﻿Correspondence — E. Wilson. 239 



my intention to refer to, but not to sanction this idea, as an impartial 

 critic will, I think, readily perceive. To speak candidly, these beds 

 require further study before their precise relationship can be satis- 

 factorily determined. 



While by no means prepared to affirm that " a perfect conformity 

 exists between the Magnesian Limestone and the New Red (meaning 

 Bunter) Sandstone in the N.E. of England," I differ widely from 

 Mr. Aveline, in his view that there is proof of a great break between 

 these formations. In support of this position, he cites the successive 

 overlaps of the Upper Permian Marls and Limestone, Middle Marls 

 and Lower Limestone, by the Bunter Sandstone, going south, from 

 the district north of Worksop, to the latitude of Nottingham. 



But has it ever occurred to him that all these cases may be of the 

 nature of conformable overlaj)s ? My own experience of the Marl 

 Slate, Lower Magnesian Limestone, and Middle Marls of this dis- 

 trict, founded on accumulated data, not attainable in Mr. Aveline's 

 time, convinces me that there is a general tendency in these sub- 

 formations to attenuate inter se, as also to become coarser in texture, 

 when followed from the north or north-east towai'ds the south or 

 south-west. To cite one or two instances of this. The attenuating 

 Lower Magnesian Limestone, which, for the last few miles of its 

 southern extension, has become in great part a flaggy, sandy, and 

 even conglomeratic rock, dies out as a coarse brecciated littoral 

 deposit. The Middle Marls' have just previously faded away. 

 Simultaneously, the Marl Slate series has diminished from 60 or 70 

 feet of shales (mostly), to 20 feet of sandstones (mostly), and from 

 that to nil, when the basal Permian, a coarse brecciated rock, comes 

 directly beneath the last degraded relic of the Magnesian Limestone.^ 

 These facts in my opinion point to the existence of an inter-Permian 

 marginal barrier immediately to the south, and somewhat more 

 remotely to the west, and to successive synchronous increments of 

 subsidence in the opposite directions. 



1 do not believe that any of the above rock series ever 

 stretched appreciably further south than they do now. Extending 

 this reasoning to the Upper Magnesian Limestone and uppermost 

 Permian Marls (as to which my data is admittedly more limited), 

 I would suggest that they never extended appreciably further south 

 than they respectively do now, and that their southerly disappear- 

 ance is due to analogous causes. Successive increments of subsidence 

 in a north-easterly direction will account for these phenomena. 

 Inter-Bunter-Permian denudations will not. Small local irregu- 

 larities undoubtedly exist between the Lower Bunter and (the 



i_ The persistent outcrop of this thin and denudable series between the Mag- 

 nesian Limestone and Lower Bunter formations negatives the idea of any great 

 amount of denudation between these two periods in this neighbourhood. 



2 It thus appears that the Magnesian Limestone overlaps its own Marl Slate base, 

 with which it appears to be perfectly conformable. Yet no one supposes there is a 

 '• great break " between them. Had, however, this overlap been concealed by a cloak of 

 Lower Bunter, that formation, and not the Magnesian Limestone, would have been 

 credited therewith, and the fact cited as an additional proof of the great break 

 between the Permian and New Ked Sandstone periods. 



