Case Studies:Case study 9

From SASSA

[edit] A Neolithic buried soil in the loess of Pegwell Bay, Kent

Weir et al. (1971) describe a buried soil in the Northern part of Pegwell Bay near Ramsgate in Kent. The site has 4m of loess overlain by 1-2m of silty hillwash containing Neolithic flint flakes. The base of the hillwash is marked by a black organic horizon, which is associated with a buried soil developed in the loess. Considerable erosion of the loess occurred before the buried soil developed, because the loess is much thinner in the area of the buried soil than in other parts of the bay. The soil formed in a broad hollow or channel cut in the loess, which was later partly filled with hillwash.

The radiocarbon date of 6120±250BP from horizon 1 of the buried soil (0-19cm depth) does not give the time of burial, because much of the organic matter in the soil would already be quite old when that happened. Modern soil profiles date organic matter at around 20 to 30cm depth to be around 1000 to 1500 years old. Therefore, the period of soil formation included the Atlantic Period (c. 5000 to 7000BP). This was the postglacial climatic optimum, a time of warm and probably wet conditions.

The soil was buried c. 5000BP and this probably caused the soil forming processes to cease. Some soil forming processes might have started before the erosion of 2 to 3m of loess ceased. The earliest phases of profile development could, therefore, be as old as the Ice Age though, it is unlikely that a well developed profile could attain its present form during cold periods, or survive unaltered the periglacial soil activity of those times. Also, as there are no impervious deposits near the buried soil and the site is now well-drained, the poor drainage conditions indicated by mottling must have occurred during a much wetter period than the present. The rapid growth and decay of plants leading to the formation of a thick organic horizon also depended on a relatively warm climate. Taken together, these features suggest that most of the profile development occurred during the 5000 to 6000 years after the younger Dryas period (12700 to 11500BP), and that some of the soil forming processes depended largely on the more oceanic climate of the Atlantic period.

Weir, A.H., J.A. Catt & P.A. Madgett (1971) Postglacial soil formation in the loess of Pegwell Bay, Kent Geoderma 5:131-149

Keywords: Buried soil, loess, radiocarbon dating, Neolithic, climate.