The history of the River Dart, Devon

Abstract

Summary The river Dart is about 30 miles long with a fall of 1800 feet. The pattern of its drainage on Dartmoor, omitting portions controlled by jointing, is explained by a scarp-land, originating in Lower Oligocene time on a marine plain sloping east, subsequently tilted southwards. Evidence is given for a river terrace graded to 1150 feet, and for the 1000-feet and 800-feet terraces of Barrow with an intermediate 920-feet. The sea then occupied a gulf near Holne. The shore shifted to the vicinity of Teignmouth and terraces graded to about 690, 595, 505 and 430 feet were formed. The great diversion southward took place in the 430-feet period. During the Sicilian, Upper Ambersham and Ambersham terraces, the river flowed by Brixham. Later terraces followed the latest diversion to Dartmouth. A terrace along an ancient valley is ascribed to the effect of beheading. The Dart valley above 1500 feet shows signs of glaciation. The relation of eyots to nicks is considered. Finally the question of subaerial versus marine planation is discussed and old sea-levels compared with those of the Mediterranean.