| Summary: | Thick succession of sedimentary rocks, ranging from the early Paleocene to late Oligocene in age, was deposited in a suite of marginal basins existed in the modern day area of the Kamchatka Peninsula. Outcrops of these deposits stretch along approximately 640 km along the shores of the western coast of the peninsula, with approximately 280 km of continuous outcrops, and approximately 60 km along the coast of the northeastern Kamchatka, reaching maximal thickness of over 4000 meters in a single section. Paleogene sedimentary sequence of the western Kamchatka can be subdivided into two large eustatic cycles: Paleocene—early Eocene regressive cycle represented by shallow marine, deltaic and terrestrial deposits, and late middle Eocene—Oligocene transgressive cycle, represented by shallow marine and deltaic deposits. Cycles are separated by a regional unconformity, involving a time gap from late Early to early middle Eocene. Volcanic rocks radiometrically (K-Ar) dated from early (Ypresian) to late (Bartonian) Eocene from western and northeastern Kamchatka suggest a repeated pulses of volcanic activity during the Eocene. Synchronous dated deposits of pyroclastic material of similar composition also indicate that the western and eastern Kamchatka basins were located along the same island arc. Paleogene rocks of the northeastern Kamchatka form a 3022 m continuous turbidite sequence which was deposited in a deep water basin in front of the volcanic arc. Analysis of facies, distribution indicated that the Western Kamchatka Basin was dominated by nearshore, lagoonal, and deltaic environments, and represent a backarc setting, whereas the Eastern Kamchatka Basin was dominated by a deep-water turbidite deposits, characteristic of a forearc setting. Paleoecological analysis of molluscan assemblages, including depth/substrate distribution and examination of trophic groups, suggested that the paleodepth of the analyzed part of the Western Kamchatka Basin, for the most part, did not exceed 50–100 m. Radiometric dating and ...
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