1997 Vol. 15, No. 4
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Display Method:
1997, 15(4): 1-4.
Abstract:
The littoral carbonate bank section has not only the most sensitive record of the sea level change butalso the distinctive parasequence pattern.By the inimitable method of sequence recognition the carbonatebank section of Songshan, Wuxi is particular and typical in studying the Middle and Lower Yangtze re-gion stratigraphycally.The analysis of the depositional site associated with microgeography is availableand reliable method in studying the sequence and parasequence.
The littoral carbonate bank section has not only the most sensitive record of the sea level change butalso the distinctive parasequence pattern.By the inimitable method of sequence recognition the carbonatebank section of Songshan, Wuxi is particular and typical in studying the Middle and Lower Yangtze re-gion stratigraphycally.The analysis of the depositional site associated with microgeography is availableand reliable method in studying the sequence and parasequence.
1997, 15(4): 11-17.
Abstract:
Guangxi and Guizhou in South Ghina are one of the famous Devonian distribution areas interestedby both Chinese and foreign geologists.By classification and correlation of sequence stratigraphy of morethan 10 sections in Guizhou and Guangxi.21 sequences and T- Rcycles were identified to correspond tothird- order sea- level changes.On the basis of the division, correlation and study of the framework ofsequences in the stable regions and rift trough in the Luofu, Dachang sections, Nandan County, the for-mation and evolution of the rift trough.Episodic tectono- setting mainly controlled the development andarchitectures of sequences in the rift trough were discussed.Episodic tectono- sequences recorded thedepositional response to the episodic tectono- setting of the rift trongh.
Guangxi and Guizhou in South Ghina are one of the famous Devonian distribution areas interestedby both Chinese and foreign geologists.By classification and correlation of sequence stratigraphy of morethan 10 sections in Guizhou and Guangxi.21 sequences and T- Rcycles were identified to correspond tothird- order sea- level changes.On the basis of the division, correlation and study of the framework ofsequences in the stable regions and rift trough in the Luofu, Dachang sections, Nandan County, the for-mation and evolution of the rift trough.Episodic tectono- setting mainly controlled the development andarchitectures of sequences in the rift trough were discussed.Episodic tectono- sequences recorded thedepositional response to the episodic tectono- setting of the rift trongh.
1997, 15(4): 24-29.
Abstract:
In this paper, the small scale Ordovician carbonate sequence stratigraphy was discussed based on theanalysis of stratigraphy and sedimentology of the Sangtamu horst Block which belongs to the first gradetectonic unit—— Tabei Rise Belt in Tarim Basin.The small scale means the local structure of the studedarea and the subordinate sequence of the studied range are relatively small.A large amount of laata, such as olgging, core, outcrop and paleontology, was utilized to constructvariation curve of relative water depth under the circumstance of the vestrict of the seismic resolution.The conclusions were as belows: ① The open platform-edge sedimentary system includes ten sedimentarytypes: algal lagoon, algal flat, oolitic shoal and so on.② The Ordovician system is classified into twofourthorder sequences in TypeⅠ sequence boundary and the corresponding fifth-order dequences are alsoclassified.③ The highstand systems tract is the best reservoir belt witout considering the anadiagenesisfactor.This snalysis made it possible to recognize the evolution of strata and facies in local structure and toforecast the distribution tendency of the reservoir.The achivenent of this study can be applied in theanalogy of other similar structures.
In this paper, the small scale Ordovician carbonate sequence stratigraphy was discussed based on theanalysis of stratigraphy and sedimentology of the Sangtamu horst Block which belongs to the first gradetectonic unit—— Tabei Rise Belt in Tarim Basin.The small scale means the local structure of the studedarea and the subordinate sequence of the studied range are relatively small.A large amount of laata, such as olgging, core, outcrop and paleontology, was utilized to constructvariation curve of relative water depth under the circumstance of the vestrict of the seismic resolution.The conclusions were as belows: ① The open platform-edge sedimentary system includes ten sedimentarytypes: algal lagoon, algal flat, oolitic shoal and so on.② The Ordovician system is classified into twofourthorder sequences in TypeⅠ sequence boundary and the corresponding fifth-order dequences are alsoclassified.③ The highstand systems tract is the best reservoir belt witout considering the anadiagenesisfactor.This snalysis made it possible to recognize the evolution of strata and facies in local structure and toforecast the distribution tendency of the reservoir.The achivenent of this study can be applied in theanalogy of other similar structures.
1997, 15(4): 38-42.
Abstract:
Carbon and Oxygen isotopic study of some representative Cambrian-Ordovician boundary strata ofvarious stratigraphic areas in East China has done.It was indicated that the variation of δ18,O values inboundary strata is larger and the regularity of variation is not conspicuous because of the difference ofsedimentary environment and the effect of diagenetic alteration.But the variation of δC values is smalland the various degree of excursion in the boundary strata occurs.The excursive stratohorizon is consis-tent with the variation boundary of major biotic population.According to the study of various data, it wasbelieved that the excurson of carbon isotopic compositions is likely attributed to the televation and subsi-dence of sea level from the Late Cambrian to Early Ordovician.
Carbon and Oxygen isotopic study of some representative Cambrian-Ordovician boundary strata ofvarious stratigraphic areas in East China has done.It was indicated that the variation of δ18,O values inboundary strata is larger and the regularity of variation is not conspicuous because of the difference ofsedimentary environment and the effect of diagenetic alteration.But the variation of δC values is smalland the various degree of excursion in the boundary strata occurs.The excursive stratohorizon is consis-tent with the variation boundary of major biotic population.According to the study of various data, it wasbelieved that the excurson of carbon isotopic compositions is likely attributed to the televation and subsi-dence of sea level from the Late Cambrian to Early Ordovician.
1997, 15(4): 50-57.
Abstract:
The sedimentological research on the Lower Triassic Xikou Formation in southwestern Fujiandemonstrated that the rocks are mainly composed of deep-water turbidites, in which 5 facies and 7 sub-facies are recognized on the basis of lithology, textures and structures of the rocks,i.e.(1) conglomeratefacies;(2) sandstone facies;(3) sandstone-mudstone facies;(4) siltstone-mudstone facies;(5) graded siltymudstone facies.These facies consist of 5 facies associations that are formed in upper-fan, mid-fan andlower-fan environments, respectively.According to the characteristics of the turbidites, the turbiditefan in the study area is inferred to an elongate fan which is mainly formed in a stable tectonic setting,such as passive continental margin.Trace fossils contained in the rocks, such as Pasichnia, Grazing traces and some horizontal traces,indicated that they once lived in a bathyal-abyssal environment.The paleocurrent directions derivedfrom the sole marks and cross-beddings are toward to southeast after rotation correction.The spatialdistribution of the facies associations, paleocurrent data and distribution of the trace fossils all suggestedthat the continental slope was once dipped toward to the southeast at that time.The tectonic setting of the sedimentary basin was interpreted as passive continental margin based onthe geochemical composition analysis of the sandstone
The sedimentological research on the Lower Triassic Xikou Formation in southwestern Fujiandemonstrated that the rocks are mainly composed of deep-water turbidites, in which 5 facies and 7 sub-facies are recognized on the basis of lithology, textures and structures of the rocks,i.e.(1) conglomeratefacies;(2) sandstone facies;(3) sandstone-mudstone facies;(4) siltstone-mudstone facies;(5) graded siltymudstone facies.These facies consist of 5 facies associations that are formed in upper-fan, mid-fan andlower-fan environments, respectively.According to the characteristics of the turbidites, the turbiditefan in the study area is inferred to an elongate fan which is mainly formed in a stable tectonic setting,such as passive continental margin.Trace fossils contained in the rocks, such as Pasichnia, Grazing traces and some horizontal traces,indicated that they once lived in a bathyal-abyssal environment.The paleocurrent directions derivedfrom the sole marks and cross-beddings are toward to southeast after rotation correction.The spatialdistribution of the facies associations, paleocurrent data and distribution of the trace fossils all suggestedthat the continental slope was once dipped toward to the southeast at that time.The tectonic setting of the sedimentary basin was interpreted as passive continental margin based onthe geochemical composition analysis of the sandstone
1997, 15(4): 64-66,71.
