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Meusydd Henge Complex, Llanrhaeadr-ym-Mochnant Archaeological Survey and Excavation 2007


Introduction

A complex of prehistoric ritual monuments has been identified from cropmark evidence 1.3km south-east of Llanrhaeadr-ym-Mochnant, in Powys (SJ 13432520). The complex includes a henge and two possible pit circles which, by comparison with similar sites elsewhere, are thought to date from the late Neolithic and Early Bronze Age (3000-1800 BC). To date none of the elements within the complex have been investigated by survey or excavation.

Meusydd henge complex

Meusydd henge complex. Photo CPAT 83-c-431

Henges are typically circular earthworks normally comprising a ditch with an internal or external bank and one or more entrances, and normally spatially associated with other funerary or ritual monuments of Neolithic or Bronze Age date. Pit circles are rather more enigmatic and can only be interpreted more fully through excavation which may show that the pits originally held upright timbers or stones, thus forming a timber circle or stone circle, but might otherwise represent a circle of cremation pits or votive pits.

The importance of the complex was highlighted during the Cadw-funded pan-Wales survey of prehistoric funerary and ritual monuments undertaken by CPAT in 1997-8. More recently, following the completion of the pan-Wales survey, a regional review of monuments and complexes has identified Meusydd as one of the areas which would benefit from further investigation. To this end a programme of survey and excavation is being funded by Cadw during the summer of 2007.

The complex

Plot of cropmarks

Right: Plot of cropmarks showing the Meusydd henge complex.

To date the complex is known to include the following elements:

  • Meusydd Henge PRN 101071: Cropmark evidence has suggested that the henge comprises three main elements: an external ditch some 3m wide and around 19m in diameter; a narrow internal ditch around 11m in diameter with an entrance on the north-east apparently flanked by large pits; and an arrangement of four large pits in the centre suggestive of a 'four-poster' type structure.
  • Meusydd Pit Circle I PRN 101724: Cropmarks suggest a small circle around 7m in diameter formed by six pits.
  • Meusydd Pit Circle II PRN 101725: Cropmarks suggest a circle around 11m in diameter formed by nine or ten pits.

Project Aims

The project includes a programme of geophysical survey and trial excavation, undertaken with the following aims:

  • enhancing the existing record
  • identifying other sites which may form part of the group but have not shown as cropmarks
  • assessing the survival and condition of the monuments
  • providing dating evidence to inform on the relationship between the various components
  • providing baseline data to assist with the future management of the complex

Geophysical Survey

Geophysics

Standard resolution magnetometer survey with the henge and double-ditched trackway clearly visible.

The survey has now been completed within an area measuring around 140m by 80m, to include the henge and both pit circles, using a fluxgate gradiometer which provides a rapid, non-invasive, method of examining large areas for magnetic anomalies. The geophysical survey used a Geoscan FM36 fluxgate gradiometer, which detects variations in the earth's magnetic field resulting from the presence of iron minerals in the soil. These minerals are generally the weakly magnetised iron oxides that are normally found in topsoil. Features cut into the subsoil can be detected by the instrument when topsoil has formed part of their fill, whether directly or by silting.

The gradiometer has an on-board data logging device which enables readings to be taken at specific time intervals. These readings can then be correlated with geographical locations. Readings were taken along parallel traverses of a 20m by 20m grid, with a traverse interval of 1m. The speed of each traverse was controlled such that readings will be taken every 0.5m, thereby giving a total number of 800 readings per full grid. A more detailed survey was then undertaken across the henge and both pit circles, with readings taken every 0.25m along traverses 0.5m apart to achieve better definition.

Geophysics

Higher resolution magnetometer survey showing the henge and pit circles.

The survey grids were laid out and then located in relation to nearby field boundaries by total station surveying, using a digital laser theodolite.

A total of thirty-five 20m by 20m grids were surveyed at the standard resolution, the results from which clearly identified the henge and both pit circles, although gave no indication of any further features in the intervening areas. Towards the south-eastern end of the survey area a double-ditched linear feature was identified which has the appearance of a trackway. This had previously been identified as a possible field boundary visible as a cropmark.

The higher resolution survey clearly identified the henge ditch, which is approximately 19.5m in diameter and 2.5m wide, with no obvious entrance, although part of the eastern side is less well defined. The survey suggests the possibility of an outer bank, and possibly also an inner bank or berm, within which there may be a remnant mound perhaps 11m in diameter. There is no indication of the possible narrow inner ditch suggested by cropmark evidence. A number of possible pits are visible in the central area, although these are not clearly defined.

