The palaeoecoloical potential of pollen records in caves: the case of Mediterranean Spain

Important palynological sequences are reviewed from caves with archaeological interest in Mediterranean Spain. Upper Pleistocene sites include Abric Romanı́ and Abric de l’Arbreda in NE Spain, and in SE Spain Cueva de la Carihuela, Cova Beneito, Cueva de Perneras, Cueva del Algarrobo and the Holocene Cova de l’Or and Cova de les Cendres. Carihuela has the longest sequence, starting in the last interglacial and covering most of the last glaciation. A pre-Würm phase was followed by two glacial maxima separated by an interpleniglacial phase, and in the Lateglacial the Younger Dryas seems present. Whereas at Carihuela harsh pleniglacial conditions caused Mediterranean associations to disappear, in the milder surroundings of Beneito and Perneras these were able to survive. At Romanı́, pollen shows acute palaeoclimatic sensitivity, pointing to upland refuges nearby. Holocene pollen from Cova de l’Or and Cendres underlines the importance of pine in natural woodlands of mature meso and thermomediterranean taxa. Some between-site comparisons and contrasts with modern bioclimatology are interpreted in the context of the palaeoclimate history. Despite taphonomical and methodological problems of cave palynology, its future in arid regions such as SE Spain is promising.     

Lateglacial and early Holocene dynamics of adjacent valley glaciers in the Western Swiss Alps

The Alps play a pivotal role for glacier and climate reconstructions within Europe. Detailed glacial chronologies provide important insights into mechanisms of glaciation and climate change. We present 26 ¹⁰Be exposure dates of glacially transported boulders situated on moraines and ice‐moulded bedrock samples at the Belalp cirque and the Great Aletsch valley, Switzerland. Weighted mean ages of ～10.9, 11.1, 11.0 and 9.6 ka for the Belalp, on up to six individual moraine ridges, constrain these moraines to the Egesen, Kartell and Schams stadials during Lateglacial to early Holocene times. The weighted mean age of ～12.5 ka for the right‐lateral moraine of the Great Aletsch correlates with the Egesen stadial related to the Younger Dryas cooling. These data indicate that during the early Holocene between ～11.7 and ～9.2 ka, glaciers in the Swiss Alps seem to have been significantly affected by cold climatic conditions initiated during the Younger Dryas and the Preboreal Oscillation. These conditions resulted in glacier margin oscillations relating to climatic fluctuations during the second phase of the Younger Dryas – and continuing into Boreal times – as supported by correlation of the innermost moraine of the Belalp Cirque to the Schams (early) Holocene stage. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

Lateglacial and early Holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium‐line altitudes at northern Folgefonna,Hardanger, western Norway

Northern Folgefonna (c. 23 km²), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal moraines with AMS radiocarbon dated glacier‐meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high‐resolution record of variations in glacier size and equilibrium‐line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short‐lived (100–150 years) climatically induced glacier readvance termed the ‘Jondal Event 1’ occurred within the ‘Preboreal Oscillation’ (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550–10 450 cal. yr BP, a second glacier readvance is named the ‘Jondal Event 2’. A third readvance occurred about 10 000 cal. yr BP and corresponds with the ‘Erdalen Event 1’ recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation‐season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an independent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the ‘Jondal Event 1’/PBO was colder and somewhat drier, and the ‘Jondal Event 2’ was much wetter. The ‘Erdalen Event 1’ started as rather dry and terminated as somewhat wetter. Variations in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folgefonna suggest that low‐altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low‐altitude cirque glaciers of suggested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger. Copyright © 2005 John Wiley & Sons, Ltd.     

Lateglacial summer temperatures in the Northwest European lowlands: a chironomid record from Hijkermeer,the Netherlands

