Glacial history of western Norway 15,000–10,000 B.P.

The deglaciation patterns of the Bergen and Nordfjord-Sunnmøre areas in western Norway are described and correlated. In the Bergen area the coast was first deglaciated at 12,600 B.P., with a succeeding re-advance into the North Sea around 12,200 B.P. Later, during the Allerød, the inland ice retreated at least 50 km, but nearly reached the sea again during the Younger Dryas re-advance, ending at 10,000 B.P. Sunnmøre was ice-free during an interstadial 28,000–38,000 B.P. Later the inland ice reached the sea. The final deglaciation is poorly dated in Sunnmøre, while further south in Nordfjord, it started slightly before 12,300 B.P., followed by a major retreat. No large re-advance of the inland ice occurred during the Younger Dryas. However, in the Sunnmøre-Nordfjord area many local glaciers formed outside the inland ice during the Younger Dryas. Limnic sediments outside one such cirque glacier have been cored and dated, proving that the glacier did not exist at 12,300-11,000 B.P., and that it was formed and disappeared in the time interval 11,000–10,000 B.P. (Younger Dryas). The erosion rate of the cirque glacier was 0.9 mm/year.     

Late Weichselian deglaciation in the Oslofjord area, south Norway

The older 'moraine lines' outside the Ra Moraine in the outer Oslofjord area have been correlated with events in Bohuslän, Sweden. Recent radiocarbon datings in the vicinity of the Ra Moraine and a radiocarbon dated sea-level curve for the Ski area show that the Ra Moraine was formed during the Early Younger Dryas, whereas the Ski Moraine was formed at the end of the Younger Dryas chronozone. An equidistant shoreline diagram together with a large number of marine limit observations have been used to establish the position of the glacier front during Late Younger Dryas and Early Preboreal chronozones. Reconnaissance mapping indicates a fairly regular recession with many short stops during the Bølling, Older Dryas and Allerød chronozones; at least two readvances to the Ra Moraine before 10,600 years B.P.; a rapid recession during the Middle Younger Dryas and a number of ice-front oscillations at the end of the Younger Dryas chronozone.     

Younger Dryas cirque glaciers in western Spitsbergen: smaller than during the Little Ice Age

The outermost moraines in front of the Scottbreen glacier in Spitsbergen date from c . AD 1900. These moraines rest on top of a marine shoreline radiocarbon-dated to about 11 200 ¹⁴C yr BP and demonstrate that the AD-1900 moraines show the maximum glacier extent since late Allerød time. This means that Scottbreen was smaller during the Younger Dryas than at AD 1900, in contrast with glaciers on mainland western Europe, which were all much larger during the Younger Dryas. The explanation is probably starvation of precipitation on western Spitsbergen during the Younger Dryas. In contrast, ice sheets and glaciers in Spitsbergen reacted more or less in concert with glaciers in western Europe, during the global Last Glacial Maximum and the Little Ice Age.     

Sedimentary facies and environmental history of the Late-glacial glaciomarine Fossvogur sediments in Reykjavík, Iceland

A detailed account of facies relationships in the Late-glacial Fossvogur beds is presented for the first time. A new interpretation in terms of sedimentary processes has been synthesized in a palaeoenvironmental reconstruction that incorporates the results of a recently completed, systematic ¹⁴C dating project for the Fossvogur beds. The present sedimentological analysis has revealed three marine fossiliferous facies and several diamictite facies. The two uppermost marine facies are separated by a horizon of local deformation and erosion which is ascribed to increased activity at a tidewater glacier margin in Fossvogur. The fact that marine fossiliferous sediments below and above this horizon have been confined to the Allerød chron indicates a temporary expansion of glaciers in the Reykjavík region towards the end of, but within, the Allersd. The relative sea level must have been at least 20 m higher than at present before the expansion, and it was probably even higher during and after the expansion. The total absence of facies indicating either lodgement or melt-out processes, and the abundance of diamictites interpreted as debris-flow deposits as well as frequent erratics in the marine mudrocks favour an interpretation based on a glaciomarine model for the Allerød deposition in Fossvogur. It is suggested that the relatively quiet, submarine conditions indicated by facies towards the top of the Fossvogur beds display continued transgression and an increased distance to the source of sediment supply during the Younger Dryas.     

