ME. A. STEAHAN ON THE LINCOLNSHIEE CAESTONE. 491 



decided whether the impersistent clay is the representative of the 

 Tealby Beds, or whether the whole of the Norfolk series should be 

 correlated with the Lincolnshire Carstone. 



A comparison of the thickness of the subdivisions in the two 

 areas would seem to show that this clay is too insignificant to be a 

 representative of the 219 feet of clay proved at Skegness, especially as 

 it thickens steadily southwards throughout Lincolnshire (see figures). 

 The Hunstanton clay is generally about ten feet thick and thins out 

 to the south. 



If, on the other hand, the whole of the Norfolk section is taken to 

 represent the Carstone only of Lincolnshire, it must be supposed that 

 the Speeton Series is entirely absent, which at first sight would 

 seem to imply a still more rapid thinning out than the former 

 theory. But on the evidence for an unconformity between the 

 Carstone and Tealby Beds in Lincolnshire it may be supposed that 

 the latter were denuded away in Norfolk before the deposition of 

 the Carstone. It may be mentioned here that boulders believed 

 to be of Spilsby Sandstone occur in the Norfolk Carstone just above 

 the clay-band*. Prof. Judd stated in 1869 that "he considered 

 that the Carstone does not represent the Tealby Series of Lincoln- 

 shire, and that it is probably Aptian or Upper Neocomian, but 

 containing in its lowest part fossils derived from the disintegration 

 of Lower Neocomian beds, in the same manner as the deposits of 

 phosphatic nodules at Potton and Upware"t. 



The correlation of the Norfolk Carstone, resting (presumably 

 unconformably) on the Kimeridge Clay, with the Upware deposits, 

 which rest with a marked unconformity on Kimeridge Clay and 

 Coral Hag, shows that the older rocks are being overlapped towards 

 the south. This is further indicated by the contained fragments, 

 which include specimens of rocks older in age further to the south. 

 Thus at Hunstanton the derived fauna includes specimens of Lower 

 Neocomian and some Kimeridge-clay forms ; further south a few 

 Neocomian, some Portlandian, a very large proportion of Kimeridge- 

 clay, and some Oxford-clay forms are found. Similarly the 

 boulders in the Red Chalk in the area between Lincolnshire and 

 Yorkshire, where the Carstone and Speeton Series are absent, are 

 made up of fragments of the Oolitic rocks, with Ammoyiites callovi- 

 censis and Amm. Koenigi from the Kellaways EockJ. It is thus quite 

 intelligible that the Carstone should in that area, where the Speeton 

 Series or its equivalents are well developed, contain only fragments 

 derived from these rocks. 



The correlation of the Lincolnshire Carstone with that of Norfolk 

 necessitates the retention of this rock in the Neocomian group as 

 at present defined. At the same time the evidence given above 



* W. Keeping, ' The Fossils and Palaeontological Affinities of the Neocomian 

 Deposits of IJpware and Brickhill ' (1883). 



t Wiltshire, " On the Eed Chalk of Hunstanton," Quart. Journ. Geol. Soc. , 

 vol. XXV. p. 192 (Discussion). 



J Blake, Proc. Geol. Assoc, vol. v. p. 248 ; and ' Geology of the Country 

 South-east of York, &c.' (Geol. Survey Memoir), p. 18. 



