Sedimentological, Stratigraphic, and Paleoenvironmental Investigations of a Tertiary Nonmarine Forearc Basin

Jacob Mongrain
University of Alaska Fairbanks, Department of Geology and Geophysics Fairbanks, Alaska
[email protected]

The southern margin of Alaska includes some impressive geologic features including: a subduction zone extending from Yakutat Bay in the east to the Kamchatka Peninsula in the west, one of the largest emergent accretionary complexes known and represented by the Chugach and Kenai mountains, a large collisional forearc basin that comprises present day Cook Inlet and Matanuska Valley, and a persistent magmatic arc of the Aleutian-Alaska Range. In addition, the upper forearc stratigraphy of the Beluga and Sterling Formations host economically significant oil and gas accumulations. Despite southern Alaska's geological and economic significance the evolution of the forearc basin is poorly understood. In particular, tectonic and climatic controls on fluvial style are virtually unknown.

The main objectives of this study are to investigate the sedimentology, stratigraphy, and paleoenvironment of the Beluga and Sterling formations of the Tertiary, nonmarine, forearc basin of Cook Inlet, Alaska. These objectives will be accomplished by:

(1): Interpreting the fluvial systems by facies analysis and architectural analysis leading to a depositional model through time of the Beluga and Sterling Formations

(2): Paleoclimatic and paleoenvironmental reconstruction based on palynology and stable isotopes of carbon and hydrogen

(3): Petrographic investigation of the Beluga and Sterling Formations for provenance, sandstone characterization, and reservoir quality

The AAPG grants-in-aid program is partly responsible for the completion of over 50 detailed measured sections, analysis of over 40 palynomorph and stable isotope samples, and collection and analysis of over 20 petrographic thin sections. This study would not be possible without this generous support.

AAPG Search and Discovery Article #90094 © 2009 AAPG Foundation Grants in Aid