The acquisition of new geophysical data, mainly seismic reflection data, followed after 1968. The first offshore well was drilled in 1971, and in 1974, the first oil field, Garopua, was discovered. Giant hydrocarbon accumulations have been discovered in water depths ranging from 400 to 1,800 m since 1984. As of mid-1989, 35 offshore oil fields have been discovered, 760 million bbl of oil, and 490 bcf of gas have been produced. The basin oil and equivalent gas reserves are estimated in 6.0 billion bbl, 60% of which is located in the deep-water giant oil fields.

  16. Glider observations of the biological response to Modified Circumpolar Deep Water Variability in the Ross Sea

    NASA Astrophysics Data System (ADS)

    O'Connell, D.; Kaufman, D.; Friedrichs, M. A.; Smith, W.

    2011-12-01

    The Ross Sea is the most productive area within the Southern Ocean, and is believed to play a significant role in the global marine carbon cycle. This region is also characterized by strong spatial and temporal variability in both physical and biogeochemical conditions; however this variability occurs on spatial and temporal scales that are difficult to resolve with traditional data sources. In order to better understand this variability, two gliders were deployed in the Ross Sea in late November 2010 during the early stages of the summer plankton bloom. Together, the two gliders made over 1500 dives and collected data (salinity, temperature, fluorescence and oxygen) throughout the water column for roughly two months. The data from these gliders were used to identify the presence of the relatively high-nutrient Modified Circumpolar Deep Water (MCDW), which has been hypothesized to be a significant factor affecting the spatial and temporal extent of the summer plankton blooms. Preliminary data analyses indicate a positive correlation between areas of MCDW and high chlorophyll concentrations. The glider data were also compared to contemporaneous cruise data and satellite data and were found to fit well with these other data, yet were better able to resolve the high temporal and spatial variability of this region. Specifically, the lower resolution of the cruise data, as compared to the glider data, made it difficult to resolve the correlation of MCDW to high chlorophyll from the cruise data alone.

  17. Pigmentation and spectral absorbance signatures in deep-water corals from the Trondheimsfjord, Norway.

    PubMed

    Elde, Anette C; Pettersen, Ragnhild; Bruheim, Per; Järnegren, Johanna; Johnsen, Geir

    2012-06-01

    The pigmentation and corresponding in vivo and in vitro absorption characteristics in three different deep-water coral species: white and orange Lophelia pertusa, Paragorgia arborea and Primnoa resedaeformis, collected from the Trondheimsfjord are described. Pigments were isolated and characterized by High-Performance Liquid Chromatography (HPLC) analysis and High-Performance Liquid Chromatography Time-Of-Flight Mass Spectrometer (LC-TOF MS). The main carotenoids identified for all three coral species were astaxanthin and a canthaxanthin-like carotenoid. Soft tissue and skeleton of orange L. pertusa contained 2 times more astaxanthin g(-1) wet weight compared to white L. pertusa. White and orange L. pertusa were characterized with in vivo absorbance peaks at 409 and 473 nm, respectively. In vivo absorbance maxima for P. arborea and P. resedaeformis was typically at 475 nm. The shapes of the absorbance spectra (400-700 nm) were species-specific, indicated by in vivo, in vitro and the corresponding difference spectra. The results may provide important chemotaxonomic information for pigment when bonded to their proteins in vivo, bio-prospecting, and for in situ identification, mapping and monitoring of corals.

  18. High diversity of microplankton surrounds deep-water coral reef in the Norwegian Sea.

    PubMed

    Jensen, Sigmund; Bourne, David G; Hovland, Martin; Murrell, J Colin

    2012-10-01

    Coral reefs that exist in the depths of the oceans are surrounded by Eukarya, Archaea and bacterial communities that may play an important role in the nutrition and health of the reef. The first interdomain community structure of planktonic organisms in seawater from a deep-water coral reef is described. Community profiling and analysis of ribosomal RNA gene sequences from a coral reef system at 350 m depth in the Norwegian Sea revealed a rich diversity of Eukarya and Bacteria and a moderate diversity of Archaea. Most sequences affiliated with marine microplankton from deep-sea to cold-surface regions, with many sequences being similar to those described in studies of mesopelagic and oxygen minimum zones. Dominant phylotypes belonged to the Alveolata (group I, II, dinoflagellates), Stramenopiles (silicoflagellates), Alphaproteobacteria (Pelagibacter ubique), Gammaproteobacteria (ARCTIC96BD-19), Bacteroidetes (Flavobacteria) and mesophilic Crenarchaeota (Nitrosopumilus maritimus). Several rare and novel members of the community fell into distinct phylogenetic groups. The inferred function of dominant community members suggested autotrophs that utilise light, ammonium or sulphide, and lifestyles based on host associations. The high diversity reflected a microplankton community structure, which is significantly different from that of microplankton collected at the same depth at a pelagic station away from reefs.

  19. The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea.

    PubMed

    Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Dushaw, Brian D; Baggeroer, Arthur B; Heaney, Kevin D; D'Spain, Gerald L; Colosi, John A; Stephen, Ralph A; Kemp, John N; Howe, Bruce M; Van Uffelen, Lora J; Wage, Kathleen E

    2013-10-01

    A series of experiments conducted in the Philippine Sea during 2009-2011 investigated deep-water acoustic propagation and ambient noise in this oceanographically and geologically complex region: (i) the 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) the 2010-2011 NPAL Philippine Sea Experiment, and (iii) the Ocean Bottom Seismometer Augmentation of the 2010-2011 NPAL Philippine Sea Experiment. The experimental goals included (a) understanding the impacts of fronts, eddies, and internal tides on acoustic propagation, (b) determining whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions, (c) improving our understanding of the physics of scattering by internal waves and spice, (d) characterizing the depth dependence and temporal variability of ambient noise, and (e) understanding the relationship between the acoustic field in the water column and the seismic field in the seafloor. In these experiments, moored and ship-suspended low-frequency acoustic sources transmitted to a newly developed distributed vertical line array receiver capable of spanning the water column in the deep ocean. The acoustic transmissions and ambient noise were also recorded by a towed hydrophone array, by acoustic Seagliders, and by ocean bottom seismometers.

  20. Evidence for the bioerosion of deep-water corals by echinoids in the Northeast Atlantic

    NASA Astrophysics Data System (ADS)

    Stevenson, Angela; Rocha, Carlos

    2013-01-01

    In situ video observations of echinoids interacting with deep-sea coral are common in the deep-sea, but paradoxically the deep-sea literature is devoid of reports of bioerosion by extant echinoids. Here we present evidence of contemporary bioerosion of cold-water coral by four species of deep-sea echinoids, Gracilechinus elegans, Gracilechinus alexandri, Cidaris cidaris, and Araeosoma fenestratum, showing that they actively predate on the living framework of reef building corals, Lophelia pertusa and Madrepora oculata, in the NE Atlantic. Echinoid specimens were collected in six canyons located in the Bay of Biscay, France and two canyons on the north side of the Porcupine Bank and Goban Spur, Ireland. A total of 44 live specimens from the four taxa (9 of G. elegans, 4 of G. alexandri, 21 of C. cidaris and 10 of A. fenestratum) showed recent ingestion of the coral infrastructure. Upon dissection, live coral skeleton was observed encased in a thick mucus layer within the gastrointestinal tract of G. elegans and G. alexandri while both live and dead coral fragments were found in C. cidaris and A. fenestratum. Echinoid bioerosion limits the growth of shallow-water reefs. Our observations suggest that echinoids may also play an important role in the ecology of deep-water coral reefs.

  1. Investigation of jack-up leg extension for deep water operations

    NASA Astrophysics Data System (ADS)

    Welaya, Yousri M. A.; Elhewy, Ahmed; Hegazy, Mohamed

    2015-06-01

    Since the first jack-up was built, jackups have become the most popular type of mobile offshore drilling unit (MODU) for offshore exploration and development purposes in shallow water. The most pivotal component of the jack-up unit is the leg, which can directly affect the global performance of the unit. In this paper, an investigation into extending the length of the jack up leg is carried out in order to study the enhancement of the rig capability to drill in deeper water approaching the range of the Semisubmersible Drilling Unit (SSDU) (300-1000ft). A study of the performance of a deep-water jack-up unit is performed with different leg lengths. Typical leg scantling dimensions and identical external loads are assigned, and then a detailed Finite Element Analysis (FEA) model is created in order to simulate the jack-up leg unit's structural behavior. A Multi-point Constraint (MPC) element together with the spring element is used to deal with the boundary conditions. Finally, a comparative analysis for five leg lengths is carried out to illustrate their performance, including the ultimate static strength, and weight.

  2. Basin-wide N2 fixation in the deep waters of the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Benavides, Mar; Bonnet, Sophie; Hernández, Nauzet; Martínez-Pérez, Alba María.; Nieto-Cid, Mar; Álvarez-Salgado, Xosé Antón; Baños, Isabel; Montero, María. F.; Mazuecos, Ignacio P.; Gasol, Josep M.; Osterholz, Helena; Dittmar, Thorsten; Berman-Frank, Ilana; Arístegui, Javier

    2016-06-01

    Recent findings indicate that N2 fixation is significant in aphotic waters, presumably due to heterotrophic diazotrophs depending on organic matter for their nutrition. However, the relationship between organic matter and heterotrophic N2 fixation remains unknown. Here we explore N2 fixation in the deep chlorophyll maximum and underneath deep waters across the whole Mediterranean Sea and relate it to organic matter composition, characterized by optical and molecular methods. Our N2 fixation rates were in the range of those previously reported for the euphotic zone of the Mediterranean Sea (up to 0.43 nmol N L-1 d-1) and were significantly correlated to the presence of relatively labile organic matter with fluorescence and molecular formula properties representative for peptides and unsaturated aliphatics and associated with the presence of more oxygenated ventilated water masses. Finally, and despite that the aphotic N2 fixation contributes largely to total water column diazotrophic activity (>50%), its contribution to overall nitrogen inputs to the basin is negligible (<0.5%).

  3. Deep water current profile measurements for operational support and design statistics

    SciTech Connect

    Moore, A.N.; Stephens, R.V.

    1995-09-01

    This paper describes the use of Acoustic Doppler Current Profilers (ADCP) to provide real-time current profile information for drilling vessels operating in deep water and also discusses the quality control and post-processing of associated recorded data to provide design current statistics. Experience gained from many such deployments over the last seven years is drawn upon to make specific recommendations for instrument system configuration and data management procedures. Practicalities and limitations of the use of ADCPs from drilling vessels are also discussed. Consideration is given to mooring design details specific to this type of deployment. Practical measurement difficulties are examined such as data contamination due to direct acoustic signal reflection from sub-sea drilling components and also the case of operating in an environment of high background acoustic noise associated with vessel dynamic positioning. Quality control procedures are discussed, both for the current profile data displayed in real-time for operational support and for subsequent post-analysis of recorded data. The paper is concluded with examples of specific details of current profile structure which have been identified using rigmounted ADCPs but would not have been possible to observe using any other measurement technology.

  4. Allochthonous deep-water basin deposits of the western US: Implications for Paleozoic paleogeography and plate margin tectonics

    SciTech Connect

    Miller, E.L. . Geology Dept.)

    1993-04-01

    The stratigraphy and sedimentology of the lower Paleozoic Roberts Mts. and upper Paleozoic Golconda allochthons can be used to reconstruct their general paleogeographic setting in the Paleozoic. Basalt pillow lavas and radiolarian chert, were once considered straightforward evidence that the allochthons represented imbricated ocean crust formed at sites far removed from continental influences. Better stratigraphic definition, provenance studies and geochemistry of lavas now indicate that clastic components were derived from the continental shelf or interior and basalts in the Roberts Mountains allochthon were erupted in an intraplate setting through thinned continental crust (Madrid, 1987). Both in the earliest Mississippian and in the Late Permian, the Antler Basin (Roberts Mts.) and the Havallah Basin (Golconda) received proximal detritus from island arc sources to the west, immediately prior to closure of the basins by thrust-faulting. These data suggest that both systems of basins formed as marginal basins by rifting on the continental shelf (Antler Basin) and along the continental margin (Havallah Basin) and were flanked to the west by active island arcs at least during part of their history. As such, their stratigraphy provides a great deal of insight regarding tectonism along the western plate margin of North America during the Paleozoic.

  5. Growth response of a deep-water ferromanganese crust to evolution of the Neogene Indian Ocean

    USGS Publications Warehouse

    Banakar, V.K.; Hein, J.R.

    2000-01-01

    A deep-water ferromanganese crust from a Central Indian Ocean seamount dated previously by 10Be and 230Th(excess) was studied for compositional and textural variations that occurred throughout its growth history. The 10Be/9Be dated interval (upper 32 mm) yields an uniform growth rate of 2.8 ?? 0.1 mm/Ma [Frank, M., O'Nions, R.K., 1998. Sources of Pb for Indian Ocean ferromanganese crusts: a record of Himalayan erosion. Earth Planet. Sci. Lett., 158, pp. 121-130.] which gives an extrapolated age of ~ 26 Ma for the base of the crust at 72 mm and is comparable to the maximum age derived from the Co-model based growth rate estimates. This study shows that Fe-Mn oxyhydroxide precipitation did not occur from the time of emplacement of the seamount during the Eocene (~ 53 Ma) until the late Oligocene (~ 26 Ma). This paucity probably was the result of a nearly overlapping palaeo-CCD and palaeo-depth of crust formation, increased early Eocene productivity, instability and reworking of the surface rocks on the flanks of the seamount, and lack of oxic deep-water in the nascent Indian Ocean. Crust accretion began (older zone) with the formation of isolated cusps of Fe-Mn oxide during a time of high detritus influx, probably due to the early-Miocene intense erosion associated with maximum exhumation of the Himalayas (op. cit.). This cuspate textured zone extends from 72 mm to 42 mm representing the early-Miocene period. Intense polar cooling and increased mixing of deep and intermediate waters at the close of the Oligocene might have led to the increased oxygenation of the bottom-water in the basin. A considerable expansion in the vertical distance between the seafloor depth and the CCD during the early Miocene in addition to the influx of oxygenated bottom-water likely initiated Fe-Mn crust formation. Pillar structure characterises the younger zone, which extends from 40 mm to the surface of the crust, i.e., ~ 15 Ma to Present. This zone is characterised by > 25% higher

  6. Highly Compressed Free Gas in Deep-Water Natural Gas Hydrate Systems

    NASA Astrophysics Data System (ADS)

    Barth, G. A.

    2006-12-01

    Natural gas, predominantly methane, is stored in a highly compact form within solid gas hydrate. The large volume of free gas that can be liberated by dissociation of hydrate (at standard surface conditions) is a prominent aspect of this potential energy resource. In contrast, the highly compressed state of free gas under pressure-temperature conditions found in deep-water marine settings is rarely noted. To facilitate comparison of gas quantities present within and below the hydrate stability zone in marine gas hydrate systems, particularly those in the deep-water Bering Sea basins, a suite of volume expansion ratios for 100% methane gas have been calculated. These ratios relate free gas volume under in-situ pressure (P) and temperature (T) conditions to free gas volume at standard surface conditions. The volume calculation is routine, using the Peng-Robinson equation of state (Peng and Robinson, 1976). Because most geophysical field studies aim to resolve the quantities of solid hydrate or free gas as a volume fraction of bulk rock in-situ, whereas gas resource volumes are reported as volume of free gas at STP, results here are presented as free gas volume ratios describing expansion between depth and surface conditions. This presentation also allows direct comparison with free gas yield of solid hydrate. Volume expansion ratio is presented for general reference for the pressure range 1 to 60 MPa and temperature range 0° to 80°C. (See USGS Open File Report 05-1451 online.) For pressures in the range 30 to 52 MPa and temperatures from 4° to 80°C, a more detailed evaluation of the P (water depth) and T (geotherm) effects on gas volumes has been undertaken. Ideal gas deviation factors, or z-factors, are also included. For free methane gas near the base of the hydrate stability zone at 360 m below seafloor in the Bering Sea, under conditions of 3,600 m water depth, 4°C seafloor temperature and 60°C/km geothermal gradient, the ratio of gas volume at standard

  7. Six new deep-water sternaspid species (Annelida, Sternaspidae) from the Pacific Ocean.

    PubMed

    Salazar-Vallejo, Sergio I; Buzhinskaja, Galina

    2013-01-01

    Most sternaspid species have been described from shallow water, and Caulleryaspis Sendall & Salazar-Vallejo, 2013 includes one deep water species: C. gudmundssoni Sendall & Salazar-Vallejo, 2013 from Iceland. In Sternaspis Otto, 1821, the most speciose genus, most species were described from shallow water and only three thrive in deep water: S. maior Chamberlin, 1919 from the Gulf of California, S. princeps Selenka, 1885 from New Zealand, and S. riestchi Caullery, 1944 from Indonesia. The study of some deep sea sternaspids from the Pacific Ocean in the collections of six research institutions resulted in the discovery of six undescribed species, and for three of them there were abundant materials showing ventro-caudal shield development. Caulleryaspis fauchaldi sp. n. is described based on specimens from Oregon and California; it differs from the known species because it has a shield with rounded anterior margins and its peg chaetae form thin, small spines. Caulleryaspis nuda sp. n. was collected off Oregon; it is unique because its shield lacks a layer of sediment particles firmly attached, but has instead a thin layer of small particles loosely attached. Four other species are newly described in Sternaspis: S. annenkovae sp. n. was collected east off the northern Kurile Islands in about 4,000 m depth; it differs from other species by having a bicolored body, with the introvert darker than the abdomen, and its ventro-caudal shield plates are divergent resulting in a divided fan. The second species, S. maureri sp. n. was found off Peru in 1296-6489 m water depths and in the Southwestern Pacific in 795-3830 m; it resembles S. williamsae sp. n. but differs because its shield has better-developed ribs, the fan has a shallow or indistinct median notch and has lateral notches well-developed. The third species, S. uschakovi sp. n., was found in the Okhotsk Sea in 592-1366 m, off California in 1585 m, Gulf of California in 1200-1274 m, and Western Mexico in 2548 m; it

  8. Six new deep-water sternaspid species (Annelida, Sternaspidae) from the Pacific Ocean

    PubMed Central

    Salazar-Vallejo, Sergio I.; Buzhinskaja, Galina

    2013-01-01

    Abstract Most sternaspid species have been described from shallow water, and Caulleryaspis Sendall & Salazar-Vallejo, 2013 includes one deep water species: C. gudmundssoni Sendall & Salazar-Vallejo, 2013 from Iceland. In Sternaspis Otto, 1821, the most speciose genus, most species were described from shallow water and only three thrive in deep water: S. maior Chamberlin, 1919 from the Gulf of California, S. princeps Selenka, 1885 from New Zealand, and S. riestchi Caullery, 1944 from Indonesia. The study of some deep sea sternaspids from the Pacific Ocean in the collections of six research institutions resulted in the discovery of six undescribed species, and for three of them there were abundant materials showing ventro-caudal shield development. Caulleryaspis fauchaldi sp. n. is described based on specimens from Oregon and California; it differs from the known species because it has a shield with rounded anterior margins and its peg chaetae form thin, small spines. Caulleryaspis nuda sp. n. was collected off Oregon; it is unique because its shield lacks a layer of sediment particles firmly attached, but has instead a thin layer of small particles loosely attached. Four other species are newly described in Sternaspis: S. annenkovae sp. n. was collected east off the northern Kurile Islands in about 4,000 m depth; it differs from other species by having a bicolored body, with the introvert darker than the abdomen, and its ventro-caudal shield plates are divergent resulting in a divided fan. The second species, S. maureri sp. n. was found off Peru in 1296–6489 m water depths and in the Southwestern Pacific in 795–3830 m; it resembles S. williamsae sp. n. but differs because its shield has better-developed ribs, the fan has a shallow or indistinct median notch and has lateral notches well-developed. The third species, S. uschakovi sp. n., was found in the Okhotsk Sea in 592–1366 m, off California in 1585 m, Gulf of California in 1200–1274 m, and Western Mexico

  9. On the interaction of deep water waves and exponential shear currents

    NASA Astrophysics Data System (ADS)

    Cheng, Jun; Cang, Jie; Liao, Shi-Jun

    2009-05-01

    A train of periodic deep-water waves propagating on a steady shear current with a vertical distribution of vorticity is investigated by an analytic method, namely the homotopy analysis method (HAM). The magnitude of the vorticity varies exponentially with the magnitude of the stream function, while remaining constant on a particular streamline. The so-called Dubreil-Jacotin transformation is used to transfer the original exponentially nonlinear boundary-value problem in an unknown domain into an algebraically nonlinear boundary-value problem in a known domain. Convergent series solutions are obtained not only for small amplitude water waves on a weak current but also for large amplitude waves on a strong current. The nonlinear wave-current interaction is studied in detail. It is found that an aiding shear current tends to enlarge the wave phase speed, sharpen the wave crest, but shorten the maximum wave height, while an opposing shear current has the opposite effect. Besides, the amplitude of waves and fluid velocity decay over the depth more quickly on an aiding shear current but more slowly on an opposing shear current than that of waves on still water. Furthermore, it is found that Stokes criteria of wave breaking is still valid for waves on a shear current: a train of propagating waves on a shear current breaks as the fiuid velocity at crest equals the wave phase speed. Especially, it is found that the highest waves on an opposing shear current are even higher and steeper than that of waves on still water. Mathematically, this analytic method is rather general in principle and can be employed to solve many types of nonlinear partial differential equations with variable coefficients in science, finance and engineering.

  10. New glass sponges (Porifera: Hexactinellida) from deep waters of the central Aleutian Islands, Alaska.

    PubMed

    Reiswig, Henry M; Stone, Robert P

    2013-01-01

    Hexactinellida from deep-water communities of the central Aleutian Islands, Alaska, are described. They were mostly collected by the remotely operated vehicle 'Jason II' from 494–2311 m depths during a 2004 RV 'Roger Revelle' expedition, but one shallow-water species collected with a shrimp trawl from 155 m in the same area is included. The excellent condition of the ROV-collected specimens enabled valuable redescription of some species previously known only from badly damaged specimens. New taxa include one new genus and eight new species in five families. Farreidae consist of two new species, Farrea aleutiana and F. aspondyla. Euretidae consists of only Pinulasma fistulosum n. gen., n. sp. Tretodictyidae include only Tretodictyum amchitkensis n. sp. Euplectellidae consists of only the widespread species Regadrella okinoseana Ijima, reported here over 3,700 km from its closest previously known occurrence. The most diverse family, Rossellidae, consists of Aulosaccus ijimai (Schulze), Aulosaccus schulzei Ijima, Bathydorus sp. (young stage not determinable to species), Caulophacus (Caulophacus) adakensis n. sp., Acanthascus koltuni n. sp., Staurocalyptus psilosus n. sp., Staurocalyptus tylotus n. sp. and Rhabdocalyptus mirabilis Schulze. We present argument for reinstatement of the abolished rossellid subfamily Acanthascinae and return of the subgenera  Staurocalyptus Ijima and Rhabdocalyptus Schulze to their previous generic status. These fauna provides important complexity to the hard substrate communities that likely serve as nursery areas for the young stages of commercially important fish and crab species, refuge from predation for both young and adult stages, and also as a focal source of prey for juvenile and adult stages of those same species.

  11. Noble gas tracers of ventilation during deep-water formation in the Weddell Sea

    NASA Astrophysics Data System (ADS)

    Nicholson, D. P.; Khatiwala, S.; Heimbach, P.

    2016-05-01

    To explore the dynamics and implications of incomplete air-sea equilibration during the formation of abyssal water masses, we simulated noble gases in the Estimating the Circulation & Climate of the Ocean (ECCO) global ocean state estimate. A novel computation approach utilizing a matrix-free Newton-Krylov (MFNK) scheme was applied to quickly compute the periodic seasonal solutions for noble gas tracers. MFNK allows for quick computation of a cyclo-stationary solution for tracers (i.e., a spun-up, repeating seasonal cycle), which would otherwise be computationally infeasible due to the long time scale of dynamic adjustment of the abyssal ocean (1000’s of years). A suite of experiments isolates individual processes, including atmospheric pressure effects, the solubility pump and air-sea bubble fluxes. In addition to these modeled processes, a volumetric contribution of 0.28 ± 0.07% of glacial melt water is required to reconcile deep-water observations in the Weddell Sea. Another primary finding of our work is that the saturation anomaly of heavy noble gases in model simulations is in excess of two-fold more negative than is suggested from Weddell Sea observations. This result suggests that model water masses are insufficiently ventilated prior to subduction and thus there is insufficient communication between atmosphere and ocean at high latitudes. The discrepancy between noble gas observations and ECCO simulations highlights that important inadequacies remain in how we model high-latitude ventilation with large implications for the oceanic uptake and storage of carbon.

  12. Deep-water sponges (Porifera) from Bonaire and Klein Curaçao, Southern Caribbean.

    PubMed

    Van Soest, Rob W M; Meesters, Erik H W G; Becking, Leontine E

    2014-10-29

    Four submersible dives off the coast of Bonaire (Caribbean Netherlands) and Klein Curaçao (Curaçao) to depths of 99.5-242 m, covering lower mesophotic and upper dysphotic zones, yielded 52 sponge specimens belonging to 31 species. Among these we identified 13 species as new to science. These are Plakinastrella stinapa n. sp., Pachastrella pacoi n. sp., Characella pachastrelloides n. sp., Geodia curacaoensis n. sp., Caminus carmabi n. sp., Discodermia adhaerens n. sp., Clathria (Microciona) acarnoides n. sp., Antho (Acarnia) pellita n. sp., Parahigginsia strongylifera n. sp., Calyx magnoculata n. sp., Neopetrosia dutchi n. sp., Neopetrosia ovata n. sp. and Neopetrosia eurystomata n. sp. We also report an euretid hexactinellid, which belongs to the rare genus Verrucocoeloidea, recently described (2014) as V. liberatorii Reiswig & Dohrmann. The remaining 18 already known species are all illustrated by photos of the habit, either in situ or 'on deck', but only briefly characterized in an annotated table to confirm their occurrence in the Southern Caribbean. The habitat investigated-steep limestone rocks, likely representing Pleistocene fossil reefs--is similar to deep-water fossil reefs at Barbados of which the sponges were sampled and studied by Van Soest and Stentoft (1988). A comparison is made between the two localities, showing a high degree of similarity in sponge composition: 53% of the present Bonaire-Klein Curaçao species were also retrieved at Barbados. At the level of higher taxa (genera, families) Bonaire-Klein Curaçao shared approximately 80% of its lower mesophotic and upper dysphotic sponge fauna with Barbados, despite a distance between them of 1000 km, indicating high faunal homogeneity. We also preliminarily compared the shallow-water (euphotic) sponge fauna of Curaçao with the combined data available for the Barbados, Bonaire and Klein Curaçao mesophotic and upper dysphotic sponges, which resulted in the conclusion that the two faunas show only

  13. Emergence of coherent wave groups in deep-water random sea

    NASA Astrophysics Data System (ADS)

    Viotti, C.; Dutykh, D.; Dudley, J. M.; Dias, F.

    2013-06-01

    Extreme surface waves in a deep-water long-crested sea are often interpreted as a manifestation in the real world of the so-called breathing solitons of the focusing nonlinear Schrödinger equation. While the spontaneous emergence of such coherent structures from nonlinear wave dynamics was demonstrated to take place in fiber-optics systems, the same point remains far more controversial in the hydrodynamic case. With the aim to shed further light on this matter, the emergence of breatherlike coherent wave groups in a long-crested random sea is investigated here by means of high-resolution spectral simulations of the fully nonlinear two-dimensional Euler equations. The primary focus of our study is to parametrize the structure of random wave fields with respect to the Benjamin-Feir index, which is a nondimensional measure of the energy localization in Fourier space. This choice is motivated by previous results, showing that extreme-wave activity in a long-crested sea is highly sensitive to such a parameter, which is varied here by changing both the characteristic spectral bandwidth and the average wave steepness. It is found that coherent wave groups, closely matching realizations of Kuznetsov-Ma breathers in Euler dynamics, develop within wave fields characterized by sufficiently narrow-banded spectra. The characteristic spatial and temporal scales of wave group dynamics, and the corresponding occurrence of extreme events, are quantified and discussed by means of space-time autocorrelations of the surface elevation envelope and extreme-event statistics.

  14. Emergence of coherent wave groups in deep-water random sea.

    PubMed

    Viotti, C; Dutykh, D; Dudley, J M; Dias, F

    2013-06-01

    Extreme surface waves in a deep-water long-crested sea are often interpreted as a manifestation in the real world of the so-called breathing solitons of the focusing nonlinear Schrödinger equation. While the spontaneous emergence of such coherent structures from nonlinear wave dynamics was demonstrated to take place in fiber-optics systems, the same point remains far more controversial in the hydrodynamic case. With the aim to shed further light on this matter, the emergence of breatherlike coherent wave groups in a long-crested random sea is investigated here by means of high-resolution spectral simulations of the fully nonlinear two-dimensional Euler equations. The primary focus of our study is to parametrize the structure of random wave fields with respect to the Benjamin-Feir index, which is a nondimensional measure of the energy localization in Fourier space. This choice is motivated by previous results, showing that extreme-wave activity in a long-crested sea is highly sensitive to such a parameter, which is varied here by changing both the characteristic spectral bandwidth and the average wave steepness. It is found that coherent wave groups, closely matching realizations of Kuznetsov-Ma breathers in Euler dynamics, develop within wave fields characterized by sufficiently narrow-banded spectra. The characteristic spatial and temporal scales of wave group dynamics, and the corresponding occurrence of extreme events, are quantified and discussed by means of space-time autocorrelations of the surface elevation envelope and extreme-event statistics.

  15. Eddy-Mediated Transport of Circumpolar Deep Water Across the Antarctic Shelf Break

    NASA Astrophysics Data System (ADS)

    Stewart, A.; Thompson, A. F.

    2014-12-01

    The continental shelves of Antarctica produce the ocean's densest water, Antarctic Bottom Water (AABW), which ventilates over 50% of the sub-surface global ocean. The heat needed to melt marine-terminating Antarctic ice sheets and produce dense water is supplied by Circumpolar Deep Water (CDW), a relatively warm, mid-depth water mass found offshore. The onshore transport of CDW is obstructed by the Antarctic Slope Front (ASF), a westward current at the continental shelf break that almost completely encircles the continent. Relatively little is understood about the processes that control the exchange of water masses and shoreward heat transport across the ASF, due to a scarcity of observations and the prohibitive cost of simulating turbulent flows in this region. Using a process model of the ASF that resolves the mesoscale eddies at the shelf break, we show that the ASF is shaped by an interplay between the surface wind forcing, transport by mesoscale eddies, and the geometry of the continental shelf. Consequently the onshore transport of CDW and the properties of the outflowing AABW are strongly sensitive to the wind and buoyancy forcing at the ocean surface, and to the geometry of the continental shelf. The onshore mass transport of CDW occurs through an eddy thickness flux. We develop a scaling for this transport that accurately captures the strong sensitivity to forcing and geometry, which is largely controlled by the eddy kinetic energy (EKE) over the continental slope. We find that the EKE is enhanced in the CDW density classes over the continental slope, but cross-slope mixing is constrained by the strong topographic potential vorticity gradient. Our results offer an explanation for the substantial changes in the structure of the ASF around Antarctica, and provide insight into future rates of dense water production and shoreward heat transport around Antarctica.

  16. Reversed flow of Atlantic deep water during the Last Glacial Maximum.

    PubMed

    Negre, César; Zahn, Rainer; Thomas, Alexander L; Masqué, Pere; Henderson, Gideon M; Martínez-Méndez, Gema; Hall, Ian R; Mas, José L

    2010-11-04

    The meridional overturning circulation (MOC) of the Atlantic Ocean is considered to be one of the most important components of the climate system. This is because its warm surface currents, such as the Gulf Stream, redistribute huge amounts of energy from tropical to high latitudes and influence regional weather and climate patterns, whereas its lower limb ventilates the deep ocean and affects the storage of carbon in the abyss, away from the atmosphere. Despite its significance for future climate, the operation of the MOC under contrasting climates of the past remains controversial. Nutrient-based proxies and recent model simulations indicate that during the Last Glacial Maximum the convective activity in the North Atlantic Ocean was much weaker than at present. In contrast, rate-sensitive radiogenic (231)Pa/(230)Th isotope ratios from the North Atlantic have been interpreted to indicate only minor changes in MOC strength. Here we show that the basin-scale abyssal circulation of the Atlantic Ocean was probably reversed during the Last Glacial Maximum and was dominated by northward water flow from the Southern Ocean. These conclusions are based on new high-resolution data from the South Atlantic Ocean that establish the basin-scale north to south gradient in (231)Pa/(230)Th, and thus the direction of the deep ocean circulation. Our findings are consistent with nutrient-based proxies and argue that further analysis of (231)Pa/(230)Th outside the North Atlantic basin will enhance our understanding of past ocean circulation, provided that spatial gradients are carefully considered. This broader perspective suggests that the modern pattern of the Atlantic MOC-with a prominent southerly flow of deep waters originating in the North Atlantic-arose only during the Holocene epoch.

  17. Millennial-scale oscillations between sea ice and convective deep water formation

    NASA Astrophysics Data System (ADS)

    Saha, Raj

    2015-11-01

    During the last ice age there were several quasiperiodic abrupt warming events. The climatic effects of the so-called Dansgaard-Oeschger (D-O) events were felt globally, although the North Atlantic experienced the largest and most abrupt temperature anomalies. Similar but weaker oscillations also took place during the interglacial period. This paper proposes an auto-oscillatory mechanism between sea ice and convective deep water formation in the North Atlantic as the source of the persistent cycles. A simple dynamical model is constructed by coupling and slightly modifying two existing models of ocean circulation and sea ice. The model exhibits mixed mode oscillations, consisting of decadal-scale small-amplitude oscillations and a large-amplitude relaxation fluctuation. The decadal oscillations occur due to the insulating effect of sea ice and leads to periodic ventilation of heat from the polar ocean. Gradually, an instability builds up in the polar column and results in an abrupt initiation of convection and polar warming. The unstable convective state relaxes back to the small-amplitude oscillations from where the process repeats in a self-sustained manner. Freshwater pulses mimicking Heinrich events cause the oscillations to be grouped into packets of progressively weaker fluctuations, as observed in proxy records. Modulation of this stable oscillation mechanism by freshwater and insolation variations could account for the distribution and pacing of D-O and Bond events. Physical aspects of the system such as sea ice extent and oceanic advective flow rates could determine the characteristic 1500 year time scale of D-O events. The model results with respect to the structure of the water column in the Nordic seas during stadial and interstadial phases are in agreement with paleoproxy observations.

  18. Lytic viral infection of bacterioplankton in deep waters of the western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Li, Y.; Luo, T.; Sun, J.; Cai, L.; Liang, Y.; Jiao, N.; Zhang, R.

    2014-05-01

    As the most abundant biological entities in the ocean, viruses influence host mortality and nutrient recycling mainly through lytic infection. Yet, the ecological characteristics of virioplankton and viral impacts on host mortality and biogeochemical cycling in the deep sea are largely unknown. In the present study, viral abundance and lytic infection were investigated throughout the water column in the western Pacific Ocean. Both the prokaryotic and viral abundance and production showed a significantly decreasing trend from epipelagic to meso- and bathypelagic waters. Viral abundance decreased from 0.36-1.05 × 1010 particles L-1 to 0.43-0.80 × 109 particles L-1, while the virus : prokaryote ratio varied from 7.21 to 16.23 to 2.45-23.40, at the surface and 2000 m, respectively. Lytic viral production rates in surface and 2000 m waters were, on average, 1.03 × 1010 L-1 day-1 and 5.74 × 108 L-1 day-1. Relatively high percentages of prokaryotic cells lysed by viruses at 1000 and 2000 m were observed, suggesting a significant contribution of viruses to prokaryotic mortality in the deep ocean. The carbon released by viral lysis in deep western Pacific Ocean waters was from 0.03 to 2.32 μg C L-1 day-1. Our findings demonstrated a highly dynamic and active viral population in these deep waters and suggested that virioplankton play an important role in the microbial loop and subsequently biogeochemical cycling in deep oceans.

  19. Large-Scale Geographic Variation in Distribution and Abundance of Australian Deep-Water Kelp Forests

    PubMed Central

    Marzinelli, Ezequiel M.; Williams, Stefan B.; Babcock, Russell C.; Barrett, Neville S.; Johnson, Craig R.; Jordan, Alan; Kendrick, Gary A.; Pizarro, Oscar R.; Smale, Dan A.; Steinberg, Peter D.

    2015-01-01

    Despite the significance of marine habitat-forming organisms, little is known about their large-scale distribution and abundance in deeper waters, where they are difficult to access. Such information is necessary to develop sound conservation and management strategies. Kelps are main habitat-formers in temperate reefs worldwide; however, these habitats are highly sensitive to environmental change. The kelp Ecklonia radiate is the major habitat-forming organism on subtidal reefs in temperate Australia. Here, we provide large-scale ecological data encompassing the latitudinal distribution along the continent of these kelp forests, which is a necessary first step towards quantitative inferences about the effects of climatic change and other stressors on these valuable habitats. We used the Autonomous Underwater Vehicle (AUV) facility of Australia’s Integrated Marine Observing System (IMOS) to survey 157,000 m2 of seabed, of which ca 13,000 m2 were used to quantify kelp covers at multiple spatial scales (10–100 m to 100–1,000 km) and depths (15–60 m) across several regions ca 2–6° latitude apart along the East and West coast of Australia. We investigated the large-scale geographic variation in distribution and abundance of deep-water kelp (>15 m depth) and their relationships with physical variables. Kelp cover generally increased with latitude despite great variability at smaller spatial scales. Maximum depth of kelp occurrence was 40–50 m. Kelp latitudinal distribution along the continent was most strongly related to water temperature and substratum availability. This extensive survey data, coupled with ongoing AUV missions, will allow for the detection of long-term shifts in the distribution and abundance of habitat-forming kelp and the organisms they support on a continental scale, and provide information necessary for successful implementation and management of conservation reserves. PMID:25693066

  20. Wave-current interactions in deep water conditions: field measurements and analyses

    NASA Astrophysics Data System (ADS)

    Rougier, Gilles; Rey, Vincent; Molcard, Anne

    2015-04-01

    The study of wave - current interaction has drawn interest in oceanography, ocean engineering, maritime navigation and for tides or waves power device design. In the context of the hydrodynamics study along the French Mediterranean coast, a current profiler was deployed near Toulon at the south of the "Port Cros" island. This coastal zone is characterized by a steep slope, the water depth varying from tens meters to several thousand meters over few kilometers from the coast. An ambient current, the "Northern Current", coming from the Ligurian sea (area of Genoa, Italy) and following the coast up to Toulon, is present all over the year. Its mean surface velocity is of about 0.30 m/s, its flow rate of about 1.5 Sv. The region is exposed to two dominating winds: the Mistral, coming from North-West, and Eastern winds. Both generate swell and/or wind waves in either following or opposing current conditions with respect to the Northern Current. A current profiler equipped with a wave tracking system (ACPD workhorse from RDI) was deployed from July to October 2014 in deep water conditions (depth of about 500m). The mooring system allowed the ADCP to measure the current profile from the sea surface down to 25m depth, which corresponds more or less to the depth of influence of waves of periods up to 10s. The collected data include energetic wave conditions in either following or opposing current conditions. The current intensity and its vertical profiles have shown a significant temporal variability according to the meteorological conditions. Effects of the wave conditions on the current properties are discussed. ACKNOWLEDGEMENTS This work was supported by the program BOMBYX and the ANR grant No ANR-13-ASTR-0007.

  1. Temporal variability of the Circumpolar Deep Water inflow onto the Ross Sea continental shelf

    NASA Astrophysics Data System (ADS)

    Castagno, Pasquale; Falco, Pierpaolo; Dinniman, Michael S.; Spezie, Giancarlo; Budillon, Giorgio

    2017-02-01

    The intrusion of Circumpolar Deep Water (CDW) is the primary source of heat, salt and nutrients onto Antarctica's continental shelves and plays a major role in the shelf physical and biological processes. Different studies have analyzed the processes responsible for the transport of CDW across the Ross Sea shelf break, but until now, there are no continuous observations that investigate the timing of the intrusions. Also, few works have focused on the effect of the tides that control these intrusions. In the Ross Sea, the CDW intrudes onto the shelf in several locations, but mostly along the troughs. We use hydrographic observations and a mooring placed on the outer shelf in the middle of the Drygalski Trough in order to characterize the spatial and temporal variability of CDW inflow onto the shelf. Our data span from 2004 to the beginning of 2014. In the Drygalski Trough, the CDW enters as a 150 m thick layer between 250 and 400 m, and moves upward towards the south. At the mooring location, about 50 km from the shelf break, two main CDW cores can be observed: one on the east side of the trough spreading along the west slope of Mawson Bank from about 200 m to the bottom and the other one in the central-west side from 200 m to about 350 m depth. A signature of this lighter and relatively warm water is detected by the instruments on the mooring at bottom of the Drygalski Trough. High frequency periodic CDW intrusion at the bottom of the trough is related to the diurnal and spring/neap tidal cycles. At lower frequency, a seasonal variability of the CDW intrusion is noticed. A strong inflow of CDW is observed every year at the end of December, while the CDW inflow is at its seasonal minimum during the beginning of the austral fall. In addition an interannual variability is also evident. A change of the CDW intrusion before and after 2010 is observed.

  2. Source rock in the Lower Tertiary and Cretaceous, deep-water Gulf of Mexico

    SciTech Connect

    Wagner, B.E.; Sofer, Z.; Claxton, B.L.

    1994-09-01

    Amoco drilled three wells in the deep-water Gulf of Mexico in 1993. One well, in Mississippi Canyon Block 84 (W.D. 5200 ft), drilled a structural feature. The well penetrated Cretaceous section and crossed the middle Cenomanian unconformity. Six sidewall cores from 14,230-15,200 ft (subsea) contained TOC values from 2.6 to 5.2% with hydrogen indices front 360 to 543 ppm in lower Tertiary and Cretaceous shales. All six cores were thermally immature, for oil generation, based on biomarker ratios and vitrinite reflectance measurements. Organic extracts from cores in the Cretaceous had biomarker characteristics similar to oil reservoired in the Miocene. The oil was probably generated from a similar, but more mature, source rock. The high structural position of the well prevented the lower Tertiary and Upper Cretaceous section from entering the oil window at this location. There are over 2000 ft of structural relief and an additional 6000-8000 ft of Lower Cretaceous section below the level penetrated by the well. It is probable that an equivalent section off structure is in the oil window. Prior to drilling, estimates of expected thermal maturities and temperatures were made using {sub BASINMOD}, a hydrocarbon generation/expulsion modeling package. The model predicted higher well temperatures (e,g., 225{degrees}F vs. 192{degrees}F) and lower vitrinite maturity (0.44% vs. 0.64%) than encountered in the well. Vitrinite reflectance equivalents of 0.41% and 0.43% were calculated from biomarker ratios of the Cretaceous core extracts, matching the {sub BASINMOD} predicted value of 0.44%.

