Laser Scan Survey of Rock-Art Panel
High-resolution photogrammetric mesh under simulated raking light from top left, image copyright AOC Archaeology Group
A programme of survey and recording was conducted by staff from Argyll Archaeology Ltd and AOC Archaeology Group to record damage to an exposed area of bedrock containing cup and ring markings at Tom nan Clach, Argyll. A machine undertaking forestry operations had tracked accross the rock, which is legally-protected as a scheduled monument, resulting in damage to the surface. This occurred because Ordnance Survey maps of the area showed the cup-markings at a position around 130m to the west of their actual location. The work comprised the clearance of debris, silt and other disturbed material left on the surface of the rock, followed by recording of the exposed rock surface by laser scanning, photography, scaled plan and written description.
Corrugated machine track (left of centre of image), image copyright Argyll Archaeology Ltd
It was clear from this work that a metal tracked machine has crossed over the surface of the glaciated bedrock panel of Tom Nan Clach. The metal track of the machine removed the upper smoothed surface of bedrock resulting in a shallow, corrugated scar up to 0.90m wide and 0.03m deep. Two cups in the north-eastern corner of the panel had clearly been damaged by the machine track. There was no surviving rock art within the main machine track scar. Given that the rock art occurs within a broad linear band which runs roughly northeast/southwest across the exposed bedrock sheet, it is very likely that rock art did also occur within the tracked area at the northern end of the panel prior to the damage occurring as described.
Local relief model using a red white colour ramp draped on hillshaded surfaces light from bottom right, image copyright AOC Archaeology Group