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Three test pits were established in an area of known early prehistoric remains approximately one kilometre to the north of the Thornborough Henges prior to the September 2005 ploughing. The objective was to determine if the normal annual agricultural ploughing regime was impacting on the archaeological deposits. Surface observations combined with re-excavation of the three test pits subsequent to ploughing proved that the 2005 ploughing had caused substantial disturbance and damage. It confirmed previous observations made during an evaluation in 2003 that ploughing is damaging the fragile early prehistoric deposits of the area.
The destructive effect of ploughing on buried remains has long been of concern to archaeologists; the debate has waged for many decades. The recent English Heritage publication, 'Ripping up History', has vividly illustrated the extent of the problem suggesting that 3000 scheduled sites are currently under threat from ploughing and that "over a quarter of the individual nationally important scheduled monuments in the Stonehenge and Avebury World Heritage Site - prehistoric landscapes of iconic significance - are under damaging arable cultivation." Ongoing work in the Vale of Pickering by the Landscape Research Centre to create a landscape scale deposit model has demonstrated significant depletion of ploughsoil and truncation of features in archaeologically sensitive areas (LRC, unpublished).
A desk based assessment (Roe, 2003) and study of aerial photographs indicated that in 1950 the Ladybridge Farm site was covered in ridge and furrow earthworks (Griffiths & Timms, 2005). These earthworks have since been levelled and the area put under intensive cultivation. The archaeological evaluation of the area indicated that the effects of this ploughing had severely truncated archaeological deposits and cropmark features, which had been visible in the aerial photographs on the Ladybridge Farm site no longer survived as cut archaeological features when physically tested during the site evaluation. The interpretation that plough damage was the major cause of this truncation was also supported by the recent work near the Thornborough Henges undertaken by Dr. Jan Harding of Newcastle University. In reference to the Three Hills Barrows and triple ring ditch barrow he stated that 'all the upstanding archaeology has been massively denuded or completely eradicated by ploughing, leaving only dug archaeological features, which presumably, are themselves being gradually eroded by the plough' (Harding & Johnson, 2004).
Current research into past land use in the Thornborough area is suggesting that the impact of agriculture on the archaeology of the area is more extensive than previously thought (Timms and Griffiths, forthcoming).
During the archaeological evaluation of Ladybridge Farm, a number of dispersed and highly truncated archaeological features were encountered (Garner-Lahire, Spall & Toop, 2005). Four of these features were shallow pits containing fragments of early prehistoric pottery. Two of the features, recorded in section, provided direct evidence for plough disturbance.
Despite the accumulated empirical evidence from many varied quarters, English Heritage stated in their letter of objection to the Ladybridge Farm Planning Application (27th June 2005) that;
'The applicant does not present any evidence to support the applicant's assertion that archaeological deposits at Ladybridge Farm are being irreversibly destroyed by the present regime of arable cultivation, although clearly archaeological deposits remain at risk of further plough damage if cultivation continues across the area owned by the applicant. There is no distinction made between the impact on subsoil features and that to earthworks; indeed the surviving features seem to have good potential to provide evidence about past human activity.'
Consequently an experiment was designed to provide data on a single ploughing event in order to provide an objective statement.
In September 2005 a project design was produced by Mike Griffiths and Associates. The methodology to be adopted in the experiment was based on that presented by John Hinchcliffe (1980) and with advice from Ian Panter (Science Advisor for English Heritage). The main basis of the experiment was to replace a specified depth of natural subsoil at three locations with green glass chippings. It was anticipated that these chippings would act as visible indicators should subsoil deposits be disturbed during ploughing. The exercise was undertaken with the co-operation of the landowner and farmer. The position of the three test pits is illustrated below.
