The in-depth analysis of the development process of the delta front is of great significance for the judgment of the sedimentary environment,and it is necessary to deeply explore the formation characteristics and mechanism of the delta front from the perspective of hydrodynamics. In this study,the vertical distribution of the flow velocity in river water bodies and the development characteristics of delta front sedimentary bodies are investigated,from multiple perspectives of hydrodynamics,flume experiments,and underwater geomorphological observations. The results show that the phenomenon of river flow velocity,exhibiting a monotonic decrease with depth,has not been given sufficient attention. The terrain undulation of the middle and lower reaches of the riverbed increases with the flow direction,resulting in the underwater sand waves perpendicular to the flow direction,while the terrain undulation of the river section perpendicular to the flow direction becomes more and more gentle. During the process of rivers entering the sea,there will be a mainstream channel without branching channels underwater. Additionally,the originally undulating riverbed will gradually be filled up,changing from a sharp V-shaped or W-shaped to a U-shaped. It can be concluded that most of the front edge of the delta are sheet-like or fan-shaped,rather than a strip of erosion surface along the flow direction. Microfacies such as underwater distributary channels and bays do not develop in the delta front subfacies,which cannot be found in the modern delta front subfacies and are not supported by flume experiments. Furthermore,a water depth velocity interaction model for river channel and delta sedimentation is proposed.

The upper Oligocene Huagang Formation is crucial for oil and gas exploration in the central and southern Xihu sag of the East China Sea Shelf Basin. However,there has been ongoing debate on the sedimentary system,and limited research has been conducted on the characteristics of sand body architecture and the controlling factors. This paper studied the sedimentary environment,microfacies types,sand body architecture,and controlling factors of the upper Oligocene Huagang Formation through a comprehensive analysis of core,logging,and seismic data. The upper Huagang Formation in the central-south part of Xihu sag shows shallow-water delta plain sedimentation,with distributary channels being the predominant type of sand body. These distributary channels are categorized into three types based on their curvature: braided(curvature=1~1.05),meandering(curvature>1.15),and braided-meander transition(curvature=1.05~1.15). The sand bodies found in braided distributary channels are wide and thick,with intertwined wide bands. Channel bars in these channels are arranged in a speckled pattern. The sand body’s vertical stacking style is mainly characterized as incised stacking. In contrast,the sand bodies in meandering channels are narrow and thin,appearing as either single strip type or bifurcation-merging type in the planar direction. Thick sand layers are distributed as point bars in the channel margin,and the vertical stacking style is mostly isolated. The braided-meandering type of diversion channel is a transitional type between braided and meandering channels. It is characterized by moderate-sized channel sand bodies containing inner channel bars and point bars. The thickness and width of these distributary channels are positively correlated in a logarithmic manner. The ratio of width to thickness follows the pattern of braided type>transitional type>meandering type. The architecture characteristics of distributary channels are primarily influenced by paleogeomorphology and changes in base levels. Paleogeomorphology controls changes in channel types within shallow water delta plain,and low curvature braided distributary channels are more likely to develop in steep terrain. As the long-term base level increases,the size of distributary channels decreases,while a rise in mid-term base level has resulted in the transition of distributary channel sand bodies from incised to superimposed and isolated stacking types. This research enhances our understanding of the sedimentary structure of shallow water deltas and provides valuable guidance for predicting and developing distributary channel reservoirs in underground shallow water deltas within oil and gas fields.

In recent years,oil and gas exploration in the Junggar Basin has gradually shifted from conventional traps outside the source to lithological traps within the source. The Upper Urho Formation is currently the main exploration target for boosting reserves and production in the basin. The distribution of sedimentary system has a controlling effect on the distribution of lithological reservoirs in the Upper Urho Formation. Using drilling cores,thin sections,combined with seismic data and drill cuttings and wireline logs,this study identified and characterized the sedimentary facies and depositional systems of the Upper Urho Formation in the Junggar Basin,and summarized the large-scale transgression. The sedimentary model of fan(braided river)delta-beach bar composite sandy conglomerate body was analyzed,and its controlling factors were analyzed. The results show that: (1)The study area is characterized by various sedimentary facies,including fan delta,braided river delta,and shallow lake beach bar. Among them,fan-delta plain and fan-delta front are mainly developed in the west of the basin,while braided river-delta plain and braided river delta front mainly developed in the east and north of the basin,and beach-bar is mainly superimposed on fan-delta and braided river-delta fronts or occurs independently at their front ends. (2)The depositional system of each member of the Upper Urho Formation developed under the background of overall lacustrine transgression. During the first member of Urho Formation,the basin was relatively small,and the deposited sand bodies were thick and of limited lateral extent,located in proximity to the depression center;during the second member of Upper Urho Formation,with continuous sediment supply and increased water depth the area of the lacustrine basin increased,with thinner but more extensive sand bodies deposited;during the third member of Upper Urho Formation,lacustrine transgression was enhanced,basin area was thus further expanded,and lacustrine mudstone was widely developed in the basinal area. (3)The fan(braided river)delta front-beach-bar composite gravel body was formed under continuous change of lake level and transformation of lake waves in the fan delta state and braided river delta front. (4)During the depositional period of the Upper Urho Formation in the Junggar Basin,the main controlling factors of the depositional system were climate,source supply,lake-level changes,and palaeotopographic slope and palaeogeomorphology at the time of deposition. This study provides a geological basis for oil and gas exploration in the Upper Urho Formation.

Uplift processes of the southern margin of the North China Block are of great significance for understanding interactions between the Qinling Orogenic Belt and the North China Basin. Based on sedimentary facies analysis,this paper studies the detrital zircon U-Pb geochronology and fission track chronology of the Permian Shihezi Formation in Luonan area,and discusses the source characteristics and uplift processes of the southern margin of the North China Block. It is expected to provide a sedimentary constraint for the subduction time of the Mianlue Ocean Basin and provide a possible source area for the Triassic recycled sediments in the southern North China Basin. The results show that the Permian Shihezi Formation in Luonan area experienced an upward change in sedimentary facies from alluvial fan to braided river,and then to delta. The sample from the lower part of the strata contains three groups of U-Pb ages,i.e.,353-280 Ma,1139-400 Ma,and 2620-1306 Ma. The fission track ages are decomposed into three peaks of 199 Ma,255 Ma,and 408 Ma. The sample from the upper part of the strata contains two U-Pb age groups,i.e.,339-259 Ma and 2655-1700 Ma,and the fission track ages were decomposed into three peaks of 205 Ma,268 Ma and 656 Ma. The results show that the southern margin of the North China Block received sediment from the Qinling Orogenic Belt during the early sedimentary period of the Shihezi Formation,but the sediments mainly came from the northern margin of the North China Block in the late depositional stage. The tectonic pattern had been transformed from high in the south to high in the north in this time. The initial uplift of the southern margin of the North China Block occurred during the Middle-Late Permian,which was related to the initial subduction of the Mianlue Ocean Basin,and became a potential provenance area to the Triassic strata in the south of the North China Basin.

Quartz is an important part of shale,making it crucial to clarify its genetic mechanism for the reconstruction of shale diagenetic process and the formation of shale oil and gas reservoir. The genesis of quartz in shale is complex,with the main types, including terrigenous detrital quartz,biogenic quartz and diagenetic authigenic quartz, identifiable through ordinary thin section observation,scanning electron microscopy,energy spectrum analysis and cathodoluminescence. The main sources of diagenetic authigenic quartz silica are clay mineral transformation,felsic dissolution and biosilicon dissolution,and volcano-hydrothermal activity. Terrigenous detrital quartz is mostly silt-grade and strongly emits light under cathodoluminescence,typically displaying a two-peak spectrum. Micron-sized biogenic quartz does not emit light,and clay mineral-derived quartz is predoninantly found around or embedded within clay minerals, such as illite. In addition to the morphology and occurrence characteristics of different types of quartz,there are also differences in geochemical elements. Quartz affected by hydrothermal activities is rich in Fe and Mn,while terrigenous detrital quartz is rich in Ti and Al elements. Detrital SiO₂ and Zr are positive correlation,as does biogenic quartz with TOC content. The biogenic quartz Fe/Ti ranges between 0.4 and 20. Diagenetic authigenic quartz is formed in multiple stages,which is closely related to the burial diagenesis process of shale and affects the properties of shale reservoirs. Diagenetic authigenic quartz is mainly formed in early and middle diagenetic stages. Terrigenous detrital quartz and biogenic quartz are conducive to inhibiting compaction and protecting primary pores. Processes involving diagenetic authigenic quartz, like clay mineral transformation and felsic dissolution create dissolution pores and organic pores,with quartz filling some pores,thereby reducing porosity. Identifying the origin of quartz in shale is of great significance to the analysis of shale sedimentary environment and the prediction of favorable reservoir distribution.

Silicate rocks are factors that influence the global carbon cycle as well as climate change by chemically reacting with carbon dioxide,removing atmospheric carbon dioxide and sequestering it in weathering products or ocean carbonate rocks. Quantifying the total amount of carbon dioxide consumed by weathering of global silicate rocks is key to understanding the Earth’s current and past climate change. This paper systematically investigates the data sources,research methods,calculation formulas,and main influencing factors of five quantitative models of chemical weathering-CO₂ consumption of silicate rocks. The CO₂ consumption calculated by the latest Celine model serves as a reference standard for comparing the advantages,disadvantages and scope of application of each model. The existing models estimate the global carbon dioxide consumption of chemical weathering of rock silicate rocks to be 69-169 Tg/yr,in which the main parameters of each model include climate(temperature,runoff)and lithology,and the secondary parameters include tectonic uplift,volcanism and plant interaction. Future exploration of the quantitative calculation of carbon dioxide consumed by the chemical weathering of silicate rocks should consider more control effects and the interconnections between factors. In addition,the use of big data analysis methods to generalize these quantitative models to the reconstruction of the palaeoclimate of the deep earth may be a future research trend.

The study of incidence and attributes of regional extreme climatic events under the background of global change is a frontier of climate change research. This paper reconstructs the extreme flooding events with a probability of 10% in the Northeast China in 1750-2020 using historical documentary records and precipitation data,and then analyzes its incidence characteristics and driving mechanism. The main conclusions include: (1)In 1750-2020,29 extreme flooding events were identified in the Northeast China,exhibiting fluctuating patterns,with 1871 to 1930 marking the period of highest frequency over the past 270 years;(2)The global and regional warming significantly enhanced the frequency of extreme flooding events in the Northeast China;(3)The anomaly of the monsoon rain belt caused by the change of the East Asian summer monsoon is the direct cause of the occurrence of extreme flooding events in the Northeast China. Particularly,periods with a stronger monsoon and a northward shift in the rain belt significantly raise the likelihood of such events;(4)The Indo-Pacific warm pool and the sea surface temperature anomalies in the tropical central and eastern Pacific caused the incidence of extreme floods events in northeast China by affecting the location of the East Asian summer monsoon and the water vapor transport. The positive anomaly of water vapor transport at the time of La Niña years is crucial for the occurrence of extreme flooding,and is a reliable predictor of extreme flooding events in the Northeast China.

The mineral composition and particle size of heavy minerals in sediment are important indicator for revealing sediment sources and hydrodynamic sorting processes. However,due to the limitations of research methods,there is still no research on the relationship between the heavy mineral composition, provenance and hydrodynamic sorting of fine-grained sediments in the Yangtze River. In this study,the TESCAN Integrated Mineral Analyzer(TIMA)was used to study the composition and particle size of heavy minerals in different water layers of the Yangtze River Estuary and East China Sea inner continental shelf. In parallel, the automatic identification results of fine-grained heavy minerals were verified by electronic probe analysis. The study shows that the characteristic heavy mineral assemblages in the suspended solids in the Yangtze River Estuary is hornblende,epidote and ferruginous metal minerals,which is consistent with the characteristic heavy mineral assemblages in the sediments of the lower reaches of the Yangtze River. There is an excellent correlation between the heavy mineral composition of suspended matter in the Yangtze River estuary and sediment in the lower reaches of the Yangtze River,indicating that its source is related to the Yangtze River. However,hematite/magnetite is relatively enriched in the suspended matter outside the Yangtze River estuary,which may be the result of the reworking and diffusion of medium density heavy minerals caused by strong tide. It is worth noting that abnormal enrichment of chromite appears in suspended matter samples at stations near Zhoushan Islands,which may be related to human production activities in the sea area. The vast majority of suspended heavy mineral particles in the Yangtze River Estuary are coarse silt to extremely fine sand,enriched in the coarser fractions(Ф<D_0.5)of suspended solids,which are mainly carried and transported by runoff. There is no significant difference in the particle size between different types of heavy minerals in suspended solids in different water layers, indicating that they are less affected by sedimentation differences.

The sand bodies of the Member 2 of the Upper Triassic Xujiahe Formation in the Xinchang structural belt of western Sichuan Basin are widely distributed,with various types of sand bodies and large thickness differences. This results in uneven distribution of interlayer barrier bed and intraformational bed in gas reservoirs,and strong reservoir heterogeneity. Therefore,it is crucial to investigate the sedimentary microfacies,distribution characteristics and architecture of reservoir sand bodies,so as to lay a foundation for the following reservoir prediction and efficient gas reservoir development. Using core,well logs,3D seismic and laboratory data,and guided by the theory of high-resolution sequence stratigraphy proposed by T.A. Cross,the authors systematically examined the structural characteristics and controlling factors of sand bodies in the second member of Xujiahe Formation in the Xinchang structural belt,western Sichuan Basin. The results show that: The study area was largely located in a shallow water delta front environment,which consists mainly of subaqueous distributary channel sand bodies with subordinate mouth bar sand bodies. These channel sand bodies are characterized by frequent lateral migration,multiple vertical amalgamation and extensive areal coverage. It is concluded that in the study area there are two main categories and nine subcategories of sand body vertical stacking patterns and three lateral contact patterns. The structural characteristics and development patterns of sand bodies are controlled mainly by base-level fluctuation and river energy. Finally,the sedimentary facies and sand body development model of the Xinchang structural belt in western Sichuan Basin are established,which has important applications for guiding exploration and development of gas reservoirs in similar settings.