Lateglacial environments at Hijkermeer, northwest Netherlands, were reconstructed by means of chironomid, diatom and pollen analyses. Diatom assemblages indicate that Hijkermeer was a shallow, oligo- to mesotrophic lake during this period. Pollen assemblages reflect the typical northwest European Lateglacial vegetation development and provide an age assessment for the record from the beginning of the Older Dryas (ca 14 000 calibrated ¹⁴C yr BP) into the early Holocene (to ca 10 700 calibrated ¹⁴C yr BP). The chironomid record is characterized by several abrupt shifts between assemblages typically found in mid-latitude subalpine to alpine lakes and assemblages typical for lowland environments. Based on the chironomid record, July air temperatures were reconstructed using a chironomid-temperature transfer-function from central Europe. Mean July air temperatures of ca 14.0–16.0 °C are inferred before the Older Dryas, of ca 16.0–16.5 °C during most of the Allerød, of ca 13.5–14.0 °C during the Younger Dryas, and of ca 15.5–16.0 °C during the early Holocene. Two centennial-scale decreases in July air temperature were reconstructed during the Lateglacial interstadial which are correlated with Greenland Interstadial events (GI)-1d and -1b. The results suggest that vegetation changes in the Netherlands may have been promoted by the cooler climate during GI-1d, immediately preceding the Older Dryas biozone, and GI-1b. The Hijkermeer chironomid-inferred temperature record shows a similar temperature development as the Greenland ice core oxygen isotope records for most of the Lateglacial and a good agreement with other temperature reconstructions available from the Netherlands. This suggests that chironomid-based temperature reconstruction can be successfully implemented in the Northwest European lowlands and that chironomids may provide a useful alternative to oxygen isotopes for correlating European lake sediment records during the Lateglacial.     

The dynamics of chironomid assemblages and vegetation during the Late Quaternary at Laguna Facil, Chonos Archipelago, southern Chile

We compare high-resolution pollen and chironomid records from the last 15,000 yr in Laguna Facil, southern Chile. Major vegetation and chironomid changes are recorded between ca 14,900 and 14,700 cal. yr BP. During the Lateglacial, changes in the chironomid stratigraphy lag behind changes in the pollen stratigraphy suggesting that the chironomids are responding to changes in the tree canopy or in soil chemistry brought about by vegetational development. At about 7200 cal. yr BP there is a change in the chironomid stratigraphy in advance of changes in the vegetation. This suggests that the response is to regional climatic change. The relatively close correlation of the chironomid and pollen stratigraphies with changes in charcoal concentrations also implicates the importance of fire and/or vulcanism in influencing the dynamics of forest and limnological systems. There is no clear evidence of cooling during the Younger Dryas chronozone in Laguna Facil.     

A record of Lateglacial and early Holocene environmental and ecological change from southwestern Connecticut,USA

Analyses of a sediment core from Highstead Swamp in southwestern Connecticut, USA, reveal Lateglacial and early Holocene ecological and hydrological changes. Lateglacial pollen assemblages are dominated by Picea and Pinus subg. Pinus, and the onset of the Younger Dryas (YD) cold interval is evidenced by higher abundance of Abies and Alnus viridis subsp. crispa. As climate warmed at the end of the YD, Picea and Abies declined and Pinus strobus became the dominant upland tree species. A shift from lacustrine sediment to organic peat at the YD–Holocene boundary suggests that the lake that existed in the basin during the Lateglacial interval developed into a swamp in response to reduced effective moisture. A change in wetland vegetation from Myrica gale to Alnus incana subsp. rugosa and Sphagnum is consistent with this interpretation of environmental changes at the beginning of the Holocene. Copyright © 2009 John Wiley & Sons, Ltd.     

Rock glaciers on the Faeroe Islands,the North Atlantic

Three sites with alleged relict rock glaciers are described from southern Faeroe Islands, in the North Atlantic Ocean. The rock glaciers represent both talus-derived and glacier-derived types and were most likely initiated during the late Weichselian. One of the rock glaciers apparently became unstable at some point during degradation of permafrost and was subsequently transformed by a landslide. The age of the rock glaciers are not known precisely, but a Younger Dryas age is suggested, partly by considering contemporary local equilibrium line altitudes. The climatic background for rock glacier initiation on the Faeroe Islands during the Younger Dryas is investigated, using various types of palaeoclimatic information. The potential of using relict rock glaciers in palaeoclimatic reconstructions is discussed, and their implications for estimates on air temperature, precipitation, permafrost, rock weathering and the contemporary extent of the Weichselian Faeroe Ice Cap is outlined. © 1998 John Wiley & Sons, Ltd.     

