ABSTRACT This field trip examines Paleoproterozoic basement, Neoproterozoic metasedimentary strata, and crosscutting Mesozoic intrusive rocks at Frazier Mountain, Placerita Canyon, and Limerock Canyon in the western San Gabriel Mountains block, California. We present new U-Pb zircon geochronology results that constrain the Proterozoic through Cretaceous tectonic and magmatic history. The excursion ends in San Antonio Canyon in the eastern San Gabriel Mountains where several large rock avalanche deposits are sourced from distinct basement rocks. 10 Be surface exposure ages and post-infrared infrared stimulated luminescence burial ages demonstrate late Pleistocene to Holocene movements for these landslides.

ABSTRACT Conglomerate-clast analysis, sandstone petrology, and detrital zircon age data determine the provenance and correlation of the Middle Miocene Mint Canyon and Caliente Formations. Detrital zircon age assemblages and sandstone compositions confirm that the Mint Canyon Formation is the upstream equivalent of the southern Caliente Formation and that both are dissimilar to the Punchbowl Formation. The Mint Canyon and Caliente Formations are remnants of an axial drainage system that was likely confined by the ancestral Sierra Pelona/Blue Ridge to the north and ancestral San Gabriel Mountains to the south; sediments derived from these local highlands dominate in the Mint Canyon Formation. This study highlights the importance of integrated-methods analysis. Sandstone detrital modes capture the variability in sandstone composition and the degree of overlap between formations; conglomerate-clast compositional data show differences within the drainage system; distinct detrital zircon age assemblages implicate particular source terranes. Analysis of all these data sets provides a robust and complete characterization of the provenance of this confined drainage system.