Upper Cenozoic dinoflagellate cysts from the continental slope and rise off New Jersey

This report contains the occurrence data for dinoflagellate cysts recorded from 163 samples taken from Sites 902 through 906, during Ocean Drilling Program (ODP) Leg 150. The dinoflagellate cyst (dinocyst) stratigraphy has been presented in Mountain, Miller, Blum, et al. (1994, doi:10.2973/odp.proc.ir.150.1994), and was based on these data. This report provides the full dinocyst data set supporting the dinocyst stratigraphic interpretations made in Mountain, Miller, Blum, et al. (1994). For Miocene shipboard dinocyst stratigraphy, I delineated 10 informal zones: pre-A, and A through I, in ascending stratigraphic order. These zones are defined in Shipboard Scientific Party (1994a, doi:10.2973/odp.proc.ir.150.103.1994), and are based on my studies of Miocene dinocyst stratigraphy in the Maryland and Virginia coastal plain (de Verteuil and Norris, 1991, 1992; de Verteuil, 1995). This zonation has been slightly revised (de Verteuil and Norris, 1996), and the new formal zone definitions are repeated below. Each new zone has an alpha-numeric abbreviation starting with "DN" (for Dinoflagellate Neogene). The equivalence between the informal zones reported in Mountain, Miller, Blum, et al. (1994), and the new DN zones is illustrated in Figure 1. For clarity, I delineated both zonations in the range charts that accompany this report (Tables 1-6). De Verteuil and Norris (1996a), using these and other data, correlated the DN zonation with the geological time scale of Berggren et al. (1995). Figure 2 summarizes these correlations and can be used to check the chronostratigraphic position of samples in this report, as determined by dinocyst stratigraphy. A thorough discussion of the basis for, and levels of uncertainty associated with, these correlations to the Cenozoic time scale can be found in de Verteuil and Norris (1996a). The Appendix lists all the dinocyst taxa recorded during shipboard analyses of Leg 150 samples. Open nomenclature is used for undescribed taxa. The range charts and Appendix also include reference to several new taxa that de Verteuil and Norris (1996b) described from Miocene coastal plain strata in Maryland and Virginia. Names of these taxa in Tables 1 through 6 and in the Appendix of this report are not intended for effective publication as defined in the International Code of Botanical Nomenclature (ICBN, Greuter et al., 1994). Therefore, taxonomic nomenclature contained in this report is not to be treated as meeting the conditions of effective and valid publication (ICBN; Article 29).

Geochemistry of continental slope and deep sea basin sediments off Uruguay

Pore water and solid phase from surface sediments of the continental slope off Uruguay and from the Argentine Basin (southwestern Atlantic) were investigated geochemically to ascribe characteristic early diagenetic reactions of iron and manganese. Solid-phase iron speciation was determined by extractions as well as by Mössbauer spectroscopy. Both methods showed good agreement (<6% deviation) for total-Fe speciation. The proportion of easy reducible iron oxyhydroxide relative to total-Fe oxides decreased from the continental slope to the deep sea which is attributed to an increase in crystallinity during transport as well as to a general decrease of iron mobilization. The product of iron reoxidation is Fe oxyhydroxide which made up less than 5% of total Fe. In addition to this fraction, a proportion of smectite bound iron was found to be redox reactive. This fraction made up to 10% of total Fe in sediments of the Argentine Basin and was quantitatively extracted by 1 N HCl. The redox reactive Fe(+II) fraction of smectite was almost completely reoxidized within 24 h under air atmosphere and may therefore considerably contribute to iron redox cycling if bioturbation occurs. In the case of the slope sediments we found concurrent iron and manganese release to pore water. It is not clear whether this is caused by dissimilatory iron and manganese reduction at the same depth or dissimilatory iron reduction alone inducing Mn(+IV) reduction by (abiotic) reaction with released Fe2+. The Argentine Basin sediment showed a significant manganese solid-phase enrichment above the denitrification depth despite the absence of a distinct pore-water gradient of Mn. This implies a recent termination of manganese mobilization and thus a non-steady-state situation with respect to sedimentation or to organic carbon burial rate.

