You might be looking for the UC Davis Geology Department.
The geology of Yolo County is in the Great Valley which is generally sedimentary with the exception of volcanic rock in the Sutter Buttes. The Sutter Buttes are not in Yolo County, but are part of the Great Valley. Our soils here are generally quite clayey with varying amounts of silt; they are fantastic in general for agricultural purposes (hence the $300,000,000 Ag economy in Yolo County)
Rocks from the sierras migrate downward. Slowly. The Northern Coast Range rocks are older sedimentary than those of the Valley. The nearby Sierra Nevada is mostly granitic rock in the south and more metamorphic rock in the foothills and the north. Both deposited most of the sediments that Davis sits on.
If you're interested in the physical location of Davis relative to settlements and topography, check out the local geography. Note that geology is not to be confused with geography though they do intersect within Physical Geography.