Geoscience

Advances on the Understanding in the Emeishan Mantle Plume and Dynamic Mechanism of the Permian Sichuan Basin Formation

SUN Ziming, BIAN Changrong, LIU Guangxiang

2023, 37(05): 1089-1099. DOI: 10.19657/j.geoscience.1000-8527.2023.043

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In recent years, significant research progress has been made on the Emeishan Large Igneous Province (ELIP) and its genetic mechanism of mantle plume, but the scope of the mantle plume on the Sichuan Basin and the dynamic mechanism for the Permian sedimentary basin formation remain unclear.Based on a number of literature research and recent studies, and the idea that deep mantle activity controls the evolution of crustal surface system, the characteristics of Emeishan LIP and its deep geology are systematically reviewed.It is recognized that the mantle plume is the dominant factor that induces the large-scale eruption of the Emeishan basalts and formed the LIP, and has direct influence on some parts of the Sichuan Basin, which is manifested by the differential denudation of the top Middle Permian Maokou Formation.This was likely caused by the upwelling of mantle plume and its control on the Permian sedimentation and sedimentary facies distribution in the central-southern part of the basin.Formation of the extensional troughs, and the alternating high-and-low sedimentary-tectonic framework in the central-northern Sichuan Basin during the Permian to Early Triassic may have been mainly controlled by the extension of the southern Qinling Ocean.

Fluvial Geomorphology of the Eastern Altyn Tagh and Its Tectonic Activity Implications

LU Fang, GAO Mingxing, ZHOU Shuxian, WANG Shun

2023, 37(05): 1100-1109. DOI: 10.19657/j.geoscience.1000-8527.2023.020

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The Altyn Tagh strike-slip fault zone is the major control fault at the northern margin of the Qinghai-Tibet Plateau, and plays a vital role in the Cenozoic crustal deformation of the plateau.We extracted and calculated five geomorphic indices (slope, relief amplitude, fractal dimension, hypsometric integral, and stream length gradient) of 173 sub-basins by ArcGIS software.The geomorphic indices of each sub-basin were classified into five types.Their arithmetic mean values were used as relative tectonic activity indices, in order to quantitatively analyze the topographical features and the tectonic activity intensity.We show that Altyn Tagh strike-slip fault zone is the dividing line for the relative tectonic activity intensity of the whole study area, and the relative tectonic activity index level gradually decreases from south to north, and from high to low mountai-nous areas.From the spatial distribution of the relative activity tectonic index grade, the tectonic activity in the Danghe and Yemahe River basins appears to be stronger, and the intensity gradually decreases from west to east.In addition, we combine the influence of rocks, precipitation, and tectonics on the geomorphic index.Our results show that tectonics is the main factor controlling the geomorphic development in the watershed of the Altyn Tagh strike-slip fault zone, the relative tectonic activity intensity in the watershed where the seismic point is located, the watershed on both sides of the fracture zone, and the stress transition zone are higher than those in other surrounding watersheds.

Structural Characteristics of Strike-Slip Fault and Its Control on Fluid Distribution in the East Ⅱ Block of the Sulige Gas Field, Ordos Basin

SONG Qing, SUN Panke, XIANG Jinyuan, TIAN Fajin, LÜ Fengqing, JIA Langbo, JIANG Shiyi, SHEN Yuhao, XU Huaimin, ZHANG Lin, HE Taihong, FANG Xiangyang

2023, 37(05): 1110-1122. DOI: 10.19657/j.geoscience.1000-8527.2023.045

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Due to the complex structure of strike-slip faults in the East Ⅱ Block of the Sulige Gas Field in Ordos Basin, the fluid differential enrichment regularity and distribution characteristics under fault control are unclear, which hamper the optimization and development adjustment of favorable target of the local target layer.To resolve the above problems, based on the fine geological interpretation of seismic data, the fault structural analysis was carried out in this study.The staging characteristics of faults and their differential control effect on fluid distribution were defined.The results show that: (1) The local strike-slip faults have two types of 5 type section structural styles,i.e. single fault type and combination type, and five types of plane structural styles, are combined on the plane i.e.linear, oblique, overlapping, feathered and braidedtypes, (2) The strike-slip fault experienced three stages of tectonic evolution: Caledonian-early Yanshanian extrusion, middle and late Yanshanian strike-slip, and Himalayan extension.From deep to shallow strata, the fault structure underwent the evolution of single fault-type, flower-like, and Yanshanian-type.According to the different fault structural styles, three segment of linear shear segment, derived shear segment and mixed shear segment are developed from west to east. (3) Faults with different structural styles control different fluid differential enrichment modes.Four types of fluid differential enrichment modes are developed in the study area, namely the single-fault-closed-stable production rise type, assembly-open and low-yield rapid decline type, and shear-semi-open and low-yield slow decline type.Among them, the single-fault-closed-stable production rising type and the drawing-semi-open and high-yield slow decline type have higher daily gas production and cumulative gas production and stable production, which are the main local natural gas enrichment area.Our results reveal the important controlling effect of strike-slip fault on fluid differential enrichment in tight sandstone reservoirs, and point out the direction for local further development and adjustment.

Development and Evolution Characteristics of Strike-slip Faults in Tarim Basin and Its Geological Significance: A Case Study of F_Ⅰ17 Fault in Fuman Oilfield

LIU Qiang, ZHANG Yintao, CHEN Shi, SONG Xingguo, Li Ting, KANG Pengfei, MA Xiaoping

2023, 37(05): 1123-1135. DOI: 10.19657/j.geoscience.1000-8527.2023.058

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The strike-slip fault in the platform Tarim basin has the characteristics of “controlling reservoir, controlling reservoir and controlling wealth”, but because it is developed in ultra-deep layer and its activity intensity is low, the fine analysis and evolution characteristic analysis of the fault is the focus and challenge of the current research.To deepen the fine analysis process of strike-slip fault structure and explore the geological significance of fault activity, we took F_Ⅰ17 fault as a case study.Based on the new high-precision 3D seismic data in the Fuman oilfield, combined with a variety of seismic attributes such as coherence, maximum likelihood and reservoir amplitude change rate, we analyzed the spatial distribution regularity, activity characteristics and evolution process of faults, and the characteristics of fault control and storage in combination with the reservoir development characteristics.Based on the reconstruction of the local structural characteristics of the Precambrian basement, the development mechanism of fault plane strike migration is preliminarily analyzed.The results show that the local F_Ⅰ17 fault plane has changed many times and its strike shifted counterclockwise from south to north.Based on the changing characteristics of the fault strike, the fault can be divided into three segments: North (NE8°), middle (NE33°) and south (NE50°).The fault has the characteristics of vertical delamination defor-mation.According to the fault deformation characteristics, it can be divided into the deep structural deformation layer characterized by vertical strike-slip (below TO₃t), and the shallow structural deformation layer with echelon normal fault (above TO₃t).The fault has the characteristic of “stratified flowering” in the deep structural deformation layer, and several flower-like structures are developed vertically, which are mainly distributed near the bottom of the Upper Cambrian (T∈₃) and the top of the Yijianfang Formation (TO₃t).Three groups of echelon normal faults are developed vertically in the shallow structural layer, which are distributed in TO₃t-TS, TS-TC and TC-TT from bottom to top.The fault evolution is likely multi-stage, and the evolution can be divided into five stages: early Caledonian, middle Caledonian Ⅰ, middle Caledonian Ⅲ, late Caledonian-early Hercynian, and middle-late Hercynian.The Precambrian basement rift structure likely affected the development and connection of the overlying strike-slip faults, resulting in the fault plane offset.

