V.—Notes on the Older Rocks of Finland

Extract

The consideration of the Archæan rocks of Finland, as pointed out in a previous article, naturally divides itself into two parts: I. The treatment of the stratified or foliated members of the series; II. That of the igneous or eruptive rocks. In describing the former, want of space compelled me to handle the subject in what I fear must be regarded as a very fragmentary manner. In addition I confined myself entirely to giving an account of the older members of the formation, omitting all mention of the younger schists, mica-clay slates, phyllites, etc., which go to make up what is in Finland regarded as corresponding to the Huronian subdivision. I did this from two reasons,—firstly, because I was personally better acquainted with the rocks in question ; secondly, because it seemed to me that it is the problem of the origin, sequence and composition of the older members of the series which at the present day possesses most interest for the student of the geology of the Archaean, and in consequence is the one with regard to which the greatest divergence of opinion prevails. In the present article I propose to give a short account of the more important eruptive rocks of Finland; but before proceeding to do so, it would not, I think, be out of place to furnish a short résumé of the conclusions to which the study of the foliated Archæan rocks of the country has led me, and which I believe to be thoroughly supported by the data published in my former article.