Description: This study is based on a reconstruction of the paleogeographic and paleobathymetric history of the South Atlantic and on a standardized set of sediment and biostratigraphic data from all Deep Sea Drilling Project sites. Standard data sets used are the lithologic description, biostratigraphic age, CaCO3 content, carbonate and carbonate-free sedimentation rates corrected for compaction, and hiatus distribution. For each site the subsidence history has been determined. Paleoceanographic variables used are the spatial and temporal lithofacies distribution, history of calcite compensation depth, surface fertility and lyocline, erosional events, and special lithologies (black shales). During its early history the South Atlantic consisted of a narrow rift divided by the Rio Grande Rise- Walvis Ridge barrier into a restricted northern and an open (to the southern ocean) southern basin. In the northern basin, evaporites are the earliest known marine sediments (Aptian) while more normal pelagic deposits formed in the southern basin. Free circulation of surface water between the southern ocean and the North Atlantic became possible late in the Mesozoic or in the early Cenozoic, and deep circulation (below 3 km depth) paths were open from north to south by the early Cenozoic. During the early and middle Mesozoic the South Atlantic had its own oceanographic character with dominantly terrigenous sedimentation and two anoxic black mudstone phases (Albian and Santonian) probably resulting from a strong oxygen minimum in mid-water caused by either excess surface fertility or old, slow moving bottom water. In the late Cretaceous the South Atlantic became part of the world ocean system and global events have overshadowed local ones since that time. After the early phase of rapid sedimentation of terrigenous material, the depositional history has been in- fluenced mainly by the increasing width and water depth of the basin and by fluctuations of the level and intensity of carbonate dissolution. At the Eocene/Oligocene boundary, the onset of a deep water circulation dominated by a cold circum-polar source of surface water is clearly marked by erosional events, a sharp drop of the calcite compensation depth and the arrival of biogenic siliceous oozes in the Argentine Basin.

Description: Plankton pump samples and plankton tows (size fractions between 0.04 mm and 1.01 mm) from the eastern North Atlantic Ocean contain the following shell- and skeleton-producing planktonic and nectonic organisms, which can be fossilized in the sediments: diatoms, radiolarians, foraminifers, pteropods, heteropods, larvae of benthic gastropods and bivalves, ostracods, and fish. The abundance of these components has been mapped quantitatively in the eastern North Atlantic surface waters (Fig. 4) in October - December 1971. More ash (after ignition of the organic matter, consisting mostly of these components) per cubic meter of water is found close to land masses (continents and islands) and above shallow submarine elevations than in the open ocean. Preferred biotops of planktonic diatoms in the region described are temperate shallow water and tropical coastal upwelling areas. Radiolarians rarely occur close to the continent, but are abundant in pelagic warm water masses, even near islands. Foraminifers are similar to the radiolarians, rarer in the coastal water mass of the continent than in the open ocean or off oceanic islands. Their abundance is highest outside the upwelling area off NW Africa. Molluscs generally outnumber planktonic foraminifers, implying that the carbonate cycle of the ocean might be influenced considerably by these animals. The molluscs include heteropods, pteropods, and larvae of benthic bivalves and gastropods. Larvae of benthic molluscs accur more frequently close to continental and island margins and above submarine shoals (in this case mostly guyots) than in the open ocean. Their size increases, but they decrease in number with increasing distance from their area of origin. Ostracods and fish have only been found in small numbers concentrated off NW Africa. All of the above-mentioned components occur in higher abundances in the surface watet than in subsurface waters. They are closely related to the hydrography of the sampled watet masses (here defined through temperature measutements). Relatively warm water masses of the southeastern branches of the Gulf Stream system transport subtropical and southern temperate species to the Bay of Biscay, relatively cool water masses of the Portugal and Canary Currents carry transitional faunal elements along the NW African coast southwards to tropical regions. These mix in the northwest African upwelling area with tropical faunal elements which are generally assumed to live in the subsurface water masses and which probably have been transported northwards to this area by a subsurface counter current. The faunas typical for tropical surface water masses are not only reduced due to the tongue of cool water extending southwards along the coast, but they are also removed from the coastal zone by the upwelling subsurface water masses carrying their own shell and skeleton assemblages. Tropical water masses contain much more shelland skeleton-producing plankters than subtropical and temperate ones. The climatic conditions found at different latitudes control the development and intensity of separate continental coastal water mass with its own plankton assemblages. Extent of this water mass and steepness of gradients between the pelagic and coastal environment limit the occurrence of pelagic plankton close to the continental coast. A similar water mass in only weakly developed off oceanic islands.