As a large continental depression oil-and gas-bearing basin formed during the Cretaceous period,Songliao Basin contains a huge thickness of lacustrine fine-grained sediments,characterized by great exploration potential for unconventional oil and gas in recent years. The Qingshankou Formation is the key breakthrough layer of shale oil in Songliao Basin,and the mechanism of organic matter enrichment in fine-grained sediments is crucial for unconventional oil and gas exploration. Three wells located in different sedimentary areas in Changling sag of southern Songliao Basin were selected for detailed studies in this study. Based on core observation,organic geochemistry and biomarkers analysis of the fine-grained sedimentary rocks of the Member 1 of Qingshankou Formation(K₂qn¹),the transgressive systems tract,and the source and preservation conditions of organic matter in different sedimentary environments and processes were analyzed. Then the key control factors of organic matter enrichment were discussed,and the relevant enrichment models were established. Our results show that the organic matter abundance of fine-grained sedimentary rocks of K₂qn¹ was relatively high,and the kerogen is dominated by type Ⅱ. The overall organic matter abundance was low values in the south but high values in the north,low values in the lower part and high values in the upper part. Normal alkanes in saturated hydrocarbons predominantly exhibit single-peak and pre-peak patterns,with a slight odd-carbon preference. The terpenoids are primarily composed of tricyclic terpenoids and pentacyclic triterpenes. C_27-29 regular steroids are dominated by C₂₇ regular steroids. The major compound of the trifluorene series in aromatic hydrocarbons is dibenzothiophene. The organic matter in fine-grained sedimentary rocks of K₂qn¹ is mostly derived from the endogenous bacteria and algae in lakes,containing a certain amount of terrestrial higher plants. The water body is a weakly reduced,brackish environment. The source of organic matter and salinity are key factors controlling the enrichment of organic matter. Horizontally,the semi-deep lake to deep lake is less affected by riverine influences compared to the delta’s outer front,exhibiting weaker terrestrial input,higher water salinity,superior organic matter types,and greater organic matter richness. Vertically,as the water depth increases,riverine influence diminishes,the water salinity trends upward,the quality of organic matter improves,and organic matter becomes more enriched.

The deep-water area of the northern South China Sea experienced a transition from lacustrine to marine environments in the Paleogene,and has rich oil and gas resources and broad exploration prospects. Due to the limitation of water depth,the provenance of sediments and the palaeogeographic evolution of the basin are not clear. In this paper,the Paleogene of the Zhu-2 depression in the Pearl River Mouth Basin is systematically studied by means of detrital zircon U-Pb ages and source-sink correlation. The results show that in the Early and Middle Eocene,the sediments of the Zhu-2 depression were mainly from local uplift area around the depression. In the Late Eocene,the Kunyingqiong River originated from the western side of the depression provided a large amount of sediments for the basin,whereas the Paleo-Pearl River sediments had little influence on the deposition in the depression. In the Oligocene,the Paleo-Pearl River crossed the Panyu low uplift and entered the Baiyun sag,carrying sediments mixed with the Kunyingqiong River sediments in the form of delta deposition in the north and mid-west of the sag,forming a dual provenance river-delta system. The Paleogene provenance evolution of the deep-water area of the northern South China Sea was obviously controlled by regional tectonic palaeogeography of the Mesozoic. Identifying the provenance evolution during this period is of great significance for restoring the regional palaeogeography pattern.

It is of great significance for understanding the initiation and evolution of sandstone-type uranium deposits from the perspective of tectono-sedimentary evolution. In this study,based on a literature review,fieldwork,logging and seismic data,the tectono-sedimentary evolution of the Shizigou and Qigequan Formations in Qigequan Anticline in the Qaidam Basin and its links to the mineralization of sandstone-type uranium deposits are revealed. Our findings indicate that: (1)The Shizigou Formation is characterized by argillaceous-sandstone-rich stratum associated with retrogradation,while the Qigequan Formation is characterized by conglomerate-rich stratum associated with progradation. The Neogene-Quaternary angular unconformity developed between the Shizigou and Qigequan Formations and the Intra-Quaternary angular unconformity developed inside the Qigequan Formation. Large-scale alluvial fans,composed of debris flow,incised-valley-fill,and sheet flow deposits,were developed in the Shizigou and Qigequan Formations,and the sandy earthquake-induced soft-sediment deformation layers were frequently developed in the Shizigou and Qigequan Formations. (2)The most intensive uplift and denudation events occurred between the Neogene and the Quaternary,resulting in the initiation of the Neogene-Quaternary angular unconformity and the tectonic setting of the Qigequan Anticline. (3)It can be inferred that these potential uranium mineralization columns of the Shizigou Formation in the Qigequan Anticline developed in the uplift and denudation events between the Neogene and the Quaternary. The uplift and denudation events led to the initiation and evolution of the uranium-bearing structure,and increased the uranium flux from the source area and dominated the spatial distribution of the potential uranium mineralization columns ultimately. The Neogene-Quaternary angular unconformity can be used for the spatial distribution predicting of the potential uranium mineralization columns as a key tectonic identification mark. In addition,the thin interbeds of sandstone(including the conglomerate)and mudstone in the middle and distal parts of alluvial fans,with sand(including the conglomerate)percentage ranging from 20% to 50%,can be used for the spatial distribution predicting of the potential uranium mineralization columns as a key sedimentary identification mark. This research provides sedimentary and stratigraphic evidence for the basin analysis of the northeastern Tibetan Plateau and is of great reference value for the exploration of sandstone-type uranium deposits in other anticlines in the Qaidam Basin.

A shallow water delta was developed in the Lower Jurassic period in the Dongdaohaizi sag,Junggar Basin,but its sedimentary evolution and main controlling factors were not fully understood. Through the analysis of well logging,core and geochemical data from the Dongdaohaizi sag and its surrounding areas,the sedimentary facies,paleogeomorphology and paleoclimate of this region were analyzed. The study identified three subfacies within the shallow water delta: delta plain,inner front,and outer front. The delta plain subfacies consisted mainly of distributary channels,forming glutenite layers over a hundred meters thick. The inner front featured medium-fine sandstone with argillaceous interlayers,while the outer front was mainly composed of sheet sandstone microfacies interbedded with mudstone and argillaceous siltstone. The paleogeomorphology of the area was higher in the east and lower in the west,categorized into paleo-highland,paleo-slope and paleo-depression based on relative positions and slopes. Analysis of geochemical indicators and sedimentary characteristics suggested fluctuations between humid and arid conditions during the Early Jurassic,with the lake level experiencing three progression-regression cycles. The progradation and regradation of the delta extended over tens of kilometers with the sedimentary distribution and evolution influenced by both paleogeomorphology and paleoclimate. The gentle overall paleogeomorphology provided a foundation for shallow water delta development,while regional paleogeomorphology height and evolution affected sedimentary system distribution and transition. Alternating dry and wet paleoclimate conditions affected lake level fluctuations,thereby controlling delta progradation and regradation. Through a comprehensive analysis,the progradational and regradational depositional models were established for shallow water delta sedimentary patterns,offering valuable insights into the impact of paleogeomorphology and paleoclimate on shallow water delta,and serving as a reference for future exploration in the area.

Beibu Gulf Basin is one of the five major oil-bearing basins in the north of the South China Sea, with great potential for oil and gas resources and good exploration prospects. However, little research has been done on the thick Weizhou Formation in the Haizhong Depression, the third-level structural unit of the Beibu Gulf Basin. This significantlyhinders the hydrocarbon exploration in the Haizhong Depression. High resolution sequence stratigraphy is an effective method for stratigraphic division in geographic exploration frontiers. Using 3D seismic, well logs and core data, and on the basis of identification of second-order and third-order sequence boundaries on seismic profiles and wells, this paper uses maximum entropy spectral analysis, wavelet transform analysis and core analysis methods to identify and subdivide the high-resolution sequences of the Weizhou Formation. The results show that the maximum entropy spectral analysis has high resolution for third-order and fourth-order sequence boundaries; wavelet transform can analyze fourth to sixth order cycles and higher order cycles; Core data can be used for short-term and ultra-short-term cycle analysis. Based on 3D seismic, well logging, maximum entropy spectral analysis, wavelet transform technology and core data, the Weizhou Formation can be divided into 1 second-order sequence that includes 6 third-order sequences, which are in turn composed of 13 fourth-order sequences. According to the comparison of 13 fourth-order sequences, the highest sand ratio occurs in SQ6 LST , which is followed by SQ6 HST, suggesting great exploration potential. This study indicates that high resolution sequence stratigraphy of multi-scale and multi-method has certain guiding significance for screening key intervals in depression with low degree of exploration.

