636 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



2,000 feet, and it rarely falls -under 1,200 feet, except along the Eome 

 barrier, where, as between Birmingham and Gadsden, it was greatly re- 

 duced locally by ijre-Ordovician erosion. The maximum thickness ob- 

 served is in Chestnut Eidge south of Sneedville, Tennessee. Here, 

 deducting some 600 to 700 feet apparently repeated by faulting, an esti- 

 mate based on dip and width of outcrop indicated a thickness of about 

 3,800 feet. Both the lower and upper members of the Knox are rela- 

 tively thin in Chestnut Eidge, the former being 360 feet, the latter only 

 about 200 feet. 



The road from Beans Station to Evans Ferry, on Clinch Eiver (see 

 Morristown quadrangle), follows Indian Creek, where it cuts through 

 Copper Eidge. A fine section is shown here, practically every foot of 

 the Knox being laid bare. Beginning on the northwest side, the section 

 begins with the upper 80 feet of the Eutledge limestone and continues 

 unbrokenly through 170 feet of Eogersville shale, 360 feet of Maryville 

 limestone, 650 feet of Nolichucky, 345 feet of lower Knox, 1,345 feet of 

 Copper Eidge dolomite (little chert is shown in the freshly cut rock), 

 100 feet of dove-colored low magnesian limestone — the lower half 

 cherty — and 470 feet of light-colored dolomite and magnesian limestone, 

 constituting, together with the preceding 100 feet, the upper Knox. The 

 last is succeeded by the Mosheim limestone, and on through Lee Valley 

 to the top of Clinch Mountain by an excellent section of the Ordovician 

 as developed in the west Knoxville trough. 



Fossils are rare in the Knox. Excluding Cryptozoon, I have never seen 

 any in either the lower or the upper member and all told only a drawer 

 full or so of prepared specimens out of the Copper Eidge chert. So far 

 as the collections go, they indicate at least two fossilif erous horizons, both 

 apparently near the middle of the Copper Eidge formation. Aside from 

 this, their stratigraphic relations are unknown. One contains Syntrophia 

 camphelli and fragments of so-called Cambrian trilobites, the other gas- 

 tropods and cephalopods found in the Eminence formation of Missouri. 

 The same or a close ally of the Syntrophia, also trilobites of very similar 

 character to those associated with it in Tennessee, are found in Shannon 

 County, Missouri, in the same formation (Eminence) ahove the gastro- 

 pods. If these faunal occurrences are trustworthy indications of one and 

 the same stratigraphic zone, then a considerable hiatus is suggested in 

 the Missouri section between the Eminence and Potosi formations. 



Several forms of Cryptozoon are found in the Copper Eidge. Two of 

 them have a broad stratigraphic significance, one, forming hemispheric 

 masses and provisionally identified as C. minnesoteiise, being confined to 

 the upper part of the chert formation; the other, a compound form ap- 



