Quaternary Planktonic Foraminiferal Paleoecological Models, Northeastern Gulf of Mexico

Glenn W. Johnson, Ronald E. Martin

Faunal data from the Pleistocene section of the Ocean Drilling Program's hole 625-B (leg 100) in the northeastern Gulf of Mexico have been subjected to vector analysis (a descendant of Q-mode factor analytic methods). Vector analysis explains a multi-dimensional data set (in this case 19 species) in terms of a smaller number of end-member assemblages. From this analysis, two Pleistocene paleoecological models are proposed.

An eight-end-member assemblage model best fits the data set, and 7 of the 8 end-member assemblages are dominated by a single species. These seven species are also the most abundant taxa in the Pleistocene section, and each appears unique in its response to environmental factors. Maximum paleoecological information is extracted not from a subassemblage model, but from single-species frequency variation.

Conscious of the fact that paleoenvironmental information is being lost, a three-end-member assemblage model is proposed that allows differentiation of the dominant paleoclimatic controlling factors. The end-member assemblages are (1) a background subtopical assemblage, (2) a glacial assemblage, and (3) an assemblage tolerant of broad changes in salinity. As would be expected from the global oxygen isotope records, the glacial assemblage shows high-frequency, high-amplitude oscillations during the Brunhes chronozone (biozones T through Z). The salinity-tolerant assemblage generally increases in abundance from the early Pleistocene to the Recent. Spikes in this assemblage during the late Pleistocene are indicative of episodes of high glacial meltwater influx via the Mississippi River.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.