7 - Buried sites

Summary

This chapter considers the alluviation and the burial of floodplain surfaces and sites that is such a common feature of the later Holocene in many different climatic environments. Just as the record is spatially variable so too are the causes and particularly the balance between the human and climatic signal contained within the alluvial record.

Late Bronze Age and Iron Age alluviation in the British Isles

From the Bronze Age onwards in the lowlands of North-West Europe, floodplain and fen-margin sites reveal evidence for increased flooding and alluviation. The picture is much less clear for upland sites (Richards, et al., 1987). This is partly due to the lack of preserved archaeological sites on the valley floors and the more dynamic response of upland rivers to individual storms. Before describing some of the evidence for lowland alluviation, it is worth considering the types of data that may be available, other than a dated increase in overbank-silt deposition. First, pedological data: a lack of soil development and soil structure, caused by a lack of bioturbation and soil development. Soil micromorphology frequently reveals a decrease in pedological fabric and an increase in unbioturbated sedimentary micro-features (Limbrey, 1992). This could be caused by an increase in flood frequency and/or an increase in the sediment loading of overbank flows. The former is probably more important than the latter as fine sediment is supply- rather than transport-limited although both may be the result of climate and land use change.