Objective The high-resolution climate reconstruction of Liaodong Peninsula is important for exploring the evolution of regional climate environment and high-quality development. The sedimentary environment of the Liaodong Peninsula is diverse and complex， studies on the types and sequence characteristics of sediments in different periods in small areas is lack. The aim of this study is to reconstruct the sedimentary environment and climate history by studying the sediments of the west coast of Dalian. Methods By analyzing AMS¹⁴C dating， lithology， and geochemical elements of the Laoyuwo （LYW） section to reveal the evolution of sedimentary environment and paleo-climate of the region. Results The sediment is mainly composed of sand， silt， and gravel， which recorded sedimentary environment and paleoclimate evolution information from the Last Glacial Maximum （LGM） to the Middle Holocene （18 815-6 802 cal. a B.P.）. The main chemical components in the profile are SiO₂， Al₂O₃， K₂O， and Fe₂O₃， the total content of which is 90.34%. The contents of major elements from large to small are SiO₂>Al₂O₃> K₂O>Fe₂O₃>Na₂O>CaO>TiO₂>MgO>P₂O₅>MnO. The sedimentary records shows that the region experienced a dry and cold alluvial （18.8 cal. ka B.P.-late LGM）， slightly warm and humid coastal intertidal （18.8-16.0 cal. ka B.P.）， warm and humid coastal subtidal （18.8-16.0 cal. ka B.P.）， warm and humid coastal subtidal（16.0-11.7 cal. ka B.P.）， warmest and wettest coastal salt marsh （11.7-6.8 cal. ka B.P.）， and dry and cold fluvial environment （6.8-0 cal. ka B.P.）. The highest sea level around 6.8 cal. ka B.P. and the rapid climatic events during Younger Dryas （DY） and 8.0-9.0 ka are also responses in the sediment. Conclusions This study provides basic data and information for the Holocene climate reconstruction of Liaodong Peninsula， particularly for the sedimentary environment evolution history of the west coast of Dalian.

Objective Carbonate-evaporite syngenetic systems are widely distributed in the Cambrian rocks of the Sichuan Basin. However， their development， depositional environments and processes and evolutionary modes have rarely been studied， and the research methods urgently need to be clarified. Methods The petrology and processes of the symbiotic system， the state of the evaporites， the depositional environment and the evolutionary pattern were investigated using drill core data， field sections， rock strata， C and O isotopes， Fe and Mn contents， and S isotopic composition. Neither the developmental characteristics of the symbiotic system and depositional environment nor its evolutionary pattern are well understood. Results （1） Five kinds of carbonate-evaporite symbiotic rock assemblages were found in the study area： interbedded carbonate rock and evaporite； evaporite sandwiched with carbonate rock； evaporite overlain by carbonate rock； carbonate rock overlain by evaporite rock； and carbonate rock sandwiched with evaporite rock. （2） The δ¹⁸O values ranged predominantly from -9.00‰ to -8.00‰， while δ¹³C values ranged between -1.00‰ and 3.00‰. Calculations of paleosalinity and paleotemperature using these isotope values gave the vast majority of Z>120 and δ¹³C>-2.00‰， with paleoseawater temperatures in the range 23.10 ℃-40.64 ℃. Fe was mainly concentrated in the range （0-2 000）×10^-5， and Mn from 10^-5 to 30×10^-5. These indicate a warm or hot paleoclimate and saline seawater environment during deposition of the Gaotai Formation， with a high degree of oxidation in the water body， and the rock-forming activity occurring in a system relatively open to precipitation of atmospheric water. （3） Deposition of marine carbonate rocks and evaporites took place in a symbiotic system against a background of an arid， hot climate and a calcium-rich， low-sulfate， highly saline calcitic sea. This period of time witnessed two types of carbonatite-evaporite symbiotic development： A falling-sea-level evaporite-dolomite deposition stage （“tidal sabkha mode”）， and a rising-sea-level dolomite-evaporite-greywacke deposition stage （“underwater condensed-deposition mode”）. Conclusions The carbonatite-evaporite symbiotic system has recorded information about the paleoenvironment， paleoclimate and paleohaline water chemistry during the deposition period， as well as the depositional process and evolutionary pattern of the symbiotic system. This study provides new ideas and understandings of the depositional environments and patterns of the carbonatite-evaporite symbiotic system in the evaporitic environment of the marine phase of the developing Cambrian Gaotai Formation.

