Loess-palaeosol Sequence Research Articles

Similarities among the Plio–Pleistocene terrestrial aeolian dust deposits in the World and in Hungary

The widely distributed Plio–Pleistocene aeolian dust deposits are one of the most important terrestrial archives of past climate and environmental changes. The alternation of loess and palaeosol layers is regarded as evidence of the cyclic nature of Pleistocene climate changes. The loess succession is underlain by aeolian red clay, which has been formed under warm–humid climates. According to the studies of red clay–loess–palaeosol sequences from China, Central Asia, Alaska, South America and Central Europe, the mineral dust deposition has shown similar patterns since the Pliocene. The typical loess of the last one million years reflects glacial–interglacial conditions, whereas the old loess–palaeosol sequences could be the product of shorter arid–humid climate cycles. The similarity of the sedimentary structures could be caused by the similar global climate conditions, controlled by orbital forcing. The investigated sections from Hungary (Central Europe) have been affected by local and regional geomorphological and climate factors. Even so, they can be correlated fairly well with the major global climate changes. The Hungarian aeolian dust deposits consist of three main groups of sedimentary formations: (1) Pliocene–Early Pleistocene aeolian red clays, (2) the oldest loess–palaeosol sequences, formed from the almost continuous Early Pleistocene dustfall, and (3) the typical, glacial–interglacial loess deposits of the last one million years, without remarkable dust deposition in the warmer periods.

Rhizoliths in loess – evidence for post-sedimentary incorporation of root-derived organic matter in terrestrial sediments as assessed from molecular proxies

Loess–palaeosol sequences are important terrestrial archives for studying Quaternary climate change. A major assumption for palaeoenvironmental reconstruction based on loess organic matter (OM) is that it represents the signal of syn-sedimentary incorporated plant biomass, i.e. predominantly grass vegetation. However, recent studies on rhizoliths (roots encrusted by secondary carbonate) formed in loess reveal the possibility of post-sedimentary penetration of loess–palaeosol sequences by deeply rooting plants. This likely led to incorporation of younger root-derived OM into surrounding loess, potentially causing an overprinting of the initial plant-derived signal of loess OM. To obtain information on the source vegetation of rhizoliths and surrounding loess OM we examined rhizoliths and loess from Nussloch, SW Germany, using alkane and fatty acid (FA) molecular proxies. Moreover, the lipid composition was compared in transects from rhizoliths via rhizosphere loess towards root-free loess for a preliminary assessment towards quantifying the post-sedimentary input of root-derived OM in loess. Loess OM gave a combined signal from shoot and root biomass from grass vegetation, confirming the assumption of deposition during glacial periods with scarce grass vegetation cover. In contrast, the lipid composition of rhizolith OM reflected roots of woody vegetation, indicating the post-sedimentary character of rhizoliths. Stronger degradation of OM, together with a large content of microorganism-derived FAs in the former rhizosphere indicated rhizodeposition associated with high microbial activity in loess adjacent to rhizoliths, at least up to a distance of 5 cm. Rhizosphere loess and reference loess at a distance of 50–70 cm showed a significantly different OM composition, thereby revealing the incorporation of considerable portions of root-derived OM into loess in the vicinity of roots. Further studies are necessary for an exact quantification of this potential overprint of the syn-sedimentary loess OM, which might cause uncertainty in palaeoenvironmental studies.

The Introduction to Geoconservation of loess-palaeosol sequences in the Vojvodina region: Significant geoheritage of Serbia

Loess-palaeosol sequences represent important palaeoclimatic and palaeoenvironmental archives on land. Furthermore, loess deposits in the Vojvodina region (North Serbia) can be regarded as one of the most important European terrestrial records of climatic and environmental changes during the last million years which makes them valuable scientific resource. Unfortunately, these sites are endangered by numerous, mostly human, factors and could be degraded permanently. Besides the scientific community, these geosites could be presented and interpreted (geotourism) to a much wider audience. This paper presents an introduction with general overview of the evaluation and conservation methods and sustainable promotion of loess sediments and their possible implications in the Vojvodina region. The proposed methods could also be further applied to other geologically equivalent locations worldwide.

