Paleogeography of the Western Tranvserse Range Province, California: new evidence from late Oligocene and early Miocene Vaqueros Formation

Abstract:

Outcrops of the Vaqueros Formation in the westernmost Transverse Ranges, and Vaqueros hydrocarbon reservoir strata in the adjacent Santa Barbara Channel, reveal dual sediment sources and a complex late Oligocene/early Miocene shoreline geometry. Shelf deposits in the central Santa Ynez Mountains separate a gently sloping, west- and soutwest-facing mainland shoreline to the east (eastern Santa Ynez Mountains and Santa Monica Mountains; all depositional coordinates are preroration) from a steep, east- and south-facing shoreline to the west (westernmost Santa Ynez Mountains). The western and central regions are dominated by lithic-rich arenites and by Franciscan-clast conglomerates (petrofacies one) derived from an emergent portion of an early Tertiary trench-slope break. The eastern region is dominated by lithic-poor quartzfeldspathic sandstones (petrofacies two) derived from older (Upper Cretaceous and (or) Paleogene) sandstones on the mainland to the east. The two lithofacies interfinger in the central region. During the late Oligocene, sediment was shed onto the Vaqueros Formation shelf from both the mainland to the east and the partially emergent trench-slope break to the west. Later, during the early Miocene, transgression proceeded across the region, drowning the westernmost shoreline. Strontium isotopic analyses suggest apparent ages for Vaqueros strata thatr get younger in the paleo-landward directions. These strata record deposition in a complex forearc basin within an obliquely convergent continental margin. The geometry of this basin was the product of early to middle Tertiary plate interactions.

Año de publicación:

1998

Keywords:

Fuente:

scopus