Abstract:
Relative changes of lake-level in continental basins are complicated controlled by multiple variablessuch as tectonic subsidence, absolute lake-level change, deposit supply and climate.Perhaps the waterlevel of lake basin is more significantly influenced by tectonic variation than that of sea basin because ofthe nonbalanced tectonic subsidence.With the total water volume of lake neglected, five changes of single-faulted basins would happenwhile blocks tilt: (1) regression at gentle slope;(2) transgression at steep slope;(3) deepening of waterbody in the centre of a lake;(4) broadness of lake-level and (5) growth of capacity.Some practical datahave proven these preliminary conclusions.
Relative changes of lake-level in continental basins are complicated controlled by multiple variablessuch as tectonic subsidence, absolute lake-level change, deposit supply and climate.Perhaps the waterlevel of lake basin is more significantly influenced by tectonic variation than that of sea basin because ofthe nonbalanced tectonic subsidence.With the total water volume of lake neglected, five changes of single-faulted basins would happenwhile blocks tilt: (1) regression at gentle slope;(2) transgression at steep slope;(3) deepening of waterbody in the centre of a lake;(4) broadness of lake-level and (5) growth of capacity.Some practical datahave proven these preliminary conclusions.
1997, 15(4): 72-77,96.
Abstract:
Marine Ordovician strata are an important hydrocarbon source in worldwide, and were studied bymany foreign workers.Now, oil and gas exploration for the Ordovician as a Source stratum has been ad-vanced for recent several years, for example, some oilfields have been found in Tarim Basin,of which oilsare from the Palaeozoic source, especially the Ordovician.The generation of hydrocarbons of the Ordovi-cian source is different from that of Mesozoic nd Cenozoic sources since there were on high plants in the Ordovician Period.In the article, several sapects on generation of hydrocarbons of the Ordovician sourcewere discussed base on geochemical features of Ordovician oilsin the world.And it is hoped that this dis-cussion may draw people' s attention to the generation of hydrocarbons of Ordovician strata.
Marine Ordovician strata are an important hydrocarbon source in worldwide, and were studied bymany foreign workers.Now, oil and gas exploration for the Ordovician as a Source stratum has been ad-vanced for recent several years, for example, some oilfields have been found in Tarim Basin,of which oilsare from the Palaeozoic source, especially the Ordovician.The generation of hydrocarbons of the Ordovi-cian source is different from that of Mesozoic nd Cenozoic sources since there were on high plants in the Ordovician Period.In the article, several sapects on generation of hydrocarbons of the Ordovician sourcewere discussed base on geochemical features of Ordovician oilsin the world.And it is hoped that this dis-cussion may draw people' s attention to the generation of hydrocarbons of Ordovician strata.
1997, 15(4): 86-90.
Abstract:
The conceptual model of paleo- hydrodynamics and mathematical model of pseudo-3D nonstationaryflow for the Es3 member were built according to "centrifugal flow" characteristics of the fluid potentialfield of compactional flow basin as well as to expelling style of fluids from mudstones.Isostatic nets ofpaleo-hydrodynamical field were superimposed on nodal nets of compaction-displacement fluids,and thediffential equations of hydrodynamics were writen by means of Darcy' s law and hydraulic isostation,which provides a numerical method for simulating paleo-hydrodynamics, paleo-fluid potential field andsecondary hydrocarbon migration.The results of numerical simulation showed that the high potentialvalues(Max.59000m 2 /s 2 ) were located in the centre of the Lijing and Niuzhang areas and descended to-wards edges of the depression at 25Ma(late Dongying).Oil migrated from higher potential belts to low-er ones in "centrifugal flow", which was the regional dynamic condition of controlling petroleum accu-mulation and distribution.The simulations also revealed that migrating velocities are 30～40km /Ma at5Ma, 5～10km /Ma at 25Ma and 5～10km /Ma at present in the Es 3 member, respectively.The main driv-ing forces of secondary migration were different in geologic times and spaces.
The conceptual model of paleo- hydrodynamics and mathematical model of pseudo-3D nonstationaryflow for the Es3 member were built according to "centrifugal flow" characteristics of the fluid potentialfield of compactional flow basin as well as to expelling style of fluids from mudstones.Isostatic nets ofpaleo-hydrodynamical field were superimposed on nodal nets of compaction-displacement fluids,and thediffential equations of hydrodynamics were writen by means of Darcy' s law and hydraulic isostation,which provides a numerical method for simulating paleo-hydrodynamics, paleo-fluid potential field andsecondary hydrocarbon migration.The results of numerical simulation showed that the high potentialvalues(Max.59000m 2 /s 2 ) were located in the centre of the Lijing and Niuzhang areas and descended to-wards edges of the depression at 25Ma(late Dongying).Oil migrated from higher potential belts to low-er ones in "centrifugal flow", which was the regional dynamic condition of controlling petroleum accu-mulation and distribution.The simulations also revealed that migrating velocities are 30～40km /Ma at5Ma, 5～10km /Ma at 25Ma and 5～10km /Ma at present in the Es 3 member, respectively.The main driv-ing forces of secondary migration were different in geologic times and spaces.
1997, 15(4): 97-102.
Abstract:
The fossils in Fenxiang Formation of the Lower Ordovician could be subdivided into three ecologicassemblages and ten communities: (1), shelly facies assemblage: Tritoechia-Pelmatozoan community, Tri-toechia-Pomatotrema community;(2) Reef facies assemblage: Archaeoscyphia community, Archaeoscyphia-Calathium community, Batostoma- pelmatozoan community,Calathium-Bluegreen algae community, and(3), stll water facies assemblage: Acanthograptus- Dendrograptus community, Nanorthis-Psilocephalinacryptocoenosis, Yichangopora? community.Among these assemblages, evolutionary successions could beobserved in the transition cycle of (1) to (2) to (3)and then back to (1) and (2).Similarly, certain succes-sion events and faunal replacements took place between the reef-building communities.The communityevolution indicated that a transgression and regression cycle led to progressive increase and decrease inwater depth, and such a process might have extended over the middle Yangtze platform and be consistentto the eustatic change of sea level during the late Tremadocian to the Early Arenigian time.
The fossils in Fenxiang Formation of the Lower Ordovician could be subdivided into three ecologicassemblages and ten communities: (1), shelly facies assemblage: Tritoechia-Pelmatozoan community, Tri-toechia-Pomatotrema community;(2) Reef facies assemblage: Archaeoscyphia community, Archaeoscyphia-Calathium community, Batostoma- pelmatozoan community,Calathium-Bluegreen algae community, and(3), stll water facies assemblage: Acanthograptus- Dendrograptus community, Nanorthis-Psilocephalinacryptocoenosis, Yichangopora? community.Among these assemblages, evolutionary successions could beobserved in the transition cycle of (1) to (2) to (3)and then back to (1) and (2).Similarly, certain succes-sion events and faunal replacements took place between the reef-building communities.The communityevolution indicated that a transgression and regression cycle led to progressive increase and decrease inwater depth, and such a process might have extended over the middle Yangtze platform and be consistentto the eustatic change of sea level during the late Tremadocian to the Early Arenigian time.
1997, 15(4): 109-114.
Abstract:
The source direction of the Middle Jurasic of Chaonan 1 Well in Tuha Basin was comprehensivelyjudged through a comparative research on its lithologic characteristics of source areas and of its stratumthickness, and special distrilution of sedimentary facies of adjcent wells.The lithological difference of thenorth and south boundary mountains in Tuha Basin is clear, i.e, the southern Jueluotage Mt.is predormi-nated by acidic igneous rocks while the northern Bogeda Mt.by intermediate to basic rocks.The Clarkevalues of petrogenic elements, K, Ca, Mg, ferric family elements, Fe, Ni, Fe, rare earth elements, Sr, Ga,Rb, Ba of the Middle Jurassic mudstones of the Chaonan 1 Well were close to those of acidic igneousrocks.The two heavy mineral associations, rich in zircon and magnetite, respectively, basicatly represented those of acidic igneous rocks.The content of quartz in sandstones was over 20 %, the microcline andorthoclase were high while the anothesite low, and the volcanicdebris were mainly intermediate acidicones, which are closely related with acidic igneous rocks.It coued initally be concluded from the abovethat the clasts of Chaonan 1 Well were derived from the southern Jueluotage Mt.From Yue 1 Well, sour-thern to Chaonan 1 Well, to Xiaochao 1 Well, northern to Chaonan 1 Well, the thickness of sandstonesbecame thin, the size smaller, and the physical properties worse.The thickness of mudstones got thicker,the color darker, the content of sands less, the content of organic matter higher and the type of organicmatter better.Because the content of clay minerals, especially kaolinite,inceased and the mudstone thick-ened, the seal conditions were better.The above research result is of great significance in perfecting thejudgement method of source direction of sedimentary basins, predicting the distribution of the most fa-vorable reservoir bodies and source-reservoir-caprock associations and guiding the exploration of oils andgases.
The source direction of the Middle Jurasic of Chaonan 1 Well in Tuha Basin was comprehensivelyjudged through a comparative research on its lithologic characteristics of source areas and of its stratumthickness, and special distrilution of sedimentary facies of adjcent wells.The lithological difference of thenorth and south boundary mountains in Tuha Basin is clear, i.e, the southern Jueluotage Mt.is predormi-nated by acidic igneous rocks while the northern Bogeda Mt.by intermediate to basic rocks.The Clarkevalues of petrogenic elements, K, Ca, Mg, ferric family elements, Fe, Ni, Fe, rare earth elements, Sr, Ga,Rb, Ba of the Middle Jurassic mudstones of the Chaonan 1 Well were close to those of acidic igneousrocks.The two heavy mineral associations, rich in zircon and magnetite, respectively, basicatly represented those of acidic igneous rocks.The content of quartz in sandstones was over 20 %, the microcline andorthoclase were high while the anothesite low, and the volcanicdebris were mainly intermediate acidicones, which are closely related with acidic igneous rocks.It coued initally be concluded from the abovethat the clasts of Chaonan 1 Well were derived from the southern Jueluotage Mt.From Yue 1 Well, sour-thern to Chaonan 1 Well, to Xiaochao 1 Well, northern to Chaonan 1 Well, the thickness of sandstonesbecame thin, the size smaller, and the physical properties worse.The thickness of mudstones got thicker,the color darker, the content of sands less, the content of organic matter higher and the type of organicmatter better.Because the content of clay minerals, especially kaolinite,inceased and the mudstone thick-ened, the seal conditions were better.The above research result is of great significance in perfecting thejudgement method of source direction of sedimentary basins, predicting the distribution of the most fa-vorable reservoir bodies and source-reservoir-caprock associations and guiding the exploration of oils andgases.
1997, 15(4): 121-126.
Abstract:
Based on such dynamic geologic functions as structure, thermal history, fluid potential developmentand the migration and accumulation of oil＆ gas, the pool-formed evolutional history was discussed andfurthermore divided into two petroleum-entrapped systems in the Wenjisang-Qiudong area.The firstpetroleum- entrapped system is from the Early and Middle Jurassic to the end of Paleogene,in which theactive period of the pool-formation is from the end of Jurassic to the Early Cretaceous, and the second isfrom Neogene to Quaternary, in which the active period is since the end of Neogene.According to thedevolopment of the fuild potential field, the relationship between the petroleum-entrapped evolution andthe hydrocarbon accumulation was analized.Furthermore, the petroleum-entrapped models were stud-ied, and it was suggested that the Wenjisang oil- pool was holded in the first petroleum-entrapped sys-tem, mainly with oil, and that the oil and gas were shared the importance in the Miden field, and thatthe Qiudong field was formed in the second petroleum-entrapped system as a gas pool.
Based on such dynamic geologic functions as structure, thermal history, fluid potential developmentand the migration and accumulation of oil＆ gas, the pool-formed evolutional history was discussed andfurthermore divided into two petroleum-entrapped systems in the Wenjisang-Qiudong area.The firstpetroleum- entrapped system is from the Early and Middle Jurassic to the end of Paleogene,in which theactive period of the pool-formation is from the end of Jurassic to the Early Cretaceous, and the second isfrom Neogene to Quaternary, in which the active period is since the end of Neogene.According to thedevolopment of the fuild potential field, the relationship between the petroleum-entrapped evolution andthe hydrocarbon accumulation was analized.Furthermore, the petroleum-entrapped models were stud-ied, and it was suggested that the Wenjisang oil- pool was holded in the first petroleum-entrapped sys-tem, mainly with oil, and that the oil and gas were shared the importance in the Miden field, and thatthe Qiudong field was formed in the second petroleum-entrapped system as a gas pool.
1997, 15(4): 134-142.
Abstract:
Study of heavy minerals of the Malan loess on the Qinghai-Xizang Plateau and its adjacent areademonstrates that two loess depositional areas in heavy mineral can be clearly divided by the boundary ofKunlun Mts.- Buqing Mts- Xiqing Shan- Min Shan.To the north of this boundary, heavy minerals inthe Malan loess are hypometamorphic rocks and come chiefly from the Asian inland desert-gobi area;Tothe south, they are characterized by weathered parent rocks of volcanic, intrusive,and hypermetamorphicrocks and come from tills and periglacial sediments on the Qinghai-Xizang Plateau.The regional differ-ence in material in the sourec area, together with the effect of particular landform of the Plateau and thedifference of atmospheric circulation, may be mainly responsible for the difference of heavy minerals andprovenance of the Chinese Malan loess.
Study of heavy minerals of the Malan loess on the Qinghai-Xizang Plateau and its adjacent areademonstrates that two loess depositional areas in heavy mineral can be clearly divided by the boundary ofKunlun Mts.- Buqing Mts- Xiqing Shan- Min Shan.To the north of this boundary, heavy minerals inthe Malan loess are hypometamorphic rocks and come chiefly from the Asian inland desert-gobi area;Tothe south, they are characterized by weathered parent rocks of volcanic, intrusive,and hypermetamorphicrocks and come from tills and periglacial sediments on the Qinghai-Xizang Plateau.The regional differ-ence in material in the sourec area, together with the effect of particular landform of the Plateau and thedifference of atmospheric circulation, may be mainly responsible for the difference of heavy minerals andprovenance of the Chinese Malan loess.
