An Evaluation of Paleogene Paleobathymetric Models: Benthic Foraminiferal Distributions in the Metrella Member of the Tejon Formation, Central California

Abstract

Benthic foraminiferal biofacies provide a useful means for estimating paleobathymetry in Mesozoic and Cenozoic marine rocks. These estimates are made on the basis of biofacies models reflecting the distribution of benthic foraminifera in the modern ocean. Paleooceanographic evidence suggests that past oceans were probably much different from the modern ocean; therefore, benthic biofacies models need to be recalibrated for periods that differ significantly from the present. An analysis of benthic foraminifera from the middle Eocene Metrella Sandstone Member of the Tejon Formation provides an opportunity to test current paleobathymetric biofacies models for continental margin settings. Sedimentologic and stratigraphic evidence identified the Metrella strandline, shelf-edge, and slope. The distribution of three taxa thought to represent deep water (lower middle bathyal or deeper), Bathysiphon eocenica, Cyclammina spp., and Plectofrondicularia packardi s. l., indicates that they all are present or abundant in outer-shelf to shelf-edge environments. The much broader bathymetric range of these taxa may reflect a less density-stratified water column than in the modern ocean.