The geology of the Devonian and carboniferous rocks of the north-west Border of the Dartmoor Granite, Devonshire
A stratigraphical succession of four lithological series has been established within the country rocks bordering the north-west corner of the Dartmoor granite mass. Upper Devonian Slates crop out to the south of the main Culm Measures boundary whilst to the north a series, in part of Famennian age, occurs as inliers in the Culm Measures. This series, here termed the Transition Series, is gradational in lithology between the Upper Devonian Slates and the Lower Culm Measures. The Lower Culm Measures, which are succeeded with a marked change in lithology by the Upper Culm Measures, occur in two main outcrops, and each is followed to the north and south by the Upper Culm Measures. Facies changes have been recognised in both divisions of the Culm Measures. 
 
Dolerite dykes and sills, with some spilitic lavas and pyroclastic deposits, are virtually confined to the Lower Culm. Sills in the southern outcrop were probably emplaced before the deposition of the Upper Culm sediments.