148 C. W. HAYES OVERTHRUST FAULTS OF THE APPALACHIANS. 



extensive ancient base-levels through which the streams flow in deeply eroded 

 channels. 



StratigrapJiic Variations west of Fault. — The rocks west of the fault are the 

 unaltered Paleozoic sediments shown in the stratigraphic column already 

 referred to. There is a gradual change in the character of the sediments in 

 passing toward the southeast. In general, limestones give place to shales 

 and sandstones in this direction, indicating an approach to a shore line. 

 Thus the blue Chickamauga limestones forming the middle division of the 

 Silurian west of Coosa river are almost entirely replaced by the Rockmart 

 slates on the eastern side of the valley, and considerable beds of sandstone 

 are developed in the Knox dolomite. These rocks have suffered meta- 

 morphism only in a very slight degree. Some calcareous shales have been 

 converted into roofing slates, but in general the valley rocks extend un- 

 changed up to the fault line. 



Rochmart-Esom Hill Division. — The region which shows most conclusively 

 the presence of a fault is that between Rockmart and Esom Hill. The fault 

 line is here nearly east and west in direction parallel with the division of the 

 Rome fault between Coosaville and Round mountain. The two faults are also 

 remarkably alike in the relation which the thrust-planes bear to the struc- 

 ture of the underlying strata. It was stated that the Rome thrust-plane 

 passes across the southward-pitching synclinals apparently undisturbed by 

 the folds and faults which have affected the rocks below. In like manner 

 the undulating synclinal already described passes directly under the Carters- 

 ville thrust-plane and all formations from Cambrian up to Carboniferous 

 come in contact with the overthrust metamorphic rocks. 



Metamorpliism east of Fault. — East of the fault metamorphism has affected 

 all the rocks, though in widely varying degree. On Hiwassee and Ocoee 

 rivers there is an almost perfect gradation from the unchanged valley rocks 

 through indurated shales and quartzites, in which cleavage is only slightly 

 developed, to black roofing slates, in which the bedding is almost wholly 

 obliterated, and so to " curly slates " and phyllites, in which the original 

 stratification is indicated only by the interbedded conglomerates. These in 

 turn pass into highly crystalline mica and garnet schists. Further south- 

 ward, at Holly creek, the transition is much more abrupt, the valley rocks 

 being directly in contact with the " curly slates " and phyllites. East of 

 Adairsville, on Pinhook creek, the garnet schists are less than a mile east of 

 the fault line, and this is their nearest approach to the valley rocks. South 

 of Cartersville the belt of semi-metamorphic rocks increases in width, and at 

 Esom Hill, on the Georgia- Alabama line, the degree of metamorphism on 

 opposite sides of the fault is slight. Although the rocks immediately east of 

 the fault thus show a wide variation in degree of metamorphism, yet they 

 appear to belong to essentially the same horizon. This great series of slates 



