CRUSTAL STRUCTURE OF THE SOUTHERN ROCKY MOUNTAINS BASED ON REFRACTION/WIDE ANGLE REFLECTION SEISMIC DATA (CD-ROM'99)

During the CD-ROM Experiment (Continental Dynamics ROcky Mountains Project) in 1999, a 950km long refraction/wide angle reflection seismic profile was acquired in the southern Rocky Mountains. The seismic line trended south to north from northern New Mexico to central Wyoming. The instrument spacing was 800m along the profile and 10 chemical sources were used ranging in size from 900kg - 4500kg (100km spacing) which provided a relatively high resolution data set. The domain of the P-wave model is 950km long and 80km deep including the extreme topographic variations between New Mexico (1000m) up to the Continental Divide in Colorado (3500m).

The seismic data require two sedimentary layers at the top of the model. Their thickness varies between 100m near the Arkansas River, Colorado to 5km in the North Park Basin, Colorado. Due to the different thickness of the sediments, the Precambrian basement in New Mexico is only 3km deep. In Colorado and Wyoming portions of the line are located on basement exposures followed by basins up to 5km depth for example the Hanna/Kindt Basin, Wyoming or the North Park Basin, Wyoming. The velocities at the top of the basement vary between 5.8km/s and 6.1km/s and increase slowly with depth.

The lower crust is about 10km thick along the profile. The Moho is ca. 45km in New Mexico and deepens in Colorado to 50km. Further north in Wyoming it rises again to 40km. The thicker crust in Colorado coincides with a lateral velocity variation within the middle and lower crust.