Mancos Shale
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Deeper down than the Mahogany zone and Green River Formation is the Mancos Shale. This resource is just emerging as a This shale formation occurs over much the same area as the Green River Formation but was deposited under much different circumstances. The Mancos shale was deposited during the latter portion of the Cretaceous period some 95 to 67 million years ago. The area of the Piceance Basin was flooded under an interior sea (Hettinger et al 2002.)
This figure shows the area of Mancos shale in Colorado.
This figure shows the area of Mancos shale in Colorado.
Layering
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Because of this deposition by an inland sea the Mancos shale is made up largly of marine shale. It is part of a greater formation of marine shales covering the western interior of North America (Johnson 2003.)
This layer lies much lower than the Green River Formation but much like its younger counterpart, the Mancos Shale butts up against another aquifer. In this case the Mesa Vverde aquifer. More information regarding this and other aquifers can be found here.
This layer lies much lower than the Green River Formation but much like its younger counterpart, the Mancos Shale butts up against another aquifer. In this case the Mesa Vverde aquifer. More information regarding this and other aquifers can be found here.
Mancos Shale Resources
Unlike the Green River Formation, the Mancos shale is not nearly as developed. It has not reached the same maturity as other resource bearing layers (Ressetar.) Because of this, estimates of the quantity and quality of contained oil and gas resources are nonexistent. That is not to say they would not produce a yield but because of their depth relative to other oil and gas plays this resource has not been explored.
Uinta Basin Mancos Shale
While not within the borders of Colorado, the Uinta Basin lies just on the Utah side of the border and shares much in common with the Piceance Basin. The Utah Geological Survey is conducting a continuous study of the Mancos Shale as a potential resource play in the state. Their research on the Mancos Shale can be found at this link. Cretaceous Shale-Gas Resources