Objective The magnetic susceptibility and chroma of sediments have been widely used as climate proxies to restore the paleoclimate environment. It is important to study the change mechanism of these parameters in different environments for paleoclimate restoration. Methods The sampling and measurement of surface soil magnetic susceptibility and chroma were conducted in the western Qilian Mountains， northwestern China. The variation characteristics of magnetic susceptibility and chroma with precipitation， temperature， and altitude and the functional relationship between magnetic susceptibility and chroma and climate factors and altitude were established through regression analysis. Results The results showed that： （1） The magnetic susceptibility of surface soil in the western Qilian Mountains showed a significant nonlinear relationship with mean annual temperature and precipitation. When the mean annual precipitation was less than 300 mm and mean annual temperature was lower than 0 ℃， the magnetic susceptibility showed a significant negative correlation with them. When the mean annual precipitation was greater than 300 mm and the mean annual temperature was higher than 0 ℃， the magnetic susceptibility shows a significant positive correlation. In addition， there was a significant linear negative correlation between magnetic susceptibility and altitude， and the negative correlation between magnetic susceptibility and altitude was more significant in the low altitude region （1 600-3 300 m）. Finally， the functional relationship between surface soil magnetic susceptibility， mean annual precipitation， and mean annual moderate altitude in the western Qilian Mountains was established through regression analysis. （2） There is a significant correlation between the brightness of the surface soil in the western Qilian Mountains and the yellowness， indicating that the yellowness has a greater influence on the brightness than the redness in the western Qilian Mountains. The relative content of goethite in the surface soil is higher than that of hematite， corresponding to the overall yellowish brown color of the surface soil. Chroma （brightness， redness， and yellowness） has no evident relationship with temperature and precipitation. Brightness and altitude showed a significant negative correlation， and the low altitude area （1 600-3 300 m） was more sensitive. Conclusions In comparison， the magnetic susceptibility of surface soil in the western Qilian Mountains can better reflect the information of climate and elevation in the western Qilian Mountains than chroma. For the changes of magnetic susceptibility， chroma， and altitude， the relationship between brightness and altitude is more significant in the low altitude area （1 600-3 300 m）， followed by yellowness and magnetic susceptibility. In the high altitude area （3 700-4 300 m）， the relationship between redness and brightness and altitude is more significant. Thus， to establish the relationship between a single index and climatic factors in the western part of Qilian Mountains， it is necessary to consider the influence of local climate， terrain， and even primitive rock on the magnetic susceptibility and colorimetry indexes.

Objective Lithium rich claystone deposits with great potential for mineralization have been found in the bauxite-bearing sedimentary strata of Yunnan-Guizhou region in Southwest China， but the current understanding of the material sources and lithium enrichment mechanisms of these bauxite-type lithium rich claystones in these areas is still significantly insufficient. Methods In this study， two sets of bauxite-type lithium rich claystone systems， the Early Permian Daoshitou Formation in Yunnan and the Lower Carboniferous Jiujialu Formation in Guizhou， were analyzed in terms of their mineralogical compositions， major and trace elements， and the compositions of rare earth elements. Combined with the results of previous research， the study systematically explored the source attributes of two sets of bauxite-type lithium-rich claystone systems， which were formed in different epochs but have very similar petrographic characteristics， as well as determining the factors that led to the anomalous enrichment of lithium.［Results and Conclusions］ The results showed that the differences in source properties between the lithium rich claystones of the Jiujialu Formation in Guizhou and the Daoshitou Formation in Yunnan had a significant influence on their lithium content. In general， the development of the Jiujialu Formation， which has relatively low lithium content， is closely related to the weathering and denudation of impure dolomite in the underlying Loushanguan Group. Its original source may have been Neoproterozoic-Middle Proterozoic neutral acidic magmatism， which is significantly influenced by Mg-Fe compositions. The formation of Yunnan Daoshitou Formation claystones with relatively high lithium content was significantly influenced by the recycling of Ordovician sedimentary rocks， while the source connection with its underlying carbonate strata was weak. Their original source was dominated by neutral acidic magmatism. In addition， the lithium rich clay rocks in the Yunnan-Guizhou region were hosted by either kaolinite or illite， and the drainage of the watershed during the depositional period and the effect of coexisting ions in the water body played important roles in restricting the lithium enrichment in the clay. Analyzing the provenance of lithium rich clay rocks in the Jiujialu Formation in Guizhou and the Daoshitou Formation in Yunnan， along with the occurrence of lithium-bearing minerals， is of significant importance for understanding the ore-forming processes and controlling mechanisms of clay-type lithium deposits.

