FAULT-PROPAGATION FOLDING IN THE LIVINGSTONE RANGE, SOUTHERN ALBERTA FOOTHILLS: FAULTING, FOLDING AND FLUIDS IN A HANGINGWALL RAMP ANTICLINE

The Centre Peak anticline of the Livingstone Range began as a fault-propagation fold when the Livingstone thrust propagated upwards from a regionally significant detachment in the Upper Devonian Palliser Formation, through Upper Devonian and Carboniferous strata, to a regional detachment in overlying Jurassic shales of the Fernie Formation. As thrusting continued, the hangingwall anticline was transported approximately 30 kilometres to the east. During transport, the anticline continued to tighten and a smaller thrust fault propagated along the axial zone in the core of the fold. The resulting Centre Peak anticline is a fault-propagation fold in which displacement on this blind thrust fault dies out upward in the core of the anticline. Above the tip line of the fault, strata in the core the anticline are unfaulted and are folded concentrically. The present day Centre Peak anticline is a tight concentric fold with planar limbs and a kink-style geometry, whereas the original fault-propagation anticline was likely a broad, open structure.

Oxygen and carbon isotope geochemistry of fault zone calcite veins and host rocks from the Centre Peak anticline and other faults along the Livingstone Range show a consistent pattern. Calcite veins from thrust faults, including veins along the blind thrust in the core of the Centre Peak anticline, contain calcite with oxygen and carbon isotope signatures indicative of meteoric water. Veins from cross faults and larger tear faults have oxygen and carbon isotope signatures indicative formation fluids. In spite of being linked during folding and thrusting, the thrust faults and cross faults did not appear to share fluid sources.