TECTONOSTRATIGRAPHY OF THE NORTHERN OLYUTOR ZONE (ANASTASIYA BAY AREA OF KORYAK HIGHLAND)

Abstract

Volcanogenic-siliceous and sedimentary-volcanogenic rock complexes are distinguished in the Anastasiya Bay area (the Koryak Highland) in the western coast of the Aleutian Basin. The age of siliceous beds in these complexes was inferred from radiolarian finds. The volcanogenic-sedimentary complex incorporates layers of the Campanian-Maastrichtian age. By lithology, it is correlated with the "Vatyna" Group, which previously was attributed to the Albian-Campanian. According to our data, the strati graphic range of these deposits should also include the Maastrichtian. The sedimentary-volcanogenic rock complex is subdivided into three units: the volcanogenic (lower), volcanogenic-terrigenous (middle or transitional), and siliceous-terrigenous (upper) subcomplexes. The siliceous-terrigenous subcomplex contains radiolarians, which allow the host rocks to be dated as the Campanian-Maastrichtian. The sedimentary-volcanogenic complex is correlated with the Machevna complex or "Achaivayam Formation." The volcanogenic-siliceous complex was probably formed within a marginal sea basin and the sedimentary-volcanogenic complex in an island-arc and its slope settings. The data obtained allow us to reconstruct the hypothetical lateral succession of the Campanian-Maastrichtian paleogeographic settings: the continental margin-marginal sea-island arc-oceanic basin.