Late Glacial Research Articles

A multibeam bathymetric survey of Bay of Islands, Newfoundland: new evidence of late-glacial and Holocene geological processes

Multibeam bathymetric imagery of Ray of Islands, Newfoundland, is interpreted within the context of late-glacial and post-glacial processes- West of Humber Arm, the fiord floor is irregular and deep. Humber Arm has steep sidewalls and a flat floor. It contains glaciomarine mud. capped by a layer of red mud probably derived from the Deer Lake Basin, which was connected to the ocean ca. 12.2 ka. In the early postglacial period, sediments on the fiord sidewalls slid into deep water, forming erosional channels. Depositional lobes, stacked in many areas, overlie glaciomarine sediments in deep water. The glaciomarine and submarine slide sediments are overlain by postglacial mud that is imprinted by elongate, ovoid, and circular fluid-escape trenches, and sedimentary furrows. The natural morphology of the fiord has been modified by anthropogenic activity at Comer Brook. Effects include an apron of bark offshore from the paper mill, dredge spoil, and a sunken vessel at the mouth of Humber River. Large submarine slides, probably triggered by wharf construction at Seal Head, formed deep channels on the fiord sidewalls and overlapping depositional lobes on the fiord floor. They are morphologically similar to the lateglacial slide failures in the fund.
 
 RÉSUMÉ
 Les images bathymétriques multifaisceaux de Bay of Islands, Terre-Neuve, sont interprétées dans le contexte des processus tardiglaciaires et post-glaciaires. À I'ouest de Humber Arm. Ie fond du l’jord est irrégulier et profond. Humber Arm est doté de parois abruptes et d'un fond plat. Il renferme de la boue glaciomarine recouverte d'une couche de boue rouge provenant probablemenl du bassin du lac Deer, qui était relié à l'océan il y a environ 12.2 millies d'années avant nos jours. Au début de la période post-glaciaire, Ies sediments sur Ies parois du l’jord ont glissé a l’intérieur de I'eau profonde en formant des chenaux d'érosion. Des lobes sédimentaires s'empilant en de nombreux endroits recouvrent les sédiments glaciomarins en eaux profondes. Les sédiments de glissement glaciomarins et sous-marins sont recouverts d'une boue post-glaciaire marquée de tranchées allongées, ovoides et circulaires d'évacuation des liquides et de silions sédimentaires. L'activité anthropique a modi fié la morphologic naturelle du l’jord a Corner Brook. Les effets de cette activité comprennent un tablier d'écorce au large de la papeterie, des matériaux de dragage et un navire ayant coulé à I'embouchure dc la riviére Humber. D'importants éboulements sous-marins, probablement causés par la construction du quai de Seal Head, ont formé des chenaux profonds dans les parois du l’jord et des lobes sédimentaires qui se superposcnt sur Ic fond du l’jord Ceux-ci sont morphologiquemcnt analogues aux fractures de glissement tardiglaciaires dans le l’jord.
 
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What was the late Pliocene Mediterranean climate like; a preliminary quantification from vegetation

Abstract Reconstruction of the composition and organisation of the late Pliocene vegetation in central Mediterranean and quantification of the climatic requirements of its main representatives allow temperature and precipitation estimates during the late Pliocene glacial/interglacial cycles, at ca 2.4 Ma. The late Pliocene climatic glacial and interglacial conditions are illustrated on a bioclimagram which correlates the mean annual temperature and precipitation criteria. Comparison between modern and late Pliocene vegetation indicates that late Pliocene interglacial climate was approximately 4 degrees C warmer, with more higher amount of precipitation than today, and that conditions similar to modern ones prevailed during late Pliocene glacials.

Holywell Coombe, Folkestone: A 13,000 year history of an English Chalkland Valley

