Garland field is an asymmetric anticlinal trap located in the north-central Big Horn basin, Wyoming. The field produces hydrocarbons from interlayered, fractured limestones and dolomites of the Madison Limestone (Mississippian). Significant karstification occurs in the form of field-wide intraformational breccias and locally developed cavernous porosity. Most breccias and caverns apparently formed during prolonged post-Madison exposure, prior to deposition of the overlying Darwin Sandstone.

Three types of karst breccia occur: (1) red, siltstone-matrix breccias, (2) clay-matrix breccias, and (3) dolomicrite-matrix breccias. Red, siltstone-matrix breccias occur in the upper 30 ft (9 m) of the Madison, and are related to the...