During Ocean Drilling Program Leg 154, five sites (Sites 925, 926, 927, 928, and 929) were drilled as a depth transect on the Ceara Rise in the western Atlantic Ocean. Each site consists mainly of pelagic carbonate sediments. Planktonic foraminifers are abundant throughout the sequences except in intervals of intense dissolution at the bathymetrically deeper sites. Faunas are typical of the low latitudes, and they are diverse and reasonably well preserved for much of the record. Recrystallization is mostly moderate, but it is severe at the greater burial depths.
A biostratigraphic framework is presented for the lower part of the stratigraphic interval, from Subzone P4c in the upper Paleocene to Zone N12 immediately below the most intensely dissolved level in the middle Miocene. This study replaces the previously published shipboard planktonic foraminifer biostratigraphy. It contains many additional datums and some revisions. Complete range charts of all the species recognized are also presented for the entire stratigraphic interval on the Ceara Rise.
Sedimentation on the plateau was almost continuous from the Paleocene to the Holocene. Although several small hiatuses are identified at individual sites, none extends across the whole plateau, so a remarkably complete geological history can be constructed. Much of this record is characterized by sedimentary cyclicity on Milankovitch time scales. This suggests that the Ceara Rise will be a key area for future advances in orbital-based chronology in which planktonic foraminifer biostratigraphy will be an important component.
1Shackleton, N.J., Curry, W.B., Richter, C., and Bralower, T.J. (Eds.), 1997. Proc. ODP, Sci. Results, 154: College Station, TX (Ocean Drilling Program).
2Department of Geology, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, United Kingdom. paul.pearson@bris.ac.uk
3Paleontological Research Institution, 1259 Trumansburg Road, Ithaca, New York 14850, U.S.A. (Present address: Institute of Marine Sciences, University of California, Santa Cruz, California 95064, U.S.A.)
|
|