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Reconstructing the tectonic architecture of the southern Altaids is of great importance to piece together the continental growth history of the Central Asian continent. In this paper, we address the subduction‐accretion process of the Paleo‐Tianshan Ocean, one branch of the South Tianshan Ocean, in the southern Altaids, through a detailed geological and geochemical investigation of the Wulanmoren Accretionary Complex (WAC). The WAC is composed of ophiolitic mélanges, ocean plate stratigraphy mélanges, and turbiditic coherent units. In this study, we present key geological, petrological, and geochemical evidence indicating back‐arc and ocean island affinity of the igneous rocks of the WAC. Zircon U‐Pb dates of these rocks ages range between 380.2 ± 1.3 and 302.0 ± 5.3 Ma. The sedimentary matrix units of the mélanges were deposited in the Early Devonian (∼405 Ma) to the Late Triassic (∼222 Ma), rather than Silurian strata as previously thought. However, the ages of some detrital zircons in the sedimentary matrix are Precambrian, pointing to a complex evolution involving multiple ocean island terrains and island arcs of different ages that accreted from the mid‐Paleozoic to the Early Mesozoic. Plain Language Summary: Well‐exposed rock outcrops of the Wulanmoren Accretionary Complex (WAC) offer an ideal opportunity to solve the enigma of the evolutionary history of the Paleo‐Tianshan Ocean (PTO) of Central Asia. We report field observations, geochemistry, and geochronology of the WAC in the southern Altaids, pointing to multiple tectonic settings of ages spanning from the Early Devonian (∼405 Ma) to the Late Triassic (∼222 Ma). These reconstructions suggest closure time of the PTO occurred post‐Triassic. Based on detrital zircons provenance analysis, we propose a multi‐island ocean model to explain the tectonic evolution of the PTO in the time period studied. Key Points: The Wulanmoren Accretionary Complex was composed of ophiolitic mélanges, ocean plate stratigraphy mélanges, and coherent unitsThe Late Paleozoic MORB‐like and OIB‐type basalts, and ∼222 Ma coherent units indicate closure of the Paleo‐Tianshan Ocean occurred post‐TriassicThe southern Paleo‐Asian Ocean was an archipelago with several subduction systems which is similar to the modern southwest Pacific [ABSTRACT FROM AUTHOR]

Our understanding of how Central Asia evolves in response to climate change remains poorly constrained primarily due to the lack of sufficient paleoclimate records across different altitudinal zones with the adequate resolution for reconstructions. Using a 23.8 m thick loess sequence in the SW Junggar Basin, we establishe a robust chronology over the past ~150 kyr based on K-feldspar pIRIR techniques and Bacon age-depth modelling. To further track the paleoclimatic evolution of this part of Central Asia, this study documents changes in grain size, magnetic susceptibility, CaCO 3 content, and sediment color. Together with previously reported loess records from the slopes and intermontane basins of the Tianshan Mountains, altitudinal and spatial variability in moisture changes during the last glacial-interglacial cycle are clarified in Central Asia. Our results indicate that loess in the SW Junggar Basin and northern slopes of Tianshan Mountains was mainly deposited during the Penultimate Glacial and Last Glacial periods. However, the deposition rates were relatively very slow deposition and/or deposited loess records have been entirely eroded possibly due to the deflation in the last interglacial and Holocene. The enhancement of the winter monsoon plays an important role in the rapid deposition of loess in Central Asia during glacial periods. Findings support that the continuous aridity prevailed in the lowlands of the Junggar Basin and the northern slope of Tianshan mountains during the last glacial-interglacial cycle, which is in opposition to the moist interglacial and dry glacial changes recorded in the higher altitude intermontane and mountain areas of the Tianshan Mountains. Limited Westerlies precipitation and high evaporation in lowland areas of Central Asia are responsible for prevailing aridity in these regions during interglacial periods. • Loess was deposited mainly during the Penultimate and Last Glacial in the Junggar Basin. • Aridity prevailed in lowlands of central Asia during last glacial-interglacial cycle. • Weakened Westerlies precipitation and high evaporation caused persisting aridity. [ABSTRACT FROM AUTHOR]