Holywell Coombe is a valley cut into the scarp-face of the North Downs Chalk cuesta, near Folkestone, Kent. Its geological importance stems from a highly fossiliferous sequence of Lateglacial and Holocene deposits that line the valley floor. These have yielded a molluscan succession of particular importance, providing a record of environmental change throughout the past 13,000 radiocarbon years. Waterlogging of the basal deposits has prevented oxidation, leading to the preservation of a range of organic fossils, such as plant and insect remains, that normally do not survive in calcareous environments. This enables linkage between faunal and vegetational records, allowing the differential rates of response of particular groups to be critically compared. The importance of the site was revealed in 1968 in trial pits connected with an aborted Channel Tunnel project. Resurrection of plans to build a tunnel led in 1987 to major ‘rescue’ excavations and multidisciplinary investigations, the results of which are reviewed here. A three-dimensional picture of the valley infill was established from a network of 180 boreholes. Critical parts of the sequence were investigated in specially excavated trenches and sections exposed during construction of the tunnel. Systematic sampling at a number of locations within the valley provided a palaeontological record from the full stratigraphical succession. A number of Lateglacial and Holocene soils were found to be represented in the sequence, including that formed during the Allerød phase of the Lateglacial interstadial. The molluscan zonation scheme previously defined at Holywell Coombe, and applicable over large areas of southern Britain and possibly further afield, has been refined and dated with greater precision. The Lateglacial sequence has been extended back to the early part of the Lateglacial interstadial by this study and the site chronology is now underpinned by over 35 new radiocarbon dates. Quantitative palaeoclimatic reconstructions from beetle remains, using the Mutual Climatic Range method, cover the period between 13,000 and 9000 yr BP. The earliest sediments, marsh deposits with thermophilous insect taxa and a species-poor molluscan assemblage, date from around 13,000–12,000 yr BP. Just before the end of this period, changes in beetle faunas record climatic cooling, heralding slope instability and the accumulation of thick colluvial deposits. By 11,500 yr BP the climate had stabilized and slope movement had ceased, allowing the formation of the ‘Allerød soil’. There followed a major deterioration to the arctic climate of the Younger Dryas, during which renewed erosion from the valley sides brought further material onto its floor, burying and sealing the earlier sediments. The beginning of the Holocene saw the onset of tufa formation around two dominant springs in the upper valley. There was progressive development of forest, hazel-dominated woodland being established by 9500 yr BP. There is some evidence for thinning of the forest canopy during the late Mesolithic and Neolithic, but the major clearance occurred during the Early Bronze Age, causing renewed instability on slopes and consequent hillwash accumulation. This final depositional phase continued, with pauses marked by soil formation in the Early Bronze Age and the Iron Age, to the present day. The hillwash seals structures relating to prehistoric human activity, including plough-marks, and contains an extensive sequence of artefacts.

Changes in lake-sediment stratigraphy associated with late glacial climate change: examples from western Nova Scotia

An investigation of lake-sediment stratigraphy in western Nova Scotia has focused on determining the environmental response to late-glacial climate change. Sediment records from Ave headwater lakes were recovered and sediment stratigraphy from four of the lakes was used to reconstruct late-glacial environments for this region.
 
 Results from Sand Lake and Canoran Lake (South Mountain) indicate that the South Mountain was deglaciated by about 11,500 B.P. The North Mountain was deglaciated slightly earlier. All cores contained till (unit 1) which was overlain by a fine-grained diamicton (unit 2) that was deposited after ice had receded. A gyttja with varying mineral sediment concentrations (unit 3) overlies unit 2. Unit 2 is interpreted as sediment that was transferred to the basin as the basin and catchment stabilized. The North Mountain sites are characterized by lack of a Younger Dryas-equivalent loss-on-ignition or mineral oscillation. The South Mountain sites both contain a thin (2 cm) Younger Dryas-equivalent mineral horizon (unit 4) bounded above and below by sandy gyttja (units 3 and 5). Image and grain size analysis of units 3,4 and 5 indicate that these units differ primarily in their amounts of fine silt and clay, as mavimiim grain size is similar in each unit. This result indicates that changes in sediment transfer mechanisms in response to climate change were subtle. The formation of unit 4 (YDimh) was primarily a consequence of intrabasin sediment transfer and reduced productivity; an increase in the extent and/or duration of lake ice cover may have been an important factor. The catchment response to Younger Dryas climate change in western Nova Scotia was probably subdued. Though aufeis and perennial snow cover may have existed at some sites, the presence of Younger Dryas-equivalent glacial ice in western Nova Scotia is unlikely.
 
 RÉSUMÉ
 Une étude stratigraphique des sédiments lacustres dans l'ouest de la Nouvelle-Écosse s'est attachée à déterminer la réaction de l'environnement au changement climatique tardiglaciaire. On a récuperé des échantilions de sédiments de cinq lacs d'amont et on a utilise les données stratigraphiques des sédiments de quatre des lacs pour reconstruire les environnements tardiglaciaires de cette région.
 
 Les résultats obtenus du lac Sand et du lac Canoran (mont South) reVelent que la déglaciation du mont South est survenue vers 11 500 avant le présent. La déglaciation du mont North s'est produite légèrement plus tôt. Toutes les carottes contenaient du till (unite 1) recouvert de diamicton à grain fin (unité 2) qui s'était déposé après la disparition de la glace. Un gyttja renfermant des concentrations de sédiments minéraux variables (unité 3) recouvre 1'unité 2. Cette demière est interprétée comme le resultat d'un transfert de sédiments dans le bassin sédimentaire au moment ou le bassin sédimentaire et le bassin hydrographique se sont stabilisés. Les points du mont North se caractérisent par une absence d'oscillation minérale ou de perte au feu équivalente au Dryas récent. Les points du mont South renferment tous deux une mince couche (2 cm) d'horizon minéral équivalent au Dryas récent (unité 4) délimitée au-dessus et au-dessous par un gyttja sableux. Les images et l'analyse de la granulométrie des unités 3,4 et 5 révèlent que ces unités sont différentes, principalement en ce qui concerne leurs teneurs en argile et en silt fins, car la taille maximale des grains est semblable dans chaque unité. Ce résultat témoigne du fait que les changements dans les mécanismes de transfert des sédiments consécutifs au changement climatique ont été subtils. La formation de l'unité 4 (YDimh) a principalement été provoquée par un transfert de sédiments à l'intérieur du bassin et une productivité réduite; l’augmentation de l’étendue ou de la durée de la couverture de glace du lac a peut-être constitue un facteur déterminant. La reaction du bassin hydrographique au changement climatique du Dryas récent dans l'ouest de la Nouvelle-Écosse a probablement été estompée. Même si un aufeis et un tapis de neige pérenne ont pu exister en certains endroits, la présence de glace de l'ère glaciaire équivalente au Dryas récent dans l'ouest de la Nouvelle-Écosse est improbable.
 
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RADIOCARBON CHRONOLOGY AND THE LATEGLACIAL AND EARLY POSTGLACIAL RESETTLEMENT OF THE BRITISH ISLES

Abstract In terms of human geography, the Pleistocene/Holocene transition in the British Isles was marked by the recolonisation of areas uninhabited during the pleniglacial. Three phases can be identified. The first, which began around 12,500 RCY BP (Radiocarbon Years Before Present), towards the end of the Lateglacial Interstadial (pollenzones 1b, Ic and II), was marked by the rapid and widespread dispersal of human groups into the lowlands of central, southern and eastern England. The second phase, corresponding to the Loch Lomond Stadial and Preboreal (Dryas III and Zone IV) and dating from 10,999 to 9000 RCY BP, was an episode of consolidation with little further spread of settlement. During both of these phases Britain remained joined to mainland Europe and developments need to be seen within the context of processes at work on a continental scale. The third phase, from 8999 to 7000 RCY BP, witnessed a further rapid extension of settlement which involved most of the rest of Britain, including Ireland but excluding the far southwest of England and northeast Scotland. Developments during this third phase were particularly marked along the Atlantic seaboard and appear to have coincided with the northwards migration of the Polar Front and the establishment of contemporary patterns of oceanic and atmospheric circulation.

Lateglacial climate change and coastal evolution in western Jura, Scottish Inner Hebrides

The geomorphic and sedimentological evidence for former sea-level changes in the exposed coastline of western Jura shows a clear coastal response to past changes in climate. In particular the rapid and high-magnitude climate changes associated with the onset and termination of the Younger Dryas appear to have been accompanied by major changes in coastal response. In western Jura, the temperate climate of the Lateglacial Interstadial was associated with beach-ridge deposition, with the earlier part of this period being associated with larger ridges than the latter. By contrast, the cold climate during the Younger Dryas appears to have been dominated by frost processes, sea-ice development and rapid rates of coastal erosion of bedrock. Cold-climate shore erosion of bedrock appears to have ended suddenly at the close of the Younger Dryas.