  3. Footprint of Deepwater Horizon blowout impact to deep-water coral communities

    PubMed Central

    Fisher, Charles R.; Hsing, Pen-Yuan; Kaiser, Carl L.; Yoerger, Dana R.; Roberts, Harry H.; Shedd, William W.; Cordes, Erik E.; Shank, Timothy M.; Berlet, Samantha P.; Saunders, Miles G.; Larcom, Elizabeth A.; Brooks, James M.

    2014-01-01

    On April 20, 2010, the Deepwater Horizon (DWH) blowout occurred, releasing more oil than any accidental spill in history. Oil release continued for 87 d and much of the oil and gas remained in, or returned to, the deep sea. A coral community significantly impacted by the spill was discovered in late 2010 at 1,370 m depth. Here we describe the discovery of five previously unknown coral communities near the Macondo wellhead and show that at least two additional coral communities were impacted by the spill. Although the oil-containing flocullent material that was present on corals when the first impacted community was discovered was largely gone, a characteristic patchy covering of hydrozoans on dead portions of the skeleton allowed recognition of impacted colonies at the more recently discovered sites. One of these communities was 6 km south of the Macondo wellhead and over 90% of the corals present showed the characteristic signs of recent impact. The other community, 22 km southeast of the wellhead between 1,850 and 1,950 m depth, was more lightly impacted. However, the discovery of this site considerably extends the distance from Macondo and depth range of significant impact to benthic macrofaunal communities. We also show that most known deep-water coral communities in the Gulf of Mexico do not appear to have been acutely impacted by the spill, although two of the newly discovered communities near the wellhead apparently not impacted by the spill have been impacted by deep-sea fishing operations. PMID:25071200

  4. Influence of Conowingo Reservoir Infill on Chesapeake Bay Deep Water Hypoxia

    NASA Astrophysics Data System (ADS)

    Linker, L. C.; Cerco, C. F.; Batiuk, R.

    2014-12-01

    The Chesapeake Bay Total Maximum Daily Load (TMDL) requires the reduction of nitrogen, phosphorus, and sediment loads in the Chesapeake watershed because of the tidal water quality impairments and the damage to living resources they cause. Within the Chesapeake watershed the Conowingo Reservoir has been filling in with sediment for almost a century, and is now in a state of near-full capacity called dynamic equilibrium. The development of the Chesapeake TMDL in 2010 was with the hydrology of a 1991-2000 simulation period, and carried with this simulation period the implicit model calibration assumption, based on the 1991-2000 nutrient and sediment observations, of a Conowingo Reservoir that was still effectively trapping sediment. In a TMDL, pollutant loads beyond the TMDL allocation, which are brought about by growth or other conditions, must be offset. Using the analysis tools of the Chesapeake TMDL for assessing the degree of attainment of living resource based water quality standards, the estimated nutrient and sediment loads from a simulated infill of the Conowingo Reservoir was determined. The influence on Chesapeake water quality by a large storm and scour event of January 1996 on the Susquehanna was estimated and the same storm and scour events were also evaluated in the more critical living resource periods of June and October. An analysis was also made on the estimated influence of more moderate but frequent high flow events. The infill of the Conowingo reservoir had estimated impairments of water quality at both the simulated high flow scour events and at the more frequent moderate storm flows. The estimated impairment was primarily on the deep water and deep channel dissolved oxygen because of increased scour and transport of dissolved particulate organic nutrients under conditions of Conowingo infill. Figure 1 describes the linked models used to assess the impact of Conowingo Reservoir infill on Chesapeake hypoxia.

  5. APL-UW Deep Water Propagation: Philippine Sea Signal Physics and North Pacific Ambient Noise and NPANL Support

    DTIC Science & Technology

    2014-09-30

    APL-UW Deep Water Propagation: Philippine Sea Signal Physics and North Pacific Ambient Noise and NPANL Support Rex K. Andrew Principal...http://www.apl.washington.edu/projects/blue water LONG TERM GOALS Understand how the fundamental statistics of broadband low-frequency acoustical...signals evolve during propagation through a dynamically-varying deep ocean , and how the oceanic ambient noise field varies throughout deep ocean

  6. Fracture zones in the Mid Atlantic Ridge lead to alterations in prokaryotic and viral parameters in deep-water masses.

    PubMed

    Muck, Simone; Griessler, Thomas; Köstner, Nicole; Klimiuk, Adam; Winter, Christian; Herndl, Gerhard J

    2014-01-01

    We hypothesized that mixing zones of deep-water masses act as ecotones leading to alterations in microbial diversity and activity due to changes in the biogeochemical characteristics of these boundary systems. We determined the changes in prokaryotic and viral abundance and production in the Vema Fracture Zone (VFZ) of the subtropical North Atlantic Ocean, where North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) are funneled through this narrow canyon and therefore, are subjected to intense vertical mixing. Consequently, salinity, potential temperature, oxygen, PO4, SiO4, NO3 were altered in the NADW inside the VFZ as compared to the NADW outside of the VFZ. Also, viral abundance, lytic viral production (VP) and the virus-to-prokaryote ratio (VPR) were elevated in the NADW in the VFZ as compared to the NADW outside the VFZ. In contrast to lytic VP, lysogenic VP and both the frequency of lytically (FIC) and lysogenically infected cells (FLC) did not significantly differ between in- and outside the VFZ. Generally, FIC was higher than FLC throughout the water column. Prokaryotic (determined by T-RFLP) and viral (determined by RAPD-PCR) community composition was depth-stratified inside and outside the VFZ. The viral community was more modified both with depth and over distance inside the VFZ as compared to the northern section and to the prokaryotic communities. However, no clusters of prokaryotic and viral communities characteristic for the VFZ were identified. Based on our observations, we conclude that turbulent mixing of the deep water masses impacts not only the physico-chemical parameters of the mixing zone but also the interaction between viruses and prokaryotes due to a stimulation of the overall activity. However, only minor effects of deep water mixing were observed on the community composition of the dominant prokaryotes and viruses.

  7. The intensification of deep-water mass changes in the deep Atlantic Ocean throughout the Mid-Pleistocene climate transition

    NASA Astrophysics Data System (ADS)

    Poirier, R. K.; Billups, K.

    2012-12-01

    We examine the deep-water hydrography at Ocean Drilling Project (ODP) Site 1063 (subtropical North Atlantic, ~4600 meter water depth) using high-resolution benthic stable isotope (δ18O, δ13C) and grain size (% coarse, % Sortable Silt - SS, SS mean diameter) analyses from ~490 to 740 ka. The benthic foraminiferal δ13C record from Site 1063 provides a proxy for changes in the relative flux of lower North Atlantic Deep Water (NADW) through time. This record will refine the timing of increases in the formation of the densest components of NADW on the orbital and millennial-scale. We explore whether or not grain size analyses provide a proxy for changes in the relative velocity of the deep current. The new stable isotope data from Site 1063, when combined with the records of Poli et al. (2000), Ferretti et al. (2005), and Billups et al. (2011), tuned to the global benthic isotope stack (LR05) of Liesicki and Raymo (2004), provides a complete deep water record spanning Marine Isotope Stage (MIS) 25 to MIS 8 (~1020 to ~240 ka). Compiling published records from 16 additional sites, we use the Ocean Data View (ODV) program (Schlitzer, 2012) to map deep-water mass distributions through time. Results reveal an increasing distribution and influence of the NADW in relation to the Antarctic Bottom Water mass within interglacial periods beginning at MIS 15 continuing though the end of the Site 1063 record within MIS 9. Preliminary grain size analyses over a short interval of time reveal regular high frequency variations on the millennial scale. We anticipate having complete, high-resolution stable isotope and grain size records to discuss the hydrographic changes within the MIS 16/15 glacial/interglacial transition, as well as throughout the Mid-Pleistocene transition (MPT).

  8. Impact of the Deepwater Horizon oil spill on a deep-water coral community in the Gulf of Mexico

    USGS Publications Warehouse

    White, Helen K.; Hsing, Pen-Yuan; Cho, Walter; Shank, Timothy M.; Cordes, Erik E.; Quattrini, Andrea M.; Nelson, Robert K.; Camilli, Richard; Demopoulos, Amanda W.J.; German, Christopher R.; Brooks, James M.; Roberts, Harry H.; Shedd, William; Reddy, Christopher M.; Fisher, Charles R.

    2012-01-01

    To assess the potential impact of the Deepwater Horizon oil spill on offshore ecosystems, 11 sites hosting deep-water coral communities were examined 3 to 4 mo after the well was capped. Healthy coral communities were observed at all sites >20 km from the Macondo well, including seven sites previously visited in September 2009, where the corals and communities appeared unchanged. However, at one site 11 km southwest of the Macondo well, coral colonies presented widespread signs of stress, including varying degrees of tissue loss, sclerite enlargement, excess mucous production, bleached commensal ophiuroids, and covering by brown flocculent material (floc). On the basis of these criteria the level of impact to individual colonies was ranked from 0 (least impact) to 4 (greatest impact). Of the 43 corals imaged at that site, 46% exhibited evidence of impact on more than half of the colony, whereas nearly a quarter of all of the corals showed impact to >90% of the colony. Additionally, 53% of these corals’ ophiuroid associates displayed abnormal color and/or attachment posture. Analysis of hopanoid petroleum biomarkers isolated from the floc provides strong evidence that this material contained oil from the Macondo well. The presence of recently damaged and deceased corals beneath the path of a previously documented plume emanating from the Macondo well provides compelling evidence that the oil impacted deep-water ecosystems. Our findings underscore the unprecedented nature of the spill in terms of its magnitude, release at depth, and impact to deep-water ecosystems.

  9. Impact of the Deepwater Horizon oil spill on a deep-water coral community in the Gulf of Mexico.

    PubMed

    White, Helen K; Hsing, Pen-Yuan; Cho, Walter; Shank, Timothy M; Cordes, Erik E; Quattrini, Andrea M; Nelson, Robert K; Camilli, Richard; Demopoulos, Amanda W J; German, Christopher R; Brooks, James M; Roberts, Harry H; Shedd, William; Reddy, Christopher M; Fisher, Charles R

    2012-12-11

    To assess the potential impact of the Deepwater Horizon oil spill on offshore ecosystems, 11 sites hosting deep-water coral communities were examined 3 to 4 mo after the well was capped. Healthy coral communities were observed at all sites >20 km from the Macondo well, including seven sites previously visited in September 2009, where the corals and communities appeared unchanged. However, at one site 11 km southwest of the Macondo well, coral colonies presented widespread signs of stress, including varying degrees of tissue loss, sclerite enlargement, excess mucous production, bleached commensal ophiuroids, and covering by brown flocculent material (floc). On the basis of these criteria the level of impact to individual colonies was ranked from 0 (least impact) to 4 (greatest impact). Of the 43 corals imaged at that site, 46% exhibited evidence of impact on more than half of the colony, whereas nearly a quarter of all of the corals showed impact to >90% of the colony. Additionally, 53% of these corals' ophiuroid associates displayed abnormal color and/or attachment posture. Analysis of hopanoid petroleum biomarkers isolated from the floc provides strong evidence that this material contained oil from the Macondo well. The presence of recently damaged and deceased corals beneath the path of a previously documented plume emanating from the Macondo well provides compelling evidence that the oil impacted deep-water ecosystems. Our findings underscore the unprecedented nature of the spill in terms of its magnitude, release at depth, and impact to deep-water ecosystems.

  10. Monitoring of Intense Events of Deep Water Formations in the Northwestern Mediterranean over the last five years

    NASA Astrophysics Data System (ADS)

    Houpert, Loïc; Durrieu de Madron, Xavier; Testor, Pierre; Bosse, Anthony; Mortier, Laurent

    2014-05-01

    A multi-platforms and integrated monitoring system in the framework of the Mediterranean Ocean Observing System on Environment (MOOSE) enables to monitor the deep water formation processes. Since 2007, it provides high frequency in-situ temperature, salinity vertical profiles, derived from CTD measurements on moorings, ships, and gliders, as well as horizontal and vertical currents from moorings. The aim of this study is to investigate the temporal scales associated to the deep convection phases. We also studied the interannual variability of the deep convection and its implication in the evolution of deep water thermohaline characteristics. Recent measurements from the mooring lines reveal the temporal evolution of the physical processes interfering in the phases of deep convection. Horizontal currents were strongly equivalent barotropic during each deployment and strong currents were also recorded during the different events of deep ocean convection: high frequencies vertical velocities exceeded 10 cm.s-1 during the violent vertical mixing phase and strong mesoscale horizontal currents reached 40cm.s-1 during the spreading/restratification phase. Using a eddy-detection method based on a kinematic model, more than 34 eddies crossing the mooring line were detected between November 2009 and July 2012, 19 cyclones and 15 anticyclones. The radii (resp. velocities) ranging from 1.9 km to 20.0 km (resp. 2.5 cm.s-1 to 25.1 cm.s-1 ). The main mode of the distribution of eddies radii is centered at 4km for the cyclones and 5km for the anticyclones. The apparition of newly-formed deep waters was detected in winter 2009, 2010, 2011 and 2012. In winter 2010, two newly-formed deep waters were detected after the deep convection event, both present a different potential temperature but a similar salinity, suggesting that both might be formed in the cyclonic gyre, but in different locations. In 2012, two new deep waters were detected at the mooring location, one was identified as

  11. Movements of a deep-water fish: establishing marine fisheries management boundaries in coastal Arctic waters.

    PubMed

    Hussey, Nigel E; Hedges, Kevin J; Barkley, Amanda N; Treble, Margaret A; Peklova, Iva; Webber, Dale M; Ferguson, Steven H; Yurkowski, David J; Kessel, Steven T; Bedard, Jeannette M; Fisk, Aaron T

    2017-04-01

    in 2014. The community fishery can now develop an open-water fishery in addition to the winter fishery to exploit the TAC, which will ensure the longevity of the fishery under projected climate-change scenarios. Telemetry shows great promise as a tool for understanding deep-water species and for directly informing fisheries management of these ecosystems that are inherently complex to study.

  12. Sulfide, iron, manganese, and phosphate in the deep water of the Chesapeake Bay during anoxia

    NASA Astrophysics Data System (ADS)

    Gavis, Jerome; Grant, Virginia

    1986-10-01

    Concentrations of dissolved oxygen and sulfide, and of dissolved and particulate iron, manganese, and phosphate were measured as functions of salinity at a station in the Chesapeake Bay during stratification and deep water anoxia in spring and summer, 1981. The observed concentration/salinity profiles showed that oxygen was transported in a direction opposite to that of salt, while dissolved sulfide was transported in the same direction as salt through the anoxic water to be oxidized in oxygen consumption zones located below the steepest parts of the halocline. Both oxygen and sulfide were transported conservatively on 18 June. Their fluxes were 1·2 and 2 mol m -2 d -1, respectively. The oxygen flux was 30% of that stoichiometrically needed to oxidize the sulfide transported, suggesting that the oxygen consumption zone was advancing to shallower, less saline water, thus increasing the volume of anoxic water. Although oxygen was transported conservatively, sulfide was produced as it was transported through the anoxic water on 8 July. The anoxic water was supersaturated with respect to ferrous sulfide on 18 June, but most of the anoxic water was saturated on 8 July. Precipitation of ferrous sulfide had little effect on the sulfide flux on 18 June. The manganese(II) concentration/salinity profile exhibited a maximum in the oxygen consumption zone on 18 June. On 8 July the profile was independent of salinity at high salinities. Iron(II) and manganese(II) consumed little if any oxygen in the oxygen consumption zone. Soluble reactive phosphate was transported conservatively through the anoxic water on 18 June. It was produced as it was transported on 8 July. All of the phosphate was consumed in the oxygen consumption zones by sulfide oxidizing bacteria. On 18 June its flux, estimated to be 2·8 mmol m -2 d -1, was less than 10% of that required for bacterial oxidation of the sulfide reaching the oxygen consumption zone. The rest was oxidized chemically. The growth and

  13. Long Term Geoelectrical Monitoring of Deep-water Horizon Oil Spill in the Gulf Coast

    NASA Astrophysics Data System (ADS)

    Heenan, J. W.; Ntarlagiannis, D.; Slater, L. D.; Atekwana, E. A.; Ross, C.; Nolan, J. T.; Atekwana, E. A.

    2011-12-01

    In the aftermath of the catastrophic Deep-water Horizon (DWH) spill in the Gulf Coast, opportunities exist to study the evolution of fresh crude oil contamination in beach sediments and marshes. Grand Terre 1 Island, off the coast of Grand Isle in southern Louisiana, is an uninhabited barrier island, heavily impacted by the DWH spill, and ideal for undisturbed long term monitoring of crude oil degradation processes. A 10 channel Syscal-Pro resistivity / IP instrument (IRIS Instruments, France) is the heart of the fully autonomous geoelectrical monitoring system; the system, which is housed in a weatherproof container, relies solely on solar power, is controlled by an energy efficient PC and can be accessed remotely via web tools. The monitoring scheme involves collecting bi-daily resistivity measurements from surface and shallow boreholes, ranging from January 2011 to the present; environmental parameters, such as T, are continuously recorded at several depths. During regular field trips we perform larger scale geophysical surveys, and geochemical measurements (pH, DO, T, fluid C) to support the continuous geophysical monitoring. The contaminated layer on site is a visually distinctive layer of crude oil, isolated by cleaner sands above and below which is identified by a clear and obvious resistive anomaly in preliminary surveys. Early results show a decrease in average of the resistance values of each dataset over time. Further processing of the data yields a linearly shaped resistive anomaly, which coincides with the location of the oil layer. The changes in subsurface resistivity appear to be focused within this anomaly. Time filtering of the data by the time that they were collected, morning or evening, reveals a diurnal variation. While both time frames follow the same overall trend, the measurements in the morning are slightly more resistive than those in the evening. This indicates that there are environmental factors, such as temperature, that need to be

  14. Total Mercury in Surface and Deep Waters in the Western and Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Varde', M.; Cofone, F.; Servidio, A.; Rosselli, A.; Hedgecock, I. M.; Ammoscato, I.; Mannarino, V.; Sprovieri, F.; Gensini, M.; Pirrone, N.

    2014-12-01

    In the framework of the Italian National Research Council (CNR) Med-Oceanor measurement program and as part of the Global Mercury Observation System (GMOS) objectives, we performed two cruise campaigns with the CNR's Research Vessel (RV) Urania, in the western and eastern Mediterranean Basin, in the summers of 2012 and 2013. Total Mercury (THg) concentration in seawater was systematically measured at different depths from the sea bottom to the surface. A total of 155 surface and deep seawater samples at 25 selected stations were collected during the cruise campaigns using a stainless-steel rosette system on which 24 Niskin bottles (10L) were mounted. Continuous monitoring of temperature, conductivity, salinity and oxygen with depth were obtained by CTD measurements. All fluorinated containers were cleaned prior to use following GMOS SOPs. The chemical reagents used were suitable for ultra-trace Hg analysis. After sampling, samples were preserved by adding HCl solution to the sample bottles, which were refrigerated during transportation and analyzed within four weeks of the end of the oceanographic campaign. Sea water samples were analyzed in the laboratory following the US-EPA 1631 method revision E (US-EPA, 2002). To assess the critical issues related to mercury (Hg) contamination and to prevent leakage of Hg through volatilization we used all necessary precautions for sampling, sample stabilization, preservation and subsequent analysis in the laboratory. Quality assurance and quality control were performed using transport blanks, laboratory blanks and use of seawater certified reference materials. The accuracy of the analytical procedures for the determination of THg in sea water was corroborated by participation in a global inter-laboratory comparison study for THg in natural waters. THg concentrations in surface and deep waters found in the Mediterranean basin during the last two cruise campaigns Med-Oceanor as well as the THg measurements in sea water

  15. Flow dynamics and sedimentation of lateral accretion packages in sinuous deep-water channels: A 3D seismic case study from the northwestern South China Sea margin

    NASA Astrophysics Data System (ADS)

    Li, Shengli; Gong, Chenglin

    2016-07-01

    The current study uses 3D seismic data to document architectural styles and flow dynamics of lateral accretion packages (LAPs) associated with sinuous deep-water channels, contributing to a better understanding of flow processes and sedimentation associated with LAPs. The documented LAPs underwent three main stages of architectural evolution, including the early incision stages characterized by intense downcutting, active migration stages characterized by active migration and avulsion of the individual channels, and late abandonment stages characterized by the termination of sediment gravity-flows and LAP growth. These three stages of LAP growth repeated through time, yielding a fining-upward pattern from sandy channel-fill turbidites, into sand-mud couplets, all capped by muddy turbidites. A river-reversed helical flow circulation was created by an imbalance, through the flow depth, of inwardly directed pressure gradient forces near the bed and outwardly directed centrifugal forces near the surface. It consists of low-velocity cores near the outer banks and low-velocity cores along the inner banks. Such river-reversed helical flow pattern is evidenced by volumetrically extensive LAPs and toplap and downlap terminations along the gentle banks and by aerially restricted, seismically unresolvable levees and truncation terminations near the steep banks. This river-reversed helical flow circulation favors asymmetric intra-channel deposition characterized by inner bank deposition versus outer bank erosion, and which, in turn, forced individual channels to consistently migrate towards outer banks, resulting in significant asymmetric cross-channel profiles with aerially extensive LAPs along inner banks.

  16. Range-Depth Tracking of Sounds from a Single-Point Deployment by Exploiting the Deep-Water Sound Speed Minimum

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Range-Depth Tracking of Sounds from a Single-Point...Deployment by Exploiting the Deep-Water Sound Speed Minimum Aaron Thode Scripps Institution of Oceanography University of California San Diego phone...mammal sounds in range and depth from a single mooring or platform (e.g. glider), by exploiting the propagation effects of the deep-water sound

  17. Permian and Triassic sedimentation in the northeastern Brooks Range, Alaska: Deposition of the Sadlerochit Group

    SciTech Connect

    Crowder, R.K. )

    1990-09-01

    Terrigenous clastic rocks of the Sadlerochit Group in the Arctic National Wildlife Refuge are separated from underlying carbonates of the Lisburne Group by a regional unconformity marking the Pennsylvanian-Permian systemic boundary. Lithologic and diagenetic patterns of rocks above and below the sub-Sadlerochit unconformity vary systematically with substantial paleotopography along the erosional surface. Within the Sadlerochit Group, nonmarine conglomerate of the basal Echooka Formation rills erosional channels and valleys and grades upsection into a retrogradational succession of tempestites deposited during episodic storm-surge in shallow-marine environments. The overlying Ivishak Formation records an abrupt reversal of environmental migration pattern and the beginning of southerly progradation of a broad suite of deltaic environments. Depositional units in the Ivishak are strongly progradational and cyclic at a variety of scales, reflecting alternating episodes of progradation and transgression inherent in delta construction. The basal Kavik Member of the Ivishak Formation is an upward-coarsening depositional assemblage recording initial migration of prodelta environments and evolution of an extensive subaqueous delta platform. The overlying Ledge Sandstone Member is organized into three depositional assemblages recording the evolution of delta-fringe, distributary-channel, and crevasse-splay environments of the lower delta plain. The Fire Creek Siltstone Member is an aggradational and transgressive assemblage deposited in shallow-marine environments that reworked sediment originally deposited on the lower delta plain. The most favorable reservoir strata are developed immediately above and below the sub-Sadlerochit unconformity and in distributary-mouth bar and distributary-channel deposits of the Ledge Sandstone Member.

  18. The Moroccan Turbidite System: a modern example of a multi-basin mixed siliciclastic-volcaniclastic deep-water sedimentary system

    NASA Astrophysics Data System (ADS)

    Hunt, James; Wynn, Russell; Talling, Peter

    2010-05-01

    restricted by basin topography. There are also a number of small volcaniclastic turbidites relating to barranco canyon outwash events, which though not regionally extensive, could still yield important information regarding climate controls on weathering rates. Adding to these siliciclastic and volcaniclastic deposits are a number of carbonate-rich turbidites originating from volcaniclastic draped seamounts such as the Selvage Islands. Understanding the provenance area of each turbidite, its composition and pathway are pivotal in understanding the mechanics of the gravity flows that deposited them. Understanding how turbidity currents, debris flows and debris avalanches react to the basin settings is in turn important, since this records how the basin is evolving through time both distally here in the deep sea and within the hinterland. Wynn, R.B., Weaver, P.P.E., Masson, D.G., & Stow, D.A.V. 2002. Turbidite depositional architecture across three interconnected deep-water basins on the north-west African margin. Sedimentology, 49, p.669-695. Talling, P.J., Wynn, R.B., Masson, D.G., Frenz, M., Cronin, B.T., Schiebel, R., Akhmetzhanov, A.M., Dallmeier-Tiessen, S., Benetti, S., Weaver, P.P.E., Georgiopoulou, A., Zuhlsdorff, C., & Amy, L.A. 2007. Onset of submarine debris flow deposition far from original giant landslide. Nature, 450, 541-544.

  19. Continental crust in deep-water basins of East Arctic region

    NASA Astrophysics Data System (ADS)

    Artyushkov, Eugene; Belyaev, Igor; Chekhovich, Peter; Poselov, Victor

    2013-04-01

    The nature of the crust in deep-water basins (1.5-4 km) in East Arctic is a matter of debates. The occurrence of continental crust has been demonstrated by deep-sea drilling only for the central part of the Lomonosov Ridge. Many authors suggest that the Mendeleev High and the Makarov and Podvodnikov basins in the Amerasian Basin are underlain by oceanic crust. In these regions the mean P-wave velocities in the consolidated crust are higher than in most continental areas. However, the thickness of this layer is several times larger (15-30 km) than that of the oceanic crust (7 km) and it includes a thin granitic layer (2-5 km). To explain this anomalous structure and thickness of the crust it is commonly supposed that in the Late Jurassic and Cretaceous the oceanic crust was formed in the above regions by sea-floor spreading accompanies by melting out of large masses of crustal material on a hot spot like on the present Iceland hot spot. Other investigators consider the crust in the above regions as a continental one. An important argument is the evolution of the subsidence in time which is quite different from a square root of time that typical of oceanic crust. Thus, according to the dredging data, the Mendeleev High remained near to sea level for 170 Myr since the Late Silurian and until the Early Permian. This would be absolutely impossible for a cooling hot spot on the oceanic crust. Furthermore, the structure of consolidated crust in these areas is similar to that in some ultradeep basins within the continents and on their passive margins, e.g., in the East Barents, North Caspian and North Chukchi basins which were originally formed on continental crust. To produce the water loaded subsidence by 1.5-4 km by lithospheric stretching, the lithosphere should be stretched by 1.5-4 times. However, in most of the seismic reflection profiles, no large tensile deformations can be observed. Under such circumstances the transformation of gabbro in the lower crust into

  20. Global Transition Zone Anisotropy and Consequences for Mantle Flow and Earth's Deep Water Cycle

    NASA Astrophysics Data System (ADS)

    Beghein, C.; Yuan, K.

    2011-12-01

    The transition zone has long been at the center of the debate between multi- and single-layered convection models that directly relate to heat transport and chemical mixing throughout the mantle. It has also been suggested that the transition zone is a reservoir that collects water transported by subduction of the lithosphere into the mantle. Since water lowers mantle minerals density and viscosity, thereby modifying their rheology and melting behavior, it likely affects global mantle dynamics and the history of plate tectonics. Constraining mantle flow is therefore important for our understanding of Earth's thermochemical evolution and deep water cycle. Because it can result from deformation by dislocation creep during convection, seismic anisotropy can help us model mantle flow. It is relatively well constrained in the uppermost mantle, but its presence in the transition zone is still debated. Its detection below 250 km depth has been challenging to date because of the poor vertical resolution of commonly used datasets. In this study, we used global Love wave overtone phase velocity maps, which are sensitive to structure down to much larger depths than fundamental modes alone, and have greater depth resolution than shear wave-splitting data. This enabled us to obtain a first 3-D model of azimuthal anisotropy for the upper 800km of the mantle. We inverted the 2Ψ terms of anisotropic phase velocity maps [Visser, et al., 2008] for the first five Love wave overtones between 35s and 174s period. The resulting model shows that the average anisotropy amplitude for vertically polarized shear waves displays two main stable peaks: one in the uppermost mantle and, most remarkably, one in the lower transition zone. F-tests showed that the presence of 2Ψ anisotropy in the transition zone is required to improve the third, fourth, and fifth overtones fit. Because of parameter trade-offs, however, we cannot exclude that the anisotropy is located in the upper transition zone as

  1. Suborbital-scale surface and deep water records in the subtropical North Atlantic: implications on thermohaline overturn

    NASA Astrophysics Data System (ADS)

    Billups, Katharina; Rabideaux, Nathan; Stoffel, Jared

    2011-10-01

    We reconstruct millennial-scale variations in sea surface hydrography and deep water flow in the northwestern subtropical Atlantic (Ocean Drilling Program Leg 172 Sites 1056 and 1063) with a focus on Marine Isotope Stage (MIS) 9. Together with published records from this region, the new data also afford a longer-term perspective on millennial-scale changes in meridional overturning circulation spanning two full interglacial intervals (MIS 9 and 11) as well as two full glacial intervals (MIS 10 and 12). Planktic foraminiferal δ 18O values indicate relatively stable conditions during the peak warmth of MIS 9, but three large cold excursions disrupt the otherwise smooth transition toward glacial MIS 8. There is no unique response in the Site 1063 benthic foraminiferal δ 13C values that would suggest a concomitant decrease in the relative flux of NADW during these events. Similarly, there is no persistent correlation between millennial-scale variations in surface and deep water hydrography over the entire MIS 8-13 interval. While millennial-scale variations at the sea surface are most pronounced during glacial intervals (and the transitions toward glacial intervals), millennial-scale variations in the deep water hydrography tend to be largest during the warm periods. This observation supports that rapid changes in thermohaline circulation are sensitive to driving forces other than those directly related to ice sheet size. Time series analysis shows that spectral power in the benthic foraminiferal δ 13C record contains periodicities related to the second (˜10 kyr) and fourth harmonics (˜5 kyr) of precession in this record (˜20 kyr) pointing to the importance of tropical processes.

  2. An eddy resolving numerical study of the general circulation and deep-water formation in the Adriatic Sea

    NASA Astrophysics Data System (ADS)

    Mantziafou, A.; Lascaratos, A.

    2004-07-01

    General circulation and deep-water formation (DWF) processes in the Adriatic basin in a climatological year were numerically simulated in a high-resolution (1/20th of a degree) implementation of the Princeton Ocean Model (POM). The "perpetual" year atmospheric data were computed from the ECMWF Reanalysis data (1°×1°) covering the period 1979-1994. The model reproduces the main basin features of the general circulation, water mass distribution and their seasonal variability. The Adriatic Deep Water exiting through the Otranto Strait is produced with two different mechanisms inside the basin: (a) by open ocean deep convection over the Southern Adriatic Pit and Middle Adriatic Pit (b) on the continental shelf of the Northern and Middle Adriatic. The estimated contributions of both mechanisms suggest that 82% of the Adriatic Deep Water is formed inside the Southern Adriatic Pit, while all the higher density water in this water mass comes from the northern regions. The role of mesoscale eddies at the periphery of the dense-water chimney in the Southern Adriatic Pit was examined and their contribution to the lateral buoyancy flux, during the convection process, found to be small. The DWF rate at Otranto Strait is 0.28 Sv with σθ over 29.15. The sensitivity of the DWF processes to interannual variability of the buoyancy forcing and river runoff was assessed with a number of process-study numerical experiments. In these experiments the effect of an imposed "extreme" buoyancy forcing during 1 year, on the DWF rates, was to modify them during the specific year, but the effects were still present in the following normal climatological year. This shows that the DWF rates and their mass characteristics at a specific year depend not only on the atmospheric conditions prevailing that specific year but on the previous year's as well, thus leading to the concept of a "memory" of the basin.

  3. Deep-water sediment transport processes in the northeastern South China Sea: Mooring and shipboard-based observations

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Zhao, Y.; Zhang, Y.; Li, J.; Li, X.; Wang, W.; Xu, J.

    2013-12-01

    Six moorings equipped with acoustic doppler current profiler (ADCP), recording current meter (RCM), and sediment trap have been deployed in the northeastern South China Sea at water depths ranging from 1700-3900 m to collect time-series data that can hopefully help better characterize the bottom current system and transport process in the region. Shipboard-based measurements including CTD, transmissometer, optical backscatter (OBS), and in-situ layered suspended particle sampling using large volume pump (LVP) were undertaken along three deep-water transects in the region during two cruises in the spring of 2012 and 2013. Preliminary results show for the first time the presence of continuous and relative stable contour currents and widespread deep-water nepheloid layers in the deep South China Sea. The contour currents flow southwestwards with average speeds of 2-4 cm/s (occasionally up to 11 cm/s) along lower slope of the northern South China Sea at depths of 1700-2500 m. The large-scale sediment waves recorded by high-resolution multibeam bathymetry appear to be related to activities of the contour currents. Intermediate and bottom nepheloid layers with an average suspended particle concentration of 0.6 mg/l are extended from the lower slope to the deep basin of the South China Sea. The intermediate nepheloid layers in depths ranging from 900 to 1100 m are thought to be controlled mainly by the interaction between the North Pacific Intermediate Water and the Pacific Deep Water masses. A sedimentary core (MD01-2905) previously collected on the sediment drift of ODP Site 1144, where three of the mooring systems are located, indicates that 60% of total fine-grained terrigenous sediment budget since the last glacial time have sourced from Taiwan. Our data suggest that the observed contour currents are the major carrier for transporting Taiwan-derived sediments to the northern slope of the South China Sea.

  4. The Plio-Pleistocene development of Atlantic deep-water circulation and its influence on climate trends

    NASA Astrophysics Data System (ADS)

    Bell, David B.; Jung, Simon J. A.; Kroon, Dick

    2015-09-01

    Using benthic stable isotope records from 10 sites in the Atlantic Ocean, including two new records from Walvis Ridge in the Southeast Atlantic (Sites 1264 and 1267), we review changes in Atlantic deep-water circulation in the context of Plio-Pleistocene climate. Overall, we find non-linear responses of Atlantic deep-water circulation to a cooling climate, with differently evolving glacial and interglacial states. Our main conclusion is that peak North Atlantic Deep Water (NADW) production was reached between ˜2.0 and 1.5 Ma, most prominently seen by a maximum in ventilated (high δ13C) conditions in the mid-depth Southeast Atlantic (Site 1264). We infer that a major source of NADW at this time was the export of dense overflow water from the Nordic Seas into the abyssal East Atlantic. Sea surface temperature records from the North and South Atlantic support this notion and indicate that the peak NADW production between ˜2.0 and 1.5 Ma was compensated by a stronger warm surface-water return flow (i.e. Atlantic Meridional Overturning Circulation (AMOC) was enhanced), causing long-term (>105 year) heat piracy from the South to the North Atlantic. In the wider picture of Plio-Pleistocene climate evolution, we find that a long-term enhancement in the average state of AMOC (˜2.4-1.3 Ma) coincides with the "41-kyr world". Hence, we speculate that the transitory negative feedback response of enhanced AMOC to a cooling climate supplied heat to key areas of ice-sheet growth, acting to limit their size and maintain the "41-kyr world". Once a threshold in global cooling was reached, the strength of AMOC lessened, providing a positive feedback for the Early-Middle Pleistocene Transition and the associated build-up of northern hemisphere ice-sheets.

  5. Update of the genus Leptochiton (Mollusca: Polyplacophora) in Chilean deep waters: three new reports and description of two new species.

    PubMed

    Sirenko, Boris; Sellanes, Javier

    2016-10-04

    We update the list of the bathyal chitons of the genus Leptochiton inhabiting Chilean waters. We report new records of Leptochiton belknapi and L. laurae, the first record of L. sigwartae for the area and the new species L. ibanezi sp. nov. and L. ferreirai sp. nov. With 12 species, including those described herein as new, the highest species richness of Leptochiton is found in Chilean deep waters. Taking into consideration the potential late Paleozoic origin of the genus Leptochiton, we propose that Leptochiton originated in the old Pacific Ocean and migrated to the young Atlantic Ocean. However, the genus has also been considered non-monophyletic.

  6. Dragmacidin G, a Bioactive Bis-Indole Alkaloid from a Deep-Water Sponge of the Genus Spongosorites

    PubMed Central

    Wright, Amy E.; Killday, K. Brian; Chakrabarti, Debopam; Guzmán, Esther A.; Harmody, Dedra; McCarthy, Peter J.; Pitts, Tara; Pomponi, Shirley A.; Reed, John K.; Roberts, Bracken F.; Rodrigues Felix, Carolina; Rohde, Kyle H.

    2017-01-01

    A deep-water sponge of the genus Spongosorites has yielded a bis-indole alkaloid which we have named dragmacidin G. Dragmacidin G was first reported by us in the patent literature and has recently been reported by Hitora et al. from a sponge of the genus Lipastrotheya. Dragmacidin G is the first in this series of compounds to have a pyrazine ring linking the two indole rings. It also has a rare N-(2-mercaptoethyl)-guanidine side chain. Dragmacidin G shows a broad spectrum of biological activity including inhibition of methicillin-resistant Staphylococcus aureus, Mycobacterium tuberculosis, Plasmodium falciparum, and a panel of pancreatic cancer cell lines. PMID:28085024

  7. Report on two deep-water caridean shrimp species (Crustacea: Decapoda: Caridea: Alvinocarididae, Acanthephyridae) from the northeastern South China Sea.

    PubMed

    Li, Xinzheng

    2015-01-16

    Two deep-water species of caridean shrimps collected during recent dives by the Chinese manned submersible "Jiaolong" represents new records for the South China Sea: Alvinocaris longirostris Kikuchi & Ohta, 1995 (Alvinocarididae) and Acanthephyra faxoni Calman, 1939 (Acanthephyridae). Specimens of these two species were collected from Jiaolong Cold Seep I, off Guangdong Province, China (depth 1138 m). Alvinocaris longirostris is known to be associated with chemosynthetic community, whereas Acanthephyra faxoni is a bathypelagic inhabitant, of which the occurrence in seep site is merely opportunistic. An identification key to species of Alvinocaris is provided. 

  8. A micropalaeontological perspective on export productivity, oxygenation and temperature in NE Atlantic deep-waters across Terminations I and II

    NASA Astrophysics Data System (ADS)

    Grunert, Patrick; Skinner, Luke; Hodell, David A.; Piller, Werner E.

    2015-08-01

    Census counts of benthic foraminifera were studied from the SW Iberian Margin to reconstruct past changes in deep-water hydrography across Terminations I and II. Detailed benthic faunal data (> 125 μm size-fraction) allow us to evaluate the limitations imposed by taphonomic processes and restricted size-fractions. The comparison of recent (mudline) and fossil assemblages at IODP Site U1385 indicates the quick post-mortem disintegration of shells of astrorhizoid taxa (~ 80% of the present-day fauna), resulting in impoverished fossil assemblages. While the application of quantitative proxy methods is problematic under these circumstances, the fossil assemblages can still provide a qualitative palaeoenvironmental signal that, while most fully expressed in the 125-212 μm size-fraction, is nonetheless also expressed to some degree in the > 212 μm size-fraction. Variations in the benthic foraminiferal assemblages reveal information about changing organic matter supply, deep-water oxygenation and temperature. MIS 2 is generally characterized by an elevated trophic state and variable oxic conditions, with oxygenation minima culminating in the Younger Dryas (YD) and Heinrich Stadials (HS) 1, 2 and 3. Low oxic conditions coincide with decreased water-temperature and lower benthic δ13C, pointing to the strong influence of a southern sourced water-mass during these periods. HS 1 is the most extreme of these intervals, providing further evidence for a severe temporary reduction or even shutdown of AMOC. With the inception of MIS 1, organic matter supply reduced and a better ventilated deep-water environment bathed by NEADW is established. For Termination II, clear indications of southern-sourced water are limited to the early phase of HS 11. During the latter part of HS 11, the deep-water environment seems to be determined by strongly increased supply of organic matter, potentially explaining the decoupling of benthic δ13C and Mg/Ca records of earlier studies as a

  9. The South American radiation of Jerrybuccinum (Gastropoda, Buccinidae), with a new deep-water species from Chile

    PubMed Central

    Fraussen, Koen; Sellanes, Javier; Stahlschmidt, Peter

    2014-01-01

    Abstract A new deep water species from off the Chilean coast, Jerrybuccinum kantori sp. n., is described. The animal is equipped with a large statocyst. Kryptos explorator Fraussen & Sellanes, 2008 from off Concepción is found to be congeneric and transferred to the genus Jerrybuccinum. Differences in size and sculpture serve to distinguish the new species from J. explorator. Both Chilean species are associated with methane seep or low oxygen environments. They are compared with J. malvinense Kantor & Pastorino, 2009 and two still unnamed species from the Falkland Plateau. PMID:24899844

  10. North Atlantic demersal deep-water fish distribution and biology: present knowledge and challenges for the future.

    PubMed

    Bergstad, O A

    2013-12-01

    This paper summarizes knowledge and knowledge gaps on benthic and benthopelagic deep-water fishes of the North Atlantic Ocean, i.e. species inhabiting deep continental shelf areas, continental and island slopes, seamounts and the Mid-Atlantic Ridge. While several studies demonstrate that distribution patterns are species specific, several also show that assemblages of species can be defined and such assemblages are associated with circulatory features and water mass distributions. In many subareas, sampling has, however, been scattered, restricted to shallow areas or soft substrata, and results from different studies tend to be difficult to compare quantitatively because of sampler differences. Particularly, few studies have been conducted on isolated deep oceanic seamounts and in Arctic deep-water areas. Time series of data are very few and most series are short. Recent studies of population structure of widely distributed demersal species show less than expected present connectivity and considerable spatial genetic heterogeneity and complexity for some species. In other species, genetic homogeneity across wide ranges was discovered. Mechanisms underlying the observed patterns have been proposed, but to test emerging hypotheses more species should be investigated across their entire distribution ranges. Studies of population biology reveal greater diversity in life-history strategies than often assumed, even between co-occurring species of the same family. Some slope and ridge-associated species are rather short-lived, others very long-lived, and growth patterns also show considerable variation. Recent comparative studies suggest variation in life-history strategies along a continuum correlated with depth, ranging from shelf waters to the deep sea where comparatively more species have extended lifetimes, and slow rates of growth and reproduction. Reproductive biology remains too poorly known for most deep-water species, and temporal variation in recruitment has

  11. Lead isotopes in North Pacific deep water - Implications for past changes in input sources and circulation patterns

    USGS Publications Warehouse

    van de Flierdt, T.; Frank, M.; Halliday, A.N.; Hein, J.R.; Hattendorf, B.; Gunther, D.; Kubik, P.W.

