Goeff:

What you are looking at is an anticline or syncline - hard to tell on a 
photo - folds caused by compressional forces from a variety of sources.  
In oil producing territory anticlines are indeed potential prospects.   
In this case surface erosion ground off the top leaving the strata 
layers looking like a sliced onion.   It could be fault related - this 
area is located at the southern end of the San Andreas fault system and 
strike-slip motion along the fault can result in local folding.  I found 
a good introduction to southern californaia geology at: 
www.grossmont.edu,  search for "Geology of Southern California.pdf" by 
DeCourten.

Bob Mansfield

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