A
series of three test pits was excavated in September 2005 prior to this year's
ploughing. Two of the three monitoring pits were hand excavated to 4 cm below
the subsoil and seeded with glass chippings and then refilled (Test Pits
A and B). The third monitoring pit was positioned directly above one of the
prehistoric pits encountered during the evaluation of the site. This heavily
truncated pit (feature 1), measuring 0.45m in diameter and 0.25m deep, was
half sectioned during the earlier evaluation. The remains of this feature
were exposed and the backfill from the excavated half of the feature removed.
Glass beads were then used to fill the excavated half of the pit to the level
of the surrounding subsoil, and the ploughsoil then was reinstated. The animated
image sequence to the right shows this monitoring pit being excavated, feature
1 half sectioned, glass beads being added, and the final level of beads in
the feature.
The field was ploughed on the 24 th of September 2005 prior to the sowing of a barley crop as part of the landowner's usual agricultural cycle. The ploughing began in the southwest corner of the field and was carried out on a north-south axis. Following ploughing the field was rolled and drilled. The regime, cultivation techniques and equipment were exactly the same as used by the landowner the previous year.
Immediately following the drilling, the locations of the three monitoring pits were re-established, and a 10m by 10m area centred on the pit was fieldwalked to recover any of the beads that had been brought to the surface during ploughing. Each bead recovered was located in three dimensions according to National Grid coordinates.
The monitoring pits were subsequently re-excavated and half sectioned, the ploughsoil being removed by trowel in a series of 5cm deep spits. Each spit was photographed to record the location of beads moved by the plough, and known targets included in the photographs in order to enable the plotting of the beads in three dimensions. Sections were recorded and the pits backfilled with ploughsoil.
surveying of beads brought to the surface over test pit c
The
image to the left illustrates the scatter of glass beads brought to the surface
by plough action in relation to the half sectioned part of the test pit (dashed
blue line). The grid is at one metre intervals.
This monitoring pit produced the most dramatic results in terms of the scatter of beads visible on the surface of the ploughsoil, the plough clearly having dragged material up to around seven metres from its original location. The distribution also clearly shows the linear movement of the artefacts, ploughing having taken place on a north-south axis. In total 450 beads were recovered during the fieldwalking exercise.
The
north facing section of this monitoring pit also clearly shows the way in
which material has been dragged upwards by the plough (part of this section
is shown at right).
The
image to the left illustrates the scatter of glass beads brought to the surface
by plough action in relation to the half sectioned part of the test pit (dashed
blue line). The grid is at one metre intervals. The results from Test Pit
B initially demonstrated a much less extensive scatter of material than that
recorded in Test Pit A, with only 68 beads recovered from the surface within
the 10m by 10m area. Despite this, one bead was dragged approximately five
metres from its original location.
Two weeks after the test pit was backfilled it became apparent that marker material had actually been displaced much further from the test pit than originally thought. A cluster of glass chippings was discovered after a period of heavy rain some 30m to the south of Test Pit B. Whilst the distribution of glass chippings around the test pit itself was a direct result of the ploughing this far wider displacement appears to have been caused by the movement of material on the wheels of farm machinery.
The
image to the left illustrates the scatter of glass beads brought to the surface
by plough action in relation to the half sectioned part of the test pit (dashed
blue line). The grid is at one metre intervals. Only 16 beads were recovered
from the ground surface, and the maximum distance they had been dragged was
approximately one metre. The much smaller number of displaced beads in this
instance is due to the much smaller size of the pit containing marker artefacts.
The video (right) shows the three dimensional distribution of beads (green) and grooved-ware sherds (red) found on the topsoil around Test Pit C, and those recovered from the individual spits excavated after ploughing had occurred. This clearly shows where the plough shear exited the feature, as indicated by the rising trail of beads evident to the south of the pit (the position of the pit itself is indicated by the lowest concentration of beads).
During the excavation of the spits through the ploughsoil above feature 1, a number of pottery sherds of Neolithic date were recovered. These were clearly of the same type as those recovered from the fill of feature 1 when the pit was half sectioned during the archaeological evaluation of the site.
