Geoarchaeological work across all periods is lacking. There is significant potential to increase our understanding of settlement and landscape changes if geological and soil science techniques are integrated into research and developer-led projects, but to date few examples exist. Detailed below are a number of ways in which geoarchaeological analysis could be utilised more effectively. However, the primary message is that there needs to be greater awareness of its potential and more collaborative engagement at the early stages of research design.
Proxy Indicators and Integrated Approaches
Evidence from Perth and Kinross formed the basis of early engagement with issues related to the soil environments of prehistoric settlements and the effects of agriculture on Scottish soils (eg Romans and Robertson 1983b). There has been little work of this type since then and this region has fallen behind other areas of Scotland, such as Orkney and the Western Isles. There is considerable potential to revisit this type of analysis and incorporate a range of additional environmental and geochemical techniques. For example, biomolecular analyses, including lipid biomarker analysis and DNA analysis, could be employed in situations where it would be beneficial to identify dung and/or decomposed plant materials to the species level (ScARF Science Section: 2 Human and Animal Sciences).
There is need to better understand the nature of settlement in the region, including the spatial organisation of structures and how buildings changed in function and form throughout time. Floor surfaces hold great potential to provide information on the activities undertaken by past communities but have proven notoriously difficult to identify (Strachan et al 2019). In structures where floor surfaces prove elusive, micromorphology should be used to identify and exploit preserved deposits. It should also be used to elucidate whether their poor clarity is the result of cultural practices (eg reuse, maintenance practices, use of floor coverings) or post-depositional transformations in the buried environment as identified through micromorphology at Moredun Top (Roy 2018). Integrated geoarchaeological work at Lair (see PKARF Early Medieval section; Reid forthcoming) will begin to address these issues. It would benefit from similar studies across various preservation environments in the region to evaluate the optimal suite of techniques required for detailed interpretations. Understanding processes of degradation and the resulting sediments from building abandonment will greatly aid such efforts, and the abandoned rural crofts and townships of Perth and Kinross hold considerable potential for experimental research.
Turf has been used as a construction material for much of the region’s settlement history but continues to prove difficult to identify in the record. Soil science techniques, such as micromorphology and phytolith analysis, can be used to identify turf and need to be more widespread when looking for settlement in rural areas (Huisman and Milek 2017; Romankiewicz 2019, 138–9). Multi-element analysis conducted on the region’s late medieval and early modern settlements (eg Wilson et al 2005, 2008, 2009; Abrahams et al 2010) also offers a methodology for identifying rural agricultural settlements in locations where surface evidence of turf structures no longer survives.
Perth and Kinross has a wealth of nationally significant sites; however, very few have been subjected to detailed micromorphological analysis. As a result, vital information regarding their preservation and/or formation has been missed. There is real opportunity to revisit sites and acquire additional profile samples which will bolster existing archaeological interpretations, enhance archives and provide broader narratives for the region. Such programmes of work should make use of old excavation trenches, resulting in workloads that are small, inexpensive and minimally intrusive. This would permit their use even on Scheduled Monuments. Such efforts would aid the identification of relic deposits not observable during excavation and help to answer heritage management questions regarding the preservation of sites, current and future threats and the impact of excavation on site integrity.
Issues of Preservation
Acidic soils, a significant number of which are highly podzolised, have resulted in poorly preserved and/or adversely altered archaeological stratigraphies and organic artefact records across the region. This has produced inherent biases in the location and type of material/sites recovered, and the extent to which we can meaningfully interpret sites reliant on organic materials (eg turf constructions). Understanding of the extent of these biases, however, is limited. There are currently very few detailed characterisations of these conditions at the site-level, which requires addressing through multi-disciplinary approaches that include geological and soil science data.
More detailed understandings of taphonomy and post-depositional transformations, and investigations of the close linkages between soil-type, geology and land use through time, will allow us to predict areas of good preservation and site survival. Alternatively, they can be used in heritage management to identify sites most at risk of further alteration. For example, work on historic loch drainage (Stratigos 2016, 2018) could be combined with environmental and soil studies to assess changes in hydration that influence the preservation of waterlogged material.
Sites would benefit from monitoring site preservation conditions in the wake of human-induced climate change and natural environmental changes. There is currently very little baseline understanding of preservation conditions across archaeological sites in the region and such an effort would produce a valuable resource for archaeological interpretations and risk mapping. Recent work by Bowes (2019) at Loanleaven and Blairhall has identified a serious threat to archaeological sites from erosion by ploughing and has devised a means of modelling where sites are most at risk and this could be employed more widely across the region. Work by Davidson and Wilson (2006) has highlighted the role of soils in the preservation of cultural landscapes and the potential of soil science to identify preservation changes.
Deposit Modelling
The term ‘deposit modelling’ describes any method used to make visual representations of the spatial and stratigraphic relationships between sediments. Such methods provide an effective strategy for investigating the subsurface stratigraphy and the potential for the preservation of associated palaeoenvironmental and archaeological remains (see Carey et al 2018).
There is a vast untapped resource of existing information held in geotechnical reports such as those prepared for flood alleviation schemes and road schemes and held within borehole logs archived by the BGS. This information could be used more widely on both a site specific and broader landscape scale to map and understand distribution and depths of below ground deposits and thus allow us to better target archaeological investigations and sampling strategies. Bowler’s (2004) summary of archaeology within Perth uses the results of borehole investigations, excavation and watching briefs to map deposit depth across the city. The results of archaeological investigations can then be built into pre-existing deposit models allowing for their ongoing refinement and for a better understanding of the archaeological and paleoenvironmental potential of specific deposit types across the region. Deposit modelling guidance released by Historic England (2020) includes a range of examples of applications that would be useful in Perth and Kinross as well as more widely across Scotland and which would help co-ordinate data to help answer some of the queries outlined below.
Collaborative Research
Though multi-disciplinary studies are increasing, more collaborative work between archaeologists and geological/soil scientists is needed. To ensure samples are collected correctly and from appropriate contexts, geoarchaeological expertise need to be consulted and integrated at an early stage in the research design.
Research and developer-led projects have produced a wide range of environmental evidence for the region, using a number of different techniques and analytical strategies. Finding this information and pulling it together for local and regional areas can prove challenging and would benefit from more centralised collation. Previously excavated blocks, cores or bulk samples that have been stored but not analysed should be sourced and made available for additional research projects.
There is a need to develop more detailed and nuanced understandings of landscapes and landscape changes through collaborative projects involving archaeologists, geologists, soil scientists, ecologists, historians and ethnologists. This can help address questions such as:
- Why are sites located where we find them and what are the biases involved?
- How and where should we prospect for new sites?
- What are the major threats to site survival?
- How have the natural and cultural landscapes of the region influenced architecture, land use and settlement patterns and how has this changed through time?
- How effectively can we identify the indicators of settlement (infield/outfield divisions, territorial markers etc) and how far back in time does this extend?
- Can we identify lowland/upland contrasts in site survival, settlement patterns and agricultural practices?