Younger Dryas and early Holocene lake-level fluctuations in the Jura mountains, France

Lake-level fluctuations in the Jura mountains (France) during the Younger Dryas and the early Holocene are reconstructed using sedimentological analyses. Major transgressive phases culminated just before the Laacher See tephra deposition, at the beginning of the Younger Dryas, between 9000 and 8000 BP and between 7000 and 6000 BP. The Younger Dryas appears to be characterized by increasing dryness. Other major lowering phases occurred during the middle Allerød and during the Preboreal. A transgressive event developed between c . 9700 and 9500 BP. These palaeohydrological changes can be related to climatic oscillations reconstructed from pollen and isotopic records in Swiss lakes, from glacier movements and timberline variations in the Alps, and from isotopic records in the Greenland ice sheet.     

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.     

Marine transgression in Younger Dryas in Norway

BOREAS Anundsen, K. 1978 03 01: Marine transgression in Younger Dryas in Norway. Boreas, Vol. 7, pp. 49–60. Oslo. ISSN 0300–9483.
The lithostratigraphy and biostratigraphy of sediment cores from two basins in southwestern Norway have been studied and radiocarbon dated. The diatom and the Hystrix content indicates a marine Younger Dryas transgression that reached its maximum level at the transition Younger Dryas/Preboreal Chronozone. No Allerød transgression to the same altitude can be demonstrated, and the suggested Allerød transgression at Bømlo (Faegri 1944) is most likely of Younger Dryas age, too.     

Surface ocean circulation in the Norwegian Sea 15,000 B.P. to present

Quantitative studies of foraminifera and radiolaria, semi-quantitative analyses of diatoms and coccoliths, and the distribution of ice-rafted sediments have been performed on cores from the southeastern Norwegian Sea. The results document large variations in sea-surface temperatures and ocean circulation, showing a strong correlation between oceanic data and palaeoclimatic data from the neighbouring coastal areas of Norway. For the first time the Allerød – Younger Dryas climatic fluctuations and the Holocene climatic optimum are shown in records from the Norwegian Sea. Starting at about 13,000 B.P. the sea surface became seasonally ice-free with productive seasons. During the Allerød a narrow wedge of temperate Atlantic water flowed into the southeastern Norwegian Sea. In Younger Dryas time the surface waters cooled by several degrees. Holocene surface conditions were relatively constant, with somewhat higher temperatures in a period possibly corresponding with Atlantic time.     

Environmental change during the Allerød and Younger Dryas reconstructed from Swiss tree-ring data

Annually resolved tree-ring width variations and radiocarbon ages were measured from a collection of 120 Lateglacial pine stumps excavated on the Swiss Plateau. These data – representing the oldest absolutely dated wood samples worldwide – extend the absolute tree-ring chronology from Central Europe by 183 years back to 12 593 cal. yr BP (10 644 cal. yr BC). They also yield a 1420-year floating chronology covering the entire Allerød and the early Younger Dryas (14 170–12 750 cal. yr BP). Radiocarbon data suggest a 250-year jump in the ¹⁴C reservoir correction around the time of the Allerød to Younger Dryas transition, although calendric dating of the floating chronology – by filling a ∼150 year gap – is necessary for confirmation. Various subgroups, based on the year of germination, were used to assess temporal changes in growth characteristics along the Allerød to Younger Dryas transition. Comparison of these Lateglacial data with a reference data set of living and historic pines from the Swiss Valais (AD 940–2000) revealed differences in both growth trend and level. The generally slower Lateglacial growth was likely influenced by higher geomorphic activity and severe climatic conditions. After removal of the biological age-trend, a strong common signal found in the tree-ring data suggests some skill in estimating interannual to multidecadal Lateglacial climatic variations.     

Exposure age dating and Equilibrium Line Altitude reconstruction of an Egesen moraine in the Maritime Alps, Italy

Four boulder samples from the Piano del Praiet frontal moraine in the Gesso della Barra Valley (Maritime Alps) have been ¹⁰Be dated. The results give a weighted mean age of 11 340±370 (870) yr, constraining the frontal moraine to the Egesen glacial stadial, during the Younger Dryas cold phase. By applying the same ¹⁰Be production rate to other Egesen moraines previously dated in the Alps, we obtain similar ages for all of them. This suggests a synchroneity of the Egesen deglaciation in the European Alps at the end of the Younger Dryas. From the palaeoshape of the Egesen glacier, reconstructed by means of geomorphological mapping, an Equilibrium Line Altitude depression (δELA) of −520 to −530 m, with respect to the present-day ELA, and of −260 to −320 m, with respect to the Little Ice Age ELA, has been calculated. Comparison with other Alpine sector δELAs indicates that the Maritime Alps experienced humid climatic conditions during the Younger Dryas.     

