"Cretaceous Oblique-Slip Reactivation of Late Paleozoic Rift-Related Faults ont he Chukchi Platform, Southern Chukchi Shelf, Alaska"

Harris Pritchard, Thesis 2016

Abstract: On the southern Chukchi Platform, a major basement high, multiple north-south trending listric normal faults penetrate acoustic basement. Well-documented lower Ellesmerian Sequence growth strata indicate that these faults originally formed during Late Devonian to Mississippian crustal rifting as subsidiary extension associated with the formation of the Hanna Trough, a north-south graben system that is a significant structural feature of Arctic Alaska. Undeformed Beaufortian and Brookian strata above many of these rift segments broadly constrain the timing of crustal-scale deformation, however previous studies have suggested reactivation has occurred along some of these faults. Interpretation of reprocessed industry seismic data; USGS high-resolution uniboom, near surface seismic; USGS shallow cores and sparse industry well control provide constraints on the detailed structural style and timing of these crustal rift-related faults on the Chukchi Platform, and allow for refined models of their temporal and spatial evolution. Reactivation, associated with oblique slip, is inferred on several of these crustal faults based on folding and high-angle faulting of post-rift Beaufortian and Brookian strata that lie directly above crustal fault segments. Furthermore, several structures show positive structural relief above fault segments indicating transpressional inversion, associated with restraining bends along the faults. In some of these cases, such reactivation occurs on multiple fault splays that coalesce during inversion as the origin for the strike change. In some crustal faults segments, transpression appears to be due to oblique reactivation without changes in the strike of crustal faults, suggesting a change in far-field stress geometry. Also present are crustal faults reactivated in transtension. The exact timing of most of the reactivation appears to be earlier than Paleogene base on cross-cutting relationships and lack of reactivation cutting the Paleogene mid-Brookian Unconformity, a feature likely related to the reactivation.

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