Paleogene conglomerates from Point Arena, California, south to Valle de las Palmas, Baja California, and from San Nicolas Island east to the Salton Sea, were investigated with the purpose of establishing identifiable clast suites based on unique and distinguishable volcanic porphyries. If such a task could be fulfilled, correlations between similar conglomerate suites could be established. Several criteria had to be met. Volcanic porphyries had to be abundant enough to be easily found in outcrop, yet not ubiquitous: they had to be readily identifiable in the field: they required a bold ''gestalt". A number of exotic rhyodacitic porphyries served this purpose. Such exotics are believed to have appeared near the end of the Paleocene in numerous conglomerates along the western North American craton. Source terrane is unknown at present: however, a northwest trending linear volcanic belt is believed to have existed just east of the present Western Cordillera, some 200- 300 km east of sites of deposition. This methodology was employed and generated correlations in four areas: 1. The early Eocene position of San Nicolas Island. 2. The original contiguity of the Sierra Madre- Piru basins. 3. The original continuity of Point Reyes and Point Lobos, California. 4. The late Paleocene and post- Miocene separation of Point Lobos from the Garcia Mountain, California, region.
