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1.
The North Atlantic Younger Dryas climatic reversal did not cause a glacier advance on Mount Rainier. The glaciers on Mount Rainier seem to have advanced in response to regional or local shifts in climate. However, the Younger Dryas climatic reversal may have affected the Mount Rainier area, causing a cold, but dry, climate unfavorable to glacier advances. Glaciers in the vicinity of Mount Rainier advanced twice during late glacial/early Holocene time. Radiocarbon dates obtained from lake sediments adjacent to the corresponding moraines are concordant, indicating that the ages for the advances are closely limiting. The first advance occurred before 11,300 14C yr BP (13,200 cal yr BP). During the North Atlantic Younger Dryas event, between 11,000 and 10,000 14C yr BP (12,900 and 11,600 cal yr BP), glaciers retreated on Mount Rainier, probably due to a lack of available moisture, but conditions may have remained cold. The onset of warmer conditions on Mount Rainier occurred around 10,000 14C yr BP (11,600 cal yr BP). Organic sedimentation lasted for at least 700 years before glaciers readvanced between 9800 and 8950 14C yr BP (10,900 and 9950 cal yr BP).  相似文献   

2.
The Vedde Ash (c. 10 300 14 C BP) provides a key time-parallel marker horizon within the Younger Dryas chronozone or GS-1 event of the GRIP stratigraphy. Until recently, the known distribution of wind-blown Vedde Ash outside Iceland was restricted to the west coast of Norway, off-shore sequences close to the Outer Hebrides and the Greenland summit GRIP ice core. The first discoveries of the Vedde Ash in Scotland were reported in 1997, following the development of a new technique for extracting rhyolitic micro-tephra particles from minerogenic deposits. Here we report on the discovery of the Vedde Ash at additional sites in Scotland and at sites in southern Sweden. The concentration of tephra particles in sediments is highest in sites in western Norway, but is also relatively high in sites in southwestern Sweden, suggesting that the main ash cloud travelled eastwards from its volcanic source of Katla, in southern Iceland. Electron microprobe analyses do not indicate any clear geochemical evolution within the samples reported here.  相似文献   

3.
This paper presents an event stratigraphy based on data documenting the history of vegetation cover, lake‐level changes and fire frequency, as well as volcanic eruptions, over the Last Glacial–early Holocene transition from a terrestrial sediment sequence recovered at Lake Accesa in Tuscany (north‐central Italy). On the basis of an age–depth model inferred from 13 radiocarbon dates and six tephra horizons, the Oldest Dryas–Bølling warming event was dated to ca. 14 560 cal. yr BP and the Younger Dryas event to ca. 12 700–11 650 cal. yr BP. Four sub‐millennial scale cooling phases were recognised from pollen data at ca. 14 300–14 200, 13 900–13 700, 13 400–13 100 and 11 350–11 150 cal. yr BP. The last three may be Mediterranean equivalents to the Older Dryas (GI‐1d), Intra‐Allerød (GI‐1b) and Preboreal Oscillation (PBO) cooling events defined from the GRIP ice‐core and indicate strong climatic linkages between the North Atlantic and Mediterranean areas during the last Termination. The first may correspond to Intra‐Bølling cold oscillations registered by various palaeoclimatic records in the North Atlantic region. The lake‐level record shows that the sub‐millennial scale climatic oscillations which punctuated the last deglaciation were associated in central Italy with different successive patterns of hydrological changes from the Bølling warming to the 8.2 ka cold reversal. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

