24 



WYOMING ROCKIES 



GENERAL CHARACTERISTICS 



The topographic features of Wyoming are for the most part large, 

 northwest-trending ranges and large intermontane basins. Study Fig. 24.1. 

 Of the ranges, die most imposing are the Beartooth, Absaroka, Wind 

 River, and Big Horn. Numerous peaks in these ranges reach elevations 

 above 12,000 feet and stand 5000 to 7000 feet above the basin floors. 

 Other ranges, now not so high and partly buried by Tertiary sediments, 

 were undoubtedly once very high and are equally important structural 

 elements. The Wyoming structural system is defined for convenience as 

 extending slightly beyond the borders of the state. The Pryor Mountains 



at the north end of the Big Horn and the Beartooth Range extend into 

 southern Montana; the Black Hills lie mostly in western South Dakota, 

 and the Uinta Range mostly in Utah. On the other hand, the Colorado 

 Rockies extend into southeastern Wyoming by way of the Laramie, 

 Medicine Bow, and Park ranges. Certainly the Colorado and Wyoming 

 rockies are closely related, and any separation structurally is arbitrary 

 and for the sake of organization. 



The Wyoming Rockies have been referred to as the outer ranges or 

 shelf ranges of the Rocky Mountain Cordillera, in contrast to the inner or 

 geosynclinal. This point has been discussed in the introduction to the 

 general subject of the Late Cretaceous and Early Tertiary Rocky Moun- 

 tain systems, Chapter 19. By inspection of the paleotectonic maps of the 

 Paleozoic and Mesozoic eras, it will be apparent that the area of the outer 

 ranges was generally one of shelf seas except in Late Cretaceous time, 

 when in certain basins of Wyoming and Colorado over 10,000 feet of 

 strata accumulated. 



In addition to a rather thin veneer of Paleozoic, Triassic, and Jurassic 

 sediments the ranges have extensive, oval-shaped cores of Precambrian 

 rock, and for the most part are asymmetrical uplifts either in the form of 

 large anticlines or great tilted fault blocks. The Absaroka Range is an 

 exception because it is composed chiefly of pyroclastics and volcanic flows 

 of a date later than most of the other mountain building. The Absarokas 

 are connected with and closely related to the volcanic plateau of Yellow- 

 stone Park. 



TETON-GROS VENTRE-WIND RIVER ELEMENT 



The Teton, Gros Ventre, and Wind River ranges are in general align- 

 ment and extend from the Idaho line south of Yellowstone Park southeast- 

 ward for 150 miles. They are of great height and beauty, and support a 

 number of small glaciers. The Grand Teton is 13,747 feet high, and Gan- 

 nett Peak in the Wind River Range is 13,785 feet high. These are tin- 

 highest peaks in Wyoming. All three ranges have Precambrian crystal- 

 line cores and fairly simple structure along dieir northeastern flank, such 

 as characterizes the great anticlinal arches of the Big Horn and Black 



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