    2003-01-01

    The sources of non-anthropogenic Pb in seawater have been the subject of debate. Here we present Pb isotope time-series that indicate that the non-anthropogenic Pb budget of the northernmost Pacific Ocean has been governed by ocean circulation and riverine inputs, which in turn have ultimately been controlled by tectonic processes. Despite the fact that the investigated locations are situated within the Asian dust plume, and proximal to extensive arc volcanism, eolian contributions have had little impact. We have obtained the first high-resolution and high-precision Pb isotope time-series of North Pacific deep water from two ferromanganese crusts from the Gulf of Alaska in the NE Pacific Ocean, and from the Detroit Seamount in the NW Pacific Ocean. Both crusts were dated applying 10 Be/9Be ratios and yield continuous time-series for the past 13.5 and 9.6 Myr, respectively. Lead isotopes show a monotonic evolution in 206Pb/204Pb from low values in the Miocene (??? 18.57) to high values at present day (??? 18.84) in both crusts, even though they are separated by more than 3000 km along the Aleutian Arc. The variation exceeds the amplitude found in Equatorial Pacific deep water records by about three-fold. There also is a striking similarity in 207Pb/204Pb and 208Pb/ 204Pb ratios of the two crusts, indicating the existence of a local circulation cell in the sub-polar North Pacific, where efficient lateral mixing has taken place but only limited exchange (in terms of Pb) with deep water from the Equatorial Pacific has occurred. Both crusts display well-defined trends with age in Pb-Pb isotope mixing plots, which require the involvement of at least four distinct Pb sources for North Pacific deep water. The Pb isotope time-series reveal that eolian supplies (volcanic ash and continent-derived loess) have only been of minor importance for the dissolved Pb budget of marginal sites in the deep North Pacific over the past 6 Myr. The two predominant sources have been young

  12. Lead isotopes in North Pacific deep water - implications for past changes in input sources and circulation patterns

    NASA Astrophysics Data System (ADS)

    van de Flierdt, Tina; Frank, Martin; Halliday, Alex N.; Hein, James R.; Hattendorf, Bodo; Günther, Detlef; Kubik, Peter W.

    2003-04-01

    The sources of non-anthropogenic Pb in seawater have been the subject of debate. Here we present Pb isotope time-series that indicate that the non-anthropogenic Pb budget of the northernmost Pacific Ocean has been governed by ocean circulation and riverine inputs, which in turn have ultimately been controlled by tectonic processes. Despite the fact that the investigated locations are situated within the Asian dust plume, and proximal to extensive arc volcanism, eolian contributions have had little impact. We have obtained the first high-resolution and high-precision Pb isotope time-series of North Pacific deep water from two ferromanganese crusts from the Gulf of Alaska in the NE Pacific Ocean, and from the Detroit Seamount in the NW Pacific Ocean. Both crusts were dated applying 10Be/ 9Be ratios and yield continuous time-series for the past 13.5 and 9.6 Myr, respectively. Lead isotopes show a monotonic evolution in 206Pb/ 204Pb from low values in the Miocene (≤18.57) to high values at present day (≥18.84) in both crusts, even though they are separated by more than 3000 km along the Aleutian Arc. The variation exceeds the amplitude found in Equatorial Pacific deep water records by about three-fold. There also is a striking similarity in 207Pb/ 204Pb and 208Pb/ 204Pb ratios of the two crusts, indicating the existence of a local circulation cell in the sub-polar North Pacific, where efficient lateral mixing has taken place but only limited exchange (in terms of Pb) with deep water from the Equatorial Pacific has occurred. Both crusts display well-defined trends with age in Pb-Pb isotope mixing plots, which require the involvement of at least four distinct Pb sources for North Pacific deep water. The Pb isotope time-series reveal that eolian supplies (volcanic ash and continent-derived loess) have only been of minor importance for the dissolved Pb budget of marginal sites in the deep North Pacific over the past 6 Myr. The two predominant sources have been young

  13. Depositional environments of the Wilcox Group, Texas Gulf Coast: Stratigraphic and early diagenetic signatures

    SciTech Connect

    May, J.A.; Stonecipher, S.A. )

    1990-09-01

    Deposition of the late Paleocene-early Eocene Wilcox Group is controversial. Are Wilcox reservoirs entirely of shallow-marine origin, or are basinal turbidites also present The authors analyzed over 5,000 ft of core from 15 wells along the Texas Gulf Coast to constrain the environments of deposition. They attribute all cores examined to date to 12 subenvironments of the delta plain to continental shelf. These include distributary channel, lake, marine bay, crevasse-splay delta, shoreface, lagoon, tidal flat, tidal channel, distributary-mouth bar, distal bar, prodelta, and shelf. Each subenvironment displays a characteristic well-log signature. Criteria for recognition in core include grain-size variations, physical sedimentary structures, trace fossils, mineralogy, bedding styles, and vertical sequences, all resulting from the interplay of specific physical, biological, and chemical processes operative in each subenvironment. They did not identify any submarine-fan deposits. They also attempted to determine the importance of depositional facies and provenance on diagenetic trends. Early diagenetic patterns appear to be related to factors such as sediment texture, detrital composition, organic content, and original water chemistry, which were, in turn, controlled directly or indirectly by depositional environment. Rapid lateral and vertical changes in depositional environments produced markedly different early diagenetic patterns in sand units only a few feet or even inches apart. Thus, diagenetic facies defined on the basis of texture, composition, and cements can be used to complement, and test, their interpretations of depositional environments based solely on traditional sedimentologic and genetic-sequence criteria.

  14. The diversity, distribution and status of deep-water elasmobranchs in the Rockall Trough, north-east Atlantic Ocean.

    PubMed

    Neat, F C; Burns, F; Jones, E; Blasdale, T

    2015-12-01

    Data from a scientific deep-water trawl fisheries survey in the north-east Atlantic were analysed to determine the spatial and bathymetric distribution of elasmobranch species and assess the change in relative abundance over the period 1998-2013. During this period, commercial fisheries for deep-water sharks went from being entirely unregulated, to being briefly managed, to being completely prohibited. A total of 22 species of shark and 10 species of skate were recorded between depths of 300 and 2030 m. All showed strong species-specific depth-related trends in abundance. Out of the 11 more common species, five showed no change in relative abundance over time, two (Centrophorus squamosus and Centroselachus crepidater) declined significantly and four increased in relative abundance (Apristurus aphyodes, Apristurus microps, Galeus melastomus and Deania calcea). Assuming these populations were depleted by fisheries in the past, the current data do not suggest there has been an overall recovery. Positive signs for some species in the most recent years suggest movement or recruitment back into the area; however, it is of concern that two species continued to decline. There is a continued need to have precautionary management of these elasmobranch species, and the current ban on landing these species in European waters remains appropriate.

  15. Endemic Lake Baikal sponges from deep water. 1: Potential cryptic speciation and discovery of living species known only from fossils.

    PubMed

    Itskovich, Valeria B; Kaluzhnaya, Oxana V; Veynberg, Elena; Erpenbeck, Dirk

    2015-07-23

    We revealed new deep-water species and cryptic speciation within freshwater sponges of the endemic family Lubomirskiidae (Porifera; Demospongiae; Spongillina) based on molecular and spicule morphology analyses of ITS and CO1 mtDNA. Lubomirskiidae contains a group of closely related species which are a dominant component of the benthos in Lake Baikal, the world's deepest and most ancient lake. Spicule morphology was similar between two Recent samples and species only known previously from fossils in Late Pliocene (3.2-2.8 mya) sediments. Despite the morphological similarity with the cosmopolitan family Spongillidae, molecular analysis of ITS sequences has reliably assigned these species to Lubomirskiidae. This not only indicates that species identification of freshwater fossil sponge spicules should be made with caution, but also suggests that the structure of megascleres may not be a reliable character for interpretations of paleoclimatic reconstructions for the Baikal region. Our results do not support the current classification of Lubomirskiidae into its morphologically defined genera and species, suggesting a strong discrepancy between molecular and morphological variation in Baikalian sponges. This present contribution is the first part of a study on the phylogenetic relationships of the Lake Baikal deep water sponge fauna.

  16. Bacterioplankton communities of Crater Lake, OR: Dynamic changes with euphotic zone food web structure and stable deep water populations

    USGS Publications Warehouse

    Urbach, E.; Vergin, K.L.; Larson, G.L.; Giovannoni, S.J.

    2007-01-01

    The distribution of bacterial and archaeal species in Crater Lake plankton varies dramatically over depth and with time, as assessed by hybridization of group-specific oligonucleotides to RNA extracted from lakewater. Nonmetric, multidimensional scaling (MDS) analysis of relative bacterial phylotype densities revealed complex relationships among assemblages sampled from depth profiles in July, August and September of 1997 through 1999. CL500-11 green nonsulfur bacteria (Phylum Chloroflexi) and marine Group I crenarchaeota are consistently dominant groups in the oxygenated deep waters at 300 and 500 m. Other phylotypes found in the deep waters are similar to surface and mid-depth populations and vary with time. Euphotic zone assemblages are dominated either by ??-proteobacteria or CL120-10 verrucomicrobia, and ACK4 actinomycetes. MDS analyses of euphotic zone populations in relation to environmental variables and phytoplankton and zooplankton population structures reveal apparent links between Daphnia pulicaria zooplankton population densities and microbial community structure. These patterns may reflect food web interactions that link kokanee salmon population densities to community structure of the bacterioplankton, via fish predation on Daphnia with cascading consequences to Daphnia bacterivory and predation on bacterivorous protists. These results demonstrate a stable bottom-water microbial community. They also extend previous observations of food web-driven changes in euphotic zone bacterioplankton community structure to an oligotrophic setting. ?? 2007 Springer Science+Business Media B.V.

  17. Unusual Deep Water sponge assemblage in South China-Witness of the end-Ordovician mass extinction.

    PubMed

    Li, Lixia; Feng, Hongzhen; Janussen, Dorte; Reitner, Joachim

    2015-11-05

    There are few sponges known from the end-Ordovician to early-Silurian strata all over the world, and no records of sponge fossils have been found yet in China during this interval. Here we report a unique sponge assemblage spanning the interval of the end-Ordovician mass extinction from the Kaochiapien Formation (Upper Ordovician-Lower Silurian) in South China. This assemblage contains a variety of well-preserved siliceous sponges, including both Burgess Shale-type and modern type taxa. It is clear that this assemblage developed in deep water, low energy ecosystem with less competitors and more vacant niches. Its explosion may be related to the euxinic and anoxic condition as well as the noticeable transgression during the end-Ordovician mass extinction. The excellent preservation of this assemblage is probably due to the rapid burial by mud turbidites. This unusual sponge assemblage provides a link between the Burgess Shale-type deep water sponges and the modern forms. It gives an excellent insight into the deep sea palaeoecology and the macroevolution of Phanerozoic sponges, and opens a new window to investigate the marine ecosystem before and after the end-Ordovician mass extinction. It also offers potential to search for exceptional fossil biota across the Ordovician-Silurian boundary interval in China.

  18. Unusual Deep Water sponge assemblage in South China—Witness of the end-Ordovician mass extinction

    NASA Astrophysics Data System (ADS)

    Li, Lixia; Feng, Hongzhen; Janussen, Dorte; Reitner, Joachim

    2015-11-01

    There are few sponges known from the end-Ordovician to early-Silurian strata all over the world, and no records of sponge fossils have been found yet in China during this interval. Here we report a unique sponge assemblage spanning the interval of the end-Ordovician mass extinction from the Kaochiapien Formation (Upper Ordovician-Lower Silurian) in South China. This assemblage contains a variety of well-preserved siliceous sponges, including both Burgess Shale-type and modern type taxa. It is clear that this assemblage developed in deep water, low energy ecosystem with less competitors and more vacant niches. Its explosion may be related to the euxinic and anoxic condition as well as the noticeable transgression during the end-Ordovician mass extinction. The excellent preservation of this assemblage is probably due to the rapid burial by mud turbidites. This unusual sponge assemblage provides a link between the Burgess Shale-type deep water sponges and the modern forms. It gives an excellent insight into the deep sea palaeoecology and the macroevolution of Phanerozoic sponges, and opens a new window to investigate the marine ecosystem before and after the end-Ordovician mass extinction. It also offers potential to search for exceptional fossil biota across the Ordovician-Silurian boundary interval in China.

  19. Unusual Deep Water sponge assemblage in South China—Witness of the end-Ordovician mass extinction

    PubMed Central

    Li, Lixia; Feng, Hongzhen; Janussen, Dorte; Reitner, Joachim

    2015-01-01

    There are few sponges known from the end-Ordovician to early-Silurian strata all over the world, and no records of sponge fossils have been found yet in China during this interval. Here we report a unique sponge assemblage spanning the interval of the end-Ordovician mass extinction from the Kaochiapien Formation (Upper Ordovician-Lower Silurian) in South China. This assemblage contains a variety of well-preserved siliceous sponges, including both Burgess Shale-type and modern type taxa. It is clear that this assemblage developed in deep water, low energy ecosystem with less competitors and more vacant niches. Its explosion may be related to the euxinic and anoxic condition as well as the noticeable transgression during the end-Ordovician mass extinction. The excellent preservation of this assemblage is probably due to the rapid burial by mud turbidites. This unusual sponge assemblage provides a link between the Burgess Shale-type deep water sponges and the modern forms. It gives an excellent insight into the deep sea palaeoecology and the macroevolution of Phanerozoic sponges, and opens a new window to investigate the marine ecosystem before and after the end-Ordovician mass extinction. It also offers potential to search for exceptional fossil biota across the Ordovician-Silurian boundary interval in China. PMID:26538179

  20. Impact of deep-water derived isoprenoid tetraether lipids on the TEX86 paleothermometry along the portuguese continental margin

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Hyun; Villanueva, Laura; Zell, Claudia; Sinninghe Damsté, Jaap S.

    2016-04-01

    The TEX86 proxy was developed based on isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) biosynthesized by Thaumarchaeota and afterwards slightly modified to TEX86-H, a logarithmic function for TEX86. However, it remains uncertain how well this proxy reconstructs annual mean SST, especially due to the water depth influence. We investigated the potential effect of deep-water dwelling Thaumarchaeota in the warm and saline Mediterranean Outflow Water (MOW) on the distribution of isoGDGTs by analysing suspended particulate matter (SPM) and surface sediments collected along five land-ocean transects along the southern Portuguese continental margin. To this end, we directly compared for the first time the composition of intact polar lipid (IPL)-derived isoGDGTs of SPM with the diversity, abundance, and activity of Thaumarchaeota based on the genetic analysis of the genes coding for the archaeal ammonia monooxygenase (amoA) and the geranylgeranylglyceryl phosphate (GGGP) synthase involved in the isoGDGT biosynthetic pathway. Our results show that the sedimentary distribution of CL isoGDGTs used in TEX86-H along the Portuguese margin is primarily influenced by water depth due to the increasing contribution of the deep-water population of Thaumarchaeota residing in the MOW.

  1. Event sedimentation in low-latitude deep-water carbonate basins, Anegada passage, northeast Caribbean

    USGS Publications Warehouse

    Chaytor, Jason D.; ten Brink, Uri S.

    2015-01-01

    The Virgin Islands and Whiting basins in the Northeast Caribbean are deep, structurally controlled depocentres partially bound by shallow-water carbonate platforms. Closed basins such as these are thought to document earthquake and hurricane events through the accumulation of event layers such as debris flow and turbidity current deposits and the internal deformation of deposited material. Event layers in the Virgin Islands and Whiting basins are predominantly thin and discontinuous, containing varying amounts of reef- and slope-derived material. Three turbidites/sandy intervals in the upper 2 m of sediment in the eastern Virgin Islands Basin were deposited between ca. 2000 and 13 600 years ago, but do not extend across the basin. In the central and western Virgin Islands Basin, a structureless clay-rich interval is interpreted to be a unifite. Within the Whiting Basin, several discontinuous turbidites and other sand-rich intervals are primarily deposited in base of slope fans. The youngest of these turbidites is ca. 2600 years old. Sediment accumulation in these basins is low (−1) for basin adjacent to carbonate platform, possibly due to limited sediment input during highstand sea-level conditions, sediment trapping and/or cohesive basin walls. We find no evidence of recent sediment transport (turbidites or debris flows) or sediment deformation that can be attributed to the ca. M7.2 1867 Virgin Islands earthquake whose epicentre was located on the north wall of the Virgin Islands Basin or to recent hurricanes that have impacted the region. The lack of significant appreciable pebble or greater size carbonate material in any of the available cores suggests that submarine landslide and basin-wide blocky debris flows have not been a significant mechanism of basin margin modification in the last several thousand years. Thus, basins such as those described here may be poor recorders of past natural hazards, but may provide a long-term record of past oceanographic

  2. Characteristics of a sandy depositional lobe on the outer Mississippi fan from SeaMARC IA sidescan sonar images

    SciTech Connect

    Twichell, D.C.; Schwab, W.C. ); Nelson, C.H.; Lee, H.J. ); Kenyon, N.H. )

    1992-08-01

    SeaMARC IA sidescan sonar images of the distal reaches of a depositional lobe on the Mississippi Fan show that channelized rather than unconfined transport was the dominant transport mechanism for coarse-grained sediment during the formation of this part of the deep-sea fan. Overbank sheet flow of sands was not an important process in the transport and deposition of the sandy and silty sediment found on this fan. The dendritic distributary pattern and the high order of splaying of the channels, only one which appears to have been active at a time, suggest that coarse-grained deposits on this fan are laterally discontinuous.

  3. The relationships between soft-sediment deformation structures and synsedimentary extensional tectonics in Upper Triassic deep-water carbonate succession (Southern Tethyan rifted continental margin - Central Sicily)

    NASA Astrophysics Data System (ADS)

    Basilone, Luca; Sulli, Attilio; Gasparo Morticelli, Maurizio

    2016-10-01

    We describe soft-sediment deformation structures into the Upper Triassic cherty limestone outcropping in the Pizzo Lupo section (Central Sicily, Italy), pertaining to the deep-water palaeodomain of the Southern Tethyan margin. In the study section, mainly consisting of thin-bedded mudstone/marl alternations with bedded chert intercalations, some lithofacies have been separated on the basis of the abundance of the calcium carbonate/clay content and the overall textural features. The deformational structures, displaying different deformational styles as folded and faulted beds, disturbed layers, clastic dikes, and slumps occur mainly in the deformed horizons that involve marl-dominated lithofacies. Small-scale water-escape structures involve beds with nodular fabric. Synsedimentary faults affect the mud-limestone dominated lithofacies, which are characterized by fault-rotating blocks producing lateral thinning. These bodies appear to have moved coherently along an overall planar surface. We relate these soft-sediment deformations to slump sheets, associated with down-slope sliding of sedimentary masses. The deformation mechanism and driving force for these soft-sediment deformations are due essentially to gravitational instability and dewatering. Detailing, rotational (slump) and translational (glide) slides and water-escape are the main processes causing the distinguished deformational styles. The synsedimentary extensional tectonics that affected the Upper Triassic pelagic deposits was the triggering process responsible for the instability of the seafloor inducing loss of coherence of the unconsolidated sediments on the sea bottom, developing a large number of gravity-driven slides. The analysis of both of these SSDSs and their relationships with the structural scenario allow us to hypothesise that they are seismically-induced.

  4. Strange bedfellows - A deep-water hermatypic coral reef superimposed on a drowned barrier island; Southern Pulley Ridge, SW Florida platform margin

    USGS Publications Warehouse

    Jarrett, B.D.; Hine, A.C.; Halley, R.B.; Naar, D.F.; Locker, S.D.; Neumann, A.C.; Twichell, D.; Hu, C.; Donahue, B.T.; Jaap, W.C.; Palandro, D.; Ciembronowicz, K.

    2005-01-01

    The southeastern component of a subtle ridge feature extending over 200 km along the western ramped margin of the south Florida platform, known as Pulley Ridge, is composed largely of a non-reefal, coastal marine deposit. Modern biostromal reef growth caps southern Pulley Ridge (SPR), making it the deepest hermatypic reef known in American waters. Subsurface ridge strata are layered, lithified, and display a barrier island geomorphology. The deep-water reef community is dominated by platy scleractinian corals, leafy green algae, and coralline algae. Up to 60% live coral cover is observed in 60-75 m of water, although only 1-2% of surface light is available to the reef community. Vertical reef accumulation is thin and did not accompany initial ridge submergence during the most recent sea-level rise. The delayed onset of reef growth likely resulted from several factors influencing Gulf waters during early stages of the last deglaciation (???14 kyr B.P.) including; cold, low-salinity waters derived from discrete meltwater pulses, high-frequency sea-level fluctuations, and the absence of modern oceanic circulation patterns. Currently, reef growth is supported by the Loop Current, the prevailing western boundary current that impinges upon the southwest Florida platform, providing warm, clear, low-nutrient waters to SPR. The rare discovery of a preserved non-reefal lowstand shoreline capped by rich hermatypic deep-reef growth on a tectonically stable continental shelf is significant for both accurate identification of late Quaternary sea-level position and in better constraining controls on the depth limits of hermatypic reefs and their capacity for adaptation to extremely low light levels. ?? 2004 Elsevier B.V. All rights reserved.

  5. Facies Variations Along an Ancient Deep-Water Axial Channel Belt: Insights from the Upper Cretaceous Cerro Toro Formation, Magallanes-Austral Basin, Patagonia

    NASA Astrophysics Data System (ADS)

    Malkowski, M. A.; Jobe, Z. R.; Sharman, G.; Graham, S. A.

    2015-12-01

    The Upper Cretaceous Cerro Toro Formation preserves a >150 kilometer long deep-water axial channel belt in the Magallanes-Austral Basin in southern Patagonia. Considerable work over the past decade in the Chilean basin sector reveals a 3.5-8 km wide channel-levee system that transported coarse-grained sediment from north to south via a range of low- to high-density turbidity currents, debris flows, and transitional/hybrid flows. In contrast, the more proximal deposits preserved in the Argentine basin sector to the north received little focus. This study documents new sedimentology, stratigraphy, and U-Pb geochronology from the Cerro Toro Formation in Argentina, allowing for a basin-scale comparison of the timing of deposition, sediment sources, and facies and grain size variability. Two ash beds from the base of the section yield U-Pb zircon ages of 90.4 ± 2 Ma and 88.0 ± 3 Ma, suggesting similar, if not slightly older, ages for the lower Cerro Toro Formation when compared to equivalent units to the south. U-Pb detrital zircon age spectra reveal similar provenance trends along the entire outcrop belt, with peak age populations at 310-260, 160-135, and 110-82 Ma. Preliminary statistical analyses of more than 5700 meters of new and previously published detailed stratigraphic sections suggest that, in general, characteristics such as mean bed thickness and net to gross remain fairly consistent along the outcrop belt. However, the bed thickness distributions are log-normal, and the northern sector has higher maximum bed thickness than the southern sector. There are also gradual variations in the down-system (north to south) proportion of lithofacies. For instance, in the northern (Argentine) sector, lithofacies representing mass wasting processes (e.g., debris flow conglomerates and mass-transport deposits) account for as much as ~80 percent of the stratigraphic thickness, whereas near the southern end of the channel belt, coarse-grained facies are almost entirely

  6. Deep Water Compositions From the Los Angeles Basin and the Origin of Formation Water Salinity

    NASA Astrophysics Data System (ADS)

    Boles, J.; Giles, G.; Lockman, D.

    2005-12-01

    Deep basin formation waters represent original depositional waters that have been modified by diagenetic processes at elevated temperatures and pressures. In addition, they may be diluted by meteoric incursion from elevated structural blocks along basin flanks. It has long been thought that deep basin formation waters have salinities greater than sea water due to various processes like clay membrane filtration or other types of water-rock interaction. However, our work and similar studies in the San Joaquin basin show that formation waters in deep basins are more likely to become diluted rather than concentrated in the absence of soluble evaporite deposits that might underlie the basin. The idea of increased salinity with depth arose from studies in which the underpinning of the basin consisted of soluble evaporate deposits such as the Texas Gulf Coast, Illinois, Michigan, and some North Sea areas. There are very few deep formation water analyses from the Los Angeles Basin. Furthermore, very few of the current produced waters from any depth can be considered pristine because of the widespread formation water injection programs and commingling of fluids from different levels. Here, we describe the first analyses from a deep, previously untouched part of the basin that is currently being developed in the Inglewood Oil Field. We have analyzed a suite of formation waters from the mid-Miocene marine Sentous sandstone from sub-sea level depths of 2250 m to 2625 m at temperatures of about 110 to 126°C and pressures of about 27 MPa. The original depositional waters in the Sentous Formation were sea water whereas the sampled waters are diluted by about 20% from sea water and some show as much as 50% dilution. Based on comparison of oxygen and deuterium isotopes between the meteoric water trend and these waters, we conclude that the smectite to illite dehydration reaction is the major cause of dilution to the original formation water. Other notable differences include

  7. A deep water turbidity origin for the Altuda Formation (Capitanian, Permian), Northwest Glass Mountains, Texas

    USGS Publications Warehouse

    Haneef, Mohammad; Rohr, D.M.; Wardlaw, B.R.

    2000-01-01

    The Altuda Formation (Capitanian) in the northwestern Glass Mountains is comprised of thin, even bedded limestones, dolostones, mixed clastic-carbonates, and silt/sandstones interbedded with basin-ward dipping wedge-shaped clinoforms of the Captian Limestone. The formation is characterized by graded bedding, planar laminations, flame structures, contorted/convolute bedding, horizontal branching burrows, and shelf-derived normal marine fauna. A detailed study of the Altuda Formation north of Old Blue Mountain, Glass Mountains, reveals that the formation in this area was deposited by turbidity currents in slope to basinal settings.

  8. Simulation of deep water wet weld microstructures using electrodes with high oxidizing potential

    SciTech Connect

    Pope, A.M.; Liu, S.; Olson, D.L.

    1994-12-31

    The properties of underwater wet (UWW) welds are greatly affected by water depth. Ibarra and Olson [1] showed that the oxygen content of the weld increases with increasing depth while the amount of deoxidants such as Mn and Si decreases. This change in chemical composition adversely affects both the tensile strength and toughness of the weld. The present research was designed to understand the influence of oxidizing ingredients in the electrode covering on the chemical composition, weld bead appearance and microstructure of wet welds. Changes in the ability of the electrode to supply oxygen to the weld pool were made through modifications of the hematite to rutile (Fe{sub 2}O{sub 3}/TiO{sub 2}) ratio in the covering.The weld deposited by the rutile electrode (no hematite addition) presented the lowest oxygen content (1700 ppm). When the oxidizing character of the electrode increased the concentration of inclusions, mainly FeO, in the weld also increased. However, the increase in oxygen pickup was not monotonous but reached a `saturation` value at approximately 2100 ppm. These results suggest that the microstructure and properties of wet welds deposited at great depths by rutile electrodes will be similar to those made by oxidizing electrodes at much shallower depths. Hence studying oxidizing electrodes and improving their properties will help the development of electrodes for wet welding at greater depths. It is also a much cheaper way of `simulating` welding at higher pressures.

  9. Multiproxy constraints on alteration and primary compositions of Ediacaran deep-water carbonate rocks, Yangtze Platform, South China

    NASA Astrophysics Data System (ADS)

    Hohl, Simon V.; Becker, Harry; Herzlieb, Steffen; Guo, Qingjun

    2015-08-01

    The occurrence of shallow and deep-water sedimentary facies has established the Yangtze Platform in South China as a key site for the study of Neoproterozoic ocean oxidation and Ediacaran animal evolution following the Marinoan glaciation. The Yanwutan section in Hunan Province is one of the few coherent sections on the Yangtze Platform where Ediacaran deep-water carbonate sediments (predominantly dolostones) are preserved together with organic carbon-rich shales. Here we present new major and trace element abundance data as well as Sr-, O- and C-isotope compositions of leachates from carbonates of the Doushantuo Formation. We evaluate the role of diagenetic modification of the carbonate rocks and constrain the redox evolution of Ediacaran seawater in space and time. 87Sr/86Sr systematically varies with δ18Ocarb, Sr- and Ba abundances, indicating variable but mostly strong modification of fluid-mobile elements by continental basin fluids. In contrast, REE+Y patterns have preserved seawater-like compositions. Cap dolostones (unit I) on top of the Nantuo diamictites differ from cap dolostones at shallow-water sections on the Yangtze Platform in that they show no Ce-anomalies, and little alteration near the top (87Sr/86Sr = 0.7078, δ18O = -4.0, δ13Ccarb = 1.1), suggesting that δ13Ccarb and δ18O of cap dolostones at many other sections were compromised by hydrothermal alteration. The overlying organic carbon poor micritic dolostone (unit II) shows negative Ce-anomalies that disappear towards the top of the unit. No Ce-anomalies occur in subsequent organic carbon-rich muddy dolostone units (units III to IV). These observations, enrichments in TOC that correlate with variations in redox-sensitive metals in the carbonates, negative δ13Ccarb in units II to IV and the decoupling of δ13Ccarb from δ13Corg argue for the existence of mostly anoxic deep-water at the Yangtze passive continental margin during the Ediacaran. The negative Ce-anomalies at the base of unit II

  10. A new genus and species of Thyasiridae (Mollusca, Bivalvia) from deep-water, Beaufort Sea, northern Alaska

    PubMed Central

    Valentich-Scott, Paul; Powell, Charles L.; II; Lorenson, Thomas D.; Edwards, Brian E.

    2014-01-01

    Abstract Bivalve mollusk shells were collected in 2350 m depth in the Beaufort Sea, Arctic Ocean off northern Alaska. Initial identification suggested the specimens were a member of the bivalve family Thyasiridae, but no known eastern Pacific or Arctic living or fossil thyasirid resembled these deep-water specimens. Comparisons were made with the type of the genera Maorithyas Fleming, 1950, Spinaxinus Oliver & Holmes, 2006, Axinus Sowerby, 1821, and Parathyasira Iredale, 1930. We determined the Beaufort Sea species represents a new genus, herein described as Wallerconcha. These specimens also represent a new species, herein named Wallerconcha sarae. These new taxa are compared with known modern and fossil genera and species of thyasirds. PMID:25589851

  11. Apristurus breviventralis, a new species of deep-water catshark (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from the Gulf of Aden.

    PubMed

    Kawauchi, Junro; Weigmann, Simon; Nakaya, Kazuhiro

    2014-11-03

    A new deep-water catshark of the genus Apristurus Garman, 1913 is described based on nine specimens from the Gulf of Aden in the northwestern Indian Ocean. Apristurus breviventralis sp. nov. belongs to the 'brunneus group' of the genus and is characterized by having pectoral-fin tips reaching beyond the midpoint between the paired fin bases, a much shorter pectoral-pelvic space than the anal-fin base, a low and long-based anal fin, and a first dorsal fin located behind pelvic-fin insertion. The new species most closely resembles the western Atlantic species Apristurus canutus, but is distinguishable in having greater nostril length than internarial width and longer claspers in adult males. Apristurus breviventralis sp. nov. represents the sixth species of Apristurus from the western Indian Ocean and the 38th species globally. 

  12. Transverse instability and viscous dissipation of forced 3-D gravity-capillary solitary waves on deep water

    NASA Astrophysics Data System (ADS)

    Cho, Yeunwoo

    2014-11-01

    The shedding phenomena of 3-D viscous gravity-capillary solitary waves generated by a moving air-forcing on the surface of deep water are investigated. Near the resonance where the forcing speed is close to 23 cm/s, two kinds of shedding modes are possible; Anti-symmetric and symmetric modes. A relevant theoretical model equation is numerically solved for the identification of shedding of solitary waves, and is analytically studied in terms of their linear stability to transverse perturbations. Furthermore, by tracing trajectories of shed solitary waves, the decay rate of a 3-D solitary wave due to viscous dissipation is estimated. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2014R1A1A1002441).

  13. An unusual new species of paguroid (Crustacea, Anomura, Paguridae) from deep waters of the Gulf of Mexico

    PubMed Central

    Lemaitre, Rafael; Vázquez-Bader, Ana Rosa; Gracia, Adolfo

    2014-01-01

    Abstract A new hermit crab species of the family Paguridae, Tomopaguropsis ahkinpechensis sp. n., is described from deep waters (780–827 m) of the Gulf of Mexico. This is the second species of Tomopaguropsis known from the western Atlantic, and the fifth worldwide. The new species is morphologically most similar to a species from Indonesia, Tomopaguropsis crinita McLaughlin, 1997, the two having ocular peduncles that diminish in width distally, reduced corneas, dense cheliped setation, and males lacking paired pleopods 1. The calcified figs on the branchiostegite and anterodorsally on the posterior carapace, and the calcified first pleonal somite that is not fused to the last thoracic somite, are unusual paguroid characters. A discussion of the affinities and characters that define this new species is included, along with a key to all five species of Tomopaguropsis. PMID:25408613

  14. Dynamic analysis for the design of C.A.L.M. system in shallow and deep waters

    SciTech Connect

    Hwang, Y.L.

    1996-12-31

    This paper presents a time domain analysis approach to evaluate the dynamic behavior of the Catenary Anchor Leg Mooring (CALM) system under the maximum operational condition when a tanker is moored to the terminal, and in the survival condition when the terminal is not occupied by a tanker. An analytical model, integrating tanker, hawser, buoy, and mooring lines is developed to dynamically predict the extreme mooring loads and buoy orbital motions, when responding to the effect of wind, current, wave frequency and wave drift response. Numerical results describing the dynamic behaviors of the CALM system in both shallow and deep water situations are presented and discussed. The importance of the line dynamics and hawser coupled buoy-tanker dynamics is demonstrated by comparing the present dynamic analysis with catenary calculation approach. Results of the analysis are compared with model test data to validate the mathematical model presented.

  15. In Equilibrium Stable Isotope Chemistry of The Deep Water Coral Stylaster Sp. From Rockall Trough: Paleoceanographic Implications

    NASA Astrophysics Data System (ADS)

    Mienis, F.

    Living corals, molluscs and associated water samples were collected from deep sea coral reefs along the margins of Rockall Trough (N. Atlantic). Oxygen (d18O) and carbon (d13C) isotope analyses of seawater and skeletal CaCO3 indicate that vari- ous organisms do not precipitate CaCO3 in isotopic equilibrium with host water. Par- ticularly the most abundant coral genera Lophelia sp and Madrepora sp fractionate markedly, as was already observed by a number of previous studies. However, our new data shows that the coral genus Stylaster, occuring in small numbers in the Rock- all Trough area, is in isotopic equilibrium with seawater. Like for the aragonitic bi- valves and gastropods inhabiting the same deep water reefs, microsampling of growth banded Stylaster specimens can be applied to obtain high resolution time series of in-equilibrium d13C and d18O data covering the life span of individual specimens.

  16. Analysis of the geological structure and tectonic evolution of Xingning-Jinghai sag in deep water area, northern South China Sea

    NASA Astrophysics Data System (ADS)

    Han, Xiaoying; Ren, Jianye; Lin, Zi; Yang, Linlong

    2015-04-01

    Recent years, oil and gas exploration of the Pearl River Mouth Basin in the northern margin of South China Sea continuously achieved historic breakthroughs. The Xingning-Jinghai sag, which is located in southeast of the Pearl River Mouth Basin, is a deep-water sag with a great exploration potential. Its tectonic evolution is extremely complex. It experienced Mesozoic subduction to Cenozoic intra-continental rifting background, and finally evolved into a deep-water sag of the northern continental margin of South China Sea. The geological characteristics and the tectonic evolution of Xingning-Jinghai sag was closely related to the process of formation and evolution of the passive continental margin of the northern South China Sea. It is confirmed by many geophysical data that compared with adjacent Chaoshan depression, the crustal thickness of Xingning-Jinghai sag was rapidly thinning, and it developed detachment faults with later magmatic intrusion. The development of detachment faults have dynamic significance for the spreading of the South China Sea. Based on the seismic geological interpretation of 2D seismic data in the study area, the characteristics of detachment fault and supra-detachment basin have been proposed in this study. The characteristics of the detachment fault are low angle and high ratio between heave and throw. The geometry of the detachment fault is a typical lisric shape, with the dip of fault decreasing generally from the seismic profile. The detachment basin where sediments are not deposited over a tilting hanging-wall block but onto a tectonically exhumed footwall which is different from the typical half graben basin. Seismic profiles indicate two different structural styles in the east and west part of Xingning-Jinghai sag. In the west of the sag, there developed two large detachment faults, which control their detachment basin systems and the typical H block, and the two detachment faults are dipping landward and seaward, respectively. In

  17. First autonomous bio-optical profiling float in the Gulf of Mexico reveals dynamic biogeochemistry in deep waters.

    PubMed

    Green, Rebecca E; Bower, Amy S; Lugo-Fernández, Alexis

    2014-01-01

    Profiling floats equipped with bio-optical sensors well complement ship-based and satellite ocean color measurements by providing highly-resolved time-series data on the vertical structure of biogeochemical processes in oceanic waters. This is the first study to employ an autonomous profiling (APEX) float in the Gulf of Mexico for measuring spatiotemporal variability in bio-optics and hydrography. During the 17-month deployment (July 2011 to December 2012), the float mission collected profiles of temperature, salinity, chlorophyll fluorescence, particulate backscattering (bbp), and colored dissolved organic matter (CDOM) fluorescence from the ocean surface to a depth of 1,500 m. Biogeochemical variability was characterized by distinct depth trends and local "hot spots", including impacts from mesoscale processes associated with each of the water masses sampled, from ambient deep waters over the Florida Plain, into the Loop Current, up the Florida Canyon, and eventually into the Florida Straits. A deep chlorophyll maximum (DCM) occurred between 30 and 120 m, with the DCM depth significantly related to the unique density layer ρ = 1023.6 (R2 = 0.62). Particulate backscattering, bbp, demonstrated multiple peaks throughout the water column, including from phytoplankton, deep scattering layers, and resuspension. The bio-optical relationship developed between bbp and chlorophyll (R2 = 0.49) was compared to a global relationship and could significantly improve regional ocean-color algorithms. Photooxidation and autochthonous production contributed to CDOM distributions in the upper water column, whereas in deep water, CDOM behaved as a semi-conservative tracer of water masses, demonstrating a tight relationship with density (R2 = 0.87). In the wake of the Deepwater Horizon oil spill, this research lends support to the use of autonomous drifting profilers as a powerful tool for consideration in the design of an expanded and integrated observing network for

  18. Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

    NASA Astrophysics Data System (ADS)

    Bostock, H. C.; Mikaloff Fletcher, S. E.; Williams, M. J. M.

    2013-10-01

    Using ocean carbon data from global datasets, we have developed several multiple linear regression (MLR) algorithms to estimate alkalinity and dissolved inorganic carbon (DIC) in the intermediate and deep waters of the Southern Hemisphere (south of 25° S) from only hydrographic data (temperature, salinity and dissolved oxygen). A Monte Carlo experiment was used to identify a potential density (σθ) of 27.5 as an optimal break point between the two regimes with different MLR algorithms. The algorithms provide a good estimate of DIC (R2=0.98) and alkalinity (R2=0.91), and excellent agreement for aragonite and calcite saturation states (R2=0.99). Combining the algorithms with the CSIRO Atlas of Regional Seas (CARS), we have mapped the calcite saturation horizon (CSH) and aragonite saturation horizon (ASH) for the Southern Ocean at a spatial resolution of 0.5°. These maps are more detailed and more consistent with the oceanography than the previously gridded GLODAP data. The high-resolution ASH map reveals a dramatic circumpolar shoaling at the polar front. North of 40° S the CSH is deepest in the Atlantic (~ 4000 m) and shallower in the Pacific Ocean (~ 2750 m), while the CSH sits between 3200 and 3400 m in the Indian Ocean. The uptake of anthropogenic carbon by the ocean will alter the relationships between DIC and hydrographic data in the intermediate and deep waters over time. Thus continued sampling will be required, and the MLR algorithms will need to be adjusted in the future to account for these changes.

  19. Sedimentation processes and new age constraints on rifting stages in Lake Baikal: results of deep-water drilling

    NASA Astrophysics Data System (ADS)

    Kuzmin, M. I.; Karabanov, E. B.; Prokopenko, A. A.; Gelety, V. F.; Antipin, V. S.; Williams, D. F.; Gvozdkov, A. N.

    With this paper we present a first attempt to combine the direct results on lithology, composition and age dating in the boreholes BDP-93, BDP-96 and BDP-97 with geological and seismic data from the areas where those sections were drilled. The sedimentary environments represented by the BDP boreholes are markedly different and possess characteristic lithological features. The results of the deep drilling provide the essential means for testing numerous age models used in geological reconstructions of the Lake Baikal rifting dynamics. Neither the basin-wide unconformity interpreted from seismic data, nor the interpreted change from shallow-water to deep-water facies at the boundary of the seismic stratigraphic complexes were found in the BDP-96 boreholes on Academician Ridge. Also, lithology does not support the proposed reconstructions of intense lake level fluctuations and transgressions during the Pliocene at Academician Ridge. The continuous deep-water hemipelagic sedimentation at Academician Ridge has existed for the past 5Ma. The beginning of an intense rifting phase of the Neobaikalian sub-stage and related drastic changes in sedimentation processes were interpreted on seismic sections as the basin-wide unconformity B10. Different age estimates for this boundary ranged from Late Pliocene (3.5Ma) to Plio-Pleistocene boundary. As shown by BDP-96 borehole, B10 is associated with a lithological change from diatomaceous ooze to dense silty clay and not with an erosional contact. The new age for this boundary in BDP-96 is approximately 2.5Ma. This new age constraint suggests that the upper sedimentary strata of Northern Baikal (1.5-1.7km thick) have formed during the past 2.5Ma with average sedimentation rates of 60-70cm/ka. The BDP-93 boreholes at Buguldeika suggest that uplift in Primorsky Range took place prior to 1.07-1.31Ma, a date which exceeds the age of previous geological models.

  20. Near-surface mixing and pronounced deep-water stratification in a compartmentalised, human-disturbed atoll lagoon system

    NASA Astrophysics Data System (ADS)

    Gardner, J. P. A.; Garton, D. W.; Collen, J. D.

    2011-03-01

    Palmyra Atoll has four partially isolated lagoons up to 50 m in depth, each with complex and variable bottom topographies. Measurements of depth, temperature, salinity, turbidity and dissolved oxygen (DO) revealed a well-mixed shallow surface layer (0-10 m depth) and below that pronounced stratification of DO in the absence of a pycnocline. Turbidity increased in a step-like manner at ~25 m depth, at the oxycline. For all deep sections of the lagoon (>30 m), DO declined uniformly to 0% saturation. As determined from filtration, mass of particulates was independent of depth. Surface mixing and deep-water stratification are both stable at different temporal scales, including day versus night, daily, weekly and annually. We suggest that lagoon circulation is represented by a shallow, westward-moving surface layer of well-to-partially mixed water with high DO and low turbidity, underlain by a relatively static and temporally stable layer with low to zero DO and elevated turbidity. This is the first report of such conditions within a deep lagoon system, and only the second report of anoxic conditions in any such system. In deep-water, stable euxinic conditions reflect bottom topography, with dysoxic and anoxic water being constrained within silled basins. The occurrence and depth of large volumes of sediment-laden and dysoxic/anoxic water need to be considered in management proposals designed to increase water flow through the lagoon. These novel water column conditions most probably arose as a consequence of military construction work, consistent with published reports of profound changes to the atoll during 1940-1945. If so, they highlight the need to better understand the possible consequences of cutting channels and modification of lagoon flow at many atolls across the central Pacific Ocean.

