Climate,fire and vegetation history from subtropical North Stradbroke Island (Minjerribah), eastern Australia,during the last three interglacials

Records of Australian palaeoclimate beyond the last glacial cycle are rare, limiting detailed analysis of long-term climate trends and associated ecosystem responses. This study analyses a discontinuous pollen and charcoal record from Fern Gully Lagoon, North Stradbroke Island (Minjerribah), subtropical Queensland, Australia, which covers much of the last ~210 ,000 years. Climate variation is inferred from changes in vegetation, while analysis of micro- and macrocharcoal is used to infer fire activity. Pollen assemblages consist of ~40% rainforest taxa during marine isotope stage (MIS) 7a–c and early MIS 5. These are inferred to result from high rainfall in the Australian subtropics, which was also evident in north-east and central Australia. Human impact from 21 ,000 years ago likely supressed post-MIS 2 rainforest expansion to some extent. However, the increased Holocene abundance of herbs and grasses and reduced representation of aquatic taxa suggest that the Holocene was relatively dry when compared with early MIS 5 and MIS 7a–c. Similar MIS 5 and early MIS 7a–c climates, in contrast to a notably drier Holocene, suggest that the progressive interglacial drying trend most strongly recorded in central Australia was not a major feature of subtropical eastern Australian climates.     

Expanded response-surfaces: a new method to reconstruct paleoclimates from fossil pollen assemblages that lack modern analogues

Pollen-based paleoclimatic interpretations of late-glacial to early Holocene climates (17–9 ka) in Midwestern North America are hampered by samples that lack modern analogues. Unresolved questions include the magnitude and direction of temperature seasonality (i.e. were these climates more or less seasonal than present) and the temporal changes in precipitation. Central to the no-analogue problem is the truncation of modern pollen-climate relationships for abundant late-glacial taxa such as Fraxinus. Here we present a new method called the expanded response-surface (ERS) method, developed to reconstruct climates from no-analogue pollen assemblages and applied to a high-resolution late-glacial pollen record from Crystal Lake, Illinois to test hypotheses about late-glacial climates. The key assumptions central to the ERS method are: (1) plant species and pollen abundances follow symmetrical unimodal distributions along climatic gradients, (2) taxa with truncated distributions in modern climate space occupy a subset of their fundamental niche, and (3) expansion of truncated distributions by mirroring around the distributional mode recovers the portion of the fundamental niche not realized in the modern climate space. With the ERS method, we expanded modern pollen-climate relationships by mirroring pollen abundances for each taxon around a mode defined with respect to four climate axes (mean winter temperature, mean summer temperature, mean winter precipitation, and mean summer precipitation). The ERS method reconstructed past temperatures and precipitation during the height of no-analogue conditions (14 160–12 370 cal yr BP) for 37% of the Crystal Lake samples where techniques that employed only modern observational data found matches for only 13% of the fossil samples. The total climate space of the expanded taxa set allowed analogue matches under more seasonal-than-present climates with higher-than-present precipitation. The ERS climate reconstructions for the height of no-analogue conditions indicated cooler-than-present summer and winter temperatures, similar-to-present seasonal range in temperatures, higher-than-present winter precipitation, and similar-to-present summer precipitation. These results thus suggest that high moisture availability helped drive the formation of the Midwestern no-analogue communities with high Fraxinus nigra abundances, but do not show higher-than-present temperature seasonality notwithstanding the higher-than-present insolation seasonality at this time. During the no-analogue late-glacial interval, Picea mariana, F. nigra, and Larix stands probably grew on low-lying, poorly drained soils in the Crystal Lake region; whereas Abies, Picea glauca, Quercus, and Ostrya/Carpinus grew on upland positions with better soil drainage.     

