AN INTEGRATED GEOPHYSICAL STUDY OF THE UNCOMPAHGRE UPLIFT, COLORADO AND UTAH

The Uncompahgre uplift that lies astride the Colorado-Utah border is a mostly buried tectonic feature that separates the Paradox basin to the south from the Piceance basin to the north. As part of the Ancestral Rocky Mountains orogenic belt, the structures of the Uncompahgre uplift are difficult to understand since they are largely covered by sediments and there is limited subsurface information.

In this study, we undertook an integrated geophysical and geological study of the Uncompahgre uplift region and is focused on expanding our structural understanding of the uplift and its evolution, as well as the intraplate deformation of the Ancestral Rocky Mountains. A particular feature of interest was the large gravity anomaly associated with the Uncompahgre uplift. Also, linkage to other ongoing studies to the southeast of the Uncompahgre uplift (such as studies of the Southern Oklahoma aulacogen and the Midcontinent rift) was an additional goal of this study.

Three crustal-scale cross-sections of the uplift were constructed using modeling of gravity as the platform for integration. These gravity profiles were modeled using seismic, well log, isopach and cross section data as constraints. The results required the existence of a mafic body under the Uncompahgre uplift, as well as heterogeneity in the upper crust underneath the southern gravity profile. Updated lithological structure contour surface maps for the top of the Precambrian, Cambrian, Mississippian, Pennsylvanian and Permian were produced with recent seismic, well log, cross sections, and isopach data as constraints. Visualization of the data in 3D revealed that the gravity anomaly under the Uncompahgre uplift is slightly shifted to the northwest of the feature. In addition, filtered gravity and magnetic maps of the Uncompahgre uplift region were produced enhancing the different structural trends and features in the region. Connection to other studies were targeted by processing and filtering regional (Utah to Oklahoma) aeromagnetic and gravity data coupled with the earth models showed that the Uncompahgre uplift is most likely a northwestern extension of the Southern Oklahoma aulacogen. It also could be, at least in part, related to Precambrian structures in the region.