Mid-Pleistocene planktonic foraminiferal composition and IRD content in ODP Sites 162-980 and 162-984

We investigated surface and deep ocean variability in the subpolar North Atlantic from 1000 to 500 thousand years ago (ka) based on two Ocean Drilling Program (ODP) sites, Feni drift site 980 (55°29'N, 14°42'W) and Bjorn drift site 984 (61°25'N, 24°04'W). Benthic foraminiferal stable isotope data, planktic foraminiferal faunas, ice-rafted debris data, and faunally based sea-surface temperature estimates help test the hypothesis that oceanographic changes in the North Atlantic region were associated with the onset of the 100-kyr world during the mid-Pleistocene revolution. Based on percentage of Neogloboquadrina pachyderma (s) records from both sites, surface waters during interglacials and glacials were cooler in the mid-Pleistocene than during marine isotope stages (MIS) 5 and 6. In particular, interglaciations at Bjorn drift site 984 were significantly cooler. Faunal evidence suggests that the interglacial Arctic front shifted from a position between the two sites to a position northwest of Bjorn drift site 984 after ca. 610 ka. As during the late Pleistocene, we find faunal evidence for lagging surface warmth at most of the glacial initiations during the mid-Pleistocene. Each initiation is associated with high benthic d13C values that are maintained into the succeeding glaciation, which we term "lagging NADW production." These findings indicate that lagging warmth and lagging NADW production are robust features of the regional climate system that persist in the middle to late Pleistocene.

Inorganic geochemistry, epoch and water content in sediments at DSDP Site 91-596

Originally, we had planned to piston core at Site 595 in order to meet the sedimentologic and biostratigraphic objectives outlined in the introductory chapter. However, consultation with our colleagues, Thomas Jordan and John Orcutt on board Melville, indicated that coring near the ocean bottom seismometer (OBS) array around Hole 595B could alter the programmed signal to noise ratio above which teleseisms trigger recording in the OBSs. They requested that we core no closer than about 8 km from three OBSs nearest Hole 595B, and selected a target for us about that distance to the west. Since a new beacon was required at this distance, a new site number, 596, was designated. Briefly, we planned to obtain oriented hydraulic piston cores to the top of the cherts, then core through the cherts using the extended core barrel (XCB) to basement. With improved recovery, we hoped to reach the sediment/basalt contact, and thus obtain a reliable biostratigraphic determination of the basement age. We planned to obtain at least one core in basement, perhaps more, with time permitting. We planned no geophysical program for the hole.

(Table 1) Primary production and chlorophyll a concentration in the Northeastern Tropical Atlantic

Results of simultaneous determinations of chlorophyll "a" concentrations and primary production in the northeastern part of the Tropical Atlantic in spring 1977 are discussed. Primary production was low (250-350 mg C/m**2/day in the open parts of the ocean and high (600-1500 mg C/m**2/day) mainly in zones of current divergences and coastal region of the West Africa. Chlorophyll "a" concentration throughout the euphotic zone varied from 6 to 36 mg/m**3 and in the surface layer from 0.05 to 0.60 mg/m**3. Uneven distribution of primary production is due to physiological condition of phytoplankton.