4.
A mean varve thickness curve has been constructed for a part of the Swedish varve chronology from the northwestern Baltic proper. The mean varve thickness curve has been correlated with the δ18O record from the GRIP ice-core using the Younger Dryas–Preboreal climate shift. This climate shift was defined by pollen analyses. The Scandinavian ice-sheet responded to a warming at the end of the Younger Dryas, ca. 10995 to 10700 clay-varve yr BP. Warming is recorded as a sequence of increasing mean varve thickness and ice-rafted debris suggesting intense calving of the ice front. The Younger Dryas–Preboreal climatic shift is dated to ca. 10650 clay-varve yr BP, about 40 yr after the final drainage of the Baltic Ice Lake. Both the pollen spectra and a drastic increase in varve thickness reflect this climatic shift. A climate deterioration, correlated with the Preboreal oscillation, is dated to ca. 10440 to 10320 clay-varve yr BP and coincides with the brackish water phase of the Yoldia Sea stage. The ages of the climatic oscillations at the Younger Dryas–Preboreal transition show an 875 yr discrepancy compared with the GRIP record, suggesting a large error in the Swedish varve chronology in the part younger than ca. 10300 clay-varve yr BP. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

5.
A Holocene sedimentary record from the deep-silled Malangen fjord in northern Norway reveals regional changes in sedimentary environment and climate. Down-core analysis of two sediment cores includes multi-core sensor logging, grain size, x-radiography, foraminifera, oxygen isotopes, dinoflagellates, pollen, trace elements and radiocarbon datings. The cores are located just proximal to the submarine Younger Dryas moraine complex, and reveal the deglaciation after Younger Dryas and the postglacial evolution. Five sedimentary units have been identified. The oldest units, V and IV, bracket the Younger Dryas glacial readvance in the fjord between 12 700 cal. years BP and 11 800 cal. years BP. This is followed by deposition of glaciomarine sediments (units IV and III) starting around 12 100 cal. years BP. Glaciomarine sedimentation ceased in the fjord c. 10 300 cal. years BP and was replaced by open marine sedimentation (units II and I). A rapid stepwise warming occurred during the Preboreal. Onset of surface water warming lagged bottom water warming by several hundred years. The δ[Formula: See Text]O record indicates a significant, gradual bottom water cooling (c. 4°C) between 8000 and 2000 cal. years BP, a trend also supported by the other proxy data. Other records in the region, as well as GCM simulations, also support this long-term climatic evolution. Superimposed on this cooling were brief warmings around 6000 cal. years BP and 2000 cal. years BP. The long-term change may be driven by orbitally forced reduction in insolation, whereas the short-term changes may be linked to for example solar forcing, meltwater and NAO changes all causing regional changes in the North Atlantic heat transport.  相似文献   

6.
Zhu, C., Ma, C., Yu, S.-Y., Tang, L., Zhang, W. & Lu, X. 2009: A detailed pollen record of vegetation and climate changes in Central China during the past 16 000 years. Boreas , 10.1111/j.1502-3885.2009.00098.x. ISSN 0300-9483.
Detailed pollen analyses, along with magnetic and loss-on-ignition (LOI) measurements, were conducted on a 3 m long peat sequence recovered from the Dajiuhu Basin, the Shennongjia Mountains in Central China. Ten AMS 14C dates provide a firm age control on this pollen record in terms of vegetation changes governed essentially by the rise and fall of the Asian summer monsoon during the past 16 000 years. Between 16 000 and 12 700 cal. yr BP, pollen assemblages were dominated by coniferous and broad-leaved trees, indicating a mixed forest landscape corresponding to the initial establishment of the monsoonal climate after the Last Glaciation. The progressive increases in percentages of evergreen tree pollen after 12 700 cal. yr BP point to a steady enhancement of the summer monsoon, which was episodically weakened during the Younger Dryas stadial. From 11 000 to 6000 cal. yr BP, values of coniferous and deciduous tree pollen decreased, while evergreen broad-leaved tree pollen increased substantially, implying a stronger than normal monsoonal climate condition corresponding to the Holocene Hypsithermal Interval. A great reduction in the values of evergreen tree pollen at about 4000 cal. yr BP indicates a sudden retreat of the summer monsoon from this area.  相似文献   