Fluvial style changes during the last glacial-interglacial transition in the middle Tisza valley (Hungary)

The Weichselian Late Pleniglacial, Lateglacial and Holocene fluvial history of the middle Tisza valley in Hungary has been compared with other river systems in West and Central Europe, enabling us to define local and regional forcing factors in fluvial system change. Four Weichselian to Holocene floodplain generations, differing in palaeochannel characteristics and elevation, were defined by geomorphological analysis. Coring transects enabled the construction of the channel geometry and fluvial architecture. Pollen analysis of the fine-grained deposits has determined the vegetation development over time and, for the first time, a bio(chrono)stratigraphic framework for the changes in the fluvial system. Radiocarbon dating has provided an absolute chronology; however, the results are problematic due to the partly reworked character of the organic material in the loamy sediments. During the Late Pleniglacial, aggradation by a braided precursor system of the Tisza and local deflation and dune formation took place in a steppe or open coniferous forest landscape. A channel pattern change from braided to large-scale meandering and gradual incision occurred during the Late Pleniglacial or start of the Lateglacial, due to climate warming and climate-related boreal forest development, leading to lower stream power and lower sediment supply, although bank-full discharges were still high. Alternatively, this fluvial change might reflect the tectonically induced avulsion of the River Tisza into the area. The climatic deterioration of the Younger Dryas Stadial, frequently registered by fluvial system changes along the North Atlantic margin, is not reflected in the middle Tisza valley and meandering persisted. The Lateglacial to Holocene climatic warming resulted in the growth of deciduous forest and channel incision and a prominent terrace scarp developed. The Holocene floodplain was formed by laterally migrating smaller meandering channels reflecting lower bank-full discharges. Intra-Holocene river changes have not been observed.     

Lateglacial oceanographic conditions off Southwest Iceland inferred from shallow-marine deposits in Reykjavík and Seltjarnarnes Peninsula

New palaeoenvironmental data from the Lateglacial in Southwest Iceland add to the record of climatic events during deglaciation of the region. Recently exposed sediments on the north coast of Seltjarnarnes Peninsula in the Reykjavik area, Southwest Iceland, contain evidence of marine deposition during the Bølling Interstadial. The glaciomarine sediments contain both slightly reworked marine macrofossils and microfossils indicating normal marine salinity and subarctic climate conditions. Previous sedimentological studies and radiocarbon dating of the sporadic sediments covering the lava bedrock in Reykjavik have revealed lateglacial marine units from the Allerød, the Allerød—Younger Dryas transition, the Younger Dryas and from the Preboreal. Until now, the only Bølling evidence has consisted of scattered radiocarbon-dated redeposited shell fragments. From the Bollagardar deposits we report the first faunas dated to the Bølling chronozone preserved in marine sediments in the Reykjavik area. Recently published work in Hvalfjördur and Borgarfjördur, West Iceland, has shown that sea level was relatively high during the Bølling and that deglaciation was rapid. Bølling, Allerød and Younger Dryas deposits in the coastal areas of the Reykjavík region accumulated in a relatively open marine environment in oceanographic conditions similar to the present ones. Combined previous and present results indicate that several episodes of glaciomarine deposition occurred.     

Late Glacial fluvial response of the Niers‐Rhine (western Germany) to climate and vegetation change

The Niers valley was part of the Rhine system that came into existence during the maximum Saalian glaciation and was abandoned at the end of the Weichselian. The aim of the study was to explain the Late Pleniglacial and Late Glacial fluvial dynamics and to explore the external forcing factors: climate change, tectonics and sea level. The sedimentary units have been investigated by large‐scale coring transects and detailed cross‐sections over abandoned channels. The temporal fluvial development has been reconstructed by means of geomorphological relationships, pollen analysis and ¹⁴C dating. The Niers‐Rhine experienced a channel pattern change from braided, via a transformational phase, to meandering in the early Late Glacial. This change in fluvial style is explained by climate amelioration at the Late Pleniglacial to Late Glacial transition (at ca. 12.5 k ¹⁴C yr BP) and climate‐related hydrological, lithological and vegetation changes. A delayed fluvial response of ca. 400 ¹⁴C yr (transitional phase) was established. The channel transformations are not related to tectonic effects and sea‐level changes. Successive river systems have similar gradients of ca. 35–40 cm km^?1. A meandering river system dominated the Allerød and Younger Dryas periods. The threshold towards braiding was not crossed during the Younger Dryas, but increased aeolian activity has been observed on the Younger Dryas point bars. The final abandonment of the Niers‐Rhine was dated shortly after the Younger Dryas to Holocene transition. Traces of Laacher See pumice have been found in the Niers valley, indicating that the Niers‐Rhine was still in use during the Younger Dryas. Copyright © 2005 John Wiley & Sons, Ltd.     

