North flank 

 Sweetwater Arch 



East end 

 Wind River Basin 



l Paleocene (Fort Union) time. Uplift of the Sweetwater arch, erosion of the crest of the arch and 

 deposition (Fort Union) in the Wind River Basin to the north. 



4. Oligocene (late Chadronion) time. Following the cessation of volcanic activity in mid-Eocene time 

 erosion removed much of the volcanic ejecto during lote Eocene time. In eorly Oligocene time the region 

 was buried for the most part or entirely by tuffs. It is believed that these tuffs come from a remote 

 source, possibly from the Yellowstone Plateau -Absoraka Mountains orea. 



fe) e^on°^ B ^in^ in „ d . R r er) iIi! ne - l, l Devel °P men ' ofVe WusMaulted' RaWesnake anticline. 



SJr^nirsn'.nrsssseTS." ,he eore of ,he on,iciine - ond (3) deposi,ion <* "™ 



gmmmmimsiwi= 



<l PRE-CAMBRIAN (->>!'> I I 



5. Mid -Miocene (Heminafordian) Jime. Erosion during late Oligocene (post-Chodronian) time and 

 probobly early Miocene (Arikareean) time removed much of the Oligocene deposits and further re- 

 duced the remnants of the Rottlesnoke ejecta. The region was again buried under deposits of 

 volcanic ashes, sandstones, coliches and conglomerates, which were laid down during mid-Miocem 

 time. Agoin these deposits came from a remote source. 



/IN.// v. --i / 

 — \ \ / \ _. 



r/-\/-.\^_~- > — \ ir/> 



'f\'\ PRE-CAMBRIAN O-'vi 



6. Recent time. Post mid-Miocene movements coused the collapse of the Sweetwater arch 

 ft?n,3 0n ,^L a ^° e T°J "S 1 '!'," 1 ? lioc . ene °" d plei s'ocene erosion has removed much 

 Miocene rocks, reduced the Rattlesnake ejecta to necks and modified the older rocks 



although 

 of the 



Fig. 24.13. Idealized evolution of north flank, Sweetwater arch. Reproduced from Knight, 1954. 



