96 ME. E. L. SHERLOCK ON THE RELATIONSHIP OF THE [Feb. I9I I, 



Above the Upper Limestone another division of the Permian, 

 the Upper Marl (e 5 ), is recognized at two places (north of Carlton 

 and at Whin Common). These occurrences are mapped as lenticles, 

 and there does not seem to be any reason why they should be 

 regarded as Permian rather than Trias, especially as such lenticles 

 of marl do occur in the Bunter, even high up in the Pebble Beds (as, 

 for example, at Blidworth, east of Mansfield). The late Mr. Pox- 

 Strangways informed me that he considered these Upper Marls to 

 belong to the Bunter. 



In the north of Nottinghamshire the Lower Mottled Sandstone 

 ceases to be traceable as a separate formation. A road-cutting at 

 Spittal Hill, about a mile east of Tickhill, shows red sandstone of a 

 character intermediate between the typical Lower Mottled Sand- 

 stone and the Pebble Beds. It is coloured on the Geological Survey 

 map as Lower Mottled ; but the outcrop is marked as very narrow, 

 and is not continued beyond the latitude of Doncaster. 



(3) Yorkshire. 



North of Tickhill superficial deposits hide the upper limit of the 

 Upper Limestone, and often the lower divisions of the Permian 

 also. 



During the cutting of the new South Yorkshire Junction 

 Railway, a temporary section was exposed at Wadworth Carr, 

 about 5 miles south-south-east of Doncaster. Mr. H. Culpin, 

 who drew my attention to the section, informs me that he saw 

 here Triassic sandy strata resting unconformably on the Upper 

 Permian Marl. 



It may be that here a local unconformity occurs between the 

 Upper Permian Marl and the Bunter, similar to that already 

 described between the Lower Mottled Sandstone and the Pebble 

 Beds at Mansfield. It is, however, a striking coincidence that 

 the section is precisely on the line of the Edlington Wood fault 

 (see Geol. Surv. map, Sheet 87, S.E.). In these soft strata a fault 

 sometimes bears a close resemblance to an unconformity, and a 

 change in the direction of throw in the Permian (which would 

 apparently be necessary on this explanation) is not uncommon. 

 Instances occur at Skegby and ISTewbound Mill, where faults proved 

 in the Coal Measures are directly in line with faults throwing in 

 the opposite direction in the Permian. The curious phenomenon of 

 the reversal of the direction of throw of a fault seems to be due to 

 a, post-Carboniferous but pre-Permian movement being followed by 

 a slight post-Permian movement in the opposite direction. It 

 may be that the second movement is due to a small recovery of 

 the strata during the period of rest following the upheaval of the 

 Pennine Chain — in fact, a movement of the kind classified by 

 Ohamberlin & Salisbury under 'Mutual Adjustment of Conti- 

 nental & Oceanic Segments.' * Whatever may be the explanation, 



1 T. C. Chamberlin & E. D. Salisbury, vol. ii (1906) p. 236. 



