2015 Vol. 33, No. 1
Display Method:
2015, 33(1): 1-9.
doi: 10.14027/j.cnki.cjxb.2015.01.001
Abstract:
The innovative achievements in basic scientific research and applied basic research are mainly published as articles in related specialized periodicals. The "Acta Sedimentologica Sinica" has been published for 31 a, which is concentrated on sedimentology, sedimentary minerals and geochemistry. This article uses the detailed bibliographic data obtained from the database to analyze the publication tendency in 31 a. Through quantificational analysis on articles' number, discipline classification, study area, core-authors group, research hot spots, annual variation of these indices have been illustrated, so do as the research content and direction, research institutes, researchers' distribution change and main funding resources. The result indicated that in recent 31 a, the number of articles published in the "Acta Sedimentologica Sinica" assumes the fluctuant growth tendency; the related research institutes has the obvious subject relevance, they are mainly concentrated on geology, mineral and oil; research hotspots include depositional environment and depositional systems, carbonate rocks, diagenesis, sequence stratigraphy, main sedimentary basin analysis and simulation, sedimentation, oil and gas reservoir sedimentology, sedimentary deposit, organic geochemistry and isotope geochemistry of the elements. The results of bibliometric analysis on citing literatures show that the citing frequency by CSCD and SCIE and impact factor enhances progressively, which further explains the attention of academia to sedimentology and the related questions strengthens unceasingly. 40 percents funding is National Natural Science Foundation. However, the core author group of "Acta Sedimentologica Sinica" has not really formed because of the new researchers' joining and the outstanding ones starting to enhance the international influence by submitting their articles to other related international journals, suggesting the new opportunity and the challenge to the future development of the journal.
The innovative achievements in basic scientific research and applied basic research are mainly published as articles in related specialized periodicals. The "Acta Sedimentologica Sinica" has been published for 31 a, which is concentrated on sedimentology, sedimentary minerals and geochemistry. This article uses the detailed bibliographic data obtained from the database to analyze the publication tendency in 31 a. Through quantificational analysis on articles' number, discipline classification, study area, core-authors group, research hot spots, annual variation of these indices have been illustrated, so do as the research content and direction, research institutes, researchers' distribution change and main funding resources. The result indicated that in recent 31 a, the number of articles published in the "Acta Sedimentologica Sinica" assumes the fluctuant growth tendency; the related research institutes has the obvious subject relevance, they are mainly concentrated on geology, mineral and oil; research hotspots include depositional environment and depositional systems, carbonate rocks, diagenesis, sequence stratigraphy, main sedimentary basin analysis and simulation, sedimentation, oil and gas reservoir sedimentology, sedimentary deposit, organic geochemistry and isotope geochemistry of the elements. The results of bibliometric analysis on citing literatures show that the citing frequency by CSCD and SCIE and impact factor enhances progressively, which further explains the attention of academia to sedimentology and the related questions strengthens unceasingly. 40 percents funding is National Natural Science Foundation. However, the core author group of "Acta Sedimentologica Sinica" has not really formed because of the new researchers' joining and the outstanding ones starting to enhance the international influence by submitting their articles to other related international journals, suggesting the new opportunity and the challenge to the future development of the journal.
2015, 33(1): 10-20.
