GEOLOGICAL AGE OF THE TERREPLEINS OF UTAH’S 
PLATEAUX 
By Charles Keyes 
, , SYNOPSIS 
Introductory 
Topographic setting of Utah’s High Plateaux 
Isostatic significance of Heights of Utah 
Highland plain of the arid region 
Peneplains of eastern Rocky Mountain Belt 
Later periods of orographic uprising 
Number and general relations 
Ancient Tucumcari erosion plain 
Corrazon planation surface 
Infraformational Raton leveling 
Preservation of Maya peneplain 
Present general plains surface 
Summit plain of Colorado Rockies 
Relief of Rocky Mountain crest 
Hypothetical extensions of summit plain 
Identification of summit plain with Great Plains surface 
Elimination of Maya horizon 
Position of Raton level 
Recent exhuming of Tucumcari peneplain 
Relations of several peneplain horizons over uplift 
Old planation levels in the High Plateaux 
Stratigraphic horizons of major unconformities 
Mid Jurassic regional depletion 
Western extension of sub-Dakota erosion plain 
Laramie hiatus in eastern Utah 
Terrepleins of the High Plateaux 
Correlation of principal planation levels 
Consummation of the Colorado (Navajo) dome 
Nomenclature 
Character of present plains surface 
Peculiarities of terranal segregation 
Extinguishment of former base-levels 
Summary 
Usually, genetically associated with the desert ranges the lofty 
Utah mesas belong not to the Great Basin province, but to an en- 
tirely different orographic type, the Colorado Dome. Upon the 
