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[1] We studied the patterns, rates and evolution of fluvial terraces and fault system during the building process of an intracontinental transpressional mountain in the Gobi-Altay (Mongolia). By analyzing incisions and offsets of fluvial terraces and alluvial fans, we show that the massif has grown by outward migration of thrust faults through time. On the northern flank, the present bounding thrust fault began its activity ~600 ka ago, while a more internal sub-parallel fault was still active until ~200-100 ka. Vertical offset of an alluvial fan abandoned ~100 ka ago allows an estimate of 0.1 mm/yr Upper Pleistocene--Holocene uplift rate. The morphology of the catchment-piedmont system strongly suggests a periodical formation of the alluvial surfaces, controlled by the climatic pulses, at the beginning of the wet interglacial periods. The abandonment of the alluvial terraces lags by several thousand years the abandonment of the alluvial fans, showing a diachronous incision propagating upstream. The incision rate deduced from the different elevations of straths exceeds of one order of magnitude the rock uplift rate. This excess is mostly due to ongoing drainage network growth at the core of the massif, and incision due to alluvial apron entrenchment near the outlet. This implies that fluvial response is mainly controlled by drainage growth, interaction with piedmont and cyclic climatic variations, rather than by rock uplift. Citation: Vassallo, R., et al. (2007), Transpressional tectonics and stream terraces of the Gobi-Altay, Mongolia, Tectonics, 26, TC5013, doi: 10.1029/2006TC002081.

SUMMARY We carried out morphotectonic studies along the left-lateral strike-slip Bogd Fault, the principal structure involved in the Gobi-Altay earthquake of 1957 December 4 (published magnitudes range from 7.8 to 8.3). The Bogd Fault is 260 km long and can be subdivided into five main geometric segments, based on variation in strike direction. West to East these segments are, respectively: the West Ih Bogd (WIB), The North Ih Bogd (NIB), the West Ih Bogd (WIB), the West Baga Bogd (WBB) and the East Baga Bogd (EBB) segments. Morphological analysis of offset streams, ridges and alluvial fans-particularly well preserved in the arid environment of the Gobi region-allows evaluation of late Quaternary slip rates along the different faults segments. In this paper, we measure slip rates over the past 200 ka at four sites distributed across the three western segments of the Bogd Fault. Our results show that the left-lateral slip rate is ∼1 mm yr-1 along the WIB and EIB segments and ∼0.5 mm yr-1 along the NIB segment. These variations are consistent with the restraining bend geometry of the Bogd Fault. Our study also provides additional estimates of the horizontal offset associated with the 1957 earthquake along the western part of the Bogd rupture, complementing previously published studies. We show that the mean horizontal offset associated with the 1957 earthquake decreases progressively from 5.2 m in the west to 2.0 m in the east, reflecting the progressive change of kinematic style from pure left-lateral strike-slip faulting to left-lateral-reverse faulting. Along the three western segments, we measure cumulative displacements that are multiples of the 1957 coseismic offset, which may be consistent with a characteristic slip. Moreover, using these data, we re-estimate the moment magnitude of the Gobi-Altay earthquake at Mw 7.78-7.95. Combining our slip rate estimates and the slip distribution per event we also determined a mean recurrence interval of ∼2500-5200 yr for past earthquakes along the different segments of the western Bogd Fault. This suggests that the three western segments of the Bogd Fault and the Gurvan Bulag thrust fault (a reverse fault bounding the southern side of the Ih Bogd range that ruptured during the 1957 earthquake) have similar average recurrence times, and therefore may have ruptured together in previous earthquakes as they did in 1957. These results suggest that the western part of the Bogd Fault system, including the Gurvan Bulag thrust fault, usually behaves in a 'characteristic earthquake' mode. [ABSTRACT FROM AUTHOR]

The Bulnay earthquake of 23 July 1905 (Mw 8.3-8.5), in north-central Mongolia, is one of the world's largest recorded intracontinental earthquakes and one of four great earthquakes that occurred in the region during the twentieth century. The 375 km long surface rupture of the left-lateral, strike-slip, N095°E-trending Bulnay fault associated with this earthquake is remarkable for its pronounced expression across the landscape and for the size of features produced by previous earthquakes. Our field observations suggest that in many areas the width and geometry of the rupture zone is the result of repeated eaxthquakes; however, in those areas where it is possible to determine that the geomoiphic features are the result of the 1905 surface rupture alone, the size of the features produced by this single earthquake are singular in comparison to most other historical strike-slip surface raptures worldwide. Along the 80 km stretch, between 97.18° E and 98.33° E, the fault zone is characterized by several meters width and the mean left-lateral 1905 offset is 8.9 ± 0.6 m with two measured cumulative offsets that are twice the 1905 slip. These observations suggest that the displacement produced during the penultimate event was similar to the 1905 slip. Morphotectonic analyses carried out at three sites along the eastern part of the Bulnay fault allow us to estimate a mean horizontal slip rate of 3.1 ± 1.7 mm/yr over the Late Pleistocene-Holocene period. In parallel, paleoseismological investigations show evidence for two earthquakes prior to the 1905 event, with recurrence intervals of ~2700-000 yrs [ABSTRACT FROM AUTHOR]

To study the interspecific differentiation characteristics of species originating from recent radiation, the genotyping‐by‐sequencing (GBS) technique was used to explore the kinship, population structure, gene flow, genetic variability, genotype–environment association and selective sweeps of Picea asperata complex with similar phenotypes from a genome‐wide perspective. The following results were obtained: 14 populations of P. asperata complex could be divided into 5 clades; P. wilsonii and P. neoveitchii diverged earlier and were more distantly related to the remaining 6 spruce species. Various geological events have promoted the species differentiation of P. asperata complex. There were four instances of gene flow among P. koraiensis, P. meyeri, P. asperata, P. crassifolia and P. mongolica. The population of P. mongolica had the highest level of nucleotide diversity, and P. neoveitchii may have experienced a bottleneck recently. Genotype–environment association found that a total of 20,808 genes were related to the environmental variables, which enhanced the adaptability of spruce in different environments. Genes that were selectively swept in the P. asperata complex were primarily associated with plant stress resistance. Among them were some genes involved in plant growth and development, heat stress, circadian rhythms and flowering. In addition to the commonly selected genes, different spruce species also displayed unique genes subjected to selective sweeps that improved their adaptability to different habitats. Understanding the interspecific gene flow and adaptive evolution of Picea species is beneficial to further understanding the species relationships of spruce and can provide a basis for studying spruce introgression and functional genomics. [ABSTRACT FROM AUTHOR]

The Mongolian Plateau in Central Asia is an intracontinental tectonic system far from active plate boundaries. Despite its distance from these boundaries, the plateau is characterized by intense crustal deformation accompanied by voluminous Cenozoic volcanism and active modern seismicity. However, the intraplate deformation mechanism has long been debated owing to the scarcity of observations and contradictions between different results. In recent years, growing geophysical studies have been conducted on the Mongolian Plateau, providing constraints on its lithospheric structure and dynamics. Here, we review the geophysical research on the Mongolian Plateau over the last decade, including seismological, geodetic, gravity, magnetotelluric, and geodynamic aspects. This review aims to (a) describe crustal and mantle structures based on multiscale seismic images; (b) describe deformation patterns based on seismic anisotropy, focal mechanisms, and global positioning system (GPS) observations; and (c) discuss the mechanisms behind intraplate deformation, volcanism, and seismic activity across the Mongolian Plateau. Seismic images show that the crustal structure of the plateau has significant east-west differences. Several blocks in the western Mongolian Plateau have thick crusts, including the Altai Mountains, Hovsgol Rift, and Hangay Dome. The lithospheric deformation across the Mongolian Plateau has strong lateral variation, with NE-SW shortening in the Altai Mountains and W-E or NW-SE shear deformation in the Hangay Dome region and the eastern part. The varied deformation may result from the superposition of multiple mechanisms, including far-field stress in the Altai Mountains, mantle upwelling, and mantle flow in the Hangay Dome region. However, it is difficult to identify the geodynamics of the formation of the entire Mongolian Plateau because the deformation is too complicated, and the present models are not sufficient and are always partial. Overall, this review encompasses recent advances in seismic observations of the Mongolian Plateau, illuminates the heterogeneities in the crust and mantle structure and deformation of the plateau, and discusses the mechanisms behind the deformation, magmatism, and seismicity. [ABSTRACT FROM AUTHOR]

Eolian sediments are extensively distributed across the Earth's surface, and their formation is intricately linked to climate change, tectonic activity, and topographic features. Consequently, the investigation of eolian sediments bears great geological significance. The northwest region of China is renowned for hosting the most extensive and thickest Late Miocene–Pliocene red clay deposits globally. Nonetheless, scholars have yet to reach a consensus regarding the precise formation processes of these red clays. The identification of the source region of the red clays is crucial for comprehending their formation mechanism. The correlation of zircon U-Pb age spectra is a frequently utilized method for determining the provenance of eolian sediments. In this study, we compared the previously published zircon U-Pb ages (n = 12,918) of the Late Miocene–Pliocene red clays in the Ordos Plateau with those from the potential provenance regions (n = 24,280). The analysis, supported by the tectonic and climatic background of the region, revealed that the Late Miocene–Pliocene red clay in the Ordos Plateau originates predominantly from the Yellow and Wei rivers, with a minor contribution from the weathering of bedrock in the western North China Craton. The transport of these detrital materials by the East Asian winter monsoon is impeded by the presence of the Qinling and Taihang Shan, resulting in their deposition on the flat surface of the Ordos Plateau. This development of red clay is consistent with the proximal accumulation model, illustrating how the hydrosphere, atmosphere, and lithosphere interacted to shape the red clay deposits during the Late Miocene and Pliocene periods in the Ordos Plateau. [ABSTRACT FROM AUTHOR]