Differential Deformation and Evolution Characteristics of the No.17 Strike-slip Fault Zone in the Tarim Basin

WANG Qinghua

2023, 37(05): 1136-1145. DOI: 10.19657/j.geoscience.1000-8527.2022.090

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The No.17 strike-slip fault zone in Tarim Basin is a large strike-slip fault zone that runs through the transitional zone between the Tazhong Uplift and the Afghani Manchu area.A series of important breakthroughs have been made in oil and gas exploration along this fault zone in recent years.Based on the new 3D seismic data in Fuman oilfield, we analyze the spatial structure and evolution processes of the northern segment of the No.17 strike-slip fault zone, and discuss the relationship between the spatial structure and oil properties.The results show that the No.17 strike-slip fault zone has stratified deformation characteristics in the profile.The fault zone in the Cambrian subsalt structural layer is straight into the basement, a few branch faults are deve-loped in the Middle Cambrian salt structural layer, and the Upper Cambrian-Middle Ordovician carbonate structural layer has strong fault activity and a large deformation range.In the Upper Ordovician-Carboniferous clastic structural layer, normal faults are developed.On plane view, the northern section of the No.17 strike-slip fault zone has variable strike direction, which can be subdivided into the north, middle and south subsections.The north subsection has long linear fault extension, the middle subsection has obvious fault overlapping characteristics, and the south subsection has a braided structure.Under the top surface of Middle Ordovician limestone, the faults are mainly linear extending, while on the top surface of Silurian, they are in an echelon pattern.The No.17 strike-slip fault zone has sinistral strike-slip activity in the Middle Ordovician and Late Ordovician-Carboniferous, and the activity intensity is strong in the north and weak in the south.According to the fault deformation and regional stress field characteristics, the evolution of the fault zone can be divided into the early Caledonian fault initial development stage, the middle Caledonian fault mature stage, and the late Caledonian-Hercynian demise stage.

Genetic Mechanism of Antiformal Negative Flower Structure in the Doseo Depression, Southern Chad Basin

ZHOU Xiaorong, CHEN Shi, ZHANG Xinshun, DING Baotong, SONG Xingguo, PAN Chuqi, PENG Zijun

2023, 37(05): 1146-1154. DOI: 10.19657/j.geoscience.1000-8527.2023.007

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The Doseo depression in the South Chad Basin is an important petroliferous basin in the Central African Shear Zone.A new kind of flower structure composed of normal faults (termed antiformal negative flower structure), is developed on the ENE-WSW-trending strike-slip fault zone.The faults there exhibit an en echelon arrangement in plane view, and have characteristics of positive flower-like and negative flower-like structures in the seismic profile, which are shown as a flower structure of lower "synform" and upper "antiform" shape.According to the development characteristics of the faults and the regional stress evolution, combined with 2D and 3D seismic data interpretation, the Doseo depression is divided into five evolution stages by the balanced cross-section reconstruction technique.Based on the strike-slip displacement, we analyzed the genetic mechanism of the antiformal negative flower structure in the depression.We considered that it is the result of superposition of the ENE-WSW-trending basement normal fault in the middle part of the depression in the formation stage of negative flower structure in the Early Cretaceous transtension period, and the antiform formation stage in the Paleogene transpression reversal.The early transtension strength is much greater than the later transpression reversal strength, and the difference between the strike-slip displacement components of the two is 10 to 30 times.The difference in strength makes it mainly present the negative flower structural style composed of normal faults, and only the antiform style formed during the inversion period is superimposed.

Lithofacies Characteristics and Sedimentary Model of the Lower Cambrian Shale in the Northeastern Margin of Tarim Basin

LIU Wangwei, LI Yifan, GAO Zhiqian, FAN Tailiang, ZHANG Tan, KUANG Mingzhi

2023, 37(05): 1155-1168. DOI: 10.19657/j.geoscience.1000-8527.2023.006

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The study of shale facies characteristics and sedimentary model can help to reveal the characteristics and distribution of fine-grained source rocks.The lithofacies assemblage and sedimentary model of the Lower Cambrian shale in the northeastern margin of the Tarim Basin are analyzed by means of outcrop description, thin-section petrographic observation and organic matter content measurement.The sea-level of the Lower Cambrian in northeastern Tarim Basin was characterized by rapid transgression, continuous deepening and rapid shallowing.The sea-level change may have directly affected the shale development.Six lithofacies and three lithofacies assemblages are developed from bottom to top in the Lower Cambrian in the study area: (1)the semi deep-water shelf lithofacies assemblage includes siliceous shale facies, siliceous clay-shale mixed facies and phosphorous shale facies; (2)the deep-water shelf lithofacies assemblage includes siliceous shale facies and clayey shale facies; (3)the shallow water shelf lithofacies assemblage includes calcareous shale facies and siliceous calcareous shale facies.In the Early Cambrian, the northeastern Tarim region was likely in a semi-deep-water shelf environment, with strong extension and frequent hydrothermal activity.The hydrothermal activity has a dual role in the enrichment of organic matter, which is not conducive to organic matter enrichment in the siliceous shale in the semi-deep-water shelf environment, and to the organic matter enrichment in the phosphorous shale in the semi-deep-water shelf environment.With the continuous sea-level rise, tectonic activity and hydrothermal activity decreased, and the deep-water shelf lithofacies assemblages began to develop.During this period, the organic matter was well preserved.The sedimentation rate was slow, and the paleoproductivity was high.The total organic carbon (TOC) content in the shale was relatively high.During the sedimentation of the Xidashan Formation, the environment was generally of shallow water shelf.During this period, the content of silicic minerals in the sediments decreased, while that of calcareous minerals increased.The preservation conditions of organic matter were poor, the sedimentation rate was high, and the TOC content in the shale was relatively low.We considered that Lower Cambrian phosphorous shale facies and the deep-water shelf lithofacies assemblage in the northeastern Tarim basin represent favorable intervals.

