Unit consists of unnamed rocks on Revillagigedo, Gravina, Annette, Mary, and Duke Islands. This heterogeneous assemblage includes metamorphosed mafic, intermediate, and subordinate felsic volcanic and volcaniclastic rocks; clastic and carbonate sedimentary rocks; and subordinate intermediate and mafic intrusive rocks. Extrusive protoliths, which are partly altered to spilite and keratophyre, include basaltic tuff, agglomerate, and pillow flows and intermediate and felsic tuff. Sedimentary protoliths include argillite, graywacke-siltstone, limestone, conglomerate, and, in the matrix of some of the pillow flows, red chert. Intrusive protoliths include medium- and coarse-grained diorite and quartz diorite. Metamorphic minerals include plagioclase, hornblende, biotite, epidote, chlorite, actinolite, sericite, almandine garnet, and possibly staurolite. Amphibolite-facies minerals define a foliation that predates randomly oriented greenschist facies minerals (Berg and others, 1988). Zircon populations do not include any inherited or entrained zircons that have ages older than Phanerozoic (Saleeby, 2000). U/Pb zircon ages ranging between 436 and 404 Ma are inferred crystallization ages for intrusive dioritic rocks (Saleeby, 2000)