C— GEOLOGY 67 



transported from Scandinavia, but had also incorporated much material 

 from the bed of the North Sea, including fragments of shells. 



The striking feature of the Norwich Brickearth, as we see it to-day, is 

 its oxidised and sometimes decalcified character ; it presents an eroded 

 appearance, and its surface is often hummocky and weathered. One 

 indication of its antiquity is the fact that the river-systems of eastern 

 Norfolk have been carved through it. The deposits of the next glacial 

 episode (the Great Chalky Boulder Clay) occur within the valleys and 

 wrap over their slopes, so that an important and probably long period 

 must have intervened between the two glaciations. During this period 

 elevation occurred, extensive valley-erosion took place, and the brickearth 

 was weathered and denuded. At certain localities near Yarmouth sands 

 were deposited (' Mid-glacial ' sands) which overlie the Norwich Brick- 

 earth and contain a cold moUuscan fauna, formerly regarded as derived, 

 but now generally believed to be indigenous. The evidence thus goes 

 to show that the interval, although protracted, was scarcely warm ; 

 nevertheless, the amelioration of climate was sufficient to ensure that 

 the North Sea ice retreated completely from the land-area of Britain, 

 giving place to sheets of shallow water, sufficiently saline to support a 

 marine fauna. At a later stage, the elevation of the area (presumably 

 consequent upon the removal of the ice-load) resulted in the excavation 

 or re-excavation of the valley-systems of eastern Suffolk and Norfolk 

 just referred to. 



While these physical changes were in operation Man was possibly 

 not absent from the scene. Although we find no undisputed evidence 

 of his remains in the sands and gravels, we should remember that he is 

 not an aquatic animal. In certain of the so-called ' Mid-Glacial Sands 

 and Gravels ' Mr. Reid Moir has found what he claims to be early points 

 and edged-worked scrapers of Acheulian type. The flaking of these 

 flints is not accepted as human by all archaeologists, and there is the 

 additional stratigraphical difficulty that the sands and gravels of diff'erent 

 parts of East Anglia (formerly mapped together as ' Mid-Glacial ') include 

 deposits which lie both above and below the Great Chalky Boulder 

 Clay. Similar sands and gravels occur also below and even within the 

 Norwich Brickearth, and have up to the present proved difficult to dis- 

 tinguish from one another. 



When the ice-sheets re-advanced over East Anglia they brought 

 with them rock-debris of a very different character from that which 

 built up the Norwich Brickearth, While the matrix of the Brickearth 

 suggests that the bottom-deposits of the North Sea, including probably 

 the unconsolidated sands and clays of the Eocene and Pliocene, were 

 largely incorporated, the boulder clay of the re-advance is constituted 

 almost entirely of material from well-known British outcrops. These 

 include igneous rocks from the north of England, the Cheviots, and 

 Scotland, Upper Palasozoic limestones and sandstones, and various examples 

 from the Triassic, Jurassic and Cretaceous Systems. Notably, the 

 Oxford and Kimmeridge Clays of the Fen area and the Chalk provided 

 the bulk of the constituents. A minor quantity of Scandinavian rocks, 

 incorporated in Cambridgeshire and Hertfordshire, represents the 



