Image:JH

Great Asby Scar National Nature Reserve lies in the central part of the Carboniferous limestone exposure on the Asby escarpement. The limestone was deposited in a warm shallow sea which covered north-west Europe 340 million years ago, and the rocks of Asby give their name to the Asbian period of the Lower Carboniferous or Mississippian. Limestone pavements are rare in Britain covering less than 3000 hectares in total. They only occur where there has previously been ice cover.

During the Hercynian Orogeny in the late Carboniferous, a period of mountain building, compression of the crust led to localised folding which is what happened to these pavements which slope down in a north-easterly direction towards the Eden Valley and the Pennine hills.

Additionally there is considerable variation in the nature of the pavements, sometimes within a very short distance of perhaps a hundred metres or so. The size of the clints, the ‘blocks’ and the depth of the grikes is of considerable interest as are the runnels or gutter-like channels.

Looking towards the Eden Valley and the Pennines.JH

Shining stones. JH

Near Castle Fold. JH

Weathering of the clints, JH

Runnels. JH

A group of seven members made the trip and unfortunately the weather was poor in the morning, wet and with poor visibility but it improved in the afternoon and we generally managed to dry off before retiring to Orton for some warming refreshments.

References:

The limestone pavements of Great Asby Scar, Cumbria, UK. H.S. Goldie

Great Asby Limestone, By Simon Webb, Walk No. 7, Exploring Lakeland Rocks and Landscapes, The Cumberland Geological Society,2008.

Text: J. Hutchinson, Images: J. Hutchinson and Peter Child

Image, JH

Post-lunch and off for more. Image:PC.