Reports and Proceedings — Geological Society of London. 91 



The bands are of wide extent and are due to inflows of fresh water 

 from the surrounding hills, which from time to time spread themselves 

 far and wide over the dry portions of the desert, and were often 

 completely desiccated before reaching any pre-existing pool. Where 

 these waters evaporated the quartzose-dolomite seams were formed, 

 bearing ripple-marks and salt-pseudomorphs. The ripples indicate 

 prevalent south-westerly winds. 



2. "The Relationship of the Permian to the Trias in Nottingham- 

 shire." l By Robert Lionel Sherlock, B.Sc, A.R.C.Sc, F.G.S. 



In South Northamptonshire the Permo-Trias consists of the following 

 divisions : — 



KEUPER . . {^ ai ; 1S \ 



LWaterstones. 



Bunter /Pebble Beds. 



(Lower Mottled Sandstone. 



[Middle Marl. 

 Permian . . -I Lower Magnesian Limestone. 



[Marl Slates and Breccia locally. 



The conformability or unconformability of the Bunter to the Permian 

 has been much discussed, but it is generally considered that there is 

 a small unconformity between them. The evidence for this is the 

 appearance of an Upper Magnesian Limestone, and locally an Upper 

 Marl, between the Middle Marl and the Bunter, as the beds are 

 followed northwards, so that the Bunter appears to overlap the Permian 

 divisions from north to south. 



In this paper a section on the Great Central Railway, near 

 Annesley, is described, which shows a gradual passage from the 

 Middle Marl into the Lower Mottled Sandstone. Detailed mapping 

 on the 6 inch scale between Nottingham and Market "Warsop has 

 confirmed this conclusion. 



From Nottingham to Mansfield the Middle Marl retains a uniform 

 character and thickness, but at Mansfield it is apparently absent, 

 and the Bunter has been thought to overlap it and rest directly on 

 the Lower Magnesian Limestone. At the same place the limestone 

 becomes very sandy, forming the Mansfield Sandstone. It is shown 

 that these two phenomena can be best explained by supposing that 

 a river deposited a sand-bar at Mansfield during Permian times, so 

 that the limestone was replaced by sandstone, as was also, later, 

 the Middle Marl. The sandy representative of the Middle Marl 

 has been mistaken for Bunter, and so given rise to the appearance 

 of an overlap. 



North of Mansfield the Middle Marl becomes normal again. Near 

 Cuckney the Upper Magnesian Limestone first appears as a very thin 

 bed, and evidence is brought forward to show that the limestone arises 

 as thin lenticular bands in the Passage Bed, which develop northwards 

 into a definite bed. In precisely the same waj^ sandstone lenticles in 

 the marl in South Nottinghamshire develop into a definite bed of 

 sand-rock, called the Lower Mottled Sandstone. At first a thin Upper 

 Magnesian Limestone is found below a diminished representative of 



1 Communicated by permission of the Director of H.M. Geological Survey. 



