490 m:e. a. steahai^ on the uncolij^shiee caestoke. 



Oolites and Lias are both at their minimum in the district a few 

 miles north of the Humber, subsequently expanding, as do the Neoco- 

 mian rocks, in what may be called the Yorkshire basin. It may be 

 supposed that there existed between the Yorkshire and Lincolnshire 

 districts an area of slower subsidence, forming a partial barrier in 

 the Jurassic and Neocomian periods, but overspread subsequently 

 by the waters of the Chalk sea. 



The fossil evidence, so far as it goes, seems to indicate that there 

 was considerable erosion of the Speeton Series before the deposition 

 of the Carstone. The fossils found in the derived phosphatic 

 nodules are believed to be jN'eocomian species, as stated above, 

 though their state of preservation does not admit of this being 

 determined with certainty. The nodules themselves are quite 

 different from those which occur as boulders in the Spilsby Sand- 

 stone, and which are known to have been derived chiefly from the 

 Kimeridge Clay ; they frequently contain the grains of iron-oxide so 

 common in the Tealby Beds, and resemble in other ways the 

 concretions that are found in situ in the Tealby Clay. The grains 

 and flakes of iron-oxide also, which are so abundant in the Carstone, 

 all appear to have been derived from the clay, while the small pebbles 

 of quartz, Lydian stone, &c. have most probably been washed out of 

 the Spilsby Sandstone. The Carstone, in fact, is made up of such 

 materials as would result from the " washing " of a mass of Tealby 

 Clay and Spilsby Sandstone. 



In the Secondary rocks Knes of erosion are often indicated by 

 bands of rolled phosphatic nodules, these being the only portions of 

 the soft clays that survive redistribution. Thus the break between 

 the Chalk and Gault in the eastern counties is marked by a 

 " coprolite-band," the nodules being imbedded in the base of the 

 Chalk. When the Chloritic Marl comes in, the nodules are scattered 

 through it sporadically. The phenomena are strictly comparable to 

 what takes place in the case of the Carstone. 



It would thus seem that the Carstoue of Lincolnshire should be 

 regarded rather as the basement-bed of the Chalk than as the top 

 subdivision of the Neocomian. On this view the difficulty of 

 correlating the Lincolnshire and Yorkshire sections is much lessened. 

 The horizon of the Carstone is marked, after the disappearance of 

 the Carstone itself, by a "coprolite-band" in North Lincolnshire, 

 and by an unconformity in Yorkshire ; and the Tealby Beds and 

 Spilsby Sandstone become then the equivalents of the Speeton 

 Series, the sandstone having thinned out or been replaced by clay 

 towards the north, as it was also towards the south-east at 

 Skegness. 



The correlation of the Lincolnshire with the Norfolk area now 

 becomes a matter of great importance, inasmuch as it determines 

 the relation of the Speeton Series to the Neocomian of the 

 southern counties. The Norfolk series consists at Hunstanton of an 

 upper and lower sandstone separated by a bed of clay, which, 

 however, dies out and leaves the two sandstones in one indivisible 

 mass. The lower sandstone rests on Kimeridge Clay. It has to be 



