Tertiary paleoceanography of the western North Atlantic Ocean

Abstract The Tertiary paleoceanography of the North Atlantic Ocean is known in greater detail than that of earlier periods because the upper part of the geologic record is more accessible to geologic sampling and geophysical observation. The Tertiary record also appears more complex, partially because of the greater data density. Nonetheless, there are large segments of this record about which we know relatively little. In particular, the Paleocene and Oligocene sedimentary records are not well represented on the shallow continental margin because erosion during sea-level low- stands removed much of the section. Equivalent records in the deep basin are poorly known because low sediment accumulation rates or erosion by abyssal currents resulted in preservation of abnormally thin sections. Many of these sections also are poorly sampled in existing Deep Sea Drilling Project (DSDP) drillsites. In contrast to earlier periods, the Tertiary North Atlantic Ocean basin was strongly affected by the action of abyssal contour-following currents, particularly following Eocene time. The currents intermittently caused extensive seafloor erosion along the continental margins and they decorated the basin with large sediment drifts. The development and patterns of surface currents, and to some extent deep currents, are dealt with from a paleobiogeographic viewpoint by Berggren and Olsson (this volume). In this paper, we summarize the Tertiary paleoceanography based on other information from the geologic record, principally seismic Stratigraphic interpretations that are correlated with rock stratigraphy at DSDP and other boreholes. These data are interpreted within the framework of the plate-tectonic evolution of the North Atlantic