Eurasian Loess Research Articles

Magnetic Proxy of Eurasian Loess Revealing Enhanced Physical Erosion Since the Mid‐Pleistocene Transition

AbstractEolian loess deposits contain valuable information about past climate changes and erosion history in dust source regions. In contrast to the extensive investigations of paleoclimatic implications of Eurasian loess, continental erosion information in the loess deposits has received less attention, particularly on the global or hemispheric scales. The present study combines citrate‐bicarbonate‐dithionite (CBD) magnetic mineral extraction procedures and linear regression of magnetic parameters to analyze Eurasian loess. We find that lithogenic susceptibility of Quaternary loess deposits in Central Asia, Europe and the Chinese Loess Plateau shows synchronous long‐term increases since ∼0.6–0.5 Ma, suggesting intensive glacial erosion and/or river incision to have occurred in the surrounding mountains of dust source regions after the mid‐Pleistocene climate Transition. The dramatic increase in lithogenic susceptibility of Eurasian loess provides new insights into the close relationships between global climate changes and dust source erosion since the late Cenozoic.

First high-resolution luminescence dating of loess in Western Siberia

The south of Western Siberia is an important part of the Eurasian loess belt, containing an extensive record of Quaternary landscape and climate evolution in up to 100 m thick loess deposits with as many as 10 pedocomplexes. However, this important Quaternary archive lacks a reliable absolute chronology, and this has prevented the linking of the widely accepted regional chronostratigraphic correlations with those of other parts of the Eurasian loess belt. Here we present the first results of detailed luminescence dating of the Late Pleistocene loess-palaeosol sequence at the Western Siberian stratotype section of Lozhok. According to the classical regional chronostratigraphic scheme, this sequence records the main stages of the environmental evolution of the region, including three palaeosols correlated with the warming stages of MIS 5e, MIS 5c and MIS 3. Our absolute chronology is based on 38 new luminescence ages (OSL, IR 50 , pIRIR 290 ). Good agreement between the OSL and pIRIR 290 ages suggests sufficient bleaching before deposition. The resulting chronology reveals that, rather than being only Upper Pleistocene in age, the loess-palaeosol sequence at Lozhok actually formed in the Middle and Upper Pleistocene. The ages of individual horizons do not correspond to the previously accepted stratigraphic units and morphological features of pedocomplexes. Our Bayesian chronological model reveals remarkable variation in dust accumulation and preservation at the site. The new results unambiguously identify the presence of an erosional boundary with a hiatus lasting ∼90 ka. The upper pedocomplex, immediately below this discontinuity, formed in sediment deposited between 131 ± 9 ka and 122 ± 11 ka and clearly corresponds to MIS 5. The lower pedocomplex is found in sediment deposited between 240 ± 12 and 199 ± 9 ka, and correlates closely with MIS 7. These new findings demonstrate the urgent need for a wider programme to date the main stratotypes of loess-palaeosol sections in Western Siberia. Only then can the global implications of the regional climate record in this important continental-scale archive be correctly interpreted.

Intensified Northern Hemisphere Glaciation Facilitates Continuous Accumulation of Late Pliocene Loess on the Western Margin of the Pamir

AbstractThick eolian loess sequences in arid Central Asia (CA) contain a wealth of information on the intensity variations of midlatitude westerlies and the aridification history of the nearby deserts. In this study, detailed lithologic and magnetostratigraphic investigations suggest that loess deposits on the western margin of the Pamir Plateau began to accumulate at around 2.7 Ma, representing the most complete and oldest loess‐paleosol sequence in western CA. The widely distributed continuous loess deposition in the region suggests a rapid desiccation of CA during the late Pliocene. A synthesis of the initial timing and spatial distribution of late Cenozoic eolian deposits on the Eurasian continent further demonstrates that the dramatic increase in global ice volume exerted a dominant role in the expansion of eolian loess deposits in CA, China, and Europe, and middle Pleistocene expansion is a crucial precondition for the establishment of modern distribution patterns of the Eurasian loess belt.

