Abstract

The Liard, Kotaneelee and Tlogotsho Ranges lie within the southern Franklin Mountains of the southwestern Northwest Territories and southeastern Yukon Territory. Within the study area, the Liard and Kotaneelee Ranges exhibit a major change in trend from south to north. In the south, the ranges trend northwest while in the north they trend north-northeast.

Geological field mapping was carried out during the summers of 2001 and 2002 to document the large-scale structures in the study area. The bedrock units exposed at the surface range in age from Late Devonian to Early Cretaceous. The topography of the study area is structurally controlled, with the Paleozoic, more resistant rocks forming the main parts of the ranges, and the Mesozoic, more recessive rocks occupying the valleys. The ranges are dominated by large-scale box anticlines and synclines, with less significant thrust faults. East–west and north–south stratigraphic variations have been documented and may have influenced the geometry of the ranges.

Physical analogue modeling was carried out at the Queen’s University Experimental Tectonics Laboratory to investigate the relationships between the mechanical stratigraphy and the structure of the study area and to identify potential causes of the dramatic change in trend of the ranges. Three possible controls on the change in trend were tested: (1) a transverse structure (the Beaver River structure); (2) changes in basement (Precambrian) elevation; and (3) stratigraphic facies variations. On the basis of the modeling it is concluded that the change in trend can be attributed to a change in basement elevation with a lesser effect due to facies changes.

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