CHALK. Aoy 



NORFOLK, ETC. 



The Chalk of Norfolk was divided into Upper, Medial, and 

 Lower Chalk in 1833 by Samuel Woodward,^ while the pal^eonto- 

 logical divisions were marked out by Dr. C. Barrois in 1876.- 

 The thicknesses given in the Table (p. 402) are approximate. 



The greater part of the Chalk is concealed by Glacial Drift : 

 the barer portions occur in West Norfolk, near Swaffham and 

 Massingham, where there are extensive sheep-walks. 



The thickness of the Chalk at Carrow, Norwich, was proved 

 by a deep well to be as much as 1 152 feet. To this at least thirty- 

 five feet must be added to give the total thickness of the Chalk at 

 Norwich, inasmuch as it rises to at least this height above the 

 river-level near Household. No trace of Red Chalk was found 

 in this boring, 



Red Chalk. — The Red Chalk, termed the Hunstanton Lime- 

 stone and Hunstanton Red Rock by Prof. H. G. Seeley, forms 

 a conspicuous band at the base of the White Chalk, and above 

 the brown Carstone (Lower Greensand) in the cliff at Hun- 

 stanton, on the north-west coast of Norfolk. (See Frontispiece.) 

 This band of Red Chalk has attracted much attention, and various 

 opinions have been expressed concerning its age and origin since 

 the days of William Smith : some geologists have grouped it as 

 Gault, others as Upper Greensand, while more recently Mr. John 

 Gunn suggested that it was the basement-bed of the Chalk, a view 

 confirmed by the observations of Mr. Whitaker.^ For our know- 

 ledge of the rock and its fossil contents we are chiefly indebted to 

 Prof. Seeley and the Rev. Prof. Wiltshire. 



The deposit is four feet in thickness, and according to Prof. 

 Wiltshire it may be divided into three bands, the upper of which 

 has a large quantity of fragments of Inocerami, the middle is rich 

 in Bclemmtes, and the lower contains numerous Terehratulce ; these 

 divisions, however, are extremely local. The bed contains rolled 

 fragments of quartz and slate. 



Amongst the more abundant fossils are Bourgeticrinus rugostis, 

 Pentacriniis Fittoni, Micrabacia, Holaster stiborbicularis, Vermicidaria 

 iimbonata, Terebratula bipUcata, T. capillata, Inoceramus Crispii, 

 Spotidylus striatus, Avicula gryphcBOides, Ostrea vesicularis, Ainmonitcs 

 auritus, A. lautus, Bfleninitcs minimus, etc. Otodus appendicnlatus 

 and Ichthyosaurus campylodon also occur. It is remarkable, as Mr. 

 Whitaker points out, that while the commonest fossils are Gault 

 species, some are Upper Greensand forms, and some are Chalk 

 fossils. Among the Chalk fossils are Cidaris sceptrifera, Rhyncho- 



^ Outline of the Geology of Norfolk. 



"^ Recherches sur le Terrain Cretace, etc. 



^ Proc. Norwich Geol. Soc. i. 207 (this paper contains a full account of the 

 labours of previous observers), P. Geol. Assoc, viii. 137 ; see also H. G. Seeley, 

 Ann. Nat. Hist. 1861, Q. J. xx. 327; T. Wiltshire, P. Geol. Assoc. 1859, Q. J. 

 XXV. 185 ; T. G. Bonney, Cambridgeshire Geology, pp. 33, 77. 



