556 



INDEX TO THE STRATIGEAPHY OF NORTH AMERICA. 



J 11. HinyiBOLDT RANGE, WESTERN NEVADA. 



The Jurassic of western Nevada was briefly described by Hague ^^ and King.'""' 

 The latter says : 



In the Nevada province the Jurassic consists of a hmestone between 1,500 and 2,000 feet 

 thick and overlying slates probably about 4,000 feet thick. 



Louderback^*^ refers to the Jurassic as composed chiefly of gray to greenish- 

 gray slate with subordinate limestone, which in Muttleberry Canyon carries Arietites 

 sp. nov., referred by Smith''*'*'' to the Lower Jiu-assic or Lias of Europe. 



J 12. SOUTHERN UTAH AND PLATEAU DISTRICT, COIiORADO. 



Button ^°° describes the Jxirassic of the High Plateaus of Utah in part as follows: 



The Jurassic series consists of two members, the lower beuig a massive sandstone of great 

 thickness, the upper a series of calcareous and gypsiferous shales from 200 to 400 feet thick. 

 Underneath the sandstone is a small group of shaly beds, which are presumed to be of Jurassic 

 age, but no determinable fossils have been taken from them. * * * Comparing the Jura- 

 Trias section of the Uintas with that of the High Plateaus and Kaibabs, we find a concordance 

 in the several members. 



" T. W. Stanton makes the following comment on the manuscript: "The marine Jurassic fauna ranges through the 

 lower 250 feet of the uppermost member of this section." 



The lithological characters of the Jurassic white sandstone render it a very conspicuous 

 formation. Through a thickness of more than 1,000 feet, sometimes of nearly 2,000 feet, it is 

 one sohd stratum, without a single heterogeneous layer or shaly parting. * * * ^]^q color 

 of the rock is almost always gray, verging toward white. Occasionally it is a very pale cream 

 color, and again pale red. The red becomes more common as we recede from the old shore line 

 toward the east. But of all the features of this rock the most striking is the cross-bedding. 

 It is hard to find a single rock face which is not hned off with rich tracery produced by the 

 action of weathering upon cross lamination. The massive chff fronts are etched from summit 

 to base with a filagree as intricate and deUcate as frost work. The same phenomenon is seen 