An early–middle Eocene Antarctic summer monsoon: Evidence of ‘fossil climates’

A warmer and mostly ice-free South polar region prevailed during the early–middle Eocene, indicative of a low latitudinal temperature gradient. Climatic models mostly fail to reconstruct such a low gradient, demonstrating our poor understanding of the mechanisms involved in heat transfer. Here we describe a new phenomenon that shaped the southern high latitude climate during the early–middle Eocene: the Antarctic summer monsoon. Our palaeoclimatic reconstruction is based on 25 morphotypes of fossil dicotyledonous leaves from the early–middle Eocene fossil leaf assemblage of Fossil Hill from King George Island, the Antarctic Peninsula. We use a novel CLAMP (Climate Leaf Analysis Multivariate Program) calibration which includes new climatic parameters that allow us to characterise better the seasonality in precipitation. Our reconstruction indicates a warm humid temperate climate with strong seasonality in temperature and precipitation. Seasonality in precipitation indicates a rainfall rate of 6.4 ± 1.30 mm/day during summer (summer daily rate of precipitation; SDR) and a summer precipitation representing more than 60.3 ± 8.28% of annual rainfall (ratio of summer precipitation; RSP), which fulfils the definition of a summer monsoon in the modern world. This implies a seasonal alternation of high- and low-pressure systems over Antarctica during the early–middle Eocene. Such a climate regime would have impacted upon global atmospheric circulation and heat transfer. This climatic regime presents a challenge for climatic models and their ability to reconstruct accurately palaeoclimates at high southern latitudes and thereby understand latitudinal heat transfer in a ‘greenhouse Earth’ regime.     

Palaeoecology of well-preserved coral communities in a siliciclastic environment from the Late Pleistocene (MIS 7), Kish Island, Persian Gulf (Iran): the development of low-relief reef frameworks (biostromes) in increasingly restricted environments

Major changes in community structure and depositional relief of high-latitude coral communities in the southern Persian Gulf between marine isotope stage (MIS) 7 and the present day suggest that the area has become increasingly restricted. Corals and bivalves from outcrops on Kish Island, Iran, were identified in order to interpret the Late Pleistocene palaeoenvironmental setting. U/Th disequilibrium dating was used to constrain the ages of the stratigraphic units. During MIS 7, two coral-bearing sequences were deposited on what is now Kish Island. The lower sequence is dated as MIS 7.5 and changes laterally from an assemblage dominated by Cyphastrea sp. and Platygyra daedalea in the west to one characterized by branching Montipora in the east. By contrast, the upper sequence, dated as MIS 7.1, transitions from an assemblage dominated by platy Montipora in the west to a diverse assemblage of Platygyra and other faviids in the east. The assemblages of both sequences are within a marl matrix and bounded by thin lithified mollusc-rich layers. Corals and bivalves indicate that the sequences were deposited on gentle slopes in sheltered environments less than 20 m deep. The MIS 7 deposits may be classified as coral carpets or biostromes that developed a low-relief framework. During MIS 5, coral communities were no longer framework building and are now limited to an Acropora-rich layer of coral rubble that covers large parts of the island, and two small incipient reefs with sparse faviids. Similarities between the MIS 5 and modern nearshore coral communities suggest that the environmental conditions during MIS 5 were comparable to those of today. The late Pleistocene coral carpets and non-framework coral communities of the southern Persian Gulf may serve as models for coral biostromes in the fossil record, which formed under restricted environmental conditions such as elevated terrigenous input, high turbidity, and strong seasonal changes in temperature and/or salinity.     