Experiments undertaken in 1988 by Swain have shown that pottery of this type does not survive the actions of a single winter within the plough zone. Whilst it is possible that the pottery may have originated from another feature in the immediate vicinity, this is highly unlikely. The abraded nature, freshly broken edges and spatial association with feature 1 indicate that this pottery must have derived from the pit. Whatever the case, it is without doubt that the pottery was disturbed from in situ archaeological deposits during the current agricultural regime. The results of the Swain experiment suggest that this material would have disappeared before the next ploughing.
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| sherds from the fill of feature 1 | sherds from the ploughsoil spits |
The
experiment has produced some interesting results and clearly shown that the
current agricultural regime is actively disturbing in situ archaeological
deposits across the southern half of Ladybridge Farm. These deposits include
a known early prehistoric archaeological feature and the material contained
within it.
The experiment has recorded the movement of a large quantity of 'marker artefacts' buried below the ploughsoil in a single ploughing. Due to the small size of these objects and their initial location within pits cut into the subsoil it should be noted that the exercise was not designed to model the movement of larger objects or material that was already in the plough zone. Whilst further research is required to address these particular issues it is still possible to state with a degree of certainty that successive ploughing and the implementation of other cultivation techniques employed on the Ladybridge Farm site have had a significant impact on the distribution of surface finds and will continue to do so.
During the experiment the marker artefacts were generally moved between 1 and 3 metres from their point of origin in a single ploughing. In one instance this displacement proved to be as much as seven metres. If in subsequent seasons the regime is started at the same point (as in this case) and the displacement of material is similar to that recorded here it can be seen that material could be moved large distances over a relatively short period of time.
The level of disturbance and movement of the indicator beads varied between each of the three pits. Whilst this could have been the result of several different factors the main one appeared to be the order in which the pits were subject to ploughing. This appears to be directly related to the condition of the ploughshare itself.
plough share fitted with shoe
When ploughing started in the southwest corner of the field, the plough had been fitted with a set of new plough shoes. Because of the gravelly nature of the soil, these shoes eroded fairly rapidly. Normally these have to be changed after every 15 to 20 hectares of land that is ploughed (landowner, pers. comm.). With a fresh set of shoes fitted, the plough bites to its maximum depth. As the shoes are gradually worn away the depth of this 'bite' is reduced. This eventually results in the plough riding up within the ploughsoil to a point where it fails to sufficiently break it up.
This effect was clearly reflected in the results of the monitoring pits. Test Pit A, which was the first to be affected by the plough when it still had relatively unworn shoes, produced a dramatically greater distribution of 'marker artefacts' in the recorded surface scatter than either of the other test pits. By the time Trench B and Trench C were ploughed the plough shoes were worn to the extent that the share cut a shallower furrow and caused less damage to underlying deposits. Despite this fact the disturbance in Trench C was still sufficient to displace Neolithic pottery from an in situ archaeological feature. Unlike flint, the pottery from such contexts will not survive once disturbed in the ploughsoil and will subsequently be lost forever.
Whilst the ploughing appears to be the main factor in the initial disturbance of material, other agricultural procedures were undertaken which may have affected the distribution and condition of surface artefacts. Having been ploughed the fields were then rolled using a toothed roller and then drilled with seed. The image below shows (top right) a close up of the toothed roller, which is designed to break up clods of earth, and (bottom right) a close up of the rotating teeth that follow behind the roller. It does not take much imagination to see how the roller and teeth would impact on the surface artefacts, in particular any fragile objects such as pottery and bone.
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The excavation of the test pits confirmed that subsequent rolling and drilling of the fields caused some of the material surface material to migrate to just below the surface of the ploughsoil. Excavation of spits in Test Pits A, B and C indicated that the incidence of indicator artefacts within the first 5cm spit was greater than that visible at the surface.
