A new volcanic vent and other new geological features on the shore, Weak Law, near Gullane

Abstract

On a former occasion I had the honour of laying before the Society certain results of observations made on the Shore at Weak Law (The “ Yellow Conglomerates of Weak Law,” vol. x., pt. iii., p. 266). Owing to the outbreak of war I was unable to complete the work, and for the same reason the map of the section which has been published is very inaccurate. During the months of July 1919 and July 1920 I was enabled to resume my study of the shore when favoured by times of low water. I soon found there was much to do, and with the kind assistance of Mr John Mathieson, a new and fairly accurate map was made. The results obtained consist in a very considerable extension of the two features already discovered, namely, the presence of a large fault running in a north-east and south-west direction along the shore, and of a great intrusive mass of a peculiar nature filling the line of fault. To these must now be added, a small intrusive boss of trachyte piercing the trachyte lava which forms the lowest bed on the shore; a volcanic vent of considerable size; a sill of white trap in the shales and connected with the main intrusive mass filling the fault; the remains of an extensive bed of very coarse conglomerate which lies unconformably over the shales exposed on the shore; and finally a considerable feature, which has the appearance of a ring fracture in the strata. A