Decoupling between circulation pattern and dust path since the last glacial in the Songnen Plain, NE China: Insights from quantitative provenance reconstruction of the Harbin dust sediments

• Potential sources of the Harbin loess during the last glacial and modern dust were quantitatively tracked. • The sandy lands of NE China figure importantly in acting as a dust transfer station. • Decoupling between circulation patterns and dust export since the last glacial in the Songnen Plain were revealed. • The SW-direction sandy land of the Songnen Plain should be treated as a priority for environmental management. Knowledge of the provenance of dust deposits in the easternmost margin of the Eurasian loess belt is essential for understanding the connection between circulation patterns and dust source-to-sink route in the Songnen Plain, NE China. Here, a total of 131 samples, from the loess-paleosol sequence since the last glacial (20) and the modern dust-storm sediments (7) in Harbin area together with potential dust source areas (104), were collected for elemental geochemical analysis to quantify the source apportionment and compare the performance of the Frequentist and Bayesian models. Fourteen geochemical properties (V, Zn, Ga, Sr, Mo, Ba, Pb, Y/Ta, MREE N /MREE N *, Th/Sc, Th/U, La/Sc, Zr/Hf and Co/Th) were selected as the optimum composite fingerprint after a range test, non-parametric Kruskal-Wallis H-test and stepwise discriminant function analysis. Based on both the models, the source contributions to the loess sequence and dust-storm deposits were in the following order: southwestern Songnen Sandy Land (57–95%, 49–97%), Horqin Sandy Land and Onqin Daga Sandy Land (2–43%, 0–31%), northwestern Songnen Sandy Land (0–21%, 0–20%) and Hulun Buir Sandy Land (0%, 0–8%). Following the goodness-of-fit and virtual mixtures, combined with root mean square error and mean absolute error, we argue that the Frequentist model is slightly more accurate than the Bayesian model in quantifying dust sources. The sandy lands figure importantly in acting as a dust transfer station. The comparison between the loess sequence and modern dust-storm source reconstructions reveals a decoupling between circulation pattern (northwesterly wind domination in the glacial) and dust path (dominantly southwestern direction), and small areas, high vegetation coverage and topographical barrier are considered to be the main reasons for the significantly limited dust emission in the NW-direction source area. Finally, the study highlights that improving land management practices in the SW-direction but not NW-direction sandy land may help ameliorate the effects of the Harbin dust pollution.

The Jaramillo subchron in Chinese loess-paleosol sequences

The Chinese loess is one of the most important terrestrial records of the Quaternary climate changes. However, the positional discrepancy of geomagnetic polarity boundaries, such as Matuyama-Brunhes boundary (MBB), between Chinese loess and marine sediments remains controversial, hampering to establish an accurate chronological framework for the Chinese loess and its correlation with marine oxygen isotope records. The Jaramillo subchron within the Matuyama Chron is an important paleomagnetic age constraint for Quaternary magnetostratigraphic dating. Here, we present a high-resolution magnetostratigraphic, rock magnetism, and relative paleointensity (RPI) study of the stratigraphic interval between paleosols S9 and S18 in two parallel loess sections from the southeastern Chinese Loess Plateau, with an aim to explore the positions of the upper and lower boundaries of the Jaramillo in the Chinese loess. The results show that significant uncertainty and variability (more than one loess-paleosol cycle) for the positions of the measured upper and lower Jaramillo boundaries among different loess sections cannot be explained by the discrepancy of loess stratigraphy, sedimentation rate or regional climate. The measured upper and lower Jaramillo boundaries in the loess can be above or below their true positions, which cannot be explained by the lock-in effect. As the measured boundaries in the loess are mostly within the intervals of low-intensity geomagnetic field, we propose that the loess deposits may have acquired unstable primary remanent magnetization during the intervals of geomagnetic reversals or excursions with low-intensity geomagnetic field, and these deposits could be easily overprinted (remagnetizated) by the ensuing high-intensity field. This hypothesis is able to explain the phenomena that the measured MBB in the Eurasian loess is downward shifted by tens centimeters to several meters relative to the true boundary, and it can also explain the anomalistic polarity zones recorded in some loess sections.

