A HISTORY OF BUCKINGHAMSHIRE 



Chalk tracts and the removal from the higher grounds of great masses of 

 Eocene strata. The relics of this denudation have mostly been worked 

 up into the Drifts which were deposited at various periods during 

 Pleistocene and recent times, but it is possible that some of the irregular 

 accumulations known as Clay-with-flints may date back to the Miocene 

 and Pliocene periods. 



CLAY-WITH-FLINTS AND LOAM 



On the higher Chalk tracts, especially about Chesham, Little 

 Missenden, Little Hampden and High Wycombe, there are thin but 

 widespread accumulations of unworn, little worn and broken chalk 

 flints and reddish-brown clay. On some ploughed fields there appears 

 to be such a mass of these flints that it is difficult to believe that any 

 crop could be grown, yet turnips and other roots flourish. 



When we see a cutting through this accumulation of Clay-with- 

 flints we find the Chalk to be irregularly eroded in great hollows or 

 ' pipes,' some of which may be 50 feet deep and 20 feet or more across. 

 These hollows are due to the dissolution of the Chalk, and the dark 

 brown Clay-with-flints which lines these pipes and occurs as a thin 

 covering on the irregular surface of the Chalk is the residue. Some, 

 if not all, of these pipes may be regarded as swallet holes, formed on 

 the margin of Eocene Clay areas, before the Eocene strata were wasted 

 away. 1 



In practice we have to include with the Clay-with-flints a very 

 variable accumulation. Preserved in some of the pipes and sometimes 

 intermixed with the Clay-with-flints are relics of Reading Beds, such as 

 mottled clays and sands and pebble beds ; and thus since some of the 

 pipes were formed there is evidence to prove that the Tertiary strata 

 have been so eroded that only small outliers, or the contents of pipes, 

 remain here and there. 



Large areas of loam or brickearth, much of it bright and mottled 

 in colour owing to its derivation from the mottled clays of the Reading 

 Beds, occur on the higher Chalk tracts at St. Leonards, Lee and Hyde 

 Heath east of Great Missenden, again to the south of Hampden, on 

 Priestwood Common and Wycombe Heath, on Bledlow Ridge, on the 

 hills above Bradenham, on Radnage Common and near Lane End. 



Numerous unworn flints occur in the loam, also irregular masses of 

 greywether, a hard sandstone, almost a quartzite, of which materials have 

 been extensively dug, broken up and squared for paving at Aylesbury 

 and other places. 



Professor Morris mentioned that blocks of the stone known as 

 Hampden Stone have been extracted 5 or 6 feet in length, and used as 

 ornamental stones or rude pillars as at Hartwell Park. 2 Masses of 

 Hertfordshire puddingstone also occur. This is but a pebbly modi- 

 fication of the local greywethers, which are indurated masses of sands 



1 See Prestwich, Quart. Jount. Geol. Sac. xi. 73, and pi. 6. 



2 Geol. Mag. p. 457 (1867) ; H. B. Woodward, ibid. p. izo (1891). 



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