Abstract

In this paper the Lower Carboniferous formation bordering the granite of Dartmoor for a length of about 4½ miles, between Whiddon Down on the west and Butterdon Down towards the east, are the only stratified rocks dealt with; but the nature of, and variations found in the granite south of the Carboniferous rocks are also considered. The area examined includes part of the deep gorge of the River Teign, known as Fingle Glen, between Hunter's Tor and about a mile east of Fingle Bridge, or rather more than two-thirds of the length of the gorge.

The area described is covered by the 6-inch Ordnance Survey quarter-sheets of Devon:—LXXVII, S.E.; LXXVIII, S.W.; LXXVIII, S.E.; XC, N.W.; and XC, N.E. Of these quarter-sheets only the whole of LXXVIII, S.W. is covered; but portions of the other sheets are required to describe the area in a comprehensive manner.

In the area dealt with, the Lower Carboniferous, or Culm Measures, may, as found by Mr. R. H. Worth (10) in the granite-border south-west of Okehampton, be divided into two groups: the Lower Aluminous Series and the overlying Calcareous Series. Both these series of rocks have been affected by contact-meta-morphism from the granite.

The Lower Aluminous Series in this district can be divided into zones: the lower zone characterized by the occurrence of much segregated or disseminated iron-pyrites, and the upper zone in which chiastolite is found.

The Lower Aluminous Series passes upwards by gradual change, and without any physical feature, from black slates into