21. Biogenic Sedimentation in the Eocene Equatorial Pacific—the Stuttering Greenhouse and Eocene Carbonate Compensation Depth1

Mitchell Lyle,2 Annette Olivarez Lyle,2 Jan Backman,3 and Aradhna Tripati4


CaCO3, Corg, and biogenic SiO2 were measured in Eocene equatorial Pacific sediments from Sites 1218 and 1219, and bulk oxygen and carbon isotopes were measured on selected intervals from Site 1219. These data delineate a series of CaCO3 events that first appeared at ~48 Ma and continued to the Eocene/Oligocene boundary. Each event lasted 1–2 m.y. and is separated from the next by a low CaCO3 interval of a similar time span. The largest of these carbonate accumulation events (CAE-3) is in Magnetochron 18. It began at ~42.2 Ma, lasted until ~40.3 Ma, and was marked by higher than average productivity. The end of CAE-3 was abrupt and was associated with a large-scale carbon transfer to the oceans prior to warming of high-latitude regions. Changes in carbonate compensation depth associated with CAE excursions were small in the early part of the middle Eocene but increased to as much as 800 m by the late middle Eocene before decreasing into the late Eocene. Oxygen isotope data indicate that the carbonate events are associated with cooling conditions and may mark small glaciations in the Eocene.

1Lyle, M., Olivarez Lyle, A., Backman, J., and Tripati, A., 2005. Biogenic sedimentation in the Eocene equatorial Pacific—the stuttering greenhouse and Eocene carbonate compensation depth. In Wilson, P.A., Lyle, M., and Firth, J.V. (Eds.), Proc. ODP, Sci. Results,199: College Station, TX (Ocean Drilling Program), 1–35. doi:10.2973/odp.proc.sr.199.219.2005

2Center for Geophysical Investigation of the Shallow Subsurface, Boise State University, MS 1536, 1910 University Drive, Boise Idaho 83725, USA. Correspondence author: mlyle@cgiss.boisestate.edu

3Department of Geology and Geochemistry, Stockholm University, 106 91 Stockholm, Sweden.

4Department of Earth Sciences/Godwin Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.

Initial receipt: 29 April 2004
Acceptance: 11 March 2005
Web publication: 2 December 2005
Ms 199SR-219