High-Resolution Biostratigraphy and Aminostratigraphy of ODP Hole 625B: Northeastern Gulf of Mexico

Glenn W. Johnson, Beverly Johnson, John F. Wehmiller, Ronald E. Martin

Quantitative census data of planktonic foraminifera from the Quaternary section of Ocean Drilling Program Hole 625B (Leg 100, northeastern Gulf of Mexico) have been analyzed. A high-resolution biostratigraphy that subdivides the Pleistocene into 21 stratigraphic units is established by the extension of the work of Ericson and Wollin, and Neff. This stratigraphy may be applied by generating the faunal percentage curves of only four "species" of planktonic foraminifera: the Globorotalia menardii complex, Globorotalia inflata, and the two coiling varieties of Globorotalia truncatulinoides. The zonation may be supplemented and calibrated by the utilization of standard industry biohorizons, or paleotops.

Foraminiferal aminostratigraphy is a useful chemical tool for correlation of Pliocene-Pleistocene sections. Prior studies generally demonstrate that (1) amino acid D/L values increase with increasing depth, (2) spinose foraminifera have lower apparent racemization rates than non-spinose foraminifera, and (3) racemic equilibrium is found in early Pliocene or late Miocene samples, depending on the taxa analyzed. Long, high sedimentation-rate sections such as 625B are potentially useful for establishing a detailed Pliocene-Pleistocene aminostratigraphic record.

D-alloisoleucine/L-isoleucine trends in Globigerinoides ruber, Orbulina universa, Neogloboquadrina dutertrei, Globorotalia menardiitumida complex, and mixed foraminifera species have been determined for the Pleistocene section of Hole 625B at 5 to 10-m sampling intervals. This preliminary study demonstrates that with dense sampling and proper sample preparation, it should be possible to use multiple taxa, each an independent "clock," for intercore correlation and for evaluation of hiatuses or reworking effects.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.