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Dakota Hogback (west of Denver, Colorado, USA) 2 | by James St. John
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Dakota Hogback (west of Denver, Colorado, USA) 2

East-west geologic cross-section through the Dakota Hogback in Colorado, USA. (west is to right; east is to the left; looking south)


The Dakota Hogback is a north-south trending ridge of eastward-dipping Mesozoic sedimentary rocks. Triassic, Jurassic, and Cretaceous rocks are present, tilted by Laramide Orogeny uplift during the Cenozoic (the Front Range of the Colorado Rocky Mountains is immediately west of here). In the cross-section shown above, Precambrian basement rocks of the Front Range are shown on the right. Dakota Hogback geology is shown near the left side of the diagram.


The western side of the Dakota Hogback consists of the Morrison Formation (Kimmeridgian Stage, middle Upper Jurassic, ~150 to 156 Ma), which has fluvial (river/floodplain) and lacustrine (lake) deposits, plus reddish-colored paleosol horizons. Dinosaur bones and dinosaur tracks have been found in the Morrison Formation in this area.


The eastern side of the Dakota Hogback consists of the Dakota Sandstone (Albian Stage, upper Lower Cretaceous), which is dominated by nearshore terrestrial to intertidal to shallow marine quartz sandstone deposits. Dinosaur tracks are common on some Dakota Sandstone bedding planes in this area.


Locality: Dakota Hogback, north & south of Interstate 70, immediately east of the Rt. 40 exit (= exit 259), west of Denver, north-central Colorado, USA


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Taken on December 16, 2012