Graeme Whittington

Lake sediments, erosion and landscape change during the Holocene in Britain and Ireland

Abstract Lakes are excellent repositories of air-borne and especially stream-borne materials. It has long been recognised that lake sediments contain a strong record of catchment soils via the inputs of minerogenic and chemical erosional products. To these may be added a variety of palaeoecological indicators including pollen, fungi, Sphagnum leaves and faunal remains. Pollen analysis, in particular, enables land use change to be assessed over many millennia and demonstrates the landscape impacts of woodland clearance, grazing and crop cultivation. Radiocarbon dating provides a chronology for environmental and agricultural change and acts as an indicator of erosion in its own right. The use of such indicators to reconstruct past instances and patterns of erosion is demonstrated with reference mainly to 50 British and Irish lake sites and especially those which have produced signals of erosion in the form of accelerated sediment accumulation and inversed or reversed sequences of radiocarbon dates during the mid and late Holocene. Sites displaying even or decreased sedimentation through time are concentrated in northern and northwestern Scotland and have either no clear signs of human impact, or only so towards the latter part of the Holocene. This pattern probably reflects a combination of factors including low population densities, thin soils and the ‘sealing’ effect of blanket peat. In contrast, all sites with accelerated erosion have indications of anthropogenic impact. This is often prior to levels of increased sedimentation showing a delay in system response. While the spread of dates for the start of the rise in sediment accumulation spans 6200–940 BP, three clusters are evident at 5295–4970, 4530–4235 and 2980–2810 BP. Radiocarbon inversions (mostly reversals) are evident for 18 sites. No obvious causal patterning is indicated and they probably demonstrate no more than the fact that catchment soils, including peats, around a particular site were pushed beyond an erosional threshold sufficient to ‘age’ the sediments deposited within the lakes. It is hoped that improvements in data quality will allow the refinement of such exercises in the future and that lakes will be valued as repositories of long-term landscape sensitivity.

Late Holocene floodplain incision and alluvial fan formation in the central Grampian Highlands, Scotland: chronology, environment and implications

A section cut across an alluvial fan and the underlying floodplain terrace in the central Grampian Highlands provides an unusually complete record of late Holocene events. At ca. 2.7–2.4 cal kyr BP floodplain aggradation was replaced by net floodplain incision. Pollen evidence and charcoal counts provide no evidence for contemporaneous anthropogenic landscape change, and the timing of the transition suggests that it reflects an increase in high-magnitude erosive flood events following overall climatic deterioration. The overlying fan was deposited by torrential hyperconcentrated flows during three brief storm-generated depositional events at ca. 2.2–2.1, 1.9–1.8 and 0.9–0.7 cal kyr BP, separated and succeeded by prolonged periods of stability and peat accumulation. During these three events, a cumulative total of ca. 6750 m3 of sediment was deposited, probably in no more than a few hours over a timescale of two millennia. These findings imply that proposed links between human activity and the development of alluvial fans or debris cones require reassessment, and that different elements of the Holocene alluvial landscape have responded in different ways to the same climatic inputs. Aggregation of dating evidence relating to aggradation or incision of alluvial landforms at different scales therefore may produce misleading results. Copyright

Stable oxygen isotope and pollen records from eastern Scotland and a consideration of Late-glacial and early Holocene climate change for Europe

The presence of marl deposits belonging to the Lateglacial period in a former lake basin at Lundin Tower in Fife, Scotland has allowed palaeoenvironmental investigations by means of carbonate δ13C and δ18O, and organic matter δ13C, in addition to palynology. The variations that emerge reveal strong similarities between the pollen and isotope records and these are interpreted as reflecting climatic shifts. The classic Late-glacial pattern of Oldest Dryas–Bolling–Older Dryas–Allerod–Younger Dryas may be evident and other climatic oscillations are shown to have occurred not only during the Allerod but also in the Preboreal. The problem of the time discordance between isotopic change and pollen representation is addressed through explanations involving lags in plant colonization. A comparison of the δ18O records from 43 sites across Europe reveals two different regional patterns, which raises fundamental questions over the nature of Late-glacial palaeoclimates.

The incidence of microscopic charcoal in late glacial deposits

Abstract Microscopic charcoal is not routinely counted by those investigating late glacial deposits — it is largely the domain of those pursuing anthropogenic questions relating to the Holocene interglacial. 23 sites dating to the Devensian late glacial (ca. 13,000–10,000 14C yr BP) in Scotland have charcoal records, and seven of these can be shown to have a high charcoal content, a phenomenon that has passed largely unremarked. We discuss patterns of charcoal representation and explore possible explanations for high charcoal abundances, especially in the Loch Lomond Stadial, including taphonomy (e.g. secondary erosion of charcoal-bearing deposits; long-distance transport); aridity (especially during the Loch Lomond Stadial); warmth and effective precipitation (especially during the late glacial Interstadial); and humanly-caused fires (Upper Palaeolithic). Available data do not allow the establishment of clear relationships between vegetation types and charcoal abundance. It is suggested that patterns of burning may need to be considered in the context of arid–wet shifts in climate. It is probable that combinations of factors are responsible for the late glacial charcoal records, but the difficulty remains that too few data are routinely collected or available for study.