Late and Middle Weichselian stratigraphy of Andøya, north Norway

BOREAS Vorren, K.-D. 1978 03 01: Late and Middle Weichselian stratigraphy of Andøya, north Norway, Boreas, Vol. 7, pp. 19–38. Oslo. ISSN 0300–9483.
Bio-stratigraphy and ¹⁴C datings from Lake Endletvatn, 69^o 44'N and 19^o05'E, approx. 35 m above sea level, suggest that the lacustrine sedimentation started about 18,000 B.P. The Middle Weichselian vegetation was probably a dry arctic, partly barren, grassland type with abundant Draba spp. and perhaps also Braya spp. Two climatic ameliorations of this chronal substage, named Endletvatn thermomers 1 and 2 (ET 1 and 2), have been recorded. During ET 2, the beginning of which has been dated at about 15,000 B.P., a humid climate prevailed, with a July temperature probably not deviating much from the present one. The colonization by low alpine and subalpine species probably started in the Bølling Chronozone. During the early Allerød Chronozone, protocratic conditions with grasses RumexlOxyria, Papaver and Sagina of. saginoides prevailed. During the middle of the Allerød, stable soil and continuous vegetation was established at sheltered places. At the transition to the Younger Dryas Chronozone a climate favouring Artemisia changed this vegetational development. The middle of the Younger Dryas was cool and humid, probably with an upper low alpine vegetation. The end of this chronozone was characterized by a vegetation of low alpine heaths with Empetrum and Dryas.
Diatom analysis (Foged 1978) suggests that there has been no direct marine influence in the basin. The marginal moraine stratigraphy, the marine limit and the climatic development are discussed.     

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.     

The Fossvogur marine sediments in SW Iceland - confined to the Allerød/Younger Dryas transition by AMS 14 C dating

An exhaustive ¹⁴C dating programme of molluscs from the Fossvogur sediments in Reykjavik. Iceland is presented. For the first time all the fossiliferous units of the sediments are dated. The results confirm earlier conclusions of a widespread occurrence of marine sediments of Allerød age in Reykjavik. The set of dates from the Fossvogur sediments shows a narrow ¹⁴C age distribution (standard deviation of ±235 years) of molluscs from all localities and from successive marine units in vertical sections. The weighted mean conventional ¹⁴C age is 11,400 BP. Assuming a reservoir effect of 400 years. this corresponds to a reservoir-corrected age of I1,000 BP. i.e. the Allerød- Younger Dryas transition for the sampled units, These new ¹⁴C dates from Fossvogur confirm the need for a revision of the Upper Pleistocene chronology of the Reykjavik region. They also have a bearing on the Late Weichselian record of glacier readvances and sea-level changes in the area. The dates suggest that the marine units in Fossvogur accumulated within a restricted time-span of a few hundred years. The sediments in Fossvogur are of volcaniclastic origin and are extremely lithified, indicating local geothermal activity soon after their deposition. This may explain anomalously high D/L amino acid ratios measured in molluscs from the Fossvogur sediments. δ¹³C and δ¹⁸O results suggest that temperatures may have ranged up to 60°C.     

Palaeoclimatic and regional implications of Older Dryas and Younger Dryas local glacier activity in the low-Arctic valley Finnkongdalen,Andøya,northern Norway

Continuous glacier margin and equilibrium-line altitude fluctuations of a former glacier on central Andøya, northern Norway, are reconstructed during the Lateglacial based on moraines and AMS ¹⁴C-dated sediments from the distal glacier-fed lake Ner-Finnkongdalsvatnet. The results indicate that a valley glacier occupied the entire valley during the Last Glacial Maximum (before 21 970±620 cal. a BP). The glacier remained large throughout the early Lateglacial until a significant glacier retreat took place about 14 300±330 cal. a BP. Major advances occurred during the Older Dryas (OD) and during the Younger Dryas (YD), while minor advances are suggested to have taken place during the Intra Allerød Cold Period and the Late Allerød Cooling. Additionally, three smaller glacier retreats/re-advances within the YD are suggested to have taken place, the latter being the largest. The glacier re-formations/advances during the Lateglacial are consistent with increases in temperature, and they are thus suggested to be the result of increased winter precipitation. Comparing the results with relevant glacier and sea-surface temperature records, a south–north migration of storm tracks may have occurred between 12 100–11 810±220 cal. a BP. The high temporal resolution of local glacier activity in Finnkongdalen improves our understanding of the climate forcing of the regional glacier fluctuations of the northwestern sector of the Scandinavian Ice Sheet during the Skarpnes- (OD) and Tromsø-Lyngen (YD) re-advances.     

