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, 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 at the coast. It is important to remember (as demonstrated by Tipping 2017, 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 (Haggart 1986, 1987; Merritt et al 2017), with other work including at Wick (Dawson and Smith 1997), Dornoch (Smith et al 1992), Skye (Dawson 2009a; Cressey et al 2010; Shelby and Smith 2007), 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 & Hansom 2011), so all coasts are now experiencing relative sea level rise.

An understanding of the local topography and offshore features 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 when it produced the largest assemblage of arrowheads known from Scotland (Bradley et al 2017, 26). Culbin Sands on the Highland-Moray border is now a forestry plantation which has changed 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 would 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 using lake basins or mires, where evidence of human activity was less. 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 (chironomids) for example are good indicators for climate, water temperature, salinity and relate to sea-level change; they are also an abundant source 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 have allowed sea level changes to be mapped, but also, in the case of Clachan Harbour on Raasay, 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 now under the water (Cressey et al 2007; Ballin et al 2010). Intertidal investigations can also provide dated information about submerged forests, providing often more complete evidence of woodlands, but little or no work has been undertaken thus far in the Highlands.

Leave a Reply