Lazonby, Armathwaite and Carlisle

A little out of Lazonby, the River Eden runs through the narrow Eden Gorge. The river has eroded away any glacial deposits and the gorge sides are Penrith Sandstone with dune cross bedding. The line runs through Penrith Sandstone virtually all the way from Lazonby to Armathwaite.

In the Baronwood Tunnels area the line crosses glacial sands and gravel deposited by melting ice. About half a kilometre to the southwest of the line (not visible from the train) is the Baronwood sand-pit where thick cross bedded sands are dug out. These sands were deposited as a small delta from a melt-water stream coming from the front of the glacier.

Armathwaite Dyke – Joe Cann

In the river, just before Armathwaite, is a natural weir formed of a layer of hard, erosion resistant rock. This is the 57 million year old Armathwaite Dyke. The dyke runs ESE-WNW along the hill that can be seen in both directions from the railway. It can be traced for 400km from Mull through Cumbria to Durham. It is a long, thin, vertical intrusion of an igneous rock called dolerite (the same rock that forms the Whin Sill, although the two intrusions are unrelated). With the opening of the Atlantic, magma from deep in the Earth was forced along weaknesses in the rocks, it never reached the surface but cooled and crystallized underground.

After Armathwaite Station, as the line curves to the northwest towards Carlisle, the landscape opens out into low rolling hills of the Permo-Triassic sediments coated in glacial till and the Pennines become less pronounced.

Beneath the till is the Triassic-aged St Bees Sandstones. Where they can be seen they are dull red sandstones and conglomerates with cross bedded layers. They were deposited in seasonal rivers that migrated across the basin. The cross bedding formed as large sand ripples on the river bed.

Approaching Carlisle, the rocks beneath the till are the Mercia Mudstones. These lie over the St Bees Sandstone. They consist of red, blue and grey shales, green siltstones and layers of gypsum, anhydrite and rock salt deposited in desert lakes (similar to the lake in Death Valley, California today).

An east-west valley through the Pennine hills marks the line of the Stublick Fault. This separates the Alston Block from the Northumberland Basin that in the Carboniferous had more open marine conditions. This fault also marks the southern boundary of the Carlisle Basin. This is filled with a thick sequence of Upper Permian-Jurassic sedimentary rocks.

• 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

						In the past the line has been blocked for periods of up to one month by snow