File:Tidwell Member of the Morrison Formation over Wanakah Formation (Jurassic; roadcut near Artists Point, Colorado National Monument, Colorado, USA) 4 (23383788324).jpg

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Colorado National Monument is a colorful and scenic park just southwest of the town of Grand Junction in western Colorado, USA. It's located in the northeastern part of the Colorado Plateau Physiographic Province, a large section of continental crust that was significant uplifted during the Cenozoic. The rocks in the park are gently folded into a large monocline that has been erosionally dissected into a series of dramatic canyons.

The brown-colored ledges near the top of the roadcut are the basal sandstone beds of the Tidwell Member of the Morrison Formation (Upper Jurassic). The Morrison is widely distributed in many western American states and consists of fluvial (river/floodplain) and lacustrine (lake) deposits. Dinosaur bones and dinosaur tracks are moderately common in Morrison Formation sediments (exceptionally rich localities include Como Bluff in Wyoming, Dinosaur National Monument in Utah, Dinosaur Ridge in Colorado, and the Cleveland-Lloyd Quarry in Utah).

The grayish- and reddish-colored slope in the middle of the roadcut is mudshales of the Middle Jurassic Wanakah Formation (formerly known as the Summerville Formation). Some weathering-resistant siltstone and sandstone interbeds are also present. The Wanakah Formation is mostly nonmarine, but some marginal marine beds have been identified. Relatively few fossils have been found in the Wanakah Formation of western Colorado and eastern Utah, but include bivalves, ostracods, fish, and trace fossils.

Locality: roadcut along Rim Rock Road next to Artists Point overlook, Colorado National Monument, southwest of the town of Grand Junction, west-central Mesa County, far-western Colorado, USA
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Source Tidwell Member of the Morrison Formation over Wanakah Formation (Jurassic; roadcut near Artists Point, Colorado National Monument, Colorado, USA) 4
Author James St. John

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This file is licensed under the Creative Commons Attribution 2.0 Generic license.
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/23383788324 (archive). It was reviewed on 6 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0.

6 December 2019

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Date/TimeThumbnailDimensionsUserComment
current04:00, 6 December 2019Thumbnail for version as of 04:00, 6 December 20193,008 × 1,594 (2.92 MB)Ser Amantio di Nicolao (talk | contribs)Transferred from Flickr via #flickr2commons

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