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1.
SOLVEIG FIMREITE KARL-DAG VORREN TORE O. VORREN 《Boreas: An International Journal of Quaternary Research》2001,30(2):89-100
Sediments from two small lakes distal to the Tromsø–Lyngen moraine at Tromsø, northern Norway, indicate that the area was deglaciated prior to c. 11.7 14 C ka BP. The earliest vegetation was dominated by calciphilous and heliophilous pioneer plants on unstable soils; this changed to a vegetation reflecting a dry continental climate until c. 10.7 14 Cka BP. A phase (10.7–10.5 14 Cka BP) with snow-bed communities was followed by one with a mosaic of plant communities. This was succeeded by Empetrum heaths c. 10.3 14 Cka BP, then by an open forest with Betula pubescens after 10.0 14 Cka BP. Ice-front oscillations in the Tromsø area are evaluated. The main part of the Younger Dryas glacial readvance, the Tromsø–Lyngen event, probably occurred between 10.7 and 10.3 14 Cka BP. 相似文献
2.
BARBARA WOHLFARTH SVANTE BJÖRCK GÖRAN POSSNERT GEOFFREY LEMDAHL LARS BRUNNBERG JONAS ISING SIV OLSSON NILS-OLF SVENSSON 《Boreas: An International Journal of Quaternary Research》1993,22(2):113-128
The increasing focus on the chronology of environmental and climatic changes of the last glacial-interglacial transition has led to several independent attempts to try to calibrate the 14 C time-scale beyond the Holocene. The Late Weichselian Gotiglacial varved clays of the Swedish Time Scale could potentially be used for this purpose. The reliability of the Swedish Time Scale is discussed as well as different ways of using the Swedish varved clays for calibrating the 14 C chronology. The strategy and initial results from an ongoing calibration project are presented. They show clearly that, if the right strategy is adopted, varved clay may be dated by accelerator mass spectrometry (AMS) 14 C measurement of terrestrial macrofossils. A Late Weichselian 'event stratigraphy', including the Vedde Ash fall-out, is established for south Scandinavia using three dating categories: clay varve measurements, terrestrial macrofossil measurement, and lake sediment (including aquatic mosses) measurements. It suggests that a 14 C chronology based on terrestrial organic remains is not consistent with the traditional Late Weichselian chronostratigraphy based on lake-sediment samples, and that 'clay varve years' exceed 'terrestrial 14 C years' by c. 900 years at the end of, and by 1100–1200 years at the beginning of the Younger Dryas Chronozone. Further back in time, the time-scales appear to converge. These results are compared with other recently published calibration studies. 相似文献
3.
BRIGITTA AMMANN RE F. LOTTER 《Boreas: An International Journal of Quaternary Research》1989,18(2):109-126
A detailed late-glacial radiocarbon stratigraphy for the Swiss Plateau has been established on the basis of over 90 accelerator 14 C dates on terrestrial plant macrofossils. Two plateaux of constant.,14 C age were observed, occurring at 12,700 B.P. and at 10,000 B.P. The consequences of these plateaux for palaeo-ecological investigations are threefold: (1) a more refined 14 C dating within the plateaux is not possible, (2) in teleconnections between different sites (if based on 14 C dating and concerning the periods around 12,700 B.P. and 10,000 B.P.) events are considered synchronous which are only synchronous within a plateau of constant age, and (3) exact time-depth relationship and therefore influx calculations are made impossible during these plateau periods. A comparison of the radiocarbon ages derived from terrestrial, telmatic and limnic material at different sites on the Swiss Plateau yields a proposal for modifying the zonation system of Welten for the Late-Glacial. By retaining the limits of chronozones (at 13, 12, 11 and 10ka B.P.) and by refining the palynostratigraphic criteria for the limits of biozones, a separation between chrono- and biozonation at the beginning of the Belling and at the beginning of the Younger Dryas becomes obvious. 相似文献
4.
