Microfacies and diagenetic alteration in a semi-deep to deep lacustrine shale: The Yanchang Formation in the Ordos Basin, China

The mineralogical development and diagenetic sequence of lacustrine shales in the Chang 7 Member of the Yanchang Formation in the Ordos Basin are detailed studied.A model of their depositional system and a diagenetic diagram are proposed in this study.Through detailed petrographic,mineralogical,and elemental analyses,four distinct shale types are identified:argillaceous shale,siliceous shale,calcareous shale,and carbonate,clay,and silt-bearing shale.The main diagenetic process in argillaceous shale is the transformation of illite to smectite,negatively impacting shale porosity.Siliceous shale undergoes carbonate cementation and quartz dissolution,contributing to increased porosity,particularly in mesopores.Calcareous shale experiences diagenesis characterised by carbonate formation and dissolution,with a prevalence of siderite.In carbonate,clay,and silt-bearing shale,the dissolution of K-feldspar contributes to illitization of kaolinite.Argillaceous shale,characterised by more clay minerals and lower mesopore volume,is identified as a potential hydrocarbon seal.Siliceous shale,with the highest pore volume and abundant inter-mineral pores,emerges as a promising shale oil reservoir.These findings contribute to a comprehensive understanding of shale properties,aiding in the prediction of shale oil exploration potential in the studied area.

Callovian-Oxfordian sedimentary microfacies in the middle of Block B on the right bank of the Amu Darya Basin,Turkmenistan

The right bank of the Amu Darya Basin enjoys abundant natural gas resources,on which the Callovian-Oxfordian strata in the middle of Block B serve as the major horizons for natural gas production.However,the characteristics and distribution patterns of the sedimentary microfacies in these strata are yet to be further explored.Based on the analysis of data on drilling,logging,cores,and thin sections from 29 typical wells,as well as the regional sedimentary background,this study inferred that the middle of Block B evolved from the Callovian ramp platform into the Oxfordian rimmed platform.Moreover,this study determined that the inner-ramp intertidal-subtidal shallow-water subfacies mainly developed during the Callovian and transitioned into the shallow shelf subfacies during the Oxfordian.This study identified eight sedimentary microfacies,namely reef knoll,reef-shoal complex,bioclastic shoal,psammitic shoal,bioherm,lime mud mound,intershoal(intermound),and static-water mud.Based on research into the high-precision sequence-sedimentary microfacies framework,this study built a geological model for the development of sedimentary microfacies in the study area.According to this geological model,the sedimentary microfacies in the study area are characterized by vertical alternation of reef-shoal complex,bioclastic(psammitic)shoal,bioherm,and intershoal microfacies.Moreover,they show the development of reef knoll,reef-shoal complex,bioclastic(psammitic)shoal,and bioherm(or lime mud mound)laterally from west to east,with the physical properties of the reservoirs deteriorating from west to east accordingly.The microfacies of reef-shoal complex and the bioclastic(psammitic)shoal predominate in the study area,and their deposition and development are controlled by sequence boundaries and are also affected by paleo-landforms.The Oxfordian reef-shoal complexes were largely inherited from the Callovian uplifts and show lateral seaward progradation.

Microfacies types and distribution of epicontinental shale: A case study of the Wufeng–Longmaxi shale in southern Sichuan Basin, China

