Sedimentology and Stratigraphy of Upper Cretaceous Strata in the Sagavanirktok River Area, East-Central North Slope, Alaska

David L. LePain¹, Paul L. Decker², Marwan A. Wartes¹, Robert J. Gillis¹, Jacob R. Mongrain³, Russell Kirkham⁴, and Diane P. Shellenbaum^2
1Division of Geological & Geophysical Surveys, Alaska Department of Natural Resources, Fairbanks, AK
²Division of Oil & Gas, Alaska Department of Natural Resources, Anchorage, AK
³Department of Geology & Geophysics, University of Alaska, Fairbanks, Fairbanks, AK
⁴Division of Mining, Land and Water, Alaska Department of Natural Resources, Anchorage, AK

Alaska’s North Slope remains one of the most promising onshore oil and gas provinces in all of North America. However, much of the Colville foreland basin remains only lightly explored and many key stratigraphic relationships remain poorly understood. In an effort to improve Brookian sequence stratigraphic models and codify regional formation nomenclature, we have begun integrating detailed outcrop observations with available well and 2-D seismic data.

Recent field work has focused on Upper Cretaceous rocks exposed along an unnamed drainage between the Sagavanirktok and Ivishak rivers in the Sagavanirktok A-3 Quadrangle. The base of the section consists of Lower Turonian deepwater sandstones and recessive weathering shales; sandstones exhibit a strong, distinctive hydrocarbon odor. The middle part of the succession includes thin- to medium-bedded, fine-grained turbidites and associated sediment gravity flow deposits of Santonian to Campanian age. Notably present in this middle interval are brown, organic-rich paper shales and tuffaceous units which often exhibit a strong hydrocarbon odor. The upper third of the exposure belt includes sandstones with abundant trace fossils of the Cruziana ichnofacies and physical structures indicative of deposition above storm wave-base in a low-energy setting. The stratigraphic top includes fine-grained sandstones of Campanian age with abundant wave ripple cross lamination and other structures suggestive of deposition in shorezone settings.

This important succession provides insight into the time-transgressive northeastward progradation of genetically related shelf, slope and deep water facies. In particular, this area allows an examination of seismic scale, internally regressive depositional sequences recorded by the Upper Cretaceous Tuluvak-Seabee and Prince Creek-Schrader Bluff-Canning formations.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas