This study explores the timing and processes of hydrocarbon evolution in the Sichuan Basin, focusing on pyrobitumen and sphalerite from the Dengying Formation. By utilizing Re-Os geochronology, we aim to refine the precise timing of hydrocarbon generation, migration, and alteration in this area, with particular attention to the effect of hydrothermal fluids. The Re-Os study of pyrobitumen provided isochron ages of 166 ± 26 and 183 ± 39 Ma, which are interpreted as representing the pyrolysis of ancient hydrocarbon reservoirs and subsequent pyrobitumen generation, potentially associated with thermochemical sulfate reduction (TSR). These findings correspond to the timing of large-scale mineralization events in the Sichuan-Yunnan-Guizhou region, reinforcing the value of Re-Os geochronology in high thermal maturity bitumen. Additionally, the study underscores the impact of hydrothermal alteration on the Re-Os system, as sphalerite samples showed lower Re-Os concentrations than bitumen. This suggests that the Re-Os isotope composition of petroleum may reflect inputs from both source rocks and hydrothermal fluid interactions. The research emphasizes the necessity for precise sampling and understanding of isotopic systematics to minimize variability in data and ensure reliable geochronological interpretations. Overall, this study enhances our understanding of hydrocarbon system evolution and provides key insights into the time-frame of critical events in hydrocarbon systems.
The interaction between the Izanagi-Pacific ridge and the northeastern Eurasian Plate during the Eocene remains controversial. We focus on oceanic crust-derived adakitic rocks due to their potential for reconstructing the slab window associated with spreading ridges. New and previously published age data suggest that these adakitic rocks can be divided into three main episodes: Early Ypresian (ca. 55 Ma), Lutetian (ca. 46 Ma), and Bartonian (ca. 36–38 Ma). These rocks, which range from andesitic to dacitic in composition, are characterized by pronounced depletions in heavy rare earth elements (HREEs), low Y, high Sr, and high Sr/Y ratios. Variations in Mg, Mg#, Cr, and Ni values indicate partial melting of the subducted slab, followed by interaction with the surrounding mantle during ascent through the mantle wedge. Spatially, the first stage is localized as a ‘spot’ in NE China, suggesting a limited ridge-trench intersection. The subsequent two stages occur in two narrow belts, indicating large-scale ridge-trench intersections subparallel to the NE Eurasian margin. The temporal and spatial variations in adakitic rocks related to slab windows are best explained by changes in the scale of the Pacific-Izanagi ridge Subduction, possibly reflecting the variations in Pacific Plate movement during the Early Eocene.
The initial timing of uplift on the southeastern side of the Longmenshan-Yalong-Yulong thrust fault zone remains under debate, with estimates ranging from the Mid- to Late Miocene to Late Eocene–Early Miocene, which requires us to explore the history of its regional exhumation. Therefore, we analyzed the AFT age of the Jiaozi Shan region in the central Yunnan Block, combined with the method of thermal history inversion. Results displayed that the Jiaozi Shan region experienced two rapid uplifting events at 40–26 and 9–3 Ma, respectively. River longitudinal profiles can record the history of regional tectonic uplift. We extracted the longitudinal profiles of the Pudu River and its 18 tributaries, and meanwhile analyzed their geomorphologic parameters, including the slope, knickpoint elevation, and normalized channel steepness index (ksn). The results show that there are generally two stages of knickpoints in the Pudu River Basin, which is in agreement with the two periods of exhumation revealed through thermal history inversion. Geomorphic parameters of the upstream and midstream segments of the tributaries display systematic trends. The observed linear variations of geomorphic parameters indicate that, apart from the surface uplift caused by tectonic extrusion, at least 26 Ma, the regional uplift of the southeastern Tibetan Plateau driven by lower crustal flow is also a pivotal factor. In the downstream segment, geomorphic parameters also exhibit more pronounced systematic variations, likely due to the mass flow of the lower crust toward the interior of the block, which commenced in the Late Miocene.
