Objective Neoproterozoin “Snowball Earth” （Cryogenian） glaciations is a long-standing hot topic in sedimentology. In South China， well-preserved sedimentary records during Cryogenian Period have been found in many places in the Yangtze Block. However， there are relatively few reports on deposits of this time in Kangdian Rift Basin on western margin of the Yangtze Block， and in the rift basin between northern margin of the Yangtze Block and southern margin of the Qingling Orogen. Methods This study focuses on the Cryogenian glacial deposits in the Gangchang-Yuanba section， Hanzhong area， northern margin of the Yangtze Block. Based on the field observations and measurements， zircons were selected from the bottom tuff layer and upper sandstones for U-Pb dating analysis using laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS）. Detailed features of the sedimentary rocks and their regional correlation are also discussed. Results Two sets of tillites were identified for the first time within the Neoproterozoic glacial sedimentary rocks in this region， both from a continental glacier. Several layers of sandstone and siltstone are presented between and above the tillite sets. Zircons from the bottom tuff yielded the earliest mean concordant age of （719 ± 11） Ma， indicating the beginning of glaciation in this region. Considering their lithological succession and sedimentary structures， these Cryogenian deposits are thought to have been formed during Sturtian glaciation， corresponding respectively to the Chang’an and Gucheng glaciation periods. The timing of this glaciation event， and the sedimentary associations， are consistent with contemporaneous sediments in the adjacent Zhenba and Chengkou areas， and also show similarities to Sturtian sediments widely distributed in other parts of South China.

Objective Significant advancements have been made in the research of sandy braided river deltas， but the sedimentary characteristics and evolution laws of sandy braided river deltas require further study， particularly the understanding of mouth bars and distributary sand bars. Methods Based on the underground reservoir data， this study used the Delft3D software to show the growth and evolution of a sandy braided river delta into a lake， summarizing its sedimentary characteristics and evolution laws. Results The evolution of a sandy braided river delta has three stages. In the early stage， the delta grows fastest， and the average diameter growth rate was greater than 6 m/step. Sediments are carried into the lake and quickly unloaded， forming a large flower-shaped mouth bar under the water. In the middle stage， the delta plain continues growing， and the delta front remains large， accounting for more than 50% of the delta area. Contiguous sand bodies are built. In the late stage， the delta grows slowly， the average diameter growth rate is maintained at 1m/step. The front area is small， less than 20% of the overall area. The delta plain has many distributary channels and ditches， leading to multiple paths for transforming the distributary sand bars. The delta front sand bars have different degrees of superposition and rhythm combination characteristics， and the distributary sand bars are built on the residual mouth bar. Conclusions A sedimentary model of a sandy braided river delta was established， providing reference for the genetic identification of distributary sand bar and mouth bar， and laying the foudation for advancing underground reservoir architecture research.

Significance The study of fine-grained sediment transport mechanisms is an important part of the “source-to-sink” system theory of fine-grained sediments， and it is significant for the restoration of sedimentary environments， understanding the distribution of fine-grained sediments and predicting the distribution of unconventional oil and gas resources. Due to the fine grain size， which makes them difficult to observe， and the diversity of transport modes， each transport mode corresponds to particular sedimentary structures. Therefore， research on the transport mechanisms of fine-grained sediments has progressed slowly. From a review of the existing research reported in China and elsewhere， it is evident that there is still a lack of sorting and summarizing research findings regarding the transport mechanisms of fine-grained sediments. Progress This study synthesizes current research， systematically sorts the transport modes and sedimentary characteristics of fine-grained sediments and classifies the transport modes of fine-grained sediments into three major categories： physical transport， chemical transport， and biological transport. Physical transport includes river water， atmosphere， bottom current， density underflow， and six types of gravity-flow transport. River water and atmospheric transport rely on the forces exerted by water flow and/or wind to overcome the gravitational force on fine-grained materials. These are mainly traction force and load force. Bottom current， density underflow， and gravity flow transport are triggered by tides， wind， earthquakes， floods， storms， volcanic eruptions and other means， with gravity being the main driving force. Clay minerals， dissolved organic carbon， carbonate minerals， iron minerals and others are transported as colloids or as true solutions. Dissolved substances are affected by environmental factors such as pH， Eh， temperature， pressure， and ion concentration or charge， and are transported by chemical means. Biological absorption and enrichment， environmental changes caused by biological activities and bioturbation all affect the formation and transport of fine-grained materials. ［Conclusion and Prospect］ Physical transport has diverse modes. With driving forces such as traction force， carrying capacity， and gravity， it can form a rich variety of sedimentary structures. Chemical transport mainly involves dissolved substances and is affected by environmental factors such as pH values and temperature. Biological transport influences the transport of fine-grained substances through absorption and enrichment， alteration of the environment， and bioturbation. In the future， attention should be focused on the interactions among the transport mechanisms of fine-grained sediments， the accuracy of identifying sedimentary structures should be improved， importance should be attached to simulation experiment research， and the quantitative analysis of chemical and biological effects should be strengthened， so as to enhance the understanding of the transport processes of fine-grained sediments and promote the development of the theory of fine-grained sedimentology.

