Page:The Journal of geology (IA journalofgeology11893univers).pdf/288

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 northeastern Minnesota is not a "flow" or a "series of flows," but is the solidified reservoir^[1] 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.