Student Blog: ‘Geoarchaeology across the ages – the Bradford Kaims, Northumberland.’

Tom Gardner

Carnegie Trust PhD Candidate at the University of Edinburgh

Within the north of Northumberland lies a large postglacial fenland, stretching at a low incline for 14km north to south, emptying to the north into Budle Bay near the village of Bamburgh. Immediately upon the deglaciation of the area, forest cover encroached upon the area, with oak and elm dominating the higher and drier glacial sand and gravel deposits, or ‘Kaims’, that flank the fenland. Lower down the slopes, alder and hazel grew from the early Mesolithic, and sedges and grasses propagated upon the mire surface as it periodically flooded and dried (Paterson et al, 2015). The formation of peat began soon after the propagation of woodland, and now the extant depths of peat in the lowest basins of the fenland reach above 10m (Boomer, 2007). They were once greater, but land improvement in the Victorian and Georgian period drained this niche environment for pasture, leading to the desiccation of all peat formed after the early Bronze Age (Dixon et al, 2015).

Figure 1: Site Location

Figure 1: Site Location

Into this lush and damp wetland environment, is dropped a massive series of prehistoric activity, beginning in the early Holocene, with tangible evidence reaching into the Iron Age (Young et al, 2014; Gething et al, forthcoming). The focus of the archaeology appears to respect the changing waterlines of the fenland, moving higher upslope as time carried on and the peat formed higher and higher. The Bradford Kaims Project (BKP) has been working at the site since 2010, and has excavated 16 trenches, 80 test pits, and has mapped the geomorphology of the landscape through numerous coring transects. Dr, Richard Tipping of the University of Stirling has reconstructed the palaeoenvironment of the area (Paterson et al, 2015), allowing the archaeologists to focus upon the prehistoric activity on site. The peaks in activity appear to be the early Neolithic and the late Bronze Age, and represent themselves through a series of burnt mound deposits, structures, and middens in and around the bottleneck of the fenland at Hoppenwood Bank.

Figure 2: Site Map

Figure 2: Site Map

Aside from the detailed open-area excavation of the archaeology on site, a suite of geoarchaeological analyses are being conducted in order to bridge the sedimentological gap between the landscape-wide geomorphology and palaeoenvironment as studied by Dr. Tipping, and the archaeology investigated by the field team of the BKP. While this geoarchaeological analyses has assessed a variety of deposits across the site, such as peat deposits, fluvial fans, palaeochannel fills, colluvial sequences, and buried landsurfaces, a central focus has been upon the many burnt mounds on site, with eight of the sixteen confirmed burnt mounds having been sampled.

Figure 3: Micromorphological sampling and sub-sampling of peat deposits in the fenland.

Figure 3: Micromorphological sampling and sub-sampling of peat deposits in the fenland.

These burnt mounds range in dates from between the Early Neolithic and the late Bronze Age, in a range of sizes and morphologies, with some accompanied by impressive structures and trough complex’s. The investigation into the burnt mounds at the Bradford Kaims came as a result of a more widespread lack of knowledge of the formation processes and depositional sequences of these site types across Northern Europe. As the most numerous prehistoric site type across Britain and Ireland, burnt mounds represent a strong facet of the socio-economic underpinnings of Neolithic and Bronze Age societies, yet their artefactual sterility leads to a poor understanding of their function and place within the landscape. The research of the BKP seeks to unpick the minute detail bound up within the sediments and deposits of the many burnt mounds on site, and so far, the results are positive.

Figure 4: Micromorphological sampling of the Early Neolithic Mound 1 and wooden trough fill at the Bradford Kaims.

Figure 4: Micromorphological sampling of the Early Neolithic Mound 1 and wooden trough fill at the Bradford Kaims.

Figure 5: Micromorphological sampling of the Late Bronze Age Mound 2 and trough fill at the Bradford Kaims.

Figure 5: Micromorphological sampling of the Late Bronze Age Mound 2 and trough fill at the Bradford Kaims.

hrough the analyses of micromorphological soil thin sections taken from the burnt mound deposits, trough fills, and buried landsurfaces directly beneath the mounds, clear evidence of internal sequences and depositional episodes has been identified. Micromorphology provides the opportunity to look in-depth at the structure, fabric, taphonomies, and sequence of archaeological sediments which, in the case of the burnt mounds at the Bradford Kaims, shows dense and well-structured sediment matrices of charcoal, alluvial silts, and high quantities of mineralised plant materials. The charcoal content, understandably high due to the highly fired nature of the burnt mound material, is homogenised by large quantities of silicified ash, indicating relatively complete firing events, rather than low-heat intensity and short lived fires. Plant sesiquioxide cast, with identifiable phytolith bodies within them, could evidence the potential for incomplete combustion of other fuels such as grasses and sedges, but may also represent partially fired and mineralised mats of vegetation from potential ‘earth oven’ use.

