Introduction

Plat stem fossil, Clara Vale in Land of Oak & IronThe survey was carried out by John Durkin from May to December 2016.

75 potential sites were identified from local knowledge, maps and aerial photos. The tufa formations cannot be identified in this way, so all streams were walked between the known parameters, which are where summer flow becomes constant and stream size is less than the Pont Burn. This amounted to just over 60 kilometres of stream bank.

A small number of sites, mainly disused quarries and springs on private land, could not be accessed, but could be assessed from a distance or from aerial photos.

Results

A range of high quality sites were recorded, including tufa formations, glacial features, rock exposures and fossil sites.

Tufa

Tufa formations, Thornley Woodlands in Land of Oak & IronSeven streams with tufa dams were recorded in Gateshead and County Durham. Some of these were found to be more extensive than previously thought. No dams were found in Northumberland, but a calcareous spring with tufa formations was discovered, and this may provide information on the origin of these geomorphological features.

The tufa was of two types, most were dominated by a filamentous alga Vaucheria, with some cyanobacterial films. Less commonly, Vaucheria was absent and the formations differed in structure.

Tufa formations, Dene BurnThe five tufa dam formations lower down the Derwent Valley and the tufa spring were all Vaucheria type formations, with the two sets of dams higher up the valley the more unusual cyanobacteria type.

All eight of these sites meet the standard for designation as Local Geological Sites, and as a group they are of national significance. Most of these sites are at least partially already in Local Wildlife Sites, and one, at Thornley Wood, is partially in a Site of Special Scientific Interest. The Northumberland spring and parts of most of the others have no designations at present.

Several minor sites with tufa features from dripping water on vertical cliffs were found. In these cases, the strata exposed in the cliffs are also important geological features, and are covered under “Rock Exposures”.

Rock Exposures

Northumberland bank, Shotley BridgePlaces where the coal measures strata can be seen in cross section occur mainly on the banks of the River Derwent. The best examples are at the Sneep, Shotley Bridge and the Chopwell area. There is also a similar feature on the Pont Burn, where iron salts seep out of the rock face. Many quarries were looked at, but exposures were usually poor, due to infilling or natural succession.

The County Durham bankIron salt formations, Pont Burn Wood in Land of Oak & Iron of the Derwent from Muggleswick to Shotley Bridge is already designated, one of only two existing designations. The Northumberland bank is similar, but not designated.

The second existing designation is on the County Durham banks of the Derwent at Chopwell Wood. Chopwell Crags is of considerably higher quality and shows good strata exposures, tufa seepages and iron salt seepages.

The Pont Burn has a good section where strata are exposed over several hundred metres and include iron seepages.

There are lesser exposures elsewhere.

Glacial Features

Glacial formations, Beda Hills in Land of Oak & IronAreas of glacial features such as eskers and drumlins were once extensive in the Land of Oak and Iron area, but have been reduced by sand and gravel quarrying and by urban spread. The best remaining example is at Beda Hills, extending into Chopwell Wood and Hookergate, with a second important area at Reeley Mires. Smaller, less intact features remain at Broad Oak and at Crawcrook and Clara Vale.

The Beda Hills and Reeley Mires areas meet the criteria for designation as Local Geological Sites. The boundaries of these landscape features will be harder to define than those of the more specifically bounded Tufa and Rock Exposure sites.

Fossil Sites

Fossil plant stems and leaves, Castleside Quarry in Land of Oak & IronSome of the rock exposures are rich in carboniferous period fossils, mostly of plants. Apart from their scientific value, they are of great interest to the public.

Several key sites were identified, at a disused quarry at Castleside, in the bed of the Tyne at Clara Vale, and in the beds of the River Derwent and the Pont Burn where shingle is deposited. Ironstone in the bed of the Derwent at
Shotley Bridge is particularly rich in fossils.

However, none of these sites was considered to be of Local Geological Site quality in its own right.