Objective Distributive fluvial systems （DFS） are widely developed in modern and ancient sedimentary strata and they are important hydrocarbon reservoirs. Multiple interacting DFS and evolving axial rivers may be developed in a narrow， shallow lacustrine basin with low accommodation. Methods Reproducing the deposition process through flume simulation experiments， this study used a high-precision three-dimensional （3D） scanner with a self-developed program to visual analyze the deposition area and clarify the stage-by-stage evolution characteristics of the DFS. Results （1） With the expansion of the DFS scale， the water flow on its surface gradually aggregates； the initial flow pattern is sheet flow， which then evolves into unrestricted and restricted flow； （2） as the basin can accommodate less space， the axial water flow in the basin gradually aggregates into an axial river， which has a destructive effect on the two sides of the DFS and constantly breaks， forming a large-scale fluvial deposition； （3） when multiple DFS are developed in a narrow， shallow lacustrine basin， the sedimentary sands are concentrated at the DFS near the source and downstream of the axial river， and the longer basin development time indicates a larger scale of fluvial deposition. Conclusions This study describes the developmental processes and sand body spreading patterns of multiple DFS and axial rivers developed in a narrow， shallow lacustrine basin with low accommodation and sufficient supply of material sources at the basin scale， providing theoretical support for oil and gas exploration and the study of distributive fluvial systems.

Objective Following the mass extinction at the end of the Permian， microbialites were widely distributed in southern China， indicating a microbial bloom in the Lower Triassic following the cataclysm. However， microbialites generally exhibit low paleo-productivity， which seems to contradict the microbial explosion. This study analyzed the microbialites at the base of the Triassic Tianwan section in the Luodian area of Guizhou province， focusing on the petrological characteristics of micritic pellets and their thermal metamorphic evolution and sources of organic matter. The study clarifies the respective influences of microbially derived and seawater-trapped organic matter on pellet formation， with the aim of providing empirical evidence for exploring carbon cycling mechanisms in post-extinction microbialite systems. Methods In situ micro-area analytical techniques （optical microscopy， fluorescence microscopy， scanning electron microscopy （SEM） with energy-dispersive spectroscopy （EDS）， and laser Raman spectroscopy） were used to conduct a detailed analysis of various types of peloids within the microbialites from the Tianwan section. These reveal the distribution patterns and thermal metamorphic evolutionary characteristics of internal organic matter. Results Based on morphology and infill materials， the various peloids were classified into six types： type I （microbially-induced peloid， MIP）； type II （recrystallized microbially-induced peloid， RMIP）； type III （aggregated detrital peloid， ADP）； type IV （intraskeletal peloid， ISP）； type V （dolomitized peloid， DP）； and type VI （aggregated microbially-induced peloid， AMIP）. Raman spectroscopy-derived metamorphic roasting temperatures provide insights into the thermal history and transformation of these peloids. The organic matter in types I， II， IV and VI （MIP， RMIP， ISP and AMIP） shows thermal maturity similar to that found in primary cyanobacteria in microbialites and shell fragments， indicating a common diagenetic history and microbial origin. Of these， peloids I， II and VI exhibit low thermal maturation temperatures， with organic matter mainly derived from the photosynthetic and metabolic processes of primary cyanobacteria and other microorganisms within microbialite systems. Specifically， peloid VI formed when micritic particles wrapped around peloid I， linked to bioclastic micritization. peloid IV shows moderate thermal maturation temperatures， resulting from a mix of microbial micritization and siliceous clastic material. By contrast， peloids III and V （ADP and DP） evidenced significantly higher metamorphic temperatures， suggesting multiple thermal alteration events. Peloid III may have been formed by neomorphism； peloid V was primarily shaped by bioclastic micritization. Conclusions In summary， after the end-Permian mass extinction， microbial blooms， especially cyanobacterial photosynthesis， led to the generation of large amounts of dissolved organic carbon （DOC） in the oceans. Due to frequent fluctuations in seawater redox conditions and rapid temperature increases， the DOC was typically oxidized into CO₂ and released into the atmosphere， with only a small fraction being preserved as particulate organic carbon （POC） and deposited on the seafloor. Raman geothermometric analysis shows that most of the organic matter in the microbialite peloids， particularly in those associated with bioclastic peloidal envelopes， originated from the metabolic activity of primary cyanobacteria， which was the original organic matter in the microbialite system. A small portion of the organic matter may have been sourced from long-stored terrestrial organic matter in seawater， which underwent multiple diagenetic thermal alterations and shows higher thermal maturation temperatures. The thermal maturation of organic matter and mineral recrystallization during diagenesis had a significant impact on the efficiency of organic matter preservation， ultimately resulting in a low total organic carbon （TOC） content in the microbialites.