This paper briefly describes the new achievements of oil and gas exploration in carbonates,deeply buried carbonate rocks,especially the genetic theory of dolomites at the 17th National Congress of Palaeogeography and Sedimentology. The relevant theme includes 55 oral presentations and 15 panels,which are related to(1)the genesis and reservoir of dolomite in Tarim,Sichuan,Ordos,Qaidam,Tuha and Bohai Bay basins,(2)formation,characteristics and preservation mechanism of deep and ultra-deep dolomite reservoirs,and(3)quantitative evaluation of bioliths and carbonate formation processes. It is worth recommending the study on the characteristics and genetic mechanism of high-quality,ultra-deep(10 km)dolomite reservoir,Exploration of the ultra-deep dolomite has become a representative result of the genetic theory of dolomite,guiding production practice. It is a supplement to the weak link in the application of basic research of dolomite genesis in the 21st International Sedimentology Congress(2022,Beijing)and in recent years. The summary of the characteristics and genetic mechanism of deep dolomite reservoirs in various parts of the Sichuan Basin comes from graduate students’ summary of the results of different university projects,which is very valuable. The theory of formation of deep dolomite reservoir,evaluation and exploration of high-quality ultra-deep dolomite reservoir is put forward. In particular,the laser ablation plasma mass spectrometry U-Pb dating technique has been widely used,which has realized the qualitative and quantitative analysis of the characteristics and genetic mechanism of dolomitization in geological time. The discussion of biolith is characteristic. They represent the close integration of sedimentology,lithofacies and paleogeography,mineralogy and petrology,new technology and dolomite genetic theory and practical application. The overall innovation depth,research means,system theory and application characteristics in oil and gas exploration deployment are significant,which is the highlight of this conference. Shortcomings are represented by the only one poster on marine reef dolomite. It is expected that the 18th Karamay Conference will further deepen the research in the above fields,and the topic of marine island dolomite research will be paid more attention.

The Academic Forum on Palaeogeography,which is mainly organized by the editorial departments of Journal of Palaeogeography in Chinese and English,jointly with the Professional Committee of Lithofacies Palaeogeography of Chinese Society of Mineralogy,Petrology and Geochemistry,International Palaeogeography Society and China University of Petroleum(Beijing),is an academic organization to promote the innovation and development of palaeogeography and advocate academic exchanges. From the beginning of the Forum in September 2022 to January 2024,a total of 17 sessions were held,and 21 experts and scholars(including four foreign experts)were invited to make oral presentations in the forum. The content of the oral reports was closely related with production practice and scientific research frontier,including the review of sedimentary palaeogeography from a strategic position,the sedimentary system and sedimentary environment,source-sink system,sequence stratigraphy and deep-water environment that are closely related with petroleum exploration,the deep palaeoenvironment reonstruction related studies including event sedimentation,ichnofacies and ichnoassemblages,paleo-wildfire,carbonate sedimentation,tectono-palaeogeography,and mineral resource sedimentology such as the genesis of bauxite research,etc. In summary,these reports closely concerning petroleum and other mineral resources attracted more attention.

To assess the potential for natural gas exploration in the Quaternary Qigequan Formation in the Sanhu area of the eastern Qaidam Basin and identify favorable lithologic gas reservoir exploration zones and targets,this paper systematically analyzes the provenance composition of the Qigequan Formation in the area. By examining parameters such as heavy mineral assemblage,ZTR index,stability coefficient of heavy mineral sand sandstone clastic composition,the study determines the provenance direction and reconstructs the parent rock type. The findings reveal that the stability coefficient and ZTR index of heavy minerals in the Sanhu area increased from the margin to the center of the Qaidam Basin during the sedimentary period of the Qigequan Formation,which was roughly distributed in a ring belt. The study identifies different main heavy mineral assemblages in various source areas and significant variations in the content of unstable heavy minerals. The study indicates that the Golmud provenance flows in a north-west direction,influencing the southern part of the Sebei area,while the Wutumeiren provenance has a smaller scale and flows northeast,impacting the southwestern part of the Tainan area and the Senan 3 well area. Additionally,the study shows that the provenance scale of Mt. Xitieshan-Emnik and Mt. Lvliang is limited,with distinct effects on surrounding regions. The Tainan-Sebei area is primarily influenced by the Wutumeiren provenance and Golmud provenance. This study establishes that the Sanhu area in the Qaidam Basin is characterized by the Wutumeiren provenance and Golmud provenances. The Kunlun Mountain gentle slope provenance system,the Qilian Mountain steep slope provenance system made up of the Xitieshan-Emnike Mountain source and the Lvliang Mountain source,and the blended source system in the Tainan-Sebei area within the basin can offer direction for natural gas exploration and development in this region.

During deposition of the Middle Ordovician Majiagou Formation,a series of paleo-uplift was discovered around the Ordos restricted sea. It remains relatively poorly studied as to how Lüliang paleo-uplift controlled deposition of the Majiagou Formation,which restricted understanding of sedimentary environments of the Majiagou Formation in the northeastern part of the basin. Through detailed measurement and sampling analysis of the Fugu outcrop in Shaanxi Province,combined with the drilling and core data,stratigraphic thickness,lithofacies and microfacies of the Majiagou Formation were studied. Lastly,controls of the Lüliang paleo-uplift on deposition of the Majiagou Formation are discussed. The research results show that: (1)the Lüliang paleo-uplift intermittently blocked the seawater circulation between the Ordos restricted sea and the North China sea. (2)The paleo-uplift was located underwater during the high sea level period,and the barrier to seawater circulation was weak;the stratal thickness in the west of the paleo-uplift has little variation;the underwater paleo-uplift formed a limestone flat,and limestone flat and limestone/dolomite flat formed in the west of the Lüliang paleo-uplift. (3)During the low sea-level period,the paleo-uplift was intermittently subaerially exposed,and obviously blocked circulation of seawater between the Ordos restricted sea and North China sea;the stratal thickness decreases in the east of the paleo-uplift,and sedimentary facies changes from muddy dolomite in the paleo-uplift to limestone in the east of the paleo-uplift. The stratal thickness increases significantly to the west of the paleo-uplift,forming argillaceous dolomite flat,gypsum dolomite flat,and gypsum and saline lacustrine facies. The study provides petrological and paleo-environmental evidence for the Majiagou Formation in the eastern part of the basin.

