The Unroofing of the Dartmoor Granite and the Distribution of its Detritus in the Sediments of Southern England

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Abstract
The Hercynian age of the Dartmoor granite is generally admitted, but little information has hitherto been available concerning the period at which this granite became contributory to sediments. The work described in this paper is an attempt to supplement this information by direct appeal to the sedimentary formations in the South of England. These have been systematically searched for detrital mineral species which, in respect of associations and both specific and varietal features, are in consistent agreement with the assemblage of accessory minerals characteristic of the Dartmoor granite as described by Dr. A. Brammall (1928). Both the coarse and fine constituents of the Permo-Triassic strata in the West of England have been investigated within recent years. In the South of England pebble-beds of post-Triassic age are rare. For the special purposes of this paper, strata investigated by other workers have been re-examined, and gaps have been bridged by the study of intervening horizons. The strata sampled and examined in the laboratory range from the base of the Watcombe Clay (Permian) to the Pliocene of the North Downs (Diestian), of St. Erth, and of St. Keverne in Cornwall. It was reasonable to assume that, in the chain of evidence sought, the first and strongest link would be found in the strata nearest the granite outcrop. West of the granite, however, the only strata known to be of post-granite age comprise a few small outliers of Permian and Pliocene. The samples collected (about 250 in all) are fairly representative of the stratigraphical