EXTENT OF FOLDING AND SUBSEQUENT EROSION 449 



em Tennessee, occurs the westernmost outcrops of the Bays. It has here 

 become a thin-bedded, red, argillaceous limestone and shale from 160 to 

 200 feet thick, but the top is worn away, the next succeeding formation 

 being the Rockwood shales. The Bays rests here on red and green shales, 

 marking the upper part of the Sevier formation. Little is seen of this 

 formation, which seems to have been cut out by faulting or crushing. 

 Nevertheless, the contact with the Bays is shown, or rather there is a 

 gradation from gray to red shales, in which fossils of the Upper Cincin- 

 nati group abound. Near Jacksboro, Tennessee, I have succeeded in 

 making the following section, which is only approximate on account of 

 the great development of shear zones and faults. Much of the soft shales 

 is probably crushed out owing to the pressure against the hard Carbonic 

 conglomerates, which are here sharply upturned. The Bays is every- 

 where succeeded by the Rockwood, which here is chiefly a clay shale, with 

 Clinton ( ?) fossils and bands of limestone and iron ore. 



Section of the Bays-Sevier near Jacksboro, Tennessee. — Along the road 

 leading up Cumberland Mountain and in the adjoining ravines (Brice- 

 ville quadrangle), beginning at the base of the section, the Chickamauga 

 limestone is exposed a short distance below the house of Mr. Sharp, the 

 last inhabited house on the road. The dip of the strata here is 6° to the 

 northwest, the strike throughout being around north 50° east. The 

 limestone is very fossiliferous, carrying Plectambonites sericeus, Asaphus, 

 etcetera. After a short concealed interval a soft, greenish gray clay 

 shale is exposed by the roadside, having the same dip. Then follows an 

 interval of about 650 feet in horizontal distance, over which no exposures 

 are found. The next exposure begins with greenish and grayish to red- 

 dish shale, with included arenytes dipping 60° to the north. This is the 

 beginning of the hill slope; between it and the limestone outcrop a valley 

 intervenes, caused by the presence of the shale. It is probably in this 

 interval that much of the Sevier shale has been crushed out. 



There is, however, another aspect of the matter which musl nol be 

 overlooked, namely, that the widespread absence of the Sevier shale from 

 this point westward is due to the fact that it was never deposited as a 

 shale. I do not believe that there was any break in deposition here be- 

 tween the Chickamauga and the Bays any more than that there was such 

 a break between the Chickamanga-Sevier and the Sevier- Havs farther 

 east. It looks more as if the Chickamauga limestone of this section '2.0(H) 

 feet or more in thickness represented in its upper pari what farther easl 

 is represented by Lower Sevier. 'Thus, in the section north oi' 1 >.*i\ s 

 Mountain (Knoxville quadrangle), (he Chickamauga ami Sexier are each 



XXXI— Bull. Geol. Soc. Am., Vol. 24, 1912 



