On the so-called ‘Gneiss’ of Carboniferous age at Guttannen (Canton Berne, Switzerland)

Abstract

As a text precedes a sermon, so two quotations may fitly begin this communication. The first comes from a letter written by Dr. Heim, and printed in this Journal as a part of the discussion on my paper entitled ‘On the Crystalline Schists and their relation to the Mesozoic Rocks in the Lepontine Alps’:—“In the Central massifs occur rocks which exactly resemble true crystalline schists in mode of occurrence. Petrographically, they are related to them by passage-rocks: at least the line of separation is not easily distinguished. Such rocks are phyllites, chlorite-schists, felsite-schists, mica-schists , and especially sericite-gneisses , all of which we regard with certainty as Palæozoic. The proofs are the following:...Traces of fossils have been often found (trunks of Calamites from Guttannen, in the Haslithal, &c.) . . . The Palæozoic formations mostly show an intimate tectonic relation to the crystalline schists, and have been converted petrographically into crystalline schists.” The second quotation is from the reply which I was permitted to append to the above letter:—“Some of these [Carboniferous rocks] I have examined, and think I know them well enough to demur to Dr. Heim's statements concerning them. I have seen, in the Berne Museum, the specimen with ‘the Calamite-like stem.’ When this rock is proved to be a gneiss I shall be prepared to consider the propriety of extending this name to the Grès Feldspathique of Normandy, or that of mica-schist to some rocks of Carboniferous age at Vernayaz, in Canton Valais, or of calling the Torridon Sandstone