Stratigraphy, provenance, and tectonic significance of the Punchbowl block, San Gabriel Mountains, California, USA

The Punchbowl block is a fault-bounded crustal sliver in the eastern San Gabriel Mountains of southern California with important implications for conflicting reconstructions of the San Andreas fault system. Detailed mapping, determination of conglomerate-clast and sandstone compositions, and dating of detrital and igneous zircon of Oligocene-Miocene strata define two distinct subbasins and document initiation of extension and vol-canism ca. 25-24 Ma, followed by local exhumation of the Pelona Schist, and transition from alluvial-fan to braided-fluvial deposition. Strata of the Punchbowl block correlate with those of other regions in southern California, confirming 40-50 km of dextral slip on the Punchbowl fault, and supporting reconstructions with 60-70 km of dextral slip on the San Gabriel/ Canton fault and similar to 240 km of dextral slip on the southern San Andreas fault. Provenance and probable correlations of Punchbowl-block strata argue against 80-110 km of dextral slip on the San Francisquito-Fenner-Clemens Well fault and limit the time interval during which such slip could have occurred. Synthesis of these findings with previous work produces paleo-geographic reconstructions of the Punchbowl block and its probable correlatives through time.