Palaeoecological Investigations of Multiple Elm Declines at a Site in North Fife, Scotland

Results from the palaeoecological study of two cores from a small lake, Black Loch, in eastern Scotland are presented, attention being focused upon the period c. 60003500 BP. A series of three elm declines are evident in one core (BLII) at dates of around 5200 BP. (first decline), 4940 BP (minor decline) and 4460 BP (second major decline); at least two declines are present in a shallower-water core (BLIV). Relative, concentration and accumulation rate pollen data are supplemented by information from radiocarbon-dating, loss on ignition and particle size analysis. The multiple coring strategy demonstrates the replication qualities of the general palynological patterns but reveals the dangers of reliance on a single core from lake sites. The data suggest that vegetational and erosional disturbance were features of the elm decline periods. It is not considered feasible here to favour anthropogenic over natural causes for the falls in elm pollen and both may have applied. Examples of multiple (mainly double) elm declines from European mainland sites are provided and it is suggested that closer attention should be given to multiple elm decline events where they are found in pollen diagrams.

Late Devensian glaciation of southern Caithness

Synopsis A formal stratigraphy is proposed for the Quaternary deposits of south-east Caithness. A shelly till from the Moray Firth, the Forse Till, overlies an early till from inland, the Balantrath Till, which demonstrates an expansion of inland ice on to the edge of the plain of Caithness. Along its south-eastern margin the Forse Till is found interbedded with the Balantrath Till in the Dunbeath Water valley and a second inland till, the Ladies’ Tent Till, in the Langwell Water valley. The stratigraphy indicates that Moray Firth ice was contiguous with inland ice at this stage and evidence from striations shows that inland ice was diverted to run northwards parallel to the margin of the inland ice. After retreat of Moray Firth ice there was a minor advance of inland ice in the Berriedale area and formation of hummocky moraine. There is no evidence of any subaerial exposure within till sequences and the tills are therefore related to a single, complex phase of glaciation. The Forse Till and the Ladies’ Tent Till are overlain by peats of Windermere Interstadial age and by gelifluctates of Loch Lomond Stadial age. A variety of relative age criteria indicate that almost all the Quaternary deposits of south-east Caithness are of Late Devensian age.

Vegetation change on Papa Stour, Shetland, Scotland: a response to coastal evolution and human interference?

The first palynological and related sedimentological studies from Papa Stour, Shetland are presented and supplement the limited data available for the study of Holocene vegetation change from the Northern Isles of Scotland. Two pollen sites were located on an isthmus which has experienced the marked influences of waterlevel changes, inundation by blown shell sand, and probable grazing and arable activity. In spite of the unpromising, calcareous nature of the mineral materials at the sites, very rich suites of pollen and spore taxa were recovered including those of taxa now absent from, or rare in the islands. The assemblages indicate a strong interplay between two major habitat types, maritime heath and grassland. In addition, the sites demonstrate the effects of intermittent pool formation. The study shows that the vegetational and geomorphological landscapes of the study area are both dynamic and closely linked.

Late- and post-glacial pollen-analytical and environmental data from a near-coastal site in north-east Fife, Scotland

Abstract The coastal areas of eastern Scotland have few sites which have been investigated palynologically. This has had several consequences: most observations on the Scottish late-glacial period have been made using evidence from the west coast or from mountain massifs; the construction of isopollen maps has suffered from a lack of evidence from the east coast; vegetation change induced by humans has not always been examined for areas where their earliest activity was likely. This paper shows that evidence does exist for the Boiling-Older-Alerod oscillation in eastern Scotland, that some presently suggested tree-spread isochrones are located too far to the south and that palynology deserves to be regarded as a diagnostic rather than merely a supporting tool for evaluating human-induced landscape change.

The little ice age and Scotland's weather

Abstract Some 10,000 years ago with the disappearance of the last Devensian ice, the climate of the British Isles began a slow but general warming. This continued until the middle of the fifteenth century when the Little Ice Age developed, ushering in several centuries of colder weather and violent fluctuations in weather associated with the expansion of the circumpolar vortex. Detailed information of the effect on Scotlands weather of this major climatic disturbance is rare but The Chronicle of Fife written in the seventeenth century by John Lamont does provide some remarkable insights.

Palynological Evidence for the Growing of Cannabis Sativa L. (hemp) in Medieval and Historical Scotland

Hemp has been exploited for its fibres since prehistoric times. For a number of areas in Britain and Continental Europe, palynological data have produced evidence of Cannabis growth and retting. The extent of its cultivation and utilization in Scotland has not, however, been the subject of previous investigation. Palynological studies in Scotland have generally taken place in highland or northern areas which were not favoured for intensive arable agriculture. The pollen records from two sites in Fife, eastern Scotland, reveal that hemp cultivation was, during medieval and later historical times, an important component in the local farming economy. The spatial and temporal variation evident from the palaeoecological record may have resulted from differences in land and labour availability, market factors, or, indirectly, climatic change. In the absence of detailed long-term documentary evidence for hemp cultivation in Scotland, it is suggested that pollen analyses from well-chosen sites can provide a comprehensive data source.