Abstract: Paleogene Sedimentary Basins and Paleogeography of Western Kamchatka: Stratigraphic Aid for Hydrocarbon Exploration.

OLEINIK, ANTON E., Dept. of Earth & Atmospheric Sciences, Purdue University, West Lafayette, IN 47907

Introduction

A thick succession of sedimentary rocks, ranging in age from the early Paleocene to late Oligocene, was deposited in a suite of marginal basins which existed in the modern day area of western Kamchatka. These deposits extend approximately 560 km along the shores of the Sea of Okhotsk, the Gulf of Shelikhov and the Gulf of Penzhina and reach a maximum thickness of over 4000 meters.

Methods and Data

Stratigraphic studies of Paleogene sedimentary basins located along the northeastern margin of the Sea of Okhotsk provide crucial information for understanding the sedimentary record and hydrocarbon potential of the adjacent basins of the Sea of Okhotsk (Penzhin, Gizhigin, TINRO, and Western Kamchatka). The Paleogene sedimentary sequence of western Kamchatka can be subdivided into two large eustatic cycles: Paleocene early Eocene regressive cycle and late middle Eocene Oligocene transgressive cycle, separated by a regional unconformity. Volcanic rocks dated from early (Ypresian) to late (Bartoninn) Eocene suggest repeated pulses of volcanic activity at that time. The Paleocene early Eocene regressive cycle in northwestern Kamchatka begins with a deep marine siltstone and shales of the lower Paleocene Getkilninskaya Formation (~680 m) overlain by shallow marine to deltaic sandstones of the Paleocene Kamtschikskaya Formation (~870 m) and with Paleocene - lower Eocene deltaic and estuarine sandstones and conglomerates of the Tkapravayamskaya Formation (~1500 m). These rocks correlate with the terrestrial Ulevenei sequence in the central part of western Kamchatka. A Middle Eocene - Oligocene transgressive cycle, best exposed in the central part of western Kamchatka, is separated from Cretaceous and Paleocene-lower Eocene rocks by an angular unconformity. Rocks of this cycle include a shallow marine sandstone of the Snatolskaya Formation (~600 m), shallow marine sandstones to deep marine shales of the Kovachinskaya Formation (~800 m), deep water claystones of the Amaninskaya Formation (~200 m) and siliceous shales of the Gakhinskaya and lower part of Utcholokskaya Formations (~1200 m).

Conclusions

The Paleogene sedimentary and faunal record indicate the existence of a large island arc, or paleo-Kamchatka Peninsula, with large high islands, or a peninsula forming a source area for continental, lake, and deltaic sediments in the lowlands and nearshore areas. Lateral facies discontinuity in the middle and upper Eocene deposits indicate a dynamic shallow marine setting with a variety of environments from nearshore sublittoral and lagoonal to a deeper water, similar to those existing today in backarc basins.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah