Origin of Asymmetric Thrust-Truncated Folds: Testing Kinematic Models Against Natural Examples, Upper Marsh Fork Area, Eastern Brooks Range, Alaska

Rebecca Bailey
University of Alaska Fairbanks
Fairbanks, Alaska
[email protected]

Thrust-related folds commonly are difficult to distinguish based solely on incomplete field exposures. This problem is exacerbated if the folds are faulted, as displacement along a thrust can modify original fold geometry. This type of ambiguity has been documented in fold-and-thrust belts worldwide, but the exceptional exposures in the Upper Marsh Fork of the Canning River, Alaska (UMF) make it an ideal place to test geometric and kinematic models against natural examples of thrust-related folds.

Previous researchers have created models for fault propagation and detachment folds that start with two-dimensional models and then compare the models to field examples. This study will use a fundamentally different approach by beginning with detailed three-dimensional data from natural fold examples and then using it to test and modify existing models or possibly to generate new models.

In order to (1) reconstruct the kinematic evolution of asymmetric thrust-truncated folds exposed along the upper Marsh Fork of the Canning River in the eastern Brooks Range, Alaska (UMF) and (2) to test existing models for fault-related folds against natural examples, I will: (1) map UMF folds in three dimensions, focusing on collecting dip data and observing geometric changes along strike, (2) construct serial sections of the folds and use my observations to reconstruct pre-breakthrough geometry, (3) test applicable fold models against these natural folds and (4) use my results as a basis to modify existing models or to develop new model(s) that most accurately represent natural fold geometry and evolution.

AAPG Search and Discovery Article #90033©2004 AAPG Foundation Grants-in-Aid