OLCHOWY, BEATA M., Department of Geology, Univ. of Calgary, Alberta

ABSTRACT: Study of the Triangular Zone and Foothills Structure in the Jumpingpound Creek Area, Alberta

The 'triangle zone' comprises a structural complex, found at the eastern edge of the deformed belt of the southern Canadian Rocky Mountains, where foreland dipping strata are juxtaposed with hinterland dipping strata. Upper and lower detachments define the top and base of an intercutaneous wedge, simultaneous motion along the two detachments allows the wedge to advance toward the foreland as it is emplaced between layers of undeformed strata in the Plains. The Jumpingpound Creek area is located approximately 30 km west of Calgary, Alberta. The surface expression of the triangle zone is an anticline and the dominant structural style exposed is folding. Shortening at the Mesozoic level is approximately 50% across the triangle zone. This particular region provides critical information on how the upper detachment develops and transfers displacement along strike. In the south, at Turner Valley, the upper and lower detachments merge with a taper angle of approximately 30 degrees, yet north of Jumpingpound, the upper and lower detachments do not merge within the triangle zone, but continue beneath the Plains as flats separated by a 300 to 500 m wide deformation zone. Several balanced 1:20,000 cross-sections and palinspastically restored sections were constructed to illustrate changes along the strike. These cross-sections are constrained by detailed surface data and subsurface data from numerous wells and seismic sections made available for this study. FIELDLOG software interfaced with AutoCAD made it possible to digitize and compile geologic field data on digital basemaps.< P>

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.