Despite significant breakthroughs in oil and gas exploration in the glutenite section of the Qingshuihe Formation in the southern Junggar Basin,the sedimentary characteristics,genetic mechanism and controlling factors of the glutenite remain unclear,which has become a key restricting factor for hydrocarbon exploration. As such,we investigated the lower Qingshuihe Formation glutenite body in the western section of the southern Junggar Basin based on wireline logs,cores,outcrops and experimental data,with a focus on the lithofacies,lithofacies assemblage and distribution of the glutenite body,as well as their main controlling factors and genetic mechanism. Six types of lithofacies and lithofacies assemblages and genetically different glutenites are identified in the lowstand and transgression systems tracts of the Qingshuihe Formation in the western section of the southern Junggar Basin. The lowstand and transgression systems tracts of the Qingshuihe Formation in the southern Gaoquan area of the western section are dominated by alluvial fan and fan delta depositional systems,and braided river delta depositional system predominates the northern Caindic area. During the depositional period of the Qingshuihe Formation,glutenite sedimentation in the south western section of the Junggar Basin was affected by the nature of the parent rock in the provenance area,sediment supply and paleoclimate. Among them,nature of the parent rock in the provenance area and sediment supply control the sedimentary type and scale of the glutenite body. While paleoclimate affects the weathering and denudation degrees of the parent rock area and the sedimentary transport environment. Based on the controlling factors and sedimentary characteristics,a sedimentary model for the southern alluvial fan-fan delta and the northern braided river delta front of the Qingshuihe Formation lowstand and transgression systems tract in the western section of the southern Junggar Basin has been established,which can provide a geological basis to aid discrimination between different glutenite bodies and hydrocarbon exploration in similar settings.

The ruins of the Qiaotou village bridge and the strip stone pavement in front of the bridge in Dongzhai port,Northern Hainan Province,are now submerged under the water surface at low tide and covered with mud,with only a small portion exposed. According to genealogical records,tombstone inscriptions,and field investigations,the bridge was still operational 45 years after the Qiongzhou earthquake,specifically in 1650 AD. It indicates that the bridge sank into the sea nearly a century after the 1605 Qiongzhou earthquake. The research shows that since 1650,the ground in Qiaotou village area of Dongzhai port has been subsiding at a rate of no less than 1.5 cm per year according to recent survey in 1984. The survey also shows that in the past 30~40 years,the ground of central and north section of Dongzhai port have slowly subsided at a rate of not less than 1 cm/a. The sinking rate was likely higher in the early period following the Qiongzhou earthquake. This paper roughly estimates that the amplitude of coseismic subsidence of this earthquake may reach about 2~3 m. The paper discusses the mechanisms behind slow subsidence after the earthquake,attributing it to persistent intense activity beneath the crust due to mantle plume uplifts,crustal stretching,and fracturing,accompanied by multiple volcanic activities or eruptions over various geological periods since the Cenozoic. Prior to the earthquake,the crust of northeastern Hainan,had been uplifting for thousands of years,accumulating significant energy and forming sub-crustal hotspots. The reduction in friction on the fault surfaces due to groundwater penetration into the tension fractures initiated the land subsidence,culminating in a significant earthquake that caused extensive land to sink into the sea. After earthquake,the residual energy continuous to stretch the fault,resulting in continuous graben type settlement of crust in Dongzhai port. The rapid and continuous penetration of seawater into the fault during and after the earthquake reduced the friction force on the fracture surface,stabilizing the post-seismic fault movement. These factors are considered the primary reasons for the prolonged,significant subsidence of Dongzhai port for centuries following the earthquake. Connecting to the historical context,Dongzhai port has undergone transformations from land to sea and back,a process that has continued from the Late Pleistocene and possibly up to the Early Holocene.

The‘Taishan earthquake’ named after Mount Taishan,occurred in 1831 BC,which was the earliest historical earthquake recorded by writing-materials in China. Bamboo Annals recorded that the strong earthquake occurred,when the emperor named “Fa” was climbing the Mount Taishan in the seventh year of Xia Di Fa(i.e.1831 BC). The earthquake shocked the emperor at that time,so for the first time,it was written and named after Mount Taishan. Apparently,the geographical position that the emperor “Fa” was threatened by the earthquake was at the hillside of the Mount Taishan. However,seismic geologists have been unable to find any seismic-geological records or traces of the historical earthquake in the Taishan area and its surroundings. Therefore,the epicenter and magnitude of the “Taishan earthquake” have been a mystery. By reobserving the discovered seismo-geological remains,combined with a series of tests,experiments and analysis,the paper provides evidences that the “Taishan earthquake” was a strong and historical earthquake with its epicenter located in the Anqiu area within the Tanlu fault zone. First of all,in the Holocene soft soil layers of limnetic facies in the Anqiu-Xiazhuang Basin of the Tanlu fault zone about 200 km away from Mount Taishan,there are macroscopical seismic traces such as seismic-subsidence synclines and co-seismic micro-faults,which recorded epicenter-intensity for degree of IX ,seismic magnitude for M7.0. Second,by means of the results of dating¹⁴C isotope,combining with calculating the sedimention time of the related soil layer,the earthquake time(i.e.1827 BC)obtained is very close to 1831 BC. Third,based on seismic intensity attenuation model in North China,the attenuation intensity induced by the earthquake is calculated to the degree of VI near Taishan. The Chinese earthquake intensity table shows that the VI intensity completely makes people stand unstable or escape outdoors,which accords with the historical records that the mountaineering emperor was frightened by the earthquake.

The palaeogeography in the northern South China Sea changed drastically in the Early Cenozoic era and the sedimentary environment underwent a transition from land to sea. The plant ecology methods are powerful in accurately revealing the transition time and processes,which is of great significance for the restoration of palaeogeography in this region. In this study,representative borehole samples are collected from the deep-water area of the Baiyun sag in the northern South China Sea to investigate the Paleogene transgression based on sporopollen algae analysis. The results show that the Baiyun sag was dominated by fluvial and lacustrine facies that was not affected by marine transgression of the Wenchang Formation in the Early to Middle Eocene. In the Enping Formation of Late Eocene,eastern and southeastern parts of the Baiyun sag developed into a shallow marine environment characterized as the development of a large number of marine sporopollen algae. The fluvial and lacustrine environments developed in the southern part in the early stage,and it transforms into marine and land transition environment. The northwestern part was dominated by large river delta environment. For the southern uplift zone of the Baiyun sag,it was characterized by fluvial lacustrine facies environment in the early stage,while it transformed into the marine and land transition environment in the late stage. The northwestern part of the depression was dominated by the large river delta environment. During the depositional period of the Zhuhai Formation in the Oligocene,it revealed a continental slope-deep sea environment in eastern and southeastern parts of the Baiyun sag,a transitional depositional environment occurred in northwestern and southern parts,and the large river delta appeared in the northwest part of the sag. Due to global sea level rise and sudden shift of the South China Sea spreading axis,most parts of the Baiyun sag were located in the continental slope environment in the early Miocene. Transgression initiated from the eastern and southeastern parts of the Baiyun sag and subsequently advanced towards the western areas,which is completely consistent with the gradual opening of the South China Sea oceanic crust from east to west.

The newly discovered hyoliths yielded from the Lower Devonian of East Junggar of Xinjiang,China,are documented herein for the first time,including three genera and three species: Fuyunotheca wangi gen. et sp. nov.,Costulatotheca schleigeri Earp,2019,and Ottomarites sp. As a new genus and species,F.wangi gen. et sp. nov. is mainly distinguished by typically oblate oval to subtriangular cross-section,swollen dorsal side with a pronounced median ridge,ventral side weakly convex. Surface sculpture prominent transverse striations and weakly longitudinal streaks on both dorsum and venter,and several sets of remarkable ribs parallel to the aperture in the anterior third of the conch. Palaeoecological analysis shows that F.wangi gen. et sp. nov. is a kind of orthothecids,which could live in a normal,oxygenated shallow-marine environment with certain degree of hydrodynamics. Furthermore,based on the Devonian hyoliths reported so far from all over the world,it has been recognized 14 genera and 66 species as valid from 12 areas in 11 countries(excluding indeterminate genera and species). Palaeogeographic distribution analysis shows that the Devonian hyoliths were mainly distributed in the southern hemisphere,that were positioned near the Laurussia and Gondwana,with a few species sporadically distributed in other plates or blocks. Newly discovered specimens of these early Devonian hyoliths not only expands the palaeogeographic distribution range of hyoliths during the Devonian period,but also provides new evidence for inter-continental biostratigraphic correlation.