7.
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.  相似文献   

8.
Detailed litho‐ and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the Isle of Skye, Scotland, UK, reveal evidence for several changes in relative sea level during the Late Devensian and Holocene. At the start of the record, relative sea level in the area was high at ca. 12 500 14C (ca. 14 800 cal.) yr BP but then fell, reaching a low point during the Younger Dryas, at ca. 11 000–10 000 14C (ca. 13 000–11 600 cal.) yr BP, when a rock platform, correlated with the Main Rock Platform, was formed. In the early–middle Holocene, relative sea level was rising by ca. 8000 14C (ca. 8800 cal.) yr BP and in northeast Skye a lagoonal surface, correlated with the Main Postglacial Shoreline, was formed at ca. 6600 14C (ca. 7500 cal.) yr BP. By the late Holocene, relative sea level was again falling, but a rise, registered at at least two sites, began probably before ca. 4000 14C (ca. 4500 cal.) yr BP, and a second lagoonal surface in northeast Skye, correlated with the Blairdrummond Shoreline, was formed, although by ca. 3000 14C (ca. 3200 cal.) yr BP relative sea level in the area had resumed its downward trend. The pattern of relative sea‐level changes disclosed is compared with evidence elsewhere in Scotland. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

9.
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.  相似文献   

10.
Accurate chronologies are essential for linking palaeoclimate archives. Carbon‐14 wiggle‐match dating was used to produce an accurate chronology for part of an early Holocene peat sequence from the Borchert (The Netherlands). Following the Younger Dryas–Preboreal transition, two climatic shifts could be inferred. Around 11 400 cal. yr BP the expansion of birch (Betula) forest was interrupted by a dry continental phase with dominantly open grassland vegetation, coeval with the PBO (Preboreal Oscillation), as observed in the GRIP ice core. At 11 250 cal. yr BP a sudden shift to a humid climate occurred. This second change appears to be contemporaneous with: (i) a sharp increase of atmospheric 14C; (ii) a temporary decline of atmospheric CO2; and (iii) an increase in the GRIP 10Be flux. The close correspondence with excursions of cosmogenic nuclides points to a decline in solar activity, which may have forced the changes in climate and vegetation at around 11 250 cal. yr BP. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

11.
A high-resolution Younger Dryas–late Holocene record of climate and environment from the Malangen fjord has been established on the basis of two marine sediment cores. Five pollen-spore assemblage zones have been defined covering the period c . 11 500 cal. yr BP (10 200 14C yr BP) to c . 1600 cal. yr BP (1600 14C yr BP) with a hiatus of c . 2000 cal. years between c . 10 200 and 8100 cal. yr BP (9000 and 7300 14C yr BP). The Holocene vegetation development from pioneer vegetation to forest development, identified in the marine pollen record, correlates well with pollen records from terrestrial sections of northern Norway. The marine pollen record was also correlated directly with marine proxy records of the bottom water temperature investigated in the same sediment cores. Correlation between the marine and terrestrial proxies suggests that changes in the influx of warm Atlantic Water to the fjord led to an instant change in the vegetation of the surrounding land area. The results thus support a strong link between marine and atmospheric mean climatic states in the North Atlantic region throughout the Holocene.  相似文献   

12.
The coastal zone of Norrbotten, northern Sweden, was gradually inundated by the Ancylus Lake following the retreating ice margin and forming a highest coastline approximately 210 m above the present sea level. The succeeding shore displacement is reconstructed based on lithological investigations and radiocarbon datings of identified isolation sequences from 12 cored lake basins. The highest lake basins, along with two basins above the highest shoreline, suggest ice-free conditions already at 10 500 cal. yr BP. This is at least 500 years earlier than previously thought and implies rapid ice-sheet break-up in the Gulf of Bothnia. The shore displacement (RSL) curve represents a forced regression of successively decreasing rate through the Holocene, from 9 m/100 yr to 0.8 m/100 yr. During the first 1000-1200 years, the isostatic uplift is exponentially declining, followed by a constant uplift rate from c. 9500 cal. yr BP to 5500-5000 cal. yr BP. The last 5000 years seem to be characterized by a low but constant rebound rate. The development of the Ancylus Lake stage of the Baltic may also be discerned in the Norrbotten RSL curve, suggesting that the chronology of the Ancylus Lake stages may have to be revised. The Littorina transgression is also reflected by the RSL curve shape. In addition, a series of early to mid-Holocene beach terraces were OSL-dated to allow for comparison with the 14C-dated shore displacement curve. Interpretations of these ages and their relation to former sea levels were clearly more problematic than the dating of the lake basin isolations.  相似文献   