Objective The East Mariana Basin of the West Pacific Ocean， which is located east of the Mariana Trench， south of the Magellan Seamounts， and north of the Caroline Seamounts， is an ideal area for the study of Asian aeolian dust deposits， but the sediment research of the East Mariana Basin is still weak. To reveal the sediment geochemical characteristics and provide background data for further sediment provenance， seabed mineral resource evaluation and climate-environment evolution research， the element geochemistry of surface sediments in the East Mariana Basin was studied. Methods Based on 28 pelagic clay surface sediment （0-10 cm） samples collected in the eastern section of the East Mariana Basin using the box and gravity samplers， contents of major， trace， and rare earth elements of the sediments were analyzed using inductively coupled plasma optical emission and mass spectroscopy methods. Then， elements geochemical characteristics were analyzed， and their influencing factors and indicative significance were discussed. Results The results show that the contents of major elements in the pelagic clay sediments in the study area are roughly the same as those in the neighboring sea areas of the West Pacific Ocean. The distribution pattern of major elements （oxides） in sediments follows SiO₂> Al₂O₃ > Fe₂O₃> Na₂O > MgO > K₂O > CaO > MnO > TiO₂ > P₂O₅. SiO₂ has the highest content of all major elements， with an average of 49.14%， followed by Al₂O₃， with an average of 15.85%. The trace element with the highest content was Ba， with an average of 770×10^-6， followed by Cu， with an average of 289×10^-6. The average of total rare earth elements （∑REE） is 284×10^-6， which is light rare earth-rich type， with the highest Ce， Nd， and La contents. Principal component analysis of elements shows that the composition of chemical elements can be divided into four categories： The first type is closely related to rare earth elements， including most rare earth elements （except Ce）， P₂O₅， and TiO₂， the second type is related to Fe-Mn micronodules， including Fe₂O₃， MnO， Cr， Co， Ni， Cu， and Ba， the third type is related to terrigenous debris， including Al₂O₃， MgO， SiO₂， U， Hf， Th， and Ce， and the fourth type is related to biological sources， including Cd， CaO， and Mo. Conclusions The element combination indices （Si/Al， Fe/Al， La/Tb， Th/Sc， etc.） and projection diagrams （La-Th-Sc triangle diagram and La/Th-Hf bivariate diagram） further revealed that the sediments sources were dominated by terrigenous materials， particular terrestrial aeolian dust materials. Furthermore， the Chemical Index of Alteration （CIA） indicates that the parent rocks in the sediment source area are in low-medium chemical weathering conditions. The redox sensitive elemental （Cr， Ni， V， U， Th， etc.） combination reveals that the bottom sedimentary environment in the study area was oxidation-weak oxidation environment. This study has reference significance for understanding the influence of the Asian aeolian dust on the sediment provenance of the East Mariana Basin， revealing the sedimentary environment characteristics of the basin and the distribution of seabed mineral resources.

