Eocene biogenic silica accumulation rates at the Pacific equatorial divergence zone

Abstract

A synthesis of Eocene biogenic silica accumulation rates in the equatorial zone of the Pacific shows several relatively broad maxima spaced a few million years apart and extending from the uppermost Eocene into the lower Eocene. There is a distinct, step-like decrease in biogenic silica mass accumulation rate at 38.5 Ma (just below the top of C18n.1n), which appears to be related to changes in oceanographic conditions in the eastern equatorial region. Eocene biogenic silica accumulation rates in the equatorial Pacific are distinctly lower than those in the Neogene. A comparison of Eocene accumulation rates and known areas of open ocean biogenic silica deposition with those in the more modern world leads us to conclude that there is no need to call upon an increased supply of dissolved silica to the world ocean to account for the siliceous-rich deposits of the Eocene. Copyright 2008 by the American Geophysical Union.