Phylum uncertain

Class Hyolitha Marek, 1963

Order Orthothecida Marek, 1966

Family INDET.

Fuyunotheca gen. nov.

Type species Fuyunotheca wangi gen. et sp. nov.

Etymology Fuyun(Gr.)is derived from the Chinese Pinyin of the word “Fuyun” of Fuyun County,Altay Prefecture,Xinjiang. The theca(Gr.)means the capsule,membrane,sheath,and shell of organisms.

Diagnosis Orthothecids having straight and middle-sized conch with oblate oval to subtriangular cross-section;swollen dorsal side with a pronounced median ridge;ventral side flat to weakly convex. Aperture straight or almost straight. Apical part of shell blunt. No apical septa were found. Surface sculpture prominent transverse striations and weakly longitudinal streaks on both dorsum and venter,and several sets of remarkable ribs parallel to the aperture in anterior third of the conch near the apertural side. The separation distances between each set of transverse ribs gradually widen from the aperture to the apical end of the shell. Operculum is unknown.

Remarks The main difference between Hyolithida and Orthothecida is that the former has protrusions(lips)on the ventral side of aperture(Malinky and Racheboeuf,2010). The aperture of the new genus Fuyunotheca gen. nov. is straight and without protrusions,so it can be attributed to the order Orthothecida Marek,1966. According to the taxonomy of Orthothecidae Sysoev,1958 revised by Malinky(2009b),its venter is concave to flat,and sculpture of conch consists of longitudinal ridges or lines,without transverse ornamentation. The new genus has the similar conch with that of the family Orthothecidae,but differs from them in having a flat to slightly convex venter and sets of unique transverse ribs on the conch. The new genus is similar to Bolitheca Marek and Isaacson,1992 and Neobactrotheca Marek and Isaacson,1992 from the Middle Devonian Icla Formation of Bolivia. However,specimens of Bolitheca exhibit pronounced longitudinal ridges on the dorsum,the semi-elliptical cross-section,and rounded lateral ridges(Malinky and Racheboeuf,2011). Specimens of Neobactrotheca have many longitudinal ridges and no median ridges on the dorsum. Besides,the conch of Neobactrotheca differs from that of this new species by having elliptical cross-section and smooth transitions to the lateral ridges(Marek and Isaacson,1992). It is for this reason that we establish a new genus,belonging to the indeterminate family.

Fuyunotheca wangi gen. et sp. nov.

Fig.2

Etymology The species is named in honor of Wang Hongzhen,the famous paleontologist who described hyoliths from China for the first time.

Holotypoe One well-preserved dorsum of conch,specimen number: XJLD-001(Fig.2-A).

Paratype One well-preserved venter of conch,specimen number: XJLD-003(Fig.2-C).

Other materials Specimen registration number: XJLD-002,004—046. Venter or dorsum of 44 conchs with incomplete aperture or initial part.

Diagnosis As for the genus.

Description The conch is straight and conical,expanding gradually and evenly from the apex to the aperture, and the aperture is thickened(Fig.2-E,ta). The growth angle of the conch is about 9.90°. The length of the shell is about 41 mm,and the diameter of the aperture is about 9 mm. The dorsum passes through the oblate lateral ridge to the venter,and its cross-section has oblate oval to subtriangular shape(Fig.2-B2). There is a median ridge running through the conch(Fig.2-A,B1,dmr)in the middle of dorsum. There are slightly inclined surfaces on both sides of the ridge,and a longitudinal groove on the right slope(Fig.2-A,gr). Sets of remarkable ribs(Fig.2-A,2-C,2-D,tr)parallel to the aperture are distributed in the anterior third of the conch. There are five groups of ridges(Fig.2-A,tr₁-tr₅)which are made up of 2-5 transverse ridges in each group. The separation distances between each set of transverse ribs gradually widen from the aperture to the apical end of the shell. Surface of shell from the middle to the initial part covered with slight growth lines(Fig.2-F,tl). In addition,the conch is also decorated with weakly longitudinal lines(Fig.2-G,ll),that are most prominent next to aperture but become fainter in direction of apex. But longitudinal lines become thicker near the lateral ridge(Fig.2-G,tll),which may be caused by pressure applied to the shell during diagenes. Ventral side almost flat to very slightly convex,and bears the same ornamentation as the dorsum without a median ridge(Fig.2-C,2-D,tr). The apex is damaged to some extent,but it still can be seen that it is bluntly rounded in form,and no septa are visible.

Locality and horizon The first member of the Tuoranggekuduke Formation,Emsian Age,Lower Devonian,Chawukar area,Fuyun County,Altay Prefecture,Xinjiang.

Seafloor pockmarks are commonly seen in various marine environments. The study on the pockmark sediments,however,have been hardly involved in the literature,causing few knowledges of their characteristics,origin and identification. In this study,we recognized the pockmark sediments from the Paleozoic fine-grained rocks for the first time in China. Based on the field observations and sampling of Upper Ordovician Wufeng Formation at Ganziping and Xiebutou in Shizhu,Chongqing,we tested pockmark rocks with microscope,scanning electron microscope(SEM),and major and trace element analyses. We found the bed chaos and arched beds in the lentoid or cuneal pockmark sediment body. Breccia carved by siliceous veins,are commonly seen,together with asphalt and barite,hematite minerals in the pockmark sediments. Observations and results of major element and REE suggest that the formation of pockmarks were unrelated with hydrothermal liquid and cold seeps. All the geological facts indicate the low-matured oil and gas generated from the Wufeng Formation as the first essential for the formation of pockmarks. The identification marks of deep-time pockmarks are thought as: (i)negative relief in seismic sections,(ii)lentoid or cuneal sediment body,(iii)chaos beds,(iv)arched beds,and(v)hiatus and temporal chaos of sediments. Meanwhile,petrological,stratigraphical,paleoenvironmental and petrogeological significances of the pockmarks in the Wufeng Formation are discussed in this study.