Development Model of Microbial Reef-shoal in the Lower Cambrian Xiaoerbulak Formation Under Transgression-Regression Transition in the Northern Tarim Basin

CHEN Gege, GAO Zhiqian, JIAO Cunli, HU Zongquan, YUAN Yuxuan, WEI Duan, ZHAI Xinqing, CHANG Zhe

2023, 37(05): 1169-1181. DOI: 10.19657/j.geoscience.1000-8527.2022.093

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Based on the outcrop observation in Aksu area in the northwestern Tarim Basin, and the analysis of logging data and thin section identification of key exploration wells there, the high-precision sequence stratigraphic framework at north Tarim Basin is established.We analyzed the development model of microbial reef-shoal and carbonate platform evolution in the Xiaoerbulak period, and suggested that the Xiaoerbulak Formation can be subdivided into two third-order sequences (SQ1 and SQ2) and five fourth-order sequences (sq1, sq2, sq3, sq4 and sq5): sq1 and sq2 developed layered microbial mats, which were middle-inner ramp deposition, corresponding to the ramp carbonate platform stage; sq3 is a transition period from ramp carbonate platform to slightly rimmed shelf carbonate platform, and the relative sea-level likely rose first and then fell, and microorganisms began to build reefs in the paleo-geomorphic highlands, and the microbiolites were basically undeveloped in the slope area of low paleo-geomorphic terrain; sq4 and sq5 represent the stage of slightly rimmed shelf carbonate platform with continuous sea-level decline; sq4 developed algal grain shoal and microbial reef deposits, whilst sq5 developed sand shoal, gravel shoal and microbial reef deposits.The high-precision sequence stratigraphic correlation shows that the sea-level change controlled the vertical development of microbial reef shoal, and the paleo-geomorphology controlled the planar microbial reef shoal distribution.

Study on Structural Dolomitization:Taking the Yingshan Formation of the Penglaiba Section in Aksu Area as An Example

TAN Cong, LIU Ce, WANG Tongshan, LI Qiufen, ZHU Xi, FU Jinglong, JIANG Hua

2023, 37(05): 1182-1193. DOI: 10.19657/j.geoscience.1000-8527.2023.008

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Through systematic field survey, lithology descriptions, sample collection, thin-section observation and geochemical analysis of the Yingshan Formation in the Penglaiba section of Aksu area in Tarim Basin, the local small-scale genesis of dolomite in the Yingshan Formation is analyzed in detail.The results show that the Yingshan Formation in Penglaiba section can be divided into upper and lower segments, and the overall lithology is limestone.The lower section comprises sparry algal arenaceous limestone, which has clear sedimentary characteristics of high-energy granular beach facies. The upper section is globular micrite limestone, which is dominated by low-energy beach and intertidal marine sediments.The profile is cut by several faults, and dolomite is locally developed near the fault of the lower segment of Yingshan Formation, distributed in lenticular or semi-layered form.The degree of dolomitization decreases gradually along the layer and away from the fault.Geochemical analysis of the dolomite shows that the rock has low Fe and Mn contents, overlapping with the surrounding limestone, and there is no distinction on Na and K contents from the limestone, reflecting that the dolomitization fluid is of marine origin.The Sr content is obviously higher than that of the surrounding limestone, indicating that the mica alteration was not supergene related.The REE compositions are characterized by enrichment of LREEs and depletion of HREEs.Eu shows obviously negative anomaly, while Ce shows slight depletion, similar to modern seawater.Carbon-oxygen isotopes of the dolomite samples are lighter than those of the limestone, indicating the evaporite property of the fluid.Through comprehensive research, we considered that the local dolomitization around the fault in the Yingshan Formation (Penglaiba section) may have occurred in the shallow burial stage.The dolomitization fluid may have come from the evaporated brine of the Middle-Upper Cambrian strata connected by the fault, which is a kind of small structural dolomite different from typical tectonic hydrothermal dolomite.

Depositional Environment and Sedimentary Model of the Fengcheng Formation in Mahu sag, Junggar Basin

NI Minjie, ZHU Hexuan, HE Wenjun, YANG Sen, ZOU Yang, ZHANG Yuanyuan

2023, 37(05): 1194-1207. DOI: 10.19657/j.geoscience.1000-8527.2023.061

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The Mahu sag is one of the most prolific oil-gas sags in the Junggar Basin.The Lower Permian Fengcheng Formation is the main high-quality lacustrine source rocks, and is considered as the key exploration target in the Mahu sag.The lithofacies distribution and sedimentary environment of the Fengcheng Formation are of great significance in studying the tectonic evolution and further oil-gas exploration of the Mahu sag.Based on the latest logging data, we established a comprehensive stratigraphic column for the Fengcheng Formation from well Maye 1, and clarified the lithofacies distribution of the Fengcheng Formation.The tectonic sedimentary environment and sedimentary model of the Fengcheng Formation are constructed subsequently.The Fengcheng Formation is mainly composed of dark fine-grained sedimentary rocks in well Maye 1, with a large number of soft-sediment deformation structures.The middle member of the Fengcheng Formation was likely deposited in (semi-)deep lacustrine facies.According to the lithofacies profile in the Fengcheng Formation, the cyclic characteristics of progradation-retrogradation-progradation developed from bottom to top, and the sedimentary facies changed from fan delta, lacustrine to river delta facies from southwest to northeast.Volcanism likely played a key role in the lower member of the Fengcheng Formation of shallow lacustrine facies in the northern part of Mahu sag.In the middle member of the Fengcheng Formation, the southern part of Mahu sag developed fan-delta deposits, which is transformed into delta-shore shallow lacustrine deposit to the west of Mahu sag, and semi-deep to deep lacustrine deposits are developed in the northern part.The middle member of (semi-)deep lacustrine facies is characterized with extensive distribution and abundant alkaline minerals in the depocenter.The chemical precipitation in the middle member of the Fengcheng Formation is the most widely distributed, indicating the maximum flooding surface.The progradation in the upper member of the Fengcheng Formation may have resulted from shrinking of the sag.Fan delta deposits are developed in the southern and western parts of the Mahu sag, and semi-deep lacustrine to shore-shallow lacustrine facies are developed in the northern part.Combined with its sedimentary evolution process, the Fengcheng Formation is likely deposited and multiple-sourced, including terrigenous clastic deposits, endogenous chemical precipitates and pyroclastic material.

