South Fork Mountain Schist of Pine Ridge Summit, northern California, is predominantly metasedimentary, of the glaucophanitic-greenschist facies, and has undergone at least two periods of folding. It was overridden by the Klamath Mountain block (Coast Range thrust fault) and later thrust over unmetamorphosed broken formation of the Franciscan Complex. The schist differs markedly from the subjacent Franciscan in being derived from a more distal submarine fan deposit. Chert breccia and volcanic boudins within the fault zone beneath the schist may have been derived from a melange terrane now situated beneath the Klamath block. The schist does not correlate lithologically or structurally with the nearby Redwood Mountain schist outlier, which may have been transported to its present position by strike-slip faulting.