Detailed study of two Pennsylvanian formations, the Glen Eyrie and the Fountain, within a limited area along the east flank of the Colorado Front Range indicates that such investigation is fundamental to a more thorough understanding of redbed stratigraphy.
The Glen Eyrie and Fountain formations in the vicinity of the Manitou embayment were deposited in a deltaic environment during mid-Pennsylvanian time. Sediments were derived from a highland whose eastern margin closely coincided with that of the present Front Range. Climatic conditions over both the highland and the delta surface were more humid than at present.
The Glen Eyrie contains a varied fauna consisting principally of ostracods and conodonts. These, in conjunction with brachiopods from a lower Fountain limestone, indicate that the two formations are of Marmaton or later age as recognized in the Mid-Continent Pennsylvanian section.
Detailed descriptions of the type sections of the Glen Eyrie and Fountain formations are presented for the first time. Maps showing the distribution of the two formations within the Colorado Springs Quadrangle and the extent of thin limestone beds within the Fountain of the southwestern quarter of the quadrangle are included. The Glen Eyrie has been raised from its former status as a member of the Fountain to the rank of formation.
Subsurface data from four wells reveal that, for a distance of 18 miles at least, the Fountain thickens eastward at a rate of approximately 100 feet per mile. Well samples indicate no marked lithologic change in the Fountain through this distance. The Glen Eyrie is represented in the two easternmost of these wells by a thin section of shales and limestones at the base of the Fountain.