Metallogeny of the Lannigou Sedimentary Rock-hosted Disseminated Gold Deposit in Southwestern Guizhou Province,China

The Lannigou deposit is a large-sized sedimentary rock-hosted disseminated gold （SRHDG） deposit located in the Youjiang Basin. It is hosted by the Middle Triassic turbidite. Wall rock alterations, including silicification, pyritization, arsenopyritization, carbonatization and argillization, commonly occur along fractures. PGE study demonstrates that either Permian basalts or Triassic ultrabasic intrnsives are unlikely to be the main source of gold mineralization. Coupled with the lack of other nmgmatic activity in the vicinity of the mining area, an amagmatic origin is proposed. Organic matter compositions and GC-MS analysis of the ores and host rocks show that the organics in the ores and the host rocks have a common source; the organic matter in the ores was mainly indigenous. The positive correlation between S2 and Au contents, along with the common occurrence of organic inclusions, suggest involvement of organic matter in the ore-forming process in terms of promoting Au leaching from the source rocks, making colloidal Au migration possible, as well as hydrocarbon reduction of sulphate. Geological and geochemical characteristics of the Lannigou deposit suggest that it was formed through circulation of meteoric water and probably less importantly organic bearing formation water driven by high geothermal gradient caused by late Yanshanian extension, which leached Au from the source bed, and then migrated as Au-bisnlfides and colloidal Au, culminating in deposition by reduction-adsorption and surface complexation of gold onto the growth surface of arsenlan pyrite.

Sedimentary Environment and Mineralization of the Black Shale Polymetallic Layer in the Early Cambrian,SW China:Constraints from in situ LA-ICP-MS Analysis of Pyrite

A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province.The mineral that makes up the polymetallic layer is related to the sedimentary facies.To analyze the differentiation mechanism between polymetallic deposits(Ni-Mo and V),the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite.The results show that δ^(34)S values of pyrite vary widely from−7.8‰to 28‰in the Gezhongwu profile,while the δ^(34)S values are relatively uniform(from 27.8‰to 38.4‰)in the Haishan profile.The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform;this indicates that the δ^(34)SO_(4)^(2−)values in seawater must be differently distributed in depositional environments.The sulfur in the Ni-Mo layer is produced after the mixing of seawater and hydrothermal fluid,while the V layer mainly originates from seawater.Overall,the Ni-Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid.

Distribution and sources of sedimentary organic matter in different aquaculture areas of northeastern Zhanjiang Bay using stable carbon and nitrogen isotopes

Zhanjiang Bay is a major aquaculture area in China with many types of mariculture products(such as oysters,fish,and shrimp).The culture area and shrimp output in Zhanjiang Bay are ranked first in China.We investigated the total organic carbon(TOC),total nitrogen(TN),TOC/TN ratio,and stable isotopes(δ^(13)C and δ^(15)N) of the fish and shrimp feed,fish and shrimp feces,and sedimentary organic matter(SOM) in and around different aquaculture areas of northeastern Zhanjiang B ay to study the impact of aquaculture activities on SOM.The average TOC contents of fish and shrimp feed were 39.20%±0.91% and 39.29%±0.21%,respectively.The average TOC content in the surface sediments of the oyster culture area,the mixed(fish and shrimp) culture area,and the cage fish farm area were 0.66%,0.88%±0.10%,and 0.58%±0.19%,respectively,which may indicate that mixed culture had a greater impact on SOM.The relatively high TOC and TN contents and relatively low TOC/TN ratios,and δ^(15)N values in the upper layer of the core sediment in the mixed culture area could also support the significant influence of mixed culture.The average δ^(13)C and δ^(15)N values of fish and shrimp feed were -20.6‰±2.2‰ and 1.8‰±1.2‰,respectively,which were different from the isotopic values of SOM in the study area.δ^(13)C and δ^(15)N values for SOM in different aquaculture areas were different from those of nearby reference stations,probably reflecting the influence of aquaculture.The δ^(13)C and δ^(15)N values in the oyster culture area(-25.9‰ and6.0‰,respectively) seemed to have reduced δ^(13)C and enriched δ^(15)N relative to those of the reference station(-24.6‰ and 5.8‰,respectively).This may reflect the influence of organic matter on oyster culture.The δ^(15)N value of the station in the mixed culture area(7.1‰±0.4‰) seemed to be relatively enriched in δ^(15)N relative to that of the reference station(6.6‰).Sedimentation and the subsequent degradation of organic matter from mixed cultures may have contributed to this phenomenon.The surface sediment at the cage fish farm area seemed to be affected by fish feces and primary production based on the indication of δ^(13)C and δ^(15)N values.The sediment core at the mixed culture region(NS6) had lower TOC/TN ratios and more positive δ^(13)C and δ^(15)N values than the sediment core at the oyster culture area,suggesting a higher proportionate contribution of marine organic matter in the mixed culture area.In summary,oyster culture,mixed culture,and cage fish culture in northeastern Zhanjiang Bay had a certain degree of impact on SOM,and mixed culture had more significant influences on SOM based on the high TOC contents and the significant vertical variations of TOC/TN ratio and δ^(15)N value in the sediment of this area.This study provides new insights into the impact of aquaculture activities on SOM content.