13.
This article is a detailed pollen analysis and accurate AMS chronology of the Lateglacial of two coastal sites in western Norway. The area was deglaciated around 14 600 cal. yr BP or shortly before. The earliest vegetation was open, with a pioneer mosaic of vegetation on mineral soils, including snowbed communities, and plants on wind-blown ridges. Later, more stable vegetation developed with Empetrum as an important constituent. Scattered tree birches were established in the area in the last part of the Bølling/Allerød (GI-1). The pollen record from Vassnestjern indicates three short-lasting cold periods: c . 14 050 to 13 900, 13 800 to 13 700 and 13 150 to 13 000 cal. yr BP. It has been suggested that the last-mentioned period, detected at both sites, corresponds with the Gerzensee/Killarney Oscillation. From about 12 750 cal. yr BP, the vegetation was affected by the Younger Dryas (GS-1) cooling, which caused the vegetation to break up and humus-soil communities to disappear. In the early Holocene, the humus-soil communities re-established and open birch forests developed. This Lateglacial vegetation development is broadly similar to the reconstructed vegetation development in other parts of southwestern Norway.  相似文献   

14.
Romundset, A., Lohne, Ø. S., Mangerud, J. & Svendsen, J. I. 2009: The first Holocene relative sea-level curve from the middle part of Hardangerfjorden, western Norway. Boreas , 10.1111/j.1502-3885.2009.00108.x. ISSN 0300-9483.
The first relative sea-level (RSL) curve from the mid-Hardangerfjorden area covering the entire Holocene is presented. The curve is based on a series of AMS 14C dates on terrestrial plant macrofossils across the isolation level in each of five lakes located between 3.5 and 74.5 m a.s.l. During the first 1200 years, the RSL fell very rapidly from the marine limit at 98 m a.s.l. to 33 m a.s.l., i.e. at a rate of 5.4 cm yr−1. The emergence rate then slowed considerably and was close to standstill 8000–6500 cal. yr BP. However, an emergence of 16.5 m has taken place during the past 6000 years. Radiocarbon dates of terrestrial plant macrofossils from the basal strata in a lake above the marine limit and mollusc shells from glaciomarine silt in the isolation basins yielded a mean age for the local ice-margin retreat of 11 300 cal. yr BP. This verifies that Hardangerfjorden was glaciated during the Younger Dryas – an interpretation that has recently been disputed. The ice margin retreated at a rate of about 300 m yr−1 from the position of the Younger Dryas moraine to this site some 60 km further into the fjord.  相似文献   

15.
We use a time-dependent two-dimensional ice-flow model to explore the development of the Green Bay Lobe, an outlet glacier of the southern Laurentide Ice Sheet, leading up to the time of maximum ice extent and during subsequent deglaciation (c. 30 to 8 cal. ka BP). We focus on conditions at the ice-bed interface in order to evaluate their possible impact on glacial landscape evolution. Air temperatures for model input have been reconstructed using the GRIP δ 18 O record calibrated to speleothem records from Missouri that cover the time periods of c. 65 to 30 cal. ka BP and 13.25 to 12.4 cal. ka BP. Using that input, the known ice extents during maximum glaciation and early deglaciation can be reproduced reasonably well. The model fails, however, to reproduce short-term ice margin retreat and readvance events during later stages of deglaciation. Model results indicate that the area exposed after the retreat of the Green Bay Lobe was characterized by permafrost until at least 14 cal. ka BP. The extensive drumlin zones that formed behind the ice margins of the outermost Johnstown phase and the later Green Lake phase are associated with modeled ice margins that were stable for at least 1000 years, high basal shear stresses (c. 100 kPa) and permafrost depths of 80-200 m. During deglaciation, basal meltwater and sliding became more important.  相似文献   

