Part of Dawson Arkose

Dawson Arkose

Rivers flowing across the basin from a renewed phase of uplift in the Front Range deposited a sequence of rocks above the paleosol, now part of the Dawson Arkose. These rocks are made of coarse-grained gravel and sandstone with smaller amounts of mudstone and siltstone—typical remnants of a fluvial environment. Fossils are present in this rock unit, but they are relatively rare. The age of these beds is Eocene, although the exact time span represented is not yet known. Typical thicknesses are 100 to 1,000 feet. These rocks form the shallow aquifers in portions of the Denver Basin.
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