Objective Clarifying the provenance composition and evolution of the Lower Jurassic Badaowan Formation and Sangonghe Formation in the Dongdaohaizi Sag， Junggar Basin， has important guiding significance for studies of the sedimentary filling response in this region of the Lower Jurassic. Methods A detailed analysis was conducted on the source characteristics and evolutionary processes of the Badaowan Formation and Sangonghe Formation based on the composition of sandstone debris， the geochemical characteristics of whole-rock elements， and U-Pb ages of detrital zircons. Results It was found that the sandstone samples from the Lower Jurassic in the study area were mainly composed of feldspathic lithic sandstone， with an average content of 37.7% of tuff and basalt lithic debris in the thin sections， along with a small amount of metamorphic rock debris. After standardization of shale samples in North America， the Badaowan Formation samples showed no significant differentiation between light and heavy rare earth elements. The Sangonghe Formation exhibited slight enrichment of light rare earths and depletion of heavy rare earths. The age distribution of detrital zircons in the sandstone samples in the Badaowan Formation is mainly concentrated in three ranges： 280-330 Ma， 400-440 Ma and 490-520 Ma； the Sangonghe Formation is dominated by three peak age ranges： 280-350 Ma， 380-430 Ma and 460-520 Ma， with similar age compositions. Conclusions A comprehensive analysis of provenance characteristics indicated that the Badaowan Formation in the Dongdaohaizi Sag is mainly sourced from the Kela Meili provenance system in the eastern Junggar Basin， and the western Urho and Karamay provenance regions had little influence. During the depositional period of the Sangonghe Formation， the western region began to supply resources， but the eastern Kela Meili provenance system remained the main source of materials in the study area. In the Middle Jurassic， the influence of the western provenance increased， and the Che-Mo paleo-uplift was formed. The Donghaizi Sag was jointly influenced by two major provenance systems. The parent rocks in the Lower Jurassic provenance area of the Dongdaohaizi Sag are mainly intermediate acid magmatic rocks and basic magmatic rocks， and the provenance is mainly from the transitional and recirculating zones of the recycled orogenic belt. The tectonic setting is dominated by continental island arcs， which is consistent with the mixed-source background formed by oceanic continental subduction around the Junggar Basin， and following closure of the ocean basin. In the context of this tectonic setting， during the sedimentation period of the Badaowan Formation the Dongdaohaizi Sag was influenced by the East Kela Meili source， forming a shallow-water delta lake sedimentary system. Distributary channel sand bodies were extensively developed， but the physical properties were poor， with few favoring hydrocarbon accumulation. During the sedimentation period of the Sangonghe Formation， the Dongdaohaizi Sag was influenced by two major source systems， east and west， and a shallow-water delta lake system developed together with underwater distributary channel microfacies composed mainly of medium and fine sandstones， as well as a small amount of estuarine dam microfacies with physical properties favorable to hydrocarbon reservoir development.