For black shales,laminae and bedding are hard to identify,grain size is difficult to measure,and trace fossils do not exist.Taking the Ordovician Wufeng–Silurian Longmaxi shale in southern Sichuan Basin,China,as an example,the types,characteristics and models of microfacies in epicontinental shale are analyzed by means of full-scale observation of large thin sections,argon-ion polishing field emission-scanning electron microscopy(FE-SEM),and kerogen microscopy.The epicontinental sea develops delta,tidal flat and shelf facies,with black shale found in microfacies such as the underwater distributary channel and interdistributary bay under delta front facies,the calcareous and clayey flats under intertidal flat facies,the calcareous and clayey shelfs under shallow shelf facies,the deep slope,deep plain and deep depression under deep shelf facies,and the overflow under gravity flow facies.Basinward,silty lamina decreases and clayey lamina increases,the grain size changes from coarse silt to fine mud,the silica content increases from about 20%to above 55%,the carbonate and clay minerals content decreases from above 40%to around 10%,and the kerogen type changes from type II2 to type II1 and type I.Provenance and topography dominate the types and distribution of shale microfacies.The underwater distributary channel,interdistributary bay,clayey flat,clayey shelf,and overflow microfacies are developed in areas with sufficient sediment supply.The calcareous flat and calcareous shelf are developed in areas with insufficient sediment supply.The deep shelf shale area is divided into deep slope,deep plain,and deep depression microfacies as a result of three breaks.The formation of epicontinental shale with different microfacies is closely related to the tectonic setting,paleoclimate,and sea level rise.The relatively active tectonic setting increases the supply of terrigenous clasts,forming muddy water fine-grained sediment.The warm and humid paleoclimate is conducive to the enrichment of organic matter.The rapid sea level rise is helpful to the widespread black shale.

Prediction of Sedimentary Microfacies Distribution by Coupling Stochastic Modeling Method in Oil and Gas Energy Resource Exploitation

In view of the problem that a single modeling method cannot predict the distribution of microfacies, a new idea of coupling modeling method to comprehensively predict the distribution of sedimentary microfacies was proposed, breaking the tradition that different sedimentary microfacies used the same modeling method in the past. Because different sedimentary microfacies have different distribution characteristics and geometric shapes, it is more accurate to select different simulation methods for prediction. In this paper, the coupling modeling method was to establish the distribution of sedimentary microfacies with simple geometry through the point indicating process simulation, and then predict the microfacies with complex spatial distribution through the sequential indicator simulation method. Taking the DC block of Bohai basin as an example, a high-precision reservoir sedimentary microfacies model was established by the above coupling modeling method, and the model verification results showed that the sedimentary microfacies model had a high consistency with the underground. The coupling microfacies modeling method had higher accuracy and reliability than the traditional modeling method, which provided a new idea for the prediction of sedimentary microfacies.

Microfacies of Deep-water Deposits and Forming Models of the Chinese Continental Scientific Drilling-SKII

Extensive transgression of lake water occurred during the Cretaceous Qingshankou Stage and the Nengjiang Stage in the Songliao basin, forming widespread deep-water deposits. Eleven types of microfacies of deep-water deposits have been recognized in the continuous core rocks from the SKII, including mudstone of still water, marlite, dolostone, off shale, volcanic ashes, turbidite, slump sediment, tempestite, seismite, ostracoda limestone and sparry carbonate, which are divided into two types： microfacies generated due to gradually changing environments （Ⅰ） and microfacies generated due to geological events （Ⅱ）. Type Ⅰ is composed of some special fine grain sediments such as marlite, dolomite stone and oil shale as well as mudstone and Type Ⅱ is composed of some sediments related to geological events, such as volcanic ashes, turbiditie, slump sediment, tempestite, seismite, ostracoda limestone. The formation of sparry carbonate may be controlled by factors related to both environments and events. Generally, mudstone sediments of still water can be regarded as background sediments, and the rest sediments are all event sediments, which have unique forming models, which may reflect controlling effects of climatics and tectonics.

