The provenance of the norber erratics, and the formation of post-devensian-deglaciation pedestal rocks with carboniferous limestone pedestals in England, Ireland and Wales

This study investigates a Devensian glacial conundrum, the provenance of the Norber erratics in North Yorkshire, and the
origins of a post-Devensian-deglaciation landform, pedestal rocks with Carboniferous limestone pedestals in England,
Ireland and Wales.
Investigations to determine the provenance of the Norber erratics were undertaken in a study area of about 2000ha. Mapping
erratic dispersal and measuring striae strike revealed that the provenance is Crummackdale, and that Devensian ice crossed
over only the Crummack, Sowerthwaite and Austwick formations en route to Norber. Petrographical and physical surveys
further revealed that the erratics are derived from the Austwick Formation only, and that provenance is a glacially-plucked
‘amphitheatre’ in the vicinity of the Old Limekiln (SD 770707).
Investigations to determine the formation of post-Devensian-deglaciation pedestal rocks with Carboniferous limestone
pedestals were undertaken at 19 sites in England, Ireland and Wales, where 162 pedestal rocks and a pedestal rock field
were examined. The study was divided into two, the formation of perched and mushroom pedestal rocks. An examination of
weathering and erosion processes at Norber, where only perched pedestal rocks with vertical sidewalls are found, revealed
that lowering of the inter-pedestal limestone surface has taken place primarily in a sub-regolith karstic environment, and
that little or no pedestal formation occurred prior to ca.10000BP. In contrast, the lowering of the inter-pedestal limestone
surface about perched pedestal rocks with sloping sidewalls, such as at Scales Moor (North Yorkshire) and the Burren
(County Clare), has taken place primarily in a subaerial environment. Moreover, pedestal formation commenced in
ca.14500BP in England and Wales, and ca.13700BP in Ireland. The pedestals of mushroom pedestal rocks have formed due
to lateral dissolution under regolith that has largely been eroded, probably following deforestation in ca.3000BP.