Objective Climate change caused by astronomical orbital parameters is closely related to biological turnover and sedimentary evolution of the ocean and lakes， which in turn affects the organic matter enrichment in the strata. The Late Paleozoic coal-bearing rock system in North China is dominated by coal， mudstone， siltstone， sandstone and tuff observed in a number of depositional cycles in the vertical direction. It is also an important system for current oil and gas exploration and development. The aim of this study is to systematically reveal the influence of the astronomical orbital cycle on organic matter enrichment in this coal-bearing system. Methods Natural gamma logging sequences were obtained for four wells （sampling distance 0.05 m） and continuous mineral elements for one well （sampling distance 1 m） in western North China. Astronomical cyclotron time series data and elemental geochemical analysis of typical samples were used to clarify the pattern of organic matter enrichment in stratigraphic cyclotrons at different scales. Results （1） Six 1.2 Myr ultra-long obliquity cycles and eighteen 405 kyr long eccentricity cycles are recognizable in the Carboniferous-Permian Benxi Formation， Taiyuan Formation and Shanxi Formation. （2） Using Mg/Ca， SiO₂/Al₂O₃， Fe/Mn and V/（V+Ni） ratios as paleoclimate and paleoredox proxies， six long-period variations and 18 medium-period variations were identified， all corresponding with ultra-long obliquities and long eccentricities. （3） Comparative analyses of paleoenvironmental restoration and organic carbon content during the depositional period of the Benxi Formation-Shanxi Formation show that paleoclimate evolution and organic matter enrichment are basically synchronized and controlled by the astronomical orbital cycle， and that during periods of increasing ultra-long obliquity or long eccentricity the climate is warm and humid and the reducing nature of bodies of water is enhanced， which promotes organic matter enrichment. Conclusions The above results reveal Carboniferous-Permian climate change in North China influenced by the astronomical orbital cycle and the development of a constrained organic matter-rich sedimentary system， and find that the paleoclimate change during the same period was obviously constrained by the long eccentricity. The findings can be used as a reference for the study of global climate evolution and organic matter enrichment mechanism in the Permian.

Objective Recent significant discoveries of marine clastic gas reservoirs in the Shiqiantan Formation （Shiqiantan Sag， Junggar Basin， NW China） necessitate the refined understanding of depositional systems to guide future hydrocarbon exploration. Methods This study reconstructs paleogeomorphology through isochronous sequence stratigraphic correlation and integrates seismic facies analysis， well-log cross-sections， and core/thin-section observations to delineate depositional facies and establish an evolutionary model. ［Results and Conclusions］ Results reveal a complete third-order sequence in the Shiqiantan Formation， subdivided by paleogeomorphic slope breaks into early transgressive systems tract （TST）， late TST， and highstand systems tract （HST）. During deposition， the sag formed a narrow NW-SE-trending marine seaway featuring rift-controlled troughs， multi-stage slope breaks， fault-bounded steep margins， and erosional valleys. Depositional systems identified include nearshore subaqueous fans， fan deltas， slope fans， and basin-floor fans. Paleogeomorphology exerted primary control on facies distribution： fan deltas and nearshore subaqueous fans developed along southern fault-controlled steep slopes； slope fans dominated the northern multi-stage gentle slopes； basin-floor fans occupied the central trough. Deposition occurred under rapid transgression， forming multi-stage imbricate retrogradational basin-floor/slope fan complexes during TST， overlain by extensive braided delta systems in HST. The TST hosts high-quality mature source rocks. Critically， basin-floor fans and slope fans on the northern gentle slope exhibit "finger-like interdigitation" with marine source rocks—creating optimal "source-on-top" and "source-adjacent" reservoir configurations. These zones represent prime targets for concealed hydrocarbon exploration due to superior charge conditions.

