| Abstract: |
Wessex Archaeology (WA) was commissioned by Mackley Construction to undertake a program of palaeoenvironmental assessment in support of the Lydd Ranges Sea Defence Scheme. A staged program of assessment and scientific dating was agreed, involving XRF core scanning, pollen and microfaunal assessment, followed by Optically Stimulated Luminescence (OSL) and radiocarbon dating of suitable deposits. XRF core scanning focused on the fine-grained above-gravel stratigraphy (defined as those deposits forming following emplacement of the gravel barrier) from across Zones C, E and G, including three rotary cores (C01/WA-S03, E01/WA-S02 and G01/WA-S01), deposits from the marsh preserved behind the current Green Wall (HHWS-107) and a monolith recovered from clay exposures on the foreshore (monolith 111, TP11). The results of core scanning were used to identify potential zones of sediment mixing to refine the scope of the OSL dating. Targeted assessment of diatoms, foraminifera and ostracods was undertaken on HHWS-107 and TP11, with pollen assessment of peat from HHWS-107. The program of works is designed to address a series of principal objectives, including dating of sediment infilling tidal inlets in the barrier system and investigation land-ocean interactions. This report assesses the preservation and quality of data to meet those research aims. OSL dates from borehole C01/WA-S03 extended from the Bronze Age to the post-medieval, while those from GO1/WA-S01 extended from the Iron Age to the Romano-British period. The OSL dates were in poor agreement with radiocarbon dates from closely associated peat deposits which dated to the Romano-British/early medieval period. The dates reflect the very low concentrations of datable fine sandy quartz grains present in the samples. Partial resetting of grains is also likely to have resulted in over-estimation of the dates, resulting in older ages that would otherwise be expected. Preservation of microfauna was uniformly poor in the samples, although one sample from clay exposures on the foreshore (monolith 111, TP 11) was suggestive of a marine-brackish environment. Pollen preservation and concentration from the peat in HHWS-107 was variable, though generally poor. There is some suggestion of mixed oak-hazel woodland in the early Romano-British period and a subsequent reduction in woodland and expansion in tall herb swamp. Local vegetation may be filtering out pollen from the extra-local environment, but in general surviving woodland is likely to be patchy and locally abundant, cleared on a large scale since the Bronze Age. Large (Cereal-type) pollen grains may represent pollen grains of wetland grass taxa or cereal pollen deposited via animal vectors (e.g. contained in faeces). Preservation of the peat is consistent with evidence for formation of organic beds of Romano-British date across Walland and Romney Marsh, attesting to a spatially and temporally dynamic relationship between marine, semi-terrestrial and dry land environments. The results of XRF core scanning provided data on the relative abundance of different elements down-core. This data is presented in counts per second (cps) rather than concentrations, which can be difficult to interpret without calibration using bulk chemistry and can also be impacted by changes in grain size and composition, water content and organic matter content. The results are variable, with considerable scattering in E01/WA-S02 and a high mean square error in monolith 111. HHWS-107, C01/WA-S03 and G01/WA-S01 produced reliable results, and are affected in the latter sequence by large voids in the sequence. The results suggest variations in elements indicative of shifts in marine and terrestrial inputs over time. Owing to variable preservation of environmental proxies and datable deposits, no further analysis is recommended. |