It is of great significance to study the mechanism of hydrothermal activity,related to the Yanshanian thermal events in Majiagou Formation,Fuxian area of the Ordos Basin,to reveal the origin of reservoirs. The two stages of hydrothermal activity related to the Yanshanian thermal events in Majiagou Formation,Fuxian area are identified,based on a comprehensive analysis of petrology and geochemistry,including core and thin section observation and cathode luminescence,homogenization temperature of fluid inclusions,carbon and oxygen stable isotopes,strontium isotope,electron probe microanalysis and rare earth element analyses. The results show that the stage-Ⅰhydrothermal activity is characterized by the development of saddle dolomite in the fissure-cavern systems,with low and negative δ¹³C and δ¹⁸O values,higher strontium isotope value than normal marine limestone,negative abnormal Eu and La in rare earth elements,rich content of MnO,FeO,SrO and poor content of K₂O and Na₂O in trace elements,and high homogenization temperature of fluid inclusions. The geochemical characteristics reveal that the saddle dolomite was formed by the combined action of internal fluids in the Ordovician strata,shallow fluids in the Carboniferous-Permian strata,and deep hydrothermal fluid under Early Cretaceous extensional fault activity,in which the deep hydrothermal fluid is post-magmatic hydrothermal fluid related to basalt eruption. The stage-Ⅱhydrothermal activity is characterized by quartz precipitation in fracture-vug systems,and the development of fractures calcite that cut saddle dolomite,with δ¹³C values close to the background value of Ordovician carbonate rocks,low δ¹⁸O value,higher strontium isotope value than saddle dolomite,negative abnormal La and positive abnormal Eu in rare earth elements,rich content of MnO,FeO,K₂O,Na₂O in trace elements,and high homogenization temperature of fluid inclusions in quartz. The geochemical characteristics reveal that the calcite and quartz were formed by the combined action of internal fluids in the Ordovician strata and deep hydrothermal fluid under Early Cretaceous extensional fault activity,in which the deep hydrothermal fluid is the post-magmatic hydrothermal fluid related to the activities of the Early Cretaceous monzonite and monzonitic diorite magmatic intrusion. Hydrothermal activity related to Yanshanian thermal events has both constructive and destructive effects on the formation and preservation of reservoir space in the Majiagou Formation,but the overall sphere of influence is limited.

The Jurassic Qigu Formation in the Yongjin area is a set of important oil-bearing strata in the central Junggar Basin. It is a typical deep-buried sandstone reservoir with a burial depth of 5400~6100 m,and its reservoir quality controls oil and gas reserves and production. In this paper,the diagenetic evolution process of deep-buried sandstone reservoirs in the Qigu Formation is studied by using the data of cast thin section,cathodoluminescence,scanning electron microscopy,XRD whole rock and clay mineral analysis. A diagenetic sequence is established,and the impacts of various diagenetic processes on reservoir quality are quantitatively assessed,integrating regional burial and hydrocarbon charge histories to delineate the reservoir’s diagenetic evolution. The lithology of the Qigu Formation reservoir in the Yongjin area is mainly composed of feldspathic lithic sandstone and lithic sandstone. The cement includes mainly carbonate minerals,siliceous minerals and clay minerals with low composition maturity and high texture maturity. The reservoir space types are mainly the remaining primary intergranular pores and secondary intergranular dissolved pores. Overall,the reservoir porosity changes are mainly controlled by compaction,cementation and dissolution,which are the main diagenetic factors reducing reservoir porosity,resulting in primary pore loss rates of 65.98% and 21.80% respectively. Dissolution increases the porosity by 5.13%,which effectively improves the physical properties of the reservoir. The comprehensive study shows that the diagenetic evolution of the Qigu Formation reservoir in the Yongjin area is mainly controlled by four factors: sedimentary environment,diagenesis,burial history and oil and gas charging. Diagenesis plays a role in the transformation of reservoir physical properties and is the critical determinant of the observed reservoir heterogeneity.

Paleocave play a crucial role in the storage and transport of karst groundwater in the covered area,and the exploration and identification of their morphological and internal structural characteristics are of certain guidance for understanding the formation process of karst in covered coal fields and the prevention and control of karst water inrush damage in mines. In recent years,through a detailed geological investigation of the Ordovician karst outcrops in the Shungeng mountain in Huainan,Anhui Province,on the southern edge of the North China Plate,a typical paleokarst cave was found at the Ordovician formations. This study analyzes the morphological features and internal structures of the paleocave using field observations,microstructural identification,paleohydrology,and paleotectonics. The cave developed along the sedimentary interfaces between the Majiagou and Xiaoxian formations,exhibiting varying widths—wider on the west side and narrower on the east. The maximum vertical height between layers reached 9.8 meters,and the cave extended over a length of 125 meters. Evidence of paleowater erosion and corrosion is preserved on the cave ceiling,and gravity-induced collapses have resulted in various fill types,including debris collapse fill,chemical fill,and mixed fill,primarily consisting of limestone and dolomite,with minerals such as calcite,dolomite,and cryptocrystalline silica. Combined with the regional geological and tectonic evolution,paleocave formation experienced four stages: the fissure development,interlayer karst formation,,interlayer cave growth,and collapse filling and compaction,which are mainly controlled by layer fissure,erosive fluid and vertical karst zoning. The results can provide useful reference for prevention and treatment of deap karst water inrush in Huainan and other North China coalfields.

The carbonate-evaporite symbiotic system is a rock symbiotic association formed by chemical depositional differentiation. Microfacies analysis and sedimentary model construction of such a system are conducive to revealing the sedimentary information that have guiding significance for oil and gas exploration in evaporatic environments. Based on a large number of borehole data of the Majiagou Formation in Ordos Basin,macro-and microscopic observation of the rocks was carried out to identify sedimentary microfacies,analyze sedimentary sequence,and construct sedimentary model.The results show that there are ten types of sedimentary microfacies(MFT1-MFT10)in the carbonate-evaporite symbiotic system of the Majiagou Formation: halite,gypsum,gypsum-bearing dolomite,laminated dolomite,crystalline dolomitic grainstone,microcrystalline dolomite,microbial dolomite,bioturbated dolomite,laminated limestone,crystalline grainstone. four types of sedimentary sequence are developed in the symbiotic system: (1)upper intertidalto supratidal dolomite-gypsodolomite-argillaceous dolostone;(2)lower intertidal evaporite-algal dolomite-dolomite;(3)subtidal laminated limestone-churned limestone-bioturbation limestone;(4)lagoonal laminated evaporite-lumpy evaporite-salt rock. Evaporites of the Majiagou Formation were formed during the shallow basins period and low sea level period,while carbonates were formed during the high sea level period.The giant carbonate-evaporite symbiotic system formed through repeated fluctuations in sea level.

The trace fossils are well developed in the Neogene strata with the huge thickness in northern Qiongdongnan Basin. Based on detailed observation of the cores from seven drilling wells,combining with the thin section analysis,imaging logging and related experiments,the ichnofabric characteristics and sedimentary environment of the Neogene Sanya Formation were studied in detail. The results show that a total of 14 genera of trace fossils have been identified in the Neogene Sanya Formation in northern part of the Qiongdongnan Basin. Based on the types,occurrence,abundance and diversity of trace fossils,biodisturbance degree,and symbiotic relationship between biological burrows,five ichnofabrics can be classified. Among them,the Ophiomorpha-Thalassinoides ichnofabric was mainly developed in the upper shoreface,the Palaeophycus ichnofabric was mainly developed in the middle shoreface,the Planolites-Talassionides ichnofabric was mainly developed in the lower shoreface,the Phycosiphon-Planolites ichnofabric is mainly developed in the upper shallow sea,and the Phycosiphon-Chondrites ichnofabric was mainly developed in the lower shallow sea. Based on analysis of the ichnofabrics and logging facies,it is believed that the coastal and offshore sedimentary environment was mainly dominated in the Neogene Sanya Formation in the study area. The first section of Sanya Formation transited from coast to shallow marine,while the second section of Sanya Formation was mainly dominated by shallow sea deposition. Based on the analysis of lithofacies,fossils,ichnofabric characteristics,logging facies and sedimentary microfacies of Sanya Formation,the sedimentary model of Neogene Sanya Formation in the northern part of the Qiongdongnan Basin has been established. It has an important guidance for the hydrocarbon exploration of the Neogene in the northern South China Sea.

