Garsdale, Kirkby Stephen and Appleby

View down Mallerstang from Ais Gill – Anthony Glossop

Out of Garsdale Station, the line crosses into the top of the Eden Valley. The Carboniferous Limestone Series has increased in thickness from a few metres just north of Horton Station to over a kilometre thickness north of Garsdale. Between Garsdale and just south of Kirkby Stephen the youngest beds of the Carboniferous rocks are confined to the valley floor and the Millstone Grit series, which has previously only be seen capping the higher hills, is now also seen in the valley sides. Fossils from the Millstone Grit include corals, bivalves, brachiopods, goniatites (similar to a nautilus), nautilus, gastropods (snails, whelks and limpets are all types of gastropods) and sponges.

As the railway approaches the Birkett Tunnel the previously near horizontal beds of the Carboniferous Limestone dip more steeply as they approach the Dent Fault. The line crosses the fault about 3km south of Kirkby Stephen, although there is no indication of it in the landscape. The Dent Fault is the western margin of the Askrigg Block which the railway has been crossing since a few miles north of Settle. The rocks on the far side of the fault are the oldest beds of the Carboniferous Limestone series and form the lowest beds of the Eden Valley. They are up to 1.5km thick beneath the centre of the Vale and can be seen in cuttings north of Kirkby Stephen. The Permian aged Penrith Sandstone lie above them. The line crosses the unconformity just after Helm Tunnel, although it is difficult to see as most of the Vale of Eden is covered in glacial till and river sediments. Look out for red soil, this indicates the presence of the Penrith Sandstone beneath.

Millstone Grit of Mallerstang Edge – Anthony Glossop

The Vale of Eden lies between the Fells to the east and the Lake District to the west. It is a sedimentary basin that has a fault on one side only. As the fault moved, it created a low lying area (like a trap door opening) into which Permian to Jurassic aged sediments accumulated. The Pennine Fault Zone separates the Eden Valley from the Ordovician volcanics and Silurian and Carboniferous sediments of the Fells (Alston Block) and forms the clear escarpment to the east. The rocks of the Fells are the same as those found in the Lake District and the same as those that lie beneath the sediments of the Vale of Eden. The glacial till that covers the Vale consists of rock fragments varying in size from boulders to sand held together by dense, impermeable clay. There are also lenses of gravel and sand from melt-water streams and finely layered clays deposited in small, temporary lakes. The till in the Vale of Eden is mainly red and contains rocks known as erratics from the local sandstones, the Lake District and rarely from Scottish granites. The till varies from 5 to 30m thick and in many places has been sculpted by glaciers into drumlins. Just after the last ice age, the River Eden was blocked by glacial till near Great Ormside and as the ice melted a lake formed, stretching from Great Ormside southeast about 5km to Warcop. When the waters finally broke through this natural dam the lake drained catastrophically, eroding the gorge between Great Ormside and Appleby.

• Introduction, Geological History and Economic Geology
• Settle, Horton and Ribblehead
• Ribblehead, Dent and Garsdale
• Garsdale, Kirkby Stephen and Appleby
• Appleby, Langwathby and Lazonby
• Lazonby, Armathwaite and Carlisle
• Geological Terms and References

						Foundations for Arten Gill viaduct were excavated to a depth of 50 feet before solid rock was found