Owing to the lack of precise and reliable mineralization ages, the origins of some sandstone-type U deposits (STUDs) are still debated. The unusual texture of U ore (commonly uraninite) and the difference between the chemical characteristics of U and its radiogenic daughter isotopes make U–Pb dating unsuitable for STUDs. However, STUDs are commonly rich in Re; therefore, Re–Os dating may be an alternative. Re–Os dating of two groups of pyrite samples from U ores in the Erlian sandstone-type U district yields two similar ages: 52.5 ± 4.7 and 53.3 ± 3.5 Ma. These ages are consistent with previous U–Pb ages (56.5 ± 7.5 and 63 ± 22 Ma) and demonstrate the reliability of sulfide Re–Os dating of STUDs. The pyrite Re–Os ages suggest that the Erlian STUDs formed at ~53 Ma, corresponding to the regional uplift of the Erlian basin during the Late Cretaceous–Early Eocene and the humid environment in the region during the Early Eocene Climatic Optimum. [ABSTRACT FROM AUTHOR]

Establishing the absolute age of palaeoearthquakes is of great significance for the assessment of the seismicity and seismic hazards of a region. As such, several different geochronological techniques to date earthquake-related material have been developed to provide answers on the time of past earthquakes. The present study is part of a wider palaeoseismic research project conducted in the Nojima Fault Zone (NFZ), where the 1995 Mw 6.9 Kobe (Japan) earthquake was triggered, to assess the suitability of the isothermal thermoluminescence (ITL) dating technique on fine-grained quartz and medium-grained feldspar and to provide a sequence of ages for fault-rock samples separated from a drilled core that was retrieved from a depth of ~506 m. Our analysis reveals that ITL can produce consistent dating results and can be considered a reliable luminescence technique for the absolute dating of fault-gouge material. The produced ITL ages signified the existence of repeated seismic events within the NFZ that took place through the late Pleistocene period, with gouge ages spanning from 78.6 ± 4.2 to 13.4 ± 1.4 ka; however, overestimation of the produced ITL dating results may be apparent. Nonetheless, even though some degree of overestimation is considered, ITL dating results denote the oldest possible age boundary of formation (or luminescence signal resetting) of the collected fault-gouge layers. [ABSTRACT FROM AUTHOR]

The lake depressions in the Mongolian Altai Mountains, and the issues related to their formation have yet to be thoroughly examined in previous research. Previous studies primarily focused on the paleogeographical evolution and glaciation dynamics of the Altai Mountains. This study presents relationships between tectonic and glacial processes that have formed the lake depressions, such as Khoton, Khurgan, Dayan, Khar (western), and Khar (eastern) in the Mongolian Altai Mountains. The depressions of Khoton, Khurgan, and Dayan lakes are situated along regional fault zones, extending in an nortwest-southeast direction, forming intermontane depressions directly connected to the Mongolian Altai Mountains. However, the depressions of Dayan, Khar (western), and Khar (eastern) lakes have been dammed by moraine deposits in the near portion of the depression. The compliance matrix of tectonic geomorphological criteria indicates that the Khoton, Khurgan, Dayan Lake, and Khar (western) Lake depressions are more than 50% compatible. Similarly, the compliance matrix for glacial geomorphological criteria indicates more than 60% compliance for all lake depressions. The Mongolian Altai intermontane depressions are thus of tectonic origin, whereas the lakes have a glacial origin, resulting from dammed moraine sediments. The significance of this work lies in demonstrating how geomorphological research can be employed to provide a detailed understanding of the pattern of lake depressions. [ABSTRACT FROM AUTHOR]

The Khangai plume is situated under Central and Eastern Mongolia and is a mantle volume with significantly reduced longitudinal (P) wave velocities. The plume has been identified as a result of the analysis of the MITP08 volumetric model of P-wave velocity variations, representing the deviations of P-wave velocities from the average values (δVp), given as a percentage. The lithospheric mantle is thinned to ca. 50 km above the plume. Especially low velocities (δVp ≤ –0.6%) are found in the sublithospheric mantle up to a depth of 400 km. The main body of the plume is located under the Khangai Highland and extends northward to the edge of Southern Siberia. The Khentei branch of the plume that is located SE of the Khentei Highland is connected with the main plume body at depths of 800–1000 km. Branches of the plume and its Khentei branch extend into Transbaikalia. The area of the plume decreases with depth, and its deepest part (1250–1300 km) is located under the southern Khangai Highland. The main body of the Khangai plume is expressed on the land surface by the Cenozoic uplift reaching 3500–4000 m in the southern Khangai Highland. From the SE, the Khangai plume and its Khentei branch territory are limited by Late Cenozoic troughs stretching along the southeastern border of Mongolia. From other sides, the Khangai uplift is bounded by a C-shaped belt of basins. The belt includes the southwestern part of the Baikal Rift Zone, the Tunka and Tuva Basins in the north, the Ubsu-Nur Basin and the Basin of Big Lakes in the west, and the Valley of Lakes in the south. The basins are filled with lacustrine and fluvial deposits of the Late Oligocene to Pliocene. In the Quaternary, the South and Central Baikal Basins, which existed as early as the Early Paleogene, became a part of the Baikal Rift, and the other basins were involved in the general uplift of the region. The structural paragenesis of the Khangai uplift and the surrounding basins is caused by the influence of the Khangai plume. On the territory above the plume, including its Khentei and Transbaikalia branches, the Cenozoic basaltic plume volcanism occurred, inheriting the Cretaceous volcanic manifestations in some places. The structural paragenesis associated with the Khangai plume is combined with the structural paragenesis produced by lithospheric plate interaction. The latter is expressed the best of all by active faults, but developed synchronously to the plume paragenesis. The active fault kinematics shows that the eastern and central parts of the region developed in the transpression conditions and the north-eastern part developed in conditions of extension and transtension. The Khangai plume is connected at depth with the Tibetan plume, which is situated under the central and eastern Tibetan Plateau north of the Lhasa block. The Tibetan plume has the shape of a funnel rising from depths of 1400–1600 km and is accompanied by thinning of the lithosphere and uplift of the land surface. The Khangai and Tibetan plumes represent a specific category of plumes. They rise from the upper Lower Mantle and differ by this from the Upper Mantle plumes and the African and Pacific superplumes rising from the core-mantle boundary. Data are presented on the possible connection of the Khangai and Tibetan plumes with the superplume branches, but independent origin of the plumes is also admitted. [ABSTRACT FROM AUTHOR]

The transboundary part of the Altai mountains has been investigated. It is established that it is characterized by a set of geomorphological elements due to the altitudinal position, geological structure, neotectonic activity, modern and paleo-climatic conditions, and exogenous relief-forming processes. In the highlands of the Mongolian Altai, landforms associated with the formation, movement, and melting of ice are widespread. The geological activity of glaciers, the work of melt water, and the presence of permafrost give rise to bright forms. The formation of the appearance of mountain landscapes and the transformation of the surface are associated with actively ongoing slope processes: avalanches, mudflows, landslides, and rock falls. It is found that the objects of cryogenic genesis are landforms differing in scale, structure, and location. They include snow–ice and rock–ice formations, solifluction forms, areas with frost mounds (palza), polygonal and structural soils, aufeis, etc. It is concluded that the most representative objects of cryogenic genesis illustrating the geological work of ice are modern glacial complexes, rock glaciers, and rock streams. Glaciers constitute the main element of the high-mountain zone for complex conjugated cryogenic forms. In addition to them, smaller forms stand out, the formation of which is associated with the processes of soil change under the influence of permafrost and gravitational processes. Regularities are observed in the structure and arrangement of the landforms in the alpine zone. On the basis of information from field routes, satellite data interpretation, and the use of GIS capabilities, we have analyzed the distribution of cryogenic landforms. Material is prepared on the basis of working with a digital elevation model. A list (catalog) of natural cryogenic objects of different categories identified within the Altai Tavan Bogd National Park has been compiled. The study confirms that the landforms of the highlands are of interest for further study, the replenishment of the catalog of objects, and the development of thematic tourism. [ABSTRACT FROM AUTHOR]

