Publication Date

Fall 2010

Degree Type


Degree Name

Master of Science (MS)




Ellen P. Metzger


Conglomerate, Late Cretaceous, Pescadero Felsite, Pigeon Point Formation, Tectonics, Vaqueros(?) Formation

Subject Areas

Geology; Petrology; Geochemistry


The depositional location of the Late Cretaceous Pigeon Point Formation, which crops out between San Francisco and Santa Cruz on the California coast, is unknown. Petrographic and chemical analysis of the conglomeratic clasts in the formation revealed several types of clasts that were helpful to constrain provenance. These included clasts of the recently identified underlying Pescadero felsite, clasts of dark porphyries with salmon-colored phenocrysts that have been identified at four other depositional locations, and granitoids for which isotopic data existed.

Synthesis of research performed for this thesis with previously published data leads to a hypothesis that suggests the Pigeon Point Formation was deposited in the mid-Campanian at a paleolatitude south of the current United States, onto the Pescadero felsite, in an accretionary complex setting. By the late Miocene, it was transported northward to a position near the present-day location of San Luis Obispo, then brought to its current location, within the past 10 Ma, by dextral slip on the San Gregorio-Hosgri fault and the San Andreas fault system.