西南极乔治王岛新生代古生物特征及古环境探讨

西南极乔治王岛发育有一套高钾低铝的拉斑玄武岩,夹火山碎屑岩,属于岛弧火山岩系列。该岛还保存了南极最长的冰川沉积记录,是研究南极冰盖演化历史的重要证据。乔治王岛出露的新生代陆相地层中含有丰富的植物叶、孢粉、茎干、无脊椎动物化石及鸟类足印的痕迹化石等,从始新世到早中新世,化石逐渐减少,表明植物多样性呈明显下降趋势,幸存的稀疏植被被严格限制在冰川周缘的苔原物种上。冰海相地层与古生物研究表明,晚渐新世海相地层主要对应高能环境,早中新世海相地层对应低能环境。对乔治王岛新生代古生物特征及古环境的探讨,不仅理解了古生物及多样性的变化趋势,也为重建南极古环境提供证据。      

Land–sea correlation of Middle Pleistocene temperate sub-stages using high-precision uranium-series dating of tufa deposits from southern England

High-precision U-series dating allows a direct correlation to be made between terrestrial records of the penultimate interglacial (Marine Oxygen Isotope Stage 7 (MIS 7)) in Britain and sub-stage climate forcing in the marine oxygen isotope sequence. U-series ages of surficial tufa deposits are of sufficient precision to correlate discrete episodes of temperate conditions with individual warm sub-stages within MIS 7. Furthermore, detailed biostratigraphy allows periods of faunal turnover to be correlated with cold climates and lowered sea level. Ecological and environmental conditions in Britain during MIS 7 are therefore driven by the short-lived, sub-stage climate forcing that is observable in the marine isotope record. It is clear that interglacial climates are highly dynamic, producing multiple climatic optima and a diverse range of environments within single warm episodes. Consequently sub-stage records of climate forcing are crucial frameworks for reconstructing terrestrial records of environmental change.     

A terrestrial record of Last Interglacial climate preserved by voluminous debris avalanche inundation in Taranaki,New Zealand

At Airedale Reef, western North Island, New Zealand, a ca. 4 m thick volcanogenic debris avalanche deposit has facilitated the preservation of an enveloping sequence of peats with interbedded andesitic tephras spanning marine isotope (MIS) 5. The sequence closely overlies a wave‐cut terrace correlated to MIS 5e and, in turn, is overlain by andic beds with tephra interbeds including the Rotoehu and Kawakawa tephras deposited during early MIS 3 and mid‐MIS 2, respectively. Pollen analysis of the organic sequence shows a coherent pattern of fluctuating climate for the Last Interglacial–Last Glacial transition that corresponds with marine isotope stratigraphy and supports the contention that orbital variations were a primary factor in late Quaternary southern mid‐latitude climate change. A five‐stage subdivision of MIS 5 is clearly recognised, with marine isotope substage (MISS) 5b drier than MISS 5d, and the cooling transition from 5a to MIS 4 also may have been comparatively dry and characterised by natural fire, perhaps associated with volcanism. Several other examples of volcanic impact on vegetation and the landscape are evident. The Airedale Reef sequence exhibits strong similarities with fragmentary MIS 5 pollen records preserved elsewhere in New Zealand and enables the proxy record of southern mid‐latitude climatic variability during the Last Interglacial–Glacial cycle to be extended. Copyright © 2004 John Wiley & Sons, Ltd.     

Early Devensian sediments and palaeovenvironmental evidence from the excavations at the Royal Oak Portal Paddington,West London,UK

This paper discusses the results of the investigation of Pleistocene sediments at the Royal Oak Portal (ROP) site on the new Crossrail scheme near Paddington Station, London. The site was sampled and recorded in May 2011 by archaeologists from Oxford Archaeology commissioned by Crossrail Ltd. The investigation revealed a sedimentary sequence associated with cool climate waterlain deposition towards the edge of the River Westbourne floodplain. During excavation an assemblage of around 100 identifiable large mammal bones was recovered, dating to the Late Pleistocene. The major concentration of bones, from bison and reindeer, was located and excavated from a shallow sequence of sediments. Analysis of the bones indicates that they represent a natural death assemblage, scavenged and subsequently disarticulated, transported by water, exposed and further dispersed and broken by trampling. The site is of regional and national importance because the assemblage derives from a well-constrained geological context, with associated dating evidence suggesting accumulation during the later parts of Marine Isotope Stage (MIS) 5 and continuing within MIS 4. The site is also of significance because it is one of a growing number of recently discovered sites away from the main fluvial archive for the British Middle and Upper Pleistocene. These sites have the potential to add significantly to our understanding of parts of the Pleistocene record that remain difficult to document through the investigation of the more active systems associated with major rivers such as the Thames, Severn or Trent.     

