THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE II. VOL. 1. 



No. IX.— SEPTEMBER, 1874. 



I. — Eemarks upon the Eelations and Grouping of the Permian 



AND TrIASSIC EoCKS. 



By Horace B. Woodward, F.G.S., 



Of the Geological Sui'vey of England and "Wales, 



THE physical history of the Permian and Triassic rocks of Great 

 Britain has been told by Professor Eamsay, who has pointed 

 out that the beds were deposited in great inland lakes, for the most 

 part salt.^ Without entering into the consideration of this subject, 

 there seems to be much that requires to be unravelled in regard to 

 the structure of the beds individually, and much that has yet to be 

 explained in regard to the relations and grouping of the rocks. 



In their general lithological characters there is a marked simi- 

 larity throughout the Permian and Triassic series, consisting as they 

 do of red sandstones, conglomerates, and marls, with occasional beds 

 of limestone. Originally, the whole of these rocks were classed as 

 New Eed Sandstone, and the name " Poikilitic," subsequently sug- 

 gested by Conybeare, as an equivalent term, is one that possesses 

 many advantages to recommend it. The ideas that as students we 

 derive from our text-books are that the Permian beds form a group 

 overlain unconformably by the Trias, and sufficiently distinct 

 in their palasontological aspect to be classed as Palaeozoic ; whilst 

 the Triassic beds (classed as Mesozoic) are divided into Bunter and 

 Keuper, and are regarded as equivalents of the same beds on the 

 Continent — the Muschelkalk being considered to be absent in the 

 British area, and the Keuper beds to rest unconformably upon the 

 Bunter. 



The exact evidence upon which these ideas are based appears, 

 however, to be conflicting when it comes to be examined into, and 

 frequently to have but a very local significance, as more recent re- 

 searches have tended to show. It may therefore be interesting to 

 draw attention to some of the points of the case, and to notice 

 some of the later opinions expressed. 



The history of the researches into the Permian and Triassic beds 

 has been given at length by Professor Hull in a work detailing the 

 investigations of the Geological Survey in the midland counties of 

 England : it will suffice therefore to refer to his Memoir^ in regard 

 to this part of the subject. 



1 Quart. Journ Geol. Soc, vol. xxvii. pp. 189, 241. 



2 J'ublished by the Geological Survey. 



DECADE II. — VOL. I. — NO. IX. 25 



