CRETACEOUS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 359 



The very small amount of iron in this specimen of slightly 

 coloured chalk is noteworthy and confirms some remarks of Mr. 

 Staniland *, who considers "So per cent, of FcOg sufficient to give 

 colour to the rock. 



Analysis of middle part of Bed 7. — Speeton, Yorkshire. 



Insohible matter, silica 6"00 



Oxide oi" iron and alumina 1 '00 



Carbonate of lime 89-80 



Carbonate of magnesia 1'66 



Undetermined matter 1*54 



The following is an analysis of the dark bluish-grey Belemnite- 

 marls of the railway-cutting east of South Cave. 



Insoluble siliceous matter 17'80 



Oxide of iron and alumina 1"20 



Carbonate of lime 66-20 



Carbonate of magnesia 6-20 



Undetermined, chiefly carbonaceous matter 8'60 



Analysis of the Grey Bed : the specimen came from Mr. Chapman's 

 pit, Louth : — 



Insoluble siliceous matter 7"40 



Oxide of iron and alumina 1*20 



Carbonate of lime 86*40 



Carbonate of magnesia 215 



Undetermined matter 2"85 



Summary and Inferences. 



There is no doubt that the Eed Chalk which forms the basement- 

 bed of the Upper Cretaceous series in Lincolnshire and Yorkshire is 

 the continuation of that bed which forms so striking a feature in 

 the Hunstanton cliffs, the relations of which to the Gault have been 

 already discussed f. This bed has been followed throughout Lincoln- 

 shire, and its outcrop in Yorkshire has been described at some length 

 in this paper. 



The evidence thus obtained shows that it has developed consider- 

 ably to the north of Hunstanton and is, in South Lincolnshire, 10 or 

 11 feet thick. Through the major part of this county this thickness 

 is maintained, but as it is followed northward it becomes thinner 

 and is, in North Lincolnshire, only 4 feet thick %. Immediately north 

 of the Humber it is not less than 7 feet in thickness ; but north of 

 Pocklington there is evidence of continued thinning to about 4| feet 

 at Garrowby Park and 2 feet at Leavening, at which point the base 

 of the Chalk reaches its highest altitude (about 600 feet) along the 

 brow of the Wolds. Although at the last two exposures the 

 position of the Sponge-bed is indicated by the paler colour of the 

 upper part of the Eed Chalk, there appears to be practically no 

 difference in the nature of the deposit. 



* " Geol. East Line," Geol. Surv. Mem. p. 35. 



t Q. J. G. S. vol. xliii. p. 590. 



\ Q. J. G. S. vol. xlii. p. 488, Strahan on the Lincolnshire Carstone. 