A loess-paleosol record of climate and glacial history over the past two glacial-interglacial cycles (~ 150 ka), southern Jackson Hole, Wyoming

Loess accumulated on a Bull Lake outwash terrace of Marine Oxygen Isotope Stage 6 (MIS 6) age in southern Jackson Hole, Wyoming. The 9 m section displays eight intervals of loess deposition (Loess 1 to Loess 8, oldest), each followed by soil development. Our age-depth model is constrained by thermoluminescence, meteoric ¹⁰Be accumulation in soils, and cosmogenic ¹⁰Be surface exposure ages. We use particle size, geochemical, mineral-magnetic, and clay mineralogical data to interpret loess sources and pedogenesis. Deposition of MIS 6 loess was followed by a tripartite soil/thin loess complex (Soils 8, 7, and 6) apparently reflecting the large climatic oscillations of MIS 5. Soil 8 (MIS 5e) shows the strongest development. Loess 5 accumulated during a glacial interval (~ 76-69 ka; MIS 4) followed by soil development under conditions wetter and probably colder than present. Deposition of thick Loess 3 (~ 43-51 ka, MIS 3) was followed by soil development comparable with that observed in Soil 1. Loess 1 (MIS 2) accumulated during the Pinedale glaciation and was followed by development of Soil 1 under a semiarid climate. This record of alternating loess deposition and soil development is compatible with the history of Yellowstone vegetation and the glacial flour record from the Sierra Nevada.     

东亚地区MIS 5时期孢粉记录的植被与气候研究进展

末次间冰期(深海氧同位素5阶段,MIS 5,71~128 ka BP)离现代间冰期最近,对其认识有助于预测未来环境,而化石孢粉是恢复古植被与古气候的重要指标。通过对选择出的东亚地区孢粉记录的具有年代数据和孢粉图谱的古植被和气候研究的综合分析,初步认为:①MIS 5的植被格局可与现代间冰期即全新世的植被格局对比。②各区孢粉记录了MIS 5气候波动,部分地区可划分出5a,5b,5c,5d和5e,存在轨道尺度变化,千年尺度事件较少发现。③东亚季风是影响现代东亚季风区环境的主要因素,但日本可能还受到西风环流和洋流的影响;西风、印度季风和地形是影响青藏高原环境的主要因素。④东亚地区,特别是干旱半干旱区,分辨率较高的孢粉记录的环境变化仍需更深入的研究。     

Vegetation and Climate Inferred from Pollen Record in East Asian Region During MIS 5: A Review

The last interglacial, Marine Isotope Stage 5 (MIS 5, about 71~128 ka BP), is the closest to modern interglacial period, in which there are identifiable patterns that could give us clues into what will happen in the future. Pollen analysis, the study of fossil pollen and spores, is one of the key methods for the reconstruction of past vegetation and environment. Pollen data from 23 sites in eastern Asian region were reviewed to document regional patterns of vegetation and climate change during MIS 5 and to understand the large-scale controls on these changes. The regional patterns of vegetation during MIS 5 can be compared with the present-day vegetation. The climate, inferred from pollen record, was not stable during MIS 5. The substages (5a, 5b, 5c, 5d and 5e) of MIS 5 can be identi?ed by pollen assemblages in some areas, which describe the imprint of orbital-scale climate oscillations. East Asian monsoons have significantly contributed to the environment of modern eastern Asian monsoon region during MIS 5. However, the climate in Japan is also affected by the ocean currents and westerly circulation. The climate of the Tibetan Plateau is controlled by interactions of competing factors, including Indian monsoons, westerlies, and topography. In eastern Asian region, particularly in arid and semi-arid regions, the high-resolution pollen records need to be further studied for the better understanding of the climate change.     