Objective The geological conditions in the Junggar Basin hinterland are diverse， and the crude oil properties are complex. To address the issues of crude oil type classification and oil and gas source identification in this area， a study was conducted on the hydrogen isotopic characteristics of n-alkanes （δ²H_alk） in the mixed-source crude oils from the Junggar Basin hinterland. Methods Gas Chromatography-Mass Spectrometry （GC-MS）， Gas Chromatography-Isotope Ratio Mass Spectrometry （GC-IRMS） and Gas Chromatography-Thermal Conversion-Isotope Ratio Mass Spectrometry （GC-TC-IRMS） techniques were employed to analyze biomarker compounds and conduct hydrogen isotope analysis of n-alkane monomers in 33 crude oil samples from different strata. Results Three types of crude oil were identified in the Junggar Basin hinterland： Type I originated from the Jurassic coal-bearing source rocks （J₁b）， with the lightest hydrogen isotopic composition due to the significant input of terrestrial higher-plant organic matter； Type II mainly originated from the Permian Fengcheng Formation source rocks （P₁f）， with Type II_A derived from lacustrine sedimentary environments in transitional marine-terrestrial settings， featuring a low Ga/C₃₀H ratio and relatively heavy hydrogen isotopic composition， while Type II_B had a lighter hydrogen isotopic composition and a higher Ga/C₃₀H ratio； Type III crude oil mainly originated from the Permian Lower Wuerhe Formation source rocks （P₂w）， with a light hydrogen isotopic composition of n-alkanes. Conclusions The combination of hydrogen isotopic analysis of n-alkanes and biomarker compound analysis is able to precisely classify crude oil types and clarify their sources， which is highly significant for oil source tracking and crude oil classification throughout the Junggar Basin.

Objective The discovery of lithium-mineralized bodies in multiple layers in the Permian to the Jurassic at the northern margin of the Yangtze Block is of great significance to the investigation， development and utilization of sedimentary lithium resources. This study aims to ascertain the nature and tectonic setting of the parent rocks in the source area of the lithium-bearing （lithium-rich） fine clastic rocks of the Jurassic Baitianba Formation， and to preliminarily discuss the influence of paleoenvironmental conditions on lithium enrichment. Methods Detailed petrological investigations were conducted on the typical lithologies within the formation， along with elemental geochemical analyses focusing on the lithium-bearing （lithium-enriched） fine clastic rocks. Results The oxide discriminant function graph of the main elements and the La_N/Yb_N-ΣREE， K₂O-Rb and La/Th-Hf diagrams indicate a mixed provenance of igneous， sedimentary and metamorphic rocks. The oxide discriminant function graph of the main elements， together with La-Th， Ti/Zr-La/Sc， La-Th-Sc， Th-Sc-Zr/10 and Th-Co-Zr/10 diagrams， show that the tectonic background of the sedimentary period was an active continental margin， and some source rocks were formed in a continental island arc environment. Lithium probably originated from arc magma material. Ga， Sr/Ba， Sr/Cu， C， CIA， U/Th， Ni/Co and other paleoenvironmental indicators indicate that the lithium-bearing rocks were deposited in a weakly oxidizing freshwater environment in a warm， humid climate. The A-CN-K and Th/Sc-Zr/Sc diagrams show that the parent rocks underwent moderate to intense weathering when the debris was first deposited. Conclusions The comprehensive study found that lithium enrichment was only superficially influenced by ancient salinity and ancient reduction-oxidation conditions. Rather， the warm humid climate was conducive to the formation of clay minerals， which increased the clay-mineral content of Li-bearing （Li-rich） fine clastic rocks and determined the extent of lithium enrichment.

Objective The Tianshan Mountains in Xinjiang are located in the inner part of the Asia-Europe continent in the transition zone between the westerly and monsoon circulations. They are sensitive to climate change. Researchers remain divided on the Holocene environmental evolution in the region， and supplementing more high-resolution climatic records in the sensitive areas is the basis for clarifying this issue. Methods Samples were taken from the Middle Tianshan Intermountain Basin， and we reconstructed the vegetation and climate change processes in the study area since the Middle and Late Holocene based on the AMS¹⁴C dating results and using sporadic pollen as a paleoclimate proxy. Results From 6 369-3 601 cal a B.P.： The period of Artemisia and Chenopodium was characterized by high content， positive pollen principal component analysis （PCA） 1 scores， and wet-dry fluctuations in the climate， with dryness as the dominant factor and abrupt climate change. From 3 601-2 512 cal a B.P： The period of spruce Picea content was characterized by elevated content， positive pollen PCA 2 scores， and a cold-wet climate. From 2 512-1 016 cal a B.P： The period of Betula was characterized by increased content， positive pollen PCA 1 transition scores， and a warm dry climate. Conclusions The three pollen zones indicate that the Middle and Late Holocene climate in the Zhongtianshan Intermontane Basin went through three phases of wet-dry fluctuations （off-dry）-cold-wet-warm-dry. Since the Middle to Late Holocene， the study area has received less solar radiation in summer， weak evaporation from the North Atlantic sea surface， and low water vapor carried by the westerly circulation； thus， the climate has been arid. In the early Late Holocene， the westerly circulation shifted to the south. The superimposed negative phase of the North Atlantic Oscillation （NAO） transported large amounts of water vapor， and the climate was cold and humid. Then， the climate became warm and dry owing to the increase of solar radiation in the late winter. The abrupt climate change characterized by cold and dry conditions during 4 766-3 601 cal a B.P. was a response to the “4.2 ka B.P.” climatic event， which may have been caused by the weakening of the westerly circulation due to the weakening of solar radiation， the intensification of the cold in the middle and high latitudes， and the lowering of the sea surface temperature in the North Atlantic Ocean.

