ABSTRACT: Graphic Correlation of Quaternary Bio-, Magneto-, and Chemostratigraphic Datums of the Tropical Atlantic and American Mediterranean: Resolution of Faunal and Stable Isotope Signals

R. E. Martin, E. Neff, G. W. Johnson, D. Krantz

Sediments of Ocean Drilling Program's hole 625B (northeastern Gulf of Mexico, south flank of DeSoto Canyon) represent a virtually continuous record of Pleistocene paleoceanographic development associated with the Florida Loop Current. Using relative abundances of the Globorotalia menardii complex, G. inflata, and left-coiling and right-coiling varieties of G. truncatulinoides, we have subdivided the pre-zone W Pleistocene of hole 625B into 17 subzones, resulting in an average duration of approximately 100,000 yr per unit. This is substantially better resolution than for the previous workers' zones, which are based on the G. menardii complex alone (average duration ^approx300,000 yr per unit). The subzones can be recognized in Eureka Core E67135 from the north margin of De oto Canyon, as well as in cores 502B (Colombia Basin, Caribbean Sea) and V16205 (tropical Atlantic). The Globorotalia inflata and G. truncatulinoides parts of the biostratigraphic signals are damped in the tropical cores (V16205 and 502B) but amplified in the subtropical Gulf of Mexico (625B). Subzonal boundaries are largely coeval between sites based on graphic correlation of paleomagnetic, biostratigraphic, and oxygen isotope datums. The subzonation reveals relatively subtle changes in sediment accumulation rate not readily apparent from visual inspection of isotopic stages. In some cases, accumulation rate changes correspond to core breaks. The subzonal scheme is useful in identifying biostratigraphic tops whose position is affected by changes in sediment accumulation rate.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990