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Palaeo-uplifts often exist in fold-and-thrust belts. However, their effects on the deformational process have not yet been well understood. To evaluate such effects, six analogue models were systematically run based on geological features of the Wupoer fold-and-thrust belt (FTB), NE Pamir, where the Wulagen palaeo-uplift with overlying gypsum bed has been clearly identified. Our analogue results demonstrated that the palaeo-uplift (its location and inhomogenous distribution), accompanied with overlying gypsum bed that serves as ductile décollement, plays a critical role in localizing the front thrust fault and shaping it into arc form. The results indicate that the front thrust fault slides along the ductile décollement (gypsum bed), and breaks through onto the surface at the region where the palaeo-uplift develops, forming a piggy-back basin in the hanging wall. It suggests that the palaeo-uplift with consequent topographic variation of the overlying ductile décollement localizes the breakthrough point of the front thrust fault. In addition, the results indicate that the front thrust fault (Pamir Front Thrust, PFT) initially broke through in the location where it develops the Wulagen palaeo-uplift and propagated aside. This resulted in the distance between the PFT and the basement-involved fault (Main Pamir Thrust, MPT) to decrease from the region with palaeo-uplift to the areas aside without palaeo-uplift, thereby forming the arc-shaped PFT in map view. The results of this study also provide a revised geological model, which emphasizes the effect of décollement layer on absorbing the slip along the PFT. Our results provide a new mechanical interpretation of the deformation of Wupoer FTB, NE Pamir. [ABSTRACT FROM AUTHOR]

Defining the northern margin of the Tibetan Plateau, the Altyn Tagh Fault system (ATFs)exerts a crucial role in accommodating intracontinental deformation during the India-Asiaconvergence. The North Altyn fault (NAF), demarcating the western boundary of the ATFs inthe Altun Shan region, was testified to exist a structural shift from sinistral along-strikeslipping to thrusting during the Cenozoic era. However, the exact timing of the shift remainsan issue to be refined. In this study, we conducted LA-ICP-MS based apatite fission trackdating at massifs of both the hanging wall and footwall along the NAF, to shed light on datingthe thrusting-related exhumation of the NAF. The results show that the hanging wall massifsof the NAF present a quasi-isothermal quiescence during the early Cenozoic, followedby a rapid cooling phase with mean cooling rate of 6.66 ± 0.72 ˚ C / Ma since∼15 Ma, resulting from accelerated exhumation which has been interpreted tomark intense vertical uplift of the NAF. Significantly younger age (∼5 Ma) buthigher rate (15.33 ± 2.10 ˚ C / Ma) of rapid-cooling event occurred at the footwallcompared to the hanging wall suggests a northward propagation of thrusting into theinterior Tarim basin. Combining previous studies, we attribute the structural shift ofthe NAF from along-strike slipping to thrusting to the Mid-Miocene kinematicreorganization of the ATFs, supporting to the two-stage evolution model of theAFTs that: (1) during ∼50-15 Ma, the NAF acted as a part of the Altyn Tagh faultexperiencing along-strike slipping, with the Altun Shan elevated north within bigrestraining-double-bends; and (2) after ∼15 Ma, the Altyn Tagh fault cut through thedouble-bends with significant thrusting along the NAF, circumscribing the presenttriangle-shaped Altun Shan featured with uplifting south beginning at ∼15 Ma. [ABSTRACT FROM AUTHOR]

The Altyn Tagh Fault (ATF) serves as a key continental‐scale controlling structural element of the Tibetan Plateau. However, its eastward extent remains controversial. Here we use high‐resolution seismic reflection profiles to investigate the subsurface structures of the easternmost ATF and use these to delimit the easternmost extent of the fault. The structural analyses show an eastward geometric change from transpressional positive flower structures to compressional thrusts, with transpression‐induced shortening magnitudes decreasing eastwards from a maximum of ~5.3 km to being absent. Stratigraphic controls indicate that the deformation took place over the last ~<1.2 Ma. Our wider findings lead us to: (a) reject the suggestion that the ATF previously extended beyond the Kuantan Shan‐Hei Shan to link with the Alxa‐East Mongolia Fault; and (b) propose that the rigid block model used to describe the Tibetan Plateau crust is not consistent with the extent and structural details of the easternmost ATF. [ABSTRACT FROM AUTHOR]

The India–Eurasia collision has produced a number of Cenozoic deep intracontinental basins, which bear important information for revealing the far‐afield responses to the remote collision. Despite their significance, their subsiding mechanism remains the subject of debate, with end‐member models attributing it to either orogenic or sedimentary load. In this study, we conduct flexural subsidence modeling with a two‐dimensional finite elastic plate model on the Hotan–Mazatagh section along the southern Tarim Basin, which defines a key region in the foreland of the West Kunlun Orogen, along the NW margin of the Tibetan Plateau. The modeling results indicate that the orogenic load of West Kunlun triggers the southern Tarim Basin to subside by up to less than ∼6 km, with its impact weakening towards the basin interiors until ∼230 km north from the Karakax fault. The sedimentary load, consisting of Cenozoic strata, forces the basin to subside by ∼2 to ∼7 km. In combination with the retreat of the proto‐Paratethys Sea and the paleogeographic reorganization of the Tarim Basin, we propose that surface processes, in particular a shift from an exorheic to an endorheic drainage system associated with the consequent thick sedimentary load, played a decisive role in forming deep intracontinental basins in the context of the India–Eurasia collision. [ABSTRACT FROM AUTHOR]

