HINTZE, GEOLOGY OF WASATCH MOUNTAINS, UTAH 127 



Structure 

 introductory statement 



The first unified account of the larger structural features of the 

 Wasatch Mountains is that given by the geologists of the Fortieth Paral- 

 lel Survey.^' In a broad way, these early observations have been verified 

 by the more recent studies of particular parts of the range, but many 

 important new facts have been added and some of the original concep- 

 tions greatly changed. 



Vital to the first conception of Wasatch structure was the supposed 

 presence of an Archean axis which had the same trend as the present 

 range, north and south, on the flanks of which were deposited the early 

 Paleozoic sediments, until they completely buried the lofty Archean 

 peaks. At the close of Mesozoic time, profound plicating and plateau 

 forming movements threw the thick conformable Paleozoic and Mesozoic 

 sediments into great pitching anticlinal and synclinal folds with axes 

 mainly north and south. After a period of erosion during which the 

 upper parts of the folds were planed off, profound faulting along the 

 present western faces of the range took place, tilting the old surface 

 eastward on the uplifted eastern side. Upon that uplifted block, erosion 

 has carved the present relief. 



It is now known that the main body of supposed Archean, the Little 

 Cottonwood granite, is intrusive, and the original conception of a pre- 

 Cambrian protaxis has been entirely discarded. Folding is known to be 

 much more intense than originally thought, and large overthrusts have 

 been discovered from Ogden northward to Willard and in the Cotton- 

 wood district. 



Since the overthrusting, there has been considerable deformation and 

 faulting which have introduced the most complicated tectonic relation- 

 ships. 



STRUCTURE OF THE CENTRAL WASATCH 



The central Wasatch is an exception, structurally, from the general 

 anticlinal aspect of the range as a whole. Within this area, extensive 

 intrusion of granite and granodiorite and widespread extrusion of ande- 

 sitic lava, with their accompanying phenomena of metamorphism, are 

 grandly displayed. Encircling the main intrusive body, the Little Cot- 

 tonwood granite, are steeply inclined quartzites, shales and limestones, 

 with varying age ranging from pre-Cambrian to late Mesozoic. Dipping 



38 U. S. Geol. Expl. 40th Par., Vol. II, Sect. 3 & 4. 