Stratigraphy of Pleistocene glaciations in the St Elias Mountains,southwest Yukon,Canada

At least five Middle to Late Pleistocene advances of the northern Cordilleran Ice Sheet are preserved at Silver Creek, on the northeastern edge of the St Elias Mountains in southwest Yukon, Canada. Silver Creek is located 100 km up‐ice of the Marine Isotope Stage (MIS) 2 McConnell glacial limit of the St Elias lobe. This site contains ~3 km of nearly continuous lateral exposure of glacial and non‐glacial sediments, including multiple tills separated by thick gravel, loess and tilted lake beds. Infrared‐stimulated luminescence (IRSL) and AMS radiocarbon dating constrain the glacial deposits to MIS 2, 4, either MIS 6 or mid‐MIS 7, and two older Middle Pleistocene advances. This chronology and the tilt of the lake beds suggest Pleistocene uplift rates of up to 1.9 mm a^?1 along the Denali Fault since MIS 7. The non‐glacial sediment consists of sand, gravel, loess and organic beds from MIS 7, MIS 3 and the early Holocene. The MIS 3 deposits date to between 30–36 ¹⁴C ka BP, making Silver Creek one of the few well‐constrained MIS 3‐aged sites in Yukon. This confirms that ice receded close to modern limits in MIS 3. Pollen and macrofossil analyses show that a meadow‐tundra to steppe‐tundra mosaic with abundant herbs and forbs and few shrubs or trees, dominated the environment at this time. The stratigraphy at Silver Creek provides a palaeoclimatic record since at least MIS 8 and comprises the oldest direct record of Pleistocene glaciation in southwest Yukon.     

Vegetation history of the penultimate glacial period (Marine isotope stage 6) at Ioannina,north‐west Greece

The vegetational history of the penultimate glacial period, Marine Isotope Stage (MIS) 6 (c. 185–135 ka), has remained relatively unexplored. Here we present a new record from the Ioannina basin, north‐west Greece, which constitutes the highest‐resolution terrestrial pollen record for this interval produced to date. It shows that the vegetation history of MIS 6 in this region can be divided into two parts: an early period (185–155 ka) with pronounced oscillations in tree population extent, and a later period (155–135 ka) with much smaller tree populations and subdued oscillations. This pattern is analogous to the MIS 3/MIS 2 division during the last glacial in the same sequence, although the early part of MIS 6 had larger Pinus populations and fewer temperate trees relative to the equivalent interval in MIS 3. This implies cooler and wetter conditions, which is somewhat counterintuitive given the high summer insolation during MIS 6e, but is in line with other palaeoclimatic evidence from the Mediterranean. Comparison with North Atlantic records suggests that despite the absence of pronounced iceberg discharges during MIS 6, North Atlantic millennial‐scale variability had a significant downstream impact on tree populations in north‐west Greece. Copyright © 2011 John Wiley & Sons, Ltd.     

Environments of the climatic optimum of MIS 11 in Britain: evidence from the tufa sequence at Hitchin,southeast England

Marine Oxygen Isotope Stage 11 (MIS 11, Hoxnian Interglacial) is an important interval for understanding both climate change in an interglacial partially analogous to the Holocene and the response of geomorphic processes, biotic systems, and hominin populations to these changes. In Britain, many sites correlated to MIS 11 have not been studied since the mid-20th century and require reinvestigation, including the Hitchin tufa sequence, where a rich, non-marine molluscan assemblage was originally recovered. Re-excavation of the Hitchin tufa sequence for this study was focussed on combined sedimentological, micromorphological and geochemical analyses of the deposits. These indicate that tufa formation occurred within a perched springline system under temperate climatic conditions. Shifts between paludal and fluvial tufa facies within this system occur concomitantly with changes in carbonate geochemistry, representing increased humidity caused by a change in rainfall amount or seasonality. This research enables a correlation of the sequence to the climatic optimum of MIS 11c, the main warm phase of MIS 11, and permits further insights into temperature and hydrological changes in this interval by generating the first geochemical records of hydroclimatic evolution during the MIS 11 thermal maximum in Britain.     