Microfacies and Depositional Environments of Miocene Isolated Carbonate Platforms from Central Luconia, Offshore Sarawak, Malaysia

The Luconia Province-offshore Sarawak-is a key geological unit for understanding the distribution of hydrocarbon resources in Malaysia. Nevertheless, little effort has been made to address the palaeoenvironmental characteristics of the Tertiary carbonates in the key sector of Central Luconia.We study the sedimentology and petrography of core samples from a well in Central Luconia, for which thirteen microfacies have been identified reflecting different depositional settings. This is the first microfacies scheme elaborated for Luconian carbonates. Lithofacies and microfacies distribution are compatible with deposition in a reef complex, originating around a framework reef, within the euphotic zone. Sediments were deposited in environments of backreef, reef crest, and forereef. The fair weather wave base is marked by the presence of coralline red algae, foraminifera, decreasing degree of bioclast fragmentation and other microfacies features. As a result, a depositional-environmental model is constructed, depicting a reef complex built around a framework reef developed on the margin of an isolated platform. In addition, an innovative, preliminary time series analysis of facies, microfacies and depositional environment data reveal the existence of seasonal cycles in the stacking patterns of facies and microfacies.

New Insights into the Depositional Environments of Ordovician Carbonate Formations in the Yubei Area of Tarim Basin Based on Standard Microfacies Types

Objective The Yubei area is located in the mid-east Maigaiti slope of southwestern Tarim Basin, China, with an exploration history of several years. Recent exploration has preliminarily indicated that the Ordovician carbonate formations in this area have some oil and gas potential. Carbonate microfacies provides material basis for reservoir development, seal formation and hydrocarbon generation. Therefore, this work utilized the standard microfacies （SMF） types to study the microfacies of the Ordovician formations in the Yubei area in order to provide theoretical basis for the next exploration.

Microbiostratigraphy, microfacies and sequence stratigraphy of upper cretaceous and paleogene sediments, Hendijan oilfield, Northwest of Persian Gulf, Iran

Hendijan oilfield is located on Northwest of Pesian Gulf offshore of Iran and geologically in the Dezful embayment. In this study, the paleosedimentary depositional environment of the Early Cenomanian to Late Eocene deposits of the Sarvak, Ilam, Gurpi, Pabdeh and JahrumPabdeh Formations was evaluated using microbiostratigraphy, microfacies and D-INPEFA curves which are an accurate method in sequence stratigraphy in terms of regression and transgression of the sea. Also, we used limited elemental geochemical data of oxygen and carbon isotopes in compare with palaeontological data to infer the upper part, 10 m, of the Sarvak Formation. Statistical correlation analyses of geochemical data from upper part of the Sarvak Formation enable inference of differences in paleoconditions at this part and Sarvak Formation, and another Formation, Ilam, was distinguished. Palaentilogical analysis using planktonic foraminifera and calcareous nannofossils enables inference about time scale of each Formation. Petrographic data and different sediment textures support those inferences resulted from Gamma ray logs as D-INPEFA curves about different paleo-conditions that occurred during the development of the studied Formations. Synthesis of the analyses leads to the final interpretation that upper Cretaceous, Sarvak, Ilam and Gurpi Formations, at the Hendijan oil field were formed in a carbonate ramp that was likely closed to the open sea, where Gurpi Formation was deposited, by a shallow barrier that allowed seawater recharge into the basin and deep marine basin where Paleogene sediments, Pabdeh and Jahrum-Pabdeh, were deposited.

Microfacies Patterns and Depositional Environments of the Sarvak Formation in the Abadan Plain, Southwest of Zagros, Iran

The Sarvak Formation is the second major oil-bearing reservoir in the south and south west of Iran. The Middle Cretaceous Sarvak formation in the Zagros Mountains (Zagros Basin) is mainly composed of carbonate sequences. Based on facies studied, thirteen microfacies were recognized in the studied area, which were categorized in the three facies groups: including inner ramp, mid ramp and outer ramp. Evidences such as the gradual changes in the facies (basin slope), the absence of extensive uninterrupted barrier reef, the lack of calciturbidite and gravity sediments as well as the high proportion of grain-supported indicated that the Sarvak Formation was deposited in the ramp like depositional system, particularly on an inner ramp setting. Inner ramp facies group is the principal setting and subdivided to tidal flat, restricted and unrestricted lagoon as well as shoal sub-environments.