Luminescence chronology of the loess record from the Tönchesberg section: A comparison of using quartz and feldspar as dosimeter to extend the age range beyond the Eemian

The loess–palaeosol sequences of the Tönchesberg section, located in the East Eifel Volcanic field (Germany) provide an excellent climate archive of the late Middle and the Upper Pleistocene in the Middle Rhine area. Loess deposits from the last Glacial (Weichselian) and the penultimate Glacial (Saalian) are up to 12 m and 15 m thick, respectively, and intercalated by palaeosols. Optically stimulated luminescence (OSL), thermally transferred optically stimulated luminescence (TT-OSL) and infrared stimulated luminescence (IRSL) measurements were carried out on 14 samples from the Tönchesberg section to determine the deposition age and to set up a more reliable chronological framework for the penultimate and last interglacial-glacial cycle. The fine-grained quartz OSL and polymineral IRSL ages are in good agreement with each other and also with the geologically estimated age, but the quartz TT-OSL ages are overestimated. The OSL and IRSL ages range from 16.8 ± 1.2 to 189 ± 16 ka indicating that the youngest loess and the weakly developed soils were deposited during marine isotope stage (MIS) 2 and 3 and that the two marker loess were most likely accumulated in the transition MIS 4/5. Loess and reworked loess postdating the Eemian soil yield ages of 110–115 ka indicating that these deposits very likely correlate to MIS 5d. Loess deposits taken below the Eemian soil are attributed to the transition MIS 6/7. A weakly developed soil above the Tönchesberg scoria yield an age of 189 ± 16 ka indicating an interstadial soil formation during MIS 7. This is in good agreement with preliminary 40Ar/ 39Ar ages for the Tönchesberg scoria and the intercalated tephra layers. Reliable age estimates up to ∼70 ka could be obtained using quartz OSL and up to ∼190 ka using the pulsed post-IR IR signal from feldspar. Hence the infrared stimulated luminescence (IRSL) is considered as the best approach to date the loess from the Middle Rhine area >70 ka.

Pliocene land snail record from western Chinese Loess Plateau and implications for impacts of the summer insolation gradient between middle and low latitudes on the East Asian summer monsoon

The East Asian monsoon probably existed as early as at the Palaeogene/Neogene boundary. However, its evolutionary process is still less well known owing mainly to the lack of long, continuous palaeoenvironmental records. The recently reported Miocene (22–6.2 Ma) and late Miocene–Pliocene (7.1–3.5 Ma) loess–palaeosol sequences from the western Chinese Loess Plateau (CLP) provide new insights into the evolution of the monsoon system. However, reports on the bioclimatic indicators from these deposits and the subsequent reconstruction of the palaeomonsoon are rare. Here we present a Pliocene terrestrial mollusk record from the western CLP and discuss the possible impact of isolation gradients on the East Asian summer monsoon. Our results show that most peak values of the dominant thermo-humidiphilous mollusk taxa, Metodontia and Punctum, a proxy of the East Asian summer monsoon, approximately correspond to maxima of mean summer insolation gradient between middle and low latitudes as well as some maximum values of the 35°N insolation, suggesting a possible causal link between the summer monsoon and the insolation parameters. The major frequencies from spectrum analysis of the sum of the two warmth- and moisture-loving taxa through the loess–palaeosol succession match those obtained from the mean summer insolation-gradient variations between middle and low latitudes over this geological period, providing further evidence for such a causal relationship. Mean summer insolation gradient between middle and low latitudes could influence atmospheric circulation (in the present condition the East Asian summer monsoon). Any elevated mean summer insolation gradients between middle and low latitudes would have intensified the East Asian summer monsoon and the flux of moisture and heat over the oceans to the interior region including the CLP, creating favorable conditions for the expansion of the mollusk fauna. As such, the mollusk record from the loess–palaeosol deposits in the western CLP provides evidence for insolation-gradient impacts on the development of the East Asian monsoon system in the Pliocene.