  1. First Autonomous Bio-Optical Profiling Float in the Gulf of Mexico Reveals Dynamic Biogeochemistry in Deep Waters

    PubMed Central

    Green, Rebecca E.; Bower, Amy S.; Lugo-Fernández, Alexis

    2014-01-01

    Profiling floats equipped with bio-optical sensors well complement ship-based and satellite ocean color measurements by providing highly-resolved time-series data on the vertical structure of biogeochemical processes in oceanic waters. This is the first study to employ an autonomous profiling (APEX) float in the Gulf of Mexico for measuring spatiotemporal variability in bio-optics and hydrography. During the 17-month deployment (July 2011 to December 2012), the float mission collected profiles of temperature, salinity, chlorophyll fluorescence, particulate backscattering (bbp), and colored dissolved organic matter (CDOM) fluorescence from the ocean surface to a depth of 1,500 m. Biogeochemical variability was characterized by distinct depth trends and local “hot spots”, including impacts from mesoscale processes associated with each of the water masses sampled, from ambient deep waters over the Florida Plain, into the Loop Current, up the Florida Canyon, and eventually into the Florida Straits. A deep chlorophyll maximum (DCM) occurred between 30 and 120 m, with the DCM depth significantly related to the unique density layer ρ = 1023.6 (R2 = 0.62). Particulate backscattering, bbp, demonstrated multiple peaks throughout the water column, including from phytoplankton, deep scattering layers, and resuspension. The bio-optical relationship developed between bbp and chlorophyll (R2 = 0.49) was compared to a global relationship and could significantly improve regional ocean-color algorithms. Photooxidation and autochthonous production contributed to CDOM distributions in the upper water column, whereas in deep water, CDOM behaved as a semi-conservative tracer of water masses, demonstrating a tight relationship with density (R2 = 0.87). In the wake of the Deepwater Horizon oil spill, this research lends support to the use of autonomous drifting profilers as a powerful tool for consideration in the design of an expanded and integrated observing network

  2. Insights into North Atlantic deep water formation during the peak interglacial interval of Marine Isotope Stage 9 (MIS 9)

    NASA Astrophysics Data System (ADS)

    Mokeddem, Zohra; McManus, Jerry F.

    2017-01-01

    Foraminifera abundance and stable isotope records from ODP Site 984 (61.25°N, 24.04°W, 1648 m) in the North Atlantic are used to reconstruct surface circulation variations and the relative strength of the North Atlantic Deep Water (NADW) formation over the period spanning the peak warmth of Marine Interglacial Stage (MIS) 9e ( 324-336 ka). This interval includes the preceding deglaciation, Termination 4 (T4), and the subsequent glacial inception of MIS 9d. The records indicate a greatly reduced contribution of NADW during T4, as observed in more recent deglaciations. In contrast with the most recent deglaciation, the lack of a significant NADW signal extended from T4 well into the peak interglacial MIS 9e and persisted nearly until the transition to the subsequent glacial stage MIS 9d. Although NADW formation resumed during MIS 9e, only depths greater than 2000 m appear to have been ventilated. The poorly ventilated intermediate depth of Site 984 (<2000 m) may have resulted on one hand from a general reduction of deep water ventilation by NADW during the study interval or, on the other hand, from different pathways of the spread of newly formed NADW that bypassed the study location. The intermediate depths may have also been invaded by southern-sourced waters as the formation of intermediate depth NADW weakened. The absence of any significant NADW signal at the water depth of Site 984 during the climatic optimum contrasts sharply with subsequent interglacial peaks (MIS 5e and the Holocene). Despite the perturbed intermediate depth circulation, oceanic heat transport northeastward was not interrupted and may have contributed to the relatively mild interglacial conditions of MIS 9e.

  3. Copper-nickel-rich, amalgamated ferromanganese crust-nodule deposits from Shatsky Rise, NW Pacific

    USGS Publications Warehouse

    Hein, J.R.; Conrad, T.A.; Frank, M.; Christl, M.; Sager, W.W.

    2012-01-01

    A unique set of ferromanganese crusts and nodules collected from Shatsky Rise (SR), NW Pacific, were analyzed for mineralogical and chemical compositions, and dated using Be isotopes and cobalt chronometry. The composition of these midlatitude, deep-water deposits is markedly different from northwest-equatorial Pacific (PCZ) crusts, where most studies have been conducted. Crusts and nodules on SR formed in close proximity and some nodule deposits were cemented and overgrown by crusts, forming amalgamated deposits. The deep-water SR crusts are high in Cu, Li, and Th and low in Co, Te, and Tl concentrations compared to PCZ crusts. Thorium concentrations (ppm) are especially striking with a high of 152 (mean 56), compared to PCZ crusts (mean 11). The deep-water SR crusts show a diagenetic chemical signal, but not a diagenetic mineralogy, which together constrain the redox conditions to early oxic diagenesis. Diagenetic input to crusts is rare, but unequivocal in these deep-water crusts. Copper, Ni, and Li are strongly enriched in SR deep-water deposits, but only in layers older than about 3.4 Ma. Diagenetic reactions in the sediment and dissolution of biogenic calcite in the water column are the likely sources of these metals. The highest concentrations of Li are in crust layers that formed near the calcite compensation depth. The onset of Ni, Cu, and Li enrichment in the middle Miocene and cessation at about 3.4 Ma were accompanied by changes in the deep-water environment, especially composition and flow rates of water masses, and location of the carbonate compensation depth.

  4. Seafloor Morphology Associated With Deep-Water Gas Plumes Near Eel Canyon

    NASA Astrophysics Data System (ADS)

    Gwiazda, R.; Paull, C. K.; Caress, D. W.; Lundsten, E.; Anderson, K.; Thomas, H.

    2011-12-01

    During a surface ship multibeam mapping cruise associated with NOAA's Ocean Exploration (OE) program, five water column acoustic anomalies that extended up to 1,400 m upwards from the seafloor were encountered above both sides of the Eel Submarine Canyon off the coast of northern California (Gardner et al., 2010). These anomalies are believed to be methane gas plumes, originating from the seafloor at depths well within the gas hydrate stability field. To explore the sources of these plumes, higher resolution multi-beam bathymetry (vertical precision of 0.15 m and horizontal resolution of 1.0 m) and 1-4.5 kHz chirp seismic reflection profiles of the seafloor, surrounding these plumes, were collected in July 2011. These surveys were conducted during four 17.5-hour-long autonomous underwater vehicle (AUV) dives in up to 2 km water depths. The largest persistent water column plume appears to emanate from a distinctive topographic mound that is ~650 m long, 350 m wide, and stands nearly 60 m higher than the surrounding seafloor at 1,850 m depth. This topographic mound occurs on a ~2 km wide relatively level bench formed at the base of a 3.5 km wide scallop-shaped slide scar. Chirp profiles show that at least 40 m of layered sediment drape the bottom and sidewalls of this scar, suggesting that the slope failure that shaped this landscape was not a recent event. The surface of this mound is characterized by a distinctive hummocky topography consisting of small sometimes circular ~0.5 m deep pits, local highs and lows, separated by ~0.5 m high ledges that could have been formed by irregular erosion of the bedding surfaces. A semicircular crater-like depression occurs on the flank of this mound that is ~80 m across and more than 10 m deep. Because similar seafloor textures have been observed in other AUV surveys associated with methane-derived carbonate bearing sites known to overlie nearby seafloor gas hydrate deposits (e.g., Hydrate Ridge, Bullseye Vent, Santa Monica

  5. 30 CFR 203.60 - Who may apply for royalty relief on a case-by-case basis in deep water in the Gulf of Mexico or...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Relief for Pre-Act Deep Water Leases and for Development and Expansion Projects § 203.60 Who may apply... field (as defined in § 203.0); (b) Propose an expansion project (as defined in § 203.0); or (c)...

  6. Dynamics of a deep-water seagrass population on the Great Barrier Reef: annual occurrence and response to a major dredging program

    PubMed Central

    York, Paul H.; Carter, Alex B.; Chartrand, Kathryn; Sankey, Tonia; Wells, Linda; Rasheed, Michael A.

    2015-01-01

    Global seagrass research efforts have focused on shallow coastal and estuarine seagrass populations where alarming declines have been recorded. Comparatively little is known about the dynamics of deep-water seagrasses despite evidence that they form extensive meadows in some parts of the world. Deep-water seagrasses are subject to similar anthropogenic threats as shallow meadows, particularly along the Great Barrier Reef lagoon where they occur close to major population centres. We examine the dynamics of a deep-water seagrass population in the GBR over an 8 year period during which time a major capital dredging project occurred. Seasonal and inter-annual changes in seagrasses were assessed as well as the impact of dredging. The seagrass population was found to occur annually, generally present between July and December each year. Extensive and persistent turbid plumes from a large dredging program over an 8 month period resulted in a failure of the seagrasses to establish in 2006, however recruitment occurred the following year and the regular annual cycle was re-established. Results show that despite considerable inter annual variability, deep-water seagrasses had a regular annual pattern of occurrence, low resistance to reduced water quality but a capacity for rapid recolonisation on the cessation of impacts. PMID:26279474

  7. Experience of cathodic protection, fabrication and installation of anodes for deep water pipelines in the North Sea and the Norwegian Sea

    SciTech Connect

    Eliassen, S.; Pettersen, N.H.

    1996-08-01

    Statoil is the major operator of the oil and gas pipelines in the North Sea and the Norwegian Sea. Different coating systems have been used for external corrosion protection of the pipelines. The paper presents the company`s experience regarding cathodic protection design and fabrication and installation of anodes for deep water pipelines.

  8. Outer Continental Shelf Deep Water Royalty Relief Act. Introduced in the Senate, One Hundred Third Congress, Second Session, April 11, 1994

    SciTech Connect

    Not Available

    1994-01-01

    This is a report on the bill (S.318) which provides for the energy security of the Nation through encouraging the production of domestic oil and gas resources in deep water on the Outer Continental Shelf in the Gulf of Mexico, and on possible amendments it.

  9. Reconstructing deglacial Atlantic deep water circulation using the Nd isotopic composition of Fe-Mn oxide coatings from planktonic foraminfera

    NASA Astrophysics Data System (ADS)

    Piotrowski, A. M.; Galy, A.; Roberts, N. L.; Nicholl, J.; Yu, J.; Clegg, J.; Pomies, C.; Scrivner, A. E.

    2009-12-01

    During the last few decades, neodymium isotopes have been increasingly used as a paleoceanographic proxy, to reconstruct past changes in deep ocean circulation [1,2] and river outputs to the surface ocean [3]. The widespread use of the Nd isotope proxy depends on whether the Nd isotopic composition of past seawater can be reliably extracted from authigenic sediment phases. Here we show that the Fe-Mn oxide coatings which are removed from planktonic foraminifera during reductive cleaning can be used to reconstruct past deep water Nd isotopic composition. In effect, we are using the planktonic foraminiferal calcite as a low-Nd carrier phase to leach authigenic Fe-Mn oxides, which have higher Nd concentration and record the Nd isotopic composition of bottom water. Leaching experiments on northeastern North Atlantic core BOFS 8K (52N, 22W, 4045mbsl) show methodological artifacts during bulk sediment leaching, but that the Fe-Mn oxide coatings from the planktonic foraminifera have the same Nd isotopic composition as bottom water. Interestingly, the Nd isotopic composition of planktonic foraminifera which have not been cleaned of Fe-Mn oxide coatings, and planktonic foraminifera which have been reductively cleaned by the Boyle and Kiegwin (1987) [4] method are within error of each other throughout the deglacial records, suggesting incomplete removal or significant re-scavenging of Nd from Fe-Mn oxides to cleaned foraminiferal calcite during reductive cleaning. There is no indication that we are incorporating a significant surface-water Nd isotopic signal. Instead, these records and laboratory tests may suggest that some published “cleaned” planktonic foraminiferal records are preserving a deep water signal, rather than a surface ocean signal. The downcore BOFS 8K record of planktonic foraminferal Fe-Mn coating Nd isotopes shows a large deglacial change consistent with benthic carbon isotopes, supporting more southern-sourced water reaching the site during the last

  10. Controls on iron distributions in the deep water column of the North Pacific Ocean: Iron(III) hydroxide solubility and marine humic-type dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Kitayama, Saori; Kuma, Kenshi; Manabe, Eri; Sugie, Koji; Takata, Hyoe; Isoda, Yutaka; Toya, Kenji; Saitoh, Sei-Ichi; Takagi, Shohgo; Kamei, Yoshihiko; Sakaoka, Keiichiro

    2009-08-01

    Dissolved Fe in the western and central North Pacific Ocean was characterized by surface depletion, middepth maxima and, below that, a slight decrease with depth similar to the vertical distributions of nutrients, apparent oxygen utilization, Fe(III) hydroxide solubility, and humic-type fluorescence (H-flu) intensity. Dissolved Fe concentrations ([D-Fe], <0.22-μm fraction) in the deep water column were one-half lower in the central region (0.3-0.6 nM) than the western region (0.5-1.2 nM) although the Fe(III) solubility ([Fe(III)sol], <0.025-μm fraction) levels and distributions in deep waters were almost the same between both regions with middepth maxima (˜0.6 nM) at 500-1500-m depth range and then a gradual decrease to ˜0.3 nM at 5000-m depth. Higher [D-Fe] than [Fe(III)sol] in the deep water column of the western region results from the higher production of dissolved Fe from the decomposition of sinking particulate organic matter in the western region than the central region because of the high atmospheric and/or lateral Fe inputs in the western region. Similarity between [D-Fe] level and [Fe(III)sol] value at each deep water depth in the central region may be attributed to [D-Fe] being nearly in the solubility equilibrium with Fe(III) hydroxide in seawater. Strong linear correlation between [D-Fe] and H-flu intensity in the central region and relatively similar linear relationships between [Fe(III)sol] and H-flu intensity in the western and central regions are the first confirmation that humic-type fluorescent dissolved organic matter may be responsible for [D-Fe] in the deep water column as natural organic ligands complexing with Fe(III).

  11. Constraining the erosional response of deep-water channel systems to growing folds and thrusts, Niger Delta.

    NASA Astrophysics Data System (ADS)

    Whittaker, A. C.; Lonergan, L.; Jolly, B. A.

    2015-12-01

    Gravity-driven folds and thrusts often characterize the slope and deep-water settings of passive margins. These structures exert a significant control on sediment gravity flows because they determine the location and configuration of sediment depo-centres and transport systems. Here we exploit 3D seismic data in the outer toe-thrust region of the deep-water Niger Delta to analyse the interaction between Plio-Pleistocene channel systems and actively-growing folds and thrusts. We first map folds and thrusts from the seismic data and we use this data to reconstruct the history of fold growth in detail. We then make quantitative measurements of the geomorphic response of submarine channels to growing tectonic structures in order to provide new constraints on their long-term erosional dynamics. This information is used to infer morphodyanamic processes that sculpted the channel systems through time, and to estimate the bed shear stresses and fluid velocities of typical flow events. The bathymetric long profiles of these channels have concavities that range from -0.08 to -0.34, and an average gradient of ~1o. Thrusts are associated with a local steepening in channel gradient of up to 3 times, and this effect extends 0.5 - 2 km upstream of the thrust. Within these knickzones, channel incision increases by approximately by a factor of 2, with a corresponding width decrease of approximately 25%. Channel incision across growing structures is achieved through enhanced bed-shear stress driven incision (up to 200 Pa) and flow velocity (up to 5 ms-1) assuming typical bulk sediment concentrations of 0.6%. Comparison of structural uplift since 1.7 Ma, and channel incision over an equivalent period, shows that many of these channels are able to keep pace with the time-integrated uplift since 1.7 Ma, and may have reached a bathymetric steady-state. Generally, bed-shear stresses of ~150 Pa are sufficient to keep pace with structural strain rates of 10-15 s-1. More widely, our data

  12. The Relationship of the Smectite-Illite Conversion to Pore Water Salinity Trends, Deep Water Offshore Niger Delta

    NASA Astrophysics Data System (ADS)

    Fitts, T. G.; Summa, L. L.

    2002-12-01

    Petroleum exploration in the deepwater Niger Delta has produced an abundance of physical property data and geochemical information in the section from 500 to 4000m below the seafloor. These have improved our understanding of the links between diagenetic processes and changes in pore fluid chemistry, and further suggest that smectite dehydration is not a major contributor to overpressure in the section. Literature data, coupled with new log, x-ray diffraction and surface area measurements, suggest that smectite and mixed-layer illite-smectite are major components of Miocene to Recent shales in key deep water wells. The smectite-illite transformation is generally complete by 2000m bml, corresponding to 80-90 degrees C. Such high percentages of hydrated clays result in sediments with low shallow overburden stresses, permeabilities and thermal conductivities. Because of the large contribution of smectite interlayer water to the total water content, diagenetic alteration of smectite more strongly affects density and pore fluid chemistry profiles here than in areas with less hydrated clay. Coincident with the conversion of smectite to illite, the total dissolved solids in the pore waters from several wells in the deepwater Niger Delta decrease from near seawater values at the sea floor to approximatly 10,000 ppm at 2000m bml. Pore fluid composition estimates are derived primarily from log calculation of water resistivity, with limited confirmation from pressure gradients in water legs, and uncontaminated MDT fluid samples. There are two models that could account for the observed decrease in salinity with depth: freshwater incursion via long-distance lateral fluid flow through continuous aquifers, and release of interlayer water from smectite during diagenesis. The available data suggest that release of interlayer water is the most likely explanation for the salinity observations from deep water Nigeria. Freshwater incursions are more likely on the shallow water shelf

  13. Geometry and Kinematics of the Lamu Basin Deep-Water Fold-and-Thrust Belt (East Africa)

    NASA Astrophysics Data System (ADS)

    Barchi, Massimiliano R.; Cruciani, Francesco; Porreca, Massimiliano

    2016-04-01

    Even if most thin-skinned fold-and-thrust belt are generated at convergent plate boundaries, in the last decades advances in seismic exploration and acquisition of large datasets have shown that they are also notably widespread along continental passive margins, driven by gravity processes in deep-water areas. In this study a composite set of modern and vintage reprocessed seismic reflection profiles is used to investigate the internal structure and kinematic evolution of the Lamu Basin Deep-Water Fold-and-Trust Belt (DW-FTB). The Lamu Basin is an example of giant-scale, gravity driven compressional belt developed in Late Cretaceous-Early Tertiary along a still poorly explored sector of the East-African continental margin, at the Kenya-Somalia border. The compressional domain extends longitudinally for more than 450 km, is up to 180 km wide and shows remarkable structural complexity both along strike and along dip. The external part is dominated by ocean-verging imbricate thrusts, above a gently landward-dipping basal detachment. The internal part is characterised by almost symmetrical detachment folds and double verging structures, sustaining bowl-shaped syn-tectonic basins. Here the basal detachment surface is almost flat. The mean fold wavelength displays a progressive landward increase, from 2.5 km, at the toe of the belt, to about 10 km. This structural variability is thought to be related to the lateral variation of the section under shortening and particularly to the different thickness of the Early Cretaceous shaly unit involved in the deformations, increasing landward from about 400 m to more than 1 km. Through the sequential restoration of regional cross-sections, we evaluated that the northern portion of the thrust belt experienced a shortening of almost 50 km (corresponding to 20%), with a shortening rate (during the Late Cretaceous-Paleocene main event) of about 3.5 mm/yr. Under many respects, the dimensions and internal structure of this thrust belt

  14. [Upward and regeneration fluxes of inorganic nitrogen and phosphorus in the deep-water areas of the Black-Sea].

    PubMed

    Krivenko, O V; Parkhomenko, A V

    2014-01-01

    Upward and regeneration fluxes of inorganic nitrogen and phosphorusin the euphotic zone of the Black Sea deep waters were estimated using data from long-term observations of nitrate and phosphate vertical distribution and modeling of plankton month- and area-averaged nutrients excretion. The upward fluxes were calculated using monthly average nitrate and phosphate concentrations and their gradients beneath the euphotic layer assuming that the vertical transport rates are controlled by the density gradient at the upper layer of the main pycnocline throughout the year. According to the calculations, the nutrient input into the euphotic layer due to physical processes changes gradually throughout the year from minimum values in July-August (0.1-0.3 mg-atN x m(-2) x day(-1) and 0.02-0.04 mg-atP x m(-2) x day(-1)) up to maximum ones in February-March (1.2-1.8 mg-atN x m(-2) x day(-1) and 0.2-0.3 mg-atP x m(-2) x day(-1)), contrary to the seasonal dynamics of the regeneration flux rates. In summer, plankton regeneration rates increase nearly five-fold as compared to the winter months. The contribution of the upward flux to the total nutrient euphotic zone input was calculated and designated as F(N)(F(P))-ratio along the lines with the f-ratio and e-ratio that reflect the ratio of "new" production and particle export to primary production, respectively. The monthly means vary for F(N) from 5 to 50% and for F(P) from 10 to 70% throughout the year in the same manner as the upward flux. Relationships between the monthly mean values of F(N,P) and vertically integrated nitrate and phosphate concentrations, chlorophyll "a", phytoplankton biomass, and primary production in the euphotic zone were established. The obtained relationships correspond to the general relationships between primary production, "new" production and the sinking flux of particles known for the Ocean. Potential values of "new", regenerated, and total production of phytoplankton in the deep-water areas of the

  15. Continuous and interval training programs using deep water running improves functional fitness and blood pressure in the older adults.

    PubMed

    Reichert, Thaís; Kanitz, Ana Carolina; Delevatti, Rodrigo Sudatti; Bagatini, Natália Carvalho; Barroso, Bruna Machado; Kruel, Luiz Fernando Martins

    2016-02-01

    This study aimed to investigate the effects of two periodized training programs of deep water running on functional fitness and blood pressure in the older adults. Thirty-six individuals were divided into continuous group (CONT) and interval group (INT). Both groups were trained for 28 weeks (twice weekly). Measures were performed before the training period, after 12 weeks and training period. Two-way ANOVA and post hoc of Bonferroni were used (α = 0.05). There were no differences between groups in functional tests, with the exception of the flexibility of the upper limbs, in which the INT group showed the highest values. There was a significant improvement in both groups of foot up-and-go test (CONT 6.45 to 5.67; INT 6.59 to 5.78, in seconds), flexibility of lower limbs (CONT -4.76 to -0.61; INT 0.54 to 4.63, in centimeters), strength of upper (CONT 18.76 to 27.69; INT 18.66 to 26.58, in repetitions) and lower limbs (CONT 14.46 to 21.23; INT 14.40 to 21.58, in repetitions), and 6-min walk (CONT 567.50 to 591.16; INT 521.41 to 582.77, in meters). No differences were shown between groups for systolic blood pressure; however, diastolic blood pressure remained higher in CONT during all training. The blood pressure decreased significantly in both groups after the training (CONT 142 ± 16/88 ± 3 to 125 ± 14/77 ± 7 mmHg; INT 133 ± 15/75 ± 7 to 123 ± 17 and 69 ± 11 mmHg). Both programs of deep water running training promoted improvements of similar magnitude in all parameters of functional fitness, with the exception of flexibility of upper limbs, and decreased blood pressure in the older individuals.

  16. Nocturnal Foraging by Red-Legged Kittiwakes, a Surface Feeding Seabird That Relies on Deep Water Prey During Reproduction

    PubMed Central

    Kokubun, Nobuo; Yamamoto, Takashi; Kikuchi, Dale M.; Kitaysky, Alexander; Takahashi, Akinori

    2015-01-01

    Narrow foraging specialization may increase the vulnerability of marine predators to climate change. The red-legged kittiwake (Rissa brevirostris) is endemic to the Bering Sea and has experienced drastic population fluctuations in recent decades, presumably due to climate-driven changes in food resources. Red-legged kittiwakes are presumed to be a nocturnal surface-foraging seabird that feed almost entirely on deep water Myctophidae fishes. However, there is little empirical evidence confirming their nocturnal foraging activity during the breeding season. This study investigated the foraging behavior of red-legged kittiwakes by combining GPS tracking, accelerometry, and dietary analyses at the world’s largest breeding colony of red-legged kittiwakes on St. George I. GPS tracking of 5 individuals revealed that 82.5% of non-flight behavior (including foraging and resting) occurred over the ocean basin (bottom depth >1,000 m). Acceleration data from 4 birds showed three types of behaviors during foraging trips: (1) flight, characterized by regular wing flapping, (2) resting on water, characterized by non-active behavior, and (3) foraging, when wing flapping was irregular. The proportions of both foraging and resting behaviors were higher at night (14.1 ± 7.1% and 20.8 ± 14.3%) compared to those during the day (6.5 ± 3.0% and 1.7 ± 2.7%). The mean duration of foraging (2.4 ± 2.9 min) was shorter than that of flight between prey patches (24.2 ± 53.1 min). Dietary analyses confirmed myctophids as the dominant prey (100% by occurrence and 98.4 ± 2.4% by wet-weight). Although the sample size was limited, these results suggest that breeding red-legged kittiwakes concentrated their foraging on myctophids available at the surface during nighttime in deep water regions. We propose that the diel patterns and ephemeral nature of their foraging activity reflected the availability of myctophids. Such foraging specialization may exacerbate the vulnerability of red

  17. Nocturnal Foraging by Red-Legged Kittiwakes, a Surface Feeding Seabird That Relies on Deep Water Prey During Reproduction.

    PubMed

    Kokubun, Nobuo; Yamamoto, Takashi; Kikuchi, Dale M; Kitaysky, Alexander; Takahashi, Akinori

    2015-01-01

    Narrow foraging specialization may increase the vulnerability of marine predators to climate change. The red-legged kittiwake (Rissa brevirostris) is endemic to the Bering Sea and has experienced drastic population fluctuations in recent decades, presumably due to climate-driven changes in food resources. Red-legged kittiwakes are presumed to be a nocturnal surface-foraging seabird that feed almost entirely on deep water Myctophidae fishes. However, there is little empirical evidence confirming their nocturnal foraging activity during the breeding season. This study investigated the foraging behavior of red-legged kittiwakes by combining GPS tracking, accelerometry, and dietary analyses at the world's largest breeding colony of red-legged kittiwakes on St. George I. GPS tracking of 5 individuals revealed that 82.5% of non-flight behavior (including foraging and resting) occurred over the ocean basin (bottom depth >1,000 m). Acceleration data from 4 birds showed three types of behaviors during foraging trips: (1) flight, characterized by regular wing flapping, (2) resting on water, characterized by non-active behavior, and (3) foraging, when wing flapping was irregular. The proportions of both foraging and resting behaviors were higher at night (14.1 ± 7.1% and 20.8 ± 14.3%) compared to those during the day (6.5 ± 3.0% and 1.7 ± 2.7%). The mean duration of foraging (2.4 ± 2.9 min) was shorter than that of flight between prey patches (24.2 ± 53.1 min). Dietary analyses confirmed myctophids as the dominant prey (100% by occurrence and 98.4 ± 2.4% by wet-weight). Although the sample size was limited, these results suggest that breeding red-legged kittiwakes concentrated their foraging on myctophids available at the surface during nighttime in deep water regions. We propose that the diel patterns and ephemeral nature of their foraging activity reflected the availability of myctophids. Such foraging specialization may exacerbate the vulnerability of red

  18. Hard- and soft-bottom thanatofacies from the Santa Maria di Leuca deep-water coral province, Mediterranean

    NASA Astrophysics Data System (ADS)

    Rosso, A.; Vertino, A.; Di Geronimo, I.; Sanfilippo, R.; Sciuto, F.; Di Geronimo, R.; Violanti, D.; Corselli, C.; Taviani, M.; Mastrototaro, F.; Tursi, A.

    2010-03-01

    Thanatofacies and the skeletonized components of the living facies, from which they originate have been studied from the Santa Maria di Leuca (SML) deep-water coral mound province. Faunal analysis was carried out by means of bottom sampling and underwater video observations, taking into account all benthic taxonomic groups, mostly corals, molluscs, serpulids, bryozoans, ostracods, foraminifers and barnacles, which permitted recognition of six different facies. These thanatofacies are easily distinguishable and appear to be largely corresponding and overlapping with related living facies. Some occur in mound areas, others in the intermound ones. They are as follows: the Framework-building Coral facies (FC), characterised by colonial corals, mostly Madrepora oculata; the Coral Rubble facies (CR), with proximal and distal aspects, characterised by large- to small-sized and densely to loosely packed coral fragments; the Solitary Coral facies (SC), dominated by different species depending on the availability and dimensions of hard exploitable surfaces; the Gryphus and Isidella facies (GI) in relatively coarse-grained bottoms; the Mollusc Mud facies (MM) and the Foraminifer Mud facies (FM) in comparably homogeneous silty bottoms. Facies distribution and spatial variability are discussed, in relation to hydrology and sea-floor topography. Furthermore, the SML facies are compared with living facies from the present-day Mediterranean and Pleistocene sediments of the same area. Data on bioclastic assemblages can serve for comparison with other recent aphotic, non-tropical carbonates.

  19. Bythaelurus tenuicephalus n. sp., a new deep-water catshark (Carcharhiniformes, Scyliorhinidae) from the western Indian Ocean.

    PubMed

    Kaschner, Carina Julia; Weigmann, Simon; Thiel, Ralf

    2015-09-07

    A new dwarf deep-water catshark, Bythaelurus tenuicephalus, is described based on one adult and one juvenile male specimen from off Tanzania and Mozambique in the western Indian Ocean. The new species differs from its congeners by its slender head and snout, which is only slightly bell-shaped in dorsoventral view without distinct lateral indention. All other Bythaelurus species have distinctly bell-shaped snouts with a strong lateral indention anterior to outer nostrils. Compared to its congeners in the western Indian Ocean, B. tenuicephalus n. sp. also has broader claspers in adult males (base width 2.1% TL vs. 1.5-1.8% TL). It further differs from B. clevai by attaining a smaller maximum size and having a color pattern of fewer and smaller blotches, larger oral papillae, a shorter snout, and broader claspers without knob-like apex and with a smaller envelope and a subtriangular (vs. subrectangular) exorhipidion. Compared to B. hispidus, the new species has a longer snout, a longer dorsal-caudal space, broader clasper without knob-like apex, and fewer vertebral centra. In contrast to B. lutarius, B. tenuicephalus attains a smaller maximum size and has a blotched (vs. largely plain) coloration, numerous (vs. lacking) oral papillae, shorter anterior nasal flaps, a longer caudal fin, a shorter pelvic anal space, and shorter and broader claspers.

  20. Influence of Chemical Composition on Microbial Communities in Deep Water Plumes After the Deepwater Horizon Oil Spill

    NASA Astrophysics Data System (ADS)

    Redmond, M. C.; Valentine, D. L.

    2012-12-01

    After the Deepwater Horizon oil spill, large amounts of natural gas and oil remained dissolved or suspended in the deep Gulf of Mexico. These deep water plumes were preferentially enriched in soluble hydrocarbons, including methane, ethane, propane, cyclohexane, benzene, toluene, and xylenes. Microbial communities responded rapidly to the influx of hydrocarbons, and were initially dominated by a novel group of Oceanospirillales. As the summer progressed, Colwellia and Cycloclasticus became more abundant, followed by an increase in methanotrophs and methylotrophs. DNA stable isotope probing experiments showed that Colwellia spp. were the primary bacteria assimilating carbon from ethane and propane, suggesting that the presence of natural gas had a significant effect on the microbes that responded to the spill. Additional incubation experiments suggested that Colwellia could also consume benzene and other hydrocarbons in crude oil, but it was unclear whether the presence of natural gas stimulated or inhibited the consumption of other hydrocarbons. In order to determine the effect of natural gas on microbial community composition and the degradation of petroleum hydrocarbons, we conducted a series of incubation experiments with seawater from the deep Gulf of Mexico. We also conducted experiments to determine the effect of individual hydrocarbon compounds on the microbial community response. We will present results from both sets of experiments.

  1. [Microbiological processes at the interface of aerobic and anaerobic waters in the deep-water zone of the Black Sea].

    PubMed

    Pimenov, N V; Rusanov, I I; Iusupov, S K; Fridrich, J; Lein, A Iu; Wehrli, B; Ivanov, M V

    2000-01-01

    Chemical and key microbiological processes (assimilation of carbon dioxide, oxidation and formation of methane, and sulfate reduction) occurring at the boundary between the aerobic-anaerobic interface in the deep-water zone of the Black Sea were investigated. Measurements were taken at depths from 90 to 300 m at intervals of 5-10 m. The integral rate of the dark assimilation of carbon dioxide varied from 120 to 207 mg C/(m2 day) with a maximum at the boundary of cyclonic currents. The organic matter (OM) formed from methane comprised less than 5% of the OM formed from carbon dioxide. A comparison between the rates of methane oxidation and methane production suggests that methane that is oxidized at depths from 100 to 300 m was formed in deeper water horizons. The maximum rate of sulfate reduction (1230 mg S/(m2 day)) was observed in the western halistatic region, and the minimum rate (490 mg S/(m2 day)), in the eastern halistatic region. The average rate of hydrogen sulfide production measured at three deep-sea stations amounted to 755 mg S/(m2 day), or 276 g S/(m2 year).

  2. Growth of a deep-water, predatory fish is influenced by the productivity of a boundary current system.

    PubMed

    Nguyen, Hoang Minh; Rountrey, Adam N; Meeuwig, Jessica J; Coulson, Peter G; Feng, Ming; Newman, Stephen J; Waite, Anya M; Wakefield, Corey B; Meekan, Mark G

    2015-03-12

    The effects of climate change on predatory fishes in deep shelf areas are difficult to predict because complex processes may govern food availability and temperature at depth. We characterised the net impact of recent environmental changes on hapuku (Polyprion oxygeneios), an apex predator found in continental slope habitats (>200 m depth) by using dendrochronology techniques to develop a multi-decadal record of growth from otoliths. Fish were sampled off temperate south-western Australia, a region strongly influenced by the Leeuwin Current, a poleward-flowing, eastern boundary current. The common variance among individual growth records was relatively low (3.4%), but the otolith chronology was positively correlated (r = 0.61, p < 0.02) with sea level at Fremantle, a proxy for the strength of the Leeuwin Current. The Leeuwin Current influences the primary productivity of shelf ecosystems, with a strong current favouring growth in hapuku. Leeuwin Current strength is predicted to decline under climate change models and this study provides evidence that associated productivity changes may flow through to higher trophic levels even in deep water habitats.

  3. Deep-water Thyasiridae (Mollusca: Bivalvia) from the Oman Margin, Arabian Sea, new species and examples of endemism and cosmopolitanism.

    PubMed

    Oliver, P Graham

    2015-08-05

    Seven species of Thyasiridae are reported from the Oman Margin of the Arabian Sea at depths between 688 m and 3356 m. Hypoxic conditions exist at depths between 400 and 1200 m and three species are restricted to this zone and to the Arabian Sea. Leptaxinus indusarium has also been recorded from the Indus Fan and Channelaxinus investigatoris from off Sri Lanka. A new species Thyasira anassa sp. nov. is described from the hypoxic zone. Another four species are recorded from the abyssal zone where oxygen levels are typical for the deep ocean. Here another new species is described, Parathyasira bamberi sp. nov. but the other species could not be conclusively identified because of close affinity with populations from other oceans.  Deep water Atlantic species Axinulus croulinensis and Mendicula ferruginosa are apparently present in the abyssal Indian Ocean while another thyasirid shell is very close to Channelaxinus excavatus from the Eastern Pacific and C. perplicata from the Atlantic. Accompanying these abyssal thyasirids were other bivalve species, Deminucula atacellana, Limopsis pelagica and Bentharca asperula that cannot be distinguished by morphology from their Atlantic populations. It is concluded that using morphology alone that the abyssal species may well be cosmopolitan in distribution.

  4. Fecundity and embryo development of three Antarctic deep-water scleractinians: Flabellum thouarsii, F. curvatum and F. impensum

    NASA Astrophysics Data System (ADS)

    Waller, Rhian G.; Tyler, Paul A.; Smith, Craig R.

    2008-11-01

    The larval development of three species of deep-water scleractinian, Flabellum thouarsii, F. curvatum and F. impensum, was examined from samples collected from the deep continental shelf off the Western Antarctic Peninsula between 1999 and 2001. All three of these species were gonochoric, with females brooding multiple stages of planulae larvae. Mean fecundity was found to be high ( F. thouarsii, 2412 oocytes per polyp (opp) (±1554sd); F. curvatum 1618 opp (±1071sd); F. impensum, 1270 opp (±884sd)). F. thouarsii has a previtellogenic oocyte size of ˜500 μm and a maximum oocyte size of ˜4800 μm. F. curvatum has a previtellogenic oocyte size of ˜800 μm and a maximum oocytes size of ˜5120 μm, and F. impensum has the largest oocyte sizes with a previtellogenic oocyte size of ˜1000 μm and a maximum oocyte size of ˜5200 μm. Larvae were found free within the gastrovascular cavity and embedded within the mesenterial gastrodermis. Three tentative stages of larvae were observed within female individuals, with the final stages having prominent tentacle buds and oral areas. A maximum of two larvae were found per mesentery in F. thouarsii and F. impensum, and four larvae were found per mesentery for F. curvatum. Four stages of spermatogenesis also were observed using histological techniques. The observations are discussed in relation to modes of reproduction in Antarctic waters and the deep sea.

  5. A decision support system for real-time management of dissolvedoxygen in the Stockton deep water ship channel

    SciTech Connect

    Quinn, N.W.T.; Chen, Carl W.; Stringfellow, William T.

    2003-07-16

    A decision support system(DSS)is under development to assistin the control and management of episodes of dissolved oxygen sag in aDeep Water Ship Channel (DWSC), located in Stockton, California. The DWSCwas formed by excavating the bed of the San Joaquin River in the 1950'sto allow navigation by ocean-going cargo ships to the Port of Stockton.The deepened channel has the effect of increasing hydraulic residencetime by a factor of ten. allowing accumulation of decaying algae andother oxygen demanding substances - which creates a barrier to themigration of anadromous fish. This problem, which manifests itself inlate summer and early autumn, is an impediment to a multimillion dollarhabitat restoration effort for the salmon fishery in the San JoaquinRiver basin (SJRB). A hydrodynamic and water quality model of the Deltaand San Joaquin River forms the basis of the DSS which will provideforecasts of dissolved oxygen sag in the DWSC and provide modelingsupport for management actions such as forced aeration to improvedissolved oxygen concentrations in the Ship Channel. A graphical userinterlace, currently used for displaying flow and salinity forecasts onthe San Joaquin River, is being adapted to allow the display of dissolvedoxygen forecasts and to encourage the formation of a stakeholder-ledentity or institution to adaptively manage the problem.

  6. Man-induced salinity and temperature increases in western Mediterranean deep water. (Reannouncement with new availability information)

    SciTech Connect

    Rohling, E.J.; Bryden, H.L.

    1992-07-15

    The historical data base is used to study property changes in both the Western Mediterranean Deep Water (WMDW) and the Levantine Intermediate Water (LIW). Changes in WMDW properties during the past century have been described previously, although on a more limited data base. We are not aware of any previous study of changes in LIW properties. In the extensive data base we used, increases appear in both WMDW temperature and salinity, from 1909 to the present, which substantiate previously reported observations. In addition, we find that the density of WMDW seems to have increased as well, which disagrees with previous suggestions that it has remained constant. We observe that the WMDW temperature increase displays a distinct acceleration starting about 1955 and that a similar, although less conspicuous, acceleration occurs in the WMDW salinity increase. From our study of historical data on LIW properties, the LIW salinity also appears to have increased since 1909. We argue that the warming trend in WMDW may well be a response to the salinity increase, which seems to be imported from the eastern Mediterranean by LIW, and as such our observations endorse a recently published hypothesis. The increase in LIW salinity, in turn, is attributed to changes in the eastern Mediterranean freshwater budget, resulting from damming of major rivers that drain either directly or indirectly into the eastern Mediterranean.

  7. Growth of a deep-water, predatory fish is influenced by the productivity of a boundary current system

    PubMed Central

    Nguyen, Hoang Minh; Rountrey, Adam N.; Meeuwig, Jessica J.; Coulson, Peter G.; Feng, Ming; Newman, Stephen J.; Waite, Anya M.; Wakefield, Corey B.; Meekan, Mark G.

    2015-01-01

    The effects of climate change on predatory fishes in deep shelf areas are difficult to predict because complex processes may govern food availability and temperature at depth. We characterised the net impact of recent environmental changes on hapuku (Polyprion oxygeneios), an apex predator found in continental slope habitats (>200 m depth) by using dendrochronology techniques to develop a multi-decadal record of growth from otoliths. Fish were sampled off temperate south-western Australia, a region strongly influenced by the Leeuwin Current, a poleward-flowing, eastern boundary current. The common variance among individual growth records was relatively low (3.4%), but the otolith chronology was positively correlated (r = 0.61, p < 0.02) with sea level at Fremantle, a proxy for the strength of the Leeuwin Current. The Leeuwin Current influences the primary productivity of shelf ecosystems, with a strong current favouring growth in hapuku. Leeuwin Current strength is predicted to decline under climate change models and this study provides evidence that associated productivity changes may flow through to higher trophic levels even in deep water habitats. PMID:25761975

  8. Growth of a deep-water, predatory fish is influenced by the productivity of a boundary current system

    NASA Astrophysics Data System (ADS)

    Nguyen, Hoang Minh; Rountrey, Adam N.; Meeuwig, Jessica J.; Coulson, Peter G.; Feng, Ming; Newman, Stephen J.; Waite, Anya M.; Wakefield, Corey B.; Meekan, Mark G.

    2015-03-01

    The effects of climate change on predatory fishes in deep shelf areas are difficult to predict because complex processes may govern food availability and temperature at depth. We characterised the net impact of recent environmental changes on hapuku (Polyprion oxygeneios), an apex predator found in continental slope habitats (>200 m depth) by using dendrochronology techniques to develop a multi-decadal record of growth from otoliths. Fish were sampled off temperate south-western Australia, a region strongly influenced by the Leeuwin Current, a poleward-flowing, eastern boundary current. The common variance among individual growth records was relatively low (3.4%), but the otolith chronology was positively correlated (r = 0.61, p < 0.02) with sea level at Fremantle, a proxy for the strength of the Leeuwin Current. The Leeuwin Current influences the primary productivity of shelf ecosystems, with a strong current favouring growth in hapuku. Leeuwin Current strength is predicted to decline under climate change models and this study provides evidence that associated productivity changes may flow through to higher trophic levels even in deep water habitats.

