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The origin and provenance of eolian sediments such as loess can potentially reveal paleo-air circulation directions that drive temporal changes in climate. The provenance of these deposits has been mostly assessed by detrital zircon U-Pb geochronology and remains debated. Recent studies reveal that constraining sediment provenance using only detrital zircon yields a restricted view of the overall sediment sources, because zircon commonly records high-temperature tectonothermal events and thus only represents a portion of provenance lithologies. We applied a new strategy for constraining the provenance of eolian sediments from the Chinese Loess Plateau—Earth's most extensive loess deposit—by using a multi-proxy (i.e., zircon, monazite and rutile) U/Th-Pb geochronology approach. We show that while zircon U-Pb-Lu-Hf isotopic data cannot conclusively discriminate the potential sources, monazite and rutile grains display dominant U/Th-Pb age peaks in the early Paleozoic, early Mesozoic, and late Cenozoic, mirroring the orogenic episodes of the northeast Tibetan Plateau. Monazite and rutile records also reveal spatial variability in sediment provenance between the western and central parts of the Chinese Loess Plateau, which is potentially affected by dust transport from westerly/northwesterly winds. Our integrated data set provides diagnostic constraints on the dust source, provenance variability, and transportation trajectory of the Chinese Loess Plateau, and highlights the importance of this new approach to provenance study of eolian deposits worldwide.

Chinese loess-paleosol sequences have long been regarded as the continental counterpart of deep-sea sediments in terms of their record of the Quaternary glacial–interglacial cycles. However, absolute chronologies for loess-paleosol sequences older than ca. 130 ka on the Chinese Loess Plateau are scarce. We conducted the first high-resolution luminescence dating, extending back to 350 ka, of the classical Luochuan loess section of the central Chinese Loess Plateau. Bacon age-depth modeling of the luminescence ages was used to obtain an age framework. The results indicate that on orbital timescales, loess accumulation at Luochuan was continuous over the last three glacial–interglacial cycles. The new age framework resolves discrepancies between orbitally tuned age models at several boundaries and provides new evidence supporting the reassignment of the Marine Isotope Stage 8/9 boundary age from 300 ka to ca. 280 ka. Our results also suggest that published astronomical timescales for the loess deposits of the Chinese Loess Plateau over the last ~2.6 m.y. are probably broadly reliable, as are the related regional and global climatic interpretations.

We conducted the first detailed mineral magnetic investigation of more than nine loess–paleosol couplets of the composite Titel-Stari Slankamen loess section in Serbia, which provides one of the longest and most complete terrestrial record of paleoclimatic changes in Europe since ~1.0 Ma. The results show that the ferrimagnetic mineral assemblage of the loess units is dominated by partially oxidized multidomain (MD) and pseudo-single domain (PSD) magnetite; however, with an increasing degree of pedogenesis, the eolian contribution is gradually masked by pedogenic superparamagnetic(SP) and single-domain (SD) ferrimagnets (mainly maghemite). The overall consistency of ferrimagnetic grain-size parameters indicates an absence of dissolution of the fine-grained ferrimagnetic fraction despite changes in climate regime over the past 1.0 Ma. The variations of normalized dJ/dT@120Kand normalized χheating@530°Creflect a long-term stepwise increase in aridity during glacials with a major step at ~0.6–0.5 Ma, over the last 1.0 Ma. Overall, the results provide an improved basis for the future use of the magnetic properties of Serbian loess deposits for paleoclimatic reconstruction.

The aeolian loess-paleosol sequences in the Chinese Loess Plateau (CLP) are an excellent archive of variations in atmospheric circulation in the geological past. However, there is no consensus regarding the roles of the East Asian winter monsoon and westerly winds in transporting the dust responsible for loess deposition during glacial and interstadial periods. We conducted detailed measurements of the anisotropy of magnetic susceptibility (AMS) on two parallel loess profiles covering the most recent 130 ka in the western CLP to determine paleowind directions. Results show that the magnetic lineations of the loess and paleosol units in both sections are significantly clustered along the northwest to southeast direction. These observations demonstrate that the prevailing wind system responsible for dust transport in the western CLP was the northwesterly winter monsoon, rather than the westerly winds. The AMS-derived dust-bearing wind direction was relatively stable during the last glacial and interglacial cycle in the western CLP, consistent with sedimentary and AMS evidence from the eastern CLP. Accordingly, it is reasonable to conclude that large areas of deserts and Gobi deserts areas located in the upwind direction were the dominant sources for the aeolian deposits of the Loess Plateau.

The Asian summer monsoon (ASM) is a vast climate system, whose variability is critical to the livelihoods of billions of people across the Asian continent. During the past half-century, much progress has been made in understanding variations on a wide range of timescales, yet several significant issues remain unresolved. Of note are two long-standing problems concerning orbital-scale variations of the ASM. (1) Chinese loess magnetic susceptibility records show a persistent glacial-interglacial dominated ~100 kyr (thousand years) periodicity, while the cave oxygen-isotope (δ18O) records reveal periodicity in an almost pure precession band (~20 kyr periodicity)—the “Chinese 100 kyr problem”. (2) ASM records from the Arabian Sea and other oceans surrounding the Asian continent show a significant lag of 8–10 kyr to Northern Hemisphere summer insolation (NHSI), whereas the Asian cave δ18O records follow NHSI without a significant lag—a discrepancy termed the “sea-land precession-phase paradox”. How can we reconcile these differences? Recent and more refined model simulations now provide spatial patterns of rainfall and wind across the precession cycle, revealing distinct regional divergences in the ASM domain, which can well explain a large portion of the disparities between the loess, marine, and cave proxy records. Overall, we also find that the loess, marine, and cave records are indeed complementary rather than incompatible, with each record preferentially describing a certain aspect of ASM dynamics. Our study provides new insight into the understanding of different hydroclimatic proxies and largely reconciles the “Chinese 100 kyr problem“ and “sea-land precession-phase paradox”.

Five dating protocols with post-infrared infrared (IR) stimulated luminescence signals (i.e. pIRIR) were performed on the K-feldspar of loess samples. Two of them were the single-aliquot regenerative-dose protocol (SAR) with two-step pIRIR stimulation, with the first IR stimulation at 50°C or 200°C and the second at 290°C (pIR50IR290, pIR200IR290). Two of them were the SAR protocols with five-step or six-step IR stimulation at multiple elevated temperatures to 250°C or 300°C (MET-pIRIR250, MET-pIRIR300). The final one was the multiple-aliquot regenerative-dose (MAR) protocol with the MET-pIRIR300 signal, together with a 500°C heat treatment administered before the test dose (‘MAR with heat’). The results show that when the equivalent dose (D e) of the sample was less than 500 Gy, all of the protocols gave consistent results; however, when D e exceeded 750 Gy, all of the SAR protocols underestimated De . The pIR50IR290 signal had the highest degree of underestimation, while the pIR200IR290, MET-pIRIR250 and MET-pIRIR300 signals had similar De values and similar degrees of underestimation. Possible reasons for the SAR D e underestimation are discussed. We suggest that only the ‘MAR with heat’ protocol is suitable for samples with D e exceeding 750 Gy.

Eco-environmental changes during interglacials with an astronomical background similar to that of the Holocene are potentially helpful for understanding the future climatic evolution. Marine oxygen isotope stage (MIS) 19 is similar to the Holocene in astronomical background, both being characterized by a low eccentricity of the Earth’s orbit. However, MIS 19 has attracted research attention only recently and therefore less is known about eco-environmental changes during this interval, especially based on terrestrial records. In the Chinese Loess Plateau (CLP), the S7 paleosol can provide valuable terrestrial paleoclimatic and paleoenvironmental record for MIS 19. Here, high-resolution terrestrial snail records from the L8–L7 strata of the Huining, Xifeng and Luochuan sequences in the CLP were analyzed in order to characterize spatio-temporal changes in climate and eco-environment during MIS 20–18. The results show that in all three sections the late part of MIS 20 was dominated by abundant cold-aridiphilous mollusc species, indicating that cold and dry climatic conditions prevailed across the entire CLP, under the strong influence of the winter monsoon. The mollusc fauna of MIS 19 were dominated by warmth-loving and thermo-humidiphilous species that enable the definition of two climatic stages. The early part of MIS 19 (~790–778 ka) was marked by warm and humid conditions, as evidenced by high abundances of warmth-loving and thermo-humidiphilous species. This interval was slightly warmer than today and it lasted for ~12 kyr. The climate of the later part of MIS 19 (~778–761 ka) was more moderate, and increased proportions of cold-aridiphilous and warmth-loving species were recorded. The warmth of this period was similar to that of today, but the climatic fluctuations were stronger. During the early part of MIS 18 (~761–745 ka), the Xifeng and Luochuan sections in the eastern CLP still maintained high abundances of warmth-loving and thermo-humidiphilous species, indicating that the moderate climatic conditions during late MIS 19 continued during early MIS 18, lasting for another ~15 kyr, and that the influence of the summer monsoon remained strong in the eastern CLP during early MIS 18. However, in the western CLP, cold-aridiphilous species in the Huining section became dominant during early MIS 18, reflecting the prevalence of a cold and dry glacial climate, with the strong influence of the winter monsoon. These findings indicate that a steeper climatic gradient and a pronounced regional environmental difference existed between the eastern and western CLP during the early part of MIS 18. Comparison of our mollusc results with the variation of Earth orbital parameters suggested that climate changes in the CLP during MIS 20–18 were likely controlled mainly by insolation changes forced by the configuration of Earth orbital parameters. The unique orbital configuration during the low eccentricity interglacial-to-glacial transition could have strengthened the East Asian summer monsoon which favored the amelioration of the eco-environment in the CLP, especially in the eastern CLP where the summer monsoon exerted a strong influence. Thus we speculate that, under natural climatic conditions, the climate of the CLP may remain in a warm, humid state for another 30 kyr, although climatic instability and the seasonal differences between winter and summer could strengthen.

This paper analyzes the karst landscape of Southeastern Serbia, Mount Kalafat. The evaluation of five representative caves was performed using M-GAM (modified geosite assessment model) and the perspectives and potentials of karst-based geotourism were presented, through speleology, paleoclimate, and archaeology. Moreover, a unique proposal was presented in the form of a karst protection project through the establishment of a karst theme park. Although there are other attractive karst regions in Serbia, Mount Kalafat has been taken as a study area, due to the willingness of the local management structures and authorities to support projects concerning the protection of geoheritage and the development of karst-based geotourism. The results of the research indicate the evident values of the karst geoheritage and geotourism potentials that can become significant indicators for the development of sustainable geotourism and geoconservation in this area. Thus, precise measures and sustainable strategies that could define the geoethical concept of geotourism development have been presented in this paper. © 2022, The Author(s), under exclusive licence to The European Association for Conservation of the Geological Heritage.

This paper presents the results of grain-size analyses of an independently-dated loess/paleosol record dating back ca. 1 Ma from SW Hungary. The record follows an upward coarsening trend with a clear prevalence of coarse silts and fine sands. Variations are mainly controlled by fluctuations in sand input highlighting iterative changes in dust aerodynamics over the past 1 Ma in the source region found 50–100 km NW of our site. Based on our results regional factors influenced the intensity and nature of dust accumulation. Contrasting trends with the Chinese Loess Plateau in certain periods reflect a greater importance of the Atlantic region driving the evolution of nearby continental ice sheets. Proximity and expansion of these had significant impact on local wind field. Low topography of the surrounding mountain belts allowed for the intrusion of stronger cold winds, higher abrasion in the source region and transportation of coarser particles to the site from 700 to 450 ka. Another marked upward increase in grain-size from 400 ka can be linked to increasing continentality which along with tectonic activity resulted in a drop in the groundwater table in the source region and intensified erosion of formerly relatively stable surfaces bringing more coarse material to our site.

Both wind strength and anthropogenic emissions have been assumed to be the dominant factors in determining the occurrence of hazy weather in China. However, few records are available with sufficient temporal length and resolution, which enable the two signals to be separated, and hence address the dynamics of haze days and the global impact of the anthropogenic emissions in China, particularly in the context of global warming. Here we present the first long-term (last 180 years) lake sediment records of changes in wind strength and atmospheric loading of anthropogenic emissions in China. Our results show that the atmospheric loading of anthropogenic emissions and haze formation are closely related to the changes in wind strength associated with temperature changes, which are likely forced by tropical sea surface temperature. Comparison of our results with Pb isotope records from Japan and with the record of Pb concentrations in Greenland ice core indicates that the anthropogenic pollutants emitted in China stagnate mainly over the source area and neighboring regions, which thus favors haze formation under a warming climate. However, they would be transported worldwide under conditions of strong winds and decreased temperature. Climatic warming, together with the periodic changes in temperature, has caused unprecedented heavy haze days in recent decades in China. The observed pattern of periodic temperature variations suggests that in the next 30 years, wind strength will increase and thus reduce the incidence of haze days. However, this reduction may be attenuated by continued climatic warming as anthropogenic greenhouse gases emissions continue.

The thick ‘Xiashu loess’ in southern China is distributed not only in the Yangtze River valley, but also and most extensively in the region between the Qinling Mountains and the lower reaches of the Yangtze River. However, there are few studies of the provenance and climatic implications of the Xiashu loess in this latter region. Here we present the results of a provenance study of Last Glacial loess samples from twenty-two typical Xiashu loess sections, using the major and trace element composition as a provenance indicator. Seventeen of the sites are located to the north of the Yangtze River and our primary aim was to determine the provenance of the Xiashu loess within this region. Our results indicate that the alluvial plain located mainly in the present drainage area of the Huai River was the primary dust source for the Xiashu loess in this region. The occurrence of multiple local dust sources within this alluvial plain, suggested by their geochemical heterogeneity, indicates that the alluvial plain experienced intensified aridity which caused it to become a dust source for local loess deposits in northern subtropical China during the Last Glacial. Our study provides strong evidence to challenge the long-held view that the occurrence of Xiashu loess resulted from the southward incursion of the CLP loess deposits sourced from deserts of the Asian interior, and it confirms the substantial role of aridification of the present humid northern subtropical region for dust emission to the climate system during the Last Glacial.

The Eocene was marked by significant cooling during which the global climate was transformed from greenhouse to icehouse conditions. Notable coeval events were the India-Asia collision and the retreat of the Paratethys Sea in Asia. The Eocene section of the long and continuous sedimentary succession of the Xining Basin in Northwest China is characterized by red mudstones with intercalated gypsum and muddy-gypsiferous layers. In this study, we conducted a semi-quantitative analysis of the mineralogy of bulk samples and the clay fraction using X-ray diffraction, with the aim of characterizing the Eocene climatic evolution of the northeastern margin of the Tibetan Plateau and inland Asia. We used a new pretreatment method to address the problem of extracting sufficient clay particles from the gypsum and gypsiferous layers. The bulk mineralogy is dominated by quartz, feldspar, calcite, gypsum and dolomite; and the clay mineralogy is dominated by illite, chlorite, and smectite (including irregular mixed-layer illite-smectite (I/S)). The variations of the clay mineral assemblages indicate the occurrence of alternations between warm humid conditions and hot dry conditions, with relatively high humidity during ~52–50, ~41.5–39 and ~35–34 Ma. Comparison of the results with the timing of Tibetan Plateau uplift, transgressions and regressions of the Paratethys Sea, and the marine oxygen isotope record suggest that the Eocene climatic evolution of the study region was driven fundamentally by global climate change.

Clay minerals in loess-paleosol sequences carry important information on dust source and the paleoenvironments of the areas of loess distribution. The loess-paleosol sequences in the Serbian part of the Carpathian Basin are among the most complete Quaternary terrestrial sedimentary sequences in Europe. However, relatively little is known about the origin and temporal variations of clay minerals in these deposits and their paleoclimatic implications. Here we present the results of high-resolution XRD clay mineral analysis of the Stari Slankamen loess-paleosol sequence through the last glacial cycle. The roughly constant composition of the clay minerals within the loess unit and most of the paleosol suggests that the clay minerals are of detrital origin and that pedogenic transformation has only occurred in the lower part of paleosol S1, which corresponds to the climatic optimum of Marine Isotope Stage (MIS) 5e. This provides a basis for addressing several important issues regarding the Carpathian Basin loess, including its provenance, glacial dust activity, and the interglacial climate. The smectite-rich characteristic of the glacial loess provides a diagnostic indicator for confirming local sources for the Carpathian Basin loess deposits, and that these sources made little contribution to the dust deposited in Greenland during the last glacial. The first application of illite crystallinity and the chlorite ratio to the Carpathian Basin loess-paleosol sequence suggests that they are more sensitive indicators than the clay mineral proxies previously used in European loess studies. The enhanced precipitation during MIS 5e indicated by the new proxies and the transformation of clay mineral potentially provide new insights into understanding the regional climatic response to future global warming.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Several attempts at reconstructing geological settings and palaeoclimatic changes of the siliciclastic deposits of the Dahomey Basin, SW Nigeria, using relative age dating and correlation methods, have resulted in serious discrepancies on the ages. Therefore, a chronology framework established by an absolute age dating method is requisite to constrain the geological interpretation. This research focuses on quartz optically stimulated luminescence (OSL) dating of the upper siliciclastic sediments to help bridge the lacuna that arose from previous relative geologic dating. Ten sub-surface sediment samples were collected from the eastern part of the basin, and quartz OSL dating using single-aliquot regenerative-dose protocol was conducted for all the samples. The OSL signals appear well bleached prior to deposition and the OSL ages are reliable and robust. Through the application of OSL, the age framework of the uppermost part of sediments in the study area was established. The OSL dating results revealed that these depositional periods fall within the Holocene and are concentrated during two groups: 3.52 ka–1.55 ka, and 0.64 ka–0.05 ka. The samples with ages of 3.52 ka–1.55 ka distribute in the belt-like inland zone approximately parallel to the coastline. This deposition episode appears to be caused by the decrease in relative sea level during late Holocene. Thus, this study sheds light on the understanding past coast dynamics in the region

Quaternary strata in China mainly comprise continental deposits in a variety of depositional settings. The continental Quaternary in temperate northern China consists mainly of eolian and fluvio-lacustrine deposits; that in subtropical southern China, mainly of vermiculated red soils, cave/fissure deposits, and fluvio-lacustrine deposits; and that in the alpine Tibetan Plateau, mainly of fluvio-lacustrine and piedmont deposits. The marine Quaternary in China consists of detrital deposits and biogenic reef deposits. The integration of biostratigraphy, magnetostratigraphy, climatostratigraphy and an astronomically calibrated chronology has led to the establishment of high-precision climatochronostratigraphic timescales for the detrital marine Quaternary in the South China Sea and the loess-paleosol sequence in the Chinese Loess Plateau. Extremely high-precision 230Th dating has provided a high-precision absolute age model for cave stalagmites over the past 640000 years as well as high-resolution oxygen isotope records representing orbital- to suborbital-scale climate changes. By combining magnetic stratigraphy and biostratigraphy, robust chronostratigraphic frameworks for non-eolian continental Quaternary deposits on the scale of Quaternary geomagnetic polarities have been established. The continental Pleistocene Series consists, from oldest to youngest, of the Nihewanian Stage of the Lower Pleistocene, the Zhoukoudianian Stage of the Middle Pleistocene, and the Salawusuan Stage of the Upper Pleistocene. Stages of the continental Holocene Series have not yet been established. This review summarizes recent developments in the Quaternary chronostratigraphy of representative Quaternary strata and associated faunas, and then proposes an integrative chronostratigraphic framework and a stratigraphic correlation scheme for Quaternary continental strata in China. In the near-future, it is hoped to establish not only a Chinese continental Quaternary climatochronostratigraphic chart on the scale of glacial-interglacial cycles but also a Quaternary integrative chronostratigraphic chart including both continental and marine strata in China.

Optically stimulated luminescence (OSL) dating on potassium feldspar has been performed with high resolution in the Luochuan section in the Chinese Loess Plateau. An age hiatus of ∼ 15 ka is found at the top of L2 layer within the loess/paleosol sequences. The age of the potassium feldspar from the calcrete nodules along the S1/L2 boundary is significantly older than those of the paleosol and loess samples lying above and below the boundary. The age overestimation of the potassium feldspar from calcrete nodules is caused by the underestimation of the dose rate, because accretion of carbonates could dilute the radioactivity. The age hiatus at the top of L2 also resulted from the underestimation of the dose rates of four loess samples beneath this hiatus. These four loess samples have high CaO concentrations. Ages of these samples are overestimated in the similar way as the nodules, but with smaller degrees. All results suggest that the accretion of carbonates happened after the loess deposition. The carbonate accretion process of the calcrete nodules has been simulated with accumulation models. The accretion can be as young as 46 ka, assuming the calcrete nodules formed rapidly at a certain time point. For slow and gradual accretion models, the carbonate started to accumulate slowly since the dust deposition and the accumulation became faster afterwards. The transition of the accretion rate may relate to the climate change or a change in the carbonate leaching and re-precipitation system.

© 2017 Elsevier Ltd In Europe, the most complete loess-paleosol sequences over the past million years are preserved in the Serbian part of the Danube River drainage basin. The similarity in stratigraphy and climatic cycles between the Serbian and the Chinese loess sequences suggests that the loess deposits in these two regions could play an important role in the study of intercontinental climatic correlations and linkage. However, previous magnetostratigraphic studies of the Serbian loess, mainly conducted using the alternating field (AF) demagnetization approach, show significant differences with the Chinese loess, especially the stratigraphic positioning of the Matuyama-Brunhes boundary (MBB). Here, we conduct a detailed magnetostratigraphic investigation of a composite Titel-Stari Slankamen loess section in the Vojvodina (northern Serbia), using thermal and hybrid demagnetization methods, aiming to establish new chronological constraints for the Danube Basin loess. Based on the analyses of the mineral magnetic properties, anisotropy of magnetic susceptibility, progressive thermal and hybrid demagnetization, the MBB was determined within S8, broadly consistent with the MBB position seen in the Chinese loess. Present evidence supports the hypothesis that the overall normal polarity in the upper part of L9, with a thickness of 2.1 m, was possibly caused by a combination of the remagnetization of remanence-carrying coarse-grained magnetite during the Brunhes normal chron and bioturbation during the forming of the overlying paleosol S8. Thus, our magnetostratigraphic results provide solid chronological evidence for the coherence of pedostratigraphy and climatostratigraphy for the loess deposits in the Danube Basin and China. The synchronous occurrence of the strongest developed paleosol S5 (corresponding to MISs 15–13) and the least weathered thick loess unit L9 (corresponding to MISs 24–22) in the two regions confirms that extreme climatic events during these two intervals are possibly common features of the climate in the Northern Hemisphere at those times.

