154 E. D. McEtvan — Ordovician of Indiana, 



Art. XII. — The Ordovician of Madison, Indiana; 1 by 

 Eitla D. McEwan. 



The present report is the result of the study in the 

 laboratory of a great amount of material collected by 

 the writer from the Ordovician section at Madison, In- 

 diana, in the summer of 1914. The collection was made 

 along the creek at the foot of the ravine, in the ravine 

 which heads at the culvert about 200 feet north of the 

 north end of the south cut, and in the south cut on the 

 P. C. C. and St. L. Railroad. 



The fossils were collected zonally, great care being 

 taken to locate their horizons exactly. The laboratory 

 work required the preparation of about three hundred 

 microscopic slides with sections of the bryozoa. 



The following classification applies to the section: 



t> • i, j\ Wa vnesville 

 Richmond i A v • 

 (Arnneim 



[Mount Auburn 

 Maysville-j Corryville 

 [Belle vue 



The lowest exposure of the section is several hundred 

 feet downstream from where the creek is joined by the 

 ravine. The lowest 20 feet consist of blue limestone and 

 shales, 2 the former varying from a few inches to nearly 

 a foot in thickness. The succeeding 7 feet consist of 

 thin layers of limestone and argillaceous limestone sepa- 

 rated by soft yellow shale layers usually an inch or only 

 a few inches in thickness. 



At an elevation of between 27 and 77 feet above the 

 base of the section the limestone layers become more 

 massive. In the lower position of these beds the lime- 

 stone has rust-like spots. At an elevation of about 53 

 to 60 feet the limestone is lumpy. 



1 The writer is under obligation to Professor E. E. Cumings of Indiana 

 University, under whose supervision all the laboratory and field work was 

 done. He offered many valuable suggestions and also furnished many 

 specimens for comparisons. 



2 For a complete discussion of these rocks consult Cumings, ' ' The Strati- 

 graphy and Paleontology of the Ordovician Rocks of Indiana," 32d 

 Annual Report of the Department of Geology and Natural Resources of 

 Indiana, 1907, pp. 634-637. 



