Mariposa Formation
Mariposa Formation
Late Jurassic, Oxfordian to Kimmeridgian
Chiefly slate and graywacke with lesser pebble conglomerate, fine-grained mafic tuff, and massive tuffaceous greenstone. Local mafic volcanic breccia, and thin mafic tuff beds. Local metachert and quartz slate. Locally intruded by porphyritic hypabyssal sills. Locally highly metamorphosed to mica- and andalusite-schist. Overlies Logtown Ridge Formation (unit CMLV).