Brains said:
The limestone is quite thin and interbedded with shales, and lies uncomformabley on the lower volcanics, forming the basel layers of the sedimentary units from the Ordovician (Ashgillian) rocks that are more typically seen as the slates well to the south of Coniston Old Man. AFAIK there are no limestone outliers in the Wasdale area. The outcrop of the limestone if only a few metres in width and can be seen from the Walna Scar Road, where its presence is marked by a series of borrow or bell pits dug for lime (burning or fertiliser), which might be mistaken as shake holes. Typically the rocks contain solitary rugose corals or their casts, and some brachiopods.
My geology texts are packed where they can no longer hurt me, and I can stand being wrong... but thats my tuppence worth.
Thanks Brains, I had reached similar conclusions myself earlier tonight after reading the Northern England British Regional Geology.
The key point is that the Coniston Limestone is upper Ashgillian, not part of the Borrowdale Volcanics but younger and deposited after some kind of interval marked by an unconformity. The main outcrop is narrow and runs broadly south-west to north-east, lying north-west of Coniston Water and passing through the northern end of Windemere, nowhere near Wasdale. As you say, no suggestion of any outliers of the Coniston Limestone in the Wasdale area. The maps I have seen are not large scale but I would have expected any significant outliers to be shown. The description of the Coniston Limestone; impure, with ashy sandstone, tuffs and lavas, does not sound promising for cave development in any case. I don’t believe these caves can be in the Coniston Limestone.
It is possible for thin limestones to be interbedded between tuffs and ashes in the sort of environment in which the Borrowdale Volcanics were deposited (some of the tuffs were deposited into water). The Regional Guide suggests this has not happened in the Borrowdale Volcanics. Although “a high percentage of carbonate is characteristic of some tuffs” this is volcanic and not bio-sedimentary in origin. There does not seem to be any chance of solution caves developing in the Borrowdale Volcanics.
There are said to be some dykes intruded into the Borrowdale Volcanics (Quartz-porphyry, spilites and andesitic), maybe cooling joints opened up.
Although the caves are on a fairly flat area, there is I should think the possibility of movement in the past opening up joints.
Anyway, the caves don’t seem to be generally known. Hopefully I’ll find out more next week.