• K-feldspar pIRIR dating can be used to date loess up to 250 ka in the Yili Basin. • Loess deposition started earlier than 350 ka in the Yili Basin. • Rapid loess deposition occurred in the Yili Basin during the last interglacial. • Loess depositional dynamics are controlled by geomorphological and climatic changes. Widely distributed loess deposits within the Tianshan Mountains are important archives for studying late Quaternary climate in this Central Asian region. However, insufficient age control for these regional loess records, especially over glacial-interglacial cycles, severely limits our understanding of loess depositional dynamics and accurate interpretation of paleoclimate conditions across central Asia. in this study, we applied K-feldspar optical dating, and magnetic susceptibility, grain size distribution, CaCO 3 and color to loess-paleosol sections in the Yili Basin of the Tianshan Mountains to constrain loess depositional dynamics, identify timing of loess-paleosol formation and clarify the role of paleoclimate influence in this region since the late middle Pleistocene. Our results demonstrate that loess deposition started as early as 350 ka in the Yili Basin. Following river down-cutting associated with glacial-interglacial transitions and exposure of riverbed sediments, enhanced dust emission from flood plains played an important role in loess deposition. Very rapid loess deposition as high as 60–120 g cm−2 ka−1 on river terraces occurred during the last interglacial, when loess accumulation at different locations of the site had remarkably different rates, ranging from 10 to 100 g cm−2 ka−1. This heterogeneous behavior indicates that not only climatic changes influenced Yili Basin loess deposition and preservation but by complex interaction of local geomorphology, wind velocity, and changes of materials in dust origins. Depositional hiatuses frequently occurred during the past 250 ka, likely induced by strong erosion resulting from increased wind strength and dry-cold climate with poor vegetation cover in the region. Magnetic susceptibility, grain size distribution, CaCO 3 and color analyses of the loess-paleosol sequences showed that paleosols formed around ~288 ka, 230–191 ka, 120–106 ka, 92–89 ka, and 84–71 ka. Hence, a generally moist climate characterized the Yili Basin before Marine Isotope Stages (MIS) 9, MIS 7, MIS 5d, MIS 5b, and the MIS 5-MIS 4 transition, respectively. This study suggests a climate pattern of moist interglacial and dry glacial periods in the Tianshan Mountains, whereas substages of interglacials had cold-moist and warm-dry climate characteristics. [ABSTRACT FROM AUTHOR]

The variability and interaction of the East Asian summer monsoon (EASM), East Asian winter monsoon (EAWM) and Westerlies dominate mid-latitude Asian hydroclimate and influence over a billion lives in Asia. However, how variation in the EASM, EAWM and Westerlies influences climate change in their transition zones in NW China remain unclear. Specifically, how these atmospheric systems interact during strong-weak phases variation over different timescales is still hotly debated. This study investigates four loess-paleosol sequences in the transition zone between EASM and Westerlies-influenced areas along the central Hexi Corridor of NW China, and presents 63 quartz optically stimulated luminescence (OSL) ages to generate the most detailed chronology for any loess record within the Hexi Corridor. In combination with sedimentology, proxy indexes of magnetic parameters (χ lf , χ fd , χ ARM /SIRM) and grain size of these loess-paleosol sequences, and TraCE-21 ka climatic modelling, the loess deposition and climatic changes at central Hexi Corridor regions over the past 25 ka are reconstructed. Our results indicate that: (1) loess deposition initiated by at least 25 ka at Hexi Corridor. Loess depositional rates decrease from late last glacial into the Holocene, with maximum accumulation rates (140–180 g/cm3/ka) occurring during the Last Glacial Maximum. Depositional hiatuses up to 8 ka are recognized in late Quaternary Hexi Corridor loess, which suggests that high-resolution chronologies are necessary for robust paleoclimatic reconstructions from loess records in the region. (2) Over glacial-interglacial cycles, climate in the Hexi Corridor demonstrates a cold-dry glacial and a warm-moist interglacial, consistent with moisture changes observed in the monsoonal Chinese Central Loess Plateau and Westerlies-dominated Central Asia. However, moisture in central Hexi Corridor increased from the early Holocene to mid-Holocene, with a wettest period at 8–7 ka, and followed by a relatively wet late Holocene. These changes are most consistent with the EASM-dominated Chinese Central Loess Plateau and suggests that Westerlies influence in the central Hexi Corridor is minor over at least the past 25 kyr. (3) EAWM intensities demonstrate an anti-phase relationship to EASM intensities over the past 25 kyr in the Hexi Corridor, with decreasing EAWM intensity into the early-mid Holocene and an increase into the late Holocene. (4). EASM precipitation variability in the Hexi Corridor appears to not to be a direct nor singular response to changes in 30°N summer insolation. EASM lags insolation by 3 kyr during the Holocene, supporting the idea that high-latitude forcing through changes in ice volume, greenhouse gases, and/or meltwater input to North Atlantic and Southern oceans can effectively modulate EASM intensity and critically influence Hexi Corridor paleoclimatic conditions. • Loess depositional hiatuses up to 8 kyr occur in the Hexi Corridor. • Over the past 25 kyr, the wettest period occurs at 8–7 ka in the Hexi Corridor. • East Asian Summer Monsoon controls central Hexi Corridor precipitation since 25 ka. • East Asian Winter Monsoon is anti-phase to East Asian Summer Monsoon since 25 ka. • High-latitude forcing modulates EASM intensity and Hexi Corridor climatic changes. [ABSTRACT FROM AUTHOR]

The coexistence of adakites, high-Mg andesites (HMAs) and Nb-enriched basalts (NEBs) records special subduction geodynamics, for instance, subduction initiation, subduction of oceanic ridges or slab tearing, which are widespread in the circum-Pacific subduction zone. The Altaids in Central Asia shared similar tectonic evolution to the western Pacific. However, slab tearing has not been widely reported, which hinders a better comparison between the Altaids and the western Pacific. In this study, we report the contemporaneous early Devonian granodiorites and mafic microgranular enclaves (MMEs) in the Sidingheishan area of the Harlik arc, southern Altaids. The granodiorites have high Sr (534–683 ppm) but low Y (7.79–10.2 ppm) and Yb (0.71–1.68 ppm) contents, with corresponding high Sr/Y values (29.78–76.93). In combination with their juvenile isotopes (initial 87Sr/86Sr = 0.70333–0.70356, εNd(t) = +7.4 − +8.01) and high Mg# numbers (50.9–53), they indicate that their primitive magmas were derived from slab melting. The MMEs show similarly high Sr contents (507–696 ppm), and identically juvenile isotopic signatures (initial 87Sr/86Sr = 0.70346–0.70356, εNd(t) = +7.14 − +7.5) to their host granodiorites. However, their relatively low silica contents (55–60 wt%), evolved Mg# numbers (44.8–55.2) and high Nb contents (12.7–24.7 ppm) demonstrate that they are the fractionation products of NEBs, which were produced by the partial melting of the mantle that was previously metasomatized by these adakitic magmas. Considering all the available evidence, we propose a slab tearing model in which the southward subducting Kelameili oceanic lithosphere underneath the Harlik arc underwent rollback in the early Devonian and its differential rollback rates caused slab tearing. Subsequent asthenosphere upwelling stimulated the Kelameili oceanic lithosphere to melt, producing the adakitic magmas, some of which intruded the crust after limited interaction with the mantle peridotites and underwent crystallization of dominant amphibole in the crust. The rest reacted completely with the mantle peridotites, which underwent further melting to produce the Nb-enriched basaltic magmas. They intruded into the adakitic magma chamber after fractional crystallization of olivine, clinopyroxene and garnet in the deep, forming the MMEs and promoting the remobilization of those hornblendites. This study reveals the development of slab tearing that are closely associated with slab rollback in the Altaids, providing further evidence that argues for the similarity between the Altaids and the western Pacific. • The granodiorites were derived from slab melting; • These adakitic magmas underwent fractional crystallization of amphibole; • The cumulates of hornblendites were remobilized in response to intrusion of MMEs; • The MMEs were produced by melting of mantle metasomatized by adakitic magmas; • They record tearing on the southward subducting Kelameili oceanic lithosphere. [ABSTRACT FROM AUTHOR]

Paleoclimatic changes in arid central Asia (ACA), one of the largest arid regions in the world, are complex and the nature of these changes on orbital cycles remains unclear. Widely distributed loess records in ACA potentially provide records of paleoclimatic variation, but these records are difficult to interpret due to a lack of robust high resolution chronologies. K-feldspar pIRIR dating was employed to date 37 samples from a 13 m loess-paleosol sequence (section KS15) in an intermontane basin of the Tianshan Mountains, central ACA, NW China. The reliability of the pIRIR ages was determined by using internal checks of luminescence characteristics of the pIR 50 IR 290 and pIR 200 IR 290 signals, and by comparing pIR 50 IR 290 and pIR 200 IR 290 ages. A high resolution chronology for the loess-paleosol sequence, spanning 130–45 ka, was established using Bacon age/depth modeling. In combination with climate proxy indexes of magnetic susceptibility, total organic material, and δ 13 C of organic remains from the sequence, our results suggest: (1) the pIRIR ages utilizing pIR 50 IR 290 and pIR 200 IR 290 signals are consistent for loess samples <150 ka; (2) eolian loess was deposited in intermontane basins of the Tianshan Mountains by at least ∼150 ka, with a steadily increasing rate of loess deposition from the last interglacial to the last glacial period; (3) ACA had a moist climate, characterized by paleosol development, during periods at 117–109, 97–85, 77–70 and 58–50 ka, corresponding to MIS 5d, MIS 5b, MIS 5–4 and MIS 3c; (4) ACA had dry climates, characterized by loess deposition, at 131–117, 109–97, 85–76, 70–58 and 50–46 ka, corresponding to MIS 5e, MIS 5c, MIS a and MIS 3b; and (5) during sub-stages of MIS 5 the ACA climate was characterized by cold-moist to warm-dry shifts which appear to be related to ∼21 ka precession cycles, but inversely related to Northern Hemisphere summer insolation patterns. Moisture variation in ACA thus has an anti-phase relationship to that in monsoonal East Asia. Orbital forcing may be responsible for this moisture variation in ACA. [ABSTRACT FROM AUTHOR]

• Single grain K-feldspar pIR 50 IR 170 dating effectively dates samples over past 1 kyr. • Highest lake levels in Qaidam Basin over past 1 kyr during Little Ice Age. • Out-of-phase Central and East Asian precipitation drive asynchronous lake change. • EASM did not penetrate as far inland as Qaidam Basin during past 1 kyr. The moisture and precipitation evolution of mid-latitude Asia are dominated by the East Asian summer monsoon (EASM) and mid-latitude Westerlies atmospheric systems. How these two systems interacted along their transition zone in the northern Tibetan Plateau remains unclear, especially over centennially to millennial timescales. This study investigates moisture evolution along the EASM-Westerlies transition zone using 10 Late Holocene paleolake shorelines from Toson Lake in the northern Tibetan Plateau. Shorelines are dated using a newly developed single-grain post infrared-infrared stimulated luminescence (pIR 50 IR 170) dating protocol for 14,500 K-feldspar grains and used to reconstruct the evolution of Toson Lake over the past millennium. Results show that Toson Lake was stable during the Medieval Warm Period (MWP), expanded during the Little Ice Age (LIA) with a distinct highstand from AD1600–1700 punctuated by short-duration low period at ∼ CE 1650. After which, Toson Lake dramatically contracted into the Current Warm period (CWP). Lake level changes are consistent with Westerlies precipitation variability across Central Asia, in contrast to records from the EASM dominated northeastern Tibetan Plateau and northern China documenting an arid LIA and wet MWP. Reanalysis of modern climatic data are combined with our lake chronology to reveal that although EASM strength influences precipitation variability across northeastern Tibetan Plateau (NETP) and northern China, EASM precipitation has not directly penetrated deep inland over the past millennium. Instead, Westerlies moisture, modulated by the see-saw of the North Atlantic Oscillation, together with the moisture controlled by the anticyclonic circulation over Mongolia and negatively related to the EASM strength, dominated water vapour transport to the mid-latitudes of Central Asia. Out-of-phase moisture transport and interaction between the Westerlies and EASM drives asynchronous lake evolution between Central and East Asia over centennial-millennial timescales. [ABSTRACT FROM AUTHOR]

The variability and interaction of the East Asian summer monsoon (EASM) and mid-latitude Westerlies have dominated Eurasian hydroclimates over orbital timescales and currently influence over a billion lives in Asia. Despite this, the mechanisms influencing EASM-Westerlies variability are still a matter of considerable debate. This study presents three loess-paleosol sequences in the NE Tibetan Plateau (NETP) dated at high-resolution by 50 K-feldspar pIRIR and 37 quartz OSL ages to produce the most detailed chronology for any loess record within the plateau. Combined with this chronology are sedimentology, magnetic susceptibility and grain size analyses with TraCE-21ka climatic modelling to constrain atmospheric controls on climatic changes over the NETP during the past 130 kyr. Our results indicate that deposition initiated by ∼130 ka with especially rapid rates during glacial periods, with maximum rates (140–180 g/cm2/ka) in early MIS 2. Over interglacial-glacial cycles, NETP climatic changes are consistent with warm-moist interglacial and cold-dry glacial conditions recorded in the monsoonal Chinese Loess Plateau and Westerlies-dominated Central Asia but anti-phase to Central Asia during interglacial and the Holocene substages. These results highlight how variation in EASM intensity strongly controls NETP moisture changes but that Holocene and last interglacial changes recorded in the NETP consistently lag 30°N summer insolation by 2–6 kyr. This study suggests high-latitude forcing effectively modulates EASM intensity and that factors such as ice volume, greenhouse gases, and freshwater input to northern Atlantic and Southern oceans critically influence NETP paleoclimatic conditions. • K-feldspar pIRIR dating can be used to date loess to at least 130 ka in the Tibetan Plateau. • A moist interglacial-dry glacial climate pattern occurred across Eurasia. • EASM dominated paleoclimatic changes during past 130 ka in the NE Tibetan Plateau. • EASM precipitation is consistently lagged 2–6 ka to July 30°N insolation. • High-latitude forcing induced lags in EASM precipitation to insolation. [ABSTRACT FROM AUTHOR]