Recent geological surveys and drilling of scientific exploration well QK-1 in the Qiangtang Basin have confirmed that the Middle Jurassic Xiali Formation comprised a thick evaporite sedimentary sequence with regional continuous distribution crucial for sealing hydrocarbon resources. However, the formation of these evaporites is still debated, with some attributing their development solely to climate while others emphasise the control of basin tectonics. Here, field outcrop investigations combined with sedimentological, geochemical and clay mineral content analyses of the evaporite-bearing sediments from well QK-1 were conducted. Geochemical paleoclimate indicators, including clay mineral content, Sr/Cu, Sr/Ba and other proxy data derived from fine-grained interlayers in evaporite sedimentary sequences, suggest a climatic shift from semi-humid to prevalent arid conditions, associated with a progressive increase in paleosalinity during deposition of the Xiali Formation. Provenance analysis of the Xiali Formation is interpreted based on bivariate diagrams (K2O/Na2O-SiO2, TiO2-Al2O3, TiO2-Zr), along with elevated REE signatures and (La/Yb)n, which reveal that the detrital material was primarily derived from felsic and intermediate igneous rocks within active continental margin and continental island-arc tectonic settings. Increased tectonic subduction during the Middle Jurassic led to the development of a semi-enclosed, tidal flat-lagoon depositional environment in the northern Qiangtang Depression. This indicates that the coupled interplay between enhanced arid paleoclimate and a semi-enclosed basin configuration jointly controlled the formation of the thick evaporite succession in the Xiali Formation. These findings provide new geological evidence for elucidating evaporite depositional mechanisms and their crucial role in sealing and preservation of hydrocarbon resources in the Qiangtang Basin.

The late Ediacaran stands as a pivotal interval in Earth's history, marked by the extensive development of microbial carbonate deposits that are crucial for documenting the biotic evolution and environmental changes of this period, as well as serving as significant hydrocarbon reservoirs. Accordingly, this study investigates the microbial carbonates of the late Ediacaran Dengying Formation on the Yangtze Platform, South China, to unravel the underlying mechanisms linking microbialite development, sea-level change, and astronomical forcing. Through a multi-proxy approach including petrography, high-resolution gamma-ray logging, Fischer plot analysis, and spectral methods (Multi-Taper, correlation coefficients), this study demonstrates that high-quality reservoirs occur predominantly within mound-shoal complexes, where microbialite abundance correlates with periods of sea-level rise. The ecological recovery following the extinction of the Ediacara-type biota created favorable niches for microbialite proliferation. Their widespread deposition occurred mainly during periods of sea-level rise, which can be attributed to both low sedimentation rates and enhanced nutrient supply. Despite its relatively short duration (<3 Myr), the studied succession contains well-preserved Milankovitch signals that point to a multi-component astronomical influence. Specifically, a clear causal relationship exists between thirdorder sea-level changes and similar to 2.2 Myr eccentricity modulation cycles, while higher-frequency, meter-scale fluctuations are paced by precession modulation cycles. Alongside the primary control of astronomical forcings, tectonic activity played a secondary role, potentially driving the prolonged lowstand associated with the final amalgamation of Gondwana. Thus, this study highlights that late Ediacaran sea-level evolution was governed by the superposition of orbital and tectonic mechanisms, providing new insights into the driving forces of this period.

The thickness and scale of the gypsum–salt rocks are critical for oil and gas preservation and accumulation. The Mesozoic Qiangtang Basin exhibits the greatest petroleum resource potential in the Tibetan Plateau and contains vital records of salt formation. However, whether large-scale gypsum–salt rock series is extensively developed in the basin remains unclear. Here, we integrated sedimentological, geochemical, and zircon U-Pb age data of the Quemoco Formation gypsum–salt rock series to elucidate the tectonic–sedimentary evolution and its responses to salt formation in the Northern Qiangtang sub-basin. The Quemoco Formation may be assigned to the Hettangian–Toarcian of the Early Jurassic (200–176 Ma), and exhibiting a deepening-upward transgressive succession. The source area of the Quemoco Formation experienced weak and moderate chemical weathering, and the provenance consists of recycled felsic and andesitic rocks from the Central Uplift Belt and proximal Late Triassic syn-rift volcanic rocks. The gypsum–salt rock series was formed in the mixed settings of rifting and collision. Late Triassic volcanic activity, Early Jurassic multiple transgression–regression cycles, relatively hot and arid climate, and restricted to semirestricted paleogeographic settings favor the formation of the gypsum–salt rocks. The thickest gypsum–salt rocks were mainly related to the migration of depositional centers of rift troughs and formed under the hottest and driest climate and the most restricted environments. These findings provide a strong case for salt formation in rift basins and offer broader insights for evaluating the preservation conditions of petroleum in the Qiangtang Basin.

To support ongoing hydrocarbon exploration of the marine Mesozoic strata in the Qiangtang Basin,we conduct surveys and reassessments of the regional petroleum geology.Accordingly,several benchmark sections of the basin's source rocks and reservoirs are established.The results indicate that the Qiangtang Basin contains three dominant source rock sequences(the Bolila,Bagong,and Quse formations),two suites of carbonate reservoirs(the limestone karst of the Bolila Formation and the dolomites of the Buqu Formation),three suites of sandstone reservoirs(the Bagong,Quemocuo,and Xiali formations)dominated by tight-sand reservoirs,and three suites of well-developed regional evaporite cap rocks(the Quemocuo/Quse and Xiali formations).Analysis of oil and gas shows reveals that the marine Mesozoic strata in the Qiangtang Basin experienced the hydrocarbon generation,migration,and accumulation processes.In this basin,oil-generating strata,reservoirs,and cap rocks are well-matched both temporally and spatially,forming two petroleum systems:the Upper Triassic-Lower Jurassic pre-salt system and the Lower-Middle Jurassic intrasalt system.Three hydrocarbon plays are identified in the basin.The first play consists of the source rocks of the Bolila Formation,the karst reservoirs of the Bolila Formation,and the mudstone cap rocks of the lower Bagong Formation.The second one is composed of the mudstone source rocks of the Bolila-Bagong formations,the sandstone reservoirs of the Quemocuo-Bagong formations,and the evaporite cap rocks of the middle-upper Quemocuo Formation.The third one comprises the source rocks of the Quse Formation,the dolomite reservoirs of the Buqu Formation,the sandstone reservoirs of the Xiali Formation,and the evaporite/mudstone cap rocks of the Xiali Formation.Three types of hydrocarbon resources occur in the Qiangtang Basin:conventional,shale,and tight hydrocarbons.In the Maqu area,play fairways cover an area of about 5×103 km2.An assessment of the hydrocarbon generation intensity and hydrocarbon accumulation coefficients(HACs)of source rocks in the Bolila-Bagong formations reveals that the Maqu area has conventional hydrocarbon resources of about 0.5×109 t when estimated using a minimum resource abundance of 100×103 t/km2.Meanwhile,the Bagong Formation contains shale oil resources of approximately 1×109 t.In the Biluocuo-Esima area,play fairways with an area of about 8×103 km2 are identified.An assessment of the hydrocarbon generation intensity and HACs of source rocks in the Quse and Bagong formations reveals that this area contains conventional hydrocarbon resources estimated at 0.8×109 t based on a minimum resource abundance of 100×103 t/km2.In this area,the Bagong and Quse formations are identified as play fairways for shale oil exploration,with shale oil resources of approximately 1.6×109 t and about 0.8×109 t,respectively.In the Shenglihe area,play fairways span an area of 5×103 km2,where the Quse Formation holds shale oil resources of about 1×109 t.

The tectonic evolution of the Bangong-Nujiang Tethyan Ocean (BNTO), a key component of the eastern Tethyan realm, provides crucial insights into the geological evolution of the Qiangtang Basin and the reconstruction of the Tethyan paleogeographic framework. However, the magmatic response to the initiation of BNTO subduction remains poorly constrained, hindering efforts to reconstruct its tectonic evolution and decipher the Mesozoic tectonic setting of the Qiangtang Basin. We present whole-rock geochemistry, Sr-Nd isotopes, and zircon U-Pb ages for newly discovered andesites from Zhaquxiang, located along the southern margin of the Qiangtang Basin. The andesites formed during the Late Triassic (211.5 +/- 4.8 Ma) and display arc-type geochemical signatures characterized by pronounced LREE-HREE fractionation, enrichment in LILEs, and depletion in HFSEs. They show relatively low initial 87Sr/86Sr ratios (0.704755-0.704966) and positive epsilon Nd(t) (+2.63 to +4.37). The andesites have high contents of SiO2 (61.5-62.7 wt%) and Al2O3 (17.3-17.8 wt%), but low values of Mg# (31-40), K2O (2.0-2.2 wt%), Cr (30-38 ppm), and Ni (21-24 ppm). They exhibit low Ba/Th and Ba/La, but high Th/Nd and (La/Sm)N ratios. These characteristics suggest that the andesites were derived from partial melting of subducted oceanic crust, triggered by the initial northward ocean-continent subduction of the BNTO. The onset of BNTO subduction is thus constrained to ca. 211.5 Ma, contemporaneous with the development of a back-arc rift basin tectonic system in the Qiangtang Basin.

The Sturtian Ice Age (∼717–660 Ma), one of the Snowball Earth events of the Neoproterozoic, terminated abruptly, but the effects of climate change during the glacial to postglacial (G-PG) transition remain poorly documented. To investigate changes in weathering intensity during this transition, we generated high-resolution records of Li concentrations ([Li]) and isotopes (δ7Li) for the detrital components of the syn-Sturtian Tiesi'ao and post-Sturtian Datangpo formations in the Nanhua Basin, South China. The lower Tiesi'ao Formation (Interval 1) is characterized by higher [Li] (mean 66.2 ppm), whereas the upper Tiesi'ao Formation (Interval 2) and the basal Datangpo Formation (Interval 3) are characterized by lower [Li] (means 14.7 and 11.6 ppm, respectively). However, the Li isotopic compositions are statistically invariant for Intervals 1, 2 and 3 (means +1.5, +1.9 and + 2.3 ‰, respectively). The Li contents and isotopic compositions can be attributed to low chemical weathering from the late stage of the Sturtian Ice Age to the early postglacial interval, although the distinctive Li features of Interval 1 may have been influenced by the presence of Li-rich primary minerals. Samples of Interval 3 can be divided into two discrete groups based on their distinct Li contents and isotopic compositions: Group 3 A: mean [Li] 12.7 ppm, mean δ7Li + 1.4 ‰; Group 3B: mean [Li] 8.4 ppm, mean δ7Li + 3.6 ‰. These two groups represent weakly and strongly weathered material, respectively, implying fluctuating chemical weathering intensity in the early postglacial interval, which may have been related to the development of short cold snaps. These records provide new insights into climate evolution during the late Sturtian Ice Age and its aftermath as well as changes in biogeochemical cycling in Cryogenian oceans.

Widespread marine anoxia is considered a key impediment to recovery following the late Ordovician mass extinction (LOME), yet the spatiotemporal evolution of early Silurian ocean redox condition remains unresolved. Benthic ecosystem recovery on the South China inner shelf coincided with a global cooling trend during the Rhuddanian-Aeronian transition, but its drivers and links to redox dynamics remain poorly understood. Here we reconstruct redox conditions across a shelf transect in the Yangtze region using iron speciation, redox-sensitive trace elements (RSTEs), Corg/P ratios, and delta 13Corg data from three sections spanning inner- to outer-shelf environments. Combined with a global compilation of 49 continental shelf sections and a new CA-ID-TIMS zircon U-Pb date of 439.51 +/- 0.23 Ma, the data indicate that reducing conditions have persisted for -2.91 +/- 0.39 million years on the inner shelf after the LOME, followed by progressive reoxygenation beginning in the late Rhuddanian and extending into the Aeronian. A sharp rise in global organic carbon burial rates-up to -23 times the Hirnantian baseline, together with coeval rises in 87Sr/86Sr ratios indicative of intensified continental silicate weathering, would have driven a drawdown of atmospheric CO2 and global cooling. This climatic shift likely enhanced shelf ventilation and oxygen solubility, facilitating benthic metazoan recovery in shallow settings, while outer-shelf environments remained anoxic until the mid-Aeronian. These findings underscore the tight coupling among carbon cycling, climate regulation, redox evolution, and biotic recovery, highlighting continental shelves as key sites of carbon-climate feedback in the aftermath of mass extinction events.

Mixed siliciclastic-carbonate sedimentation, formed by in-situ intermixture of carbonate and terrigenous materials, is critical in sedimentary dynamics, paleoenvironment, paleoclimatology, and unconventional hydrocarbon. A representative mixed siliciclastic‑carbonate system was found in the Bolila Formation of well QZ-8, eastern Qiangtang Basin, whose sedimentary characteristics, provenance, age, and controlling factors remain unclear. We integrated the sedimentology, geochronology, and cyclostratigraphy to constrain sedimentary environment, provenance, high-resolution chronostratigraphic framework, and formation mechanism of above mixed system. 18 lithofacies were identified in the Bolila Formation and formed in a distally steepened carbonate ramp environment. The proximal Middle–Late Triassic subduction-related magmatic rocks are primary provenance for mixed rocks evidenced by poor textural maturity, unimodal detrital zircon U–Pb age (~242 Ma), and corroded igneous quartz luminescing in bluish violet–violet. A newly high-resolution astronomical timescale of the Bolila Formation constrains its age to the Ladinian–Carnian based on the Gamma-ray logging series (170.00–497.25 m), nineteen extracted 405-kyr long eccentricity cycles, and an anchor age of 236.4 Ma at 286 m. The interaction of tectonic-volcanism and astronomical forcing drive the formation of this mixed system. The granular mixed rocks are mainly controlled by the Middle–Late Triassic tectonic-volcanism triggered by the northward subduction of the Longmu Co–Shuanghu Paleo-Tethys Ocean and long eccentricity, while the fine-grained mixed rocks are primarily governed by the Late Triassic tectonic subsidence and short eccentricity. These findings offer broader insights for understanding the controlling factors of mixed systems in global active continental margin setting and provide a reference for the Triassic stratigraphic correlation.

The Shabaosi gold field is located in the western Mohe Basin, part of the northern Great Xing’an Range, NE China, and contains multiple gold deposits. However, the sources of the ore-forming materials, the fluid evolution, and the genesis of these gold deposits have been disputed, especially regarding the classification of these deposits as either epithermal or orogenic gold systems. Based on detailed field geological investigations and previous research, we conducted systematic research on the Shabaosi, Sanshierzhan, Laogou, and Balifang gold deposits using fluid inclusion and H-O-S-Pb isotope data, with the aim of constraining the fluid properties, sources, and mineralization processes. Fluid inclusion analyses reveal diverse types, including vapor-rich, vapor–liquid, CO2-bearing, CO2-rich, and pure CO2. Additionally, only a very limited number of daughter mineral-bearing fluid inclusions have been observed exclusively in the Laogou gold deposit. During the early stages, the peak temperature primarily ranged from 240 °C to 280 °C, with salinity concentrations between 6 and 8 wt% NaCl equiv., representing a medium–low temperature, low salinity, and a heterogeneous CO2-CH4-H2O-NaCl system. With the influx of meteoric water, the fluids evolved gradually into a simple NaCl-H2O system with low temperatures (160–200 °C) and salinities (4–6 wt%). The main mineralization stage exhibited peak temperatures of 220–260 °C and salinities of 5–8 wt% NaCl equiv., corresponding to an estimated formation depth of 1.4–3.3 km. The δDV-SMOW values (−138.3‰ to −97.0‰) and δ18OV-SMOW values (−7.1‰ to 16.2‰) indicate that the magmatic–hydrothermal fluids were progressively diluted by meteoric water during mineralization. The sulfur isotopic compositions (δ34S = −0.9‰ to 1.8‰) and lead isotopic ratios (208Pb/204Pb = 38.398–38.579, 207Pb/204Pb = 15.571–15.636, and 206Pb/204Pb = 18.386–18.477) demonstrate that the gold predominantly originated from deep magmatic systems, with potential crustal contamination. Comparative analyses indicate that the Shabaosi gold field should be classified as a epizonal orogenic gold system, which shows distinct differences from epithermal gold deposits and corresponds to the extensional tectonic setting during the late-stage evolution of the Mongol–Okhotsk orogenic belt.

The Carnian Pluvial Episode (CPE; ca. 234–232 million years ago) is an interval with increase in humidity and siliciclastic input, which is linked to global warming, enhanced hydrological cycle, water mass hypoxia caused by the eruption of the Wrangellia Large Igneous Province (Wrangellia LIP). Interestingly, preceding the CPE, there were discernible shifts in paleoenvironmental conditions, manifested through fluctuations in detrital, freshwater, and terrigenous higher plant inputs during that period. This investigation employed various methodologies, including organic geochemistry, elemental geochemistry, and mineralogy analysis of the Bagong and Boli La Formation in the Qiangtang Basin (Tibetan Plateau), to study paleoenvironmental evolution preceding the CPE. The aim was to investigate how these conditions influenced the accumulation of organic matter during this timeframe. Oraganic and elemental geochemical proxies indicated a gradual increase in detrital input prior to the CPE. Combined with decreased paleosalinity indicators, we proposed that enhanced continental inputs prior to the CPE could be associated with an intensified hydrological cycle. Framboidal pyrite morphology and size along with redox sensitive trace element content and ratio indicated anoxic to euxinic bottom water conditions during deposition. Persistently low P/Ti and Ni/Al ratios supported a low biotic productivity, which is adverse for organic matter production. The weak relationship between TOC and redox and productivity proxies indicated that organic matter accumulation was not mainly controlled by reducing condition and low primary productivity. We proposed that three-stage (Intervals A, B, and C) paleoenvironmental evolution before the CPE controlled the accumulation of organic matter in the Bagong Formation. This study provides new insights to paleoenvironmental evolution prior to the CPE, which is of paramount interest for a comprehensive understanding of the CPE.

