GLACIAL BEDS. 5OI 



The Glacial Drifts of the Eastern Counties have been divided as follows : — 



Upper ( Plateau Gravel. Coarse "cannon-shot " gravel and sand. 

 Glacial \ Chalky or Upper Boulder Clay. 

 J 1' "Middle Glacial" Sand and Gravel, 



p, . , < Contorted Drift. Stony loam or brickearth. ) Lower 



( Cromer Till. ) Boulder Clay. 



Our knowledge of these beds is largely due to the observations of Mr. S. V. 

 Wood, Jan., and Mr. F. W. Harmer ; ' while the occurrence of an Upper and 

 Lower Boulder Clay at Gorton in Suffolk was first pointed out by Mr. John Gunn.- 



The Lower Glacial Beds of Norfolk have a maximum thickness of about 

 200 feet ; they are well shown in the ' Mud cliffs ' between VVeybourn and 

 Eccles, that in places rise to a height of upwards of 200 feet, but the thickness 

 of the beds is often exaggerated by contortion.^ As a rule, the Lower Glacial 

 Drifts rest on a very even surface of the Forest Bed Series, which consists of 

 sands, gravels, and laminated clays. Mr. Reid mentions, however, that in places 

 where the Till rests on laminated clays, the beds have been slightly crumpled. 



Cromer Till. — This is a tougli bluish-grey unstratified Boulder Clay, containing 

 fragments of Tellina Balthica, Mya arenaria, Cardium edule, and Cyprina 

 Islandica. It contains also many glaciated fragments of Chalk and flint, of 

 septaria (probably from the Kimeridge Clay), fragments of Lias, and Carboniferous 

 Limestone ; as well as many Igneous and Metamorphic rocks, such as mica-schist, 

 granite, felstone, basalt, etc. In this Till fine examples of glaciated stones are 

 more abundant than in any other Drift in Norfolk, and Mr. Reid has observed that 

 the fragments of septaria and Chalk have sometimes been bored by Annelides, and 

 subsequently striated. The Till rests in places on an Arctic Freshwater Bed (see 

 p. 474), below which are the Pliocene strata (Forest Bed Series, etc.) ; it is best 

 exhibited in the neighbourhood of Happisburgh (Hasboro) and Mundesley, but 

 is impersistent in the coast-section, for Mr. Reid has not traced it so far west as 

 Cromer. It forms a band that can generally be recognized, but it is sometimes 

 separated into an upper and lower Till, by intervening laminated and ripple-marked 

 clays and marls.* (See p. 484.) Inland it is not to be distinguished from the 

 Contorted Drift. 



Contorted Drift. — This deposit consists largely of brown stony loam, sometimes 

 well stratified and containing seams of gravel and sand, at others containing seams 

 of chalky loam or boulder clay, and exhibiting most violent and remarkable 

 contortions. Hence the name Contorted Drift, applied by Lyell. It can be 

 studied in the cliffs between Eccles and Mundesley, where the main portion of the 

 cliffs is made up of this brown loamy deposit, which rests on the blue Cromer Till ; 

 here the beds are but little disturbed. The contortions become conspicuous west 

 of Mundesley, and thence near to Cromer, and between Cromer and Weybourn 

 seams of very chalky loam, marl, or boulder clay occur here and there in isolated 

 irregular and lenticular masses ; the Drift becomes, in fact, a conglomeration of 

 all kinds of sediments, containing masses or nests of sand with marine shells, and 

 sometimes coarse gravel, although loam and marl predominate. In many places 

 the beds are disturbed and twisted into S-shaped contortions. 



Among the remarkable features of this Contorted Drift are the large boulders 

 which it contains, not merely those of quartzite, grit, schists, gneiss, granite, and 



^ G. Mag. 1870, p. 18 ; see also Supplement to Crag Mollusca (Palaeontograph. 

 Soc), with geological map of the Crag district ; and Wood, Q. J. xxxvi. 457, 

 xxxviii. 667. For list of works on the Geology of Norfolk, see Geol. Norwich 

 (Geol. Survey) ; and for list of works on Suffolk, see Geol. Ipswich, by W. 

 Whitaker. 



* Trimmer, Q. J. xiv. 171. 



^ See diagrams of Coast-sections by S. Woodward, Geol. Norfolk, 1833 ; Wood, 

 jun.. Remarks in Explan. of Map, 1865 (privately printed) ; C. Reid, Horizontal 

 Section (Geol. Survey), Sheet 127. 



* Reid, Geol. Cromer, p. 86. 