Objective The sand and gravel in the Sanjie area of Juren town， Bin county， Heilongjiang province， was once considered as the lower limit of the Quaternary Luojiawopeng Formation in the Harbin area， but research on its stratigraphic properties and sedimentary environment has been relatively poor to date. This has greatly limited the in-depth understanding of the regional surface processes recorded in this stratum. Methods To discuss and compare the sedimentary environment and stratigraphic division， this study adopted a range of research methods. Sedimentology， mineralogy， elemental geochemistry and detrital zircon U-Pb chronology were used to investigate the chemical weathering characteristics， source rock properties， sedimentary environment and structural background of the source area in this section to determine the effects of chemical weathering， sedimentary cycles and material sources， and to explore the structural background and indicators of stratigraphic delineation and regional magmatic tectonic events. Results It was found that the sediment in the three sections is mainly composed of brownish-yellow sand and gravel mixed with muddy interlayers， with local oblique bedding. The weathering degree of the sand and gravel is low， the sorting is moderate， the roundness is good， and there is no obvious directional arrangement. The gravel rock is mainly granite （46.31%） and quartzite （28.19%）， with some syenite （0.2%）， tuff （0.01%） and schist （0.01%）. The heavy minerals are mainly spinel （65.18%） and epidote （11.87%）， with minor quantities of zircon （2.28%）， apatite （5.60%）， ilmenite （2.77%）， hematite （3.41%） and magnetite （5.15%）； white titanium （0.54%） and pyrrhotite （0.1%） account for less than 1%， and other heavy minerals account for 3.11%. Elemental geochemical analysis revealed that the fine-grained components in the sediments have experienced weak to moderate chemical weathering， and most have undergone initial weathering cycles. Gravel lithology and geochemical composition indicate that the parent rock of the sediments was mainly medium- to acidic magma. The geochemistry of the migration and enrichment of elements in the sediments， paleoclimate discrimination diagrams and sedimentary facies definition indicate that the regional environment of the sediments was a meandering river that transported the sediments over short distances in an arid oxidative environment. The distribution range of detrital zircon U-Pb ages is relatively narrow （134.2-220.3 Ma， peaking at about 168 Ma）. Comparison of the zircon ages of the surrounding potential source areas together with their geomorphological location suggests the detrital contribution of the Zhangguangcai Ridge and indicates the collision and assembly of the Jiamusi and Songnen Blocks， as well as the continuous subduction of the eastern oceanic plate. Significant differences were found between the three sections in terms of their sedimentological characteristics， genetic types and geomorphological features when compared with the standard strata of the Luojiawopeng Formation. It is speculated that formation of the three sections was roughly contemporaneous with the formation time of the Baitushan Formation in western Harbin. Conclusions This study is of great significance for the reconstruction of geological events such as Quaternary stratigraphic divisions and Upper Jurassic tectonic geomorphological-climate-water system evolution in the Harbin area.

Objective The levels of oxygen in shallow waters and the atmosphere during the Mesoproterozoic period （approximately 1.8-1.0 Ga） have raised controversy. Currently， it is widely believed that there may have been fluctuating high and low oxygen levels at that time. However， the spatiotemporal heterogeneity of the ancient planet during this period limits our understanding of the redox state of the ancient oceans， but accumulated evidence tends to indicate dynamic fluctuations in the oxygen content of shallow seas. Methods This study， which focused on the carbonate strata of the Longjiayuan Formation in the Guandaokou Group， western Henan province （oldest age 1.59 Ga）， carried out petrological， elemental geochemical and C and O isotope geochemical analyses， mainly using Ce anomalies δ. Indicators such as δ¹³C and Y/Ho restored the redox state of the shallow sea in the region. Results Microscopically， the formation lithology consisted mainly of relatively pure fine-grained， powdery， and mud crystalline dolomite， with main structures containing different forms of laminated stones and siliceous bands. The main geochemical data indicated overall Th content <0.5 µg/g， Y/Ho > 26， ΣREE <12 µg/g， and Ce/Ce^*， Pr_（N）/Yb_（N） and Y/Ho. There was no significant correlation between ΣREE and Th concentration， indicating that the sample material was not affected by terrestrial debris interference to any great extent. Mn/Sr was generally low （average<6），δ¹⁸O>-10‰， and there was no significant correlation between Ce/Ce^*， Eu/Eu^* and Dy_（N）/Sm_（N）， indicating that the original seawater signal was relatively well preserved during diagenesis. The rare earth element distribution indicated significant negative Ce anomalies （0.53-0.94） and positive Y anomalies in the region around 1.54 Ga， similar to the value for modern seawater rare earth elements. This was accompanied by a significant increase in Y/Ho （mean 64）， followed by δ¹³C， which experienced a significant positive deviation and later recovered to the original level of the Mesoproterozoic era. Conclusions These findings indicated that there may have been a brief oxidation event in the region during the Mesoproterozoic. The range （0.53-0.94） and time （~1.54 Ga） of negative Ce anomalies in the Longjiayuan Formation were reasonably consistent with values in the second and third segments of the Gaogaozhuang Formation， and in the lower part of the Yangzhuang Formation. These indicated that the atmosphere and shallow sea environment in the North China Craton underwent an overall oxygenation process of common amplitude during this period. The negative Ce anomaly and its rapid rebound indicated that the low oxygen state in the shallow sea and atmosphere of the Mesoproterozoic continued to dominate， interspersed with a pulse-type oxygenation process that may have been widespread throughout the North China Craton at that time. This study provided direct evidence of pulse oxygenation events during the Mesoproterozoic， which was useful in determining the redox state of shallow waters during this period， and to explore the impact of oxygen level on the evolution of eukaryotes.

