AN INTEGRATED GEOPHYSICAL STUDY OF LARAMIDE AGE BASINS: CENTRAL COLORADO

The North Park, South Park, and Raton basins of Colorado were created in the compressive environment of the Late Cretaceous-Early Tertiary Laramide orogeny (70-35Ma). Rugged intermontane topography defines the North Park and South Park basins of Colorado. The Sangre de Cristo Range borders the Raton basin of south-central Colorado, the easternmost of the Laramide age basins of Colorado, on the west. These extensive basins are known for their flat topography yet detailed studies of the subsurface are few. The purpose of this study is to determine the structure and origin of these basins and integrate the results with other studies carried out by the CD-ROM (Continental Dynamics-Rocky Mountain) project. Smoothed and filtered gravity maps and several 2.5D profiles were produced from the extensive gravity database at UTEP. Gravity and topography when overlaid on DEM’s produce 3D images of the Park basins. The gravity low over North Park is the result of basin fill. South Park consists of two sub-basins separated by a structural high and is bounded on the east by the Elkhorn Thrust fault. A deep gravity low over northern South Park can be attributed to the Colorado Mineral Belt and is modeled as a batholithic intrusion in the subsurface. Widest in the north and thinning to a sliver in southern Colorado the Sangre de Cristo Mountains bound the Raton basin on the west. The Raton basin is asymmetrical and synclinal on the gravity profile; basin fill consists of Paleozoic, Mesozoic, and Laramide age rocks. TM images are being used in the construction of other overlays to clarify spatial relationships.