Tuolumne ophiolite-mélange
Tuolumne ophiolite-mélange
Triassic(?) and Permian
Deformed blocks of harzburgite, dunite, wehrlite, gabbro, serpentinized ultramafic rocks, greenstone, and limestone. Local minor basalt layers. Local narrow chrysotile veins and pods of chromite. Includes a metaplagiogranite block that yielded a zircon U-Pb age of roughly 280-300 Ma (Saleeby, 1982). Structurally overlain by Penon Blanco Volcanics (unit CPPB) and Jasper Point Formation (unit CPJP). Large mass in the southern part of the terrane is named the Tuolumne ultramafic complex (e.g. Wills and others, 2022). Occurs along and east-northeast of the Bear Mountains fault. Interpreted as part of the basement of an Early Jurassic to Late Triassic island arc.