Cretaceous and early Cenozoic sediments on the Blake Nose in the western North Atlantic (Fig. 1) offer an ideal record for reconstructing variability in deep-water circulation and sedimentation history, both of which are closely linked to climate change across the Blake Nose. Paleogene and Barremian­Maastrichtian strata crop out, or are present at shallow burial depths, in present water depths of 1200 m to ~3000 m. The Blake Nose spanned a similar range of depths in the early Cenozoic, because margin subsidence was largely complete by the Early Cretaceous, and minor subsidence since then is partly offset by reduced sea level after the Eocene. Thus, a depth transect of cores along the paleoslope provides information on depth-dependent sedimentation, deep ocean chemistry, and biota that can be used to reconstruct the past vertical structure and circulation of the western North Atlantic. In addition, studies of well-preserved Paleogene and Cretaceous fossil groups from the Blake Nose area should make a significant contribution to the interpretation of their evolution in response to episodes of changes in deep-water circulation and impact events.

The Cretaceous and Paleogene contain numerous events of paleoceanographic and biological significance that may be studied with the cores from Blake Nose. Short-term perturbations like the mid-Maastrichtian cooling, the Cretaceous/Paleogene extinction, the late Paleocene extinction, and the late Eocene impact horizons are all preserved in sedimentary sequences from Blake Nose. Several longer term trends can also be documented such as the middle Cretaceous anoxic events, the Aptian-Albian warm period, the Paleocene carbon isotope increase, the early Eocene warm period, and the middle to late Eocene cooling. These events and trends are commonly associated with changes in the Earth's biota, biogeochemical cycling, and oceanographic circulation. Many of the previously obtained records of the Cretaceous and Paleogene events are poorly dated and poorly understood owing to their sparse representation in deep-sea cores or their occurrence at great burial depth. The sedimentary record on Blake Nose has the combination of good microfossil preservation, unlithified sediments of great age exposed near the seafloor, and continuity of sedimentary packages that span a variety of depths across the slope that are needed to reconstruct a detailed history of the Paleogene and Cretaceous periods.

Geophysical and Geological Background
Blake Nose, or Blake Spur, is a salient on the eastern margin of the Blake Plateau, due east of northern Florida (Figs. 1, 2). Water depths at the Blake Plateau are mostly less than 1000 m deep but drop sharply to >4000 m at the Blake Escarpment because of erosion of the continental slope. In contrast, the Blake Nose is a gentle ramp that reaches a maximum depth of about 2700 m at the Blake Escarpment. The Blake Plateau and Blake Nose are composed of an 8­ to 12-km-thick sequence of Jurassic and Lower Cretaceous limestones that are capped by less than 1 km of Upper Cretaceous and Cenozoic deposits (Benson, Sheridan, et al., 1978; Fig. 3).

Depth-Transect Strategy
The water depths of the Blake Nose transect range from 1293 to 2586 mbsl (total vertical range of 1293 m; Fig. 2) and the transect spans the upper and lower boundaries of modern intermediate waters and Upper North Atlantic Deep Waters. The transect was designed to monitor the vertical structure of intermediate waters in the Cretaceous and Paleogene as well as depth-related changes in sedimentation and benthic fauna. In addition, our sites can be compared with recent onshore coring by the United States Geological Survey (USGS) to provide a total vertical depth range of nearly 3000 m and a horizontal transect of more than 320 km from the Carolina coast to the edge of the Blake Escarpment.

To 171B Scientific Objectives

To 171B Table of Contents

Publications Homepage

ODP Homepage