Abstract

New gravity data indicate a large unexpected anomaly in the Saline Range and other anomalies in neighboring ranges and valleys of eastern California. Residual gravity anomalies, calculated by subtracting the field due to an Airy model of isostatic compensation, show the effects of lateral density contrasts in the upper crust. A well-defined negative gravity anomaly is centered over the Saline Range and connects the Eureka Valley and Saline Valley gravity minima. Apparently, the Saline Range is a thin veneer of young volcanic material lying on a major alluvium-filled basin connected on the north with Eureka Valley and on the south with Saline Valley. We suggest that the basin formed in a pull-apart zone that filled with low-density alluvium and became the site of voluminous Pliocene volcanic eruptions. The age of this depression predates volcanism of the Saline Range dated at about 4 Ma. Other significant anomalies are as follows: (1) An offset in the Owens Valley fault at lat 37°01′N appears in the isostatic residual gravity data and marks the western end of a major gravity depression that continues across the Inyo Mountains at Papoose Flat. The gravity depression suggests that the Papoose Flat pluton is larger than suggested by its surface exposure and may extend on the order of 10 km below the topographic surface. (2) A density boundary trends west-northwest across the Inyo batholith and Proterozoic and Paleozoic rocks of the White Mountains. This trend is anomalous to exposed geologic structures and may reflect a structural boundary buried at relatively shallow depth. (3) A large gravity low, unexpected on the basis of exposed geologic features, is in the eastern Sierra Nevada southwest of the town of Lone Pine.

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