Extended orbitally forced palaeoclimatic records from the equatorial Atlantic Ceara Rise

Abstract

We extend existing high-resolution Oligocene–Miocene proxy records from Ocean Drilling Program (ODP) Leg 154. The extended record spans the time interval from ~17:86 to 26.5 Ma. The data are age calibrated against a new astronomical solution that affords a reevaluation of the intricate interaction between orbital (‘‘Milankovitch’’) forcing of the climate and ocean system, and the fidelity with which this forcing is recorded in oxygen and carbon stable isotope measurements from benthic foraminifera, and associated lithological proxy records of magnetic susceptibility, colour reflectance, and the measured sand fraction. Our records show a very strong continual imprint of the Earth’s obliquity cycle, modulate in amplitude every ~41 ka, a very strong eccentricity signal in the carbon isotope records, and a strong, but probably local, imprint of climatic precession on the coarse fraction and magnetic susceptibility records. Our data allowed us to evaluate how the interaction of long, multi-million year beats in the Earth’s eccentricity and obliquity are implicated in the waxing and waning of ice-sheets, presumably on Antarctica. Our refined age model confirms the revised age of the Oligocene–Miocene boundary, previously established by analysis of the lithological data, and allows a strong correlation with the geomagnetic time scale by comparison with data from ODP Site 1090, Southern Ocean