GEOLOGICAL EXPLORATIONS AND LITERATrKE— 18!);$. 143 



Smyth, H. Ij. A coutact between the Lower Iluroiiiiiii and I he luiderlying 

 granite in the Itepnblic trough, near Republic, Michigan. Jour, of (ieol., Vol. I, 

 1893, pages 208-274. 



Sinvth describes as existing south of the Rei)uhlic mine, in tlu' l)en(l 

 of the horseshoe made by the ontcro|)pino-s of tlie iron-l)eiiring rocks, 

 the first proved unconformity between what is regarded as the lowest 

 member of the Lower Iluronian series in the Marquette district and the 

 imderl>ing Basement Complex. The existence of this unconformity was 

 inferred by Brooks from the fact that the strike of the cpiartzites and actin- 

 olite-schists near this place runs directly across the foliation in the neigh- 

 boring granite. Smyth discovered the iictual contact of the two series, 

 and found the basal member of the overlying one to be a coarse conglom- 

 erate containing large bowlders of the same granite as that below the 

 coutact. Between the conglomerate and the granite h a thin band of a 

 schistose rock, in all probability representing a sheared portion of the 

 granite or of the conglomerate. 



Van Hise, C. R. An historical sketch of the Lake Superior region to ('ambriau 

 time. Jour, of Geol., Vol. I, 1893, pages 113-128. With map. 



]\Iuch of the information imparted in this summary statement of the 

 knowledge concerning the relations of the pre-Cambrian formations to one 

 another in the Lake Superior region is contained also in the coi-i-elation 

 essay on the Archean and Algonkian, already referred to. There are 

 described, however, a few additional facts of detail that are of interest. 



The Lower Huronian is now said to be composed of three members, 

 instead of the two recognized in earlier papers. In ascending order they 

 are as follows: (1) Conglomerates and quartzites; (2) limestone and chert; 

 (3) the iron-bearing formation. These three members are not often seen 

 in a single section, in consequence, in some cases at least, of the entire 

 absence of one or the other of them. Basic eruptive rocks are also 

 abundant in the Lower Huronian, and acid eruptives occur not infrequently. 



At the end of Lower Huronian time the Lake Superior region was 

 raised above the sea, folded, and subjected to erosion, and the U^jper 

 Huronian sediments were deposited upon the Lower Huronian ones. Like 

 the Lower series, the Upper series consists also of three formations, which are 



