Type Geological formation Country United States Regions Colorado, Utah | Underlies Mancos Shale Formation Named for Naturita | |
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Overlies Cedar Mountain Formation, Burro Canyon Formation | ||
The Naturita Formation is a Cretaceous Period sedimentary geologic formation, found in western Colorado and eastern Utah.
Contents
It was named for a rock outcrop of the formation located near Naturita, Colorado.
Geology
The formation overlies the Cedar Mountain Formation, and underlies the Mancos Shale formation, thus occupying the position of sedimentary strata that have historically been called the Dakota Formation. That term is no longer used for Cretaceous strata that were deposited on the western side of the Cretaceous Seaway.
In most areas, the Naturita Formation is composed of a lower unit of conglomeratic sandstone, a middle part of lignitic mudstones and coal, and fine- to medium-grained sandstones in the upper part. The Naturita is not uniform in thickness and in many places is very thin or missing so that the Mancos Formation is in direct contact with the Cedar Mountain Formation.
Where missing, a lag of conglomerate may be present to indicate winnowing of sediments, which occurred by advancing Cretaceous seas. In other places, deposition of Naturita sediments did not occur, and these areas may have been quiet lagoons.
Coastal coal swamps also formed in low areas as the encroaching sea raised the base level of rivers and the water table.
Fossils
Fossils from the Naturita include dinosaur bone fragments of ceratopsians, a possible primitive tyrannosaurid, nodosaurid ankylosaurs, a brachiosaurid sauropod, and the bothremyid turtle Paiutemys.
Abundant fossil plants are also known from the coal-rich layers.