SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL.^65 



The well known marble beds of east Tennessee and associated 

 shales and sandstones of Upper Chazyan age with a thickness of 

 over 3,000 feet have never been found in central Tennessee, or in 

 fact in any area west of the Appalachian Valley. The first problem 

 was therefore to determine either the corresponding rocks in the 

 more western areas or, if such strata were wanting, to discover the 

 unconformity representing this great thickness. After some days 

 of careful stratigraphic work it was learned that the Lower Chazyan 

 or Stones River rocks of central Tennessee are succeeded directly 

 by the lowest Black River or Lowville formation. In other words, 



Fig. 18. — Exposure of black shale and underlying Silurian strata at Bakers, 

 Tenn. Photograph by Bassler. 



all of the Upper Chazyan rocks are wanting entirely, and central 

 Tennessee therefore was presumably a land area during the time of 

 deposition of the celebrated east Tennessee marbles. The uncon- 

 formity between the two groups of strata is shown in figure 17, 

 where it may be seen as an undulating line in a single ledge of 

 limestone. 



The second problem entailed further work on the determination of 

 the age of the widespread Chattanooga black shale, which previously 

 had been considered to be middle to late Devonian. In recent years 

 this determination had been questioned and facts had accumulated 

 showing it to be of younger age. Two features of considerable 



