Paleontology and geology
Most of California was under water during the Carboniferous, and the warm coastal waters were inhabited by algae, bryozoans, crinoids, molluscs, corals, and cartilaginous fish. On land, the swamps and estuarine environments were home to horsetails, ferns, and large seed-bearing plants (gymnosperms) like seed ferns (extinct gymnosperms) and club mosses (lycophytes), as well as very large insects. Carboniferous rocks containing marine fossils are not shown on this map, but can be found to the north in Shasta County and to the south in Inyo County. All of these rocks were most likely exotic terranes that rafted in from the west by tectonic activity, and accreted onto the continent.