A HISTORY OF DERBYSHIRE 



shales. The north side is formed of a dip slope of a bed of sandstone 

 which crops out from under the shales. The river runs along the top of 

 the lower sandstone with a steep cliff of shale on the south, which it is 

 undermining and wearing backwards. 



A third class of valley has been caused by streams flowing down the 

 escarpment of one of the parallel valleys and cutting back into the hill 

 until at length a transverse valley is formed. 



The oldest rocks in the county are found in the hilly districts. 

 Their position with regard to the newer rocks by which they are 

 surrounded and the folds into which they have been bent afford evidence 

 of the Pennine upheaval and the subsequent denudation which the 

 rocks have undergone. The sedimentary rocks which were deposited in 

 horizontal beds have, subsequently to their formation, been bent into 

 numerous folds by lateral pressure. Consequently a bed may be hori- 

 zontal in one place and inclined to the horizon in another. The amount 

 of inclination or dip may also vary from place to place. A horizontal 

 section through the country would show a series of arches or anticlines, 

 in which the strata dip away from a point to the east and west, and of 

 troughs or synclines, in which the strata dip towards a point from the 

 west and east. A comparison of several sections parallel to one another 

 shows that the anticlines and synclines are bent over lines or axes, which 

 are called anticlinal and synclinal axes. Where the rocks have been 

 also folded by a second pressure almost at right angles to the first they 

 form domes and basins. In the former they dip away in all directions 

 from a central point or line, in the latter they dip from all sides to a 

 central point or line. 



A well marked anticline passes through the district in a north- 

 westerly direction. The beds dip steeply to the west under the Coal 

 Measures of Lancashire and Staffordshire, and with a more gentle dip to 

 the east, under those of Yorkshire and Derbyshire. The Coal Measures 

 of East Derbyshire in their turn dip under the Permian or Magnesian 

 Limestone series. In the northern part of the county a dome-shaped 

 mass of mountain limestone has been brought up. The severed strata 

 on the west and east sides of the anticline which were once continuous 

 across the arch have been removed by denudation which has not only 

 laid bare the mountain limestone, which is the lowest rock reached in 

 Derbyshire, but also removed a small thickness of the uppermost beds of 

 limestone. If we were to start on the mountain limestone and travel a 

 short distance in a westerly or easterly direction we should pass over the 

 various members of the Carboniferous series of rocks in succession up to 

 the Coal Measures, and on the eastern side of the county should arrive 

 at the Permian limestone. 



A smaller anticline parallel to that of the Pennine Chain passes 

 through Ashover. At Matlock the limestone dips to the east beneath 

 the Yoredale Shales and Millstone Grit series which form a small basin 

 and soon dip west, and then roll over in an anticline and dip beneath the 

 east Derbyshire coalfield and Permian rocks. 



