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Submerged Forest, Llanrhystyd

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NPRN417481
Map ReferenceSN56NW
Grid ReferenceSN5056566659
Unitary (Local) AuthorityCeredigion
Old CountyCardiganshire
CommunityLlansantffraed
Type Of SiteNATURAL FEATURE
PeriodMesolithic
Description
Lying beneath the present-day artificially maintained cobble and beach head shingle at Llanrhystud there is an exposure of a post-glacial land surfaces. The exposure appears not to attain a depth greater than 0.40m, but may exceed 400m in length orientated north-northwest/south-southeast in line with the coast edge. The width most obviously exposed at time of visiting (21 August 2012) was approximately 3-4m tained. The exposure is capped by a layer of peat on average about 0.15m deep. It exhibits root systems, twigs/branches, plant macrofossils and even occasional tree stumps. This peat lies upon what appears to be an organic soil up to 0.15m deep, itself developed over a fine blue-grey anaerobic clay of roughly the same thickness. The entire eroding exposure rests directly upon a cryoturbated periglacial deposit consisting of highly compacted angular fragmented rock cemented in clay, the uppermost component of a local glacial head deposit itself containing broken and rounded locally-derived galets again strongly cemented in clay with occasional sands and gravels, best seen in cliff sections to the south.

This exposure is subject to erosion at high tide. The peat dries out at low tide, shrinks and fragments. The clay deposit beneath is also reported to dry out, assuming a white, kaolin-like appearance and becoming powdery. Substantial pieces of timber have become exposed and lost over the years. Futher pollen and sediment analysis is really required to confirm the the nature and date of the peat/woodland environment.

Observations of the exposed land surfaces have been made intermittently for around twenty years by Mr and Mrs J Evans, Montrose, and Dr C.S.Briggs, Llwyn Deiniol, both of Llanddeiniol.

Dyfed Archaeological Trust recorded a section of the exposure running from NGR SN 52336 68875 to SN52380 68958 in September 2012. They noted that base of the peats extended c0.8m beyond the line drawn as the seaward extent of the shingle ridge as recorded on OS mapping.

Sources include:
NMRW Cat. Ref. DAT22/010

Maritime Officer, RCAHMW, January 2015
Resources
DownloadTypeSource
application/pdfDAT - Dyfed Archaeological Trust Reports
application/pdfRCAHMW Exhibitions