Objective The aim was to update the sedimentary characteristics of the widely distributed Triassic dolomite-evaporite paragenesis system in the Sichuan Basin and clarify its development and distribution patterns and main influences， provide new insights for its study and guide the reconstruction of the regional paleogeography. Methods Drill core and seismic data were used to investigate the sedimentary characteristics in the study area from a number of viewpoints and determine the genetic mechanisms of the different types of symbiotic systems and reveal their spatiotemporal distribution patterns and main controlling factors. Results （1） Overall， four types of symbiotic systems are present in the Leikoupo Formation， northwestern Sichuan Basin： （i） thick layers of dolomite interbedded with thin layers of evaporate； （ii） interbedded dolomite-evaporate； （iii） thick layers of evaporite interbedded with thin layers of dolomite； and （iv） overlapping thick layers of evaporite. Types （i） and （iv） are widely distributed throughout the four sedimentary periods in the Leikoupo region. Stacking of thick evaporite and thick dolomite occurs most frequently in the central part of the Lei-3 and Lei-4 sedimentary periods. （2） The uplift of the Longmen Mountain island chain on the western side caused southeastern compression on the basin， and the Xuefeng Mountain uplift to the east restricted the southward migration of the ancient Luzhou Kaijiang paleo-uplift， and the contemporaneous Qinling Mountains southward subduction has been occurred.formed a structural pattern trending almost northeast–southwest in the Sichuan Basin， which controlled the overall northeast⁃southwest distribution of gypsum rocks and symbiotic systems. （3） The significant extent of the Luzhou Kaijiang paleo-uplift caused subsequent migration of the Leikoupo Formation subsidence center toward the west， and the gypsum sedimentary center and four coexisting systems also migrated westward from their earlier dispersed locations. Conclusions The sedimentary properties and distribution patterns of the symbiotic system resulted in four types of symbiotic system： gypsum-dolomitic lagoons， dolomitic gypsum lagoons， gypsum salt lakes， and gypsum salt basins. The paleogeography of each of the four sedimentary periods of the Leikoupo Formation was reconstructed from the distribution patterns of these types of symbiotic system.

Objective The end-Permian mass extinction event （EPME） led to a global decline in flora and biota. The thick coal seams prevalent during the Permian， no longer appear following this event， resulting in a prolonged coal shortage throughout the Triassic. In the Sichuan Basin， following the EPME， peat-forming spore plants that contributed to coal-forming period were lost in the lowlands， with no recorded subsequent coal seam development. This period is called "coal gap".The climate was hot during the Lower and Middle Triassic， and the turbulent sedimentary environment in the Sichuan Basin suppressed the growth and development of peat-forming plants. Coal seams re-appear in the Sichuan Basin during the deposition of the First member of the Upper Triassic Xujiahe Formation （T₃x₁）， characterized by thin coal seams and poor spatial continuity. During the middle to late sedimentation stages in the Xujiahe Formation， thicker coal seams developed with highly regular spatial distribution. Current studies of the Upper Triassic paleoclimate in the Sichuan Basin have mainly concentrated on the middle and late stages of Xujiahe Formation sedimentation， leaving a gap in research on paleoclimatic conditions during the initial coal-forming phase of the Late Triassic （early stage of the Xujiahe Formation）. To fill this gap， a focused study was conducted on the T₃x₁ （specifically the Gongnongzhen and Wangjialiang sections） in the northwestern part of the Sichuan Basin. Methods Conducted on the paleoclimate and coal-forming mechanism of the coal bearing strata （Gongnongzhen and Wangjialiang sections） of the Xujiahe Formation in the northwest Sichuan Basin based on field outcrop observation， petrological microscopy analysis， and principal and trace element analysis. Results It was found that the sedimentary facies of the T₃x₁ in the Gongnongzhen section are mainly delta front subfacies， whereas those in the Wangjialiang section are mainly delta plain subfacies. Weathering indices （CIA_corr， Rb/Sr） and climate indices （Sr/Cu and C values） of the T₃x₁ in the Gongnongzhen and Wangjialiang sections displayed an overall fluctuating trend. The humid and hot climate corresponds to strong chemical weathering intensity， whereas the period of warm semi-arid/semi-humid climate corresponds to moderate chemical weathering intensity. Conclusions The paleoclimate during the initial coal-forming period of the Upper Triassic Xujiahe Formation in the northwestern Sichuan Basin is of two types： （1） a hot， humid climate； and （2） alternating warm， semi-arid to semi-humid climates. Coal seams in the study area are associated with Type 1. The hot， humid conditions promoted the reproduction of peat-forming plants， providing abundant source material for the formation of coal seams. The paleoclimate alternating between dry to wet during the T₃x₁ in the region is closely related to super-monsoon activity.After the Middle Triassic， the South China Block gradually moved closer to the mid-latitude humid climate zone，amd the high concentration of pCO₂ combined with the influence of monsoonal activity in the study area jointly promoted the formation of a humid climate and consequent strong chemical weathering. Further research indicated that coal deposition requires both a suitable paleoclimate and an appropriate preservational environment. For instance， coal seams tend to be well-developed and preserved in the swamps of high-level system tracts.

