--> Abstract: Tear Faults in Anticlinal Folds, Thermopolis Anticline, Wyoming, USA, by C. K. Zahm; #90925 (1999)

Datapages, Inc.Print this page

ZAHM, C. K., Colorado School of Mines, Department of Geology and Geological Engineering, Golden, Colorado

Abstract: Tear Faults in Anticlinal Folds, Thermopolis Anticline, Wyoming, USA

Tear faults are widely observed features in compressional folds. However, the detailed mechanics of tear faulting is largely unknown. This research will explore fundamental relationships between tear-fault geometry and areas of maximum strain. The first step toward addressing these issues is through quantitative outcrop mapping of faults and fault geometry at the King, Rose, and Cedar Ridge domes in the southern Bighorn basin. These domes are part of the Laramide-age Thermopolis anticline, and are separated by large, oblique-slip tear faults.

Permeability anisotropy has been observed in subsurface reservoirs near the Thermopolis anticline, mainly through pressure interference testing. This anisotropy occurs in the form of high directional permeabilities oriented roughly perpendicular to the fold axes. Reconnaissance measurements of fault spacing, length, orientation, and offset are available from Rose dome in the Alcova Limestone, a unit contained within the red sandstones of the Triassic Chugwater Formation. Most faults are tear faults which occur at high angles to the fold axes. Tear faults may cause the high permeability anisotropy observed in the subsurface reservoir. This does not appear to be a unique situation. Numerous other fields in the Bighorn basin exhibit high permeability anisotropy oriented roughly perpendicular to the fold axis. Determination of tear-fault mechanics in this study should provide fundamental data for many other anticlinal reservoirs. 

AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid