A HISTORY OF NORFOLK 



for meadow land, is modified by down-washes of sand from the adjacent 

 tracts of Lower Greensand and Drift, 



The Kimeridge Clay represents a portion of the sea-bed somewhat 

 distant from land, comprising marine mud, which is free from coarse 

 materials, and in which many organic remains have been entombed. 

 Among the more prominent are bone? of large reptiles, such as 

 Pliosaurus^ and of fishes, such as Asteracanthus. Ammonites biplex and the 

 small ovate bivalve known as Lucina minuscula are not uncommon. The 

 characteristic oyster, Ostrea deltoidea, met with in the deep well at Lynn, 

 occurs in the lower part of the formation. Bituminous shale, which 

 may have been caused by the decomposition of animal matter, was met 

 with at Southery. The Kimeridge Clay is not a water-bearing stratum, 

 but it is noteworthy that some supply was met with in a boring at 

 Downham Market, derived probably from stone bands which may have 

 received the rainfall through the covering of Lower Greensand. 



LOWER GREENSAND 



A considerable interval of time may have elapsed between the 

 deposition of the Kimeridge Clay and the overlying strata grouped as 

 Lower Greensand, an interval represented elsewhere by the Portland stone 

 and perhaps in part by the Purbeck and Wealden Beds. On this point 

 however we must speak with reserve, as it seems probable from the 

 observations of Mr. G. W. Lamplugh that the basal portions of the 

 Norfolk Lower Greensand may represent in time the Wealden Beds of 

 southern England.* 



The Lower Greensand comprises a group of sands and ferruginous 

 sandstones locally hardened into Carstone. It is familiar in the brown 

 pebbly sandstone which lies below the Red Chalk in the cliffs at 

 Hunstanton. It is familiar also on the foreshore, where the double 

 system of jointing in the rock has marked the pavement of Carstone into 

 quadrangular masses separated one from another by the erosive action of 

 the sea. Here children delight to disport themselves, jumping from one 

 block to another by the aid of poles. 



The Lower Greensand stretches southwards beneath the Red Chalk 

 and Gault and the overlying White Chalk, from Hunstanton to Downham 

 Market, with small outlying masses at Southery and Hilgay ; the main 

 outcrop sinking below the fen levels between Downham Market and 

 Stoke Ferry. Where the outcrop is broad and there is an absence of 

 boulder clay, the formation presents a diversified and picturesque tract of 

 sloping ground, broken anon into two minor escarpments and intersected 

 by the waters of the Middleton stream, Nar and Wissey. To the north 

 of Dersingham the formation contains a central clayey portion between 

 two masses of sand and sandstone. The lowermost subdivision is a mass 

 of sharp silvery sands with streaks of fine clay about loo feet thick, 

 known as the Sandringham Sands — beds which take their name from the 



* See ' Geology of the Borders of the Wash ' {Geol. Survey), 1899, pp. 16-25. 



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