Distribution Characteristics of Oolitic Beach in the 2^nd and 3^rd Members of Lower Triassic Feixianguan Formation, Southeastern Chongqing

ZHAO Lingli, SONG Jinmin, YUAN Haifeng, XU Guaosheng, DENG Shuanglin, ZHAO Cong, JIN Xin, LI Liji, LI Pengwu, REN Jiaxin, LI Keran, FENG Yuxiang, FAN Jianping

2023, 37(05): 1208-1220. DOI: 10.19657/j.geoscience.1000-8527.2022.100

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The Feixianguan Formation (FXGF) subdivision in southeastern Chongqing is established based on the lithologic-electrical identification mark by the outcrop measurement, thin-section microscopic observation, logging data and seismic data analysis.The distribution patterns of oolitic beach in the 2^nd and 3^rd members of FXGF are discussed.The results show that the stratigraphic framework of FXGF in southeastern Chongqing can be divided into four parts.The FXGF 1^st Member is mainly composed of limestone with the characteristics of 80~105 API GR value and 75~200 Ω·m LLD value.The FXGF 2^nd Member is mainly composed of micritic limestone and silty oolitic limestone.The GR value reduced to 11~31 API, and the resistivity value increased to 200~4205 Ω· m compared with the FXGF 2^nd Member.While the FXGF 3^rd Member is mainly composed of oolitic limestone and silty limestone.The logging value has little change compared with the FXGF 2^nd Member.Only the top and bottom of the FXGF 3^rd Member can be seen with high GR value.Argillaceous dolomite and argillaceous limestone are developed in the FXGF 4^th Member with GR value increasing to 35~66 API and resistivity decreasing to 74~280 Ω·m (compared with the FXGF 3^rd Member).In the study area, oolitic beach in the FXGF 2^nd Member is developed in Quxian-Liangping and Fengdu-Zhongxian-Lichuan areas.Oolitic beaches of the FXGF 3^rd Member were mainly developed around the Dianjiang-Liangping intertidal depression, which were distributed in a ring belt.The oolitic beach developed in the FXGF 3^rd Member is thicker, more connectivity, more widely distributed, and larger in scale than that in the FXGF 2^nd Member.The local sedimentary model during Feixianguan period is a rimmed carbonate platform.After clarifying the stratification scheme, we considered that the beach center in the platform migrated eastward with the regression during the 3^rd Member of Feixianguan period.

Controlling Factors of Pressure Dissolution of Cambrian Carbonate in the Northern Sichuan

HU Liwen, ZOU Huayao, YANG Weiqiang, LI Ting, DENG Chengkun, CHENG Zhongzhen, ZHU Dancheng, CHEN Xingyue

2023, 37(05): 1221-1231. DOI: 10.19657/j.geoscience.1000-8527.2022.099

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Previous studies of the stylolites prefer qualitative analysis, lacking quantitative analysis of mineral composition, textures, lithofacies and their impacts on stylolites (density and amplitude).The paper clarifies the quantitative relationship between the density and amplitude of stylolites, mineral composition, rock textures and lithofacies, and expounds the controlling factors of stylolite formation in the study area.Based on the database of outcrops, cores and thin sections, the stylolite characteristics, mineral composition, textures and lithofacies of Cambrian carbonate in the northern Sichuan Basin are quantitatively evaluated.The results by the observations of cores and microscope show that: (1) The terrigenous clastics in carbonates leads to the enhancement of rock heterogeneity, which facilitates the formation of stylolite with a content of 10%-15%; (2) The carbonates are strongly resistant to pressure solution, with a content of 50%-70% grains, 25%-30% cements, and no matrix; (3) Different lithofacies of one well could have different resistance to pressure dissolution.The density and amplitude of stylolites increase successively from granular dolostone, mixed siliciclastic-carbonate rocks, and crystalline dolostone through micrite dolostone in the same well, indicating that their resistance to pressure dissolution decreases gradually.

Sedimentary Characteristics of Beach Bar in the Paleogene Upper Shahejie Formation (4^th Member) in Shanghe Area, Huimin Depression, Bohai Bay Basin

SHU Qinglin, ZHAO Hui, JIANG Zaixing, ZHAO Guoguang

2023, 37(05): 1232-1242. DOI: 10.19657/j.geoscience.1000-8527.2023.021

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In recent years, the research of the Shanghe area is based on a large range of regional background, and the research of the refinement of the Upper Shahejie Formation (4^th Member) in Shanghe area is relatively scarce.Based on core logging data, we analyzed the types and characteristics of sedimentary microfacies in the Upper Shahejie Formation (4^th Member) in Shanghe area.The planar distribution and control factors of sedimentary microfacies in each period are analyzed based on system tract.The results show that the Upper Shahejie Formation (4^th Member) in Shanghe area is mainly located in a littoral and shallow lacustrine sedimentary environment, and there are mainly two sedimentary facies types (i.e., wind-wave beach bar and storm beach bar).The sedimentary structure includes mainly wave-like sand lamination and wave-like bedding reflecting wind and wave action, and cross-bedding of mounds and depressions reflecting storm action.The logging curves comprise four types: tooth funnel, low amplitude tooth, middle-high amplitude finger and box.The lowstand systems tract of the Upper Shahejie Formation (4^th Member) is dominated by a lakeside sedimentary environment, where wind-wave beach bar is mainly developed, while two types of beach bar are developed in the transgressive systems tract and the highland systems tract.The beach bars are controlled by the paleosource, the paleobathymetry and the paleogeomorphology, especially during periods of lake transgression and high elevation, wind-wave beach bar is developed in the low uplift area in the northwest of Shanghe area.Meanwhile, storm beach bars are developed in the deep low-lying area in the southeast of Shanghe area.

Carbon and Oxygen Isotope Characteristics of Late Cretaceous Lacustrine Dolomite in the Songliao Basin and their Paleoenvironmental Implications

ZHANG Yifan, GAO Yuan, CHEN Jiquan, HUANG Shuai, HAI Lun, WU Zhengxuan, YANG Liu, DONG Tian

2023, 37(05): 1243-1253. DOI: 10.19657/j.geoscience.1000-8527.2023.023

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The Late Cretaceous Qingshankou and Nenjiang Formations in the Songliao Basin, extensively deposited with dark mudstone, and interspersed with layers of dolomite and dolomite nodules, are regarded as important source rock strata.Studying important oil-bearing dolomite can help to understand the terrestrial paleoenvironment evolution and source rock reservoir characteristics.In this study, carbon and oxygen isotopes of dolomites from the Qingshankou Formation (the first member) in Niaohe section and the Nenjiang Formation (the first member) in Lijiatuozi section in the southeastern margin of Songliao Basin are analyzed to explore paleoenvironmental significance.The results show that δ¹³C values of dolomites in both sections are relatively high (δ¹³C_Niaohe=-5.89‰~0.78‰, δ¹³C_Lijiatuozi=-8.36‰~6.70‰), while δ¹⁸O values are relatively low (δ¹⁸O_Niaohe=-10.03‰~-7.84‰, δ¹⁸O_Lijiatuozi=-11.30‰~-3.82‰), and the correlation between δ¹³C and δ¹⁸O is high (R²>0.7). This demonstrates that the late Cretaceous dolomites in the Songliao Basin were the product of closed (semi-)brackish lacustrine system with a long retention time.According to the empirical equation Z=2.048×(δ¹³C+50)+1.498×(δ¹⁸O+50), the average values of dolomites in Qingshankou and Nenjiang Formations are 124 and 126.5, respectively, indicating that the dolomites may be affected by seawater intrusion during the formation process.Furthermore, we estimated the scale of transgression using a mixing model of seawater and freshwater oxygen isotopes.In conclusion, we consider that the Late Cretaceous lacustrine dolomite in the Songliao Basin was deposited in closed (semi-)brackish lacustrine system with a long retention time, under a transgressive background.

