Thrust-breakthrough of asymmetric anticlines: Observational constraints from surveys in the Brooks Range,Alaska |
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Affiliation: | 1. Euskal Herriko Unibertsitatea Zientzia eta Teknologia Fakultate Estratigrafia eta Paleontologia Saila, Barrio Sarriena, s/n 48940 Leioa (Bizkaia), Spain;2. Departamento de Geología, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los caídos s/n, 37003 Salamanca, Spain;3. Department of Stratigraphy and Paleontology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), P.O. Box 644, E-48080 Bilbao, Spain |
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Abstract: | To gain insights into the processes governing the thrust-truncation of anticlines, we conducted a field study of the thrust-truncated folds in the remote Brooks Range of northern Alaska, where there is a transition in fold style from symmetric detachment folds to thrust-truncated asymmetric folds. In order to document the detailed geometry of the km-scale folds exposed in cliff-forming, largely inaccessible outcrops, a new surveying technique was developed that combines data from a theodolite and laser range finder. The field observations, survey profiles, and cross section reconstructions, indicate that late-stage thrust breakthrough of the anticlines within the mechanically competent Lisburne Group carbonates accommodated continued shortening when other mechanisms became unfeasible, including fold tightening, forelimb rotation, and parasitic folding in the anticline forelimbs. These results provide constraints on the processes that govern the transition from buckle folding to thrust truncation in fold-and-thrust belts worldwide. |
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Keywords: | Crustal deformation Foreland fold-and-thrust belts Detachment folds Alaska Brooks Range Structural geology |
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