  9. Challenge to the model of lake charr evolution: Shallow- and deep-water morphs exist within a small postglacial lake

    USGS Publications Warehouse

    Chavarie, Louise; Muir, Andrew M.; Zimmerman, Mara S.; Baillie, Shauna M.; Hansen, Michael J.; Nate, Nancy A.; Yule, Daniel L.; Middel, Trevor; Bentzen, Paul; Krueger, Charles C.

    2016-01-01

    All examples of lake charr (Salvelinus namaycush) diversity occur within the largest, deepest lakes of North America (i.e. > 2000 km2). We report here Rush Lake (1.3 km2) as the first example of a small lake with two lake charr morphs (lean and huronicus). Morphology, diet, life history, and genetics were examined to demonstrate the existence of morphs and determine the potential influence of evolutionary processes that led to their formation or maintenance. Results showed that the huronicus morph, caught in deep-water, had a deeper body, smaller head and jaws, higher eye position, greater buoyancy, and deeper peduncle than the shallow-water lean morph. Huronicus grew slower to a smaller adult size, and had an older mean age than the lean morph. Genetic comparisons showed low genetic divergence between morphs, indicating incomplete reproductive isolation. Phenotypic plasticity and differences in habitat use between deep and shallow waters associated with variation in foraging opportunities seems to have been sufficient to maintain the two morphs, demonstrating their important roles in resource polymorphism. Rush Lake expands previous explanations for lake charr intraspecific diversity, from large to small lakes and from reproductive isolation to the presence of gene flow associated with strong ecological drivers.

  10. Two new species and two new records of deep-water caridean shrimps from Brazil (Decapoda: Pandalidae, Palaemonidae, Crangonidae).

    PubMed

    Anker, Arthur; Pachelle, Paulo P G; Tavares, Marcos

    2014-06-13

    The present study deals with four species of benthic deep-water caridean shrimps collected on the continental slope off southeastern Brazil, between 360 m and 900 m. The deepwater pandalid Bitias stocki Fransen, 1990, previously known only from a few localities in the eastern Atlantic, is reported for the first time from the western Atlantic (Brazil). The Brazilian material of B. stocki also represents the first record of the genus Bitias Fransen, 1990 in the western Atlantic. The palaemonid Periclimenes tenellus (Smith, 1882), previously known only from South Carolina and New Jersey, USA, is reported for the first time from Brazil, representing a considerable range extension of this uncommon species into the southwestern Atlantic. Another deepwater palaemonid shrimp is described as new: Periclimenes bathyalis sp. nov. The new species is morphologically closest to the echinoid associates Periclimenes milleri Bruce, 1986 and Periclimenes ingressicolumbi Berggren & Svane, 1989. Finally, the bizarre deepwater crangonid genus Prionocrangon Wood-Mason in Wood-Mason & Alcock, 1891 is reported for the first time from Brazil and the southwestern Atlantic, where it is represented by a new species, Prionocrangon brasiliensis sp. nov.

  11. Occurrence of deep-water corals on the Mid-Atlantic Ridge based on MAR-ECO data

    NASA Astrophysics Data System (ADS)

    Mortensen, P. B.; Buhl-Mortensen, L.; Gebruk, A. V.; Krylova, E. M.

    2008-01-01

    Occurrence of deep-water corals on the Mid-Atlantic Ridge between the southern part of the Reykjanes Ridge and the Azores has been examined based on video surveys using remotely operated vehicles (ROV) and bycatch from longline and bottom trawl. Eight sites were surveyed with ROVs, and the bycatch material came from 16 trawl hauls and nine longline sets. Corals were observed at all sites surveyed with ROVs at depths between 800 and 2400 m, but most commonly shallower than 1400 m. The species richness of corals was high, with a total of 40 taxa recorded. Octocorals dominated the coral fauna with 27 taxa. Lophelia pertusa was one of the most frequently observed corals, present at five of the eight surveyed sites. It occurred on basaltic outcrops on the seamounts but always as relatively small colonies (<0.5 m in diameter). Massive live reef structures were not observed. The deepest record of Lophelia was at 1340 m, south of the Charlie Gibbs Fracture Zone. Accumulations of dead debris of coral skeletons could indicate a presence of former large Lophelia reefs at several locations. The number of megafaunal taxa was 1.6 times higher in areas where corals were present compared to areas without corals. Typical taxa that co-occurred with Lophelia were crinoids, certain sponges, the bivalve Acesta excavata, and squat lobsters. Signs of destructive fishing and lost gillnets were observed at several locations. The impact of fishing on deep-sea corals is discussed.

  12. A pragmatic community-based intervention of multimodal physiotherapy plus deep water running (DWR) for fibromyalgia syndrome: a pilot study.

    PubMed

    Cuesta-Vargas, Antonio I; Adams, Nicola

    2011-11-01

    Evidence-based recommendations support the use of multimodal therapy and hydrotherapy for fibromyalgia syndrome; however, there is little standardisation of such programmes. The aim of the study was to assess the effectiveness of a pool-based exercise using deep water running (DWR) as part of a multimodal physiotherapy programme for patients with fibromyalgia syndrome. For a non-randomised clinical study, 44 patients diagnosed with fibromyalgia were recruited from primary care. Patients in the experimental group received a multimodal programme incorporating pool-based exercise using DWR three times a week for an 8-week period. The control group received a leaflet containing advice and continued with normal activities. Patients were evaluated for physical function (Fibromyalgia Impact Questionnaire, FIQ), pain, general health (Short Form-12 Health Survey) and quality of life (European Quality of Life Scale-5D) pre- and post intervention. Statistically significant results were found for the experimental group for FIQ total score, incorporating physical function, pain, fatigue, stiffness and psychological variables (p < 0.05). Statistically significant differences between the experimental group and control were also found for general health (p < 0.05) and quality of life (p < 0.05). The results of this pilot study and the high level of compliance and adherence and low level of attrition suggest that this multimodal programme incorporating DWR is a safe and effective intervention for fibromyalgia syndrome that is acceptable to patients.

  13. Spatiotemporal bioerosion patterns in deep-water scleractinians from off Santa Maria di Leuca (Apulia, Ionian Sea)

    NASA Astrophysics Data System (ADS)

    Beuck, L.; Freiwald, A.; Taviani, M.

    2010-03-01

    This study focuses on the carbonate biodegradation processes of deep-water scleractinians from off Apulia at Santa Maria di Leuca (SML) in the Ionian Sea, including living colonies of Lophelia pertusa, Madrepora oculata and Desmophyllum dianthus. The corallites were grouped into three zones: the live zone, edge zone and dead zone. In total, 13 trace types were encountered and are attributed to borings of sponges (3), fungi (6), foraminifers (2), bacteria (1) and annelids (1). Their relative spatial appearance within the host skeletons led to the distinction between six succession stages of bioerosion. The first endobiontic traces are exclusively produced by bacteria and fungi and are already present in the edge zone, which could be attributed to their fast growth rates and/or temporal exposure of the bare skeleton to the water column. In D. dianthus the entire ichnospecies assemblage has been documented within the first 1.9 cm below the live zone and represents the most condensed bioerosion succession amongst the coral species studied. The strongest degradation of corallites at SML is made by boring sponges, which can excavate 70% or more of the skeleton. The finding of a unilateral condensed succession of bioerosion stages may be linked to prevailing unidirectional strong currents. A comparison of the present ichnocoenosis with bioerosion studies from the Eastern Atlantic evidences a reduced ichnodiversity in Ionian Sea bathyal corals.

  14. Swimming in Deep Waters

    ERIC Educational Resources Information Center

    Schussler, Deborah; Feiman-Nemser, Sharon; Diez, Mary E.; Murrell, Peter

    2012-01-01

    The authors respond to a review of their book, "Teaching as a Moral Practice: Defining, Developing, and Assessing Dispositions". The authors emphasize a vision of shared commitments for quality teaching whereby teacher-educators instill and nurture the wisdom and virtue that a moral teacher must possess in order to teach in a variety of…

  15. Deep Water Acoustics

    DTIC Science & Technology

    2016-06-28

    Estimates of basin-wide sound speed ( temperature ) fields obtained by the combination of acoustic, altimetry, and other data types with ocean...of acoustic coherence at long ranges in the ocean. Estimates of basin-wide sound speed ( temperature ) fields obtained by the combination of acoustic...index.html Award Number N00014-13-1-0053 LONG-TERM GOALS The ultimate limitations to the performance of long-range sonar are due to ocean sound speed

  16. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2015-04-15

    31, 20 15 I. Introduction The goal of this research is to increase our understanding of the impact of the ocean and seafloor environmental...agree the following things had to be done: 1.) Adjust the peregrine water depth so that the seafloor depth matched that of Ram (this involved 1...requirement for examining sonar performance issues associated with coherence, signal time spread and multi path stability . In Figure## below, the

  17. Characterizing, modelling and understanding the climate variability of the deep water formation in the North-Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Somot, Samuel; Houpert, Loic; Sevault, Florence; Testor, Pierre; Bosse, Anthony; Taupier-Letage, Isabelle; Bouin, Marie-Noelle; Waldman, Robin; Cassou, Christophe; Sanchez-Gomez, Emilia; Durrieu de Madron, Xavier; Adloff, Fanny; Nabat, Pierre; Herrmann, Marine

    2016-08-01

    Observing, modelling and understanding the climate-scale variability of the deep water formation (DWF) in the North-Western Mediterranean Sea remains today very challenging. In this study, we first characterize the interannual variability of this phenomenon by a thorough reanalysis of observations in order to establish reference time series. These quantitative indicators include 31 observed years for the yearly maximum mixed layer depth over the period 1980-2013 and a detailed multi-indicator description of the period 2007-2013. Then a 1980-2013 hindcast simulation is performed with a fully-coupled regional climate system model including the high-resolution representation of the regional atmosphere, ocean, land-surface and rivers. The simulation reproduces quantitatively well the mean behaviour and the large interannual variability of the DWF phenomenon. The model shows convection deeper than 1000 m in 2/3 of the modelled winters, a mean DWF rate equal to 0.35 Sv with maximum values of 1.7 (resp. 1.6) Sv in 2013 (resp. 2005). Using the model results, the winter-integrated buoyancy loss over the Gulf of Lions is identified as the primary driving factor of the DWF interannual variability and explains, alone, around 50 % of its variance. It is itself explained by the occurrence of few stormy days during winter. At daily scale, the Atlantic ridge weather regime is identified as favourable to strong buoyancy losses and therefore DWF, whereas the positive phase of the North Atlantic oscillation is unfavourable. The driving role of the vertical stratification in autumn, a measure of the water column inhibition to mixing, has also been analyzed. Combining both driving factors allows to explain more than 70 % of the interannual variance of the phenomenon and in particular the occurrence of the five strongest convective years of the model (1981, 1999, 2005, 2009, 2013). The model simulates qualitatively well the trends in the deep waters (warming, saltening, increase in the

  18. Lessons learnt from the Indian Ocean Tsunami 2004: the role of surface and subsurface topography in deep water tsunami propagation

    NASA Astrophysics Data System (ADS)

    Pattiaratchi, C. B.

    2014-12-01

    The Indian Ocean experienced its most devastating natural disaster through the action of a Tsunami, resulting from of an earthquake off the coast of Sumatra on 26th of December 2004. This resulted in widespread damage both to property and human lives with over 250,000 deaths in the region and many millions homeless. Our understanding of tsunami generation and propagation has increased significantly over the past decade. In this presentation, results obtained from detailed analysis of sea level data from Western Australia and Sri Lanka together with numerical modelling are presented to highlight the effects of topography both at the surface and subsurface. The major effects are due to wave reflection and refraction. Examples of wave reflection include: impacts on Malaysia/Thailand, Sri Lanka and Western Australia due to wave reflection from Sri Lanka, Maldives and Mascarene Ridge, respectively. In the case of Sri Lanka, the maximum wave height recorded along the west coast during the 2004 tsunami was due to the reflected wave from Maldives impacting 3 hours after the arrival of the initial waves. Similarly, along the West coast of Australia highest waves occurred 15 hours after the arrival of the first wave. Here, based on travel times, we postulate that the waves were reflected from the Mascarene Ridge and/or the island of Madagascar (Figure 1b). The conclusions based on observations were verified using numerical model simulations using the MOST and ComMIT models. Numerical modelling using the MOST model indicated the role of offshore susurface topography on tsunami propagation through wave wave refraction. Examples of wave refraction included the effects of deep water seamounts (Venin Meinesz) and plateaus (Wallaby, Cuvier and Exmouth) on tsunami propagation along the West Australian coast. The tsunami waves are first scattered by the Venin Meinesz seamounts and were then refracted by the Wallaby and Cuvier plateaus resulting in waves being deflected onto the

  19. Is Ekman pumping responsible for the seasonal variation of warm circumpolar deep water in the Amundsen Sea?

    NASA Astrophysics Data System (ADS)

    Kim, T. W.; Ha, H. K.; Wåhlin, A. K.; Lee, S. H.; Kim, C. S.; Lee, J. H.; Cho, Y. K.

    2017-01-01

    Ekman pumping induced by horizontally varying wind and sea ice drift is examined as an explanation for observed seasonal variation of the warm layer thickness of circumpolar deep water on the Amundsen Sea continental shelf. Spatial and temporal variation of the warm layer thickness in one of the deep troughs on the shelf (Dotson Trough) was measured during two oceanographic surveys and a two-year mooring deployment. A hydrographic transect from the deep ocean, across the shelf break, and into the trough shows a local elevation of the warm layer at the shelf break. On the shelf, the water flows south-east along the trough, gradually becoming colder and fresher due to mixing with cold water masses. A mooring placed in the trough shows a thicker and warmer layer in February and March (late summer/early autumn) and thinner and colder layer in September, October and November (late winter/early spring). The amplitude of this seasonal variation is up to 60 m. In order to investigate the effects of Ekman pumping, remotely sensed wind (Antarctic Mesoscale Prediction System wind data) and sea ice velocity and concentration (EASE Polar Pathfinder) were used. From the estimated surface stress field, the Ekman transport and Ekman pumping were calculated. At the shelf break, where the warm layer is elevated, the Ekman pumping shows a seasonal variation correlating with the mooring data. Previous studies have not been able to show a correlation between observed wind and bottom temperature, but it is shown here that when sea ice drift is taken into account the Ekman pumping at the outer shelf correlates with bottom temperature in Dotson Trough. The reason why the Ekman pumping varies seasonally at the shelf break appears to be the migration of the ice edge in the expanding polynya in combination with the wind field which on average is westward south of the shelf break.

  20. Effects of deep-water coral banks on the abundance and size structure of the megafauna in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    D'Onghia, G.; Maiorano, P.; Sion, L.; Giove, A.; Capezzuto, F.; Carlucci, R.; Tursi, A.

    2010-03-01

    The Santa Maria di Leuca (SML) coral banks represent a rare example of living Lophelia-Madrepora-bearing coral mounds in the Mediterranean Sea. They are located between 350 and 1100 m in depth, in the northern Ionian Sea (eastern-central Mediterranean). Using a multi-beam echo sounder, side-scan sonar, high-resolution seismics and underwater video, the zones were identified for the sampling demersal fauna without damaging the coral colonies. During September-October 2005 experimental samplings were carried out with longlines and trawl nets inside the coral habitat and outside, where fishery exploitation occurs. No significant differences were shown between the abundance of fish recorded using longlines in the coral and non-coral habitat even though some selachians and teleosts were more abundant in the former than in the latter. Large specimens of rockfish ( Helicolenus dactylopterus) and blackspot seabream ( Pagellus bogaraveo) were commonly caught using longlines in the coral habitat. Data from trawling revealed refuge effects in the coral habitat and fishing effects outside. Significant differences were detected between the recorded abundances in the two study areas. Greater densities and biomasses were obtained inside the coral area, and fish size spectra and size distributions indicate a greater abundance of large fish inside the coral habitat. The SML coral habitat is a spawning area for H. dactylopterus. The remarkable density of the young-of-the-year of the deep-water shark Etmopterus spinax as well as of Merluccius merluccius, Micromesistius poutassou, Phycis blennoides and H. dactylopterus, indicates that the coral habitat also acts as nursery area for these demersal species, which are exploited outside. Considering the evidence of the negative impact of bottom trawling and, to a lesser extent, of longlining, the coral banks can provide a refuge for the conservation of unique species and habitats as well as in providing benefit to adjacent fisheries

  1. Intermediate and deep water paleoceanography of the northern North Atlantic over the past 21,000 years

    NASA Astrophysics Data System (ADS)

    Thornalley, David J. R.; Elderfield, Harry; McCave, I. Nick

    2010-03-01

    Benthic foraminiferal stable isotope records from four high-resolution sediment cores, forming a depth transect between 1237 m and 2303 m on the South Iceland Rise, have been used to reconstruct intermediate and deep water paleoceanographic changes in the northern North Atlantic during the last 21 ka (spanning Termination I and the Holocene). Typically, a sampling resolution of ˜100 years is attained. Deglacial core chronologies are accurately tied to North Greenland Ice Core Project (NGRIP) ice core records through the correlation of tephra layers and changes in the percent abundance of Neogloboquadrina pachyderma (sinistral) with transitions in NGRIP. The evolution from the glacial mode of circulation to the present regime is punctuated by two periods with low benthic δ13C and δ18O values, which do not lie on glacial or Holocene water mass mixing lines. These periods correlate with the late Younger Dryas/Early Holocene (11.5-12.2 ka) and Heinrich Stadial 1 (14.7-16.8 ka) during which time freshwater input and sea-ice formation led to brine rejection both locally and as an overflow exported from the Nordic seas into the northern North Atlantic, as earlier reported by Meland et al. (2008). The export of brine with low δ13C values from the Nordic seas complicates traditional interpretations of low δ13C values during the deglaciation as incursions of southern sourced water, although the spatial extent of this brine is uncertain. The records also reveal that the onset of the Younger Dryas was accompanied by an abrupt and transient (˜200-300 year duration) decrease in the ventilation of the northern North Atlantic. During the Holocene, Iceland-Scotland Overflow Water only reached its modern flow strength and/or depth over the South Iceland Rise by 7-8 ka, in parallel with surface ocean reorganizations and a cessation in deglacial meltwater input to the North Atlantic.

  2. Examples of deep-water-bottom multiple dereverberation techniques applied to seismic-reflection data from the Atlantic Outer Continental Shelf

    USGS Publications Warehouse

    Peterson, Steven D.; Balch, A.H.; Patterson, W.C.; Taylor, D.J.

    1979-01-01

    Seismic-reflection data recorded in deep water over the Atlantic Outer Continental Shelf are often dominated by multiply-reflected seismic energy. This energy reverberates between the surface of the water and the seafloor (or other strong reflectors), and makes portions of the seismic data completely useless. Several different data-processing techniques can be applied to partially suppress these multiples and enhance the interpretability of the data. These techniques include (1) the three-point operator, (2) predictive deconvolution, (3) near-trace muting, (4) spatially variant bandpass filters, (5) Nth root stack, and (6) trace distance weighting. Application of these methods to several seismic lines indicates that trace distance weighting is the most useful method studied for suppressing deep-water-bottom multiples for data from the Atlantic Outer Continental Shelf.

  3. Redescription of Odontozona edwardsi (Bouvier, 1908) (Decapoda: Stenopodidea: Stenopodidae) and description of a new species of Odontozona commensal on the deep-water coral, Lophelia pertusa (Linneaus, 1758).

    PubMed

    Goy, Joseph W; Cardoso, Irene A

    2014-03-11

    Odontozona edwardsi, a rare stenopodid shrimp from deep waters of the northwest African coast off Morocco and Western Sahara is redescribed and figured based on type material and an additional 26 specimens including some from the Gulf of Cadiz and off Roscoff, France. Specimens of another Odontozona from the Gulf of Mexico, off Sapelo Island, Georgia, and off Rio de Janeiro, Brazil have been confused with O. edwardsi and O. spongicola. This Odontozona is associated with the deep sea hard coral Lophelia pertusa and is herewith designated as a new species. Both these Atlantic species of Odontozona are distinguished from the deep-water Pacific O. spongicola as well as the recently described southwestern Atlantic O. meloi by several morphological characters. A key to the Atlantic species of Odontozona is presented.

  4. Characteristics of the deep ocean carbon system during the past 150,000 years: SigmaCO2 distributions, deep water flow patterns, and abrupt climate change.

    PubMed

    Boyle, E A

    1997-08-05

    Studies of carbon isotopes and cadmium in bottom-dwelling foraminifera from ocean sediment cores have advanced our knowledge of ocean chemical distributions during the late Pleistocene. Last Glacial Maximum data are consistent with a persistent high-SigmaCO2 state for eastern Pacific deep water. Both tracers indicate that the mid-depth North and tropical Atlantic Ocean almost always has lower SigmaCO2 levels than those in the Pacific. Upper waters of the Last Glacial Maximum Atlantic are more SigmaCO2-depleted and deep waters are SigmaCO2-enriched compared with the waters of the present. In the northern Indian Ocean, delta13C and Cd data are consistent with upper water SigmaCO2 depletion relative to the present. There is no evident proximate source of this SigmaCO2-depleted water, so I suggest that SigmaCO2-depleted North Atlantic intermediate/deep water turns northward around the southern tip of Africa and moves toward the equator as a western boundary current. At long periods (>15,000 years), Milankovitch cycle variability is evident in paleochemical time series. But rapid millennial-scale variability can be seen in cores from high accumulation rate series. Atlantic deep water chemical properties are seen to change in as little as a few hundred years or less. An extraordinary new 52.7-m-long core from the Bermuda Rise contains a faithful record of climate variability with century-scale resolution. Sediment composition can be linked in detail with the isotope stage 3 interstadials recorded in Greenland ice cores. This new record shows at least 12 major climate fluctuations within marine isotope stage 5 (about 70,000-130,000 years before the present).

  5. Characteristics of the deep ocean carbon system during the past 150,000 years: ΣCO2 distributions, deep water flow patterns, and abrupt climate change

    PubMed Central

    Boyle, Edward A.

    1997-01-01

    Studies of carbon isotopes and cadmium in bottom-dwelling foraminifera from ocean sediment cores have advanced our knowledge of ocean chemical distributions during the late Pleistocene. Last Glacial Maximum data are consistent with a persistent high-ΣCO2 state for eastern Pacific deep water. Both tracers indicate that the mid-depth North and tropical Atlantic Ocean almost always has lower ΣCO2 levels than those in the Pacific. Upper waters of the Last Glacial Maximum Atlantic are more ΣCO2-depleted and deep waters are ΣCO2-enriched compared with the waters of the present. In the northern Indian Ocean, δ13C and Cd data are consistent with upper water ΣCO2 depletion relative to the present. There is no evident proximate source of this ΣCO2-depleted water, so I suggest that ΣCO2-depleted North Atlantic intermediate/deep water turns northward around the southern tip of Africa and moves toward the equator as a western boundary current. At long periods (>15,000 years), Milankovitch cycle variability is evident in paleochemical time series. But rapid millennial-scale variability can be seen in cores from high accumulation rate series. Atlantic deep water chemical properties are seen to change in as little as a few hundred years or less. An extraordinary new 52.7-m-long core from the Bermuda Rise contains a faithful record of climate variability with century-scale resolution. Sediment composition can be linked in detail with the isotope stage 3 interstadials recorded in Greenland ice cores. This new record shows at least 12 major climate fluctuations within marine isotope stage 5 (about 70,000–130,000 years before the present). PMID:11607737

  6. 30 CFR 203.60 - Who may apply for royalty relief on a case-by-case basis in deep water in the Gulf of Mexico or...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false Who may apply for royalty relief on a case-by-case basis in deep water in the Gulf of Mexico or offshore of Alaska? 203.60 Section 203.60 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR MINERALS REVENUE MANAGEMENT RELIEF OR REDUCTION IN ROYALTY...

  7. 30 CFR 203.60 - Who may apply for royalty relief on a case-by-case basis in deep water in the Gulf of Mexico or...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 2 2014-07-01 2014-07-01 false Who may apply for royalty relief on a case-by-case basis in deep water in the Gulf of Mexico or offshore of Alaska? 203.60 Section 203.60 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR MINERALS REVENUE MANAGEMENT RELIEF OR REDUCTION IN ROYALTY...

  8. 30 CFR 203.60 - Who may apply for royalty relief on a case-by-case basis in deep water in the Gulf of Mexico or...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false Who may apply for royalty relief on a case-by-case basis in deep water in the Gulf of Mexico or offshore of Alaska? 203.60 Section 203.60 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR MINERALS REVENUE MANAGEMENT RELIEF OR REDUCTION IN ROYALTY...

  9. Nursery areas of red mullet ( Mullus barbatus), hake ( Merluccius merluccius) and deep-water rose shrimp ( Parapenaeus longirostris) in the Eastern-Central Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Carlucci, Roberto; Giuseppe, Lembo; Porzia, Maiorano; Francesca, Capezzuto; Alessandra, Marano Chiara; Letizia, Sion; Teresa, Spedicato Maria; Nicola, Ungaro; Angelo, Tursi; D'Onghia, Gianfranco

    2009-08-01

    The spatial pattern of the nursery areas of red mullet ( Mullus barbatus), hake ( Merluccius merluccius) (Linnaeus, 1758) and deep-water rose shrimp ( Parapenaeus longirostris) (Lucas, 1846) was studied in the South Adriatic and North Ionian Seas (Eastern-Central Mediterranean) applying geostatistical techniques and data from time series trawl surveys conducted in the area. The analysed variables were: R (number of recruits/km 2) and R/Tot (fraction of recruits on the total sampled population). The structural analysis showed a spatial pattern of both variables characterized by continuity on a small scale. Predictions of nursery area localization with probability of finding recruits at different threshold values were obtained through median indicator kriging. For the red mullet the nurseries were mainly identified in the South Adriatic Sea off the Gargano peninsula and between Molfetta and Monopoli within 50 m in depth. The main concentration of hake juveniles was found to be between 100 and 200 m in depth along the Gargano peninsula and between Otranto and Santa Maria di Leuca, where a nursery of deep-water rose shrimp was also detected. An overlapping depth, between 100 and 200 m, was identified for hake and deep-water rose shrimp nurseries. Protection of these areas through limitations of fishing pressure is discussed.

  10. Hummocky cross-stratification-like structures and combined-flow ripples in the Punta Negra Formation (Lower-Middle Devonian, Argentine Precordillera): A turbiditic deep-water or storm-dominated prodelta inner-shelf system?

    NASA Astrophysics Data System (ADS)

    Basilici, Giorgio; de Luca, Pedro Henrique Vieira; Poiré, Daniel G.

    2012-08-01

    Turbidity-current and storm-induced deposits may exhibit similarities, in particularly when the latter is laid down by a combination of oscillatory and unidirectional flows. Recent progress in facies analysis helps to discriminate the sedimentary effects of oscillatory from unidirectional components of the flow. On the basis of detailed analysis of sedimentary facies, strata geometry, and palaeocurrent data, the present study reinterprets the Punta Negra Formation (PNF) (Lower-Middle Devonian, Argentine Precordillera), previously considered as a depositional system of deep-water, as a storm-dominated prodeltaic shelf depositional system. In the sandstone beds of the PNF, planar, low-angle and undulating laminations with weakly asymmetric hummocky and swaley bedforms, combined-flow ripples, accretionary hummocky cross-stratification-like (HCS-like), and anisotropic HCS-like suggest the action of oscillatory currents combined with unidirectional currents in forming the deposits. Different hypotheses on the origin of the oscillatory currents have been examined. The most convincing interpretation is that the oscillatory component of the velocity is attributed to storm-induced waves. The palaeocurrent data indicate offshore current directions, suggesting that the unidirectional flow was a gravity-induced bottom current. Inverse grading at the base and overlying normally graded divisions of the sandstone beds testify to waxing-waning behaviour of the depositional flows; interbedding of sedimentary structures (undulating laminations, low-angle and parallel laminations, and combined-flow ripples) in the lower and intermediate divisions of the beds indicate fluctuations of flow velocity. This organisation of the sedimentary structures permits association of the unidirectional component with hyperpycnal bottom currents. The terrestrial origin of the hyperpycnal flows is suggested by the abundance of terrestrial plant remains, the mineralogical and textural immaturity of the

  11. A method for simulating transient ground-water recharge in deep water-table settings in central Florida by using a simple water-balance/transfer-function model

    USGS Publications Warehouse

    O'Reilly, Andrew M.

    2004-01-01

    A relatively simple method is needed that provides estimates of transient ground-water recharge in deep water-table settings that can be incorporated into other hydrologic models. Deep water-table settings are areas where the water table is below the reach of plant roots and virtually all water that is not lost to surface runoff, evaporation at land surface, or evapotranspiration in the root zone eventually becomes ground-water recharge. Areas in central Florida with a deep water table generally are high recharge areas; consequently, simulation of recharge in these areas is of particular interest to water-resource managers. Yet the complexities of meteorological variations and unsaturated flow processes make it difficult to estimate short-term recharge rates, thereby confounding calibration and predictive use of transient hydrologic models. A simple water-balance/transfer-function (WBTF) model was developed for simulating transient ground-water recharge in deep water-table settings. The WBTF model represents a one-dimensional column from the top of the vegetative canopy to the water table and consists of two components: (1) a water-balance module that simulates the water storage capacity of the vegetative canopy and root zone; and (2) a transfer-function module that simulates the traveltime of water as it percolates from the bottom of the root zone to the water table. Data requirements include two time series for the period of interest?precipitation (or precipitation minus surface runoff, if surface runoff is not negligible) and evapotranspiration?and values for five parameters that represent water storage capacity or soil-drainage characteristics. A limiting assumption of the WBTF model is that the percolation of water below the root zone is a linear process. That is, percolating water is assumed to have the same traveltime characteristics, experiencing the same delay and attenuation, as it moves through the unsaturated zone. This assumption is more accurate if

  12. The roles of MCDW and deep water iron supply in sustaining a recurrent phytoplankton bloom on central Pennell Bank (Ross Sea)

    NASA Astrophysics Data System (ADS)

    Kustka, Adam B.; Kohut, Josh T.; White, Angelicque E.; Lam, Phoebe J.; Milligan, Allen J.; Dinniman, Michael S.; Mack, Stefanie; Hunter, Elias; Hiscock, Michael R.; Smith, Walker O.; Measures, Chris I.

    2015-11-01

    During January-February 2011 standing stocks of phytoplankton (chl a) in the Pennell Bank region of the Ross Sea were variable over 10-100 km spatial scales. One area of elevated chl a on central Pennell Bank (CPB) appeared to be a recurrent mid-summer feature. The western flank (WF) of Pennell Bank had pronounced signatures of Modified Circumpolar Deep Water (MCDW). We evaluated the spatial extent of Fe limitation and net primary production and tested whether MCDW may provide elevated amounts of Fe to the CPB region, through a combination of in situ measurements, shipboard incubations and a horizontally resolved physical model. Regional fluxes of dissolved Fe from deep to surface waters were compared to calculated Fe demands. Low in situ variable to maximum fluorescence (Fv/Fm; 0.24-0.37) and surface water dissolved Fe concentrations (~0.12-0.21 nM) were suggestive of widespread limitation, corroborated by the consistent responses (Fv/Fm, growth, and nutrient removal ratios) of incubation treatments to Fe addition. MCDW from the WF region had lower dissolved Fe concentrations than that measured in CDW (Circumpolar Deep Water), which suggests on-shelf modification with Fe deplete surface waters and is consistent with the lack of stimulation due to incubation amendments with filtered MCDW. Model results and empirical data suggest MCDW from the WF region is further modified and mixed en route to the CPB region, leading to both the erosion of the canonical MCDW signature and an elevated dissolved Fe inventory of CPB region deep water. This suggests the addition of Fe possibly via diagenesis, as suggested by Marsay et al. (2014). Calculated deep water supply rates to the surface waters of CPB were ~0.18-0.43 m d-1, while calculated rates at the WF or northern Pennell Bank (NPB) regions were negative. The CPB populations exhibited ~4.5-fold higher net production rates compared to those in the WF and NPB regions and required 520-3200 nmol Fe m-2 d-1. The modeled vertical

  13. Fluid flow during slab unbending and dehydration: Implications for intermediate-depth seismicity, slab weakening and deep water recycling

    NASA Astrophysics Data System (ADS)

    Faccenda, Manuele; Gerya, Taras V.; Mancktelow, Neil S.; Moresi, Louis

    2012-01-01

    Subducting oceanic plates carry a considerable amount of water from the surface down to mantle depths and contribute significantly to the global water cycle. A part of these volatiles stored in the slab is expelled at intermediate depths (70-300 km) where dehydration reactions occur. However, despite the fact that water considerably affects many physical properties of rocks, not much is known about the fluid flow path and the interaction with the rocks through which volatiles flow in the slab interior during its dehydration. We performed thermomechanical models (coupled with a petrological database and with incompressible aqueous fluid flow) of a dynamically subducting and dehydrating oceanic plate. Results show that, during slab dehydration, unbending stresses drive part of the released fluids into the cold core of the plate toward a level of strong tectonic under-pressure and neutral (slab-normal) pressure gradients. Fluids progressively accumulate and percolate updip along such a layer forming, together with the upper hydrated layer near the top of the slab, a Double Hydrated Zone (DHZ) where intermediate-depth seismicity could be triggered. The location and predicted mechanics of the DHZ would be consistent with seismological observations regarding Double Seismic Zones (DSZs) found in most subduction zones and suggests that hydrofracturing could be the trigger mechanism for observed intermediate-depth seismicity. In the light of our results, the lower plane of the DSZ is more likely to reflect a layer of upward percolating fluid than a level of mantle dehydration. In our models, a 20-30 km thick DSZ forms in relatively old oceanic plates without requiring an extremely deep slab hydration prior to subduction. The redistribution of fluids into the slab interior during slab unbending also has important implications for slab weakening and the deep water cycle. We estimate that, over the whole of Earth's history, a volume of water equivalent to around one to two

  14. Geomagnetic field intensity, North Atlantic Deep Water circulation and atmospheric Δ 14C during the last 50 kyr

    NASA Astrophysics Data System (ADS)

    Laj, Carlo; Kissel, Catherine; Mazaud, Alain; Michel, Elisabeth; Muscheler, Raimund; Beer, Juerg

    2002-06-01

    We present simulated records of past changes in the atmospheric Δ 14C for the last 50 kyr due to changes in geomagnetic field intensity and in the strength of the North Atlantic Deep Water (NADW). A new geomagnetic record was used, largely based on the NAPIS-75 record [Laj et al., Phil. Trans. R. Soc. London A 358 (2000) 1009-1025] which has been extended for the 0-20 kyr interval using archeomagnetic and volcanic data. Past changes of the NADW were derived from a mineral magnetic study of the cores used in the construction of NAPIS-75. Two box models of different complexity (4 and 17 boxes) were used to simulate the carbon cycle. Calculated records of Δ 14C are consistent with experimental determinations for the last 24 kyr. For older ages, the records calculated with variable oceanic circulation conditions reach values as high as 600‰ (with an average of 500‰) between 20 and 40 kyr with maxima around 21, 30 and 38 kyr (GISP2 age model), while low values are observed prior to 42 kyr. Although large inconsistencies in experimental data preclude precise comparison, the average record simulated with the 17-box model is overall consistent with the Icelandic Sea record [Voelker et al., Radiocarbon 40 (1998) 517-534; 42 (2000) 437-452], except for the extremely high peak observed in this record at 40.5 kyr. On the other hand, the results recently reported from a stalagmite recovered from a submerged cave in the Bahamas [Beck et al., Science 292 (2001) 2453-2458] are inconsistent with all our model simulations. In the 20-45 kyr interval, the improved geomagnetic record combined with the new NADW profile allows us to give a modeled evaluation of the relative contribution of these factors to changes in atmospheric Δ 14C. The average simulation provides a first order modeled correction for conventional radiocarbon ages older than 25 kyr for which no calibration curve is available as yet.

  15. Australia's deep-water octocoral fauna: historical account and checklist, distributions and regional affinities of recent collections.

    PubMed

    Alderslade, Philip; Althaus, Franziska; Mcennulty, Felicity; Gowlett-Holmes, Karen; Williams, Alan

    2014-05-20

    The number of deep-water (>80 m) octocoral species recorded from Australian waters has more than tripled from 135 to 457 following six surveys undertaken between 1997 and 2008 on the deep continental margin of south-eastern, western and north-western Australia and the Tasman Sea.  This rapid increase in knowledge follows a slow accumulation of records since the earliest collections were made by vessels such as the Géographe and the Naturaliste in the early years of the 19 century. Consistent identification and alpha-labelling of the octocoral fauna between surveys has permitted a multi-region description and comparison.  We detail the identities, distributions and regional affinities of 457 octocoral species in 131 genera and 28 families from the orders Alcyonacea and Pennatulacea, including 69 new species, 17 new genera and 43 first records for Australia. Five of the more common genera were widely distributed (present at 35 and 66 sampling stations spanning all of the 4 survey regions), but two were restricted to south-eastern Australia-Pleurogorgia Versluys, 1902 and Tokoprymno Bayer, 1996-and were only sampled from depths below 700 m.  The great majority of species (81%) and nearly half of all genera (47%) were only sampled once or twice.  The highest average number of species per sampling station (3.2) was reported from the outer shelf. The proportion of new species was highest (22%) on the upper and lower slope bathomes, intermediate (13-15%) on the mid-slope bathome and lowest (8%) on the outer shelf bathome.  Species overlap between bathomes was low, but all families were shared across bathomes. Most described species (55 of 69) have an Indo-West Pacific affinity, 20 have an Indian Ocean affinity, while three were previously recorded from the Atlantic Ocean only; 20 appear to be Australian endemics. Octocorals can now be added to an emerging set of taxon-specific data sets-including fishes, ophiuroids and galatheids-that permit regional-scale analysis

  16. Sustained observations in the Weddell Sea spanning more than 20 years show gradual increase of the deep water heat content

    NASA Astrophysics Data System (ADS)

    Strass, Volker; Rohardt, Gerd; Hoppema, Mario

    2014-05-01

    Beginning in 1989, Eberhard Fahrbach established and maintained until his premature death an observational programme in the Weddell Sea, which outstandingly contributed to alleviate the grave problem of undersampling of the Southern Ocean. Continuation of his legacy by the Alfred-Wegener-Institut has yielded a time series that now extends into 2013, hence covers almost 24 years. Here we analyse this data set for long-term changes of the heat content in the deep Weddell Sea. We exclusively evaluate the calibrated temperature records obtained with ship-lowered CTD (conductivity-temperature-depth sonde) casts at repeated hydrographic stations and along repeated sections. Using this approach we avoid introducing potential temperature offsets that can result from combination of different measurement technologies and potential biases resultant from differences in geographic positions. Our results show that the deep water masses below 700 m gradually warmed over the past two decades by 0.001 - 0.004 K a-1. Superimposed inter-annual to multi-annual variations appear as largely uncorrelated horizontally across the Weddell Gyre. The long-term (21 - 24 years) trends of increasing temperatures in different depth layers below 700 m at all stations and sections can be approximated by linear regression that explains between 27 and 91 % of the variance, where the coefficients of correlation tend to increase with depth. No significant trends are found in the top 700 m. The heating rate of the water masses below 700 m is estimated to 0.79 ± 0.14 W m-2, which is more than twice as high as determined for the global deep ocean in general. Our results hence corroborate the view that Southern Ocean processes make an above-average contribution to the deep ocean warming, and so add to bring global estimates of the deep ocean heating rate and of the net energy flux into the Earth's climate system at the top of the atmosphere of 0.5 - 1 W m-2 closer in line with each other. Thus they help

  17. Habitat characterization of deep-water coral reefs in La Gaviera Canyon (Avilés Canyon System, Cantabrian Sea)

    NASA Astrophysics Data System (ADS)

    Sánchez, Francisco; González-Pola, Cesar; Druet, María; García-Alegre, Ana; Acosta, Juan; Cristobo, Javier; Parra, Santiago; Ríos, Pilar; Altuna, Álvaro; Gómez-Ballesteros, María; Muñoz-Recio, Araceli; Rivera, Jesus; del Río, Guillermo Díaz

    2014-08-01

    Surveys conducted at the complex Avilés Canyon System (southern Bay of Biscay) in order to identify vulnerable habitats and biological communities revealed the presence of noteworthy deep-water coral reefs in one of the tributaries of the system (La Gaviera Canyon). The aim of the present study is to determine why this deep-sea canyon provides suitable environmental conditions for corals to grow. This hanging canyon is characterized by an irregular U-shaped floor with two narrow differentiated flanks. Sand ripples and rocky outcrops structured in diverse W-E directed steps are observed on the canyon floor, suggesting intense hydrodynamic activity. Accordingly, high-frequency near-bottom current and thermal structure profiles showed that there occur strong shifts in currents/hydrography behaving as front-like features at each tidal cycle. These involve the sudden increase of along-axis velocities to over 50 cm/s and vertical velocities of over 5 cm/s in each tidal cycle associated with the passage of sharp thermal fronts and thermal inversions suggesting overturning. A year-long near-bottom current record showed events with near-bottom velocities well over 1 m/s lasting for several days. Three cold-water coral settings were distinguished: a dense coral reef located on stepped rocky bottoms of the eastern and western flanks, carbonate mounds (20-30 m high) located on the canyon floor, and a cluster of shallower water dead coral framework at the head sector of the canyon. Video and still images from a towed sled and ROV verified the presence of dropstones and rippled sand sheets surrounding the mounds and revealed changes in the coral population (alive or dead; total or patchy coverage) in coral reef and carbonate mound areas. The dominant species of the reef are Lophelia pertusa and Madrepora oculata, which considerably increase the habitat‧s complexity and biodiversity in relation to other facies described in the canyon. The presence of living cold-water reefs is

  18. Effects of climate change on deep-water oxygen and winter mixing in a deep lake (Lake Geneva)

    NASA Astrophysics Data System (ADS)

    Schwefel, Robert; Alfred, Wüest; Damien, Bouffard

    2016-04-01

    Oxygen is the most important dissolved gas for lake ecosystems. Because low oxygen concentrations are an ongoing problem in many parts of the oceans and numerous lakes, oxygen depletion processes have been intensively studied over the last decades and were mainly attributed to high nutrient loads. Recently, climate-induced changes in stratification and mixing behavior were recognized as additional thread to hypolimnetic oxygen budgets in lakes and reservoirs [Matzinger et al., 2007; Zhang et al., 2015]. Observational data of Lake Geneva, a deep perialpine lake situated between France and Switzerland showed no decreasing trend in hypoxia over the last 43 years, despite an impressive reduction in nutrient input during this period. Instead, hypoxic conditions were predominantly controlled by deep mixing end of winter and in turn by winter temperatures. To test the sensitivity of Lake Geneva on future climate change and changes in water transparency, we simulated the hydrodynamics and temperature of Lake Geneva under varying conditions for atmospheric temperature and water clarity performed with the one-dimensional model SIMSTRAT [Goudsmit, 2002]. The results show, that the stratification in lakes is only weakly affected by changes in light absorption due to varying water quality. For conditions expected for the end of the century, a decrease in the annual mean deep convective mixing of up to 45 m is predicted. Also complete mixing events over the whole lake are less likely to occur. A change in the hypolimnetic oxygen concentration of up to 20% can thus be expected in the future. These results show, that changes in deep mixing have an equally strong impact as eutrophication on the deep-water oxygen development of oligomictic lakes and have to be considered in the prediction of the future development of lakes. References: Goudsmit, G. H., H. Burchard, F. Peeters, and A. Wüest (2002), Application of k-ɛ turbulence models to enclosed basins: The role of internal

  19. Along-dip variations of structural style in the Somali Basin deep-water fold and thrust belt (East Africa)

    NASA Astrophysics Data System (ADS)

    Cruciani, Francesco; Rinaldo Barchi, Massimiliano

    2014-05-01

    Continental passive margins are place of extended slope-failure phenomena, which can lead to the formation of gravity-driven deep-water fold and thrust belts (DW-FTBs), in regions where no far-field compressional stress is active. These giant geological features, which are confined to the sedimentary section, consist of extensional-compressional linked systems detached over a common décollement, generally salt or shales. The continental passive margin of northern Kenya and southern Somalia is an excellent and relatively unexplored site for recognizing and understanding the DW-FTBs originated over a regional shale décollement. In this study we have interpreted a 2D seismic data-set of the 1980s, hosted by Marine Geoscience Data System at Lamont-Doherty Earth Observatory of Columbia University (http://www.marine-geo.org), and recently reprocessed by ENI, in order to investigate the structural style of a DW-FTB developed offshore of northern Kenya and southern Somalia (Somali Basin). This region records the oldest sedimentary section of the Indian Ocean since the breakup of Gondwana began in the Middle-Lower Jurassic separating Madagascar from Africa. From the Upper Cretaceous to at least the Lower Miocene, the margin has been characterized by gravitational collapse leading to the formation of a DW-FTB extending more than 400 km along-strike. The northern portion of the DW-FTB is about 150 km wide, whilst in the southern portion is few tens of km wide. We analysed the northern portion along a regional seismic section. Our study represents the first detailed structural interpretation of this DW-FTB since its discovery in the 1980s. The good quality of the available reprocessed seismic data has allowed us to identify remarkable along-dip variations in the structural style. The basal detachment constantly deepens landward, in agreement with a prevailing gravity-spreading deformation process (as in the case of the Niger Delta). On the seismic data are not visible, as

  20. A comparison of the physiological exercise intensity differences between shod and barefoot submaximal deep-water running at the same cadence.

