Distribution and Juxtaposition of Mesozoic Lithotectonic Elements in the Basement of the Santa Maria Basin, California (Chapter B)

摘要

Approximately 150 wells in the Santa Maria Basin have been drilled to basement. Core samples from more than 80 wells indicate that basement is composed mainly of melange of the Mesozoic Franciscan assemblage, ophiolitic rocks, and smaller areas underlain by Great Valley sequence sedimentary rocks. Upper Cretaceous sandstone and mudstone underlie the western part of the Santa Maria Valley oil field and most of the Guadalupe oil field. The latter is on structural trend with outcrops of lithologically similar rocks of the Point San Luis slab, located approximately 25 km to the northwest. Petrographic data from surface rocks exposed around the margin of the basin define three sandstone petrofacies. Petrologic similarities between sandstone knockers in Franciscan melange and Great Valley sequence sandstones suggest that the Franciscan rocks may represesent variably metamorphosed Upper Jurassic to Upper Cretaceous Great Valley sequence rocks.