Geology
Jeannette Island consists of folded Paleozoic graywackes overlain by Cenozoic conglomerates. The graywacke is coarse-grained and contains local lenses of conglomerate. An unconformity separates the Cenozoic conglomerate from the underlying graywacke. The Cenozoic conglomerate contains well-rounded pebbles, cobbles, and boulders of quartz sandstone, quartzite, diorite, andesite-basalts, and altered granite.
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