Age determination and stable isotope record of sediment cores at 9°S in the Indian Ocean

A continuous 10-m-long section consisting of roughly two thirds Ethmodiscus rex (a diatom) and one third mixed planktonic foraminifera was identified in a core from 3800 m depth at 9°S on the Indian Ocean's 90°E Ridge. Radiocarbon dates place the onset of deposition of this layer at >30,000 years B.P. and its termination at close to 11,000 years B.P. However, precise dating of the foraminifera from the Ethmodiscus layer itself proved to be impossible owing to the presence of secondary calcite presumably precipitated from the pore waters. During the Holocene, high calcium carbonate content ooze free of diatoms was deposited at this locale. As the site currently lies beneath the pathway taken by upper ocean waters entering the Indian Ocean from the Pacific (via the Indonesian Straits), it appears that during glacial time, thermocline waters moving along this same path provided the silica and other nutrients required by these diatoms.

Compilation of measurements from two interdisciplinary STAR-shaped surveys in the North Sea: The ZISCH - Dataset

The measurements were obtained during two North Sea wide STAR-shaped cruises during summer 1986 and winter 1987, which were performed to investigate the circulation induced transport and biologically induced pollutant transfer within the interdisciplinary research in the project "ZISCH - Zirkulation und Schadstoffumsatz in der Nordsee / Circulation and Contaminant Fluxes in the North Sea (1984-1989)". The inventory presents parameters measured on hydrodynamics, nutrient dynamics, ecosystem dynamics and pollutant dynamics in the pelagic and benthic realm. The research program had the objective of quantifying fluxes of major budgets, especially contaminants in the North Sea. In spring 1986, following the phytoplankton spring bloom, and in late winter 1987, at minimum primary production activity, the North Sea ecosystem was investigated on a station net covering the whole North Sea. The station net was shaped like a star. Sampling started in the centre, followed by the northwest section and moving counter clockwise around the North Sea following the residual currents. By this strategy, a time series was measured in the central North Sea and more synoptic data sets were obtained in the individual sections. Generally advection processes have to be considered when comparing the data from different stations. The entire sampling period lasted for more than six weeks in each cruise. Thus, a time-lag should be considered especially when comparing the data from the eastern and the western part of the central and northern North Sea, where samples were taken at the beginning and at the end of the campaign. The ZISCH investigations represented a qualitatively and quantitatively new approach to North Sea research in several respects. (1) The first simultaneous blanket coverage of all important biological, chemical and physical parameters in the entire North Sea ecosystem; (2) the first simultaneous measurements of major contaminants (metals and organohaline compounds) in the different ecosystem compartments; (3) simultaneous determinations of atmospheric inputs of momentum, energy and matter as important ecosystem boundary conditions; (4) performance of the complex measurement program during two seasons, namely the spring plankton bloom and the subsequent winter period of minimal biological activity; and (5) support of data analysis and interpretation by oceanographic and meteorological numerical models on the same scales.

Results of biological and geological bottom investigations carried out during Cruise 43 of R/V Akademik Kurchatov in the South Atlantic

The book is devoted to investigations of benthic fauna and geology of the Southern Atlantic Ocean. These works have been carried out in terms of exploring biological structure of the ocean and are of great importance for development of this fundamental problem. They are based on material collected during Cruise 43 of R/V Akademik Kurchatov in 1985-1986 and Cruise 43 of R/V Dmitry Mendeleev in 1989. Problems of quantitative distribution, group composition and trophic structure of benthos in the Southern Scotia Sea, along the east-west Transatlantic section along 31°30'S, and offshore Namibia in the area of the Benguela upwelling are under consideration in the book. Authors present new data on fauna of several groups of deep-sea bottom animals and their zoogeography. Much attention is paid to analysis of morphological structure of the Scotia Sea floor considered in terms of plate tectonics. Bottom sediments along the Transatlantic section and facial variation of sediments in the area of South Shetland Islands and of the continental margin of Namibia are under consideration.

Glacial-interglacial record of ODP Site 181-1119 in the Canterbury Bright, Southwest Pacific Ocean

Ocean Drilling Program (ODP) Site 1119 is located at water depth 395 m near the subtropical front (STF; here represented by the Southland Front), just downslope from the shelf edge of eastern South Island, New Zealand. The upper 86.19 metres composite depth (mcd) of Site 1119 sediment was deposited at an average sedimentation rate of 34 cm/kyr during Marine Isotope Stages (MIS) 1-8 (0-252 ka), and is underlain across a ~25 kyr intra-MIS 8 unconformity by MIS 8.5-11 (277-367 ka) and older sediment deposited at ~14 cm/kyr. A time scale is assigned to Site 1119 using radiocarbon dates for the period back to ~39 ka, and, prior to then, by matching its climatic record with that of the Vostok ice core, which it closely resembles. Four palaeoceanographic proxy measures for surface water masses vary together with the sandy-muddy, glacial-interglacial (G/I) cyclicity at the site. Interglacial intervals are characterised by heavy delta13C, high colour reflectance (a proxy for carbonate content), low Q-ray (a proxy for clay content) and light delta18O; conversely, glacial intervals exhibit light delta13C, low reflectance, high Q-ray and heavy delta18O signatures. Early interglacial intervals are represented by silty clays with 10-105-cm-thick beds of sharp-based (Chondrites-burrowed), shelly, graded, fine sand. The sands are rich in foraminifera, and were deposited distant from the shoreline under the influence of longitudinal flow in relatively deep water. Glacial intervals comprise mostly micaceous silty clay, though with some thin (2-10 cm thick) sands present also at peak cold periods, and contain the cold-water scallop Zygochlamys delicatula. Interglacial sandy intervals are characterised by relatively low sedimentation rates of 5-32 cm/kyr; cold climate intervals MIS 10, 6 and 2 have successively higher sedimentation rates of 45, 69 and 140 cm/kyr. Counter-intuitively,and forced by the bathymetric control of a laterally-moving shoreline during G/I and I/G transitions, the 1119 core records a southeasterly (seaward) movement of the STF during early glacial periods, accompanied by the incursion of subtropical water (STW) above the site, and northwesterly (landward) movement during late glacial and interglacial times, resulting in a dominant influence then of subantarctic surface water (SAW). The history of passage of these different water masses at the site is clearly delineated by their characteristic delta13C values. The intervals of thin, graded sands-muds which occur within MIS 2-3, 6, 7.4 and 10 indicate the onset at times of peak cold of intermittent bottom currents caused by strengthened and expanded frontal flows along the STF, which at such times lay near Site 1119 in close proximity to seaward-encroaching subantarctic waters within the Bounty gyre. In common with other nearby Southern Hemisphere records, the cold period which represents the last glacial maximum lasted between ~23-18 ka at Site 1119, during which time the STF and Subantarctic Front (SAF) probably merged into a single intense frontal zone around the head of the adjacent Bounty Trough.