--> ABSTRACT: Comparative Ecostratigraphy of Pleistocene: ODP Site 625 and DSDP Site 502, by Ronald E. Martin and G. W. Johnson; #91022 (1989)

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Comparative Ecostratigraphy of Pleistocene: ODP Site 625 and DSDP Site 502

Ronald E. Martin, G. W. Johnson

Sediments of Ocean Drilling Program's hole 625B (Leg 100, northeastern Gulf of Mexico) represent a continuous record of Pleistocene paleo-oceanographic development associated with the Florida Loop Current. Planktonic foraminiferal abundances from the Quaternary section of hole 625B have been used to construct a high-resolution ecostratigraphic zonation (calibrated against standard industry markers and magnetostratigraphy) that subdivides the Pleistocene into 21 stratigraphic units. The zonation has been tested successfully against Eureka core E67-135. The zonation was erected using only four species and operational taxonomic groups (OTGs) of planktonic foraminifera: the Globorotalia menardii complex, Globorotalia inflata, and left- and right-coiling varieties of Globorota ia truncatulinoides. Vector analysis of census data indicates that planktonic foraminiferal species are reacting independently to ecological conditions associated with the Florida Loop Current. A four-end-member mixing model is proposed that allows differentiation of the dominant climatic controls on the planktonic fauna: temperature, salinity, and productivity. Ecological factors may, however, be estimated just as accurately by the use of a few key species and OTGs.

An ecostratigraphic zonation for the Pleistocene of Deep Sea Drilling Project Site 502 (Colombia basin) has also been constructed and is compared to that of Site 625. Site 502 is linked to Site 625 via the Caribbean and Florida Loop Currents and is fed, in turn, by the North Atlantic Equatorial and Guiana currents. Hence, comparison of the two sites provides further tests of ecostratigraphic zonations and the influence of global vs. regional ecosystems on their formation.

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