150 C. W. HAYES — OVERTHRUST FAULTS OF THE APPALACHIANS. 



upon younger would be produced as by the Rome fault — that is, Cambrian 

 shales would be found resting upon middle Silurian. 



Features common to the Rome and Cartersville Thrust Faults. 



The characteristics which the tAvo faults under discussion hold in common 

 are (1) low inclination of the thrust plane; (2) great horizontal displace- 

 ment ; (3) constant relation of the thrust plane to the overlying beds, the 

 faultincr in both cases having taken place in thinly laminated rocks of low 

 rigidity overlain by more rigid beds ; and (4) absence of any uniform rela- 

 tion between the thrust plane and the underlying strata, the thrust plane in 

 both cases being in contact with all formations from the Cambrian up to 

 Carboniferous. 



Similar Faults in other Parts of the Appalachian Province. 



While the Appalachian overthrust faults probably reach their highest 

 development in the region above described, a few have been discovered in 

 other parts of the same province. Three small overthrusts having essentially 

 the same characteristics as the Rome fault have been mapped by Keith* a 

 few miles northeast of Knoxville, Tennessee. The largest of these has a hori- 

 zontal displacement of about two miles and extends for about eight miles 

 along the strike, being simply a modification for that distance of one of the 

 ordinary east Tennessee faults. 



In the Taconic region of New York a fault, probably in most respects 

 similar to those of the southern Appalachians, has been figured by Walcott.f 

 Of this he says : '" The section of Bald mountain proves that the strata of 

 the ' Upper Taconic ' are pushed over on to the Chazy terrane." A photo- 

 graph of the locality shows the exact position of the thrust plane, dipping at 

 a low angle toward the east. 



Theoretical Considerations. 



From purely theoretical considerations, certain conditions would appear 

 to be necessary, or at least highly favorable, for the production of broad 

 thrusts such as have been described. The most important is the relation of 

 rigidity of strata to superincumbent load. 



The curve at the left of the stratigraphic column shown in figure 1 (page 

 143) expresses the relative rigidity of the strata, the vertical coordinate being 



*Mavnardville Atlas Sheet, Appalachian Division, U. S. Geological Survey; Geology by Arthur 

 Keith (unpublished). 



f'The Taconic System of Emmons and the use of the name Taconic in Geologic Nomenclature ; " 

 Charles D. Walcott, Am. Journ. Sci., 3d ser., vol. XXXV, 1888, p. 317. 



