On rock sections exposed in cutting for the suburban railway: with observations on the geology of the district around Edinburgh

Abstract

The sections to the south-west of Edinburgh in a cutting made for the Suburban Railway are as extensive and interesting as any that have ever been exposed in our neighbourhood. The Suburban line branches off from the Edinburgh and Glasgow Railway about a mile west of Haymarket Station, and is carried by an embankment southwards over the road from Gorgie to Edinburgh to within a hundred yards of the Slateford Road, at which point the first excavations begin. The sections here exposed consist of a series of sands, gravels, and clays, with boulders of greenstone and other rocks. The cutting through these deposits extends southwards for about 300 yards, to the point at which the new line passes under the Caledonian Railway, and where the first exposure of the older rocks is observed. The present paper deals with these older rocks only. The section is continued in a south-west direction for about 1200 yards, passing through a descending series of Lower Carboniferous strata. The first series of rocks met with on the south-east side of the Caledonian Railway bridge is a set of dark-coloured shales and thin grey sandy beds, with a dip to the north-west by west of 45°. They extend south-east for about 120 feet, and are underlaid by an immense mass of intrusive doloritic greenstone, 150 feet in extent. This mass appears to dip conformably with the sedimentary strata in contact with it, but its intrusive character can be readily made out by the altered and indurated