Mountain glacier mass balance is affected by factors other than climate, such as topography, slope, and aspect. In midlatitude high-mountain regions, the north–south aspect contrast can cause significant changes in insolation and melt, resulting in local asynchrony in glacial dynamics. This study documents the asynchronous response of two paleoglaciers in southwestern Mongolia to the local topoclimatic factors using 10 Be exposure age dating and 2D ice surface modeling. 10 Be surface exposure age dating revealed that the Ikh Artsan south-facing valley glacier culminated (M IA1) at 20.1 ± 0.7 ka, coinciding with the global Last Glacial Maximum (gLGM). In contrast, the north-facing Jargalant paleoglacier (M J1) culminated at 17.2 ± 1.5 ka, around Heinrich Stadial 1 and during the post-gLGM Northern Hemisphere warming. Our temperature-index melt model predicts that ablation will be substantially lower on the north-facing slope, as it is exposed to less solar radiation and cooler temperatures than the south-facing slope. The 2D ice surface modeling also revealed that the south-facing Ikh Artsan Glacier abruptly retreated from its maximum extent at 20 ka, but the Jargalant Glacier on the shaded slope consistently advanced and thickened due to reduced melt until 17 ka. The timing of the modeled glacier culmination is consistent within ± 1 σ of the 10 Be exposure age results. Extremely old ages ranging from 636.2 to 35.9 ka were measured for the inner moraines in the Jargalant cirque (M J2 –M J4), suggesting a problem with inheritance from boulders eroded from the summit plateau. [ABSTRACT FROM AUTHOR]

The north-striking sinistral reverse Papatea Fault ruptured with a very large (up to 12 m) oblique slip as part of the 2016 MW 7.8 Kaikōura earthquake in the northeastern South Island. Paleoseismic studies were undertaken at three sites along the Papatea Fault, named Murray's roadcut, Jacqui's Gully (both on the main strand), and Wharekiri trench (western strand). These sites provide evidence for up to three Late Holocene paleoearthquakes prior to 2016 (=E0) on this previously unmapped active fault, with preferred OxCal-modelled timings of 98–149 (E1), 546–645 cal yr BP (E2), and >738 cal yr BP (E3). Event correlations between the sites are generally consistent across these past events, implying that the two strands of the Papatea Fault link at depth and rupture together co-seismically as in 2016. Comparisons of its paleoseismic record with the Kekerengu Fault and uplift data from Waipapa Bay and Kaikōura, suggest that the Papatea Fault may have three distinct rupture modes: (i) Kaikōura-type multi-fault ruptures with multi-metre, anelastic block displacements and associated major landscape change; (ii) multi-fault earthquake ruptures with other regional fault combinations; and (iii) single-fault Papatea ruptures with metre-scale displacement. OxCal models offer the possibility that the E1 fault rupture occurred in 1855 CE. [ABSTRACT FROM AUTHOR]

Fluvial terrace formation is a complex process governed by the interplay of climatic and tectonic forcings. From a climatic perspective, an incision is usually related to climatic transitions, while valley aggradation is attributed to glacial periods. We have reconstructed the formation of Late Pleistocene fluvial terraces along the middle, mountainous section of a temperate zone river (Mureş/Maros) in order to identify the roles of different climatic periods and potential vertical displacement in terrace development. Investigations were based on two profiles representing two different terrace levels. The profiles were subjected to sedimentological and detailed geochronological analyses using optically stimulated luminescence (OSL). The results indicated that the investigated terraces represent different incision events coinciding with climatic transition periods. However, a joint MIS 3 valley aggradation period can be identified at both of them. Thus, the relatively mild but highly variable climate of the MIS 3 facilitated sediment mobilization from upland catchments. On the other hand, there is no evidence of aggradation under the cold and stable climate of MIS 2. However, the tectonic setting favours incision at the site. Based on our results, we concluded that the timing of the main events was controlled primarily by climatic forcing. The terrace formation model recognised might also be applied at other rivers in the region. [ABSTRACT FROM AUTHOR]

The Altai is an enigmatic, relatively young mountain belt with sharp relief (up to 4,500 m high) that developed thousands of kilometers away from the nearest current plate margins. The Fuyun area, at the interface between the southern margin of the Chinese Altai and the Junggar Basin, represents a key locality for understanding the Meso‐Cenozoic deformation and exhumation history of the Altai. The complex structural architecture of the Fuyun area suggests that multiple deformation events affected the area, which ultimately led to the exhumation of the Altai. Furthermore, the area hosts orogenic‐type mineralization, suggesting a history of fluid alteration. However, in contrast to the well‐constrained Palaeozoic history, the timing of Meso‐Cenozoic deformation, metasomatism and exhumation has not been comprehensively studied. This study presents new apatite U‐Pb, trace element and fission track data for the Fuyun area and integrates these with previous studies for the Altai to shed more light on the Meso‐Cenozoic tectonic history. The apatite U‐Pb dates, associated with LREE‐depleted trace element profiles, suggest that a phase of Middle–Late Jurassic (∼170–160 Ma) metasomatism affected the Keketuohai area, which is potentially linked to the timing of rare‐metal mineralization. The apatite fission track results and thermal history models reveal rapid early Late Cretaceous (∼100–75 Ma) cooling linked to tectonic exhumation throughout the Chinese Altai, associated with distant plate‐margin processes. In addition, samples taken in vicinity to the frontal thrusts of the Altai record evidence for Cenozoic partial resetting of the apatite fission track system. Plain Language Summary: The Altai Mountains are a high elevation, sharp relief mountain belt within central Asia. Despite their location thousands of kilometers from the present day plate margin, the Altai preserve young mountains induced by tectonic forces originating at the plate boundaries. Integrating new low‐temperature data with existing studies reveals extensive uplift of the Altai during the Late Cretaceous, induced by the reactivation of major structures. A subsequent pulse of Cenozoic uplift further developed the topography observed today. In addition to mountain building, alteration of crystalline rocks associated with mineralization has also been observed. The chemical signatures within apatite grains suggests they grew from a fluid that altered the crystalline rocks, which may have links to nearby economic mineralization. Key Points: The Fuyun area records Jurassic metasomatism in apatites corresponding to the timing of hydrothermal rare‐metal mineralizationLate Cretaceous rapid cooling is preserved throughout the Altai, coeval with km‐scale deposition of coarse sediments in adjacent basinsThe Altai shows partial fission track resetting in the Cenozoic during India‐Eurasia convergence, where exhumation has outpaced denudation [ABSTRACT FROM AUTHOR]

The thrust nappe played an important role in the Mesozoic tectonic evolution of the middle part of the Central Asian Orogenic Belt (CAOB). However, the timing, structural style and kinematic processes of the thrust nappe remain controversial, particularly the detail of the thrust nappe in the Guaizihu region (110 km east of Ejinaq). In this study, we investigate new field mapping, seismic sections, geochronology and low‐temperature thermochronometric dating to provide constraints on the history of this thrust nappe in the Chaheilingashun area (northwestern Guaizihu region). The field mapping, seismic sections and structural analysis reveal that the autochthonous system had developed a series of strong fold structures in the upper Permian strata. The allochthonous system mainly contains Devonian monzogranite (U‐Pb age, ranges from 386.7 to 389.0 Ma) and Meso–Neoproterozoic schists (the maximum depositional age, ∼880 Ma), which were thrust upon the upper Permian strata during Middle to Late Triassic. Based on similar rocks, geochronological dating and the Yagan thrust, we suggest that the postulated root zone of this allochthon might have originated from the Huhetaoergai area (40–60 km northwest of the study area). The geochronological results reveal that the lower age limit of this thrust nappe is constrained by the Lower–Middle Triassic syntectonic sediments (tuffaceous sandstone, ∼247 Ma), which is the sedimentary response of the fold structure., The timing of the termination of this thrust nappe is defined by the cooling age (40Ar/39Ar data, 217–211 Ma) of the Devonian monzogranite and Meso–Neoproterozoic schists. Thus, we consider this thrust event in the study area to potentially have occurred in the period from 247 Ma to 211 Ma, which may represent the tectonic response to the closure of the Paleo‐Asian Ocean. [ABSTRACT FROM AUTHOR]

Most mid-latitude mountain glaciers reached their maximum extent around the global Last Glacial Maximum (gLGM). However, some also strongly responded to the regional climate change or local non-climatic factors such as topography, leading to asynchronous maximum advances. This study documents the maximum extent and chronology of two paleoglaciers in the Ih Bogd massif of Mongolia: one facing north into the Jargalant Valley and the other facing south into the Ih Artsan valley. 10Be surface exposure age dating revealed that the Ih Artsan short valley glacier reached its maximum position (MIh1) around 20.1 ± 0.7 ka, coinciding with the gLGM. In contrast, the Jargalant paleoglacier (MJ1) reached its maximum extent around 17.2 ± 1.5 ka, around Heinrich 1 stadial and during the post-gLGM northern hemisphere warming. Our 2D ice surface model, which includes the temperature-index melt model, suggests that an aspect can result in a melt difference between north and south-facing slopes. Glaciers retreated from their maximum modeled extent asynchronously when we assign a 0.5° lower temperature for Jargalant valley (northern slope), based on the observation that present-day mean annual Jargalant temperatures are lower than in the south-facing Ih Arstan. Modelled timing of the maximum extents (20.23 ka in Ih Artsan, 17.13 ka in Jargalant) are consistent with 10Be exposure age results (20.1 ka in Ih Artsan, 17.2 ka in Jargalant). We also observed several sequences of post LGM or/and Holocene moraines in both cirques. Extremely old ages ranging from 636.2 ka to 35.9 ka were measured for the inner moraines in the Jargalant cirque (MJ2-MJ4), suggesting a problem with inheritance from boulders eroded from the summit plateau. [ABSTRACT FROM AUTHOR]