Barremian organic-rich black shales are significant source rocks in the eastern Tethyan Qiangtang Basin. Based on petrological, inorganic and organic geochemistry analyses, the black shales are divided into three units from bottom to top. Unit 1 micritic limestones exhibit high total organic carbon (TOC) contents and Type II2 kerogen, indicating a mixture of marine microalgae and land plants. Unit 2 black shales show the highest TOC contents, predominantly Type II1 kerogen suggesting marine microalgal source. In contrast, Unit 3 marls have relatively low TOC contents, Type II2 kerogen, indicating mixed terrestrial and marine OM sources. The black shales show a low organic maturity, and the hydrocarbon generation potential of the black shale and micritic limestone samples is substantially higher than that of the marl samples. Palaeoredox proxies indicate that Unit 1 deposited under dysoxic-anoxic conditions, and Unit 2 formed under anoxic-euxinic conditions, while Unit 3 deposited under oxic-suboxic conditions. Primary productivity proxies reflect high productivity in Units 1 and 2, and low productivity in Unit 3. Rb/K and total sulfur/TOC ratios suggest brackish environment in Units 1 and 2 and brackish or seawater condition in Unit 3. Hydrothermal activity during Unit 2 black shale deposition provided essential nutrients for phytoplankton in the photic zone, leading to high OM production. Upwelling/restriction proxies imply deposition under moderately restricted conditions for Unit 1, strongly restricted conditions for Unit 2, and upwelling/weakly restricted conditions for Unit 3. Palynological analysis indicates a warm, semi-humid to humid temperate climate during deposition of Units 1 and 2, contrasting with a hot, arid to semi-arid climate during Unit 3 marl deposition. OM accumulation of Unit 1 micritic limestone was primarily controlled by stratified dysoxic-anoxic conditions, high primary productivity, warm humid/semi-humid climate, and moderate watermass restriction. For Unit 2 black shale, the main controlling factors were stratified anoxic-euxinic environment, warm humid temperate climate, strongly restricted water condition, and intermittent strong hydro-thermal activity. During Unit 3 marl deposition, low primary productivity, an oxygen-rich water environment leading to OM degradation, combined with a hot arid/semi-arid climate, resulted in organic-lean deposition.

The Precambrian basement structure in the Sichuan Basin profoundly influences the sedimentary lithofacies and paleogeographic evolution, which is related to the distribution of source rocks, large-scale reservoirs, hydrocarbon migration pathways, and the development of a complete petroleum system. We have determined a high-resolution three-dimensional P-wave velocity model at 0 similar to 30 km depths to establish a comprehensive Precambrian basement structure in the Sichuan Basin. This model was constructed by a joint inversion algorithm of multiple seismic phases together with a double-difference relocation, utilizing an extensive dataset comprising 104358 travel time measurements of Pg, P, and Pn phases. These multi-phase travel times were recorded by a network of seismic stations consisting of 98 permanent and 335 temporary installations deployed in the Sichuan Basin and its surrounding regions. The imaging results reveal the presence of a Chengdu-Mianyang-Guangyuan-Wanyuan depression in the northwest and a Wanzhou-Fuling-Chishui depression in the Northeast of the basin, respectively, forming a horseshoe-shaped depression zone with a southwest opening. Meanwhile, a Suining-Leshan-Weixin uplift with a L-shaped tectonic belt has been developed to the center and southeast of the basin. The uplift and depression structures of the basin are coupled with each other, constituting a new pattern of the Precambrian basement in the Sichuan Basin. A spatial analysis of 855 oil and gas drilling data determined that over 90% of the hydrocarbon sources are distributed within the depression belt or its slope. The proposed "two-depression-one-uplift" basement pattern constrains the distribution of hydrocarbon-generating depressions and the occurrence of large-scale reservoirs in oil-bearing basins. The findings hold significant implications for assessing the hydrocarbon resource potential within the basin and provide novel geophysical evidence for exploring such resources in the Sichuan Basin.