 

Figure 6: Heavily fired material and macro-charcoal from within a singular event at burnt mound at Mound 1.

Figure 6: Heavily fired material and macro-charcoal from within a singular event at burnt mound at Mound 1.

These deposits of burnt mound material vary, and between the individual events of burning and deposition lie interleaving flood deposits, soil formation lenses, and evidence of organic growth. While it has long been appreciated that burnt mound deposits, although often given a single context in the field, must comprise of multiple individual events of deposition, it has not been possible to identify these events until this point. Interestingly, this allows us to begin quantifying the number of deposits taking place within individual mounds, and to interpret the spaces between them as potential hiatuses in deposition where floods or organic growth cover the mound before deposition continues. The regular appearance of flood deposits between burnt mound deposits, and the evidence of seasonal flooding of the area from geomorphological reconstructions, suggests that single or multiple year hiatuses interrupted the burnt mound deposition, both in the Neolithic and the Bronze Age at the Bradford Kaims. In-washed and fluvially sorted alluvial silts and sands divide many mounds into separate entities when viewed under the microscope, bringing in microfossils that then translocate through the more porous areas of the burnt mound, sadly contaminating any chances of well-defined plant microfossil stratification within the mound deposits.

Figure 7: Flood deposit material within Mound 3

Figure 7: Flood deposit material within Mound 3

Equally interesting, are the subsoil surfaces onto which the burnt mounds have been deposited. Again, in both the Neolithic and the Bronze Age at the Bradford Kaims, the burnt mounds are laid upon desiccated colluvial clay surfaces at the edge of the fenland. As we know of the seasonal flooding during winters on the site, it stands to reason that the burnt mounds are laid during the drier seasons, or Summer and Autumn. That this trend spans both the Bronze Age and the Neolithic, along with the evidence for hiatuses in site use of more a year or more, then we may be coming to a suggestion of the burnt mounds at the Bradford Kaims being interpreted as seasonal monuments within the landscape. While a far larger dataset is needed to assess this possibility across larger areas, it poses many interesting questions about land use and socio-economics throughout the Neolithic and Bronze Age, if the most numerous prehistoric monument type in Britain and Ireland is effectively seasonal.
Excavations at the Bradford Kaims will continue in the summer of 2017, and the geoarchaeological sampling of other sites across the Orkneys, Wester Ross, and Ireland should add mass to the dataset of burnt mound thin sections. Hopefully in the future we will be able to come to a more informed understanding of the role which burnt mounds play in prehistoric Europe, through an idea of their depositional sequences and microscopic characteristics.

Bibliography:
Boomer, I., 2007, ‘Preliminary Report on Coring at Bradford Kaims, May 2007,’ Unpublished report submitted to the University of Birmingham.
Dixon, G., Young, G., Gardner, T., Gething, P., Paterson, D., Pedersen, K. & Tipping, R., 2014, ‘Bradford Kaims Wetland Heritage Project: Interim Archaeological Report No.2,’ Bamburgh Research Project, available at;    http://bamburghresearchproject.co.uk/wp-content/uploads/2013/07/Bradford-Kaims-Archaeological-Final-Report-2014.pdf
Gething, P., Gardner, T., & Lally, T., ‘Bradford Kaims Wetland Heritage Project: Interim Archaeological Report No. 3,’ Bamburgh Research Project (Forthcoming).
Gething, P., Gardner, T., & Lally, T., ‘Bradford Kaims Wetland Heritage Project: Interim Archaeological Report No. 4,’ Bamburgh Research Project (Forthcoming).
Paterson, D., Tipping, R., Young, G., Ross, M., Gething, P. & Pedersen, K., 2014, ‘Environmental Changes at the Mesolithic-Neolithic Transition from Embleton’s Bog, near Lucker, Northumberland,’ Archaeologia Aeliana, Vol.43, pp.1-18.
Young, G., Gething, P., Paterson, D., Pedersen, K. & Tipping, R. 2013, ‘Bradford Kaims Wetland Heritage Project: Interim Archaeological Report No. 1,’ Bamburgh Research Project, available at; http://bamburghresearchproject.co.uk/wp-content/uploads/2013/07/Bradford-Kaims-Archaeological-Report-reiew-Nov-13.pdf

 

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