Objective A typical gravity-flow sedimentation set is present in the Ordovician Lashizhong Formation at the western margin of the Ordos Basin. This study investigated the formation process of gravity flows in the third member of the Lashizhong Formation with the aim of summarizing the sedimentary characteristics and evolutionary pattern， and to establish a sedimentary model. Methods Outcrop observation， thin-section examination， grain size analysis and paleocurrent measurement were used in the analysis. Results Eight kinds of lithofacies and six litho-facies associations were found in the study area： horizontal bedded shale （A1）； lens-shaped massive bedded calcirudite （B1）； lens-shaped parallel-bedded sandstone （B2）； lens-shaped cross-bedded sandstone-siltstone （B3）， wedges of cross-bedded sandstone-siltstone （C1）， graded beds of sandstone-siltstone （D1）， parallel-bedded siltstone （D2）， and bedded pebbly sandstone （D3）. These indicate channel axis deposition （B1）， vertical aggradation channels （B2， C1， A1）， distributary channels （B3， C1， A1）， proximal lobes （D1， A1）， distal lobes （D2， A1） and mass transport deposits （D3）. Channel axis deposition， vertical aggradation channels， distributary channels， proximal lobes and distal lobes have been successively developed in the lowest part of the Third member of the Lashizhong Formation， which is divided into five stages. The middle and upper parts of the Third member of the Lashizhong Formation show the development of mass transport deposits， proximal lobes and distal lobes， and is divided into seven stages. Conclusions The evolution of these strata is closely related to the type and energy of gravity flow. At the initial stage， gravity flow was dominated by debris flow， then， as the debris flow energy weakened， turbidity current dominated. The vertical aggradation channels were developed during multi-stage periods of erosion and sedimentation. Distributary channels and lobes then developed with further weakening of the turbidity flow. Tectonic movement increased the sand content of sediment supply， leading to the initial development of massive transport deposition followed by large-scale lobes with higher sand content. The vertical evolution of gravity flow sedimentation was governed by a combination of factors， including sea-level fluctuations， sediment supply and its composition， as well as tectonic movement. An initial rise in sea level followed by a sub-sequent fall are suggested by a decrease and then increase in the scale of gravity flow development. Variations in sediment supply types gave rise to diverse sedimentary units， including channel-axis deposition composed mainly of calcirudite， as well as vertical aggradation channels， distributary channels， proximal lobes and distal lobes mainly comprising fine sandstone and siltstone. Moreover， the magnitude of sediment supply significantly impacted the morphological features， dimensions and sand-to-mud ratio of these sedimentary units. During the depositional period of the Lashizhong Formation， relatively subdued tectonic activity facilitated the formation of a channel-lobe system that is relatively modest in size compared to the scale typically encountered in exploration contexts. The interplay of the above factors ⁃ sea-level changes， sediment-supply dynamics， and tectonic setting ⁃ together shaped the architectural complexity and distribution patterns of the gravity flow deposits in the basin. Understanding these controls is crucial for accurate reservoir characterization and prediction in hydrocarbon exploration and production. This study helps in the understanding of gravity-flow evolution in the study area， and provides a theoretical reference for oil and gas exploration.

Objective The formation of sedimentary systems within straits is intricately linked to the unique topographical constraints that influence both facies characteristics and sediment distribution patterns. Although current research mainly focuses on narrow straits （less than 50 km wide） ， where sedimentation is dominated by tidal processes， wider straits introduce more complex hydrodynamic dynamics， leaving many aspects of the sedimentation processes yet to be fully understood. Methods This study focuses on the Bohai Strait （a shallow strait with a width of 106 km） and is based on an extensive dataset of surface sediment grain sizes， combined with four shallow seismic profiles， to characterize the sedimentary environment within the Bohai Strait. Additionally， a regional ocean modeling system （ROMS） simulation was employed for winter （December 2020⁃February 2021） to better understand the hydrodynamic processes influencing sediment dynamics and control over sediment distribution within and surrounding the Bohai Strait. Results Our results reveal significant differences in sediment dynamics between the northern and southern parts of the strait. The northern region exhibits a high-energy environment dominated by erosion， whereas the southern region displays a lower-energy environment conducive to deposition. Surface sediment types vary spatially， with coarser grains predominating in the north and narrow regions， with finer grains observed on both sides （east⁃west） and in the south. A large-scale， sandy flood-tidal delta appears around the Laotieshan Channel in the north. The asymmetric tidal currents flowing in and out of the channel are likely responsible for this feature， and ebb-tidal delta is not prominent. In contrast， the southern part of the strait exhibits two distinct sedimentary systems：（1） Shandong mud wedge： This system lies along the coast of the Shandong Peninsula， shaped by the substantial sediment supply from the Yellow River and the influence of coastal currents. （2） Scour troughs and sandy tidal deltas： These smaller features are attributed to the protective effect of islands present in the southern strait， combined with the abundant supply of fine-grained sediments. Conclusions This study highlights the critical role of the complex topography of the strait in the confinement in shaping regional sediment transport dynamics and the resulting distribution of sedimentary systems.

