Wikipedia
Brickearth is a term originally used to describe superficial windblown deposits found in southern England. The term has been employed in English speaking regions to describe similar deposits.
Brickearths are periglacial loess, a wind-blown dust deposited under extremely cold, dry, peri- or postglacial conditions. The name arises from its early use in making house bricks, its composition being suitable for brick-making without additional material being added. Its composition also allows the clay to be fused at temperatures attainable in a wood fired kiln.
The Brickearth is normally represented on 1:50,000 solid and drift edition geological maps. In the Thames Valley area, where the Brickearth overlies some River Terrace Gravels, it has been reclassified on more recent maps as the "Langley Silt Complex".