REVISED PRINCIPLES OF CORRELATION 479 



Finding it impossible to reach a definite conclusion from the conflicting 

 fossil data, I made a special visit, accompanied by Mr. T. E. Williard, to 

 Big Stone Gap in October last, hoping that a study of the stratigraphy 

 might throw some light on the problem. 



Briefly stated, these investigations enabled me to divide the 150 feet 

 of limestone between the Cayugan below and the base of the overlying 

 black shale series into eight zones. It was established further that the 

 corals are of one fauna; that they occur as scattered colonies in zones III 

 and IV; more abundantly and locally in reef-like associations in zone V; 

 again rather abundantly, but in scattered colonies, in the upper part of 

 zone VI, and finally in great abundance at the top of zone VII. Zone 

 VIII is without the corals and was observed in only one section, the 

 Upper Devonian black shale being in contact with zone VII in the others. 

 In zone I also the coral fauna is absent, the 31 species of fossils collected 

 from this zone being, moreover, a very typical ISTew Scotland association. 

 Overlying it is zone II, a 2-foot bed of conglomeratic sandstone. 



Associated with the corals and occupying the beds between and above 

 the three main coral-bearing beds are many other fossil remains that 

 clearly belong to a single slowly modifying fauna. The general aspect 

 of this fauna is decidedly late Helderbergian, Avith at first a few and 

 finally a considerable percentage of species known elsewhere to range 

 upward into the Oriskanyi But the proportion of these Oriskany fossils 

 is no greater than is observed in the late Helderbergian deposits of Mary- 

 land and New York. Besides, they include none of the really diagnostic 

 species of the Oriskany, such as occur abundantly and in associations 

 indicating both the Lower and Upper Oriskany at localities less than 50 

 miles east of Big Stone Gap. Schuchert, therefore, seems to have been 

 fully warranted in claiming absence of Oriskany deposits in the Big Stone 

 Gap sections. 



Now, as to the large coral fauna found in association with these 

 Helderbergian fossils. No one can justly deny their striking resemblance 

 to the Onondaga corals found at the Falls of the Ohio. But critical 

 comparison with excellent suites of the latter showed that, with possibly 

 a single exception, none is exactly like its representative in the typical 

 Onondaga limestone. That these corals belong to an earlier age is fur- 

 ther corroborated by the fact that none of the associated Helderberg and 

 Oriskany species have ever been found in unquestionable Onondaga lime- 

 stone. 



Taking all the facts into consideration, Ave must, then, conclude that a 

 dangerously similar phase of the Onondaga coral fauna existed and in- 