Element Composition and Sedimentary Environment of Chang 9 Shale Source Rocks in the Ordos Basin

SHI Liang, FAN Bojiang, WANG Xia, LI Yating, HUANG Feifei, DAI Xinyang

2023, 37(05): 1254-1263. DOI: 10.19657/j.geoscience.1000-8527.2023.039

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The research on the element characteristics of Chang 9 shale in Erdos Basin is inadequate, and the sedimentary environment is not fully revealed.Based on energy dispersive X-ray fluorescence technology, we used the optimized energy setting method to characterize the major and trace elements, which increases the number of measured effective elements to 29.Based on the element composition characteristics of the Chang 9 shale, the sedimentary environment (incl.paleo-climate, paleo-salinity, paleo-redox state, paleo-productivity, and provenance input) is systematically analyzed.The results show that the average content of 11 major elements in Chang 9 shale is 38,341.54 μg/g; the average content of 18 trace elements is 160.12 μg/g.Si, Al, Fe, Ca and K have the highest contents among the major elements; Ba, Rb, Sr and Zr have the highest contents among the trace elements.For the trace elements of the Chang 9 shale, elements including V, Cu, Th, Rb, Zr and Nb are relatively depleted; elements including Co, Ni, Zn, Ga, Pb, U, Y and Cr are weakly enriched; elements including Ba, Sr and Mo are moderately enriched; arsenic is highly enriched.The sedimentary environment of Chang 9 shale has the following characteristics: humid climate, freshwater water and weakly oxidized, medium to weak closing lake, stable terrigenous materials input, and strong primary productivity.

Reconstruction of Provenance and Paleo-sedimentary Environment of the Chang 8 Oil Layer in the Southwestern Margin of the Ordos Basin: Evidence from Petrogeochemistry

CHEN Xi, XIAO Ling, WANG Mingyu, HAO Chenxi, WANG Feng, TANG Hongnan

2023, 37(05): 1264-1281. DOI: 10.19657/j.geoscience.1000-8527.2023.037

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Geochemical characteristics of sedimentary rocks recorded important sedimentary and source region tectonic information, which can be an effective means to understand the provenance and paleo-sedimentary environment.Based on geochemical analysis of 14 mudstone and silty mudstone samples in combination with core logging data, the provenance and paleoenvironment of the Chang 8 oil layer of the Yanchang Formation in the southwestern margin of Ordos Basin have been systematically studied.The main conclusions are as follows: The source region was an active continental margin, and the local source of the Chang 8 oil layer is mainly from the metamorphic and igneous rocks of the Qin-Qi orogenic belt in the southwestern margin of the Basin.Combined with different element abundance and ratios and sedimentary marker, our results show that the paleoclimate was dominated by semi-humid-semi-arid, hot arid climatic conditions, and the paleotemperature was generally higher than 15 ℃ and the average temperature of the Yanchang period.Water depth during the Chang 8 deposition was shallow, the paleosalinity was dominated by freshwater environment.The paleo-redox environment was oxidizing under shallow water.The paleoenvironment conditions and sufficient material source provided favorable conditions for the development of the shallow water deltaic sedimentary system.

Development Characteristics and Reservoir Controlling Factors of Microbial Carbonate Microfacies Longitudinal Assemblage in the Dengying Formation (the 4^th Member) of Sinian System in Gaoshiti Area, Sichuan Basin

ZHANG Yuhui, ZHU Zhengping, LUO Wenjun, PAN Renfang, LIU Xixiang

2023, 37(05): 1282-1292. DOI: 10.19657/j.geoscience.1000-8527.2023.027

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In this paper, we clarified the microfacies combination characteristics and main factors controlling the reservoir development of the microbial carbonates in the Dengying Formation (the 4^th member) of Sinian System in Gaoshiti Area, Sichuan Basin by utilizing the core observation, microscopic identification, and well-connected sedimentary comparison.The results indicate that: (1) Sedimentary microfacies of the Dengying Formation (the 4^th member) is compose of microbial mounds and grain shoals.The grain shoals upwardly evolve into microbial mounds, and four types of sedimentary sequences are recognized, including the mound base-mound core-mound wing, mound base-mound core-mound cover, mound base-mound core, and inter beach sea-storm beach. (2) The mound-shoal complex and weathering crust are the predominant factors controlling the reservoir development.The mound-shoal complex provides good material basis for reservoirs, and weathering crust karstification greatly improves the reservoir petrophysical properties.Whereas, the burial hydrothermal process performs dual roles in the contribution of reservoir development. (3) There are two main reservoir genetic types in the Dengying Formation (the 4^th member), i.e., the sedimentary-dominated reservoirs and supergene-karst reservoirs, which are developed in the lower and upper part of Dengying Formation, respectively.This study provides basic materials and research examples for the enrichment and improvement of the microfacies classification and controlling factor analysis for the microbial carbonate reservoirs in the Gaoshiti area, which could guide subsequent exploration and development in this region.

Organic Nano-pore Textural Characteristics of the Longmaxi Formation Shale in the Southeastern Sichuan Basin

LI Dongsheng, GAO Ping, GAI Haifeng, LIU Ruobing, CAI Yidong, LI Gang, ZHOU Qin, XIAO Xianming

2023, 37(05): 1293-1305. DOI: 10.19657/j.geoscience.1000-8527.2023.054

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The widely developed nano-pores in organic-rich shale are important storage space for shale gas.To determine the pore development characteristics of organic matter in shale, the Lower Silurian Longmaxi Formation shale in Dingshan area, southeast Sichuan Basin is taken as the research object.The surface porosity of organic matter was evaluated and the nano-pore structure characteristics were characterized based on scanning electron microscopy (SEM) and low-pressure N₂ and CO₂ adsorption analysis.The results indicate that total organic carbon (TOC) content was the major factor influencing the specific surface area and pore volume of nanopores in the Longmaxi Formation shale.With increasing TOC contents, the specific surface area and volume of organic pores increase.With higher TOC contents, the specific surface area and volume of organic pores played a dominant role over that of inorganic pores.The pore volume contribution of the 2-10 nm-sized pores to the total pore volume is the largest in the Longmaxi shale samples, and the pyrobitumen contains larger numbers of mesopores than the other types of organic matter (e.g., kerogen).The pyrobitumen content increase would significantly increase the mesopore volumes of the shale.However, the oil expulsion efficiency can indirectly affect the nanopore development via the variation of pyrobitumen contents.The volume of mesopores and total pores in the shale would be reduced due to high oil expulsion efficiency.In the exploration and development of Longmaxi Formation shale, the influence of TOC content, oil expulsion efficiency and pyrobitumen content on the reservoir conditions of shale gas should be considered comprehensively.

