Vol. 67.] PERMIAN TO THE TRIAS IN NOTTINGHAMSHIRE. 77 



views held by some geologists, that the Permian was perfectly 

 conformable to the Trias in the Nottingham district. To this he 

 objected, on the ground that the Bunter overlaps the divisions of 

 the Permian successively from north to south. Wilson, 1 iu reply, 

 pointed out that the successive disappearance of the Permian divi- 

 sions might be due to conformable overlap, and as an illustration, 

 he cited the case of the thinning of the Marl Slate Series 2 from 

 60 or 7" feet of shales to 20 feet of sandstones and then to nil, 

 between the basal breccia and the succeeding limestone. As a 

 result, the Ma^nesian Limestone appears to overlap the Marl 

 Slates ; he remarks, however, that this points, not to a break, but 

 to the presence of a Permian shore-line to the south. 



The Rev. A. Irving 3 supported Wilson, and thought that, while 

 there might be a slight unconformity locally between Permian and 

 Bunter, such breaks were not greater than those that occurred 

 between individual beds of the Permian, and especially between 

 the Middle Marls and the Lower Limestone. In Aveline's 4 reply 

 he states that he did not consider the Permo-Bunter break an 

 important one, and would not give an opinion as to whether the 

 break is more important than that between the Lower Limestone 

 and the Middle Marls. He considers the relationship of the Permian 

 to the Trias an important problem yet to be worked out : — 



' If a perfect passage from the one up into the other was found, it would go- 

 far to settle the question. As far as 1 know, that passage has not been found, 

 and, I contend, it does not exist in the neighbourhood of* Nottingham.' 



As will be seen farther on, this passage has now been found. 



After Aveline's second letter the discussion ended for the time, but 

 was revived in 1879-82 round the question of the age of the Pennine 

 uplift and the correlation of the Lancashire and Yorkshire deposits. 

 Dr. Irving, 5 who in the interval had been examining deposits in 

 other districts, modified his view of the relationship of the Bunter 

 to the Permian at Nottingham and considered that there must be a 

 break between the two. The discussion need not be further 

 referred to here, as it does not bear closely upon the nature of the 

 Permo-Bunter boundary, but rather on the age of the Pennine 

 uplift. 



Other works will be mentioned as occasion arises, and a complete 

 list of references will be found at the end of this paper. 



Although the views here expressed on the relations of the 

 Permian and the Trias are opposed to those of Aveline, who mapped 

 much of the area for the Geological Survey, his facts are in no case 

 disputed, but it is hoped to show that new evidence leads to a 

 different interpretation of his results. 



» Geol. Mag. dec. 2, vol. iv (1877) pp. 238-40. 



2 See p. 79 for table of strata. 



3 Geol. Mag. dec. 2, vol. iv (1877) pp. 309-12. 



4 Ibid. p. 380. 



5 Ibid. vol. ix (1882) p. 163. 



