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Structural geometry and kinematics of deformation in the Stanley Head region, western Cornwallis Island, Nunavut Henrichsen, Michael C.

Abstract

The Stanley Head region of western Cornwallis Island, Nunavut is located southeast and along strike from the Late Devonian Zn-Pb Polaris mine. The area incorporates Middle Ordovician - Lower Devonian strata that is folded and faulted and constitutes a part of the Lower Devonian Cornwallis fold belt. 1:15000 scale mapping of the Stanley Head region led to the identification of previously unrecognized shallow level folds and thrust faults that collectively define the Stanley Head anticline. These structures exhibit some of the characteristic elements of "evaporite detachment thin-skinned contractional deformation" (Davis and Engelder, 1985), and are interpreted to represent an evaporite based fold and thrust system in which there are multiple levels of detachment. Three phases of deformation have been documented in the study area: 1) northeast and southwest verging folds and thrust faults associated with an east-west compressional D1 event, 2) strike slip faulting and folding associated with a north-south compressional D2 event, and 3) normal faulting associated with an east-west extensional D3 event. The D1 , D2, and D3 events are interpreted to correspond with the Boothia Uplift, Ellesmerian Orogeny, and Eurekan deformational event respectively. Pervasive calcite veins related to the D2 and D3 events were precipitated from meteoric fluids based on oxygen and carbons stable isotope analysis. To characterize the structural geology of the Stanley Head region six structural cross sections that transect the study area have been produced. "Balanced" cross sections were constructed using the integration of surficial data and a kinematic model of deformation for the multiple detachment, evaporite based Parry Islands fold belt (Harrison and Bally, 1988). Cross sections from the study area provide a useful analogue to construct a regional cross section across Cornwallis Island. Both the regional and Stanley Head cross sections are characterized by 1) Southwest and northeast verging folds and thrust faults, 2) a variety of fold - thrust fault interactions, and 3) a proposed structural disharmony between the surficial fold belt and an underlying fold and thrust system.

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