The Younger Dryas in the English Lake District: reconciling geomorphological evidence with numerical model outputs

The geomorphology of the south‐western and central Lake District, England is used to reconstruct the mountain palaeoglaciology pertaining to the Lateglacial and Younger Dryas. Limitations to previous ice‐mass reconstructions and consequent palaeoclimatic inferences include: (i) the use of static (steady‐state) glacier reconstructions, (ii) the assumption of a single‐stage Younger Dryas advance, (iii) greatly varying ice‐volume estimates, (iv) inexplicable spatial variations in ELA (Equilibrium Line Altitude), and (v) a lack of robust extent chronology. Here we present geomorphological mapping based on aerial photography and the NextMap Britain Digital Elevation Model, checked by ground survey. Former glacier extents were inferred and ELAs were calculated using the Balance Ratio method of Osmaston. Independently, a time‐dependant 2‐D ice‐flow model was forced by a regional ELA history that was scaled to the GRIP record. This provided a dynamic reconstruction of a mountain ice field that allowed for non‐steady‐state glacier evolution. Fluctuations in climate during the Younger Dryas resulted in multiple glacial advance positions that show agreement with the location of mapped moraines, and may further explain some of the ELA variations found in previous local and static reconstructions. Modelling based on the GRIP record predicts three phases: an initial maximum extent, a middle minor advance or stillstand, and a pronounced but less extensive final advance. The comparisons find that the reconstructions derived from geomorphological evidence are effective representations of steady‐state glacier geometries, but we do propose different extents for some glaciers and, in particular, a large former glacier in Upper Eskdale.     

Geomorphology and palaeoecology of the Mark valley (southern Netherlands): geomorphological valley development during the Weichselian and Holocene

Vandenberghe, Jef, Bohncke, Sjoerd, Lammers, Wim & Zilverberg, Liesbeth 1987 03 01: Geomorphology and palaeoecology of the Mark valley (southern Netherlands): geomorphological valley development during the Weichselian and Holocene. Boreas , Vol. 16, pp. 55–67. Oslo. ISSN 0300–9483.
The actual area of the Mark valley is limited by the borders of an Early Weichselian erosion phase. The subsequent accumulation has resulted in the formation of a Weichselian Pleniglacial terrace which has been deeply dissected by Late Glacial erosion. The present alluvial plain is formed by Late Glacial and Holocene infilling. The maximum incision of the Late Glacial fluvial phase was reached slightly before 11,780 B.P. and involved locally dry conditions which have given rise to aeolian activity during this period (Older Dryas). On the deepest parts of the Pleniglacial terrace, a backswamp environment was established until the end of the Alleröd. At the beginning of the Younger Dryas the river invaded the terrace but shortly afterwards aeolian activity progressively increased. At the climax of the Younger Dryas, deep seasonal frost or local permafrost characterized the Mark valley.     

Lateglacial vegetation and palaeoenvironment in W Norway,with new pollen data from the Sunnmøre region

Krüger, L. C., Paus, A., Svendsen, J. I. & Bjune, A. E. 2011: Lateglacial vegetation and palaeoenvironment in W Norway, with new pollen data from the Sunnmøre region. Boreas, 10.1111/j.1502‐3885.2011.00213.x. ISSN 0300‐9483. Two sediment sequences from Sunnmøre, northern W Norway, were pollen‐analytically studied to reconstruct the Lateglacial vegetation history and climate. The coastal Dimnamyra was deglaciated around 15.3 ka BP, whereas Løkjingsmyra, further inland, became ice‐free around 14 ka BP. The pioneer vegetation dominated by snow‐bed communities was gradually replaced by grassland and sparse heath vegetation. A pronounced peak in Poaceae around 12.9 ka BP may reflect warmer and/or drier conditions. The Younger Dryas (YD) cooling phase shows increasing snow‐bed vegetation and the local establishment of Artemisia norvegica. A subsequent vegetation closure from grassland to heath signals the Holocene warming. Birch forests were established 500–600 years after the YD–Holocene transition. This development follows the pattern of the Sunnmøre region, which is clearly different from the Empetrum dominance in the Lateglacial interstadial further south in W Norway. The Lateglacial oscillations GI‐1d (Older Dryas) and GI‐1b (Gerzensee) are hardly traceable in the north, in contrast to southern W Norway. The southern vegetation was probably closer to an ecotone and more susceptible to climate changes.     

