Equatorial Ocean Circulation in an Extremely Warm Climate

The warm climates of the early Paleogene and the associated diminished near-surface winds should have resulted in a reduction in near-surface ocean circulation. One check on this deduction is the delineation of biogenic sediments associated with an equatorial current system of the early Eocene Pacific. A latitudinal seismic reflection transect across the tropical Pacific along early Paleogene ocean crust reveals a basal high-amplitude reflection package that we take to be the lower Eocene section. This unit varies in thickness by a factor of about two, with the thickest portion forming a low mound some 3˚–4˚ north of the 56 Ma paleoequator. This mound may represent the position of a divergence generated in the frontal region between two currents flowing in opposite directions, and its position suggests that the wind-driven equatorial circulation of the early Eocene was one without a pronounced equatorial divergence