[3] The Monterey has been extensively investigated and mapped for petroleum potential, and is of major importance for understanding the complex geological history of California.

Its lower Miocene members show indications of weak coastal upwelling, with fossil assemblages and calcareous-siliceous rocks formed from diatoms and coccolithophorids.

Its middle and upper Miocene upwelling-rich assemblages, and its unique highly siliceous rocks from diatom-rich plankton, became diatomites, porcelainites, and banded cherts.

Most of the formation's sediments appear to represent siliceous shales deposited at the edge of the continental shelf or in abyssal plains in the lower to middle bathyal zone.

Since 2011, the possibility that hydraulic fracturing might make the Monterey Shale productive over large areas has gained widespread public attention.

A widely cited March 2013 study released by the University of Southern California (USC) estimated that if extensive resource play development of the Monterey through hydraulic fracturing were successful, it could generate as many as 2.8 million jobs and as much as $24.6 billion in state and local taxes.

[14] Richard Behl, a geology professor who heads the "Monterey And Related Sediments" (MARS) consortium at California State University Long Beach, said that "The [EIA] numbers probably were overblown, but it was a simple method and had an essence of truth."

He found the EIA report's assumptions on prospective well productivity to be "extremely optimistic," and the total estimate of 15.4 billion barrels of recoverable oil "highly overstated."

He also found the USC study's assumption that development of the Monterey shale could increase California oil production as much as seven-fold to be "unfounded," and the economic projections regarding jobs and tax revenue to be "extremely suspect.

"There's a lot of discussion around the Monterey Shale that it doesn't require fracking, that acidizing will be enough to open up the rock," said Chris Faulkner, chief executive officer of Breitling Oil and Gas.

[29] The bill, which Governor Jerry Brown promised to sign, provided for disclosure of chemical used, pre-testing of nearby water wells, and a study on environmental and safety issues to be completed by January 2015.

In 2013, the county planning commission declined its staff's recommendation to approve the project, calling for more study on concerns raised by environmentalists about greenhouse-gas emissions.

The most diverse assemblage with the most well-preserved, articulated specimens originates from the presumably Tortonian-aged diatomite deposits exposed in the former Celite Company/Johns Mansfield quarry in Lompoc.