Jurassic through Oligocene Pre-Basin Stratigraphy in the Santa Maria Basin Area, California

Abstract

Compilation from published records of 30 pre-Miocene stratigraphic columns in the Santa Maria basin area of California (west of the Sur-Nacimiento fault and north of the Santa Ynez fault) reveals two basement units and 22 overlying sedimentary units. This article displays the stratigraphic columns and includes descriptions and environmental interpretations of the 24 rock units. The basement rocks include an Upper Jurassic ophiolite sequence and the Lower Jurassic through Upper Cretaceous Franciscan Complex. Most of the 22 sedimentary units were deposited along a subduction-type margin prior to development of the late Tertiary Santa Maria basin. Overlying and generally in fault contact with the basement rocks are four Upper Jurassic through Lower Cretaceous units that were deposited in basin plain and out continental margin environments. Unconformably overlying these units are eight Upper Cretaceous units that were deposited in a wide range of environments that ranged from trench, slope, and submarine fan up through shelf and nonmarine fluvial environments. Lower Tertiary units onlap unconformably onto the Cretaceous rocks and were deposited only in the southernmost part of the area. These rocks include lower Eocene basin plain and outer submarine fan deposits; middle Eocene mid-fan and slope deposits; upper Eocene inner fan, shelf,more » shoreface, and foreshore deposits; and Oligocene shoreface, foreshore, and nonmarine fluvial deposits.« less