Mineralogical and geochemical characteristics of Quaternary sediments from the Island of Susak (Northern Adriatic, Croatia)

Middle and Upper Pleistocene loess–palaeosol sequences up to 90 m thick are exposed on the Island of Susak located in the Northern Adriatic Sea in Croatia. During glacial times the sea level was up to about 120 m lower and a significant part of the Adriatic became land. The source area of the primary aeolian sediments was in the vicinity of the island and is related to the southward extended River Po plain. The loess has a mainly clayey to sandy silt or sand grain-size and is intercalated by at least three tephras, numerous palaeosols and calcareous segregations. The heavy mineral association points to metamorphic and igneous rocks from Alpine regions as source material of the loess. Geochemical and mineralogical properties of loess and palaeosols differentiate one from another and reflect the intensity of weathering and pedogenesis. The oldest tephra contains vitroclasts and serrated clinopyroxene while the middle and the youngest tephra along with vitroclasts, contain idiomorphic augite as diagnostic volcanic features. Based on bulk rock and vitroclast chemistry, morphology of pyroxenes, and the age of the loess sandwiching the tephra, the potential source of this volcanic material could very likely be the Campanian or Aeolian volcanic province in southern Italy. Infrared stimulated luminescence dating-results show that the major part of the aeolian deposits including the tephra layers correlates to MIS 3–MIS 5.

Holocene vegetation characteristics of the southern Loess Plateau in the Weihe River valley in China

The Loess Plateau has a varied topography that creates a mosaic of hydrological and soil microclimatic conditions, and the study of its vegetation characteristics has been controversial. Two loess–palaeosol sequences of Xindian and Beizhuangcun were selected at different topographic units in the Weihe River valley to reconstruct the vegetation history for the Holocene period using high-resolution pollen analysis. Herb plants typically dominated the Xindian region during the Holocene, and sparse-wood grasslands became prominent around 8200–7700 years BP and 5500–4700 years BP. Forest-grassland covered the area between 7700 and 5500 years BP. Sparse-wood grassland dominated the Beizhuangcun region for most of the Holocene. This region contained mixed coniferous and broad-leaved forest dominated by Pinus between 6800 and 5300 years BP. Around 40% of the arboreal pollen indicates that the forest was relatively open with some grasses and shrubs. Therefore, the sparse-wood grasslands and grasslands were the dominant vegetation types in the Weihe River valley, which has the best hydrothermal conditions on the southern margin of the Loess Plateau. The forest in the Weihe valley only became extensively developed in the Holocene Optimum. Topographic units, terrain composition and loess thickness are the important factors controlling the development of this arboreal vegetation, along with temperature and precipitation.

Clay mineralogy and geochemistry and their palaeoclimatic interpretation of the Pleistocene deposits in the Xuancheng section, southern China

AbstractA red soil profile in Xuancheng, Anhui province, southern China, in the middle to lower reaches of the Yangtze River, was investigated using X‐ray diffraction, X‐ray fluorescence spectrometer, and scanning electron microscopy. The mobile components K2O and Na2O and trace elements Ba and Sr of the Xuancheng section exhibit a general trend of decrease downward along the red soil profile, together with an increase downward of chemical index of alteration (CIA) values, suggesting more intense depletion in the lower portion than in the upper portion. The major components SiO2, Al2O3 and Fe2O3, as well as SiO2/Al2O3, SiO2/Fe2O3 and Al2O3/Fe2O3 ratios, show notable fluctuations along the soil profile, indicating intense climatic oscillations in the area during the Pleistocene age. The clay mineral assemblage of the Xuancheng section can be generally subdivided into three groups, suggesting a general trend of three stages of climate changes. The lower portion of ∼10.4–6.3 m depth has a lower illite content and higher abundance of kaolinite and illite–smectite (I/S) clays, indicating that a warm and wet climate prevailed over the episode of ca. 600–350 ka BP. A decrease in abundance of kaolinite and I/S clays and increase in illite content at a depth of ∼6.3–2.2 m probably indicate a transition stage of climate change from warm/humid to cool/dry in the period ca. 350–80 ka BP. The higher illite content and lower abundance of kaolinite and I/S clays in the upper portion of ∼2.2–0 m depth suggest that a relatively cool and dry climate dominated since ca. 80 ka BP. Based on changes in clay mineralogy and chemical indices of the sediments, seven warm/cold fluctuations were determined in the area since the Middle Pleistocene. Climate changes documented in the Xuancheng section are in agreement with the δ18O records of sediments from the equatorial Pacific Core V28‐238 and the loess–palaeosol sequences in the Loess Plateau of northwestern China. Correlated to the episode of S4 and S5 soil units in the Loess Plateau, the period of ca. 600–350 ka BP in the Xuancheng area was dominated by the particularly strong East Asia summer monsoon, as indicated by its most abundant kaolinite and I/S clays. Fluctuations in clay mineralogy along the Xuancheng soil profile were mainly controlled by both the East Asia summer and winter monsoons in response to the global changes in the Middle–Late Pleistocene. Copyright © 2009 John Wiley & Sons, Ltd.