doi: 10.14027/j.cnki.cjxb.2015.01.002
Abstract:
As a major focus of both academic and industrial circles, deep-water sandy sedimentation is not only a record of gravity flows transporting a great deal of continental sediments into basin, but also important reservoir of oil and gas with great economic value. Subaqueous sediment density flows are one of the most important processes for moving sediments from provenance to depositional basins, but people still know little about these subaqueous gravity flows such as slump, sandy debris flow, muddy debris flow, granular flow, fluidized flow, turbidite current, and so on. What is more, they are extremely difficult to monitor directly. A new kind of gravity flow sandstone deposits diferent to sandy debris flow and slumping turbidity current was discovered in the sixth and seventh member of Yanchang Formation (for short, YC6 and YC7 members) in the southern part of the deep lacustrine Ordos Basin. Characteristics of the gravity flow deposits dominated by: ① a series of upward coarsening interval (inverse grading) and upward fining interval (normal grading) always exist in pairs; ② changes of relative high clay content (high-low-high) consistent with that of granularity (fine-coarse-fine) in each size-graded couplet; ③ inner micro-erosion surface sometimes separated a couplet of an upper, upward fining interval and a lower, upward-coarsening interval; ④ sandstone interbedded with dark mudstone and grey siltstone; and ⑤ granularity changes in silty mudstone is similar to that of sandstone. It was considered as flood-generated hyperpycnal flow deposit in the late Triassic deep lacustrine Ordos Basin, based on drill core observation and slice identification. A hyperpycnal flow is a kind of sustainable turbidity current occurring at a flooding river mouth when the concentration of suspended sediment is so large that the density of the river water is greater than that of lake (sea) water. It is turbid river plume that can plunge to form turbidity current where it enters a water body with lesser density and flow at basin floor. Associated with high-suspended concentration, hyperpycnal flow can transport considerable volume of sediment to lacustrine basins. Mapping of individual flow deposits (beds) emphasizes how a single event can contain several flow types, with transformations between flow types. Flow transformation may be from dilute to dense flow, as well as from dense to dilute flow. Turbid river flow must move through transfer belt of a backwater zone, depth-limited plume, and plunging zone before becoming a turbidity current. The transfer belt can extend tens of kilometers offshore and significantly affect the transfer of momentum from river to turbidity current. Sedimentary architecture of deep lacustrine gravity flows in the southern part of the late Triassic Ordos bain consist of sandy debris flow deposits, turbidites and hyperpycnites, interbedded with fine-grained deposits (thin turbidites, hyperpycnites, and deep lacustrine mudstones). Sand and mud rich turbidite systems fed by mountainous “dirty” rivers and slumps at deep angle deltas front. Storm-influenced, hyperpycnal flows generated subaqueous channelized forms at the mouth of the river deltas, which later filled with sand. The typical deposit of hyperpycnal flow in the YC6 and YC7 members in the southern part of the deep lacustrine Ordos Basin is a compound of a basal coarsening-up unit, deposited during the waxing period of discharge, and a top fining-up unit formed during the waning period of discharge. Hyperpycnites differ from other turbidites because of their well-developed inversely graded intervals and intrasequence erosional contacts. Deposits of hyperpycnal flow, hyperpycnite is different to others turbidite as for well developed upward-coarsening interval and inner micro-erosion surface in size-graded couplets. The lower, upward-coarsening interval represents deposition of waxing hyperpycnal flow. The upper, upward-fining interval was generated from waning hyperpycnal flow. The two parts of the size-graded couplet of upward-coarsening interval and upward-fining interval in pairs represent a cycle of event sedimentary of flood-generated hyperpycnal flow. The micro-erosion surface that sometimes divides the two parts of the size-graded couplet resulted from waxing flows of sufficiently high velocity to erode the sediment previously deposited by the same flow. Some bed forms and sediment grading patterns in hyperpycnal- flow deposits can record multiple flow accelerations and decelerations even during a simple single-peaked flood. Because hyperpycnal flow provides one of the most direct connections between terrestrial sediment sources and lacustrine depositional basin, its deposits might preserve an important record across a variety of climatic and tectonic settings. Depositional processes in the late Triassic deep lacustrine in the studied area were dominated by sediment gravity flows originating from gravity induced slumps and mountainous “dirty” river discharged hyperpycnal flow. Gravity flows deposits in the YC6 and YC7 members in the southern part of the deep lacustrine Ordos Basin appear to be primarily controlled by the strong climatic and tectonic forcing parameters. The basin also must be deep enough, in some cases greater than tens of meters, in order for the plume to collapse and form a turbidity current. All in all, controlling factors of hyperpycnal flow include seasonal flood river, deep angle depositional slope, enough water depth and large density difference between basinal water mass and discharged flood river. The discovery of hyperpycnite in Yanchang Formation in the Ordos Basin can not only provide an example to probe hyperpycnal flow deposits in continental lacustrine environment, but also has theoretical and realistic significances to study on genesis of deep water sandbodies, to reservoir forecasting and oil-gas exploration.