The results of this experiment have clearly demonstrated that material buried beneath the ploughsoil is being actively disturbed by the agricultural practices currently being followed at the Ladybridge Farm site, and that archaeological features are in themselves being truncated. This agricultural activity is part of the normal agricultural regime carried out year after year. More importantly this experiment has recorded the disturbance and displacement of Neolithic pottery from an in situ pit feature on the site. It has confirmed the observations made in the evaluation of Ladybridge Farm in 2004.
The experiment has also shown that the processes of displacement and truncation are far more complex than the authors had originally thought. Different levels of truncation were observed which were relative to the amount of wear on the plough shoes at particular points across the site. Other factors, such as depth of ploughsoil, the dryness of the soil and the nature of the subsoil may have also affected this pattern. It is clear that recorded surface distributions have undergone a far more complex redistribution throughout time through various farming practices than originally anticipated. In one instance this had a dramatic effect with material being moved up to 30m from their point of origin by post ploughing activity. Without a full comprehension of these practices it is difficult to see how artefact patterning within the ploughsoil can be interpreted at a level beyond general site/activity identification.
This experiment has recorded the effects of a single season of ploughing and planting of barley over an area of a relatively level field. The affects of other regimes of crop planting or field preparation in the area have not been evaluated. Discussions with the farmer have shown that in living memory a wide range of crops and cultivation techniques have been employed on the fields. In addition to normal ploughing there has been episodal subsoiling of the site. Deep regular plough scars have been recorded in many of the evaluation trenches and subsoiling is still employed as part of the regular agricultural regime on the farm to combat the affects of panning and soil compaction. The archaeological trenches that were excavated as part of the evaluation in 2003 and 2004 have created particular problems for the farmer, reportedly initially creating soft spots in the field then eventually forming areas of compacted ground. Such activities could accelerate the cycle of truncation recorded here at Ladybridge Farm. Research has shown that even sites being ploughed to a constant depth can be damaged as soil is compacted or lost to erosion (English Heritage 2003).
It should not be assumed that the impact of agriculture on archaeological deposits is limited to only Ladybridge Farm. Work undertaken by Mike Griffiths and Associates and Dr Jan Harding in and around the Thornborough area have shown that the serious erosion of archaeological deposits by modern agriculture is both a widespread and current phenomenon. Recent discussions with local farmers have indicated that potato farming and the de-stoning of land were, until recently, widespread activities around the Thornborough Henges themselves. Further research is currently being undertaken to assess the impact of such activity on the archaeological record and our current interpretation of the archaeological landscape.
Post Script - 12th November 2005. Discussion of comments received.
English Heritage. Ripping
up History.
http://www.english-heritage.org.uk/upload/pdf/030725_RippingUpHistory.pdf consulted
13th October 2005.
Garner-Lahire, J, Spall, C & Toop, N. 2005. Archaeological
Evaluation. Ladybridge Farm, Nosterfield, North Yorkshire. (Field Archaeology
Specialists Ltd.)
http://www.archaeologicalplanningconsultancy.co.uk/mga/projects/noster/speciali/lady_pdf.html
consulted
13th October 2005.
Griffiths, M. & Timms, S. 2005. An
archaeological Assessment of Nosterfield, Ladybridge and the Thornborough
Plain.
http://www.archaeologicalplanningconsultancy.co.uk/mga/projects/noster/speciali/mga2005p1.html
consulted 13th October 2005.
Harding, J. & Johnson, B. 2004. Topographic
Survey of the Surviving Round Barrows at The Thornborough Monument Complex,
North Yorkshire.
http://www.thornborough.ncl.ac.uk/reports/pubs_reports_rbsurvey/rbsurvey_conclusion.htm
consulted 13th October 2005.
Roe, A. 2003. Draft
Desk Based Assessment.
(Field Archaeology Specialists Ltd.)
http://www.archaeologicalplanningconsultancy.co.uk/mga/projects/noster/speciali/envass/envass.html
consulted 13th October 2005.
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