    PubMed

    Killgore, Garry L; Coste, Sarah C; O' Meara, Susan E; Konnecke, Cristina J

    2010-12-01

    The purpose of this investigation was to identify whether physiological exercise intensity differed with the use of aquatic training shoes (ATS) during deep-water running (DWR) compared to using a barefoot condition. Eight male intercollegiate (National Collegiate Athletic Association Division III [NCAA III]) varsity distance runners were videotaped from the right sagittal view while running on a treadmill (TR) and while barefoot in deep water at 60-70% of their TR VO2max for 30 minutes. Based on the stride rate of the barefoot DWR trial, a subsequent 30-minute session was completed while wearing ATS. Variables of interest were energy expenditure, oxygen consumption (VO2), heart rate, respiratory exchange ratio (RER), and rating of perceived exertion (RPE). Multivariate omnibus tests revealed statistically significant differences for energy expenditure (p < 0.011), VO2 (p < 0.001), RPE (p < 0.001), and RER (p < 0.002). The post hoc pairwise comparisons revealed significant differences between barefoot and shod DWR conditions for energy expenditure (p < 0.005) and VO2 (p < 0.002), representing a 9 and 7.6% increase in exercise intensity demand while running shod vs. barefoot. These comparisons also revealed significantly higher RPE and RER values while DWR than those found in TR. Wearing the ATS may be recommended as a method of statistically significantly increasing the exercise intensity while running in deep water as compared to not wearing a shoe. Shod compared to TR yields very small differences, which indicates that the shoes may help better match land-based running exercise intensities.

  1. Reconstruction of east-west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years

    NASA Astrophysics Data System (ADS)

    Howe, Jacob N. W.; Piotrowski, Alexander M.; Hu, Rong; Bory, Aloys

    2017-01-01

    Radiogenic neodymium isotopes have been used as a water mass mixing proxy to investigate past changes in ocean circulation. Here we present a new depth transect of deglacial neodymium isotope records measured on uncleaned planktic foraminifera from five cores spanning from 3300 to 4900 m on the Mauritanian margin, in the tropical eastern Atlantic as well as an additional record from 4000 m on the Ceara Rise in the equatorial western Atlantic. Despite being located under the Saharan dust plume, the eastern Atlantic records differ from the composition of detrital inputs through time and exhibit similar values to the western Atlantic foraminiferal Nd across the deglaciation. Therefore we interpret the foraminiferal values as recording deep water Nd isotope changes. All six cores shift to less radiogenic values across the deglaciation, indicating that they were bathed by a lower proportion of North Atlantic Deep Water during the Last Glacial Maximum (LGM) relative to the Holocene. The eastern Atlantic records also show that a neodymium isotope gradient was present during the LGM and during the deglaciation, with more radiogenic values observed at the deepest sites. A homogeneous water mass observed below 3750 m in the deepest eastern Atlantic during the LGM is attributed to the mixing of deep water by rough topography as it passes from the western Atlantic through the fracture zones in the Mid-Atlantic Ridge. This implies that during the LGM the low latitude deep eastern Atlantic was ventilated from the western Atlantic via advection through fracture zones in the same manner as occurs in the modern ocean. Comparison with carbon isotopes indicates there was more respired carbon in the deep eastern than deep western Atlantic during the LGM, as is also seen in the modern Atlantic Ocean.

  2. Late quaternary depositional systems and sea level change-Santa Monica and San Pedro Basins, California continental borderland

    SciTech Connect

    Nardin, T.R.

    1983-07-01

    A suite of seismic reflection data that provides different degrees of resolution and penetration was used to map the depositional systems that have developed in Santa Monica and San Pedro basins during the late Quaternary. Submarine fan growth, particularly at the mouths of Hueneme and Redondo Canyons, has been the dominant mode of basin filling. Mass movement processes, ranging from creep to large-scale catastrophic slumping, have been important locally. In general, large-scale fan growth fits Normark's model in which the suprafan is the primary locus of coarse sediment deposition. Smaller scale morphologic and depositional patterns on the Hueneme and Redondo fans (e.g., distributary channels and coarse sediment concentrations basinward of the inner suprafan) suggest that a significant amount of coarse sediment presently bypasses the suprafans, however. Long-distance coarse sediment transport was particularly pronounced during late Wisconsinan lowstand of sea level and resulted in progradation of lower mid-fan and lower fan deposits.

  3. Lung anatomy and histology of the extant coelacanth shed light on the loss of air-breathing during deep-water adaptation in actinistians

    PubMed Central

    Meunier, François J.; Herbin, Marc; Clément, Gaël; Brito, Paulo M.

    2017-01-01

    Lungs are specialized organs originated from the posterior pharyngeal cavity and considered as plesiomorphic for osteichthyans, as they are found in extant basal actinopterygians (i.e. Polypterus) and in all major groups of extant sarcopterygians. The presence of a vestigial lung in adult stages of the extant coelacanth Latimeria chalumnae is the result of allometric growth during ontogeny, in relation with long-time adaptation to deep water. Here, we present the first detailed histological and anatomical description of the lung of Latimeria chalumnae, providing new insights into its arrested differentiation in an air-breathing complex, mainly represented by the absence of pneumocytes and of compartmentalization in the latest ontogenetic stages.

  4. Lung anatomy and histology of the extant coelacanth shed light on the loss of air-breathing during deep-water adaptation in actinistians.

    PubMed

    Cupello, Camila; Meunier, François J; Herbin, Marc; Clément, Gaël; Brito, Paulo M

    2017-03-01

    Lungs are specialized organs originated from the posterior pharyngeal cavity and considered as plesiomorphic for osteichthyans, as they are found in extant basal actinopterygians (i.e. Polypterus) and in all major groups of extant sarcopterygians. The presence of a vestigial lung in adult stages of the extant coelacanth Latimeria chalumnae is the result of allometric growth during ontogeny, in relation with long-time adaptation to deep water. Here, we present the first detailed histological and anatomical description of the lung of Latimeria chalumnae, providing new insights into its arrested differentiation in an air-breathing complex, mainly represented by the absence of pneumocytes and of compartmentalization in the latest ontogenetic stages.

  5. Up-Scaling Field Observations to Ground Truth Seismic Interpretations and Test Dynamic Models of Deep Water Rifted Margins: What are the Challenges?

    NASA Astrophysics Data System (ADS)

    Manatschal, G.; Nirrengarten, M.; Epin, M. E.

    2015-12-01

    Recent advances on the study of rifted margins resulted from the development of new, high-resolution seismic imaging methods and dynamic modelling that enable to image the crustal scale structure of rifted margins and experiment under what conditions they formed. However, both the used parameter space as well as the seismic interpretations and model results need to be ground truth by direct observations and data. In the case of deep-water rifted margins, the problem is that drill hole data is expensive, rare and only available from a handful of examples worldwide. In contrast, remnants preserving kilometre-scale outcrops of former deep-water rifted margins have been described from the Alps and the Pyrenees in Western Europe. These large-scale outcrops provide a direct access to mantle and crustal rocks and the associated sedimentary sequences and magmatic additions. The combination of world-class outcrops, classical, field-based mapping and analytical methods can provide the missing data that is necessary to calibrate and test dynamic models as well as to ground truth seismic interpretations. In my presentation I will use observations and data from key outcrops from the most distal fossil Alpine Tethys margins exposed in SE Switzerland with the aim to describe the deformation processes and conditions during final rifting and to test rift modes (semi-ductile flow vs. brittle poly-phase faulting). I will in particular focus on the way strain is distributed and the bulk rheology evolves during hyper-extension and mantle exhumation and compare the observations with model results and seismic interpretations. Up-and down scaling observations/data and bridging multiple spatial and temporal scales is a key to understand the large-scale extensional processes that are at the origin of the formation of hyper-extend and exhumed mantle domains. The major challenge is to understand how the learnings obtained from the well-documented examples in the Alps and Pyrenees can be used

  6. Influence of the Amazon River on the Nd isotope composition of deep water in the western equatorial Atlantic during the Oligocene-Miocene transition

    NASA Astrophysics Data System (ADS)

    Stewart, Joseph A.; Gutjahr, Marcus; James, Rachael H.; Anand, Pallavi; Wilson, Paul A.

    2016-11-01

    Dissolved and particulate neodymium (Nd) are mainly supplied to the oceans via rivers, dust, and release from marine sediments along continental margins. This process, together with the short oceanic residence time of Nd, gives rise to pronounced spatial gradients in oceanic 143Nd/144Nd ratios (εNd). However, we do not yet have a good understanding of the extent to which the influence of riverine point-source Nd supply can be distinguished from changes in mixing between different water masses in the marine geological record. This gap in knowledge is important to fill because there is growing awareness that major global climate transitions may be associated not only with changes in large-scale ocean water mass mixing, but also with important changes in continental hydroclimate and weathering. Here we present εNd data for fossilised fish teeth, planktonic foraminifera, and the Fe-Mn oxyhydroxide and detrital fractions of sediments recovered from Ocean Drilling Project (ODP) Site 926 on Ceara Rise, situated approximately 800 km from the mouth of the River Amazon. Our records span the Mi-1 glaciation event during the Oligocene-Miocene transition (OMT; ∼23 Ma). We compare our εNd records with data for ambient deep Atlantic northern and southern component waters to assess the influence of particulate input from the Amazon River on Nd in ancient deep waters at this site. εNd values for all of our fish teeth, foraminifera, and Fe-Mn oxyhydroxide samples are extremely unradiogenic (εNd ≈ - 15); much lower than the εNd for deep waters of modern or Oligocene-Miocene age from the North Atlantic (εNd ≈ - 10) and South Atlantic (εNd ≈ - 8). This finding suggests that partial dissolution of detrital particulate material from the Amazon (εNd ≈ - 18) strongly influences the εNd values of deep waters at Ceara Rise across the OMT. We conclude that terrestrially derived inputs of Nd can affect εNd values of deep water many hundreds of kilometres from source. Our

  7. Plastic responses to different types of cue: predator-induced and deep-water-induced polyphenisms in a salamander Hynobius retardatus.

    PubMed

    Hangui, Jun-Ichi; Wakahara, Masami; Michimae, Hirofumi

    2009-02-01

    Certain plastic morphological responses of animals induced across a range of environmental conditions may be adapted for effective locomotor performance. Larvae of the salamander, Hynobius retardatus, occasionally swim upward to the surface to breathe air because aquatic respiration alone is insufficient to meet their increasing respiratory requirements for growth. We hypothesized that H. retardatus larvae living in deep water would show an induced plastic response affecting locomotor structures, namely, a deeper tail, similar to that induced by predatory dragonfly larvae (Aeschna juncea), to improve their swimming performance. In this study, larval salamanders responded similarly to different cues (waterborne chemicals in a predatory environment and distance to the water's surface) by developing deeper tails. The similar modifications in tail shape presumably increase a larva's swimming performance, thereby improving its ability both to escape an attacking predator and to swim to the surface for air. The response in tail shape induced by the predatory environment was rapid, but was more gradual in larvae raised in deep water, suggesting that animals may quickly assess a dangerous environment and immediately respond, whereas assessment of an environment not requiring an immediate response for survival may be slower, accounting for the delayed response.

  8. Parallelism of amino acid changes at the RH1 affecting spectral sensitivity among deep-water cichlids from Lakes Tanganyika and Malawi.

    PubMed

    Sugawara, Tohru; Terai, Yohey; Imai, Hiroo; Turner, George F; Koblmüller, Stephan; Sturmbauer, Christian; Shichida, Yoshinori; Okada, Norihiro

    2005-04-12

    Many examples of the appearance of similar traits in different lineages are known during the evolution of organisms. However, the underlying genetic mechanisms have been elucidated in very few cases. Here, we provide a clear example of evolutionary parallelism, involving changes in the same genetic pathway, providing functional adaptation of RH1 pigments to deep-water habitats during the adaptive radiation of East African cichlid fishes. We determined the RH1 sequences from 233 individual cichlids. The reconstruction of cichlid RH1 pigments with 11-cis-retinal from 28 sequences showed that the absorption spectra of the pigments of nine species were shifted toward blue, tuned by two particular amino acid replacements. These blue-shifted RH1 pigments might have evolved as adaptations to the deep-water photic environment. Phylogenetic evidence indicates that one of the replacements, A292S, has evolved several times independently, inducing similar functional change. The parallel evolution of the same mutation at the same amino acid position suggests that the number of genetic changes underlying the appearance of similar traits in cichlid diversification may be fewer than previously expected.

  9. Wave breaking in the surf zone and deep-water in a non-hydrostatic RANS model. Part 2: Turbulence and mean circulation

    NASA Astrophysics Data System (ADS)

    Derakhti, Morteza; Kirby, James T.; Shi, Fengyan; Ma, Gangfeng

    2016-11-01

    Field-scale modeling of wave-breaking-induced turbulence and mean circulation is still challenging. Although Boussinesq-type models have been successfully used to study field-scale wave transformation and wave-breaking-driven circulation, they cannot provide turbulence or the vertical structure of the velocity field. In addition, the applicability of such models is limited to shallow water. In Part 1 (Derakhti et al., 2016b) of this study, we showed that the non-hydrostatic σ-coordinate RANS model NHWAVE, as described by Derakhti et al. (2016a), accurately predicts organized wave motions and total wave-breaking-induced energy dissipation from deep-water up to the swash zone using a few vertical σ-layers. In this paper, our goal is to examine what level of detail of wave-breaking-induced turbulence and mean circulation, both in depth- and steepness-limited breaking waves, can be reproduced by NHWAVE. Further, effects of modeled turbulent eddy viscosity on the predicted time-averaged velocity distribution is discussed. We establish that NHWAVE is capable of predicting the structure of the mean velocity and vorticity fields including large-scale breaking-induced coherent vortices in deep-water breaking events; where the absence of turbulence-induced eddy viscosity results in the overprediction of the velocity and vorticity field in the breaking region. We show that NHWAVE reduces the required CPU time up to two orders of magnitude in comparison with a comparable VOF-based simulation.

  10. Observations of open-ocean deep convection in the northwestern Mediterranean Sea: Seasonal and interannual variability of mixing and deep water masses for the 2007-2013 Period

    NASA Astrophysics Data System (ADS)

    Houpert, L.; Durrieu de Madron, X.; Testor, P.; Bosse, A.; D'Ortenzio, F.; Bouin, M. N.; Dausse, D.; Le Goff, H.; Kunesch, S.; Labaste, M.; Coppola, L.; Mortier, L.; Raimbault, P.

    2016-11-01

    We present here a unique oceanographic and meteorological data set focus on the deep convection processes. Our results are essentially based on in situ data (mooring, research vessel, glider, and profiling float) collected from a multiplatform and integrated monitoring system (MOOSE: Mediterranean Ocean Observing System on Environment), which monitored continuously the northwestern Mediterranean Sea since 2007, and in particular high-frequency potential temperature, salinity, and current measurements from the mooring LION located within the convection region. From 2009 to 2013, the mixed layer depth reaches the seabed, at a depth of 2330m, in February. Then, the violent vertical mixing of the whole water column lasts between 9 and 12 days setting up the characteristics of the newly formed deep water. Each deep convection winter formed a new warmer and saltier "vintage" of deep water. These sudden inputs of salt and heat in the deep ocean are responsible for trends in salinity (3.3 ± 0.2 × 10-3/yr) and potential temperature (3.2 ± 0.5 × 10-3 C/yr) observed from 2009 to 2013 for the 600-2300 m layer. For the first time, the overlapping of the three "phases" of deep convection can be observed, with secondary vertical mixing events (2-4 days) after the beginning of the restratification phase, and the restratification/spreading phase still active at the beginning of the following deep convection event.

  11. North Atlantic Deep Water export to the Southern Ocean over the past 14 Myr: Evidence from Nd and Pb isotopes in ferromanganese crusts

    USGS Publications Warehouse

    Frank, M.; Whiteley, N.; Kasten, S.; Hein, J.R.; O'Nions, K.

    2002-01-01

    The intensity of North Atlantic Deep Water (NADW) production has been one of the most important parameters controlling the global thermohaline ocean circulation system and climate. Here we present a new approach to reconstruct the overall strength of NADW export from the North Atlantic to the Southern Ocean over the past 14 Myr applying the deep water Nd and Pb isotope composition as recorded by ferromanganese crusts and nodules. We present the first long-term Nd and Pb isotope time series for deep Southern Ocean water masses, which are compared with previously published time series for NADW from the NW Atlantic Ocean. These data suggest a continuous and strong export of NADW, or a precursor of it, into the Southern Ocean between 14 and 3 Ma. An increasing difference in Nd and Pb isotope compositions between the NW Atlantic and the Southern Ocean over the past 3 Myr gives evidence for a progressive overall reduction of NADW export since the onset of Northern Hemisphere glaciation (NHG). The Nd isotope data allow us to assess at least semiquantitatively that the amount of this reduction has been in the range between 14 and 37% depending on location.

  12. Influence of runoff, high frequency atmospheric forcing and model resolution on deep water mass formation regions and Atlantic Meridional Overturning Circulation, from a numerical model.

    NASA Astrophysics Data System (ADS)

    Garcia Quintana, Yarisbel; Courtois, Peggy; Hu, Xianmin; Pennelly, Clark; Myers, Paul G.

    2016-04-01

    Water mass formation regions act as windows to the deep ocean where surface waters are transformed to intermediate and deep waters. Within the North Atlantic, Labrador Sea Water (LSW) is convectively produced in the Labrador Sea while in the Nordic Seas the source waters for Denmark Strait Overflow Water (DSOW) and Iceland-Scotland Overflow Water (NEADW) are formed. They are the main components of the North Atlantic Deep Water (NADW) which forms the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). We explore the changes of the LSW formation rates and in AMOC strength as consequence of runoff glacial melt, high frequency atmospheric forcing influence and variations in model's resolution. We use 1/4° resolution Arctic and Northern Hemisphere Atlantic (ANHA4) configuration from the Nucleus for European Modelling of the Ocean (NEMO) model. A nest using ANHA4 and the Adaptive Grid Refinement in FORTRAN (AGRIF) package was used to increase the resolution to 1/12° in the sub-polar gyre. The formation rate is calculated based upon a kinematic subduction approach where the exchange through the dynamic mixed layer base is calculated based on shallowing and deepening in the mixed layer, and convergence of horizontal transport into or out of the mixed layer. Lastly we use a Lagrangian tool (Ariane) to track the path of the DSOW and the NEADW from their formation source.

  13. Effects of Deep Water Source-Sink Terms in 3rd generation Wave Model SWAN using different wind data in Black Sea

    NASA Astrophysics Data System (ADS)

    Kirezci, Cagil; Ozyurt Tarakcioglu, Gulizar

    2016-04-01

    Coastal development in Black Sea has increased in recent years. Therefore, careful monitoring of the storms and verification of numerical tools with reliable data has become important. Previous studies by Kirezci and Ozyurt (2015) investigated extreme events in Black Sea using different wind datasets (NCEP's CFSR and ECMWF's operational datasets) and different numerical tools (SWAN and Wavewatch III). These studies showed that significant effect to results is caused by the deep water source-sink terms (wave growth by wind, deep water dissipation of wave energy (whitecapping) and deep water non-linear wave-wave interactions). According to Timmermans(2015), uncertainty about wind forcing and the process of nonlinear wave-wave interactions are found to be dominant in numerical wave modelling. Therefore, in this study deep water source and sink term solution approaches of 3rd generation numerical tool (SWAN model) are tested, validated and compared using the selected extreme storms in Black Sea. 45 different storms and storm like events observed in Black Sea between years 1994-1999 are selected to use in the models. The storm selection depends on the instrumental wave data (significant wave heights, mean wave period and mean wave direction) obtained in NATO-TU Waves project by the deep water buoy measurements at Hopa, Sinop, Gelendzhik, and wind data (mean and peak wind speeds, storm durations) of the regarding events. 2 different wave growth by wind with the corresponding deep water dissipation terms and 3 different wave -wave interaction terms of SWAN model are used in this study. Wave growth by wind consist of two parts, linear growth which is explained by Cavaleri and Malanotte-Rizzoli(1981),and dominant exponential growth. There are two methods in SWAN model for exponential growth of wave, first one by Snyder et al. (1981), rescaled in terms of friction velocity by Komen et. al (1984) which is derived using driving wind speed at 10m elevation with related drag

  14. Tektite-bearing, deep-water clastic unit at the Cretaceous-Tertiary boundary in northeastern Mexico

    NASA Technical Reports Server (NTRS)

    Smit, J.; Montanari, A.; Swinburne, N. H.; Alvarez, W.; Hildebrand, A. R.; Margolis, S. V.; Claeys, P.; Lowrie, W.; Asaro, F.

    1992-01-01

    The hypothesis of Cretaceous-Tertiary (K-T) boundary impact on Yucatan, Mexico, predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves. An outcrop along the Arroyo el Mimbral in northeastern Mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic-marl sequence deposited at more than 400 m water depth. The marls were found to be unsuitable for determining magnetostratigraphy, but foraminiferal biostratigraphy places the clastic unit precisely at the K-T boundary. We interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact. The clastic unit comprises three main subunits. (1) The basal "spherule bed" contains glass in the form of tektites and microtektites, glass spherules replaced by chlorite-smectite and calcite, and quartz grains showing probable shock features. This bed is interpreted as a channelized deposit of proximal ejecta. (2) A set of lenticular, massive, graded "laminated beds" contains intraclasts and abundant plant debris, and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water. (3) At the top, several thin "ripple beds" composed of fine sand are separated by clay drapes; they are interpreted as deposits of oscillating currents, perhaps a seiche. An iridium anomaly (921 +/- 23 pg/g) is observed at the top of the ripple beds. Our observations at the Mimbral locality support the hypothesis of a K-T impact on nearby Yucatan.

  15. Tektite-bearing, deep-water clastic unit at the Cretaceous-Tertiary boundary in northeastern Mexico.

    PubMed

    Smit, J; Montanari, A; Swinburne, N H; Alvarez, W; Hildebrand, A R; Margolis, S V; Claeys, P; Lowrie, W; Asaro, F

    1992-02-01

    The hypothesis of Cretaceous-Tertiary (K-T) boundary impact on Yucatán, Mexico, predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves. An outcrop along the Arroyo el Mimbral in northeastern Mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic-marl sequence deposited at more than 400 m water depth. The marls were found to be unsuitable for determining magnetostratigraphy, but foraminiferal biostratigraphy places the clastic unit precisely at the K-T boundary. We interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact. The clastic unit comprises three main subunits. (1) The basal "spherule bed" contains glass in the form of tektites and microtektites, glass spherules replaced by chlorite-smectite and calcite, and quartz grains showing probable shock features. This bed is interpreted as a channelized deposit of proximal ejecta. (2) A set of lenticular, massive, graded "laminated beds" contains intraclasts and abundant plant debris, and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water. (3) At the top, several thin "ripple beds" composed of fine sand are separated by clay drapes; they are interpreted as deposits of oscillating currents, perhaps a seiche. An iridium anomaly (921 +/- 23 pg/g) is observed at the top of the ripple beds. Our observations at the Mimbral locality support the hypothesis of a K-T impact on nearby Yucatán.

  16. Sedimentology of rift climax deep water systems; Lower Rudeis Formation, Hammam Faraun Fault Block, Suez Rift, Egypt

    NASA Astrophysics Data System (ADS)

    Leppard, Christopher W.; Gawthorpe, Rob L.

    2006-09-01

    In most marine rift basins, subsidence outpaces sedimentation during rift climax times. Typically this results in sediment-starved hangingwall depocentres dominated by deep-marine mudstones, with subordinate local development of coarser clastics in the immediate hangingwall derived from restricted catchments on the immediate footwall scarp. To highlight the spatial variability of rift climax facies and the controls upon them, we have investigated the detailed three-dimensional geometry and facies relationships of the extremely well exposed Miocene, rift climax Lower Rudeis Formation in the immediate hangingwall to the Thal Fault Zone, Suez Rift, Egypt. Detailed sedimentological analyses allows the Lower Rudeis Formation to be divided into two contemporaneous depositional systems, (1) a laterally continuous slope system comprising, hangingwall restricted (< 250 m wide) slope apron, slope slumps, fault scarp degradation complex and laterally extensive lower slope-to-basinal siltstones, and (2) a localized submarine fan complex up to 1 km wide and extending at least 2 km basinward of the fault zone. Interpretation of individual facies, facies relationships and their spatial variability indicate that deposition in the immediate hangingwall to the Thal Fault occurred via a range of submarine concentrated density flows, surge-like turbidity flows, mass wasting and hemipelagic processes. Major controls on the spatial variability and stratigraphic architecture of the depositional systems identified reflect the influence of the steep footwall physiography, accommodation and drainage evolution associated with the growth of the Thal Fault. The under-filled nature of the hangingwall depocentre combined with the steep footwall gradient result in a steep fault-controlled basin margin characterised by either slope bypass or erosion, with limited coastal plain or shelf area. Sediment supply to the slope apron deposits is controlled in part by the evolution and size of small

  17. Lagoonal deposits in the Upper Cretaceous Rock Springs Formation (Mesaverde Group), southwest Wyoming

    USGS Publications Warehouse

    Kirschbaum, M.A.

    1989-01-01

    Most paleogeographic reconstructions of the Rock Springs Formation show shorelines having lobate to arcuate deltas. These shorelines are oriented NE-SW, with the sea to the southeast. Brackish-water bodies are usually shown in interdistributary areas or associated with abandoned delta lobes, and are open to the sea. In this study, a sedimentary sequence 30-50 m thick is interpreted as interdeltaic deposits. Brackish-water deposits within the sequence are interpreted as interdeltaic lagoons rather than interdistributary bays. Three facies associations (units) are recognized in nine measured sections of the study interval. Unit A consists of interbedded sandstone, mudrock and coal which occur in both fining- and coarsening-upward sequences less than 10 m thick. Fining-upward sequences decrease in thickness and frequency upwards in unit A and are interpreted as distributary channels. Coarsening-upward sequences associated with the channels are interpreted as crevasse splays that filled lakes or interdistributary bays. In the upper part of the unit where only minor channels are present, the coarsening-upward sequences are interpreted as bay deltas. Unit B consists of fossiliferous silty shale and bioturbated sandy siltstone. A low-diversity fauna of bivalves, gastropods, ostracods and foraminifers indicates that brackish-water conditions existed. Unit B intertongues with unit A to the northwest and with unit C to the southeast, and is interpreted as lagoonal deposits. Unit C consists of crossbedded and burrowed sandstone in beds 0.5-9 m thick. Sandstones are laterally continuous in the southeast but become tabular bodies enclosed within unit B to the northwest. Laterally continuous sandstones are interpreted as shoreface deposits on the basis of multidirectional crossbeds, marine trace fossils and continuity. Tabular sandstones are interpreted as flood-tidal deltas on the basis of NW-oriented crossbeds, pinchouts to the northwest and enclosure within unit B. Scoured

  18. Recent bright gully deposits on Mars: Wet or dry flow?

    USGS Publications Warehouse

    Pelletier, J.D.; Kolb, K.J.; McEwen, A.S.; Kirk, R.L.

    2008-01-01

    Bright gully sediments attributed to liquid water flow have been deposited on Mars within the past several years. To test the liquid water flow hypothesis, we constructed a high-resolution (1 m/pixel) photogrammetric digital elevation model of a crater in the Centauri Montes region, where a bright gully deposit formed between 2001 and 2005. We conducted one-dimensional (1-D) and 2-D numerical flow modeling to test whether the deposit morphology is most consistent with liquid water or dry granular How. Liquid water flow models that incorporate freezing can match the runout distance of the flow for certain freezing rates but fail to reconstruct the distributary lobe morphology of the distal end of the deposit. Dry granular flow models can match both the observed runout distance and the distal morphology. Wet debris flows with high sediment concentrations are also consistent with the observed morphology because their rheologies are often similar to that of dry granular flows. As such, the presence of liquid water in this flow event cannot be ruled out, but the available evidence is consistent with dry landsliding. ?? 2008 The Geological Society of America.

  19. Sand remobilization enhanced complexity to mounded geometry, Early Tertiary deep water sand reservoirs, Balder Oil Field North Sea

    SciTech Connect

    Bergslien, D.; Rye-Larsen, M.; Jenssen, A.I.

    1996-12-31

    Sand remobilization played a major role in generating the high relief mounded geometries that trap oil in the early Tertiary reservoirs at Balder Field in Norwegian North Sea blocks 25/10 and 25/11. The thick massive submarine-fan sandstones were shed from the East Shetland Platform and deposited from high density turbidity currents. These thick massive sandstones lie in the distal portions of the fan system on the northwestern margin of the Utsira High. An intricate interaction between deposition and soft sediment deformation processes generated the complex cluster of thick mounded sand geometries comprising the Balder oil field. Slumping, sliding and sand remobilization with associated sand injections into overlying shales were the dominant deformation processes that mainly occurred during the early Eocene. The field is comprised of three reservoirs, the Paleocene Heimdal and Hermod Formations and the Early Eocene Balder Formation. The sandstones, which have excellent reservoir properties, share a common pressure system and oil-water contact. This is probably related to the soft-sediment deformation and associated sand injections establishing cross-stratal communication.

  20. Sand remobilization enhanced complexity to mounded geometry, Early Tertiary deep water sand reservoirs, Balder Oil Field North Sea

    SciTech Connect

    Bergslien, D.; Rye-Larsen, M.; Jenssen, A.I. )

    1996-01-01

    Sand remobilization played a major role in generating the high relief mounded geometries that trap oil in the early Tertiary reservoirs at Balder Field in Norwegian North Sea blocks 25/10 and 25/11. The thick massive submarine-fan sandstones were shed from the East Shetland Platform and deposited from high density turbidity currents. These thick massive sandstones lie in the distal portions of the fan system on the northwestern margin of the Utsira High. An intricate interaction between deposition and soft sediment deformation processes generated the complex cluster of thick mounded sand geometries comprising the Balder oil field. Slumping, sliding and sand remobilization with associated sand injections into overlying shales were the dominant deformation processes that mainly occurred during the early Eocene. The field is comprised of three reservoirs, the Paleocene Heimdal and Hermod Formations and the Early Eocene Balder Formation. The sandstones, which have excellent reservoir properties, share a common pressure system and oil-water contact. This is probably related to the soft-sediment deformation and associated sand injections establishing cross-stratal communication.

  1. Spatial and vertical gradients in the stable carbon isotope composition of Lower Circumpolar Deep Water over the last 900 thousand years

    NASA Astrophysics Data System (ADS)

    Williams, T.; Hillenbrand, C. D.; Piotrowski, A. M.; Smith, J.; Hodell, D. A.; Frederichs, T.; Allen, C. S.

    2014-12-01

    Changes in stable carbon isotopes (δ13C) recorded in benthic foraminiferal calcite reflect that of the dissolved inorganic carbon (DIC) of ambient seawater, and thus are used to reconstruct past changes in water mass mixing. Records of benthic foraminiferal δ13C from the Atlantic Ocean have revealed the development of a sharp vertical δ13C gradient between 2300-2500m water depth during successive glacial periods throughout the Late Quaternary, with extremely negative δ13C values recorded below this depth. It had been hypothesised that this gradient resulted from an increased stratification of water masses within the glacial Atlantic Ocean, and that these extreme δ13C values originated in the Southern Ocean. However the mechanisms behind the formation of this gradient and extreme δ13C depletion have remained unclear. This is in part due to the poor preservation of calcareous microfossils in the corrosive waters below 2500-3000m found in the Southern Ocean, which hampers our understanding of this key region. Here we present a unique new δ13C deep water record measured on benthic foraminifera (Cibicidoides spp.) from a sediment core recovered from 2100m water depth in the Amundsen Sea, south-eastern Pacific sector of the Southern Ocean. The site is bathed in Lower Circumpolar Deep Water (LCDW) today, and combined palaeomagnetic and oxygen isotope stratigraphy show that the sediments continuously span at least the last 890 ka. A comparison of this new δ13C data with other LCDW records from ODP Sites 1089/1090 in the South Atlantic and ODP Site 1123 in the Southwest Pacific demonstrate a clear spatial gradient in circum-Antarctic LCDW during glacial periods. The pool of extremely depleted glacial deep marine δ13C is restricted to the Atlantic Sector of the Southern Ocean, with increasingly positive δ13C values found in the Southwest Pacific and the south-eastern Pacific sector of the Southern Ocean. This implies that the δ13C depletion in the deep glacial

  2. Depositional model for carbonate-evaporite cyclicity: Middle Pennsylvanian of Paradox basin

    SciTech Connect

    Kendall, A.C.

    1987-05-01

    The Paradox basin is a classic area for the study of relations between carbonates and evaporites. Previous depositional models assume carbonates and evaporites are coeval, implying that the evaporites were deep water deposits. Stratigraphic relationships are, however, complicated by previously unrecognized salt dissolution. Restoration of the missing salts indicates that evaporites entirely postdate marine carbonates in each cycle. Anhydrites and silty dolomites that succeed halites are reinterpreted as shallow hypersaline to subaerial deposits. These playa-like sediments are abruptly overlain by organic-rich shales that represent anoxic and the deepest-water deposits in the sequence. Paradox basin salts and succeeding playa deposits formed in a deep but desiccated basin. Sea level rises drowned the formerly exposed basin rims, causing sudden complete floodings of the basin and the abrupt contacts between playa deposits and deep-water shales. The shale-carbonate-evaporite sequences that form lower parts of cycles resulted from sea level falls. These ultimately exposed basin rims, isolating the basin, and allowed evaporative draw down and the deposition of basin-central evaporites. In contrast, the halite-anhydrite-silty dolomite sequences of the upper parts of cycles arose when sediment aggradation caused expansion of the evaporite depositional area onto basin flanks. There brine reflux became more significant. This reduced residence times of brines in the basin so that, progressively, salinities decreased and only less-saline sediments were able to persist in the playa environment. Cycles end (or begin) when renewed sea level rises drowned the basin-central playas.

  3. Confined deep water system development on the accretionary wedge (Miocene, Kahramanmaraş Foreland Basin, S turkey)

    NASA Astrophysics Data System (ADS)

    Gül, Murat; Cronin, Bryan T.; Gürbüz, Kemal

    2012-09-01

    According to theoretical studies, the foreland basin consists of: accretionary wedge (including wedge top or piggyback basin), foredeep, forebulge and backbulge depozones. All of them are parallel to the orogenic belts of the overlying and underlying plates. The closure of the southern branch of the Neotethys during the Late Cretaceous led to an oblique collision of the Arabian Plate and the Anatolide-Taurides Platform, leading to the development of the Miocene Kahramanmaraş Foreland Basin (KFB). Thus, the promontory shape of the Arabian Plate prevented the development of an accretionary wedge parallel to the orogenic belt. The accretionary wedge of the KFB includes blocks of various sizes and age (mainly Mesozoic limestone) scattered within an Early Tertiary matrix (mass wasting deposits and shallow to deep marine sediments). At the beginning of the Miocene, transtensional tectonism led to the development of half-graben basins on top of the accretionary wedge. These basins (namely; the Tekir and Çukurhisar) also cut the foredeep of the KFB obliquely (in contrast with the theoretical study). This paper focuses on the evolution and fillings of those basins. Initially, claystone and basin margin reef deposits filled the half-graben basins as a consequence of the Lower Miocene sea invasion. Then, long and narrow conglomeratic channels starting from the northern edge of the basins (fan-delta) progressed southwards, passing into sandy lobes, then into claystones. An activation of the boundary faults of the wedge top basin stopped the progression of the Lower-Middle Miocene sediments and led to their deformation. Then, the sedimentation of the KFB shifted towards the basin centre during the Middle Miocene.

  4. Southern hemisphere deep-water stylasterid corals including a new species, Errinalabrosa sp. n. (Cnidaria, Hydrozoa, Stylasteridae), with notes on some symbiotic scalpellids (Cirripedia, Thoracica, Scalpellidae).

    PubMed

    Pica, Daniela; Cairns, Stephen D; Puce, Stefania; Newman, William A

    2015-01-01

    A number of stylasterid corals are known to act as host species and create refuges for a variety of mobile and sessile organisms, which enhances their habitat complexity. These include annelids, anthozoans, cirripeds, copepods, cyanobacteria, echinoderms, gastropods, hydroids and sponges. Here we report the first evidence of a diverse association between stylasterids and scalpellid pedunculate barnacles and describe a new stylasterid species, Errinalabrosa, from the Tristan da Cunha Archipelago. Overall, five stylasterid species are found to host eight scalpellid barnacles from several biogeographic regions in the southern hemisphere (Southern Ocean, temperate South America and the southern Indo-Pacific realms). There is an apparent lack of specificity in this kind of association and different grades of reaction to the symbiosis have been observed in the coral. These records suggest that the association between pedunculate barnacles and hard stylasterid corals has a wide distribution among different biogeographic realms and that it is relatively rare and confined largely to deep water.

  5. A new Glossocephalus (Crustacea: Amphipoda: Hyperiidea: Oxycephalidae) from deep-water in the Monterey Bay region, California, USA, with an overview of the genus.

    PubMed

    Zeidler, Wolfgang; Browne, William E

    2015-10-05

    A new species of Glossocephalus, G. rebecae sp. nov., is described from deep-water in the Monterey Bay region of California, Eastern Pacific Ocean. It seems to be associated exclusively with the mesopelagic ctenophore Bathocyroe fosteri. This association has been observed from 541-830 m depth. It is readily distinguished from G. milneedwardsi Bovallius, 1887 by the shape of the eye fields. The retina is organised into a crescent-shaped organ, occupying about one-quarter of the back half of the head, with the crystalline cones projecting both anteriorly and laterally. An updated review of the genus is provided, taking into account the new species, together with an overview of G. milneedwardsi, and three new records of associations with ctenophores for G. milneedwardsi. New observations on the interaction of G. milneedwardsi with one of its ctenophore hosts, Mnemiopsis sp., are also documented.

  6. Assessing the potential impact of water-based drill cuttings on deep-water calcareous red algae using species specific impact categories and measured oceanographic and discharge data.

    PubMed

    Nilssen, Ingunn; dos Santos, Francisco; Coutinho, Ricardo; Gomes, Natalia; Cabral, Marcelo Montenegro; Eide, Ingvar; Figueiredo, Marcia A O; Johnsen, Geir; Johnsen, Ståle

    2015-12-01

    The potential impact of drill cuttings on the two deep water calcareous red algae Mesophyllum engelhartii and Lithothamnion sp. from the Peregrino oil field was assessed. Dispersion modelling of drill cuttings was performed for a two year period using measured oceanographic and discharge data with 24 h resolution. The model was also used to assess the impact on the two algae species using four species specific impact categories: No, minor, medium and severe impact. The corresponding intervals for photosynthetic efficiency (ΦPSIImax) and sediment coverage were obtained from exposure-response relationship for photosynthetic efficiency as function of sediment coverage for the two algae species. The temporal resolution enabled more accurate model predictions as short-term changes in discharges and environmental conditions could be detected. The assessment shows that there is a patchy risk for severe impact on the calcareous algae stretching across the transitional zone and into the calcareous algae bed at Peregrino.

  7. A new deep-water species of Odontozona (Decapoda: Stenopodidea: Stenopodidae) from the East Pacific, and new record of O. foresti Hendrickx, 2002.

    PubMed

    Hendrickx, Michel E; Ayón-Parente, Manuel

    2014-07-11

    A new species of the stenopodid shrimp Odontozona is described from deep-water off the west coast of Mexico. It is distinguished from the three other species of the genus known in the area, from O. rubra Wicksten, 1982, and O. foresti Hendrickx, 2002, by the absence of a series of spines on the posterior half of the carapace, behind the post-cervical groove, and from O. spongicola (Alcock & Anderson, 1899) by the presence of spines on the ventral margin of somites 1-5 (smooth in O. spongicola) and by the much slender third pair of pereiopods in the new species. A new record is provided for O. foresti, and the first male specimen, the third specimen on record, is compared with the female holotype.

  8. Elements of a decision support system for real-time management ofdissolved oxygen in the San Joaquin River deep water ship channel

    SciTech Connect

    Quinn, N.W.T.; Jacobs, Karl; Chen, Carl W.; Stringfellow, WilliamT.

