Some Aspects of Granite Weathering and Tor Formation on Dartmoor, England

Abstract

This paper describes the products of weathering and pneumatolytic alteration on the granite of Dartmoor in south western England; and discusses the relation of the weathered granite to the tors of the area. Textural and mineralogical investigations enable the authors to distinguish between the products of alteration and those of weathering, and the latter are found to resemble “sandy weathering” products on granite elsewhere in Europe. The occurrence of a deeply weathered zone is recognized but this differs in character from zones of deep weathering described in the humid tropics. Field seismic investigations suggest that the deep weathering on Dartmoor may have been confined to the margin of the granite and to the main river valleys. In conclusion, the authors accept that the tors of the Dartmoor granite were exhumed from the zone of deep weathering.