Page:The Journal of geology (IA journalofgeology11893univers).pdf/170

This page has been proofread, but needs to be validated.
596
THE JOURNAL OF GEOLOGY.

of the lake, and of the gabbro, diabases, diorites, melaphyres and porphyrites of the Keweenawan overlying the Penokee series to the north, while Hall[1] has described a few hand specimens of diabases and gabbros from the Archæan of Central Wisconsin.

Further, in a discussion as to the nature of the diabase sheets interbedded with the Animikie slates and quartzites in Minnesota and Canada, which leads to the conclusion that the former are subsequent intrusions between the clastic beds, Lawson[2] gives a short generalized description of the petrographical characteristics of these rocks, and in a second article[3] he treats of the structure and composition of the anorthite rock of Irving, to which he gives the name anorthosyte. Finally, the writer in two articles refers to the coarse gabbro[4] of north-eastern Minnesota and to the peridotites and pyroxenites[5] associated with it along its northern border.

W. S. Bayley.

  1. ↑ C. W. Hall: Notes of a Geological Excursion into Central Wisconsin.Bull. Minn. Acad. Nat. Sciences, III., No. 2., p. 251.
  2. ↑ A. C. Lawson: The Laccolitic Sills of the Northwest Coast of Lake Superior.Bull. No. 8, Geol. and Nat. Hist. Survey of Minnesota, p. 30.
  3. ↑ A. C. Lawson: The Anorthosytes of the Minnesota Coast of Lake SuperiorIb., p. 2.
  4. ↑ W. S. Bayley: A Fibrous Intergrowth of Augite and Plagioclase, resembling a Reaction-rim, in a Minnesota Gabbro.Amer. Jour. Science, XLIII.1892, p. 515.
  5. ↑ W. S. Bayley: Notes on the Petrography and Geology of the Akeley Lake Region, in North-eastern Minnesota, 1892, p. 193.
This article is issued from Wikisource. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.