The extensive loess deposits in southern China (‘Xiashu’ loess) are a valuable paleoclimatic archive in the subtropical monsoon region. We carried out a combined study of iron oxide mineralogy, pedostratigraphy, and magnetostratigraphy of three new loess sections in subtropical China. A detailed comparison of the iron oxides content of the Xiashu loess and the loess of the Chinese Loess Plateau reveals that the iron oxides of paleosol units in the Xiashu loess are partially dissolved. The estimated minimum mean annual precipitation levels required for the dissolution of maghemite, hematite, and goethite and the 95% confidence bounds are ~793 mm (679–907 mm), 728 mm (683–772 mm), and 941 mm (834–1048 mm) respectively. A regional comparison of the stratigraphy and magnetic susceptibility of the loess deposits in subtropical China reveals a general lack of correlation. The relatively low continuity of dust deposition combined with iron oxide dissolution is the main cause of the spatial inconsistency of the stratigraphy and magnetic properties. Magnetostratigraphic analysis reveals a basal age of 1.1 Ma for the loess deposits in subtropical China, which demonstrates that the intensification of aridification of the subtropical regions and a strengthened East Asian winter monsoon began by at least 1.1 Ma. Thus, the loess deposits in subtropical China provide terrestrial evidence from mid−low latitudes for global cooling and enhanced aridity across the Mid-Pleistocene Transition.

The discovery of the ancient city of Loulan in Xinjiang, China, at the beginning of the 20th century was of great significance for understanding the evolution of culture and civilization in Inner Asia. However, due to the lack of systematic chronological studies, the history of this ancient city remains unclear, particularly the date of its construction and abandonment. Here, we present the results of the first systematic radiocarbon (14C) dating carried out on artifacts from ancient Loulan. Our results show that human activity began as early as 350 cal BC, flourished during the interval from the 1st to 4th centuries AD, and completely disappeared around 600 AD. Most of the buildings in the city were constructed during the Eastern Han Dynasty rather than in Wei/Jin Dynasty, as previously indicated by excavated documents and letters (Hedin 1898; Xiao 2006). The development and flourishing of Loulan coincided with the interval of high ice accumulation and meltwater supply from surrounding mountains. The city began to decline and was finally abandoned following an abrupt decrease in ice accumulation and meltwater supply (Yao et al. 1996; Lauterbach et al. 2014), suggesting that natural climate change was the major factor responsible for the abandonment of Loulan.

Compared to other parts of the country, the region of Central Iran still remains mainly outside of major tourism flows even though there are significant geosites with great value for geotourism development. Two of those sites, the Shadow Canyon and the Canyon of Jinns, have excellent qualities for the development of this form of tourism in the future. The goal of this research is to gain information about the preferences of Iranian geotourists and to determine the current state and geotourism potential of Shadows Canyon and Jinn Canyon located in Central Iran by applying the modified geosite assessment model (M-GAM). The results indicate that Iranian geotourists consider rarity and the number of viewpoints the most important when choosing which geosite to visit, while the least important are tour guide service as well as hostelry and restaurant service. The results also show that more attention should primarily be concentrated toward promotional activities and basic tourist infrastructure construction in the future to attract even more tourists to these and other geosites in Iran.

The East Asian summer monsoon affects precipitation and hence vegetation in the densely populated Northwest Pacific region, yet a long-standing controversy exists concerning the spatial and temporal dynamics of the Holocene Optimum (HO) in the East Asian Monsoon Region. Here we use a detailed 14,000-year record reconstructing vegetation variations from a strategically selected crater lake from Northeast China, as well as a compilation of previous paleoclimatic studies, to show that the HO began around 6,000 Cal a BP in Northeast China, significantly later than generally recognized. By comparing our paleoenvironmental data with Holocene vegetation records from other regions of East Asia, we identified a marked northward shift for the onset of the HO from ∼ 10 , 260 Cal a BP in South China to ∼ 6 , 000 Cal a BP in Northeast China. The gradual northward transgression of the vegetation change could be caused by both the temperature and precipitation changes in different regions. Finally, we fitted a regression model of the start of the HO period versus latitude, which allowed us to make predictions for the beginning of the HO at different geographical locations. This study reveals a strong relationship between latitude and the initiation of the HO, and provides a window towards better understanding the forcing of vegetation changes in the East Asian monsoon region.

