Preston: Geology South of Grantham. 249 
Stone, often called, from their fissile character, the Paper Shales. 
Both these lower zones have been bared during working in 
Rudd’s brickyard, but they are not now visible. 
At the top of the fossiliferous portion of the Communis beds 
in Rudd’s pit, there occurs a bed of iron-stained nodular concre- 
tions about two feet thick, with numerous oolitic grains about 
One-sixteenth of an inch in diameter, mixed loosely with the 
nodules. The oolitic grains are not iron-stained. This bed has 
yielded about a dozen species of Gasteropods, including Onustus, 
Cerithium, Turbo, Pleurotomaria,and others, together with Mucula 
hammer? (very common), small Ammonites, Belemnites, etc. 
Coming now to the physical features of the geology south of 
Grantham, I would call to your mind the well-known north and 
south trend of the Lincolnshire cliff. This cliff is formed by the 
escarpment of the limestone beds, which dip at a gentle angle 
towards the S.E., and it is westwards from this escarpment that 
the older rocks, ranging from the Upper Lias downwards, may 
be studied. At the south end of Grantham, the cliff ends its 
southward course and takes a more or less westerly direction, 
of the cliff is due to physiographical causes, rain and river action, 
coupled with the general lie of the rocks and the protection 
given to the Limestone by the capping of Boulder Clay. The 
westerly course of the cliff from Grantham will be seen to 
correspond more or less with the tributary valleys on the west 
of the river Witham (Fig. 1). 
That portion of the river Witham which lies to the south of 
Grantham is comparatively of a recent date, whilst the ancient 
Stream which did the work of carving out the valley of Grantham 
and northwards originated in large springs which rose to the 
-S.W. of the town. The watershed of these ancient springs 
appears to have been formed chiefly of Marlstone Rock. his 
Was gradually cut away until the underlying and impervious 
Lower Lias Clay was reached. With the removal by denudation 
of the gathering ground, the springs decreased in size until now 
they are very small indeed, and we have only the old valleys 
With with their alluvial a to tell of their former work. 
Avene 1898. : 
