26 PROCEEDINGS OF MADISON MEETING. 



geologist of Missouri, Professor Eaymond and the writer. Professor Jeiiney finds 

 that not only the Wisconsin zinc and lead-bearing strata, but also those of Joplin, 

 Missouri, and its vicinity, are extensively faulted and broken, and that these faults 

 and breaks following or related to the main axes of uplift have determined the 

 position of the metalliferous deposits. He further claims that the metallic deposits 

 are formed by ascending solutions, and that in their origin and formation they are 

 no exception to the general phenomena of mineral veins. This may be said to be 

 a complete reversion to the original view of Percival and to the then generally 

 prevalent idea of the deep-seated plutonic origin of the ores of metals. 



While in accord with Percival and with Jenney upon the existence of faults and 

 dislocations in both Wisconsin and Missouri, I am not prepared to accept their 

 views of the origin of the ores, my own observations confirming, in general, those 

 of Whitney and of Chamberlin and his associates upon the last survey of Wis- 

 consin, and inclining me to the theory of the original distribution of the sulphides 

 of lead and of zinc in the substance of the limestone and dolomites at the time of 

 their deposition and the subsequent concentration of these sulphides in the fissures 

 of the rocks by lateral and downward flow of solutions of the metals rather than 

 by the ascent of such solutions from lower strata. 



An objection to Percival' s views of a connection between the faults and the 

 mineral deposits is found by Professor Chamberlin in the fact, so claimed, that 

 the faults specifically mentioned b}^ Percival are not contiguous to mineral deposits. 

 If this is indeed so, it shows only that faulting is not necessarily in all cases accom- 

 panied by mineralization. It has yet to be shown that the mineralized*areas are 

 not upon or contiguous to lines of faulting or dislocation, and that they are so con- 

 tiguous I shall endeavor to show in this paper. 



Professor Chamberlin* thinks it not a little strange that, though Percival seems 

 to have believed that the centers of elevation, which I understand to mean rather 

 lines of disturbance and of break, were indices of agencies influential in the depo- 

 sition of the ores, he should not have observed that none of them are centers of 

 ore-deposits. He thinks Doctor Percival's observations do not show close connec- 

 tion or clear relation between elevations and ore-deposits, but rather the contrary. 



Professor Chamberlin admits the existence of disturbed or flexed strata in the 

 lead region. He calls them ''local flexures," and refers them to unevenness in 

 the original deposition of the strata, and does not find the deposits of ore to be 

 coincident in place with the convexities of the beds and rocks, but does find the 

 ore-deposits in the depressed areas. He asks "but if the deposits are not upon 

 the swells of the strata are they in the sags?" f and answers this by citing an in- 

 stance of such an occurrence at Dutch Hollow, where the mineral ranges lie within 

 a trough or syncline the flanks of which have a dip of 15°. The rock in the axis 

 is brecciated and the ores deposited in the brecciated mass form a true stockwork. 

 Professor Chamberlinf cites this as a ' ' marked instance of productiveness along 

 an axis of depression, and of barrenness along that of elevation." 



A notable arching of the beds is noted as lying south of the Potosi district, and 

 the conclusion is stated that the Potosi diggings lie in a stratigraphic basin. The 

 Trenton limestone seems to thin out and the Saint Peter's sandstone rises rapidly, 

 and he finds the phenomena consonant with his view that the undulations had 

 their beginnings in submarine inequalities, and he cites where ore-deposits appear 

 to occupy synclinal depressions rather than anticlines, and he arrived at the con- 



* Geology of Wisconsin, vol. iv, p. 429. 

 tOp. cit., p. 432, 



