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.