714 



THE JOURNAL OF GEOLOGY. 



coarseness of their grain, the plagioclase is always older than the 

 diallage, and it always possesses in greater or less perfection the 

 lath-shaped sections characteristic of diabasic feldspar. This 

 being the case, it seems possible that the great gabbro of north- 

 eastern Minnesota is not a " flow" or a " series of flows," but is 

 the solidified reservoir x in which later flows originated or is a 

 batholitic mass, as Winchell 2 has latterly come to call it. 



Further field work on the geological relationships of the mass 

 will probably show either that it is a batholite within the 

 Keweenawan series, well down toward its base, or that, like the 

 anorthosites of Lawson it is an eroded " massive " upon the top of 

 which the later Keweenawan beds have been deposited. 



List of Specimens of Normal Gabbros Studied and their 



Locations. 



1103 (338) 400 N. 200 W. S.E. corner Sec. 34, T. 53 N., R. 13 W., 



Minn. 

 6007 (141 5) S. side Cross Lake, S. side Sec. 29-64-1 W. 



(1416) 



(1424) 

 6011 (1126) S.E^ Sec. 21-64-3 W. 

 6013 (n 2 7) N.W. side Copper Lake, Sec. 9-64-4 W. 



6127 (1171) N.E# S.W# Sec. 36-65-3 W. 



6128 (1172) S.E^ S.W# Sec. 36-65-3 W. 

 6130 (3203) S.E# S.E^ Sec. 36-65-3 W. 



7025 (2091) S. shore Akeley Lake, Sec. 29-65-4 W. 



8589 (4025) S. shore of small lake in S.E^ S.E^ Sec. 19-63-9 W. 



8786 (3520) Near S.^post of Sec. 35-61-12 W. 



8788 (3528) N. shore Birch Lake, 200 paces E. of S.^post Sec. 24- 

 61-12 W. 



8789 (3529) W. side Birch Lake, opposite N.E. arm of lake, Sec. 24- 

 61-12 W. 



8792 (3532) N.WX S.W# Sec. 9-62-10 W. 



8793 (4259) N.W^ S.E^ Sec. 23-62-10 W. 



8794 (3522) On Mishiwishiwi river, near centre Sec. 34-62-9 W. 



1 Cf. ante, p. 696. 



2 Bull. No. 8, Geol. and Nat. Hist., Sur. of Minn. Preparatory note, P. xxiv. et seq. 