Objective Research on the weathering process of the aggradation red earth in subtropical China has long been crucial for understanding the evolution of the Quaternary environment. However， a comprehensive know-ledge of the weathering environment of the aggradation red earth is hampered by the infrequent reporting of research on the weathering characteristics of the aggradation red earth at the spatial scale. Methods Based on a systematic analysis of the weathering characteristics of the aggradational red earth sections in southern China， this study focused on the Jinqu Basin， where non-zonal factors have a significant impact. The research primarily explored the chemical weathering characteristics and formation mechanisms of red earth within the basin， to deepen our understanding of the weathering features of aggradational red earth. Results （1） On a large scale， the weathering intensity of aggradational red earth in southern China is strongly correlated with hydrothermal conditions， with weathering intensifying as latitude decreases. However， the chemical weathering of red earth in certain locations or specific sections does not entirely conform to the latitudinal zonality in the mid-subtropical region between 25° N and 31° N， where aggradational red earth is widely spread. （2） The geochemical composition of aggradational red earth in the Jinqu Basin exhibits good consistency， with minimal differences in element enrichment or depletion among samples. However， there is regional variability in the degree of chemical weathering in the developmental stages of vermicular and typical red earth following the stagnation of vermicularization in the Jinqu Basin， compared with the chemical weathering characteristics of other aggradational red earth sections at the same latitude. （3） Influenced by a combination of factors such as provenance， topography， and local climate， the weathering characteristics of the aggradational red earth in the Jinqu Basin exhibit certain non-latitudinal zonal features. Conclusions The weathering characteristics of the aggradational red earth in southern China primarily follow a latitudinal zonal pattern under the large-scale monsoon evolution pattern. However， owing to the influence of non-zonal factors including topography， water， and differences in the geographic features of potential provenance， the chemical weathering of aggradational red earth also exhibits certain non-zonal characteristics within the mid-subtropical region between 25° N and 31° N. The relatively small and enclosed basin terrain of the Jinqu Basin， along with local microclimate conditions and contribution of bedrock weathering products to the red earth provenance， plays a significant role in interpreting the chemical weathering information of the red earth. Therefore， it is crucial to consider regional impacts while discussing the chemical weathering characteristics in different areas.

Significance Peat bogs play an important role in the global carbon cycle as a depositional carrier of paleo-wildfire events and paleoclimate information. By systematically sorting wildfires types in peat bogs and clarifying the academic terminology related to wildfire products such as charcoal， the carbon source and sink effects of wildfires in peat bogs were discussed. This information is useful for the study of the carbon cycle in deep time. Progress Wildfire product charcoal， approximately equivalent to the inertinite in coal， is a relatively stable carbon store of plant-incomplete combustion residues， which can provide a record of wildfire activities in geological history， from millennia to billions of years. Changes in charcoal material composition （e.g.， polysaccharides and lignin） and microstructure （e.g.， cell wall homogenization） can reflect the temperature range of paleo-wildfires. Wildfire types can be recovered and atmospheric oxygen content can be constrained using inertinite reflectance and content. The impacts of wildfires on the global carbon cycle include both short-term carbon source and long-term carbon sink effects. Wildfires lead to direct large carbon emissions and carbon release from deep peat burning. However， wildfire-driven persistent changes in soil microorganisms， aggregates， and organic matter can directly offset certain carbon losses， and charcoal provides a stable carbon store. Conclusions and Prospects Based on the carbon cycle model of peatland under normal burial conditions， the influence factors of wildfire， soil aggregates， fungi， and bacteria were introduced to propose a post-fire peatland carbon cycle model. Using the inertinite wildfire genesis and greenhouse gas emission models， and taking the carbon emission and carbon storage of wildfires in Early Cretaceous peat （coal-forming） bogs in Northeast China as an example， the results show that the long-term （million-year time scale） carbon sinks of forest vegetation growth and peatland are fully capable of neutralizing the short-term （year time scale） carbon source effect brought by wildfires. In the future， when evaluating the deep-time carbon cycle response to wildfires， it is necessary to consider the length of the time period and wildfire intensity， improving our understanding of climate change and environmental evolution caused by wildfire to promote the in-depth integration of deep-time and present-day climate change and carbon cycle research.