1997, 15(4): 148-151.
Abstract:
The principle of K-Ar isochron method was introduced in this paper.The k-Ar isochron data of il-lites from the Ordos basin were successfully used to evaluate the two distinct diagenetic stages identifiedby conventional K-Ar dating.Both the Permian-Triassic and Cambrian-Ordovician samples yield well de-fined40K-40Ar isochrons, which indicate intercepts almost equal to zero and similar isochron ages to theconventional K-Ar ages.In addition, the Permian-Triassic samples gave also a well-defined40K/36Ar-40Ar / 36 Ar isochron, which yields an intercept of nearly the atmospheric argon ratio(295.5) and a similarisochron age to the conventional K-Ar ages.These facts indicated that the illite K-Ar clock belongs actu-ally to a closed system, and thus can validly be used to determine diagenetic ages of sedimentary rocks.The Jurassic(170～160 Ma) and Silurian-Devonian(420～370 Ma) diagenetic stages revealed by conven-tional K-Ar data were proved to be reliable.K-Ar isochron methods can supply additional information toevaluating the validity of conventional K-Ar isochron methods.It can also Provide improved constrintson interpreting K-Ar data and their geological meanings.
The principle of K-Ar isochron method was introduced in this paper.The k-Ar isochron data of il-lites from the Ordos basin were successfully used to evaluate the two distinct diagenetic stages identifiedby conventional K-Ar dating.Both the Permian-Triassic and Cambrian-Ordovician samples yield well de-fined40K-40Ar isochrons, which indicate intercepts almost equal to zero and similar isochron ages to theconventional K-Ar ages.In addition, the Permian-Triassic samples gave also a well-defined40K/36Ar-40Ar / 36 Ar isochron, which yields an intercept of nearly the atmospheric argon ratio(295.5) and a similarisochron age to the conventional K-Ar ages.These facts indicated that the illite K-Ar clock belongs actu-ally to a closed system, and thus can validly be used to determine diagenetic ages of sedimentary rocks.The Jurassic(170～160 Ma) and Silurian-Devonian(420～370 Ma) diagenetic stages revealed by conven-tional K-Ar data were proved to be reliable.K-Ar isochron methods can supply additional information toevaluating the validity of conventional K-Ar isochron methods.It can also Provide improved constrintson interpreting K-Ar data and their geological meanings.
1997, 15(4): 159-164.
Abstract:
The Salawusu River area is one of the standard sections of the Late Pleistocene strata in North Chi-na.However, there have been a lot of different views about the strata since the establishment of alawusu Formation, especially in the aspects of sedimentary facies, stratigraphic data and its climate sig-nificance.According to the stratigraphic subdivision, age dating and the analysis of the sedimentary fa-cies, the following recognitions can be gained: 1 The original Salawusu Formation could be further divided into Lishi Loess interbeded with sandysediments(Q22 ), Salawusuu Formation(Q,13 ), Cheng-chuan Formation(Q2,3 ), Dagouwan Formation (Q4 )and Dishaogouwan Formation(Q34 ).2 Salwusu Formation is mainly a fluvial-lacustrine deposit corresponding to the Stage 5 of deep seainδ18O and formed between about 140- 70 Ka.BP.Chengchuan Formation is mainly fossil aeolian sands,with some lacustrine silty-clay in the middle part, correspording to Stages 2- 4 of deep sea inδ18O andformed between 70- 10 Ka.BP.Dagouwan Formation is lacustrine sediments and black-paleosoil, indi-cating the warm-humid climate and formed in the middle-early period of Holocene.Dishaogouwan For-mation is mainly sub-loess and aeolian sands, representing the cold-dry climate and being believed to be-long to the late Holocene.3 As a fluvial-lacustrine sedimentary stratum, Salawusu Formation is quite different from its upperChengchuan Formation both in geochronology, lithology and sedimentary facies and in palaeontology.Chengchuan Formation and Malan Loess belong to heteropic deposits(sandy and loessic facies) formedcontemporaneously under the same wind action.4 As a flurial-lacustrine-aeolian-sand sequence by observing the Dishaogou profile in the SalawusuRiver area,its climatic records can compete with the records of loess and deep sea deposits, they may bedivided into 5 climatic periods just by oxygen isotope.It is suggested that the climatic change of this re-gion during the last interglacial period is synchronous withthat of the whole earth.
The Salawusu River area is one of the standard sections of the Late Pleistocene strata in North Chi-na.However, there have been a lot of different views about the strata since the establishment of alawusu Formation, especially in the aspects of sedimentary facies, stratigraphic data and its climate sig-nificance.According to the stratigraphic subdivision, age dating and the analysis of the sedimentary fa-cies, the following recognitions can be gained: 1 The original Salawusu Formation could be further divided into Lishi Loess interbeded with sandysediments(Q22 ), Salawusuu Formation(Q,13 ), Cheng-chuan Formation(Q2,3 ), Dagouwan Formation (Q4 )and Dishaogouwan Formation(Q34 ).2 Salwusu Formation is mainly a fluvial-lacustrine deposit corresponding to the Stage 5 of deep seainδ18O and formed between about 140- 70 Ka.BP.Chengchuan Formation is mainly fossil aeolian sands,with some lacustrine silty-clay in the middle part, correspording to Stages 2- 4 of deep sea inδ18O andformed between 70- 10 Ka.BP.Dagouwan Formation is lacustrine sediments and black-paleosoil, indi-cating the warm-humid climate and formed in the middle-early period of Holocene.Dishaogouwan For-mation is mainly sub-loess and aeolian sands, representing the cold-dry climate and being believed to be-long to the late Holocene.3 As a fluvial-lacustrine sedimentary stratum, Salawusu Formation is quite different from its upperChengchuan Formation both in geochronology, lithology and sedimentary facies and in palaeontology.Chengchuan Formation and Malan Loess belong to heteropic deposits(sandy and loessic facies) formedcontemporaneously under the same wind action.4 As a flurial-lacustrine-aeolian-sand sequence by observing the Dishaogou profile in the SalawusuRiver area,its climatic records can compete with the records of loess and deep sea deposits, they may bedivided into 5 climatic periods just by oxygen isotope.It is suggested that the climatic change of this re-gion during the last interglacial period is synchronous withthat of the whole earth.
1997, 15(4): 5-10.
Abstract:
Zhangxia Formation of the Middle Cambrian in North China is particularly famous for the well-de-veloped oolitic limestone.Many kinds of meter-scale cyclic-sequences, belonging to subtidal carbonatetype are discerned in Zhangxia Formation, and they are characteristic of "upward thickening of rock-bed" and "upward coarsening of sedimentary grain" as well as "upward shallowing of depositional enviroment".The stacking pattern of 1 ∶ 4 indicates that one meter-scale cyclic-sequence is genetically relatedto short-precession cycle of the Milankovitch cycle.In strata of Zhangxia Formation, various order cyclic-sequences and their regularly vertical stacking patterns constitute a typicall carbonate cyclic-sequence ofcomposite sea-level changes.On basis of the nature of the carbonate cyclic-sequence of composite sea-level changes developed inZhangxia Formation,it could be concluded as follows:① Cyclic-sequence ought to be a genetically relative facies-succession at first, the meaning of whichis that this facies-succession can reflect a process of relative sea-level changes.There are various ordersfor cyclic-sequences, which are genetically related to various periods of sea-level changes.② The surface of cyclic-sequence is a facies-changing surface that generally coexists with punctuatedsurface, which includes exposing punctuated surface and deepening-starve punctuated surface.③ In the research of cyclostratigraphy and sequeuce stratigraphy, especially the study of outcrop aswell as rock-core section, "lithology and lithofacies as well as facies-succession" are the key to discerncyclic-sequences, various order cyclic-sequences and their regularly vertical stacking patterns are thecore.④ Condensed section that is defined by stratigraphy, does not exist in the third-order cyclic-se-quence.In some depositional environment, there is also "condensed section" in the fourth-order cyclic-se-quence(subsequence).So it must be careful to pay attention to the belonging of coudensed section in var-ious order cyclic-sequences.⑤ There are two important factors for cyclic-sequences: regularity of facies-succession in space andsimultarity of environment change in time, both of which endow with particular meanings on stratigraphyand sedimentology to cyclic-sequences.