Differentiation of MIS 9 and MIS 11 in the continental record: vegetational,faunal, aminostratigraphic and sea-level evidence from coastal sites in Essex,UK

Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2 °C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus, appears to have formed during the Ipswichian (MIS 5e). This evidence is compared with other important sites of late Middle Pleistocene age in Britain and elsewhere on the continent and the importance of a multidisciplinary approach is stressed.     

A 7500-year peat-based palaeoclimatic reconstruction and evidence for an 1100-year cyclicity in bog surface wetness from Temple Hill Moss,Pentland Hills,southeast Scotland

Analyses of plant macrofossils, peat humification and testate amoebae were used to reconstruct a proxy climate record spanning the last 7500 years from an ombrotrophic bog, Temple Hill Moss, in southeast Scotland. The plant macrofossil data were subjected to detrended correspondence analysis (DCA) which modelled effectively the significant wet shifts within the record. A mean water table depth transfer function was applied to the testate amoebae data to provide quantifiable changes. The three proxy records show coherent phase changes which are interpreted as variability in past effective precipitation. Two tephra horizons (Glen Garry and Lairg A) were used in conjunction with radiocarbon dates to construct an age/depth model, producing a robust geochronology from which a time series was calculated. The palaeoclimatic reconstruction identified major wet shifts throughout the Holocene, with specific events occurring around cal. 6650, 5850, 5300, 4500, 3850, 3400, 2800–2450, 1450–1350 and 250–150 BP. Spectral analysis of the plant macrofossil DCA and colorimetric humification data produced a millennial scale periodicity of 1100 years. The same periodicity has also been found in a palaeoclimatic reconstruction from a site in Cumbria (Walton Moss), and may be linked with millennial scale periodicities found in oceanic palaeoclimatic records.     

Late Pleistocene Climatic Variations at Achenheim, France, Based on a Magnetic Susceptibility and TL Chronology of Loess

New field investigations of the Achenheim sequence (Alsace, France) allow for the characterization of variations in the low-field magnetic susceptibility over most of the last climatic cycle, i.e., the past 130,000 yr. New stratigraphic data and thermoluminescence measurements permit reassessment of the previous chronological interpretation of the Upper Pleistocene at Achenheim. A high-resolution analysis of magnetic susceptibility discloses the occurrence of a fine-grained “marker” horizon which was also found recently in another section. This horizon is interpreted as a small-scale dust layer deposited prior to the main interval of loess deposition. The horizon, deposited at the marine isotope stage (MIS) 5/4 boundary, has been found in other loess sequences and is especially prevalent in central Europe. It is characterized by low susceptibility values and a grayish color. New thermoluminescence dates indicate that the loess deposition took place after the MIS 5/4 boundary, i.e., after 70,000 yr. These results are consistent with the Greenland GRIP ice-core dust record which also demonstrates a dusty atmosphere after 72,000 yr ago. On a more regional scale, the Achenheim loess sequence demonstrates a reliable correlation between the western side of the Eurasian loess belt and the dust record of the Greenland ice cores.     

