GEOLOGY 



coals have originated from the growth of forests in situ, and were buried 

 by beds of sand when the delta or coal jungle subsided and its surface 

 was covered by water. The succession of coal seams through a great 

 thickness of deposits points to a prolonged and extensive subsidence, 

 marked by pauses sufficiently long for the silting up of the lagoons and 

 jungles. 



But while we have proof that these coal seams were formed in situ, we 

 have evidence likewise that some of the coal was formed by the drifting 

 of vegetation into lakes by rivers and floods. The conditions of soil and 

 climate must have been favourable to the growth of the prodigious 

 masses of vegetation which, whether swept out to sea by floods or 

 accumulated in forests and jungles, became submerged and were finally 

 compressed and mineralized into our seams of coal. 



PERMIAN 



The Coal Measures are overlain unconformably by a series of lime- 

 stones, sandstones and marls which belong to the Permian series. The 

 name Permian was given to these rocks because of their wide develop- 

 ment in the Russian province of Perm. Compared with the Carboniferous 

 the Permian rocks are comparatively barren of life. Their fauna contains 

 an admixture of carboniferous types with others which are more akin to 

 those of the Mesozoic which succeeded them. The general character 

 of the Permian rocks and their impoverished fauna have been considered 

 as evidence that they were formed in isolated basins or inland salt lakes 

 in which the water underwent evaporation until chemical precipitation 

 took place. In Derbyshire the Permian formation covers no large extent 

 of the surface. It is found only in a narrow strip running north and 

 south near the eastern boundary of the county. The high ground which 

 it occupies forms a well defined escarpment resting on the Coal Measures 

 below. This escarpment and the lower lying land of the Coal Measures 

 are well seen between Chesterfield and Bolsover, and form a well known 

 feature in the landscape. The Permian rocks of Derbyshire consist 

 mainly of the Lower Magnesian Limestones and Sandstones, the Upper 

 Magnesian Limestone being absent. 



In some places underneath the Magnesian Limestones there are 

 present beds of coarse sandstone and conglomerate with marls and 

 thin bands of limestone, and sometimes coarser beds containing frag- 

 ments of sandstone and water-worn fragments of Mountain Limestone. 

 Their maximum thickness is about 15 feet. 



It is difficult to estimate the thickness of the Magnesian Limestone 

 owing to the false bedding which occurs in it, and the variations in 

 character which take place at short distances render it impossible to 

 correlate the beds. Near Bolsover it is supposed to be from 100 to 

 200 feet thick, but further south near Eastwood to be only about 30 

 feet. It has been largely quarried at Bolsover, Langwith, Stoney 

 Haughton and Pleasley. It varies lithologically from a crystalline 

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