San Emigdio and Pleito Formations
San Emigdio and Pleito Formations
Oligocene to upper Eocene
Consists of a sequence of marine sandstone, shale, and minor conglomerate that crops out in the San Emigdio Mountains in the southwestern map area.
This sequence exhibits both stratigraphic and lateral changes in grain size and fossil type and abundance, reflecting cyclic sea-level changes and, more prominently, lateral changes reflecting position within the basin. Sandstone is arkosic and fine- to medium-grained, locally pebbly, grading to massive to thickly bedded medium- to coarse-grained and variably conglomeratic; shale is typically planar-bedded, micaceous, and locally sandy; granitic breccia is present locally; strata range from nonfossiliferous to abundantly fossiliferous with a variety of molluscan fauna and foraminifera (Nilsen and others, 1973; Kellogg and others, 2008; Chapman and Saleeby, 2012). 
Maximum thickness exceeds 2,700 m but varies laterally (e.g., Nilsen and others, 1973). Interfingers with and laterally grades into nonmarine strata of Tecuya Formation. Late Eocene to Oligocene age based on fossil fauna and stratigraphic relations (e.g., Nilsen and others, 1973).