Zhangxia Formation of the Middle Cambrian in North China is particularly famous for the well-de-veloped oolitic limestone.Many kinds of meter-scale cyclic-sequences, belonging to subtidal carbonatetype are discerned in Zhangxia Formation, and they are characteristic of "upward thickening of rock-bed" and "upward coarsening of sedimentary grain" as well as "upward shallowing of depositional enviroment".The stacking pattern of 1 ∶ 4 indicates that one meter-scale cyclic-sequence is genetically relatedto short-precession cycle of the Milankovitch cycle.In strata of Zhangxia Formation, various order cyclic-sequences and their regularly vertical stacking patterns constitute a typicall carbonate cyclic-sequence ofcomposite sea-level changes.On basis of the nature of the carbonate cyclic-sequence of composite sea-level changes developed inZhangxia Formation,it could be concluded as follows:① Cyclic-sequence ought to be a genetically relative facies-succession at first, the meaning of whichis that this facies-succession can reflect a process of relative sea-level changes.There are various ordersfor cyclic-sequences, which are genetically related to various periods of sea-level changes.② The surface of cyclic-sequence is a facies-changing surface that generally coexists with punctuatedsurface, which includes exposing punctuated surface and deepening-starve punctuated surface.③ In the research of cyclostratigraphy and sequeuce stratigraphy, especially the study of outcrop aswell as rock-core section, "lithology and lithofacies as well as facies-succession" are the key to discerncyclic-sequences, various order cyclic-sequences and their regularly vertical stacking patterns are thecore.④ Condensed section that is defined by stratigraphy, does not exist in the third-order cyclic-se-quence.In some depositional environment, there is also "condensed section" in the fourth-order cyclic-se-quence(subsequence).So it must be careful to pay attention to the belonging of coudensed section in var-ious order cyclic-sequences.⑤ There are two important factors for cyclic-sequences: regularity of facies-succession in space andsimultarity of environment change in time, both of which endow with particular meanings on stratigraphyand sedimentology to cyclic-sequences.
1997, 15(4): 18-23.
Abstract:
Based on the outcrop sequence- stratigraphic principle and method, the authors first studied theCarboniferous section of the seamount carbonate platform in Paleo- Tethys(the Changning- Menglianbelt), Southwestern Yunnan, China.6 third- order sequences were examined in detail with particular at-tention to the key surface of the parasequence.There are l sequence in Early Namurian, 3 sequences bothin Late Namurian- Westphalian(Weining) and Stephanian- Sakmarian(Yutangzhai F., the upper mostsequence belongs to Permian).Third- order sequences and eustatic transgressive- regressive cycles atthe Yutangzhai (in Southwestern Yunnan) can be correlated with ones in Southern Guizhou excentparasequences.Carbon and oxygen isotopes at the Yutangzhai were lighter than those in SouthernGuizhou, Probably, the same eustasy and different tectonic background were the main causes of theabove facts during the Late Carboniferous.
Based on the outcrop sequence- stratigraphic principle and method, the authors first studied theCarboniferous section of the seamount carbonate platform in Paleo- Tethys(the Changning- Menglianbelt), Southwestern Yunnan, China.6 third- order sequences were examined in detail with particular at-tention to the key surface of the parasequence.There are l sequence in Early Namurian, 3 sequences bothin Late Namurian- Westphalian(Weining) and Stephanian- Sakmarian(Yutangzhai F., the upper mostsequence belongs to Permian).Third- order sequences and eustatic transgressive- regressive cycles atthe Yutangzhai (in Southwestern Yunnan) can be correlated with ones in Southern Guizhou excentparasequences.Carbon and oxygen isotopes at the Yutangzhai were lighter than those in SouthernGuizhou, Probably, the same eustasy and different tectonic background were the main causes of theabove facts during the Late Carboniferous.
1997, 15(4): 30-37.
Abstract:
The difference between intracontinental basin and marginal basin exists in many aspects, such astectonic settings, depositional scale, infilling pattern, paleomotography, sediment components and sedi-mentary sequences.The intracontinental basin is characterized by multi-sedinent-sources, multi-sediment| system, narrow lateral facies extension and rapid facies alternation.The Xianfeng basin is a Tertiaryfaulted intracontinental basin in Yunnan Province, Southwest China.This paper studied its infilling se-quence, sedimentary framework, structure framework and the loacal tectonic setting.Furthermore, thefeatures of an intracontinental basin under a strike-slip tectonic setting and the sequence characters werediscussed.Bwsides the features appearing in all inland basins, the Xianfeng basin showed a clear strike-slip character.it controlled the variation of accomadtion and the evolution of sediment source providingpattern.The infilling sequences were charactorized by the migration of the depositional cen along theboundary faults, the lateral onlap of sediment system and the active infilling along the mqjor axis of thebasin.Through carefully study, four types of sruface have been recognized to divide the sequence and thesystem tracts: tectogenesis surface(TCS), tectonic stress field transition surface(T TS).large-scale flood-ing surface(FDS) and coal bed surface(CBS).On the basis of sequence surfaces listed the above, the in-filling sequence could be divided into two sequences.LST, TST, HST and AST were recognized.Coal-bearing sequences were well developed in the Xianfeng basin, mainly appearing in the upper part of LSTand HST.Coal bed M 8 spreaded on a whole basin scale with the depth as thick as 236.6m.As we allknow, a coal bed is a sensitive indicator which reflects the fluctuation of alke surface and water depth.Therefore, the locally spreaded coal beds are the ideal surfaces to determine a parasequence and parase-quence sets.in addition, it should be pointed out that the tectonic movement plays a great role in tehbasin infilling including tectonic subsidence, strike-slip movement and tectonic inversion.
The difference between intracontinental basin and marginal basin exists in many aspects, such astectonic settings, depositional scale, infilling pattern, paleomotography, sediment components and sedi-mentary sequences.The intracontinental basin is characterized by multi-sedinent-sources, multi-sediment| system, narrow lateral facies extension and rapid facies alternation.The Xianfeng basin is a Tertiaryfaulted intracontinental basin in Yunnan Province, Southwest China.This paper studied its infilling se-quence, sedimentary framework, structure framework and the loacal tectonic setting.Furthermore, thefeatures of an intracontinental basin under a strike-slip tectonic setting and the sequence characters werediscussed.Bwsides the features appearing in all inland basins, the Xianfeng basin showed a clear strike-slip character.it controlled the variation of accomadtion and the evolution of sediment source providingpattern.The infilling sequences were charactorized by the migration of the depositional cen along theboundary faults, the lateral onlap of sediment system and the active infilling along the mqjor axis of thebasin.Through carefully study, four types of sruface have been recognized to divide the sequence and thesystem tracts: tectogenesis surface(TCS), tectonic stress field transition surface(T TS).large-scale flood-ing surface(FDS) and coal bed surface(CBS).On the basis of sequence surfaces listed the above, the in-filling sequence could be divided into two sequences.LST, TST, HST and AST were recognized.Coal-bearing sequences were well developed in the Xianfeng basin, mainly appearing in the upper part of LSTand HST.Coal bed M 8 spreaded on a whole basin scale with the depth as thick as 236.6m.As we allknow, a coal bed is a sensitive indicator which reflects the fluctuation of alke surface and water depth.Therefore, the locally spreaded coal beds are the ideal surfaces to determine a parasequence and parase-quence sets.in addition, it should be pointed out that the tectonic movement plays a great role in tehbasin infilling including tectonic subsidence, strike-slip movement and tectonic inversion.
