Calcareous dinoflagellates in Maastrichtian to early Miocene sediments of DSDP Hole 39-357

The evolution of calcareous dinoflagellate communities has been investigated for the latest Cretaceous to earliest Neogene interval of the mid-latitude South Atlantic. In doing so, the response of calcareous dinoflagellates to Cenozoic climatic change has been addressed for the first time. Trends in species composition and distribution patterns of wall types indicate significant changes which correlate with major palaeoenvironmental modifications. A first major shift concerning the relative abundance of species and wall types occurred across the Cretaceous-Tertiary boundary. The associations remained stable during the entire Paleocene and Eocene. Only in the late Eocene did a dramatic decrease in temperature cause a slight diversification. A second major shift in the abundance patterns occurred across the Eocene-Oligocene boundary. The early Miocene warming is possibly reflected in the distinct increase in relative abundance of one species. The assemblages of calcareous dinoflagellates evidently react to major climatic changes during the Cenozoic. These poorly investigated organisms may thus provide an important contribution to the understanding of earth's palaeoclimatic evolution.

Isopollen maps for 18,000 years B.P. of the offshore of Northwest Africa: Evidence for paleowind circulation

Distribution patterns of the most important pollen types from southern European and northwest African source areas for the 18,000 years B.P. time slice are reconstructed from pollen records of 14 well-dated deep-sea cores located between 37° and 9°N and compared with the modern pollen distribution in this area. It is concluded that the belt with maximum African Easterly Jet transport did not shift latitudinally during the last glacial-interglacial transition but remained at about 20°N. Furthermore, it is substantiated that the trade winds did not shift latitudinally during the last glacial-interglacial transition. This evidence is not compatible with an atmospheric circulation model that assumes a zone of surface westerlies in the northern part of northwest Africa. Trade winds during glacial episodes did, however, intensify, especially from about 36° to 24° N.

Age models and stable isotope ratios of SO12 and SO35 sediment cores

Based on organic carbon accumulation rates, nine time slices of oceanic export paleoproductivity (Pnew) are presented which depict the variability of Pnew on a global scale through the last 30,000 years and document that the basic distribution patterns did not change through glacial and interglacial times. However, the glacial ocean shows an increased contrast of high- versus low-productivity zones. d13C values of near-surface-dwelling planktonic foraminifera Globigerinoides ruber suggest that the same contrast applies to the glacial nutrient inventories of the ambient surface waters, with a significant glacial transfer of PO4 from low- to high-productivity zones. In this way, glacial Pnew increased by a global average of about 2-4 Gt C/yr and led, via an enhanced CaCO3 dissolution and alkalinity in the deep ocean, to a significant extraction of CO2 from the surface water and the atrnosphere.