Sedimentary architecture of submarine channel-lobe systems under different seafloor topography:Insights from the Rovuma Basin offshore East Africa

Seafloor topography plays an important role in the evolution of submarine lobes.However,it is still not so clear how the shape of slope affects the three-dimensional(3-D)architecture of submarine lobes.In this study,we analyze the effect of topography factors on different hierarchical lobe architectures that formed during Pliocene to Quaternary in the Rovuma Basin offshore East Africa.We characterize the shape,size and growth pattern of different hierarchical lobe architectures using 3-D seismic data.We find that the relief of the topographic slope determines the location of preferential deposition of lobe complexes and single lobes.When the topography is irregular and presents topographic lows,lobe complexes first infill these depressions.Single lobes are deposited preferentially at positions with higher longitudinal(i.e.across-slope)slope gradients.As the longitudinal slope becomes higher,the aspect ratio of the single lobes increases.Lateral(i.e.along-slope)topography does not seem to have a strong influence on the shape of single lobe,but it seems to affect the overlap of single lobes.When the lateral slope gradient is relatively high,the single lobes tend to have a larger overlap surface.Furthermore,as the average of lateral slope and longitudinal slope gets greater,the width/thickness ratio of the single lobe is smaller,i.e.sediments tend to accumulate vertically.The results demonstrate that the shape of slopes more comprehensively influences the 3-D architecture of lobes in natural deep-sea systems than previously other lobe deposits and analogue experiments,which helps us better understand the development and evolution of the distal parts of turbidite systems.

Assessment of Radiological Hazards of Sedimentary, Igneous and Sediments Natural Rocks

Gamma-ray spectroscopy based on a 100% efficiency hyper-pure germanium detector was used to evaluate the activity concentrations of 226Ra, 232Th, and 40K natural radionuclides in sedimentary, conglomerate, igneous and sedi-ments rock samples collected from four different locations in Eastern desert in Egypt. The obtained activity concentrations are used to evaluate the radi-ological hazards indices, absorbed dose rate, annual effective dose equivalent in air, radium equivalent, external and internal hazard index, radiation level index, annual gonadal dose equivalent, excess lifetime cancer risk and expo-sure rate. The results show that 1) the absorbed dose rate depends on the rock type, 2) the annual effective dose equivalent in air in 71% of sample below 20 mSvy-1 (permissible limit for workers), 3) the conglomerate rocks show low radioactivity level, 4) sedimentary rocks are rich in radium while igneous rocks are rich in thorium and the sediments rocks are rich in both radium and thorium.

Biogeochemistry of sedimentary organic matter in the Yongjiang River estuary in the southern part of Hangzhou Bay,China,since the Late Pleistocene

A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare earth elements(REEs)to determine the sources and diagenesis of sedimentary organic matter(OM)of the estuary and adjacent areas since the Late Pleistocene.δ^(13)C values(-24.80‰–-23.60‰),total organic carbon/total nitrogen(TOC/TN)molar ratios(8.00–12.14),and light rare earth element/heavy rare earth element ratios(LREE/HREE=8.34–8.91)revealed the predominance of terrestrial sources of OM,mainly from the Changjiang(Yangtze)River.The lignin parameters of syringyl/vanillyl(S/V=0.20–0.73)and cinnamyl/vanillyl(C/V=0.03–0.19)ratios indicate the predominance of nonwoody angiosperms,and the vanillic acid/vanillin ratios[(Ad/Al)_(V)=0.32–1.57]indicate medium to high degrees of lignin degradation.An increasing trend ofΛ(total lignin in mg/100-mg OC)values from ca.14500 a BP to ca.11000 a BP reflected the increase in temperature during the Late Pleistocene.However,a time lag effect of temperature on vegetation abundance was also revealed.The relatively higher and stableΛvalues correspond to the higher temperature during the mid-Holocene from ca.8500 a BP to ca.4500 a BP.Λvalues decreased from ca.4000 a BP to the present,corresponding to historical temperature fluctuations during this time.Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change.