1997, 15(4): 43-49.
Abstract:
Based on the genetic relation between sedimentary architecture, paleo- drainage systems and faciesdistribution, and the comparative sedimentology analysis, the paper discussed the uniformity existing inthe primary sediment fillings in the Lower- Middle Jurassic developed of the present Ordos basin and inNingwu and Datong to the east of the basin.The uniformity confirmed that the strata were deposited inthe same Large Ordos basin.The Early- Middle Jurassic paleogeography reconstruction,in terms of fourdeposition stages, revealed the tectonic stages of downwarping- uplifting- redow nwarping and the mi-gration of dynamic setting during the formation and evolution of the basin.The study on the tectonic set-ting for continental downwarping could determine the transformation of Indosinian- Yanshanian tecton-ics and the time of tectonic transformation in North China on a smaller scale.
Based on the genetic relation between sedimentary architecture, paleo- drainage systems and faciesdistribution, and the comparative sedimentology analysis, the paper discussed the uniformity existing inthe primary sediment fillings in the Lower- Middle Jurassic developed of the present Ordos basin and inNingwu and Datong to the east of the basin.The uniformity confirmed that the strata were deposited inthe same Large Ordos basin.The Early- Middle Jurassic paleogeography reconstruction,in terms of fourdeposition stages, revealed the tectonic stages of downwarping- uplifting- redow nwarping and the mi-gration of dynamic setting during the formation and evolution of the basin.The study on the tectonic set-ting for continental downwarping could determine the transformation of Indosinian- Yanshanian tecton-ics and the time of tectonic transformation in North China on a smaller scale.
1997, 15(4): 58-63.
Abstract:
Anastomosing river systems in the Sanshui Basin, northwestern part of the Pearl River deltaplain,were studied.They are multi-channel systems showing low gradients, low width /depth ratios and re-peated branching and rejoining.Channels, natural levees, interchannel lakes and wetlands are importantmorphological and sedimentary units.Well data revealed that the depositional records of the anastomos-ing river systems are mainly composed of fine grained sediments deposited in interchannel areas, coarsegrained channel deposits, on the other hand, are string-like and of limited lateral extent, and encased inthe overbank fine sediments.Trunk channels are more stable and often associated with deposits of thickchannel sand-bodies.Smaller channels are more easily abandoned bacause of crevasse and avulsion, thusthin sand-bodies are deposited in the fine-sediment-dominated deposits.Pet and silt rich in organic mate-rials are deposited in swamps and interchannel lakes.Tectonic subsidence and eustatic sea level haverisen since the Late Pleistocene, and the rapid vertical accretion in the floodplain hase been the maincause for the development of anastomosing river systems in the Pearl River deltaplain.
Anastomosing river systems in the Sanshui Basin, northwestern part of the Pearl River deltaplain,were studied.They are multi-channel systems showing low gradients, low width /depth ratios and re-peated branching and rejoining.Channels, natural levees, interchannel lakes and wetlands are importantmorphological and sedimentary units.Well data revealed that the depositional records of the anastomos-ing river systems are mainly composed of fine grained sediments deposited in interchannel areas, coarsegrained channel deposits, on the other hand, are string-like and of limited lateral extent, and encased inthe overbank fine sediments.Trunk channels are more stable and often associated with deposits of thickchannel sand-bodies.Smaller channels are more easily abandoned bacause of crevasse and avulsion, thusthin sand-bodies are deposited in the fine-sediment-dominated deposits.Pet and silt rich in organic mate-rials are deposited in swamps and interchannel lakes.Tectonic subsidence and eustatic sea level haverisen since the Late Pleistocene, and the rapid vertical accretion in the floodplain hase been the maincause for the development of anastomosing river systems in the Pearl River deltaplain.
1997, 15(4): 67-71,66.
Abstract:
Six sediment cores, collected in Yangpu Harbour on Hainan Island, Out of Xiamen Harbour in Fu-jian Province and Xiangshan Harbour in Zhejiang Province, were analyzed for Cs- 137 activity, both theposition of the peak (corresponding to the period of maximum deposition) and the position of the horizon(corresponding to the first appearance of Cs- 137 in the environment)were been used to determine sedi-mentation rates.The results showed that it is possiable to use the Cs- 137 profile to determine sedimen-tation rate in estuaries, Rates for these cores based on the position of peak of Cs- 137 profile were 1.14cm /a, 1.56cm /a, 0.82cm /a, 0.75cm /a, 1.26cm /a, respectively.1.66cm /a, which are in good agreementwith that based on Pb- 210 dating and rates based on the occurrence of the horizon were larger than thatbased on Pb- 210 dating, Nhieh this indicates physical mixing or reworking of seidments in estuaryies.
Six sediment cores, collected in Yangpu Harbour on Hainan Island, Out of Xiamen Harbour in Fu-jian Province and Xiangshan Harbour in Zhejiang Province, were analyzed for Cs- 137 activity, both theposition of the peak (corresponding to the period of maximum deposition) and the position of the horizon(corresponding to the first appearance of Cs- 137 in the environment)were been used to determine sedi-mentation rates.The results showed that it is possiable to use the Cs- 137 profile to determine sedimen-tation rate in estuaries, Rates for these cores based on the position of peak of Cs- 137 profile were 1.14cm /a, 1.56cm /a, 0.82cm /a, 0.75cm /a, 1.26cm /a, respectively.1.66cm /a, which are in good agreementwith that based on Pb- 210 dating and rates based on the occurrence of the horizon were larger than thatbased on Pb- 210 dating, Nhieh this indicates physical mixing or reworking of seidments in estuaryies.
1997, 15(4): 78-85.
Abstract:
In this paper, the problems of oil-form Coal in Junggar basin were discussed on the basis of organicpetrology and organic geochemistry.It was showed that Jurassic coals contain a lot of liptinites, higherliptinite content (especially higher Cutinite content of liptinites) of coals may cause the qeneration ofhigh-wax oils, the contents of liptinites and desmocollinites in coals depend on the value of hydrogen in-dex and Rock-Eval pyrolysis yield (S2), they are main oil-generating macerals, the fact of some oil gener-ating from Jurassic coals was confirmed by identifying oil drops, micrinites and bituminites under micro-scope.the characteristics of oil-expulsion from coals was further studied with hydrocarbon expulsionsimulation.In addition, we studied Jurassic sedimentary organic facies and divided coal measures intofour facies types based on comprehensive studies of organic petrology, organic geoehemistry and sedi-mentary environment,i.e.high moor organic facies, forest swamp organic facies, running water facies andopen water organic facies, among them forest swamp organic facies and running water swamp organic fa-cies are the best organic facies of hydrocarbon generation.
