A HISTORY OF NORFOLK 



Shouldham and South Runcton. A brickyard showed 15 feet of 

 Kimeridge Clay, and a well proved the clay to be 50 feet thick and to 

 rest on Lower Greensand. 



It may be observed that ordinary Chalk weathers at the surface into 

 a kind of rubble. No doubt when the ice-sheet was forming over the 

 district much of this rubbly Chalk was frozen to its base, and thus were 

 incorporated in the Boulder Clay numerous pellets and tiny boulders of 

 Chalk, which during the movement of the ice-sheet would become 

 scored by pressure against tiny fragments of flint along the shearing 

 planes of the ice. 



The Chalky Boulder Clay spreads in a tolerably connected mass 

 over the low plateau of South-east Norfolk. In these tracts it is a much 

 more tenacious clayey drift than it is in West Norfolk, where it is not 

 only less continuous but is thinner and the soil is more marly and sandy, 

 and forms large heaths and warrens.' There sand-storms occur after dry 

 weather, when strong winds arise, and the soil is blown away from the 

 surface. The heaths between Watton and East Harling which extend 

 to the south-west from Croxton to near Thetford, form what is known as 

 the ' Breck district.' Here the Chalk is thinly covered by Boulder 

 Clay, and the whole has been sprinkled over with sand, for the most part 

 wind-drifted. As Henry Stevenson remarked, the ' brecks ' include 

 tracts which have been ' broken up ' by the plough at one time and after- 

 wards abandoned as arable ground, but the district also includes extensive 

 areas which have never been cultivated.^ The sand is derived partly 

 from patches of drift sand found here and there on the Boulder Clay and 

 Chalk, and partly from the decomposition of the sandy Boulder Clay. 



A remarkable sand-storm occurred in 1668 on the Suffolk borders, 

 at a place called Santon Downham,^ and much of the sand at that time 

 spread into Norfolk. 



Wherever the Chalky Boulder Clay occurs there are found in almost 

 every field evidences of old ' marl pits,' now usually ponds. In some of 

 the large fields two or more of these excavations may be found. Some, like 

 the Brooke meres, may have been excavated for other purposes as reservoirs 

 of water for cattle, or even for the human population. The Boulder 

 Clay itself weathers into a brown stony loam, and this decalcified Boulder 

 Clay, which rests on a piped surface like that of the Chalk, is occasionally 

 dug for brick-making, as at East Rudham and Harpley. It is con- 

 spicuous again near Burlingham and Lingwood. A Roman kiln found 

 at Kirby Cane, indicates the early working of one of the deposits. 



Apart from the surface brickearth the Boulder Clay has been largely 

 used for the manufacture of ' clay-lumps,' rectangular blocks of clay, well 

 worked up with chopped straw and made in moulds 18 inches long by 

 9 inches wide and 6 inches thick. Then dried in the sun the clay-lumps 



* See F. J. Bennett, 'Geology of Diss,' {Geol. Survey), p. 14. 



* Stevenson, Birds of Norfolk, vol. i. p. li. 



* F. J. Bennett, 'Geology of Attleborough,' etc. [Geol. Survey), 1884, p. 15; and 

 ' Geology of Diss,* etc. [Geol. Survey), 1884, p. 5. 