Material Composition of the Newly Discovered Zongzhuo Formation Sedimentary Mélange in the Dingri Area,Southern Tibet,and its Constraints on the Basin Controlling Dingri-Gamba Fault

The study of sedimentary mélanges holds pivotal importance in understanding orogenic processes and unveiling geodynamic mechanisms.In this study,we present findings on zircon U-Pb isotopes and whole-rock elemental data concerning the recently uncovered Zongzhuo Formation sedimentary mélanges within the Dingri area.Field observations reveal the predominant composition of the Zongzhuo Formation,characterized by a matrix of sandstone-mudstone mixed with sand-conglomerates within native blocks exhibiting soft sediment deformation.Moreover,exotic blocks originating from littoral-neritic seas display evidence of landslide deformation.Our study identifies the depositional environment of the Zongzhuo Formation in Dingri as a slope turbidite fan,with its provenance traced back to the passive continental margin.Notably,this contrasts with the Zongzhuo Formation found in the Jiangzi-Langkazi area.Based on existing data,we conclude that the Zongzhuo Formation in the Dingri area was influenced by the Dingri-Gamba fault and emerged within a fault basin of the passive continental margin due to Neo-Tethys oceanic subduction during the Late Cretaceous period.Its provenance can be attributed to the littoral-neritic sea of the northern Tethys Himalaya region.This study holds significant implications for understanding the tectonic evolution of Tethys Himalaya and for reevaluating the activity of the Dingri-Gamba fault,as it controls the active deposition of the Zongzhuo Formation.

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.

Sedimentary systems of the Oligocene Huagang Formation in the central anticline zone of the Xihu Depression,East China Sea Shelf Basin

The Xihu Depression is the largest hydrocarbon-bearing depression of the East China Sea Shelf Basin(also referred to as the ECSSB).However,the depositional systems and reservoir distribution of the Oligocene Huagang Formation in the Xihu Depression are still controversial.Under the guidance of sedimentology and stratigraphy,this study documented a marine-terrestrial transitional environment in the restricted bay setting of the Oligocene Huagang Formation through core description,well logging,and seismic data analysis.This study also revealed that the Oligocene Huagang Formation is dominated by tidal delta,estuary,and gravity flow deposits in the central anticline zone of the Xihu Depression.The new understanding of the sedimentary systems and the discovery of the transgressive gap in the eastern Diaoyu Islands uplift explain the origin of fine-grained sediments and the EW-trending sand bodies in the central depression and the sand bodies parallel to shoreline in the west slope belt,which cannot be explained by previous study results,such as southern transgression or fluvial deltas and even lacustrine deposition.Moreover,the tidal channels,tidal sand flats,and gravity flow sand bodies formed by the transgressive tides are high-quality reservoirs.The study will provide a basis for well placement and serve as guidance for the selection of favorable hydrocarbon exploration areas in the Xihu Depression.

Method and Description of Sedimentary System Characterization Based on Sequence Stratigraphy

A Oilfield is the most representative mid to deep oil field in the Bohai Sea, with the main oil bearing intervals being the upper and middle Shahejie-3 sections of the Paleogene Shahejie Formation. By combining well seismic analysis, the middle section of Shahejie-3 is divided into high-level system tract and forced lake retreat system tract, corresponding to the II oil formation and I oil formation, respectively. Using sequence stratigraphy methods, based on seismic profiles and drilling lithological cycles, the high stand system tract is divided into 5 stages of delta progradation. The first and second stages are high angle S-type progradation with large sedimentary thickness, the third stage is oblique progradation, and the fourth and fifth stages are S-oblique composite progradation;By combining seismic data, we characterized the large-scale (8 small-scale) progradation bodies of 5 periods, clarified the distribution characteristics of reservoir planes, and laid the foundation for the later exploration of oilfield potential.