The Late Devensian Lateglacial palaeoenvironmental record from Whitrig Bog, SE Scotland. 2. Chironomidae (Insecta: Diptera)

Changes in chironomid midge larval assemblages in Lateglacial (c. 13.5–10 ka yr BP) lake sediments from Whitrig Bog are used to infer climatic (temperature) change. The earliest sediments contain few, predominantly cold stenothermic taxa. This fauna is replaced by an assemblage dominated by thermophilic taxa, indicating rising temperatures. The relatively warm Interstadial is punctuated by at least two brief cold oscillations which are characterized by the return of certain cold‐water taxa and the demise of some elements of the thermophilic fauna. The earlier of the two oscillations was apparently shorter and colder than the second. The highest Lateglacial Interstadial temperatures were attained either shortly before or after the first cold oscillation. This timing of the Lateglacial thermal maximum is apparently later than has been previously inferred from fossil beetle data. The Lateglacial Interstadial is terminated by the Loch Lomond (Young Dryas) Stadial, which is indicated in this monolith by an abrupt return of cold stenothermic Chironomidae and the virtual elimination of thermophilic taxa. Temperatures during the Younger Dryas appear to have been colder than during either of the previous minor cold oscillations. Climatic inferences from chironomid analysis broadly support and augment conclusions drawn from sediment chemistry and palynological evidence derived from the same monolith, although there is evidence that the vegetation and chironomid responses to early postglacial warming were out of phase.

Upland vegetation in the north-west Iberian peninsula after the last glaciation: Forest history and deforestation dynamics

This paper presents the results of pollen analyses from organic sediments of seven cores (299 spectra) in a mountainous area of the north-west Iberian peninsula. The pollen diagrams, supported by seven14C dates, are used to construct a regional pollen sequence covering the main stages of vegetation dynamics, from the last phases of the Late-glacial until the present. During the Late-glacial Interstadial an important development of cryophilous forests (Betula andPinus) was recorded, although various mesophilous and thermophilous tree elements were also present. The Younger Dryas, palynologically clearly defined, is characterized by an important reduction in tree pollen percentages and the expansion of steppe formations (Poaceae andArtemisia). At the beginning of the Holocene, there was an expansion ofQuercus and a spread of other trees, which combined to give a vegetation cover of varied composition but dominated by mixed deciduous forests. Such forest formations prevailed in these mountains until 3000 years ago, when successive deforestation phases are recorded at various times as a result of increased farming activity. The results are compared with data from other mountainous areas in the northern Iberian peninsula and southern France.

Late-glacial marine invertebrate macrofossils from Point Lepreau, New Brunswick

A late-glacial shell fauna from Point Lepreau, New Brunswick produced a radiocarbon date of 13,500 years B.P. The assemblage contained well-preserved subarctic to boreal molluscs and barnacles typical of late Pleistocene marine deposits from the region. Rare specimens of sea urchin, crab and brittlestar may be the oldest recorded occurrence of these animals in the late-glacial Bay of Fundy. The assemblage fits into a previously defined Zone 3, late-glacial marine invertebrate assemblage in the Bay of Fundy-Gulf of Maine region, characterized as a Diverse Arctic assemblage.
 
 RÉSUMÉ
 La datation par le radiocarbone a situé à 13 500 ans BP une faune invertébéie tardiglaciaire de la pointe Lepreau, ou Nouveau-Brunswick. L'assemblage renferme des mollusques et des bernacles subarctiques à boréaux bien conservés caractéristiques des dépôts marins du Pléistocène tardif de la région. Les spècimens rares d'oursins, de crabes et d'ophiures pourraient constituer les manifestations les plus anciennes de la présence de ces animaux relevées dans la région tardiglaciaire de la baie de Fundy. L'assemblage se situé à l’intérieur de l'assemblage d'invertébrés marins tardiglaciaires de la zone 3 antérieurement défini dans la région de la baie de Fundy et du golfe du Maine, caractérisé en tant qu'assemblage arctique hétéiogene.
 