Pre-Younger Dryas resurgence of the southwestern margin of the Cordilleran ice sheet, British Columbia, Canada

Clague, J. J., Mathewes, R. W., Guilbault, J.-P., Hutchinson, I. & Ricketts, B. D. 1997 (September): Pre-Younger Dryas resurgence of the southwestern margin of the Cordilleran ice sheet, British Columbia, Canada. Boreas , Vol. 26, pp. 261–278. Oslo. ISSN 0300–9483.
A lobe of the Cordilleran ice sheet readvanced into the central Fvaser Lowland, southwestern British Columbia, Canada, on at least two occasions near the end of the last glaciation. This ice also flowed into the previously deglaciated, lower reaches of mountain valleys adjacent to the Fraser Lowland and into Washington state. The first of these advances occurred before about 11900 BP and ended with glacier retreat and the establishment of lodgepole pine forest on newly deglaciated terrain. Parts of this forest were overridden by ice during a second advance, shortly after 11300 BP. The younger advance is most likely older than the Younger Dryas Chronozone (11000–10000 BP) and may correlate with an intra-Allerad cooling event (the Killarney-Gerzensee oscillation). The older advance may have occurred during the Oldest Dryas or Older Dryas cold period. Non-climatic factors could also be involved, as emergence of the Fraser Lowland before the older advance greatly reduced or eliminated calving at the glacier margin and thus altered the mass balance of the ice lobe.     

Palynological and oxygen isotope investigations on Late-Glacial sediment cores from Swiss lakes

Results from detailed pollen and ¹⁸O/¹⁶O studies on two sediment profiles from small Swiss lakes are reported. ¹⁸O/¹⁶O records in lacustrine carbonate contain paleoclimatic information because they reflect mainly the isotope ratio in rain and snow which is correlated to temperature. Several transitions between different climatic periods determined palyno-logically are also indicated by marked changes in the isotope ratios in both profiles, namely the transitions Oldest Dryas - Bøiling and Allerød - Younger Dryas - Preboreal. ¹⁸o/¹⁶O was 2 to 3 %0 lower during Younger Dryas than during the adjacent periods, corresponding to a temperature drop of a few degrees Centigrade according to a tentative estimate.     

Calendar year age estimates of Allerød–Younger Dryas sea‐level oscillations at Os,western Norway

A detailed shoreline displacement curve documents the Younger Dryas transgression in western Norway. The relative sea‐level rise was more than 9 m in an area which subsequently experienced an emergence of almost 60 m. The sea‐level curve is based on the stratigraphy of six isolation basins with bedrock thresholds. Effort has been made to establish an accurate chronology using a calendar year time‐scale by ¹⁴C wiggle matching and the use of time synchronic markers (the Vedde Ash Bed and the post‐glacial rise in Betula (birch) pollen). The sea‐level curve demonstrates that the Younger Dryas transgression started close to the Allerød–Younger Dryas transition and that the high stand was reached only 200 yr before the Younger Dryas–Holocene boundary. The sea level remained at the high stand for about 300 yr and 100 yr into Holocene it started to fall rapidly. The peak of the Younger Dryas transgression occurred simultaneously with the maximum extent of the ice‐sheet readvance in the area. Our results support earlier geophysical modelling concluding a causal relationship between the Younger Dryas glacier advance and Younger Dryas transgression in western Norway. We argue that the sea‐level curve indicates that the Younger Dryas glacial advance started in the late Allerød or close to the Allerød–Younger Dryas transition. Copyright © 2004 John Wiley & Sons, Ltd.     

Composite stable isotope records from a Late Weichselian lacustrine sequence at Grrenge, Lolland, Denmark: evidence of Allerød and Younger Dryas environments

Stable oxygen and carbon isotope data from a lacustrine sequence at Grænge, southeast Denmark, revealed distinct cnvironmental changes related to Late Weichselian climatic development in the region. Comparison of isotopic records obtained from sedimentary carbonates and freshwater molluscs enabled reconstruction of changes in the lacustrine environment. The degree of thermal and chemical stratification of the lake was evaluated and supported by pollen data from an earlier study of the site. During the Allerød interstadial, dimictic and stagnant conditions characterized the lake, whereas the stratification was disturbed during thc Younger Dryas stadial probably as a result of deforestation and increased wind impact. The origin of sedimentary carbonates was examined by mineralogic and morphologic studies. A considerable input of clastics and detrital carbonates, associated with pronounced enrichment of ¹⁸O and ¹³C. wds recorded in the Younger Dryas sediments indicating soil degradation and increased erosion. A climatic warming preceding the Pleis-tocene/Holocene boundary is clearly reflected in the different stable isotope records and in the lithostratigraphy.     

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.