Page:The Journal of geology (IA journalofgeology21894univers).pdf/143
interglacial, deuteroglacial, and postglacial periods, all very clearly denoted by these names.
The proteroglacial period came at last to an end. The ice retired very much; an interglacial period followed. Of this warmer period we know very few certain traces in Norway. Almost every deposit referable to it has been swept out by the last—the deuteroglacial—ice sheet at least in the parts best studied. At Jaederen we certainly have some layers of gravel and sand between the undermost bottom moraine carrying boulders from the Kristiania territory, and the uppermost one bearing boulders from the mountains close by on the east, but these layers do not contain, as far as known, any fossils giving information about the climate, and it may very probably be that they must be referred to the retiring proteroglacial or the advancing deuteroglacial ice.
The part of the proteroglacial country which was not covered by the deuteroglacial ice sheet or sea—and which, therefore, might have retained interglacial deposits—is very poor in loose matter and it has, as yet, not been possible to distinguish any interglacial debris. In the center of the country at Våge, near the highest mountains in Norway, there was some years ago found in river gravel a molar of a mammoth. It may now be said, that this tooth is certainly neither postglacial, protero- nor deuteroglacial, as the tract in these periods was quite ice-covered. There remains the assumption that it is preglacial or interglacial, and as it is not very probable that this molar has remained unmolested through the very long first glaciation by which the whole country was deeply eroded, it is perhaps permissible to take it for interglacial. In this case we may conclude that the country in interglacial time was covered with forest up to the highest plateaus; and, therefore, the proteroglacial inland ice was entirely gone.
It is, however, more reliable to seek for support by a comparison with neighboring countries. The peats in parts of Denmark not deuteroglaciated show an arctic flora with Dryas, Salix polaris, herbacea, and reticulata, which followed the great retreating proteroglacial ice sheet, and this was superseded by a vegetation char-