AGE OF JURASSIC VOLCANISM AND TECTONISM, SOUTHERN OWENS VALLEY REGION, EAST-CENTRAL CALIFORNIA

Remnants of the eastern fringe of the volcanic and volcanogenic sedime ntary cover of the Mesozoic Sierra Nevada batholith are exposed in the southern Inyo Mountains and adjacent Alabama Hills of east-central Ca lifornia. Six new U-Pb dates on volcanic units and crosscutting intrus ions reveal that the upper parts of both the Inyo Mountains and Alabam a Hills sections accumulated during Middle and Late Jurassic time. Dur ing this same interval, both sections were steeply tilted and locally folded during one or more episodes of contractile deformation occurrin g in the east Sierran thrust belt. Differences between the largely und ated lower parts of the Inyo Mountains and Alabama Hills sections sugg est that they were once located farther apart, then later brought into proximity by thrust faulting or strike-slip faulting. The Inyo Mounta ins and Alabama Hills sections are similar to partly coeval strata in the White Mountains, in that both contain abundant sedimentary strata that were in part deposited in or near terrain of moderate topographic relief. Together, these areas seem to compose a distinctive arc-margi nal depositional province different than that represented by partly co eval strata preserved in pendants to the west.