Luminescence chronology of the upper part of the Stari Slankamen loess sequence (Vojvodina, Serbia)

A thick Middle and Late Pleistocene loess-palaeosol sequence is exposed at the Stari Slankamen section in the Vojvodina region situated in the south-eastern part of the Pannonian basin, Serbia. The profile exposes an about 45 m thick series of loess intercalated by at least eight pedocomplexes. Ten samples were dated by luminescence methods using a modified single aliquot regenerative dose (SAR) protocol for polymineral fine grains and for quartz extracts from the upper part of the Stari Slankamen loess sequence. The infrared stimulated luminescence (IRSL) and post-IR optically stimulated luminescence (OSL) signals from all polymineral samples showed anomalous fading, suggesting that the post-IR OSL signal is still dominated by feldspar OSL. The ages ranging from 4.6 to 193 ka were obtained after fading correction. These ages indicate that the loess unit V-L1L1, the weakly developed soil complex V-L1S1 and the loess unit V-L1L2 were deposited during marine isotope stage (MIS) 2, 3, and 4, respectively, and also indicate that the loess unit V-L2 is of the penultimate glacial age.

Holocene environmental change inferred from the loess–palaeosol sequences adjacent to the floodplain of the Yellow River, China

Chinese loess deposits are generally considered to be the product of dust storms and dust falls from the central Asia arid zones that were transported across China by the northwesterly continental monsoon. In contrast, the Zhengzhou Loess found southeast of the Loess Plateau, adjacent to the floodplain of the Yellow River, records a different eolian regime and dust source. The Zhengzhou Loess was investigated by field observations, measurements of magnetic susceptibility, particle-size distribution, loss-on-ignition, CaCO 3 and chemical contents. Both field observations and the laboratory results indicate that, during the last glacial, the Zhengzhou Loess was supplied by two different eolian regimes and dust sources, one was from the fresh flood deposits of the Yellow River driven by the northeast winds from the low-lying floodplain, and the other was from the dust storms and dust falls that traveled across the Loess Plateau driven by the northwesterly continental monsoon from the central Asian arid lands. The early Holocene, 11,500–8500 a BP, was a transition during the change in eolian regime and dust source because of the weakened northwesterly monsoon along with the global climatic amelioration. Following the retreat of the northwesterly monsoon from the onset of the mid-Holocene Climatic Optimum at 8500 a BP, dust supply from the drifting sand zone on the Yellow River floodplain became dominant because of the intensified strength of the northeast winds from the Bohai Sea. From 3100 a BP onwards, climatic aridity and extensive human disturbance have resulted in intensive eolian processes causing the incursion of the drifting sand into the Zhengzhou Loess zone. These results show that loess accumulation is more complex than traditionally assumed. The origin of loess deposits elsewhere outside the Loess Plateau may be related to dust sources derived from alluvial sediments of major river systems.

Uranium-series dating of travertine from Süttő: Implications for reconstruction of environmental change in Hungary