    2004-07-15

    A decision support system (DSS) has been designed and will be implemented over the next three years to assist in the control and management of episodes of low dissolved oxygen (DO) in a Deep Water Ship Channel (DWSC), located near Stockton, California. The DSS integrates three information technology functions. The first part is the collection and management of data on flow, pollution loads and water quality. The second part is the simulation model which can forecast the dissolved oxygen sag in the DWSC and determine management actions necessary to improve dissolved oxygen concentrations. The third part is the graphical user interface, which facilitates the computer simulations and posting of the forecasted dissolved oxygen and remedial measures to a stakeholder group for implementations.

  9. Disturbance of deep-water reef communities by exploratory oil and gas operations in the Santa Maria basin and Santa Barbara channel. Final report, September 1992-September 1995

    SciTech Connect

    Diener, D.; Benech, S.V.; Busnardo, M.; Davis, N.; Evans, J.

    1995-09-01

    A study was undertaken to investigate the impacts to deep-water, hard-bottom benthic communities associated with disturbances caused by oil and gas exploratory operations on the Outer Continental Shelf of California. A literature survey compiled a history of exploratory oil and gas development and located wellsites where disturbances due to anchoring or discharges probably impacted hard-bottom communities. A photographic survey of the selected sites collected data for subsequent analyses on the type, distribution, and longevity of anchoring disturbances. Analyses of the field data revealed that less than one percent of hard-bottom habitat within the area of the mooring system was disturbed. The results of the study indicated that hard-bottom epifaunal communities do recover from these disturbances; however, recovery is highly dependent on the type of disturbance.

  10. Effect of Capillarity on Fourth Order Nonlinear Evolution Equation for Two Stokes Wave Trains in Deep Water in the Presence of Air Flowing Over Water

    NASA Astrophysics Data System (ADS)

    Dhar, A. K.; Mondal, J.

    2015-05-01

    Fourth order nonlinear evolution equations, which are a good starting point for the study of nonlinear water waves, are derived for deep water surface capillary gravity waves in the presence of second waves in which air is blowing over water. Here it is assumed that the space variation of the amplitude takes place only in a direction along which the group velocity projection of the two waves overlap. A stability analysis is made for a uniform wave train in the presence of a second wave train. Graphs are plotted for the maximum growth rate of instability wave number at marginal stability and wave number separation of fastest growing sideband component against wave steepness. Significant improvements are noticed from the results obtained from the two coupled third order nonlinear Schrödinger equations.

  11. Southern hemisphere deep-water stylasterid corals including a new species, Errina labrosa sp. n. (Cnidaria, Hydrozoa, Stylasteridae), with notes on some symbiotic scalpellids (Cirripedia, Thoracica, Scalpellidae)

    PubMed Central

    Pica, Daniela; Cairns, Stephen D.; Puce, Stefania; Newman, William A.

    2015-01-01

    Abstract A number of stylasterid corals are known to act as host species and create refuges for a variety of mobile and sessile organisms, which enhances their habitat complexity. These include annelids, anthozoans, cirripeds, copepods, cyanobacteria, echinoderms, gastropods, hydroids and sponges. Here we report the first evidence of a diverse association between stylasterids and scalpellid pedunculate barnacles and describe a new stylasterid species, Errina labrosa, from the Tristan da Cunha Archipelago. Overall, five stylasterid species are found to host eight scalpellid barnacles from several biogeographic regions in the southern hemisphere (Southern Ocean, temperate South America and the southern Indo-Pacific realms). There is an apparent lack of specificity in this kind of association and different grades of reaction to the symbiosis have been observed in the coral. These records suggest that the association between pedunculate barnacles and hard stylasterid corals has a wide distribution among different biogeographic realms and that it is relatively rare and confined largely to deep water. PMID:25632246

  12. A Multi-Band Analytical Algorithm for Deriving Absorption and Backscattering Coefficients from Remote-Sensing Reflectance of Optically Deep Waters

    NASA Technical Reports Server (NTRS)

    Lee, Zhong-Ping; Carder, Kendall L.

    2001-01-01

    A multi-band analytical (MBA) algorithm is developed to retrieve absorption and backscattering coefficients for optically deep waters, which can be applied to data from past and current satellite sensors, as well as data from hyperspectral sensors. This MBA algorithm applies a remote-sensing reflectance model derived from the Radiative Transfer Equation, and values of absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. There are only limited empirical relationships involved in the algorithm, which implies that this MBA algorithm could be applied to a wide dynamic range of waters. Applying the algorithm to a simulated non-"Case 1" data set, which has no relation to the development of the algorithm, the percentage error for the total absorption coefficient at 440 nm a (sub 440) is approximately 12% for a range of 0.012 - 2.1 per meter (approximately 6% for a (sub 440) less than approximately 0.3 per meter), while a traditional band-ratio approach returns a percentage error of approximately 30%. Applying it to a field data set ranging from 0.025 to 2.0 per meter, the result for a (sub 440) is very close to that using a full spectrum optimization technique (9.6% difference). Compared to the optimization approach, the MBA algorithm cuts the computation time dramatically with only a small sacrifice in accuracy, making it suitable for processing large data sets such as satellite images. Significant improvements over empirical algorithms have also been achieved in retrieving the optical properties of optically deep waters.

  13. Wave breaking in the surf zone and deep-water in a non-hydrostatic RANS model. Part 1: Organized wave motions

    NASA Astrophysics Data System (ADS)

    Derakhti, Morteza; Kirby, James T.; Shi, Fengyan; Ma, Gangfeng

    2016-11-01

    We examine wave-breaking predictions ranging from shallow- to deep-water conditions using a non-hydrostatic σ-coordinate RANS model NHWAVE as described in Derakhti et al. (2016a), comparing results both with corresponding experiments and with the results of a volume-of-fluid (VOF)/Navier-Stokes solver (Ma et al., 2011; Derakhti and Kirby, 2014a,b). Our study includes regular and irregular depth-limited breaking waves on planar and barred beaches as well as steepness-limited unsteady breaking focused wave packets in intermediate and deep water. In Part 1 of this paper, it is shown that the model resolves organized wave motions in terms of free-surface evolution, spectral evolution, organized wave velocity evolution and wave statistics, using a few vertical σ-levels. In addition, the relative contribution of modeled physical dissipation and numerical dissipation to the integral breaking-induced wave energy loss is discussed. In steepness-limited unsteady breaking focused wave packets, the turbulence model has not been triggered, and all the dissipation is imposed indirectly by the numerical scheme. Although the total wave-breaking-induced energy dissipation is underestimated in the unsteady wave packets, the model is capable of predicting the dispersive and nonlinear properties of different wave packet components before and after the break point, as well as the overall wave height decay and the evolution of organized wave velocity field and power spectrum density over the breaking region. In Part 2 (Derakhti et al., 2016b), model reproduction of wave-breaking-induced turbulence and mean circulation is examined in detail. The same equations and numerical methods are used for the various depth regimes, and no ad-hoc treatment, such as imposing hydrostatic conditions, is involved in triggering breaking. Vertical grid resolution in all simulated cases is at least an order of magnitude coarser than that of typical VOF-based simulations.

  14. Influence of the hydrodynamic conditions on the accessibility of Aristeus antennatus and other demersal species to the deep water trawl fishery off the Balearic Islands (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Amores, Angel; Rueda, Lucía; Monserrat, Sebastià; Guijarro, Beatriz; Pasqual, Catalina; Massutí, Enric

    2014-10-01

    Monthly catches per unit of effort (CPUE) of adult red shrimp (Aristeus antennatus), reported in the deep water bottom trawl fishery developed on the Sóller fishing ground off northern Mallorca (Western Mediterranean), and the mean ocean surface vorticity in the surrounding areas are compared between 2000 and 2010. A good correlation is found between the rises in the surrounding surface vorticity and the drops in the CPUE of the adult red shrimp. This correlation could be explained by assuming that most of the surface vorticity episodes could reach the bottom, increasing the seabed velocities and producing sediment resuspension, which could affect the near bottom water turbidity. A. antennatus would respond to this increased turbidity disappearing from the fishing grounds, probably moving downwards to the deeper waters. This massive displacement of red shrimp specimens away from the fishing grounds would consequently decrease their accessibility to fishing exploitation. Similar although more intense responses have been observed during the downslope shelf dense water current episodes that occurred in a submarine canyon, northeast of the Iberian peninsula. The proposed mechanism suggesting how the surface vorticity observed can affect the bottom sediments is investigated using a year-long moored near-bottom current meter and a sediment trap moored near the fishing grounds. The relationship between vorticity and catches is also explored for fish species (Galeus melastomus, Micromesistius poutassou, Phycis blennoides) and other crustacean (Geryon longipes and Nephrops norvegicus), considered as by-catch of the deep water fishery in the area. Results appear to support the suggestion that the water turbidity generated by the vorticity episodes is significant enough to affect the dynamics of the demersal species.

  15. Southwest Pacific deep water carbonate chemistry linked to high southern latitude climate and atmospheric CO2 during the Last Glacial Termination

    NASA Astrophysics Data System (ADS)

    Allen, Katherine A.; Sikes, Elisabeth L.; Hönisch, Bärbel; Elmore, Aurora C.; Guilderson, Thomas P.; Rosenthal, Yair; Anderson, Robert F.

    2015-08-01

    A greater amount of CO2 was stored in the deep sea during glacial periods, likely via greater efficiency of the biologic pump and increased uptake by a more alkaline ocean. Reconstructing past variations in seawater carbonate ion concentration (a major component of alkalinity) enables quantification of the relative roles of different oceanic CO2 storage mechanisms and also places constraints on the timing, magnitude, and location of subsequent deep ocean ventilation. Here, we present a record of deep-water inorganic carbon chemistry since the Last Glacial Maximum (LGM; ∼19-23 ka BP), derived from sediment core RR0503-83 raised from 1627 m in New Zealand's Bay of Plenty. The core site lies within the upper limit of southern-sourced Circumpolar Deep Water (CDW), just below the lower boundary of Antarctic Intermediate Water (AAIW). We reconstruct past changes in bottom water inorganic carbon chemistry from the trace element and stable isotopic composition of calcite shells of the epibenthic foraminifer Cibicidoides wuellerstorfi. A record of ΔCO32-(ΔCO32- = [COCO32-] in situ - [CO32-] saturation) derived from the foraminiferal boron to calcium ratio (B/Ca) provides evidence for greater ice-age storage of respired CO2 and reveals abrupt deglacial shifts in [CO32-] in situ of up to 30 μmol/kg (5 times larger than the difference between average LGM and Holocene values). The rapidity of these changes suggests the influence of changing water mass structure and atmospheric circulation in addition to a decrease in CO2 content of interior waters.

  16. Patterns of deep-water coral diversity in the Caribbean Basin and adjacent southern waters: an approach based on records from the R/V Pillsbury expeditions.

    PubMed

    Hernández-Ávila, Iván

    2014-01-01

    The diversity of deep-water corals in the Caribbean Sea was studied using records from oceanographic expeditions performed by the R/V Pillsbury. Sampled stations were sorted according to broad depth ranges and ecoregions and were analyzed in terms of species accumulation curves, variance in the species composition and contributions to alpha, beta and gamma diversity. According to the analysis of species accumulation curves using the Chao2 estimator, more diversity occurs on the continental slope (200-2000 m depth) than on the upper continental shelf (60-200 m depth). In addition to the effect of depth sampling, differences in species composition related to depth ranges were detected. However, the differences between ecoregions are dependent on depth ranges, there were fewer differences among ecoregions on the continental slope than on the upper continental shelf. Indicator species for distinctness of ecoregions were, in general, Alcyonaria and Antipatharia for the upper continental shelf, but also the scleractinians Madracis myriabilis and Cladocora debilis. In the continental slope, the alcyonarian Placogorgia and the scleractinians Stephanocyathus and Fungiacyathus were important for the distinction of ecoregions. Beta diversity was the most important component of gamma diversity in the Caribbean Basin. The contribution of ecoregions to alpha, beta and gamma diversity differed with depth range. On the upper continental shelf, the Southern Caribbean ecoregion contributed substantially to all components of diversity. In contrast, the northern ecoregions contributed substantially to the diversity of the Continental Slope. Strategies for the conservation of deep-water coral diversity in the Caribbean Basin must consider the variation between ecoregions and depth ranges.

  17. Patterns of Deep-Water Coral Diversity in the Caribbean Basin and Adjacent Southern Waters: An Approach based on Records from the R/V Pillsbury Expeditions

    PubMed Central

    Hernández-Ávila, Iván

    2014-01-01

    The diversity of deep-water corals in the Caribbean Sea was studied using records from oceanographic expeditions performed by the R/V Pillsbury. Sampled stations were sorted according to broad depth ranges and ecoregions and were analyzed in terms of species accumulation curves, variance in the species composition and contributions to alpha, beta and gamma diversity. According to the analysis of species accumulation curves using the Chao2 estimator, more diversity occurs on the continental slope (200–2000 m depth) than on the upper continental shelf (60–200 m depth). In addition to the effect of depth sampling, differences in species composition related to depth ranges were detected. However, the differences between ecoregions are dependent on depth ranges, there were fewer differences among ecoregions on the continental slope than on the upper continental shelf. Indicator species for distinctness of ecoregions were, in general, Alcyonaria and Antipatharia for the upper continental shelf, but also the scleractinians Madracis myriabilis and Cladocora debilis. In the continental slope, the alcyonarian Placogorgia and the scleractinians Stephanocyathus and Fungiacyathus were important for the distinction of ecoregions. Beta diversity was the most important component of gamma diversity in the Caribbean Basin. The contribution of ecoregions to alpha, beta and gamma diversity differed with depth range. On the upper continental shelf, the Southern Caribbean ecoregion contributed substantially to all components of diversity. In contrast, the northern ecoregions contributed substantially to the diversity of the Continental Slope. Strategies for the conservation of deep-water coral diversity in the Caribbean Basin must consider the variation between ecoregions and depth ranges. PMID:24671156

  18. Distribution of chemical warfare agent, energetics, and metals in sediments at a deep-water discarded military munitions site

    NASA Astrophysics Data System (ADS)

    Briggs, Christian; Shjegstad, Sonia M.; Silva, Jeff A. K.; Edwards, Margo H.

    2016-06-01

    There is a strong need to understand the behavior of chemical warfare agent (CWA) at underwater discarded military munitions (DMM) sites to determine the potential threat to human health or the environment, yet few studies have been conducted at sites in excess of 250 m, the depth at which most U.S. chemical munitions were disposed. As part of the Hawai'i Undersea Military Munitions Assessment (HUMMA), sediments adjacent to chemical and conventional DMM at depths of 400-650 m were sampled using human occupied vehicles (HOVs) in order to quantify the distribution of CWA, energetics, and select metals. Sites in the same general area, with no munitions within 50 m in any direction were sampled as a control. Sulfur mustard (HD) and its degradation product 1,4-dithiane were detected at each CWA DMM site, as well as a single sample with the HD degradation product 1,4-thioxane. An energetic compound was detected in sediment to a limited extent at one CWA DMM site. Metals common in munitions casings (i.e., Fe, Cu, and Pb) showed similar trends at the regional and site-wide scales, likely reflecting changes in marine sediment deposition and composition. This study shows HD and its degradation products can persist in the deep-marine environment for decades following munitions disposal.

  19. Contourite Deposition in the North Atlantic Ocean Moderated By Mantle Plume Activity: Evidence from Seismic Reflection Images

    NASA Astrophysics Data System (ADS)

    Parnell-Turner, R. E.; McCave, I. N. N.; White, N. J.; Henstock, T.; Murton, B. J.; Jones, S. M.

    2014-12-01

    It is generally accepted that the strength of Northern Component Water overflow, the ancient precursor of North Atlantic Deep Water, has varied throughout Neogene times. Variations in dynamic support of the lithosphere, due to transient behavior of the Iceland mantle plume, probably control spatial and temporal water depth variations this region. Pathways and intensities of oceanic bottom currents, together with deposition of contourite drifts, are strongly influenced by changing bathymetry. Here, we combine detailed observations of contourite drift deposits from seismic reflection profiles with a chronology of plume activity, to test the relationships between deep-water circulation, sedimentary drift accumulation and mantle convection. We present multi-channel seismic reflection profiles acquired over Bjorn, Gardar and Hatton Drifts in the Iceland Basin and over the northernmost portion of Eirik Drift, east of Greenland. Depositional hiatuses are easily identified and correlated between these high-quality images and nearby boreholes, which allows us to construct history of sedimentation across the North Atlantic Ocean over the past 5 Ma. We observe kilometer-scale westward-migration of Bjorn Drift, which can be explained by varying current strength and sediment supply, probably moderated by fluctuating dynamic support on overall subsidence. We place these observations into a new continuous 55 Ma record of Iceland mantle plume activity. There is compelling evidence to support the hypothesis that variations in mantle convection deep beneath the plates has profound consequences for deep-water flow and sediment deposition at Earth's surface.

  20. Provenance and accommodation pathways of late Quaternary sediments in the deep-water northern Ionian Basin, southern Italy

    NASA Astrophysics Data System (ADS)

    Perri, Francesco; Critelli, Salvatore; Dominici, Rocco; Muto, Francesco; Tripodi, Vincenzo; Ceramicola, Silvia

    2012-12-01

    The northern Calabria along the southeastern coast of Italy provides a favorable setting in which to study complete transects from continental to deep-marine environments. The present northern Ionian Calabrian Basin is a wedge-top basin within the modern foreland-basin system of southern Italy. The Ionian margin of northern Calabria consists of a moderately developed fluvial systems, the Crati and Neto rivers, and diverse smaller coastal drainages draining both the Calabria continental block (i.e., Sila Massif) and the southern Apennines thrust belt (i.e., Pollino Massif). The main-channel sand of the Crati and Neto rivers is quartzofeldspathic with abundant metamorphic and plutonic lithic fragments (granodiorite, granite, gneiss, phyllite and sedimentary lithic fragments). Sedimentary lithic fragments were derived from Jurassic sedimentary successions of the Longobucco Group. The mud samples contain mostly phyllosilicates, quartz, calcite, feldspars and dolomite. Traces of gypsum are present in some samples. The I-S mixed layers, 10 Å-minerals (illite and micas), chlorite and kaolinite are the most abundant phyllosilicates, whereas smectite and chlorite/smectite mixed layers are in small amounts. The geochemical signatures of the muds reflect a provenance characterized by both felsic and mafic rocks with a significant input from carbonate rocks. Furthermore, the degree of source-area weathering was most probably of low intensity rather than moderately intense because CIA values for the studied mud samples are low. Extrapolation of the mean erosion budget from 1 to 25 Ma suggests that at least 5 to 8 km of crust have been removed from the Calabrian orogenic belt and deposited in the marine basins. The Calabrian microplate played an important role in the dynamic evolution of southern Italian fossil and modern basins, representing the key tectonic element of the entire orogenic belt.

  1. Deep-water microbialites of the Mesoproterozoic Dismal Lakes Group: microbial growth, lithification, and implications for coniform stromatolites.

    PubMed

    Bartley, J K; Kah, L C; Frank, T D; Lyons, T W

    2015-01-01

    Offshore facies of the Mesoproterozoic Sulky Formation, Dismal Lakes Group, arctic Canada, preserve microbialites with unusual morphology. These microbialites grew in water depths greater than several tens of meters and correlate with high-relief conical stromatolites of the more proximal September Lake reef complex. The gross morphology of these microbial facies consists of ridge-like vertical supports draped by concave-upward, subhorizontal elements, resulting in tent-shaped cuspate microbialites with substantial primary void space. Morphological and petrographic analyses suggest a model wherein penecontemporaneous upward growth of ridge elements and development of subhorizontal draping elements initially resulted in a buoyantly supported, unlithified microbial form. Lithification began via precipitation within organic elements during microbialite growth. Mineralization either stabilized or facilitated collapse of initially neutrally buoyant microbialite forms. Microbial structures and breccias were then further stabilized by precipitation of marine herringbone cement. During late-stage diagenesis, remaining void space was occluded by ferroan dolomite cement. Cuspate microbialites are most similar to those found in offshore facies of Neoarchean carbonate platforms and to unlithified, buoyantly supported microbial mats in modern ice-covered Antarctic lakes. We suggest that such unusual microbialite morphologies are a product of the interaction between motile and non-motile communities under nutrient-limiting conditions, followed by early lithification, which served to preserve the resultant microbial form. The presence of marine herringbone cement, commonly associated with high dissolved inorganic carbon (DIC), low O2 conditions, also suggests growth in association with reducing environments at or near the seafloor or in conjunction with a geochemical interface. Predominance of coniform stromatolite forms in the Proterozoic--across a variety of depositional

  2. Factors controlling localization of uranium deposits in the Dakota Sandstone, Gallup and Ambrosia Lake mining districts, McKinley County, New Mexico

    USGS Publications Warehouse

    Pierson, Charles Thomas; Green, Morris W.

    1977-01-01

    Geologic studies were made at all of the uranium mines and prospects in the Dakota Sandstone of Early(?) and Late Cretaceous age in the Gallup mining district, McKinley County, New Mexico. Dakota mines in the adjacent Ambrosia Lake mining district were visited briefly for comparative purposes. Mines in the eastern part of the Gallup district, and in the Ambrosia Lake district, are on the Chaco slope of the southern San Juan Basin in strata which dip gently northward toward the central part of the basin. Mines in the western part of the Gallup district are along the Gallup hogback (Nutria monocline) in strata which dip steeply westward into the Gallup sag. Geologic factors which controlled formation of the uranium deposits in the Dakota Sandstone are: (1) a source of uranium, believed to be uranium deposits of the underlying Morrison Formation of Late Jurassic age; (2) the accessibility to the Dakota of uranium-bearing solutions from the Morrison; (3) the presence in the Dakota of permeable sandstone beds overlain by impermeable carbonaceous shale beds; and (4) the occurrence within the permeable Dakota sandstone beds of carbonaceous reducing material as bedding-plane laminae, or as pockets of carbonaceous trash. Most of the Dakota uranium deposits are found in the lower part of the formation in marginal-marine distributary-channel sandstones which were deposited in the backshore environment. However, the Hogback no. 4 (Hyde) Mine (Gallup district) occurs in sandy paludal shale of the backshore environment, and another deposit, the Silver Spur (Ambrosia Lake district), is found in what is interpreted to be a massive beach or barrier-bar sandstone of the foreshore environment in the upper part of the Dakota. The sedimentary depositional environment most favorable for the accumulation of uranium is that of backshore areas lateral to main distributary channels, where levee, splay, and some distributary-channel sandstones intertongue with gray carbonaceous shales and

  3. Facies transition and depositional architecture of the Late Eocene tide-dominated delta in northern coast of Birket Qarun, Fayum, Egypt

    NASA Astrophysics Data System (ADS)

    Abdel-Fattah, Zaki A.

    2016-07-01

    Late Eocene successions in the Fayum Depression display notable facies transition from open-marine to brackish-marine realms. Stratigraphic and sedimentologic characteristics of the depositional facies are integrated with ichnological data for the recognition of four facies associations (FA1 to FA4). The transition from open-marine sandstones (FA1) to the brackish-marine deposits (FA2) heralds a transgressive - regressive dislocation. The shallowing- and coarsening-upward progradation from the basal prodelta mudstone-dominated facies (FA2a) to deltafront heterolithics (FA2b) and sandstone facies (FA2c) are overlain by finning-upward delta plain deposits which are expressed by the delta plain mudstone (FA2d) and erosive-based distributary channel fills (FA4). Prodelta/deltfront deposits of FA2 are arranged in thinning- and coarsening-upward parasequences which are stacked in a shallowing-upward progressive cycle. Shallow-marine fossiliferous sandstones (FA3) mark the basal part of each parasequence. Stratigraphic and depositional architectures reflect a tide-dominated delta rather than an estuarine and incised valley (IV) model. This can be evinced by the progressive facies architecture, absence of basal regional incision or a subaerial unconformity and the stratigraphic position above a maximum flooding surface (MFS), in addition to the presence of multiple tidally-influenced distributary channels. Stratigraphic and depositional characteristics of the suggested model resemble those of modern tide-dominated deltaic systems. Accordingly, this model contributes to our understanding of the depositional models for analogous brackish-marine environments, particularly tide-dominated deltas in the rock record.

  4. Multi-proxy evidence for climate and North Atlantic Deep Water variability spanning the mid to late Holocene at the Erik sediment drift

    NASA Astrophysics Data System (ADS)

    Kleiven, H. F.; Ninnemann, U. S.; Irvali, N.

    2012-12-01

    The origin of Holocene abrupt climate changes like the 8.2 ka BP event, the 4.2 ka BP anomaly and the Little Ice Age, and in particular the role of ocean dynamics in these events, is a matter of considerable debate. The paucity of marine records capable of portraying both climate and North Atlantic Deep Water (NADW) properties during these anomalies has confounded efforts to determine how, or even if, deep ocean ventilation changed at these times. To elucidate the timing, magnitude, and nature of climate and deep-water changes spanning the mid to late Holocene we have generated a suite of high-resolution multi proxy records in cores MD03-2665 and GS06-144-MC03 (57°26.56N, 48°36.60W, 3440 m water depth) from the Erik Drift. The Holocene in this core is represented by ~5.6 m of sediment, and previous studies (Kleiven et al., 2008) demonstrate that the site is sensitively situated and provides the temporal fidelity to detect abrupt climate and deep circulation events. We reconstruct the bottom water physical and chemical properties of the deep overflowing branches from the Nordic Seas using oxygen and carbon isotopes of benthic foraminifera, whereas changes in the vigor of near bottom flow are inferred from size variations in mean sortable silt. Changes in North Atlantic hydrography are portrayed using records of planktonic foraminiferal isotopes and assemblage counts, ice-rafted debris counts, as well as modern analog technique sea surface temperature estimations. Major elements are also obtained throughout the core by XRF scanning. The planktonic foraminiferal oxygen isotopic and sea surface temperature reconstructions from 7 to 0 ka BP exhibit a distinct sequence of multi-centennial to millennial-scale cooling events. The first of these prominent coolings that characterize the late Holocene is initiated ~4.6 ka BP, and culminates at 4.0 ka BP. Similarly strong coolings occur between 2.9-2.5ka and at the onset of the Little Ice Age at ~0.5 ka BP (1450 AD). Many of

  5. Salt Marsh Sediment Biogeochemical Response to the Deep Water Horizon BP Oil Spill (Skiff Island, LA, and Cat Island, Marsh Point, and Salt Pan Island, MS)

    NASA Astrophysics Data System (ADS)

    Guthrie, C. L.; McNeal, K. S.; Mishra, D. R.; Blakeney, G. A.

    2012-12-01

    The large scale impact of the Deep Water Horizon BP Oil Spill on biological communities can be better predicted by developing an understanding of how carbon loading from the spill is affecting the microbial and biological communities of salt marshes along the Mississippi and Louisiana Gulf Coast. Sediment biogeochemical processes that degrade enriched carbon pools through sulfate reduction are primarily responsible for the biological breakdown of spilled hydrocarbons (Shin et al., 2000). Determination of sulfide concentration in contaminated areas, therefore, allows for an assessment of the oil spill impact on salt marsh at Skiff Island, LA, and Marsh Point, Cat Island, and Salt Pan Island, MS. As a result of carbon loading, porewater hydrogen sulfide (H2S) concentrations are expected to show an increase in the largely anoxic wetland sediment, making the sediment more toxic and inhospitable to marsh vegetation (Alber et al., 2008). High sulfide levels due to carbon loading in hydrocarbon contaminated salt marshes cause microbial activity to increase at the plant rhizospere, leading to plant browning and die back (Eldridge and Morse 2000). Preliminary analysis of the Marsh Point study area was conducted in Fall 2010. Sediment cores indicated that sulfate reducing bacteria are significantly more active in contaminated sediments, producing sulfide concentrations 20x higher than in non-contaminated sediments. The difference in the sediment biogeochemistry between the contaminated site and non-contaminated site at Marsh Point, MS indicated that the effects of hydrocarbon contamination on sulfur cycling in salt marshes should be more spatially explored. In Fall 2011, the study was expanded to include Skiff Island, LA, and Cat Island, and Salt Pan Island, MS in addition to Marsh Point, MS. Sediment electrode profiles (H2S, O2, pH, and Eh), degree of hydrocarbon contamination (GC), grain size analysis, microbial community substrate level carbon utilization profiles, and

  6. Body condition of the deep water demersal resources at two adjacent oligotrophic areas of the western Mediterranean and the influence of the environmental features

    NASA Astrophysics Data System (ADS)

    Rueda, L.; Moranta, J.; Abelló, P.; Balbín, R.; Barberá, C.; Fernández de Puelles, M. L.; Olivar, M. P.; Ordines, F.; Ramón, M.; Torres, A. P.; Valls, M.; Massutí, E.

    2014-10-01

    Body condition indices not only are often used as reliable indicators of the nutritional status of individuals but also can they be utilized to provide insights regarding food availability and habitat quality. The aim of this study was to evaluate the connection between the body condition of the demersal species and the environmental features in the water column (i.e. the hydrographic conditions and the potential trophic resources) in two proximate areas, the north and south regions of the Balearic Islands (western Mediterranean), viz., the Balearic sub-basin (BsB) and the Algerian sub-basin (AsB), respectively, with different geomorphological and hydrodynamic features. Body condition indices were calculated for individuals of 21 demersal species including 11 teleosts, 4 elasmobranchs, 3 cephalopods and 3 crustaceans, which represented > 70-77% of the deep water resources, captured by bottom trawling. The morphometric indices, viz., Relative Condition Index (Kn) and Standardised Residuals (SR) from the length-weight relationship, were used. The results for each one of the 21 species indicated a significantly better condition in terms of Kn and SR in the BsB, for 7 and 9 species, respectively. In addition, a general model, including the 21 species together, showed better body condition in the BsB, and during the summer. The spatial and temporal differences in the body condition are discussed in the context of the environmental variables characterising both the study areas, which showed significant variations, for some of the hydrographic features (chlorophyll a, dissolved oxygen, salinity, potential density and temperature), as well as for some of the potential trophic resources (mesopelagic and epibenthic fauna). These findings suggest an environmental effect on the body condition of the deep-water resources in the Balearic Islands, one of the most oligotrophic areas of the western Mediterranean, and reveal more suitable environmental conditions for these species

  7. Deep-water seamounts in the NE Atlantic, sources of landslides-induced tsunamis: Slope stability analysis and tsunami numerical modelling

    NASA Astrophysics Data System (ADS)

    Baptista, M. A.; Omira, R.; Ramalho, I.; Vales, D.; Matias, L. M.; Terrinha, P.

    2015-12-01

    Submarine mass failures (SMFs) present one of the significant marine Geo-hazards. Their importance as contributors to tsunami hazard has been recognized over the last 20-30 years, but they are seldom considered in the evaluation of quantitative tsunami impact or in the design of warning strategies. This study aims to investigate the slope stability of the SMFs in the NE Atlantic, their companion tsunami and the associated hazard at the target coasts. It focuses on two major deep-water seamounts of the NE Atlantic, the Gorringe Bank and the Hirondelle, where evidences of large SMFs have been found. Slope stability analysis is often based on relationships between landslides and earthquakes. Here, within each considered seamount, slope failure potential is investigated through the pseudo-static method. This analysis allows establishing a relationship between the size of the SMF and the critical earthquake peak ground acceleration necessary to initiate it and therefore define the possible SMF scenarios. Numerical modelling of SMF-induced tsunami generation is then employed to test the tsunamigenic potential of each defined scenario. It is performed using a multi-layers viscous shallow-water model, where the lower layer represents the deformable slide that is assumed to be a viscous-incompressible fluid, and bounded by the upper layer of seawater assumed to be inviscid and incompressible. The propagation of tsunami waves is simulated employing non-linear shallow water equations. Results are presented in terms of: 1) slope stability curves that establish the relationship between the probable earthquake magnitudes and the possible sizes of SMFs, 2) possible SMF scenarios within each seamount, 3) potential of tsunami generation for each SMF, 4) tsunami coastal impact at target coasts. Results show that SMFs in the NE Atlantic have the potential of generating large tsunamis with significant impact along the surrounding coasts. Therefore, more attention must be accorded to

  8. Early Cretaceous shelf-edge deltas of the Baltimore Canyon Trough: principal sources for sediment gravity deposits of the northern Hatteras Basin

    USGS Publications Warehouse

    Poag, C. Wylie; Swift, B. Ann; Schlee, John S.; Ball, Mahlon M.; Sheetz, Linda L.

    1990-01-01

    We present evidence that the principal sources for Early Cretaceous (Berriasian-Valanginian) gravity-flow deposits of the northern Hatteras Basin were three large shelf-edge deltas located along the outer margin of the Baltimore Canyon Trough, ∼ 100 km southeast of Cape Charles, Virginia, Ocean City, Maryland, and Long Branch, New Jersey. Sedimentary detritus from the central Appalachian highlands and the Maryland-Virginia coastal plain was transported across the Early Cretaceous continental shelf to form the Cape Charles and Ocean City deltas, whereas deposits of the Long Branch delta came chiefly from the Adirondack and New England highlands. Each delta supplied sediment gravity flows to large slope aprons and submarine-fan complexes on the Early Cretaceous continental slope and rise. The most conspicuous distributary of sediment on the Early Cretaceous continental rise extends 500 km basinward from the Ocean City delta, where its distal deposits were cored at Deep Sea Drilling Project Site 603.

  9. Lithostratigraphy of Shell 272-1 and 273-1 Wells: implications as to depositional history of the Baltimore Canyon Trough, Mid- Atlantic OCS.

    USGS Publications Warehouse

    Libby-French, J.

    1981-01-01

    The Shell 272-1 and 273-1 wells, located c106km SE of Atlantic City, in the NW part of the Baltimore Canyon Trough penetrate strata from Cenozoic down to Upper Jurassic, and the lithology of each is described. 7 major lithologic units were established and correlated to the COST B-2 and B-3 wells. The depositional environments of the Upper Jurassic rocks range from an upper delta plain facies to a back-reef facies. The Lower Cretaceous strata, in a vertical sequence, consist of upper delta plain, lower delta plain, marginal marine, and distributary-mouth-bar deposits. A Cenomanian sandstone is the youngest indicator of deltaic deposition; marine strata dominate the remainder of the Upper Cretaceous and Cenozoic.-from Authors

  10. Liquefaction probability curves for surficial geologic deposits

    USGS Publications Warehouse

    Holzer, Thomas L.; Noce, Thomas E.; Bennett, Michael J.

    2011-01-01

    Liquefaction probability curves that predict the probability of surface manifestations of earthquake-induced liquefaction are developed for 14 different types of surficial geologic units. The units consist of alluvial fan, beach ridge, river delta topset and foreset beds, eolian dune, point bar, flood basin, natural river and alluvial fan levees, abandoned river channel, deep-water lake, lagoonal, sandy artificial fill, and valley train deposits. Probability is conditioned on earthquake magnitude and peak ground acceleration. Curves are developed for water table depths of 1.5 and 5.0 m. Probabilities are derived from complementary cumulative frequency distributions of the liquefaction potential index (LPI) that were computed from 927 cone penetration tests. For natural deposits with a water table at 1.5 m and subjected to a M7.5 earthquake with peak ground acceleration (PGA)  =  0.25g, probabilities range from 0.5 for beach ridge, point bar, and deltaic deposits. The curves also were used to assign ranges of liquefaction probabilities to the susceptibility categories proposed previously for different geologic deposits. For the earthquake described here, probabilities for susceptibility categories have ranges of 0–0.08 for low, 0.09–0.30 for moderate, 0.31–0.62 for high, and 0.63–1.00 for very high. Retrospective predictions of liquefaction during historical earthquakes based on the curves compare favorably to observations.

  11. Study on characteristics of 3-D translating-pulsating source green function of deep-water havelock form and its fast integration method

    NASA Astrophysics Data System (ADS)

    Xu, Yong; Dong, Wen-Cai

    2011-09-01

    The singularities, oscillatory performances and the contributing factors to the 3-D translating-pulsating source Green function of deep-water Havelock form which consists of a local disturbance part and a far-field wave-like part, are analyzed systematically. Relative numerical integral methods about the two parts are presented in this paper. An improved method based on LOBATTO rule is used to eliminate singularities caused respectively by infinite discontinuity and jump discontinuous node from the local disturbance part function, which makes the improvement of calculation efficiency and accuracy possible. And variable substitution is applied to remove the singularity existing at the end of the integral interval of the far-field wave-like part function. Two auxiliary techniques such as valid interval calculation and local refinement of integral steps technique in narrow zones near false singularities are applied so as to avoid unnecessary integration of invalid interval and improve integral accordance. Numerical test results have proved the efficiency and accuracy in these integral methods that thus can be applied to calculate hydrodynamic performance of floating structures moving in waves.

  12. The relative roles of modified circumpolar deep water and benthic sources in supplying iron to the recurrent phytoplankton blooms above Pennell and Mawson Banks, Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Hatta, Mariko; Measures, Chris I.; Lam, Phoebe J.; Ohnemus, Daniel C.; Auro, Maureen E.; Grand, Maxime M.; Selph, Karen E.

    2017-02-01

    The role that dissolved iron (dFe) rich Circumpolar Deep Water (CDW) might play in sustaining the consistently observed discrete patches of high chlorophyll biomass over Pennell Bank (PB) and Mawson Bank (MB) in the Ross Sea, was investigated during January/February 2011. Over a 26-day period, hydrographic and trace metal clean water sampling was carried out adjacent to both of these banks, in some cases repeatedly. Particulate sampling was also accomplished at selected stations by in situ pumping. The results indicate that the dFe content of the CDW is in fact reduced by on-shelf mixing with Antarctic Surface Water as it transitions into modified CDW (MCDW). Our stations above PB, where the maximum bloom is encountered, show no evidence of MCDW presence. In contrast, above MB, where there is a smaller persistent bloom, MCDW was observed. Although both of these stations displayed the imprint of sedimentary Fe input connected to the strong tidal cycles above the banks, the stronger near-bottom density gradient that MCDW produces appears to contribute to reduced vertical mixing of the sedimentary source. Thus, ironically, the presence of MCDW may be hindering the Fe supply to the surface waters, rather than being the source, as originally hypothesized.

  13. Consequences of long-distance swimming and travel over deep-water pack ice for a female polar bear during a year of extreme sea ice retreat

    USGS Publications Warehouse

    Durner, G.M.; Whiteman, J.P.; Harlow, H.J.; Amstrup, Steven C.; Regehr, E.V.; Ben-David, M.

    2011-01-01

    Polar bears (Ursus maritimus) prefer to live on Arctic sea ice but may swim between ice floes or between sea ice and land. Although anecdotal observations suggest that polar bears are capable of swimming long distances, no data have been available to describe in detail long distance swimming events or the physiological and reproductive consequences of such behavior. Between an initial capture in late August and a recapture in late October 2008, a radio-collared adult female polar bear in the Beaufort Sea made a continuous swim of 687 km over 9 days and then intermittently swam and walked on the sea ice surface an additional 1,800 km. Measures of movement rate, hourly activity, and subcutaneous and external temperature revealed distinct profiles of swimming and walking. Between captures, this polar bear lost 22% of her body mass and her yearling cub. The extraordinary long distance swimming ability of polar bears, which we confirm here, may help them cope with reduced Arctic sea ice. Our observation, however, indicates that long distance swimming in Arctic waters, and travel over deep water pack ice, may result in high energetic costs and compromise reproductive fitness. ?? 2011 US Government.

  14. High matrix interference affecting detection of PAH metabolites in bile of Atlantic hagfish (Myxine glutinosa) used for biomonitoring of deep-water oil production.

    PubMed

    Sundt, Rolf C; Beyer, Jonny; Vingen, Sjur; Sydnes, Magne O

    2011-06-01

    The characteristic biology and wide distribution of hagfish species makes them relevant for use in pollution biomonitoring at great water depths, particularly in regions where deep-water oil production may take place. The exposure of fish to petrogenic contaminants can normally be detected from the level of polycyclic aromatic hydrocarbon (PAH) metabolites in bile fluid. Some of these metabolites are strong fluorophores, allowing analytical detection by means of simple fluorometric techniques such as fixed wavelength fluorescence (FF) and synchronous fluorescence scanning (SFS). In the present study bile from Atlantic hagfish (Myxine glutinosa) collected in pristine areas (Barents Sea and southwestern Norway) displayed strong bile fluorescence levels, suggesting the presence of PAH contaminants. However, gas-chromatography-mass spectrometry (GC-MS) analyses ruled out PAHs as the origin for this fluorescence signal. Rather, the bile of Myxine contains components resulting in unusually strong background fluorescence interfering at the wavelength pairs used for detection of PAH metabolites. Possible background for the observed matrix interference and implications for detection of PAH metabolites in hagfish is discussed.

  15. New case of lateral asymmetry in fishes: A new subfamily, genus and species of deep water clingfishes from Papua New Guinea, western Pacific Ocean.

    PubMed

    Fricke, Ronald; Chen, Jhen-Nien; Chen, Wei-Jen

    2017-01-01

    The unusual clingfish Protogobiesox asymmetricus n. gen, n. sp. is described on the basis of four specimens collected in deep water off the north coast of Papua New Guinea in 2012. The species is characterized by its 9-10 dorsal rays, 8 anal rays, 17-24 pectoral-fin rays, 15 principal caudal-fin rays, 3 gills, third arch with 3 gill rakers, 34-35 total vertebrae, with asymmetrical lateral bending starting behind the skull, bent at an angle of 85°-92°; skull asymmetrical in frontal view; skin naked, surface of head and body without striae; disc without adhesive papillae. A new subfamily Protogobiesocinae is described for this species and Lepadicyathus mendeleevi Prokofiev, 2005, which is redescribed. The new subfamily is compared within the family; keys to the subfamilies of Gobiesocidae and the species within the new subfamily are presented; its phylogenetic relationship to other gobiesocids is inferred based on a multi-locus DNA dataset.

  16. Two species of the deep-water shrimp genus Nematocarcinus A. Milne-Edwards, 1881 (Crustacea, Decapoda, Caridea, Nematocarcinidae) from the Mexican Pacific.

    PubMed

    Hernandez-Payan, J C; Hendrickx, M E

    2016-06-21

    The distribution of two species of the deep-water shrimp genus Nematocarcinus A. Milne-Edwards, 1881, occurring off the west coast of Mexico is analyzed based on a large series of recently collected material. Nematocarcinus faxoni Burukovsky, 2000, is by far the most common and abundant species in the area and it is distributed throughout the central and southern Gulf of California and off the entire Baja California Peninsula south to 17º10'15"N. Based on characteristics observed in the new samples and in the type material, N. agassizii Faxon, 1893, is reinstalled as a valid species, and no longer considered a junior of N. gracilipes A. Milne-Edwards, 1881, as proposed by Cardoso & Burukovsky (2014). Along the Pacific coast of Mexico, N. agassizii exhibits a more restricted distribution and it was collected only off the Baja California Peninsula. Previous records of this species in the Gulf of California, where N. faxoni was the only representative of the genus captured during this survey, are considered doubtful.

