ABSTRACT

The Turner Valley structure is a triangle zone located at the leading edge of the foreland fold and thrust belt of the Canadian Cordillera. Detailed surface mapping, good quality seismic data, and abundant well control demonstrate that the structure is a complexly faulted duplex within undeformed autochthonous strata of the Plains. The upper and lower detachment surfaces, which are common to the entire deformed belt, bound the upper and lower surfaces of this duplex.

A significant hanging wall lateral ramp exists within one of the larger thrust blocks of the duplex. This ramp cuts upsection to the south from Paleozoic strata in the north to Mesozoic strata in the south. The effect of this ramp is to increase the size and displacement of the duplex to the north. As the deformed wedge increases in size to the north, the upper detachment surface is folded, uplifted, eroded, and eventually abandoned.

Restored, balanced cross-sections indicate that up to 50 per cent shortening has occurred within the wedge. Much of the shortening has occurred along extensive flats within the Exshaw and Fernie formations.

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