Terrestrial carbonate formations, such as travertines, speleothems and lake sediments, are important archives of terrestrial climate forcing. At the Süttő section in Hungary, a complex succession of travertine is covered by a loess-palaeosol sequence; both are high resolution terrestrial archives of climate and environment change. Uranium-series ( 230Th/U) dating was carried out to set up a more reliable chronological frame for the travertine. As the growth of travertine is very complex, pore cements may cause serious problems for precise dating. The state of alteration of primary spar and micrite was characterised by microscopic, cathodoluminescence and microprobe analyses. The travertine from Süttő showed homogeneous phases of primary calcite, minor micropores and rare pore cements. The carbon isotopic composition indicates that the source of carbon was a mixture of atmospheric and soil derived CO 2. Calculated water temperatures based on oxygen isotope data range from 22 °C to 31 °C. An attempt to provide an independent relative dating approach by palaeomagnetic techniques failed. 230Th/U ages were determined applying an isochron approach using the leachate/leachate method. As the travertine deposits have a dense structure, the bulk sampling method was successfully applied in determining uranium-series ages with much higher precision than former studies with alpha spectrometry. Travertines from Süttő yielded Mid-Pleistocene ages ranging from the antepenultimate glacial to the penultimate interglacial (310–240 ka). These results are in agreement with those from optically stimulated luminescence (OSL) dating and amino acid racemisation (AAR) dating of the overlying sediment indicating at least an MIS 7 age for the travertine.

Optical dating of Romanian loess using fine-grained quartz

Romanian loess -palaeosol sequences are amongst the thickest and most complete available in Europe. These deposits represent an extended continental record of environmental and climatic change during at least five glacial/interglacial cycles. Their chronology, however, is mainly based on relative methods. In this paper, we investigate whether SAR–OSL dating of fine-grained quartz can be used to establish a reliable chronology for Romanian loess. The samples were collected from the loess–palaeosol sequence near Mircea Vodă (Dobrogea, SE Romania). The luminescence characteristics of the fine-grained quartz extracts are investigated to some extent, and indicate that the applied laboratory measurement procedure (SAR) is reliable. An internally consistent set of optical ages is obtained for the loess deposited up to ∼70 ka, and evidence is presented for a varying loess accumulation rate during the Last Glacial. Comparison with independent age control (pedostratigraphy and a newly-developed palaeomagnetic time–depth model) indicates that the optical dating procedure underestimates the true burial age from the penultimate glacial period onwards (i.e. for samples below the last interglacial S1 palaeosol). These results indicate that an apparently reliable laboratory measurement procedure not necessarily yields accurate sedimentation ages. We suggest that quartz-based SAR–OSL ages obtained using the high dose linear region of the growth curve are interpreted with caution.

Cyclic variability in microstructure and physio-mechanical properties of the Xiashu Loess–palaeosol sequence in Nanjing, China

For the Xiashu loess–palaeosol sequence in Nanjing, China, further to our work on the cyclic variability in its chemical composition and swelling-shrinkage properties [Xia, J., Huang, G.L., Liu, Z. T., Chen, X.M., 2007. Cyclic variability in chemical composition and swelling–shrinkage properties of the Xiashu loess stratum near Nanjing, China. Pedosphere 17 (5), 666–672.], this paper studies the cyclic variability in its microstructure and physico-mechanical properties and the corresponding influence on its engineering behaviour for geotechnical and geological practices. In addition, the cyclic variability in the soil's grain-size distribution and geochemical characteristics is compared with that of the loess–palaeosol sequences at two other sites in China, indicating a geographical pattern of cyclic variation of the sequences.

Climate change dynamics in Northern Eurasia over the last 200 ka: Evidence from mollusc-based ESR-chronostratigraphy and vegetation successions of the loess–palaeosol records

The time span of the past 200 ka has been marked by many large-scale global and regional climate changes, between warmer and cooler conditions. As is usually the case when studying the past, palaeoenvironmental data become scarcer with increasing age. Therefore, every detailed palaeoenvironmental record may be of special interest to Quaternary geologists in terms of palaeoenvironmental reconstructions, correlations and general stratigraphy of the Quaternary. In this paper we present a long palynological record of terrestrial flora and an ESR-dated marine record of global-scale climatic variation obtained from a loess–palaeosol sequence in the East European Plain and continental margin of Northern Eurasia for the time span starting from the penultimate glacial period correlating with Marine Isotope Stage (MIS) 6. These records show that in combination they have a potential of assigning warm/cold climate related deposits to the chronostratigraphically organised sequence of the late Pleistocene palaeoenvironmental events.

