110 THE MARQUETTE IROF-BEAMNG DISTRICT. 



country rocks. From the south end of tlie wider portion of Lake Michi- 

 gamine a looj) of Iluronian rocks extends southeastward, cuhninating- at 

 Republic Mountain, where tlie entire lower and upper series are beautifully 

 represented. 



It is needless to add that Puinpelly's Upper and Lower Huronian are 

 not coordinate with the Upper and Lower Marquette as understood in the 

 present voluiue. Some of his Upper Huronian rocks are unquestionably 

 members of the Lower Marquette. Many of the "beds of diabase" are 

 now known to be intrusive masses. 



Putnam, Bayakd T. Notes on the samples of iron ore collected in Micliigan 

 and northern Wisconsin. Ibid., pages 421-4.:>7. With geological map. 



In the same volume Putnam, in the introduction of his remarks upon 

 the analyses of the Marquette ores, declares that the Marquette strata "form 

 a broad synclinal trough, corrugated in the direction of its axis by several 

 minor folds, resting on Laurentian rocks." He repeats some of Pumpelly's 

 statements and gives an abstract of jiortions of Brooks's report. Samples of 

 ores were taken from all the important mines of tlie district and were 

 analyzed. In addition to the geological map accompanying the report, 

 which, by the way, is a reproduction of the Brooks map, there are sketch 

 maps of the New York, Lake Angeline, and Salisbury mines. 



1887. 

 Irving, R. D. Is there a Huronian group? Am. Jour. Sci. (3), Vol. XXXIV, 

 1887, pages 204-216, 249-263, 365-374. Read before the Nat. Acad, of Sci., April 

 22, 1887. 



Ill this paper Irving returns to the discussion begun by him in 1885 

 The purpose of his present article is — 



to inquire if there can be carved off of the upper portion of the great complex which 

 has been called Archeau, a series of Iluronian rocks, a series entitled — by structural 

 and genetic separateness, by clastic origin, by largeness of volume, and by being made 

 up of subordinate divisions of the formation rank — to the rank of a group, i. e., to a 

 rank equal in classificatory value to the Cambrian, Silurian, etc. (P. 207.) 



After deciding that the series of rocks on the north shore of Lake 

 Huron, called Huronian by Logan and ]\Iurra}', deserves the title of group, 



