ENVIRONMENTAL EVOLUTION OF ORDOS DESERT IN CHINA SINCE 1.1MA B. P. AS INDICATED BY YULIN STRATIGRAPHICAL SECTION AND ITS GRAIN-SIZE ANALYSIS RESULTS

Yulin section is a typical sedimentary record for reflecting the environmental evolution of Ordos Desert, China in the past 1.1Ma. By analyzing its sequence and grain-size composition some views have been put forward in this paper as follows. The layers of sand, loess and palaeosol in Yulin section were respectively formed by wind and the pedogenesis on parent material of the sand and loess. Since 1.1Ma B. P., Ordos Desert has alternately experienced 11 stages of shifting dunes under extreme cold-dry climatic environment, 7 stages of fixed and semi-fixed dunes and 8 stages of dust (loess) under cold-dry climatic condition; and the pedogenesis environment under 15 times of warm-humid climate and 3 times of temperate-humid climate (brownish-drab soils and black soils formed respectively). The aeolian sand had already existed in Ordos Desert at latest by 1.1Ma B. P., and from that time on it has undergone a series of alternative processes of shifting sands, fixed and semi-fixed dunes, loess and soils. Ordos Desert has been situated in the transitional belt of the Mongolian High Pressure and margin of the southeast summer monsoon since 1.1Ma B. P., and influenced repeatedly by migration of the lithofacies belts of shifting sands, fixed and semi-fixed dunes, loess and soils, which have been caused by the climatic fluctuations of glacial and interglacial periods.

The Low Lake-Level Record according to the Selin Co Stratigraphical Basis and Multi-Proxies during the Last Glacial Maximum in the Central Tibetan Plateau

Objective The lake levels in the eastern and southern Asia are regarded as low lake-level owing to precipitation decreasing based on the records of lake-level fluctuation in the continental interior lakes since the last glacial maximum（LGM）（14C 18±1 kaBP,since 20 kaBP）in the Central Asia.Higher lake-level appeared in the transition belt between western Kunlun Mountain and the central Tibetan Plateau.

Stratigraphical Time——Correlation and Mass Extinction Event Near Permian——Triassic Boundary in South China

Shaw's method used to correlate 40 sections across the Permo-Triassic boundary in South China is applied in the paper. Two steps are adopted to get an Integral Composite Section (ICS) by synthesizing these data : First , South China is divided into five areas and composite section developed for each area . Then the second step . the Changxing composite section is regarded as a composite standard (CSRS) while the ICS is produced by matching the CSRS with composite sections of the other areas. Three biozones in the Changxingian and two biozones in the Griesbachian can be discerned on the basis of computing Z values in the ICS. These biozones are marked by the Z values which quantitatively represent their time ranges ; therefore , they may increase accuracy of stratigraphic time correlation . The mass extinction at the end of the Permian is an abrupt event that is supported by the relative rate of extinction near the P/T boundary . About 90% of invertebrate species died out by the end of the Permian . The duration of the mass extinction is rather short ,approximately 0.018Ma .

Geochemical Properties and StratigraphicalCorrelation of Frasnian-Famennian TransitionalStrata in Wuzhishan Section

The qualities of petrology and paleobiology in Wuzhishan Section are studied. Several geo-chemical anomalies are recognized, such as: high rare earth element content, high pyrite content and Ni anomalies. It could be correlated with Nandong Section in Xiangzhou County and the F/F boundary could be determined according to Ni anomalies. The results of the study indicate that the geochemical anomaly plays an important role in stratigraphic correlation in non-fossil stratum.

Relationship between sequence stratigraphical boundary and chronostratigraphical boundary

Sequence stratigraphy is a science studying the genetically related facies within achronostratigraphic framework. Sequence is the basic unit of sequence stratigraphy,which is a 'succession of genetically related, essentially conformable strata bounded

Tectonic evolution and source rocks development of the super oil-rich Bohai Bay Basin,East China

