Detachment folds form as a result of shortening and displacement of a layer of strong rock, such as limestone or sandstone, above a weak layer, such as shale or salt. Tom Homza completed a Ph.D. study with Wes Wallace to determine how detachment folds vary in shape, how they evolve, and what controls their shape and evolution. One result of the study was to document the geometry and kinematics of detachment folds in the northeastern Brooks Range, which contains among the worldıs best-exposed examples of detachment folds. A second result was to produce geometric and kinematic models of detachment folds. These models have been used to evaluate assumptions commonly used to allow the construction of cross sections with only incomplete information, which is typically all that is available in real geologic situations. The observations of natural detachment folds in the northeastern Brooks Range indicate that fold hinges remain fixed throughout the evolution of detachment folds and that the weak layer that underlies these folds varies in thickness as the folds evolve. Both of these results differ from the assumptions using in previously published models for detachment folds. This study has defined criteria for the recognition of detachment folds, which commonly are misinterpreted as other types of folds, and has provided new models for the construction of cross sections of detachment folds from incomplete information. These results will be useful for the assessment of subsurface structures for petroleum exploration and production and for earthquake hazard.
NSF Grant EAR 93-04482.
Scientific personnel:
W.K. Wallace
and T.X. Homza.
Student Research Opportunities at the University of Alaska Fairbanks
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Last updated on March 7, 1997