The type Tejon Formation of the San Emigdio Mountains is a marine clastic sedimentary sequence of middle and late Eocene age that was deposited primarily in a variety of shallow-marine environments during an eastward transgression followed by a westward regression. It lies unconformably on a pre-Tertiary crystalline basement complex and is overlain by the marine San Emigdio Formation and the nonmarine Tecuya Formation. It is more than 4,000 ft thick in the center of the range, but thins and grades laterally eastward into nonmarine conglomerates and sandstones. Paleocurrent data indicate dominant transport of sediments toward the west.

Marks defined four members of the Tejon Formation (in ascending order): Uvas Conglomerate, Liveoak Shale, Metralla Sandstone, and Reed Canyon Siltstone. The Uvas contains medium- to large-scale cross-stratification, ripple markings, well-sorted planar-stratified beach-type sandstones, large burrows, boulder beds, locally abundant megafauna, and was deposited adjacent to the transgressive shoreline. The Liveoak shale is primarily an extensively bioturbated silty shale with locally abundant microfauna and abundant sandstone interbeds in its lower and upper parts; it grades laterally eastward from a deep-water shale into shallow-marine sandstones. The Metralla Sandstone Member is typically a bioturbated silty fine-grained sandstone which contains interbedded conglomerates, medium- and la ge-scale cross-stratification, ripple markings, beach-type sandstones, and abundant megafauna in its eastern exposures where it was deposited adjacent to the regressive shoreline; however, on the west it grades laterally into thinly bedded flyschlike sandstones and shales deposited in deeper water. The Reed Canyon Siltstone Member is in an extensively bioturbated thin unit that locally contains some megafauna, microfauna, and thin coal interbeds.

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