Loess accumulation in Harbin with implications for late Quaternary aridification in the Songnen Plain, Northeast China

The Harbin loess in Northeast China, located in the easternmost part of the Eurasian loess belt, has great potential to reconstruct the aridity history of the Songnen Plain and to reveal its dynamic process. However, the relationship between coupled tectonic-climate-drainage evolution and the aridification in the Songnen Plain is currently poorly understood. In this study, we present a high-resolution magnetic susceptibility, grain-size, trace element, SrNd isotope, total organic carbon (TOC), and organic carbon isotope composition (δ13C) record retrieved from the Harbin loess-paleosol sequences to reveal the aridification history in the Songnen Plain. These results reveal a long-term drying trend in the Songnen Plain since 0.46 Ma, indicating the birth of the Songnen Sandy Land at that time. Superimposed on the major aridification trend, two significant abrupt drying events were found at ~300 ka and ~ 380 ka. However, the climate in the Songnen Plain became wetter and warmer under the background of the long-term drought since 180 ka. The global ice/temperature changes, regional tectonics (i.e., uplift of the Songliao divide) and drainage change (i.e., river pattern shift in the Songnen Plain from endorheic to exorheic drainage, and termination of the Songnen paleolake) were collectively responsible for the aridification in the Songnen Plain. This study has further improved knowledge of the process of the aridification in Northeast China, which is of great significance to control land desertification and ecological imbalance.

Late Pleistocene loess-paleosol sequence at the Belovo section, south of Western Siberia, Russia: Preliminary results

Eurasian loess-paleosol sequences provide continuous records of global change in mid-latitude Northern Eurasia. The loess-paleosol sequence of West Siberia located in the central part of the mid-latitude Eurasian loess belt extending from West Europe to Yakutia is an outstanding paleoclimate archive in Northern Asia. The stratigraphy has been best documented on the left bank of the Ob River, in the so-called Ob Loess Plateau. This study focuses on the stratigraphy of the most complete Middle-Late Pleistocene loess-paleosol sequence at the Belovo section. The suggested high-resolution model of the Belovo Late Pleistocene stratigraphy is based on magnetic and sedimentological proxies and is correlated with other Eurasian loess records and with the global marine δ18O stratigraphy. The enviromagnetic signal at Belovo Loess-paleosol sequences shows a transitional pattern comparable with both typical Eurasian loess magnetic records. Detailed paleopedological interpretations of the magnetic and sedimentological data from the Belovo section have important implications for appropriate linking different Late Pleistocene climates and environments of other the well-known Eurasian loess provinces.

Late Quaternary loess accumulation at the Rudak section in Uzbekistan, central Asia: Chronology and palaeoclimate implications

Many studies have been carried out to understand the nature of the loess formation and its palaeoenvironmental significance in different parts of Eurasia, especially Europe and China. However, in spite of its key position, our knowledge about the loess deposits at the core of the Eurasian loess belt in central Asia is still limited, particularly in terms of absolute dating. This study presents a new luminescence chronology of a loess-palaeosol sequence (Rudak section) in the vicinity of the Gissar Range, Uzbekistan, using both quartz optically stimulated luminescence dating and polymineral post-IR IRSL dating techniques. The dating results suggested a loess accumulation history over the past 180 kyr at Rudak section, characterized by a great depositional hiatus during the entire last glacial period, likely owing to too harsh climate conditions for favouring dust accretion and loess preservation in the piedmont areas of central Asia. Hence, contrasting with the traditional concept of continuous (quasi-continuous) deposition of loess, the direct stratigraphical correlation might be problematic for climatic interpretation of loess-palaeosol sequence in this area. Furthermore, magnetic susceptibility of Rudak section demonstrated the moisture peaks in phase with ice-volume minima over the glacial and interglacial cycles, indicating moisture variation in the Westerlies-dominated central Asia was broadly consistent with that in monsoonal Asia on orbital timescales, but nearly contrasting picture with each other on the suborbital timescales, at least through the Holocene epoch. The Westerlies-dominated central Asia has generally experienced a dry first half and a wet second half of the Holocene, which has likely been driven by solar insolation gradients between mid-latitudes and high-latitudes as well as the melt-water flux.

