Volcanic and shallow intrusive deposits, very old
Volcanic and shallow intrusive deposits, very old
early Pleistocene to Pliocene
Predominantly undifferentiated basalt, olivine basalt, pyroxene basalt, basaltic andesite, lesser andesite, and minor rhyolite and dacite, scattered across the central and northern Sierra. May locally include alkalic rocks (e.g. latite). Silicic rocks are restricted to the region west of Antelope Valley; these consist of rhyolitic to dacitic lava flows, pyroclastic flows, and hypabyssal intrusions, including those at Tryon Peak. Includes Tuscan and pre-Tuscan age lavas. Age is generally regarded as Pliocene to Pleistocene but may include a minor component of Miocene lavas. Likely includes both magmatic arc and post-arc volcanic products.
In the Tehachapi Mountains, this unit also includes the dacite and red andesite of Michael (1960), who interpreted these lavas as Quaternary based on interpreted stratigraphic relations and thermoluminescence dating.