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Jiudong Sandy Land in the western Hexi Corridor is one of the dust source regions of the Chinese Loess Plateau and is highly sensitive to climate change. Determination of when this sandy land formed would help resolve major questions about the desertification history of inland Asia; however, until now, this has been hindered by the lack of depositional records. Here, we report the results of optically stimulated luminescence (OSL) dating, grain size and grain surface analyses from a new drill core obtained from Jiudong Sandy Land. Our aims are to constrain its age of formation. Analysis of sedimentary facies reveals that the sediments in the lower part of the core (35.2–16.7 m) were deposited by fluvial processes, but that the sediments in the upper part consist primarily of aeolian sand. The OSL dating results indicate that the transition from fluvial to aeolian facies occurred at ∼89.8 ± 7.6 ka. Combined with various loess-based environmental proxies from Jiudong Basin, the new litho- and chronostratigraphic evidence reported in this study indicates that the age of ∼89.8 ± 7.6 ka represents the formation age of the Jiudong Sandy Land. [ABSTRACT FROM AUTHOR]

Highlights • Key parameters are calibrated in the shear-stress bedrock-incision model. • Differential rock uplift rates are inferred from bedrock channel longitudinal profiles. • Tectonic deformation pattern and controlling factors are explored in active orogen. Abstract Bedrock channel profile analysis is a robust reconnaissance tool for examining the rates and patterns of deformation in active orogens. Here, steepness and concavity indices were extracted from bedrock channels draining the northern Qilian Mountains based on the universal shear stress incision model. The profile analysis reveals a systematic spatial distribution of steepness and concavity indices. The average steepness index for channels draining the western part is approximately 1.6 times higher than that for the eastern part. Through empirical calibration of erosion coefficient K , the influence of channel width, rock strength, discharge and sediment flux are identified, and an approximately 1.1–1.2 times difference in K values is found between the west and east under the hypothesis that lithologic resistance and sediment flux have no contribution. Correlating profile analyses with parameter calibration, an approximate 2–3 times increase in the rock uplift rate is found from the eastern part to the western part of the orogen. The integration of this study with previous work in the eastern part of the mountains indicates that cross-strike (2–4 times) and along-strike (2–3 times) differential rock uplift both exist in the northeastern margin of the Tibetan Plateau. In addition, the abnormal values of concavity are apparently associated with the channels transecting large thrust fault zones. Thus, the shortening deformation may play a dominant role in controlling the differential rock uplift through folding and thrusting of the northeast-directed thrust faults across the northeastern margin of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Fluvial response to allogenic and autogenic controls concerns the understanding of landform evolution related to the interaction between tectonic movements, climate, surface process and human activity. Paleo-channels, as part of geomorphic archives, have been widely employed to study this issue during recent decades. Previous work has however concentrated on the mechanisms driving river migration. A new approach, in which multiple elements are considered, is employed here in the examination of paleo-channel formation in the Jiudong Basin, located at the northeastern margin of the Tibetan Plateau and characterized by active tectonic deformation, a dry climate and ancient human activity. Based on geomorphic and sedimentary analysis, eight paleo-channels formed by the Taolai and Hongshuiba rivers (two tributaries of the Beida River catchment) have been identified. AMS14C dating of the overlying lacustrine sediments defined their respective abandonment at ca. 22.2, 20.9, 15.3, 18.8, 13.9, 11.9, 3.5 and 1.1 cal. Ka BP. The migration histories of the two rivers have been reconstructed, and then well correlated with reference to archives of tectonic, climatic and human influence. Our results suggest that these controlling factors seem to be coupled and have a competitive relationship in driving river migration. In the northeastern margin of the Tibetan Plateau, channel migration can therefore be regarded as a result of fluvial response to the interaction between rapid tectonic activity, climatic fluctuation and human influence. • 8 paleo-channels have been identified in the northeastern margin of the Tibetan Plateau. • These paleo-channels have been constrained by AMS14C dating in the last glacial period. • These paleo-channels are coupled record of climate, tectonics and human influence. [ABSTRACT FROM AUTHOR]

The upper–middle Yellow River flows through the Fenwei graben, a structure resulting from extensional tectonism that was formed and repeatedly extended during the Cenozoic. The drainage system within this graben was formerly isolated from the lower reaches of the Yellow River system by the Xiaoshan mountains, an actively growing ∼ NW–SE trending range. The modern course of the Yellow River takes it through this range along the Sanmen gorge, the formation of which was of great significance in that it initiated through-going drainage between the upper–middle and lower reaches of the system. The timing of this event, which was clearly a critical point in the evolution of the Yellow River, can be established by dating the terraces in the gorge. Intermittent deepening of this gorge by the Yellow River from a high-level planation surface capping the mountain range has resulted in the formation of five terraces. Magnetostratigraphic records from aeolian deposits accumulated on these surfaces provide a geochronological sequence for this geomorphic archive, in which the ages of the planation surface and of terraces T5, T4, T3, T2, and T1 have been determined as ∼3.63 Ma, ∼1.24 Ma, ∼0.86 Ma, ∼0.62 Ma, ∼129 ka, and ∼12 ka, respectively. Under the constraint of this chronological framework, a model for landscape evolution is proposed here. Uplift of the inner Fenwei graben and of the surrounding mountain ranges led to dissection of the 3.63 Ma old planation surface in conjunction with the formation of the Sanmen gorge. Drainage of the lake previously occupying the basin would have promoted incision into the fluvio-lacustrine graben sediments; indeed, gorge formation through the Xiaoshan may have been initiated or intensified by lake overflow. The ages obtained for the planation surface and uppermost terrace suggest that the formation of the Sanmen gorge and the initiation of the through-going eastward drainage of the Yellow River occurred between 3.63 and 1.24 Ma. Before the start of gorge entrenchment, the products of erosion in the modern upper catchment of the Yellow River were unable to reach the sea. The dramatic increase in deposition rates in the Bohai Gulf (at the mouth of the modern Yellow River in the East China Sea), ∼1.0 Ma ago, thus resulted from the initiation of an integral (enlarged) Yellow River catchment drainage through the Sanmen gorge; it does not imply an increase in erosion rates at that time. [ABSTRACT FROM AUTHOR]

The uplifting of the Tibetan Plateau has significantly changed the environment in surrounding areas by delivering abundant water and sediment. The Heihe River draining the Qilian Shan in the NE Tibetan Plateau acts as a dominant sediment routing system from the uplifted NE Tibetan Plateau to the Hexi Corridor as well as the Badain Jaran Desert. Reconstructing the evolution of the Heihe River could provide evidence for the birth of the Badain Jaran Desert and enhance the understanding of sedimentary basin fill and the relationship between tectonism, drainage evolution and environmental changes. With this aim, two parallel cores (DWJ and XKJD with depths of 140 and 68.2 m, respectively) were drilled in the floodplain of the Heihe River. The facies analysis of the sedimentary sequences from the drilling cores showed that the sedimentary environment changed from the lake system to a delta system and finally to a fluvial system at the depths of ∼133.3 and ∼68 m, respectively. The magnetostratigraphic results revealed ages of approximately 1.75 and 1.12 Ma for the DWJ and XKJD cores, respectively, and an age of approximately 1.1 Ma for the transition from delta to fluvial environment in both the cores. The change of the sedimentary environment at approximately 1.1 Ma was caused by the formation of the integrated Heihe River. The integrated Heihe River may have developed via mechanisms such as river capture and river diversion due to the uplifting of the North Qilian Shan and the Longshou Shan. The present study suggested that the formation of large inland rivers, such as the Heihe River and the Shiyang River in NW China, played an important role in the evolution of the deserts and the Loess Plateau. [ABSTRACT FROM AUTHOR]