The Bohai Bay Basin,as a super oil-rich basin in the world,is characterized by cyclic evolution and complex regional tectonic stress field,and its lifecycle tectonic evolution controls the formation of regional source rocks.The main pre-Cenozoic stratigraphic system and lithological distribution are determined through geological mapping,and the dynamics of the pre-Cenozoic geotectonic evolution of the Bohai Bay Basin are investigated systematically using the newly acquired high-quality seismic data and the latest exploration results in the study area.The North China Craton where the Bohai Bay Basin is located in rests at the intersection of three tectonic domains:the Paleo-Asian Ocean,the Tethys Ocean,and the Pacific Ocean.It has experienced the alternation and superposition of tectonic cycles of different periods,directions and natures,and experienced five stages of the tectonic evolution and sedimentary building,i.e.Middle–Late Proterozoic continental rift trough,Early Paleozoic marginal-craton depression carbonate building,Late Paleozoic marine–continental transitional intracraton depression,Mesozoic intracontinental strike-slip–extensional tectonics,and Cenozoic intracontinental rifting.The cyclic evolution of the basin,especially the multi-stage compression,strike-slip and extensional tectonics processes in the Hercynian,Indosinian,Yanshan and Himalayan since the Late Paleozoic,controlled the development,reconstruction and preservation of several sets of high-quality source rocks,represented by the Late Paleozoic Carboniferous–Permian coal-measure source rocks and the Paleogene world-class extra-high-quality lacustrine source rocks,which provided an important guarantee for the hydrocarbon accumulation in the super oil-rich basin.

Well Logging Stratigraphic Correlation Algorithm Based on Semantic Segmentation

Well logging curves serve as indicators of strata attribute changes and are frequently utilized for stratigraphic analysis and comparison.Deep learning,known for its robust feature extraction capabilities,has seen continuous adoption by scholars in the realm of well logging stratigraphic correlation tasks.Nonetheless,current deep learning algorithms often struggle to accurately capture feature changes occurring at layer boundaries within the curves.Moreover,when faced with data imbalance issues,neural networks encounter challenges in accurately modeling the one-hot encoded curve stratifi cation positions,resulting in signifi cant deviations between predicted and actual stratifi cation positions.Addressing these challenges,this study proposes a novel well logging curve stratigraphic comparison algorithm based on uniformly distributed soft labels.In the training phase,a label smoothing loss function is introduced to comprehensively account for the substantial loss stemming from data imbalance and to consider the similarity between diff erent layer data.Concurrently,spatial attention and channel attention mechanisms are incorporated into the shallow and deep encoder stages of U²-Net,respectively,to better focus on changes in stratifi cation positions.During the prediction phase,an optimized confi dence threshold algorithm is proposed to constrain stratifi cation results and solve the problem of reduced prediction accuracy because of occasional layer repetition.The proposed method is applied to real-world well logging data in oil fi elds.Quantitative evaluation results demonstrate that within error ranges of 1,2,and 3 m,the accuracy of well logging curve stratigraphic division reaches 87.27%,92.68%,and 95.08%,respectively,thus validating the eff ectiveness of the algorithm presented in this paper.

Main controlling factors and exploration enlightenment of aluminous rock series gas reservoirs in Ordos Basin,NW China

Based on the data of outcrop,core,logging,gas testing,and experiments,the natural gas accumulation and aluminous rock mineralization integrated research was adopted to analyze the controlling factors of aluminous rock series effective reservoirs in the Ordos Basin,NW China,as well as the configuration of coal-measure source rocks and aluminous rock series reservoirs.A natural gas accumulation model was constructed to evaluate the gas exploration potential of aluminous rock series under coal seam in the basin.The effective reservoirs of aluminous rock series in the Ordos Basin are composed of honeycomb-shaped bauxites with porous residual pisolitic and detrital structures,with the diasporite content of greater than 80%and dissolved pores as the main storage space.The bauxite reservoirs are formed under a model that planation controls the material supply,karst paleogeomorphology controls diagenesis,and land surface leaching improves reservoir quality.The hot humid climate and sea level changes in the Late Carboniferous–Early Permian dominated the development of a typical coal-aluminum-iron three-stage stratigraphic structure.The natural gas generated by the extensive hydrocarbon generation of coal-measure source rocks was accumulated in aluminous rock series under the coal seam,indicating a model of hydrocarbon accumulation under the source.During the Upper Carboniferous–Lower Permian,the relatively low-lying area on the edge of an ancient land or island in the North China landmass was developed.The gas reservoirs of aluminous rock series,which are clustered at multiple points in lenticular shape,are important new natural gas exploration fields with great potential in the Upper Paleozoic of North China Craton.

