The upper reaches of the Bannock are in peat bog on a base of volcanic rocks, mainly basalt, of Carboniferous age. Moving downstream, at approximately NS742876, where the Bannock begins to enter a significant valley, the basalt gives way to the Lower Limestone Formation of the Carboniferous era, with minimal soil cover on the right bank, while the volcanic formation continues to form or come close to the left bank. In the Craigend area and Touchadam Quarry the lower limestone is exposed on both sides of the burn, and in its bed, and was mined as described below. The Bannock briefly crosses the Stirling Sill, at NS770907, in a region where it transgresses (changes its level within the sedimentary formation) and is therefore at a lower level than in the craggy cliffs of Craigend and Murrayshall, where it forms the uppermost strata.