The geology of Tian Shan provides an excellent example for understanding the intracontinental orogeny in the context of Indian–Eurasian convergence. Previous studies leave much space in basinfill deposition process to be assessed in the regions west to the Talas–Fergana fault (TFF). We improve the understanding by conducting new investigations on sedimentology and magnetostratigraphy in the Tierekesazi section of the foreland region of south West Tian Shan. Four lithofacies have been identified, (i) marine lithofacies from the Aertashi to Bashibulake Formations, (ii) lacustrine to fluvial (plain) lithofacies from the Keziluoyi to the middle Pakabulake Formations, (iii) alluvial sand–gravel sheet lithofacies in the upper Pakabulake Formation, and (iv) conglomerate lithofacies from the Atushi to Xiyu Formations. Magnetostratigraphic analysis, accompanied with biostratigraphic correlation, indicates that four lithofacies cover age intervals of ca. 65 Ma to 34 Ma, ca. 22.1 Ma to 12 Ma, 12 Ma to 5.2 Ma, and 5.2 Ma to approximately present (?), with the sediment accumulation rates increasing from ca. 2.4/3.3–3.5 (compacted/decompacted) cm/ka in the lithofacies (i), to 12.3/16–17 cm/ka in the lithofacies (ii), to 16.3/19.5–20.6 cm/ka in the lithofacies (iii), and finally to > 22.8/> 22.8 cm/ka in the lithofacies (iv). These results suggest three episodes of sedimentary events. Combined with previous results, these episodes of sedimentary events are attributed to tectonic activities that are widespread along south Tian Shan. We speculate that the Oligo-Miocene boundary event more directly and likely marks the initial underthrusting of the Tarim block beneath the south Tian Shan. The mid-Miocene and Mio-Pliocene boundary events, although approximately synchronous between the regions east and west to the TFF, have different structural expressions in the two regions. Such difference is proposed to cause the dextral slipping of the TFF, and more fundamentally, likely be driven by the northward indentation of the Pamir at this time. [ABSTRACT FROM AUTHOR]

The amount of fault slip and timing of fault activation are two fundamental elements of quantitatively structural analysis. Currently, these two parameters are mainly determined by the geometry of fault-related folds and the growth strata over the fault ramp. In this study, we propose a new type of growth strata that directly constrain both the amount of fault slip and the timing of fault activity at the fault flat based on interpretations of seismic reflection profiles and related numerical modeling of the Manan Structure along the southern Tarim Basin. The seismic sections show a rootless synform beyond the north limb of the Manan Anticline with the hinge dipping toward north. Numerical modeling suggests that this synform is a result of northward migration of the growth strata along with the slip of the underlying detachment thrust with a bulge at the fault surface. We define this type of growth strata 'migrating growth strata (MGS)'. The dipping direction of the hinge of the synform marks the slip direction, the projecting distance of the hinge on the fault surface measures the slip amount, and the timing of the MGS represent the timing of the activity of the underlying detachment thrust. Analyses of the Manan MGS along the southern Tarim Basin suggest ∼13–22 km of northward fault slip passed by the Manan Structure along the basal Cenozoic detachment and was finally absorbed by the Mazatagh Belt, which confirms a ∼230-km-long detachment thrust along the southern Tarim Basin and provide key evidence to establish a kinematic linkage between the Hotan and Mazatagh Belts. Two-segment style of the hinge of the synform indicates that the Manan Structure has undergone two-stage evolution related to the lower Cambrian and the basal Cenozoic detachments, respectively. These results imply that detachments in difference depths and their sequential activities are key in transmitting strain from the Tibetan Plateau into the Eurasian continental interiors. • Seismic sections show a rootless synform in Manan Structure, southern Tarim Basin. • The synform was produced by growth strata migrating with the detachment thrust. • Such a structure was defined as 'migrating growth strata (MGS)'. • MGS provide a new tool for quantitatively analyzing the fold-thrust belts. • The results demonstrate a ∼230-km-long detachment thrust in southern Tarim Basin. [ABSTRACT FROM AUTHOR]

Paleo-uplift is one of the main controlling factors that influence the style of deformation in salt-bearing fold-and-thrust belt (FTB). Whereas, how paleo-uplift amplitude influences salt-related deformations in FTB remains unclear. Here we designed four series of experimental models that contain a basal brittle décollement and a shallow ductile décollement. Our studies show that the presence of paleo-uplift in the ductile décollement has a profound impact on deformation propagation in the supra-salt overburden during the contraction, which localizes shortening strain in the proximal and central parts of the models and deters rapid deformation propagation towards the distal part. As the amplitude of the paleo-uplift increases, its influence on deformation propagation becomes stronger, resulting in out-of-sequence deformation towards the hinterland. The increase of paleo-uplift amplitude also controls the distribution and migration of rock salt during the contraction. Particularly, when the paleo-uplift height equals or exceeds the thickness of salt layer, the position of salt pinch-out or welding point localizes shortening strain and thereby initiates folding and thrusting deformation over the salt-base high. This process leads to salt fed into the fold and fault belt over the paleo-high and the uplift of the supra-salt layers. Our modeling results are highly comparable with natural examples of Kuqa FTB and provide insights to the salt-influenced deformations in the Qiulitage structural belt. • The presence of paleo-uplift has a profound impact on deformation propagation in the supra-salt overburden. • The increase of paleo-uplift amplitude controls the distribution and migration of rock salt during the contraction. • Higher amplitude paleo-uplift results in localized deformation and salt thickening. [ABSTRACT FROM AUTHOR]

Transverse drainages are prominent landscape features in active foreland thrust-and-fold belts. Understanding their response to folding processes is pivotal for comprehending landscape evolution and erosion-deformation interactions within the foreland. Here, we focus on the extensively developed transverse drainages across the Tugerming anticline in the southern Tian Shan foreland. Based on fold topography, drainage patterns, and various morphometric indices, we conducted a detailed geomorphological analysis of the Tugerming anticline. Our results suggest that the Tugerming fold laterally grows towards both ends, exhibiting notable segmentation along its strike. The westward lateral fold growth is characterized by interactions between the Tugerming anticline and two adjacent anticlines (Yiqikelike and Tuziluoke). At its eastern termination, lacking nearby folds, the Tugerming anticline laterally propagates without other adjacent folds, resulting in an elongated, gentle termination. Additionally, the hinterland catchment controls sediment and water flux of foreland transverse rivers, and its size has a significant influence on both channel morphology and river-fold interactions of the Tugerming anticline. Among the transverse rivers studied, those with large hinterland catchments (>80 km2) were dominated by braided river channels. In these cases, rivers respond to changes in channel gradient due to fold growth primarily through aggradation and degradation processes. Conversely, rivers with limited hinterland catchments (<80 km2) or originating within the fold, show a prevalence of incised meander channels. Moreover, channels accommodate gradient changes induced by the growing fold, primarily altering channel morphology, including channel sinuosity, slope, and width-to-height ratio. Our study reveals the significance of considering the hinterland catchment size in interpreting river-fold interactions and associated channel morphology within foreland transverse drainages. • We study transverse drainages in the Tugerming anticline in South Tian Shan foreland. • Geomorphic indices suggest lateral growth of the Tugerming fold towards both ends. • The lateral fold growth exhibits significant along-strike segmentation characters. • Hinterland catchment sizes affect channel morphology and river-fold interaction. [ABSTRACT FROM AUTHOR]

The Eastern Tian Shan, one of the most active intracontinental orogenic belts, should bear important information on the mechanisms of intracontinental mountain building. In this study, detrital zircon U-Pb geochronological analysis of the Cenozoic Tiereke section succession in the northern Tarim Basin-Eastern Tian Shan convergence zone, combined with stratigraphic results, reveals the provenance histories of the Cenozoic sediments in the northwestern Kuqa Depression of northern Tarim Basin. Nine Cenozoic samples obtained from the strata of the Kumugeliemu Group to the lowest Kangcun Formation of the Tiereke section exhibit high resemblance to provenances of the south-Eastern Tian Shan, indicating existence of a prolonged eroding relief within this mountain since the early Cenozoic (∼54 Ma). This prolonged state of eroding relief requires continuous intracontinental deformation of the Eastern Tian Shan to sustain a provenance region, implying immediate deformation responding to the initial Indian-Eurasian collision. Furthermore, the south-Eastern Tian Shan served as the only source region for the northwestern Kuqa Depression of northern Tarim Basin, demonstrating that the upper-crustal boundary between the south-Eastern Tian Shan and the northern Tarim Basin was possibly stationary during most of the Cenozoic Era (∼54 Ma to ∼9.7 Ma). Such a stationary basin-orogenic boundary would favor the predictions of the pure-shear-like thickening model for the intracontinental mountain building during this period. We suggest that the long-lived mountain building of the Eastern Tian Shan may be due to its small convergence rate. • Kuqa Depression received sediments from south-Eastern Tian Shan during ∼54–9.7 Ma. • N. Tarim-Eastern Tian Shan boundary was a stationary feature. • Uplift of south-Eastern Tian Shan driven by pure-shear-like crustal thickening. [ABSTRACT FROM AUTHOR]

• L Neoproterozoic deposits in SW Tarim record alluvial to shallow marine evolution. • The sequence indicates evolution from rift to passive margin/cratonic basins. • The basin evolution produced source rocks and reservoirs. The Late Neoproterozoic sedimentary sequences in the Tarim Basin are pivotal for understanding basin evolution and related tectonic setting, and evaluating the hydrocarbon perspective. In this study, tectonostratigraphic investigation has been conducted on the Late Neoproterozoic succession in the Yutang area, including strata of the Kexili, Yutang, Kuerkake and Kezisuhumu formations, along the Xinjiang-Tibet Highway ~90 km southwest of the Yecheng at the southwest Tarim Basin. The results indicate that the sediments represent a fluvial/alluvial-lacustrine-shallow marine tectonostratigraphic sequence complex upward the section, which is comparable with the deposition of sedimentary basin obeying evolution path from syn-rifting, late-rifting, transitional to post-rifting stage. These results lead to an interpretation of evolution from rift basin to passive margin or cratonic basin for the southwest Tarim Basin during the Late Neoproterozoic. Of these strata, the lacustrine dark shales of the late-rifting stage and the dolomites of the post-rifting stage can server as high-quality source rocks and reservoirs, respectively. [ABSTRACT FROM AUTHOR]

The Western Kunlun ranges and its foreland basin, the Tarim Basin, define the northwestmargin of the Tibetan Plateau, and provide important information on the Cenozoic expansionof the plateau after the India-Asia collision. In this study, we present a high-resolutionseismic reflection profile along the Hotan-Mazatagh transect of the Western Kunlun thrustsbelt in order to decipher the distribution of deformation and its propagation. Deformation inthis transect can be separated into three roughly east-west striking structures fromthe south to the north: the Hotan anticline, the Manan anticline, and the Mazataghthrust belt. The Hotan anticline is a fault-bend fold, mainly formed by the hangingwall sliding from the lower decóllement along the lower Cambrian units over apre-existing fault ramp into the upper decóllement that is located at the base ofthe Cenozoic strata. The Manan anticline, located ∼100 km north to the Hotananticline, is a reactivated low-amplitude fold with decreasing deformation upwards, theformation of which is mainly controlled by the lower decóllement. The Mazatagh thrustbelt, located ∼230 km north to the Hotan anticline, is controlled by both the upperdecóllement and the lower decóllement with the former ramping to the surface and thelatter building the Mazatagh anticline. The balanced cross-section reveals a totaldeformation of ∼28.93 km along this transect, with most deformation (∼25.0 km)transmitted by the upper decóllement among which at least 7.7 km of shortening hasbeen accommodated by the layer parallel compaction. The rest of shortening hasbeen absorbed by the Manan anticline (0.17 km) and the Mazatagh anticline (∼3.7km), respectively, transmitted along the lower decóllement. Our study highlightsthe effects of decóllement layer on transmitting deformation from the orogen intothe intracontinental region, the pre-existing structures on localizing distribution,and the penetrative strain on accommodating relatively homogeneous shortening. [ABSTRACT FROM AUTHOR]

Abstract The structural evolution of the Keping fold-thrust belt in the South Chinese Tian Shan, NW China is poorly understood. Here, we present the results of a series of scaled sandbox models based on the structural architecture of the Keping fold-thrust belt in our investigation of the effect of overburden thickness on deformation mechanisms in fold-thrust belts. These models simulated the evolution of the Keping fold-thrust belt, where the western segment was shortened with a thicker overburden relative to the eastern segment. Model results confirm that fewer thrust faults with wider spacing develop in thicker cover units, whereas more thrust faults with narrower spacing develop in thinner cover units. Transfer zones also form as a result of faster and farther propagation in a segment with thicker overburden, consistent with the prediction of the critical taper theory. Our modeling further shows that due to the episodic accretion of thrust wedges and non-simultaneous formation of thrust faults, the deformation front may locally propagate farther in the thinner overburden. Alternatively, there may not be so much difference between two parts of sand layers with different thicknesses, an observation that is inconsistent with the theoretical prediction. The similarities between the model and real geological observations suggest that the variations in the overburden thicknesses across the Piqiang Fault transfer zone strongly influenced the development of the structural architecture of the Keping fold-thrust belt. They further indicate that the growth of fold-thrust belts in nature is episodic, and that the propagation of deformation front cannot be simply predicted by the critical taper theory. The overburden thickness variations across the Piqiang Fault transfer zone were produced by high angle reverse faulting along the pre-existing Piqiang-Selibuya Fault during the late Pliocene and associated crustal uplift and erosion of the hanging wall strata. Highlights • The width of a fold-thrust belt and the spacing of its thrusts are controlled by overburden thickness. • Thicker cover units generate fewer thrust faults with wider spacing. • Development of thrust wedges is episodic and formation of thrust faults in a fold-thrust belt is non-simultaneous. • Thickness variations in overburden cause variations in deformation in different segments of a fold-thrust belt. • Propagation of deformation front cannot be simply predicted by the critical taper theory. [ABSTRACT FROM AUTHOR]

Abstract In this study, we report a bimodal magmatic suite of gabbroic-granitic rocks in the Cuona area of the eastern Tethyan Himalayas, which is related to the rifting event between Greater India and western Australia in eastern Gondwana. Whole-rock major and trace elements, SHRIMP zircon U-Pb geochronology and Hf isotopic analysis were conducted to reveal the petrogenesis of the bimodal suite and through this to explore the tectonic implications. Our main findings include the following. First, the gabbros and granites were emplaced synchronously at 140–137 Ma, considering the field relationships they comprise a bimodal suite. Second, the gabbros are enriched in light rare-earth-elements (LREE), depleted in heavy rare-earth-elements (HREE) with slight Eu anomalies, and have εHf(t) values of +0.04 − +8.30, which as a whole, suggests that they were derived from an ocean island basalt (OIB)-like mantle source. Third, the granites display low MgO, CaO, and Al 2 O 3 , marked enrichment in LREE, highly refracted HREE with strongly negative Eu anomalies and εHf(t) values of −2.01 to +1.71, all of which ultimately gives the characteristics of A1-type granites. Based on these observations, we propose that the bimodal suite is formed in a continental rift. Specifically, the gabbros originated from the mantle plume, whereas the granites derived from the upper crust with garnet-bearing metapelite. This rifting event initiated at 140 Ma, which places bounds on the initial breakup of eastern Gondwana, specifically the separation of Greater India from western Australia. Highlights • A bimodal suite in the eastern Tethyan Himalayas was emplaced at 140–137 Ma. • The bimodal suite is generated by magma mixing in a continental rift. • The rifting records the initial breakup of East Gondwana at 140 Ma. [ABSTRACT FROM AUTHOR]

Abstract The Tibetan Plateau offers an example for understanding the processes of continental collision and subsequent intracontinental deformation. The Jiuxi Basin, located at the northeastern margin of the plateau, bears crucial information on the growth processes of the NE Tibetan Plateau. Combined with published magnetostratigraphic constraints, integration of stratigraphic investigation and detrital zircon geochronological analysis on the sediments of the Cenozoic Hongliuxia section in western Jiuxi Basin suggests a major reorganization of the basin infill process at the period between depositions of the Baiyanghe and Shulehe formations at ~17 Ma. This finding is documented by (1) a generally upward-thinning sequence followed by an upward-coarsening sequence with corresponding changes in sedimentary facies, (2) shifting of the paleocurrent from the south to the north, and (3) shifting of the provenance from the Bei Shan-Kuantan Shan-Hei Shan in the north to the North Qilian Shan in the south. These results suggest that tectonic deformation arrived in the North Qilian Shan by ~17 Ma and lend support to the outward-growth model for the Tibetan Plateau. Highlights • Reorganization of basin infill process in the western Jiuxi Basin at ~17 Ma. • Indication that convergence-related deformation arrived in North Qilian Shan. • Support for the outward-growth model of the NE Tibetan Plateau. [ABSTRACT FROM AUTHOR]

• The northern Tarim Craton experienced Ediacaran rift-drift transition. • Two stages of continental rift were recorded by basin filling and magmatism. • A distributed lithospheric deformation was followed by a localized rifting. • The second stage of rifting migrated toward the craton margin led to the continental breakup. • Comparable stratigraphy and magmatism with YCTB supports conjugate rifted margins. The spatiotemporal evolution of late Neoproterozoic sedimentary basins and their tectono-magmatic context provide essential information regarding the continental rift process of the Tarim Craton during the fragmentation of the Rodinia supercontinent. However, the incomplete exposure of strata and magmatism in the distal continental margin hinders the understanding of different rift phases that trigger continental breakup. The Sawapuqi region is currently located at the northernmost margin of the Tarim Craton and presents an uninterrupted sedimentary sequence and volcanic rocks from the latest Precambrian to the Cambrian period. Herein, we perform an integrated analysis of the Sawapuqi sub-basin and provide critical insights into the Ediacaran stratigraphic and tectono-magmatic evolution that shed light on the final rifting phase. The Sawapuqi sub-basin preserves regressive and transgressive successions, ranging from thick-bedded siltstones and siliceous rocks at the lower unit of the Sugetbrak Formation, through shore gravel-bearing laminated sandstone accumulation (upper unit), and restricted platform stromatolitic carbonates (Qigebrak Formation), to Cambrian mature passive margin sedimentation. An alkaline basaltic layer is interbedded within the coarsening-upward sedimentary packages of the early Ediacaran, recording the final rift-related magmatic pulse in the northwestern Tarim margin. The geochemical signatures of these basalts suggest a relatively shallow-depth derivation from the enriched mantle reservoir in an intraplate setting. The detrital zircon provenance of the coarse-grained siliciclastic to pebbly feldspathic debris sandstone sequence of the upper Sugetbrak Formation indicates the hybrid sediment infills from local metamorphic basements and Neoproterozoic igneous rocks, with progressively increased contribution from the coeval granites in the northern periphery of the Tarim Craton. The stratigraphic evolution from syn -rift clastic rocks to post-rift carbonates and the transition of detrital provenance observed in the Sawapuqi sub-basin suggest the development of a breakup succession at the end of the early Ediacaran period. The margin-localized continental extension and mantle-derived volcanism during the early Ediacaran differed from the distributed extension and bimodal magmatism during the Cryogenian, indicating two-stage extensional modes and subsidences prior to the lithospheric breakup. The rift system of the latter stage, which migrated oceanwards, eventually led to the continental breakup in the northwestern margin of the Tarim Craton. Comparable late Neoproterozoic stratigraphy and magmatic pulses between the Tarim Craton and Yili-Central Tianshan Block (YCTB) support their reconstructions as two conjugate rifted margins. This study indicates that the rift-drift tectonics triggered by this prolonged episodic rifting between the Tarim Craton and the YCTB was closely associated with the final fragmentation of Rodinia. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Pamir bears essential information for understanding intracontinental tectonic processes within the context of India-Asia convergence. However, it is unclear whether the arcuate shape of the Pamir is entirely the result of the India-Asia collision, or may have been in part an inherited, pre-Cenozoic feature. In this study, we address the evolution of the NE Chinese Pamir during the Paleogene by reviewing the stratigraphy of twelve sections in the western Tarim Basin and the establishment of sedimentary facies. The results indicate three episodes of deposition of alluvial coarse sediments in the foreland regions of NE Chinese Pamir during the (1) early Paleocene, (2) late Paleocene to early Eocene and (3) middle Eocene to Oligocene, respectively. These are correspondingly attributed to (1) retroarc deformation in an Andean-type margin of the southern Asia during subduction of the Neo-Tethys Ocean, (2) the immediate response in the Pamir to the India-Asia collision, and (3) continued India-Asia convergence. The alluvial conglomerates with grain-size up to 5–10 cm, imply a transport distance <60 km from the fan apex. This result, together with the 20–50 km northward thrust displacements, suggests that the orogen/basin boundary between the Pamir and the Tarim-Alai Basin was located less than ca. 80–110 km to the south from the present location of the Main Pamir Thrust during the Paleogene, indicating the arcuate shape of the Pamir was already largely established by the Paleogene, rather than entirely a result of the India-Asia continental collision. [ABSTRACT FROM AUTHOR]

The Sikouzi Section is located towards the northern limits of the East Asian summer monsoon, providing the opportunity of placing the stratigraphic record into the context of the East Asian summer monsoon history. We present here the results of the details of the sedimentology of the Neogene succession of the section and use these to provide insights into the evolving history of the East Asian summer monsoon. The record is marked by a strongly expressed early Miocene lacustrine phase. A well-defined evaporate bed defines the top of the lacustrine succession, marking the onset of more arid conditions during the middle Miocene. The overlying succession is dominated by a series of alluvial packages, extending into the late Pleistocene with varying stratigraphic architectures and including a subordinate lacustrine component. Given the regional setting, the onset of drier conditions during the middle Miocene must relate to a downturn of summer monsoon activity. We focus on the question: what 'forced' this palaeoclimate event? Earlier biostratigraphic work places the explanation of this change into the context of the global-scale middle Miocene climate reorganisation. Here we explore this question in the context of regional-scale climate dynamics and propose that the onset of drier conditions over the study area was a response to atmospheric subsidence driven by circulation changes related to the growth of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

[Display omitted] • Onset time of the basin was the late Miocene to early Pliocene (∼5.8–4.6 Ma). • Multiple depocenters existed in the basin and intergraded to one in the Quaternary. • Eastward migration of the depocenter records the collision between the Pamir and South Tian Shan. The Pamir salient is the preeminent example of an intracontinental collision and defines the western end of the Himalayan-Tibetan orogen. Previous work has paid much attention to reveal the internal evolution of the Plateau. However, the structural growth and expansion of the Northern Pamir still have several unknowns. To address this process of the indentation, we describe the architecture of the Wupoer Piggyback Basin (WPB), the westernmost tip of the Tarim Basin, in between the northeastern Main Pamir Thrust (MPT), and the Pamir Frontal Thrust (PFT). The geometry of the WPB growth strata and its relationship with the compressive structures were explored through six seismic sections, five cutting the WPB along dip and one along strike. According to the sense prevailing in the literature, we define the onset of a piggyback basin with the first evidence of tectonic deformation within the basin fill. Interpreted from the seismic sections and field work, an unconformity between the Atushi Fm. and the underlying strata marks the base of the WPB, dated the onset of the basin at the latest Miocene to early Pliocene (∼5.8–4.5 Ma). The growth strata were separated into 6 units above the unconformity (G1-G6). The relative isopach maps reveal the existence of three main depocenters, evolving to a single one in the Quaternary. The structural interpretation documents the PFT is significantly segmented by transfer faults and lateral ramps. The eastward migration of the depocenter since the Quaternary points to the oblique collision between the Pamir and the South Tian Shan and gradual encroachment of deformation towards the east. [ABSTRACT FROM AUTHOR]

This work studies new petrological and geochemical data and zircon U-Pb ages for bimodal intrusive rocks from Xinglong region, Hainan Island. Zircon U-Pb dating yields mean U/Pb ages of 238 ± 2 Ma and 234 ± 2 Ma for diabasic and granitic phases, respectively, representing the Middle Triassic emplacement. The diabase and granite bodies were formed from discrete mafic and acidic magma sources that experienced local mechanical mixing at their mutual contacts. Although SiO content of intrusions is bimodal, trace element ratios indicate that both were formed in a post-orogenic extensional setting. Sr-Nd isotopic composition reflects a shared EMII type enriched mantle source component, possibly influenced by subduction-fluid metasomatism. [ABSTRACT FROM AUTHOR]

Measurements of anisotropy of magnetic susceptibility (AMS) were performed on a gabbro pluton and 7 diabase dykes in the Wanning area, southeast Hainan Island. Rock magnetism showed that pseudo-single domain (PSD) to multidomain (MD) Ti-poor magnetite carries the magnetic fabric in the gabbro pluton whereas MD Ti-poor magnetite carries the magnetic fabric in the diabase dykes. The corrected anisotropy degree ( P) in most specimens was found to be less than 1.2 which is indicative of a possible flow-related magnetic fabric. The AMS eigenvectors within each site are generally well grouped. The maximum susceptibility axes ( K) of the gabbro pluton are inclined towards the north at low angles (< 30°). K axes of the diabase dykes are inclined towards the NNW and SSE with dip angles of ⩽ 30°. From this study, it appears that the emplacement mode of the gabbro pluton was characterized by intrusion from the north to the south at a low angle whereas the diabase dykes were emplaced from the NNW to the SSE at low to moderate angles. This was verified by comparison of the rock fabric to the magnetic fabric. All of this evidence leads to the conclusion that the Wanning gabbro pluton and diabase dykes were the products of pulsative intrusion from the same magma chamber in the area far to the north of Wanning, which suggests that basic rocks may exist beneath the Indosinian granite in the area to the north of Wanning. [ABSTRACT FROM AUTHOR]

Abstract: The Cenozoic evolution of the Liupan Shan, situated at the northeast of the Tibetan Plateau, will provide constraints to test the models and mechanisms of the evolution of the plateau. In this contribution, the Sikouzi section, at the east of the Liupan Shan, has been selected to study Liupan Shan’s uplift history. At around 9.5Ma, constrained by the magnetostratigraphy, the sediment and depositing architecture characteristics obviously changed. Synchronously, flow direction changed from E→W to W→E, and accumulation rate increased to more than double. All these evidences suggest that the Liupan Shan initiated uplifting at around 9.5Ma. Subsequently, a stage of intense uplift happened during 8.2–7.3Ma, indicated by the apatite fission-track (AFT) data across the Liupan Shan. Regional comparison indicates that this stage of uplift is not only with local but also regional significance. The Miocene uplift of the Tibetan Plateau triggered the intensification of the East Asian Monsoon and Asian intercontinental aridity, which has been implied by the pollen results of the Sikouzi section. [Copyright &y& Elsevier]

In northeastern China, Cenozoic ‘reverse faults’ can be found in most basins. It was proposed that these faults were the products of inversion tectonics during a Cenozoic regional compressional event. This explanation is inconsistent with regional structures that are dominated by normal faults on seismic profile. As a typical example, the Rongxintun fault in northeastern Liaohe basin is systemically analyzed on the basis of deformation style, sedimentary character, and systemic mapping using seismic data. We conclude that the Rongxintun fault was related to right-lateral strike slipping of the Yannan main fault during the late Paleogene when the Dongying deposition occurred, and it was a secondary right-lateral/reverse fault (P Plane Fault) of the Yannan strike-slip fault system. The fold was a fault related fold formed as a result of movement along the Rongxintun fault. According to this analysis of the Rongxintun fault, we conclude that the Cenozoic ‘reverse fault’ in northeastern China was a secondary right-lateral/reverse fault of a strike-slip fault system and did not represent a compressional event. This kind of mechanism of ‘reverse faulting’ is consistent with the fact that there was large-scale strike-slip faulting in northeastern China during the Cenozoic. [Copyright &y& Elsevier]

The western Kunlun Mountains and the adjacent southwestern Tarim Basin define the northwestern boundary of the intensely deformed Cenozoic Tibetan Plateau, and thus should bear important information on the growth processes of the NW Tibetan Plateau. In this study, the integration of a stratigraphic investigation of the Cenozoic Keliyang succession section and a seismostratigraphic analysis on the seismic reflection profile reveal the sedimentary evolution and basin-filling processes of the southwestern Tarim Basin. Our results suggest a significant depositional shift from marine facies during the depositional periods of the Aertashi to Bashibulake Formations to continental facies during the depositional periods of the Keziluoyi to Xiyu Formations. This shift, which corresponds to southward depositional thickening, has been attributed to the uplift of South Kunlun and the onset of foreland basin subsidence along the southwestern Tarim Basin. Strata from the Keziluoyi to Xiyu Formations form an upward-coarsening sequence that is interrupted by a subordinate upward-thinning sequence in the Anjuan Formation. These results, in combination with the northward migration of the depocenter by at least ~56 km since the depositional period of the Artux Formation and previous studies on basinward deformation propagation, demonstrate that the tectonic loading of the western Kunlun has propagated northward to North Kunlun, which suggest expansion of the NW Tibetan Plateau since this period. We posit that the upper-crustal boundary between western Kunlun along the NW Tibetan Plateau and the Tarim Basin is a northward movable feature. This would support the hypothesis that the substantial lower Tarim Plate (>~56 km if calculated from the magnitude of the northward depocenter migration) has underthrusted southward beneath western Kunlun. • Onset of Cenozoic SW Tarim foreland basin since the Keziluoyi period. • Foredeep of the foreland basin migrating northward by >~56 km. • Upper crustal Tarim/W. Kunlun boundary is a northward movable feature. • >~56 km lower Tarim Plate has underthrusted southwards beneath W. Kunlun. [ABSTRACT FROM AUTHOR]

The Miocene Aertashi Debris-Avalanche Deposits at the southwestern Tarim Basin, the foreland basin of the Eastern Pamir (NW Tibetan Plateau), have an incredibly long-runout distance (much longer than 130 km) and provide critical constraints on the evolution of drainage patterns, tectonics, and geochronological framework of the region. To investigate when and how the deposits formed, we conducted extensive field and microstructural observations, as well as geochronologic analyses. The deposits are massive, poorly sorted, and matrix-supported, containing massive blocks, jigsaw-fractured clasts, and fluidal-shaped cataclastic lava bodies. Some cataclastic lava bodies up to ~25 m across are compact on the hand-specimen scale but are pervasively fragmented on the microscale. Microstructural observations of particles show abundant diagnostic features of highly-energetic collisions, such as conchoidal fractures and microcracks. Both field and microstructural observations indicate that the deposits were derived from a debris avalanche. Pervasive cataclasis of many fluidal-shaped lava bodies is interpreted to record intense shear of hot, semisolid lavas close to the glass-transition temperature, in which phenocrysts deformed brittlely while the glassy components mainly deformed plastically and controlled the rheology of the bodies as ductile material. The mechanical properties of clasts are important in controlling their deformation within debris avalanches. The presence of abundant hot, semisolid lavas in the studied deposits may be critical for the survival of megaclasts after a long-runout distance. The field and microstructural observations and geochronologic analyses show that debris-avalanche deposits can aid in constraining regional geochronologic framework. These results consistently confirm that the Aertashi Debris-Avalanche Deposits were deposited at ~11 Ma, during rather than long after the eruptive period. • The massive, poorly-sorted volcaniclastic deposits within the Xiyu Formation at Aertashi was formed by a debris avalanche. • The intense cataclasis of many fluidal-shaped lava bodies occurred when they cooled close to the glass-transition. • The mechanical properties are critical in controlling debris-avalanche clasts fragmentation behaviors during transport. • The Aertashi debris-avalanche deposits were emplaced at ~11 Ma, rather than long after the volcanic activity ceased. [ABSTRACT FROM AUTHOR]

• Cona rift is the easternmost rift in the Himalayas. • Multi-thermochronometers suggest 3.0–2.3 Ma rift initiation. • Initiation of Himalayan rifts youngs monotonically eastward. • Lithospheric flow driven by asynchronous GPE gradients caused E–W extension. Several competing hypotheses have been proposed to explain east-west extension observed across the Himalayan orogen, based primarily on observations from the western and central Himalaya. They make predictions for the temporal and spatial patterns of deformation in the eastern Himalaya. These tectonic models include radial spreading or oroclinal bending of the Himalayan arc, oblique convergence of the Indian continent, tearing or lateral detachment of the Indian slab and eastward flow of lithosphere. Here, for the first time we constrain the activity history of the Cona rift, the only north-trending rift currently recognized in the eastern Himalaya, based on biotite and K-feldspar 40Ar/39Ar and zircon and apatite (U–Th)/He thermochronology, to evaluate these proposed rifting mechanisms. Low-temperature thermochronological results suggest that the Cona rift is the youngest rift system in the Himalayas: after a slow phase of exhumation since ∼14 Ma (∼0.2–0.13 mm/yr), normal faulting initiated here at ∼3.0–2.3 Ma with a fault slip rate of ∼3.8–1.6 mm/yr and a horizontal extension magnitude of ∼2–5 km. Analysis of rifting across the Himalayas shows that rift initiation ages young eastward, which is matched by eastward decreasing rift-extension magnitudes. Monotonically eastward younging rift development is consistent with the tectonic model involving eastward lithospheric flow driven by Indian slab dynamics and coupled asynchronous gravitational potential energy gradients. [ABSTRACT FROM AUTHOR]

The Cenozoic India-Asia collision reactivated several ancient thrust belts in the interior of the Asian continent, including the West and East Kunlun ranges in central Tibet, and the Tian Shan and Qilian Shan further north. Both basin sedimentary records and thermochronological data show that the uplift of the South Tian Shan and Qilian Shan at the north occurred earlier than that of the West and East Kunlun ranges at the south. Diachronous continental deformation and initiation of uplift during orogeny are contrary to the general notion that the stress transfer in response to the India-Asia collision should propagate sequentially from south to north. Here we systematically conducted 2D thermo-mechanical simulations to investigate possible factors for this diachronous deformation pattern. The results show that a hotter Tian Shan lithosphere, with Moho temperature >100 °C hotter than that of the proto-southern Asia, leads to an earlier and higher uplift of the Tian Shan. Additionally, a faster convergence rate of the India-Asia collision results in a more efficient transfer of boundary force into the upper plate's interior, giving rise to a larger amount of uplift in the Tian Shan. We conclude that intra-continental ranges with weaker lithosphere, such as the Tian Shan or Qilian Shan, uplift earlier than stronger regions, such as the West and East Kunlun ranges. Faster convergence rates amplify this situation. Our results imply that the unique diachronous growth of the Tibetan plateau arises from its complex pre-collisional history, which includes collided arc-continent terranes with hotter and weaker lithosphere that respond to the effects of far-field stress transfer. • Controls on intra-continent diachronous rise are investigated by numerical modeling. • Intra-continent thrust belts with weaker lithosphere uplift earlier. • Faster convergence rate at the boundary amplifies the diachronous rise situation. • Evolution of Tibetan plateau is controlled by the complex pre-collisional history. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau offers an ideal region for understanding the processes of continental collision and related intracontinental deformation. However, when the Cenozoic deformation was initiated in the present northeastern margin of the plateau, >2000 km north to the Indian-Eurasian collision front, remains an issue in debate. Two competing end-member models have been proposed, involving immediate deformation response and progressive deformation propagation. Solving this problem partly relies on determining whether there was contemporaneous deformation with initial Indian-Eurasian collision along the northeastern margin of the Tibetan Plateau. In this study, we employ apatite fission track (AFT) analysis to shed new light on the exhumation history of the Kuantan Shan-Hei Shan along the northeastern margin of the Tibetan Plateau, with a motivation to determine whether deformation-related exhumation during initial collision stage occurred in the region. The 22 granite samples produce AFT ages ranging from 22.3 ± 2.6 Ma to 175 ± 18 Ma and mean track lengths from 11.17 ± 2.26 μm to 13.63 ± 1.93 μm. Thermal history modeling indicates five episodes of rapid exhumation-related cooling, which took place in the early Jurassic, early Cretaceous and late Cretaceous, during/since the Eocene and since the middle Miocene. The exhumation events prior to the Cenozoic are attributed to far-field responses of successive closure of fossil oceans and assembly of blocks along the southern margin of the Eurasian continent. The Eocene exhumation along the Kuantan Shan-Hei Shan is speculated to represent an immediate response to the initial Indian-Eurasian collision. These results lend support to the immediate deformation response model along the northeastern plateau. The episodic exhumation observed in this study, combined with previous geophysical findings, implies that the Kuantan Shan-Hei Shan represents the southern margin of the Alashan Block, serving as a significant and long-lived lithospheric weak zone susceptible to intracontinental deformation during episodes of far-field tectonic event. • AFT analysis conducted in Kuantan Shan-Hei Shan at NE Tibetan Plateau margin • Eocene exhumation occurred in the Kuantan Shan-Hei Shan. • Data supports the immediate deformation response model. [ABSTRACT FROM AUTHOR]