CRETACEOUS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 



355 



Hunstanton Limestone. — Specimens of this formation obtained in 

 Lincolnshire and along- the western escarpment of the Yorkshire 

 Wolds, from various localities mentioned in this paper, show that it 

 is a deposit laid down in quiet water, beyond the action of mud- 

 bearing currents, and is throughout this line of outcrop as purely a 

 calcareous deposit as that at Hunstanton. Between Welton at the 

 southern end of the Lincolnshire "Wolds and Leavening at the most 

 north-western point of the Wolds of Yorkshire there is practically 

 no difference in its structure. Disunited or primordial cells of Por- 

 aminifera form a very large part of its mass ; shell fragments are few, 

 and the finer amorphous material appears to be made up entirely of 

 calcareous atoms. 



In Lincolnshire mineral fragments, probably derived from the 

 underlying Neocomian sands, are found in the lower part of it. In 

 Yorkshire these fragments are much coarser, and their character 

 frequently suggests derivation from Neocomian rocks even in localities 

 where the Eed Rock now appears to rest on still older formations. 

 Gritty Ked Chalk sometimes rests on Kimmeridge Clay, having 

 probably overlapped the Neocomian sands. 



In some localities large pieces of oolitic ironstone and phosphatic 

 nodules, besides fragments of quartz and other minerals, are in such 

 abundance as to give a conglomeratic appearance to the rock. 



As the Ited Chalk thins, a proportionally larger part of it is 

 affected by the working up of finer material of the strata over which 

 it passes, but its upper part everywhere shows the calcareous nature 

 of the deposit. 



It has been stated (p. 336) that the Eed Chalk thins to the jST.W. 

 in Yorkshire, and at the exposure near the Wharram Grange, almost 

 its most north-westerly point, the material which is the representative 

 of the Red Bock presents to the eye a different appearance in colour 

 and character. Its examination by means of thin sections shows 

 that here coarse shelly fragments, large Foraminifera, detached 

 sponge-spicules, and glauconitic grains of large size (these latter not 

 occurring in any other specimen from Lincolnshire or Yorkshire) 

 are conspicuouly abundant, and there is a corresponding diminution 

 in the amount of the single Foraminiferal cells which usually form 

 so large a part of it. It would appear that at Wharram the bed which 

 contains Belemnites minimus^ Inoceramus sulcatus, and other un- 

 doubted Gault forms presents at this point peculiarities which are 

 associated in Yorkshire rather with the Inoceramus-bed than with 

 the Hunstanton Limestone. 



With the thickening of the Red Chalk along the northern escarp- 

 ment of the Wolds a change comes over the character of the deposit. 



At Speeton, in the lower third, shelly fragments of small size are 

 abundant, and Eoraminiferal cells common : but the amorphous matrix 

 is largely composed of fine inorganic material, with larger particles, 

 probably quartz, sparsely distributed throughout it, calcareous atoms 

 forming quite a subordinate part in its composition. 



In the middle third, where the nodular character is most pro- 

 nounced, single Foraminiferal cells again form the greater portion of 



