Stable isotope compositions of fossil mollusks from southern California: Evidence for a cool last interglacial ocean.

Stable isotope compositions have been determined for modern mullusks and fossil mollusks collected from uplifted marine terraces at three localities in southern California. By using a paleoclimatic model that decouples the temperature and ice-volume signals in ocean water, ocean-water temperatures off southern California are estimated to have been −3.8 °C at ∼85 ka, −3.0 °C at ∼107 ka, and −2.2 °C at ∼125 ka relative to present temperature. These results indicate rather cool conditions during the peak of the last interglacial stage at 125 ka and conflict with results from terrace faunal studies that suggest water temperatures were warm or warmer than at present.