184 
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
Geology 
The whole area is underlain by Middle and Upper Chalk, which are here 
very pure, containing approximately 95-98% CaCCU Apart from the river 
valleys, most of the area is covered by a very sandy, chalky till containing only 
about 5% of clay, including that in the contained chalk, and its décalcification 
products. The till is believed to be of Gipping (probably equivalent to Saale) 
Age [Baden Powell 1948, West 1962]. To the west the Breckland is bounded 
by the Fen Basin, which is in many respects similar to the peat regions of Hol 
land, and on the other sides by areas of heavier textured drifts. 
Soils and vegetation 
Décalcification of the sandy chalky till presumably commenced during the 
Ipswichian (= Eemian) Interglacial, and, apart from interruption during the 
Hunstanton (= Early Weichselian) Advance, has continued to the present. 
The till is often strongly indurated, possibly due to frost action, but removal of 
carbonate leaves a very loose sand which, in the absence of an effective vege 
tation cover, is readily redistributed by wind and has locally formed dunes. In 
very general terms, the soil pattern consists of fairly deep podzolic sandy soils 
on plateau sites and especially on stabilised dunes, shallow calcareous soils 
on slopes and deep podzolic soils, sometimes with groundwater influence, in 
low-lying sites. 
The soil pattern is naturally reflected in the vegetation which ranges from 
heath (now often replaced by coniferous plantations) on the acid sandy soils to 
communities dominated by calcicoles where chalk or chalky till comes near to 
the surface. 
Patterned Ground 
In many parts of the area, well-marked patterns may be seen in topsoils. 
On plateau sites they are reticulate in plan; with increasing slope they become 
first vermicular and then elongated (figs. 1 and 2). 
Where sections have been cut across these patterns they are found to be 
associated with very characteristic disturbances below the surface (fig. 3). 
In a typical case these consist of alternate ridges or pillars of chalky till and 
deep troughs or pockets filled with loose sand apparently derived from décalci 
fication of the till. The ridges are often much more chalky than the rest of the 
till and contain angular chalk stones apparently forced up from the surface of 
the underlying horizontally-bedded chalk. The long axes of the stones gradu 
ally change from being horizontal at the base to nearly vertical in the ridges. 
Sometimes, however, the latter have spreading mushroom-like tops and the 
chalk stones in these tops again tend to be horizontal. 
Examples of the patterns were first observed before the war by Watt [1955] 
as colour-patterns in agricultural soils, particularly where chalk was ploughed 
up to the surface, but especially as stripes in natural or semi-natural vegetation 
on hillsides. The most striking examples were shown up by alternating stripes