Cosumnes River pluton
Cosumnes River pluton
Late Jurassic, ~150 Ma
Small bodies of unfoliated granodiorite and hornblende diorite north and south of the Cosumnes River between the Melones and Bear Mountains faults. Intrudes Mariposa Formation and Sierra Foothills mélange members of the Mother Lode subterrane of the Cosumnes terrane (units CMMS and CMFM). This unit has a preliminary zircon U-Pb age of ~150 Ma (J. Saleeby, California Institute of Technology, written commun., in Graymer and Jones, 1994).