The Norber Erratics near Austwick are testimony to the powerful transportive forces of Ice Age glaciers. The photograph shows just one of many erratic boulders on Norber Brow near Austwick. As the ice moved down Crummack Dale, these enormous blocks of Silurian basement were deposited on top of the limestone upland.
These erratics are commonly known as the Norber erratics (SD 770 704) and their origin has attracted a great deal of scientific debate and speculation over many years. They have been described by Howson (1850), Phillips (1855), Hughes (1886), Daykins (1872), Tiddeman et al (1890), Kendall & Wroot (1924), Dunham (1950), Brumhead (1979), Waltham (1987), and Arthurton et al (1988). Interestingly enough these authors have widely different opinions on where these erratics came from. Some support a local origin of about 1 kilometre, others further a field such as Ribblesdale, Chapel-Le-Dale, the Howgills, the Lake District and even Northumberland!
The locality of the Norber erratics is situated in one of the Lower Palaeozoic Craven Inliers (an area where pre-Carboniferous basement rocks outcrop at the surface surrounded by younger sub-horizontal Carboniferous limestone) found on the southern margin of the Askrigg Block just north of the North Craven Fault. The junction between the basement rocks and the Carboniferous limestone is an unconformity. In this region the unconformity is a classic angular unconformity as seen in Crummack Dale itself, Thornton Force in Chapel Le Dale, and at Combs Quarry in Foredale (SD 800 701).
The actual Norber erratics are large, angular greywacke / siltstone (turbidites) belonging to the Silurian Austwick Formation. Here at Norber some of the erratic blocks stand on pedestals of limestone.