After further study and identification of this area as a quarry, it appears that this is one of a series of cuts into the bedrock associated with quarry machinery. This one, specifically, may have accommodated one of the posts to which cranes’ tie-rods were tied

This circular cut in the bedrock may have been a posthole. The top of the cut has been eroded, especially on the northern side. The undercut in the southwestern part of the cut appears to have been intentional but the fill in this part of the cut was no different from the rest of SU228.