0 INTRODUCTION Water-resource and aqueous-environment explora-tion on Mars is one of the central themes in deep-space exploration and planetary habitability research(Zhang et al.,2023;Ye et al.,2019).Geological and geomorphologi-cal evidence accumulated over the past decades indi-cates that liquid water was widespread on Mars during the Noachian-Hesperian,forming diagnostic aqueous landforms such as paleochannels,deltas,and lacustrine basin deposits(Xiao,2023);these features provide key conditions supporting the possibility that early Mars host-ed environments suitable for life(Kite and Conway,2024;Rampe et al.,2020;Banham et al.,2018).Subsequently,with long-term climatic cooling and progressive atmo-spheric thinning,near-surface liquid water markedly di-minished,primarily through sequestration in polar ice caps and loss via evaporation/sublimation and atmo-spheric escape processes(Ojha et al.,2020;Villanueva et al.,2015).Recent studies further propose that a sub-stantial fraction of early Martian water(approximately 30％-99％)may have been trapped and stored in the subsurface through mineral binding and/or encapsulation(Scheller et al.,2021).
The unique sedimentary environments and subsequent diagenetic transformations in continental saline lake basins markedly shape the varied nature and characteristics of saline lacus-trine shales,thereby ultimately affecting how lacustrine organic matter(OM)accumulates.Howev-er,what chiefly governs OM enrichment in such settings is still not fully understood.This research focuses on the Damintun sag as a prime research example,utilizing an extensive array of methods like total organic carbon(TOC)analysis,X-ray diffraction,pyrolysis,trace element analysis,and iso-topic studies on shales from the Paleogene period.The objective was to shed light on the variability in OM concentration and its ties to the paleoenvironment.Findings reveal that the Es4 shale lithofa-cies largely consist of mixed and siliceous shales,exhibiting significant OM accumulation,where TOC content varies between 0.17％and 7.27％.Notably,TOC distribution reveals a significant verti-cal heterogeneity across different sequences.The level of OM enrichment within the saline lake ba-sin is primarily determined by paleoclimate,paleosalinity,paleooxidation,and paleoproductivity.Among these critical factors,the primary considerations with regard to influencers of organic materi-al enrichment are productivity and paleosalinity.Conditions conducive to organic matter enrichment include low salinity,anoxic environments,and suitable nutrient inputs.Furthermore,the deposition-al environment can have a strong impact on the determination of what type of organic matter accu-mulates.To illustrate,biomarker analysis tends to suggest that humid freshwater lakes are more welcoming to organic matter derived from higher terrestrial plants,whereas dry and saline lakes predominantly accumulate plankton,such as algae.Finally,this study establishes an OM enrich-ment model which effectively outlines the various stages of organic matter evolution and enrich-ment that occur within the saline lake basin.This model integrates the consideration of various pri-mary factors,including paleoclimate shifts,sedimentary dynamics,and organic matter preservation mechanisms,offering valuable insights into the complex processes governing OM distribution and enrichment within similarly structured geological settings.
The Yuying River catchment, a hilly watershed serving as a critical drinking water source for Taihu Lake, exhibits hydrogeochemical characteristics essential to regional water supply safety. To assess potential risks to Taihu Lake, this study collected rainwater, surface water, and groundwater samples from the catchment for comprehensive hydrochemical analysis, including isotopic measurements of δ2H, δ18O, and 3H. Results revealed that groundwater hydrochemical types were predominantly HCO3·SO4-Na·Ca and HCO3-Na·Ca. Groundwater renewal rates in the catchment ranged from 34
Shale oil is generally considered to be petroleum generated from organic-rich mudstones and retained in place, or having migrated over a short distance and stored in adjacent organic-lean interbeds. However, in our study on the origin of petroleum in the Upper Xiaganchaigou Formation (E32), Ganchaigou area, western Qaidam Basin, China, we found that the E32 shale reservoirs have experienced large-scale and long-distance hydrocarbon migration and accumulation. This study utilizes organic geochemistry and basin modeling to characterize the maturity of crude oil and source rocks within the E32 shale reservoir. The results indicate that crude oil found in the immature to low-mature zone exhibits mature to overmature characteristics in organic geochemical and physical properties. In the strata within the oil window, the biomarker parameters and their absolute concentrations in crude oil still show significant differences from those of in-situ source rocks, indicating that the maturity of oil samples is notably higher than the in-situ source rock. Additionally, petroleum system modeling suggests that hydrocarbons generated solely from the in-situ source rocks cannot account for the high gas-oil ratio (GOR) fluids observed in actual production. Therefore, it is inferred that the E32 unconventional shale plays in the Ganchaigou area have undergone large-scale hydrocarbon migration and accumulation. Besides the contribution of hydrocarbons in-situ, the shale plays also have contributions from the deeper and more mature oil and gas from the down-dip direction. Lateral hydrocarbon migration distances are estimated to exceed 5 km, with vertical migration distances surpassing 1 km based on the relationship of source kitchen and reservoirs.