 [Traduit par la rédaction]

Termination of the Last Glaciation in the Iberian Peninsula Inferred from the Pollen Sequence of Quintanar de la Sierra

A 4.5-m-thick late-glacial pollen sequence, supported by 17 AMS14C dates, has been investigated at the Quintanar de la Sierra marshland (Iberian cordillera, north-central Spain). Pollen zones were defined that correspond to successive phases in vegetation history during the end of the Late Würm, late-glacial interstade, and Younger Dryas periods. A transfer function approach has been adopted to derive quantitative climate estimates from the pollen assemblage data. A first expansion ofJuniperusandHippophae,about 13,50014C yr B.P., indicates the beginning of the late-glacial interstade which is characterized by aJuniperus–Betula–Pinussuccession that suggests higher temperatures and moisture than during full-glacial time. The Younger Dryas interval is recorded by a 120-cm-thick sediment unit that is dominated by herbaceous pollen. Transfer function estimates suggest that the climate during this period was cold, with low precipitation during most of the year, although not in summer. The Holocene arboreal recolonization in the area started about 10,00014C yr B.P., with a renewedJuniperus–Betula–Pinussuccession related to a strong increase in annual temperature and precipitation. The start of this process was synchronous with mean sea-surface temperature changes, as recorded from the nearby SU 81-18 marine core. The strong affinity with other European late-glacial pollen sequences demonstrates that the pattern of climatic changes during the last glacial–interglacial transition was similar in both northwestern and southwestern Europe.

Glacier fluctuations in western Scotland

Glacier fluctuations between the Last Glacial Maximum (LGM) and the early Holocene are reviewed. At the LGM (< 25 ka BP) most of Scotland was covered by an ice sheet that terminated on the continental shelf, mostly beyond the present coastline. Deglaciation was interrupted by stillstands or readvances in many parts of western Scotland, which may reflect climatic oscillations or glaciodynamic changes that occurred during the transition from marine-based to land-based conditions. By the later part of the Late-glacial Interstade (ca. 13-11 ka BP), glaciers had retreated into restricted areas or had disappeared completely. A major glacier readvance occurred during the Younger Dryas (Loch Lomond) Stade (ca. 11-10 ka BP) when an icefield occupied most of the western Highlands and smaller ice masses developed elsewhere on the Mainland and on some Hebridean islands. Initially, retreat of many Loch Lomond Readvance glaciers was interrupted by stillstands or readvances, which may reflect declining precipitation towards the end of the stade. Final deglaciation was more rapid, and was probably forced by rapidly rising temperatures.

REVIEWING THE BRITISH LATE UPPER PALAEOLITHIC: NEW EVIDENCE FOR CHRONOLOGICAL PATTERNING IN THE LATEGLACIAL RECORD

Summary. Variation in Lateglacial lithic assemblages has led some researchers to sub‐divide the British Later Upper Palaeolithic into two or more typologically distinct phases (Campbell 1977; Jacobi 1988). Until now, however, the chronological relationships between the different phases have been difficult to demonstrate. In this paper we present new dating evidence for two distinct blade technologies of Lateglacial type found in southwest Britain. The first corresponds to the ‘Creswellian’(as defined by Jacobi 1991; Jacobi and Roberts 1992), and is dated to the earlier part of the Lateglacial Interstadial (c. 13–12,000 years BP); the second technology compares with European Federmessergruppen assemblages (literally, ‘penknife group’ industries, as described in Schwabedissen 1954) of the ‘forested’ phase of the Interstadial (c. 12–11,000 years BP). In addition to presenting the new dates, this paper explores the implications of treating the technologies as separate entities and puts forward preliminary ideas on differences in raw material use and other human subsistence behaviour.

The vegetation and climate of northwest Iberia over the last 14,000 years

A new pollen record from an upland lake in north-west Spain, Laguna de la Roya, spans the last ca 14,500 yrs and includes clear evidence of a Weichselian Lateglacial event correlative with the Younger Dryas. Pollen-climate response surfaces have been used to make quantitative reconstructions of palaeoclimate conditions at this and two other sites in the region. These reconstructions indicate that the climate was dry and cool during both the Late Weichselian and the Younger Dryas; in contrast, conditions during the Lateglacial Interstadial were relatively moist. During the early Holocene the climate was more continental in character than it has been for the last three millenia. Human activity has had a substantial impact upon the upland vegetation around Laguna de la Roya only during the last two millennia.

The high sensitivity of the palynological record in the Vico maar lacustrine sequence (Latium, Italy) highlights the climatic gradient through Europe for the last 90 ka

The palynological study of the Vico maar lacustrine sequence (Italy) is realized from the correlation of three drillholes. The time span covers a period from the end of Oxygen Isotope Substage 5b till the beginning of Stage 1 (from ca. 90 to ca. 10 ka BP). At the base of the pollen diagram (pollen zone 0), a Younger Dryas-like fluctuation is observed. After pollen zone 1, which is a well developed forest period (Substage 5a), the forests of pollen zones 3 and 5 correspond to extensive climate improvements. These last two zones are correlated to the Ognon complex of the Grande Pile (France) and to interstadial periods 20 and 19 defined in the GRIP ice core (Greenland) (72.6−66.2 ka) before the Stage 5/4 transition. These two interstadial periods are global events found in the Greenland and Antarctica ice sheets, as well as in North Atlantic marine cores. In other pollen records from north of the Alps, changes have been recorded but they are less pronounced than in Vico. Pollen zone 7 (Stage 3) shows ca. 7 warm/humid fluctuations, that might have a link to the Dansgaard-Oeschger events (Greenland). During zone 9, the Lateglacial interstadial is recorded as well as the Younger Dryas event. The localization of Vico near plant refugia and far from the ice cap enables its pollen diagram to record abrupt and intense response to climate changes, possibly through a link to the Atlantic Ocean via westerly winds.

Late-glacial Coleoptera and the paleoclimate at Hirtles, Nova Scotia

Paleoentomological studies of Coleoptera from a late-glacial site at Hirtles, Nova Scotia, Canada, produced a tundra-treeline to northern boreal assemblage during the interval 12,300 to 11,700 years B.P. This is one of the oldest late-glacial buried organic deposits in the Maritime Provinces of Canada and provides fossil beetle evidence for recently deglaciated environments in the region. Bark beetles indicate the presence of trees, perhaps as early as 11,900 years B.P. A comparison can be made with contemporaneous sites in central and eastern North America where coleopteran evidence suggests warmer temperatures. Coleoptera fossils demonstrate evidence of a climatic gradient from the Great Lakes to eastern Canada during this time interval possibly greater than occurs today.&#x0D; &#x0D; RÉSUMÉ&#x0D; Des études paléoentomologiques de coléopteres d'un emplacement tardiglaciaire, à Hirtes, en Nouvelle-&amp;#xX9;cosse, au Canada, ont permis l'etablissement d'une limite de végétation des arbres et de toundra pour la florizone boréale septentrionale pendant l'intervalle de 12 300 à 11 700 ans avant le present. Il s'agit de l'un des plus anciens dépôts organiques tardiglaciaires enfouis dans les provinces maritimes canadiennes; il fournit une preuve de l'existence de coléopteres fossiles dans la région. L'existence de scolytes révèle la présence d'arbres, peut-être des 11 900 ans avant le présent. On peut effectuer une comparaison avec des emplacements contemporains dans le centre et Pest de l'Amérique du Nord, oû la preuve de la présence de coléopteres permet de supposer des températures plus chaudes. Les fossiles de coléoptères demontrent qu'il a existé pendant cet intervalle un gradient climatique possiblement supérieur à celui d'aujourd'hui, des Grands Lacs à l'Est du Canada.&#x0D; &#x0D; [Traduit par la rédaction]

The Record of Younger Dryas Event in Lake Sediments From Jalai Nur, Inner Mongolia

Younger Dryas has been highlighted by paleoclimatologists in recent years becauseof the abrupt change of temperature and CO_2 concentration within a short timeof several centuries or even less. At present, there exist virtually two viewpointsabout the event: one is that Younger Dryas only affects Circum-North Atlanticregion. The influx of the floating iceberg and the melt water from Arctic area to theNorth Atlantic Ocean due to the global warming in the Late Glacial suppressed the

D/H in beetle chitin from the late-glacial Lismore site in eastern Canada: supplementary note

D/H (Deuterium-Hydrogen) analysis of chitin from a late-glacial site in eastern Canada demonstrates promising results and lends support to other evidence for the Killarney Oscillation.&#x0D; &#x0D; RÉSUMÉ&#x0D; L'analyse du rapport D/H (Dentérium-Hydrogène) de chitine provenant d'un site tardi-glaciaire dans l'Est du Canada démontre des résultats prometteurs et vient appuyer d'autres données pour l'oscillation de Killarney.&#x0D; &#x0D; [Traduit par la rédaction]

Lateglacial vegetation and environment in Ireland: First results from four western sites: A contribution to the ‘North Atlantic seaboard programme’ of IGCP-253, ‘Termination of the Pleistocene’

