The Cleaven Dyke: A Neolithic Cursus Monument/bank Barrow in Tayside Region, Scotland

Article excerpt

The Cleaven Dyke is a complex earthwork running in an almost straight line for about 2 km across a flat river terrace bounded by the confluence of the rivers Isla and Tay, and the Lunan Burn, in Perth and Kinross District, Tayside Region, Scotland [ILLUSTRATION FOR FIGURE 1 OMITTED]. For two centuries it has been interpreted as associated with Roman military operations in the area (Pennant 1772), but an earlier date and different function have more recently been suggested. A multi-disciplinary team has begun to investigate the nature and date of the Dyke and its palaeoenvironment. This paper reports on preliminary survey, excavation, soils analysis and radiocarbon dating.

Background

The Cleaven Dyke comprises a bank (some 8-10 m across and 1-2 m high) and two roughly equidistant flanking ditches between 45 and 51 m apart [ILLUSTRATION FOR FIGURE 2 OMITTED]. It survives in woodland as an upstanding monument from NGR NO 1566 4086 to NO 1725 4000, a distance of about 1820 m. It can be seen as a cropmark for a further c. 350 m to the southeast [ILLUSTRATION FOR FIGURE 3 OMITTED], where it appears to terminate on the slopes or top of a low hill. No trace of the monument has been seen in the fields further to the southeast. The surviving northwest terminal, where the bank rises and broadens considerably (to c. 16 m), lies at the edge of the wood. Beyond, in arable ground, there is no trace of the monument visible on the ground or from the air. Some 100 m beyond this terminal the ground drops steeply away to a stream valley. Three more recent tracks hollowed into the slope, and now visible only on aerial photographs, have at times been interpreted as an extension of the Dyke.

The Cleaven Dyke is built on a level river terrace of limited width, at the confluence of the rivers Tay and Isla. The immediate area in which it is built is bounded also by two further watercourses - the Lunan Water to the east, and an un-named stream to the north of the northwest terminal.

The central bank of the Dyke appears to consist of linked dumps, and the ditches are made up of linked segments, each dump and segment on a slightly different alignment from its neighbours. At certain points (for example the northwest terminal) the bank is higher and broader; in another section the ditches markedly splay outwards. There are up to five original, apparently deliberate, breaks in the bank. In the northwest portion (from the northwest terminal to the main Perth-Blairgowrie road which cuts the monument) the Dyke is relatively straight and consistent in form and appearance, making only minor variations in line. To the southeast its line is far less constant; at a number of points either the central bank or the whole earthwork makes an appreciable change of alignment [ILLUSTRATION FOR FIGURE 4 OMITTED]. Smaller-scale variations can be detected with ease over the whole length of the earthwork by the observer on the ground, but no comprehensive large-scale survey has yet been undertaken. However, this pattern of small-scale variation has been recorded in a hachure survey [ILLUSTRATION FOR FIGURE 5 OMITTED] of a length of c. 250 m by RCAHMS (1994) and by the first phase of a full contour survey being undertaken in the current project.

Until recently the Dyke was interpreted as an earthwork associated with the 1st century AD Roman legionary fortress (the northernmost in Britain) 4 km to the west at Inchtuthil. A trench was cut across it in 1901 at the time of the first excavations of the fortress (Abercromby 1902), but the sections are described only in general terms, and the description of the monument itself misleads. It was excavated again in 1939, by Sir Ian Richmond (1940), who interpreted it as a surviving fragment of a longer earthwork, forming the boundary of the military territorium of the fortress. He noted in his three trenches that the gravel bank was turf-capped and turf-revetted, and that the revetment continued round the end of the mound at one of the constructed breaks. …