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End of Fieldwork at High Pasture’s - 2006

Posted by steven on 16/11/2006 at 11:05 AM

The 2006 fieldwork season has now closed at the High Pasture Cave site. Read on for the latest update.....

The 2006 fieldwork season at the High Pasture Cave site was finalised at the end of October, after what has proved to be another excellent year. We have investigated some great archaeology and recovered some wonderful finds at the site, which is helping us to piece together the story and function of this incredible place in Skye. Finds from this years excavations indicate that the site has been visited and used over a long period of time, possibly in excess of 5000 years.

The tail-end of the season this year attracted an increasing number of volunteers to the site, which provided the necessary impetus to finish the excavation of a number of trenches and allowed us to start new areas of fieldwork, including the excavation of trail trenches to investigate anomalies identified by the geophysical survey conducted earlier this year. The following update reviews this work and provides an up to date account of the excavation results.

Martin Wildgoose entering the top of the stairwell

Work in the cave (Bone Passage) focused on the completion of excavations in Trench 6 and the removal of the remaining archaeological deposits in Trench 1, the trial trench that was sectioned during our first year in the field in 2004. The excavations continued to provide a wide range of finds, while the continuation of the two main floors identified in Trench 6 were also revealed in Trench 1. Significant quantities of animal bone were recovered, especially in the lower contexts (C107), some of which was semi-articulated, while other material could be identified to individual animal carcasses that had been deposited in the cave during prehistory. We also recovered a wide range of burnt plant remains, fish bone and shellfish, and a large amount of well-preserved charcoal. Small finds included metalworking residues, stone tools including quern rubbers and coarse pebble tools, fragments of copper-alloy, worked pumice, clay crucible fragments, worked flint, re-fitting pottery sherds, and a number of items of worked bone and antler including pins, needles and awls.

Trench 1 in Bone Passage during excavation, showing a deposit of fire-cracked pebbles and animal bone. Re-fitting pottery sherds of possible Late Bronze Age date and a number of bone pins and awls were also recovered from this deposit

A large amount of burnt bone and fire-cracked stone/pebbles was also recovered from the excavations in the cave, material most likely related to feasting and cooking activities that were taking place on the surface above the cave. These deposits were then ‘curated’ by placing them in the cave along with the artefacts mentioned above.

The excavated south-facing section of Trench 1, with Kubiena tins in-situ. The samples taken in these tins will be analysed using thin-section micromorphology at the University of Stirling by Ian Simpson and Jo MacKenzie.

On the surface, work has been focusing on the burnt mound/spreads, a possible standing stone to the east of the cave, a stone-built structure located just to the southeast of the stairwell, and a number of other features identified from geophysical survey.

Trench 11 was positioned to investigate the northern sector of the u-shaped enclosure, that consists of a bank of stone arcing around the main focus of the site, centred on the stairwell entrance to the cave.

The image above shows the north end of Trench 11, with the mound of granite and limestone boulders contained by a low revetment wall. The 1m scale is resting on a compact layer of fire-cracked pebbles and stone, comprising the burnt mound/spread, which survives immediately below a thin turf and topsoil layer.

The image above shows the same area of the trench after removal of wall collapse to reveal the facing stones of the revetment wall. The compact layer of fire-cracked stone runs up to these facing stones. No finds were recovered during this stage of the excavation within the trench.

Removal of the turf and bracken matt on the south side of Trench 11 revealed a chaotic mound of boulders giving way to a dark soil with the odd fragment of fire-cracked stone (see image above). Trench 2 is in the foreground. Removal of the loose granite boulders eventually revealed a low revetment wall, shown here by the two low orthostats. Therefore, it appears that a low revetment wall approximately 1.4 metres wide was built over the burnt mound to retain a fill of granite and limestone boulders.

The low orthostat wall on the inner, south face of the u-shaped enclosure (scale=1m)

Fire-cracked stone and pebbles was identified resting against the face of the revetment wall, as on the north side of the enclosure. However, it appears that within the confines of the u-shaped enclosure, the archaeological deposits have been disturbed at a later period in time. The compact layer of fire-cracked stone seen in the image above has been truncated, the material removed and re-deposited elsewhere. This probably explains why we have recovered small finds spanning several thousand years from the dark soil inside the enclosure, including iron slag, a shale bracelet fragment and a broken section of a leaf-shaped arrowhead. It is possible that the inside of the enclosure was used during a later period as some form of garden, activities that may be contemporary with the shieling structures identified on site (see below).