Spatial vegetation patterns based on palynological records in the loess area between the Dnieper and Odra Rivers during the last interglacial–glacial cycle

Pollen analysis was done on loess–palaeosol sequences situated to the north of the Carpathians and Sudetes, in the belt characterized by stronger influence of oceanic climate in the West and continental climate in the East. This fact conditioned the occurrence of loess as isolated patches in the West and thick continuous covers in the East, as well as the diversity of natural vegetation cover from deciduous forests and mixed coniferous forests, through forest-steppe to steppe zone. Three loess sites were examined in Poland (Biały Kościół, Tarnawce, Polanów Samborzecki), and three in Ukraine (Yezupil, Velyka Andrusivka, Stari Kodaky). Local pollen zones, distinguished in each site, were correlated in order to define the phases of vegetation development from the end of the penultimate glacial, through the Eemian Interglacial to the end of the Vistulian. The obtained picture of vegetation changes supplements the analysis results of organogenic deposits with the description of flora in cold periods when aeolian deposition occurred. In the area under study, the common features of vegetation development were conditioned by a general trend of climatic changes during the last interglacial–glacial cycle. They overlapped with the vegetation changes, expressed by the eastward rising proportion of open landscape elements, which resulted from the increasing continentality of climate. The proportion of trees and shrubs in plant communities during interstadials was also influenced by the proximity of refuges occurring in the Carpathians and Sudetes, and the situation of the examined profiles in river valleys, which were also natural refuges. Other differences in vegetation composition between individual sites resulted from their different meso- and micro-palaeomorphologic situation.

Dust supply from river floodplains: the case of the lower Huang He (Yellow River) recorded in a loess–palaeosol sequence from the Mangshan Plateau

AbstractThe Mangshan Plateau is located on the south bank of the Huang He (Yellow River) just west of the city of Zhengzhou, well outside the Loess Plateau in central China. Mixing models of the grain‐size data indicate that the loess deposits are mixtures of three loess components. Comparison of the mixing model with existing models established for a series of loess–palaeosol sequences from the Loess Plateau indicates that the Mangshan loess has been supplied from a proximal dust source, the Huang He floodplain, during major dust outbreaks. The high accumulation rates, the composition of the loess components, and especially the high proportions of a sandy loess component support this. Owing to the exceptionally high accumulation rates, the Mangshan grain size, magnetic susceptibility and carbonate records provide a high‐resolution archive of environmental and climate change. Copyright © 2008 John Wiley & Sons, Ltd.

Periglacial markers within the Late Pleistocene loess–palaeosol sequences in Poland and Western Ukraine

Stratigraphic loess–palaeosol sequences represent exceptional, climate-controlled, terrestrial records of interglacial–glacial cycles. One of the most spectacular features within the northern part of the European loess belt is the occurrence of well-preserved relicts of the periglacial structures. From a variety of periglacial structures, three types are especially useful to reconstruct the former periglacial environment: cryogenic wedges with primary mineral infilling, cryoturbation and gelifluction structures; and ice-wedge casts. These structures form well-distinguishable horizons within loess–palaeosol sequences and their stratigraphic positions are not random. Periglacial horizons recorded in the Late Pleistocene loess–palaeosol sequences in the study area were formed as a result of extreme climatic conditions and/or rapid environmental changes during cold events of the Last Glacial period. These horizons are noted in almost all investigated sections, and thus they can be used as stratigraphic markers. The number of periglacial horizons and their morphological features vary, depending on their geographical settings and local conditions. The periglacial record indicates the occurrence of four main cold stages during the Last Glacial period. Two earlier stages are recorded in the last interglacial–early glacial palaeosol complex. Their onset was probably rapid. These short cold periods can be correlated with MIS 5d and 5b. The next two periglacial stages most probably correspond with MIS 4 and 2. Only during the last two stages were ice-wedges formed in the northern zone of the investigated loess area. This record indicates the twofold expansion and disappearance of the permafrost during the Last Glacial period.