Investigation of the Petrological and Geochemical Characteristics of Siderite in the Early Cretaceous Sandstone of Lacustrine Sedimentary Sequence in the Erlian Basin from Northeastern China

Siderite is a prevalent authigenic mineral in siliciclastic rocks, which usually occurred in eodiagensis period and could be used as an indicator of sedimentary environment. Some siderite precipitated in burial depth with geochemical information of basin fluid evolution. The crystal morphology, geochemical composition, and isotope values are influenced by physical and geochemical environment of precipitation. In this study, samples from the Early Cretaceous of Erlian basin in the northwestern China were collected, and mineralogy, bulk and in-situ geochemistry, C and O isotopes were analyzed to comprehensively investigate the sedimentary and diagenetic environment that the sediments experienced. Six lithofaices with three types of crystal habits were recognized in the siderite-rich sandstone, bundle crystal in spherical forms, blocky rhombs in intergranular pore and cleavage of muscovite, and micro bundle and mosaic crystals aggregates in nodular. The siderite growth proceeds through micro bundle and mosaic crystals to bundle siderite aggregates and then into blocky rhombs. The crystal evolution is also reflected by geochemical composition. The micro bundle and mosaic crystals are Casiderite. The spheritic shaped bundle aggregates are Ca-Mn-siderite. The blocky rhomb siderite shows gray part and bight part with Ca, Mg and Mn varies. Increase of Ca in block rhomb siderite suggests burial and mesodiagenesis, the high content of Mn may have linkage with eogenetic effects. The relatively positive and slightly negative δ13C value indicates meteoric water domination and influence of organic matter evolution in shallow buried time. The narrow ranges negative δ18O value suggest a small span of temperature of siderite formation.

Application of 9-component S-wave 3D seismic data to study sedimentary facies and reservoirs in a biogasbearing area:A case study on the Pleistocene Qigequan Formation in Taidong area,Sanhu Depression,Qaidam Basin,NW China

To solve the problems in restoring sedimentary facies and predicting reservoirs in loose gas-bearing sediment,based on seismic sedimentologic analysis of the first 9-component S-wave 3D seismic dataset of China,a fourth-order isochronous stratigraphic framework was set up and then sedimentary facies and reservoirs in the Pleistocene Qigequan Formation in Taidong area of Qaidam Basin were studied by seismic geomorphology and seismic lithology.The study method and thought are as following.Firstly,techniques of phase rotation,frequency decomposition and fusion,and stratal slicing were applied to the 9-component S-wave seismic data to restore sedimentary facies of major marker beds based on sedimentary models reflected by satellite images.Then,techniques of seismic attribute extraction,principal component analysis,and random fitting were applied to calculate the reservoir thickness and physical parameters of a key sandbody,and the results are satisfactory and confirmed by blind testing wells.Study results reveal that the dominant sedimentary facies in the Qigequan Formation within the study area are delta front and shallow lake.The RGB fused slices indicate that there are two cycles with three sets of underwater distributary channel systems in one period.Among them,sandstones in the distributary channels of middle-low Qigequan Formation are thick and broad with superior physical properties,which are favorable reservoirs.The reservoir permeability is also affected by diagenesis.Distributary channel sandstone reservoirs extend further to the west of Sebei-1 gas field,which provides a basis to expand exploration to the western peripheral area.

Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales,southwest Yangtze Plate,China:Insights from geochemical and petrological evidence

Upper Ordovician-Lower Silurian Wufeng-Longmaxi Formation is the most developed strata of shale gas in southern China.Due to the complex sedimentary environment adjacent to the Kangdian Uplift,the favorable area for organic-rich shale development is still undetermined.The authors,therefore,focus on the mechanism of accumulation of organic matter and the characterization of the sedimentary environment of the Wufeng-Longmaxi Shales to have a more complete understanding and new discovering of organic matter enrichment and favorable area in the marginal region around Sichuan Basin.Multiple methods were applied in this study,including thin section identification,scanning electron microscopy(SEM)observations and X-ray diffraction(XRD),and elemental analysis on outcrop samples.Five lithofacies have been defined according to the mineralogical and petrological analyses,including mudstone,bioclastic limestone,silty shale,dolomitic shale,and carbonaceous siliceous shale.The paleo-environments have been reconstructed and the organic enrichment mechanism has been identified as a reduced environment and high productivity.The Wufeng period is generally a suboxic environment and the early Longmaxi period is a reducing environment based on geochemical characterization.High dolomite content in the study area is accompanied by high TOC,which may potentially indicate the restricted anoxic environment formed by biological flourishing in shallower water.And for the area close to the Kangdian Uplift,the shale gas generation capability is comparatively favorable.The geochemical parameters implied that new favorable areas for shale gas exploration could be targeted,and more shale gas resources in the mountain-basin transitional zone might be identified in the future.

