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Seeley, T.P., 2009

Tectonostratigraphic evolution of the Mackenzie Delta - Beaufort Sea fold belt

Bibliographic Reference

Seeley, T.P., 2009, Tectonostratigraphic evolution of the Mackenzie Delta - Beaufort Sea fold belt: Calgary, Alberta, Canada, University of Calgary, Ph.D. dissertation, xii, 183 p., (chiefly color) illust., 2 folded maps.


Convergence rates between the proto-Pacific, Pacific, and North American plates are used to empirically classify the style of strain in Alaska from the Jurassic to present and to create the Alaska strain class model. This model is modified from tectonostratigraphic terrane models for the pre-Jurassic. The Alaska strain class model demonstrates that deformation across Alaska in the pre-Jurassic was largely tensional with pulses of contractional deformation in the Silurian - Devonian and Mississippian. The transition from slow plate convergence rates in the Early Jurassic to rapid plate convergence rates in the Cretaceous resulted in a change from tensional to compressional strain. Regional rifting across Alaska and initial middle Hauterivian opening of the Canada basin document the tensional style of deformation. Uplift of the Brooks and northeastern Brooks ranges with development of a foreland fold belt occurred in response to compressional strain in the mid to Late Cretaceous. Continuation of the compressional strain regime in the Paleocene through Eocene produced shortening and uplift of the Mackenzie Delta - Beaufort Sea fold belt (MDBSFB). Interpretation of 2D seismic data shows that the MDBSFB consists of low-amplitude, long-wavelength faulted anticlines and folds. Filling of backlimb synclines by stratal convergence packages and uplift-related erosion allow dating phases of contractional deformation in the MDBSFB during the middle - late Paleocene, middle Eocene, early Oligocene, late Oligocene and early Miocene. Basement normal faults formed buttresses to the basal detachment in the northern part of the study area, resulting in contraction and uplift along north- and south-verging thrust sheets forming a previously undocumented Foreland High. Deformation in the Foreland High places the northern limit of the MDBSFB 30 to 40 km farther basinward. A topographic low, the Central Region, developed between the hinterland of the study area and the Foreland High. This Central Region became the focal point for deposition from the Oligocene through the late Miocene. The shelf, slope, and toe of slope were structurally controlled during this time with syndepositional deformation occurring in the early and late Oligocene and Miocene. Using the MDBSFB rock record, the Alaska strain class model has been revised to recognize these phases of deformation.

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