POST -CRETACEOUS HLSTORY OF WESTERN WYOMING 103 



the lower sides of these overthrusts. South and southwest of Jack- 

 son Hole most of the folds are much more closely appressed, and 

 the strata generally stand upright. It is a fact worth noting that 

 this deformation was apparently not accompanied by volcanic activ- 

 ity within the region under consideration. I have attempted to 



TABLE I 

 CoxDEXSED Table or Fokmatioxs 





Tikkness in Feet 



Description 



Quateman- 



Superficial 

 deposits 



1-500 Glacial drift, talus, landslides and 



earth-flows, ri\'er gravel and silt, 

 loess, and residual soils 



Tertiar\- 

 fdightly 

 disturbedj 



Volcanics 



Wind River 

 formation 

 and associ- 

 ated strata 



Over ^.cco Stratified agglomerate and tuff with 

 a few lava flows 



1,500 to 6|000 Largely clay and soft sandstone with 

 local conglomerates and lava beds 



Mesozoic 

 (ftdded; 



Shale and 

 sandstone 



6.000 to 10.000 Lareel 



Paleozoic Limestone. 



folded etc. 



Archean 



Meta.: 



2 poo to j.foc Largely limestone or dolomite, some 

 I beds ver>' ma^ve and thick. 



Interbedded with ^lale, thin lime- 

 stone, sandstone, and. chert 





Massive gneisses and some schists, 

 with granitoid intrusions 



show by means of a stereogram (Fig. 4) the general character of the 

 folds and faiilts produced at this time as they might have app)eared 

 if they had been completed without being eroded. The effects of 

 subsequent warping, faulting, and erosion have been eliminated. 

 It is probable that there are more folds in the district than are 

 shown on this model, for in other parts of the Rocky Mountains 

 sharp folds in the Cretaceous rocks are occasionally re^-ealed in 

 canyons which locally cut through the superficial Tertiary cover. 

 The geologic age of the folding may be roughh' ascertained with- 

 out difficult}', but to determine it with a high degree of accurac}' 



