THE NORTH AND SOUTH PARK BASINS OF CENTRAL COLORADO: AN INTEGRATED GEOPHYSICAL STUDY

The North and South Park basins of the Rocky Mountains are a geological enigma because they are flat expanses of land set amongst high mountains. The purpose of this project is to determine the origin of the Park basins and integrate the results with other studies carried out by the CD-ROM project. Analysis of gravity data has resulted in preliminary models for the Park basins of Colorado. Data, from the gravity database at UTEP, was used to produce two 2 1/2 dimensional models for the North Park and South Park basins. Furthermore, the data were smoothed and filtered resulting in a smoothed (10km lowpass) gravity map and two bandpass (10-75,10-150km) filtered maps. Previous work has pointed out the low anomaly values that define the Park basins with distinct trends in gravity values coincident with known faults. The 2 1/2 dimensional model for North Park reflects the synclinal structure of the underlying basement. A major offset in the Mesozoic basement correlates with the Spring Creek fault on the surface. The 2 1/2 dimensional model for South Park displays a steep gravity gradient along the eastern boundary coincident with the South Park fault. A steep gradient of unknown origin is present along the western boundary of the model for South Park. A distinct regional trend evident in both models needs further investigation. The smoothed (10km) gravity map displays a distinct gravity low for South Park that persists throughout the bandpass filtering process. The same is not obvious for North Park. Bandpass filtering of the data at increasing wavelengths brings out the gravity low of the North Park basin. Available magnetic data are being analyzed and compared with modeled gravity data. We are integrating these results with other spatial data to clarify the origin of the Park basins. The methods being employed include overlays of gravity and magnetic contours over topography using a DEM. TM, Landsat and Aster images are being used in the construction of other overlays.