Richard Tipping

EVIDENCE FOR LATE‐GLACIAL ICE DAMMED LAKES IN THE CENTRAL STRAIT OF MAGELLAN AND BAHÍA INÚTIL, SOUTHERNMOST SOUTH AMERICA

ABSTRACT. This paper critically appraises the evidence for a succession of ice‐dammed lakes in the central Strait of Magellan (c. 53°S) c. 17 000–12 250 cal. yr BP. The topographic configuration of islands and channels in the southern Strait of Magellan means that the presence of lakes provides compelling constraints on the position of former ice margins. Lake shorelines and glacio‐lacustrine sediments have been dated by their association with a key tephra layer from Volcan Reclús (c. 15 510–14 350 cal. years bp) and by 14C‐dated peats. The timing of glacial lake formation and associated glacier readvances is at odds with the rapid and widespread glacier retreat of the Patagonian ice fields further north after c. 17 000 cal. yr bp, suggesting rather that the lakes were coeval with the Antarctic Cold Reversal and persisted to the Late‐glacial/Holocene transition. This apparent asymmetrical latitudinal response in glacier behaviour may reflect overlapping spheres of northern hemisphere and Antarctic climatic influence in the Magellan region.

Analysis of pollen in soils: processes of incorporation and redistribution of pollen in five soil profile types

Abstract In order to interpret soil pollen diagrams, knowledge on the processes of pollen incorporation and redistribution is essential. It has been suggested, with little direct supporting evidence, that pollen can move in soils through association with translocated organic matter, with soil water or as a result of soil faunal activity. We report the results of investigating pollen redistribution in a range of soil types through micromorphological analysis. It was possible to categorise, using fluorescent microscopy, the location of pollen grains within soil thin sections. The overall conclusion is the key role of soil fauna in causing the redistribution of pollen. It is only in accumulating organic horizons of peaty soils or podzols that pollen can be stratified and thus interpreted for palaeoenvironmental reconstruction.

The extent and significance of bioturbation on 137Cs distributions in upland soils

Abstract Differences between measured 137Cs activity–depth profiles and idealised undisturbed profiles generated from an exponential model suggest that faunal turbation has redistributed 137Cs in mineral and organic upland soils in southern Scotland. Bioturbation is also demonstrated by the vertical displacement of other inputs to the soils of known age (non-native tree pollen and spheroidal carbonaceous particles, SCPs). The causes and mechanisms of bioturbation were further investigated by soil micromorphology. Well-drained mineral soils with active populations of earthworms are the most bioturbated, showing near-complete homogenisation to depths of about 20 cm. Enchytraeids also seem to remobilise 137Cs by the digestion of organic matter and may be the main cause of 137Cs redistribution in organic-rich upland soils. Relative rates of mixing are evaluated by comparing 137Cs depth profiles.

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.

Holocene evolution of a lowland Scottish landscape: Kirkpatrick Fleming. Part III, fluvial history

Mapping and radiocarbon dating of fluvial terrace fragments along the greater length of the Kirtle Water resulted in the definition of five major terrace surfaces. Correlations with proxy records of climate change (Part I) and anthropogenic activity (Part II) are made to understand causal mechanisms in fluvial behaviour. The limitations of such correlations are emphasized. The highest terrace (Kirtle I) is thought to be of Devensian Lateglacial age. The remaining four are of Holocene age. An early Holocene gravel aggradation (Kirtle II) may have been sustained from c. 7250 14C years BC until close to c. 455 cal. BC. The establishment of Alnus on floodplains may have led to channel stability. Incision after c. 3250 cal. BC may have been due to greater discharges at a time of deteriorating climate. Terrace Kirtle III is undated. Prior to aggradation of Terrace Kirtle IV, beginning at around cal. AD 300, a period of lowered fluvial activity and floodplain stability is recorded from c. 850 cal. BC. Anthropogenic activity is thought to be responsible for the diachronous initiation of aggradation of Terrace Kirtle IV. Terrace Kirtle V is late historic in age, but the cause cannot be readily isolated.

Blanket peat in the Scottish Highlands: timing, cause, spread and the myth of environmental determinism

This contribution describes the geomorphic, stratigraphic, palaeoclimatic, palaeoecological and 14C dating evidence for the timing within the present interglacial of blanket peat initiation and extension (‘spread’) from five localities throughout the upland and northern regions of Scotland. The results suggest that blanket peat was common or abundant over much of the highland landscape within a few thousand years of the beginning of the Holocene period. Blanket peat developed either as an inevitable but rapid end-stage to soil development in this generally cold and wet climate or was promoted by climatic change. There is no evidence from this data-set that blanket peat developed as a result of anthropogenic activities. It is suggested, indeed, that farming communities successfully resisted the natural spread of peat across their fields.

