The Purgatoire Formation is an abandoned (1987)
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
period
Period may refer to:
Common uses
* Period (punctuation)
* Era, a length or span of time
*Menstruation, commonly referred to as a "period"
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (o ...
geologic
formation
Formation may refer to:
Linguistics
* Back-formation, the process of creating a new lexeme by removing or affixes
* Word formation, the creation of a new word by adding affixes
Mathematics and science
* Cave formation or speleothem, a secondary ...
classification. The classification was used in
Colorado
Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
,
New Mexico
New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
, and
Oklahoma
Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
, with mentions in older geologic literature in neighboring states.
[Griggs and Read, 1959.]
Units previously classified as members of the abandoned formation, including
Lytle,
Mesa Rica,
Pajarito,
Romeroville, and
Glencairn, have been generally elevated to formation rank. Particularly, significant divisions of the Purgatoire classification,
Lytle and
Glencairn, were realized as having characteristics of formations in their own right as well as representing the greatest
disconformity
An unconformity is a buried erosion surface, erosional or non-depositional surface separating two Rock (geology), rock masses or Stratum, strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer ...
in the Lower Cretaceous sediments of the
Western Interior Seaway
The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea (geology), inland sea that existed roughly over the present-day Great Plains of ...
. Rather than including these promoted formations in an elevated Purgatoire Group, the Mesa Rica, Pajarito, and Romeroville were placed in a definition of the
Dakota Group
The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western In ...
local to the
Dry Cimarron.
See also
*
List of fossiliferous stratigraphic units in Colorado
This is a list of fossil-bearing stratigraphic units in the U.S. state of Colorado.
Sites
See also
*Paleontology in Colorado
*Bibliography of Colorado
*Geography of Colorado
*History of Colorado
*Index of Colorado-related articles
*List of ...
*
Paleontology in Colorado
Paleontology in Colorado refers to paleontological research occurring within or conducted by people from the United States, U.S. state of Colorado.
The geologic column of Colorado spans about one third of Earth's history. Fossils can be found almo ...
References
Cretaceous Colorado
{{Cretaceous-stub