Golden Trout volcanic field
Golden Trout volcanic field
late to early Pleistocene
Consists of at least eight mafic to felsic cinder cones and lava domes, with associated lava flows and fragmental deposits, extruded onto the Kern Plateau, in the southern Sierra Nevada, at approximately 2,750 m elevation. Includes volcanics mapped as the Toowa volcanic field by earlier workers (e.g. Webb, 1950). Compositions range from basalt to rhyolite, and include trachybasalt and basaltic trachyandesite (Browne and others, 2017a). The more mafic lavas typically contain phenocrysts of plagioclase, olivine, and clinopyroxene (Browne and others, 2017a). Though there is substantial overlap in ages, spatial-compositional patterns are more discrete: rhyolitic domes are generally older and occur in the eastern/southeastern part of the field whereas mafic vents are generally younger and occur in the northwestern part of the field. Multiple ~2.4 Ma ages on rhyolitic domes, determined by K-Ar and Ar-Ar (Bacon and Duffield, 1981) establish maximum determined ages for the volcanic field. A minimum age of 52-59 ka was determined by cosmogenic 36Cl dating of the unglaciated basaltic Groundhog cone (Browne and others, 2017b) and is the youngest age determination for a volcanic unit within the southern part of the Sierran block.