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1.
Palaeoecological study on the Holocene valley development of the River Main, southern Germany 总被引:1,自引:0,他引:1
BERND BECKER WOLFGANG SCHIRMER 《Boreas: An International Journal of Quaternary Research》1977,6(4):303-321
Tree-ring studies carried out on subfossil oak trunk deposits within the Holocene valley fills of the River Main can reconstruct phases of increased fluvial activities. These phases have been dated on the base of two absolutely tree-ring dated chronologies and in addition by 11 C-datings of eleven floating tree-ring scries of subfossil oaks.
Geological-pedological investigations reveal an alternation between increased and reduced fluvial activity during the Holocene.
Periods of increased gravel redeposition are dated by dendrochronology, and by14 C and cultural findings. Increased fluvial activity becomes more frequent towards Modern Times with culminations in the Middle Atlantic, the Subboreal, the Iron-Roman Age, the Main Middle Ages till earliest Modern Times, and in the last century.
On the sequence of Holocene river deposits there developed specific soil types as indicators for the age of the river deposits since the Last Glacial.
Among other palaeoecological results an important finding is the correlation between tree-ring width, flood-loam sedimentation, and soil development. 相似文献
Geological-pedological investigations reveal an alternation between increased and reduced fluvial activity during the Holocene.
Periods of increased gravel redeposition are dated by dendrochronology, and by
On the sequence of Holocene river deposits there developed specific soil types as indicators for the age of the river deposits since the Last Glacial.
Among other palaeoecological results an important finding is the correlation between tree-ring width, flood-loam sedimentation, and soil development. 相似文献
2.
MATT S. FORBES EVELYN S. KRULL ERICK A. BESTLAND ROD T. WELLS 《Boreas: An International Journal of Quaternary Research》2009,38(4):705-717
The timing of the extinction of the Australian Megafauna and whether it was simultaneous and widespread has been a much researched topic in Quaternary geoscience. The Black Creek Swamp Megafauna site on Kangaroo Island was thought to be a refugium for Megafauna; however, recent and multidiscipline age determinations have established that the fossils are considerably older than the well-quoted extinction age of 45 kyr. Further radiocarbon age determinations, δ13 C isotope analysis and 13 C-NMR spectroscopy of the fossil containing organic matter demonstrates that it is highly soluble and accumulated as recently as 31–18 cal. kyr BP. These radiocarbon ages are much younger than the 100–50 kyr age bracket ascertained for the fossil material itself, implying separate episodes of death, deposition and burial. The soluble nature of the organic matter and increasing radiocarbon ages with depth suggests lateral accumulation, probably transported by subsurface waters from elevated areas proximal to the low-lying swamp. Such depositional conditions and 14 C age range implies that the site may have experienced an unusually wet Last Glacial Maximum, due maybe to its proximity to the continental shelf and thus to maritime conditions. C3 vegetation dominates the Black Creek Swamp and its organic matter (δ13 C; −30‰ and −23‰); however, variations in δ13 C may indicate climatic shifts. 13 C-enrichment and an abundance of salt-tolerant gastropods within the site's final phase of sediment accumulation (<6 cal. kyr BP) suggest that conditions during this most recent period were not as wet as those of the Last Glacial Maximum. 相似文献
3.
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
4.
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
5.
RUDOLPH R. STEA ROBERT J. MOTT 《Boreas: An International Journal of Quaternary Research》1989,18(2):169-187
The start of deglaciation is recorded in the Minas Basin region of Nova Scotia by the deltaic, glaciofluvial and glaciomarine sediments of the Five Islands Formation. Shell dates on bottomset beds of a delta at Spencers Island range from 14,300 to 12,600, 14 C yearsB.P. The time of complete deglaciation of Nova Scotia is still unknown; the uncertainty is at least partially due to evidence for a climatic oscillation at the end of the Late Wisconsinan. Peat beds were deposited during the interval between 12,700 and 10,500 B.P. They overlie previous glacial and fluvial deposits and are overlain by deposits of various origins. Pollen in these peat beds records the migration of spruce into the region indicating climatic warming, and a subsequent deterioration of climate is recorded by the return of tundra-like flora. The peat beds are truncated by a variety of deposits, including fluvial gravel and sand, lacustrine sand, silt and clay, and diamictons. Periglacial landforms and structures have been observed in some of these deposits. At Collins Pond, on the shore of Chedabucto Bay, a diamicton overlying a peat bed is characterized by strong fabrics parallel to the trend of other ice-flow landforms in the region. The evidence suggests that at least some of these deposits are glacigenic, indicating that glaciers were active in Nova Scotia until about 10,000 B.P. 相似文献
6.
ABSTRACT The Tripoli Formation (Lower Messinian) in Sicily includes diatomites irregularly alternating with marl and carbonate beds and lies, stratigraphically, between the Tortonian pelagic marls and the evaporitic Calcare di base. The relationships between mineralogy, textural features and oxygen-carbon isotopic compositions of carbonate components point to a wide variability of depositional conditions and suggest that Tripoli sedimentation occurred in small basins characterized by periodic and marked restriction from the open sea.
The isotopic values of calcite and dolomite in the diatomites suggest an evolution from normal marine towards more restricted environments. Evaporating conditions are also indicated by the occurrence of anhydrite, length-slow chalcedonic quartz and moulds of gypsum. In a more advanced stage, the precipitation of heavy δ18 0 dolomite in the interstitial pores of fossil-poor diatomites denotes an environment with highly evaporated water. Mixing of meteoric and marine waters, on the other hand, might have favoured the precipitation of a dolomite characterized by relatively low δ18 0 and δ13 C values.
The deposition of marl and carbonate beds alternating with or overlying the diatomites took place in an environment with highly evaporated marine waters on the basis of δl18 O values of dolomite (up to + 9.10‰) and aragonite (up to + 5.83‰), occurrence of evaporitic minerals and lack of fossils. The presence at these levels of calcite with extremely negative δ13 C values (down to - 38.40‰), filling gypsum moulds, suggests activity of sulphate-reducing bacteria. Some aragonitic marls, however, bear evidence of deposition in relatively normal marine conditions. 相似文献
The isotopic values of calcite and dolomite in the diatomites suggest an evolution from normal marine towards more restricted environments. Evaporating conditions are also indicated by the occurrence of anhydrite, length-slow chalcedonic quartz and moulds of gypsum. In a more advanced stage, the precipitation of heavy δ
The deposition of marl and carbonate beds alternating with or overlying the diatomites took place in an environment with highly evaporated marine waters on the basis of δl
7.
SHI JINLIANG 《Boreas: An International Journal of Quaternary Research》1986,15(4):279-288
Reaches with very thick deposits alternate with deeply incised reaches in the DaDu river valley. The river sediments are described and a number of 14 C dates are given. The deposits are alluvium, Pleistocene slope-wash deposits, marginal moraines and beds of fluvio-lacustrine origin. The valley development is explained as the result of neotectonic movement and glacial aggradation. From the point of view of water-power development, three different types of valley can be distinguished, each with its own consequences for hydraulic engineering works. 相似文献
8.
NAJA MIKKELSEN HELMUT ERLENKEUSER JOHN S. KILLINGLEY WOLFGANG H. BERGER 《Boreas: An International Journal of Quaternary Research》1982,11(2):163-171
The ahermatypic coral Lophelia pertusa which produces aragonitic skeletons is widely distributed along the Norwegian coast. Specimens from a number of localities have been analyzed for oxygen and stable carbon isotope composition and 14 C age. Stable isotope ratios of recent corals provide information on growth rate and seasonality of oceanographic conditions. Lophelia can be useful in paleoenvironmental reconstructions. 14 C dates of fossil Lophelia from Drøak in the Oslofjord, collected from 20 m ahove and 40 m below present day sea-level, indicate regional extinction between 8700 and 7800 years ago. We suggest that the extinction resulted from the cut-off of deep waters by a rising sill in connection with the postglacial shoreline displacement. Radiocarbon dating of coral bushes suggests a fairly rapid growth rate as older and younger parts of recent corals do not reveal any difference in activity despite the short time scale of the history of bomb-produced 14 C in the oceans. 相似文献
9.
