GEOLOGY 



overlapping the eroded Permian. Traced to the east by borings the 

 base descends at Gedling to 250. feet below O.D., at Thurgarton to 

 656 feet, at South Scarle to 1,503 feet, these being along a north-east 

 line ; at East Retford to 730 feet and at Southcar to 1,165 ^ eet - 



In all the above cases the Bunter rests on the Permian, but in the 

 south it passes beyond this limit and rests on various parts of the Coal- 

 Measures. It is here carried down to a lower level partly by erosion of 

 its support and partly by faulting. At the Radford gasworks the basal 

 breccia was found at about 60 feet above O.D. From this point it 

 gradually rises westward to 220 feet in Broomhill Plantation and to 320 

 feet at Catstone Hill outlier. Farther south it is affected by the first east 

 and west fault, and is found at Clifton Colliery 74 feet below O.D., at 

 Highfield Park 167 feet below O.D. a difference due in part to a greater 

 erosion of the underlying coal strata to the west. The base of the 

 Bunter is not seen again in the county, but at a boring for water at 

 Wilsthorpe, just on the Derbyshire side of the Erewash, the top of the 

 whole Bunter is 153 feet below O.D. 1 ; how much lower the base may be 

 is not known. South of another fault the base of the Bunter is found to 

 be 367 feet below O.D. in the Chilwell boring, 377 feet at Clifton, 579 

 feet at Ruddington, 602 feet at Edwalton and 888 feet at Owthorpe 

 all below O.D. Those figures show a slope to the east at a lower 

 level but of a slower rate than between Gedling and Thurgarton but 

 owing to there being known post-Triassic faults in the district, e.g. one of 

 275 feet throw at Clifton Colliery, it is impossible to be certain of any 

 interpretation of this. Nevertheless it suggests that a pre-Triassic valley 

 of erosion may be the cause. 



The Lower Red Sandstone usually contains no pebbles and the grains 

 of sand are finer than in the Pebble Beds. They are coated with a film 

 of red hsmatitic colouring matter which may be removed by hydrochloric 

 acid, leaving them white. This bleaching action by other acids takes 

 place sporadically in nature, and gives a mottled appearance to the rock. 

 There is in many cases much falsebedding. Although the body of the 

 rock does not usually contain pebbles there is found at or near the base in 

 several localities a bed of breccia or conglomerate. Such a breccia, 5 to 

 8 feet thick, occurred in the excavations for the gas works at Old 

 Radford. 2 In the brickyard south of the railway at Cinderhill this has 

 long been noticed, and at one time was thought to represent the line of 

 separation between Trias and Permian. In the Hempshill railway cutting 

 described by Mr. Wilson 3 this semi-basal breccia ' is alternately sandy, 

 marly and calcareous and it contains semi-angular green, blue and purple 

 slates, more or less rounded grits, quartzites, and numerous white and 

 discoloured slabs and nodular balls of fossiliferous Carboniferous Lime- 

 stone Chert.' It is plain that new sources of material were available for 

 its production. Similar pebbly bands have been met with at Annesley 



1 Shipman, 'Geol. of Sandiacre,' Trans. Nott. Nat. Sue. for 1891 (interpretation modified). 

 8 Shipman, Trans. Nott. Nat. Sac. for 1889. 

 8 Quart. Journ. Geol. Soc. vol. xxxii. 



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