120 Kindle — Unconformity at the Base of the 



Art. XVII. — The Unconformity at the Base of the Chatta- 

 nooga Shale in Kentucky ; * by Edward M. Kindle. 



Introduction. — It is proposed to describe in this paper the 

 physical evidences of the unconformity which exists at the base 

 of the Chattanooga shale in Kentucky. This unconformity 

 occurs in a region of horizontal or but slightly inclined rocks, 

 so that there is no discordance of the strata involved to render 

 it conspicuous or easily detected. For this reason, perhaps, 

 physical evidence of it appears to have been generally over- 

 looked by the authors of State and Federal reports on the 

 geology of the region. Professor Foerste and others, however, 

 in various papers on the geology of Kentucky, have evidently 

 inferred an unconformity at the base of the shale on the evi- 

 dence of missing faunas at its base. 



A photograph and description of the contact of the Chatta-. 

 nooga shale and Devonian limestone in middle Tennessee has 

 been published by Professor Schuchertf to illustrate the com- 

 plete absence of evidence of unconformity between the two 

 formations, aside from the age of their faunas, and our depend- 

 ence upon the discordance in the superposed faunas for our 

 knowledge of the hiatus between them. 



In eastern Tennessee an unconformity at the base of the 

 Chattanooga has been reported in several of the folios.^ 



The writer § has previously called attention to the evidence 

 of an erosion interval at the base of the shale at one or two 

 points on the western side of the Cincinnati geanticline. But 

 the widely distributed evidence of land conditions and a con- 

 siderable amount of subaerial erosion immediately preceding 

 the deposition of the Chattanooga shale interval, if recognized in 

 Kentucky by any geologist, has thus far remained unrecorded. 



The photographs which accompany this paper (figs. 2 and 

 3) make it sufficiently clear that physical evidence of the most 

 unequivocal kind is available to supplement the evidence of 

 unconformity furnished by the faunas. Such evidence in con- 

 nection with faunal breaks substitutes a known for an unknown 

 factor in problems where a hiatus is involved. If this factor 

 of the geologic equation is left for deductive resolution from 

 the faunal factors alone, it may turn out very differently in the 



, * Published with the permission of the Director of the IT. S. Geological 

 Survey. 



f Paleogeography of North America, Bull. Geol. Soc. America, vol. xx, 

 p. 441, pi. 47, 1910. 



^Knoxville, Loudon, Maynardsville, Morristown, and Columbia Folios, 

 U. S. Geol. Survey. 



§ Williams, H. S., and Kindle, E. M., Contributions to Devonian Paleon- 

 tology, 1903, Bull. U. S. Geol. Survey, No. 244, pp. 20-21, 1905. 



