SUMMARYPercentage and concentration pollen diagrams from tbe sediments of two adjacent inter-drumlin bollow lakes near Dungannon, and in two cores frot-n Lougb Catherine, suggest tbat only small reductions in tbe pollen frequencies of trees sucb as pine and, at some sites, birch and oak, accompanied reduced Ulmus at the elm decline in tbese parts of Co. Tyrone. Tbey also confirm tbat Pteridium aquilinum could sporulate and many berbs were able to flower more freely owing to an opening of tbe tree canopy. Seventeen radiocarbon dates provide cbronologies for tbe sites and date tbe elm decline to between 5050 and 5375 B.P., the subsequent start of increased elm pollen percentages to between 5010 and 4850 B.P., and tbe beginning of a second decline in elm pollen to hetween 4330 and 4260 B.P. Tbe initial decline in elm pollen values may have been caused by disease and tbis reduction was superimposed upon a background of small-scale clearances wbicb continued after a general elm regeneration. Tbe question of a general similarity and causation of tbe second elm decline in Ireland and elsewhere is considered. Chemical, magnetic and pollen preservation data from tbe Co. Tyrone sites suggest episodes of erosion occurring at tbe first elm decline and otbers at tbe second elm decline.
Hebridean sites of the coastal sand cliffs and associated machair, or sandy plain have been known for many years. Artefacts and ecofacts of various types have long been collected from archaeological sites in the eroding sand-cliffs of the machairs of the Outer Hebrides. Early in 1983, personnel of the then Central Excavation Unit of Historic Scotland's predecessor revisited very nearly all of the coastal archaeological sites then known in the Long Isle, with the specific task of identifying those at immediate threat from coastal erosion and of assessing the feasibility of their excavation or preservation. Some 32 sites were seen to be undergoing active erosion; at nine of them preservation was not being pursued and excavation was feasible. These sites were of two morphotypes: sites exposed in roughly vertical sand-cliffs and sites exposed over relatively large horzontal areas of sand deflation. It was decided to examine one sand-cliff site along its exposed face. The site selected was Balelone in North Uist, its excavation designed to explore both the problems associated with the excavation of deep midden sites with complex stratigraphy and the not-inconsiderable problems of excavation in sand. In the light of the Balelone trial excavation, a new approach was called for. A structured approach aimed firstly at establishing the three-dimensional extent of the sites to be examined. Four sites were then sampled (the sand-cliff sites of Baleshare, on the island of the same name off the west coast of North Uist and Hornish Point, South Uist and the deflation sites of South Glendale, South Uist and Newtonferry, North Uist) within a rigorously-defined research framework.The machair sites were formed by sand accretion, facilitated by human activities ranging from construction to refuse disposal and cultivation. Their formation was intermittent and they underwent episodes of major erosion, isolating the sites from the landscape mass of the machair sands. Despite their apparent wealth of suitable material, the dating of Hebridean coastal sites presents special problems. The strategy here was to provide a dating framework for the sequences on each site, from which the dates of archaeological significant structures and events could then be arrived at by extrapolation. Preliminary dates from the earliest and latest strata at Balelone spanned such a small period that a First Millennium BC date-range could be assigned. At Baleshare, the deposits investigated were chiefly later Bronze Age; following abandonment (roughly 200 radiocarbon years) of the Period I cultivated soil Period II represented extensive, manured, cultivated fields in the vicinity of a settlement now lost to the sea. As Period II went on. the settlement seems to have moved closer to the excavated area. After another hiatus of a minimum of 350 radiocarbon years, there were further cultivated plots and associated settlement of Iron Age date (Period III). By contrast, the site at Hornish Point (including successive wheelhouses and associated cultivation areas) is considered to be all of one - dynamic, Iron Age - period, lasting some 300 radiocarbon years (with potentially earlier structures unexcavated). A post-medieval blackhouse of characteristic Lewisian form had been cut into the settlement mound. The three dates from Newtonferry suggest that some Early Medieval activity took place at the site, while the bulk of the deposits date from the thirteenth-fourteenth centuries AD. At South Glendale, the radiocarbon dates indicate occupation sometime between the thirteenth and fifteenth centuries AD; stratigraphically lower, fragmented and truncated remains were prehistoric, probably early Bronze Age.
SUMMARYThe Inner Hebridean island of Rhum lies between the once wooded mainland of north-west Scotland and the now largely treeless islands of the Outer Hebrides. Rhum is more exposed than the nearby larger islands and is of particular interest since it has been occupied by humans for at least 8500 years. Pollen, charcoal and radiocarbon studies were carried out on a peat profile from Kinloch in the most sheltered eastern part of the island, some 300 m from the site of the earliest known Mesolithic occupation site in Scotland.From an estimated 7800 BP, the local mire surface was open with some hazel and willow scrub. Alder replaced willow at c. 6500 BP and with hazel, remained the dominant woody vegetation until c. 4000 BP when both were reduced and by which time evidence for agriculture is discernible. A period of reduced Alnus and Corylus between 5950 and 5700 BP, with high concentrations of charcoal, may result from human infiuence. An Alnus reduction dated to between 5250 and 4950 BP may have been caused by changes in mire hydrology. The woodland was more open than that at nearby mainland sites but it was comparable to well-wooded sites on Skye and Mull. Birch was notably less significant at the Rhum site and the preponderance of Alnus along with persistently high Osmunda values may indicate that adaptation to exposure and salt tolerance were important factors in determining the character of the early postglacial vegetation.
Exposures in blanket mire deposits in the Galloway Hills, southwest Scotland, have revealed the presence of minerogenic layers within the peat stratigraphy. These deposits are studied by a variety of methods with a view to the investigation of ecological influences upon deposition, the timing of events and aspects of their geomorphology. The layers were deposited under both wooded and unwooded conditions in the vicinity of the sites, but vegetational disturbances consistent with anthropogenic activity including agriculture, were coeval with minerogenic deposition at various times. The evidence points to a dissimilarity in the formation times of individual layers of pronounced minerogenic deposition, although deposition has been a continuous event over the last 5000 years. The greatest development of distinct layers would seem to be in peat lying at the break of slope, where mineral material came to rest following its removal by water from rotted boulder and sandy podsolic soil sources lying upslope.
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