Biostratigraphy,Microfacies and Depositional Environment of the Sarvak Formation at the Pyun Anticline(Zagros Basin,Southwest of Iran)

The Sarvak Formation is a carbonate sequence of Late Albian–Early Turonian age in Zagros Basin in Iran.In this investigation,the Sarvak Formation at the Pyun Anticline section(Izeh Zone)has been studied.It consists of 797 m thick limestone which overlies the Kazhdumi Formation conformably and underlies the Gurpi Formation unconformably at the Pyun Anticline.A very rich fossil association(85 genera and 132 species)characterizes the Pyun section.Based on the stratigraphic distribution of diagnosed foraminifera,five biozones are established:1,Muricohedbergella-Globigerinelloides sp.assemblage zone(Late Albian);2,Praealveolina iberica-Chrysalidina gradata interval zone(Early Cenomanian);3,Chrysalidina gradata-Cisalveolina fraasi(fallax)and C.lehneri interval zone(Middle Cenomanian);4,C.fraasi(fallax)and C.lehneri-Praetaberina bingistani assemblage zone(Late Cenomanian);5,Nezzazatinella picardi-MangashtiaDicyclina assemblage zone(Early Turonian).Based on the petrographic and sedimentological analyses,some 13 carbonate microfacies were identified.The investigated microfacies confirm a ramp-type paleoenvironment.These microfacies,from distal to proximal environments,consist of:MF1:planktonic foraminifera wackestone-packstone;MF2:Oligostegina planktonic foraminifera wackestone to packstone;MF3:planktonic-benthic foraminifers sponge spicules wackestonepackstone;MF4:rudist floatstone;MF5:rudist rudstone;MF6:bioclast intraclast grainstone;MF7:peloid intraclast grainstone;MF8:benthic foraminifers rudist grainstone-packstone;MF9:peloid bioclast grainstone-packstone;MF10:bioclast(benthic foraminifers)wackestone-packstone;MF11:peloid bioclast packstone;MF12:dacycladacea benthic foraminifera packstone-wackestone;MF13:miliolids wackestone-packstone.

Auto recognition of carbonate microfacies based on an improved back propagation neural network

Though traditional methods could recognize some facies, e.g. lagoon facies, backshoal facies and foreshoal facies, they couldn't recognize reef facies and shoal facies well. To solve this problem, back propagation neural network(BP-ANN) and an improved BP-ANN with better stability and suitability, optimized by a particle swarm optimizer(PSO) algorithm(PSO-BP-ANN) were proposed to solve the microfacies' auto discrimination of M formation from the R oil field in Iraq. Fourteen wells with complete core, borehole and log data were chosen as the standard wells and 120 microfacies samples were inferred from these 14 wells. Besides, the average value of gamma, neutron and density logs as well as the sum of squares of deviations of gamma were extracted as key parameters to build log facies(facies from log measurements)-microfacies transforming model. The total 120 log facies samples were divided into 12 kinds of log facies and 6 kinds of microfacies, e.g. lagoon bioclasts micrite limestone microfacies, shoal bioclasts grainstone microfacies, backshoal bioclasts packstone microfacies, foreshoal bioclasts micrite limestone microfacies, shallow continental micrite limestone microfacies and reef limestone microfacies. Furthermore, 68 samples of these 120 log facies samples were chosen as training samples and another 52 samples were gotten as testing samples to test the predicting ability of the discrimination template. Compared with conventional methods, like Bayes stepwise discrimination, both the BP-ANN and PSO-BP-ANN can integrate more log details with a correct rate higher than 85%. Furthermore, PSO-BP-ANN has more simple structure, smaller amount of weight and threshold and less iteration time.