Development Characteristics of Fracture-Cave and Their Formation Mechanism in Carbonate Rocks of Ordovician Majiagou Formation in Northwestern Henan Province

SHAO Weimeng, NIU Yongbin, CHENG Mengyuan, HAN Kelong, SUN Fengyu, CHENG Yigao, JING Chuhan

2023, 37(05): 1306-1320. DOI: 10.19657/j.geoscience.1000-8527.2023.014

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The reservoir space of fracture-caves is well developed in the Ordovician Majiagou Formation carbo-nate rocks in northwestern Henan Province.Based on observations of local field outcrops, we studied the development characteristics of fracture-caves using geostatistics, and analyzed their formation mechanism in detail in relation to the regional tectonic evolution.The results show that: (1) the local caves can be divided into three types,i.e.small caves (height <1 m), medium caves (height 1-5 m) and large caves (height >5 m), among which medium and small caves predominate; (2) Based on the development characteristics and distribution rules of fracture-caves, fracture-caves can be divided into three development modes,i.e.fault-controlled, strata-controlled and superficial karst-controlled, among which the development scale of the fault-controlled fracture-caves is the largest; (3) The local reservoir space was mainly formed in the Paleozoic and Cenozoic. Tectonics, lithology and hydrological conditions are the most important factors controlling the development of fracture-cave reservoir space, among which tectonics has a greater influence on the spatial development and distribution pattern of fracture-caves, controlling the development intensity, and the location and direction of fracture-caves; lithology and hydrological conditions have also substantial influence on the development degree of fracture-cave reservoir space.The high calcite content in the rocks and the rich surface runoff, the reservoir space of fracture-caves were better developed.This study provides a good outcrop analogy, which is important for the understanding of the genetic mechanism of fracture-cave carbonate reservoirs and prevention and control of coal-bottom water in the North China basin.

Kinetic and Hydrocarbon Generation of Middle Permian Black Shale Around the Bogda Mountain, Southern Junggar Basin: Implications for Petroleum Exploration

JIN Xiao, FENG Yanfang, LUO Xiaoling, WEN Xinyu, ZHANG Suowen, ZHANG Zhihuan

2023, 37(05): 1321-1335. DOI: 10.19657/j.geoscience.1000-8527.2023.005

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To explore the hydrocarbon potential of Middle Permian organic-rich mudstone around the Bogda Mountain, the hydrocarbon generation kinetics were studied in different tectonic units.Furthermore, we discussed the physicochemical significance of kinetic results from different methods and the chemical mechanism affecting activation energy.The results show that: controlled by heating temperature, the isothermal hydrous pyrolysis was mainly focused on the oil generation from kerogen, while Rock-Eval experiments show bulk hydrocarbon generation from the source rocks; major peaks of hydrocarbon generation activation energy of source rocks are ~55 kcal/mol (northeast of Bogda Mountain), ~60 kcal/mol (Quanzijie section, northern Bogda Mountain), and 65 to 70 kcal/mol (Jingjingzigou and Chaiwobu); activation energy required for alkane cyclization (higher than that of other dehydrogenation) may be the driving force of high pyrolysis activation energy of type-I organic matter, with abundant alkane components; large-scale hydrocarbon accumulation may have occurred in deep strata under thrust faults.

Genesis of Carbonate Cement and Influence on Reservoir Quality of the Badaowan Formation in AH5 Well Block of Junggar Basin

YU Jingwei, DING Wei, ZHANG Xin, QI Liqi, HUANG Shuya, ZHANG Zhiyue, ZHANG Yile

2023, 37(05): 1336-1344. DOI: 10.19657/j.geoscience.1000-8527.2023.035

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To deeply investigate the genesis of carbonate cement in reservoirs of Jurassic Badaowan Formation in AH5 well block of the Junggar Basin, and to discuss the influence on the reservoir physical property and oiliness for evaluating/predicting reservoirs in later period, we studied the types, forming period, genesis and the influence on reservoir quality through combining thin-section petrography and carbon-oxygen isotope analyses in carbonate cement.The results show at least two periods of carbonate cement in the Badaowan Formation: micritic siderite and crystalline calcite in the early diagenetic stage (limited distribution), and granular siderite, ferrocalcite and ankerite developed in the late diagenetic stage (secondary dissolution pore infill), and ankerite has the highest volume.δ¹³C_PDB of carbonate cement=-13.6‰ to -6.5‰, and δ¹⁸O_PDB=-21‰ to -18.1‰.The paleosalinity and paleotemperature estimated from the carbon-oxygen isotope compositions show that the carbonate cement was formed in freshwater environment at 112 to 136.1 ℃, based on that the forming time was the middle diagenetic period.The carbon source in carbonate cement was of organic origin through carbon diagram and analysis on natural gas isotopes.Reservoirs with carbonate cement have always bad physical property, and reservoirs with ankerite cement have better physical property through combining physical property, fluorescence thin-section and carbonate cement content analysis.The higher volume of ankerite would have more early secondary dissolved pores and better reservoir oiliness.

Geochemical Characteristics and Hydrocarbon Generation Potential of Different Lithologic Source Rocks in the Second Member of Funing Formation in Qintong Sag, Subei Basin

