i6 Geology and Physiography 



Rubbling and thrusting of the Chalk took place where the ice met the 

 Chalk escarpment, and the consequent structures are well exposed south 

 of Royston and on Chalk Hill, north-east of Newmarket. The Boulder 

 Clay is generally confmed to the high ground and upper slopes. It is 

 characterised by a blue colour, and by erratics of chalk, Lincolnshire flint, 

 Yorkshire sandstones and coals, and Scottish quartz dolerites, quartzites 

 and granites, as well as by rocks of Scandinavian origin. 



Upon the retreat of the ice, the land, several hundred feet higher than 

 to-day, was strongly eroded. Deep, steep-waUed valleys were formed, and 

 these were subsequendy fdled up either by glacial drift or during a period 



TRAVELLERS' REST 



Si ' 



BAIWWELL AND CHESTERTON 



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Fig- 5- 

 Diagrammatic Composite Section of the Terraces around Cambridge. 



1. Gault with surface rucked by sludging. 



2. Lower even-bedded series of Travellers' Rest Pit, with erratics derived from 

 Lower Chalky Boulder Clay. 



3. Uneven-bedded series of Travellers' Rest Pit, with rolled Lower Palaeolithic 

 tools and cold fauna. 



4. Loess-loam. 



5. Upper Chalky Boulder Clay in lenses. 



Si Solifluxion band with frost cracks and polygonal soil forms of Upper Chalky 

 Boulder Clay age. 



6. Succeeding interglacial aggradation gravels. 



7. Middle Terrace gravels with warm fauna and Late Clacton-Levallois-Acheul 

 industry. 



8. Loams and gravels with cold fauna and associated solifluxion band (Sj). 



9. Lower Terrace; fine gravel and silt with poorly marked solifluxion band (S3). 



of rapid aggradation and change of base level. Conglomerates and coarse 

 gravels were deposited on the north of the main Chalk escarpment between 

 bosses of Chalk (Barnham), Boulder Clay and outwash fans ; and the 

 finer facies were laid down as a flattened spread in the Fen region, deter- 

 mining the essential features of the present-day landscape (ShrubhiU, 

 near Feltwell) . A warm fauna has been found in a gravel of a late stage 

 of aggradation (Fakenham), and it is probable that the Barrington gravels 

 are of this age. During a subsequent wet period the surface of the gravels 

 carrying the warm fauna was sludged, and, on this sludged surface, during 

 a drier time, brown loess-like loams accumulated (Brandon; Travellers' 

 Rest Pit, Cambridge). 



