Reconnaissance geology of northern Baranof Island, Alaska

Abstract

The rocks of northern Baranof Island range in age from Paleozoic (?) to Mesozoic ; they are tightly folded, intricately faulted, and regionally metamorphosed. "*' They are also contact metamorphosed near the borders of dioritic intrusive rocks. that are probably related to the Coast Range batholithic complex. To the west, on Kruzof Island, rocks of Mesozoic age are unconformably overlain by volcanic rocks that were extruded from Mount Edgecumbe and other vents during Quaternary time. On Baranof Island the strike of most of the contacts, bedding, and Js niineralogical layering, as well as the trend of the lineations, is northwest; however, between Rodman Bay and Saook Bay where strata of Triassic(?) age show two episodes of folding, the rocks commonly strike north and east. Fieldwork combined with the study of aerial photographs shows that many well-defined ""* lineaments are probably faults and shear zones. For mapping purposes the bedded rocks are herein divided into seven lithologic-" stratigraphic units. Although no fossils have been found in or reported from the rocks of northern Baranof Island, the ages of many of the units are tentatively established by lithologic correlation with rocks that are better dated else-"' where in the region, particularly those on Chichagof Island.