The northern pit circle (PRN 101724) has been confirmed as comprising six pits, spaced equidistantly to form a circle 7.5m in diameter, with no indication of any internal features. The southern pit circle (PRN 101725) is less well defined, although at least five pits can be discerned, forming a circle 10.5m in diameter, with no indication of any internal features. The southern side of the circle is less obvious and may be partly obscured by the double-ditched trackway.

Excavation

The results from the geophyscial survey were used to locate three excavation trenches, positioned to investigate the henge and pit circles. Each trench was initially excavated using a machine under close supervision to remove the topsoil and reveal the uppermost archaeological deposits. Having received special permission from Cadw we were able to enlist the help of two local metal detectorists to scan the excavation spoil. Unfortunately, although they discovered several iron nails and a button, no artefacts were recovered which were of particular significance. Despite this it was a useful exercise and demonstrated how archaeologists and metal detectorists can work together,

trowelling

CPAT staff and volunteers hand cleaning the trench across the henge.

The excavation was planned as a generally non-destructive exercise, designed to determine the nature, survival and condition of the archaeology. A sampling strategy was developed to investigate features and provide sufficient information without total excavation. The main intention was to identify the components of the henge and recover dating evidence, comprising either artefacts or material for radiocarbon dating, which could shed light on the potential relationship between the elements of the complex.

Although the pasture field in which the complex is situated appears to be completely flat the excavation of the henge has demonstrated that slight remains of an internal turf mound do survive. This was reinforced following the completion of a digital topographical survey undertaken with the assistance of local volunteers. This demonstrated that the mound survives to a height of only 10-15cm and has been elongated by centuries of ploughing in the same direction.

Survey

Volunteers being instructed in the use of digital surveying.

The excavations quickly identified the extent of the main henge ditch and a section was excavated to its base, showing to have been around 2.8m wide and 1.3m deep with an external diameter of 19.5m. The geophysical survey suggested that the ditch might have an entrance, or causeway, on the north-east side, outside the excavated area. Although no artefacts were recovered from the ditch samples of charcoal were taken which have provide a radiocarbon date which calibrates to 2390 to 2390 BC and 2340 to 2130 BC.

henge

Excavation trench across the henge with the stone-filled pit in the foreground and the henge ditch in the background.

Inside the ditch the excavation uncovered the remains of a mound composed of decayed turves which either sealed, or had been spread across, a narrow inner ditch around 0.9m wide and 0.5m deep. In the centre of the mound an area of river cobbles was revealed immediately beneath the ploughsoil. Further investigation showed that they had been placed within a large pit which had been cut through the turf mound. Samples of charcoal have provided a radiocarbon date which calibrates to 2480 to 2280 BC and 2240 to 2240 BC. In the centre of the mound an area of river cobbles was revealed immediately beneath the ploughsoil. Further investigation showed that they had been placed within a large pit which had been cut through the turf mound. Towards the base of the pit numerous sherds of pottery were revealed which were carefully excavated and are now awaiting conservation and reconstruction. The sherds were all part of the same vessel, a type of prehistoric pottery known as 'Beaker', which is likely to date from around 2,000 BC.

pottery

Rim and decorated body sherds of the Beaker found within the henge.

The smaller of the two pit circles proved to be the most interesting and two of the six pits were identified within the excavation trench. After the inital hand cleaning small fragments of cremated bone were visible in the surface of both pits. The excavation was restricted to investgiating one pit which proved to have been dug as a post-pit to erect a large timber upright 0.5m in diameter, the outer edge of which had been charred, presumably to improve preservation. Unusually, and of particular interest, a human cremation had been placed up against the post at some time after its erection. Charred oak from the post has now been radiocarbon dated, with the calibrated date being 3320 and 3230 BC and Cal BC 3110 to 2910, while the cremation produced a date of 2920 to 2870 BC. One of the aims of the excavation was to determine whether the pits had originally held posts and the results now indicate that this site was a timber circle comrising six upright posts.

post pit

Taking samples from the post-pit in the smaller pit circle.

The trench excavated across the larger pit circle also investigated only one pit, demonstrating that this had also originally held an upright post, although in this case there was no evidence for a cremation.

Further information

Although the excavations have been completed the process of post-excavation analysis will continue for several months, including the eagerly awaited radiocarbon dates. The website will be updated again as soon as new information is available.

For further information about the project as it unfolds contact Nigel Jones at CPAT.


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