Evolutions of sedimentary facies and palaeoenvironment and their controls on the development of source rocks in continental margin basins:A case study from the Qiongdongnan Basin,South China Sea

Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China.However,the development of high-quality source rocks in this basin,especially in its deep-water areas,are still not fully understood.In this study,evolutions of sedimentary facies and palaeoenvironment and their influences on the development of source rocks in diverse tectonic regions of the Qiongdongnan Basin were investigated.The results show that during the Oligocene and to Miocene periods,the sedimentary environment of this basin progressively varied from a semi-closed gulf to an open marine environment,which resulted in significant differences in palaeoenvironmental conditions of the water column for various tectonic regions of the basin.In shallow-water areas,the palaeoproductivity and reducibility successively decrease,and the hydrodynamic intensity gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In deep-water areas,the water column of the Yacheng and Lingshui strata has a higher palaeoproductivity and a weaker hydrodynamic intensity than that of the Sanya-Meishan strata,while the reducibility gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In general,the palaeoenvironmental conditions of the water column are the most favorable to the development of the Yacheng organic-rich source rocks.Meanwhile,the Miocene marine source rocks in the deep-water areas of the Qiongdongnan Basin may also have a certain hydrocarbon potential.The differences in the development models of source rocks in various tectonic regions of continental margin basins should be fully evaluated in the exploration and development of hydrocarbons.

Controls of accommodation to sediment-supply ratio on sedimentary architecture of continental fluvial successions

The applicability of sequence stratigraphic models to continental fluvial successions has long been topic for debate. To improve our understanding of how fluvial architectures record responses to changes in the ratio between accommodation rate and sediment-supply rate (A/S), two case studies are analyzed, including a densely drilled subsurface fluvial reservoir imaged with a seismic cube, and an outcropping fluvial succession. The subsurface dataset provides a larger, three-dimensional perspective, whereas the outcrop dataset enables observation at higher resolution. On the basis of both datasets, channel-body density, channel-body stacking patterns and their formative river types are interpreted at different scales, and how these may reflect responses to A/S change (the rate of accommodation creation relative to the rate of sediment supply) are discussed. The results indicate that (i) channel-body stacking patterns undergo four evolutionary stages along with the A/S increase, i.e., multi-story, mixed multi- and two-story, two-story, and isolated patterns;(ii) channel-body density decreases along with the channel-body stacking patterns varying from multi-story to isolated;(iii) formative rivers types are interpreted as evolving from braided planforms to braided-meandering planforms and then to meandering ones, with the increase of A/S.

Lateral downslope transport and tentative sedimentary organic carbon box model in the southern Yap Trench,western Pacific Ocean

Sediment collapse and subsequent lateral downslope migration play important roles in shaping the habitats and regulating sedimentary organic carbon(SOC)cycling in hadal trenches.In this study,three sediment cores were collected using a human-occupied vehicle across the axis of the southern Yap Trench(SYT).The total organic carbon(TOC)and total nitrogen(TN)contents,δ13C,radiocarbon ages,specific surface areas,and grain size compositions of sediments from three cores were measured.We explored the influence of the lateral downslope transport on the dispersal of the sediments and established a tentative box model for the SOC balance.In the SYT,the surface TOC content decreased with water depth and was decoupled by the funneling effect of the V-shaped hadal trench.However,the sedimentation(0.0025 cm/a)and SOC accumulation rates(∼0.038 g/(m^(2)·a)(in terms of OC))were approximately 50%higher in the deeper hadal region than in the abyssal region(0.0016 cm/a and∼0.026 g/(m^(2)·a)(in terms of OC),respectively),indicating the occurrence of lateral downslope transport.The fluctuating variations in the prokaryotic abundances and the SOC accumulation rate suggest the periodic input of surficial sediments from the shallow region.The similar average TOC(0.31%–0.38%),TN(0.06%–0.07%)contents,and SOC compositions(terrestrial OC(11%–18%),marine phytoplanktonic OC(45%–53%),and microbial OC(32%–44%))of the three sites indicate that the lateral downslope transport has a significant mixing effect on the SOC composition.The output fluxes of the laterally transported SOC(0.44–0.56 g/(m^(2)·a)(in terms of OC))contributed approximately(47%–73%)of the total SOC input,and this proportion increased with water depth.The results of this study demonstrate the importance of lateral downslope transport in the spatial distribution and development of biomes.

