Geochemistry of recent marine sediments, interstitial water, and sea water from the West African continental margin

Carbon dioxide, ammonia, and reactive phosphate in the interstitial water of three sediment cores of the West African continental margin result from oxidation of sedimentary organic matter by bacterial sulfate reduction. The proposed model is a modification of one initially suggested by Richards (1965) for processes in anoxic waters: (CH2O)106 (NH3)8 (H3PO4) (0.7-0.2) + 53 SO4**2- =106 CO2 + 106 H20 + 8 NH3 + (0.7 - 0.2) H3PO4 + 53 S**2- The amount of reduced interstitial sulfate, the carbon-to-nitrogen-to-phosphorus atomic ratio of the sedimentary organic matter, as well as small amounts of carbon dioxide, which precipitated as interstitial calcium carbonate, are included in the general oxidation-reduction reaction. Preferential loss of nitrogen and phosphorus from organic matter close to the surface was recorded in both the interstitial water and sediment composition. It appeared that in deeper sections of the core organic carbon compounds were oxidized which were probably in an even lower oxidation state than that indicated by the proposed model. An estimated 2 % of the amount of organic matter still present was oxidized after it became incorporated into the sediment; whereas sulfide sulfur contents indicate that a much larger percentage (15-20%) seemed to have been subject to bacterial oxidation during the Pleistocene period, when a very thin oxidizing layer on the sediment allowed the above decomposition process to start relatively early favoured by almost fresh organic matter, and by almost unrestricted exchange of sulfate with the overlying water.

Sedimentology on cores off Filchner Shelf Ice, Weddell Sea, Antarctica

Sediment sampling with box corer and gravity corer was conducted along a profile parallel to the Filchner/Rønne Ice Shelf, from 48° to 61°W. Twenty-two sampling locations were determined after evaluation of 12 and 3.5 kHz sub-bottom profiling records. The sediment retrievals show a wide diversity, varying from very well sorted pure sands in the SE of the profile to heavily glacially influenced, pebbly muds close to the foot of the Antarctic Peninsula. In the middle part of the profile mainly soft sediments of muddy to sandy muds were found which were partially influenced by glacially derived dropstones or accumulations of pebble-sized material. The striking changes of surface sediments (marine to glacial) observed along the profile led to an attempt to investigate the concurrence of marine and glacial depositional processes controlling the accumulation of these recent sediments.

Marine palynomorph abundance estimates of sediment core CRP-2A (Fig. 2)

A diverse assemblage of marine palynomorphs was recovered from the Oligocene - Miocene section of CRP-2/2A. Most of the assemblage is composed of previously unrecognised species. Three distinct groups of marine palynomorph were recognised: (1) prasinophytes, mainly Cymatiosphaera, (2) acritarchs, mainly Leiosphaeridia and Sigmopollis although Leiofusa is an important component of the bottom half of the hole, and (3) dinoflagellate cysts. About 27 species of in situ dinoflagellate cysts were recorded, of which seven apparently undescribed species of Lejeunecysta form a prominent component. Reworked specimens of several species of the Paleogene Transantarctic Flora occur in CRP-2/2A sediments. Several abundance peaks of reworked taxa from the Transantarctic Flora are recorded. Three marine palynomorph zones were recognised (MP3, MP2, MP1), considered to be early Oligocene, late Oligocene, and late Oligocene/early Miocene in age respectively. Samples from the Quaternary and Pliocene part of CRP-2/2A were also examined. These proved either barren or yielded very sparse low diversity floras.

Clay mineralogy and shear strength of subglacial and glaciomarine sediments in the southern Bellingshausen Sea

The Belgica Trough and the adjacent Belgica Trough Mouth Fan in the southern Bellingshausen Sea (Pacific sector of the Southern Ocean) mark the location of a major outlet for the West Antarctic Ice Sheet during the Late Quaternary. The drainage basin of an ice stream that advanced through Belgica Trough across the shelf during the last glacial period comprised an area exceeding 200,000 km**2 in the West Antarctic hinterland. Previous studies, mainly based on marine-geophysical data from the continental shelf and slope, focused on the bathymetry and seafloor bedforms, and the reconstruction of associated depositional processes and ice- drainage patterns. In contrast, there was only sparse information from seabed sediments recovered by coring. In this paper, we present lithological and clay mineralogical data of 21 sediment cores collected from the shelf and slope of the southern Bellingshausen Sea. Most cores recovered three lithological units, which can be attributed to facies types deposited under glacial, transitional and seasonally open-marine conditions. The clay mineral assemblages document coinciding changes in provenance. The relationship between the clay mineral assemblages in the subglacial and proglacial sediments on the shelf and the glacial diamictons on the slope confirms that a grounded ice stream advanced through Belgica Trough to the shelf break during the past, thereby depositing detritus eroded in the West Antarctic hinterland as soft till on the shelf and as glaciogenic debris flows on the slope. The thinness of the transitional and seasonally open-marine sediments in the cores suggests that this ice advance occurred during the last glacial period. Clay mineralogical, acoustic sub-bottom and seismic data furthermore demonstrate that the palaeo-ice stream probably reworked old sedimentary strata, including older tills, on the shelf and incorporated this debris into its till bed. The geographical heterogeneity of the clay mineral assemblages in the sub- and proglacial diamictons and gravelly deposits indicates that they were eroded from underlying sedimentary strata of different ages. These strata may have been deposited during either different phases of the last glacial period or different glacial and interglacial periods. Additionally, the clay mineralogical heterogeneity of the soft tills recovered on the shelf suggests that the drainage area of the palaeo-ice stream flowing through Belgica Trough changed through time.

