ABSTRACT

The Indianhead Creek map area encompasses a four mile segment of the Third Range of the Rocky Mountain Front Ranges and is immediately north of the Clearwater River in West Central Alberta.

The map area contains a part of the Third Range thrust sheet, a minor thrust fault, and a series of four normal faults. The normal fault blocks are tilted to the south with the lower beds of each fault block being progressively truncated by the Third Range thrust fault. Two of the normal faults cut through the Third Range thrust fault into the underlying formations, with a substantially reduced stratigraphic separation.

Two hypotheses are proposed to explain the time relationships and causes of the normal faulting. The first is that the normal faulting and associated tilting occurred before the development of the Third Range thrust fault. During thrust faulting, the minor thrust and progressive northward truncation of the lower beds of each normal fault block occurred. A recurrence of normal faulting along the planes of the previously existing normal faults, took place after the completion of thrust faulting in which the Third Range thrust block and the underlying formations were displaced.

The second hypothesis is that the normal faulting, the tilting of the normal fault blocks, and the thrust faulting developed concurrently. A monoclinal warp in the plane of the Third Range thrust fault is suggested, to explain the progressive truncation to the south of the lower beds of the tilted normal fault blocks, and the loss in stratigraphic separation on two of the normal faults where they pass through the thrust fault.