The Temblor Formation

When Frank M. Anderson first came up with the name Temblor Formation in the early 1900s, he used it designate the sandy interval that was beneath the Monterey Formation, which in outcrop is dominantly shale. Today the Temblor generally refers an interval of Lower Miocene to Oligocene (Saucesian to Refugian stages) shale that contains several sand bodies, which from bottom to top are named the Wygal, Phacoides, Agua, Carneros and Buttonbed. Because the Buttonbed in many places has a pretty significant unconformity at the base of it, there is a bit of a dispute as to whether the Buttonbed is the uppermost sand of the Temblor or the lowermost sand of the Monterey Formation.

The Temblor Formation in some parts of the valley is defined differently, and includes rocks as young as Middle Miocene in age. For example, the upper Temblor in the Coalinga area includes Middle Miocene units that would be classified as the Devilwater Siltstone and Gould Shale in the Elk Hills area, and at Sharktooth Hill in the hills east of Bakersfield the Middle Miocene Round Mountain Siltstone is also considered to be part of the Temblor.

The Temblor on the west side of the valley has acquired a bit of notoreity in the oil patch in recent years due to two significant events. The first is the blowout in 1998 of the Bellevue No. 1 well up at Lost Hills from sandstones at a depth of 17,657 feet that are believed to be in the Temblor Formation. The second is the 2009 discovery of a significant amount of oil and gas in Temblor Formation Sandstones, specifically the Carneros sandstone, at the so-called "Gunslinger Pool" just on the northwest edge of the giant Elk Hills oil field. Gunslinger is said to be the largest oil field discovered in California in the last forty years.