- Author: Ruth Gruhn and Alan L. Bryan
Excavations at Abrigo de los Escorpiones, a large rockshelter on Baja California’s northwest coast, revealed archaeological deposits exceeding six meters in depth. Three distinct midden zones accumulated over more than 10,000 years. A rich faunal assemblage provides detailed information regarding the paleoenvironmental record of this coastal region.
Excavations at Abrigo de los Escorpiones, a large rockshelter nestled in an ancient volcanic crater on Baja California’s northwest coast, revealed archaeological deposits to a maximum depth of six meters. A total of 95 radiocarbon dates, obtained from charcoal and bone collagen, document a continuous occupation over 10,000 years. The midden layers were divided into three zones based on sedimentary matrix differences. The earliest intensive occupation dated to about 10,000 to 7,500 years ago and overlie a Late Pleistocene rubble stratum. A second period of occupation. the middle midden zone, continued to about 5,500 years ago. The uppermost midden appears to have accumulated up until the historic period. Identification and analyses of this site’s rich faunal assemblage provide detailed information regarding the paleoenvironmental changes since the end of the Pleistocene. Identified species include mammals and birds, such as the flightless duck Chendytes lawi, that have gone extinct and others whose ranges no longer extend into this region. Analysis of oxygen and carbon isotopes from systematically collected California Mussel shells document what is likely the longest continuous proxy record of changes in sea surface temperature and upwelling strength from the late Pleistocene through the Holocene. Faunal remains suggest a moist environment, cooler sea temperatures, an offshore kelp forest, and nearby saltmarsh during the Early Holocene. A warm, dry climate episode and disappearance of the estuarine environment is indicated by species present during the Middle Holocene. Unique bone artifacts were recovered from cultural deposits found in the middle midden zone. The upper midden zone contained extensive shell lenses, abundant remains of fish species, marine mammals, small terrestrial fauna, and a great deal of cultural debris. The site served as a seasonally occupied camp focused on harvesting marine resources throughout prehistory. The scarcity of fresh water during the summer, suggests a primary use during the rainy season. The faunal assemblage and artifacts from the earliest occupation at this site are consistent with the Paleocoastal Tradition, a maritime-focused subsistence economy, which has been reported on Isla Cedros further south and in the Santa Barbara Channel region to the north.