DESCRIPTION OF THE SEDIMENTOLOGY AND TAPHONOMY OF THE LATE UINTAN TALEGA BONEBED FROM ORANGE COUNTY, CALIFORNIA

Eocene terrestrial vertebrates from Southern California are known from Ventura, San Diego, and Orange Counties. Relative to the other two counties, the sites and specimens from Orange County are poorly known. Paleontology mitigation monitoring of the Talega Housing Development in San Clemente, Orange County, California in 1998 excavated a vertebrate bonebed from the Eocene-aged Santiago Formation. The bonebed, named the Talega Bonebed, represents just the second Orange County locality with Eocene terrestrial vertebrates. The bonebed was excavated as 46 cubic meter blocks, five of which have been prepared using standard mechanical techniques and heavy liquid separation. The bonebed is approximately 10 cm thick and comprised of densely deposited, disarticulated skeletal elements with no obvious associations. Sparsely distributed fossils can be found in the overlying layer. Sedimentologically, the Talega Bonebed matrix comprises a compositionally immature, orange-tan, muddy, very fine to coarse-grained sandstone. Fossils prepared from the bonebed exhibit varying degrees of weathering with denser skeletal elements, such as vertebrae, astragali, mandibles, and isolated teeth exhibiting better preservation. The Talega Bonebed is a highly productive fossil locality with 22 taxa identified to date. Based on the mostly poor state of fossil preservation, spatial density, and diversity of taxa, it is likely the formation of the Talega Bonebed can be attributed to hydraulic concentration in which skeletal elements from multiple sources accumulated overtime in a fluvial environment. The high density of fossils within the bonebed may suggest that sediment input was low during deposition of the Talega Bonebed and categorizes it as a time-averaged, attritional accumulation. Comparison of the Talega Bonebed assemblage with assemblages from contemporaneous strata in Ventura and San Diego Counties show that the identified taxa are typical of the Southern California late Uintan fauna. The absence of taxa known from either Ventura or San Diego Counties in the Talega Bonebed is likely due to taphonomic and collecting biases. The similarities among fossil assemblages in all three counties suggest that the paleoenvironment was similar across Southern California during the late Uintan.