INTRODUCTION

Site 1051 (30°03'N, 76°21'W) is located at a water depth of 1980 m at Blake Nose, western North Atlantic. This site includes an expanded and virtually entire Paleogene section of pelagic and hemipelagic sediments, from Paleocene to early late Eocene age. The sediments consist predominantly of a siliceous nannofossil and foraminifer ooze (Norris, Kroon, Klaus, et al., 1998). The middle Eocene foraminifers recovered at this site are highly suitable for isotopic examination as they are well preserved. In this data report we detail the isotopic analyses conducted on planktonic and benthic foraminifers from the late middle Eocene of Hole 1051B.

Whereas the climatic shifts during the Eocene are understood in general terms, many specific questions remain unanswered, particularly in terms of the variability of climate, the timing of oceanic cooling, and the effect on oceanographic structure. This is because high-resolution, low-latitude Paleogene records are scarce and previously acquired Eocene records are either incomplete, intermittently cored, or disturbed by drilling through Eocene chert.

Tropical sea-surface temperatures (SSTs) have been shown to be essential to verify the character of forcing and feedback of warm climatic states. However, a disparity prevails between proxy temperature interpretations from isotopic (e.g., Boersma et al., 1987; Zachos et al., 1994; Bralower et al., 1995) and paleontological indices for the middle Eocene tropics (e.g., Adams et al., 1990; Graham, 1994).

We have produced ¹⁸O and ¹³C profiles from well-preserved planktonic foraminifers, which will be used to obtain late middle Eocene SSTs from the subtropical Atlantic. The stable isotope record from Site 1051 will be applied to document and assess the scale and timing of relatively short term climatic changes associated with the switch from the early Eocene greenhouse to the late Eocene icehouse world in the Atlantic Ocean. Benthic foraminifers are analyzed to compare benthic temperatures with nearby Ocean Drilling Program Site 1052 and to obtain a direct measurement of thermal gradients in the intermediate waters over the Blake Nose. In addition, the comparison of temperature records derived from planktonic and benthic foraminifers permits reconstruction of the surface-to-benthos thermal gradient in the western North Atlantic.