First results of investigations that include pollen and chemical analyses of lateglacial lake sediments from four sites in western Ireland are presented, and the evidence for environmental change from these and previously published studies is reviewed. Fresh evidence is presented for a period with a cold, arid, continental-type climate immediately after deglaciation. This period is informally defined as the Pre-interstadial. It is represented by a Pinus-Artemisia-Gramineae pollen assemblage, with a high proportion of long-distance transported pollen, recorded in highly minerogenic sediments immediately overlying outwash gravels and sands. The interval between this and the Younger Dryas Stadial, informally defined as the Lateglacial Interstadial, is characterised in the early part by maximum tall shrub development, consisting mainly of Juniperus; tall shrub vegetation is subsequently replaced by Gramineae and Cyperaceae-dominated open vegetation at many sites. It is argued that the Lateglacial Interstadial is characterised by a number of climatic oscillations, the most severe and sustained being responsible for this general shift in favour of herbaceous taxa at mid-Interstadial (ca. 12 ka BP). Prior to the onset of the Younger Dryas deterioration, a modest expansion of Juniperus at several sites and Betula at some sites suggests a period of ameliorating climate. The severity of climatic conditions during the Younger Dryas Stadial is well expressed in the pollen, lithological and chemical data. There is some evidence to suggest that vegetation development in terrestrial environments at the transition to the Holocene lagged behind developments in aquatic habitats and the thermal environment generally.

The Devensian (Weichselian) Lateglacial palaeoenvironmental record from Gransmoor, East Yorkshire, England: A contribution to the ‘North Atlantic seaboard programme’ of IGCP-253, ‘Termination of the Pleistocene’

Palynological and coleopteran data are described from a section through Late Devensian (Weichselian) deposits at Gransmoor, East Yorkshire, England. The pollen evidence shows that, following an initial open-habitat episode, first Juniperus scrub and later Betula woodland became established in the area during the Lateglacial Interstadial. This woodland was replaced during the Loch Lomond (Younger Dryas) Stadial by a predominatly herbaceous flora with arctic/alpine, steppe and halophytic elements. The coleopteran evidence indicates a similar local environment and that the thermal maximum of the Interstadial, when mean July temperatures may well have exceeded 18°C, occurred prior to the deposition of the earliest polleniferous sediments. By the time of the Juniperus expansion, summer temperatures had fallen by 2–4°C to levels comparable with those of the present day. A further temperature decline followed the expansion of Betula during the later Interstadial and another fall occurred at the Lateglacial Interstadial/Loch Lomond Stadial boundary. During the Loch Lomond Stadial mean July temperatures of 9–11°C are implied, with winter temperatures as low as −15 to −20°C. Collectively the evidence reemphasises the point that for the first 1000 years or so of the Lateglacial Interstadial, there was a disequilibrium between the palynological and coleopteran records in terms of climatic signal. During the later Interstadial, however, a closer relationship is apparent between both proxy data sources. Of particular significance in this respect is the fluctuation in reconstructed summer and winter temperatures, and a rise and subsequent fall in Betula pollen frequencies. This may be the correlative of one of the pre-Younger Dryas climatic oscillations recorded in other proxy data sources including palynological records from Britain and eastern Canada, oxygen isotope traces from Swiss lake sediments, isotopic and electrical conductivity profiles from the Greenland ice sheet, and diatom and foraminiferal records in cores from the Norwegian Sea and the North Atlantic Ocean.

Lateglacial and early Holocene pollen stratigraphy of the northern Apennines, Italy: A contribution to the ‘North Atlantic seaboard programme’ of IGCP-253, ‘Termination of the Pleistocene’

Pollen diagrams, supported by 25 radiocarbon dates, are presented for four sites in the Ligurian-Emilian Apennines, Northern Italy, which collectively span the Late Weichselian Lateglacial and Holocene. Coleopteran evidence is available for the Lateglacial and early Holocene sediments from one of the sites. Collectively the data provide: (a) an internally consistent series of local pollen assemblages zones, such that regional pollen assemblage zones are defined; (b) a detailed chronology of vegetation changes in the region; (c) an impression of environmental changes during the Lateglacial-Holocene transition. Of particular note is the clear evidence for a marked Younger Dryas event, which, together with evidence from other parts of southern Europe, indicates that the climatic severity of this event did not diminish southwards on the European continent. Also of significance is the pollen and coleopteran evidence for mixed woodland in the region during the Lateglacial Interstadial, which is not in keeping with previous reconstructions.