Geology Map of Mount Diablo

Geologic Map

Legend

Quarternary - surficial deposits

Quarternary - landslide deposits

Jurassic/Cretaceous - dark 
greenish-gray shale sandstone 
interbeds (Knoxville Formation)

Miocene/Pliocene - non-marine

sandstone, siltstone, and conglomerate

Miocene - marine fossiliferous

sandstone and shale

Jurassic/Cretaceous - melange 
(Franciscian Complex)

Jurassic - chert and basalt with some graywacke and shale 
(Franciscan Complex)

Miocene - silicic intrusive rocks

Jurassic - basalt and diabase 
(Coast Range Ophiolite)

Eocene - massive pebbly sandstone

with shale

Cretaceous - shale, siltstone, and

sandstone (Great Valley Sequence)

Jurassic - serpentinite (Coast Range Ophiolite)

Silica carbonate rock (altered serpentinite)

Thrust Fault

Thrust Fault - inferred

Fault

Fault - Inferred

Roads

Streams

Data Source Preliminary Geologic Map Emphazing Bedrock Formations in Contra Costa County, California. Compiled by R.W. Graymer, D.L. Jones, and E.E. Brabb U.S. Geological Survey Open-File Report 94-622 Arc/Info Data Files

Simplified with minor modifications by Roi Peers and Craig Lyon, September 1996.

Geologic Information Systems Map by Eric R. Sheehan, Martinez, California.

© 2019 by Mount Diablo Interpretive Association