CHAPTER II. 



STEUCTUEAL GEOLOGY. 



Homology of faults and monoclinal flexures. — Their systematic arrangement. — Those of the High 

 Plateaus belong to the same system as those of the Kaibabs. — The Grand Wash fault. — Hurri- 

 ricane fault. — Tushar fault. — Toroweap fault. — Sevier fault. — Western and Eastern Kaibab 

 faults. — Thousand Lake fault. — Musinia faults. — Age of these displacements.^Their relative 

 recency. — Difficulty of assigning their periods in definite terms. — Argument of recency from 

 amounts of erosion. — Argument from the amounts of accumulation of valley deposits. — Age of the 

 faults with reference to evidencesof glaciation. — Importance of knowingthe ages of these faults. — 

 Some are more recent than others. — -An older system of faults of Cretaceous-Eocene age. — Water- 

 Pocket flexure. — San Rafael flexure. — Parallelism of recent major faults to the old Cretaeeous- 

 Eoceno shore-line. — Evidences of recent uplifting in the caiions. — Comparison of structural forms 

 in the throe provinces, the Basin, the Plateaus, and the Parks. — Types of the Parks. — Effects of 

 erosion upon structure. — Absence of horizontal forces in .the elevation of the Plateaus. 



The great structural features of the High Plateaus are the faults and 

 monoclinal flexures. Faulting is an almost universal concomitant of great 

 disturbances of the strata and of the uplifting of mountains and plateaus. 

 Of their causes geology has taught us but little beyond the bare fact that 

 they are produced in the great majority of cases by differential uplifting 

 by vertical forces, which is hardly more than an identical proposition. The 

 nature of the forces we know not, and can only speculate vaguely about 

 them. We do not always know even whether a fault is produced by uplift- 

 ing upon one side of a given vertical plane or by sinkage on the other, and 

 there must always be an implicit reservation when we speak of them as 

 produced by upliting, so that nothing more is meant than that the strata 

 have been sheared vertically, and that one portion is left on a hig'her plane 

 than the other. Why the vertical forces should undergo an abrupt change 

 or even total extinction in passing from one side of a given line to the other 

 is a mystery which we cannot hope to solve until we know the origin of 

 the force itself. All that is left us at present is to study the faults them- 

 selves carefully, ascertaining, as far as practicable, what movements have 