The image above shows the north end of Trench 11 during the section excavation. Due to the complexity of the deposits and structures within them, we have started to remove half of the trench, leaving the other half in-situ. After removal of the compact layer of fire-cracked stone in this section of the trench we uncovered more burnt mound material, although the stone in the lower layers had not been so intensively processed. Few finds were recovered from the excavations except for two possible coarse stone tools, a fragment of a quern rubber, degraded animal bone and teeth, and fragments of charcoal. Layers of peat ash were also identified in these layers. As mentioned above, other structures were uncovered in this part of the trench including a second revetment wall at a lower level than that mentioned above. Finally, below the layers of fire-cracked stone, around 0.5 metres below the turf line, we uncovered a layer of grey clay with numerous charcoal flecks. This is as far as we proceeded with excavations in this part of the trench for 2006.

Within the south side of the trench excavations reached the natural karstic clay, over which was a charcoal-rich deposit. This may be related to features cut into the natural clay, features that will be excavated fully during 2007.

The image above shows a view over the u-shaped enclosure from the southeast with Trenches 9 and 5 in the foreground, and Trench 11 beyond. All of these trenches are investigating the burnt mound/spreads and the features they contain. Further trenches will be opened next year to investigate other areas of this important feature and relationship to adjoining areas of the site.

Elsewhere on site we have focused on a number of visible features and on anomalies identified through geophysical survey. Visible features included a large granite standing stone located within a post-medieval turf and stone dyke.  The dyke surrounds the High Pasture Cave site, but we were drawn to the upstanding stone to see if it was an earlier feature that had been incorporated into the dyke.

The image above shows the west-facing aspect of the stone after removal of moss and the adjoining dyke, or field boundary. We cut a section through the dyke taking in one edge of the stone, to investigate the relationship of this feature to the dyke and to look at the method of construction of the dyke itself.

Charles Burney, one of out regular volunteers on site, was responsible for the excavation of Trench 12 and the image above shows Charles nearing completion of the work. This view, taken from the south, shows the exposed side of the stone in relation to the dyke, and the massive pile of bracken roots that caused such problems during the excavation. Unfortunately, the excavation proved that the stone had been raised and merely rested against the inner face of the field boundary. There was no socket cut into the natural clay for the stone, while the image above shows how the stone tapers towards its base. It therefore appears that the stone and the dyke are contemporary, although the reason why the stone was raised and positioned in this location in the first place remains a mystery. The stone does not form a post for a former entrance or gateway through the dyke, so we are at somewhat of a loss as to its potential function.

However, the excavation of the dyke proved the method of construction. Starting with the cleaned off natural clay, a bank was initially formed using re-deposited clay and small facing stones placed along the inside face of the feature. Additional clay and sub-soil were then used to provide height to the dyke, after which turves were built up on both faces to complete the structure. Unfortunately, no finds were made during the excavation, so the date of construction remains elusive although a similar feature excavated in Waternish on Skye proved to have been built during the later stages of the 19th Century.

Another feature visible at the site targeted for excavation was the remains of a small rectangular stone-built structure, hidden by stands of bracken and nettles. The structure was initially cleaned of the overlying vegetation and turf, and loose stone removed from both inside and outside of the walls.

The image above shows the structure after cleaning, taken from the southeast, while in the image below the stone-built structure can be seen to be taking shape. Constructed from large basal stones of granite and limestone, the walls of the building are slightly bowed and the corners are rounded. A doorway was uncovered in the south west face. After cleaning it was decided to excavate a section through the structure, the section line passing through the east side of the doorway.

The building stands to a maximum of three courses high (around 0.6m) and during excavation of the interior a compact earth floor was uncovered. A dark stain within the floor may be a post-hole, but time did not permit excavation of this potential feature this year.

The images above and below show the limit of excavation in this trench for 2006, work that will continue next year. The structure is well defined and it appears that we have uncovered the full depth of the wall, which has been built on a comapct earth footing (although this requires clarification through further excavation next year). The excavation generated few finds, these being a fragment of worked stone and two re-fitting clay pipe stem fragments. We are fortunate that one of the stem fragments contains a makers mark, that of Christie’s of Glasgow. Manufacture of the pipes in Glasgow by this company took place between the mid-nineteenth and early twentieth centuries, providing us with a tentative date for the later stages of use of the structure, which is most likely a shieling or bothy.

Such a building may have been used for transhumance activities at the site, when livestock was taken to the higher pastures and hill ground for grazing. This took grazing pressures away from the more fertile lower ground around the settlements, which could be retained for making hay and for growing other crops. It is also possible that produce such as butter and cheese was manufactured during the summer months at the shielings. Adjacent to the excavated structure we have identified a second circular stone-built cell, around 2.5 metres in diameter, which provided a strond magnetic response from magnetometry during the geophysical survey earlier this year. We will be investigating this structure during 2007.

