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Show CHAPTER IX DINOSAUR NATIONAL MONUMENT Dinosaur National Monument was originally established as an 80- acre area by proclamation of President Wilson on October 4, 1915, under authority of the Antiquities Act, for the purpose of preserving a rich deposit of fossilized dinosaur bones found here in an excellent state of preservation. By proclamation of July 14, 1938, signed by President Franklin D. Roosevelt, the area was extended to include other resources of great scientific interest, such as the canyon of the Yampa River and the Canyon of Lodore, Whirlpool Canyon, and Split Mountain Canyon on the Green River. The total area, including State and private lands within the exterior boundaries, as of October 1945, is approximately 209,744 acres. LOCATION The monument lies in semiarid northwestern Colorado and northeastern Utah; about 70 percent falls within Colorado and 30 percent in Utah. It is essentially a canyon- plateau area. Earth processes of a past geological age with contemporaneous biological developments of a spectacular nature have produced its outstanding features. It lies on the southern flanks of the eastern end of the great east- west Uinta Mountain uplift. While there are other notable geological, wilderness, and scenic values in the vicinity, the monument is, from the standpoint of such values, the spectacular core of a considerable region on the Upper Colorado River Basin. Between the northern end of the monument and the Utah- Wyoming State line are noteworthy canyons on the Green River, such as Red Canyon and Flaming Gorge. Fine as they are, they do not possess such exceptional qualities as are present in the monument. SCIENTIFIC, SCENIC, AND RELATED VALUES OF THE MONUMENT Functionally, the monument consists of two contiguous units which will be referred to as the Quarry Unit and the Canyon Unit. The comparatively small Quarry Unit, comprising three or four thousand acres, includes not only the 80 acres of the original national monument, but also surrounding land west and north of the Green River and south of Split Mountain. The Canyon Unit, consisting of about 206,000 acres, comprises the rest of the monument. Operationally, the monument is split into three distinct units of roughly equal size by the virtually impassable canyons of the Green and Yampa Rivers. Quarry Unit.- The most remarkable single feature of the monument is the world- famous dinosaur fossil deposit in the Quarry Unit. The fossils are found in the Morrison formation ( upper Jurassic) on the south limb ol the Split Mountain anticline. This formation underlies the shales and sandstones of the Cretaceous, and is underlain by other strata of the Jurassic. Below the Jurassic lie the " red beds" of the Triassic group. In the vicinity of the " Quarry," the strata of the Cretaceous, Jurassic, and Triassic dip sharply to the south. Extensive excavations have been carried out, and considerable removals of important fossils have been made. Ii is to be expected that the unexcavated parts of the formation at the " Quarry" are just as rich in quality and variety of fossil specimens as was the excavated part. Near the " Quarry" the upturned sedimentary rock formations tell a geological story of events preceding and following the era when dinosaurs roamed over a landscape much different from that of the present. The tilted rocks exposed in the Quarry Unit are part of the thousands of feet of 192 |