Microfacies Analysis and Paleoecology of the Oligocene Succession in a Central Tethyan Carbonate Platform,Zagros Basin,SW Iran

Two stratigraphic sections(Arjooieh and Firoozabad)of the Mymand anticline,located in the Interior Fars subbasin of the Zagros Mountains,were measured and sampled,in order to document sedimentological characteristics,microfacies types and paleo-seagrasses indicators of the Oligocene succession(Asmari Fm.).Planktonic and benthic foraminifera and coralline red algae are the principal fossils from these strata.Foraminifera are represented by the following families:Soritidae,Peneroplidae,Austrotrillinidae,Alveolinidae,Planorbulinidae,Discorbidae,Lepidocyclinidae,Amphisteginidae,Rotaliidae,Nummulitidae and Globigerinidae.Nine microfacies types were recognized,namely planktonic foraminifera-peloidal packstone(MF1),bioclast nummulitid/Nerorotalia/Amphistegina packstone-grainstonerudstone-floatstone(MF2),Neorotalia-echinoid coralline red algae packstone-grainstone(MF3),coral boundstone(MF4),coral/coralline red algae rudstone-floatstone-packstone-grainstone(MF5),diverse imperforate foraminifera bioclast packstone-grainstone(MF6),peloid wackestone-packstone-grainstone(MF7),fenestrated mudstone and microbial mats(MF8)and anhydrite(MF9).MF1 indicates an outer ramp,MFs 2-4 represent a mid-ramp and MFs 5-9 are interpreted as inner ramp environment.Paleo-seagrass indicators consisting of foraminifera,hooked and tabular forms of coralline red algae and corals.They were identified in MFs 5 and 6,reflecting the presence of vegetated environments within the mid/inner ramp setting.The Mymand anticline was dominated by the outer ramp environment at the start of the Rupelian.Mid to inner ramp environments prevailed during the Rupelian.The Chattian corresponds to the spread of the inner ramp setting over the Mymand anticline.

Characteristics and impacts on favorable reservoirs of carbonate ramp microfacies: A case study of the Middle-Lower Ordovician in Gucheng area,Tarim Basin,NW China

Based on the latest drilling core, thin section, 3D seismic, well logging data as well as exploration results, the sequence stratigraphy and sedimentary microfacies of the Middle-Lower Ordovician carbonates in Gucheng area, and their controlling effects on the development of reservoir were examined by the theories and methods of fine carbonate sedimentology.The results show that the Middle-Lower Ordovician in Gucheng area is a set of typical carbonate ramp deposits, which can be divided into 10 microfacies in 4 subfacies as follows: back ramp, inner shallow ramp, outer shallow ramp, and deep ramp. The back ramp subfacies consists of muddy-dolomitic flat and dolomitic lagoon microfacies;it is dominated by lamellar micrite dolomite tight in lithology. The inner shallow ramp subfacies includes dolomitic shoal and dolomitic flat in shoal top and dolomitic flat between shoals microfacies;it is mainly composed of crystal dolomite with metasomatic residual structure, as well as abundant karst vugs and intercrystalline pores. The crystal dolomite has an average porosity of 4.36%. The outer ramp subfacies includes medium-high and low energy grain shoal and inter-shoal microfacies;it is dominated by sandy limestone,oolitic limestone, and micrite limestone with few pores. The deep ramp subfacies is dominated by low-energy argillaceous deposits, with local presences of storm shoal microfacies. The Lower-Middle Ordovician has six third-order sequences from bottom to top, among which sequence(SQ3) represents the third member of Yingying Formation. The main reservoir has three fourth-order high-frequency sequences. Apparently, the favorable reservoir in the study area is jointly controlled by sedimentary microfacies and high frequency sequence in the carbonate ramp. The former controls the primary pore structure, and the latter controls the intensities of karstification exposure and dolomitization in the penecontemporaneous period. The dolomitic shoals and top dolomitic flats of different stages, superimposed and connected into favorable reservoirs of considerable scale like "platform margin", are favorable exploration facies in the carbonate ramp.

