Bulletin No. 8. I. The Anorthosytes of the Minnesota Coast of Lake Superior; II. The Laccolitic Sills of the North-west coast of Lake Superior

Abstract

Among the problems which were named in instructions given to Dr. Lawson when he entered upon the season's work for the Minnesota. Geological and Natural History Survey along the northern coast of lake Superior, one was the following. To determine if possible the date and stratigraphic relations of the gabbro invasion. How well he has answered that question his report on the "Anorthosytes of the Minnesota coast of lake Superior" bears ample testimony. In order, however, that the important bearing which his results have on the geology of the northeastern part of the state, may be made more apparent, it is deemed best to preface this publication with a short exposition of the history of the investigation, and a few paragraphs on the extent of the gabbro rocks and on the significance of the term gabbro.