In its upper-middle reaches the Yellow River has high sand contents after traversing through large areas of desert and the China Loess Plateau. Understanding riverbed sediment composition in the channel is critical for the interpretation of the potential provenance, aeolian sand transport and the linkage between the Loess Plateau and the Yellow River. To address these issues, we collected 52 samples from the modern riverbed, proximal deserts, and major tributaries and used analyses of grain size, grain morphology, and heavy-mineral compositions, to establish the spatial distribution and characteristics of source regions and riverbed sediments. The heavy-mineral assemblages demonstrate significant variations for the different sections of the Yellow River. The riverbed samples from the upper reach are dominated by opaque minerals (limonite and magnetite), amphibole and epidote, with minor zircon, tourmaline and rutile. Riverbed sediments from the middle reach are garnet-rich, reflecting the widespread distribution of Mesozoic sandstones. This variability closely reflects the source regions. Our data show that seasonal tributaries (the “Ten Great Gullies”) carrying detritus from the Ordos Plateau may account for the localized high garnet concentrations in the Inner Mongolia section of the upper reach. Scanning electron microscope (SEM) imaging of quartz grains show that the river sediments are characterized by composite microtextures acquired in both fluvial and eolian environments of the Hedong, Ulan Buh and Kubuq Deserts. The mineralogical composition in the upper reach (Lanzhou–Yinchuan) is similar to that of sediments in the Loess Plateau and Northeast Tibet Plateau (Western Lanzhou). However, the composition differs markedly from that in the Inner Mongolia section of the upper and middle reaches. This variation indicates that in the upper reach the Northeast Tibet Plateau contributes significant volumes of sediment to the Yellow River and Loess Plateau, but compositions change across the Inner Mongolia section of the upper and middle reaches owing to local sediment supply from arid desert areas and seasonal tributaries. [ABSTRACT FROM AUTHOR]

In North China, the Ordos block located northeast of the Tibetan Plateau is regarded as a stable craton surrounded by the Yinchuan graben to the west, the Hetao graben to the north, and the Fenwei graben to the southeast. The major tectonic structure around this block in the Cenozoic reflects intensive extension as a response to the eastward extrusion of the Tibetan Plateau. Intermittent downcutting by the Yellow River, starting from the planation surface level on the Ordos block and penetrating the bedrock, resulted in the formation of the Jinshaan gorge. A series of well-preserved fluvial terraces was identified along this gorge, providing new insight into the far-field effect of the eastward extrusion of the Tibetan Plateau. Magnetostratigraphic records from the planation surface and uppermost terrace suggest that this gorge has been entrenched over its total length in the period from 3.7 to 1.2 Ma. A preliminary explanation is proposed here for the morphological evolution of the Yellow River in the Jinshaan gorge. On the basis of terrace correlation between seventeen geomorphic sections, multiwave headward erosion initiated by the Yellow River along this gorge has been reconstructed. This process may be attributed to the lowering of the base level (the Fenwei graben). This graben has been formed during the Cenozoic as the Tibetan Plateau extruded eastwards resulting in accelerated ground subsidence. A combined approach of magnetostratigraphy, pedostratigraphy, and optically stimulated luminescence (OSL) was adopted to establish a new geochronology for terraces in the gorge at 1.2 Ma, 1.1 Ma, 787 ka, 412 ka, 245 ka, 128 ka, 29 ka, and 11 ka. These ages provide an excellent framework for calculating the extension within the Fenwei graben. The average incision rate appears to be enhanced significantly since 412 ka, indicating a rapid extension within the Fenwei graben during this time. [ABSTRACT FROM AUTHOR]

