TRANSVERSE FAULTS 541 



Bear Eiver plateau, 4 to 8 miles east of Hunts ville. There the great 

 series of Algonkian quartzite and slate with the overlying Cambrian beds 

 is suddenly cut off, and immediately in the line of strike there is an expo- 

 sure of Middle Cambrian fossiliferous limestone with east-west strike 

 and vertical or variable dips. The fault doubtless passes between these 

 outcrops. This fault is of the type usually called "normal'' — that is, it 

 is nearly vertical and dips toward the down-thrown side. 



Presumably the direction of displacement along this plane had a large 

 vertical component, but the precise direction has not been ascertained. 

 The greatest shifting of outcrops amounts to about 3% miles in the hills 

 east of Huntsville. A horizontal displacement of such dimensions would 

 involve changes of volume on one side or the other on a scale which seems 

 impossible. With the observed dips, a vertical displacement of about 

 12,000 feet would seem to be required to explain the shifting of the out- 

 crops. If the movement was diagonal, the amount of displacement would 

 be still different, but in any case the facts indicate a fault of large 

 dimensions. 



The transverse faults, including the Huntsville fracture, no longer 

 have any topographic expression, except that which is due to the relative 

 resistance of the rocks on one side or the other. The scarps have been 

 wholly removed by erosion. From this fact it seems probable that they 

 are older than Quaternary or even than late Tertiary. Their age can 

 be fixed more definitely in the future by a careful study of the relation 

 of the Eocene beds to the fault. From certain meager observations the 

 writer expects that the faults will be found to have cut the Wasatch sedi- 

 ments (Lower Eocene) .^® 



QUATERNARY FAULTING 



The evidence that the front of the Wasatch range is a great fault-scarp 

 or series of scarps, of comparatively recent date geologically, has been 

 ably discussed by Gilbert, Davis, and others. The important evidence is 

 almost wholly physiographic. The question was given only casual atten- 

 tion last summer, and such observations as were made do not appear to 

 conflict with the current interpretation. 



CON-CLUSION-S 



The chief conclusions presented in this paper are these : 

 (a) The Cambrian system has a basal quartzite of moderate and toler- 

 ably uniform thickness, and this is separated by a traceable unconformity 



29 Vermilion Creek formation of the 40th Parallel Survey. 