Stable isotope ratios of foraminifera from the continental shelf off Troms, Northern Norway

A stable oxygen and carbon isotope stratigraphy is established for a Late Weichselian/Holocene glaciomarine/marine seguence in Andfjorden and Malangsdjupet on the continental shelf off Troms, Northern Norway. The stratigraphy demonstrates that the global signals, Termination I B and possibly also I A (upper parts), are present and radiocarbon date to 10.3-9.7 kyr B.P. and >14-13.5 kyr B.P., respectively. A temperature increase of 5°-6°C and possibly a small salinity increase occurred during Term. I. A near-glacial environment between 13 and 14 kyr B.P. was characterized by poorly ventilated bottom waters followed by a meltwater pulse at circa 13 kyr B.P. During the beginning intrusion of Atlantic Water between 13 and 10 kyr B.P., the bottom water was characterized by somewhat fluctuating temperatures and salinities. Temperatures close to those of the present were established around 9.7 kyr B.P. and seem to have been rather stable since.

Calcium carbonate, isotopes and Rock-Eval pyrolysis at DSDP Holes 77-535 and 77-540

At DSDP Sites 534 (Central Atlantic) and 535 and 540 (Gulf of Mexico), and in the Vocontian Basin (France), Lower Cretaceous deposits show a very pronounced alternation of limestone and marl. This rhythm characterizes the pelagic background sedimentation and is independent of detritic intercalations related to contour and turbidity currents. Bed-scale cycles, estimated to be 6000-26,000 yr. long, comprise major and minor units. Their biological and mineralogic components, burrowing, heavy isotopes C and O, and some geochemical indicators, vary in close correlation with CaCO3 content. Vertical changes of frequency and asymmetry of the cycles are connected with fluctuations of the sedimentation rate. Plots of cycle thickness ("cyclograms") permit detailed correlations of the three areas and improve the stratigraphic subdivision of Neocomian deposits at the DSDP sites. Small-scale alternations, only observed in DSDP cores, comprise centimetric to millimetric banding and millimetric to micrometric lamination, here interpreted as varvelike alternations between laminae that are rich in calcareous plankton and others rich in clay. The laminations are estimated to correspond to cycles approximately 1,3, and 13 yr. in duration. The cyclic patterns appear to be governed by an interplay of continental and oceanic processes. Oceanic controls express themselves in variations of the biogenic carbonate flux, which depends on variations of such elements as temperature, oxygenation, salinity, and nutrient content. Continental controls modulate the influxes of terrigenous material, organic matter, and nutrients derived from cyclic erosion on land. Among the possible causes of cyclic sedimentation, episodic carbonate dissolution has been ruled out in favor of climatic fluctuations with a large range of periods. Such fluctuations are consistent with the great geographic extension shown by alternation controls and with the continuous spectrum of scales that characterizes limestone-marl cycles. The climatic variations induced by the Earth's orbital parameters (Milankovitch cycles) could be connected to bed-interbed alternations.

