TEIASSIC BKECCIAS AND CONGLOMERATES OP SOUTH DEVON. 79 



belief in the causal association of igneous action. " Near Tiverton 

 the igneous rocks would seem to have been ejected after a certain 

 thickness of conglomerate had been accumulated. . . . Near Exeter 

 igneous action seems to have accompanied the earliest deposit " *. 

 He also directs attention to the fact that " the igneous rocks asso- 

 ciated vrith the lower part of the red sandstone series near Exeter 

 . . . .occur in the prolonged direction of the granitic bosses and 

 elvans extending from the Scilly Isles to Dartmoor, themselves 

 apparently ranging in a line through which trappean matter had 

 been previously erupted " f. 



Next, discussing the occurrence of fossiliferous Devonian frag- 

 ments in the Trias of Tiverton, the late Kev. W. Downes, E.G.S., 

 was led to postulate the existence of " an active volcano upon the 

 coast of the early Triassic sea " ^ ; and in 1885 Mr. A. Somervail 

 suggested a volcanic origin for the basal breccias of the Sonth-Devon 

 Trias §. 



The highly interesting group of rocks which have been classed as 

 the felspathic traps of Devonshire are commonly, though not uni- 

 versally, associated with the South-Devon Trias. They make their 

 " appearance at or near the junction of the Carboniferous and 

 Triassic formations, from Washiield, near Tiverton, on the north, to 

 Haldon on the south. They extend westward along the strip of 

 Trias which runs from Bradninchto Jacobstow, and occur frequently 

 along both north and south lines of junction of the two formations 

 as far as Green slade near North Tawton " ||. 



To this it must be added that a member of the series occurs 

 associated with a Triassic outlier at Cawsand on the shore of Ply- 

 mouth Sound, and that a dyke of mica trap at Roseash, unconnected 

 with Trias, appears to be of similar character %. 



These traps are in part antecedent to, and in part contemporaneous 

 with, the breccias and conglomerates which we are considering. 

 They are pre-Triassic, because their fragments are found in these 

 beds. They are continuous into the Triassic era, because at certain 

 points they overlie and alter the Trias. 



They are commonly red or reddish-brown in colour, but by no 

 means universally so, and appear in this respect to have been 

 somewhat influenced by the Triassic rocks in situ, as well as in the 

 breccias and conglomerates, where, indeed, they display this colour- 

 character more constantly. The trap of Cawsand very well illustrates 

 this Triassic influence. In contact with the remnants of the Triassic 

 outlier it is red, but the veins sent off into the Devonian rocks for a 

 considerable distance become drab and grey. The Roseash rock is 

 yellowish brown ; so is much of the Killerton, where the rock 

 occurs in mass. 



One of the most important points connected with the chronology 



* Report, p. 215. t Report, p. 216. 



J Trans. Dev. Assoc, xiii. p. 297. § Ibid. xvii. p. 2Sn. 



II *' On the Feldspathic Traps of Devonshire," W. Vicary, F.G.S., Trans. 

 Dev. Assoc, i. pt. iv. p. 43. 



^ Trans. Dev. Assoc, xvi. p. 498. 



