Abstract: Lowstand Depositional Systems Related to Early Cretaceous Rifting of the Arctic Alaska Plate: A New Stratigraphic Play on Alaska's North Slope

R. Keith Crowder, Charles G. (Gil) Mull, Karen E. Adams

The Arctic Alaska plate experienced a series of pronounced continental rifting events during the Early Cretaceous related to opening of the Canada basin and Arctic Ocean. The breakup event is recorded across much of northern Alaska by a regional Lower Cretaceous unconformity (LCU). Erosional truncation along the LCU produced the trap for the supergiant Prudhoe Bay oil field, and deposition of mature Neocomian sandstone above and below the unconformity formed hydrocarbon reservoirs in the nearby Kuparuk River field. These sandstone intervals related to the breakup unconformity formed within shallow-marine depositional systems. Recent analysis of Neocomian strata exposed in the western Brooks Range demonstrates that significant reservoir-quality sandstone also accumulated w thin turbidite depositional systems at basinal depths. This potential reservoir, informally known as the Tingmerkpuk sandstone, is a 130 m succession of fine-grained quartzarenite. Correlative Neocomian sandstones have also been identified in the Tunalik well of the National Petroleum Reserve in Alaska, and in the Shell Burger and Klondike wells in the Chukchi Sea. Partial Bouma cycles and upward thickening parasequences indicate that the Tingmerkpuk was produced by repeated progradation of submarine depositional lobes built by turbidity currents. The submarine lobes were probably deposited as a lowstand wedge beyond the southern edge of the Neocomian shelf during the time of maximum erosion along the LCU to the north. Recognition of mature Neocomian sandstone within a lowstand setting related to rifting and breakup warrants a systematic exploration for this unique stratigraphic play in the western Arctic Slope and adjacent Chukchi Sea. A collaborative study of the depositional environments, sequence stratigraphy, petrology, and organic geochemistry of the Tingmerkpuk and related strata in northwest Alaska has been initiated by the Alaska Geological Survey, University of Alaska-Fairbanks, Bureau of Land Management, U.S. Geological Survey, and Alaska Division of Oil and Gas.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California