Objective In the western Sichuan Basin， the Middle Permian extensively features marine carbonate rocks， with dolomite being a focal point of geological investigation. However， the diverse and irregular distribution of dolomite types in the Middle Permian results in significant variations in dolomite characteristics across different regions. The rich variety of these dolomite types constitutes an excellent set of natural gas reservoirs in the Sichuan Basin. Methods To unravel the fluid dynamics of dolomites in the study area and reconstruct their diagenetic environments， this study extensively reviewed a substantial body of previous literature and references. Samples from 16 well cores and nine sections underwent a comprehensive analysis. Utilizing techniques such as microscopic thin section observation， cathodoluminescence， carbon-oxygen isotopes， strontium isotopes， and inductively coupled plasma mass spectrometry （ICP-MS） rare earth element （REE） analysis， the petrological and geochemical features were thoroughly investigated. Results The research findings can be summarized as follows： （1） Dolomite types： Dolomites in the region can be broadly categorized into homogeneous and zebra-like dolomite. The primary type of homogeneous dolomite is granular， whereas zebra-like dolomite includes homogeneous dolomite with dark bands， predominantly filled with hydrothermal saddle dolomite. （2） Isotopic analysis： Carbon isotopes： Samples from the study area exhibit positive anomalies in carbon isotopes. Oxygen isotopes： Oxygen isotope values show significant differences， with the filling material （saddle dolomite） exhibiting notably lower values than the homogeneous dolomite. Oxygen isotope values in samples from southwestern Sichuan are significantly lower than those from northwestern Sichuan. （3） Rare earth elements： REE analysis reveals a negative anomaly in δCe and a positive anomaly in δEu， indicating that the oxidation conditions of the products were influenced by later-stage hydrothermal alteration. （4） Strontium isotopes： Strontium isotopic values of homogeneous dolomite fall within the range of contemporaneous seawater. However， the filling material in southwestern Sichuan exhibits strontium isotopic values higher than the seawater range and significantly higher than that of homogeneous dolomite. Conclusions （1） Hydrothermal modification： The diagenetic fluids responsible for the formation of homogeneous dolomite in the western to northern Sichuan region are primarily derived from contemporaneous seawater. Subsequent hydrothermal activities lead to modifications， resulting in the formation of hydrothermal saddle dolomite. Notably， the intensity of hydrothermal activity is more pronounced in the southwestern region and relatively weaker in the northwestern part of western Sichuan. （2） Diagenetic environments： The diagenetic environments of dolomites in the study area encompass three types： marine diagenetic settings， shallow-to-intermediate burial diagenetic environments， and intermediate-to-deep burial diagenetic environments. The marine environment refers to an open-sea， grain shoal environment， predominantly developing fine to medium-crystalline dolomite. Inclusions exhibit a uniform temperature below 85 °C. Shallow-to-intermediate burial environments， with burial depths ranging from approximately 800-2 000 m， primarily foster homogeneous fine-crystalline and medium-to-coarse-crystalline dolomites. Inclusions exhibit a uniform temperature above 112 °C. Hydrothermal saddle dolomite mainly develops in intermediate-to-deep burial environments with burial depths exceeding 3 000 m， and inclusions exhibit a uniform temperature above 175 °C. This comprehensive research provides nuanced insights into the diverse dolomite types and their diagenetic histories， contributing significantly to the broader understanding of sedimentary processes and geological evolution in the western Sichuan Basin during the Middle Permian.