As a major focus of both academic and industrial circles, deep-water sandy sedimentation is not only a record of gravity flows transporting a great deal of continental sediments into basin, but also important reservoir of oil and gas with great economic value. Subaqueous sediment density flows are one of the most important processes for moving sediments from provenance to depositional basins, but people still know little about these subaqueous gravity flows such as slump, sandy debris flow, muddy debris flow, granular flow, fluidized flow, turbidite current, and so on. What is more, they are extremely difficult to monitor directly. A new kind of gravity flow sandstone deposits diferent to sandy debris flow and slumping turbidity current was discovered in the sixth and seventh member of Yanchang Formation (for short, YC6 and YC7 members) in the southern part of the deep lacustrine Ordos Basin. Characteristics of the gravity flow deposits dominated by: ① a series of upward coarsening interval (inverse grading) and upward fining interval (normal grading) always exist in pairs; ② changes of relative high clay content (high-low-high) consistent with that of granularity (fine-coarse-fine) in each size-graded couplet; ③ inner micro-erosion surface sometimes separated a couplet of an upper, upward fining interval and a lower, upward-coarsening interval; ④ sandstone interbedded with dark mudstone and grey siltstone; and ⑤ granularity changes in silty mudstone is similar to that of sandstone. It was considered as flood-generated hyperpycnal flow deposit in the late Triassic deep lacustrine Ordos Basin, based on drill core observation and slice identification. A hyperpycnal flow is a kind of sustainable turbidity current occurring at a flooding river mouth when the concentration of suspended sediment is so large that the density of the river water is greater than that of lake (sea) water. It is turbid river plume that can plunge to form turbidity current where it enters a water body with lesser density and flow at basin floor. Associated with high-suspended concentration, hyperpycnal flow can transport considerable volume of sediment to lacustrine basins. Mapping of individual flow deposits (beds) emphasizes how a single event can contain several flow types, with transformations between flow types. Flow transformation may be from dilute to dense flow, as well as from dense to dilute flow. Turbid river flow must move through transfer belt of a backwater zone, depth-limited plume, and plunging zone before becoming a turbidity current. The transfer belt can extend tens of kilometers offshore and significantly affect the transfer of momentum from river to turbidity current. Sedimentary architecture of deep lacustrine gravity flows in the southern part of the late Triassic Ordos bain consist of sandy debris flow deposits, turbidites and hyperpycnites, interbedded with fine-grained deposits (thin turbidites, hyperpycnites, and deep lacustrine mudstones). Sand and mud rich turbidite systems fed by mountainous “dirty” rivers and slumps at deep angle deltas front. Storm-influenced, hyperpycnal flows generated subaqueous channelized forms at the mouth of the river deltas, which later filled with sand. The typical deposit of hyperpycnal flow in the YC6 and YC7 members in the southern part of the deep lacustrine Ordos Basin is a compound of a basal coarsening-up unit, deposited during the waxing period of discharge, and a top fining-up unit formed during the waning period of discharge. Hyperpycnites differ from other turbidites because of their well-developed inversely graded intervals and intrasequence erosional contacts. Deposits of hyperpycnal flow, hyperpycnite is different to others turbidite as for well developed upward-coarsening interval and inner micro-erosion surface in size-graded couplets. The lower, upward-coarsening interval represents deposition of waxing hyperpycnal flow. The upper, upward-fining interval was generated from waning hyperpycnal flow. The two parts of the size-graded couplet of upward-coarsening interval and upward-fining interval in pairs represent a cycle of event sedimentary of flood-generated hyperpycnal flow. The micro-erosion surface that sometimes divides the two parts of the size-graded couplet resulted from waxing flows of sufficiently high velocity to erode the sediment previously deposited by the same flow. Some bed forms and sediment grading patterns in hyperpycnal- flow deposits can record multiple flow accelerations and decelerations even during a simple single-peaked flood. Because hyperpycnal flow provides one of the most direct connections between terrestrial sediment sources and lacustrine depositional basin, its deposits might preserve an important record across a variety of climatic and tectonic settings. Depositional processes in the late Triassic deep lacustrine in the studied area were dominated by sediment gravity flows originating from gravity induced slumps and mountainous “dirty” river discharged hyperpycnal flow. Gravity flows deposits in the YC6 and YC7 members in the southern part of the deep lacustrine Ordos Basin appear to be primarily controlled by the strong climatic and tectonic forcing parameters. The basin also must be deep enough, in some cases greater than tens of meters, in order for the plume to collapse and form a turbidity current. All in all, controlling factors of hyperpycnal flow include seasonal flood river, deep angle depositional slope, enough water depth and large density difference between basinal water mass and discharged flood river. The discovery of hyperpycnite in Yanchang Formation in the Ordos Basin can not only provide an example to probe hyperpycnal flow deposits in continental lacustrine environment, but also has theoretical and realistic significances to study on genesis of deep water sandbodies, to reservoir forecasting and oil-gas exploration.
