328 ME. W. HILL ON THE LOWEE BEDS OF THE TJPPEE 



have been oveiiooked. But tlie recognition of its true horizon is of 

 the greatest importance in considering the correlation of the Chalk 

 of this northern area with that of the south. 



(D.) The Grey ChalTc. 



The section of the Chalk of South Lincolnshire is continued up- 

 wards for 12 feet more above the '' Grey Bed " in the pit opposite 

 to the Cross Xeys Inn (for section see page 326). Above the " Grey 

 Bed " is a rather nodular course of greyish-white chalk, and over this 

 the chalk becomes indefinitely bedded, weathers into rubbly or 

 nodular fragments, and is divided into courses by bands of buff- 

 coloured shaly marl. The sequence of " Grey Bed,'' and hard, compact, 

 nodular course, followed by 10 or 12 feet of indefinitely bedded 

 chalk with marked marl bands, seems always to occur throughout 

 the county, although in pits which have been freshly quarried, the 

 peculiarities of the marly chalk are not so evident. To the north, 

 at Thoresby, Louth, Withcall, and Donnington, it is this vaguely 

 bedded chalk with marl bands which is partly coloured pink — the 

 lower pink band — the colour of which at once takes the eye ; but 

 this chalk is always described as, " marly," or '' shaly," or " with 

 marly layers," (fee. 



Between the top of this pit, opposite the Cross Keys Inn, and the 

 base of the exposure showing the summit uf the " Grey Chalk " 

 there is a gap. 



In the pit half a mile west of Welton church (Memoir, page 51) 

 the chalk is capped by two bands of laminated marl enclosing a band 

 of hard whitish chalk. Prom evidence obtained further to the 

 north these bands are without doubt the representatives of the 

 Belemnite-marls (zone of Belemnitella plena) of Hertfordshire and 

 Cambridge, and the rock below them is therefore the summit of the 

 Grey Chalk. 



In this pit it is seen to be fairly massive and evenly bedded ; it 

 appeared to pass down into rough and more nodular Chalk with 

 marly bands, and I should judge that 20 feet of Chalk below the 

 Maiis is exposed here. Prom its appearance and from the know- 

 ledge obtained of this horizon further to the north, I believe the floor 

 of this pit is not very far above the top of that at the Cross Keys. 



Many exposures fiU the gap which occurs at this point, and by 

 reference to the Memoir it will be seen that on the whole the upper 

 l)art of the Grey Chalk is evenly bedded, and divided into courses 

 of uncertain thickness by bands of grey marl. Prom South Thoresby 

 to Louth it is seen to be coloured pink immediately beneath the 

 Belemnite-marls, but this coloration is lost in the northern part of 

 the county. It will be seen in the sequel that the recognition of 

 the sequence of the beds described above is of hardly less importance 

 than that of the " Grey Bed." 



The incoming of the marly chalk at the base of this division is 

 foreshadowed in Norfolk. It will be seen in the diagram of the 

 Hunstanton cliff * that indefinite marly bands are mentioned ; these 

 * Quart. Journ. Geol. Soc. vol. xliii. p. 562. 



