Week 6 - Geological Interpretations

California geology map with Santa Clara County superimposed

I visited Santa Clara County in California. The geology here is quite complex with rocks of several different compositions and ages throughout the region and two faults running through the area. The first area I visited was in Santa Clara city in the northern part of this county. I found outcrops there with several different sedimentary layers. The topmost layer was composed of rust-colored rock which implies that the sediment here was deposited by some water source then oxidized. The lower layers, however, do not have this coloring. My question here would be when did the nearby body of water form? This would help me get an idea of when the different layers of sediment formed.
I also visited the area near the Coyote Reservoir Dam, in the southern part of the county. The Calaveras fault runs through this area. Striations on some outcrops in the area showed past movement of the fault as not horizontal but at an oblique angle. For this area, it would help to know how often this particular fault sees activity and when the last slip occurred. This would help to ascertain when this outcropping was revealed by fault movement. Also in this area, much of the rock is composed of serpentinite. This is a metamorphic rock that requires intense pressure and/or heat in order to form. It would be helpful to know if this rock was formed from pressure alone or if there is any volcanic activity or magma pockets in the area that may have provided heat. This would help to determine how this particular type of rock was formed.

Evidence of Calaveras fault movement
http://geologycafe.com/images/slickensides_coyote.jpg

 

Serpentinite rock in southern Santa Clara
https://www.researchgate.net/profile/Paula_Messina2/publication/242662816/figure/fig6/AS:298430632087558@1448162815324/Serpentinite-outcrop-near-Chesbro-Reservoir-Dam_Q320.jpg