A model for improving the precision of paleobathymetric estimates: an example from the northwest Gulf of Mexico

Abstract

Intraspecific variation in test morphology of ten commonly occurring, benthic foraminiferal species collected from 47 stations and from water depths ranging from 53 to 3230 m in the northwest Gulf of Mexico were subjected to canonical discriminant analysis in order to statistically define an a priori bathymetric zonation. Three species (Bolivina subspinescens, Gavelinopsis translucens, and Uvigerina peregrina) had intraspecific variation capable of statistically dividing the bathyal zone into six contiguous 200 m intervals. Statistical analysis of the remaining seven species (Bolivina albatrossi B. lowmani, Cassidulina subglobosa, Cibicidoides pachyderma C. robertsonianus, Epistominella exigua, and Qridorsalis umbonatus) divided the bathyal zone into five contiguous 250 m intervals. The statistical differences in morphologic variability found in this study appear to be the organism's physiologic response to biogeochemical changes in sea floor habitat as they transcend various water masses. As such, the statistical analyses is a direct measure of the effect of those environmental factors, allowing better resolution and reliability of paleodepth estimates and geodynamic modelling than that commonly attained through faunal association.