Date of this Version
RECONNAISSANCE BATHYMETRY OF BASINS OCCUPIED BY PLEISTOCENE LAKE LAHONTAN, NEVADA AND CALIFORNIA, By L. V. Benson and M. D. Mifflin. U.S. GEOLOGICAL SURVEY, Water-Resources Investigations Report 85-4262
Beginning about 12,500 years B.P., Lake Lahontan began to decline (fig. 1: Black Rock Desert data from Davis ; Truckee River Delta data from Born ; tufa data from Benson ; packrat-midden data from Thompson and others ) . As water levels declined, their altitudes fell below sill altitudes (table 1); locations of these sills are shown in figure 2. Today, five surface-water bodies (Black Rock Playa, Humboldt-Carson Sink, Walker Lake, Pyramid Lake, Honey Lake) exist in four of the seven subbasins (fig. 2).
The collective surface area of the modern lakes today (1985) totals less than 1,600 km2 . This area is fourteen times smaller than the surface area existing 14,000 to 12,500 years B.P. The remarkable change in lake surface area, volume, and altitude, that occurred between 12,500 and 11,500 years B.P., has led various workers to speculate on the nature of climate change that occurred during this period of time (Antevs, 1952; Broecker and Orr, 1958; Morrison, 1964; and Benson, 1981). To perform calculations of climate change, based in part on surface area and volume change as a function time, the relation of surface area and volume to altitude of age-dated, shoreline-related materials must be quantified.
The purpose and scope of this study is to provide bathymetric parameters (volume and area) for each of the Lahontan subbasins as a function of lake level (altitude above sea level). This information can be used to calculate t he change in lake area and volume for individual subbasins, in which datable evidence for shorelines exists . In this way, estimates of climate change can be made for times when Lake Lahontan consisted of two or more bodies of water. To illustrate the usefulness of the bathymetric data, one hypothetical example is described for the changing topology of the Lake Lahontan system as a function of decline in lake level(s) from the 1,330-m highstand.