The loess deposits in Northeast China: The linkage of loess accumulation and geomorphic-climatic features at the easternmost edge of the Eurasian loess belt

The study of the loess deposits is the key for understanding the linkage between dust accumulation, tectonics, landform and climate change. However, little is known about loess accumulation in NE China. Loess deposits at the easternmost edge of the Eurasian loess belt are represented by those in the Xinwopu (XWP), Kulungou (KLG) and Huangshan (HS) sections of NE China. These loess deposits are much coarser than the loess in the southern Chinese Loess Plateau, with a sand (>63 μm) content of 6–39% in the loess deposits, and show distinct grain-size distribution with a trimodal or bimodal pattern. There are markedly different geochemical compositions between the studied loess deposits: the XWP loess is characterized by the highest content of CaO (9.81%) and MgO (2.06%), and the highest 87Sr/86Sr ratios (0.713119); the KLG loess is highlighted by the lowest content of the element Sc (7.68 ppm), V (54.1 ppm), Cr (36.4 ppm), Co (6.32 ppm), Ni (15.6 ppm), Cu (16 ppm), Zn (38.8 ppm), Ga(12.8 ppm) and ∑REE (113 ppm); the HS loess is of the lowest content of CaO (1.15%), and the highest content of the element Y (84.8 ppm), Zr (242 ppm), Nb (18.1 ppm), Hf (7.2 ppm), Ta (1.45 ppm), Th (12.7 ppm) and ∑REE (185 ppm); the XWP and KLG loess samples have similar εNd(0) values (−7.9), moderately higher than those (−8.9) of the HS loess. The comparison between various geochemical indicators (e.g., low values of SiO2/Al2O3, Zr/Sc and CIA, and high ICV values) shows that these loess deposits have undergone a different and low degree of chemical weathering with a low maturity and recycling history. Integrated methods including grain size, elemental and isotopic composition, multidimensional scaling as well as physical geographical elements (including the geomorphic and climatic features), clearly revealed the Onqin Daga Sandy Land, the Horqin Sandy Land and the Songnen Sandy Land as main dust provenances of the XWP, KLG and HS loess, respectively.

Late Pleistocene paleosols in the extra-glacial regions of Northwestern Eurasia: Pedogenesis, post-pedogenic transformation, paleoenvironmental inferences

Recent revision of the eastern boundary of the last glaciation of Eurasia opened new perspectives in the search of the paleopedological records in the north of Eastern Europe and Western Siberia. We studied paleosol-sedimentary sequences in the Upper Volga and Middle Ob basins as a regional paleoecological record for the Late Pleistocene thermochrons.Two key sections Cheremoshnik and Belaya Gora containing MIS3 and MIS5 paleosol units and additional section Koskovo 2 with polycyclic MIS3 paleosol were investigated. Their timescale are based on C14 and U/Th datings as well as on stratigraphic and paleobotanical correlations. Macro-, meso- and micromorphological observations together with fossil insects and plant macrofossil were used as paleoenvironment proxy. MIS3 paleosols show abundant redoximorphic and cryogenic features that allow interpreting them as gleyic Cryosols. Sub-fossil insects and plant macrofossil reflect the cold climate conditions. Three incipient Ah horizons in Koskovo 2 pedocomplex point to multiple phases of pedogenesis, correlative to the MIS3 paleosol levels in different sections of the Eurasian loess belt and to the major interstadials of the Middle Pleniglacial of the NW Europe MIS5 paleosols are also characterized by gleyzation and peat accumulation, in this case we suppose geomorphological control on hydromorphic pedogenesis; however paleosol in Belaya Gora has clear signs of polygenesis including the phase of clay illuviation. Insect and plant remains from the lower paleosol level of the Belaya Gora section show the transition from cold (terminal phase of MIS6) to warm first, and then to a moderately cold climate (within MIS5). The obtained results contribute to understanding of soil and landscape zonality in the largest plains of Eurasia mostly during the warm phases of Late Pleistocene.