TORE O. VORREN LIV PLASSEN 《Boreas: An International Journal of Quaternary Research》2002,31(2):97-125
This paper reviews the deglaciation history and palaeoclimate from 22 to 9.5 14 Cka BP in the Andfjord-Vagsfjord area. Eight main glacial events are recorded: The Egga-I (>22 14 Cka BP), the Bjerka, the Egga-II (>14.6 14 Cka BP), the Flesen (14.5 14 Cka BP), the D (13.8–13.2 14 Cka BP), the Skarpnes (12.2 14 Cka BP), the Tromsø–Lyngen (10.7–10.3 14 C ka BP) and the Stordal (10.0–9.5 14 Cka BP). Onset of the final deglaciation occurred about 14.6 14 Cka BP. Most of the western part of the Fennoscandian and Barents Sea Ice Sheets receded from the outer continental shelf 15–14 14 Cka BP. The delivery and melting of icebergs at this time to the Norwegian-Greenland Sea resulted in a low oxygen isotope event recorded in a number of cores in the region. Atlantic water intruded the area 13.2 14 Cka BP, and an atmospheric warming commenced 12.9/12.8 14 Cka BP. A marked glacial recession occurred before the Skarpnes event. During Allerød time, the glaciers retreated to the fjord heads or even farther inland. The Fennoscandian outlet glaciers readvanced (locally more than 40 km), reached their Younger Dryas outer limit after 10.7 14 Cka BP and retreated from this position before about 10.3 14 Cka BP. 相似文献
5.
ÁRNÝ E. SVEINBJÖRNSOTTIR JÓN EIRÍKSSON ÁSLAUG GEIRSDÓTTIR JAN HEINEMEIER NIELS RUD 《Boreas: An International Journal of Quaternary Research》1993,22(2):147-157
An exhaustive 14 C 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 14 C age distribution (standard deviation of ±235 years) of molluscs from all localities and from successive marine units in vertical sections. The weighted mean conventional 14 C 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 14 C 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. δ13 C and δ18 O results suggest that temperatures may have ranged up to 60°C. 相似文献
6.
ANNE JENNINGS JAMES SYVITSKI LINDA GERSON KARL GRÖNVOLD ÁSLAUG GEIRSDÓTTIR JÓRUNN HARDARDÓTTIR JOHN ANDREWS SVEINUNG HAGEN 《Boreas: An International Journal of Quaternary Research》2000,29(3):163-183
Foraminifera, sedimentology, and tephra geochemistry in core 93030-006 LCF from the southwestern Iceland shelf were used to reconstruct paleoenvironments between 12.7 and 9.4 14 C ka BP. Seismic-reflection profiles place the core in glacial-marine and marine sediments within one meter of the underlying glacial till. Foraminifers in the earliest glacial-marine sediments provide a record of ice-distal conditions and immigration of slope species onto the shelf in association with warm Atlantic water. Meltwater increased during the Allerød under a weakened Atlantic water influence. Arctic conditions began by 11.14 14 C ka BP with an abrupt increase in meltwater and near exclusion of boreal fauna from the shelf. Meltwater diminished in the early Younger Dryas, coinciding with sea-surface cooling between 11.14 and 10.5 14 C ka BP. A slight warming recorded in the uppermost glacial-marine sediments was interrupted by an inferred jökulhlaup event emanating from glacier ice on the Western Volcanic Zone. Retreat of the ice margin from the sea sometime between c. 10.3 and 9.94 14 C ka BP coincided with this event. The onset of postglacial marine sedimentation occurred along with increasing evidence of Atlantic water c. 9.94 14 C ka BP and was interrupted by a short-lived Pre-boreal cooling of the Irminger Current c. 9.91 14 C ka BP. Conditions similar to those today were established by 9.7 14 C ka BP. 相似文献
7.
ELSE KOLSTRUP REW MURRAY GÖRAN POSSNERT 《Boreas: An International Journal of Quaternary Research》2007,36(3):314-325
The chronology of two adjacent Danish Lateglacial sedimentary sequences with well-developed layering of alternating aeolian sand and organic matter has been investigated using both Optically Stimulated Luminescence (OSL) and Accelerator Mass Spectrometry (14 C). Both sites are known to cover at least the period Bølling to Younger Dryas, with the so-called older and younger coversand types present at both localities. Typical overall uncertainties with the OSL data are about two to five times those of the 14 C ages, but both data sets contain clear outliers. When these are excluded, OSL ages appear to be systematically slightly younger than the 14 C ages, by about 10%; possible reasons for this are discussed. The investigation stresses the importance of making several age estimates from any single locality. The older coversand type makes up the pre-Bølling and most, or possibly all, of the Bølling (which also has the highest net accumulation rate). Deposits of the younger coversand type are dominant in layers younger than the Bølling. 相似文献
8.
Younger Dryas cirque glaciers in western Spitsbergen: smaller than during the Little Ice Age 总被引:3,自引:0,他引:3
JAN MANGERUD JON Y. LANDVIK 《Boreas: An International Journal of Quaternary Research》2007,36(3):278-285
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 14 C 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. 相似文献
9.