Climatic variations in MIS 11 recorded by stable isotopes and trace elements in a French tufa (La Celle,Seine Valley)

Marine Isotope Stage (MIS) 11 palaeoclimate has so far been documented in marine and ice sheet isotopic records. However, excepting some lacustrine pollen records, very little is known about palaeoclimatic conditions in continental areas. This study uses geochemical records in calcareous tufa deposits from rivers as a basis for reconstructing temperate palaeoclimatic conditions. Tufa deposits are now proven to record high‐quality palaeoclimatic information in recent to Holocene deposits. Work on older interglacial tufas is just starting and in this paper we present the first comprehensive results from a MIS 11 tufa. The tufa comes from the Seine Valley (La Celle, northern France). Geochemical data in the tufa calcite are interpreted to record primarily air temperature (δ¹⁸O) and humidity (δ¹³C and Mg/Ca and Sr/Ca). The combined data identify a warm and wet climatic optimum followed by two temperature decreases associated with oscillations in humidity. These marked climatic variations recorded through the La Celle profile are strongly coherent with the palaeoenvironmental reconstructions from malacological data. The abrupt climatic and environmental events recorded could be related to short‐term degradation of vegetation cover in Europe, which is itself controlled by global palaeoclimatic events. Copyright © 2012 John Wiley & Sons, Ltd.     

Highstands in the interior of the Qinghai–Tibetan Plateau since the last interglacial: evidence from grain‐size analysis of lacustrine core sediments in Zabuye Salt Lake

Highstands in the Marine Isotope Stage (MIS) 3 based on ¹⁴C dating in the Qinghai–Tibetan Plateau (QTP) are widely documented. Recent records from shoreline sediments dated using U‐series and/or optically stimulated luminescence (OSL), however, reveal that the highstands originally dated in MIS 3 should now be considered to fall in MIS 5. This paper provides new evidence from the interior of the QTP, based on the grain‐size from a continuous lake core in the Zabuye Salt Lake, to verify the MIS 5 highstand in the QTP. Grain‐size analysis of the core sediments also distinguishes two other highstands in MIS 3 and MIS 2, respectively. The MIS 5 highstand is considered as the maximum lake level since the Last Interglacial, as cored sediments contain very low values of Median Diameter (Md) during MIS 5. Compared with the discontinuous records from lake shorelines sediments, the grain‐size records from the continuous lake centre core sediments provide a more complete dataset to infer lake level variations, and make it possible to make wider palaeoclimatic and palaeoenvironmental interpretation. In the interior of the QTP, highstands might have continued into cold climate periods due to the reduced evaporation rates in the latter. The influence of the moisture‐bearing southerly‐shifted Westerly wind pathway may also have contributed to the highstands in the glacial period. Copyright © 2015 John Wiley & Sons, Ltd.     

Middle to Late Pleistocene lake‐level fluctuations of Lake El'gygytgyn,far‐east Russian Arctic

Lake El'gygytgyn, located in central Chukotka, Russian Arctic, was the subject of an international drilling project that resulted in the recovery of the longest continuous palaeoclimatic and palaeoenvironmental record for the terrestrial Arctic covering the last 3.6 million years. Here, we present the reconstruction of the lake‐level fluctuations of Lake El'gygytgyn since Marine Isotope Stage (MIS) 7 based on lithological and palynological as well as chronological studies of shallow‐water sediment cores and subaerial lake terraces. Reconstructed lake levels show an abrupt rise during glacial–interglacial terminations (MIS 6/5 and MIS 2/1) and during the MIS 4/3 stadial–interstadial transition. The most prominent lowstands occurred during glacial periods associated with a permanent lake‐ice cover (namely MIS 6, MIS 4 and MIS 2). Major triggering mechanisms of the lake‐level fluctuations at Lake El'gygytgyn are predominantly changes in air temperature and precipitation. Regional summer temperatures control the volume of meltwater supply as well as the duration of the lake‐ice cover (permanent or seasonal). The duration of the lake‐ice cover, in turn, enables or hampers near‐shore sediment transport, thus leading to long‐term lake‐level oscillations on glacial–interglacial time scales by blocking or opening the lake outflow, respectively. During periods of seasonal ice cover the lake level was additionally influenced by changes in precipitation. The discovered mechanism of climatologically driven level fluctuations of Lake El'gygytgyn are probably valid for large hydrologically open lakes in the Arctic in general, thus helping to understand arctic palaeohydrology and providing missing information for climate modelling.