Composition of volcanic rocks from the Alchan Basin, Northwestern Primorie

Geological, petrochemical, and geochemical data are reported for volcanic rocks of a Cretaceous pull-apart basin in the Tan Lu strike-slip system, Asian continental margin. A comparison of these volcanic rocks with magmatic rocks from typical Cenozoic transform margins in the western North America and rift zones of Korea made it possible to distinguish some indicator features of transform-margin volcanic rocks. Magmatic rocks from strike-slip extension zones bear island-arc, intraplate, and occasionally depleted MORB geochemical signatures. In addition to calc-alkaline rocks there are bimodal volcanic series. The rocks are characterized by high K2O, MgO, and TiO2 contents. They show variable enrichment in LILE relative to HFSE, which is typical of island-arc magmas. At the same time they are rich in compatible transition elements, which is a characteristic of intraplate magmas. Trace element distribution patterns normalized to MORB or primitive mantle usually show a negative Ta-Nb anomaly typical of suprasubduction settings. Their Ta/Nb ratio is lower, whereas Ba/Nb, Ba/La, and La/Yb ratios are higher than those of some MORB and OIB. In terms of trace element systematics, for example, Ta-Th-Hf, Ba/La-(Ba/La)_n, (La/Sm)_n-La/Hf, and others, they fall within the area of mixing of magmas from several sources (island arc, intraplate, and depleted reservoirs). Magmatic rocks of transform settings show a sigmoidal chondrite-normalized REE distribution pattern with a negative slope of LREE, depletion in MREE, and an enriched or flat HREE pattern. Magmas with mixed geochemical characteristics presumably originated in a transform margin setting in local extension zones under influence of mantle diapirs, which caused metasomatism and melting of the lithosphere at different levels, and mixing of melts from different sources in variable proportions.

Benthic respiration and physical oceanography on two contrasting continental margins in the western Indian Ocean: the Yemen-Somali upwelling region and the margin off Kenya

During the Netherlands Indian Ocean Project (NIOP, 1992-1993) sediment community oxygen consumption (SCOC) was measured on two continental margins in the Indian Ocean with different productivity: the productive upwelling region off Yemen-Somalia and the supposedly less productive Kenyan margin, which lacks upwelling. The two margins also differ in terms of river input (Kenya) and the more severe oxygen minimum in the Arabian Sea. Simultaneously with SCOC, distributions of benthic biomass and phytodetritus were studied. Our expectation was that benthic processes in the upwelling margin of the Arabian Sea would be relatively enhanced as a result of the higher productivity. On the Kenyan margin, SCOC (range 1-36 mmol/m**2/d) showed a clear decrease with increasing water depth, and little temporal variation was detected between June and December. Highest SCOC values of this study were recorded at 50 m depth off Kenya, with a maximum of 36 mmol/m**2/d in the northernmost part. On the margin off Yemen-Somalia, SCOC was on average lower and showed little downslope variation, 1.8-5.7 mmol/m**2/d, notably during upwelling, when the zone between 70 and 1700 m was covered with low O2 water (10-50 µM). After cessation of upwelling, SCOC at 60 m depth off Yemen increased from 5.7 to 17.6 mmol/m**2/d concurrently with an increase of the near-bottom O2 concentration (from 11 to 153 µM), suggesting a close coupling between SCOC and O2 concentration. This was demonstrated in shipboard cores in which the O2 concentration in the overlying water was raised after the cores were first incubated under in situ conditions (17 µM O2). This induced an immediate and pronounced increase of SCOC. Conversely, at deeper stations permanently within the oxygen minimum zone (OMZ), SCOC showed little variation between monsoon periods. Hence, organic carbon degradation in sediments on a large part of the Yemen slope appears hampered by the oxygen deficiency of the overlying water. Macrofauna biomass and the pooled biomass of smaller organisms, estimated by the nucleic acid content of the sediment, had comparable ranges in the two areas in spite of more severe suboxic conditions in the Arabian Sea. At the Kenyan shelf, benthic fauna (macro- and meiofauna) largely followed the spatial pattern of SCOC, i.e. high values on the northern shelf-upper slope and a downslope decrease. On the Yemen-Somali margin the macrofauna distribution was more erratic. Nucleic acids displayed no clear downslope trend on either margin owing to depressed values in the OMZ, perhaps because of adverse effects of low O2 on small organisms (meiofauna and microbes). Phytodetritus distributions were different on the two margins. Whereas pigment levels decreased downslope along the Kenya margin, the upper slope off Yemen (800 m) had a distinct accumulation of mainly refractory carotenoid pigments, suggesting preservation under low 02. Because the accumulations of Corg and pigments on the Yemen slope overlap only partly, we infer a selective deposition and preservation of labile particles on the upper slope, whereas refractory material undergoes further transport downslope.