The chronology of Late Quaternary fluvial activity in part of the Milfield Basin, northeast England

The sediment stratigraphy of a 4 m thick intercalated Holocene alluvial fill and valley floor peat at a site in the Milfield Basin, Northumberland, has been dated by a series of eight 14C assays, and related to a previously analysed pollen record. The sequence extends from the earliest Holocene until c. 2800 cal. BP. Prior to the onset of peat inception, substantial amounts of channel-trenching can be demonstrated to have occurred in the Milfield Basin during the Loch Lomond Stadial. There is no measurable early Holocene accelerated fluvial activity, but a major flooding event occurred at c. 7500 cal. BP, much earlier than recorded elsewhere in the region. The explanation for this is not clear. However, the cessation of mid-Holocene overbank sedimentation at c. 4000–3500 cal. BP is tentatively correlated with slope stability associated with woodland regeneration.

Mid-Holocene charcoal fall in southern Scotland: Temporal and spatial variability

Abstract Four securely 14 C-dated pollen and microscopic charcoal stratigraphies, and measures of peat humification, from sites representing a range of environmental settings and altitudes within one small region of southern Scotland are examined for the period 7000–5000 cal. BP to identify the consistency of representation, spatial patterning and temporal variability of the mid-Holocene charcoal fall. Charcoal falls are identified at three lowland sites, but not in the upland sequence. The charcoal falls at these sites may reflect an increase in fire regime in the later Mesolithic, determined in part by a shift to drier regional climate, rather than a subsequent reduction in burning. The charcoal fall is not synchronous within the region, but differs between sites over c. 1000 cal. years. Each fall is associated with one of two shifts to drier soil conditions at c. 6100 or 5400 cal. BP. At two sites the charcoal fall also coincides with Ulmus declines.

Use and abandonment of a Neolithic field system at Belderrig, Co. Mayo, Ireland: Evidence for economic marginality

This paper presents evidence for the nature of early and middle Neolithic farming activity, its impact upon the landscape and environment, and its vulnerability to climatic change, at a sub-peat field system at Belderg Beg, North Co. Mayo, Ireland. Pollen analyses of a 14C dated peat deposit close to the field system indicates that basin peat accumulated from c. 5590 to 5330 cal. BP, probably triggered by farming activities. The palynological evidence indicates that the field system was constructed for pastoral farming, surrounded by woodland. Sediment-stratigraphic analyses show that the soil in the field system was subject to significant erosion, which may have been a causal factor in the local cessation of agriculture in the late sixth millennium cal. BP. Peat humification analyses indicate that surface wetness was greatest at c. 4940 cal. BP, several centuries after abandonment of the field system, coincident in age with evidence for higher precipitation from other sites in North Mayo. Comparison with other records of early and mid-Neolithic agricultural activity and abandonment in the region suggests that the well-recognised mid-Neolithic agricultural decline occurred in the broad context of a shift to a more oceanic climate, but that local factors such as soil quality may have been more important in the exact timing of local agricultural abandonment.

Holocene relative sea-level change in the lower Nith valley and estuary

Synopsis Detailed morphological, lithostratigraphical and biostratigraphical studies in the lower Nith valley and estuary, Scotland, disclose evidence for changing relative sea levels during the Holocene. The Main Postglacial Transgression was in progress in the area around c. 7500 14C years bp (8350 cal. years bp) to c. 7800 14C years bp (c. 8600 cal. years bp), perhaps by c. 7675 14C years bp (c. 8490 cal. years bp); relative sea levels fell briefly after c. 7200 14C years bp (c. 8020 cal. years bp); then resumed their rise after c. 7000 14C years bp (c. 7800 cal. years bp) and culminated by c. 590014C years bp (c. 6720 cal. years bp) reaching the Main Postglacial Shoreline, the evidence for which is widespread in the lower Nith valley. Subsequently, relative sea levels may have fluctuated, modifying or exceeding Main Postglacial Shoreline features along the estuary coastline before falling to a lower shoreline and then falling farther to reach present levels at c. 1760 14C years bp (c. 1800 cal. years bp), after which there is no evidence for relative sea-level change in the area. This sequence is considered broadly comparable with sequences recorded at other sites along the northern shore of the Solway Firth, in particular confirming evidence for a fluctuation in the Main Postglacial Transgression and for the age of the Main Postglacial Shoreline.