Current Issue http://www.gdlxb.cn/gdlxb EN-US http://www.gdlxb.cn/gdlxb/EN/current.shtml http://www.gdlxb.cn/gdlxb 5 -3 μm² to 4.87×10^-3 μm²(average of 0.59×10^-3 μm²). The dominant control factors for the distribution of the Es3L fine-grained reservoir development include lithofacies,sedimentary environment,diagenesis and thermal evolution of organic matter. In the middle and lower part of the Lower Sub-member of Third Member of Shahejie Formation,the amount of terrestrial input is low,the water salinity is high,and the water stratification is strong. The main lithofacies area LF2 and LF4,which are prone to the development of Class I and Class II high-quality reservoirs. The fine-grained reservoirs in Es3L are in the intermediate diagenetic stage A. The transformation of clay minerals,dissolution,recrystallization and dolomitization,as well as the thermal evolution of organic matter produce secondary pores and fractures,which improve the physical properties of the reservoir.]]> Marine dolomite cement is widely developed in the Precambrian era,whereas its occurrence in the Phanerozoic is scarce. Precambrian marine dolomite cement has attracted extensive attention in recent years due to its diversity,complex origins,and potential implications for Precambrian seawater chemistry. Research on Precambrian marine dolomite cement mainly focuses on two aspects: one is the formation mechanism through mineralogical analysis,and the other is the investigation into the unique Precambrian‘aragonite-dolomite sea' conditions as reflected by marine dolomite cement. The origin of marine dolomite cement incorporates both primary precipitation and mimetic dolomitization. However,due to a lack of reliable geochemical evidence,there is ongoing controversy in this field. In addition,both the precipitation mechanism of the primary dolomite and the corresponding seawater chemical conditions remain unclear. The identification of precursor minerals for mimetic dolomite is controversial. Based on previous studies,it can be summarized the spatial and temporal distribution,petrological and mineralogical characteristics,and geochemical characteristics. Subsequently,the current research status on the formation mechanism of marine dolomite cements from three aspects,including primary precipitation,secondary replacement,and growth assemblage morphology. Finally,it can be proposed that three aspects should be enhanced: (1)The genesis of diverse types of marine dolomite cements should be investigated based on the principles of mineral nucleation and growth theory,combining with micro area or in-situ geochemical analysis;(2)he specific contribution of microorganisms to the formation of marine dolomite cements requires assessment;(3)To gain a comprehensive understanding of the evolution of Precambrian seawater properties,exploration of the origin of marine dolomite cement is imperative.

]]> -3 μm²,while the average permeability of the latter is only 0.35×10^-3 μm². (3)A comprehensive analysis of diagenetic evolution reveals that the microbial carbonate reservoirs of the fourth member of the Dengying Formation have undergone a sequence of stages: sedimentary-quasi-symbiotic,supergene,shallow-to-medium burial,and deep-to-ultra-deep burial stages. (4)Analysis of reservoir distribution patterns in the study area indicates that the reservoir distribution weakens from the platform interior to the platform edge. Overall,the ultra-deep dolomite in the fourth member of the Dengying Formation in the Penglai area follows a ternary reservoir model characterized by “sedimentary facies-fault-dissolution.” This study provides key insights into the characteristics and controlling factors of the ultra-deep dolomite reservoirs in the Penglai area of the Sichuan Basin,offering significant guidance for future ultra-deep oil and gas exploration in the region.]]> -3~0.074×10^-3 μm²)are lower than those of Class Ⅱ dolomites(φ: 0.4%~2.0%;K: 0.009×10^-3~0.055×10^-3 μm²). However,Class I dolomites can enhance the ratio of dolomite-limestone interbedding,and there are fractures to transform into reservoir potential. This study is of significant reference value for ultra-deep dolomite oil and gas exploration in the Shunbei area of the Tarim Basin.]]> In this study,we investigate the Meiyan borehole located on the southeastern shore of Taihu Lake. Based on a reliable chronological sequence established by AMS¹⁴C dating,we use elemental geochemistry,including Rb and Sr concentrations and the Rb/Sr ratio,to reconstruct Holocene climate changes. Additionally,foraminifera analysis is employed to explore whether the Taihu Lake region was affected by transgressions. The results show that from 11.0-9.1 cal. ka BP,the climate of Taihu Lake Basin gradually changed from humid to dry;from 9.1-6.1 cal. ka BP,the general climate was generally humid,with the wettest period occurring during 8.8-7.1 cal. ka BP;from 6.1~2.0 cal. ka BP,the climate was generally dry with the lowest precipitation;from 2.0-0 cal. ka BP,the precipitation gradually increased and the climate was humid. During the whole Holocene period,the eastern area of Taihu Lake was unlikely to have been influenced by transgressions. Regional comparisons show that the Rb/Sr record in Taihu Lake are consistent with environmental proxies record in neighboring regions during the middle and late Holocene,which is characterized by gradually drying climate in the Middle Holocene and wet climate since 2.0 cal. ka BP. To further explore the climate dynamics,we compared the environmental proxy index with the 30° solar radiation in the northern hemisphere,ENSO frequency records and Holocene mean sea level records. We found that the climate of Taihu Lake Basin was controlled by the solar radiation and ENSO changes,with distinct phases of dominance and coupling between the two factors. Solar radiation affected the early and middle Holocene climate of Taihu Lake Basin through direct and indirect effects. Since 2.0 cal. ka BP,the climate has exhibited an El Niño-like state,with an intensified ENSO frequency balancing the effects of weakened solar radiation on precipitation in the monsoon region. As a result,ENSO frequency became the main controlling factor of the climate in the Taihu Lake Basin. The results will provide a reliable basis for understanding the relationship between monsoon and climate change in the lower reaches of the Yangtze River since the Holocene.

]]> As climate models are increasingly applied in palaeoclimate studies,the reconstruction of more accurate palaeogeographic boundary conditions has become a key factor in understanding deep-time climate change mechanisms. However,the uncertainty in this reconstruction process has received little attention. This study investigates this uncertainty and its impact on model simulation results,based on reconstruction methods and data selection for palaeo-sea-land distribution,palaeo-sea depth,and palaeo-topography. Our results show that: (1)When reconstructing sea-land distribution,choice of reference plate movement models significantly affects the latitude and longitude of the reconstructed plates,so this demonstrate that model selection should align with research goals. Moreover,accurate correction of sea-land distribution requires multiple palaeoenvironmental proxy indicators,considering their uncertainties. (2)The reconstruction of palaeo-sea depth is more uncertain due to its complex process. Updating the oceanic crust age,choosing a depth-crust age relationship model,selecting a sediment model,and adjusting depth in key areas can all lead to different ocean depth reconstruction results. In particular,special attention should be paid to critical areas like sea channels,the state of this areas directly affect ocean current patterns and temperature-salinity changes in some ocean basins. (3)The uncertainty of palaeo-topography reconstruction is mainly influenced by factors such as the richness and uncertainty of height proxy indicators. (4)Correcting sea-land distribution and reconstructing sea depth leads to differences in basin size and seabed topography. These differences directly impact ocean currents and air-sea exchanges. In summary,uncertainty arises at every step of the palaeogeographic boundary conditions reconstruction process,which will greatly affect the accuracy of model output. To mitigate this,optimizing reconstructions by adding more proxy indicators will be required. Additionally,using multi-model results and geological records for verification is critical when analyzing climate model output,involving palaeogeographic boundary uncertainty.

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