Temperate glaciers are more sensitive to climate change than are polar or continental glaciers, and can drive remarkable runoff variation in local water catchments. Changes in the glacier area and surface elevation of the three monsoonal temperate glaciers in the Gongga Mountains, China, were analyzed using series of remote sensing images and digital elevation model (DEM) data. All possible sources of uncertainty were considered in detail. The results showed that the total glacier area decreased by 4.3 km 2 (6.7%) between 1966 and 2010. A comparison of glacier surface elevations using DEMs derived from dual-frequency differential GPS (DGPS) surveys in 2010, and from 1966 to 1989 from topographic maps. The three glaciers underwent significant mass loss from 1966 to 2010 and the mean surface elevation changes were −0.90 ± 0.45 m/y, −1.06 ± 0.45 m/y, and −1.12 ± 0.45 m/y for Hailuogou (HLG), Dagongba (DGB) and Yanzigou (YZG) Glaciers, respectively, from 1966 to 2010. Analysis of the meteorological data showed that the mean annual air temperature increase was the main reason for the thinning and volume loss. Thinning of the glacier tongue and volume loss was more intense in the period 1989–2010 than in 1966–89. Debris thickness and other factors are also believed to play important roles in differential thinning among different areas and periods. [ABSTRACT FROM AUTHOR]

The response of bedrock channels to differential rock uplift in eastern Qilian Mountain significantly dictates the topographic evolution of the northeastern margin of the Tibetan Plateau. Our ability to extract tectonic information directly from channel profiles mainly depends on the calibration of incision processes laws. Here we assess the degree and nature of channels response to differential rock uplift in eastern Qilian Mountain base on an empirical calibration of the shear-stress incision model utilizing field survey data (lithologic resistance, sediment flux, discharge and channel width). Parameters calibration indicates that channels developed in the high mountain zone (HMZ) show an approximate 1.1–1.3 times increase in erosion coefficient K than in the low mountain zone (LMZ), mainly attributing to the adjustments of channel width and discharge. Moreover, profiles analysis reveals a systematic geographic distribution of steepness indices and concavity in this area. The regions of high and low steepness indices are spatially associated with the higher (high rock uplift rates) and lower (low rock uplift rates) parts of landscape, respectively, suggesting that the spatial distribution pattern of channel steepness mainly reflects the differential rock uplift. Channels with abnormal high concavity values apparently associate with the major thrust faults, suggesting that the differential rock uplift is controlled by the thrusting of major active faults. Combining parameters calibration with profile analysis between the two zones, the possible increase in rock uplift rates is 2–4 times in the HMZ than in the LMZ indeed. [ABSTRACT FROM AUTHOR]

Abstract: A total of 41 spore species and 63 pollen taxa, including seven angiosperms, were identified from 24 samples of the Early Cretaceous succession (latest Barremian to Aptian) at the Wulan Section in the east part of the Yingen-Ejinaqi Basin, Inner Mongolia, China. In a stratigraphically upward order, three types of palynomorph assemblages were identified. Palynological assemblage I (PA I) was dominated by bisaccate pollen, whereas palynological assemblages II (PA II) and III (PA III) were characterised by abundant Classpollis associated with more spores. PA III contained the highest spore content. Angiosperm pollen display an increasing trend in diversity and abundance from PA I to PA III. PA I is most likely correlated to the Chinese Cretaceous palynofloral Transitional Zone and northern Disacciatrileti – Cicatricosisporites Province, whereas the assemblages II and III represent the transitional zone. The composition of these assemblages suggests that the climate was cool and humid within the basin during the latest Barremian, subsequently warmer and drier during the Early Aptian and, finally, became slightly wetter and warmer during the Late Aptian. Early angiosperm pollen occur frequently in this section, including that of Clavatipollenites, Asteropollis and Songipollis. On the stratigraphical order, these angiosperm pollen show a clear and continuous increase regarding the relative abundance and diversity of angiosperm, which most likely reflects the incipient dispersion of angiosperm plants during the latest Barremian to Late Aptian in inner East Asia. Lastly, a comprehensive compilation of published literature indicates that the emergence and evolution of early Asteropollis was not simultaneously worldwide, most likely occurring earlier in Eurasia than in other regions with a dramatic increase in both diversity and abundance prior to the emergence of tricolpate pollen. [Copyright &y& Elsevier]

