Poison Canyon Formation
The Poison Canyon Formation is a geologic formation in the Raton Basin of Colorado and New Mexico. The formation was deposited from the late Cretaceous through the Paleocene.
Description
The Poison Canyon Formation consists of thick sandstone beds separated by beds of mudstone and siltstone. It is found throughout most of the Raton Basin. The sandstone is arkosic and coarse-grained to conglomeratic. The mudstone and siltstone beds weather to yellow, are rich in mica, and are not resistant to erosion. The total thickness of the formation is up to.The formation grades below into the Raton Formation, with the transition often very gradual, up to. In the western part of the Raton Basin, the formation intertongues with and partially replaces the Raton Formation. The two are distinguished by color, by the absence of arkosic sandstone in the Raton Formation, and by the absence of coal from the Poison Canyon Formation. In addition, river channel deposits in the Raton Formation are up to six times wider and five times deeper than river channels in the Poison Canyon Formation, and the channels in the Poison River Formation tend to be isolated and lack any sheet-like amalgamation.
The Poison Canyon Formation underlies the Cuchara Formation in the northern part of the Raton Basin.
The formation derived its sediments from the San Luis uplift to the southwest and the Wet Mountains uplift to the north and northwest. Its age ranges from late Cretaceous to Paleocene.