Sedimentary microfacies of the H8 member in the Su14 3D seismic test area

The distribution of sedimentary microfacies in the eighth member of the Shihezi formation（the H8 member） in the Sul4 3D seismic test area was investigated.A Support Vector Machine（SVM） model was introduced for the first time as a way of predicting sandstone thickness in the study area.The model was constructed by analysis and optimization of measured seismic attributes.The distribution of the sedimentary microfacies in the study area was determined from predicted sandstone thickness and an analysis of sedimentary characteristics of the area.The results indicate that sandstone thickness predictions in the study area using an SVM method are good.The distribution of the sedimentary microfacies in the study area has been depicted at a fine scale.

Microfacies and Sedimentary Environments of the Fahliyan Formation from the Southwest of Iran (Shiraz, Zagros)

The Fahliyan Formation is a carbonate sequence of Lower Cretaceous (Berriasian-Hauterivian) in age and was deposited in the Zagros sedimentary basin. This formation is a part of Khami Group and is a reservoir rock in Zagros Basin. This formation was investigated by a detailed petrographic analysis in order to clarify the depositional facies and sedimentary environment in the Kuh-e-Gadvan in Fars Province. Petrographic studies led to the recognition of nine microfacies that were deposited in four facies belts: tidal flat, lagoon, and barrier and shallow open-marine. An absence of turbidite deposits, reefal facies, and gradual facies changes indicate that the Fahliyan Formation was deposited on a carbonate ramp.

Microfacies and palaeoenvironments of lateCisuralian and Guadalupian(Early to MiddlePermian)alatoconchid-bearing limestone inLoei fold belt,Indochina Terrane

This study presents the first record of Early Permian alatoconchid bivalves from Thailand,theErawan section,in the north of Loei fold belt with prolific fusulines in association with gastropods,and brachiopods.Fusuline taxa are dominated by Pseudofusulina sp.with Darvasites sp.,Staffella cf.labanalensis,Staffella sp.,Nankinella sp.,Neofusulinella sp.,Schubertella sp.,Pamirina darvasica,Pseudoendothyra sp.and others,indicating an Artinskian age.Fusuline wackestone with common,well-preserved smaller foraminifers,Pseudovermiporella sp.and ostracods indicates a restricted lagoon environment with low to moderate water circulation.These fossils,along with well-preserved,articulated alatoconchids in life-position,suggest the autochthonous nature of the deposits in an intertidal environment.In the central part of the fold belt,the Pak Chong section exhibits intervals of alatoconchid biostromes andcoquinites.Carbonate build-ups of the alatoconchid biostromes with gregarious bivalves,in life-positionembedded in a micritic wackestone matrix,suggest their preferred life habit and environment.The bivalvecoquinites containing packed bivalve shells and fragments,however,indicate a high-energy event.This rockfabric along with common fusuline storm sheets suggests occasional storm events in a restricted,with moderate water circulation to open lagoon environment.Fusulines are predominated by staffellids and othersincluding Staffella sphaerica,Staffella sp.,Sphaerulina croatica,Pisolina subsphaerica,Nankinella sp.,Neoschwagerina simplex,Presumatrina sp.,Afghanella sp.and others,indicating a Wordian(Middle Permian)age.In the southern portion of the fold belt along the Thai-Cambodian border,the Khao Taa Ngog sectioncontains limestone with alatoconchid shells with massive rugose corals which formed local carbonate build-upsin high-energy open platform environments.Poorly-sorted bioclasts with common fusuline tests,shell fragments and coated grains suggest an open marine,lagoon,back reef environment.The occurrence of a fusulineassemblage including Neoschwagerina sp.,Yabeina sp.,Lepidolina sp.,Codonofusiella sp.,Verbeekina verbeeki and Chusenella sp.indicates the Capitanian(late Middle Permian)age.