Objective Trace elements play an important role in the reconstruction of the paleoredox states of marine sediments. Among them， molybdenum（Mo） has become an ideal proxy for the reconstruction of the redox state of ancient water bodies because it is mainly enriched in the form of autogenetic chemical deposition and less affected by terrigenous debris. However， compared with the ocean， lakes are more susceptible to terrigenous detritus and have more complex sedimentary environment， and the difference in the environment affects the settlement， distribution， and enrichment of Mo. In this study， the surface sediment of Qinghai Lake， the largest lake in China is the main research object. The enrichment mechanism and controlling factors of Mo element in alkaline， suboxic， and brackish water lakes were identified to provide a scientific basis for the applicability of Mo element in the reconstruction of lake paleoenvironment. Methods The planar distribution characteristics of Mo in the surface sediments of Qinghai Lake were determined by high density sampling and systematic testing， including X-ray fluorescence spectrometer （XRF） and inductively coupled plasma-mass spectrometry （ICP-MS）. In addition， the coupling relationship between Mo content and terrigenous input， particle size， element content， total organic carbon （TOC）， and depositional environment was established to determine the main controlling factors of Mo enrichment in the surface sediments of Qinghai Lake. Results The preliminary results show that Qinghai Lake is a brackish water lake with alkaline and weak oxidation. The planar distribution of Mo in the surface sediments of Qinghai Lake increases from the coastal shallow water area to the deep water area in the lake， and Mo is slightly enriched in the deep water area. Under sulfidic conditions， the soluble Mo in the water body is converted to particle reactive thiomolybdates. Because the overall water body of Qinghai Lake is in a state of oxidation， the enrichment of Mo in the sediments is unrelated. The enrichment of Mo in the surface sediments of Qinghai Lake may be controlled by the adsorption effect， that is， it is adsorbed and precipitated by clay minerals， Fe-Mn oxyhydroxides， organic matter， and other substances. The correlation analysis between Mo content and terrigenous input， particle size， element content， and TOC in the selected two transects shows that Mo has a positive correlation with TOC， and the change is similar， whereas Mo has a weak correlation with Al₂O₃ and Zr， which represents the terrigenous detritus input， and the change is significantly different. There was no correlation with clay minerals and Fe-Mn oxyhydroxides. This indicates that the influence of terrigenous detrital input on the distribution of Mo content in Qinghai Lake sediments is weak. Affected by the pH of water and the redox state of surface sediments， clay minerals， Fe-Mn oxyhydroxides have little influence on Mo enrichment in this environment， and TOC is the main controlling factor of Mo enrichment. Conclusions For alkaline and brackish water lakes with weak oxidation of bottom water， such as Qinghai Lake， organic matter adsorption and preservation are the main controlling factors for Mo enrichment in sediments. The type of organic matter could also affect the application effect of Mo as a proxy for redox identification of palaeolakes. Although the type of organic matter may influence the identification of redox conditions by Mo enrichment degree， Mo enrichment in weakly oxidized lake sediments is mainly controlled by the adsorption and preservation of organic matter， and Mo enrichment in sulfidic lake sediments is controlled by both the adsorption and preservation of particles such as organic matter and the reaction with H₂S in the water and the final preservation in the sediment （MoS₂）； thus， the Mo enrichment capacity is stronger. Therefore， Mo is an effective proxy for judging the redox state of palaeowater in the lake basin.