312 Bernard Robson — Permian Breccias of S. Devon Coast. 



inches across, but I saw a limestone pebble measuring 1 ft. by 4| in. 

 The fragments, mostly angular, are chiefly Devonian limestone 

 (which occurs in situ within | mile). In addition vein quartz 

 and purplish red sandstone occur, 



2. Preston Cliffs {Tor Bay). 

 In these cliffs, below the Volunteer Battery, at the northern end 

 of the sea wall, which extends northwards from Red Cliff, six feet of 

 breccia are exposed at the foot of the cliff, overlain by orange-red 

 current-bedded sandstone or rock-sand, and the dip of the beds is 

 gently southwards. (This direction of dip is unusual.) The breccia 

 is fine, the rock fragments being from 1 to 4 inches, exceptionally 

 6 inches long, and several fragments of the typical red quartz-porphyry, 

 which is a very frequent and characteristic constituent of these breccias, 

 were seen, one of them 4 inches long, besides which purplish sand- 

 stone and (not abundant) limestone fragments occur. The small 

 size of the quartz-porphyry and scarcity of limestone fragments are 

 noteworthy, 



3. Petit Tor Crags,^ Babbacombe Bay. 

 In the conglomerate of Petit Tor Crags and in the talus of fallen 

 blocks of conglomerate at their foot probably nineteen-twentieths of 

 the subangular fragments consist of grey Devonian limestone, often 

 visibly fossiliferous, besides which there occur reddish quartzite and 

 reddish sandstone and a few pieces of red quartz-porphyry, all in a 

 very hard coarse sandy matrix. The fragments are mostly from 1 to 

 6 inches in diameter, though liaiestone boulders up to 1ft. Sin. 

 by 1 ft. 1 in. by 8 in. are not uncommon. Thin beds of breccia 

 alternate with layers a foot or two thick of finer material. The 

 abundance of Devonian limestone is not surprising, as it occurs in 

 situ in Petit Tor close by. 



4, Watcombe Cove. 



At the south side of the cove the breccio-conglomerate is thrown 

 down by a fault against the Watcombe Clay,* and dips at 45° 

 northwards. By far the greater proportion of the fragments consist 

 of fossiliferous Devonian limestone, of which an unusually large 

 block measured 1ft. 10 in. by 10 in. by 6 in. -{■ (partially 

 embedded). Next in abundance (but at a long interval) come 

 fragments of reddish and purplish sandstone, boulders resembling 

 Permian felspathic trap, and a few bits of vein quartz. 



A microscopical section of the matrix of the breccia-conglomerate 

 at Watcombe Cove shows large limestone fragments, bits of slate 

 and grit, many angular quartz sand grains, and abundant fragments 

 of volcanic rock. One of the volcanic fragments is crowded with 

 minute spherulites, showing well-defined black cross by polarized 



1 See Plate XXI, Fig. 2, and for section of Petit Tor see W. A. E. Ussher, Geol. 

 of Torquay, Geol. Survey Mem., 1903, p. 109 ; and " Coast Section from Babbacombe 

 to Watcombe," by W. A. E. Ussher, Proc. Geol. Assoc, vol. xvi (1900), p. 434. 



* W. A, E. Ussher, " On the Age and Origin of the Watcombe Clay " : Rept. 

 and Trans. Devon Assoc. Adv. Sci., ix (1877), p. 298; also section in Proc. Geol. 

 Assoc, xvi, p. 434, 



