Abstract: A Structural History of Divide Creek Anticline, Piceance Basin, Northwest Colorado

Bret Gunneson, Michael Wilson, Jim Labo

A new seismic program over Divide Creek Anticline gives a clear image of the structure. Analysis of older seismic data showed that standard shot holes and charges did not produce consistently good reflections over the top of the anticline. Field tests of a variety of shot-hole patterns and charges led to new acquisition parameters.

Interpretation of the new seismic data demonstrates the complex structural development of the Divide Creek Anticline. During the Pennsylvanian ancestral Rockies orogeny, a northwest-southeast trending basement reverse fault created an uplifted fault block at Divide Creek. Lower Pennsylvanian sediments, including salt and anhydrite of the Eagle Valley Evaporite, pinch out on the northeastern flank of this structure. In the late Pennsylvanian, the structure was buried under several thousand feet of arkosic conglomerate of the Maroon Formation. During the Late Cretaceous and Paleocene (Laramide T) the Pennsylvanian fault reactivated and folded the overlying Mesozoic sediments. As the Grand Hogback basement thrust began to form to the east, a deep detachment formed in the Eagle Valley Eva orite west of the Grand Hogback. On the northeastern flank of Divide Creek Anticline, where the evaporates pinch out, the detachment ramped up to form a pop-up structure in the overlying sediments. As the Grand Hogback structure continued to develop during the Eocene (Laramide II), a shallower detachment zone developed within the Cretaceous Mancos Shale. Westward thrusting along this detachment decapitated the top of the previously formed pop-up structure and slid it over the top of the older Pennsylvanian structure. This complex history accounts for the unusual structure seen on the seismic and well data at Divide Creek Anticline.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994