Duncan Canal description and information

From Wood and Kienle (1990): "Olivine-bearing tholeiitic basalt with average K-content, together with minor sodic alkalic basalts, overlie volcanic-rich gravel and glacial till along the southern coast of Kupreanof Island west of Duncan Canal. The flows are recognized in the field by their conspicuous fresh-appearing pahoehoe and aa surfaces. Two probable vents lie within the Mesozoic and Paleozoic rocks of the Duncan Canal fault zone north of the main exposures; the northern one contains scattered peridotite nodules. The relations of the main exposures to the subjacent middle Tertiary volcanic rocks of the Kuiu-Etolin volcanicplutonic belt are not clear at the western end of the field because the Holocene basalt is difficult to differentiate from the adjacent older basalt."