Quartz OSL dating of late quaternary Chinese and Serbian loess: A cross Eurasian comparison of dust mass accumulation rates

Reconstructing dust Mass Accumulation Rate (MAR) from loess deposits is critical to understanding past atmospheric mineral dust activity and requires accurate independent age models from loess deposits across Europe and Asia. Previous correlations of loess in Europe and China have tended to focus on multi-millennial timescales, with no detailed examination of dust MAR at the two ends of the Eurasian loess belt on shorter, sub-orbital scales. Here we present a detailed quartz optically stimulated luminescence (OSL) chronology from the Serbian Titel Loess Plateau (Veliki Surduk loess core) and the Chinese Loess Plateau (Lingtai section). The luminescence ages pass internal tests and show consistent increases in age with depth, with no obvious major hiatuses. However, as reported before, it seems the quartz OSL technique is only capable of accurate age determination up to accrued doses of ca. 150 Gy (ca. 30–40 ka) due to approaching field saturation of the quartz OSL signal. Two age-depth models were used to reconstruct dust MARs, where one utilises OSL data solely and the other additionally makes assumptions about sedimentation rates. Although short-term fluctuations in MAR are model dependent, general MAR patterns between the two sites are very similar, with peak MAR occurring rather late in the last glacial (ca. 13–25 ka). This suggests that at least broad scale trends in dust activity within the last glacial period may be similar at a continental scale.

The Last Glacial aeolian record of the Island of Susak (Croatia) as seen from a high-resolution grain–size and rock magnetic analysis

The loess-palaeosol record on the island of Susak in Croatia is a unique archive of Late Glacial climate changes in the Adriatic region, possibly even in the wider area. On Susak up to 90 m of thick Quaternary sediments were deposited, and are accessible for detailed palaeoclimate reconstructions. In this paper, the results of a high-resolution grain-size and rock magnetic investigation on the Last Glacial (Upper Pleniglacial) Sand Pit section from Susak are presented. In spite of its significant thickness, the Sand Pit section does not represent a continuous record; it is a result of a very dynamic environment. There, the deposition of dust and formation of loess has been interrupted by pedogenesis, periods of increased sand accumulation, erosion due to slope wash and water activity, redeposition and wildfires, and all in the time period of about 10.000 years of the Upper Pleniglacial, as seen from the IRSL dating results. The grain-size data clearly show a shift towards coarser grain sizes which differs from typical loess regions. Such predominance of the coarser-grained over the fine-grained fraction, very likely resulted from the predominance of deposition over pedogenesis, increased wind activity and proximal source of material. The rock magnetic signal preserved in the sediment also differs compared to loess-palaeosol records from other regions. The susceptibility values are several times higher than in the records from the Pannonian basin and from typical Eurasian loess. Both the increased susceptibility values and the grain-size are very likely the result of a significant proximal material input from the Po River plain.

Geochemistry of loess deposits in northeastern China: constraint on provenance and implication for disappearance of the large Songliao palaeolake

The Harbin loess, typical of the loess in NE China, is located in the easternmost margin of the Eurasian loess belt, and was recently investigated from the perspective of an Asian aeolian dust system. Before this study, the geochemical composition and provenance of the Harbin loess remained poorly understood. More importantly, the study of the Harbin loess also provides a unique opportunity to understand the geomorphological evolution process of the large Songliao palaeolake in the Northeast Plain. This study presents the results on the geochemical characteristics (major elements, trace elements, rare earth elements and Sr–Nd isotope) of the Harbin loess. There are markedly consistent geochemical compositions in and between the loess and palaeosol sediments, revealing stable dust sources and identical sources for the loess and palaeosol. Various indicators illustrating weathering and recycling indicate that the Harbin loess–palaeosol sediments were derived from sources with a low degree of weathering and from material with first-cycle alluvial–lacustrine deposits. Combinations of various provenance tracing indicators indicate that the Harbin loess has a strong geochemical affinity with the Songnen Sandy Land and to a certain extent the Horqin Sandy Land but not with the Hulun Buir Sandy Land, which indicates that these loess deposits are derived from a mixed provenance, with the dominant source being the neighbouring Songnen Sandy Land and a second, distal source being the Horqin Sandy Land. Finally, we advocate that the Harbin loess accumulation could serve as the direct record of the Songliao palaeolake disappearance. Supplementary material: Data for the NE Sandy Lands of China, and full provenance discrimination diagrams are available at https://doi.org/10.6084/m9.figshare.c.3835009 .

