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1.
Gough's Cave is still Britain's most significant Later Upper Palaeolithic site. New ultrafiltered radiocarbon determinations on bone change our understanding of its occupation, by demonstrating that this lasted for only a very short span of time, at the beginning of the Lateglacial Interstadial (Greenland Interstadial 1 (GI-1: Bølling and Allerød)). The application of Bayesian modelling to the radiocarbon dates from this, and other sites from the period in southwest England, suggests that re-colonization after the Last Glacial Maximum took place only after 14,700 cal BP, and is, therefore, more recent than that of the Paris Basin and the Belgian Ardennes. On their own, the radiocarbon determinations cannot tell us whether re-colonization was synchronous with, just prior to, or after, Lateglacial warming. Isotopic studies of humanly-modified mammalian tooth enamel may be one way forward.  相似文献   

2.
The high topographic complexity of the Alpine region is the origin of important climate differences that characterise the different areas of the Alps. These differences might have had a strong influence on vegetation and on migrations of human populations in the past. Based on an improved database containing about 3000 modern pollen samples, the standard “Modern Analogue Technique” has been applied to five pollen sequences from the subalpine belt of the South-western Italian Alps (Laghi dell’Orgials, 2240 m, Lago delle Fate, 2130 m, Torbiera del Biecai, 1920 m, Rifugio Mondovì, 1760 m, Pian Marchisio, 1624 m) to provide quantitative climate estimates for the Lateglacial and Holocene periods. Consistent climate trends are reconstructed for the different sequences. Sites recorded in detail the climate variations when they were located at the limit of two ecotones. Sites above the tree line recorded lower temperature values and less important variations. Climate was cold and dry during the Oldest and Younger Dryas and close to present-day values during the Bølling/Allerød interstadial. At the beginning of the Holocene, climate changed to warmer and moister conditions; a high number of climate fluctuations are recorded at several sites. A climate optimum is recorded in the Atlantic period, which caused a development of fir above its present-day altitudinal distribution. Climatic differences recorded at the various sites are discussed taking into account the limits of the method.  相似文献   

3.
A Lateglacial and early Holocene sequence of coleopteran assemblages is described from La Taphanel in the Massif Central, France. The site is a sediment-filled small lake at an altitude of almost 1000 m. The insect fauna provides evidence for a detailed palaeoecological reconstruction, and in particular enables a reconstruction of climatic changes at the close of the last glaciation. A sudden climatic warming occurs at about 13000 yr BP followed by a temperate episode equivalent in time to the Bølling period. There is clear evidence of a short cold period between the Bølling and Allerød that is approximately equivalent to the Older Dryas period. The Allerød phase is decidedly cooler than the Bølling, as is shown by the Coleoptera from several sites in northwest Europe. A clear Younger Dryas signal is provided by the Coleoptera, with climates similar in severity to those of the glacial period. The climatic improvement at the start of the Holocene is also sudden, so that by Preboreal times temperatures were equivalent to those of the present day.  相似文献   

4.
Numerous cirques of the Lofoten–Vesterålen archipelago in northern Norway have distinct moraine sequences that previously have been assigned to the Allerød-Younger Dryas ( 13,400 to 11,700 yr BP) interval, constraining the regional distribution of the equilibrium-line altitude (ELA) of cirque and valley glaciers. Here we present evidence from a once glacier-fed lake on southern Andøya that contests this view. Analyses of radiocarbon dated lacustrine sediments including rock magnetic parameters, grain size, organic matter, dry bulk density and visual interpretation suggest that no glacier was present in the low-lying cirque during the Younger Dryas-Allerød. The initiation of the glacial retreat commenced with the onset of the Bølling warming ( 14,700 yr BP) and was completed by the onset of Allerød Interstade ( 13,400 yr BP). The reconstructed glacier stages of the investigated cirque coincide with a cool and dry period from  17,500 to 14,700 yr BP and a somewhat larger Last Glacial Maximum (LGM) advance possibly occurring between  21,050 and 19,100 yr BP.  相似文献   

5.
High-temporal resolution analyses of pollen, chironomid, and lake-level records from Lake Lautrey provide multi-proxy, quantitative estimates of climatic change during the Late-Glacial period in eastern France. Past temperature and moisture parameters were estimated using modern analogues and ‘plant functional types’ transfer-function methods for three pollen records obtained from different localities within the paleolake basin. The comparison of these methods shows that they provide generally similar climate signals, with the exception of the Bölling. Comparison of pollen- and chironomid-based temperature of the warmest month reconstructions generally agree, except during the Bölling. Major abrupt changes associated with the Oldest Dryas/Bölling, Alleröd/Younger Dryas, and the Younger Dryas/Preboreal transitions were quantified as well as other minor fluctuations related to the cold events (e.g., Preboreal oscillation). The temperature of the warmest month increased by ∼5°C at the start of Bölling, and by 1.5°-3°C at the onset of the Holocene, while it fell by ca. 3° to 4°C at the beginning of Younger Dryas. The comparative analysis of the results based on the three Lautrey cores have highlighted significant differences in the climate reconstructions related to the location of each core, underlining the caution that is needed when studying single cores not taken from deepest part of lake basins.  相似文献   

6.
The Upper Doubs River Valley is a 910-km2watershed feeding into Lake Chaillexon. The lake was formed by a natural rockfall at the end of the Bølling Chronozone (around 14,250 cal yr B.P.) and since then has trapped material eroded from the watershed. The filling process and variations in sediment yield have been investigated by mechanical coring, seismic surveys, and electric soundings. The detrital sediment yield of the upstream watershed can be calculated by quantifying the sedimentary stocks for each climatic stage of the Late-Glacial period and Holocene Epoch and estimating the lake's entrapment capacity. This enables us to determine the intensity of the erosion processes in relation to climate and environmental factors. The Bølling–Allerød Interstade produced the greatest yields with mean values of 19,500 metric tons per calendar year (t/yr). The Younger Dryas Chronozone saw a sharp fall (8900 t/yr) that continued into the Preboreal (2100 t/yr). Clastic supply increased during the Boreal (4500 t/yr) before declining again in the Early Atlantic (2400 t/yr). Since then, yields have risen from 4500 t/yr in the Late Atlantic to 6800 t/yr in the Subboreal and 11,100 t/yr in the Subatlantic. Comparison of quantitative data with the qualitative analysis of the deposits and with the paleohydrologic curve of the watershed based on level fluctuations in lakes around Chaillexon shows that climate was the controlling factor of sediment yield until the Late Atlantic. From the Late Atlantic–Subboreal around 5400 cal yr B.P. (470014C yr B.P.) and especially from the end of the Subboreal Chronozone and during the Subatlantic Chronozone (2770 cal yr B.P./270014C yr B.P.–present) climatic constraints have been compounded by human activity related to forest clearing and land use.  相似文献   

7.
The timing and magnitude of sea-surface temperature (SST) changes in the tropical southern South China Sea (SCS) during the last 16,500 years have been reconstructed on a high-resolution, 14C-dated sediment core using three different foraminiferal transfer functions (SIMMAX28, RAM, FP-12E) and geochemical (Uk′37) SST estimates. In agreement with CLIMAP reconstructions, both the FP-12E and the Uk′37 SST estimates show an average late glacial–interglacial SST difference of 2.0°C, whereas the RAM and SIMMAX28 foraminiferal transfer functions show only a minor (0.6°C) or no consistent late glacial–interglacial SST change, respectively. Both the Uk′37 and the FP-12E SST estimates, as well as the planktonic foraminiferal δ18O values, indicate an abrupt warming (ca. 1°C in <200 yr) at the end of the last glaciation, synchronous (within dating uncertainties) with the Bølling transition as recorded in the Greenland Ice Sheet Project 2 (GISP2) ice core, whereas the RAM-derived deglacial SST increase appears to lag during this event by ca. 500 yr. The similarity in abruptness and timing of the warming associated with the Bølling transition in Greenland and the southern SCS suggest a true synchrony of the Northern Hemisphere warming at the end of the last glaciation. In contrast to the foraminiferal transfer function estimates that do not indicate any consistent cooling associated with the Younger Dryas (YD) climate event in the tropical SCS, the Uk′37 SST estimates show a cooling of ca. 0.2–0.6°C compared to the Bølling–Allerød period. These Uk′37 SST estimates from the southern SCS argue in favor of a Northern Hemisphere-wide, synchronous cooling during the YD period.  相似文献   

8.
Environmental changes are reconstructed from a Lateglacial and early Holocene sequence at Conty, northern France. The molluscan succession is put into a chronostratigraphic framework supported by numerous radiocarbon dates. Malacofaunas from the Bølling chronozone are reported for the first time in northern France and show progressive expansion of marshy communities within organic deposits. This biozone ended in a calcareous silt with the appearance of several species of arctic-alpine affinities. These sedimentological and malacological data point to colder climatic conditions after 12 220 ± 90 BP, but before 11 640 ± 80 BP, allowing allocation to the Older Dryas event. The first part of the Allerød appears to have been drier and relatively stable. After 11 400 BP, a decline in species richness and diversity in the malacofaunas suggests increasing dryness. During the Younger Dryas, two molluscan biozones are identified in a homogeneous calcareous silt, reflecting an early wet phase followed by a drier episode. At the onset of the Holocene malacofaunas show a higher diversity, suggesting climatic improvement.  相似文献   

9.
Twenty-six form-species of plant macrofossils occur in the Coal Measures exposed in the Howgill Head Quarry, Whitehaven, Cumbria, UK. They belong to the Neuropteris semireticulata Subzone in the lower part of the Paripteris linguaefolia Zone, indicating the uppermost Duckmantian. They confirm that the sandstones exposed in this part of the West Cumberland Coalfield are part of the Whitehaven Sandstone Formation, and not a stratigraphically lower unit as previously suggested. The Howgill head fossils represent the only well documented example of a N. semireticulata Subzone assemblage in Britain, although comparable assemblages are known from coeval strata in northern France, Belgium, northern Germany and Poland.  相似文献   

10.
Within a period of a few weeks toward the end of the Allerød Interstadial, the major Plinian eruption of the Laacher See volcano produced some 20 km3 of eruptiva, covering and preserving the late-glacial landscape in the German Central Rhineland over an area of more than 1000 km2. Correlation of terrestrial archives with the Greenland ice-core records and improved calibration of the radiocarbon timescale permit a precise, accurate age determination of the Laacher See event some 200 yr before the onset of the Younger Dryas cold episode. Carbonized trees and botanical macrofossils preserved by Laacher See Tephra permit detailed regional paleoenvironmental reconstruction and show that open woodland were typical for the cool and humid hemiboreal climatic conditions during the late Allerød. This woodland provided the habitat for a large variety of animal species, documented at both paleontological and Final Paleolithic archeological sites preserved below Laacher See deposits. Of special interest are numerous animal tracks intercalated in Middle Laacher See deposits at the south of the Neuwied Basin. This knowledge may help to evaluate possible supraregional impacts of this volcanic event on northern hemispheric environment and climate during the late Allerød.  相似文献   

11.
A 10 m sediment core from Academician Ridge in Lake Baikal was analyzed for its molecular composition using on-line TMAH (tetramethylammomium hydroxide) thermochemolysis. Major products are lignin phenols, n-C14 to C30 fatty acids (alkanoic acids), cutin acids, hydroxy acids and aliphatic dicarboxylic acids. Lignin phenols are abundant in warmer periods (the interglacial: marine isotope stage (MIS) 5e and MIS 1), but extremely low in the other (colder) periods. This result coincides well with pollen records reported for a core near the present site, where an expansion of coniferous forests in sub-stage 5e and MIS 1 was implied. Normal C24–C30 alkanoic acids, important components of plant wax esters, are abundant in 5e and MIS 1 and are present in significant amounts in the other (colder) periods, unlike the lignin phenols. A high abundance of n-C24 to C30 alkanoic acids relative to lignin phenols in the Bølling–Allerød warm period suggests an enhanced development of herbs.It is implied from comparison of the sedimentary lignin phenol record with fossil pollen records and lignin phenol analysis of modern pollen that the ratio of cinnamyl phenols to vanillyl phenols may serve as an indicator of pollen contribution to sedimentary organic matter.  相似文献   

12.
Measured 18O/16O ratios from the Greenland Ice Sheet Project 2 (GISP2) ice core extending back to 16,500 cal yr B.P. provide a continuous record of climate change since the last glaciation. High-resolution annual 18O/16O results were obtained for most of the current millennium (A.D. 818-1985) and record the Medieval Warm Period, the Little Ice Age, and a distinct 11-yr 18O/16O cycle. Volcanic aerosols depress central Greenland annual temperature (1.5°C maximally) and annual 18O/16O for about 4 yr after each major eruptive event. On a bidecadal to millennial time scale, the contribution of solar variability to Holocene Greenlandic temperature change is 0.4°C. The role of thermohaline circulation change on climate, problematic during the Holocene, is more distinct for the 16,500-10,000 cal yr B.P. interval. (Analogous to 14C age calibration terminology, we express time in calibrated (cal) yr B.P. (A.D. 1950 = 0 cal yr B.P.)). The Oldest Dryas/Bølling/Older Dryas/Allerød/Younger Dryas sequence appears in great detail. Bidecadal variance in 18O/16O, but not necessarily in temperature, is enhanced during the last phase of lateglacial time and the Younger Dryas interval, suggesting switches of air mass transport between jet stream branches. The branched system is nearly instantaneously replaced at the beginning of the Bølling and Holocene (at 14,670 and 11,650 cal yr B.P., respectively) by an atmospheric circulation system in which 18O/16O and annual accumulation initially track each other closely. Thermodynamic considerations of the accumulation rate-temperature relationship can be used to evaluate the 18 O/16O-temperature relationship. The GISP2 ice-layer-count years of major GISP2 climate transitions also support the use of coral 14C ages for age calibration.  相似文献   

13.
The Bølling–Allerød interstadial is the closest warm time period to the Holocene. The study of the climate variability during this most recent warm scenario provides a natural record of potential environmental changes related with global temperature variations. Little is known about this interstadial in the Southern Iberian Peninsula. Therefore, the exceptional climatic record of the Otiñar paleo-lake (ca. 14.5–14.0 cal ka BP), provides environmental information about the first part of this interstadial (Bølling) in this key region. Although the studied high-resolution isotopic record point to almost invariant hydrological conditions in the paleo-lake, with little change in the carbon budget and important limestone dissolution, the pollen record shows an increase in forest species that can be interpreted as a warming trend and an increase in humidity during the Bølling in the area. This record is one of the few continental archives that show this climatic trend in Southern Iberia, agreeing with many other regional records from the western Mediterranean. This does not agree with higher latitude records that show an opposite trend. This opposite pattern in precipitation between the western Mediterranean and more northern latitudes could be explained by a persistent and increasing negative NAO mode during the Bølling in this area.  相似文献   

14.
The freshwater sediments exposed on the cliffs at Nørre Lyngby northern Jutland has long been a classical locality for the study of Danish Quaternary geology, palaeontology and archaeology. These deposits date from the latter part of the Allerød period (i.e. G I-1). Samples for insect analysis have been taken from both the northern and southern exposures of these deposits. Ninety-five- taxa of Coleoptera (beetles) were obtained, of which 69 could be named to species. Of the latter, 23 are not found living in Denmark today. Most of these are still living in northern Fennoscandia but one species is now confined to Mongolia. These assemblages have enabled a detailed picture of the local environment to be reconstructed, showing that the basin-like profile of the deposits represents a section through a channel with slowly moving water. It has been possible to quantify the thermal climate of the time using the Mutual Climatic Range method indicating that mean July temperatures were about 10°C and mean January temperatures were about – 12°C. These figures are considered in the context of Lateglacial climatic reconstructions obtained from coleopteran assemblages elsewhere in northwestern Europe.  相似文献   

15.
We present a Lateglacial and early Holocene chironomid‐based July air temperature reconstruction from Foppe (1470 m a.s.l.) in the Swiss Southern Alps. Our analysis suggests that chironomid assemblages have responded to major and minor climatic fluctuations during the past 17 000 years, such as the Oldest Dryas, the Younger Dryas and the Bølling/Allerød events in the Lateglacial and the Preboreal Oscillation at the beginning of the Holocene. Quantitative July air temperature estimates were produced by applying a combined Norwegian and Swiss temperature inference model consisting of 274 lakes to the fossil chironomid assemblages. The Foppe record infers average July air temperatures of ca. 9.9 °C during the Oldest Dryas, 12.2 °C during most of the Bølling/Allerød and 11.1 °C for the Younger Dryas. Mean July air temperatures during the Preboreal were 14 °C. Major temperature changes were observed at the Oldest Dryas/Bølling (+2.7 °C), the Allerød/Younger Dryas (?2 °C) and the Younger Dryas/Holocene transitions (+3.9 °C). The temperature reconstruction also shows centennial‐scale coolings of ca. 0.8–1.4 °C, which may be synchronous with the Aegelsee (Greenland Interstadial 1d) and the Preboreal Oscillations. A comparison of our results with other palaeoclimate records suggests noticeable temperature gradients across the Alps during the Lateglacial and early Holocene. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

16.
High-time resolution 14C dating of Lake Baikal sediment cores indicates negative and positive anomalies of calculated linear sedimentation rate (LSR; 1.1 and 35.6 cm/ka, respectively) during the period of climate transition from the last glacial to Holocene. The timing of the Lake Baikal apparent LSR anomalies is consistent with that of the changes in the atmospheric radiocarbon concentration (Δ14C) during Younger Dryas rapid cooling event. 14C dating of lipids in the Lake Baikal surface sediments revealed that the sources of sedimentary lipids were different in each basin. In the Northern Basin of Lake Baikal, the 14C age of total lipids from the surface sediment (4.0 14C ka) was found to be older than that of TOC (1.6 14C ka). By contrast, the 14C age of total lipids in the Southern Basin was younger than that of the TOC by ca. 0.7–3.0 ka.In the Lake Hovsgol sediment cores, ages of the main lithologic boundaries during the last glacial–interglacial transition were estimated based on new 14C data sets. TOC concentration in the cores started to rapidly increase at 13.8 ± 0.3 14C ka at the base of the basinwide finely laminated layer deposited during Bølling/Allerød. The base of the layer diatomaceous mud corresponds to the end of Younger Dryas event (10.6 ± 0.1 14C ka).  相似文献   

17.
Biostratinomic analysis (processes acting between death and burial) of Lateglacial mammal bone assemblages from three caves in northern England demonstrates the value of re‐examining archived assemblages. With AMS radiocarbon dating of key specimens, these assemblages shed light on the ecology of a region at the northern limit of Lateglacial human activity in Britain. During the Lateglacial Interstadial bears, wolves and humans expanded into the region, bears by around 12 500 14C yr BP, and the earliest evidence for human presence is around 12 300 14C yr BP. At Victoria Cave, wolf activity included predation and scavenging of large ungulates and scavenging bear carcasses apparently resulting from hibernation deaths. The scavenging of bear carcasses is possibly confined to the first part of the Lateglacial Interstadial, whereas evidence for wolf scavenging large ungulates increases later in the Interstadial, after about 11 800 14C yr BP, perhaps reflecting changes in the productivity of the Lateglacial ecosystem, and in human subsistence patterns. The assemblage from Sewell's Cave is wolf den debris from the very end of the Lateglacial Interstadial around 10 800 14C yr BP, whilst that from Kinsey Cave is dominated by large‐bodied carnivores, and is argued to have a quite different taphonomic history. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

18.
Krüger, L. C., Paus, A., Svendsen, J. I. & Bjune, A. E. 2011: Lateglacial vegetation and palaeoenvironment in W Norway, with new pollen data from the Sunnmøre region. Boreas, 10.1111/j.1502‐3885.2011.00213.x. ISSN 0300‐9483. Two sediment sequences from Sunnmøre, northern W Norway, were pollen‐analytically studied to reconstruct the Lateglacial vegetation history and climate. The coastal Dimnamyra was deglaciated around 15.3 ka BP, whereas Løkjingsmyra, further inland, became ice‐free around 14 ka BP. The pioneer vegetation dominated by snow‐bed communities was gradually replaced by grassland and sparse heath vegetation. A pronounced peak in Poaceae around 12.9 ka BP may reflect warmer and/or drier conditions. The Younger Dryas (YD) cooling phase shows increasing snow‐bed vegetation and the local establishment of Artemisia norvegica. A subsequent vegetation closure from grassland to heath signals the Holocene warming. Birch forests were established 500–600 years after the YD–Holocene transition. This development follows the pattern of the Sunnmøre region, which is clearly different from the Empetrum dominance in the Lateglacial interstadial further south in W Norway. The Lateglacial oscillations GI‐1d (Older Dryas) and GI‐1b (Gerzensee) are hardly traceable in the north, in contrast to southern W Norway. The southern vegetation was probably closer to an ecotone and more susceptible to climate changes.  相似文献   

19.
We present here the results of the first‐ever Quaternary entomological research in China. The Halashazi Wetland, located in the southern Altai Mountain region in the northernmost part of Xinjiang Province, yielded Holocene insect fossils (mostly beetles) from two peat profiles. In total, 55 Coleoptera taxa were found, including 37 identified species. A new species, Helophorus sinoglacialis, was identified. The fauna is strongly northern Holarctic in character. The interval from 10 424 to 9705 cal a BP was probably a cold and wet period, and the study site was above the treeline. From 9665 to 9500 cal a BP it was probably warmer and drier, and treeline moved to higher elevations. Following a depositional hiatus, mid‐Holocene (5400–4400 cal a BP ) insect assemblages represent cold conditions with the site above the treeline. The exception was a brief warming around 5450 cal a BP , when bark beetle evidence suggests that the treeline moved to a higher elevation. Of the 37 identified beetle species from the Halashazi site, 34 (92%) have modern records in Siberia. The Altai Mountains probably served as a dispersal corridor between the Siberian arctic and alpine regions of northern China. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献   

20.
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 (14C). 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 14C ages, but both data sets contain clear outliers. When these are excluded, OSL ages appear to be systematically slightly younger than the 14C 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   

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