The southern Great Xing'an Range in southeastern Inner Mongolia, north of the North China Craton, is a region influenced by different tectonic regimes. The Mesozoic–Cenozoic geological and topographic evolution remains controversial. In this study, we decipher the thermal evolution of the southern Great Xing'an Range by applying zircon and apatite (U-Th)/He and apatite fission-track thermochronology to granitoids to constrain the history of exhumation induced by the superposition of different tectonic activities and the history of geomorphological evolution. Zircon (U-Th)/He dating yields Early Cretaceous ages (109.1–134.9 Ma) and one early Permian age (292.0 Ma). Apatite (U-Th)/He dating and fission-track dating yield Early Cretaceous to early Late Cretaceous ages of 89.8–117.6 and 97.8–99.9 Ma, respectively. Combining these ages with previously published zircon U-Pb data and thermal history modeling, we suggest that the southern Great Xing'an Range experienced rapid cooling and exhumation during the Early Cretaceous. This cooling stage coincided with widespread extensional tectonics in northeastern China, which are thought to have been induced by the postorogenic collapse of thickened crust associated with the Mongol-Okhotsk Ocean and backarc extension associated with subduction of the Paleo-Pacific plate. This study implies that the southern Great Xing'an Range does not record significant exhumation during the Cenozoic. [ABSTRACT FROM AUTHOR]

The Tannuola Terrane of Tuva, which is located in the northern part of the Central Asian Fold Belt, formed as a result of island-arc and accretionary-collision events in the Early Paleozoic. Further tectonic evolution of the terrane is related to a multiple reactivations of large and mostly normal fault structures. In the middle Paleozoic, the extension of the crystalline basement of the terrane led to the active uplift of mafic melts along the faults to the surface and formation of subalkaline igneous rocks. The Mesozoic and Cenozoic igneous complexes within the Tannuola Terrane are unknown; thus, its tectonic evolution in the Mesozoic and Cenozoic could be considered only after a sedimentary record, which is preserved in the Mesozoic intermountain depressions of Tuva and adjacent Cenozoic Ubsunur Basin. This geological information, however, is insufficient for an exhaustive consideration of the regional tectonic regime taking into account the lack of confirmation of present-day precise methods. The understanding the Mesozoic–Cenozoic tectonic evolution of the Tannuola Terrane is impossible without the analysis of data on low-temperature thermochronology for rocks of the crystalline basement. In our study, fission-track analysis of apatite from 12 samples of the early Paleozoic granitoids of the Tannuola Terrane is conducted in order to recognize the stages of activation and tectonic stability within the absolute time scale. The analysis showed a wide range of ages from 83.4 ± 4.7 (Late Cretaceous) to 35.5 ± 2.2 (late Eocene) Ma at variation of the mean fission-track length from 11.4 to 12.3 µm. The modeling of the thermal evolution of the basement of the Tannuola Terrane, which is based on these data, indicated three stages of tectonic activation of various origins and intensities divided by stages of tectonic quiet periods for the last ~185 million years: (i) ~185–135 Ma (Jurassic–Cretaceous), (ii) ~90–35 Ma (Cretaceous–Paleogene), and (iii) ~15–0 Ma (Neogene–Quaternary). [ABSTRACT FROM AUTHOR]

A large proportion (∼80%) of the Indian subcontinent's precipitation comes from the Indian summer monsoon (ISM), which influences one‐fifth of the world's population. A long‐term reliable proxy for ISM is fundamental to understanding previous global climate change. We establish a mass‐wasting‐inferred proxy to examine the paleo‐hydrogeology (river undercutting history) of the Southeast Tibetan Plateau and reconstruct the dramatic variability of ISM intensity (precipitation) in the past 130,000 years. Our data suggest that mass‐wasting events, which provides us sufficient samples for paleoclimate research, are prone to dramatic climate changes, especially extreme climate environments. The Southeast Tibetan Plateau was subjected to at least four distinct ISM intensity phases in the past 130,000 years. We conclude that ISM intensity has a cyclicity featured by the Earth's orbit with obliquity, and that ISM intensity transition lags the global ice volume (sea level) change by 8–15 kyrs. Plain Language Summary: The role of Indian summer monsoon (ISM) in the global climatic conditions has attracted considerable research attention. We reported a new long‐term proxy collected in Tibetan Plateau mass‐wasting deposits for ISM reconstruction, which is significant for coupling of tectonic evolution of Asia and global climate change in the context of global warming. This study has revealed the mutuality of paleo‐mass‐wasting events and climate changes, which confirms the relationship between surge of mass‐wasting events and global climate change (warming and increasing precipitation). ISM variability derived in our work for the last 130,000 years deduces new views of cyclicity and lag characteristics of ISM intensity. Key Points: The correlation between the occurrence of mass‐wasting deposits and the dramatic global climate changes is revealedThe variability of Indian summer monsoon (ISM) is reconstructed based on our proposed mass‐wasting‐inferred proxyNew views of cyclicity and lag characteristics of ISM intensity are deduced based on the variability of ISM intensity [ABSTRACT FROM AUTHOR]

We present first constraints from tectonic geomorphology and paleoseismology along the newly discovered Sharkhai fault near the capital city of Mongolia. Detailed observations from high-resolution Pleiades satellite images and field investigations allowed us to map the fault in detail, describe its geometry and segmentation, characterize its kinematics, and document its recent activity and seismic behavior (cumulative displacements and paleoseismicity). The Sharkhai fault displays a surface length of ∼ 40 km with a slightly arcuate geometry, and a strike ranging from N42 to N72 ∘. It affects numerous drainages that show left-lateral cumulative displacements reaching 94 m. Paleoseismic investigations document faulting and depositional/erosional events for the last ∼ 3000 years and reveal that the most recent event occurred between 775 and 1778 CE and the penultimate earthquake occurred between 1605 and 835 BCE. The resulting time interval of 2496 ± 887 years is the first constraint for the Sharkhai fault for large earthquakes. On the basis of our mapping of the surface rupture and the resulting segmentation analysis, we propose two possible scenarios for large earthquakes with likely magnitudes of 6.7 ± 0.2 or 7.1 ± 0.7. Furthermore, we apply scaling laws to infer coseismic slip values and derive preliminary estimates of long-term slip rates. Finally, these data help build a comprehensive model of active faults in that region and should be considered in the seismic hazard assessment for the city of Ulaanbaatar. [ABSTRACT FROM AUTHOR]

The Hangay Dome in central Mongolia, a typical intraplate plateau far from plate boundaries, is characterized by rapid uplift and widespread volcanic activities in the Cenozoic. However, thermodynamics process for the landform in Cenozoic remains mysterious. Seismic Lg-wave, which is sensitive to crustal thermal status, can provide constraints on the crustal attenuation structure; thus, may be helpful to understand the thermodynamics. In this study, we estimate the Lg-wave quality factor QLg across the Hangay Dome and its surroundings from 231 crustal earthquakes recorded by 136 regional broadband seismic stations distributed throughout north China and Mongolia. Using a joint tomographic method, we construct a broadband Lg attenuation model at 58 discrete frequencies distributed evenly in log scale between 0.1 and 20.0 Hz. The obtained QLg model provides new insights into crustal attenuation in the region. The strong Lg wave attenuation observed in the northeastern Hangay Dome and western Gobi-Altai, associated with crust low-resistivity anomalies, low S-wave velocity region, heat flow and volcanic activities, suggest the existence of possible partial melting due to asthenospheric upwelling. The widespread moderately-low QLg values around the perimeter of the Hangay Dome imply that the margin of the Hangay Dome has been weakened. The center part of the uplift is a small high QLg nucleus, which is possibly the residue of the Precambrian basement. The above observations suggest that the Hangay Dome is lifted by small-scale asthenospheric upwellings. During this process, the very hot mantle materials strongly modified the Hangar Dome and also caused the Cenozoic volcanism and major earthquakes. [ABSTRACT FROM AUTHOR]

