ABSTRACT: Biostratigraphic Expression of Plio-Pleistocene Sequence Boundaries

MARTIN, RONALD E., University of Delaware, Newark, DE, RUTH R. FLETCHER, University of Hawaii, Honolulu, HI, and DAVID E. KRANTZ, University of Delaware, Lewes, DE

Ocean Drilling Program (ODP) Core 625B (northeast Gulf of Mexico) represents a virtually continuous record of paleoceanographic history and sea-level change during the Pliocene-Pleistocene. Utilizing relative abundances of the warm-water Globorotalia menardii complex and cool (temperate)-water G. inflata, we have subdivided the Pleistocene of Core 625B into 17 subzones. The subzones are recognizable in other cores (Eureka Core E67-135 [northeastern Gulf of Mexico], DSDP Core 502B [Caribbean Sea] and V16-205 [tropical Atlantic]) and in an industrial well (Garden Banks Block 412 Unocal #1). Based on graphic correlation, subzonal boundaries are coeval between sites and can provide high-resolution subdivision of the Pleistocene of industrial wells on an operational basis. Moreover, the su zonation reveals changes in sediment accumulation rate (and sand influx) that reflect seismic sequence boundaries at the Zone Y/X (~0.09 Ma), W/V1 (~0.2 Ma), U/T (~0.525-0.620 Ma), T3/T4 (~0.7-0.9 Ma), T4/S1 (~1.0 Ma), R2/R3-R3/Q1 (~1.4-1.5 Ma), and P/Pliocene (~1.8-1.9 Ma) boundaries, and a regionally condensed section in Subzone R1 (~1.3 Ma).

In the Pliocene sections of Sites 625 and 502, relative abundance of keeled globorotalids (analogous to the G. menardii complex) serves as a proxy for the oxygen isotope curve. Ages have been tentatively assigned to Pliocene sequence boundaries using a globorotalid-based ecostratigraphic zonation consisting of individual numbered stages. Possibly, this scheme could be adapted to industrial wells.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)