OVERTHRUSTS NEAR OGDEN 539 



brian limestone. Beneath the fault the thin-bedded limestone and shale 

 are bent into recumbent folds which were noted by Hague and Emmons 

 in their first visit to the canyon, about 1870. In fact we can not read 

 their description^^ of this canyon without perceiving that they recorded 

 the essential features of this overthrust without recognizing it as such. 

 Since this fault lies almost entirely within the thick succession of Paleo- 

 zoic limestones, its exact course is difficult to trace without detailed study. 

 It is cut off both north and south of Ogden Canyon by the overlapping of 

 the great Willard thrust. 



Northeast of the village of N'orth Ogden, also, there are several subor- 

 dinate yet important thrust-planes beneath the dominant overthrust first 

 described. Some of the overthrusts in Ogden Can^^on have been traced 

 into this locality. Others can probably be extended in the same way 

 when more detailed work is done. It is clear that there are also several 

 small overthrusts which do not appear in the Ogden region. The front 

 of the Wasatch Eange near l^orth Ogden has indeed a highly complex 

 structure, in which overthrusts and recumbent folds are the characteristic 

 features. Even in the low plateau-like extension of Paleozoic rocks near 

 Hot Springs the rocks are much disturbed in detail and the faults appear 

 to be overthrusts. 



So far as present information goes, the overthrusts seem to be confined 

 to that part of the Wasatch range which lies south of Brigham. There 

 can be little doubt that the overthrusts were made at the same time that 

 the Paleozoic rocks were folded; and that disturbance is generally as- 

 signed to the close of the Cretaceous period. It seems to be a fact that 

 the Lower Eocene (Wasatch) sediments cover the outcrops of the over- 

 thrusts in several places, thus indicating that the folded and overthrust 

 structures had been deeply eroded before the Eocene period was far 

 advanced. ^ '^^^ • 



TRANSVERSE FAULTS 



In the reports of the Survey of the 40th Parallel several faults with 

 general east-west trend are postulated to explain abrupt changes in the 

 Paleozoic outcrops. Of these, the one about a mile north of Ogden Can- 

 yon was identified and traced by the present writer. The one in N'orth 

 Ogden Canyon was not found, and the structure there seems to be ex- 

 plained more readily as folding, without any assumption of faulting. 



East of the city of Ogden, in a small valley now locally known as 

 ''Waterfall Canyon," there is another fault which appears to be of the 

 normal type and which is described in the report of the Survey of the 



U. S, Geological Exploration of the 40th Parallel, vol. II, p. 400, 