Three climatic cycles recorded in a loess-palaeosol sequence at Semlac (Romania) – Implications for dust accumulation in south-eastern Europe

Recent inve\stigations of the Semlac loess section in the south-eastern Carpathian Basin, which is situated at an undercut slope position on the right bank of the Mures River in its lower reaches (Banat region, western Romanian), are presented and discussed. Dating back to marine isotope stage (MIS) 10, the more than 10 m thick loess sequence includes four fossil soil-complexes developed in homogenous and relatively fine silty loess. Because of the good preservation of the sediment, Semlac is regarded as a key section for the Carpathian Basin, which offers possibilities to a) improve the understanding of the type and composition (loess homogeneity and pedogenic alteration) of the lowland loess sequences in the Carpathian Basin also beyond the last interglacial palaoesol complex, b) to reconstruct the temporal evolution of the local loess-palaoesol successions, c) gain better insight into the regional paleoenvironments of the last 300ka and d) to compare the loess of the region to loess-sequences in adjacent areas and to dust proxy data in the northern hemisphere. An integrated age model based on correlation to reference records and luminescence dating is compiled. Applying this age model we compare climate proxy data from Semlac to both global data and to data from the very southeast of the Carpathian Basin (Vojvodina, Serbia). The obtained results provide new insight into the dust accumulation regime for the eastern Carpathian Basin and offer new palaeoenvironmental information for the region and are an important step towards establishing a catena from the thin loess-like sediments of the Banat foothills in the East towards the thicker and seemingly more complete loess sections of the south-eastern and central Carpathian Basin. Disentangling grain size data from soil formation proxies is used to investigate patterns of non-local dust. Patterns of non-pedogenetic fine material are similar to grain size proxies from China and other parts of the northern hemisphere, suggesting western and eastern Eurasian loess to have (at least partly) similar mechanistic/climatic origins. (C) 2016 Elsevier Ltd. All rights reserved.

Loess accumulation in the Tian Shan piedmont: Implications for palaeoenvironmental change in arid Central Asia

Whilst correlations have been made between the loess of Europe and China, deposits in Central Asia have remained largely overlooked by scientific investigation. The nature of the relationship between loess accumulation and palaeoclimate at the core of the Eurasian loess belt is particularly poorly understood.Here we reconstruct palaeoenvironmental change in Central Asia over the last 40 ky based on data from the Remizovka loess profile, in the northern foothills of the Tian Shan in southern Kazakhstan. Our interpretations are based on synthesis of chronostratigraphic, colour and magnetic susceptibility data, supported by chronostratigraphies from two additional sites nearby, Maibulak and Valikhanova. All three sites record substantially increased loess accumulation during late MIS 3 into the global last glacial maximum (gLGM). At Remizovka, increased loess flux occurred in two pulses at c. 38-25 ka and 22-18 ka, with the intervening period involving incipient pedogenesis. At Maibulak, two loess pulses at c. 40-30 ka and c. 28-22 ka are separated by a weakly developed paleosol which may date to the same time as pedogenesis at Remizovka. There is additional possible periglacial influence at Maibulak from c. 40–33.5 ka. At Valikhanova, there is some age overlap between paleosol and loess samples, but overall loess accumulation appears to have increased at c. 42-35 ka, c. 30 ka and the gLGM, with pedogenesis occurring >40 ka and c. 32 ka. At all three sites, Holocene loess accumulation is minimal; this period is characterised by pedogenesis.The chronostratigraphic variability between our sites highlights a need to interrogate climate-driven models for loess formation in piedmont environments. We interpret our data in the context of regional palaeoenvironmental archives to indicate that loess accumulation increased coeval with MIS 3 glacial advance in the Tian Shan, which was facilitated by northward expansion of the Asian monsoon and associated increase in precipitation. We hypothesise that increased ice volume impeded teleconnections with the temperate zone westerlies to the north; these were compressed against the piedmont resulting in increased wind strength and facilitating increased loess flux. Peak loess accumulation during the gLGM occurred under colder, drier climatic conditions, with reduced but sustained glacial ice volume and persistent influence of the westerlies in the arid Central Asian piedmont loess belt. In the absence of more widespread, reliably dated palaeoenvironmental records from the region, our data become of critical importance for understanding past environmental conditions in Central Asia, relative to elsewhere in Eurasia and globally.

