100 Mil PEBMIAM FORMATION. 



to the Permian, hut to the oarboniferous system, for they have showu 

 that the maimesian limestone is unconformable to the strata beneath ; 

 that those red rocks and the limestone often strike in different and 

 sometimes in diametrically opposite directions; that, except in local 

 cases, these underlying sandstones and shales have the common 

 characteristics of, and are perfectly conformable to, the rocks of the 

 carboniferous formation ; and that they often contain characteristic 

 coal plants, or carboniferous marine mollusca. Neither also in Notts or 

 Derbyshire, either west of the magnesian limestone escarpment, or in 

 vertical explorations for coal to the east, have any red sandstones or other 

 rocks that could possibly be considered " Rothliegende " been met with at 

 the base of the Permian rocks. The marl slates with their basement 

 breccia are the lowest Permian strata in this district we know anything 

 about. The narrow fringe to the magnesian limestone coloured on the 

 geological survey maps as " lower red sandstone " really consists of 

 these last-named rocks ; while the two small areas similarly coloured 

 between Derby and Ilkeston, as I have heretofore shown, consist in one 

 place (Morley) of brecciated lower bunter sandstone and purple lower 

 coal measure shales, and in the other (Dale Mill) of massively bedded 

 lower coal measure sandstone, (a) 



The study of this subject shows that in our district the following 

 very dissimilar rocks have, at one time or another, been mistaken for 

 " Rothliegende," viz., millstone grit, lower,middle, and upper coal measure 

 sandstones and shales, marl slat is, and breccia, and lower bunter 

 sandstone and breccia, in fact almost every imaginable coarse or red 

 rock belonging to the contiguous formations, the horizon of which had 

 aot at the time been clearly defined. I venture to affirm that, with 

 die exception of the marl slate breccia in Notts, and the very thin and 

 local deposits of quicksand in Yorkshire and (?) Durham, there are no 

 coarse, or red, or yellow coloured Permian rocks beneath the magnesian 

 limestone. Whatever may eventually turn out to be the case with the 

 " lower red sandstones" in other parts of England, the " Rothliegende " 

 of the north-east of England mast certainly be considered as a thing 

 of the past. 



Classification. 

 The Permian rocks of the north-east of England are now generally 

 classified as follows : — f b ) 



Upper Permian Marls. 



Upper Magnesian Limestone. 



Middle Permian Marls. 



Lower Magnesian Limestone. 



Marl Slates. 



Quicksand. 



I now proo iribe these sub-divisions as they exist in the 



above area, beginning with the lowest and oldest. 



- •!! ill.' Oncomformability >>f the Keuper and Hunter, by E. Wilson, F.G.S., 

 Geological Magazine, vol. vii., lbMO, p. :J08. 



l iiis classification holds yood in a goneral way for Yorkshire and .Notts, 

 but requires modification for Durham, (See pp, 13-14.) 