The western North China Craton (NCC) entered a stage of craton thinning concentrated on its margin in the Cenozoic, but its Late‐Cretaceous conditions were previously deduced to be relatively quiescent. Therefore, whether the Late‐Cretaceous tectonic reactivation existed on the margin of this block is critical to understanding how the craton evolved into a thinned one. To investigate this possible margin reactivation in the Late Cretaceous, we apply zircon (U‐Th)/He thermochronology to Taibai Mountain on the southern margin of the western NCC. From an ∼3‐km‐high vertical profile with ages decreasing from 98 ± 5 Ma at the peak to 52 ± 7 Ma at the foot, the age‐elevation relationship suggests the rapid exhumation at ca. 78–71 Ma bracketed by two slow exhumation phases. This interpretation is confirmed by 1D half‐space modeling and QTQt inverse modeling, with the rapid exhumation stage having an exhumation rate of 0.1–0.6 km/Myr and a cooling rate of ∼10°C/Myr. Together with previously reported thermochronological data from the margin of the western NCC, the rapid exhumation at ca. 78–71 Ma implies a reactivated margin in the Late Cretaceous before widespread Cenozoic thinning of the craton margin. This Late‐Cretaceous reactivation likely resulted from WNW‐ESE extension expressed by thermo‐tectonic events, basin subsidence, and volcanism in East Asia. Excluding impacts from climate change, lithospheric delamination, and India subduction beneath Eurasia, we infer that the Late‐Cretaceous reactivation on the margin of the western NCC was driven by the far‐field effect of Izanagi Plate subduction beneath the Eurasian Plate during slab rollback of the subducted plate. Key Points: Rapid exhumation of Mt. Taibai at ca. 78–71 Ma is confirmed by the age‐elevation relationship, 1D half‐space modeling, and QTQt modelingSynchronous Late‐Cretaceous rapid exhumation suggests a reactivated margin of the western North China Craton before Cenozoic thinningThis reactivation was triggered by the far‐field effect of Izanagi Plate subduction beneath the Eurasian Plate [ABSTRACT FROM AUTHOR]

The μ Dose system is a recently developed analytical instrument applying a combined α - and β -sensitive scintillation technique for determining the radioactivity arising from the decay chains of 235U , 238U and 232Th as well as from the decay of 40K. The device was designed to meet the particular requirements of trapped charge dating methods and allows the assessment of environmental (i.e. low) levels of natural radionuclides. The μ Dose system was developed as a piece of low-cost laboratory equipment, but a systematic test of its performance is still pending. For the first time, we present results from a comprehensive performance test based on an inter-laboratory comparison. We compare the results obtained with μ Dose measurements with those from thick source alpha counting (TSAC), inductively coupled plasma optical emission spectrometry (ICP-OES) and low-level high-resolution gamma spectrometry (HRGS) applied in five participating laboratories. In addition, the reproducibility and accuracy of μ Dose measurements were tested on certified reference materials distributed by the International Atomic Energy Agency (IAEA; RGU-1, RGTh-1 and RGK-1) and on two loess standards (Nussy and Volkegem) frequently used in trapped charge dating studies. We compare μ Dose-based results for a total of 47 sediment samples with results previously obtained for these materials by well-established methods of dose rate determination. The investigated natural samples cover a great variety of environments, including fluvial, aeolian, littoral, colluvial and (geo-)archaeological sites originating from high and low mountain regions as well as from lowlands in tropical areas, drylands and mid-latitude zones of Europe, Africa, Australia, Central Asia and the Americas. Our results suggest the μ Dose system's capability of assessing low-level radionuclide contents with very good accuracy and precision comparable to well-established dosimetry methods. Based on the results of our comparative study and with respect to the practical experiences gained so far, the μ Dose system appears to be a promising tool for trapped charge dating studies. [ABSTRACT FROM AUTHOR]

The Northeastern Gobi Altai region of Mongolia contains a wide range of impressive geological features of unique and superlative value that comprise an important geoheritage meriting long-term protection. World-class examples of earthquake rupture zones, restraining bend massifs, dinosaur fossil localities, volcanic landforms, large landslides, and other interesting geological and geomorphological features are concentrated in a single region that includes the southern flanks of the Hangay Dome, the Mongolian Valley of Lakes, and the NE Gobi Altai mountains. In addition, the region includes important endemic flora and fauna in diverse and in some cases, threatened ecosystems. The NE Gobi Altai is also an important geo-cultural region; traditional nomadic pastoralists have lived in the area for millennia closely connected to the region’s geology, landscapes, and natural resources. The region’s geoheritage and geo-culture face modern development threats including resource exploration/production, overgrazing, unregulated tourism, and lack of environmental management. It is recommended that the region be evaluated for Geopark status under the UNESCO umbrella to preserve its natural assets. If successful, the NE Gobi Altai region would be Mongolia’s first Geopark and could stimulate interest in a long-term conservation strategy for other Mongolian regions with important geoheritage. In this report, the scientific, educational and aesthetic value of the NE Gobi Altai is summarized and illustrated to raise international awareness of its valuable geoheritage. [ABSTRACT FROM AUTHOR]

Central Asia hosts the most extensive and highest topography on Earth, which is the result of the feedbacks among rock uplift, atmospheric circulation and moisture transport, and erosion. Here, we analyze 2,511 published low‐temperature thermochronometric ages as a proxy of the regional‐scale erosion of Central Asia. We compare these ages to tectonic and climate proxies, and state‐of‐the‐art paleoclimate simulations to constrain the influences of climate and tectonics on the topographic architecture of Central Asia. We observe a first‐order relationship between younger cooling ages in areas of high precipitation and older ages (Mesozoic) in areas that have been sheltered from precipitation, despite high strain rates. Thus, we suggest that climate enhances erosion in areas where rock uplift produces significant orographic gradients, whereas in the continental interior, areas which are tectonically active but have been sheltered from significant precipitation record older ages and a longer erosional history. Plain Language Summary: Modern topography represents the product of the relationships among climate, tectonics, and erosion through time. Central Asia is one of the most topographically diverse regions on Earth. However, the relative role of tectonics versus climate on erosion of continental Asia remains one of the major debates in Earth sciences. One way to investigate this is through the analysis of erosional proxies. In this study, we present the first regional‐scale analysis of thermochronometric ages from Central Asia as a proxy of erosion. We compare these data to tectonic processes, climate proxies, and state‐of‐the‐art paleoclimate simulations in order to constrain the relative influences of climate and tectonics on the topographic architecture and erosion of Central Asia. There is a first‐order relationship between more recent erosion and active tectonic boundaries. However, more recent erosion is also associated with areas of high precipitation, whereas areas that have been sheltered from significant precipitation retain a signal of older erosional events. Thus, we suggest that climate plays a key role in enhancing erosion in areas with developed topography and high precipitation, whereas areas which experienced sustained aridity record less erosion and preserve a record of older erosion. Key Points: Despite the magnitude of the India‐Asia collision, erosion throughout Central Asia reflects Phanerozoic tectonicsRegions of "old" erosion are preserved in more arid areas, whereas more recent erosion is concentrated in areas of high precipitationTectonic mechanisms are required to initiate erosion; however, climate modulates the magnitude of erosion [ABSTRACT FROM AUTHOR]

Intracontinental deformation is an inseparable element of the evolutionary history of orogenic belts. It can reactivate and intensely modify the structures of previous orogenic belts due to remote effects of plate margin orogenesis. As an important part of the Phanerozoic Central Asian Orogenic Belt (CAOB), the Alxa Block and its vicinity experienced multistage intracontinental deformation during the Mesozoic and Cenozoic and became a representative region to study remote effects from plate margins. Both the previous structures of the CAOB and continuous accretion to the Eurasian continent from different directions controlled and affected the Mesozoic evolution of the Alxa Block. However, mantle loading can't pertinently explain the geological phenomena alone. In the Late Triassic, the Alxa Block was deformed by large-scale left-lateral shearing along largely northeast-southwest-trending faults and rotated anticlockwise caused by the collision between the North China Craton and Yangtze Craton and the northward movement of the North China Craton. In the Late Jurassic, the low-angle westward subduction of the Paleo-Pacific Ocean beneath the Eurasian Plate, the closure of the Mongol-Okhotsk Ocean to the north and/or the Lhasa-Qiangtang collision to the south combined to deform the Alxa Block from different directions, forming contraction structures with various strikes and invert previous extensional basins. In the Late Cretaceous, the Eurasian Plate experienced oblique collision along its southeastern margin and the subduction of the Neo-Tethys along its southern boundary, an intraplate sinistral transpressional megashear system developed along the eastern Alxa Block, and the uplift of mountain ranges along the basin margins. The multistage Mesozoic intracontinental deformation of the Alxa Block supports the view that they are driven by stresses generated at plate boundaries largely, and controlled by previous complicated orogenic structures in the upper crust. [ABSTRACT FROM AUTHOR]

The evolutionary history of organisms with poor dispersal abilities usually parallels geological events. Collisions of the Indian and Arabian plates with Eurasia greatly changed Asian topography and affected regional and global climates as well as biotic evolution. However, the geological evolution of Asia related to these two collisions remains debated. Here, we used Eranthis, an angiosperm genus with poor seed dispersal ability and a discontinuous distribution across Eurasia, to shed light on the orogenesis of the Qinghai–Tibetan, Iranian and Mongolian Plateaus. Our phylogenetic analyses show that Eranthis comprises four major geographical clades: east Qinghai–Tibetan Plateau clade (I-1), North Asian clade (I-2), west Qinghai–Tibetan Plateau clade (II-1) and Mediterranean clade (II-2). Our molecular dating and biogeographic analyses indicate that within Eranthis, four vicariance events correlate well with the two early uplifts of the Qinghai–Tibetan Plateau during the Late Eocene and the Oligocene–Miocene boundary and the two uplifts of the Iranian Plateau during the Middle and Late Miocene. The origin and divergence of the Mongolian Plateau taxa are related to the two uplifts of the Mongolian Plateau during the Middle and Late Miocene. Additionally, our results are in agreement with the hypothesis that the central part of Tibet only reached an altitude of less than 2.3 km at approximately 40 Ma. This study highlights that organismal evolution could be related to the formation of the three great Asian plateaus, hence contributing to the knowledge on the timing of the key tectonic events in Asia. [ABSTRACT FROM AUTHOR]