A view looking into the shieling structure through the entrance, from the south west, showing the compact earth floor. The clay pipe fragments were recovered from this surface

Excavation of the shieling structures will continue next year, investigating the buildings themselves and the relationship with other possible contemporary features on site. We will also be looking at the underlying archaeology to see if there are earlier structures and features within the trench. From our excavations at the High Pasture’s site over the past two years, a pattern is starting to emerge showing how these later phases of construction have impacted on the prehistoric remains. In particular, the interior of the large circular structure (roundhouse - Trenches 7 and 10) and the u-shaped enclosure (Trenches 5 and 11) have been modified at a later stage in their use. This is apparent from the ad-mixing and truncation of archaeological deposits and features within these structures.

Other features targeted for trial excavation include a large boulder-built wall in the eastern sector of the site, which partially defines a level area of grass-covered ground. The excavation of this feature (Trench 8) produced no finds or dating material, but it did indicate the construction of a wall at least 1.2 metres wide that comprised an inner and outer face, with a rubble core. A trial trench located on a large anomaly located using magnetometry and resistivity, around 3 metres northeast of the outer wall of the u-shaped enclosure, was also opened during the latter stages of the year. Unfortunately. time and some aweful weather conditions did not allow us to proceed very far with this trench, but we did uncover a compact layer of fire-cracked stone and pebbles just below the turf. This may be a continuation of the burnt mound/spread feature, which covers a large area of the site, and work will continue in this sector of the site in 2007.

Another trench opened up in the east sector of the site, bounding the edge of the grass-covered platform mentioned above, was also located on a geophysical anomaly. Resistivity picked up a possible ditch or pit feature at the base of a slope leading onto the platform and Trench 13 was opened to investigate this. The turf was removed on the 1 metre square trench to reveal a compact layer of small stone.

Below this a layer of sub-soil was removed to reveal a ditch cut into the natural clay, that had been back-filled with large to medium-sized stone. Removal of the stone in the ditch showed a feature with a V-shaped profile, with a rounded bottom. A small lens of sediment, possibly relating to silting of the feature before it was back-filled, was identified in the base of the ditch. The image above shows the sectioned ditch feature, which may be some form of land drain or prehistoric boundary marker. Further excavation of this feature is planned for 2007.

Finally, Ian Simpson and Jo Mackenzie of the University of Stirling spent a very wet day with us at the High Pasture’s site in October, during which they collected sediment samples from Trench 2 and Trench 6 (cave) for specialist analysis. This aspect of fieldwork and analysis, funded by the Highland 2007 Fund, will be crucial in helping us to understand site formation processes on site including the possible types of activities that were responsible for generating the deep midden deposits identified in Trench 2, outside the stairwell entrance to the cave. Although the weather conditions were testing for such work, good samples were recovered and these are now being prepared in Stirling ready for further work. We hope to have some preliminary results from this important work in 2007.

Ian and Jo braving the elements, taking tin samples from the deep sections in Trench 2

Another important development to report, is that Historic Scotland have kindly provided funding for 17 radiocarbon dates on materials recovered from ‘key’ contexts and features identified on site. The submissions will provide a series of bracketing dates for the site and will provide the necessary detail to allow us to start to build a chronology for the archaeology. In particular, we are interested to see how the post-hole and pit features uncovered in Trenches 7 and 10 relate to the use of the cave. Could these be the earliest features on site, relating to Mesolithic or Neolithic transitional visits to the cave? We also hope to have dates to fix the formation and use of the burnt mound and spreads, one of the larger features identified at High Pasture’s. We also hope to get results that will allow us to build a chronology for the formation of the deep midden deposits in Trench 2 and how these relate to the material uncovered in Bone Passage (cave). Finally, two dates on the female inhumation blocking the back-filled stairwell will provide a potential date for the closure of the cave.

A significant amount of work has been undertaken at the site during the 2006 fieldwork season, but 2007 will be a crucial year in the overall development of the project. We have a number of trenches from the 2006 season that have to be completed next year, while we have other excavations planned to target other areas of the site. Therefore, we will be looking to recruite a core of volunteers for the 2007 fieldwork season to help achieve our planned objectives. We will be posting news bulletins throughout the winter, along with any specialist reports we receive on post-excavation analysis. So please, keep visiting the site and we look forward to meeting friends, old and new, during our work on site in 2007. May we take this opportunity to say a big thank you to our sponsors and major funding agencies, the numerous specialists who continue to provide valuable assistance to the project, and of course to the volunteers who have helped us on site over the past two years.

Steven Birch

Martin Wildgoose

George Kozikowski

Next entry: Start of fieldwork at High Pasture Cave - 2007

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