AbstractsEarth & Environmental Science

The Facey Rock area includes approximately 4 square miles in the Eastern Paleozoic Subprovince of the Klamath Mountains north of Callahan, California. The structurally complex terrain is composed of sparcely fossiliferous Silurian graywacke, sparsely fossiliferous Ordovician limestone, Devonian to Cretaceous chloritic quartzite and minor gabbroic and dioritic intrusive rocks. The two limestone lithologies recognized in the area are the Late Ordovician Platy Limestone Member and the Middle Ordovician Massive Limestone Member of the Facey Rock Limestone. These are interpreted as shallow water carbonate bank and deeper water carbonate deposits respectively. Both contain minor amounts of primary bedded chert. The graywacke is interpreted as a proximal turbidite. The chloritic quartzite is believed to be an upper plate remnant of the Devonian to Cretaceous, regional Mallethead Thrust. Several large, recent landslides are located in the vicinity of Facey Rock. Portions of the landslide debris along with talus deposits have been cemented into a loose breccia by groundwater supersaturated with calcium carbonate. Thrust faults separate the two limestone members from each other and from the underlying graywacke. They are responsible for the successively older, upward sequence of units observed at Facey Rock. These thrusts are considered subsidiary to the regional Mallethead Thrust. There are numerous high angle faults in the area postdating the thrusts.