386 Horace B. Woodward — On the Permian and Trias. 



In our tables of British ' strata we generally find a classification 

 similar to the following : — 



rKed and Variegated Marl. 

 Keuper < Lower Sandstone and Marl. 

 (Dolomitic Conglomerate. 

 Trias ^ (Muschelkalk wanting in England.) 



IrUpper Mottled Sandstone. 

 Bunter -< Pebble-beds. 

 ^_ (Lower Mottled Sandstone. 



f Upper or flipper Red Marl and Sandstone. 



I Miignesian J Upper Magnesian Limestone. 



. I Limestone j Lower Red Marl and Sandstone. 



Permian^ Series. (Lower Magnesian Limestone. 



I R thl' w dp I ^^^ Marl, Sandstone, Breccia and Conglomerate. 



For this series the term " Poikilitic " has been employed by Prof. 

 Phillips ; and in his recent work on the " Geology of Oxford and 

 the Valley of the Thames," he has treated all the beds "between the 

 Coal and the Ehaetic base of the Lias as one great physical 'Poikilitic' 

 series." He observes (p. 88) that " in some respects and in some 

 districts it is, however, more convenient to adhere to the old estab- 

 lished alliance of the Permian many-coloured deposits, with the 

 variegated sandstones and clays of the New Eed series ; for the 

 pTiysical history of these two great groups is, on the whole, one 

 great sequence of natural operations. There are indeed cases, as in 

 Lancashire and Cheshire, and in a less degree in Derbyshire, where 

 a kind of gradation appears between the Coal formation and the 

 Permian sandstones, which are locally conformed to it ; so that, in 

 fact, we shall do wisely to adapt our classification to the region 

 which specially engages attention, for local description and limited 

 inference." 



In East Yorkshire there is considerable similarity between the 

 beds at the base of the Permian series and those at the top of the 

 Coal Measures, and the beds have been differently classified in places 

 by geologists.^ 



Prof. Hull, however, believes that there is an unconformity 

 between the Permian and Carboniferous rocks in Lancashire and 

 Yorkshire.^ 



It is considered by some that the difierent members of the Permian 

 formation are not strictly conformable to one another. A most de- 

 cided instance of unconformity is stated to be in the railway-cutting 

 at Tadcaster. "The Middle Marl has there thinned away to a mere 

 seam, so that the Upper I<imestone rests almost directly on the 

 Lower, and at the base of the former there is a thin bed of gravel 

 formed of Lower Limestone pebbles."* 



In isolated masses, as might be expected, it is not always easy to 

 distinguish between the Permian and Triassic beds. Tlius certain 



1 See Mr. Bristow's " Tables of Strata" (published by Stanford.). 



2 See Kxplanation of Quarter Sheet 98 S.E. of the Geological Survey Map of 

 England, pp. 28, 29. 



■^ Quart. Journ. Geol. Soc, vol. xxiv. p. 327. 

 * Explanation of Quarter Sheet 93 S.W., p. 10. 



