On the Leaf-beds and Gravels of Ardtun, Carsaig, &c., in Mull

Abstract

The Ardtun leaf-beds have once before formed the subject of a communication to this Society. Its author was the Duke of Argyll, and its interest exceptional, as it once for all fixed the age of the great Trap formation of the Inner Hebrides; and geologists learned that, even since a period so recent as the Tertiary, beds of most stubborn rock, exceeding 1000 feet in thickness, had been denuded and abraded until, over extensive areas, little more than the merest vestiges of them remained. The value of this discovery to the geologist can hardly be overestimated, for the data then furnished materially assisted to determine the age of the Traps stretching from Antrim to Greenland. The fossil plants, to which so much importance attached, were briefly described in this paper by Edward Forbes, and all the most characteristic forms were figured. He inclined to the idea that they might be of Miocene age, but did not commit himself definitely ; while the Duke of Argyll, even though author of the paper, refrained from expressing any opinion. Prof. Heer, however, who was then describing the Miocene flora of (Eningen, pronounced them to be Miocene; and the weight of his authority has been such, that no serious attempt has ever been made to reexamine the evidence on which his opinion was based. This ruling was extended to the fossil plant-beds of Greenland, with the result that a vast series of physical changes, which extended over the entire Tertiary period, have been crowded