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Geophysical Survey

Date 2013

Event ID 993522

Category Recording

Type Geophysical Survey

Permalink http://canmore.org.uk/event/993522

NN 9440 8740 and NO 0170 8855 The first season of investigation in a partnership project which aims to characterise the nature of early prehistoric settlement on The National Trust for Scotland’s Mar Lodge Estate, which will ultimately inform woodland expansion strategies, took place May – October 2013.

Caochanan Ruadha, Glen Geldie Located at c550m OD and overlooking a notable topographic basin, the site of a lithic scatter identified in 2005 was investigated in May 2013 by Rose Geophysical Consultants, using geophysical techniques. Anticipated features associated with a Mesolithic site include stakeholes, scoops, and areas of burning. A gradiometer survey was undertaken over an area of c1ha centred on the flint scatter. Given the size of potential targets, gradiometer data was collected at 0.5 by 0.125m intervals rather than the more traditional 1 by 0.25m. A small resistance survey, 40 x 40m, collected at 0.5 by 0.5m intervals, was also carried out over the immediate area of the flint scatter.

Within the gradiometer data a relatively coherent cluster of pit type anomalies was recorded in the vicinity of the lithic scatter. While potentially archaeologically significant, a natural origin was thought equally likely. Other isolated responses of potential archaeological interest were also noted. The resistance survey appears to have mapped variations in the make-up of the till, with the exception of one possible small, ephemeral, high resistance circular anomaly.

A team of 11 from University College Dublin (UCD) undertook trial excavations over three weeks in May–June 2013. All excavations were by hand, and all sub-peat spoil dry sieved to 5mm. Nearly 80 test pits (1 x 0.5m) and three small trenches were excavated. These aimed to explore anomalies identified by the geophysical survey and establish the extent of the flint scatter.

Trench 1 focused on the largest area of anomalies but did not identify any clear correlation between these and archaeological remains. Only one certain feature was identified, a substantial deposit of charcoal found in Trench 3 (a 1.5 x 1.5m extension of a test pit). The full extent of this charcoal deposit was not recorded, but it was thick (>100mm) and immediately underlay the peat. Samples have been sent for radiocarbon dating.

All excavation trenches and test pits showed similar soil profiles: variable depths of peat covering heavily-podzolised fine sands which provide a thin overlay to compacted gravels/boulder tills. The sands are provisionally interpreted as deriving from solifluction and other movement of materials downslope. Geomorphological assessments of the area demonstrate that the area of the main lithic scatter is a landform of pre-Mesolithic age and that the archaeological material may be in situ. The surface is cut by some visible drainage channels which may have moved archaeological material, and two artefacts were recovered from a drainage feature in Trench 1.

Only a very small number of artefacts were recovered during fieldwork: Ten flints and a small number of possible worked quartz. The flint artefacts were uniformly very small and included high proportions of fragmentary microliths characteristic of the Later Mesolithic, a retouched flake and small debitage. They were scattered across almost the whole area covered by test pits (>100 x 50m), with little sense of any overall concentration. One test pit contained four flints, but those surrounding it contained none. The impression is of an extremely low density artefact scatter mainly comprised of very small material.

Chest of Dee, Glen Dee The UCD team undertook fieldwalking along the path from White Bridge to waterfalls at the Chest of Dee in June 2013, where a scatter numbering hundreds of pieces had been previously identified near the confluence of the Geldie Burn and the Dee. A total of 152 artefacts were recovered from the path (c400m), with the most northerly being tucked up against the outcropping rock of the waterfalls. The lithics included many pieces of Later Mesolithic type. The small size of one platform core is especially notable.

In October 2013 a team from the University of Aberdeen excavated a series of test pits as part of the department’s third year Advanced Archaeological Practice module. The aim was to determine the location of the lithics in relation to the peat deposits at the Chest of Dee and to determine if any in situ features survived. Forty test pits measuring from 0.5m2 to 1m2 were excavated.

Four test pits were excavated at the confluence of the Geldie and the Dee (Area E). No lithics were identified, but there were traces of possible features dug into the subsoil below the peat. Ten test pits were dug on either side of the Dee near the White Bridge. On the S side of the Dee, extensive deposits of peat were revealed, but no archaeological features (Area A). On the N side six test pits revealed shallower peat deposits overlying a leached E horizon above the subsoil and no lithics (Area B). Four test pits were placed on a prominent ridge a short distance to the N (Area C). A single small isosceles triangle microlith was found just below the peat, at the junction with the subsoil below.

Area D was a more productive area, with a line of 18 test pits laid out following the path through the peat. Towards the western end of the line, greater numbers of lithics were found as the test pits approached the banks of the Dee. The numbers of lithics were small, ranging from one to five pieces, and all were found towards the base of the peat at the junction with the subsoil below. Some test pits contained layers of burning and one (TPD12) contained a sub-rectangular pit or scoop filled with loamy sand and fine charcoal. TPD11 contained a shallow gully or slot associated with three lithics, and a number of other pits showed more ephemeral layers of burning or occupation. All of the features were found below the peat, cut into the subsoil.

Near to the line of test pits in Area D, two small eroding pits were found at an eroding face near the N bank of the Dee. Both pits were associated with lithics and both contained significant quantities of charcoal which were sampled for dating. One pit contained an isosceles triangle microlith.Four 0.5m2 test pits were dug near the waterfalls at the Chest of Dee, near to a large pool located just E of the falls (Area F). Here, another eroding face revealed over 60 lithics, including a microblade core and flakes, mainly of flint, but with other raw materials present, which had been eroded out of the section created by the Dee. Extensive evidence of pits and cultural layers was evident in the erosion face below the peat. The test pits dug here revealed extensive evidence for repeated pit digging, with a complicated series of intercutting deposits. These pits contained extensive deposits of charcoal which were sampled for dating. A large pit was also identified directly overlooking the waterfalls in another erosion face. No lithics were identified here, but charcoal samples were obtained for dating.The lithics recovered from the excavations total over 100 pieces and include microblade cores, isosceles trangles, obliquely backed points, blades and flakes, all on very fresh flint. The assemblage is a classic Scottish Narrow Blade type.

Archive: RCAHMS (intended)

Funder: The National Trust for Scotland, Aberdeenshire Council, University of Aberdeen and University College Dublin

SM Fraser, The National Trust for Scotland

R Knecht, Rose Geophysical Consultants

K Milek, University of Aberdeen

G Noble, University College Dublin

S Ovenden,

G Warren,

C Wickham-Jones, 2013

(Source: DES)

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