ABSTRACT

The early Permian McCloud Limestone crops out in a north-south belt in the Shasta Lake area of northern California. The McCloud ranges in thickness from less than 100 feet to about a half mile. Much of the McCloud consists of calcarenite composed of varying proportions of crinoid plates, fusulinids, and fenestrate bryozoans. However, pisolites are locally abundant toward the south end of the outcrop belt, and limestone conglomerate is present toward the north end. Most of the sedimentary rocks in the region are typically eugeosynclinal, consisting of graywacke, tuff, siltstone, agglomerate and conglomerate. The McCloud is interpreted to have formed in clear water as a bank or shoal that lay close to sea level. However, some of the carbonate sediment probably spilled off into deeper wa er and interfingered with eugeosynclinal sediments that were deposited by turbidity currents.