Outcrops as windows to petroleum systems:Insights from the southern Bida Basin,Nigeria

The study assessed petroleum systems in the southern Bida Basin,Nigeria,focusing on the Cretaceous sediments.Reservoirs comprise Lokoja and Patti Formation sandstones,while shales,claystone,and siltstone serve as source rocks and stratigraphic traps/seals.Detailed studies delineating the key elements of the petroleum systems in the basin have not been conducted due to a lack of subsurface data.The goal of the current study was to use field observations,Scanning Electron Microscopy(SEM),X-ray diffraction(XRD),and geochemical and geomechanical data to evaluate key components of petroleum systems in the southern Bida Basin.The results presented in this investigation are intended to attain specific objectives,especially those lacking in the basin's study sections.Petrophysical analysis revealed that the Lokoja Sandstone has porosity of 37%-39.5%and moderate permeability of 23.22-42.29 mD.The Patti Formation sandstone reservoirs exhibited high porosity(38%-42%)and moderate to good permeability(31.54-66.48 mD),suggesting good potential reservoirs.SEM results revealed intragranular pores and micro-fractures in the Patti Shale,whereas the sandstone reservoirs in the Lokoja and Patti formations displayed fractures,facilitating hydrocarbon migration.Quartz was the dominant mineral in the sandstone units of both formations.XRD analysis revealed that brittle and clay minerals influenced the microstructure of Patti Shale.Geochemical analysis indicated promising petroleum potential in the Patti Shale,with a total organic carbon(TOC)content of 1.87 wt%,free hydrocarbon from kerogen(S1)of 0.41 mg/g,hydrogen index(HI)of 0.75 mg HC/g TOC,and production index(PI)of 0.17.The Patti and Lokoja formations'shale,claystone,and siltstone exhibited sealing potential,with a plasticity index of 24-35 and coefficient permeability of 2.8×10^(-4)-3.6×10^(-4)cm/s.Field studies,XRD,geochemical data,and geomechanical index values have confirmed the key components of the petroleum system,which in turn facilitate hydrocarbon generation,migration,accumulation,and entrapment in the basin.

An intelligent automatic correlation method of oilbearing strata based on pattern constraints:An example of accretionary stratigraphy of Shishen 100 block in Shinan Oilfield of Bohai Bay Basin,East China

Aiming at the problem that the data-driven automatic correlation methods which are difficult to adapt to the automatic correlation of oil-bearing strata with large changes in lateral sedimentary facies and strata thickness,an intelligent automatic correlation method of oil-bearing strata based on pattern constraints is formed.We propose to introduce knowledge-driven in automatic correlation of oil-bearing strata,constraining the correlation process by stratigraphic sedimentary patterns and improving the similarity measuring machine and conditional constraint dynamic time warping algorithm to automate the correlation of marker layers and the interfaces of each stratum.The application in Shishen 100 block in the Shinan Oilfield of the Bohai Bay Basin shows that the coincidence rate of the marker layers identified by this method is over 95.00%,and the average coincidence rate of identified oil-bearing strata reaches 90.02% compared to artificial correlation results,which is about 17 percentage points higher than that of the existing automatic correlation methods.The accuracy of the automatic correlation of oil-bearing strata has been effectively improved.

Sedimentary Facies Characteristics of Chang 6 and Chang 7 Members of Yanchang Formation in Heshui Area, China

This paper takes Chang 6 and Chang 7 of Yanchang Formation in Heshui area of China as the research object. This study first divides the strata of Chang 6 and Chang 7. According to the review data, significant geological activities have caused a large settlement of the strata in this area. During the Chang 6 period, a lacustrine basin sedimentary system developed, reaching its peak in the Chang 7 period. The Chang 6 and Chang 7 members primarily feature deep-water gravity flow sedimentary systems, which can be categorized into three subfacies: outer fan, middle fan, and inner fan. These systems also exhibit turbidite fan sedimentary patterns, ranging from deep lake to semi-deep lake facies. By examining these sedimentary models, we can identify different types of turbidite deposits. Understanding the process of gravity flow deposition and the evolution of ancient lakes is crucial for guiding oil and gas exploration and conducting paleogeographic research.

华北克拉通南缘安沟群的SHRIMP年龄及地层对比

华北克拉通南缘安沟群的时代及地层划分对比一直存有争议。侵吞安沟群的许台花岗岩原划为古元古代,本文通过SHRIMP测试,获得其精确的形成年龄为2503±11Ma。安沟群石梯沟组变质酸性火山岩的SHRIMP锆石U-Pb年龄为2521±11Ma,安沟群寨沟组变质酸性火山岩的SHRIMP锆石U-Pb年龄为2517±12Ma,表明安沟群形成于新太古代,与登封群和五台群的形成时代基本一致。安沟群地层的原岩组合为基性火山岩—中酸性火山岩、泥质-碎屑沉积岩和少量碳酸盐岩,总体上与登封群和五台群的原岩组合类似。

Magnetostratieraphy of the Red Beds in the Hengyang Basin

This paper discusses the Cretaceous-Tertiary magnetic polarity sequence of the the Hengyang Basin on the basis of magnetostratigraphic study. The age of each stratigraphic unit has been determined with the magnetic polarity time scale combined with 39Ar/40Ar dating, thus providing evidence for determining the geological ages of different formations. The authors assign the age of the Dongjing Formation of the Hengyang Basin to Early Cretaceous, the Shenhuangshan Formation to Early-Late Cretaceous, the Daijiaping Formation to Late Cretaceous, and the Dongtang and Xialiushi formations to Palaeocene.