In this paper, the problems of oil-form Coal in Junggar basin were discussed on the basis of organicpetrology and organic geochemistry.It was showed that Jurassic coals contain a lot of liptinites, higherliptinite content (especially higher Cutinite content of liptinites) of coals may cause the qeneration ofhigh-wax oils, the contents of liptinites and desmocollinites in coals depend on the value of hydrogen in-dex and Rock-Eval pyrolysis yield (S2), they are main oil-generating macerals, the fact of some oil gener-ating from Jurassic coals was confirmed by identifying oil drops, micrinites and bituminites under micro-scope.the characteristics of oil-expulsion from coals was further studied with hydrocarbon expulsionsimulation.In addition, we studied Jurassic sedimentary organic facies and divided coal measures intofour facies types based on comprehensive studies of organic petrology, organic geoehemistry and sedi-mentary environment,i.e.high moor organic facies, forest swamp organic facies, running water facies andopen water organic facies, among them forest swamp organic facies and running water swamp organic fa-cies are the best organic facies of hydrocarbon generation.
1997, 15(4): 91-96,77.
Abstract:
Fossil crust of weathering played an important role in the reservior, migration and accumulation ofoil and gas, for example the formation of Some important oil or gas pools in the North of China, OrdosBasin and Tarium Basin, which is related to the fossil crust of weathering on the top of carbonate forma-tions.The synthetically fluid dynamics, chemical dynamics and chemical thermodynamics were used tomodel dynamically the rock- fluid reaction process of and to restore the fluid dynamic field and chemicaldynamic field of the fossil crust of weathering during the period of weathering and leaching, so as to pre-dict the changes of physical parameters, such as porosity and permeability, and to provide the parametersfor reservior quantative evaluation.The modelling reseach on the rock- fliud dynamics is to restore dy-namically the interaction process between the rock and fluid, which has important theoretical and practi-cal meanings.
Fossil crust of weathering played an important role in the reservior, migration and accumulation ofoil and gas, for example the formation of Some important oil or gas pools in the North of China, OrdosBasin and Tarium Basin, which is related to the fossil crust of weathering on the top of carbonate forma-tions.The synthetically fluid dynamics, chemical dynamics and chemical thermodynamics were used tomodel dynamically the rock- fluid reaction process of and to restore the fluid dynamic field and chemicaldynamic field of the fossil crust of weathering during the period of weathering and leaching, so as to pre-dict the changes of physical parameters, such as porosity and permeability, and to provide the parametersfor reservior quantative evaluation.The modelling reseach on the rock- fliud dynamics is to restore dy-namically the interaction process between the rock and fluid, which has important theoretical and practi-cal meanings.
1997, 15(4): 103-108.
Abstract:
The GC /MS analyses for alkanes from Late Jurassic source rocks of the Liudong depression, KailuBasin, northeastern China showed that the concentration of diasteranes in some samples decreasesanomalously with depth, suggesting that in this case the formation of these compounds may be not de-pended on maturity.On the other hand, there is not an obvious relationship between the content of di-asteranes and the composition of clay minerals in rocks,indicating that the acid catalytic nature of differ-ent clay minerals is similar.It is found that the formation of diasterane is related to the oxidation-reduc-tion nature of depositional environment.The anoxic and high reducing deposits(Pr /Ph < 0.5) may lead tosuppress the acid catalyzed rearrangement process of sterene formed early during diagenesis.So, thesesediments contain a low content of diasteranes.Conversely, when the depositional condition becomes lessanoxic and oxic, with an increase in Pr /Ph, the concentration of diasteranens increases significantly.Itseems that the oxicity of sediments during diagenesis may be responsible for the formation of diaster-anes.
The GC /MS analyses for alkanes from Late Jurassic source rocks of the Liudong depression, KailuBasin, northeastern China showed that the concentration of diasteranes in some samples decreasesanomalously with depth, suggesting that in this case the formation of these compounds may be not de-pended on maturity.On the other hand, there is not an obvious relationship between the content of di-asteranes and the composition of clay minerals in rocks,indicating that the acid catalytic nature of differ-ent clay minerals is similar.It is found that the formation of diasterane is related to the oxidation-reduc-tion nature of depositional environment.The anoxic and high reducing deposits(Pr /Ph < 0.5) may lead tosuppress the acid catalyzed rearrangement process of sterene formed early during diagenesis.So, thesesediments contain a low content of diasteranes.Conversely, when the depositional condition becomes lessanoxic and oxic, with an increase in Pr /Ph, the concentration of diasteranens increases significantly.Itseems that the oxicity of sediments during diagenesis may be responsible for the formation of diaster-anes.
1997, 15(4): 115-120.
Abstract:
The hydrodynamics field in the Songliao basin is obviously asymmetrical with the characteristics ofgravity- induced centripetal flow recharged by meteoric water mainly in its northern region, centrifugalflow and cross-formational flow in the basin center area, groundwater discharged by cross-formationalflow and evaporation in its southern area, and meteoric water permeating dow nwards only along thebasin rim and uplifted areas locally and unabidingly.Centrifugal flow caused by mudstone-compactedwater is the main dynamic force which induces the petroleum migration and accumulationin the Songliaobasin.Paleohydrogeologic cycles and centrifugal flow stages induced the migration by stages and step-mannular distribution of oil and gas in an independent hydrodynamic system.Multidepressions for theSongliao basin would have developped several hydrodynamic systems.Of which two major ones are lo-cated at the Sanzhao and Qijia-Gulong depressinons, and they made up a double step-annular distributionof oil and gas in the Songliao basin.Inside are multirings of oil, which are encapsulated by uncontinuousnatural gas pools.All of them are concentric with their depressions mainly due to symmetric and concen-tric centrifugal flow.
The hydrodynamics field in the Songliao basin is obviously asymmetrical with the characteristics ofgravity- induced centripetal flow recharged by meteoric water mainly in its northern region, centrifugalflow and cross-formational flow in the basin center area, groundwater discharged by cross-formationalflow and evaporation in its southern area, and meteoric water permeating dow nwards only along thebasin rim and uplifted areas locally and unabidingly.Centrifugal flow caused by mudstone-compactedwater is the main dynamic force which induces the petroleum migration and accumulationin the Songliaobasin.Paleohydrogeologic cycles and centrifugal flow stages induced the migration by stages and step-mannular distribution of oil and gas in an independent hydrodynamic system.Multidepressions for theSongliao basin would have developped several hydrodynamic systems.Of which two major ones are lo-cated at the Sanzhao and Qijia-Gulong depressinons, and they made up a double step-annular distributionof oil and gas in the Songliao basin.Inside are multirings of oil, which are encapsulated by uncontinuousnatural gas pools.All of them are concentric with their depressions mainly due to symmetric and concen-tric centrifugal flow.
1997, 15(4): 127-133,147.
Abstract:
Through the systematic study of trace elements and REE geochemistry of mudstones deposited inthe basin and lower slope environments from the Upper Proterozoic to the Triassic in the SouthwestYangtze Massif, three geochemical abnormal horizons, Lower Cambrian, Upper Devonian and Upper Per-mian, were discovered.Because of the alternate occurrence of three geochemical abnormal horizons, threegeochemical cycles in geological history were distinguished.The geochemical cycles are corresponding tothe geotectonic ones in this area.The geochemical abnormal horizons are corresponding to the pull-apartstages of geotectonic cycles and to a series of geological events, such as hydrothermal sedimentaryevents, anoxic events, extinct events of living things and so on.That so many events occur red in the geo-chemical abnormal horizons at the same time indicated these geochemical anomalies are the result ofearth evolution.They are the products originating in the particular stages of earth evolution.So thesegeochemical anomalies, conversely, are the effective geochemical tracer to understand the earth, especiallythe crustal evolution.
