Named as an upper member of South Platte formation of Dakota group for exposures in vicinity of Van Bibber Creek, Golden quad, Jefferson Co, CO in Denver basin. Type section is a composite of adjacent exposures measured on scarp of hogback between 200 and 500 yds north of Van Bibber Creek. Is a refractory clay. Composed of gray to dark gray, silty shale with scattered ferruginous ooliths, oolitic laminae and local concretions and interbeds of gray siltstone and fine grained, rusty brown sandy to argillaceous sandstone. Two beds of yellow-white kaolinitic clay. Helmer claystone bed which lies 12.5 to 14.5 ft above base of member in the Helmer Mine named. Is 50 ft thick at type. Usually ranges between 35 to 45 ft thick. Overlies Kassler sandstone member (new) of South Platte; underlies unconformably an unnamed sandstone of the South Platte. Is of nonmarine origin. Correlates with Dry Creek Canyon member of Dakota sandstone of the Canon City area (figure 19). Correlation with other Cretaceous units in Powder River basin northeast WY, Wind River basin central WY and Denver basin southeast WY, northeast and south-central CO shown on fig 19.

Source: GNU records (USGS DDS-6; Denver GNULEX).