LI Zhipeng, YU Qiling, ZAN Lin, YU Wenduan, ZHANG Zhihuan

2023, 37(05): 1345-1357. DOI: 10.19657/j.geoscience.1000-8527.2023.049

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The second member of Paleogene Funing Formation (E₁f₂) is the main target interval of shale oil exploration and has good prospects of oil and gas exploration in Qintong Sag.Predecessors have studied the hydrocarbon generation potential and geochemical characteristics of source rocks in the E₁f₂ in the study area systematically, but the study on the geochemical characteristics and forming environment of source rocks in different sub-members and lithology of the E₁f₂ is still relatively weak, which brings difficulties to the prediction of shale oil sweet spots and resource potential evaluation, as well as the correlation of oil-sources in the E₁f₂ in the study area.In this paper, some representative shale samples of the E₁f₂ in typical wells are selected, and the geochemical characteristics, hydrocarbon generation potential and formation environment of different sub-sections and lithologic source rocks of E₁f₂ in the study area are compared by using geochemical experimental techniques.The results show that the source rocks of E₁ $f 2 4$ and E₁ $f 2 5$ in the study area have the highest abundance of organic matter, mainly type Ⅱ₁ organic matter.The abundance of organic matter in E₁ $f 2 2$ and E₁ $f 2 3$ source rocks is high, mainly type Ⅱ₁ and Ⅱ₂ organic matter.The abundance of organic matter in E₁ $f 2 1$ is relatively low, and the type of organic matter is Ⅱ₂.The lithology of source rocks in the E₁f₂ in the study area is relatively complex, mainly including mudstone, calcareous mudstone and calcareous shale.Mudstone is mainly distributed in E₁ $f 2 4$ and E₁ $f 2 5$ , with the highest abundance of organic matter, mainly type Ⅱ₁ and type Ⅰ organic matter, deposited in weak oxidation-weak reduction freshwater environment, mixed source organic matter dominated by lower aquatic organisms.The calcareous shale and calcareous mudstone are mainly distributed in E₁ $f 2 1$ , E₁ $f 2 2$ and E₁ $f 2 3$ .The organic matter abundance of calcareous shale is higher, and the organic matter type is mainly type Ⅱ₁, a few Ⅱ₂, which is deposited in a strongly reducing saline water environment and mixed source organic matter source.The organic matter abundance of the calcareous mudstone is low-medium, and the type of organic matter type is mainly Ⅱ₂, with a small amount of Ⅱ₁ and Ⅲ, which is deposited in the reducing environment of brackish water and is the source of mixed source organic matter.The source rocks of E₁f₂ are in low mature-mature stage.According to the distribution characteristics of Pr / Ph, Ga / C₃₀H, C₂₄TeT / C₂₆TT and ααα20RC₂₇ sterane / ααα20RC₂₉ sterane, the source rocks of three different lithologies in the E₁f₂ can be distinguished.These understandings can provide geochemical basis for the evaluation of oil and gas resource potential, oil-source correlation and shale oil exploration in different intervals and lithologic source rocks of the E₁f₂ in the study area.

Characteristics and Evaluation of Cretaceous Source Rocks in the Northeastern Jiaolai Basin

KE Xing, ZHAO Qingfang, WU Piao, YANG Chuansheng, LIAO Jing, GONG Jianming

2023, 37(05): 1358-1368. DOI: 10.19657/j.geoscience.1000-8527.2022.083

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Previous research shows that the Jiaolai Basin has shale gas formation conditions and exploration potential.This study encompasses systematic sampling and organic geochemistry analysis on shale outcrops in the Shuinan and Xiaoxianzhuang members of the Cretaceous Laiyang Formation in the middle and southwestern Laiyang Sag and Haiyang Sag in the Jiaolai Basin.The study aims to contribute basic data to future shale gas research and exploration in the basin.Data analysis shows that the overall quality of local Cretaceous Laiyang Formation source rocks is medium to poor.For the Shuinan Member, only 22% of the samples from the Laiyang depression are type Ⅱ₂ mature source rocks with medium organic matter abundance, only 16% of the samples from the central Haiyang depression are type Ⅱ₂ mature source rocks with low organic matter abundance, and only 22% of the samples from the southwest Haiyang depression are type Ⅱ₂ low mature source rocks with low organic matter abundance.Except for certain samples that meet the effective source rock standard, the remaining samples from these three sampling spots are non-source rocks.Through analyzing the various organic geochemical data, we considered that the samples have undergone from strong weathering and dripping, resulting in generally low content, which plays a limited role in the evaluation of local source rocks.However, our study can contribute basic data as a reference for sampling in the Laiyang Formation of the Jiaolai Basin.The quality of outcrop samples differs greatly from that of core samples, and some outcrops with stable structures may have better preservation conditions of source rocks.Combined with the comprehensive analysis of a substantial published data, we considered that the source rocks in the Shuinan Member (Laiyang Formation) underwent strong weathering in the late stage, and thus the samples show an oxidizing environment that is not conducive to organic matter preservation.Meanwhile, our results on core samples show that the source rocks were formed in the original environment and the source rocks are mainly algae, so the actual quality of Laiyang Formation source rocks may be much better than this sample.Therefore, we speculated that there is a set of good source rocks in the Shuinan Member of Laiyang Formation.

Source Rock Characteristics and Its Accumulation Contribution in the Lower Congo Basin, South Atlantic

YANG Xiongbing, WANG Hongyu, SU Yushan, GUAN Chao

2023, 37(05): 1369-1384. DOI: 10.19657/j.geoscience.1000-8527.2023.064

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The Lower Congo Basin, located along the African coast of the South Atlantic, is a petroliferous basin characterized by the salt tectonic development, which is composed of the Mesozoic rift basin and the Cenozoic passive continental margin basin.Based on two-dimensional seismic, well logging and geochemical data, combined with previous exploration and research results, we defined the types and sedimentary environments of source rocks in this basin, and clarified the source rock development characteristics and revealed their contributions to hydrocarbon accumulation.The study was conducted through thermal evolution simulation of source rocks, anatomy of typical hydrocarbon reservoirs, and analysis of the temporal-spatial distribution characteristics of hydrocarbon reservoirs.The results show that lacustrine source rocks are developed in the Bucomazi Formation under the salt layer, and marine source rocks are developed in the Iabe and Landana Formations above the salt layer.Lacustrine source rocks are developed in dry and reducing lacustrine basin environment with high organic matter content.Marine source rocks have large cumulative thickness, and developed in (semi-)abyssal environment.After the Miocene, the Bucomazi Formation source rocks entered the gas generation stage, and the Iabe Formation source rocks entered the oil generation stage, providing the main hydrocarbons in the region.The type and distribution of hydrocarbon reservoirs in the Lower Congo Basin are affected by multiple factors, such as the source rocks, faults and salt tectonics, among which the maturity and distribution of source rocks are the key ones.The subsalt oil and gas reservoirs are mostly formed by the late supply of lacustrine source rocks near the shore, while the soil and gas reservoirs above the salt were formed by the multi-stage supply of hydrocarbon from multiple source rocks.

Geochemical Characteristics and Provenance Analysis of Clastic Reservoirs in Sub-Salt Rift Period in Gabon Basin

CHEN Quanhong, YANG Huaizhong, ZHAO Hongyan, ZHANG Ke, HUANG Haibin, GUO Jiaming, LIU Xinying, YUAN Ye

2023, 37(05): 1385-1397. DOI: 10.19657/j.geoscience.1000-8527.2023.044

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Provenance of the subsalt reservoir in the Gabon basin mainly comes from the upper crust, mainly felsic rocks, together with the ancient metavolcanic-sedimentary rocks under Proterozoic convergence and subduction tectonic setting. There is certain amount of mixing of alkaline basalt and granite, with good inheritance of provenance composition and tectonic background of the source region, and no obvious difference. Differences in major and trace element compositions in Gamba and Dentale formations are unobvious. Analyses of major elements, trace elements and rare earth elements show that the provenance mainly comes from the convergence and subduction zones of active continental margin, with trench-Arc basin system. They are featured by low SiO₂ and Na₂O, similar to the Katanga supergroup and Pore group deposited in Proterozoic back-Arc basin on the western margin of Congo Craton. The Delonggu group is related to each other. The sub-salt reservoirs in the basin have high total REE content. The REE distribution pattern is related to the Proterozoic Lufili orogenic belt on the western margin of Congo Craton, but differs greatly from the Proterozoic Archean tectonic belts of San Francisco Craton in South America. This indicates that they are not the main provenance of the basin, and that the provenance is mainly the Congo Craton.

