MESOZOIC SYSTEMS ALONG THE PACIFIC 



261 



Fig. 17.1. Index map showing significant features 

 and localities of Mesozoic orogeny in the western 

 Cordillera. G.P., Grants Pass quadrangle; Med., Med- 

 ford quadrangle; Winn., Winnemucca quadrangle; 

 Gol., Golconda quadrangle; Tobin, Mt. Tobin quad- 

 rangle; Moses, Mt. Moses quadrangle; Gun. P., Gun- 

 nison Plateau. 



TERTIARY 





WINN 



GOL. 





TOBIN 



% 



MOSES 



» 



t 







OLCimcs 



IDAH O 



~ NEVADA I UTAH 



SIERRA NEVADA AND 

 KLAMATH BATHOLITHS 

 AND SATELLITES 



\ 



\ 



UINTA 



t -* * 



"\ » \ t— • 



CANYON, ; 

 RANGE ,' I 





IRON 

 SPRINGS 

 OISTRICJ--^ 



UTAH _ 

 ~ARlZQN* 



\ 



\J 



ble with underlying and overlying formations. Deposition was continuous 

 from Triassic to Jurassic time, while the western orogenic belt remained 

 fairly quiet. Its relief was evidently low, and volcanism is not recorded in 

 the shales, limestones, and sandstones of the Sunrise formation which 

 were deposited in the trough. 



At this stage in early Jurassic time, the sediments of the trough were 

 sharply folded ( Ferguson and Muller, 1937 ) . The most intense deforma- 

 tion was approximately coextensive with the area of deposition of the 

 Upper Triassic deposits. The orogeny began apparently with the forma- 

 tion of a marginal trough at the border of the geosyncline. In the trough, 



the Dunlap formation of Early Jurassic age was deposited. It consists 

 dominantly of fanglomerate, conglomerate, and sandstone with an upper 

 volcanic member of andesitic, quartz-latitic, and rhyolitic composition. 

 The fanglomerates and conglomerates were derived chiefly from the 

 limestones of the Luning formation and only locally from the great Ex- 

 celsior volcanic series. The Dunlap has been observed resting on upturned 

 cherts of the Excelsior formation with an angular discordance of 90 de- 

 grees, and also to be truncating folds of the Luning limestones. The 

 Dunlap is characteristically an orogenic deposit, and Ferguson and Muller 

 (1937) recognize a continuation of deformation during its deposition. 



