The upper 605 feet is assigned to the Rocky Mountain formation, which is here amended to comprise strata of Permian age. The formation is divided into an upper quartzitic sandstone member, 503 feet thick, for which the term Storm Creek is proposed. The lower member is believed to be the equivalent of Warren's (unpublished) Norquay member of the Banff region, on both faunal and lithologic grounds.

The name Tunnel Mountain is redefined to cover the underlying 602 feet of resistant dolomite and limestone with interbedded gray and green shale, of Chester age. Below this, a topographically weak unit comprises 557 feet of Meramecian strata and is correlative with Douglas' (1953) Mt. Head formation. Its upper 188 feet is interbedded black bituminous shale and black bituminous dense limestone, while Lithostrotion-bearing biostromes are intercalated in the lower portion. Finally some 300 feet of resistant Livingstone (Osage) strata intervene between the base of the Mt. Head and the thrust which terminates the section below.

Two major faunal zones have been discriminated in the Tunnel Mountain and three in the Mt. Head. Indicated affinities of these are with the late Chester, Ste. Genevieve, St. Louis, and Salem units of the standard Mississippi Valley section. Corals in the Mt. Head also permit correlations with the Brazer limestone of Utah. More locally, lithologic and faunal evidence indicates a close correlation with type sections at Mt. Head and Banff.

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