Objective The Yuzhou area is the most highly studied Upper Paleozoic coal-bearing strata of the southern part of North China Block， which has abundant sedimentological and stratigraphic paleontological research basis； however， owing to the lack of absolute chronology data， the division of chronostratigraphy， and regional large-scale stratigraphic correlation are affected. Methods In this study， laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） was applied to date the U-Pb age of detrital zircon of two mudstone samples near the stratigraphic boundary of the Taiyuan Formation-Shanxi Formation and Xiashihezi Formation-Shangshihezi Formation in the Yuzhou area and determine their maximum depositional ages. Results （1） The 40 detrital zircons from the bottom sample of the Shanxi Formation （ZK1006-5） constitute a continuous young component spectrum ranging from 283-343 Ma， with the youngest single zircon age （YSG age） is 283±9.4 Ma. The 18 detrital zircons from the bottom sample of the Shangshihezi Formation （ZK2387-3） constitute a continuous young component spectrum ranging from 257-299 Ma， with the YSG age is 257±6.8 Ma. They represent the maximum deposition age of the sample strata， indicating that the deposition time is no earlier than 283±9.4 Ma and 257±6.8 Ma. （2） The deposition of the Shanxi Formation and Shangshihezi Formation in the Yuzhou area began in Kungurian and Wuchiapingian， respectively， which is consistent with regional biostratigraphic data. （3） The Upper Paleozoic coal-bearing strata of the North China Block have a large span of penetrating rock strata， and the overall performance is characterized by inward penetration of the plate edge gradually through the new characteristics. Conclusions Based on the previous studies on volcanic events in the Late Paleozoic basin of the North China Block， the eastern margin of the basin was found to be strongly active in which the same sedimentary period， and the induced magmatism， tectonic activity， biological succession， and transgression may be related to the formation of the ancient continent of Laurisia land at the same time.

Objective The Paleogene Shahejie Formation around the Bozhong Sag， Bohai Bay Basin， contains mixed-rock reservoirs with abundant oil and gas resources. The unique biomass cavity pores （lumens） in mixed-rock reservoirs are such that their initial porosity cannot be obtained by conventional formulas. No methods are known in China or elsewhere for recovering the initial porosity for mixed rocks， although accurate recovery is a key element in determining the evolution of the reservoir. Methods Experimental and numerical methods were used to determine the volume of the body cavity in modern snail samples. A physical simulation experiment was then conducted to simulate the cavity infill conditions in an actual depositional environment. Finally， a formula for calculating the initial porosity of mixed-rock reservoirs was derived based on commonly used formulas. Results Studies have shown that differences in the snail species have the greatest effect on the percentage of body cavity pore volume （i.e.， body cavity porosity）. Within the same species， the main reason for the difference in body cavity porosity is the size of the body cavity. For example， the mixed-rock sample from well QHD36-3-A at a depth of 3 765.03 m， with a high content of fragmented bioclasts， has an initial porosity of 51.68%. Conclusions A new calculation method for finding the initial porosity of mixed rocks is proposed based on previous formulas combined with physical simulation experiments. This is highly significant in the study of mixed-rock reservoir evolution.

Objective Limestone-marlstone alterations （LMAs） are important archives of climatic， hydrological， and geological events. However， as a typical endmember of the LMAs， knowledge regarding the genesis of the LMAs with eyelid-eyeball structure from First member of the Maokou Formation in the Sichuan Basin is not widely accepted. This not only seriously affects environmental research of the LMAs with eyelid-eyeball structure， but also affects the efficiency of its exploration. Dolomitization is developed in the LMAs with eyelid-eyeball structure （mainly in the eyelids） of First member of the Maokou Formation of well DB1 during the penecontemporaneous and early diagenetic phase can be used to constrain the depositional environments of carbonate rocks. Methods Petrological and geochemical analyses have been conducted in detail， the process and the fluid properties of dolomitization has been discussed to constrain the process of LMAs with eyelid-eyeball structure. Results Three types of dolomitization developed in First member of the Maokou Formation， which are muddy dolomitic （EDM-I）； limy dolomitic （EDM-II）； and dolomitic marlstone （EDL）. EDM-I has the highest degree of dolomitization， distinct bands of cathodoluminescence， a flat rare earth partitioning