The central band is a mix of volcanic and sedimentary rocks of mid-to-late Ordovician age comprising the lavas and tuffs of the Borrowdale Volcanic Group, erupted as the former Iapetus Ocean was subducted beneath what is now the Scottish border during the Caledonian orogeny.
The south eastern band comprises the mudstones and wackes of the Windermere Supergroup and which includes (successively) the rocks of the Dent, Stockdale, Tranearth, Coniston and Kendal groups.