Sedimentary microfacies of Member 5 of Xujiahe Formation in the Dongfengchang area, Sichuan Basin

Member 5 of the Upper Triassic Xujiahe Formation(T_(3)X_(5))in central Sichuan Basin has made a breakthrough in exploration recently.However,this new stratum has not been investigated sufficiently with respect to basic geology,making its types and distribution of sedimentary facies unclear,which severely restricts its subsequent exploration evaluation.In this study,types of sedimentary microfacies in the first sand group of T_(3)X_(5)(T_(3)X_(5)^(1))are clarified through core observation and logging interpretation using core,log and seismic data,and then distribution of sedimentary microfacies in T_(3)X_(5)^(1) is determined according to seismic waveform features and seismic prediction.The results show that T_(3)X_(5)^(1) in the Dongfengchang area is mainly composed of deltaic deposits of several microfacies,such as delta front underwater distributary channel,sheet sand,and interdistributary bay.On seismic sections,different microfacies are significantly different in waveform features,the underwater distributary channel is characterized by one trough between two peaks,while diversion bay exhibits chaotic reflections between T6 and T51.The sedimentary microfacies varied greatly during the depositional period of T_(3)X_(5)^(1) in the Dongfengchang area,this is because that the sediment supply was mainly controlled by the southwest and southeast provenance regions.Three superimposed underwater distributary channels are developed in the Dongfengchang area.The phase-1 superimposed underwater distributary channel in the northwest transition to sheet sand in the northeast,the phase-2 superimposed underwater distributary channel in the south extends shortly,the phase-3 superimposed underwater distributary channel in the northeast has a large development scale.These research findings are helpful to guide the subsequent exploration of T_(3)X_(5) gas reservoir and also theoretically significant for investigating the depositional evolution of the Xujiahe Formation in central Sichuan Basin.

Carbonate Ontology and Its Application for Integrating Microfacies Data

Carbonate rocks record essential information on changes in paleoclimate and paleoceanography. Abundant geological and geochemical data of carbonate rocks have been accumulated over the past decades;however, most of the data are stored in the published literature with highly unstructured forms, and are thus difficult to reuse. The ontology is a standard knowledge model for data integration, which can promote data storage and reutilization. This study proposes a carbonate ontology that represents the concepts in carbonate microfacies. The carbonate ontology constructed by the top-down process contains 215 terms of classifications and petrographic descriptions of carbonate rocks. Furthermore, carbonate microfacies of the Cretaceous(Aptian) carbonate platform in the Betic Cordillera and Jurassic carbonate platform in Tibet provide the data from case studies for the testing and initial validation of the proposed ontology. The carbonate ontology is under continuous expansion following the bottom-up approach and open access on the website of the deep-time digital Earth(DDE) program.

A knowledge graph for standard carbonate microfacies and its application in the automatical reconstruction of the relative sea-level curve

The reconstruction of high-resolution sea-level variation curves in deep time based on the standard car-bonate microfacies knowledge graph(SMFKG)is of great scientific significance for exploring the Earth system evolution and predicting future sea-level and climate changes.In this study,the concepts,attri-butes,and relationships among standard carbonate microfacies(SMF)are comprehensively analyzed;an ontology layer is established and its data layer is constructed using thin-section descriptions;and finally,the SMFKG is established.Additionally,based on the knowledge graph,an application for automatically identifying SMF using identification markers and reconstructing the high-resolution relative sea-level variation curve using the SMF and facies zones is compiled.Then,all thin sections of the late Ediacaran Dengying Formation in the western margin of the Yangtze Platform are observed and described in detail,the SMF and facies zones are identified automatically,and the relative sea-level curve is recon-structed automatically using the SMFKG.The reconstruction results show that the Yangtze Platform experienced four sea-level rise and fall cycles in the late Ediacaran,of which two intense regressions led to subaerial-exposed unconformities in the interior and top of the Dengying Formation,which is highly consistent with previous research results.This shows that the high-resolution relative sea-level variation curve in deep time can be reconstructed efficiently and intelligently using the SMFKG.Additionally,in the near future,the combination of an automatic digital slide-scanning system,machine-learning techniques,and the SMFKG can achieve one-stop fully automatic SMF recognition and reconstruction of high-resolution relative sea-level variation curves in deep time,which has a high application value.