PIERRE LASALLE WILLIAM W. SHILTS 《Boreas: An International Journal of Quaternary Research》1993,22(1):25-37
Occurrences of Balanus hameri-bearing diamicts described in this paper and pertinent ( Balanus plates and pelecypods shells) 14 C dates suggest that there was glacial activity in the Champlain Sea basin between 11,000 BP and 10,400 BP and that this activity can be ascribed to a climatic cooling episode correlative with the Younger Dryas of the late-glacial sequence of northeastern Europe. 相似文献
10.
KLAUS FELIX KAISER UELI EICHER 《Boreas: An International Journal of Quaternary Research》1987,16(3):293-303
Pollen and mollusc deposits in a sedimentation series laid down in the Dattnau valley during the Late Glacial and early Post-glacial were studied. For the first time δ13 C and δ18 O in land-snail shells were measured. It was possible to reconstruct vegetational and climatic developments from the Bölling ( c . 12,500 B.P.) until well into the early Boreal ( c . 9,000 B.P.). The two sets of findings agree well. The Late Glacial is seen to comprise two intervals: the continuous, locally rather moist, warm Bölling/Alleröd period, and the subsequent dry . cold Younger Dryas. The profile ceases after the changeover from the Late Glacial to the Post-glacial. The transitions from the Alleröd to the Younger Dryas and hence to the Preboreal and Boreal are both clearly identifiable in the pollen diagram; the mollusc record, however, ceases to be interpretable shortly before the climatic change to the Post-glacial. The δ18 O curve shows a clear distinction between the AllerÖd and the Younger Dryas. The Gerzensee fluctuation, immediately before this transition. is evident as a negative deviation. 相似文献
11.
Palynological and oxygen isotope investigations on Late-Glacial sediment cores from Swiss lakes 总被引:2,自引:0,他引:2
ULRICH EICHER ULRICH SIEGENTHALER 《Boreas: An International Journal of Quaternary Research》1976,5(2):109-117
Results from detailed pollen and 18 O/16 O studies on two sediment profiles from small Swiss lakes are reported. 18 O/16 O 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. 18 o/16 O 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. 相似文献
12.
ÓLAFUR INGÓLFSSON HREGGVIDUR NORDDAHL HAFLIDI HAFLIDASON 《Boreas: An International Journal of Quaternary Research》1995,24(3):245-259
In connection with a new deglaciation concept for Iceland, implying an extensive glaciation during the Younger Dryas and the decay of the Icelandic inland ice sheet during the Preboreal, the history of relative sea-level changes on Iceland has been re-evaluated. New field data from the Reykjavik area, in Faxaflói Bay southwestern Iceland, were obtained in order to construct the first stratigraphically controlled curve of relative sea-level displacements for Iceland. The curve is constructed on the basis of radiocarbon-dated shells in raised marine deposits and on tephrostratigraphically controlled and radiocarbon-dated, submerged peat deposits. The curve suggests that a post-glacial relative sea-level change of about 45 m, from + 43 m a.s.1. to — 2 m a.s.l, occurred over a period of 900 14 C-years in the Reykjavik area between 10 300 BP and 9400 BP. The sea-level curve shows a shoreline displacement of c . 5 cm 14 Cyr-1 for that period. The mean absolute uplift rate is calculated to be 6.9 cm 14 C yr-1 , which is about double the fastest rate reported from any other coastal North Atlantic site. Although this rapid uplift can probably be partly explained by a 14 C plateau around the termination of the Pleistocene, it is more than likely controlled by rapid Preboreal deglaciation, together with low asthenosphere viscosities below Iceland and the release of hydroisostatic stresses in connection with the deglaciation. 相似文献
13.
14.
DAN HAMMARLUND BJØRN BUCHARDT 《Boreas: An International Journal of Quaternary Research》1996,25(1):8-22
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 18 O and 13 C. 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. 相似文献
15.
MATS RUNDGREN ÓLAFUR INGÓLFSSON SVANTE BJÖRCK HUI JIANG HAFLIDI HAFLIDASON 《Boreas: An International Journal of Quaternary Research》1997,26(3):201-215
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 cm14 C 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 14 C 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
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
16.
The first Holocene relative sea-level curve from the middle part of Hardangerfjorden, western Norway
ANDERS ROMUNDSET ØYSTEIN S. LOHNE JAN MANGERUD JOHN INGE SVENDSEN 《Boreas: An International Journal of Quaternary Research》2010,39(1):87-104
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 AMS14 C 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
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
17.
