Conglomerate-Bearing Formations in California

Abstract

Conglomerates and related coarse detrital deposits often have great economic value and are indicators of past tectonic conditions. To date, over 200 significant conglomerate-bearing formations have been identified within California. For each of the formations, the authors have obtained data on age, type locality, areal extent, lithology, stratigraphy, thickness, stratigraphic relationships with adjoining formations, depositional environment, provenance, transport direction, dating methodology, timing of the generative orogenic event, mineral and hydrocarbon resources, and other pertinent data. The time-space distribution of these conglomeratic formations is such that the volume of these deposits peaks in the late Proterozoic, Cretaceous, and Miocene, and is at a minimum in the early Paleozoic and early Tertiary. Conglomerates make up a significant part of the stratigraphic column in all of the geologic provinces of California except the Modoc Plateau where they may be buried by basalt flows. Late Cenozoic conglomerates are most common in coastal southern California whereas Cretaceous units dominate in the north. Precambrian and Paleozoic formations generally occur in the northern deserts and northern Sierra. Thicknesses of these units range from less than 1 m in persistent members to over 9,000 m in the thickest formation.