Matilija Sandstone

Matilija Sandstone Stratigraphic range: Eocene epoch
Outcrop of the Matilija Sandstone in the Santa Ynez Mountains, California.
Type	sedimentary
Underlies	Cozy Dell Shale
Overlies	Juncal Formation
Thickness	0–2,500 feet (0–762 m)
Lithology
Primary	sandstone
Location
Region	Coastal southern California
Country	United States
Type section
Named by

The Matilija Sandstone (/məˈtɪləhə/) is a sedimentary geologic unit of Eocene epoch in the Paleogene Period, found in Santa Barbara and Ventura Counties in Southern California.

It consists of thick layers of sandstone, made up of grains of feldspar and quartz from a granitic source rock, interbedded with thin layers of siltstone and shale. Hard, massive, and exceptionally resistant to weathering, it forms the high rocky summits of the Santa Ynez Mountain range north of Santa Barbara, eastward into Ventura County.

The type locality of the unit is at Matilija Hot Springs, along the Ventura River about ten miles (16 km) northwest of Ojai, near to California State Route 33. At its type locality it is around 2,500 feet (760 m) thick, and consists of both marine and non-marine sandstones with occasional thin beds of micaceous shale separating massive sandstone layers. The sandstone layers are made up of well-sorted grains of quartz and feldspar. The unit can be found along the crest of the Santa Ynez range all the way from the western extremity of the mountains near Point Arguello, to its type locality north of Ojai, and east and northeast into the Ventura County backcountry, where Piru and Sespe creeks cross through the formation. It accounts for the highest peaks in the Santa Ynez range, dipping underneath the younger Coldwater Sandstone, Cozy Dell Shale, and Sespe Formation near San Marcos Pass in the center of the range.