DAN HAMMAKLUND 《Boreas: An International Journal of Quaternary Research》1993,22(3):236-243
Values of δ13 C obtained from conventional bulk sediment radiocarbon dates encompassing the Pleistocene Holocene boundary have been compiled and plotted against 14 C age. In all. 286 lake sediment dates from southern Sweden in the range 8.000 to 13.000 BP have been evaluated. A significant decrease in δ13 C values, initiated shortly before 10.000 RP and amounting to 5%, is distinguished. This change is accompanied by increased limnic productivity. decreased erosive input and increased organic carbon content of the sediments. A probable explanation for the δ13 C decline in organic material is decreased importance of dissolution of silicates at the transition to the Holocene. During the Late Weichselian. extensive weathering of exposed minerogenic material with subsequent input of bicarbonate to the lake water may have caused a relative enrichment of 13 C in dissolved inorganic carbon. Furthermore, the early Holocene increase in terrestrial vegetation cover probably led to an increased supply of 13 C depleted carbon dioxide to the lake water by root respiration. Altered limnic vegetation, presumably towards increased production of phytoplankton. could also have contributed to the observed decreasing δ13 C trend. The importance of these processes compared to other possible influencing factors. mainly endogenic carbonate production and changes in the global carbon cycle. is discussed. 相似文献
10.
DAVID J. LUBINSKI SERGEY KORSUN LEONID POLYAK STEVEN L. FORMAN SCOTT J. LEHMAN FRANCES A. HERLIHY GIFFORD H. MILLER 《Boreas: An International Journal of Quaternary Research》1996,25(2):89-100
A study of two piston cores and a 3.5 kHz seismic profile from the Franz Victoria Trough provides new stratigraphic, stable isotopic and foraminiferal AMS 14 C data that help constrain the timing of ice-sheet retreat in the northern Barents Sea and the nature of the deglacial marine environment. Silty diamicton at the base of each core, interpreted as till or ice-marginal debris flow, suggests that the Barents ice sheet was grounded at the core sites (470 m water depth). Eight AMS 14 C dates on sediment overlying the diamicton indicate that the ice sheet retreated from both core sites by 12.9 ka and that postglacial sedimentation began 10 ka ago. These dates, combined with a recently published 14 C date from a nearby core, suggest that the Franz Victoria Trough may not have been deglaciated until c . 13 ka, 2000 years later than modeled ice-sheet reconstructions indicate. In the trough, oxygen isotopic ratios in planktonic foraminifera N . pachyderma (sinistral) were 0.5–0.750, lower during deglaciation than after, probably as a result of ice-sheet and/or iceberg melting. Foraminiferal assemblages suggest that Atlantic-derived intermediate water may have begun to penetrate the trough c . 13 ka ago. 相似文献
11.
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
12.
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
13.
ABSTRACT The carbon-isotope signature of terrestrial organic matter (OM) offers a valuable tool to develop stratigraphic correlations for near-shore deposits. A mid-Cretaceous coastal succession of the western Algarve Basin, Portugal, displays a marked negative δ13 C excursion ranging from − 21.2‰ to − 27.8‰ in the Early Aptian followed by two shifts towards higher values (up to − 19.3‰) during the Early and Late Aptian, respectively. The dominance of cuticle and leaf debris in the bulk OM fraction is confirmed by optical studies, Rock-Eval pyrolysis and by comparison with the δ13 C signature of four different types of fossilized land-plant particles. Correlation of two terrestrial δ13 Cbulk OM records from different study sites leads to a significant enhancement of the intrabasinal stratigraphic correlation within the Algarve Basin. Three prominent excursions in the Portuguese records can be correlated with existing δ13 C curves from pelagic and terrestrial environments. The general carbon-isotope pattern is superimposed by small-scale fluctuations which can be explained by compositional variations within the OM. 相似文献
14.
Expanded sedimentary records from the Tethys reveal unique faunal and isotopic changes across the Palaeocene-Eocene (P-E) transition. Unlike in the open oceans, the Tethys exhibits a gradual decrease of 1.5% in δ13 C values prior to the rapid δ13 C excursion. Associated with the 613 C excursion is a decrease in calcite burial, increase in detrital content and appearance of a unique opportunistic planktic foraminifera1 assemblage (e.g. compressed acarininids). The existence of a prelude decrease in δ13 C values in the Tethys suggests that the P-E δ13 C excursion may have occurred in two steps and over a few hundred thousand years, rather than as one step over a few thousand years as previously suggested. This slower excursion rate is readily explained by changing organic carbon weathering or burial rates and avoids the need of invoking ad hoc scenarios. 相似文献
15.
