CORRELATION OF PRECAMBRIAN COAL CREEK CANYON QUARTZITE WITH QUARTZITE IN THE LATE EOCENE CASTLE ROCK CONGLOMERATE, DENVER BASIN, COLORADO

Since 1933 (Gabriel), it has been proposed that quartzite in the Castle Rock Conglomerate (Tcr) was derived from Precambrian quartzite exposures in Coal Creek Canyon, 40 miles northwest of the northernmost Tcr outcrops mapped in Douglas County.

This study provides a petrographic comparison of quartzite clasts in the Tcr with the in-place quartzite in Coal Creek Canyon confirming that the unique high grade andalusite/sillimanite metamorphic facies found in Coal Creek Canyon (Wells, 1967) can be identified in quartzite clasts in the Tcr. The unique andalusite-bearing quartzite clasts in the Tcr extend 45 miles southeast of Rueter-Hess Reservoir to the Calhan Paint Mines, south of Calhan.

Other Tcr clast lithologies derived from the North include a stretched-pebble quartzite conglomerate unique to Coal Creek Canyon and early to middle Proterozoic (1.7 to 1.4 Ga) intrusives northwest of Denver.

No other source of andalusite-bearing quartzite is known to exist in the provenance for the Denver Basin during Tertiary time. This makes the Coal Creek Canyon Quartzite, and its very specific location a special tool for coarse clastic provenance studies in the Tertiary of the Denver Basin.

This proven quartzite correlation will allow better provenance and paleodrainage reconstructions in the Denver Basin. It also allows the Castle Rock Conglomerate to be subdivided into a western- and northern-derived lithofacies.