OP THE UPPER CRETACEOUS 1ST WEST SUFFOLK AND NORFOLK. 583 



similar to that of the Gault. But the quantity of shell-fragments, 

 entire tests and disunited cells of Foraminifera, and calcareous atoms 

 prove the marl to be mainly of organic origin, though at this point 

 impurely so. At Charlton it passes up into a purely calc marl, 

 yellowish-grey in colour, the tint becoming lighter with its 

 increasing purity as a calcareous deposit. 



Following the marl to the N.E., we rind a gradual diminution in 

 the amount of recognizable quartz-particles and gradually increasing 

 purity from inorganic matter, till at Stoke Ferry hardly a trace of 

 the bluer and most impure marl was noted in our boring, and the 

 deposit, as a whole, appeared almost purely calcareous. 



As previously mentioned, the upper part of the marl, at Feltwell, 

 White Dyke, &c, increases in hardness. This is marked by an 

 increase in the quantity of shell-fragments, principally prisms of 

 Inoceramus-sheMs, which give it a gritty touch not unlike the 

 Totternhoe Stone. 



At Stoke Ferry layers of hard Chalk-marl, rendered gritty to 

 the touch by the presence of many minute pieces of shell, and 

 separated by layers of less shelly material, extend for some distance 

 below the Totternhoe Stone. Below this, in the softer Chalk-marl, 

 the amount of the coarser organic remains, such as shell-fragments 

 and Foraminifera, is small compared with the proportion of amor- 

 phous material of which the Marl consists. Particles of quartz are to 

 be found throughout it; grains of glauconite oecur commonly in the 

 top and lower portion, but are less abundant in specimens from the 

 centre. 



To this point every specimen of the Chalk-marl we examined 

 contained minute grains of glauconite and quartz in varying 

 proportions ; beyond it the glauconite does not occur in the base- 

 ment-bed, and is restricted to that part of the marl which we 

 believe to be the equivalent of the Inoceramus-loed. and to the 

 Totternhoe Stone, while particles of quartz are few and small. 



Thin sections of the hard creamy-white limestone which lies 

 immediately above the Gault at Roydon and in the neigh- 

 bourhood of Grimston show that this bed does not differ 

 materially in its structure from the base of the marl above the 

 glauconitic bed at Shouldham. Single Foraminiferal cells and 

 more or less perfect tests of Foraminifera are conspicuously abun- 

 dant ; but these and a few shell-fragments form hardly 25 per 

 cent, of the material. The so-called Sponge-bed at Hunstanton is 

 comparable in all respects to the base of the Chalk-marl at Grim- 

 ston and Roydon. 



In the hard grey chalk above the creamj^-white limestone at 

 Roydon we find the gritty character of the Marl, which we have 

 noted gradually increasing to the northward, still more marked. 

 Here it closely resembles the Totternhoe Stone in appearance and 

 structure, consisting of about 60 per cent, of coarse, irregularly 

 sorted shell-fragments, mostly prisms of Inoceramus-shells ; grains 

 of glauconite are abundant, and the whole is set in a matrix of 

 amorphous calcareous material. The green-coated nodules at its 