  17. Isolation By Distance (IBD) signals in the deep-water rose shrimp Parapenaeus longirostris (Lucas, 1846) (Decapoda, Panaeidae) in the Mediterranean Sea.

    PubMed

    Lo Brutto, S; Maggio, T; Arculeo, M

    2013-09-01

    The identification of boundaries of genetic demes is one of the major goals for fishery management, and few Mediterranean commercial species have not been studied from a genetic point of view yet. The deep-water rose shrimp Parapenaeus longirostris (Lucas, 1846) is one of the most important components of commercial landings in Mediterranean, its fishery aspects have received much attention, regrettably without any concern for the genetic architecture of its populations. The population structure in the central and eastern Mediterranean Sea (captures from six Italian and two Greek landings) has been analysed on the basis of surveys carried out with mitochondrial and AFLP markers. Data revealed the presence of a gradual discrepancy along a west-east axis. This species, occurring mainly at a depth of between 100 and 400 m, is not strongly confined in isolated demes, but it demonstrates an 'Isolation By Distance' model, within the Mediterranean Sea, which includes geographical areas with a some degree of isolation. The role of hydrodynamic forces, such as currents, water fronts, is discussed; and a further evidence of the 'Levantine isolation' within Mediterranean basin is shown.

  18. Wave–current interaction in the presence of a three-dimensional bathymetry: Deep water wave focusing in opposing current conditions

    SciTech Connect

    Rey, V. Charland, J. Touboul, J.

    2014-09-15

    Large scale experiments were carried out in the Ocean Engineering Basin FIRST, France. A tri-dimensional bathymetry consisting of two symmetrical submerged mounds was displayed on the flat bed on both sides of the basin. Regular waves of frequency corresponding to deep water conditions above the bathymetry were generated in opposing current conditions. A strong tri-dimensional behaviour is observed for the wave amplitude, leading to a strong focusing (up to twice the incident amplitude) of the wave energy towards the central deeper zone. This amplification cannot be ascribed to the increase of the current intensity in the main wave direction, nor to a current gradient normally to the wave direction. A wave phase gradient, normal to its main direction, is observed up-wave (or downstream) the mounds. This phase lag depends on the wave amplitude, it is the higher for the moderate amplitude case. The experimental data are compared with calculations of a refraction-diffraction model assuming a depth-averaged current. If the model qualitatively predicts the wave amplification in the centerline of the basin, discrepancies are observed in the vicinity of the depth changes. The observed mean current vertical profile shape is then supposed to play a significant role in the wave focusing, especially near the steep slopes down-stream the mounds. In addition, the waves are found to modify substantially both horizontal and vertical current fields.

  19. Oil biodegradation by Bacillus strains isolated from the rock of an oil reservoir located in a deep-water production basin in Brazil.

    PubMed

    da Cunha, Claudia Duarte; Rosado, Alexandre S; Sebastián, Gina V; Seldin, Lucy; von der Weid, Irene

    2006-12-01

    Sixteen spore forming Gram-positive bacteria were isolated from the rock of an oil reservoir located in a deep-water production basin in Brazil. These strains were identified as belonging to the genus Bacillus using classical biochemical techniques and API 50CH kits, and their identity was confirmed by sequencing of part of the 16S rRNA gene. All strains were tested for oil degradation ability in microplates using Arabian Light and Marlin oils and only seven strains showed positive results in both kinds of oils. They were also able to grow in the presence of carbazole, n-hexadecane and polyalphaolefin (PAO), but not in toluene, as the only carbon sources. The production of key enzymes involved with aromatic hydrocarbons biodegradation process by Bacillus strains (catechol 1,2-dioxygenase and catechol 2,3-dioxygenase) was verified spectrophotometrically by detection of cis,cis-muconic acid and 2-hydroxymuconic semialdehyde, and results indicated that the ortho ring cleavage pathway is preferential. Furthermore, polymerase chain reaction (PCR) products were obtained when the DNA of seven Bacillus strains were screened for the presence of catabolic genes encoding alkane monooxygenase, catechol 1,2-dioxygenase, and/or catechol 2,3-dioxygenase. This is the first study on Bacillus strains isolated from an oil reservoir in Brazil.

  20. Slope-confined submarine canyons in the Baiyun deep-water area, northern South China Sea: variation in their modern morphology

    NASA Astrophysics Data System (ADS)

    Li, X. S.; Zhou, Q. J.; Su, T. Y.; Liu, L. J.; Gao, S.; Zhou, S. W.

    2016-06-01

    On the basis of newly collected multibeam bathymetric data, chirp profiles and existing seismic data, we presented a detailed morphological interpretation of a series of slope-confined canyons in water depths of 300-2000 m in the Baiyun deep-water area, northern margin of the South China Sea. Although these canyons are commonly characterized by regular spacing and a straight-line shape, they vary in their lengths, starting and ending water depths, canyon relief, slope gradients, wall slope gradients and depth profiles along the axis. The eastern canyons (C1-C8) have complex surface features, low values in their slope gradient, canyon relief and wall slope gradient and high values in their length and starting and ending depth contrasting to the western ones (C9-C17). From the bathymetric data and chirp profiles, we interpret two main processes that have controlled the morphology and evolution of the canyons: axial incision and landsliding. The western part of the shelf margin where there were at least four stages of submerged reefs differs from the eastern part of the shelf margin where sedimentary undulations occurred at a water depth of ~650 m. We consider that the variation in morphology of submarine canyons in the study area is the result of multiple causes, with the leading cause being the difference in stability of the upper slope which is related to the submerged reefs and sedimentary undulations.

  1. DEEP WATER ISOTOPIC CURRENT ANALYZER

    DOEpatents

    Johnston, W.H.

    1964-04-21

    A deepwater isotopic current analyzer, which employs radioactive isotopes for measurement of ocean currents at various levels beneath the sea, is described. The apparatus, which can determine the direction and velocity of liquid currents, comprises a shaft having a plurality of radiation detectors extending equidistant radially therefrom, means for releasing radioactive isotopes from the shaft, and means for determining the time required for the isotope to reach a particular detector. (AEC)

  2. Thin Ice over Deep Water.

    ERIC Educational Resources Information Center

    Lane, Neal

    1996-01-01

    Discusses the need for the integration of scientific research and science education, graduate education in astronomy, the current status of federally funded research and education, and the impact of budget cuts on scientific research and education. (JRH)

  3. Deep Water Munitions Detection System

    DTIC Science & Technology

    2010-03-01

    UXO unexploded ordnance GPS global positioning system MTA marine towed array TG towed gradiometer Mag magnetic nT nanotesla rms root mean square...other sites were used which had been surveyed with Geometrics Towed Gradiometer (TG) systems. In both of the gradiometer based surveys the data from...the individual magnetometers that made up the gradiometer were available. Magnetic anomalies from each site were reanalyzed to produce uniform target

  4. North Atlantic Deep Water Formation

    NASA Technical Reports Server (NTRS)

    Bennett, T. (Editor); Broecker, W. S. (Editor); Hansen, J. (Editor)

    1984-01-01

    Various studies concerning differing aspects of the North Atlantic are presented. The three major topics under which the works are classified include: (1) oceanography; (2) paleoclimate; and (3) ocean, ice and climate modeling.

  5. Sinobatis brevicauda n. sp., a new deep-water legskate (Rajiformes, Anacanthobatidae) and first generic record from the western Indian Ocean.

    PubMed

    Weigmann, Simon; Stehmann, Matthias F W

    2016-07-13

    A new deep-water legskate, Sinobatis brevicauda, is described based on two specimens caught on the remote Saya de Malha Bank in the central western Indian Ocean. The new species is easily distinguished from all other described anacanthobatids by the short tail. It is the only Sinobatis species described from the western Indian Ocean and differs from the other anacanthobatid legskates in this area by its large size and light coloration. All other species of Sinobatis are described from the eastern Indian and, particularly, western Pacific oceans. In addition to the short tail, the new species clearly differs from its morphologically closest congener, the Australian S. bulbicauda, in a bicolored white and grayish ventral coloration with gray and white blotches (vs. uniformly pale or white and skin somewhat translucent) and a filamentous tail without flattened, bulbous tip. Furthermore, it is distinguished by several morphometric and meristic differences, e.g. a longer body (length 65% TL vs. 39-61% TL), longer head (dorsal length 34% TL vs. 21-31% TL, ventral length 41% TL vs. 23-36% TL), longer snout (preorbital length 28-29% TL vs. 14-26% TL, preoral length 30% TL vs. 16-28% TL, prenasal length 28% TL vs. 14-25% TL), and fewer diplospondylous (102-112 vs. 121-142) and total (131-141 vs. 148-168) vertebrae. S. brevicauda clearly differs from the other anacanthobatids in the western Indian Ocean, Anacanthobatis marmorata and Indobatis ori, by having a much shorter tail, strongly different coloration, much larger size, and in many morphometric and meristic differences.

  6. Spatial variability of surface-sediment porewater pH and related water-column characteristics in deep waters of the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Shao, Changgao; Sui, Yi; Tang, Danling; Legendre, Louis

    2016-12-01

    This study analyzes the pH of surface-sediment porewater (i.e. 2-3 cm below the water-sediment interface), and concentrations of CaCO3 and organic carbon (OC) in 1192 sediment cores from the northern South China Sea, in water depths ranging from 137 to 3702 m. This is the first study in the literature to analyze the large-scale spatial variability of deep-water surface-sediment pH over a large ocean basin. The data showed strong spatial variations in pH. The lowest pH values (<7.3) were observed south of Hainan Island, an area that is affected by summer upwelling and freshwater runoff from the Pearl and Red Rivers. Moderately low pH values (generally 7.3-7.5) occurred in two other areas: a submarine canyon, where sediments originated partly from the Pearl River and correspond to a paleo-delta front during the last glacial period; and southwest of Taiwan Island, where waters are affected by the northern branch of the Kuroshio intrusion current (KIC) and runoff from Taiwan rivers. The surface sediments with the highest pH (⩾7.5, and up to 8.3) were located in a fourth area, which corresponded to the western branch of the KIC where sediments have been intensively eroded by bottom currents. The pH of surface-sediment porewater was significantly linearly related to water depth, bottom-water temperature, and CaCO3 concentration (p < 0.05 for the whole sampling area). This study shows that the pH of surface-sediment porewater can be sensitive to characteristics of the overlying water column, and suggests that it will respond to global warming as changes in surface-ocean temperature and pH progressively reach deeper waters.

  7. Carbon isotope (δ13C) excursions suggest times of major methane release during the last 14 kyr in Fram Strait, the deep-water gateway to the Arctic

    NASA Astrophysics Data System (ADS)

    Consolaro, C.; Rasmussen, T. L.; Panieri, G.; Mienert, J.; Bünz, S.; Sztybor, K.

    2015-04-01

    We present results from a sediment core collected from a pockmark field on the Vestnesa Ridge (~ 80° N) in the eastern Fram Strait. This is the only deep-water gateway to the Arctic, and one of the northernmost marine gas hydrate provinces in the world. Eight 14C AMS dates reveal a detailed chronology for the last 14 ka BP. The δ 13C record measured on the benthonic foraminiferal species Cassidulina neoteretis shows two distinct intervals with negative values termed carbon isotope excursion (CIE I and CIE II, respectively). The values were as low as -4.37‰ in CIE I, correlating with the Bølling-Allerød interstadials, and as low as -3.41‰ in CIE II, correlating with the early Holocene. In the Bølling-Allerød interstadials, the planktonic foraminifera also show negative values, probably indicating secondary methane-derived authigenic precipitation affecting the foraminiferal shells. After a cleaning procedure designed to remove authigenic carbonate coatings on benthonic foraminiferal tests from this event, the 13C values are still negative (as low as -2.75‰). The CIE I and CIE II occurred during periods of ocean warming, sea-level rise and increased concentrations of methane (CH4) in the atmosphere. CIEs with similar timing have been reported from other areas in the North Atlantic, suggesting a regional event. The trigger mechanisms for such regional events remain to be determined. We speculate that sea-level rise and seabed loading due to high sediment supply in combination with increased seismic activity as a result of rapid deglaciation may have triggered the escape of significant amounts of methane to the seafloor and the water column above.

  8. Stable isotope data from deep-water antipatharians: 400-Year records from the southeastern coast of the United States of America

    USGS Publications Warehouse

    Williams, B.; Risk, Michael J.; Ross, S.W.; Sulak, K.J.

    2007-01-01

    In this study, time-series stable isotope results (δ13C and δ15N) from three deep-water Leiopathes glaberrima(Esper, 1788) specimens Collected off the southeastern Coast of the United States of America and one specimen from the Gulf of Mexico are presented. The specimens were Collected live in 2004 and are estimated to be 200–500 yrs old based on 210Pb measurements and band Counts. The δ13C and δ15N long-term trends are reproducible within and among specimens from a similar location, suggesting a common environmental influence. Three western Atlantic specimens have average δ13C values of −15.7‰, −16.3‰, and −16.1‰, with the most depleted values from the oldest specimen. The oldest specimen records an enrichment in 13C of 0.5‰ corresponding to the Little Ice Age. All three specimens show a depletion of 13C over the past 150 yrs Corresponding to the δ13C Suess Effect. The fourth specimen from the Gulf of Mexico has an average δ13C value of −16.4‰ and shows no trend in13C value with time. All four specimens Contain an enrichment in 15N over the most recent 75 yrs, with the largest enrichment (3‰) in the Gulf of Mexico specimen. This enrichment is likely a result of increased terrestrial effluent (sewage and manure) reaching the offshore specimens.

  9. Application of KISOS for the Monitoring Environmental Risks Assessment in Deep-water Gas Hydrate Test Production in the Ulleung Basin, East Sea of Korea

    NASA Astrophysics Data System (ADS)

    Lee, S. R.; Chun, J. H.

    2015-12-01

    Korea Institute of Geoscience and Mineral Resources (KIGAM) has developed the KIGAM Seafloor Observation System (KISOS) for the baseline studies in the monitoring gas hydrate test production in the deep-water (>2,000m) Ulleung Basin of the East Sea of Korea. The KISOS consists of an acoustic positioning system (USBL), altimeter, still camera, video camera, water sampler, measuring devices (dissolved methane, dissolved oxygen, turbidity, chlorophyll, and currents) mounted on the unmanned ROV, and a seafloor sediment collecting device. The ultimate goals of the seafloor monitoring are to assess environmental risks (gas leakage and production water/drilling discharge, and so on) which may occur during and after the gas hydrate test production drilling. The KISOS was applied to solely conduct baseline studies during the last three years. We will conduct the KIGAM seafloor monitoring system (KIMOS) of the Korean gas hydrate program in the future. The large scale of environmental monitoring program includes the environmental impact assessments such as seafloor disturbance and subsidence, detection of methane gas leakage around well and cold seep, methane bubbles and dissolved methane, change of marine environments, chemical factor variation of water column and seabed, diffusion of drilling mud and production water, and biological factors of biodiversity and marine habitats before and after production drilling test well and nearby areas. Topics that will cover include:1) configuration of KISOS and general layout/operational design of KIMOS, 2) numerical simulation of gas and materials transport using SIMAP/CHEMMAP + MUDMAP softwares, 3) sensitivity analysis such as gas leakage modeling, operational produced water discharge, and 4) modeling of drilling discharge with cuttings and mud. Key words: gas hydrate, environmental monitoring, KISOS, KIMOS, Ulleung Basin

  10. Deep water running and general practice in primary care for non-specific low back pain versus general practice alone: randomized controlled trial.

    PubMed

    Cuesta-Vargas, A I; Adams, N; Salazar, J A; Belles, A; Hazañas, S; Arroyo-Morales, M

    2012-07-01

    There is equivocal evidence regarding the benefits of aquatic aerobic exercise for non-specific chronic low back pain (NSCLBP) in addition to standard care in general practice consisting of education and advice. The purpose of this study was to compare the addition of deep water running (DWR) to standard general practice (GP) on NSCLBP versus GP care alone on pain, physical and mental health and disability. In this single-blind randomised controlled trial, 58 subjects with NSCLBP were recruited from primary care. The control group received GP care consisting of a physician's consultation and educational booklet only. The experimental group received additional 30-min sessions of DWR three times a week for 15 weeks at the individualized aerobic threshold. Measurements were made pre- and post-intervention and at 1-year follow-up. Both groups showed improvement. The difference between treatment effects at longest follow-up of 1 year was -26.0 (-40.9 to -11.1) mm on the VAS (p < 0.05), -2.5 (-5.7 to -0.2) points in RMQ for disability (p < 0.05), 3.3 (10.0 to 24.7) points on physical health in the physical summary component of the Spanish Short Form 12 (SF-12; p < 0.05) and 5.8 (8.6 to 34.7) points on the mental summary component of the SF-12 (p < 0.05), in favour of the DWR group. For patients with NSCLBP, the addition of DWR to GP was more effective in reducing pain and disability than standard GP alone, suggesting the effectiveness and acceptability of this approach with this group of patients.

  11. Gas hydrates (clathrates) causing pore-water freshening and oxygen isotope fractionation in deep-water sedimentary sections of terrigenous continental margins

    USGS Publications Warehouse

    Hesse, R.; Harrison, W.E.

    1981-01-01

    The occurrence of gas hydrates in deep-water sections of the continental margins predicted from anomalous acoustic reflectors on seismic profiles has been confirmed by recent deep-sea drilling results. On the Pacific continental slope off Guatemala gas hydrates were brought up for the first time from two holes (497, 498A) drilled during Leg 67 of the DSDP in water depths of 2360 and 5500 m, respectively. The hydrates occur in organic matter-rich Pleistocene to Miocene terrigenous sediments. In the hydrate-bearing zone a marked decrease in interstitial water chlorinities was observed starting at about 10-20 m subbottom depth. Pore waters at the bottom of the holes (near 400 m subbottom) have as little as half the chlorinity of seawater (i.e. 9???). Similar, but less pronounced, trends were observed during previous legs of the DSDP in other hydrate-prone segments of the continental margins where recharge of fresh water from the continent can be excluded (e.g. Leg 11). The crystallization of hydrates, like ice, excludes salt ions from the crystal structure. During burial the dissolved salts are separated from the solids. Subsidence results in a downward motion of the solids (including hydrates) relative to the pore fluids. Thawing of hydrates during recovery releases fresh water which is remixed with the pore fluid not involved in hydrate formation. The volume of the latter decreases downhole thus causing downward decreasing salinity (chlorinity). Hydrate formation is responsible for oxygen isotope fractionation with 18O-enrichment in the hydrate explaining increasingly more positive ??18O values in the pore fluids recovered (after hydrate dissociation) with depth. ?? 1981.

  12. Late Pleistocene and Holocene depositional trends, processes, and history of Astoria deep-sea fan, Northeast Pacific

    USGS Publications Warehouse

    Nelson, H.

    1976-01-01

    The asymmetrical Astoria Fan (110 ?? 180 km) developed off the Columbia River and Astoria submarine canyon during the Pleistocene. Morphology, stratigraphy, and lithology have been outlined for a Pleistocene turbidite, and a Holocene hemipelagic sedimentary regime to generate geologically significant criteria for comparison with ancient equivalent deposits. Both gray silty clay of the Late Pleistocene and olive-gray clay of the Early Holocene are interrupted by turbidites. The few deeply incised fan valleys of the more steeply sloping upper fan contain thick, muddy and very poorly sorted sand and gravel beds that usually have poorly developed internal sedimentary structures. The numerous shallower fan valleys and distributaries of the flatter middle and lower fan contain thick, clean, and moderately sorted medium to fine sands that are vertically graded in texture, composition and well-developed internal sedimentary structures. Tuffaceous turbidites (containing Mazama ash, 6600 B.P.) can be traced as thick deposits (ca. 30-40 cm) throughout the Astoria Channel system and as thin correlative interbeds (ca. 1-2 cm) in interchannel areas. Similarly, sand/shale ratios are high throughout the fan valleys and the middle and lower fan areas of distributaries, but are low in the upper-fan interchannel areas. These depositional trends indicate that high-density turbidity currents carry coarse traction loads that remain confined in upper but not lower fan valleys. Fine debris selectively sorts out from channelized flows into overbank suspension flows that spread over the fan and deposit clayey silt. A high content of mica, plant fragments, and glass shards (if present) characterizes deposits of the overbank flows, a major process in the building of upper fan levees and interchannel areas. In the Late Pleistocene, turbidity currents funneled most coarse-grained debris through upper channels to depositional sites in middle and lower fan distributaries that periodically shifted

  13. Satellite and airborne oil spill remote sensing: State of the art and application to the BP DeepWater Horizon oil spill

    USGS Publications Warehouse

    Leifer, I.; Clark, R.; Jones, C.; Holt, B.; Svejkovsky, J.; Swayze, G.

    2011-01-01

    The vast, persistent, and unconstrained oil release from the DeepWater Horizon (DWH) challenged the spill response, which required accurate quantitative oil assessment at synoptic and operational scales. Experienced observers are the mainstay of oil spill response. Key limitations are weather, scene illumination geometry, and few trained observers, leading to potential observer bias. Aiding the response was extensive passive and active satellite and airborne remote sensing, including intelligent system augmentation, reviewed herein. Oil slick appearance strongly depends on many factors like emulsion composition and scene geometry, yielding false positives and great thickness uncertainty. Oil thicknesses and the oil to water ratios for thick slicks were derived quantitatively with a new spectral library approach based on the shape and depth of spectral features related to C-H vibration bands. The approach used near infrared, imaging spectroscopy data from the AVIRIS (Airborne Visual/InfraRed Imaging Spectrometer) instrument on the NASA ER-2 stratospheric airplane. Extrapolation to the total slick used MODIS satellite visual-spectrum broadband data, which observes sunglint reflection from surface slicks; i.e., indicates the presence of oil and/or surfactant slicks. Oil slick emissivity is less than seawater's allowing MODIS thermal infrared (TIR) nighttime identification; however, water temperature variations can cause false positives. Some strong emissivity features near 6.7 and 9.7 ??m could be analyzed as for the AVIRIS short wave infrared features, but require high spectral resolution data. TIR spectral trends can allow fresh/weathered oil discrimination. Satellite Synthetic Aperture Radar (SSAR) provided synoptic data under all-sky conditions by observing oil dampening of capillary waves; however, SSAR typically cannot discriminate thick from thin oil slicks. Airborne UAVSAR's significantly greater signal-to-noise ratio and fine spatial resolution allowed

  14. Deep-Water Chemosynthetic Ecosystem Research during the Census of Marine Life Decade and Beyond: A Proposed Deep-Ocean Road Map

    PubMed Central

    German, Christopher R.; Ramirez-Llodra, Eva; Baker, Maria C.; Tyler, Paul A.

    2011-01-01

    The ChEss project of the Census of Marine Life (2002–2010) helped foster internationally-coordinated studies worldwide focusing on exploration for, and characterization of new deep-sea chemosynthetic ecosystem sites. This work has advanced our understanding of the nature and factors controlling the biogeography and biodiversity of these ecosystems in four geographic locations: the Atlantic Equatorial Belt (AEB), the New Zealand region, the Arctic and Antarctic and the SE Pacific off Chile. In the AEB, major discoveries include hydrothermal seeps on the Costa Rica margin, deepest vents found on the Mid-Cayman Rise and the hottest vents found on the Southern Mid-Atlantic Ridge. It was also shown that the major fracture zones on the MAR do not create barriers for the dispersal but may act as trans-Atlantic conduits for larvae. In New Zealand, investigations of a newly found large cold-seep area suggest that this region may be a new biogeographic province. In the Arctic, the newly discovered sites on the Mohns Ridge (71°N) showed extensive mats of sulfur-oxidisng bacteria, but only one gastropod potentially bears chemosynthetic symbionts, while cold seeps on the Haakon Mossby Mud Volcano (72°N) are dominated by siboglinid worms. In the Antarctic region, the first hydrothermal vents south of the Polar Front were located and biological results indicate that they may represent a new biogeographic province. The recent exploration of the South Pacific region has provided evidence for a sediment hosted hydrothermal source near a methane-rich cold-seep area. Based on our 8 years of investigations of deep-water chemosynthetic ecosystems worldwide, we suggest highest priorities for future research: (i) continued exploration of the deep-ocean ridge-crest; (ii) increased focus on anthropogenic impacts; (iii) concerted effort to coordinate a major investigation of the deep South Pacific Ocean – the largest contiguous habitat for life within Earth's biosphere, but also the

  15. Long-term, High Frequency, High Precision pH Measurements on the MBARI deep-water FOCE Experiment at the MARS Cabled Observatory in Monterey Bay, CA

    NASA Astrophysics Data System (ADS)

    Peltzer, E. T.; Maughan, T.; Barry, J. P.; Brewer, P. G.; Headley, K. L.; Herlien, R.; Kirkwood, W. J.; Matsumoto, G. I.; O'Reilly, T. C.; Salamy, K. A.; Scholfield, J.; Shane, F. F.; Walz, P. M.

    2012-12-01

    The MBARI deep-water FOCE experiment was deployed on the MARS cabled observatory in Monterey Bay on May 4th, 2011. It has been in continuous operation (excluding a few minor shore based power outages) ever since. During the fifteen months of deployment, we have been able to observe both the daily variation in pH in response to water mass movements associated with the semi-diurnal tides, internal waves and longer-term trends as a function of the seasonal variations in the water masses within the Monterey Bay Canyon. Our experimental site is located at 890 meters, just below the oxygen minimum for Monterey Bay, and we clearly see the anticipated inverse correlation between seawater temperature and pH. Daily variation in pH is on the order of 0.020-0.030 pH units with longer term trends adding an additional variation of similar magnitude. Instrumentation on this experiment included two CTDs with oxygen sensors (Sea-Bird 52). One CTD is mounted on the external FOCE framework to measure the background conditions, and one CTD is installed within the FOCE pH control area to monitor the experimentally manipulated conditions. In addition, 6 MBARI modified Sea-Bird 18 pH sensors were mounted on the FOCE apparatus. Four of these pH sensors monitored pH inside the experimental chamber and two monitored the external background seawater conditions. Although we originally intended to conduct several in situ CO2 enrichment experiments to study the impact of ocean acidification on the benthic biology and then recover the apparatus after one year, unanticipated changes in the ship schedule have left the FOCE experiment in place for nearly fifteen months at the time of this writing. Throughout this time period, all sensor data has been logged by the MBARI Shore-Side Data System (SSDS) resulting in the longest continuous record of high precision pH measurements in the intermediate water column. We present an analysis of the data obtained from this unique data set, and discuss our in

  16. Orbitally resolved records of Oligocene ice-sheet dynamics and deep-water chemistry from ODP Site 689 (Maud Rise, Weddell Sea)

    NASA Astrophysics Data System (ADS)

    Bohaty, Steven M.; Huck, Claire E.; Liebrand, Diederik; Röhl, Ursula; Wilson, Paul; van de Flierdt, Tina; Pälike, Heiko

    2016-04-01

    The early stages of the modern 'Icehouse' climate state first developed in the Oligocene following rapid global cooling and the onset of Antarctic glaciation at the Eocene-Oligocene Transition (34 Ma). However, the size and stability of the early Antarctic ice sheets that existed during the Oligocene under atmospheric CO2 levels higher than present day are poorly known. Here we report on an ongoing investigation of Oligocene (hemi)pelagic drillcores recovered at Ocean Drilling Program (ODP) Site 689, drilled on Maud Rise in the eastern Weddell Sea in late 1980s (Leg 113). Shipboard physical properties data were not routinely collected from pre-Quaternary cores at this site, and the lack of continuous composite sections and supporting data has previously been a considerable hindrance to high-resolution paleoceanographic studies. New high-resolution XRF scanning, discrete magnetic susceptibility, and benthic foraminiferal stable isotope records were collected from the upper Eocene-upper Oligocene interval of ODP Sites 689. The XRF datasets allow compositing of Holes 689B and 689D, which fortuitously contain offset cores throughout the sequence. Although condensed in two intervals, Site 689 contains a complete ~12-Myr record spanning Chron C17n.1n to Chron C8n.1n (~37 to 25 Ma). The composited records from Sites 689 exhibit prominent orbital-scale cyclicity in XRF-derived iron/calcium ratios, enabling development of an astronomical age model and detailed reconstruction of carbonate dissolution intensity of South Atlantic deep waters. These composited and well-dated records from Site 689 will, for the first-time, provide an Oligocene pelagic reference section for the Southern Ocean and serve as stratigraphic stepping stone between proximal Antarctic shelf records and high-resolution proxy records from lower latitude locations. Further development of high-resolution benthic foraminiferal and detrital neodymium isotope records at Site 689 will address the timing and

  17. Oil-material fractionation in Gulf deep water horizontal intrusion layer: Field data analysis with chemodynamic fate model for Macondo 252 oil spill.

    PubMed

    Melvin, A T; Thibodeaux, L J; Parsons, A R; Overton, E; Valsaraj, K T; Nandakumar, K

    2016-04-15

    Among the discoveries of the Deepwater Horizon blowout was the so-called "sub-surface plume"; herein termed the "oil-trapping layer". Hydrocarbons were found positioned at ~1100-1300m with thickness ~100-150m and moving horizontally to the SW in a vertically stratified layer at the junction of the cold abyssal water and the permanent thermocline. This study focuses on its formation process and fate of the hydrocarbons within. The originality of this work to the field is two-fold, first it provides a conceptual framework which places layer origin in the context of a horizontal "intrusion" from the near-field, vertical, blow-out plume and second, it offers a theoretical model for the hydrocarbon chemicals within the horizontal layer as it moves far-afield. The model quantifies the oil-material fractionation process for the soluble and fine particle. The classical Box model, retrofitted with an internal gradient, the "G-Box", allows an approach that includes turbulent eddy diffusion coupled with droplet rise velocity and reactive decay to produce a simple, explicit, transparent, algebraic model with few parameters for the fate of the individual fractions. Computations show the soluble and smallest liquid droplets moving very slowly vertically through the layer appearing within the trapping layer at low concentration with high persistence. The larger droplets move-through this trapping zone quickly, attain high concentrations, and eventually form the sea surface slick. It impacts the field of oil spill engineering science by providing the conceptual idea and the algorithms for projecting the quantities and fractions of oil-material in a deep water, horizontal marine current being dispersed and moving far afield. In the field of oil spill modeling this work extends the current generation near-field plume source models to the far-field. The theory portrays the layer as an efficient oil-material trap. The model-forecasted concentration profiles for alkanes and aromatics

  18. Benthic foraminifera from the deep-water Niger delta (Gulf of Guinea): Assessing present-day and past activity of hydrate pockmarks

    NASA Astrophysics Data System (ADS)

    Fontanier, C.; Koho, K. A.; Goñi-Urriza, M. S.; Deflandre, B.; Galaup, S.; Ivanovsky, A.; Gayet, N.; Dennielou, B.; Grémare, A.; Bichon, S.; Gassie, C.; Anschutz, P.; Duran, R.; Reichart, G. J.

    2014-12-01

    We present ecological and isotopic (δ18O and δ13C) data on benthic foraminifera sampled from 4 deep-sea stations in a pockmark field from the deep-water Niger delta (Gulf of Guinea, Equatorial Atlantic Ocean). In addition, a series of sedimentological and (bio)geochemical data are shown to back up foraminiferal observations. All stations are located within 1.2 km of each other, so prevailing oceanographic conditions can be assumed to be similar at each site. Two of the sites (GMMC-01 and GMMC-02) are located in a pockmark (named "pockmark A") where current methane seepages were recorded by ROV observations. A third station (GMMC-03) is located in the topographic depression interpreted as a collapsed pockmark (named "pockmark B"). The fourth site (GMMC-04) is a reference station, without evidence of past or present seepages. Our observations show that degraded organic matter with low bio-availability is present at all stations with a preferential burial of organic compounds in topographic depressions (GMMC-03 station). Authigenic aragonite is abundant in surface sediments at stations GMMC-01 and -02. Its precipitation is likely related to high rates of methane oxidation during past seep events in episodically active pockmark A. In contrast, the absence of anaerobic methanotrophic Archaea (ANME) during the sampling period (November 2011) suggests that only moderate sulphide and methane oxidation take place close to the sediment-water interface. Compared to the reference site GMMC-04, living foraminifera at the collapsed and episodically active pockmarks show minor changes in terms of diversity, standing stocks and faunal composition. However, the δ13C signal of living and dead (but well-preserved) foraminiferal species (Ceratobulimina contraria, Melonis barleeanus, Uvigerina peregrina) is depleted in the episodically active pockmark A compared to the other stations. Overgrowth of authigenic carbonate on altered foraminifera generates an important shift to lower

  19. Tectonic vs. eustatic controls on Ordovician deposition in the Alabama Appalachians

    SciTech Connect

    Benson, D.J. . Dept. of Geology)

    1992-01-01

    The Lower Ordovician section consists of a thick (> 1,500 ft.) sequence of peritidal to shallow subtidal carbonates deposited on a broad, stable platform. Initial Taconic orogenic activity during Late Canadian time downwarped the southeastern margin of the continent and resulted in deposition of a unique subtidal unit. A fall in eustatic sea level during Early Whiterockian time exposed the majority of the platform and produced the Post-Knox unconformity, a major regional unconformity that truncates Upper Cambrian-Lower Ordovician carbonates across the Alabama Appalachians. Middle Ordovician deposition began as a result of eustatic sea level rise and continued downwarping of the SE margin of the North American continent. Initial Middle Ordovician deposits are peritidal carbonates that onlap the Post-Knox unconformity from SE to NW. Continued loading of the margin of the continent led to formation of a deep-water basin to the SE and the concurrent development of a peripheral bulge in the vicinity of what is now the Birmingham anticlinorium. Peritidal carbonates to the SE pass upward into shallow ramp carbonates, deep-ramp mixed carbonate/clastic deposits, and, finally, basinal organic shales. As the deep-water basin evolved, shallow ramp carbonates onlapped the peripheral bulge to the NW. The rapidly evolving basin trapped terrigeneous deposits shed from tectonic highlands to the E and SE permitting deposition of shallow to deep ramp, skeletal carbonates to the NW. Continued tectonic loading led to migration and the ultimate inundation of the peripheral bulge. By Late Mohawkian time, filling of the basin allowed terrigeneous sediments derived from the tectonic highlands to prograde westward, onlap and carbonate ramp, and, finally, terminate carbonate deposition.

  20. Changes in Sediment Provenance to the Southeast Newfoundland Ridge from the late Eocene to the Early Oligocene; Northern Hemisphere Glaciation or Deep Water Circulation?

    NASA Astrophysics Data System (ADS)

    Scher, H. D.; Romans, B.; Moffett, Z. J.; Buckley, W. P.; Gibson, K.

    2013-12-01

    continents. There is not a long term trend nor prominent inflections in the fossil fish tooth ɛNd record that are associated with terrigenous ɛNd values so it does not appear likely that changes in sediment provenance were accompanied by a reorganization of deep water masses. Thus the preliminary results are cautiously interpreted as reflecting a sedimentological response to an overall increase in weathering/erosion of ancient continental crust, possibly on Greenland, over the investigated interval. In this context these results may reflect the emplacement of northern hemisphere ice sheets in the latest Eocene, preceded by prominent short-lived glacial events in the Eocene. The first short-lived event falls within polarity chron C17n.1n, which corresponds with the timing of a known Eocene glaciation on Antarctica and suggests that the greenhouse climate in the late Eocene supported a bipolar glacial event. We are currently generating a record of relative paleo-bottom current intensity from U1411 using the sortable silt proxy to further evaluate the role of bottom currents in terrigenous sediment provenance on the SENR.

  1. Depositional systems and petroleum potential, Mesaverde Formation southeastern Wind River basin, Wyoming

    SciTech Connect

    Hippe, D.J.; Needham, D.W.; Ethridge, F.G.

    1986-08-01

    Depositional environments and systems of the Wind River basin Mesaverde Formation were interpreted from an analysis of outcrops along the Casper arch and Rattlesnake Hills anticline and cores and wireline logs from the adjacent subsurface. The Fales Sandstone and Parkman Sandstone/unnamed middle member are deposits of eastward progradational, wave-dominated strand-plain and deltaic complexes. Basal portions of the Fales Sandstone and the Parkman Sandstone are composed of a thickening- and coarsening-upward sandstone sequence whose facies represent storm-dominated inner-shelf and wave-dominated shore-zone environments. Facies sequences in the upper Fales Sandstone interval and the unnamed middle member are interpreted as deposits of lower coastal plain (marshes, bay fills, distributary channels, and crevasse splays) and upper coastal plain (alluvial channels, crevasse splays and fine-grained flood basin) sequences. The Teapot Sandstone is interpreted as an alluvial deposit. Analysis of facies sequences in the Teapot suggests a change in fluvial style, from braided-belt deposits along the southwest flank to meander-belt deposits along the northeast flank of the basin. These fluvial systems fed the Teapot deltas to the east. Stratigraphic plays for oil and gas include alluvial valley fills and point-bar deposits in the Teapot Sandstone, storm-dominated shelf sands in the upper Cody Shale and the Fales and Parkman Sandstones, and a transgressive barrier-bar sequence in the upper Fales Sandstone. Laterally continuous shore-zone sandstones may form combination traps where pinch-outs occur on structure.

  2. Deep-water lithofacies and conodont faunas of the Lisburne Group, western Brooks Range, Alaska: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1992

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, Anita G.; Schmidt, Jeanine M.

    1993-01-01

    Deep-water lithofacies of the Lisburne Group occur in thrust sheets in the western part of the foreland fold and thrust belt of the Brooks Range and represent at least three discrete units. The Kuna Formation (Brooks Range allochthon) consists mostly of spiculitic mudstone and lesser shale; subordinate carbonate layers are chiefly diagenetic dolomite. Predominantly shale sections of the Kuna that contain few sponge spicules occur in the western part of the study area. The Akmalik Chert (Picnic Creek allochthon) is mostly radiolarian-spiculitic chert; rare limy beds are calcitized radiolarite. The Rim Butte unit (Ipnavik River allochthon) consists chiefly of calcareous turbidites, derived from both shallow- and deep-water sources, interbedded with spiculitic mudstone. Much of the material in the turbidites came from a contemporaneous carbonate platform and margin, but some fossils and lithic clasts were eroded from older, already lithified carbonate-platform rocks. All three units appear to be roughly coeval and are chiefly Osagean (late Early Mississippian) in age in the study area.Shallow-water lithofacies of the Lisburne Group exposed in the Howard Pass area (Brooks Range allochthon) are mostly of Meramecian (early Late Mississippian) age. Thus, these carbonate-platform rocks were not the source of the calcareous turbidites in the Rim Butte unit. Rim Butte turbidites could have been derived from older platform carbonate rocks such as those of the Utukok Formation (Kelly River allochthon) exposed mainly to the west of the Howard Pass quadrangle.

  3. Growth pattern research on the modern deposition of Ganjiang delta in Poyang lake basin by spatio-temporal remote sensing images

    NASA Astrophysics Data System (ADS)

    Zhou, Hongying; Yuan, Xuanjun; Zhang, Youyan; Dong, Wentong; Liu, Song

    2016-11-01

    It is of great importance for petroleum exploration to study the sedimentary features and the growth pattern of shoal water deltas in lake basins. Taking spatio-temporal remote sensing images as the principal data source, combined with field sedimentation survey, a quantitative research on the modern deposition of Ganjiang delta in the Poyang Lake Basin is described in this paper. Using 76 multi-temporal and multi-type remote sensing images acquired from 1973 to 2015, combined with field sedimentation survey, remote sensing interpretation analysis was conducted on the sedimentary facies of the Ganjiang delta. It is found that that the current Poyang Lake mainly consists of three types of sand body deposits including deltaic deposit, overflow channel deposit, and aeolian deposit, and the distribution of sand bodies was affected by the above three types of depositions jointly. The mid-branch channels of the Ganjiang delta increased on an exponential growth rhythm. The main growth pattern of the Ganjiang delta is dendritic and reticular, and the distributary channel mostly arborizes at lake inlet and was reworked to be reticulatus at late stage.

  4. Cretaceous shelf-sea chalk deposits

    SciTech Connect

    Hattin, D.E.

    1988-01-01

    The word ''chalk'' is linked etymologically to the Cretaceous, but chalky facies neither dominate that system nor are confined to it. As used commonly, the term ''chalk'' refers to a variety of marine limestone that is white to light gray very fine grained, soft and friable, porous, and composed predominantly of calcitic skeletal remains, especially those derived from coccolithophores. No simple definition suffices to embrace all Cretaceous chalks, which include sandy, marly, shelly, phospatic, glauconitic, dolomitic, pyritic and organic-rich lithotypes. Most of the world's exposed Cretaceous chalk deposits were formed at shelf depths rather than in the deep sea. Cretaceous shelf-sea chalks are developed most extensively in northern Europe, the U.S. Gulf Coastal Plain and Western Interior, and the Middle East, with lesser occurrences alo in Australia. Most Cretaceous shelf-sea chalks formed in the temperature zones, and in relatively deep water. Cretaceous chalks deposited on well-oxygenated sea floors are bioturbated and massive where deficient in terrigenous detritus, or bioturbated and rhythmically interbedded with argillaceous units where influx of terrigenous detritus varied systematically with climate changes. Accumulation of sufficient pelagic mud to form vast deposits of Cretaceous shelf-sea chalk required (1) sustained high productivity of calareous plankton, (2) extensive development of stable shelf and continental platform environments, (3) highstands of seal level, (4) deficiency of aragonitic skeletal material in chalk-forming sediments, and (5) low rates of terrigenous detrital influx. These conditions were met at different times in different places, even within the same general region.

  5. Influence of climate on deep-water clastic sedimentation: application of a modern model, Peru-Chile Trough, to an ancient system, Ouachita Trough

    USGS Publications Warehouse

    Edgar, N. Terence; Cecil, C. Blaine

    2003-01-01

    Traditionally, an abrupt and massive influx of siliciclastic sediments into an area of deposition has been attributed to tectonic uplift without consideration of the influence of climate or climatic change on rates of weathering, erosion, transportation, and deposition. With few exceptions, fluvial sediment transport is minimal in both extremely arid climates and in perhumid (everwet) climates. Maximum sediment transport occurs in climates characterized by strongly seasonal rainfall, where the effect of vegetation on erosion is minimal. The Peru–Chile trench and Andes Mountain system (P–CT/AMS) of the eastern Pacific Ocean clearly illustrates the effects of climate on rates of weathering, erosion, transport, and deep-sea sedimentation. Terrigenous sediment is virtually absent in the arid belt north of lat. 30° S in the P–CT, but in the belt of seasonal rainfall south of lat. 30° S terrigenous sediment is abundant. Spatial variations in the amount and seasonality of annual precipitation are now generally accepted as the cause for this difference. The spatial variation in sediment supply to the P–CT appears to be an excellent modern analogue for the temporal variation in sediment supply to certain ancient systems, such as the Ouachita Trough in the southern United States. By comparison, during the Ordovician through the early Mississippian, sediment was deposited at very slow rates as the Ouachita Trough move