MIS3 paleosols in the center-north of Eastern Europe and Western Siberia: Reductomorphic pedogenesis conditioned by permafrost?

The MIS3 paleosol units comprise a prominent element of the loess-paleosol sequences throughout the Eurasian Loess Belt. To the north of the loess regions, the findings of MIS3 paleosols were few: it was supposed that geomorphic processes related to the extensive ice cover of the Last Glacial Maximum destroyed the earlier soil mantle. Recently, much smaller extent of continental ice in the east of Northern Europe and ice-free West Siberian Plain during MIS2 has been hypothesized, supposing preservation of MIS3 and earlier paleopedological records. We discovered in the center-north of European Russia (Upper Volga basin) and Western Siberia (Middle Ob basin), MIS3 paleosols within the Late Pleistocene alluvial and lacustrine sequences and correlated the studied profiles on the basis of macro- and micromorphological characteristics and radiocarbon datings of the paleosol organic materials. Paleosols are represented by hydromorphic profiles with Histic horizons and gleyic color pattern. Conspicuously, they are developed in the well drained geomorphic positions, where modern soils are non-gleyic. We suppose that the presence of permafrost was responsible for water logging and generation of reductomorphic soil environment. We further hypothesize a northern zone of MIS3 soil mantle, comprised of Histic and Reductaquic Cryosols different from synchronous Cambisols and Chernozems formed within loess sequences to the south.

The Agh Band loess-palaeosol sequence – A terrestrial archive for climatic shifts during the last and penultimate glacial–interglacial cycles in a semiarid region in northern Iran

Abstract The Northern Iranian loess profiles host important information on Quaternary climate and palaeoenvironmental changes in the region. They build an important link between the Eurasian loess belt and European and Central Asian archives. Due to a climatic gradient with decreasing precipitation from the west to the east and from the south to the north, loess-palaeosol sequences formed synchronously under different climatic conditions can be studied over short distance in the Iranian Caspian Lowland. The Agh Band profile is located in the so called Iranian “Loess Plateau”, a semi-arid region with 200–350 mm annual precipitation. The loess deposits at Agh Band reach a thickness of >60 m. An about 50 m thick step-profile was prepared and the litho/pedostratigraphy was investigated. Samples for laser-diffractometry grain-size measurements were taken every 2 cm. The magnetic susceptibility was measured in 4 cm intervals and the CaCO3-content in 8 cm intervals. To establish a chronological framework a pIRIR290 luminescence dating approach was applied to the 4–11 μm polymineral fraction. The results show that the Agh Band profile yields a climate archive reaching from MIS 7 to MIS 2. Several chronological hiatuses of some 10 ka show that periods of intense loess accumulation were interrupted by phases of only minor loess sedimentation and/or erosion. The Agh Band profile is subdivided by several shifts in grain-size distribution. The coarsening- and fining up trends correlate with increasing and decreasing wind-velocity, respectively. In the central part of the Agh Band loess sequence a weakly developed palaeosol is preserved which was developed at around 80 ka. Furthermore, the loess deposits formed from about 100 ka to 60 ka ago show banded structures. A pedocomplex including two well-developed palaeosols consisting of Bw(y) horizons and a CB-horizon as well as intercalated loess can be found in the lower part of the sequence also evidenced by the increased values of magnetic susceptibility. The corresponding luminescence age estimates indicate that the palaeosols represent a period of increased humidity and landscape stability during late MIS 7 and MIS 6. Hence, in the Agh Band loess, various changes in the palaeo-sedimentary system, triggered by changes in climate can be observed. This yields important information on the sensitive response of sedimentary systems and landscapes within semi-arid regions to shifts in moisture and possibly temperature.

