Oil Springs and Flat Top Anticlines, Carbon County, Wyoming: an unusual fold pair : Mountain Geologist, 31(2), 1994, pp 53–60

Abstract

Oil Springs Anticline, northwest of Medicine Bow, Wyoming, and located at the northeast corner of the Hanna Basin, lies near the junction of the Freezeout Hills Anticline, the Shirley thrust fault and the Flat Top Anticline. The surface fold as defined by the outcrop of the Wall Creek Sandstone Member of the Frontier Formation is disharmonic to deeper structure at the level of the Jurassic Sundance Formation. The fold is wedged between two major folds and is the result of a space problem between larger structural elements. The controlling Flat Top Anticline is an excellent example of a fold controlled by a well constrained fault in the Precambrian crystalline basement. The basement is bowed upward and outward to the northwest in the hanging wall of the Flat Top Anticline. The purpose of this paper is to describe the geologic structure of the Oil Springs and Flat Top anticlines and their relationship to the Freezeout Hills and the Hanna Basin. Commercial production of petroleum and natural gas occurs on the west flank of the Laramie-Cooper Lake Basin as far north as the northeast corner of the Hanna Basin. Stone reviewed the producing formations in the Laramie and eastern Hanna basins andmore » noted that 11 commercial accumulations of petroleum and natural gas are directly related to anticlinal structures. Production derived from the Permian-Pennsylvanian Tensleep Sandstone in this region has a special geologic framework. Fields that produce from the Tensleep Sandstone are well defined anticlines bounded by faults or fault systems, a situation also reported by Biggs and Espach, Blackstone and in the Wyoming Geological Association Symposium. The Tensleep Sandstone reservoirs in these faulted anticlines are in juxtaposition to potential source rocks of either Jurassic or Cretaceous age in the footwalls of the faults. 17 refs., 9 figs., 1 tab.« less