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Dinosaur bone in sandstone (Morrison Formation, Upper Jurassic; western side of Dinosaur Ridge, Colorado, USA) | by James St. John
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Dinosaur bone in sandstone (Morrison Formation, Upper Jurassic; western side of Dinosaur Ridge, Colorado, USA)

Dinosaur bone in sandstone in the Jurassic of Colorado, USA.

 

Dinosaur Ridge is a particularly dinosaur fossil-rich section of the Dakota Hogback in north-central Colorado. It is a north-south trending ridge of eastward-dipping Mesozoic sedimentary rocks. The western side of Dinosaur Ridge (see above photo) has exposures of the Morrison Formation, an Upper Jurassic succession consisting of fluvial (river/floodplain) and lacustrine (lake) deposits, plus reddish-colored paleosol horizons. Dinosaur bones and dinosaur tracks have been found here.

 

The fossil shown above is a cross-section through a dinosaur bone in a fluvial sandstone matrix. Several dinosaur bones occur at this site - part of a river channel sandstone deposit. Paleocurrent indicators show that the river system was flowing to the southeast.

 

Stratigraphy: Morrison Formation, Kimmeridgian Stage, middle Upper Jurassic, ~150 to 156 Ma

 

Locality: "Quarry 5" (= one of Arthur Lakes' dinosaur excavation sites during the Cope-Marsh Bone Wars of the late 1800s), western side of Dinosaur Ridge, between Interstate 70 and the town of Morrison, west of Denver, north-central Colorado, USA

 

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Taken on July 16, 2015