Knowledge of dust sources is crucial for understanding the aeolian system of the Xiashu loess which is distributed in the middle and lower reaches of the Yangtze River and in the Huai River region, and provides a unique long-term record of the environmental evolution of the humid subtropical region of East Asia. The debate on the dust source of the Xiashu loess arises partly from the lack of spatial information on its source signatures. In this study, we investigated spatial changes in the grain-size distributions of samples from 20 Xiashu and 6 Chinese Loess Plateau (CLP) loess sections of the Last Glacial period. The aims were to determine the genetic relationship between the Xiashu and the CLP loess, and to determine the transport pathway of the Xiashu loess. The grain-size data reveal that the trends in fining and sorting of the Xiashu loess do not conform to its being an extension of the CLP loess. This conflicts with the early view that the Xiashu loess represents a southward extension of the CLP loess. The southward-fining trend indicates that the Xiashu loess was mainly transported from north-to-south, and that the prevailing aeolian transport agent is the East Asian winter monsoon. We also examined present and published records of the transport pathway of the Xiashu loess and concluded that the deposits are mainly linked to the adjacent dessicated fluvial system of the Huai River. Thus, the Xiashu loess is mainly a repository of information on the evolution of this adjacent fluvial system.

The thick sedimentary sequences of the East Asian continental shelves are archives of information on tectonics, sea-level fluctuations, flood plain evolution, and changes in the East Asian monsoon climate. However, long sedimentary sequences with a reliable chronological framework from this setting are scarce. Here, we present an integration of lithostratigraphic, rock magnetic, and magnetostratigraphic results for the sedimentary sequence of a 285.0 m core (GZK01) recovered from the northern Jiangsu coastal plain of the onshore South Yellow Sea, eastern China. Alluvial, fluvial, lacustrine, and marine deposits were identified according to lithofacies analysis, and detrital magnetite and hematite are the main magnetic carriers. The magnetostratigraphic results show that core GZK01 records the Brunhes, Matuyama, Gauss, and Gilbert chrons, and has an extrapolated basal age of ∼5.1 Ma. This record is the oldest sedimentary sequence yet reported from the continental shelf of the South Yellow Sea. Integrating the geochronological framework with changes in lithofacies, a conceptual model of the environmental evolution of the northern Jiangsu coastal plain is proposed. For a long interval during the Pliocene, the drilling area was a lacustrine environment. From the Late Pliocene to the Early Pleistocene, the disappearance of the paleolake and a transition to a fluvial and marine environment suggests the peneplanation of the northern Jiangsu coastal plain. Cumulative land-sea interactions since 0.8 Ma subsequently shaped the modern geomorphology. The observed process of sedimentary evolution was possibly controlled by regional tectonics and long-term climate changes.

The entrance of Earth's climate into the present icehouse state during a time of rapid temperature decline in the late Pliocene was intensively investigated during the past decade. Even though it is well documented in marine archives, a detailed reconstruction of the Pliocene-Pleistocene climatic evolution of Central Europe is hampered by a general lack of data. The work presented here is based on sedimentary material from drill cores obtained at three sites within the Heidelberg Basin (Germany). The scientific relevance of this unique archive was discovered only in the last decade. The hundreds of metres thick sequences of mainly fluvial sediments record the evolution of the environment and climatic conditions during the late Pliocene and the entire Pleistocene of western Central Europe. In our present study, we implement unpublished mineral magnetic S-ratio data, and new evidence from X-ray analysis into two previously completed studies on the magnetic polarity stratigraphy, and the magnetic mineralogy of the Pliocene to Pleistocene sediments of the Heidelberg Basin. The total set of data enables distinction of environmental and climatic processes, and unveil details on the climatic conditions of continental Europe during this period. We demonstrate the dominance of a warm climate with alternation of humid and dry periods during the Pliocene. Cyclic variations in the groundwater table in the Rhine flood plain resulted in redox fluctuations, which led to the decomposition of the primary detrital mineral assemblage. Authigenic Fe oxides, particularly haematite, formed during dry periods. A rapid transition into cooler and moister conditions occurred at the end of the Pliocene, as indicated by the persistence of Fe sulphides, especially greigite. A high groundwater table and the associated reducing conditions have largely persisted to the present day. We show that the rapid transition from warm to cooler and moister climatic conditions in Central Europe during the final Pliocene is a regional response to the intensification of Northern Hemisphere glaciation (iNHG). This work supplements existing knowledge of the climatic evolution of Central Europe during the Pliocene-Pleistocene transition by data from a region from which little data has been available. A sideglance to climatic archives elsewhere in the Northern Hemisphere (e.g., North Atlantic Ocean, Chinese Loess Plateau, Russian arctic) is used to show the coincidence of the iNHG events in quite different environmental regimes.

