ROCKS OF SOMERSET AND DEVON. 379 



Here, then, we have five distinct and mappahle divisions of the Trias, 

 occupying an area of about 500 square miles — that is, between 

 Watchet and Minehead on the north and Paignton and Axmouth 

 on the south, and between Durston on the cast and Wiveliscombe 

 on the west. Of this area, however, the only member of the 

 Trias of Devon and Somerset that we can speak confidently about, 

 regarding persistence, viz. the Upper Marls, occupies about a half. 

 Whether borings made at Taunton or Axmouth would cut through 

 all the other divisions in vertical succession, beneath the Upper 

 Marls, or subsidence over the whole area proceeded unequally, so 

 that the other divisions were local, and conformably overlain in some 

 places, and overlapped in others, by the marls resting on the older 

 rocks, as we proceed eastwards, is entirely conjectural. 



"We will now treat briefly of each division in descending order, 

 beginning with 



•tv 



The Tipper Marls. 



These, from their outcrop beneath the Penarth, or Bhretic beds, 

 cover a larger area, superficially, than any other member of the 

 series. Between Durston and Langport, East Ninohead (north 

 of Wellington), and the Lias plateau of Hatch Beauchamp, Sidmouth 

 and Axmouth, they extend, concealed by the overlapping Upper 

 Grecnsands of the Black Downs, over many places between Taunton 

 and the coast. 



They consist of red marls, variegated greenish grey, sometimes 

 with slightly bluish bands in their upper portions — locally, as at 

 Dumpdon, north of Honiton, greenish grey, mottled red. In the 

 coast sections of Watchet and South Devon they are intersected, 

 in places, by numerous gypseous veins; occasionally, as on the 

 coast* west of Sidmonth, potato-stones arc to be found in them. 

 In the coast section, in their lower beds, we find them retaining 

 their marly structure, but losing their calcareous nature, and in the 

 beds immediately overlying the sandstones, in places, almost passing 

 into rock-sancl ; in the cuttings north of Sidmouth, on the branch 

 line, a thick bed or two of sandstone occurs in them near their 

 junction with the underlying sandstones. Many disused marl-pits 

 are to be met with over the area they cover. 



TJiicJcness. — In estimating the thickness of these beds we cannot 

 take a persistent dip across the wide area they cover, ignoring 

 probable undulations and faults; this would give an enormous 

 thickness, in excess even of that which we should infer from their 

 exposure on the coast, where we have a distance of about 8 miles 

 between their outcrop south of Axmouth and the mouth of the 

 river Sid, where they overlie the sandstones. In this distance their 

 continuity is broken by a large fault at WhiteclirT, near Seaton. A 

 considerable allowance must be made for the synclinal trough which 



* Pseudomorphs of rock-salt crystals have been obtained between Peak and 

 High-Peak Hills and near Salcombe mouth in the coast-section marls by Mr. 

 Ormerod. the author, and others. 



