Roth, Sven1, John J. G. Reijmer1
(1) GEOMAR Research Center for Marine Geosciences, D-24148 Kiel, Germany
ABSTRACT: Holocene Climate-Induced Variations in Carbonate Sedimentation on the Leeward Slope of Great Bahama Bank
We present a multi-proxy study of a sediment core (MD992202) taken from the leeward margin of Great Bahama Bank. Sedimentation rates vary from 13.8m/ka (bottom) to 2.7m/ka (top). Decadal-scale stable isotope variations (bulk and planktonic foraminifera) could be detected in these periplatform sediments. These variations have been used to reconstruct sea surface temperatures (SST) for the past 7230 years. Changes in SST, associated with the Little Ice Age and the Medieval Warm Period are unequivocally detected in the sedimentary record. A good correlation exists between the isotopic changes in the periplatform sediments and the Greenland GISP ice core on millennial to decadal timescales, whereas the Antarctic Vostok record shows only minor accordance. Aragonite mass accumulation rates and age offset between planktonic foraminifera and aragonite sediments shown by C-14 datings, combined with the temperature distribution were used to deduce aragonite production changes and paleo-current strengths. Aragonite precipitation rates on GBB are controlled by current strength dependent exchange of carbonate ions and CO2 loss due to temperature-salinity conditions and biological activity. Paleo-surface current strengths on GBB vary on century to millennial time-scales. Bahamian surface currents are directly linked to the North Atlantic atmospheric circulation. Periods with high (low) current speeds are proposed to be in phase with periods of strong (weak) atmospheric circulation. The close relation between Bahamian sea surface temperatures, Greenland temperatures and the North Atlantic atmospheric circulation shows the sensitivity of the carbonate sedimentation system to far-field and local climatic changes.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.