Societies and Academies

    Abstract

    LONDON. Geological Society, June 15.—J. E. Richey: The structural relations of the Mourne granites (Ireland). The Maurne Mountains are some 13 miles long by about 5 miles wide, and include many peaks of more than 2000 feet in height. The granite-massif of inferred Tertiary age is intruded into Silurian shales, and truncates a north-westerly basic dyke-swarm. The massif consists of at least four distinct intrusions, composed of different granite varieties. The Western Granite extends outwards on all sides below a slightly domed roof of shales, cappings of which rest upon the granite. The Eastern Granites are deeply eroded enough to show bounding walls as well as roofs. Floors are nowhere seen. These Eastern Granites are arranged one within the other, with a marked excontricity towards one side. The outermost granite is the oldest, the innermost the youngest. Features observed by Traill are that granite-margins transgress the bedding of the Silurian shales, and that the direction of the dip of the shales is unaffected by the intrusion of the granites. The absence of xenoliths, except at actual margins, and the plane surfaces of contacts, are other noteworthy features. The spaces occupied by the various granites have been provided by subterranean cauldron-subsidence of the preexisting rocks. The intrusion of the Eastern Granites successively one within the other may be then explained by assuming renewed subsidence of the first-subsided block.—W. F. Whittard: The stratigraphy of the Valentian rocks of Shropshire: the main outcrop. It is the first of these that is described in this paper. The threefold classification of Salter and Avoline has been adopted, but their nomenclature has been modified: the rocks are subdivided as follows: (3) Purple shales; (2) Pentamerus beds; (1) Arenaceous beds. The Arenaceous beds extend from near Cardington north-eastwards to the Wrekin, and consist essentially of conglomerates, grits, and sandstones. Evidence is given for a southerly derivation of the pebbles comprising these beds, and a north-easterly longshore drift is postulated. The Purple shales consist almost entirely of purple, maroon, or green mudstones or shales; shelly limestones and calcareous sandstones occur irrespective of horizon. The Valentian rocks are displaced by a series of dip-faults, but no folding, other than that caused by slip, has been detected. The Valentian rocks of the main outcrop seem to have been deposited in partly isolated or protected waters. The few graptolites so far obtained show that only Upper Valentian rocks are exposed.

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    Societies and Academies. Nature 120, 245–248 (1927). https://doi.org/10.1038/120245b0

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