THE GEOLOGY OF THE DISTRICT 51 



interbedded with layers of magnesian limestone in its lower and beds of 

 sandstone in its upper portions. The latter are frequently lenticular in 

 section as though they had been deposited in current channels excavated 

 in the clay from time to time during its formation. The marl is overlaid 

 by fine grained red sandstone which is usually classed as Bunter. There 

 is, however, no clear boundary between the two, for the sandy beds just 

 mentioned have the same characteristics, whilst the lower portions of 

 the sandstone contain much clay both in the substance of the sandstone 

 itself and as films and layers interbedded with the sandstone. Traced 

 southwards the Permian thins away rapidly and disappears in the western 

 outskirts of the city. 



It is worthy of note that Edward Wilson, who was a very careful and 

 cautious observer and had unique opportunities for examining exposiu-es, 

 would not refer these lower sandy beds to either the Permian or the Trias. 

 In 1876 the Geologists Association visited this district and in the report 

 of their visit they state quite emphatically that the passage from the 

 Marl to the Bunter is ' perfectly continuous '. After the lapse of twenty 

 years and the examination of many new exposures local geologists see no 

 reason for altering this description. 



The Trias 



The Bunter Sandstone or Lower Mottled Sandstone is well exposed at 

 a number of points on the western side of the city. It is predominantly 

 red in colour with lines and patches of yellow and greenish yellow. It 

 has a fine grain and in its lower portions contains so much clay that it 

 constitutes a good moulding sand used both for iron and bell founding. 

 These lower parts are usually well bedded often with layers of clay and 

 sometimes strings of angular pebbles. The upper portions on the other 

 hand are usually false bedded. 



The Bunter Conglomerate is predominantly current bedded though 

 occasionally well defined strata may be seen. They are coarse grained 

 and yellow though patches of red fine-grained sand occur. Pebbles are 

 always present sometimes scattered sporadically through the rock, at 

 other times concentrated in the bottom portions of the current channels. 

 A very large proportion of the pebbles consist of quartzite ranging in 

 colour from light grey to dark red, and in rare instances they have yielded 

 fossils. The remaining pebbles form a mixed assemblage including vein 

 quartz, lydian stone, Torridonian sandstone and various kinds of volcanic 

 rock. In this district they rarely exceed three inches in length. Clay 

 boulders nine inches or a foot long form an interesting feature in pits 

 where the rock is being excavated for use in mortar and plaster. The 

 outside of these is coated with small pebbles picked up by the clay as it 

 was rolled along by the currents. The junction of the conglomerate with 

 the Lower Mottled is often a sharply marked irregular hne, and con- 

 stitutes the first clearly marked break from the Permian breccia upwards. 



The Bunter as a whole varies greatly in thickness. This rises to a 

 maximum of more than 600 feet north of Mansfield. From thence it 

 also spreads out fanwise becoming thinner as it passes north, east and 

 south. Southwest of Nottingham it is 200 feet thick and at Dale it has 



