118 Van Ilise — Attempt to harmonize some apparently 



also a part of the rocks included in Irving's Fundamental 

 Complex, Lawson's Coutchichiug, and Frof. Winchells' Ver- 

 milion Lake series. Irving* has shown conclusively that cer- 

 tain of the rocks on the south shore of Lake Superior, first 

 loosely placed with the Hnronian are to be excluded from it. 

 This work has been so thoroughly supplemented in the United 

 States by the Profs. Wiuchell, and in Canada by Lawson that 

 at the present time this conclusion can hardly be questioned. 



It is believed that many of the difficulties as to correlation 

 in the districts about Lake Superior have largely arisen from 

 the failure to generally recognize a physical break, which has 

 a very wide if not universal extent in the Lake Superior 

 region. So far as I know, the first descriptions of this break 

 are by Foster, and Foster and Whitney f in the Marquette 

 district. It was next noted by Brooks. $ By Romingerg it was 

 seen at many points which lead to the suggestion " That great 

 disturbances of not only a local extent, must have occurred at 

 the end of this era of iron sediments." Wadsworth || says of it, 

 these conglomerates " Mark old beaches water-worn after the 

 jasper and ore were in situ, in nearly their present condition, 

 and, if the logic of the geologists of the Michigan and Wis- 

 consin surveys were carried out, these unconformable detrital 

 formations would mark a new geological age." 



Foster C. Whitney and Dr. Wadsworth, however, maintain- 

 ing the eruptive origin of the jasper and ore, do not believe 

 that the conglomerates thus mark a new geological age. The 

 real significance of the break was recognized by Prof. Irving, ^f 

 who not only found it in the Marquette district, but knew of 

 its equivalent in the Vermilion • Lake district of Minnesota. 

 The break in the Marquette district was lately noted by Prof. 



* In papers above cited. 



f Report on the Mineral Lauds of Lake Superior, J.W.Foster: Ex. Docs., 

 1848-49, 2d Sess., 30th Cong., vol ii, No. 2, p. 161. Geology of the Lake 

 Superior Land District, J. W. Foster and J. D. Whitney: Senate Docs., 1851, 

 Spec. Sess., 32d Cong., vol. hi, No. 4, pp. 23, 43 and 67. 



\ Iroa-Bearing Rocks of the Upper Peninsula of Michigan, T. B. Brooks; 

 Mich. Geol. Survey, 1873, vol. ii, pp. 128-129, 133. 



§ Upper Peninsula of Michigan, C. Rominger, Mich. Geol. Survey, 1881, vol. 

 iv, pp. 74-75. 



I Notes on the Geology of the Iron and Copper Districts of Lake Superior, M. 

 E. Wadsworth: Bull. Mus. Comp. Zool., 1880, vol. vii, pp. 30-31. 



^[ Preliminary Paper on an Investigation of the Archaean Formations of the 

 Northwestern States, R. D. Irving: Fifth Ann. Rept. U. S. Geol. Survey, 1885, p. 

 193. "I refer to the occurrence in the quartzites overlying the ores, at several of 

 the Marquette mines, of abundantly rounded fragments derived from the ore 

 below. A very much more striking occurrence of this kind is met with in the 

 Vermilion Lake district of Minnesota, where the fragments included in the con- 

 glomerate overlying the iron belt, are often several feet in length, and angular. 

 That these fragments prove the existence of the jaspery and chalcedonic material 

 in its present condition before the formation of the quartzite is sufficiently evi- 

 dent." 



