STR ATKiliAl'IIN <)l<^ 'I'i I K VVAI^DI^ON SIIAI.K, 



401 



laceous and shaley limestone, often brownish in color. The Louis- 

 ville limestone shows its maximum thickness in this region. At 

 the Utica lime quarry 30 feet of it are exposed without showing 

 the total thickness. It probably has a total thickness of 50 feet 

 or more at this point. 



Two significant facts appear in connection with the distribution 

 of the AValdron shale. Its outcrops occupy a narrow belt parallel 

 to the axis of the Cincinnati geanticline. This belt is about 90 

 miles in length in Indiana and reappears again in west Tennes- 

 see* flanking the westei'ii slope of the southern extension of the 

 same general uplift. Con-elative with this considerable north and 

 south extension amounting to about 280 miles, is the notable fact 

 that the formation is entirely unknown in Ohio and Kentucky on 

 the eastern side of the uplift. Professor Foerste" has shown that 

 the Clinton is represented by a similar fauna and lithology on both 

 sides of the geanticline and that the only evidence which we have 

 of land masses at that time relates to one or more small islands in 

 southeastern Indiana. 



The evidence furnished by the distribution of the Clinton and 

 its similarity in Ohio and Indiana, even to the salmon brown color, 

 is opposed to the existence of any considerable land area in the 

 region of the present Cincinnati geanticline during the deposition 

 of the Clinton. The distribution of the Waldron shale, however, 

 furnishes equally strong evidence of the existence of such a land 

 mass separating the Silurian basin of southwestern Ohio and north- 

 eastern Kentucky from that of southeastern Indiana and northern 

 Kentucky during the latter part of the Niagaran epoch. The Rip- 

 ley island and probably other undetermined small land masses 

 were doubtless the early Silurian forerunners of the later and more 

 extended uplift, of which the Waldron shale is believed to be an 

 off shore deposit. In harmony with the evidence furnished by the 

 absence of the Waldron shale in Ohio is the lithologic unlikeness 

 of the upper Silurian section on the two sides of the Cincinnati 

 geanticline. 



The Ohio section contains no formations which can be con- 

 sidered identical with the Louisville limestone and the Waldron 

 shale. On the Ohio side the Silurian limestones above the Clinton 

 are almost invariably dolomites or highly magnesian limestones. 



a Bull. Geol. Soc. of Am., Vol. 12, 1901, p. 407. 



b The Ordovician-Siliii ian contact in the Ripley Island area of southern Indiana, 

 with notes on the age of the Cincinnati geanticline. Am. .Tour, of Sci., Vol. XVIII, 

 1904, pp. .321-342. 



[26] 