Crustal architecture strongly influences the development and emplacement of mineral zones. In this study, we image the crustal structure beneath a metallogenic belt and its surroundings in the Bayankhongor area of central Mongolia. In this region, an ophiolite belt marks the location of an ancient suture zone, which is presently associated with a reactivated fault system. Nearby, metamorphic and volcanic belts host important mineralization zones and constitute a significant metallogenic belt that includes sources of copper and gold. However, the crustal structure of these features, and their relationships, are poorly studied. We analyze magnetotelluric data acquired across this region and generate three-dimensional electrical resistivity models of the crustal structure, which is found to be locally highly heterogeneous. Because the upper crust (< 25 km) is found to be generally highly resistive (> 1000 Ωm), low-resistivity (< 50 Ωm) features are conspicuous. Anomalous low-resistivity zones are congruent with the suture zone, and ophiolite belt, which is revealed to be a major crustal-scale feature. Furthermore, broadening low-resistivity zones located down-dip from the suture zone suggest that the narrow deformation zone observed at the surface transforms to a wide area in the deeper crust. Other low-resistivity anomalies are spatially associated with the surface expressions of known mineralization zones; thus, their links to deeper crustal structures are imaged. Considering the available evidence, we determine that, in both cases, the low resistivity can be explained by hydrothermal alteration along fossil fluid pathways. This illustrates the pivotal role that crustal fluids play in diverse geological processes, and highlights their inherent link in a unified system, which has implications for models of mineral genesis and emplacement. The results demonstrate that the crustal architecture—including the major crustal boundary—acts as a first‐order control on the location of the metallogenic belt. [ABSTRACT FROM AUTHOR]

Two Cenozoic prominent features are spatio-temporally associated in central Mongolia, i.e., the continental basalts and regional uplift, but their genesis and relationship remain unclear. This study presents major- and trace-element compositions for olivine phenocrysts and xenocrysts, as well as data of bulk-rock geochemistry and Sr-Nd-Hf isotopes for the host basalts. The studied basalts mostly have trachybasalt compositions with high total alkali (Na2O + K2O = 5.1–8.2 wt%) contents and all display OIB-like trace element patterns (e.g., spikes of Ba, Nb, and Ta and troughs of Th and U) and EM1-like Sr-Nd-Hf isotopic compositions. Compared to the partial melting products of mantle peridotite, these basaltic samples have higher FeO/MnO, Zn/Mn, and Zn/Fe ratios. Meanwhile, phenocrystic olivines are characterized by lower Ca, Mn, Mn/Zn, and Mn/Fe but higher Ni than their counterparts in the peridotitic melts, indicating a pyroxenite-rich mantle source. The above geochemical data suggest that the source of the studied basalts was mainly made up of secondary pyroxenite produced by the reaction of recycled oceanic crust with its ambient mantle peridotite. The calculated magma oxygen fugacities (ΔFMQ-0.26 to +0.42) and mantle melting temperatures (1343–1430 °C) do not support a genetic link with the stagnant Pacific slab or with a deep mantle plume. Instead, the far-field effect of India-Eurasia convergence possibly tapped the upper asthenospheric mantle, subsequent melting of which gave rise to the dispersive Cenozoic basalts. On the other hand, the xenocrystic olivines exhibit zoned textures with high-Fo (up to 92) cores and low-Fo (down to 76) rims, reflecting the melt-rock interaction. Preservation of zoned olivine xenocrysts indicates rapid magma ascent and widespread melt-rock reaction in the mantle lithosphere, which may modify the rheology and accelerate the mechanical erosion of mantle lithosphere. Consequently, mass deficit in the lithosphere could have caused isostatic uplift of central Mongolia in the Cenozoic. [ABSTRACT FROM AUTHOR]

The Ovacık Fault (OF) is one of the internal structures of the Anatolian Block, located close to its eastern boundary. Although it shows a very clear surface trace, there are no instrumentally recorded surface rupturing earthquakes on this fault. This study concludes results of the first palaeoseismological trench study on the OF with the evidence for three surface rupturing earthquakes for the last 6 kyr. Structural, stratigraphical and geochronological constraints show that the oldest event happened between 4700 and 3022 BCE, whereas the penultimate event was between 2262 and 1643 BCE. The youngest event happened after 56 BCE, which we could only delimit from below because of the absence of any dateable material from the upper layers of the relevant horizons. The derived mean interevent time of these three palaeoevents is 2400 ± 765 years. We could not correlate any of these palaeoevents with historical earthquakes due to the absence of records in catalogues for the region of interest. Moreover, we used cumulative offsets of the major drainages to calculate the long-term slip rate of 2.7 mm/year since the Pliocene, which exceeds slip rates of other internal faults of Anatolia almost by the factor of two. Our results do not only show significant deformation for the internal parts of Anatolia but also point out a seismic potential of the OF. [ABSTRACT FROM AUTHOR]

The siliciclastic rocks in the Xishanyao (XSY) and Toutunhe (TTH) formations recorded the Middle Jurassic palaeogeographic evolution processes of the Bogda Mountains. To explore their provenance, the geochronological, geochemical, and petrological characteristics of the Middle Jurassic sandstones from the west Bogda area are analyzed in this study. The detrital grains of sandstones are generally poorly to moderately sorted and subangular to subrounded. Low to moderate CIA* (chemical index of alteration), PIA (plagioclase index of alteration), CIW (chemical index of weathering) and relatively high ICV (index of compositional variability) values indicate the overall low to moderate weathering intensity, low sediment recycling, and abundant first-cycle siliciclastics supply. The abundant acid volcanic lithic fragments and element contents/ratios of the sandstones indicate source areas dominated by felsic rocks. The detrital zircon U-Pb age spectrum of the lower XSY Formation is dominated by a single Carboniferous age group. Multiple Palaeozoic zircon U-Pb age groups exist in the middle-upper XSY Formation. The TTH Formation has a typical age of late Middle Jurassic. Combined with the sedimentological characteristics, it reveals that (1) the Eastern Bogda Mountains (EBM) were the only provenance for the lower XSY Formation; (2) both the Yemaquan arc and the EBM provided detritus for the middle XSY Formation; (3) the Yemaquan arc became a minor provenance for the TTH and upper XSY formations. Middle Jurassic palaeogeographic evolution in the EBM is inferred as follows: (1) during the deposition of the lower XSY Formation, the EBM suffered a rapid uplift and became an obvious positive relief; (2) the palaeorelief became high in the Yemaquan arc area and low in the EBM during the deposition of the middle XSY Formation; (3) the Yemaquan arc was considerably eroded, which caused the palaeotopography to decline sharply during the deposition of the upper XSY Formation; (4) the EBM uplifted again during the TTH Formation period, accompanied by volcanic activities at ~165Ma. [ABSTRACT FROM AUTHOR]

Moderate-large earthquakes usually trigger a large number of landslides. The prehistoric large landslides can be analyzed to determine the probability of its seismic origin, and further recognized as an indicator of fault activity and earthquake intensity. Based on field investigation, high-resolution satellite image interpretation and cosmogenic exposure dating of landslide deposit, the paper presents a large, long-runout Luanshibao rock avalanche (the LSB rock avalanche), southeast Tibet. The study reveals that (1) the LSB rock avalanche straddles the Litang active strike-slip fault and deposits on the open-flat Quaternary Maoya basin, with a deposit volume of 67 Mm3 and an apparent coefficient of friction of 0.22. (2) Totally, 8 granite blocks from the proximal to the medial part of deposit dated by the Terrestrial Cosmogenic Nuclide method suggests an average 10Be exposure age of 3510 ± 346 a B.P. for the LSB rock avalanche; (3) the spatial-temporal intercutting relationships among the LSB rock avalanche, Quaternary sediments, and the Litang active fault suggest five strong paleoseismic events in the Maoya basin, which is temporally in accordance to the result defined by paleoearthquake-trench research; (4) the corresponding maximum magnitude could reach MW 7.1 ± 0.1 by the empirical equations between landslide volume and earthquake magnitude. It suggests that the Maoya section of Litang fault is probably more dangerous than other sections due to the high density of large co-seismic landslides, which could present useful reference for the alignment selection of future Sichuan-Tibet railway. [ABSTRACT FROM AUTHOR]

The Yucatán Peninsula, Mexico, has typically been considered a tectonically stable region with little significant seismic activity. The region though, is one that is regularly affected by hurricanes. A detailed survey of ca 100 km of the eastern Yucatán and Cozumel coast identified the presence of ridges containing individual boulders measuring >1 m in length. The boulder ridges reach 5 m in height and their origin is associated with extreme wave event activity. Previously modelled tsunami waves from known seismically active zones in the region (Muertos Thrust Belt and South Caribbean Deformed Belt) are not of sufficient scale in the area of the Yucatán Peninsula to have produced the boulder ridges recorded in this study. The occurrence of hurricanes in this region is more common, but two of the most destructive (Hurricane Gilbert 1988 and Hurricane Wilma 2005) produced coastal waves too small to have created the ridges recorded here. In this paper, a new tsunami model with a source area located on the Motagua/Swan Island Fault System has been generated that indicates a tsunami event may have caused the extreme wave events that resulted in the deposition of the boulder ridges. [ABSTRACT FROM AUTHOR]

The red clay and loess‐paleosol sediments of the Xiaoshuizi and Halagu planation surfaces of the northeastern Tibetan Plateau (TP) provide insights into the response of paleo‐atmospheric circulation and surface processes to TP uplift and global climate changes. We present silicate Sr‐Nd isotope compositions and bulk sediment grain‐size parameters of the red clay and loess‐paleosol sequences, with the aim of reconstructing changes in the transporting wind systems and sediment source regions. The results indicate that the red clay on the planation surface was transported mainly by the westerlies from the Tarim Basin and the Qilian Mountains, while the loess‐paleosol sediments were transported mainly by the East Asian winter monsoon (EAWM) from the Badain Jaran Desert, Tengger Desert, and Qaidam Basin. These shifts in transport mechanism and source were likely related to major changes in the topography of the TP and the expansion of Northern Hemisphere glaciation since the Middle Pliocene. In addition, we reconstructed the evolution of the paleo‐atmospheric circulation from the Late Miocene to the Middle Pliocene. During the Late Miocene, both the paleo‐EAWM and East Asian summer monsoon (EASM) were weak, and westerly winds dominated the climate of the study area. During the Early Pliocene, both the paleo‐EAWM and EASM exerted an increasing influence on the study area. We ascribe the slight enhancement of the paleo‐EAWM to the gradual growth of the northern TP and the significant enhancement of the paleo‐EASM to global climate changes. Key Points: A major transition in the sediment source and transport dynamic of eolian sediments on the NE TP occurred between the red clay and the overlying loess depositsFrom the Pliocene onward, the paleo‐EAWM and EASM were intensified and exerted an increasing influence on the XSZ planation surfaceThe contribution of the CAO to the XSZ red clay showed an increasing trend from the Late Miocene to the Middle Pliocene [ABSTRACT FROM AUTHOR]

Optically stimulated luminescence (OSL) of quartz is an established technique for dating late Pleistocene to late Holocene sediments. Unfortunately, this method is often limited to up to 100 ka (thousands of years). Recent developments in new extended-range luminescence techniques show great potential for dating older sediments of middle and even early Pleistocene age. These methods include thermally transferred OSL (TT-OSL) and violet stimulated luminescence (VSL) for quartz and post-infrared infrared stimulated luminescence (pIRIR) for feldspar. Here we investigate the luminescence behaviour of the TT-OSL, VSL, and pIRIR signals of quartz and feldspar minerals of aeolian sediments of Nilotic origin from the eastern Mediterranean. We sampled a 15m thick sequence (Kerem Shalom) comprising sandy calcic palaeosols, which is part of a sand sheet that covers an extensive region in south-western Israel. Dose recovery and bleaching experiments under natural conditions indicated that the pIRIR250 signal is the most suitable for dating the Nilotic feldspar. Luminescence intensity profiles revealed natural saturation of the three signals at the same depth of ~6 m, indicating that ages of samples below that depth are minimum ages. Using TT-OSL and pIRIR250, a minimum age of 715 ka for the base of the section was obtained, suggesting aeolian sand accumulation along the eastern Mediterranean coastal plain already since the early Pleistocene. Our results indicate that both TT-OSL and pIRIR250 can accurately date aeolian sediments of Nilotic origin up to 200 ka and that minimum ages can be provided for older samples up to the early Pleistocene. [ABSTRACT FROM AUTHOR]

Mountains are believed to have played an important role in the evolution of modern arid climate over central Asia. The main topography of the Tibetan Plateau (TP) suppresses the regional atmospheric rainfall by both the modulation of atmospheric circulation and blocking of water vapor transport from the ocean. In this study, the effect of Yunnan–Guizhou and Mongolian Plateaux (YGP and MP, respectively), two marginal topographies around the main TP, on the central Asian aridity are evaluated using general circulation model experiments. The results show that the precipitation over central Asia is significantly decreased by these two topographies. Compared to the whole TP-induced annual precipitation decrease of 0.45 mm/d, the contributions of the YGP and MP reach 0.14 mm/d and 0.08 mm/d, respectively. These two marginal mountains occupy approximately one half of the total change by the TP although they are much smaller in heights and sizes. The orographic forcing of the TP suppresses the precipitation significantly throughout the year while those of YGP and MP are mainly effective in boreal winter. A moisture budget analysis shows that all the mountains examined drive increases in subsidence and resulting decreases in humidity over central Asia, with smaller or opposing roles for changes in horizontal winds. These subsidence changes dominate the drying of Central Asia due to the TP and MP, and are largely driven by the influences of the topography on stationary waves. In contrast, the YGP dries Central Asia primarily through altering transient eddies. The forcing of YGP and MP originate from the mechanical blocking of the tropical easterly and mid-latitude westerly, respectively, which exert significant changes in atmospheric circulation. This implies that the effect of small-scale mountains on arid climate over central Asia might be underestimated and a considerable proportion of mechanical effect of the TP on the Asian aridity actually comes from its margins. [ABSTRACT FROM AUTHOR]

The ~400‐km‐long Talas‐Fergana Fault is one of a series of major right‐lateral strike‐slip faults that cross the Tien Shan Range. This fault has been recognized as active in the late Holocene and accommodates part of the deformation induced by the ongoing Indo‐Asian collision. The kinematics and the role of this strike‐slip fault are poorly understood with no large earthquakes reported in the instrumental or historical catalogs, and no well‐constrained geological slip‐rate estimates. Here we used high‐resolution satellite imagery to present a first detailed analysis of the fault segmentation. We identified nine geometric segments based on strike variations for the Talas‐Fergana Fault. Along the Kyldau segment, through morphological analyses of an offset alluvial fan and the application of multiple dating methods (10Be, 26Al, 36Cl, luminescence, and radiocarbon), we calculated a late Quaternary slip rate ranging from 2.2 to 6.3 mm/year. This rate is higher than the geodetic measurements, but the discrepancy can be partly explained if the Talas‐Fergana Fault accommodates shortening by counterclockwise rotation around a vertical axis. Paleoearthquakes identified by trenching indicate that at least two primary surface ruptures (and possibly a third) occurred in the past 3,800 years, and that no large earthquake has ruptured the Kyldau segment since at least 420 years B.P. (possibly within the last 2,700 years), making this fault segment a potential candidate to generate an earthquake with M > 7 in the near future. Key Points: The 400‐km‐long Talas‐Fergana Fault (TFF) can be subdivided into nine geometric segmentsA first geological slip rate of 2.2–6.3 mm/year is constrained by geochronological dating of an alluvial fanThe TFF may be associated with counterclockwise rotations around a vertical axis. This model reconciles geodetic and geologic slip rates [ABSTRACT FROM AUTHOR]

Concealed and fossilized geothermal systems are not characterized by obvious surface manifestations like hotsprings and fumaroles, therefore, could not be easily identifiable using conventional techniques. In this investigation, the applicability of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Hyperion data-sets were evaluated in discriminating hydrothermal alteration minerals associated with geothermal systems as a proxy in identifying subtle Geothermal systems at Yankari Park, Nigeria. Feature-oriented principal component selection, spectral angle mapper, linear spectral unmixing were applied to ASTER data based on spectral characteristics of hydrothermal alteration key minerals for a systematic selective extraction of the information of interest. Analytical imaging and geophysics-developed processing methods were applied to Hyperion data for mapping iron oxide/hydroxide minerals and clay mineral assemblages in hydrothermal alteration zones. The results indicate that ASTER and Hyperion could be complemented for reconnaissance stage of targeting subtle alteration mineral assemblages associated with geothermal systems. [ABSTRACT FROM AUTHOR]

Identification of the planation surfaces (PSs) is key for utilizing them as a reference in studying the long-term geomorphological evolution of the Upper Yangtze River Basin in the Sichuan-Yunnan region, Southwest China. Using a combined method of DEM-based fuzzy logic and topographic and river profiles analysis and based on a comprehensive analysis of four morphometric parameters: slope, curvature, terrain ruggedness index, and relative height, we established the relevant fuzzy membership functions, and then calculated the membership degree (MD) of the study area. Results show that patches with a MD >80% and an area >0.4 km2 correspond well to the results of Google Earth and field investigation, representing the PS remnants. They consist of 1764 patches with an altitude, area, mean slope, and relief of mostly 2000-2500 m above sea level (asl), 0-10 km2, 4°-9°, 0-500 m, respectively, covering 9.2% of the study area's landscape, dipping to southeast, decreasing progressively from northwest to southeast in altitude, and with no clear relation between each patch's altitude and slope, or relief. All these results indicate that they are remnants of once regionally continuous PSs which were deformed by both the lower crust flow and the faults in upper crust, and dissected by the network of Upper Yangtze River. Additionally, topographic and river profiles analysis show that three PSs (PS1-PS3) well developed along the main valleys in the Yongren-Huili region, indicating several phases of uplift then planation during the Late Cenozoic era. Based on the incision amount deduced from projection of relict river profiles on PSs, together with erosion rates, breakup times of the PS1, PS2, and PS3 were estimated to be 3.47 Ma, 2.19 Ma, and 1.45 Ma, respectively, indicating appearance of modern Upper Yangtze River valley started between the Pliocene to early Pleistocene. [ABSTRACT FROM AUTHOR]

Because of the natural (aleatoric) variability in earthquake recurrence intervals and coseismic displacements on a fault, cumulative slip on a fault does not increase linearly or perfectly step-wise with time; instead, some amount of variability in shorter-term slip rates results. Though this variability could greatly affect the accuracy of neotectonic (i.e., late Quaternary) and paleoseismic slip rate estimates, these effects have not been quantified. In this study, idealized faults with four different, representative, earthquake recurrence distributions are created with equal mean recurrence intervals (1000 years) and coseismic slip distributions, and the variability in slip rate estimates over 500- to 100 000-year measurement windows is calculated for all faults through Monte Carlo simulations. Slip rates are calculated as net offset divided by elapsed time, as in a typical neotectonic study. The recurrence distributions used are quasi-periodic, unclustered and clustered lognormal distributions, and an unclustered exponential distribution. The results demonstrate that the most important parameter is the coefficient of variation (CV= standard deviation / mean) of the recurrence distributions rather than the shape of the distribution itself. Slip rate variability over short timescales (< 5000 years or 5 mean earthquake cycles) is quite high, varying by a factor of 3 or more from the mean, but decreases with time and is close to stable after ∼40000 years (40 mean earthquake cycles). This variability is higher for recurrence distributions with a higher CV. The natural variability in the slip rate estimates compared to the true value is then used to estimate the epistemic uncertainty in a single slip rate measurement (as one would make in a geological study) in the absence of any measurement uncertainty. This epistemic uncertainty is very high (a factor of 2 or more) for measurement windows of a few mean earthquake cycles (as in a paleoseismic slip rate estimate), but decreases rapidly to a factor of 1–2 with > 5 mean earthquake cycles (as in a neotectonic slip rate study). These uncertainties are independent of, and should be propagated with, uncertainties in fault displacement and geochronologic measurements used to estimate slip rates. They may then aid in the comparison of slip rates from different methods or the evaluation of potential slip rate changes over time. [ABSTRACT FROM AUTHOR]

The Harletz loess‐palaeosol sequence is located in northwestern Bulgaria and represents an important link between well‐studied loess sequences in eastern Romania and further sites to the west of the Carpathians (e.g. Serbia and Hungary). The aim of this study was to establish a chronostratigraphy of the deposits, using various methods of luminescence dating, together with basic stratigraphical field observations as well as magnetic properties. Luminescence dating was carried out using the quartz fine grain fraction and a SAR protocol, and the feldspar coarse grain fraction, applying the MET‐pIRIR protocol. Due to underestimation of the quartz fine grain fraction in the lower parts of the sequence, the resulting chronology is mainly based on the feldspar ages, which are derived from the stimulation temperature at 150 °C. A comparison with nearby sequences from Serbia, Hungary and Romania, and interpretations obtained through the stratigraphical and sedimentological signature of the sequence, supports the established chronology. Our data suggest that the prominent palaeosol (soil complex) in the upper quarter of the sequence was formed during MIS 5. It would follow that large parts of the Last Glacial loess overlying this palaeosol were probably eroded, and that the thick loess accumulation underlying this soil complex can be allocated to the penultimate glacial (MIS 6). A prominent MIS 6 tephra, which has been reported from other sequences in the area, is also present at Harletz. [ABSTRACT FROM AUTHOR]

The Late Mesozoic--Cenozoic topographic and climate evolution of Central Asia remains highly debated. The final retreat of the proto-Paratethys Sea from the western Tarim Basin is thought to correspond in time with the onset of tectonic uplift in the Pamir, Tian Shan and Altai ranges, as well as with regional aridification. The oxygen and carbon isotope compositions of the sediment deposits in the various Central Asian basins have already been used to decipher both the topographic and climatic changes that occurred in that region during the Cenozoic, generally concentrating on one sedimentary section and/or on a limited time range and either using multiple-type samples including sandstone calcitic cements, marine carbonates, fossils, or paleosols. In order to get a homogeneous dataset, minimizing variations in the isotopic composition of the material depending on its type and/or depositional environment, we selected only calcareous paleosols sampled in several continuous sections covering a wide time range from the Late Jurassic to the Pliocene. Our sampling also covers a wide area encompassing the whole Tian Shan region, which allows detecting regional variations in the δ18O and δ18C values. We show that the influence of the distance to the proto-Paratethys Sea on the paleosol δ18O record was not significant. Besides local factors such as the occurrence of large lakes that can have a significant effect on the isotopic composition of the calcareous paleosols, the long-term evolution of both the δ18O and δ18c values possibly reflects the hypsometry of the river drainage systems that bring water to the basins. However, as it is commonly accepted that the δ18O of soil carbonates is controlled by the δ18O of in-situ precipitation, this last conclusion remains to be further investigated. [ABSTRACT FROM AUTHOR]

Abstract: The Hangay Mountains are a high‐elevation, low‐relief landscape within the greater Mongolian Plateau of central Asia. New bedrock apatite (U‐Th)/He single‐grain ages from the Hangay span ~70 to 200 Ma, with a mean of 122.7 ± 24.0 Ma (2σ). Detrital apatite samples from the Selenga and Orkhon Rivers, north of the mountains, yield dominant (U‐Th)/He age populations of ~115 to 130 Ma, as well as an older population not seen in the Hangay granitic bedrock data. These low‐temperature data record regional exhumation of central Mongolia in the Mesozoic followed by limited erosion of <1–2 km since the Cretaceous, ruling out rapid exhumation of this magnitude associated with any late Cenozoic uplift. Apatite (U‐Th)/He age elevation patterns suggest long‐term thermal stability of the upper crust and thermal model inversions require late Mesozoic uplift, spatially variable exhumation, and/or relief evolution to produce the observed cooling ages in the Hangay. Regionally, modeling suggests reduction of topography in the Jurassic followed by relief growth that was completed by the mid‐Cretaceous. These results support Mesozoic topographic evolution and relative stability of the landscape throughout the Cenozoic with very little subsequent exhumation. Alpine cirques and intact moraines are indicative of more recent, modest climate‐driven erosion in the higher peaks of the western Hangay. These data reinforce the notion that in the absence of strong tectonic or climate forcing, erosion is limited and remnant landscapes can persist over tens to hundreds of millions of years in a state of disequilibrium. [ABSTRACT FROM AUTHOR]

Multi-method thermochronology along the Vakhsh-Surkhob fault zone reveals the thermotectonic history of the South Tian Shan-Pamirs boundary. Apatite U/Pb analyses yield a consistent age of 251 ± 2 Ma, corresponding to cooling below ~550- 350°C, related to the final closure of the Palaeo-Asian Ocean and contemporaneous magmatism in the South Tian Shan. Zircon (U-Th-Sm)/He ages constrain cooling below ~180°C to the end of the Triassic (~200 Ma), likely related either to deformation induced by the Qiangtang collision or to the closure of the Rushan Ocean. Apatite fission track thermochronology reveals two low-temperature (<120°C) thermal events at ~25 Ma and ~10 Ma, which may be correlated with tectonic activity at the distant southern Eurasian margin. The late Miocene cooling is confirmed by apatite (U-Th-Sm)/He data and marks the onset of mountain building within the South Tian Shan that is ongoing today. [ABSTRACT FROM AUTHOR]

Abstract: In 1905, 14 days apart, two M ~ 8 continental strike‐slip earthquakes, the Tsetserleg and Bulnay earthquakes, occurred on the Bulnay fault system, in Mongolia. Together, they ruptured four individual faults, with a total length of ~676 km. Using submetric optical satellite images “Pleiades” with ground resolution of 0.5 m, complemented by field observation, we mapped in detail the entire surface rupture associated with this earthquake sequence. Surface rupture along the main Bulnay fault is ~388 km in length, striking nearly E‐W. The rupture is formed by a series of fault segments that are 29 km long on average, separated by geometric discontinuities. Although there is a difference of about 2 m in the average slip between the western and eastern parts of the Bulnay rupture, along‐fault slip variations are overall limited, resulting in a smooth slip distribution, except for local slip deficit at segment boundaries. We show that damage, including short branches and secondary faulting, associated with the rupture propagation, occurred significantly more often along the western part of the Bulnay rupture, while the eastern part of the rupture appears more localized and thus possibly structurally simpler. Eventually, the difference of slip between the western and eastern parts of the rupture is attributed to this difference of rupture localization, associated at first order with a lateral change in the local geology. Damage associated to rupture branching appears to be located asymmetrically along the extensional side of the strike‐slip rupture and shows a strong dependence on structural geologic inheritance. [ABSTRACT FROM AUTHOR]