pattern， higher δ¹³C and δ¹⁸O values， but lower Y/Ho values relative to seawater； it was dolomitized by penecontemporaneous seawater mixed with a small amount of meteoric freshwater during the penecontemporaneous phase. EDM-II has a middle degree of dolomitization， a left leaning rare earth partitioning pattern， and values of δ¹³C， δ¹⁸O， ⁸⁷Sr/⁸⁶Sr， and Y/Ho similar to seawater； it was dolomitized by seawater with high Mg/Ca， which was induced by frequent sea-level rise and fall changes during the syn-sedimentary and penecontemporaneous phase. EDL has the lowest degree of dolomitization， a left leaning rare earth partitioning pattern， higher δ¹³C and δ¹⁸O values relative to EDM-II， and seawater-like Y/Ho values. EDL was dolomitized by the sealed seawater of the syn-sedimentary phase that has been alterated with the wall rocks in the early diagenetic stage. Conclusions The dolomitization of the LMAs with eyelid-eyeball structure by weakly evaporating seawater and seawater mixed with freshwater during the penecontemporaneous and early diagenetic phase requires that the LMAs deposited in a shallower water. The high mud content， high strontium isotope and rare earth element values， low carbon and oxygen isotope values，and Y/Ho values of the eyelid-like marlstone relative to the eyeball-like limestone indicate that the depth of water for the eyelid-like marlstone is shallower than that of the eyeball-like limestone during deposition. Therefore， the LMAs in First member of the Maokou Formation were produced under cyclic oscillation in the depositional environment， and their genesis may have been mainly influenced by sedimentary process.

Objective Since 2019， CNPC has conducted exploration on the Upper Cretaceous Donga strata in the Trakes slope of the Termit Basin， Niger. Several wells obtained industrial oil flows， demonstrating good exploration potential. Compared to the Paleogene fluvial-deltaic Sokor1 Formation， the detailed characteristics of the Upper Cretaceous marine sandstones of the Donga Formation have not yet been fully examined. Methods In the present study， based on seismic， wireline， and mud logging data， 53 side wall cores and cutting samples from four wells were analyzed with thin sections， casting thin sections， X-ray diffraction， scanning electron microscopy， gamma-ray spectral logging， etc. Therefore， this study investigated the marine sandstone reservoir characteristics of DS1 member and DS3 member in the Donga Formation and analyzed their controlling factors. Results The results show that the rock type of the DS1 member is mainly fine-medium grained quartz sandstone with high component maturity， whereas the DS3 member is dominated by fine grained lithic quartz sandstone with mass calcareous mineral cement. The reservoir rock quartz grain is sub-round to round with moderate to poor sorting in the Donga Formation， the rock matrix is mainly composed of kaolinite and calcite， and most of quartz grains have point to line contact. Reservoir rock diagenesis have strong compaction and cementation， with common dissolution， and the pores are primarily intergranular with medium to ultra-low porosity and permeability. The high quality reservoirs in the Donga Formation are mainly distributed in the DS1 member， and reservoir physical property improves from west to east in Trakes slope. The analysis results show that the development of marine quartz sandstone in the Donga Formation is controlled by three factors. Firstly， vertical distribution of the sedimentary face and marine quartz sandstone was controlled by sea level changes， which manifested widespread marine distributary channel sandstones in the DS1 member that deposited in the early stage of marine transgression， whereas the DS3 member， in the highest sea level of marine deposit with high salinity， formed high contents of carbonate cement and poor reservoir physical property. Secondly， the stable gentle slope geomorphology in the Late Cretaceous was favorable for the development of marine sand bodies， and the intense strike-slip fault activities in the Paleogene induced the formation of micro-fractures in reservoir rock， which effectively improved the reservoir physical properties. Thirdly， the rigid construction of marine quartz sandstone granules was favorable for the preservation of rock primary pores， and the dissolution of unstable minerals such as feldspar and calcareous minerals improved the pore structure of the reservoir rock. Conclusions The development of a regional cap rock of marine mudstone and shale was conducive to the formation of self-generation and self-preservation reservoir in the Donga Formation. Compared with the lower slope zone of the Trakes slope， marine quartz sandstone has better reservoir physical properties and widespread distribution in the middle and high slope zones closer to the eastern sediment source area and are favorable for further exploration in the Donga Formation.