NEW GEOLOGIC DATA ON BERING ISLAND, KOMANDORSKY ISLANDS

Abstract

Our work gave new paleontologic and radiometric data on the age of the sedimentary, volcanogenic-sedimentary and igneous rocks in the structurally most complex northern part of Bering Island, which supplement existing schemes of the geologic evolution of the Komandorsky Islands. The following conclusions were drawn from our work. 1. Sedimentary rocks separating the two igneous rocks series in the section and containing rich Oligocene diatom assemblages can now be dated considerably more accurately. 2. There were two clearly separate stages of igneous activity, i.e., middle to late Eocene (37 to 45 m.y.) and Miocene (16 to 25). 3. The finding of igneous rocks of middle to late Eocene age on Bering Island shows that the 'initial' igneous activity in this Aleutian island-arc area was far more widespread than was noted earlier.