Favorable Drilling Target Selection Based on Drillability Analysis and 3D Geological Modeling: A Case Study in the Wumishan Formation, Xiong’an New Area

LU Kai, LIU Ling, BAO Zhidong, JI Hancheng, LIU Jinxia, LI Lei, LI Jin, BAO Yifei, NIU Bo, CHEN Zhenliang, CAO Yingzhuo, CHEN Xinyi, LI Zongfeng

2023, 37(05): 1398-1410. DOI: 10.19657/j.geoscience.1000-8527.2022.088

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Aiming at the characteristics of strong heterogeneity and poor drillability of deep dolomitic geothermal reservoirs in the Wumishan Formation in the Xiong’an New Area, and based on the abundant drilling, core, thin sections and logging interpretation data, we established the lithologic logging interpretation models for the strata at Xiong’an, and divided the lithologies of the Wumishan Formation into five types, i.e., crystalline dolomite, granular dolomite, microbial dolomite, siliceous dolomite and brecciated dolomite.Combined with the drillability parameters such as compressive strength, hardness and abrasiveness, the drillability of brecciated dolomite and columnar stromatolitic dolomite in the Wumishan Formation are classified as easy-drill level, that of granular dolomite and laminite are classified as medium-drill level, and that of massive dolomicrite and siliceous dolomite are classified as hard-drill level.The 3-D geological model of Xiong’an is established by using geological modeling, to clarify the strata and lithology distribution regularity and drillability variety in the study area.The Niutuozhen uplift and Rongcheng uplift are finally delineated as the drilling target areas with the highest drilling efficiency and lowest drilling cost.Gaoyang low uplift, Tongkou-Yanling low buried-hill zone, Renqiu low buried-hill zone, Niubei slope and Lixian slope are sub-favorable potential drilling targets.The depression areas are the highest risk drilling target due to their high cost and technical challenge.The results provide reference for drilling geological design, technical optimization and efficiency improvement of deep karstic geothermal reservoirs at Xiong’an.

Route Planning and Ponder of Geoscience Study Travel in Hualong County, Qinghai Province

LI Junlei, ZHANG Xujiao, WANG Yifan, ZHANG Xiangge, WANG Chongge, YUAN Xiaoning, LIU Xinlan, WANG Kaiya, RAO Haoshu, LIU Jiang, QIN Yuan

2023, 37(05): 1411-1422. DOI: 10.19657/j.geoscience.1000-8527.2023.113

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Geoscience study travel is a new engine to utilize the resources of geological heritage to carry out the popularization of geoscience, which in turn leads to geotourism. Yet, due to the fact that the guiding ideology and methodology of study route planning are still unclear, there are problems such as limited study objects, superficial course contents, insufficient scientific inquiry, and emphasizing on touring but not on studying, etc. in geoscience study in general. Hualong County in Qinghai Province, which is located in the upper reaches of the Yellow River, preserving significant geological heritage such as the convergence of Rodinia supercontinent, the subduction and closure of the Proto-Tethys Ocean, the uplift of the Tibetan Plateau and the Yellow River evolution, etc., which is a unique resource to carry out geoscience study travel. This paper discusses the design ideas of geoscience study planning from the guiding ideology, scientific questions and supporting facilities, taking Huarong County as an example.Based on the detailed field geological survey, the characteristics, types, distribution and scientific value of geological heritage in Hualong County have been systematically researched and deeply excavated. Taking the Early Paleozoic Ophiolite Suite in Laji Mountain, Xining Group-Hualong Complex Angular Unconformity, Danxia landform, Red Soil Forest landform and paleoseismic dammed-lake as the key points of the study, we have planned out the Lamu Gorge-Heshijia “the Meeting of one Billion Years”, Ahetan Village-Gongbo Gorge “Flowing Water-the Sculptor of Nature”, Keba Village-Jinyuan Township “Double-edged Sword of Neotectonic Movement”, Yaoshuiquan-Ansiduo Township “Conversion of Sea and Land with Ophiolite”, Xiaqiong Temple-Gangshan Mountain “the Winding Yellow River, the Forest Sea of Plateau”, a total of five geoscience study routes. It also proposes the methods of planning and designing geoscience study routes oriented by geoscience questions and guided by the earth system view and the theory of harmonious coexistence between man and nature. It can provide a scientific basis for the development of geotourism in Hualong County, and also has a certain reference value for the development of geoscience study in other areas.

Value and Excavation of Geological Culture: Taking Ahetan Geological Culture Village in Hualong County, Qinghai Province as An Example

WANG Yifan, ZHANG Xujiao, ZHANG Xiangge, LI Junlei, YUAN Xiaoning, WANG Kaiya, LIU Xinlan, WANG Chongge, RAO Haoshu, LIU Jiang, QIN Yuan

2023, 37(05): 1423-1434. DOI: 10.19657/j.geoscience.1000-8527.2023.114

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The construction of geological culture villages is in full swing across the country. However, its theoretical basis is not very clear, and especially most villages’ geological culture has not been fully excavated and demonstrated. Therefore, the excavation of geological culture becomes an urgent problem to be solved in the construction of geological culture villages. In 2022, Ahetan Geological Culture Village was awarded the first three-star geological culture villages in Yellow River Basin and Qinghai Province. It has made beneficial attempts and obtained good effects on geological culture excavation and three-dimensional expansion of rural culture revitalization. Based on the investigation and evaluation of heritages in Ahetan, including Yellow River terraces, ancient springs, ancient city, hollow elm tree, etc., and the in-depth excavation of geological culture, this paper systematically summarizes the definition, value, and excavation method of geological culture, and proposes it should be the theoretical basis of the construction of geological culture villages. Geological culture is all the material and spiritual wealth formed by human beings in the process of understanding, adapting, utilizing, and reforming the earth. The excavation of geological culture should focus on the close connection between geological processes and human civilization, reconstructing the history of geological processes and the harmonious relationship between humans and the planet, and demonstrating it to the public by commentary system. Through systematic summarization of geological culture and its excavation method, this paper aims to provide references for the construction and development of geological culture villages across the country.

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