WISCONSIN LEAD AND ZINC DEPOSITS. 25 



The following paper was presented informally : 



THE GEOLOGICAL EXHIBITS AT THE WORLD's COLUMBIAN EXPOSITION 



BY G. H. WILLIAMS 



Vice-President Chamberlin announced the purpose and proposed pro- 

 gram of the World's Congress of Geology to be held in Chicago August 

 21-26. 



The following paper was then read : 



WISCONSIN LEAD AND ZINC DEPOSITS 

 BY WILLIAM p. BLAKE 



Co7itents 



Page 



Introduction 25 



Review of recent and former Investigations 25 



Relation of Deformation to Deposition of Ore 27 



Position of Accumulations of Ore 27 



Examples of Faulting 27 



Localization of mineral Deposits by Faults 28 



Relation of the Oil-rock to the Ore-deposits 28 



Evidences of Deformation 29 



CreviflRS 29 



" Barren Bai-s" 29 



Relation of the Driftless Area to the Ore-deposits 29 



General Distribution of Zinc in Sea-water in Silurian Time 30 



Conclusions 31 



Discussion 32 



Introduction. 



In a critical review of the progress of geologic work in Wisconsin, which I had 

 the honor to present last winter to the AVisconsin Academy of Sciences, after giv- 

 ino; in detail the views of Percival, Whitney and Chamherlin upon the existence of 

 faults and dislocations of the strata, I stated my conviction that faults or disloca- 

 tions do exist, and that they have a direct though perhaps obscure relation to the 

 localization of the mineral deposits. It was then and is now my purpose to main- 

 tain that Peirival's original observations and explanations of the cause of the Avell- 

 kiiown irregularities in the position of the strata were correct, and that the true 

 path leading to the solution of the problem of the origin of the zinc and lead de- 

 posits of the Mississippi valley lies in the direction indicated by that gifted man 

 rather than in the path marked out by later observers in the same field. 



Review of recent and former Investigations. 



The subject, which has special interest to the region in which we meet, derives 

 additional interest and importance at this time from the attention it is receiving 

 from others. A memoir upon the subject has just been presented to the American 

 Institute of Mining Engineers by Professor W. P. Jenney,* and was under discus- 

 sion in one of the sessions of the -Engineering Congress by Arthur Winslow, state 



*The Lead and Zinc Deposits of the Mississippi Valley, by Walter P. Jenney : Trans. Am. Inst. 

 Mining Engineers, August, 1893, p. 55. 



IV-BuLi,. Geoi,. Soc. Am., Vol. 5, 1893. 