联合古陆演化与矿产资源的关系

联合古陆演化与矿产资源的关系覃建雄（成都理工学院沉积所）联合古陆计划共分五个工作组，其中第四工作组的活动内容构成了整个联合古陆计划的目的和宗旨，其中心任务是研究联合古陆演化与矿产资源之间的内在联系。更详细地说，就是研究联合古陆演化过程中形成了哪些主要...

国外沉积学期刊文献摘要选登

国外沉积学期刊文献摘要选登王承书编译（成都地质矿产研究所）《沉积学》３９卷第５期１９９２年１０月１枕状层－－地震岩的一种新类型：以西班牙阿利坎特渐新世浊积扇形组合体为例７ｉｆ被叫做＂枕状层＇他一种新型的软沉积物变形层，原为一套砂屑石灰岩质浊积岩，呈现...

ISO TOPIC AGE AND STRATIGRAPHYCAL CORRELATION OF VOLCANIC ROCKS IN FINDES PENINSULA, KING GEORGE ISLAND

The ages of volcanic rocks from the Fildes Peninsula of King George Island, West Antarctica, have been determined with K-Ar, 39 Ar -40Ar, Rb -Sr methods by the authors. The results show that:a. The volcanism on the Fildes Peninsula has been from later Paleocene to early Middle Miocene; b. The formation time of the volcanic rocks of Jasper Hill Member belongs to later Paleocene becarse of the isotope age being 54Ma and 55Ma determined with Rb -Sr and 39 Ar -40Ar methods, respectively, c. The volcanic rocks of Agate Beach Member are the products of the volcanic activities during Early Eocene according to K -Ar isochron(45 -50Ma); d. The geological age of fossil Hill member is about Middle Eocene to Early Oligocene; e. the formation time of Block Hill member is probably early Middle Miocene.These data combining with the geological adn palaeontological evidences strongly support to best understand the stratigraphical correlation adn reveal the volcanism in studied area.

Carboniferous-Permian Stratigraphy and Sedimentary Environment of Southeastern Inner Mongolia,China:Constraints on Final Closure of the Paleo-Asian Ocean

In this paper we discuss the timing of final closure of the Paleo-Asian Ocean based on the field investigations of the Carboniferous-Permian stratigraphic sequences and sedimentary environments in southeastern Inner Mongolia combined with the geology of its neighboring areas. Studies show that during the Carboniferous-Permian in the eastern segment of the Tianshan-Hinggan Orogenic System, there was a giant ENE-NE-trending littoral-neritic to continental sedimentary basin, starting in the west from Ejinqi eastwards through southeastern Inner Mongolia into Jilin and Heilongjiang. The distribution of the Lower Carboniferous in the vast area is sparse. The Late Carboniferous or Permian volcanic-sedimentary rocks always unconformably overlie the Devonian or older units. The Upper Carboniferous-Middle Permian is dominated by llttoral-neritic deposits and the Upper Permian, by continental deposits. The Late Carboniferous-Permian has no trace of subduction-collision orogeny, implying the basin gradually disappeared by shrinking and shallowing. In addition, it is of interest to note that the Ondor Sum and Hegenshan ophiolitic melanges were formed in the pre-Late Silurian and pre-Late Devonian respectively, and the Solonker ophiolitic melange formed in the pre-Late Carboniferous. All the evidence indicates that the eastern segment of the Paleo-Asian Ocean had closed before the Late Carboniferous, and most likely before the latest Devonian （Famennian）.