Dyfamed-benthos time series observations

In 1990, a benthic component to the DYFAMED (dynamics of fluxes in the Mediterranean) program, the DYFAMED-BENTHOS survey, was established to investigate the possible coupling of benthic to pelagic processes at a permanent station in >2700 m water depth, 52 km off Nice, France. Surface sediment was first sampled at different periods of the year to assess the importance of the biological compartment (particularly metazoan meiofauna) and its relation to seasonally varying particulate matter input to the sea floor (estimated by measuring surface sediment particle size and porosity, as well as chloroplastic pigments, organic carbon, nitrogen and calcium carbonate contents). Beginning in 1993, surface sediment was sampled at an average interval of 1.4 months for over five consecutive years using multicorers. Biogeochemical techniques such as deployments of a free-vehicle benthic respirometer and a near-bottom sediment trap, along with analyses of sediment vertical profiles for dissolved oxygen, nutrients and dissolved metals in the porewater, were developed in conjunction with more extensive biological analyses to characterize the recycling of organic matter, and ultimately increase our understanding of the oceanic carbon cycle. This article provides the scientific background and motivation for the development of the on-going DYFAMED-BENTHOS survey, the general characteristics of the benthic site, as well as a detailed description of the sampling design applied from late 1990-2000.

Results of an in situ stable isotope labeling study in intertidal sediment

We report the results of an in situ tracer experiment in an intertidal sediment, where bacterial carbon was tagged with stable carbon-isotope label, after the injection of 13C-glucose. The appearance of label in bacteria (based on label incorporation in bacteria-specific, phospholipid-derived fatty acids) and subsequent transfer to meiobenthos (group level) and macrobenthos (species level) was followed for 36 days. The label dynamics of benthic taxa were either fitted with a simple-isotope model or evaluated against enrichment in bacteria, to derive the importance of bacterially derived carbon for the meiobenthos and macrobenthos. Although selective uptake of bacteria was evident, as 2.4 times more bacterial carbon was grazed as expected from indiscriminate feeding, bacterial carbon accounted on average for only 0.08 and 0.11 of the carbon requirements of meiobenthic and macrobenthic taxa, respectively. Additionally, the contribution of bacterial carbon to total carbon requirements did not depend on the living/feeding depth in the sediment or organism size (evaluated over a size range of four orders of magnitude). The observed overall low contribution of bacterial carbon implies that most intertidal benthic fauna depend primarily on other carbon resources that may assert a stronger control on the structure of intertidal-sediment communities.

Benthic fauna of an offshore borrow area in Broward County, Florida /

Benthic fauna from two stations within a 5-year-old borrow area and two control stations off Hillsboro Beach (Broward County), Florida, were sampled quarterly from June 1977 to March 1978 to evaluate the long-term impact of offshore dredging. Generally enhanced productivities occurred within the borrow area, although there was much seasonal variation among stations. Species diversities were usually higher at the borrow stations than at the control stations. The single exception was due to a high concentration of the bivalve E. nitens at one of the control stations in June. Although faunal similarity analysis revealed a qualitative change in the fauna of the borrow area, this change is not considered detrimental. Conspicuous patterns of heterogeneous faunal distributions were evident in this study, particularly for the bivalve E. nitens. No lasting detrimental effects, in terms of numbers of species, faunal densities, or species diversity, resulted from the dredging operation. (Author).

Regional geology of the southern Lake Erie (Ohio) bottom : a seismic reflection and vibracore study /

"December 1982."

Effects of dredging and disposal on some benthos at Monterey Bay, California /

"October 1976."

Technical manual, unit maintenance : truck, utility, cargo/troop carrier, 1-1/4 ton, 4x4, M998 (2320-01-107-7155) ... truck, ambulance, 2-litter, soft top, 4x4, M1035 (2310-01-146-7194).

Includes index.

Unit maintenance repair parts and special tools list for truck, utility, cargo/troop carrier, 1-1/4 ton, 4x4, M998 (2320-01-107-7155) ... truck, ambulance, 2-litter, soft top, 4x4, M1035 (2310-01-146-7194).

"August 1991."

Direct support and general support maintenance [microform] : truck, utility, cargo/troop carrier, 1-1/4 ton, 4x4, M998 (2320-01-107-7155) ... truck, ambulance, 2-litter, soft top, 4x4, M1035 (2310-01-146-7194); M1035A1 (2310-01-371-9585).

"August 1991."