Detailed biostratigraphy in Site 1006 based on planktonic foraminifers and nannofossils shows large-scale sedimentation rate variability in the Florida Strait west of the Great Bahama Bank. A 'floating' cyclostratigraphy based mainly on resistivity logs and magnetic susceptibility data has been fixed to the biostratigraphy in the absence of magnetostratigraphy. The strongest orbital cycle present is the precessional beat, which is present in the borehole logs throughout the record. Counting the cycles resulted in an accurate time scale and thus a sedimentation rate time series.
Spectral analysis of the sedimentation rate time series shows that the short-term cycle of eccentricity (~125 k.y.) and the long term cycle of eccentricity (~400 k.y.) are pervasive throughout the Miocene record, together with the long-term ~2-m.y. eccentricity cycle. The Great Bahama Bank produced pulses of shallow carbonate input once every precessional (sea level) cycle during the Miocene and perhaps two pulses per cycle in the early Pliocene. The amount of sediment exported in these pulses appears to be controlled by eccentricity modulation of the precessional amplitude and therefore the amplitude of the sea-level rise. Finally, an increase in sedimentation rate just after the Miocene/Pliocene boundary is attributed to a change in the location and strength of sediment drift currents in the Florida Strait due to reorganization of the currents following the closure of the Panama Isthmus.
1Swart, P.K., Eberli, G.P., Malone, M.J., and Sarg, J.F. (Eds.) , 2000. Proc. ODP, Sci. Results, 166: College Station TX (Ocean Drilling Program). Available from World Wide Web: <http://www-odp.tamu.edu/publications/166_SR/166TOC.HTM>. [Cited YYYY-MM-DD]
2Department of Geology and Geophysics, University of Edinburgh, Grant Institute, West Mains Road, Edinburgh EH9 3JW, Scotland, United Kingdom. D.Kroon@glg.ed.ac.uk
3Leicester University Borehole Research, Department of Geology, Leicester University, Leicester, LE1 7RH, United Kingdom.
4Borehole Research Group, Lamont-Doherty Earth Observatory, Columbia University, Palisades NY 10964-8000, USA. (Present address: Deepwater Reservoirs Group, Exxon Production Research Co., PO Box 2189, Houston TX 77252, USA.)
5Geological Institute, ETH-Zentrum, 8092 Zürich, Switzerland.
6Institute of Applied Earth Sciences, Mining College, Akita University, Tegata Gakuencho 1-1, Akita 010, Japan.
7Department of Geological Sciences, Rutgers University, Piscataway NJ 08854-8066, USA.
Date of
initial receipt: 22 March 1999
Date of acceptance: 27 September 1999
Ms 166SR-127