Abstract
The Great Basin is the largest section of the Basin and Range physiographic province (Fenneman, 1930). It includes most of Nevada and western Utah, with fringes extending into Oregon, Idaho, and California (Fig. 1). The basin was named by Fremont (1845), who established that no water drained to the ocean from this huge (>500, 000 km2) region. The Great Basin is an internally drained complex of more than 150 intermontane alluviated basins, separated by about 160 subparallel mountain ranges. Adjoining basins and ranges generally are about the same width, but the basins tend to be longer than their bordering ranges. Mountain ranges typically are elongate, a few being 80 to 190 km long, but some ranges are irregular to almost equidimensional, especially in the Walker fault zone and Mojave Desert. Most of the ranges and basins trend north or northeast but a few are northwest to east-westerly. The northern and central Great Basin resembles a collapsed dome, lowest along its margins, bulging in the center. In western Nevada and western Utah the floors of principal intermontane basins are at altitudes of 1,150 to 1,400 m, and the higher mountain summits are chiefly between 1,800 and 2,500 m, rarely above 3,000 m. In northeastern and east-central Nevada (the highest part of the Great Basin), elevations of intermontane-basin floors are 1,600 to 1,900 m and many mountain summits are above 2,400 m, dominated by Mt. Wheeler (3,984 m). However, in the southern and southwestern one-third of