308 Bernard Smith—Upper Keuper, East Nottinghamshire. 
Depth and Extent of Waters.— Waterstones and Keuper Marls 
alike were deposited in what was presumably a shallow salt sea or lake 
of great extent, situated to the east of a southerly projecting spur 
(the Pennines) of an upland which was under continental climatic 
conditions; so that in the hot season a great amount of weathering 
took place in the dry way. In the wet season the debris was swept 
down into the inland sea, which temporarily increased in extent and 
depth owing to the influx of fresh water. 
All the time that the basin was filling up with sediment the bottom 
must have been slowly sinking—perhaps most rapidly towards the 
end of the period—so that the water-level and depth was more or 
less constant. 
The abundance of the skerries in the lower part of the marls and the 
large deposits of massive gypsum in the higher parts suggests that the 
waters were deepening and at the same time becoming more saline. 
But, on the other hand, the skerries never entirely ceased to be formed, 
and even the higher ones (which contain quartz-grains of two sizes and 
therefore may indicate deeper water'), a long way from the western 
shore, are ripple-marked and bear salt pseudomorphs; hence the 
increase in depth must have been trifling. In fact, isostatic conditions 
seem to have prevailed throughout the area. 
The abundance of rather coarse red sandstone, a basal conglomerate, 
and sandy shales, together with the frequency of salt pseudomorphs, 
ripple-marks, and sun-cracks,” suggests that the Waterstones near their 
outcrop were accumulated in very shallow water, or even that large 
tracts with isolated pools were laid bare from time to time. Again, 
the plant and fish remains found in the Waterstones, and in the 
Keuper Marls elsewhere, are usually fragmentary, and occur in 
sediment obviously deposited near a shore-line where the rivers 
would bring down drift vegetation and render the salt-waters com- 
paratively fresh and suitable for animal life. The fish found by the 
late E. Wilson at Colwick Wood were supposed by him to have been 
trapped in the shallows of a lagoon and destroyed either by the 
waters drying up*® or becoming increasingly saline. When traced 
eastward beneath the surface, however, the Waterstones become more 
like the Marls above them. In a boring at Rampton they were 
with difficulty separated off from the Marls, and at Lincoln‘ their 
distinguishing characters are almost wholly absent, only a very 
little sandstone indeed being present. 
Thus in the east we seem to have a more open water area which in 
the first case was probably quickly flooded, so that the typical shore- 
line phenomena of the Waterstones were not there developed and the 
conditions of sedimentation were similar for both Marls and Waterstones. 
The thickness of the Keuper between Tuxford and Lincoln is 
1 The coarser sediment of the higher skerries was probably wind-borne to the face 
of the waters. 
: ‘ I have only seen one slab with casts of sun-cracks from the Keuper Marls of this 
district. 
3 Dr. H. H. Swinnerton has recently discovered footprints and fish-remains in the 
Waterstones of Sherwood, Nottingham (Grou. Mac., May, 1910, p. 229). 
+ According to Mr. Henry Preston, Grantham. 
