EVOLUTION OF MODERN SURFACE FEATURES 



21 



area toward the continental interior; the Cretaceous deformation of 

 the Great Basin area occupies an intermediate position in place and 

 time. In any particular part of the eastern Cordillera the observ-ed 



w&E* 



N5 



,500 



1000 



Miles 



Fig. 5. Map of western United States, showing generalized conditions 

 during late part of orogenic phase (latest Cretaceous and Paleocene time). 

 1, Oceanic area. 2, Marine sediments along Pacific border. 3, Folds pro- 

 duced by Laramide orogeny: (a) narrow folds and fault blocks in geo- 

 synclinal sediments, (b) broad folds in foreland area, involving basement 

 rocks. 4, Volcanic centers. 5, Transverse faults with major components of 

 lateral displacement. 6, Sedimentary basins of nonmarine deposition be- 

 tween folds and along their eastern border. 7, Land areas; shaded areas 

 indicate approximate extent of plutonic rocks of Nevadan age that had 

 been unroofed by erosion, 



deformation of the rocks can be placed in this sequence only if 

 stratigraphic evidence is available; as a matter of convenience, all 

 such structures are ascribed to the Laramide orogeny. 



Laramide movements compressed the sedimentary rocks of the 

 miogeosyncline into long, closely spaced folds and thrust blocks, 



