Paleoecologic analysis and age of a late Pleistocene fossil assemblage from upper Newport Bay, Newport Beach, Orange County, California

A new fossil site containing abundant late Pleistocene marine invertebrates was exposed during grading activities near the northeastern end of Upper Newport Bay, in the city of Newport Beach, Orange County, southern California. The site has since been destroyed but yielded an assemblage of at least 103 species, represented by 98 species of mollusks (54 bivalves, 43 gastropods, and one scaphopod), at least three species of arthropods (barnacles and crabs), and two echinoids from six spot collections. The composite assemblage from the Fletcher Jones site (Orange County Paleontological Collections [OCPC] localities 2601 through 2606) represents a mixed thanatocoenosis, including representatives from protected bay, sandy-bottom and rocky-bottom, protected to open coasts, and offshore environments. The percentage (12.6%) of extralimital southern species indicates warmer-water temperatures than presently exist along the Orange County coast. The age of the fauna (similar to 120,000 yr) is inferred from correlation with similar, U-series dated faunas from the same marine terrace around Upper Newport Bay. Correlative faunas from nearby localities contain extralimital southern species, and date to marine oxygen-isotope (delta O-18) substage 5e. Turritella mariana Dall is reported as a fossil for the first time.