A Multi-Proxy Approach for Provenance Evaluation of the Stevens Sandstone, San Joaquin Basin, California

Abstract

The Stevens sandstone is a prolific hydrocarbon reservoir in the southern San Joaquin Basin that has produced greater than five billion barrels of oil equivalent and represents an important exploration target. Understanding the Stevens sandstone’s provenance is critical for predicting mineralogic composition and subsequent controls on reservoir characteristics. To address this, a multi-proxy provenance analysis of the Stevens sandstone was conducted to characterize sandstone mineralogy (thin section modal point-counts), geochemistry (portable X-ray fluorescence), heavy mineral analysis, and detrital zircon U-Pb geochronology. Stevens sandstone provenance likely varies around the basin margin, with probable sediment sourcing from the Sierra Nevada highlands to the east, the ancestral Tehachapi Mountains to the south, and the Temblor Range to the west. Samples collected in this study span both the basin margins (zones of sediment input and bypass) and basin center (zone of sediment mixing). Preliminary petrographic results show that the Stevens sandstone is variably quartzo-feldspathic (QmFLt portions range from 52:44:4 to 27:61:11) and has varying abundances of volcanic and sedimentary rock fragments. Geochemical data reflect both framework grain mineralogy and diagenetic effects, including mineralogy of cements and other authigenic components. Samples are currently undergoing processing and preparation for heavy mineral analysis and detrital zircon U-Pb geochronology. We anticipate that integrated, multi-proxy provenance analysis will yield a more complete picture of Stevens sandstone provenance than using any method in isolation. Ultimately, this research aims to better constrain the link between sandstone provenance, reservoir characteristics, and hydrocarbon production in the southern San Joaquin Basin, and analogous settings worldwide.

AAPG Datapages/Search and Discovery Article #90372 © 2020 AAPG Pacific Section Convention, 2020 Vision: Producing the Future, Mandalay Beach, Oxnard, CA, April 4-8, 2020 (Cancelled)