Plas Newydd historic RIGS site

NRW RIGS no. 129 [SH 51990 69722]

GeoMôn Global Geopark original webpage

RIGS Statement of Interest:

This is the largest double chambered tomb in Anglesey built with deliberate choice of dark-coloured Precambrian metamorphic erratic boulders.

Plas Newydd historic RIGS site, the largest double chambered tomb in Anglesey is situated on lawns, adjacent to the ornate stables block above Plas Newydd, the seat of the Marquis of Anglesey at Llanedwen. It has been selected as a RIGS to illustrate the deliberate choice of dark-coloured Precambrian metamorphic erratic boulders, to erect the tomb, in an area of Carboniferous Limestone country rock during the Neolithic Period (4,000–2,200 BC). The monument is constructed throughout of dark blue glaucophane (crossite) schist with the exception of one supporting orthostat in the larger chamber, which is a green, mica-schist. The nearest outcrop of the blue schists occurs some 2 km to the north-east, at the Marquis of Anglesey’s Column, Llanfairpwll. The stones used appear to be glacial erratics. This site shows the discernment in choice of site and geological materials of the prehistoric tomb builders.

Geological setting/context: There are three main categories of RIGS selected for their historical importance: 1. Historical constructions (arbitrarily up to 2,000 years old) and/or archaeological constructions (arbitrarily more than 2,000 years old) where rock has been used and where the relevance of geology can be demonstrated. This type of RIGS can include castles, churches, ruins, lanes, walls, cromlechs and standing stones. 2. Sites or features related to the development of geological thought, research and geology as a science, such as sites where certain concepts or theories were developed or types of feature first explained (e.g. Hutton’s Unconformity). 3. RIGS commemorating the work and contributions of important geologists. These usually take the form of a monument (such as a grave) or memorial.

Network context of this site: Plas Newydd has been selected as an historical RIGS as part of category 1, archaeological constructions (see above). Although the site was undoubtedly used by Neolithic people, the stones may have been somewhat modified by the famous 18th century landscape gardener Humphrey Repton, to enhance their romantic appearance. However, they are referred to in many early pioneering archaeological works, and the site is of undoubted importance. There is continued interest in the stones as important features of the local landscape.

References:

BAYNES, E.N. (1912). The Megalithic Remains of Anglesey (with Illustrations). Transactions of the Honourable Society of Cymmrodorion, Session 1910–1911, 3–91.

LYNCH, F.M. (1995). A Guide to Ancient and Historic Wales – Gwynedd. CADW Welsh Historic Monuments, London HMSO.

GREENLY, E. (1919). The geology of Anglesey. Memoirs of the Geological Survey of Great Britain. HMSO, London, 980pp. (2 vols)

GREENLY, E. (1920). 1:50,000 (and 1 inch to 1 mile) Geological Map of Anglesey. Geological Survey of Great Britain, Special Sheet No. 92 and (93 with parts of 94, 105 and 106).

GRIFFITH, J.E. (1900). Portfolio of Photographs of The Cromlechs of Anglesey and Caernarvonshire. Jarvis & Foster, Lorne House, Bangor.

THE ROYAL COMMISSION ON ANCIENT & HISTORICAL MONUMENTS IN WALES & MONMOUTHSHIRE (1937). An Inventory of the Ancient Monuments in Anglesey, HMSO, London, 96–97 & plate 2.