Stratigraphy and geochemistry of the volcaniclastic Miocene Pickhandle Formation in the Northern Calico Mountains

The Early Miocene Pickhandle Formation in the central Mojave Desert was deposited in an extensional basin coeval with regional crustal thinning. The volcaniclastic Pickhandle Formation deposits record recurrent, explosive, rhyolitic volcanism associated with an unknown source that was likely nearby, and is composed of abundant volcanic ash and coarse clastic deposits. In the northern Calico Mountains, the Pickhandle Formation is characterized by Yermo dacite domes that interbed with the ash-rich volcaniclastic sediments, and geochemistry that indicates the subalkaline rocks share a similar geochemical signature, but have different mineral assemblages. The Pickhandle Formation stratigraphy in the northern Calico Mountains is consistent with previous research that indicates the volcaniclastic deposits were deposited in an environment with alluvial fan, lacustrine, and fluvial influences. Freshwater gastropod and bivalve trace and body fossils of Early Miocene age are found in the study area