Gold (Au) and antimony (Sb) are two critical metals that commonly co-occur in sedimentary rock-hosted deposits. However, the genetic relationship between Au and Sb mineralization remains unclear. The Youjiang Basin, located in the low-temperature metallogenic domain of South China, hosts many important Au-Sb deposits. Among these, the Qinglong Deposit stands out as the largest vein-type Sb deposit in the basin, with approximately 300 kilotons of Sb and extensive Au mineralization. In this study, novel data from Nano-SIMS elemental mapping and sulfur isotopic analysis on paragenetically-constrained pyrite from Qinglong are provided, aiming to better understand the origin of reduced sulfur in the Au and Sb mineralization stages, as well as the genetic mechanism of Au and Sb mineralization. Four types of pyrite were identified at Qinglong based on microtextural observations and chemical features. Framboidal pyrite (Py1) and columnar pyrite (Py2) are mainly identified from the least-altered host rocks, contain no Au and Sb, and display largely negative δ34S values (−52.1‰–−44.5‰) and positive δ34S values (7.5‰–10.5‰), respectively, suggesting they formed during sedimentary and diagenetic stages. Zoned pyrite (Py3), which only occurs in hydrothermal mineralized samples, exhibits core (Py3a)-mantle (Py3b)-rim (Py3c) textures. Py3b contains elevated Sb and Pb but no Au, and has high δ34S values (−0.5‰–10.4‰), recording a possible episode of hydrothermal fluids that predated Au mineralization. Additionally, the alteration and recrystallization of Py1 by this episode of fluids led to the formation of Py3a. Py3c contains high As and Au contents, and shows most δ34S values between −1‰ and 3.2‰, representing Au mineralization stage. The sharp boundaries, distinct trace elements, and different δ34S values between Py3b and Py3c suggest that they formed from two discrete hydrothermal events. Relatively homogeneous pyrite (Py4) is intergrown with stibnite and formed specifically during Sb mineralization stage. Both Py3c and Py4 display similar δ34S signatures consistent with magmatic sulfur. Based on these observations, we propose that ore-forming fluids of Au and Sb mineralization at Qinglong may be originated from same deep magmatic-hydrothermal system, and fluids evolution and precipitation mechanism were the key factors controlling their differentiation. Meanwhile, our study demonstrates that the high-resolution in situ sulfur isotopic and trace elemental analysis of pyrite can effectively discern ore-forming fluid events and elucidate the differentiation mechanism of ore-forming elements.
Na-metasomatite uranium deposits are an important type of large-tonnage low-grade uranium deposit. They are characterized by an intimate association between uranium minerals and albite, and by the common development of syn-ore hydrothermal zircons. Similar to other types of uranium deposits, constraining an accurate age of mineralization remains a challenge for the Na-metasomatite type ones. In this study, we present for the first time, an approach that combines age dating results from the syn-ore albites (40Ar-39Ar) and hydrothermal zircons (U-Pb) for a typical Na-metasomatite uranium deposit, the Xinshuijing deposit in the Longshoushan metallogenic belt of Northwest China. The hydrothermal zircon U-Pb and albite 40Ar-39Ar ages are consistent with each other (378−366 Ma; within error), but also identical to the previously reported uraninite chemical U-Pb ages (approximately 370 Ma). The coupled application of hydrothermal zircon U-Pb and albite 40Ar-39Ar age dating is thus regarded as a robust approach for constraining the age of mineralization for Na-metasomatite uranium deposits. An age gap of approximately 70 Myr between uranium mineralization (∼ 370 Ma) and host granitoid emplacement (about 440 Ma) suggests no direct genetic linkage between the two. Further exploration in the surrounding metamorphic units is therefore suggested, rather than only focusing on the host granitoids, especially where intensive wallrock alteration and structural features are pervasive. The varied hydrothermal zircon δ18O isotope compositions are attributed to the significant fluid-wallrock interaction during the uranium mineralization, which is consistent with our previous fluid inclusion and geochemical studies. Our study highlights the importance of selecting appropriate isotopic dating methods, which is informed by detailed paragenetic and geochemical analysis of dateable minerals formed before or coeval to the main-stage uranium mineralization. Moreover, it is underlined that the exact ore-forming age determination is of great significance since it sheds light on the ore genesis and provides valid constraints on the ore-controlling factors during further exploration.
