 It is unlikely that the lake was ephemeral, however, given the presence of fossils in the lake sediments of foraminifera which do not tolerate such drying.Probably owing to uplift of the Sierra Nevada and expansion of the catchment, water levels at Lake Tecopa increased during the Pleistocene and reached highstands concurrently with other lakes in the Great Basin.The highest shoreline occurs at about elevation (subsequently tectonically deformed) about 186,000 years before present; it appears to coincide with the Eetza highstand of Lake Lahontan and oxygen isotope stages 8, 7 and 6.