Societies and Academies

Abstract

LONDON. Geological Society, January 9.—Dr. Alfred Harker, president, in the chair.—L. D. Stamp: The highest Silurian rocks of the Clun Forest District (Shropshire). Clun Forest is a district in which Upper Silurian rocks crop out over a wide area, interrupted by outliers of Old Red Sandstone. The district is separated from the typical Silurian area of Ludlow by the great line of disturbance that passes through Church Stretton and Old Radnor. The succession of beds compares closely with that in the Ludlow district. The main differences are:—(1) That the Aymestry Limestone is represented by mudstones west of the great fault-line, and (2) that all other divisions show increased thicknesses. There is no evidence of any strati-graphical break. The sequence is complete from the Lower Ludlow rocks up into the Old Red Sandstone, and the changes in lithology are gradual. The extent of Old Red Sandstone, as indicated on present maps, must be restricted, since most of the supposed Old Red Sandstone has been found to belong to the Teme-side group, which here attains a great development. The Silurian age of the beds is shown by the occurrence of Lingula minima and of characteristic lamelli-branchs. A comparison with other districts in which Upper Silurian rocks are developed shows that deposition attained its maximum along the Welsh Border, the thickness of the formations decreasing rapidly southwards and eastwards. On the east of the district-in the neighbourhood of the fault-line the strata are folded along axes ranging north-north-eastwards parallel to the main fault. Away from the major faults the folding is gentler, and folds ranging nearly due east and west make their appearance. Farther west the north-north-eastward folding and fracturing reappear.