16.
In the summer of 1999, the Maritimes and Northeast Pipeline Company excavated a 3-m-deep trench across northern Nova Scotia exposing a continuous transect of surficial deposits along a 237-km corridor. A Lateglacial palaeosol with preserved A horizon (peat and wood) buried under 2-10 m of surface till consisted mainly of herbaceous plant material with few large wood fragments. Large pieces of wood from two sites yielded conventional radiocarbon ages of 10.9 14C kyr BP (GSC-6435) and 10.8 14C kyr BP (GSC-6419). Previous to these finds, only a few localities were known to reveal till overlying peat, so the extent of Younger Dryas (YD) glaciers could not be clearly established. Glacial flow lines indicated by fabric and fluting of the YD surface till sheet in northern Nova Scotia and ice-marginal deposits imply an ice cap centred over eastern P.E.I. and the southern Gulf of St. Lawrence. This glacier also dammed a series of glacial lakes against the highland-rimmed west coast of Cape Breton Island. Glaciers developed and advanced during the YD in the uplands and offshore shelf areas from small remnants of Late Wisconsinan ice. Renewed ice growth was enabled by increased precipitation and local cooling in the Gulf of St. Lawrence due to deflection of the jet stream and expanded sea-ice cover in the North Atlantic. The YD may provide an analogy to glacier development in Maritime Canada during the interglacial/glacial transition.  相似文献   

17.
《Quaternary Science Reviews》2005,24(1-2):105-121
Pollen analysis of radiocarbon-dated lake sediment from northern Vancouver Island, southwest British Columbia reveals regional changes in forest vegetation over the last 12,200 14C yr (14,900 cal yr). Between at least 12,200 and 11,700 14C yr BP (14,900–13,930 cal yr BP), open woodlands were dominated by Pinus contorta, Alnus crispa, and various ferns. As P. contorta decreased in abundance, Alnus rubra and more shade-tolerant conifers (i.e., Picea and Tsuga mertensiana) increased. Increases in T. mertensiana, P. contorta, and A. crispa pollen accumulation rates (PARs) between 10,600 and 10,400 14C yr BP (11,660–11,480 cal yr BP) reflect a cool and moist climate during the Younger Dryas chronozone. Orbitally induced warming around 10,000 14C yr BP (11,090 cal yr BP) allowed the northward extension of Pseudotsuga menziesii, although Picea, Tsuga heterophylla, and A. rubra dominated early Holocene forests. By 7500 14C yr BP (8215 cal yr BP), shade-tolerant T. heterophylla was the dominant forest tree. Cupressaceae (Thuja plicata and Chamaecyparis nootkatensis) was present by 7500 14C yr BP but reached its maximum after 3500 14C yr BP (3600 cal yr BP), when a cooler and wetter regional climate facilitated the development of temperate rainforest. The highest rates of vegetation change are associated with Lateglacial climate change and species with rapid growth rates and short life spans.  相似文献   

18.
Rundgren, M., Ingólfsson, Ó., Björck, S., Jiang, H. & Haflioason, H. 1997 (September): Dynamic sea-level change during the last deglaciation of northern Iceland. Boreas , Vol. 26, pp. 201–215. Oslo. ISSN 0300–9483.
A detailed reconstruction of deglacial relative sea-level changes at the northern coast of Iceland, based on the litho- and biostratigraphy of lake basins, indicates an overall fall in relative sea level of about 45 m between 11300 and 9100 BP, corresponding to an isostatic rebound of 77 m. The overall regression was interrupted by two minor transgressions during the late Younger Dryas and in early Preboreal, and these were probably caused by a combination of expansions of local ice caps and readvances of the Icelandic inland ice-sheet margin. Maximum absolute uplift rates are recorded during the regressional phase between the two transgressions (10000–9850 BP), with a mean value of c . 15 cm 14C yr-1 or 11–12 cm cal. yr-1. Mean absolute uplift during the regressional phase following the second transgression (9700–9100 BP) was around 6 cm 14C yr-1, corresponding to c . 3 cm cal. yr-1, and relative sea level dropped below present-day sea level at 9000 BP.  相似文献   

