ALLUVIAL DEPOSITS. 529 



have been estimated to have a thickness of 170 feet; but this may inchide some 

 Pliocene deposits. 



In the CHff section at Mundesley on the Norfolk coast there is a freshwater deposit, 

 known as the Mundesley river-bed, resting in a trough of the Glacial deposits. It 

 consists, according to Prof. Prestwich, of sandy loam and black and lirown peaty 

 beds, containing Recent Freshwater shells, Insects and Fish-remains.' Remains 

 also of Emys lutaria, and of the Red-throated Diver [Colyiiibits septentyioiialis) 

 have been obtained.- The lowest beds consist of subangular flint-gravel. 



In West Norfolk remains of Emys httaria were obtained at West or Hill Mere, 

 near Wretham, and this was the first record of the occurrence of this freshwater 

 Tortoise in England.'' 



A considerable area of Alluvium occurs in the district known as Holderness 

 in Yorkshire ; it forms the eastern borders of Lincolnshire, and also the Fenland. 



At Hull the following is a general section of the beds : ■* — 



Feet. 



Soil I 



Clay 6 



Silt 23 



Peat with large trees 2 



Lacustrine deposits with Cyclas cornea (Cyclas-marls), Biihynia tentacitlata, etc., 

 have been detected at Holmpton, between Withernsea and Owthorne, and near 

 Hornsea.* 



At Hornsea the beds, seen at low tide, were thus noted by Prof. Phillips : — 



Blue clay 2 or 3 feet. 



Brown clay, Anodon I to 3 ,, 



Laminated plant-bed 3 in. 



Cyr/rtj-marls 4 in. to I foot. 



Peat and black root-bed 6 in. 



In Holderness peaty beds occupy small lacustrine areas, which were formerly 

 meres : while Shell-marl occurs at Driffield. Mr. Reid observes that often the 

 name Mere is the only relic of the old meres for which Holderness was once so 

 famous. Submerged or Buried Forests have been proved in wells and docks on 

 the borders of the Humber (at Grimsby, etc. ) to a depth of 50 feet beneath high 

 water. There is also a second Buried Forest at about the present low-water level. 

 The latter is the ordinary Submerged Forest seen on the foreshore.^ 



The Humber warp is a marine and estuarine silt and clay, which occurs above 

 the Peat beds ; it contains TcUina Balthka, Scrohiailaria plana, Macf7-a siibtrun-' 

 cata, Littorina littorca. Bulla obtiisa, Rtssoa (Hydrobia) tilva, etc. 



Mr. Clement Reid remarks that " The amount of material annually removed 

 from the Holderness coast by the sea may be estimated at about 6,000,000 tons, 

 of which the greater part, probably 5,000,000 tons, is sand and mud. The coarser 

 sand largely goes to form the sand-banks which block the Humber and North Sea, 

 or the sand-dunes which cover Spurn Plead and protect the Lincolnshire coast. 

 But the fine mud and silt is carried to much greater distances. Not only are the 

 Humber and Lincolnshire flats raised by it, but the enormous quantity of warp 

 which is annually deposited in the Wash can have no other source ; for there are 

 no cliffs to yield it in Lincolnshire, and the mud of the Norfolk cliffs appears to 

 travel principally to the southward. In the Humber, as in the Wash, the warp 



' Geologist, iv. 68 ; Lyell, Phil. Mag. (3), xvi. 352 ; Reid, Geol. Cromer, p. 119. 

 - E. T. Newton, G. Mag. 1879, p. 304, 1883, p. 97. 



^ A. Newton, Ann. Nat. Hist. (3), x. 224 ; C. J. F. Bunbury, Q. J. xii. 355 ; 

 F. J. Bennett, Geol. Attleborough, etc., p. 18. 



* Phillips, Geol. Yorkshire, Part I, ed. 3, pp. 66, 76. 



* See also Morris, Q. J. ix. 321. 



8 C. Reid, Geol. Holderness, p. 77, 82, 86 ; Wood and Rome, Q. J. xxiv. 182 ; 

 J. C. Hawkshaw, Q. J. xxvii. 237. 



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