The Qiangtang Basin, situated on the Tibetan Plateau, is a basin that contains hydrocarbons and has significant potential for hydrocarbon exploration. However, reconstructing sea-level changes and understanding the sedimentary evolution of the Qiangtang Basin has been hindered by the lack of robust high-resolution geochronology. Meanwhile, the Late Triassic stratigraphy of the Qiangtang Basin has also reported the Carnian pluvial episode, the driving mechanism of which is controversial. In this study, the cyclostratigraphy of the Late Triassic Boli La and Bagong Formations in the Qiangtang Basin was analyzed using high-resolution gamma-ray data. Time series analysis shows that there are 405 kyr eccentricity cycles in the gamma-ray data series. The gamma-ray series was tuned to 405 kyr. Then, we establish a floating astronomical timescale with a length of 17.04 Myr. This astronomical time scale establishes an anchored astronomical time scale using the age of the volcanic rocks found in the top of the Bagong Formation in the drill core as an anchor point. Using the anchored astronomical chronology, we reconstructed the Late Triassic sea level change in the Qiangtang Basin using a recently developed sediment noise model. The reconstructed sea level change is generally consistent with the global sea level curve. The antiphase relationship between the filtered long-term obliquity cycles and the sea-level curves reconstructed from the sedimentary noise model suggests that the long-term obliquity cycles may have been the main driver of the Late Triassic greenhouse sea-level change. Meanwhile, the modulation maxima of the long-term obliquity-modulated cycles correlate well with high sea level, episodic negative carbon isotope excursions, global warming, and marine biotic crises, suggesting that obliquity forcing may have played a prominent role during the Carnian Pluvial Episode. Our results suggest that orbital forcing enhanced the hydrological cycle during the Carnian Pluvial Episode. Our study provides a precise, high-resolution time scale for studying the sedimentary evolution of the Qiangtang Basin, as well as a broader perspective on the relationship between the Carnian Pluvial Episode and astronomical forcing.

The tectonic evolution of the Bangong–Nujiang Tethyan Ocean (BNTO), a key component of the eastern Tethyan realm, provides crucial insights into the geological evolution of the Qiangtang Basin and the reconstruction of the Tethyan paleogeographic framework. However, the magmatic response to the initiation of BNTO subduction remains poorly constrained, hindering efforts to reconstruct its tectonic evolution and decipher the Mesozoic tectonic setting of the Qiangtang Basin. We present whole-rock geochemistry, Sr–Nd isotopes, and zircon U–Pb isotopes for newly discovered andesites from Zhaquxiang, located along the southern margin of the Qiangtang Basin. The andesites formed during the Late Triassic (211.5 ± 4.8 Ma) and display arc-type geochemical signatures characterized by pronounced LREE–HREE fractionation, enrichment in LILEs, and depletion in HFSEs. They show relatively low initial 87Sr/86Sr ratios (0.704755−0.704966) and positive εNd(t) (+2.63 to +4.37). The andesites have high SiO2 (61.5–62.7 wt%), Al2O3 (17.3–17.8 wt%) contents but low Mg# (31–40), K2O (2.0–2.2 wt%), Cr (30–38 ppm), and Ni (21–24 ppm) concentrations. They also exhibit low Ba/Th and Ba/La ratios, along with elevated Th/Nd and (La/Sm)N values. These characteristics suggest that the andesites were derived from partial melting of subducted oceanic crust, triggered by the initial northward ocean–continent subduction of the BNTO. The onset of BNTO subduction is thus constrained to ca. 211.5 Ma, contemporaneous with the development of a back-arc rift basin tectonic system in the Qiangtang Basin.

The Tibetan Plateau plays a crucial role in Asian and global geomorphology and climate change, yet how it grew and how its deep geodynamic processes control surface systems remains unclear. We present a novel model to explain this by multistage bilateral subduction, lithospheric breakoff, and subsequent foundering. Modelling based on a global tomography method reveals four distinct stepwise high-velocity anomalies in the mantle. The high-resolution seismic velocity model was inverted using >16 million arrival times of P, Pn, pP, PP, PKP, and PKiKP phases from the International Seismological Center and EHB bulletins and ~3 million arrival times of P, PP, and PcP phases from the 1,034 China Seismic stations in Tibet. We also collected hundreds of volcanic rocks to analyze their spatio-temporal distribution in the Tibetan Plateau since 60 Ma. The locations and morphology of the remanent slabs associated with the subducted/subducting Neo-Tethyan Ocean, Greater Indian plate, and Asian lithosphere have been constrained using plate reconstruction and the surface igneous rock data. We find that discrete episodic surface volcanism and plate uplift at 56-44 Ma, 44-28 Ma, 28-18 Ma, and 18-0 Ma in the Tibetan Plateau coincide with the four-stage stepwise lithosphere processes. We observe paired slab-like anomalies during the second and third steps, indicating the simultaneous detachment of subducting lithosphere from opposing directions. Building upon this observation, we propose a two-sided breakoff model, where bilateral subduction and lithospheric gravitational subsidence triggered extensive volcanism and episodic uplift of the plateau. This model indicates that subsidence from both past and present lithospheric break-offs of the Indian and Asian plates spawned extensive volcanism that had a significant impact on climate patterns. By shedding new light on the deep-seated geodynamic mechanisms at play, our study establishes a systematic framework linking lithospheric processes and surface phenomena in Tibet.

