Excavation

Date 5 August 2007 - 6 August 2007

Event ID 558665

Category Recording

Type Excavation

Permalink http://canmore.org.uk/event/558665

NN 66298 37497 In 2004, as part of the Ben Lawers Historic Landscape Project, an area of fallen trees and stumps was located in Loch Tay. It consists of a strip of submerged land, about 160m long and about 15m wide, with tree stumps projecting up through the loch bed and other timbers at different angles that appear to be the remains of fallen trees. At first count, 25 major timbers were identified in what was described as ‘Neolithic woodland’, but a shallow sondage around two of the larger, upright stumps showed that there were other tree remains, both upright and at an angle, underneath the lochbed silts (DES 2005, 109-10).

Between 5–6 August 2007, a project carried out by The Scottish Trust for Underwater Archaeology and supported by Historic Scotland was undertaken to define more clearly the area of submerged trees and the method of their deposition. The results of radiocarbon dating from the 2007 work mean that the term ‘Neolithic woodland’ is no longer appropriate, as one date was cAD 500, and a number of others fall into the Mesolithic.

The term ‘submerged woodland’ will be used instead.

A team of underwater archaeologists laid out a baseline along the middle of the site and all of the observed timbers were numbered and plotted. Fifty-six timbers were recorded, rather than the 25 in the original survey. The species of each sample was noted by observation. The great majority are obviously oaks, a few softer samples are probably alder and two samples are probably pine. The on-site identifications were upheld in the

cases of 10 samples for radiocarbon dating where eight were oak, one was alder and one was pine, according to Dr Jennifer Miller of GUARD.

Trench A A trench was laid out encompassing a number of tree remains, with the main aim of establishing the depth under the loch bed of the root systems of the two upright timbers. It was hoped that this would produce a base level for the old land surface in which they had grown. However, with excavation to 1.7m, it became obvious not only that the root systems were deeply embedded but also that the deposits in which they exist

now are probably the result of land slippage or avalanche in the past and therefore not in their original position.

The stratified deposits in the trench were made up of typical shoreline gravels, sands and silts with occasional layers of more earth-like material. It is possible that these are deposits that have slipped into the loch at different times, overlying loch bed layers of material that have been washed in and then covered by similar

deposits over time. The situation is highly complex and is further complicated by consideration of the radiocarbon dates that have been retrieved so far.

A number of tree remains in the trench, one stump that was already very obvious and other timbers that came to light through excavation, support the hypothesis of shoreside collapse as they are severely damaged in a way that shows significant natural force. In particular, the S side of Timber 16, a large oak stump, has a large gash in which stones and gravel were embedded, as if the tree had been forced down onto this material. The gash extends half way through the tree, to a depth of some 0.2m, indicating the massive force required.

The spread of radiocarbon dates is hard to explain. The range of dates is from Mesolithic to Dark Age, but with no examples from the Bronze or Iron Ages so far. It is interesting that the adjacent shore is an SSSI made up of natural oak woodlands. The shore is very steep and rocky and it is hard to see how it might have been

exploited in the past except for foraging for nuts and berries and other plant products. It would not be possible to carry out any form of agriculture and even exploitation for charcoal would be difficult because of the rugged terrain. It is possible that the existing woodland is the modern extension of the woods that are represented under the water. If this is the case, the examination of trees from the broad range of periods represented will give a useful picture of the environmental history of the area and of the conditions that prevailed in different periods. Relevant research areas include loch level variations, climate change and geological activity in Loch Tay.

The complexity of the situation is characterised by two very large oak stumps (T16 and T17), close together but 1500 years apart in time, with the one closest to the shore being the earliest. If the shoreline is collapsing into the loch it is hard to see how the later tree can end up further into the loch than the earlier one and still appear to be in an upright rooted position.

Sample T1 is an alder tree that appears to have fallen towards the shore. It is still projecting above the loch bed even though it is a very soft timber and about 7000 years old. It should be completely flattened by erosion and protected under a layer of loch bed silt. Alder timbers at Oakbank Crannog, further to the east, are eroded completely flat after 2500 years.

Sample 34 is pine. It is the oldest timber dated so far at about 8000 years old. It is notable that it is one of the samples closest to the shore while others 3000–4000 years younger are further out into the loch and up to a metre deeper under the water. While so far no evidence of human activity has been discovered, it is notable that three Neolithic stone axes, two of them decorated, and a carved stone ball were discovered nearby and Scotland’s only stone axe factory site is nearby at Killin.

Dates from 2005 and 2007 excavations. T12 and T45 from 2005. (OxCal v3.10):

Sample no, Lab code, Sample mat, Yrs BP, d13C(‰), Cal 2 sigma

NW07 T48, SUERC-15548, Quercus, 1570±35, -26.5, 410–570AD (95.4)

NW07 T20, SUERC-15541, Quercus, 3760±35, -25.8, 2290–2120BC (80.1)

NW07 T16, SUERC-15539, Quercus, 3780±40, -26.4, 2350–2120BC (87.4)

NW07 T12, SUERC-6489, Quercus, 3905±35, -26.1, 2480-2280BC (95.4)

NW07 T27, SUERC-15545, Quercus, 4470±35, -26.8, 3340–3020BC (95.4)

NW07 T31, SUERC-15546, Quercus, 4535±35, -26.5, 3250–3100BC (60.9)

NW07 T45, SUERC-6490, Quercus, 4705±40, -26.4, 3540-3370BC (70.8)

NW07 T17, SUERC-15540, Quercus, 5335±35, -27.2, 4270–4040BC (92.4)

NW07 T9, SUERC-15538, Quercus, 5405±35, -26.0, 4350-4220BC (87.9)

NW07 T50, SUERC-15549, Quercus, 5780±35, -24.8, 4720–4540BC (95.4)

NW07 T1, SUERC-15537, Alnus, 6180±35, -25.2, 5230–5010BC (95.4)

NW07 T34, SUERC-15547, Pinus Sylv, 7080±40, -24.7, 6050–5880BC (95.4)

Archive deposited with BLHLP, RCAHMS, Perth and Kinross

Heritage Trust, STUA, Historic Scotland.

Funder: Historic Scotland. The Scottish Trust for Underwater Archaeology.