318 C. SCHUCHERT — LOWKK ttELDERBERG-ORISKANY FORMATIONS 



rppcr Silurian to the Devonian systems. . . . Wo have, therefore, drawn the 

 dividing line between the Devonian and Upper Silurian, in our general section, 

 through this limestone group underlying the Oriskany sandstone" (pp. 125, 126). 



Ill the second volume, Meek and Worthen * state that ''the name 

 'Clear Creek limestone' was provisionally used for a series of strata 

 holding a position, in Union and some of the adjoining southern coun- 

 ties, between the so-called Hudson River group of the Lower Silurian, 

 and a Devonian sandstone that had been identified with the Oriskany 

 sandstone of New York." Mr Engehnann secured more fossils "at dif- 

 ferent horizons above the middleof the doubtful series, " and these were 

 " found to indicate that at least a considerable portion of these beds are 

 more nearly allied to the Oriskany sandstone than to the Upper Silurian." 

 Meek and Worthen sought to avoid this uncertainty and delayed the 

 printing of volume ii until the region could be revisited by them. This 

 trip resulted in their finding fossils of Helderbergian age in the lower 

 200 feet of the Clear Creek limestone, a result in harmony with that at- 

 tained by Doctor Shumard in 1855. f In the upper part of the Clear 

 Creek limestone, or "cherty limestone, or chert formation, as it might 

 properly be called," was found a fauna confirming the conclusion — 



" That a considerable portion of the cherty limestone forming the upper part of 

 the Clear Creek series, as first understood, belongs to the Oriskany period, and that 

 this line between the Upper Silurian and the Devonian, of this region should be 

 drawn between these cherty beds and the strata below, equivalent to those from 

 which we collected the Lower Helderberg. Exactly how far down in the series 

 this line should be carried we are unable to say, as we found no abrupt lithological 

 change, and we saw no fossils near the horizon of the probable junction. From 

 all the facts, however, we are led to believe that possibly as much as 200 feet, and 

 probably more, of these beds should be included in the Oriskany." J 



The " Clear Creek group" is from this time restricted to the cherty 

 limestones, above a thin band of brown shale of the " Clear Creek lime- 

 stone," as formerly defined, while the lower half, 200 feet in thickness, 

 is referred to the New Scotland horizon of the Helderbergian. It should 

 also be borne in mind that the passage from the latter into the Clear 

 Creek limestone, as restricted, is not marked, agreeing in this with the 

 passage from the Becraft limestone into the Lower Oriskany at Becraft 

 mountain, near Hudson and Port Jervis, New York. 



According to Meek and Worthen ,§ the ''quartzose sandstone" over- 

 lying the Clear Creek limestone contains a small Zaj)hrentis, Pleurodic- 



* Geol. Survey of III., vol. ii, 1866, p. x. 



fGeol. of Mo., 1855, i>. 109. 



X Loo. cit., p. xii. 



g Geol. Survey, of III., 1866, pp. xiii, xiv. 