The Jenkyns Event (i.e. the early Toarcian Oceanic Anoxic event, ca. 183 Ma) represents a notable short-term environmental and climatic perturbations. It is hypothesized to have originated from a substantial release of 13C-depleted carbon into the global ocean-atmosphere system, culminating in a globally synchronized negative carbon isotope excursion (N-CIEs). While this event has been extensively studied within the Tethyan Ocean, it remains inadequately characterized in continental domains beyond Europe. Here, lower Toarcian lacustrine successions from the QZ-16 well in the Qiangtang Basin, situated along the northern passive continental margin of the Meso-Tethys Ocean, is studied based on a multi-proxy approach of organic and inorganic and isotope geochemistry, mineralogy, sedimentology, and palynology.Chronostratigraphic calibration of the successions within the Quemo Co Formation is achieved through carbon isotope (δ13Corg and δ13Ccarb) records and palynostratigraphy. Notably, a long-term positive δ13C trend is identified, which is interrupted by pronounced 4–5‰ N-CIEs in δ13Corg and δ13Ccarb during the early Toarcian. This perturbation is interpreted as the terrestrial counterpart of the marine Jenkyns Event within the Qiangtang Basin, reinforcing a synchronicity to marine records. The Toarcian interval of the Qiangtang Basin is characterized by fully oxidizing conditions intermittent with minor phases of dysoxic settings, especially during the Jenkyns Event, resulting in a low organic carbon burial within the Quemo Co Formation.Sedimentological analyses within the Jenkyns Event interval indicate the presence of storm deposits, as evidenced by siltstones, graded siltstones, small-scale hummocky cross-stratification, and sharp erosive bases. These features suggest a strong correlation between warming events and increased tropical storm activity during this period, leading to intensified hydrological cycles. Furthermore, elevated ratios of fluvial detrital proxies, such as Si/Al and Ti/Al, along with the deposition of silty mudstone facies at the onset of the Jenkyns Event point to enhanced terrigenous input. This can be attributed to accelerated continental weathering, coinciding with the climatic changes at this time.Palynological analyses reveal a progressive shift from arid to humid climate conditions, consistent with the carbon-isotope perturbation, supporting the accelerated hydrological cycling during the Toarcian. However, the enhanced freshwater input, associated with the enhanced hydrological cycling, was counterbalanced by a decline in lake levels. These records were completely documented in lacustrine deposits within the Qiangtang Basin dating from the isotope perturbation, which is consistent with the early Toarcian global regression. Lacustrine deposits with marine influences suggest sporadic connectivity between the Qiangtang Basin and the Tethys Ocean during the Toarcian, underscoring a strong link between regional shoreline progradation and evolution of global climate and sea-level.

