The Carboniferous Lisburne Group
of northern Alaska has been deformed into a variety of map-scale structures
in both compressional and extensional structural settings, thus providing
a series of natural experiments for observing the formation, distribution,
and behavior of fractures in this thick carbonate unit. Two fracture sets
dominate the Lisburne Group carbonates of the North Slope subsurface and
the nearby northeastern Brooks Range fold and thrust belt. North-northwest-striking
regional extension fractures probably formed in front of the northeastern
Brooks Range fold and thrust belt. In the North Slope subsurface, this
fracture set overprints east-northeast-striking fractures related to earlier
extensional deformation; in
contrast, in the fold and thrust belt, the
north-northwest-striking fracture set is overprinted by younger east-northeast-striking
fractures related to subsequent contractional deformation.
Lithology is the primary control on the fracture
density of both sets. In mildly deformed Lisburne
1997. The American Association of Petroleum Geologists. All rights reserved.
received February 20, 1996; revised manuscript received November 25, 1996;
final acceptance June 5, 1997.
Institute, University of Alaska Fairbanks, Fairbanks, Alaska 99775.
National Laboratories, MS 0705, Albuquerque, New Mexico, 87185.
of Petroleum & Natural Gas Engineering, New Mexico Institute of Mining
& Technology, Socorro, New Mexico 87801, and Sandla National Laboratories,
MS 0705, Albuquerque, New Mexico, 87185.
study was supported by a Department of Energy subcontract administered
by Sandia National Laboratories. Additional support was provided by ARCO
Alaska, BP Alaska, Chevron, Exxon, Mobil, and Japan National Oil Company.
We would like to thank ARCO Alaska and BP Alaska for giving us permission
to view selected Lisburne Group cores, W. Wallace for helpful discussions
on deformational styles of detachment folds, A. J. Mansure for help in
interpreting the interference tests, and W. Wallace, K. Biddle, W. Belfield,
N. Hurley, and J. Kelley for helpful reviews of the manuscript.