The Lower Cambrian Niutitang Formation is a crucial stratum for the exploration of normal-pressure marine shale gas in southern China,with great development potential.To re-search the normal-pressure shale gas accumulation of the Niutitang Formation in the complex tec-tonic zone,the shale cores in northern Guizhou were subjected to X-ray diffraction(XRD)and field emission scanning electron microscopy(FE-SEM)observation,and tests were conducted to deter-mine total organic content(TOC),bitumen reflectance,and nitrogen isotopes.The results indicate that the equivalent vitrinite reflectance of cores varies from 2.30％to 3.73％,and the TOC content of cores varies from 3.8％to 7.8％.The total gas content of three wells in northern Guizhou is 0.5,0.3,and 1.4 m3/t,respectively.The TOC content of the shale in the syncline structure is higher than that of the shale in the anticline structure.Nitrogen in shale gas originates primarily from the ther-mal ammoniation of organic matter,the atmosphere,and the deep crust.Shale gas preservation is favorable in regions with a large range of lifting,and small lifting differences.The syncline is broad and gentle with few faults have better gas accumulation conditions.The Niutitang Formation in the residual syncline of the study area has better gas content than that of other structures.Exploration of shale gas accumulation sweet spots in northern Guizhou should focus on the broad-gentle syn-clines with minimal changes in stratigraphic lifting,few faults,and no hydrothermal activity at the edges of paleo-uplifts.
0 INTRODUCTION The radiogenic uranium isotope composition,ex-pressed as δ234U=((234U/238U)activity ratio-1) × 1 000),serves as a valuable geochemical tracer in the surface environ-ments due to its unique fractionation processes associat-ed with α-recoil (Kigoshi,1971). When 238U undergoes α-decay,the resulting 234Th nucleus (which decays into 234U with a half-life of～24 days) recoils in the opposite direc-tion,with a typical recoil distance of～30 nm in solid min-erals (Kigoshi,1971). If this decay occurs near mineral grain boundaries,234U can be directly ejected into the sur-rounding solution,thus enriching the aqueous phase. Ad-ditionally,α-recoil damages crystal lattices,making 234U preferentially susceptible to leaching during weathering.These processes collectively explain why 234U is more mobile than 238U,leading to a modern seawater δ234U val-ue that is 146.8‰±0.1‰ above secular equilibrium(Chutcharavan et al.,2018;Andersen et al.,2010).
Granite mountainous regions not only exhibit stunning natural landscapes but also play a vital role in the terrestrial carbon cycle. The Silicate Weathering Rates (SWR) serves as a critical factor influencing both landscape formation and carbon consumption. The common method of estimating the watershed SWR by combining the ion flux at watershed outlets with average annual runoff depth does not consider geological-vegetation effects and cannot accurately reflect the actual weathering rate in small watersheds. This study, based on the typical granite geomorphic landscape of Jiuhuashan in eastern China, refines the classification of granite types and vegetation distributions in the region. The chemical composition and instantaneous flow rate of river water in 27 small granite watersheds in Jiuhuashan are systematically measured, thereby the Instantaneous Silicate Weathering Rate (ISWR) is estimated. The results revealed that the river water at Jiuhuashan is primarily of the HCO3-Ca type and that the dissolved substances are controlled mainly by rock weathering. The average contribution of silicate weathering is 66.41
A new self-starting drainage anchor that combines prestressed anchor cables with self-starting drainage is proposed.The novelty of the self-starting drainage method is the realization of the drainage and anchoring in the one inclined borehole.Reduction in the number of boreholes can greatly decrease the construction cost and duration of the project.The adverse effect of drilling con-struction disturbance on the slope is reduced.To tackle the possible blockage of the drainage cavi-ty due to slurry leakage during the solidification process after finishing grouting in the blocking sec-tion.To this end,a theoretical equation for the slurry diffusion radius under slurry self-weight pres-sure boundary conditions is deduced.The result is verified for precision through comparison with numerical simulation.The findings reveal that the permeability coefficient of rock and soil mass has the most significant impact on the slurry diffusion radius,succeeded by the length of the grouting blocking section,slurry initial setting time,and drilling inclination in descending order of influence.With the 5％mass ratio of a"711"type slurry quick-setting agent,the maximum slurry diffusion radi-us can be reduced from 0.925 to 0.449 m,a reduction of 0.476 m,which is comparatively more rec-ommended.
