Productivity along the California margin during early Pliocene warmth

Abstract

The early Pliocene is the most recent time in Earth history when average global temperatures were warmer than today. This study presents smear slide derived phytoplankton MAR from ODP Sites 1016 and 1022 along the California margin from 2.5-4.5 Ma. At ODP site 1016 a 2 to 10 g/cm2/ky increase in bulk sedimentation and a 0.30 to 1.00 g/cm2/ky increase in diatom MAR from the early to late Pliocene, split at at 3.5 Ma, is likely the result of tectonic movement from within an upwelling shadow zone to a location more directly influenced by the California Current. Significant increases in coccolith MAR at both sites and a decrease in diatom MAR from the early to late Pliocene at ODP Site 1022 suggests a decrease in surface nutrient availability as SST cooled. Existing SST and paleo-productivity records suggest sustained upwelling from 2.5-4.5 Ma, and changes in diatom and coccolith productivity can be explained by a deepening nutricline from 4.5 to 2.5 Ma.