CRETACEOUS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 323 



appears that, in spite of greatly reduced thickness and considerable 

 lithological change, the zonal divisions of the lower beds of the 

 Upper Cretaceous series in these counties agree with those established 

 in the Midlands and South of England. 



It is shown, in the paper referred to, that the Melbourn Eock is 

 continuous from Newmarket to Hunstanton, thus defining the upper 

 limit of the Lower Chalk, although the Belemnite-marls were 

 found to die out ; that the Grey Chalk became thinner and harder 

 as it was followed northwards ; that the Chalk Marl passed laterally 

 into a pure and very hard chalk, its summit, however, still marked 

 by the Totternhoe Stone, which, like the whole series, shared in a 

 general attenuation. The Cambridge Greensand was found to die 

 out gradually, and the Gault, also thinning and becoming more cal- 

 careous, appears to be represented in the extreme north-west corner 

 of Norfolk by theEed Chalk or Hunstanton Limestone, the so-called 

 " Sponge-bed " overlying it being included in the Chalk Marl (see 

 Section I. p. 366). 



The very full and minute details concerning the Chalk, published 

 in the " Geology of part of East Lincolnshire " *, render it scarcely 

 necessary to do more than review the Lower Chalk of this county, 

 adding only the results of my own work which confirm and 

 strengthen the opinions of Mr. Jukes-Browne, and noting such facts 

 as may be of service in the correlation of the series in Yorkshire. 



The Lower Chalk of Lincolnshire is divided in the Memoir into 

 two portions, which are considered separately, viz. a lower, which 

 includes, besides the basement-bed of Eed Chalk or Hunstanton 

 Limestone, some 36 feet of rough greyish-white chalk, and an upper 

 portion, about 40 feet, which contains locally some pink bands, the 

 line being drawn about 7 feet below the lowest of these t. 



The summit of the Lower Chalk is fixed at certain marly bands 

 which are considered to be the representatives of the Belemnite- 

 marls of Cambridge, Hertfordshire, &c. 



This division so nearly corresponds with my own reading of the 

 strata, that it will be convenient to follow the Memoir in discussing 

 the Lower Chalk of this county, separating only the basement-bed 

 of Eed Chalk, which has been shown to be the probable equivalent 

 of the Gault. 



It is fortunate that in South Lincolnshire, near Welton, at a point 

 nearest to the Hunstanton cliff, there are pits which give almost a 

 complete section of the lower beds of the Upper Cretaceous series. 

 It will be seen from the accompanying diagrams (facing p. 366), and 

 by reference to the text, that there is a remarkable similarity in the 

 sequence of the beds at both places ; certain points of difference will 

 be noted in the sequel. 



The sequence and general character of the various beds seen in 



* Mem. Geol. Survey, Sheet 84. 



t This division was only adopted for the sake of convenience in describing 

 the exposures. In the fossil lists the Lower Chalk is divided into three portions, 

 a lower, central, and upper, the division-line between the central and upper 

 parts being taken at the base of the pink band. 



