Loch nan Gabhar, Machrie Moor

Islay has a remarkably rich natural as well as a cultural heritage. At Loch nan Gabhar, Machrie Moor, Islay’s natural and cultural heritage coincide in a dramatic fashion. Bog oaks, emerging from the peat and waters of the loch, provide a direct insight into the woodlands and potentially the climate in which the early prehistoric communities of Islay hunted game and gathered plants during the Mesolithic.

The bog oaks have long been known by those cutting peat around Loch Machrie, but were first brought to the attention of Islay Heritage by Niall Colthart in 2015. In that year the water in the loch was especially low exposing a number of tree stumps.

The age of the stumps was entirely unknown but thought to be two thousand years old at most. However, radiocarbon dating from the outer growth rings of an exposed tree stump identified as oak (Quercus) gave a date of 7840-7680 cal BP (calibrated years before present).

This was 5000 years earlier than expected and provided us with a glimpse of a tree that would have been within the woodland exploited by the Mesolithic hunter-gatherers on Islay.  Islay Heritage has been reconstructing the lifestyle of those Mesolithic people through its excavations at Rubha Port an t-Seilich, Storakaig and Bolsay and here was one of the actual trees within the woodland of their prehistoric world.

The tree stumps provide a remarkable data source for reconstruction the Mesolithic environment. Not only will they be able to tell us about the composition of the woodland, complementing the evidence from pollen trapped within the peat, but also they should be able to tell us about the climate. This can be done by measuring the tree rings within the stumps, as the width of these are sensitive to annual growing conditions. We also hope to be able to extract chemical signatures from the wood itself, and this will provide us with actual measurements for the summer and winter temperatures (by a method called isotopic analysis). Perhaps most importantly, we will be able to see how the climate may have changed during the Mesolithic period, how this might have then influenced growth and decline in the local population and the eventual transition to the Neolithic farming lifestyle.

Islay Heritage supported two days of fieldwork at a at Loch nan Gabhar during Summer 2016, enabling this important work to explore the past environments of Islay to start. The fieldwork was carried out by a team of specialists from the University of Reading, led by Dr Karen Wicks with Dr Rob Fry as the surveyor, and the University of Lampeter, led by Dr Roderick Bale, a dendrochronologist. A report of the fieldwork is available here ‘Loch nan Gabhar Fieldwork Report 2016’.

The fieldwork included a topographic survey to record the position of the tree stumps and branches exposed on the foreshore in relation to the edge of the water body and surrounding habitats. All in situ tree stumps and substantial branches were labelled according to a site code (e.g. MM16-01, MM16-02… and so on), photographed and sampled for 14C dating and wood identification, with a proportion of larger wood samples being selected for dendrochronological analysis. Peat deposits underlying the fossil woodland were sampled using a Russian peat sampler whilst the peat bank overlying the fossil woodland was sampled using monolith tins.

The fieldwork has recovered an outstanding data-set of tree stumps and sediments. The next stage of the research requires raising funds to cover the costs of radiocarbon dates, pollen analysis, dendrochronology and isotopic analysis. Doing this work will help us to build up a more accurate picture of Islay’s past environments, helping us to better understand how Islay’s first people lived.