UCLA

The Middle Miocene Mint Canyon and Caliente formations represent sedimentation after triple-junction extension in southern California. Sandstone and conglomerate petrology, combined with detrital-zircon analysis, determines provenance of the Mint Canyon and Caliente formations. These data indicate that most detritus is locally derived, rather than being derived from the Chocolate Mountains across the San Andreas fault. The Mint Canyon and Caliente formations received Proterozoic anorthosite-syenite-gabbro and Triassic Lowe plutonic detritus from the San Gabriel Mountains throughout their depositional history, but show variations geographically from more locally derived sources, including Pelona Schist from Sierra Pelona.

Discriminant analysis of sandstone and conglomerate indicates strong correlation between the Mint Canyon and Caliente formations. Each group for the Mint Canyon Formation (schist (S), volcanic (V) and plutonic (P)) shows a distinct age peak (based on detrital zircons) from a nearby source rock. The plutonic group has a strong Lowe Pluton signal (220 Ma), the volcanic group has a strong Vasquez and related volcanics signal (25 Ma) and the schist group has a strong Lowe Pluton and Pelona Schist signal (220 Ma and 75 Ma). The Caliente Formation is less distinctive, but shows the same Lowe Pluton (220 Ma), unknown local plutons (150 Ma), volcanic (25 Ma) and schist (75 Ma) signals. All samples show Proterozoic anorthosite-syenite-gabbro and gneiss signals (1200 Ma and 1700 Ma) that are weaker to the west.

This study supports the importance of integrated multi-method analyses. Conglomerate petrology, sandstone petrology and detrital-zircon analysis constrain drainage styles of Mint Canyon and Caliente provenance. Independently, each method provides limited provenance information about rock type or age, but together, they demonstrate correlation between the Mint Canyon and Caliente formations, and refine our understanding of source rocks and paleogeography.