Tansill shelf margin facies exposed in the quarry near the mouth of Dark Canyon are characterized by patchy dedolomitization, small vertical faults, collapse breccias associated with the faults, and abundant white coarse-crystalline blocky calcite cement filling breccia voids, fault planes, and intergranular porosity. Timing of these features is problematic. Collapse, dedolomitization, and breccia fabrics are commonly associated with the modern cycle of meteoric diagenesis and cave formation. Elsewhere in the Guadalupe Mountains (such as Walnut Canyon and Rocky Arroyo), Quaternary evaporite and meteoric dissolution is associated with a characteristic brown, transparent calcite cement, but this cement and the associated abundant open pore system is absent here.

Bedding-plane, vertical , and oblique stylolites are common near the mouth of Dark Canyon. Bedding-plane stylolites are crosscut by faults and rotated in breccia clasts, but dedolomite patches, breccia clasts, and cloudy, coarse-crystalline, white calcite are cross-cut by the tectonic and oblique stylolites. The oblique and tectonic stylolites show no systematic relationship to each other.

Vertical stylolites occur across trans-Pecos Texas. Orientation, intensity, and crosscutting relationships data indicate that these stylolites are cogenetic and date to Laramide (Late Cretaceous) deformation centered on the Chihuahua trough. The diagenetic features at Dark Canyon are therefore post-Permian and pre-Late Cretaceous in age.

The karst-related diagenetic features are probably related to the pre-Cretaceous unconformity, which lies about 70 m above the Dark Canyon quarry. Karsting and dissolution of shelf evaporites occurred along this surface long before the Quaternary cave-forming event.