Nature of the Angular Unconformity between the Paleozoic Metasedimentary Rocks and the Mesozoic Metavolcanic Rocks in the Eastern Sierra Nevada, California
Two major wall-rock sequences, the Paleozoic metasedimentary rocks and the Mesozoic metavolcanic rocks, in the eastern Sierra Nevada, California, are separated by an angular unconformity rather than by a fault as has been proposed by other investigators. The unconformity is parallel to formation contacts in the younger metavolcanic rocks and crosscuts formation contacts in the older metasedimentary rocks. Locally, basal conglomerate with pebbles derived from the older metasedimentary rocks occurs just above the unconformity. The older metasedimentary rocks consist mostly of former marl, chert, and mudstone; they contain three generations of superposed structures. The younger metavolcanic rocks consist mostly of former andesite flows, tuff, and graywacke; these contain only the younger two generations of superposed structures. The sinuous trace of the unconformity is primarily the result of superposed deformations of regional scale which occur in most roof pendants of the eastern Sierra Nevada.