Resource Potential and Exploration Techniques of Stratigraphic and subtle Reservoirs in China

The onshore oil and gas exploration has stepped into a new stage in China, with equal attention paid to both stratigraphic and subtle reservoirs and structural reservoirs. In the past few years, the increases in oil reserves in most basins were found mainly in the stratigraphic and subtle reservoirs. Latest resource evaluation shows that the onshore stratigraphic and subtle reservoirs in China account for 42% of the total remaining resource, the highest in the four major exploration regions. Therefore, these reservoirs will be the most practical, potential and prevalent fields for long-lasting oil and gas exploration in onshore China. Among PetroChina's annual oil geologic reserves of 4.3 × 108t^4.6× 108t, the stratigraphic and subtle reservoirs account for more than 50%. In such basins as Songliao, Ordos, Bohai Bay, Junggar, Tarim, Sichuan and Erlian basins, stratigraphic and subtle reservoirs with geologic reserves ranging from 5×107t to 3×108t were discovered, including Ansai, Jing'an, Daqingzijing, Liuxi, well-21 area in Shinan, and Hadexun. Stratigraphic and subtle reservoirs in the four types of inland basins differ from each other in the formation conditions and the distribution patterns. While continental basins are controlled by unconformity surface, maximum flooding surface and fracture surface, the Paleozoic marine basins are influenced by paleouplift, unconformity surface, and fluctuation of the sea level. Through exploration practices and research, PetroChina has formed its own technique series focused on 3-D seismics and sequence stratigraphy.

Genesis of sandstone-type uranium deposits along the northern margin of the Ordos Basin,China

Sandstone-type U mineral resources are among the important sources for nuclear energy.The U deposits in the Ordos Basin in China form part of the northern segment of the sandstone-hosted Central Asian Uranium MegaProvince.Two types of mineralizations are recognized in this basin:"phreatic permeable type"and"interlayer permeable type",both exhibiting features equivalent to roll-front subtypes.The"interlayer permeable type"is widely accepted as the dominant mineralization type for sandstone-type uranium deposits within large-scale basins,also designated as the"interlayer oxidation zone type",based on the horizontal color zoning model representing changing redox conditions.Here we synthesize data from several drill holes within the Ordos Basin,which suggest that major Mesozoic tectonic movements controlled the evolution of the sedimentary system in the basin.These tectonic movements contributed to the formation of three angular unconformities and four parallel unconformities as inferred from the stratigraphic relationships.In addition,other features such as vertical color zoning,paleo-channel controlled tabular or lentoid ore bodies(without roll-type)and a group interlayer horizontal zoning of altered minerals are also documented.Sequence stratigraphic analysis indicates that the Ordos Basin generally witnessed four cycles of water level variations during Mesozoic.During the variations,three high water level and three low water level events were recorded.Biological characteristics imply that the Ordos Basin went through multiple arid to humid climatic evolutions during Mesozoic.Combining the newly documented features with some novel concepts on the hydrodynamic mechanism for supergene ore-forming fluids,we propose a metallogenic model which invokes the importance of tectonic movements and water level fluctuations to explain the genesis of uranium deposits along the northern margin of the Ordos Basin.

Geochemical Stratigraphy and Microvertebrate Assemblage Sequences across the Silurian/Devonian Transition in South China

Carbon isotope （δ13Corg） analyses of non-marine clastic rocks and neritic carbonates and black shales spanning the Silurian/Devonian transition are compared from two richly fossiliferous sequences in Qujing of East Yunnan and Zoige of Sichuan, South China. The two sections, Xishancun and Putonggou sections in South China, reveal positive δ13Corg shifts happening in the Upper Pridoli and Lower Devonian and reaching peak values as heavy as -25.2‰ （Xishancun） and -19.9‰（Putonggou） in the lowermost Lochkovian following the first occurrence of the thelodont Parathelodus and the conodont Icriodus woschmidti woschmidti （only in Putonggou Section and together with Protathyris-Lanceomyonia brachiopod fauna）. These results replicate a globally known positive shift in δ13Corg from the uppermost Silurian to the lowermost Devonian. The δ13Corg variations across the Silurian/Devonian Boundary （SDB） at the two sections in South China exhibit a shift in carbon isotopic composition similar to the detailed SDB curves from the borehole Klonk-1 drilled at top of the Klonk Global Standard Stratotype-Section and Point （GSSP） in the Prague Basin, Czech Republic. In addition, four microvertebrate assemblages, including the Liaojiaoshan, Xishancun, Yanglugou and Xiaputonggou assemblages, are recognized from the Silurian/Devonian transition exposed in the Xishancun and Putonggou sections, respectively. The results from both carbon isotope stratigraphy and microvertebrate assemblage sequences suggest that the SDB in South China is located at the base of the Xishancun Formation （between sample QX-20 and sample QX-21） in the Xishancun Section and the lower part of the Xiaputonggou Formation （between sample ZP-09 and sample ZP-10） in the Putonggou Section. The isotopic trend for organic carbon together with the changes of microvertebrate remains across the SDB can offer an approach to a potential correlation of the SDB from different sedimentary facies, which help to correlate the marine with non-marine deposits.