LAKE ROGERS: A LATE PLEISTOCENE LAKE IN NORTHERN DEATH VALLEY REVISITED

Lake Rogers, a sequence of interbedded white silt and sand in northern Death Valley, was first described by Clements (1952). He estimated the age of Lake Rogers to be late Wisconsin based on the presence of large mammal fossils (e.g., Mammuthus, Equus) contained within the deposits. The Lake Rogers deposits are about 12 meters thick and have been found to contain plant and aquatic mollusk remains, humic layers, and several thin tephra beds. A geochemical analysis (EMA) of a 3-cm-thick tephra bed from the upper part of the section indicates a composition that most closely resembles one of the Wilson Creek tephra (beds 9-19) at Mono Lakes that were erupted between 25 ka and 50 ka. Additionally, radiocarbon analysis of tufa found in Mesquite Flat that correlates stratigraphically to the top of the Lake Rogers section yielded an unleached radiocarbon age of 13,450±80 14C yrs BP (16400-15750 cal yrs BP) further supporting the late Wisconsin age estimate of Lake Rogers by Clements.

Contrary to Clements' interpretation however, Lake Rogers was probably not a lake in the strictest sense, but more of a marsh or spring meadow. The elevation at the top of the Lake Rogers section on the northwestern edge of the basin is 792 m, about 37 m higher than on the eastside of the basin. While this difference could be the result of tectonic deformation, for which there is ample evidence in the area, stratigraphic indications are that the Lake Rogers beds are in or close to their original depositional position. The beds rest conformably on alluvium along the margins of the basin and slope in a direction subparallel to the current channel of Death Valley Wash (12.5m/km). Along the margins of the basin, gravelly alluvium interfingers with Lake Rogers deposits fining laterally from matrix-supported gravel to well-sorted sand and silt towards the center of the basin. Stratigraphic and geomorphic evidence suggest that the lake ponded spring flow emanating from the toes of alluvial fans along the Last Chance Range. The most compelling evidence that Lake Rogers formed as a shallow marsh is the lack of a topographic sill behind which to pond a lake or evidence that the basin was closed.

Clements, T., 1952, Lake Rogers, a Pleistocene lake in the north end of Death Valley, California: Geological Society of America Bulletin [abs.], v. 63, no. 12, pt. 2, p. 1324.