ENVIRONMENTAL CONDITIONS OF THE TECOPA BASIN DURING THE MIDDLE PLEISTOCENE BASED ON FOSSILIZED DIATOM ASSEMBLAGES BELOW THE BISHOP TUFF

Sedimentary deposits found within the Tecopa Basin of southeastern California, located in the Basin and Range physiographic province, are thought to have formed in a lake that persisted throughout the Pleistocene. Sparse evidence from fossilized ostracodes found within basin sediments suggest that the Tecopa Basin may have been primarily a spring-fed hydrologic system. Diatom samples from within the basin were collected near the town of Shoshone, California and analyzed to better determine the paleohydrologic enviornment of the Tecopa Basin. The diatoms found within these samples are similar to modern diatoms found at Mono Lake and other hypersaline and alkaline lakes throughout the Basin and Range province and are dominated by the genera Denticula, Fragillaria, and Navicula. Diatom specimens from modern spring systems found within the basin were collected for comparison to Tecopa Basin diatoms. Diatoms were rare and only poorly preserved in the modern spring samples but included Anomoeoneis and Stauroneis. Further research in the area may prove useful to determine the paleontological conditions and depositional environments of the Tecopa Basin deposits.