150 E. C. Martin — New Red Gravels of the Tiverton District. 



III. — The New Red (Permian) Gkavels of the Tiverton District. 



By Edgar C, Martin, B.Sc, A.I.C. 



Introduction. 



AMONGST the Lower New Eed deposits of the Tiverton area are 

 loose rubbly aggregations of angular and subangular fragments 

 of grit and sandstone of all sizes in a loose earthy or sandy matrix.' 

 These deposits, which seem best described by the term gravel, rest 

 unconformably on the grits and shales of the Culm-measures, from 

 which they appear to have been largely derived. In the deeper areas 

 of deposit, further from the Cxilm margin, they pass into finer breccias 

 and sand.* . These gravels were formerly regarded as superficial deposits, 

 and it has been suggested that they may be Boulder-clays.^ Detailed 

 mapping, however, proved their distinct connection with the Lower 

 New Red Sandstones and breccias, and they have been found in places, 

 as at Washfield and Silverton, underlying the trap, which corresponds 

 to the German Permian Melaphyre (Middle Sotern) ; hence they are 

 now regarded as deposits of Permian age. 



About forty years ago Mr. J. T, Underbill found amongst the 

 fragments in the Exeter Hill gravel-pit, Tiverton, some with an 

 assemblage of Upper Devonian fossils. These were placed in the 

 Exeter Museum, where, some time later, they attracted the attention 

 of the Rev. W. Downes. On the occasion of the construction of the 

 Exe Vallej' Railwaj' he examined the cuttiugs between Tiverton and 

 Bolham and noticed fragments of grit with Spirifer Ferneuili, Murch., 

 Stropholosia productoides, Murch., sp., and other Pilton fossils.* 

 These fragments wei-e associated with pieces of trap, and having 

 regard to the proximity of the Washfield trap, Downes was led to the 

 conclusion that the Devonian fragments were ejected during the 

 volcanic outbursts. 



The present investigation was undertaken at the suggestion of 

 Mr. Underbill with the object of examining the whole area where the 

 gravels occur in order to find how far Devonian fragments could be 

 traced, and in the hope of thi-owing light on the source from which 

 these fragments have been derived. 



In the following account the area has been divided into districts, in 

 order that the places mentioned may be more easily found on the map. 



1. District north-west of Tiverton. 



2. District north-east of Tiverton. 



3. Butterleigh District. 



4. Silverton and Braduinch District. 



5. Thorverton District. 



The first three districts are included in Sheet 310 of the Ordnance 

 Survey (1 inch scale), and the last two districts in Sheet 325 of the 

 Geological Survey. 



1 Quart. Journ. Geol. Soc, 1876, pp. 387-389. 



- Memoirs of the Geol. Survey, Exeter District, 1902, pp. 29, 33. 



' Geol. Mag., 1872, p. 574:: " Boulder-clay in Devonshire." 



* Rev. W. Downes, B.A., F.G.S., "On the occurrence of Upper Devonian 

 Fossils in the component fragments of the Trias near Tiverton " : Transactions of 

 the Devonshire Association, 1881. 