The Carnian Pluvial Episode (CPE; similar to 233 Ma) is marked by global warming associated with an intensified hydrological cycle and increased siliciclastic input, coinciding with a widespread crisis in carbonate production. It was further linked to the eruption of the Wrangellia Large Igneous Province (W-LIP), seawater hypoxia, and significant biotic turnover. While some studies have investigated the CPE in Tibet, the environmental and oceanographic processes leading up to this event have received limited attention. In this study, total organic carbon (TOC), biomarker, inorganic geochemistry, and pyrite framboid petrography of samples collected from the Upper Triassic (Carnian) Bagong Formation in the QZ8 well of the Qiangtang Basin (Tibet) were performed to explore the environmental, paleoceanographic, and organic matter controlling processes preceding the CPE. Results exhibit moderate to high enrichments of trace element redox proxies, such as U, Mo, and V, suggesting that the Bagong Formation was deposited under deoxygenation conditions, from severe anoxia to intermittent euxinia prior to the CPE. The presence of pyrite framboids with small mean diameters and narrow distribution ranges further support this interpretation of deficient redox conditions in bottom and pore waters. Additionally, the moderate to strong positive correlations between enrichment factor values of Mo and V and TOC content indicate that the available organic matter was controlled by oxygen-depleted conditions. Enrichment of Cu, Cd, and Zn, along with their Al-normalized ratios that show strong positive correlations with TOC content, reveal high marine primary productivity before the CPE. Meanwhile, the Si/Al, Ti/Al, and Zr/Al ratios showed cyclic patterns around moderate values, suggesting a modest terrigenous sediment supply, consistent with high Sr/Ba and Sr/Al ratios indicating a predominantly saline environment interspersed with enhanced terrestrial/riverine runoff during deposition. Biomarker analysis reveals a substantial contribution of tricyclic and tetracyclic ter- panes, with the C-19/C23TT and C-20 /C-23 TT ratios indicating increased terrestrial organic matter input, supported by the presence of Type III kerogen in the Bagong Formation. Prior to the CPE, the climate was warm and humid, leading to accelerated hydrological cycling and freshwater influx of terrestrial organic matter into the Qiangtang Basin. This likely triggered an increase in nutrient supply under severe deoxygenation conditions and a high sedimentation rate, resulting in enhanced organic matter production and preservation regimes while minimizing the carbonate dilution effect.

The structural configuration of the pre-Cambrian basement in the Sichuan Basin, a highly promising region for hydrocarbon exploration, has been a subject of long-standing debate. Here, we determined the fine-scale three-dimensional seismic models of the Sichuan Basin using 187,356 high-quality P- and S-wave travel time pairs recorded by 627 recently installed seismic stations. Meanwhile, 595 petroleum wells were collected to investigate their spatial distribution associated with the basement structures. Our findings reveal two depression belts, one extending through the western regions of Chengdu, Mianyang, and Wanyuan, and another in the eastern regions of Wanzhou, Fuling, and Chishui, forming a distinctive horseshoe-shaped depression structure. Concurrently, the central and southwest regions exhibit two uplift zones, constituting an L-shaped uplift structure. Approximately 76% of the petroleum wells are situated within the L-shaped uplift structure and its slope, while around 21% of the gas wells are located in the transitional zones between the depression structures or along their edges. The development of the depression structure is attributed primarily to the complex triple collision system involving the Qinghai-Tibet block in the west, the Cathsysia block in the southeast, and the North China block in the north. Conversely, the uplift structure is mainly caused by the southeastward movement of the Songpan-Ganze block and the northwestward movement of the Cathsysia block. These new findings reveal a significant correlation between the paleo-uplift structures, the distribution of hydrocarbon resources, and the geological conditions conducive to petroleum reservoirs in the Sichuan Basin, providing valuable insights for predicting potential petroleum reservoirs.

The Cryogenian Sturtian (717-660 Ma) and Marinoan glacial deposits (∼650-635 Ma), typically consisting of alternating layers of glaciogenic diamictite and clast-free lithofacies, indicate dynamic glaciers or glacial-interglacial cycles during the global glaciations. This may result from ice sublimation in tropics under a Snowball Earth condition. However, this model fails to explain the deposition patterns observed in mid-latitude continents. We propose the presence of unfrozen oceans while the continents are covered, i.e., the icy-continents. The open-ocean condition requires low atmospheric pCO2 level. We argued that the mantle CO2 degassing could be counterbalanced by a growing pool of dissolved organic carbon (DOC) in the deep ocean, maintaining a small marine dissolved inorganic carbon (DIC) pool and a low atmospheric pCO2 level. The persistent marine productivity in the open ocean would support the expanded DOC pool due to reduced ocean ventilation and limited terrestrial inputs of oxidants. However, the global glaciation with open oceans was climatically unstable. The fluctuation of the DOC pool on a local or regional scale likely contributed to the frequent glacial-interglacial oscillations recorded in the rock records. Additionally, the expansion of the DOC pool removed seawater nutrients, e.g., phosphorus (P), and insufficient nutrient supply prevented the transfer of mantle-degassing carbon as DOC, ultimately leading to the termination of global glaciation. The turnover of the DOC pool, caused by deep ocean ventilation in the deglacial period, significantly increased the atmospheric pCO2 level. This event was followed by intense continental weathering, increased seawater pH, recovery of primary productivity, cap carbonate precipitation, and eventually, the emergence of new life forms and innovations in the biosphere.