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Bwlch yr Avan Dyke is a prehistoric linear earthwork situated in Wales on bedrock belonging to the South Wales Upper Coal Measures Formation. This geological sequence, laid down during the Westphalian period, comprises mudstone, siltstone, sandstone with seams of coal and ironstone, capped by ferricrete deposits. The underlying geology would have shaped both the construction methods and the local resources available to those who built the monument.
The dyke represents a form of boundary or defensive work characteristic of prehistoric societies in Britain. Such linear earthworks typically served to demarcate territorial divisions, manage livestock movement, or provide protection across vulnerable landscape positions. The monument's location and alignment would have been chosen to take advantage of the local topography and natural features of the coal measures landscape.
Bwlch yr Avan Dyke is protected as a scheduled monument by Cadw, the Welsh heritage agency, under reference GM246. This designation recognises its archaeological significance as a surviving example of prehistoric land organisation and engineering. The monument remains an important record of early Welsh settlement patterns and the relationship between human communities and their physical environment during prehistoric times.
Bwlch yr Avan Dyke is a scheduled monument protected by Cadw under reference GM246. View the official record →
Bwlch yr Avan Dyke is a prehistoric linear earthwork situated in Wales on bedrock belonging to the South Wales Upper Coal Measures Formation. It is designated a Scheduled Ancient Monument by Cadw under reference GM246.
Bwlch yr Avan Dyke dates from the prehistoric period, and is classified as a dyke. It is one of over 32,000 scheduled monuments protected across the UK.
Bwlch yr Avan Dyke is a Scheduled Ancient Monument, legally protected by Cadw — the body responsible for designating and safeguarding heritage sites in Wales. The official designation reference is GM246.
Several scheduled monuments lie within 10 km, including Carn y Hyrddod & Neighbouring Cairn (1.7 km), Mynydd Ton Cairns (3 km), Round Cairn 567m East of Bryn Defaid (4.7 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Bwlch yr Avan Dyke's history, each drawn from the record and mapped to the exact spot:
Every location is different. Not every section appears for every place, only what the historical record actually holds turns up in a report.
Bwlch yr Avan Dyke stands on South Wales Upper Coal Measures Formation, bedrock that formed in the Westphalian. The rock here is mudstone, siltstone, sandstone, coal, ironstone and ferricrete.