Gwynedd Archaeological
Trust Regional Historic Environment Record
Round Cairn, Trwyn Du, Aberffraw
Primary Reference Number (PRN) : 3003 Trust : Gwynedd Community : Aberffraw Unitary authority : Ynys Mon NGR : SH35236787 Site Type (preferred type first) : BRONZE AGE ROUND CAIRN Status : Scheduled Monument
Summary : Approximately 5000 years after the site was used for Mesolithic flint working, an Early Bronze Age burial mound (cairn) was constructed on top of the earlier ground surface at Trwyn Du (in c. 2000 BC). The cairn was excavated in 1956 by C. Houlder, and was found to have been built over a narrow D-shaped grave (similar to that found at Tyn y Pwll, Llanddyfnan, Anglesey). The body did not survive due to the acidic conditions created by sandy soil.
The mound was built of stone - mainly boulders and large water-rolled pebbles - retained by an unusual kerb of large slabs. The slabs were alternately one large and two small, and six of the larger stones are still visible through the grass. Excavations by R. B. White in 1974 also revealed a smaller, un-edged cairn immediately next to the main cairn.
Description : This is a Bronze Age round cairn, overlying a Mesolithic flint industry excavated by C. H. Houlder in 1956. About 60% was excavated at that time which yielded a 'D'-Shaped enclosure. It was a Bronze Age grave with no trace of a body.
Trwyn Du is on the coast today, it would have been 2 or 3 miles inland during Mesolithic occupation, therefore it can be described as inland rather than coastal. By summer 1974 erosion had resulted in a hole 6m square cutting through and destroying old ground surface. The soil was sieved and 563 pieces of flint and a range of implements comparable to those already published were found.
The excavations in 1974 produced 7000 flints and rough outs for 2 Neolithic axes. There were also a number of flint packed pits. Occupation was dated to the first half of the C7th BC.
The cairn is probably beaker. The 'D'-shaped arrangement of stones in the grave parallel to other sites on Anglesey and Glamorgan. In the absence of dateable finds, all that can be said with certainty is that the cairn post dates the Mesolithic deposits over which it is built, for the cairn is 7000BC. The kerb around the cairn shows work of the Bronze Age of a more sophisticated structure, from an archaeological point of view, than simple piles of stone or turf.
Two tranchet axes were found showing the direct response to the spread of forests which characterised the transition from glacial to post glacial periods. <1>
The cairn is now well grassed over although 4 kerb stones can be seen. Because it has been left in a half excavated state after archaeological work it is not obvious what it is. On a low cliff edge promontory, not prominent from the land nearby but provides a dramatic viewpoint and would be prominent to any boats entering the estuary. (Smith, 2003)
The monument comprises the remains of a burial cairn, probably dating to the Bronze Age (c.2300 BC - 800 BC) and situated on the leading edge of the rocky foreshore on the NW side of Aberffraw Sands. The grass-covered cairn is roughly circular on plan and measures about 9m in diameter and up to 0.6m in height. It has been partially excavated in the past (Houlder 1957; White 1978), the work revealing a well-preserved kerb cairn coincidentally overlying flint debris and occupation material of early Mesolithic date (c.7000 BC). <5>