Four stratigraphic sections in the southern part of the Columbia Basin preserve a sequence of aeolian and non-aeolian sediments ranging in age from 9·43 to >47·0 14 C ka based on accelerator mass spectrometry radiocarbon dating of fossil molluscs, geochemistry of Cascade Mountain-sourced tephra and association with formally recognized pedostratigraphic units (the Washtucna and Old Maid Coulee soils). Study sections are interpreted as representing concurrent deposition of loess and distal Missoula Flood rhythmites in valleys tributary to main drainages backflooded during the Missoula Floods, and formation of carbonate and iron-rich soils. Sediments belong to the formally recognized L-1 and L-2 loess units established for the Palouse loess, which were deposited in the Columbia Basin subsequent to events of glacial outburst flooding. Sediments associated with the Mount Saint Helens set S and set C tephras in the study sections preserve a fauna of five species of gastropod mollusc which have not been reported previously from sediments of late Pleistocene age in the Palouse region. The fossils comprise two distinct faunules stratigraphically separated by the Mount Saint Helens So tephra. Accelerator mass spectrometry radiocarbon dating of the fossils collected above the tephra in two of the sections yielded ages of 12·48 ± 0·06 and 9·43 ± 0·05 14 C kyr. These ages suggest that independent determinations of the 13·35 14 C kyr age of the So tephra in other areas where Missoula Flood sediments are preserved are probably accurate, and help to refine the age of the latest events in the most recent sequence of catastrophic glacial outburst flooding. 相似文献
16.
MEINRAD KÜTTEL 《Boreas: An International Journal of Quaternary Research》1977,6(3):259-274
New pollen-analytical investigations and two 14 C series indicate that, at the Bedrina on Mount Piottino (Tessin, Switzerland), the post-Allerød NAP phase (Piottino oscillation) represents the well-marked Younger Dryas at least for the most part. The late-glacial part of the profile is re-classified, and the term Piottino oscillation is rejected, as it is largely identical with the Younger Dryas. Individual 14 C dates from the transition between the Younger Dryas and the Preboreal should be considered critically. Considerable fluctuations in the 14 C level are supposed for this period. 相似文献
17.
Abstract. Carboniferous-Permian limestones of the Akiyoshi Plateau, in the Inner Zone of southwestern Japan, are composed of essentially pure calcium carbonate containing only small amounts of other elements, and they are accompanied by marble and copper skarn deposits near the contact with late Cretaceous granitoids. The δ18 O values of the Akiyoshi limestones range widely from 7.6 to 28.3% and are mostly lower than those of other areas of the same age (23–29%), whereas the differences among the δ13 C values are small. The δ18 O values are negatively correlated with Mn and Fe contents. Samples with high δ18 O (>25%) and δ13 C (>2%) values do not contain Fe, Zn, or Pb, but those with low δ18 O values tend to be rich in these elements, indicating that these elements were introduced by interaction with H2 O dominant fluids, possibly of magmatic origin. Potential scores for evaluating the degree of interaction with hydro thermal fluids were calculated for δ18 O, δ13 C, Fe, Mn, Zn, Pb, and Sr. Higher scores implying much hydrothermal interaction were evident in the Mt. Hananoyama area, where there are many skarn deposits, and along faults oriented mainly NNW-SSE. Therefore, these are promising areas for exploring for blind deposits. It is likely that the hydrothermal fluid traveled through the limestones along fractures at the time of the granitic intrusions. However, the potential scores here are much smaller than those in the Pb-Zn mineralized area of the Kamioka mine, so more detailed petrological and mineralogical investigations are necessary. 相似文献
18.
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
19.
A breccia vein sampled from a shear zone in greenschist facies metapelites at Mount Isa, Queensland, Australia, shows a systematic variation in vein geometry that is related to the geometry of folding and faulting within the sample. Calcite vein-fill is coarse grained and equigranular, suggesting precipitation in a fluid-filled space. Partially folded veins suggest that veining occurred during folding and faulting. The breccia vein contains a central zone in which dilation has occurred simultaneously in all directions in the plane of section, implying that this was a zone of high fluid pressure and nearly isostatic differential stress during folding and faulting. From these observations, it can be inferred that the breccia vein was a zone of high permeability and a likely fluid channel during deformation. This hypothesis was tested by stable isotope analysis of veins and host rocks. The calcite veins have δ13 C values of -11.1 ± 0.1% and δ18 O values of 6-10%o , whereas the host metapelite has δ13 C values of -10.62 and -10.11% and δ18 O values of 14-15%o . These values are consistent with an igneous-derived, H2 O-dominated fluid that exchanged little oxygen with the host rocks, but derived much of its carbon from the wall rock. The isotopic disequilibrium between the veins and the wall rock confirms that the fluid was externally derived, and that the breccia vein acted as a channel for large-volume fluid flow within the shear zone. 相似文献
20.
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