HOLOCENE ALLUVIAL FAN HISTORY AND ARCHAIC PERIOD OCCUPATION IN THE PHOENIX BASIN, ARIZONA

Falcon Landing (FL) (AZ T:7:419 [ASM]) is a multicomponent prehistoric archaeological site located on the distal bajada of the White Tank Mountains in the western Phoenix Basin. This site was excavated as part of the Luke Solar Archaeological Data Recovery Project on Luke Air Force Base in Glendale, Arizona. The objectives of this research were to fully characterize alluvial fan soils and sediments and establish absolute age control for the alluvial stratigraphy in the 44-acre footprint of the site. The lower stratigraphic units at FL were characterized by laterally continuous distal alluvial fan sheet flood deposits separated by pedogenic unconformities. A single date from the lower unit yielded a calibrated age of 18,200-18,600 cal BP while dates from the overlying alluvium bracketed deposition from 8990 to 7950 cal BP. Following a depositional hiatus in the middle Holocene, pulses of alluvial fan sedimentation were radiocarbon dated to 5000-4350, 3300-2850, 2650-2150, and 1350-750 cal BP. Archaeological features stratified in the Holocene alluvium indicate the site experienced light use during the early Archaic and was subsequently abandoned in the middle Holocene from 8000 to 5000 cal BP. Intensified use by Archaic peoples began shortly after 5000 cal BP and was generally coeval with periods of late Holocene fan deposition. The post-5000 cal BP fan deposits are concordant with fluvial regime changes along the middle Gila River and other alluvial fan chronologies in the Phoenix Basin, northern Sonora, and southwestern Arizona. The emerging picture of Holocene fan history in the Sonoran Desert points to widespread aggradation on medial to distal bajadas from 5000 to 4000 and 3300 to 2200 cal BP in response to intensified summer monsoons. At FL the increase in warm-season precipitation along with local hydrological conditions resulted in the expansion of mesquite bosques which in-turn prompted intensified occupation by Archaic hunter-gatherers.