Through the systematic study of trace elements and REE geochemistry of mudstones deposited inthe basin and lower slope environments from the Upper Proterozoic to the Triassic in the SouthwestYangtze Massif, three geochemical abnormal horizons, Lower Cambrian, Upper Devonian and Upper Per-mian, were discovered.Because of the alternate occurrence of three geochemical abnormal horizons, threegeochemical cycles in geological history were distinguished.The geochemical cycles are corresponding tothe geotectonic ones in this area.The geochemical abnormal horizons are corresponding to the pull-apartstages of geotectonic cycles and to a series of geological events, such as hydrothermal sedimentaryevents, anoxic events, extinct events of living things and so on.That so many events occur red in the geo-chemical abnormal horizons at the same time indicated these geochemical anomalies are the result ofearth evolution.They are the products originating in the particular stages of earth evolution.So thesegeochemical anomalies, conversely, are the effective geochemical tracer to understand the earth, especiallythe crustal evolution.
1997, 15(4): 143-147.
Abstract:
The multiple - stage diagenesis was revealed by the cathodoluminescence of carbonate rock samples.The minerals pre-cipitated in shallow - burial condition where the primary diagenesis occured are higha in a Mn content with weak lumines-cence, which resulted from the drop of Eh and pH values due to the decomposition of organic substances.With furtherfalling of the Eh and pHvalues, the increase of Fe 2+ contained in the minerals quenched the luminescence.Being in a deep -burialcondition, the pHvalue was controlled by the equilibrium between carbonate minerals and water, so the environmentis alkalescent.The condition is favourable to the formation of M n (Ⅱ ) cation and contrary to Fe (Ⅱ ) cation.As a result,this precipitated minerals have a bright luminousness.The carbon and oxygen isotope compositions of the whole rocks deviated from the range of marine environment butweve close to that of fresh - water diagenetic environment.Diagenetic solution based on the Sr / Ca ratio in the minerals wasanalogous to that of fresh - water mixed with less than 10 % marine - water.This solution made the minerals in lime - mudsediments dissolved and brougt about dissolved - reprecipitatlon a dynamic equilibrium with the increase of saturation.Baced on the studies above, the authors suggested “ dissolved - solidification ” is a new diagenetic pattem of lime - mudsediments solidified in fresh - water by way of dissolved - reprecipitation, which made the new minerals arranged inseparably.
The multiple - stage diagenesis was revealed by the cathodoluminescence of carbonate rock samples.The minerals pre-cipitated in shallow - burial condition where the primary diagenesis occured are higha in a Mn content with weak lumines-cence, which resulted from the drop of Eh and pH values due to the decomposition of organic substances.With furtherfalling of the Eh and pHvalues, the increase of Fe 2+ contained in the minerals quenched the luminescence.Being in a deep -burialcondition, the pHvalue was controlled by the equilibrium between carbonate minerals and water, so the environmentis alkalescent.The condition is favourable to the formation of M n (Ⅱ ) cation and contrary to Fe (Ⅱ ) cation.As a result,this precipitated minerals have a bright luminousness.The carbon and oxygen isotope compositions of the whole rocks deviated from the range of marine environment butweve close to that of fresh - water diagenetic environment.Diagenetic solution based on the Sr / Ca ratio in the minerals wasanalogous to that of fresh - water mixed with less than 10 % marine - water.This solution made the minerals in lime - mudsediments dissolved and brougt about dissolved - reprecipitatlon a dynamic equilibrium with the increase of saturation.Baced on the studies above, the authors suggested “ dissolved - solidification ” is a new diagenetic pattem of lime - mudsediments solidified in fresh - water by way of dissolved - reprecipitation, which made the new minerals arranged inseparably.
1997, 15(4): 152-158.
Abstract:
The elemental geochmical analysis results on 18 samples taken from a 115m thick loess sectionwhich is located in Wuwei on the south vicinity of Tengger Desert, showed that the 8 common elementaloxides make up 88.99 % of the material with a very narrow variable range, from 87.26 to 90.46 per cent,indicating the Similarity of the loess material in the whole section.The average weathering indices ex-pressed by the ratios of Fe 2 O 3 /FeO and Al 2 O 3 /SiO 2 are 1.46 and 0.19, ranging from 1.02 to 2.86 and0.17 to 0.22, respectively.The average content of REE is 185.42 μ g /g, ranging from 169.31 to199.82 μ g /g and the REE distribution pattern is of a relatively big slope and obvious anomal and of Eu,in the reference with the ratio of LREE/HREE, which is 8.23 averagely, ranging from 7.38 to 9.60 andshowing a relatively stong fractionation which indicates a considerable degree of weathering.At thesametime, the indices of Eu /Sm, Sm /Nd, Nd /La,δ Eu andδ Ce proved that the loess materials of differentages are transported from a common source area that is similar to the typical loess in Loess Plateau.
The elemental geochmical analysis results on 18 samples taken from a 115m thick loess sectionwhich is located in Wuwei on the south vicinity of Tengger Desert, showed that the 8 common elementaloxides make up 88.99 % of the material with a very narrow variable range, from 87.26 to 90.46 per cent,indicating the Similarity of the loess material in the whole section.The average weathering indices ex-pressed by the ratios of Fe 2 O 3 /FeO and Al 2 O 3 /SiO 2 are 1.46 and 0.19, ranging from 1.02 to 2.86 and0.17 to 0.22, respectively.The average content of REE is 185.42 μ g /g, ranging from 169.31 to199.82 μ g /g and the REE distribution pattern is of a relatively big slope and obvious anomal and of Eu,in the reference with the ratio of LREE/HREE, which is 8.23 averagely, ranging from 7.38 to 9.60 andshowing a relatively stong fractionation which indicates a considerable degree of weathering.At thesametime, the indices of Eu /Sm, Sm /Nd, Nd /La,δ Eu andδ Ce proved that the loess materials of differentages are transported from a common source area that is similar to the typical loess in Loess Plateau.
1997, 15(4): 165-168.
Abstract:
The paper "The Existence of Allophane Heated Metakaolinite" was published by He Hongping et alin No4 of Acat Mineralogica Sinica, 1995.In the paper, the author thought that the spectrum peak ar-round -79.0 × 10- 6of M ASNMR spectra was originated from allophane, not from Al-Si spinel.This opin-ion is relatively rational because Liu Changling had stated that pianlinite originated from allophane dur-ing diagenetic stage.Howeuer, we don't agree with the opinion that heated kaolinite became allophanethrough late hydration, we think allophane is originally deposited in swamp;during diagenesis it changesinto planlinite, thus pianlinite is not formed by coal combustion, Some of its physical and chemical prop-erties are different from that of metakaolinite.
The paper "The Existence of Allophane Heated Metakaolinite" was published by He Hongping et alin No4 of Acat Mineralogica Sinica, 1995.In the paper, the author thought that the spectrum peak ar-round -79.0 × 10- 6of M ASNMR spectra was originated from allophane, not from Al-Si spinel.This opin-ion is relatively rational because Liu Changling had stated that pianlinite originated from allophane dur-ing diagenetic stage.Howeuer, we don't agree with the opinion that heated kaolinite became allophanethrough late hydration, we think allophane is originally deposited in swamp;during diagenesis it changesinto planlinite, thus pianlinite is not formed by coal combustion, Some of its physical and chemical prop-erties are different from that of metakaolinite.
