GEOLOGICAL EXPLORATIONS AND LITEKATUKE— ISCU. 45 



conglomerate, which he thoug'lit was embe<kled iu tlie gneisses. Largely 

 because of this observation, he concludes that the whole Laurentian series 

 is a bedded one of metamorphosed fragmental sediments. 



In the Marquette area the oldest member of the Iluroniau series is a 

 quartzite impregnated with iron oxide. In the northern pttrtion of the dis- 

 trict siliceous hematite replaces the quartzite, and in both portions of the 

 region limestone is the next succeeding rock. Serpentines, chlorite-schists, 

 talc-schists, and diorites are interbedded with the quartzites. This series 

 of rocks, according- to the author, was deposited close to the shore-lines, 

 whereas the Menominee series to the south was a deep-sea deposit. The 

 ores of the Marquette district were examined quite closely. They are 

 described as consisting of magnetite, martite, and hematite. 



Structurally the Marquette Huronian forms a great synclinal basin 

 made up of minor synclinal and anticlinal folds, of which there are six iu 

 the neighborhood of Marquette. Underlying this folded series unconform- 

 ably is the Laurentian, and above it unconformably is the Lake Superior 

 sandstone. 



1SG9. 



Gredner, Hermann. Die vorsilurischeu Gebilde iler "oberen Halbiusel von 

 Michigan" in 25'ord-Amerilva. Zeits. der dentscheu geoL Gesellschaft, VoL XXI, 186!), 

 pages .516-568. With map and three plates of sections. 



In the second article Credner gives more specific details concerning 

 the geology of the Upper Peninsula of jMichigan. The geology of Smiths 

 Mountain (now Republic I\Iountain) and of the Negaunee region is fully 

 described. The sequence of rocks in both districts is given as the author 

 saw them, and inferences are di-awn from the observations. The schistose 

 greenstones associated with the quartzites and ores are regarded as inter- 

 bedded chlorite-schists, and the massive greenstones as interleaved diorites. 

 In the vicinity of Negaunee the lowermost beds are (juartzites, replaced 

 locally by limestones and interbedded with chlorite-schists, and above these 

 is a schist complex of a white and brown banded quai-tzite, red jaspers, and 

 hematites, and beds of pure hematite, with two interbedded diorite sheets 

 and a bed of chlorite-schist. The character of the ores is discussed. Limon- 

 ites I'eplace the hematites locally, as at the Foster mine, and magnetites 



