190 THE PERMIAN FORMATION. 



In Nottinghamshire and Lincolnshire the Magnesian Limestone series 

 consist of the following subdivisions : — (a ) 



Lower Magnesian Limestone. — The rocks of this series vary much in 

 character. Some of the beds are of a pale yellow colour and coarsely 

 crystalline; others are white or reddish and finely grained, flaggy or 

 thick bedded, sometimes false bedded, occasionally cherty or pseudo- 

 brecciated. Ordinarily this rock is a true dolomite. Sometimes, how- 

 ever, it contains a large amount of sedimentary material in the form 

 of sand, seams of mioaoeons marl, and even bands of grit and con- 

 glomerate. I observe that this fe iture is more especially characteristic 

 of the formation in its westerly limits. At Mansfield, this rock locally 

 loses its character of a true dolomite, and becomes intermixed with 

 siliceous particles in proportions up to fifty per cent. This arenaceous 

 dolomite yields the valuable and well known white and red " Sandstone*" 

 of Mansfield. These sandstones probably occur as large lenticular 

 masses, 60ft. thick or more at their maximum, surrounded on all sides 

 by dolomitic Limestone. At Shin-oaks Colliery, on the northern 

 borders of the county, the Lower Limestone proved to be 56ft. in 

 thickness: between Worksop and Mansfield the thickness of the 

 Limestone is not certainly known, but appears to lie between 70ft. and 

 80ft; 65ft. were passed through in Langwith Colliery, and from ">0ft. 

 to 00ft. of this rock are exposed in the craggy sides of the picturesque 

 ravines, known as Creswell Crags ; south of Mansfield, in the Leen 

 valley district, the Lower Limestone has an average thickness of about 

 30ft., e.g., at New Watnall Colliery it was only 23ft. ; at Kimberley, 

 Hempshill, and Newcastle Collieries, 27ft. ; and at Ciuderhill and 

 J Jest wood Collieries, 80ft. 



The Lower Magnesian Limestone dies out along a line drawn from 

 Radford to Strelley to the west of Nottingham. Along this line the 

 Limestone consists of impure sandy and pebbly flagstones. At Bobber 

 Mill (Radford) during the progress of the Leen Valley Sewage Works, 

 I noticed the dying out Limestone gradually pass, in the last 200 yards 

 of its range, from an ordinary crystalline yellow dolomite into a grit, 

 and from this into a coarsely brecciated rock, an evident marginal 

 deposit. The Lower Magnesian Limestone at its southern termination 

 l- evidently very much attenuated, apparently owing, not to subsequent 

 denudation, but to the coal measures rising up from beneatli the 

 Limestone to form aland margin on the south. Hence the Limestone 

 forms no escarpment along its south boundary. As a rule this rock 

 iB destitute oi visible traces of organic remains, and when th°se do 

 ooour they are confined to a few thin beds, and are generally in the 

 form of hollow oastB or moulds of a very tew species of mollusca, 

 ohieflj A. nun. and Myalina. At South Scarle the Lower Magnesian 

 Limestone is a cream-coloured, fine-grained, fossiliferous Limestone, 

 26ft. m thickni 



mi i. ittfl and Deryshire, Mem Geo] Burvey., W. T. 



Aveline,F.G.8 Gi of the country around Nottingham. Ditto, 2nd 1 



