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New Archaeological Survey Techniques to be used at Newgrange to search for hidden chambers

There will be a high-tech archaeological survey conducted at Newgrange National Monument in the Brú na Bóinne World Heritage Site in Co. Meath over the week beginning Monday 17th October.

The key objective of the survey is to investigate whether there are any hidden passageways and chambers in Newgrange Passage Tomb and the survey team will be using some techniques not used before on archaeological sites in Ireland.

The work is being carried out by a specialist team from Comenius University, the Slovakian Academy of Sciences and the University of Technology from Bratislava, Slovakia with support from the Slovakian Scientific Academy (VEGA) in collaboration with Dundalk Institute of Technology (DkIT), Landscape and Geophysical Services (LGS), the National Monuments Service of the Department of Arts Heritage and the Gaeltacht (NMS) and the Office of Public Works (OPW).

A microgravity survey at Newgrange was originally a component of a joint funding application to the Irish National Strategic Archaeological Research (INSTAR) programme administered by the Heritage Council. The project proposed the large-scale application of multiple remote sensing and geophysical surveys in the Brú na Bóinne WHS in order to comprehensively map the low-visibility and subsurface archaeology of the area. The proposal received very favourable reports from the anonymous reviewers but was not funded due to a drastic cut in the INSTAR budget for 2011 which saw only one applicant project being funded.

Comenius University and the University of Technology, partners in the original application, are bringing their cutting-edge science and technology to investigate one of Ireland’s world-class archaeological treasures. They consider the microgravity survey as a unique opportunity to further the scientific investigation of the tomb and refine the use of their technique (microgravity survey) for use on worldwide archaeological sites of this type. The technique has already been used very successfully at the pyramids in Egypt to identify the locations of passages and chambers. Comenius University has managed to find some limited funds to carry out part of the original survey programme and this is gratefully welcomed by the project team.

Microgravity

The Microgravity method is based on state-of-the-art precise recording of anomalies in the Earth's gravity field with the objective of detecting the responses of small-scale, sub-surface density inhomogeneities. Microgravity is a specialised method in archaeogeophysical prospection where it has been successful in the detection and description of shallow-lying cavities such, as crypts, chambers, tombs, cellars etc. The state-of-the-art relative gravity meters, such as the Scintrex CG-3M, CG-5 and ZLS Burris can measure the changes in the gravity field with a precision of approx. ±5 microGals (1 microGal = 10-8 m·s-2), so cavities with anomalous gravitational effect above 10 microGals (taken in absolute value) can be detected.

The potential for detecting gravity anomalies when using the microgravity method is of course dependent on the depth of the target - cavities with a volume of several m3 can be recognized at shallow depths of the order of a few metres (depth is taken to the top of the cavity).

Preparatory fieldwork carried by Landscape & Geophysical Services has allowed Comenius University to create a computer model of the Newgrange passageway and chamber (Fig 1). A computer simulation of microgravity measurements made over the passage tomb (Fig 2) has indicated that they would detect the presently known chamber. These results are being used to inform the microgravity survey commencing on 17th October.

Figure 1: 3D view of the modelled passageway/chamber structure in the Newgrange mound.

Figure 2: 3D view of the Newgrange Passage Tomb together with the modelled passageway/chamber structure and its simulated gravitational anomaly when measurements are made on the top surface of the tomb.

The microgravity survey will be complemented by standard magnetic gradiometry, earth resistance and electrical resistivity tomography geophysical techniques and the trial of a newly developed electromagnetic mapping instrument.

Dr. Conor Brady, Humanities and Social Science Research Centre, Dundalk IT.

Prof. Roman Pasteka, Department of Applied and Environmental Geophysics, Comenius University, Bratislava, Slovakia.
Kevin Barton, Landscape and Geophysical Services, Claremorris, Co. Mayo.