Basement Geology of the National Petroleum Reserve Alaska (NPRA), Northern Alaska

By

R. Saltus (U.S. Geological Survey), T.L. Hudson (Applied Geology, Inc), J.D. Phillips, C.S. Kulander, and J.A. Dumoulin (U.S. Geological Survey)

Gravity, aeromagnetic, seismic, and borehole information enable mapping of basement characteristics within the National Petroleum Reserve Alaska (NPRA). In contrast to the basement beneath the northern portion of NPRA, the southern basement is 20% thinner, is made up of denser and more magnetic rocks, is more strongly normal-faulted, underlies thicker accumulations of Ellesmerian sediments, and is deeper. Mafic rocks within the basement and local occurrences within the deeper Ellesmerian sedimentary section, particularly in the Mississippian-aged Endicott basins, could explain the observed density and magnetic variations. Because these variations spatially overlap the thicker Ellesmerian sediment accumulations, they probably developed during Ellesmerian extension and basin formation. If this period of extension, and postulated mafic magmatism, was accompanied by higher heat flow, then early Ellesmerian clastic sediments may have become mature for hydrocarbon generation, producing the earliest petroleum system in the North Slope basin.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.