Sedimentary architecture and distribution of intra-platform shoal in sequence framework of Permian Changxing Formation in central Sichuan Basin,SW China

Based on the comprehensive analysis of core, thin section, logging and seismic data, this study carried out the identification and comparison of Permian Changxing Formation sequences, clarified the typical sedimentary architectures of intra-platform shoal, investigated the vertical and horizontal development and distribution of intra-platform shoal in each sequence, and thus established the sedimentary evolution model of shoal body. The study results are reflected in four aspects.First, there are two complete third-order sequences(SQ1 and SQ2) in Changxing Formation in central Sichuan Basin. SQ1 is generally thick in the north and thin in the south, and SQ2 shows a thickness differentiation trend of “two thicknesses and three thinnesses”. Second, the Changxing Formation in central Sichuan Basin mainly develops intra-platform shoal, inter-shoal sea and intra-platform depression subfacies. In the vertical direction, the intra-platform shoal mainly presents two typical sedimentary sequences: stable superposed and high-frequency interbedded. Third, the stable superimposed sedimentary sequence is developed in the shoal belt at the edge of intra-platform depression, which is composed of two shoal-forming periods and located in the highstand systems tracts(HSTs) of SQ1 and SQ2. The high-frequency interbedded sedimentary sequence is developed in the southern shoal belt of intra-platform depression, which is composed of four shoal-forming periods and mainly located in the HST of SQ2. Fourth, during the SQ1 deposition, the intra-platform shoal was mainly developed at the edge of the intra-platform depression on the north side of the study area, and the inter-shoal sea subfacies was mainly developed on the south side. During the SQ2 deposition, the intra-platform shoal was widely developed in the area, forming two nearly parallel intra-platform shoal belts. The study results provide direction and ideas for exploration of Changxing Formation intra-platform shoal reservoirs in central Sichuan Basin.

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.

Effects on Sedimentary Processes via Upper Triassic Climate Forcing Caused by Multiple Impacting and Large Igneous Provinces (LIP)-Rifting/Degassing: Jordanian Platform/Arabian Plate and Germanic Basin/Central Europe

Upper Triassic sedimentary systems of both the Arabian Plate and the Germanic Basin reveal climate- and plate tectonic-forced effects through certain time-intervals experienced by architectural elements, lithofacies types, unconformities, flash flood deposits, maximum flooding surfaces/sequence boundary (MFS/SB), mineralogy, and isotope anomalies. Further, Moon recession and changes of Earth’s rotation velocity (core/mantle boundary) are associated with multiple impacting and large igneous provinces/Mid Oceanic Ridge Basalt, LIP/MORB-rifting/degassing. While acidification (by degassing, sturz-rain) does influence tectosilicates and carbonates, montmorillonite represents a key mineral as transformation of volcanic/impact glass (Tephra) to be found as co-components in and in certain pelite units as “boundary clay-suspicions” (mixture of eolian paleoloess, pelite, paleosol, and tephra → tuffite). Obviously, unconformities and sequence boundaries of both study areas separate and dislocate interrupted ∂13C and 87Sr/86Sr-data groups along the isotope curves. Both Proto-Arctic Ocean rifting/degassing comprising kimberlitic pyroclastic eruptions and Neotethys rifting/degassing as well as multiple impacting played the most important role during the Norian, followed by the incipient Central Atlantic Magmatic Provinces rifting since the Rhaetian. The following associations are encountered and dealt with in this study: Sequence boundaries-∂13C, maximum flooding surfaces-(FUCs)-∂13C, unconformities-plate motion, tephra-pelite-tuffite-montmorillonite. Norian: maximum flooding surfaces (MFSs)-“paleosol”/boundary clay?-rifting-volcanism, Moon/Earth data change. So the Norian (~221 - 206 Ma) hosts anomalous “amalgamated maximum flooding surfaces (MFSs)”, amalgamated paleosol (Jordanian Platform), multiple impacting (~219 - 214 Ma), the maximum opening of the Proto-Arctic Ocean (PAO) (~230 - 200 Ma), Neo-Tethys (NT)-subvolcanic (sills, dikes) in the NE Dead Sea area prior the Rhaetian, and a significant change of Earth/Moon relation data. The study concludes that rare and extreme events are very strongly shaping the geologic constellations in the Earth System.