TAPHONOMY OF THE MID-IRVINGTONIAN FAIRMEAD LANDFILL LOCALITY, MADERA COUNTY, CALIFORNIA

Located a few miles north of Madera, California, Fairmead Landfill is a mid-Pleistocene (0.78-0.55 Ma) attritional fossil assemblage. The biota, including 72 taxa (2 fish, 2 amphibians, 3 reptiles, 6 birds, 29 mammals, 1 bivalve, 1 gastropod, 12 plants/palynomorphs, 16 diatoms), is dominated by large herbivores. Of the identifiable specimens, 61% are Equus, 15% are Camelops, 7% are Mammuthus, 3% are Paramylodon, and all other taxa combined account for the remaining 14%. Pollen indicates a predominantly grassland habitat, an interpretation supported by the abundance of grazing mammals. Situated on the distal Chowchilla River alluvial fan, the sediments represent channel fill, overbank flood/sheetflood and marsh/lacustrine depositional environments. The fossil assemblage has undergone extensive bone modification. Most skeletal elements occur as fragmented, isolated finds, although some dense bone concentrations occur, as well as occasional associated or articulated remains. Associated and articulated remains are typically medium to large ungulate vertebrae and partial limbs. Pond turtle specimens are the most common non-mammalian remains, and are represented mainly by fragments of the plastron and carapace. In terms of subaerial weathering, most specimens from the site exhibit Behrensmeyer (1978) weathering stage 0, 1 or 2. Biotic agents of bone modification include carnivore activity (puncture marks, gnaw marks, breakage) and large herbivore trampling (parallel striae on bone surfaces and breakage). Canus dirus is likely responsible for much of the carnivore modified bone. A bone orientation analysis by Anglen et al. (2008), of specimens from the 2007 field season, determined that elongate bones showed no alignment with paleocurrent direction, suggesting attrition and preservation of bones in situ rather than accumulation due to fluvial transport. Most elongate elements plunged less than 10 degrees, although a few specimens plunged up to 30 degrees; the latter measurement is consistent with an interpretation of large mammal trampling. Fairmead Landfill is a diverse fossil assemblage representing a variety of depositional environments and exhibiting fossil preservation under numerous taphonomic conditions.