DEVELOPMENT OF THE MIDDLE THAMES LANDSCAPE AT DORNEY, BUCKS, UK DURING THE LATE HOLOCENE: HUMAN - ENVIRONMENT INTERACTIONS

Large scale excavations at Dorney, Bucks, UK, has provided the opportunity to investigate a block of floodplain of the middle Thames valley approximately 0.75 km wide running for about 2.0 km alongside the present channel of the Thames. It comprised an area of Shepperton (floodplain) gravel dissected by palaeochannels filled with fine alluvial sediments and low-lying areas of alluvial clay.

High-resolution (decadal) palaeobotanical and sedimentological analyses from a late Holocene palaeochannel has enabled detailed reconstruction of the landscape spanning from ca. 2850 C14 yr. BP (Late Bronze Age), through the Iron Age, Roman, Saxon Periods and into the Medieaval period (ca. 450 C14 yr BP). The application of mineral magnetic analyses coupled with the use of simultaneous R and Q mode factor analysis help to underpin phases of active channel flow, phases of channel 'ponding', and alluviation. These phases developed in response to human activity and land use within the region resulting from deforestation, changes from pastoral to arable practice, burning and the associated destabilisation and inwash of soils into the channel.

As series of wooden bridges and timber structures were constructed across this channel between the middle Bronze Age and Late Iron Age which influenced local sedimentation patterns, fluvial energy and competency within the channel. A number of erosive events coupled with in washing due to clearance of the last vestiges of woodland for agriculture into an active channel were identified. Evidence for erosive inputs of soil are provided by peaks in C:N ratio, increased grain size, and the high concentration of ferrimagnetic material (magnetite, associated with burning).

During the Roman period, flow along the Thames channel ceased forming a pond-like feature in which peaty silts rapidly accumulated. The phase of ponding was punctuated by renewed channel activity in which inorganic carbonate sediments rich in ferrimagnetic minerals was deposited. This coincides with a major peak in cereal production and related catchment disturbance of soils due to ploughing with associated run off and in wash of soils associated with probable flooding. This view is supported by the macrofossil remains of spelt wheat and the presence of corn cockle a weed of cereal fields introduced during Roman times.