Lateglacial and early Holocene summer temperatures in the southern Swiss Alps reconstructed using fossil chironomids

We present a Lateglacial and early Holocene chironomid‐based July air temperature reconstruction from Foppe (1470 m a.s.l.) in the Swiss Southern Alps. Our analysis suggests that chironomid assemblages have responded to major and minor climatic fluctuations during the past 17 000 years, such as the Oldest Dryas, the Younger Dryas and the Bølling/Allerød events in the Lateglacial and the Preboreal Oscillation at the beginning of the Holocene. Quantitative July air temperature estimates were produced by applying a combined Norwegian and Swiss temperature inference model consisting of 274 lakes to the fossil chironomid assemblages. The Foppe record infers average July air temperatures of ca. 9.9 °C during the Oldest Dryas, 12.2 °C during most of the Bølling/Allerød and 11.1 °C for the Younger Dryas. Mean July air temperatures during the Preboreal were 14 °C. Major temperature changes were observed at the Oldest Dryas/Bølling (+2.7 °C), the Allerød/Younger Dryas (?2 °C) and the Younger Dryas/Holocene transitions (+3.9 °C). The temperature reconstruction also shows centennial‐scale coolings of ca. 0.8–1.4 °C, which may be synchronous with the Aegelsee (Greenland Interstadial 1d) and the Preboreal Oscillations. A comparison of our results with other palaeoclimate records suggests noticeable temperature gradients across the Alps during the Lateglacial and early Holocene. Copyright © 2011 John Wiley & Sons, Ltd.     

Vegetation dynamics during the Younger Dryas-Holocene transition in the extreme northern taiga zone, northeastern European Russia

Vegetation dynamics during the Younger Dryas-Holocene transition in the extreme northern taiga zone of the Usa basin, northeastern European Russia, were reconstructed using plant macrofossil and pollen evidence from a sediment core from Lake Llet-Ti. The pollen stratigraphy during the Younger Dryas (about 12 500-11 500 cal. yr BP) is characterized by pollen types indicative of treeless arctic vegetation, whereas the macrofossil evidence shows the occurrence of scattered spruce and birch trees around the lake. The Younger Dryas-early Holocene transition is characterized by a rapid increase in vegetation density, including an increase in the birch population, followed by the expansion of the spruce population at about 10 000 cal. yr BP. Dense spruce-birch forest dominated until 5000 cal. yr BP. Our results contribute to the debate about the Lateglacial environments in northern Russia, and illustrate the importance of plant macrofossil records in Lateglacial vegetation reconstructions.     

Palynological analyses in the laminated sediment of Lake Holzmaar (Eifel, Germany): duration of Lateglacial and Preboreal biozones

The laminated sediment of Lake Holzmaar (Germany) has provided a continuous varve chronology for the last 3500 varve years (vy) and beyond that a floating varve chronology back to more than 22500 vy BP. This chronology in calendar years, in combination with palynology, enables us to determine the timing and the magnitude of Lateglacial and Early Holocene environmental changes on land (from 13838 to 10930 vy BP). The palynological diagram has a mean time resolution of 27 vy between samples. This paper establishes for the first time the biozonation for Lake Holzmaar below the Laacher See Tephra. Fifteen pollen subzones grouped in four biozones are defined by cluster analysis. After a period disturbed by microturbidites, only a part of the Bølling is present. Three cold periods have been evidenced by pollen analyses: the Older Dryas (96-vy-long), the Younger Dryas (654-vy-long) and the Rammelbeek phase (237-vy-long). The Allerød (883-vy-long) is bipartite with a first Betula -dominated period followed by a Pinus -dominated one. The Younger Dryas is also bipartite, with first a decrease of winter temperatures along with a change to a more continental climate. It is followed by a drier phase with a second decrease in temperatures, probably this time also affecting summer temperatures. The Preboreal is 702-yr-long. The duration of most phases corresponds to published records, except for that of the Younger Dryas. Cluster and rate-of-change analyses indicate a sharp change in the terrestrial vegetation assemblages that may be caused by a sedimentary hiatus of erosive origin during this cold and dry period. As a result, the chronology of Holzmaar has to be revised most likely below the middle of the Younger Dryas. Comparison with the varve record of Meerfelder Maar, a neighbour maar lake, suggests adding 320 vy below 12025 vy.     

Longitudinal profile evolution of the Rhine–Meuse system during the last deglaciation: interplay of climate change and glacio-eustasy?

