CHAPTER VII. 



THE WASATCH PLATEAU. 



Situation and structure of the Wasatch Plateau.- — Of what strata composed. — The gTeat monoclinal. — 

 The Cretaceous platform south of it. — Salina Canon. — The Jurassic Wedge. — East and West Gun- 

 nison faults. — San Pete Plateau. — Sedimentary heds composing the Wasateh Plateau ; Bitter Creek, 

 Lower Green River, and Upper Green Eiver heds. 



The name of Wasatch Plateau has been given to the northernmost of 

 those highlands of tabular form which are the subject of the present mono- 

 graph. It is in some sense an outlier of the group, and presents features 

 peculiarly its own, though sharing with them a common history and many 

 similar features. It slightly overlaps at its northern end the main range 

 of the Wasatch Mountains, and stands en echelon to the southeast of Mount 

 Nebo, the last great mountain of that beautiful chain. The interval between 

 Nebo and the plateau is about 15 miles, and is filled partly by a medley of 

 low hills and partly by a depression called San Pete Valley, which lies 

 along the base of the table. The western flank of the uplift is a mono- 

 clinal flexure of the grandest proportions. Along a base line nearly 50 

 miles in length the Tertiary strata bend upward to the summit in a single 

 sweep, diversified by minor inequalities arising partly from minor fractures, 

 partly from erosion, but never of such magnitude as to mask the general 

 plan of the uplift, nor even to greatly disfigure its symmetry. The minor 

 features, though elsewhere they might seem of considerable moment, are 

 mere ripples upon the great wave. At the summit the strata suddenly flex 

 back to horizontality, and when we reach it we find oui'selves upon a long 

 narrow platform, nowhere more than 6 miles in width, usually much nar- 

 rower, and here and there reduced to a knife-edge or even eaten through 

 by erosion. To the eastward the profile at once drops down, often by a 

 great cliff, always abruptly, by a succession of leaps across the edges of 

 the sensibly horizontal strata, to lower terraces, succeeding each other at 

 intervals of 3 to 6 miles, and consisting of older and older formations. 



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