Geology of Mount Diablo
Geologic Map

Refer to Guide to the Geology of Mt. Diablo State Park     Rock Descriptions and Ages Page

Legend

Quarternary - surficial deposits

 Jurassic/Cretaceous - dark
greenish-gray shale sandstone
interbeds (Knoxville Formation)		 Thrust Fault
Quarternary - landslide deposits
 Jurassic/Cretaceous - melange
(Franciscian Complex)		 Thrust Fault - inferred
Miocene/Pliocene - non-marine
sandstone, siltstone, and
conglomerate
 Jurassic - chert and basalt with some graywacke and shale
(Franciscan Complex)		 Faultt
Miocene - marine fossiliferous
sandstone and shale
 Jurassic - basalt and diabase
(Coast Range Ophiolite)		 Fault - Inferred
Miocene - silicic intrusive rocks
 Jurassic - serpentinite (Coast Range Ophiolite)
 Roads
Eocene - massive pebbly
sandstone with shale		 Silica carbonate rock (altered serpentinite)
 Streams
Cretaceous - shale, siltstone, and sandstone (Great Valley Sequence)

 

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.

Also refer to:

Guide to the Geology of Mount Diablo State Park for more information on
          the mountain geology and geologic history.
Rock Descriptions and Ages for more information on the rock units and descriptions.

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MOUNT DIABLO INTERPRETIVE ASSOCIATION
P.O. Box 346 - Walnut Creek, CA 94597-0346
(925) 927-7222 / FAX: (877) 349-5016