AN INTEGRATED GEOPHYSICAL STUDY OF THE NORTH PARK, SOUTH PARK, AND RATON BASINS OF COLORADO

The compressive environment of the Late Cretaceous-Early Tertiary Laramide Orogeny (70-35Ma.) formed the North Park, South Park, and the Raton basins of Colorado. The Pennsylvanian-Permian Ancestral Rocky Mountains (~240-280Ma) and Neogene (~33Ma) extension in southern Colorado has also affected some of these basins. 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. Filtered (smoothed and bandpassed) gravity maps and computer models (2.5-D) have been created for the different basins. The gravity low over North Park is the result of basin fill. Southern South Park consists of two sub-basins separated by a structural high. The Elkhorn Thrust fault bounding South Park on the east shows on the maps as a region with a high gravity gradient. Both the Raton and the North Park basins are asymmetrical and synclinal. The Raton basin is the easternmost of the Laramide age basins and has a similar history and structure to the northern basins. A northwest trending gravity low, following the trend of the Colorado Mineral Belt, is probably associated with a batholithic intrusion. Work in progress includes spatial analysis of gravity data, digital elevation models, and satellite imagery that will be used to further clarify the structure and origin of these basins.