GLACIAL GEOMORPHOLOGY OF THE WHITE MOUNTAINS,CALIFORNIA AND NEVADA: ESTABLISHMENT OF A GLACIAL CHRONOLOGY

The White Mountains, astride the California-Nevada stateline, are the highest and westernmost of the Great Basin ranges. This range was extensively glaciated during the Quaternary Period. Glacial landforms and scattered erratics were identified in the field using primarily morpho-and lithostratigraphic criteria, and mapped on aerial photographs and topographic maps. Topographic characteristics of the glacial deposits were analyzed using standard statistical procedures. A sequence of glacial deposits was identified in terms of six glacial stages, these glaciations named according to type site, and relative ages inferred. With the exception of perched Stage I (early) deposits along the range crest, reconstructed equilibrium-line altitudes and elevation of the glacier termini increase to the present, with glacier length and inferred size decreasing through time. Preliminary data suggest that weathering and pedogenesis are also progressive, though environmental gradients mask some of these distinctions between deposits. It is hypothesized that the White Mountains have a similar glacial chronology to the adjacent Sierra Nevada, but that with the intensification of the Sierran rainshadow during the Quaternary, the extent of glaciation in the White Mountains apparently decreased through time owing to regional tectonic uplift. This had led to the preservation of a more complete sequence of glacial deposits than in the Sierra Nevada, making the delineation of multiple mid-Quaternary events possible in many valleys. Further radiometric and chronometric dating of these deposits is in progress. [Key words: Glaciation, Quaternary, glacial geomorphology, White Mountains, California, Nevada.