About This Item
- Full TextFull Text(subscription required)
- Pay-Per-View PurchasePay-Per-View
Purchase Options Explain
Share This Item
Devonian and Mississippian rocks cover most of the central part of the Colorado Plateau and range in thickness from a few feet in the eastern part to a combined total thickness of approximately 2,000 ft. along the western part. The Mississippian is composed predominantly of pure carbonate rocks whereas the Devonian is composed of carbonate rocks, sandstone, and varicolored shale.
Through most of the area the Devonian rests on Cambrian rocks and the contact is a disconformity, perhaps even a paraconformity. The three major units of the Devonian in ascending order are the Aneth, Elbert, and Ouray Formations. There is an intergrading facies relation between the Aneth Formation and the carbonate of the Elbert Formation. Numerous individual sandstone bodies are in the Elbert Formation. As a result, identification of the basal McCracken Sandstone Member, as differentiated from other Elbert sandstone units, is a major problem in mapping the Devonian in this area. The Upper Elbert Member represents continued transgression of the Late Devonian sea. The Ouray Formation is composed of carbonate rocks that are both Devonian and Mississippian in age. Devonian sediments pro ably accumulated slowly in shallow, sometimes restricted bays, on tidal flats, and on a relatively shallow-marine shelf, where some carbonates at different times mixed and alternated with terrigenous sediments. Low land was on the east; deeper-marine waters were on the west. The environment of deposition of Mississippian sediments was that of a marine shelf, relatively more open than during the Devonian and receiving little or no terrigenous sediment.
The correlation of the Mississippian Redwall Formation into the subsurface of the Four Corners area is considered to be sufficiently well established to justify the use of the term Redwall Formation through much of the area of this report. The Leadville Formation of the San Juan Mountains area is considered to be equivalent to the Redwall Formation. Member names for the Redwall are given by McKee, all named after Grand Canyon localities. The Thunder Springs Member contains a distinctive chert on which widespread subsurface correlations are based. The upper surface of the Mississippian carbonate has a well-developed karst topography. This surface is the best seismic reflecting horizon although a map of the surface may not show true subsurface structure.
Pay-Per-View Purchase Options
The article is available through a document delivery service. Explain these Purchase Options.
|Watermarked PDF Document: $14|
|Open PDF Document: $24|
Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].