GEOLOGICAL EXPLORATIONS AND LITERxVTUUK— 189->. 135 



chloritic, finely laniiiiated schist. The thicikness of this series has not been worked 

 out with accuracy, but at its maximum it is probably more than 5,000 feet. As the 

 term Huronian has been for many years ai^plied not only to the Upper Huronian 

 series, but to this inferior .series about Lake Superior, it is (tailed Lower Huronian. 



Above this series is a more gently folded one of conglomerates, quartzites, slates, 

 shales, mica-schists, ferruginous beds, intcrbedded and cut by greenstones, the whole 

 having a maxiniiiin thickness of at least 12,000 feet. » * » In its volume, degree 

 of folding, and little altered character the I'pi)cr Huronian is in all iesi)ects like 

 the ujiper series of the original Huronian, and can be correlated with it with a con- 

 siderable degree of certainty. Above the Up])er Huronian is tlie great Koweenawan 

 series. * * * 



The unconloriiiity which sei)arates the Ijower Huronian fioni the Tip])er Huro- 

 nian and that which separates the latter from tlic Keweenawan each represents an 

 interval of time sufficiently long to raise the land above the sea, to fold the rocks, to 

 carry away thousands of feet of sediments, and to depress the land again below the 

 sea. That is, each represents an amount of time which perhajis is as long as any 

 of the periods of deposition themselves. In parts of tlie region the lowest clastic 

 series rests unconformably upon the Fundamental Oomi)lex, but in certain areas the 

 relations have not been ascertained. The upper of the three clastic; series, the 

 Keweenawan, rests unconformably ])el()\v the Cambrian. (Pp. 409-500.) 



VVadswortii, M. E. a sketch of tlie geology of the iron, gold, and copper 

 districts of Michigan. Nature, December 1, 1802, page 117. 



Ill this same year, at a meeting- of the Geological Society of London, 

 Wadsworth gave an advance abstract of his report for 1891-92 as State 

 geologist of Michigan. In this paper all tlie rocks below the Cambrian are 

 still called Azoic, but they are separated into three formations, beginning 

 with the Cascade as the oldest, as in the brochures of the Dulutli, South 

 Slioi-e and Atlantic Railway. 'I'lie Cascade formation embraces gneissoid 

 granites, basic eruptives and schists, jaspilites, and the associated iron 

 ores and granites. Next follows the Republic formation. Beginning with 

 the oldest beds, this embraces conglomerates, breccias and conglomeratic 

 schists, quartzite, dolomite, jaspilite and associated iron ores, argillite, schists, 

 granite, felsite, diabase, diorite, peridotite, and porphyrite. In ^•iew of dis- 

 coveries made l)y the State survey of Michigan and by tlie United States 

 Geological Survey regarding the jaspilites, the author is inclined to give 

 up his former view of the eruptive origin of these rocks and their associated 

 ores. The newest Azoic formation is the Holyoke (the Keweenawan is 



