The Middle and Upper Cambrian Sedimentary Rocks of Bornholm

Abstract

The alum shales of Bornholm and their stinkstones were mentioned as long ago as by Ørsted & Esmarck, though these authors occupied themselves chiefly with the question of their practical utility, their conclusion being that they are not so bituminous as to permit of their being used for fuel in the burning of lime, as for instance the shales of Västergötland are still used today. (Ørsted & Esmarck 1819).

Forchammer also refers to these alum shales and names a few fossils, but his description of "the transitional formation" includes the whole of the series that extends from Middle Cambrian to Upper Graptolith Shales inclusive (Forchammer 1835).

It is only with Johnstrup that there begins a more comprehensive investigation of the fossiliferous Cambra-Silurian and an attempt at a more exact division of it on a palaeontological basis, on the lines of the stratigraphical surveys that were started at the same time in Scania (Johnstrup 1891).

But we obtain no closer knowledge of the stratigraphy and fossil contents of this series until Grönwall and later Poulsen complete their investigations (Grönwall 1902, Poulsen 1923). Both authors, it is true, describe a number of characteristic features of the rocks, but hitherto there has been no systematic petrographical examination of them; and as the present investigation has been able to elucidate still more peculiarities in the development of the series, a more detailed description of the various localities will be necessary.