Abstract: The uplift rate and pattern of the Qilian Shan Mountain, which lies in the northeast margin of the Tibetan Plateau, are key to understanding the dynamics of crustal deformation in the northeastern Tibetan Plateau. In this work, late Quaternary terraces in seven river valley sections in the eastern Qilian Shan Mountain are studied to determine terrace abandonment ages by OSL (optical simulating luminescence) and terrace heights by GPS (global positioning system) surveys. River incision rates since ~76kaBP are calculated ranging from 0.37mm/a to 1.49mm/a. Distribution of river incision rates shows that higher river incision rates (0.85–1.49mm/a) are located at the rivers'' upstream reaches where mean mountain elevation is ~4000m, and relatively lower incision rates (0.32–0.62mm/a) are located at the mountain front where the mean mountain elevation is <3200m. This difference of the river incision rate reflects spatial difference in rock uplift patterns within the eastern Qilian Shan Mountain. The high mountain range is characterized by a high river incision rate (on average of 1.2±0.4mm/a) and high relief, suggesting high rock uplift rate; whereas the low mountain range is characterized by low river incision rate (on average of 0.5±0.2mm/a) and lower relief, suggesting relatively low rock uplift rate. Based on fault distributions and slip rates, we propose that the differential rock uplift of eastern Qilian Shan is mainly controlled by the thrusting along active thrust faults separating different mountain ranges and by oblique thrusting along strike-slip faults near the mountain crest. [Copyright &y& Elsevier]

Abstract: Dust transported by sandstorms has been an important feedback in climate change in the past, and its environmental effects are predicted to have a great impact on future global climatic change. Investigating the grain-size classes and the standard deviations of the modern sandstorm samples, and the samples in the Shagou section (situated in the eastern Hexi Corridor), lead us to suggest that the sand fraction within the range of 275.4–550μm in this section can be used as a sensitive indicator of severe sandstorms. We selected the size range in the L1 stratum of the Shagou loess section as indicative of temporal changes in sandstorm intensity in the eastern Hexi Corridor and found that during the Last Glacial period, severe sandstorms in the eastern Hexi Corridor occurred with high frequency during these periods: I (70–54ka B.P.), II (51–48ka B.P.), III (45–42ka B.P.), IV (38–33ka B.P.), V (31–28ka B.P.) and VI (26–12ka B.P.) In general, the frequency and intensity of dust storms in the early (MIS 4) and late (MIS 2) periods were both high but they were reduced in the middle period (MIS 3). The primary factors controlling severe sandstorms are hydrology and wind power, followed by the expansion of the source extent. Reduced precipitation caused the source region of sandstorms to expand; in addition, wind speeds also increased at this time. These factors may have directly contributed to the abundance of severe sandstorms. Based on the grain size from a loess section (the Shagou section) in the eastern Hexi Corridor, we propose an evolutionary sequence of the severe sandstorms during the Last Glacial period. This sequence is consistent with the dust records in the Arctic, the Antarctic and low-latitude (the central equatorial Pacific) areas. Thus globally synchronous periods of high dust activity occurred in the Last Glacial period. The strong winds proposed here provide a potential explanation for the global consistency of dust flux changes during the Last Glacial period. [Copyright &y& Elsevier]

Abstract: The key to understanding the fluvial response to climate change and surface uplift is a thorough distinguishing between their roles in terrace formation. Previous studies have tended to attribute the fluvial behavior of deposit–incision alternation to climate cyclicity. A preliminary explanation is proposed here for terrace formation in the eastern part of the Fenwei Basin, China. The observed fluvial terrace sequence was developed by the Yellow River deeply downcutting into the Emei Platform, which was uplifted within the eastern Fenwei Basin, and therefore it probably records the tectonic history of this platform. On the basis of the magnetostratigraphy and optically stimulated luminescence (OSL) dating, a ca. 1.2Ma chronology was established for this terrace sequence. Pedostratigraphic analysis of the loess deposits accumulated on each tread reveals that the terrace deposits are overlain immediately by a paleosol bed, suggesting that the abandonment of these terraces due to fluvial incision occurred at the transitions from glacial to interglacial climates. The glacial–interglacial climate cycle probably has a temporal control on the fluvial behavior of deposit–incision alternation, even though the Yellow River develops in the subsiding Fenwei Basin. The terrace generation may be sporadic and in the form of unusual stacked pattern before the Emei Platform was uplifted within the eastern Fenwei Basin. The terrace staircases however, formed in synchrony with glacial–interglacial climate cycles since this platform began to uplift in the late Middle Pleistocene. This result indicates that uplift may be necessary in large terrace staircase genesis. It can force the river system to downcut deeply enough during climatic transitions to separate terrace levels adequately, favoring the generation and subsequent preservation of the terrace treads. The terrace sequence of the Yellow River in the eastern Fenwei Basin therefore can be considered as a combined archive of climate change and local tectonic activity. [Copyright &y& Elsevier]

Abstract: A continuous fluviolacustrine record provides the geochronological framework to reconstruct the fluvial landscape evolution of the middle reach of the Huanghe (Yellow River). Magnetostratigraphic records from six sections at the north of the Jinshaan Gorge indicate that an isolated fluviolacustrine system occupied this gorge from 8.3 to 3.7Ma. Local fluvial incision initiated at the lake margin around 5.3-4.9Ma, and concomitant fluvial deposits intruded laterally into fine lacustrine strata increasing the sedimentation rate (ca. 3.1cm/ky) within the isolated lake. The temporal coincidence of the onset of uplift-driven valley incision at 3.7Ma along the Yellow River and the onset of basin excavation suggest that uplift possibly played an important role in the late Pliocene-Quaternary drainage evolution. Consequently, incision of the Yellow River upstream in the Jinshaan Gorge initiated at 3.7Ma. [Copyright &y& Elsevier]

Abstract: The competing roles of bedrock uplift and climatic change in the formation of fluvial terraces remain uncertain. Most of recent studies have attributed terrace formation to climatic changes and held that, even in tectonically active settings, climate variations control cycles of terrace planation and abandonment. Based on field investigations of loess-paleosol sequences, magnetostratigraphy and optically stimulated luminescence (OSL) dating, we develop a new chronology for a spectacular flight of terraces along the Yellow River near Lanzhou, China over past 1.24Ma. All the terraces are strikingly similar in that they have several meters of paleosol developed directly above fluvial deposits on the terrace treads, suggesting that the abandonment of each terrace due to river incision occurs during the transition from glacial to interglacial climates. However, the ages of terraces cluster in two relatively short time periods (1.24–0.86Ma and 0.13Ma – present). During the intervening time between 0.86Ma and 0.13Ma, terraces either did not form or were not preserved. We suggest that this record indicates that rock uplift rates varied through time and influenced terrace formation/preservation. Thus, our results demonstrate the utility of deep chronologic records from fluvial terraces for deconvolving the effects of tectonics and climate on fluvial incision. [Copyright &y& Elsevier]

Abstract: Acquisition of high-resolution loess sections allows study of climate change events on sub-orbital time scales. Two high-resolution loess section records from China (Wangguan and Shagou, located east and west of the Liupanshan Mountains, respectively) are compared with the GRIP record to evaluate climatic changes during the last deglaciation. The results show that both sections recorded the Younger Dryas, the Heinrich-1 and the Bølling and Allerød events of the last deglaciation. Loess records of those events occurred almost simultaneously with those recorded in the GRIP. The characteristics of the climate change events in the two loess sections were quite different. It was found that (1) the Heinrich-1 event was more obvious in the Shagou section than in the Wangguan section; (2) the Bølling and Allerød events recorded in the Shagou section have more fluctuations than in the Wangguan section; (3) the Younger Dryas terminated suddenly in the Shagou section whereas in the Wangguan section it came to a gradual end; and (4) the records show a larger fluctuation range and higher frequency on the millennium scale in the Shagou section than in the Wangguan section. It is suggested that the differences were caused by the effects of latitudinal differences. [Copyright &y& Elsevier]

Seven terraces along the Weihe River in Longxi basin have been investigated. These terraces all consist of archetypal duality in structure, namely the floodplain deposits and the layer of gravels overlaid by varying thickness of the bess. By resorting to various dating approaches such as palaeomagnetic, optically stimulated luminescenece (OSL), 14C and loess-paleosol sequence, we provide preliminary timing of these seven terraces along upper Weihe River. Analysis on sedimentation characteristics and dating of these terraces showed that seven terraces may be jointly generated by tectonic uplifts and climatic changes. Tectonic uplifts may accommodate initial river incision, and climatic change may be responsible for processes of subsequent channel widening and aggradation. Aggradation normally occurs during glacial periods, in contrast to down-cuttings during transitions from glacial to interglacial period. Moreover, on the basis of the timings and heights of these terraces, we infer that the long-term rate of river incision was determined to be 0. 2 m/kyr during the last 870 kyr, which differs from other river incision rates. This discrepancy may reflect spatio-temporal differentiation of tectonic activities in the Qinling orogenic belt during the Pleistocene. [ABSTRACT FROM AUTHOR]

Based on the aeolian loess sequence-stratigraphic division and paleomagnetic datings on terraces, we found that an undiscovered terrace with the age of 1.0 Ma BP lies between the Dunwashan terrace and Wuyishan terrace. This terrace recorded an intensive Yellow River incision event during that period. Results of paleomagnetic dating and optically stimulated luminescence (OSL) dating of the Wuyishan loess section and Zaoshugou loess section on the fourth Yellow River terrace (T4) show that the age of the fourth Yellow River terrace in Lanzhou area is 0.86 Ma BP rather than the previously believed 0.6 Ma BP. This result answers a long-term question in the geomorphology community of whether there exists a 0.8 Ma terrace in Lanzhou area. The discovery of the 1.0 Ma Yellow River terrace and redating of the age of 0.6 Ma terrace in Lanzhou area provide new insights into further research on the evolution of Yellow River. [ABSTRACT FROM AUTHOR]

Abstract: The high-resolution Shagou loess section near the northwest limit of the East Asian Summer monsoon, northwest China, was analyzed. The timescale of this section was set up based on a grain size age model and age controls. The record of the Shagou section shows that the millennial-scale oscillations are superimposed on an orbital-scale trend which can be correlated with the variations found in Greenland and the Sulu Sea. Differences in the corresponding Dansgaard–Oeschger cycles between the records in Greenland and the Chinese loess sections, including the orbital-scale trend, the timing and the amplitude, suggest that the climatic signals in Chinese loess might not be singularly regulated by the North Atlantic. The differences in trend and amplitude can be reasonably explained when compared with the Sulu Sea record. This suggests that the western tropical Pacific also exerted an important influence on climatic signals found in the Chinese loess record, possibly countering the impact of high latitude factors during the Last Glacial. [Copyright &y& Elsevier]

Analysis of morphological properties in the San men Gorges region of the Yellow River shows that four river terraces have been developed at the entrance to the gorges. Commonly, thick aeolian loess-paleosol sequence was deposited on the terraces, which makes it easy to date the terraces. The dating of paleomagnetic, loess-paleosol sequence matching and thermoluminescence show that terraces T2, T3 and T4 were formed 0.129 Ma, 0.625 Ma and 0.865 Ma ago, respectively. The formation of these terraces in this region indicates that the Yellow River has experienced four intensive downcutting events during the last 0.9 Ma. The Yellow River cut through the Sanmen Gorges and inpoured into the East China Sea no later than 0.865 Ma. [ABSTRACT FROM AUTHOR]