Mineral and chemical composititon of sediments from ODP Hole 119-740A

ODP Hole 740A is located on the inner part of the East Antarctic continental shelf in Prydz Bay, at the seaward end of a major onshore rift structure known as the Lambert Graben. Drilling at this site led to the recovery of some 65 m of continental sediments (Prydz Bay red beds) that form part of a much thicker (2-3 km) pre-continental breakup sequence, the development of which may be related to the initiation and rifting of the Lambert Graben. Palynological and paleomagnetic studies have not been able to determine the age of the sediments; they may be equivalent to the onshore late Permian Amery Group or younger. The succession consists predominantly of sandstone, siltstone, and claystone arranged in erosively based, pedogenically influenced fining-upward sequences up to 5 m thick. These were deposited by shallow, braided streams draining an extensively vegetated alluvial plain, with sufficient topographic relief to trap fine-grained sediment and inhibit rapid channel shifting. Pedogenic processes were initiated on the alluvial plain, but climatic conditions were generally unsuitable for extensive pedogenic carbonate formation and the development of mature soil profiles. The sediments were probably derived from a rapidly uplifted fault block terrain composed of upper Proterozoic and Archaean gneisses lying to the southeast of the depositional site. Uplift may have taken place along the tectonically active seaward extension of the eastern faulted margin of the Lambert Graben, which passes immediately southeast of Hole 740A. Differences in mineralogical composition between the Amery Group and the Prydz Bay red beds probably reflect differences in rock composition in the source area. The age of the Prydz Bay red beds has still to be resolved.

Rocks of the Western Kamchatka-Koryak continental margin volcanogenic belt: age, chemical and mineral compositions

An isotope-geochemical study of Eocene-Oligocene magmatic rocks from the Western Kamchatka-Koryak volcanogenic belt revealed lateral heterogeneity of mantle magma sources in its segments: Western Kamchatka, Central Koryak, and Northern Koryak ones. In the Western Kamchatka segment magmatic melts were generated from isotopically heterogeneous (depleted and/or insignificantly enriched) mantle sources significantly contaminated by quartz-feldspathic sialic sediments; higher 87Sr/86Sr (0.70429-0.70564) and lower 143Nd/144Nd [eNd(T) = 0.06-2.9] ratios in volcanic rocks from the Central Koryak segment presumably reflect contribution of an enriched mantle source; high positive eNd(T) and low 87Sr/86Sr ratios in magmatic rocks from the Northern Koryak segment area indicate their derivation from an isotopically depleted mantle source without significant contamination by sialic or mantle material enriched in radiogenic Sr and Nd. Significantly different contamination histories of Eocene-Oligocene mantle magmas in Kamchatka and Koryakia are related to their different thermal regimes: higher heat flow beneath Kamchatka led to crustal melting and contamination of mantle suprasubduction magmas by crustal melts. Cessation of suprasubduction volcanism in the Western Kamchatka segment of the continental margin belt was possibly related to accretion of the Achaivayam-Valagin terrane 40 Ma ago, whereas suprasubduction activity in the Koryak segment stopped due to closure of the Ukelayat basin in Oligocene.

Raster grids detailing habitat suitability for Lophelia pertusa reefs in the Irish continental margin

This dataset contains raster grids in GeoTIFF format describing the habitat suitability for living Lophelia pertusa reefs in the Irish continental margin (extended continental shelf claim). The habitat suitability map is given in continuous and binary (based on the 10th percentile threshold) format. The geographic extent is 25°53.801'W - 6°42.401'W and 46°45.033'N - 57°27.033'N. The spatial resolution is 0.01°x0.01°. The map projection is WGS 1984.