GEOARCHAEOLOGY OF EL FIN DEL MUNDO, A CLOVIS SITE IN SONORA, MEXICO

The highest concentration of in situ Clovis/mammoth sites, representing the oldest widely-accepted archaeological assemblage in North America, is in the Upper San Pedro River Valley, southeast Arizona, within 50km of the Mexican border. Until recently little was known about early sites in northwestern Mexico. Inventory of collections and survey in northern Sonora has begun to change that situation. Diagnostic Paleoindian artifacts, including Clovis and unfluted point styles, are now known from 25 localities, ranging in size from extensive site complexes to isolated finds. Most are located on the broad alluvial plain of the lower Rio Sonora whose headwaters share a drainage divide with the headwaters of the San Pedro. In volcanic hills north of the Rio Sonora our efforts resulted in discovery of the first intact Clovis site found in Mexico: El Fin del Mundo. The site was exposed in an arroyo incising valley fill in an intermontane basin ~400-500m higher than the surrounding alluvial plain. El Fin del Mundo preserves multiple areas of Clovis activity, with a buried bone bed and an upland camp. The bone bed includes remains of two disarticulated mastodon buried under diatomaceous deposits >10,000 ¹⁴C years BP. Lithic flakes were recovered from the bone bed; two out-of-place Clovis points, one fragmentary fluted point with characteristic impact damage, and one large cutting tool were found near the eroded margins of the feature. The camp site consists of a wide range of tools, including fragmentary Clovis points, end scrapers, blades and blade core rejuvenation flakes, most of which are made of high quality raw material, resting on a well developed soil (Bt-Btk profile) that began forming <36,000 ¹⁴C years BP. Locally the soil is buried by a thin but extensive marl that began forming ~15,000 ¹⁴C years BP. Dating is still in progress, but marl formation is probably partially contemporaneous with deposition of the diatomaceous earth, both representing a regionally high water table that declined in the early Holocene.