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Pleistocene-Holocene Lower Bathyal Benthic Foraminifera: A Pilot Study in Keathley Canyon, Northwestern Gulf of Mexico

JONES, MEGAN J., Louisiana State University, Baton Rouge, LA

Recent work on the shelf and upper slope have linked the distribution of benthic foraminifera to the presence of several Gulf of Mexico water masses. A pilot study consisting of three piston cores from lower bathyal depths (1308 m, 1543 m, 1815 m) was undertaken to examine the distribution of benthic foraminifera across the Pleistocene-Holocene boundary and at several depths within the lower slope environment. The primary objective of this study was to test the hypothesis that abundance variations of benthic foraminifera can be used to refine the bathymetric zonation of deep Gulf of Mexico depositional environments based on their water mass associations.

Preliminary results from this study support this hypothesis by showing a distinct variation in benthic foraminiferal abundances between the shallower cores (1308 m, 1543 m) and the deeper core (1815 m). The cores from 1308 m and 1543 m contain a fauna that exhibits a moderate abundance (ca. 10-15%) of several species: Bolivina lowmani, Bulimina aculeata, Cassidulina subglobosa, Gyroidina soldanii and Oridorsalis spp., while the core from 1815 m contains a fauna strongly dominated (25-60%) by two species: Eponides turgidus and Nuttallides decorata. Abundance variations downcore or across the Pleistocene-Holocene boundary are subtle but present nonetheless. The abundance of Cassidulina subglobosa decreases (from 10-15% to 2-10%) across the Pleistocene-Holocene boundary, while Osangulari culter and Bulimina alazanensis are present only in the Holocene sediments.

The preliminary results from this study suggest that the distribution of deep Gulf of Mexico benthic foraminifera may be related to the distribution of water masses comprising the deep gulf and that further bathymetric refinement of the lower slope may be possible.


AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)