City of Edinburgh, The Dean, Edinburgh - an excursion

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City of Edinburgh - The Dean

Author: C. D. Waterston. From: Lothian geology: an excursion guide . Edited by A.D. McAdam and E.N.K. Clarkson. 1996.

O.S. 1:50000 Sheet 66 Edinburgh

BGS 1:50 000 Geological Survey of Scotland map. Bedrock

BGS 1:50 000 Geological Survey of Scotland map. Bedrock and Superficial

BGS 1:25 000 series - Classical areas of British geology Edinburgh District

Walking Time Distance: 1.5 hours 2km

Water of Leith Valley

The excursion starts at Stockbridge (NT 246 746) reached by Lothian Region Transport bus from the city centre.

Between Drumsheugh and Stockbridge the Water of Leith has cut its course through the sandstones and shales of the Granton Sandstones, which belong to the Lower Oil-Shale Group. The valley exposes what is virtually a strike section of the beds which here dip westwards and occupy the west limb of the St. Andrew's Square Anticline which is an expression within the city of the Pentland Anticline. This anticline is followed to the west by the Granton-Wardie Syncline.

1. St. Bernard's Well: Granton Sandstones, Quartz-dolerite Dyke

Proceed to St. Bernard's Well (Figure 9) by way of Saunders Street, which follows the Water of Leith upstream from the bridge at Stockbridge, and the footpath by the waterside when the Dean Park is reached. St. Bernard's Well was a sulphurous medicinal well whose waters were prized for many years, as the classic 18th century well-house shows. In the river bank opposite the well, a quartz-dolerite dyke is exposed cutting shales and flaggy sandstones of the Granton Sandstones. The dyke is about 1 m in thickness and trends west-north-westwards.

Skirt the well by the waterside, and follow the path up-stream for 25 m where a current-bedded sandstone with good ripple-marks is well seen dipping westwards.

2. St. George's Well: Sandstones, Dyke

Return to St. Bernard's Well, mount the steps to the main pathway and, turning right, follow the path upstream for 200 m when, in the river under a small building, St. George's Well, to the right of the path, another quartz-dolerite dyke cutting a bed of sandstone is exposed. This dyke is some 3 m in thickness and its trend is parallel to the St. Bernard's Well dyke.

A poor coal occurs in the river bed some 105 m above the second dyke and some 30 m downstream from the Dean Bridge. Unfortunately access to this coal is not possible.

FIG 9. St. Bernard's Well

3. The Dean Bridge: Shales in Granton Sandstones

Follow the path upstream for a further 30 m when on the left-hand side, in the cliff below the Dean Bridge, occurs a fine exposure of shales with ironstone nodules and sandstone above, It is possible to collect from the shales at this exposure where, in addition to plant, entomostracan and fish remains, Naiadites obesus (R. Eth. jnr.) has been obtained.

4. Miller Row: Granton Sandstones/Wardie Shales Junction

Passing under the Dean Bridge reach the ornamental mill-wheels in Miller Row. Here the Water of Leith occupies a westerly loop of its course and the shales and sandstones of the Granton Beds, which were seen at the last exposure to be dipping westwards at some ISO, plunge into the river bed and are succeeded on the opposite cliff, under the church building, by 55 m of bituminous shales. From fossil evidence obtained further along the strike at Drumsheugh, it is known that these bituminous shales belong to the succeeding Wardie Shales.

5. Dean Gorge: Post-Glacial Cut

From this viewpoint in Miller Row the post-glacial cut of the Dean gorge is well seen. Upstream from Belford Bridge the Water of Leith occupies a valley filled with deep boulder-clay which presumably represents its pre-glacial course. At Stockbridge the river meanders over the late-glacial Raised Beach deposits. At the Dean, however, the valley is steep-sided and cut in rock with no boulder-clay filling. It is probable that in post-glacial times the river was deflected from its original course by the resistant dolerite sills at Belford Bridge, causing the river, heavy with glacial melt-water and rejuvenated by the rising land level, to cut the spectacular gorge of Dean.

Follow Miller Row to the small bridge and, turning left, ascend Bell's Brae to Queensferry Road which leads to the West End of Princes Street.

At all times follow: The Scottish Access Codeand Code of Conduct for Fieldwork .