Brickearth is a term originally used to describesuperficial windblown deposits found in southernEngland. The term has been employed in English-speaking regions to describe similar deposits.
Brickearths areperiglacialloess, a wind-blown dust deposited under extremely cold, dry, peri- or postglacial conditions. The name arises from its early use in making housebricks, its composition being suitable for brick-making without additional material being added; unlike clay, its bricks can be hardened (fused) at lower temperatures, including in wood-fired kilns.
The brickearth is normally represented on 1:50,000 solid and drift edition geological maps.[1] In theThames valley, in broad patches brickearth overliesfluvial terrace gravel; it has been reclassified on later maps as the "Langley Silt Complex".[2]
Brickearth is a superficial deposit of homogeneousloam orsilt[3] deposited during thePleistocene geological period.[4] Brickearth typically occurs in discontinuous spreads, across southern England and South Wales, south of a line from Pembroke in the west to Essex in the east in depths of up to a metre. Commercially useful deposits of about 2m to 4m thick are present in Kent, Hertfordshire and Hampshire, overlyingchalk,Thanet Beds orLondon Clay. The original deposition of the sediments occurred under cold climates wherefluvial out-wash sediments from glaciers were subject to windy dry periods. The exposed finer-grained sediments were picked up and transported by the wind and were deposited wherever the wind strength decreased.[5]
There are extensive brickearth deposits inKent, particularly on theNorth Downs dip slope and on theHoo peninsula, sections of theMedway andStour valleys. Its mineral content is critical to its applicability inbrickmaking and requires precise proportions ofchalk,clay, andiron.[6]
Brickearth requires little or no admixture of other materials to render it suitable for the manufacture of 'stock bricks'.[3] When used forbrick making, it was often dug from small temporary holes and baked into bricks on the spot inbrick clamps, and used for building nearby. The hole often remained and became apond.[citation needed] In 1986, four active stock brick works were in Kent: atOtterham Quay,Funton,Murston andOspringe.
The brickearth gives rise to rich and fertile soils which have been exploited for agriculture.[7] It is prone to rapid'collapse' settlement when saturated with water and does not provide a firm foundation for buildings.[6]
InChichester, the brickearth is a flint-rich brown silty clay up to five metres thick, which occurs on the coastal plain. The brickearth is unfossiliferous but occasionally yields man-made flint implements.[4]
doi: 10.1144/GSL.QJEGH.1996.029.P2.04May 1996 Quarterly Journal of Engineering Geology and Hydrogeology, 29, 147-161.
