STRUCTURAL GEOLOGY OF BANKS ISLAND - IMPLICATIONS TO THE STRUCTURE OF THE NORTH AMERICAN CONTINENTAL MARGIN

Banks Island is situated in the western Canadian Queen Elizabeth Islands at the margin of the North American continent facing the Amerasian Basin (Arctic Ocean). Exposures of Precambrian clastic rocks and sills occur in the south while Devonian clastic rocks and limestones of the Franklinian Basin are found in the north. Most of the island is overlain by unconsolidated Upper Cretaceous and Cenozoic deposits. Structural geology field work has shown that the earliest Carboniferous north-to-south Ellesmerian deformation, did not affect exposed Devonian and Precambrian strata. The front of the Ellesmerian Orogen most likely trends more or less east-west through M’Clure Strait between the Parry Islands to the north and Banks Island to the south. Cretaceous/Paleogene deposits are affected by a number of NNE-SSW trending faults. These are characterized by minor deformation on both sides of a fault and often show down-to-the-WNW normal faulting parallel to the recent continental margin, probably related to the extensional regime of the margin towards the Amerasian Basin. However, in several places, Cretaceous and Paleogene deposits are heavily deformed in restricted outcrops and areas exposed over a maximum of 0.5 km². These isolated, deformed areas are characterized by NNE-SSW trending shear planes, fold-structures and thrust-faults from mm to 100 m-scale with variable orientations. The isolated deformed areas are situated in overlapping sectors between en echelon strike-slip faults. Structural analyses of the orientations of the folds and thrusts with respect to the NNE-SSW trending faults indicate that Banks Island was affected by both sinistral and dextral opposing movements parallel to the continental margin after deposition of the Cretaceous and Paleogene sediments. This complex tectonic situation is similar to the structures and complicated tectonic history of Ellesmere Island in the northern Archipelago and to the Rapid Depression between the Richardson and British mountains on Yukon North Slope to the SW. The timing and similarity of structures, characterized by opposing lateral tectonic movements, ,indicate that the continental margin NW of Banks Island was most likely affected by movements similar to the pre-Eurekan and Eurekan history of the North American margin parallel to Ellesmere Island and North Greenland.