VII. The Permian Breccia of Arran

Abstract

The Breccia which forms the subject of this paper is part of the formation which is mapped by the Geological Survey as Trias. They divide the red sandstones as follows:— Upper Trias Keuper? {Red and mottled shales or marls with thin beds of white, yellow, or grey sandstone, and occasional thin bands of nodular limestone. Lower Trias. {False-bedded red sandstones of Brodick and Corrie. Conglomerates alternating with sandstones. Reddish sandstones with some conglomerates. Light-coloured and yellowish sandstones, sometimes red with calcite in cavities. The stratum with which we have to deal is No. 2, that is, “conglomerate alternating with sandstones.” The Survey classification is based on the unconformity between the red sandstones and the Carboniferous below, especially at Corrie; on the lithological similarity to the English Trias; and on the finding of a portion of the upper marls immediately connected with beds of Rhætic Age in a fragment in the Ard Bheinn volcanic agglomerate. Against this, however, Sir Archibald Geikie was disposed to class the standstones as Permian on account of the close similarity to those of Ballochmyle, in Ayrshire. The question of age was finally disposed of by Professor Gregory in his paper, “The Permian and Triassic Rocks of Arran,” in the Transactions of this Society, vol. xv., Part II. (1913-14). Recently a fresh and confirmatory piece of evidence was discovered by Dr. Tyrrell. This is a bed of volcanic tuff in the bed of the burn in Glen Dubh. Reference to this was made in the programme for This 250-word extract was created in the absence of an abstract