Description: High concentrations of fine-grained and probably wind-blown quartz with an Australian provenance have been mapped in Holocene sediments in the southwest Pacific. During the last glacial maximum a narrow zone of high eolian input, as reflected in a higher abundance of quartz, extended more than 20° longitude farther east than today. This zone, which was significantly farther north than at present, is centered around lat 30° S but curves around the northern tip of New Zealand. These quartz distributions imply that the westerly winds that blew the airborne quartz over the southwest Pacific had shifted considerably to the north under the influence of intensified atmospheric circulation during the last glacial maximum.

Description: The paleo-oceanography of the southeastern North Atlantic Ocean during the last 150,000 yr has been studied using biogenous and terrigenous components of hemipelagic sediments sampled close to the northwest African continental margin. Variations of oxygen isotope ratios in shells of benthic calcareous foraminifers in two cores allow the assignment of absolute ages to these cores (in the best case at 1000 yr increments). The uncorrected bulk sedimentation rates of the longest core range from 3.4 to 7.6 cm/ 1000 yr during Interglacial conditions, and from 6.5 to 9.9 cm/1000 yr during Glacial conditions; all other cores have given results of the same order of magnitude, but with generally increasing values towards the continental edge. The distribution of sediment components allow us to make inferences about paleo-oceanographic changes in this region. Frequencies of biogenic components from benthic organisms, oxygen isotope ratios measured in benthic calcareous foraminiferal shells, the total carbonate contents of the sediment and distributions of biogenic components from planktonic organisms often fluctuate in concert. However, all fluctuations which can be attributed to changes of the bottom water masses (North Atlantic Deep Water) seem to precede by several thousand years those which can be linked to changes of the surface water mass distributions or to changes of the climate over the neighboring land masses. Late Quaternary planktonic foraminiferal assemblages in the cores from the northwest African continental margin can be defined satisfactorily in the way that distributions of assemblages found in sediment surface samples from the northeast Atlantic Ocean have been explained. The distributions of assemblages in the northwest African cores can also be used to estimate past sea surface temperatures and salinities. The downcore record of these estimates reveals two warm periods during the last 150,000 yr, the lower one corresponding to the oxygen isotope stage 5 e (equivalent to the Eemian proper in Europe), the upper one to the younger half of the Holocene. Winter surface water temperatures during oxygen isotope stages 6, 4, 3, and 2 are remarkably constant in most cores, while summer sea surface temperatures during stage 3 reach values comparable to those of the warm periods during the Late Holocene and Eemian. Estimated winter sea surface temperatures range from 〉 16 °C to 〈 11°C, the summer sea surface temperatures from 〉 22 °C to 〈 15 °C during the last 150,000 yr. Estimates of the winter sea surface salinities fluctuate between 36.6‰ and 35.5‰, the higher values being restricted to the warm periods since the penultimate Glacial. Estimates for sea surface temperatures and salinities for two cores from the center of today's coastal upwelling region show less pronounced fluctuations than the record of the open ocean cores in the case of the station 12379 off Cape Barbas, more pronounced in the case of station 12328 off Cape Blanc. Seasonal differences between winter and summer sea surface temperatures derived from the estimated temperatures are today more pronounced in the boundary region of the ocean to the continent than further away from the continent. The differences are generally higher during warm climatic periods of the last 150,000 yr than during cooler ones. The abundance of terrigenous grains in the coarse fractions generally decreases with increasing distance from the continental edge, and also from south to north. The dominant portion of the terrigenous detritus is carried out into the ocean during the relatively cool climatic periods (stage 6, 4, later part of stage 3, stage 2 and oldest part of stage 1). The enhanced precision of dating combined with the stratigraphic resolution of these high deposition rate cores make it clear that the peaks of the terrigenous input off this part of the northwest African continental margin occur simultaneously with times of rapid sea level fluctuations resulting from large volume changes of the large Glacial ice sheets.