At the Middle Jurassic Wenda tracksite, in eastern Tibet, at least eight surfaces bearing dinosaur footprints are exposed. One of them, the WD6 track-bearing surface, shows the highest density of tracks, with forty-eight tridactyl tracks. They are assigned to Eubrontes isp., Wildeichnus isp. and indeterminate theropod tracks (including Morphotype 1 and Morphotype 2). The newly reported large carnivorous dinosaur track, Eubrontes isp., represents one of the best preserved theropod ichnotaxon found in Tibet, and its morphology is characterized by clear digit pads and blunt claw imprints. Wildeichnus isp. is a common small theropod footprint of the Wenda tracksite, which is less than 8 cm long and smaller than the Theropod Indeterminate Morphotype 2. Although Theropod Indeterminate Morphotype 1 shows some features of Anchisauripus, this study do not consider a distinct attribution at the ichnogenus or ichnospecies-level, because the key taxonomical characters of the digits are missing. The current study suggests that the Middle Jurassic theropod ichnoassemblage of eastern Tibet can be assigned to a Eubrontes-Grallator plexus. The ichnoassemblage of eastern Tibet are somewhat similar with the adjoining areas, and the eastern Tibet was inhabited by abundant dinosaurs, during the Middle Jurassic.
The scale of the outburst flood resulting from a landslide dam failure significantly influ-ences the extent of the disaster and losses downstream.This study proposes a method for control-ling the discharge of landslide dam failure using the artificial structure(AS).The primary approach involves strategically arranging the designed AS on both sides of the excavated spillway.As the breach is eroded,ASs gradually fall into the breach,serving to control the discharge.Fourteen sets of flume experiments were conducted to investigate the impact of various factors,including AS types,distances from the breach boundary,arrangements,columns,numbers,on the discharge control effectiveness.The mechanism how AS controls outburst discharge was revealed.Results in-dicate a pronounced control effect of AS on landslide dam-break discharge,with the maximum re-ducing rate of the peak discharge in the experiment reaching 47.4％.In controlling outburst dis-charge,four-sided framed structures demonstrate superior performance compared to four-sided sol-id structures,and serial structures outperform discrete structures.When arranging ASs,it is essen-tial to ensure that the structure initiates its descent into the breach at the onset of the rapid increase in outburst discharge and continues until the peak discharge occurs.Building upon this foundation,augmenting the number of ASs and columns significantly enhances the efficacy of discharge con-trol.The fundamental rationale for this discharge control lies in the AS's capacity to reduce the headward scarp height,constrain sediment transport,and diminish the erosion capacity of the out-burst flood,ultimately lowering the breach erosion rate.Lastly,a calculation method for the size de-sign of the AS is established based on mechanical analysis.The research findings offer a new tech-nological option for the emergency disposal of landslide dams.
Microfossils play a crucial role in biostratigraphy and paleoenvironmental reconstruc-tions,as the first appearance datum(FAD)and last appearance datum(LAD)of specific microfos-sils enable precise stratigraphic correlations and age determinations.However,traditional identifica-tion methods are often time-intensive and heavily dependent on expert knowledge.To overcome these limitations,we propose a dual-path deep learning model,MicroViT,which integrates convolu-tional neural networks(CNNs)and vision transformers(ViTs)to automate the identification of Ceno-zoic ostracods(Microlimnocythere,Cyprideis,Qaidamocythere,Hemicyprinotus,Qaibeigouia,Aus-trocypris,and Candoniella)from the Qaidam Basin.MicroViT achieves an accuracy of 95.34％,demonstrating superior performance across all classification metrics.Furthermore,we utilized Gra-dient-weighted Class Activation Mapping(Grad-CAM)to visualize the decision-making process of the model,revealing that DL models focus on morphological features such as reticulation and hon-eycomb-like spots.We also investigated the potential for extending this approach to other microfos-sil groups,such as charophytes and sporopollen,as well as to diverse ostracod populations.These results highlight the significant potential of deep learning techniques for rapid and accurate micro-fossil classification,offering promising applications in micropaleontology and stratigraphic studies.
