CONSTRAINING THE GEOMORPHOLOGY OF THE RICO DOME IN SOUTHWESTERN COLORADO WITH GIS AND FIELD STUDIES

The Rico dome in southwestern Colorado is an uplifted structural feature cored by a ca. 68 Ma pluton. The dome deforms the surrounding strata into a 15-mile-long and 12-mile-wide structure. It was previously thought that the longest dimension of the dome was oriented ~280° and that its geometry was directly tied to emplacement of the stock along east-west trending fault zones. In this investigation, the elevation, slope, and position data for several exposed stratigraphic contacts were employed along with GIS software to construct 3D models of the pre-erosional architecture of the dome. These results reveal new insight into the subsurface morphology and geomorphic controls on the Rico dome.

The digital models are derived from published geologic maps at 1:24,000. We first established points along several prominent geologic contacts within the study area and assigned elevation values to them using a 30 m elevation model. For each contact, Esri ArcGIS software was applied to build a 3D surface fitting between each point. The result is a series of digital 3D surfaces which represent the subsurface stratigraphy of the structure. Strike and dip measurements of strata at several stations throughout the study area were measured in the field to confirm the data presented on the geologic maps.

The results of this study show that the structure’s longest dimension is oriented ~218°, contrary to the originally suggested direction. Due to the discrepancy between this direction and the dominantly east-west striking faults, we argue that the faults were not dominant controls on the position and geometry of the dome. Results from this investigation invite a new interpretation of factors which could have influenced the dome’s formation. This opens the possibility of previously unexplored controls such as weak stratigraphic zones or deep, unexposed fractures.