3.2.3 Sea Level Changes

As noted in the National ScARF, it is important to chart prehistoric sea level changes as distributions of archaeological sites make more sense when this is factored in; this includes coasts as well as estuaries (ScARF Palaeolithic and Mesolithic section 3.4; ScARF Bronze Age section 3.1). A useful summary of work on Holocene sea level change in Britain and Ireland has been gathered by Shennan et al (2018), including data from a number of Highland sites. In general, this shows Holocene relative sea level change in step with isostatic readjustment following deglaciation, with much of the Highland coastline experiencing relative sea fall over the last 7000 years. At the peripheries of ice domes, for example on the north coast, the curve is relatively flat. Rapid relative sea level rise in the region prior to this, however, will have destroyed evidence of earlier Mesolithic and Upper Palaeolithic activity on the coast. It is important to remember (as demonstrated in RARFA 4.4.1) that local sea level curves may deviate significantly from regional trends.

Recent work in Scotland is summarised in Smith et al (2019) and Dawson (2018). The Moray Firth in particular has been studied often (Haggart 1986, 1987; Merritt et al 2017), with other work at Wick (Dawson and Smith 1997), Dornoch (Smith et al 1992), Skye (Shelby and Smith 2007; Dawson 2009a; Cressey et al 2010), Wester Ross (Hardy et al 2015), northwest Sutherland (Long et al 2016) and Lochaber (Shennan et al 2018). The rate of current sea level rise as a result of global warming is outpacing isostatic rebound in all parts of Scotland (Rennie and Hansom 2011), so all coasts are now experiencing relative sea level rise.

An understanding of the local topography and offshore features as they would have been in the past due to sea level changes is important. The highly productive sand dune lithic site at Littleferry near Golspie, Sutherland was an offshore island during the Neolithic; it produced the largest assemblage of Neolithic arrowheads known from Scotland (Bradley et al 2017, 26). Culbin Sands on the Highland-Moray border is now a forestry plantation. This has changed the nature of what was a volatile dune environment in historic times; more work on its prehistoric topography might provide further indications of its earlier nature, although the planting will have destroyed much evidence. It would be interesting to compare this to other long-lived beach sites with human activity in the Highlands.

In the Highlands, the coastal areas were intensely settled due to generally good soils near the coast, marine resources and good connections. In some places sea level changes have resulted in small basins which provide good potential to shed light on a local environment coinciding with human activity. A good example is investigation of a site on the Coigach peninsula in Wester Ross. It revealed a different landscape picture from other studies in the region using lake basins or mires, where there was less evidence of human activity. However, the researchers noted problems of interpretation, particularly the spatial patterning of vegetation within the wetland, which must be addressed in any reconstruction (Bunting and Tipping 2004).

Analysis of some insects can provide information on temperature and vegetation conditions. Midgies/midges (chironomids) for example, are good indicators for climate, water temperature and salinity and they relate to sea level change; they are also an abundant source of information for the Highlands.

There has been relatively little work done on intertidal areas in the Highlands. Several studies on Skye (Selby and Smith 2007; Cressey et al 2007) are the exception. These studies have allowed for sea level changes to be mapped, but also, in the case of Clachan Harbour on Raasay, the investigation of peat formation. There the finds of worked stone tools together with worked wood and charcoal suggested Late Upper Palaeolithic and Early Mesolithic activity in an area that is now under the water (Cressey et al 2007; Ballin et al 2010). Intertidal investigations can also provide dated information about submerged forests, which would provide often more complete evidence of woodlands, but little or no work has been undertaken thus far in the Highlands.

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