Extending the typhoon sequence before the instrumental era can provide data support for longer time scale climate research. Utilizing historical documents,this paper has reconstructed a total of 1447 typhoon events that affected the coastal areas of China from 1368 to 1911,categorized by subregion. This study employs wavelet analysis,GIS spatial analysis,and other methods to analyze the spatio-temporal characteristics of these events,verifying the reconstruction’s reliability through precipitation and dry/wet sequences. The results show that: (1)During the Ming and Qing Dynasties,the total number of incoming typhoons in North China,East China,and South China was 157,596,and 853,respectively. Most typhoons impacting North China’s coast also affected East China’s coast,with fewer typhoons simultaneously entering East and South China. (2)The monthly distribution of reconstructed typhoons closely mirrors that of modern tropical cyclones,which cause winds of magnitude eight or higher. Typhoons are most frequent along North China’s coast in June and July;in East China,during June,July,and August;and in South China,from May through September. (3)Typhoon activities in various coastal areas were very frequent during the 1570-1590,1660,1850,and 1890's,while during the 1460's,1560's,1700's,1760's,and 1780's,were relatively calm. (4)Wavelet analysis,based on a 128 yr cycle,shows the first,second,and third main periods of typhoon activity along the North China coast during the Ming and Qing Dynasties were 123 yr,86 yr,and 10 yr,respectively,while those along East China coast were 122 yr,85 yr,and 42 yr,while those along the South China coast were 73 yr,116 yr,and 40 yr,respectively. The first,second,and third main periods of typhoon activity for the entire coastal area of China during the Ming and Qing Dynasties was 122 yr,75 yr,and 42 yr. (5)Throughout the Ming and Qing Dynasties,typhoon disasters were primarily concentrated in coastal plains,and showed a significant trend of weakening from south to north and from coastal areas to inland. In North China,typhoon impacts were predominantly observed on the Jiaodong and Liaodong peninsulas and around Bohai Bay. Beyond these coastal regions,the southeast Haihe Plain also experienced notable typhoon effects. (6)During the Ming and Qing Dynasties,there was a moderate correlation between typhoon sequences and precipitation patterns in their respective coastal regions.

The property of coal seams is a dominant factor for the enrichment and high-yield of coal-bed methane(CBM). Sedimentary environments control the distribution and thickness of coal seams,the maceral composition and properties of coal,and the superimposed model of surrounding rocks as well as their thickness,and thus controlling the enrichment of CBM. In this study,sedimentary environments and sequence stratigraphy of the Taiyuan Formation in Shouyang area,northern Qinshui Basin were analyzed based on drilling cores,loggings and previous studies. Lithofacies and palaeogeography of the roof and floor systems of the No.15 coal bed were described in detail. The relationship between sedimentary environments and gas contents of the CBM was finally summarized,and the favorable zone for CBM exploration was delineated. The lower part of the Taiyuan Formation in Shouyang area mainly developed in shallow marine shelf,barrier island,and lagoon depositional system,whereas the upper part formed in the delta plain. The Taiyuan Formation records a 3^rd-order transgressive-regressive sequence,which can be further divided into six 4th-order sequences(S₁-S₆). The S₁ mainly developed on tidal flat,lagoon and barrier island. The gas content of different sedimentary facies declines is an order from lagoon,tidal flat to barrier island. The S₂ mainly formed in barrier island,lagoon,tidal flat,shallow marine shelf depositional system. The gas content declines in an order of lagoon(with thick limestone),muddy shelf,carbonate shelf,lagoon,tidal flat,and barrier island. According to the relationship between sedimentary facies of the S₁ and S₂ and gas content of No.15 coal bed,the CBM reservoir of No.15 coal bed was subdivided into three types. Type Ⅰ reservoir is favorable for CBM exploration,which is mainly distributed in the east of the research area. Type Ⅱ reservoir is relatively favorable for CBM exploration,which is distributed in the east and west of the research area. Type Ⅲ is of poor CBM exploration prospect,which is mainly distributed in the northwest and the middle area the research area.

Mockina slovakensis is one of the important species of conodont in Norian period. It plays a significant role in stratigraphy and acts as an indication for certain distinctive sedimentary environments. In this study,a significant abundance of conodont species M. slovakensis was discovered in the limestone deposits located in the lower parts of the Dashuitang Formation in the Hongyan section of Baoshan,Yunnan. Based on the conodont biostratigraphy,the age of the sedimentary strata in this section has been constrained to the late Alaunian of Norian period. Its presence and abundance can provide valuable insights into the paleoenvironmental conditions and depositional settings. M. slovakensis is known for strong adaptability to a diverse living environments,including both shallow and deep oceanic environment,as well as restricted sea to open sea. However,various records indicate that M. slovakensis conodont indicates the restricted depositional environment. Considering the abundance of dominant M. slovakensis found in the Hongyan section of Baoshan,combined with previous studies on the sedimentary environment of the Dashuitang Formation in the Baoshan block,it is reasonable to conclude that the Baoshan area formed a restricted sedimentary basin during the Alaunian stage under a tectonic stretching setting. The results are helpful for understanding the evolution of the sedimentary environment during the Late Triassic period in eastern Tethys.

A series of tectonic movements during the Late Mesozoic greatly changed the topography and landform in eastern China,forming a geomorphic pattern of “high in the east and low in the west”. There is still a controversial issue on the existence of plateaus or mountains in eastern China during the Cretaceous,and thus the evolutionary processes,paleoaltitude and the extensional range of plateaus or mountains need further studies. In this paper,we collected the palynological data of xerophyte and disaccate pollen from vorious localities of China during the Cretaceous,and further discussed the paleovegetation succession and palaeoclimate evolution,which provides paleontological evidence for the interpretation of the geomorphology in eastern China at that time. The result shows that there were three climate zones in China during the Cretaceous: (i)the northeastern region was a warm and humid subtropical-warm climate zone;(ii)the northern region was a semi-arid tropical-subtropical transitional climate zone;(iii)the Tibet,Xinjiang and southern China were a hot and tropical-subtropical climate zone. The interpretation of the geomorphology shows that there was a high-altitude landform in northeast China during the early Early Cretaceous. Additionally,it is likely that coastal mountains existed in the Fujian and Zhejiang regions during the Early Cretaceous. In early Late Cretaceous,the range of coastal mountains in eastern China reached its maximum. From the late Late Cretaceous to Early Paleocene,the mountains in eastern China gradually collapsed,and by the Early Paleocene,the mountains were probably disappeared.

Load structures are known as an important type of soft sediment deformation structure,and are characterized by gravity(density difference)as the main driving force and deformation occurring at the lithologic interface with inverted density. According to whether the deformation structures are separated from the parent body,load structures can be divided into three categories including,non-separated load structures,separated load structures,and composite load structures. The non-separated load structures include heavy load(mold)structures,flame structures,water drop structures and diapir(extrusion)structures,and the separated load structures includes sand ball(false nodule),ball pillow layer and mud ball. A large number of load structures were recognized in the cores and outcrops of the Yanchang Formation of the Late Triassic in the Ordos Basin. Through the analysis of the characteristics,formation conditions and triggering mechanisms of different types of load structures,it is believed that the load structures were the result of the dual mechanisms of earthquakes and gravity. In addition to gravity,seismic disturbance was also the main reason for the formation of various deformation structures. It reflects the characteristics of strong tectonic activity in the Ordos basin during the Middle Indosinian Movement.