Oxygen and carbon stable isotope composition of authigenic carbonates in loess sequences from the Carpathian margin and Podolia, as a palaeoclimatic record

Samples were collected from the outcrops situated in the north and east of the Carpathian Margin, in the transition zone between the area of loess covers of Eastern and Western Europe. The chosen localities include two zones of temperate climate with slightly different prevailing wind directions. These loess–palaeosol sequences formed and develop in different time intervals: Early Quaternary Epoch (Podolia, Ukraine) and Late Quaternary Epoch (Carpathian Foothills, Poland). The isotopic analysis was carried out on many types of authigenic soil carbonates, including nodules, rhizoliths, rhizocretions, calcified root cells and bioclasts. The carbon isotopic compositions (δ 13C) of different types vary markedly. These differences seem to be more important than the variations within one type of carbonate at a particular section. The δ 13C values for authigenic carbonate cements (rhizoliths, rhizocretions and nodules) vary in a narrow range from about −11‰ to −8‰, suggesting that calcite cements were precipitated under roughly similar conditions, with a considerable supply of CO 2 derived from biomineralization of organic matter, predominantly from C 3 plants. The δ 18O record of the calcite cements within the upper Quaternary deposits exhibits relatively slight variability, suggesting that δ 18O values in soil water were homogeneous. The significant depletion of 13C as well as 18O in calcite from calcified root cells (−12‰ and −7‰, respectively), and to a lesser extent from calcitic globules with respect to calcite cements, points to different environments of formation. The morphology of calcite crystals replacing root cells, and their carbon and oxygen isotopic composition indicate that they may precipitate inside the root cells from fluids with organic compounds. In general, the temperature reconstructions yield an average MAT about 11 °C for the upper Quaternary sediments deposited during MIS 2. The estimated MAT for sediments of MIS 3–5 range from 12 to 14 °C. Mean annual temperatures estimated for the lower Quaternary of Podolia fall in the range from 9 to 11 °C with two single minimums (about 7 °C) probably corresponding to short-lived environmental changes. The MAT curve throughout the lower part of lower Quaternary is more variable and shows several local shifts (up to 3 °C).

Characterisation and palaeoclimate of a loess-like permafrost palaeosol sequence in NE Siberia

We studied a 15 m high loess-like permafrost palaeosol sequence (the Tumara Palaeosol Sequence, TPS), which developed on a Middle Pleistocene fluvio-glacial terrace of the Tumara River. Various analytical methods were applied to characterise the TPS. Similar to typical loess–palaeosol sequences (e.g. in China, Europe etc.), pedogenetic clay formation, mineral weathering and smaller grain sizes are interpreted as representing warmer and more favourable climatic conditions (interglacials or interstadials). Soil organic matter (SOM), however, reveals an unfamiliar, inverse pattern: High organic carbon contents (C org > 1%) characterise the dark grey glacial palaeosols, whereas lower contents (C org ≤ 0.5%) are found in the brown interglacial/-stadial palaeosols. This can be explained with permafrost and water logging having inhibited SOM mineralisation during cold periods. d/ l ratios of aspartic acid and lysine proved to be useful proxies for both SOM aging and palaeotemperature with amino acid racemization being enhanced in interglacial/-stadial palaeosols. On the basis of the geochemical and grain size results, further palaeoclimatically relevant proxies describing the palaoewind-strength (U-ratio), the mineral weathering (Chemical Index of Alteration, Rb/K) and the changing mineral input signal (Ba, Ti/Zr, Ti/Al) were applied to the TPS. In combination with numeric dating results (radiocarbon and luminescence) and in the context of other northern hemispheric records, the simple warm-cold stratigraphy as derived from the palaeoenvironment/-climate proxies suggests that the TPS represents the last ∼ 240,000 years.

A record of Holocene climate change in the Guanzhong Basin, China, based on optical dating of a loess-palaeosol sequence

Optical dating was used to obtain a chronology for a loess-palaeosol sequence in the Guanzhong Basin on the Loess Plateau in China. The sedimentary sequence recorded two dry episodes (3.7~2.4 ka and 1.2~0.8 ka ago) in the Holocene as shown by the presence of two layers of loess within the Holocene deposits. These two arid events are consistent with records of global climate change in the Holocene and also coincident with major historic events in China. This finding suggests that loess-paleosol sequences in China can record global climate changes and implies that rapid climate change affected the progress of human civilization. In addition, changes in the sedimentation rate through the section suggest that agricultural expansion may have accelerated the rate of dust accumulation.