Editing Morrison Formation (section)

{{short description|Rock formation in the western United States}}
{{Infobox Rockunit
| name           = Morrison Formation
| image          = Green River UT 2005-10-14 2104.jpg
| caption        = The distinctive banding of the Morrison Formation, a group of rock layers that occur throughout [[Dinosaur National Monument]] and the source of fossils like those found at the Dinosaur Quarry
| type           = [[Geologic formation]]
| age            = [[Upper Jurassic]] ([[Kimmeridgian]] to [[Tithonian]]), {{fossilrange|156.3|146.8|earliest=158.3|latest=145.8}}
| period         = Upper Jurassic
| prilithology   = [[Mudstone]]
| otherlithology = [[Sandstone]], [[siltstone]], [[limestone]]
| namedfor       = [[Morrison, Colorado]]
| namedby        =
| region         = [[Arizona]], [[Colorado]], [[Idaho]], [[Kansas]], [[Montana]], [[Nebraska]], [[New Mexico]], [[North Dakota]], [[Oklahoma]], [[South Dakota]], [[Texas]], [[Utah]], [[Wyoming]]
| country        = [[United States]]<ref name=CGKN>{{cite web|title=Morrison Formation|url=http://cgkn1.cgkn.net/weblex/pdf/010000/GSCC00053010132.pdf|publisher=CGKN|access-date=25 May 2013}}{{dead link|date=February 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
| coordinates    = {{coord|39.651|N|105.188|W|display:inline}}
| unitof         =
| subunits       =
| underlies      = [[Cedar Mountain Formation]], [[Cloverly Formation]], [[Lakota Formation]], [[Burro Canyon Formation]]
| overlies       = [[Summerville Formation]], [[Beclabito Formation]], [[Curtis Formation]], [[Bell Ranch Formation]], [[Sundance Formation]]
| thickness      = Up to 200 m
| extent         =[[File:Stratotypes for members of the Morrison Formation.jpg|thumb|Stratotypes for members of the Morrison Formation]]
| area           =
| map            =
| map_caption    =
|paleocoordinates={{coord|40.4|N|53.2|W|display:inline}}}}
[[File:USGS Dakota Hogback Morrison 1926.jpg|thumb|Type locality for the Morrison Formation above the town of Morrison, Colorado.]]
The '''Morrison Formation''' is a distinctive sequence of [[Late Jurassic|Upper Jurassic]] [[sedimentary rock]] found in the western United States which has been the most fertile source of [[dinosaur]] [[fossil]]s in North America. It is composed of [[mudstone]], [[sandstone]], [[siltstone]], and [[limestone]] and is light gray, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the [[Jurassic]] period.

It is centered in [[Wyoming]] and [[Colorado]], with outcrops in [[Montana]], [[North Dakota]], [[South Dakota]], [[Nebraska]], [[Kansas]], the panhandles of [[Oklahoma]] and [[Texas]], [[New Mexico]], [[Arizona]], [[Utah]], and [[Idaho]]. Equivalent rocks under different names are found in Canada.<ref name=PPT0404>{{cite journal |last=Parrish |first=J.T. |author2=Peterson, F. |author3= Turner, C.E. |year=2004 |title=Jurassic "savannah"-plant taphonomy and climate of the Morrison Formation (Upper Jurassic, Western USA) |journal=Sedimentary Geology |volume=167 |issue=3–4 |pages=137–162 |doi=10.1016/j.sedgeo.2004.01.004 |bibcode = 2004SedG..167..137P |url=http://doc.rero.ch/record/14574/files/PAL_E1788.pdf }}</ref> It covers an area of 1.5&nbsp;million square kilometers (600,000&nbsp;square miles), although only a tiny fraction is exposed and accessible to [[geologist]]s and [[Paleontology|paleontologists]]. Over 75% is still buried under the prairie to the east, and much of its western paleogeographic extent was eroded during [[Exhumation (geology)|exhumation]] of the [[Rocky Mountains]].

It was named after [[Morrison, Colorado]], where some of the first fossils in the formation were discovered by [[Arthur Lakes]] in 1877. That same year, it became the center of the [[Bone Wars]], a fossil-collecting rivalry between early paleontologists [[Othniel Charles Marsh]] and [[Edward Drinker Cope]]. In Colorado, New Mexico, and Utah, the Morrison Formation [[Uranium mining in the United States|was a major source]] of [[uranium]] ore.