Abstract: Paleooceanographic Variations and Their Implication to Paleobathymetric Interpretation

Gregg H. Blake, R. G. Douglas

Present-day deep sea benthic foraminiferal assemblages appear to be controlled more by the distribution and migration of bottom-water masses than by bathymetry. Recent studies in the North Atlantic by Streeter and Schnitker suggested that deep-sea benthic faunas have experienced major changes in depth distributions during the Pleistocene. The sedimentary record of the California borderland also indicates that the upper depth limit of the deep-water benthic foraminiferal species, such as Melonis pompilioides, fluctuated through the glacial stages. The expansion, contraction, and migration of water masses caused a change of several hundred meters in the depth ranges of benthic foraminiferal assemblages.

Prevalent concepts of foraminiferal paleobathymetric interpretations are based on the modern distributional patterns of living benthic faunas and assume that species depth habitats have not changed with time. Studies in the California borderland suggest that this assumption is not necessarily correct. The depth distribution of benthic foraminiferal assemblages has not been constant, but has fluctuated through time, especially during the Pleistocene.

AAPG Search and Discovery Article #90976©1976 AAPG-SEPM-SEG Pacific Section Meeting, San Francisco, California