19.
We present here the results of pollen analysis of two sequences of about 8.06 m and 11.90 m length, originating from two adjacent peat bogs in the southern part of Transylvania province, Romania (155 and 122 pollen spectra). The vegetation record, which is supported by 17 14C dates, begins in the Late Glacial interstadial when forest recolonisation began with the development of Pinus, without a pioneer Betula phase. Picea began to expand from regional refuges. After a well‐defined Younger Dryas, the Holocene opens with the expansion of Betula, Ulmus and Picea, followed, at about 10 400 cal. yr BP, by Fraxinus, Quercus and Tilia. The Corylus optimum is correlated with the Atlantic chronozone (after 8600 cal. yr BP). The local establishment of Carpinus occurred at about 6500 cal. yr BP, with a maximum at about 5700 cal. yr BP. Fagus pollen is regularly recorded after 8200 cal. yr BP. This taxon became dominant at about 3700 cal. yr BP. The first indications of human activities appear at around 7200 cal. yr BP. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

20.
Palynological and sedimentological analyses of a sedimentary sequence sampled at Hauterive/Rouges‐Terres, Lake Neuchâtel (Switzerland) provide documentation of changes in vegetation and lake‐level during the Bølling, Younger Dryas and Preboreal pollen zones, and have allowed a comparison with sequences covering the same period from other sites located in the western part of the Swiss Plateau. The Juniperus–Hippophaë zone (regional pollen assemblage zone (RPAZ) CHb‐2, first part of the Bølling, ca. 14 650–14 450 cal. yr BP) was characterised by a generally low lake‐level. A weak rise occurred during this zone. The Juniperus–Hippophaë to Betula zone transition coincided with a lake‐level lowering, interrupted by a short‐lived but marked phase of higher lake‐level recorded at the neighbouring site of Hauterive‐Champréveyres, but not present at Hauterive/Rouges‐Terres owing to an erosion surface. Shortly after the beginning of the Betula zone (RPAZ CHb‐3, second part of the Bølling, ca 14 450–14 000 cal. yr BP), a marked rise in lake‐level occurred. It was composed of two successive periods of higher level, coinciding with high values of Betula, separated by a short episode of relatively lower lake‐level associated with raised values in Artemisia and other non‐arboreal pollen. The last part of RPAZ CHb‐3 saw a fall in lake‐level. The lower lake‐levels during RPAZ CHb‐2 to early RPAZ CHb‐3 can be correlated with the abrupt warming at the beginning of the Greenland Interstadial (GI) 1e thermal maximum. The successive episodes of higher lake‐level punctuating the GI 1e might be linked to the so‐called Intra‐Bølling Cold Oscillations identified from several palaeoclimatic records in the North Atlantic area, and also documented in oxygen‐isotope data sets from Swiss Plateau lakes. The Hauterive/Rouges‐Terres lake‐level record provides evidence for marked climatic drying through the second part of the Younger Dryas event (GS1), during the GS1–Preboreal (RPAZ CHb‐4b–4c) transition (except for a rise at ca. 11 450–11 400 cal. yr BP), and at the RPAZ CHb‐4c–5 (Preboreal–Boreal) transition, following the Preboreal Oscillation (after 11 150 cal. yr BP). The Preboreal Oscillation coincided with higher lake‐levels, its end being followed by a rapid expansion of Corylus, Quercus, Ulmus and Tilia. The Hauterive/Rouges‐Terres lake‐level record suggests that radiocarbon plateau at 12 600, 10 000 and 9500 14C yr BP corresponded to periods of generally lower lake‐level. This suggests that an increase in solar activity may have contributed to both climatic dryness and a decrease in atmospheric radiocarbon content. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

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