The global climate system experienced a series of drastic changes during the Cenozoic. In Asia, these include the climate transformation from a zonal pattern to a monsoon-dominated pattern, the disappearance of typical subtropical aridity, and the onset of inland deserts. Despite major advances in the last two decades in characterizing and understanding these climate phenomena, disagreements persist relative to the timing, behaviors and underlying causes. This paper addresses these issues mainly based on two lines of evidence. First, we compiled newly collected data from geological indicators of the Cenozoic environment in China as paleoenvironmental maps of ten intervals. In confirming the earlier observation that a zonal climate pattern was transformed into a monsoonal one, the maps within the Miocene indicate that this change was achieved by the early Miocene, roughly consistent with the onset of loess deposition in China. Although a monsoon-like regime would have existed in the Eocene, it was restricted to tropical-subtropical regions. The latitudinal oscillations of the climate zones during the Paleogene are likely attributable to the imbalance in evolution of polar ice-sheets between the two hemispheres. Secondly, we examine the relevant depositional and soil forming processes of the Miocene loess-soil sequences to determine the circulation characteristics with emphasis on the early Miocene. Continuous eolian deposition in the middle reaches of the Yellow River since the early Miocene firmly indicates the formation of inland deserts, which have been constantly maintained during the past 22 Ma. Grain-size gradients between loess sections indicate northerly dust-carrying winds from northern sources, a clear indication of an Asian winter monsoon system. Meanwhile, well-developed Luvisols show evidence that moisture from the oceans reached northern China. This evidence shows the coexistence of two kinds of circulations, one from the ocean carrying moisture and another from the inland deserts transporting dust. The formation of the early Miocene paleosols resulted from interactive soil forming and dust deposition processes in these two seasonally alternating monsoonal circulations. The much stronger development of the early Miocene soils compared to those in the Quaternary loess indicates that summer monsoons were either significantly stronger, more persistent through the year, or both. These lines of evidence indicate a joint change in circulation and inland aridity by the early Miocene and suggest a dynamic linkage of them. Our recent sensitivity tests with a general circulation model, along with relevant geological data, suggest that the onset of these contrasting wet/dry responses, as well as the change from the "planetary" subtropical aridity pattern to the "inland" aridity pattern, resulted from the combined effects of Tibetan uplift and withdrawal of the Paratethys seaway in central Asia, as suggested by earlier experiments. The spreading of South China Sea also helped to enhance the south-north contrast of humidity. The Miocene loess record provides a vital insight that these tectonic factors had evolved by the early Miocene to a threshold sufficient to cause this major climate reorganization in Asia.

© 2017 Elsevier B.V. Loess-paleosol sequences are the most extensive terrestrial paleoclimate records in Europe and Asia documenting atmospheric circulation patterns, vegetation, and sedimentary dynamics in response to glacial-interglacial cyclicity. Between the two sides of the Eurasian continent, differences may exist in response and response times to glacial changes and finding these is essential to understand the climate systems of the northern hemisphere. Therefore, assessment of common patterns and regional differences in loess-paleosol sequences (LPS) is vital, but remains, however, uncertain. Another key to interpret these records is to constrain the mechanisms responsible for the formation and preservation of paleosols and loess layers in these paleoclimate archives. This study therefore compares LPS magnetic susceptibility records as proxies for paleosol formation intensity for selected sites from the central Chinese Loess Plateau and the Carpathian Basin in Europe over the last 440 kyr. Inconsistencies and crucial issues concerning the timing, correlation and paleoclimate potential of selected Eurasian LPS are outlined. Our comparison of Eurasian LPS shows generally similar patterns of paleosol formation, while highlighting several crucial differences. Especially for paleosols developed around ~ 200 and ~ 300 ka, the reported timing of soil formation differs by up to 30 ka. In addition, a drying and cooling trend over the last ~ 300 ka has been documented in Europe, with no such evidence in the Asian records. The comparison shows that there is still uncertainty in defining the chronostratigraphic framework for these records on glacial-interglacial time scales in the order of 5–30 kyr for the last ~ 440 ka. We argue that the baseline of the magnetic susceptibility proxy in loess from the Carpathian Basin is the most striking difference between European LPS and the Chinese Loess Plateau. In our opinion, many of the current timing/age differences may be overcome once a comparable stratigraphic interpretation is achieved.

© 2018 Elsevier B.V. The correlation of loess sequences across global, hemispheric, regional and local scales is one of the most fundamental aspects to loess research. However, despite recent progress in stratigraphic and chronometric methods, the correlation of many loess sequences is often still based on untested assumptions over loess deposition, preservation, soil type and age. As such, the aim of this overview is to provide an adequate framework for evaluation of the accuracy of loess correlations applied on different temporal and spatial scales across Eurasia. This opens up possibilities for detailed temporal and spatial environmental reconstructions across the huge loess provinces of the Eurasia and provides a framework for future extension of this to North America. Additionally, we evaluate the potential development of appropriate sub-millennial scale loess correlations, as well as essentially important chronological approaches for establishing valid correlations between different loess records, such as current improvements in tephrochronology, 14C and luminescence dating techniques.