Lytle Formation
The Lytle Formation/Lytle Sandstone is an Early Cretaceous geologic unit with its northern exposure running north and south within the Front Range foothills and the Dakota Hogback in northern Colorado and southern Wyoming where it is assigned formation rank within the Dakota Group. In south-central Colorado, the Lytle is a member of the Purgatoire Formation.
The Lytle was the last non-marine unit to form in the Denver Basin before the region was fully inundated by the Western Interior Seaway. It was formed above sea level from sediments carried by heavily laden rivers flowing from the eroding uplifts of the Sevier orogeny several tens of millions of years before the Rocky Mountains rose. It is particularly noted for abundant brown chert pebbles washed in from the uplifted Permian rock far to the west.
Detrital zircon geochronology of the Lytle Formation in the Raton Basin suggests a late Jurassic age for this unit. However, it is possible that the lack of younger zircons reflects a hiatus in deposition of airfall material.
Known fossils are fragments of petrified wood eroded from the west as well as nondescript animal burrows.
