PROGRESSIVE OVERLAP 603 



points far distant from one another. The absence of coarse detrital material 

 suggests that the region of deposition was practically flat. The preservation 

 of fragments of land plants indicates that it was probably a region of marshes. 

 It may be imagined that the same particles traveled in many directions before 

 finding a final lodgment. Marshes at one point may have dried up, and the 

 material accumulated in it may have again turned into dust, thus permitting 

 the frequent shifting by the wind of the materials which now form the shale." 



Safford records the occurrence of thin seams of bituminous matter 

 from an eighth of an inch to an inch in thickness. "The bitumen of these 

 shales is hardly an asphaltum, being generally, perhaps, more like the 

 bitumen of cannel coal."* Petroleum also oozes from the shale in a 

 few places and can be readily distilled from it. 



In Wayne county, south central Tennessee, the following section was 

 made by Safford at T. A. White's mill, on Buffalo river, a few miles below 

 the mouth of Green river: 



Feet 

 (4) A thin bed of gravel (water-worn pebbles) on top, with some loose, 

 angular chert. The gravel is found at the top of all the high ridges 

 in this region. Specimens of Lithostrotion canadense (oot water- 

 worn) are also found loose on the surface. 

 (3) Siliceous group: 



Rocks concealed, surface covered with small, angular, cherty masses, 



to top of ridge 190 



Bluish shale, with layers of chert 15 



Bluish shale 24 



In all 238 



(2) Black Shale group: 



(c) Layer of kidneys ^ 



(o) Black shale 2 



(a) Sandstons, at top thin bedded, surfaces abounding in Lingulse. . 9 



In all 11% 



(1) Meniscus limestone (Niagara) : 



Gray, mostly crinoidal limestone; contains the characteristic 

 Haplocrinus hemispTiericus immediately below the sandstone; 

 thickness down to the water 67 



In eastern Tennessee (McMinnville folio) the Chattanooga Black 

 shale rests on the Chickamauga limestone (Ordovicic) and has a thick- 

 ness of from 10 to 30 feet. It consists mainly of highly carbonaceous 

 non-fissile shale. The upper stratum, about 2 feet in thickness, is 

 generally bluish green, somewhat sandy, and contains a layer of sma); 

 phosphatic concretions an inch or less in diameter. "It seems probable 

 that this upper greenish layer of shale represents an ancient ash bed, 

 the material of which was ejected from a volcano and transported a long 



* J. M. Safford : Geology of Tennessee, 1867, p. 334. 



