Tor H. Nilsen¹, S. A. Reid², David R. D. Boote³

(1) Consulting Geologist, San Carlos, CA
(2) Occidental of Elk Hills, Inc
(3) Consulting Geologist, London, United Kingdom

ABSTRACT: Tectonic, Paleogeographic, and Relative Sea Level Controls on Deep-Water Depositional Systems of the Southern San Joaquin Basin, California

The southern San Joaquin Valley forms one of the most productive onshore basins in the world. The principal reservoirs consist of Eocene to Pliocene deep-sea fans and related turbidite systems. Large amounts of subsurface and outcrop data provide a regional framework for defining reservoir geometry and the depositional framework. The primary hydrocarbon source rocks are Miocene siliceous shales of the Monterey Formation. The basin has had a complex geologic history, originally having formed as a forearc in the Late Mesozoic. Accretionary events in the early Tertiary along the western flank of the basin resulted in reorganization of the basin and formation of new provenance areas. Extensional events during the Oligocene yielded new depocenters. In the Miocene, strike-slip deformation associated with the San Andreas fault system caused renewed subsidence and extensive deformation around the margins of the basin. The major constant throughout most of this history has been the deposition of mostly sand-rich turbidite systems that form excellent reservoirs. The interplay between changing tectonic framework, paleogeography, and relative sea level has yielded a complex temporal and spatial distribution of the deep-marine reservoirs. The basin has been partly to almost wholly restricted during most of its history, with a regionally extensive granitic and metamorphic provenance for the turbidite systems along its eastern and southern flanks. Along the western margin of the basin, terranes of granitic and metamorphic rocks migrated northward through time and space along the San Andreas fault and shed a complex system of turbidites into a deep-marine sea floor undergoing strike-slip deformation.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado