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The Altyn Tagh fault (ATF) is a large lithospheric left-lateral strike-slip fault, marking the northwestern boundary of the Tibetan Plateau. Understanding the tectonic history of the ATF provides insights into the growth pattern of the Tibetan plateau, as well as the deformation mechanism of complex fault systems.However, despite numerous research efforts, the deformation of the ATF is still a subject of discussion, especially its interaction with the other two major faults in the northeast Tibetan Plateau: the strike-slip Eastern Kunlun fault and the Qilian Shan fold-thrust belt. The triple junction analysis has proven successful in explaining the spatial-temporal variations of fault kinematics. Therefore, here we use the principles of triple junctions to discuss the transformation of the ATF in its intersections with the Qilian Shan and Eastern Kunlun Shan, with the assistance of geological evidence from fieldwork and satellite images. We propose that the initiation of the left-lateral motion of the Eastern Kunlun fault led to an FFF triple junction in the former western end of the ATF. Meanwhile, the deformation on the southern Qilian Shan forms an TFF triple junction with the splays of the ATF. The unstable triple junctions will trigger the growth of the ATF and complicate the deformation the Qilian Shan and the Eastern Kunlun Shan. Our research firstly applies triple junction principles to both ends of the ATF, and presents a new model of the evolution of the ATF and its surrounding orogens, shedding lights on the history of Tibetan Plateau.

The Steptoean Positive Carbon Isotope Excursion Event (SPICE) represents one of the largest carbon cycle perturbations in the Cambrian, which coincided with climatic changes and dramatic extinction of shallow-shelf faunas. This carbon perturbation has been linked to a global expansion of marine euxinia (SPICE-OAE), but the precise timing, duration and extent of changing redox conditions across the SPICE event, as well as its influences on the coeval biotic evolution, remain unclear. Here, we report paired δ98Mo–δ238U data across this event, constrained by a radioisotopically anchored astrochronology, based on Alum Shale samples from the Albjära-1 and Billegrav-2 drill-cores in Scandinavia. The δ98Mo profiles are largely invariant around 1.08±0.21‰ with short-term fluctuations parallelling changes in pyritization of iron, possibly as a result of locally varying [H2S]aq in the water column and/or fluctuating reactive iron delivery. The bottom water is interpreted to have been primarily anoxic, but with frequent local variations between oxic and sulfidic conditions in a moderately restricted basin. A novel analytic method based on variation of Mo concentrations at millimeter scale stratigraphic resolution was applied to distinguish between local and global redox signatures, revealing that cyclic redox changes are recorded in the Alum Shale sea with periods of ∼0.3 Myr, ∼0.9 Myr and ∼0.15 Myr before, during and after the SPICE-OAE, respectively. Stratigraphic profiles of Mo, U, Mo/TOC ratios and δ238U in the two cores show comparable trends, facilitating recognition of three chemically distinct stages across the SPICE event: 1) global expansion of marine euxinia (SPICE-OAE; 497.9–496.6 Ma), 2) global contraction of euxinia accompanied by enhanced carbonate weathering inputs (496.6–495.8 Ma) and 3) general global oxygenation (495.8–494.4 Ma). The first in situ correlation between the onset of the SPICE-OAE and the end-Miaolingian extinctions in Baltica corroborates that expansive anoxic and sulfidic water masses likely contributed to the biotic crisis. The time gap between the start of the extinction and the appearance of the new fauna in Baltoscandia is estimated to be ∼600 kyr.

This work proposes a new lateral foreland thrusting model based on geological evidence and 3-D particle discrete-element simulation to explain the Longmenshan southeastward thrusting during the closure of the Songpan-Ganze basin. The Late Triassic NE−SW compression caused by the northward movement of the Qiangtang Block and the resulting differential shortening within the wedge-shaped Songpan-Ganze terrane produced southeastward topographic gradient. The thick sedimentary pile, driven by the horizontal tectonic force and the deviatoric stress generated from gravitational effect, and decoupled from the subducting basement by the low-strength décollement, was laterally extruded and resulted in the southeastward Longmenshan thrusting. Therefore, the Longmenshan thrust belt is a lateral foreland thrust belt of the Songpan-Ganze terrane. For the first time, 3-D particle discrete-element simulation was used for the geological study of the Longmenshan area, and it clearly reproduces the dynamical process of the Longmenshan southeastward thrusting and well predicts the Xiaojin Arcuate Zone. The particle discrete-element simulation results verify the new model and reveal that two key factors facilitate the lateral foreland thrusting: the wedge-shaped geometry that produces differential shortening and lateral topographic gradient, and the low-strength décollement that decouples the extruded sedimentary pile from the basement. The lateral foreland thrust belt, which is unique in its tectonic location and dynamic behavior, is a new kind of foreland thrust belt that is different from the pro-foreland and retro-foreland thrust belts, and it provides new insight into the tectonic evolution of collisional orogens.

The Yingxiong Range is the largest anticlinal belt within the triangular overlapping zone between the Altyn Tagh Fault and the Eastern Kunlun Fault and thus records the critical information concern...

The Junggar Basin, bounded by the West Junggar along late Carboniferous strike-slip faults in the west, is a post- orogenic successor basin within the Neoproterozoic to Paleozoic Central Asian Orogenic Belt (CAOB). The Junggar Basin is a key region for understanding the Permian rifting processes since it is located in an extensional step-over zone between the Irtysh and North Tianshan strike-slip fault zones that were most active in the Permian. Based on new seismic reflection profiles, detrital petrology and zircon U-Pb ages, together with regional geological data and a refraction seismic profile, this study investigates the tectonic evolution and the geodynamic mechanics of the basin. The early Permian phase of syn-rift mechanical subsidence in the western Junggar Basin formed half grabens. Volcanic detritus is abundant, and detrital zircon U-Pb ages show sediment supply was entirely local. During the middle Permian post-rift phase with thermal subsidence, sediment supply exceeded subsidence, and there are increasingly distant sources of sediment. The Permian regional extensional stress field between major post- accretionary strike-slip fault zones triggered the reactivation of the pre-existing late Carboniferous strike-slip faults in West Junggar and produced thinning of the crust beneath the Junggar Basin, with a β crustal stretching factor of 1.74. Seismic refraction data reveals asthenospheric upwelling resulted in underplated mafic lower crust (6–10 km). The location of initial rift axis in the Junggar Basin was controlled by the juxtaposition of thin and weak crust beneath the basin and relatively strengthened thick crust in the West Junggar attributed to the cooling of A-type granites, resulting from localized strain. Similar location of post-orogenic rifting in southwestern CAOB, in areas of high heat flow following collision, suggests that Junggar Basin is an example of a more general process.

Figures of simulation results, U-Pb data set for syn-tectonic calcite veins and codes for the simulation of the lateral foreland thrusting model created for this study using PFC3D 5.0.

The Duobagou Permian–Triassic granites of the Dunhuang orogenic belt are of great importance in understanding the tectonic evolution of the southernmost Central Asian Orogenic Belt. LA-ICP-MS U–Pb zircon ages indicate that Permian–Triassic granitic intrusions from the Duobagou area formed at 276–274 Ma and 246 ± 1 Ma. These granites have high SiO2, Na2O and K2O, but low Al2O3, CaO and MgO contents and belong mainly to the high-K calc-alkaline I-type granite series. Based on whole-rock geochemistry and Sr–Nd and zircon Hf isotopes, the Duobagou Permian–Triassic granites were dominantly derived from the partial melting of lower continental crust formed during late Palaeoproterozoic to Mesoproterozoic times in a post-collisional extensional setting. Permian granites with zircon ϵHf(t) values of −5.4 to +3.1 and Hf model ages of TDM2 = 1.14–1.70 Ga indicate the involvement of a mantle component in their petrogenesis. Triassic granites with higher zircon ϵHf(t) values (+0.5 to +3.8) and TDM2 = 1.08–1.31 Ga suggest more juvenile sources caused by a greater contribution of mantle-derived melts, indicating a significant crustal growth. Regional extension from lithospheric delamination and heating from asthenospheric upwelling were proposed to have triggered the partial melting of lower crust, resulting in the generation of the Permian–Triassic magmatism. This may have been the mechanism for the significant crustal growth during Permian and Triassic times in the southernmost Central Asian Orogenic Belt.

Forming the northern margin of the Cenozoic Himalayan–Tibetan orogen, the area surrounding the Qaidam Basin is a key region to study the mechanisms that govern the long-term evolution of intracontinental orogenic processes. Indeed, tectonic deformation in this region involves newly formed and inherited crustal and lithospheric structures, partition between horizontal and vertical movements, and a strong influence from external factors such as climate and erosion. This study proposes a description of the topography and crustal structure of the north Tibet ranges as an insight into their tectonic deformation characteristics. The topographic study includes the integrated analysis of regional topographic profiles, river profiles, slope maps and thermochronology data. The available geophysical, geological and structural data are used to draw regional, crustal-scale geological sections across northern Tibet to describe the regional crustal structure. We show that three deformation modes are expressed (block uplift, distributed shortening and crustal buckling) in structural compartments that involve either complete mountain ranges or some specific regions inside those ranges. We propose that a new crustal structure may develop parallel to the Altyn Tagh fault, connecting the eastern tip of the Qimen Tagh with the Haiyuan fault, across the Qaidam Basin. Supplementary material : Supplementary figures are available at https://doi.org/10.6084/m9.figshare.c.5841461 Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

The India-Eurasia convergence since early Cenozoic has established the Tibetan Plateau and the Circum-Tibetan Plateau Basin and Orogen System (CTPBOS). When and how the convergence-driving strain has propagated into the CTPBOS is of significant importance in deciphering the growth process of the Tibetan Plateau. In this study, we conduct a structural analysis of the West Kunlun-southern Junggar transect along the NW margin of the Tibetan Plateau to establish the deformation propagation and through this to determine the plateau growth processes. The results suggest a two-phase deformation mode. The first stage features deformation confined in pre-existing weak zones like the West Kunlun orogen, Buchu Uplift and Tian Shan orogen during Paleogene, in which the intracontinental strain was speculated to be mainly consumed by shortening of these weak zones. The second stage is characterized by deformation propagating into foreland regions since early Miocene, in which shorting along foreland fold-and-thrust belts of a scale of tens of kilometers and decreasing basinwardly plays a key role in absorbing intracontinental strain. We suggest that this two-phase deformation mode possibly reflects a shift of governing mechanism of the expansion of the Tibetan Plateau from a rigid-block manner to a critical wedge taper style. Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

The modern Tianshan Mountains and their surrounding basins have mainly been shaped by the far field effects of the Cenozoic India-Asia collision. However, precollision topographic evolution of the Tianshan Mountains and its impacts on the Junggar and Turpan Basins remain unclear due to the scarcity of data. Detrital zircon U-Pb dating of 14 new and 23 published samples from Permian to Neogene strata in the northern Western Tianshan Mountains, northern and southern Bogda Mountains and Central Turpan Basin, are combined with sedimentary characteristics (lithofacies, petrofacies and paleocurrent data) to investigate the temporal and spatial changes in sediment provenances. Based on the age characteristics of the source rocks in the Tianshan Mountains, the detrital zircons are divided into three groups: pre-Carboniferous zircons, mainly from the Central Tianshan Mountains; Carboniferous to Permian zircons, mainly from the North Tianshan and Bogda Mountains; and Mesozoic zircons, mainly from syn-depositional volcanic activity. The topographic evolution of the Tianshan Mountains and their relation to the Junggar and Turpan Basins can be generally divided into six stages. (1) Positive-relief Tianshan and Bogda Mountains and a rifted marine basin formed during the Early Permian to early Middle Permian following late Carboniferous orogenesis, as evidenced by interbedded alluvial fan conglomerates and postcollisional extension-related volcanic rocks along the basin margins, by marine deposits far from the basin margins and by the predominance of Carboniferous to Permian detrital zircons. (2) Fluvial to lacustrine deposits in the modern southern Junggar and Turpan Basins are characterized by abundant pre-Carboniferous zircons and consistently northward-flowing paleocurrents, indicating the submergence of the Bogda Mountains and a contiguous Junggar-Turpan continental depression basin during the late Middle Permian to the Triassic. (3) The Bogda Mountains began to uplift in the Early Jurassic, resulting in opposing paleocurrent directions, a sudden increase in sedimentary lithic detritus and the dominance of Carboniferous to Permian detrital zircons along the southern and northern margins of this range. (4) In contrast to the uplift of the Bogda Mountains, the other parts of the Tianshan Mountains experienced gradual peneplanation from the Early Jurassic to the Middle Jurassic, as confirmed by widespread fluvial to lacustrine deposits, even inside the modern Tianshan Mountains, and by the dominance of pre-Carboniferous detrital zircons. (5) The dominance of Carboniferous to Permian zircons in the southern Junggar Basin suggests the West Tianshan Mountains were uplifted during the Late Jurassic, while the dominance of pre-Carboniferous zircons in the Central Turpan Basin indicates continuous peneplanation in the Eastern Tianshan Mountains. (6) The initial shape of the Tianshan Mountains-Junggar Basin-Turpan Basin system was constructed in the Late Jurassic but was modified in the Cenozoic by the India-Asia collision, resulting in much higher Western Tianshan and Bogda Mountains, low Eastern Tianshan Mountains and well-developed foreland basins. These Cenozoic changes were recorded by the rapid cooling of apatites, the dominance of Carboniferous to Permian zircons in the southern Junggar Basin and northern Turpan Basin, and the dominance of pre-Carboniferous zircons in the Central Turpan Basin.

The evolution process and petroleum significance of two groups of fault structures, the NW-SE trending and near EW trending ones in the Cenozoic of Dongping-Niuzhong area of the Altyn slope, Qaidam Basin, were investigated using high precision 3-D seismic data. The NW-SE faults were generated in Oligocene, causing the formation of a series of folds related to transpression faults in the Niuzhong and Dongping area. After the Miocene, with the continuous extension of the Altyn Tagh strike-slip fault zone, the EW trending faults began to develop massively in Altyn slope. The activity of near EW trending faults and large-scale uplift of the bedrock in the northern Niuzhong area shared most of the compression torsion in Niuzhong and Dongping area, consequently, the activity of NW-SE trending faults weakened significantly after the Miocene. Then good hydrocarbon source rocks developed in the inherited Jurassic sags. The faults were effective pathways for oil and gas migration in Dongping and Niuzhong areas, and the oil and gas charging time matched well with the formation period of the NW-SE trending faults and their related structures, making the fault-related anticlines favorable targets for oil and gas accumulation. The Niuzhong area has been less affected by the Cenozoic movement after the Miocene, and thus has better conditions for gas reservoir preservation. Key words: Qaidam Basin, Altyn slope, Cenozoic, tectonic analysis, strike-slip fault, petroleum significance, Dongping-Niuzhong area

The relationship between the sinistral strike-slip Altyn Tagh Fault (ATF) and the internal tectonic deformation of the Qaidam Basin remains a controversial issue. Uncovering the relationship betwee...

The Tuoge Complex, the oldest basement block exposed in the northeastern Tarim Craton, northwest China, consists mainly of supracrustal rocks, tonalite-trondhjemite-granodiorite (TTG) gneis...

In this paper, high-resolution three-dimensional seismic data are used to interpret a transpressional salt tectonic structure in the Yingxiongling area, Qaidam Basin, China. The geometries of the salt structure and the Shizigou fault system that intersects it are precisely depicted. The Shizigou fault system is composed of suprasalt and subsalt components. The suprasalt component is a Y-shaped reverse fault, and the subsalt component is a complex flower structure. In previous studies, suprasalt and subsalt components were interpreted as two independent fault systems. This paper proposes instead that the suprasalt and subsalt faults are kinematically related and decoupled across the salt layer.

The Emeishan large igneous province (LIP) was emplaced on the western Yangtze plate during the Permian and its formation is primarily attributed to a mantle plume. Recent research has shown that material from this plume modified the melts in the Palaeotethys subduction zone. However, it remains poorly understood whether, in turn, the subduction of Palaeotethys affected the formation of the Emeishan LIP. We report here geochronological, petrological, geochemical and isotopic studies of a gabbroic intrusion located in Jiangwei, in the Dali area of the Emeishan LIP. The gabbro has a weighted mean SHRIMP U–Pb age of c. 262 Ma. The key geochemical features include: depletion in Nb, Ta and Ti; enrichment in Th, U and Sr; low light to heavy rare earth element ratios; 87Sr/86Sr(t) values of c. 0.707; and eNd(t) values of c.−0.21. We conducted pMELTS thermodynamic modelling and batch-melting calculations to evaluate the origin and evolution of the gabbro based on real components of low-Ti picrites and xenoliths from the Yangtze lithosphere. Our results show that 3% melting of a hydrated spinel peridotite source from the Yangtze lithosphere can produce magma equivalent to the gabbroic intrusion. Integrating this conclusion with the tectonic background of the western Yangtze plate and the volcano-stratigraphic record of the Emeishan LIP, we infer that the early-stage magmatism of the Emeishan LIP was triggered by Palaeotethys back-arc extension with fluid modification from the subducting slab. Supplementary material: Tables S1–S7 are available at https://doi.org/10.6084/m9.figshare.c.5433267

International audience; The early Cenozoic topography of the northern Tibetan plateau remains enigmatic because of the paucity of independent paleoelevation constraints. Long‐held views of northward propagating deformation imply a low Paleogene elevation, but this prediction is speculative. We apply flexural modeling to reconstructed Paleogene isopach data obtained from the Qaidam basin, which requires a larger topographic load in the Qilian Shan and a smaller load in the Eastern Kunlun Shan. Incorporating knowledge of proto‐Paratethys marine incursions in the Paleogene Qaidam basin, we infer a topographically low (0.4‐1.0 km) Eastern Kunlun Shan and a higher (0.4‐1.5 km) Qilian Shan during the Paleogene. This implied paleo‐relief contrasts with previous predictions and suggests more recently, Neogene surface uplift in the Eastern Kunlun Shan has been more significant than in Qilian Shan, highlighting diachronous growth of the northern Tibetan plateau. The low‐moderate paleoelevation implies a warmer and more humid climate in Northern Tibet during the Paleogene.

Table S1. The SHRIMP U–Pb testing results.

Accumulating sediments is an inherent attribute of endorheic basins. Overall aggradational stratigraphic architecture can be predicted in endorheic basins, whereas the offlap process can be regarded as an important geological indicator in closed basins. This study theoretically proposes the possible offlap process in endorheic basins, and then explores the actual pattern of the offlap process in the Qaidam basin, the largest endorheic basin in the northern Tibetan Plateau. According to the interpretation of drilling well data and seismic reflection profiles, widespread offlap is identified at all the three boundaries of the Qaidam basin since the late Miocene. The offlap process in endorheic basins is controlled by newborn faults or new isostatic flexures inside the previous basin margin. Interpretation of seismic reflection profiles reflects that the rigid Qaidam block was gradually broken during the India‐Eurasian collision and the plateau progressively expanded from pre-existing mountains to basins.

International audience; As the largest depression in the Tibetan plateau, the Qaidam basin preserves over 10 km thick of Cenozoic sediments. Those sediments represent a unique archive of the evolution of the northern part of the Tibetan plateau and of intracontinental deformation in general. Yet, several critical issues associated with the evolution of the Qaidam basin remain controversial, preventing a full understanding of the evolution of the northern margin of Tibet during the Cenozoic. Here we comprehensively review these issues, synthesize records from structural geology, sedimentology, geochronology, and geophysics, and finally propose a holistic view of the Cenozoic evolution of the Qaidam basin. We infer that: 1) the traditional age model that assigned a Paleocene to Eocene basal age to the Cenozoic strata in the basin seems to fit reasonably well the deformation history obtained from combining growth-strata observations and thermochronology data across the basin; 2) basement-involved faults, with both dip-slip and strike-slip components, developed within the Qaidam basin. In particular, the Neogene initiation of strike-slip faulting along the south-dipping faults that roots into the Eastern Kunlun Shan played an important role in the evolution of the southern Qaidam basin; 3) The Eastern Kunlun Shan was already exhumed during the deposition of the Lulehe Formation, serving as a significant source of clastic material deposited in the Qaidam basin and separating the latter from the Hoh Xil basin to the south. We conclude that the Qaidam basin is a superimposed sedimentary basin that successively experienced flexural subsidence, outwards expansion, isolation and partitioning during the Cenozoic. Finally, the Cenozoic evolution of the basin results from a tight interplay between tectonics and climate.

Figure S1. Binary plot for evaluating the effect of alteration on mobile elements (a) Zr vs. Rb; (b) Zr vs. Sr; and (c) crustal contamination (SiO2 vs. Nb/La).

Soil respiration (Rs), the production of carbon dioxide in soils, increases dramatically from deserts to forested ecosystems. Rs values thus provide a potential tool to identify past ecosystems if recorded in sedimentary archives. Here, we propose a quantitative method to reconstruct past Rs values from paleosols. This method reverses the soil paleobarometer, a proxy that estimates past atmospheric CO2 concentration values (CO2atm) from paleosols while considering a narrow range of variation for Rs. We use past CO2atm values from marine proxies to reconstruct soil respiration from a 20 million year-long isotopic record from northeastern Tibet covering the transition from the Eocene greenhouse to the Oligocene icehouse. We show that Rs dropped at least 4-fold through the transition into the Oligocene icehouse, marking the spread of boreal desert-steppes of Central Asia. We show that increasing aridity and the decline of monsoonal rainfall, in parallel with global cooling, caused the fall of soil respiration. These highly dynamic Rs emphasize the need for a systematic screening of paleosol isotopic data before using the soil paleobarometer to reconstruct CO2atm

Despite the continuously growing understanding of dolomite over the years, the dolomite problem remains unclear. Lacustrine dolomite found in the Anjihaihe Formation (E3a) on the margin of the southern Junggar Basin provides an opportunity to look into the dolomite formation process in a lacustrine environment. The Anjihaihe dolomite occurs as 10- to 20-cm-thick white-gray layers interbedded with lacustrine dark mudstone and silty mudstone. Based on scanning electron microscopy, X-ray diffraction, major and trace elements, and carbon and oxygen isotopes, as well as magnesium isotope analyses, the Anjihaihe dolomite is a syndepositional low-order dolomicrite formed under a reducing environment in a saline lake. Unlike the usual bacterial sulfate reduction and evaporation background of lacustrine dolomite, no bacteria or evaporite evidence is found in this study. Rather, increased Mg concentrations and carboxyl group catalysis may be the main factors that facilitate the dolomitization process. The results of a one-dimensional diffusion-advection-reaction numerical model of the Mg isotopes indicate that the dolomitization time, degree of dolomitization and diffusion in thin dolomite layers have little effect on the Mg isotopes in the Anjihaihe dolomicrite. Under the assumptions that seawater δ26Mg equals −0.82‰ and the fractionation factor is 1.75‰ at 25 °C, seawater as the Mg source for the Anjihaihe dolomicrite would be a plausible explanation and fits well with our other results. This explanation suggests that the contemporaneous adjacent proto-Paratethys might have provided the magnesium ions by episodic transgression and had a paleoenvironmental influence on the northern Tianshan area during the Oligocene.

The Lower-Middle Jurassic sandstone reservoirs in the northern margin of Tianshan are considered a significant area of tight sandstone gas. Sedimentary, petrologic and petroleum geologic criteria have been surveyed in six sections along continuous outcrops and cores. Thin sections and scanning electron microscope (SEM) images combined with mercury injection techniques are used to restore the evolution of pore-throat structures. The Lower-Middle Jurassic sandstones are mainly low-porosity and extra-low-permeability reservoirs. The results of constant-rate mercury injection reveal that the distribution pattern of the pore radii is not related to permeability, whereas the throat radii increase with increasing permeability. The microcosmic heterogeneity in reservoirs is dominated by a high proportion of narrow throats. An analysis of the reservoirs' physical properties and diagenesis indicates that the quality of the Lower-Middle Jurassic sandstone reservoirs is controlled by sedimentary environment, eodiagenesis, and diagenesis that developed in different sedimentary microfacies. The pore-throat structures can be divided into six types. In coal-bearing formations that are rich in organic matter, compaction decreases the quality of the reservoirs, and the reaction of early-formed kaolinite with remnant, undissolved K-feldspar may cause diagenetic illite to block the throats. At the bottom of the fluvial channels in braided river delta plains or at the top of mouth bars in braided river delta fronts, eodiagenesis can inhibit compaction via early basal carbonate cementation, and the unfavorable reservoirs are extra-low-porosity and extra-low-permeability sandstones. Infiltration-related clay is widespread. Smectite coats covered grains, and kaolinite filled remnant intergranular pores as aggregations, which increased the heterogeneity of the pore-throat structures. Authigenic chlorite coats protect intergranular pores from compaction and cementation by quartz overgrowths. Reservoirs with medium to low porosity and medium to low permeability come from the middle-upper portions of fluvial channels in braided river delta plains of the Xishanyao Formation or from the upper part of sub-water fluvial channels in the Badaowan Formation and the Sangonghe Formation or mouth bars in braided river delta fronts of the Sangonghe Formation. In near-surface settings, such as the bottom of fluvial channels or the top of mouth bars in braided river deltas, infiltration-related dissolution leads to more intergranular dissolution pores. However, the development of the highest-quality reservoirs, i.e., medium porosity and medium permeability, is limited. Other types exist between these end members in quality. Due to good sorting and low matrix content, the barrier bars of the Toutunhe Formation and the Sangonghe Formation with good lateral connectivity in the lacustrine facies are widespread in the northern margin of Tianshan and are considered to be high-quality reservoirs.