Younger Dryas deglaciation at Mt. Billingen, and clay varve dating of the Younger Dryas/Preboreal transition 总被引:1,自引:0,他引:1
BO STRÖMBERG 《Boreas: An International Journal of Quaternary Research》1994,23(2):177-193
A clay varve chronology has been established for the Late Weichselian ice recession east of Mt. Billingen in Västergötland, Sweden. In this area the Middle-Swedish end moraine zone was built up as a consequence of cold climate during the Younger Dryas stadial. A change-over from rapid to slow retreat as a result of climatic deterioration at the Alleröd/Younger Dryas transition cannot be traced with certainty in the varve sequences, but it seems to have taken place just before 11,600 varve years BP. The following deglaciation was very slow for about 700 years — within the Middle-Swedish end moraine zone the annual ice-front retreat was only c . 10 m on average. A considerable time-lag is to be expected between the Younger Dryas climatic event and this period of slow retreat. The 700 years of slow retreat were succeeded by 200 years of more rapid recession, about 50–75 m annually, and then by a mainly rapid and uncomplicated retreat of the ice-front by 100–200 m/year or more, characterizing the next 1500 years of deglaciation in south and central Sweden. The change from about 50–75 m to 100–200 m of annual ice-front retreat may reflect the Younger Dryas/Preboreal transition. Clay-stratigraph-ically defined, the transition is dated at c . 10,740 varve years BP, with an error of +100 to -250 years. In the countings of ice layers in Greenland ice cores (GRIP and GISP-2) the end of the Younger Dryas climatic event is 800–900 years older. However, a climatic amelioration after the cold part of the Younger Dryas and in early Preboreal should rapidly be reflected by for example chemical components and dust in Greenland ice cores, and by increasing δ13 C content in tree rings. On the other hand, the start of a rapid retreat of the inland ice margin can be delayed by several centuries. This can explain at least a part of the discrepancy between the time-scales. 相似文献
18.
KAREN LUTSE KNUDSEN KELD CONRADSEN SUSANNE HEIER-NIELSEN MARIT-SOLVEIG SEIDENKRANTZ 《Boreas: An International Journal of Quaternary Research》1996,25(2):65-78
The study of a c. 18 m thick Late Weichselian- Early Holocene (isotope stage 2/1) marine succession (original water depth 100–150 m) from the Skagen 3 borehole, northern Denmark, has led to a better understanding of the palaeoenvironmental changes during the last deglaciation. The palaeoenvironmental interpretation is based on benthic foraminifera, stable isotope composition and lithology, whereas the chronostratigraphy and sedimentation rates are based on AMS radiocarbon dates. Marine conditions were established in the area at between 15 000 and 14 500 BP (reservoir corrected 14 C years), and the first influence of Atlantic water masses imported through the Norwegian Channel is registered from 13 100 BP to 10 900BP (the Bølling- Allerrad interstadial complex). This was followed by the Younger Dryas cooling event between 10 900 and 10 100 BP. The hydrographic change at the Pleistocene-Holocene transition after the Younger Dryas occurred in two stages. Arctic/subarctic deep-water assemblages persisted continuously at Skagen after the first stage at 10 200 BP, while cold boreal assemblages existed in shallower water environments in the Kattegat-Skagerrak basin during the same period of time. The slight warming in the early Holocene seems to have been interrupted by a short-term cooling at about 9700–9600 BP. Finally, at 9600 BP the arrival of warm Atlantic water masses created full-interglacial conditions in the whole region. 相似文献
19.
Exposure age dating and Equilibrium Line Altitude reconstruction of an Egesen moraine in the Maritime Alps, Italy 总被引:1,自引:0,他引:1
PAOLO ROBERTO FEDERICI DARRYL E. GRANGER MARTA PAPPALARDO ADRIANO RIBOLINI MATTEO SPAGNOLO ANDREW J. CYR 《Boreas: An International Journal of Quaternary Research》2008,37(2):245-253
Four boulder samples from the Piano del Praiet frontal moraine in the Gesso della Barra Valley (Maritime Alps) have been 10 Be 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 10 Be 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. 相似文献
20.
Younger Dryas end moraines between Hardangerfjorden and Sognefjorden, Western Norway 总被引:1,自引:0,他引:1
End moraines (called the Herdla Moraines) from the Younger Dryas Stadial arc morphologically mapped along the western coast of Norway, from Hardangerfjorden to north of Sognefjorden. The submarine position of the moraines are found by means of a conventional echo sounder. Stratigraphieal studies with many C14 datings are used for age determination, giving Late Younger Dryas (10,000–10,500 C14 years B.P.) for the Herdla Moraines. The moraines are correlated with the Ra-Salpausselkä Moraines. Isobases for the Younger Dryas are obtained from marine terraces formed contemporaneously with the moraines. 相似文献