THE HURRICANE FAULT IN SOUTHWESTERN UTAH. 



TABLE OF CONTENTS. 



Intkoduction. 



The Rock Series in the Toquerville Region. 



The Sequence of Events since the Eocene Period. 



Deformation and Volcanic Eruptions. 



a) Earlier folding. 



b) Andesite eruptions. 



The Hurricane Fault — the Earlier Faulting. 

 The Inter-Fault or Plateau Cycle of Erosion. 



a) The lava-covered Hurricane fault at Coal Spring. 



b) The lava-covered surface on the Shivwits plateau. 



c) The old fault, the old lowland surface, and the new fault. 



d) The mature topography of the Colob plateau. 



e) The differential recession of cliffs on the two sides of the old fault. 



f) General review of the topography at the end of the inter-fault cycle. 

 The Hurricane Fault — the Later Faulting. 



The Post-Fault or Canyon Cycle of Erosion. 

 Summary. 



During the summer of 1902 the writers, under the direction 

 of Professor William M. Davis, of Harvard University, made a 

 study of the region around Toquerville, in the southwestern cor- 

 ner of Utah, on the line between the High Plateau province and 

 the Basin Range province. Some stratigraphic work was done, 

 and an area of about two hundred square miles was mapped. 

 The main interest, however, centered in the relative age of the 

 two displacements by which the plateaus of the Colorado river 

 were elevated above the region of the Basin Ranges, and by the 

 last of which the cutting of the Grand Canyon was inaugurated. 

 These displacements were studied for about a hundred miles, 

 from a point near Kanarra, twenty-five miles north of Toquer- 

 ville, to the Colorado river. The older one runs almost directly 

 south from Kanarra to the Colorado, along the Hurricane Ledge; 

 the younger follows nearly the same course, but at the Arizona 

 line all except a small branch turns west along a monocline and 

 finally joins the Grand Wash fault. In this paper we shall give 



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