Stable isotope geochemistry of pedogenic carbonates in loess-derived soils of northeastern Iran: Paleoenvironmental implications and correlation across Eurasia

Despite the occurrence of pedogenic carbonates in loess/paleosol sequences of northern and northeastern Iran, there is no information about stable isotope geochemistry of pedogenic carbonates in these regions. This paper presents the first stable isotope data on pedogenic carbonates in loess derived soils of northeastern Iran, southern Eurasian loess belt. Carbon and oxygen stable isotope values of pedogenic carbonates in different landforms were measured using mass spectrometry. Based on climatic data, there is no possibility for soil leaching and pedogenic carbonate formation under the present arid conditions. Stable oxygen and carbon isotopic data suggest two separate periods of carbonate formation. These periods are characterized by either lower or higher temperatures during post glacial than today and paleoecological conditions dominated by C3 and C4 plants, respectively. Hemispheric correlation of loess deposits based on isotopic data of pedogenic carbonates shows a strong positive correlation for the post glacial carbonates nodules of northeastern Iran and European Russia. This suggests a similar mechanism of carbonate formation and also the impact of Westerlies in these regions. We present the first quantitative isotopic data for paleoenvironment of northeastern Iran. However, more quantitative investigations about the Holocene and the last interglacial paleoenvironments of northeastern Iran are needed.

New magnetostratigraphic and pedostratigraphic investigations of loess deposits in north‐east China and their implications for regional environmental change during the Mid‐Pleistocene climatic transition

ABSTRACTLittle is known about the long‐term climatic evolution of north‐eastern (NE) China, because well‐preserved terrestrial paleoenvironmental archives are scarce in this vast region. The extensive loess deposits in the Chifeng region are the thickest and most complete loess–paleosol sequence in NE China, and have significant potential for reconstructing the paleoclimate of the region. Here, we present new high‐resolution magnetostratigraphic results from two loess–paleosol sections in the Chifeng region: the Sanbahuo (SBH) and Toudaojingzi (TDJZ) sections. The results demonstrate that both sections record the Brunhes normal polarity chron and the upper portion of the Matuyama reversed polarity chron. Based on these new results, the base of the TDJZ loess sequence is dated at ca. 1.22 Ma, representing the oldest known loess deposits in NE China. The initiation of loess accumulation in NE China was roughly synchronous with the large expansion of the Eurasian loess belt during the late Early Pleistocene (1.2–0.7 Ma), probably reflecting a widespread intensification of aridity in northern mid‐latitudes. We suggest that global cooling during the Mid‐Pleistocene climatic transition led to increased aridity and more favorable conditions for promoting the availability of silt for entrainment, transport and deposition.

Loess–palaeosol sequences in China and Europe: Common values and geoconservation issues

Loess–palaeosol sequences preserve the most significant continental record of climatic and environmental changes during the Quaternary available for scientific study. The Eurasian loess belt in particular could be regarded as one of the most important Quaternary terrestrial records of climatic and environmental changes on a global scale. The Preliminary stratigraphical correlation has determined that loess sections in south-east Europe and China have, perhaps surprisingly, shown many similarities. Unfortunately, these sites, due to their economic (e.g. agriculture and brickyards) and functional (e.g. remote sections as waste disposal sites) values, share the same (both human-induced and natural) threats and are constantly endangered by numerous causes and could be naturally degraded or permanently exploited as a georesource.Conversely, this valuable segment of Earth's geodiversity has gained much attention within the nature conservation community. There are certain individual attempts to protect and promote loess to the general public, which is the case in China (National Geoparks with protected loess, e.g. Luochuan, Huoshi Chai, Kungdongshan, Jingtai, Yellow River), and also in Serbia and Poland. These could serve as good platform for establishing common strategies towards national and international recognition of important loess sections. Thus, the aim of this study is to provide a preliminary and universal strategy concerning conservation, interpretation and promotion (geotourism) of significant Eurasian loess–palaeosol sequences. Once implemented and tested, they could serve for all similar soft-rock exposures and soils.