This paper analyzes the main erosive evidence identified on the Matalascañas beach (Huelva, SW Spain) and its surroundings during the years 2020 and 2021. To the northwest of this beach, the El Asperillo cliff has receded 1.5 m during this period, with the ephemeral exposure of a Pleistocene substrate with numerous paleoichnological evidence of hominids, elephants, bovids and birds. On the Matalascañas beach, the winter storms caused the partial destruction of the promenade and adjoining gastronomic establishments, as well as the exhumation of the underlying sandy substrate. In summer, the dissipative dynamics of the beach brought out a level of ostreids in its eastern sector, occupied by a temporary lagoon that completely covered the recreational bathing area. In the Doñana Park, a Biosphere Reserve, coastal erosion once again brought out a level of peat with an abundant paleoichnological record from the bioerosive action of bivalves. The historical record of this erosive evidence points to a progressive increase in its intensity during the 21th century, with a growing social pressure on the public institutions responsible for its maintenance, given the great socioeconomic impact generated by its dependence on summer tourism. In addition, the progressive sea-level rise will lead to the loss of the recreational area of this beach in the next century, as well as the need to rethink the location of its promenade and the reinforcement of the defensive structures that protect the private housing developments closest to the coastline.
The Eocene Shahejie Formation in the Zhanhua sag of the Bohai Bay Basin has abun-dant shale oil resources.However,lacustrine shale is heterogeneous in mineralogy,sedimentary structure,organic matter,pore structure,paleoenvironment,and oil content.Therefore,the laminae assemblages are divided into laminated(lamina thickness of<0.01 m),layered(0.01-0.1 m)and massive(no layer or layer spacing of>0.1 m)types shale to investigate the core,X-ray diffraction(XRD),thin section,field emission-scanning electron microscopy(FE-SEM),mercury injection capil-lary pressure(MICP),N2 adsorption and geochemical experiments.The results show that the oil shale of the Shahejie Formation in Zhanhua sag is abundant in calcite.The TOC content ranges be-tween 1.35％and 5.55％.Rock-Eval S1 and S2 values range from 0.30 to 2.56 and 0.97-15.47 mg/g,respectively.Variable kinds of nanopores,micropores,and microfractures are commonly observed.The connectivity of pores in laminated and layered shale samples is relatively better than massive shale.The massive shale was formed in a sedimentary environment with a warm and humid cli-mate,moderate salinity,weak reduction conditions,high productivity,and paleo-setting rate.Organ-ic matter is derived from lower bacteria,algae,and terrigenous plants.Laminated and layered shale are formed in an arid and cold environment with high salinity,strong reducibility,and low paleo-setting rate.Laminated shale is located on a gentle slope at the basin margin,which is the focus of shale oil exploration because of its higher hydrocarbon generation potential,reservoir quality,and advantaged horizontal fracturing conditions.The above results have implications for the sweet spot prediction in shales with similar geological settings.
Marine-continental transitional (MCT) shale gas is an important successor of unconventional natural gas resource in China. Based on integrated analyses of published data including outcrop investigation, exploration practice, drilling cores, and experimental testing, the recent progresses of both global and domestic shale gas development were systematically reviewed and compared, and we further examined the exploration progress and challenges of MCT shale gas in the Ordos Basin, Sichuan Basin, and their adjacent areas, and conducted a comprehensive discussion of the key geological conditions for the formation of shale gas and its resource potential, challenges, and counter measures. The results show that MCT shale in China is mainly developed within the Carboniferous–Permian strata (Benxi, Shanxi, and Longtan formations), dominated by lagoon, swamp, and tidal flat facies, and possesses favorable conditions for shale gas formation and development potential. They mainly include the generation and storage of shale gas as follows: (1) The organic-rich intervals are thick and widespread, dominated by Type III organic matter with high total organic carbon (TOC) content (⩾3.0
Paleogeographic reconstruction provides a key surface boundary condition for the study of many first-order Earth systems and geodynamic processes. However, scarcity of robust Early Paleozoic paleomagnetic data leads to a controversial reconstruction between the South China Block (SCB) and Gondwana. Here, we performed rock-magnetic, mineralogical and paleomagnetic analyses on the Ediacaran and Cambrian strata in the Jiulongwan and Gunshi’ao sections in the Three Gorges area, Hubei province in South China. Rock-magnetic and mineralogical analyses suggested that the secondary magnetite—formed via pyrite oxidation—is the main remanence carrier, recording a post-tilting remagnetization event associated with fluid alterations. Paleomagnetic measurements showed a new Early Silurian paleopole (5.0°N, 194.1°E, A95 = 3.0°) from the overprinted Ediacaran–Cambrian carbonates. These results indicated that the SCB was positioned in the equatorial region during the Early Silurian. Comparison of the Early Paleozoic apparent polar wander paths between the SCB and Gondwana further suggests that the SCB was united to northwestern Australia, part of Gondwana, from Late Cambrian to Early Devonian. These findings refine the paleogeographic reconstructions of the Early Silurian and favor the proximity between South China and Gondwana during the Early Paleozoic.
