GEOLOGY 



Perhaps the most instructive of these localities is that at the south- 

 west corner of Wollaton Park. Here the pebbles are large, various, 

 close together and with a strong calcareous cement, the rock in every 

 respect differing from any near the Hemlock Stone only if miles away, and 

 resting on a lower part of the Bunter Series seen in the sand pit below. 

 Elsewhere also it rests on various parts of the Bunter, showing the un- 

 conformity between the two series, but it is nowhere known to reach 

 the Lower Red Sandstone. 



Overlying the conglomerate are other beds, which differ from the 

 normal Waterstones, as may be seen in the following section. 



Section of the junction between Keuper and Bunter in an excavation for drainage at the junction 

 of Sneinton Dale and the Hollows. Communicated by IV. N. Blair, 1884. 



Shaly beds of red marl, 6 ft. 6 in. 



ft. in. 



Shaly beds of bluish grey marl, sandy towards the bottom ... 2 8 



Yellowish grey sandstone, with yellow spots and a few pebbles . o 10 

 Conglomerate of yellow sandy matrix with pebbles of various 



material, becoming more calcareous towards the base . . 3 9 

 Very hard conglomerate, with red matrix full of pebbles ...06 



Sandstone rock (Bunter) with a few scattered pebbles 40 ft. + 



These basal beds are not separated by any marked line from the rest 

 of the Keuper Sandstones, though differing from them in character. We 

 find the yellow spotted sandstone in many walls near the junction line. 

 The bluish grey marl is found in a similar position at Farnsfield, Ollerton, 

 Retford and Everton (at the extreme north of the county). 1 



The alternations of dark red marls with thin sandstones or fine 

 marly limestone, which constitute the lower part of the Keuper Sand- 

 stones, may be very well seen at the Carlton Hill brickyard. They are 

 similar to those described above the conglomerate at Blue Bell Hill and 

 Rough Hill Wood excavations by Dr. Irving 2 and Messrs. Wilson and 

 Shipman. 3 The limestones have flat surfaces and the sandstones are often 

 ripple-marked. The latter often contain on their undersurfaces pseudo- 

 morphs in sand after hopper-shaped crystals of salt. Such have been 

 noticed also at Colwick and Blue Bell Hill as well as in the Keuper 

 Marls at Tuxford and Newark and many other places. The origin of these 

 is as follows : As the salt water from which the underlying clay has been 

 deposited slowly dries the salt crystals form, partly embedded in the clay, 

 which then becomes hardened. On the rewetting of the surface the salt 

 crystal is soon dissolved, while the hollow it has occupied still remains 

 hard for a time. The fine sand enters this and takes a cast of it, which, 

 when the sand consolidates into sandstone, projects from the under surface.* 

 In the Keuper Marls the thin sandstones are likewise often ripple- 

 marked, as at the Rifle Butts north of Nottingham, where they are pitted 

 on the surface as by annelid borings, and in Lambley Dumble and at 



1 Metcalfe, 'Geology of Nottinghamshire,' loc. cit. 



* Proc. Geol. Asm. vol. iv. 1875. * **/. Mag. 1879, p. S3*- 



* See Strickland, S^art. Journ. Geol. Sot. vol. ix. 



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