Salinas Basin, California
The Salinas basin is a Cenozoic strike-slip basin in the Coast Ranges of central California. Underlying the modern Salinas River Valley, this elongate, narrow basin is situated to the west of the San Andreas fault and Gabilan Uplift, and to the east of the Santa Lucia Range. Basin fill comprises Cretaceous through Quaternary strata, but is dominated in thickness by the Miocene Monterey Formation. The Monterey Formation owes its appreciable thickness to rapid subsidence in a localized basin during Middle Miocene time. Following ~3.5 km of burial, this accumulation of Monterey Formation now serves as the source rock to a petroleum system that culminates in the half-billion barrel San Ardo oil field. This giant oil field dwarfs the six other oil fields in the basin, the total oil production from which is less than 2% the volume produced from San Ardo. A through-going strike-slip fault, the Reliz-Rinconada Fault (RRF), offsets two partial paleo-depocenters that were once whole prior to RRF displacement. The eastern partial depocenter, the Hames Valley Trough, located 9 km from the San Ardo oil field, contains the generative source rock feeding the San Ardo accumulations. The western partial depocenter, the Arroyo Seco Trough, is offset ~40 km to the north. Although this depocenter is also in the oil window, there are no known oil accumulations on this western side of the RRF.
Graduate Student Tess Menotti has undertaken a basin and petroleum system modeling study of the Salinas basin. The motivations of the study are: 1) Determining the timing of source rock maturation to provide a foundation for understanding the entire petroleum system development, and 2) evaluating burial history (and basin exhumation) as controlled by local structural and diagenetic modifications to the sedimentary record to reduce uncertainty in evaluating regional heat flow histories.
Ongoing work includes refinement of 1D burial history models to account for Monterey Formation diagenesis, and evaluating the associated impact of paleo-geothermal gradients. These pyrolysis- and silica phase boundary-calibrated 1D models will constrain 3D basin models of the Salinas basin as described in the study, Incorporating strike-slip faulting in BPSM