206 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



The sedimentary series everywhere presents undoubted evidence of 

 great erosion following the uplift of the range, antedating the extravasation 

 of the volcanic rocks which now so generally mantle it. That this period 

 of denudation was long is indicated by the profound gorges which were 

 cut in the rocks and carved deeply into the underlying schists. The 

 Mesozoic beds, if present, were entirely removed, and no trace of them 

 has been found within this area or in its immediate proximity. It is 

 further evidence of the long period of uplift and erosion which followed 

 the deposition of the Laramie. 1 



The following table presents a generalized section of the sedimentary 

 formations of the region. 



Snoicy Mountain section. 



Feet, 

 i Limestones, carrying fossils 150 



} Massive beds of indurated gray limestones; no fossils 175 



Three Forks J Thinly bedded limestones; characteristic Devonian fossils from lowest beds 200 



' Purplish-colored, thinly bedded, fissile limestones, carrying gasteropod remains.. 20 



C Brown, earthy-colored, clayey limestone conglomerate 25 



J Light and dark gray, thinly bedded limestones 150 



Jefferson .... -^ 



Crackled white limestones , 20 



I Persistent cliff- forming bed of massive light-gray limestone 200 



("Thinly bedded limestones, carrying fossils at base 100 



„ ,, ,. Thinly bedded limestones and limestone conglomerate. Fossils from summit are 



Gallatin ' 



Middle Cambrian , 250 



I Dark-gray mottled limestones, forming persistent cliff 100 



rBlack limestones; thinly bedded, carrying fossils (Middle Cambrian) ^ 



I Limestones and shales i 



Flathead l Thinly bedded limestones 200 



| Shales 200 



' Sandstone and quartzite ,. 100 



Archean Gneiss and schist. 



BUFFALO PLATEAU. 



This flat-topped mountain tract, lying between Hellroaring and Buffalo 

 creeks, together with adjacent areas across these streams, constitutes the 

 true southern termination of the Snowy Range. The plateau is of gneiss, 

 on which remnants of sedimentary rocks now form the highest points. The 

 gneiss presents considerable variety, but consists usually of feldspathic 

 forms, and shows a well-defined lamination toward the east. The surface 

 is glaciated, smooth ice-worn bosses and striated surfaces being common, 



'The Laramie and the overlying Livingston formation in Montana, by W. H. Weed: Bull. U. S. 

 Geol. Survey No. 105, Washington, 1893. 