Fluvial longitudinal profiles reconstructed from abandoned floodplains contain significant evidence about the role of relative sea level vs. climatic and tectonic controls on depositional systems. Two Weichselian floodplain surfaces that occur as terraces updip of the hinge zone of the Rhine–Meuse system have recently been mapped beneath the Holocene Rhine–Meuse Delta (The Netherlands). Their vertical offset is several metres in the upstream area and decreases to only 0.4 m in the central part of the delta. The older and higher of the two floodplain surfaces is generally assumed to have been formed around the Last Glacial Maximum, whereas the younger dates to the Younger Dryas, following a phase of climatically induced fluvial incision during the Bølling-Allerød. The downstream convergence of these two floodplain surfaces may be related to the relative rise of sea level, forcing the Rhine–Meuse system to become graded to a higher base level during the Younger Dryas. The upper Weichselian Rhine–Meuse system then provides an example of a basin-marginal fluvial system that responds, in terms of its longitudinal profile, to the combined effects of upstream control (primarily climate change affecting water and sediment flux from the hinterland) and downstream control (glacio-eustatically driven relative sea-level change). This new evidence may therefore revitalize the presently unfashionable concept of relative sea-level control penetrating many hundreds of kilometres inland.     

Late-glacial cirque glaciation in parts of western Norway

Younger Dryas cirque glaciers are known to have existed beyond the Scandinavian Ice Sheet in parts of western Norway. At Kråkenes, on the outermost coast, a cirque glacier formed and subsequently wasted away during the Younger Dryas. No glacier existed there during the Allerød. Large cirque moraines, some with marine deltas and associated fans, extend into the western part of Sykkylvsfjorden. Comparison with existing late-glacial sea-level curves shows that the uppermost marine sediment in these features was deposited well above Younger Dryas sea-level, demonstrating that the cirques were occupied by glaciers before the Younger Dryas. During the Younger Dryas the cirque glaciers expanded, and some advanced across the deltas, depositing till and supplying the sediment to form lower-level fans and deltas controlled by Younger Dryas sea level. The extent of the Younger Dryas advance of some of the glaciers was, at least in part, controlled by grounding on material deposited before the Younger Dryas. The depositional history of the glacial–marine deposits in the Sykkylven area indicates that cirque glaciers existed throughout Late-glacial time and only expanded during the Younger Dryas. The sediment sequence in glacial lakes beyond cirque moraines and reconstructions of glacier equilibrium lines indicate that this was true for most cirques in western Norway. Only on the outermost coast were new glaciers formed in response to Younger Dryas climate cooling. © 1998 John Wiley & Sons Ltd.     

Evolution of a Lateglacial mountain icecap in northern Scotland

Finlayson, A., Golledge, N., Bradwell, T. & Fabel, D. 2011: Evolution of a Lateglacial mountain icecap in northern Scotland. Boreas, Vol. 40, pp. 536–554. 10.1111/j.1502‐3885.2010.00202.x. ISSN 0300‐9483. Detailed geomorphological mapping of the Beinn Dearg massif, northern Scotland, was conducted to examine the maximum (Younger Dryas) extent, and earlier interstadial evolution, of an icecap that existed during the Lateglacial period (14.7–11.7 cal. ka BP). Landform evidence indicates a plateau icecap configuration during the Younger Dryas. The interpreted age is supported by new cosmogenic exposure ages and previously reported interstadial sediments beyond the icecap margin. The reconstructed Younger Dryas Beinn Dearg icecap covered 176 km². Equilibrium line altitudes (ELAs) of ～570–580 m were calculated for the icecap as a whole. The empirically reconstructed icecap is compared with recent numerical model simulations. The two methods produce an icecap with a similar configuration; however, differences are apparent in the extent of eastern and western outlets (±1–5 km), and in the spatial variation of ELAs. Results suggest that the numerical simulation overestimates the western and underestimates the eastern icecap extent. We attempt to quantify these differences in terms of icecap mass balance and assess their possible causes. Geomorphological evidence for the pre‐Younger Dryas icecap configuration indicates that the Beinn Dearg massif remained an important source during earlier deglaciation. In contrast, the neighbouring Fannich mountains acted as an ‘unzipping’ zone, and were ice‐free on their northern side by the Allerød (Greenland Interstadial 1c to 1a). Deglaciation continued over the western Beinn Dearg plateau, with the possibility that glaciers remained in some central and eastern catchments prior to (Younger Dryas) icecap (re)growth.