Figure 4. The Monterey Formation crops out in the central and southern California Coast Ranges. This chart shows the age and stratigraphic relationships in the Santa Maria Basin, location of the Arco Bixby #1 well (Figure 2).

The depositional framework for the Monterey formation across California is complex because during Miocene time, basins on the Pacific borderlands were actively being uplifted or subsiding depending on the local tectonic regime.

Rocks of the Monterey Formation include mudstone (or shale) with minor sandstone and conglomerate. The principal rocks discussed in this web site are organic-rich mudstones, which are the potential source rocks for petroleum.

Note: Wavy horizontal lines on chart indicate unconformities between rock units. Areas with vertical lines indicate episodes of hiatus when rocks either were not deposited or were removed by erosion.

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http://geology.wr.usgs.gov/wreg/env/strat_mont.html
Contact: Margaret A. Keller (mkeller@usgs.gov)
Western Region Energy Group–Environmental Studies
Modified: July 31, 2000

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