2015, 33(1): 21-35.
doi: 10.14027/j.cnki.cjxb.2015.01.003
Abstract:
To further investigate the Paleozoic organic-rich shale development and distribution characteristics in the Yangtze Continental Block, and the depositional model, we systematically collected and compiled large data sets of organic-rich shales for the Lower Cambrian Niutitang equivalent Formation and Upper Ordovician Wufeng-Lower Silurian Longmaxi equivalent Formation. Outcrop in Zhalagou of Sandu county, Guizhou province and Zhao 104 wells Junlian Prefecture, Sichuan Province were selected for the systematic observation, sample tests, sedimentary facies, and so on. Regional reconstruction of paleogeography and correlation between different regions show that the Yangtze block was passive continental margin during the early Paleozoic and peripheral foreland during early Silurian. Niutitang equivalent shales were deposited in a passive continental margin environment, the upwelling nutrient flow and anoxic events in complex depositional model is interpreted for the depositional model of Lower Cambrian shale in Yangtze Block, organic-rich thick shale was mainly developed in the southeastern margin of the Yangtze block deep water shelf to slope facies; Ordovician Wufeng- Lower Silurian Longmaxi equivalent shales were deposited in the Caledonian orogenic front of the periphery foreland environment, organic-rich thick shale was mainly developed in in the anoxic intra-shelf low setting in southeastern margin of the Upper to middle Yangtze block.
To further investigate the Paleozoic organic-rich shale development and distribution characteristics in the Yangtze Continental Block, and the depositional model, we systematically collected and compiled large data sets of organic-rich shales for the Lower Cambrian Niutitang equivalent Formation and Upper Ordovician Wufeng-Lower Silurian Longmaxi equivalent Formation. Outcrop in Zhalagou of Sandu county, Guizhou province and Zhao 104 wells Junlian Prefecture, Sichuan Province were selected for the systematic observation, sample tests, sedimentary facies, and so on. Regional reconstruction of paleogeography and correlation between different regions show that the Yangtze block was passive continental margin during the early Paleozoic and peripheral foreland during early Silurian. Niutitang equivalent shales were deposited in a passive continental margin environment, the upwelling nutrient flow and anoxic events in complex depositional model is interpreted for the depositional model of Lower Cambrian shale in Yangtze Block, organic-rich thick shale was mainly developed in the southeastern margin of the Yangtze block deep water shelf to slope facies; Ordovician Wufeng- Lower Silurian Longmaxi equivalent shales were deposited in the Caledonian orogenic front of the periphery foreland environment, organic-rich thick shale was mainly developed in in the anoxic intra-shelf low setting in southeastern margin of the Upper to middle Yangtze block.
2015, 33(1): 36-48.
doi: 10.14027/j.cnki.cjxb.2015.01.004
Abstract:
Through comprehensive analysis of U-Pb age analysis of detrital zircons in sandstones, change of the content of tephra component, seismic multi-attributes analysis, sequence stratigraphic framework and sedimentary filling, considering that in the Donger member sedimentary period, the provenance supply mode, the sequence stratigraphic framework and sedimentary filling characteristics of the west of Bozhong sag changed obviously. In the sedimentation of SQd2L and it's earlier stage, lake basin was in the intense rift stage, structure activities were intense, basin was interphase concave-convex, sedimentation rate of the basin was accelerated, depth of water deepened, stratum deposited thickly as a whole, lithology were mainly gray-dark grey mudstones conainning lamina medium-fine sandstones and siltstones, granularity was fine as a whole, provenance was mainly the local provenance like Shijiutuo uplift and Shaleitian uplift and Mesozoic igneous rock basement inside the basin, et al, content of tephra in sandstones was high, Mesozoic zircons were also rich, seismic multi-attributes ichnography show that sandstones in the Shijiutuo uplift and Shaleitian uplift two sides were rich, area of red zone is large, sedimentary sequence was obviously controlled by the lower uplifts inside the basin and faults around them, sequence characteristics have remarkable differences between the direction parallel and perpendicular to the provenance, in the direction parallel to the provenance, sequence at Shaleitian side was ansymmetrical cycle which took declining half cycle as principal, it's GR electrical characteristics were smooth finger, the braided river delta sand bodies which distributed approximately to EW were developed, however, sequence at Shijiutuo uplift side took LST which was rising half cycle as principal, it's GR electrical characteristics were infundibulate and box combination, multi-phase fan delta lobes were developed, in the seismic section passing the fan along the provenance direction at the two uplifts, typical foreset features were visible. In the direction perpendicular to the provenance, however, there mainly no significant difference, sequence was ansymmetrical cycle which took declining half cycle mainly, it's GR electrical characteristics were medium-high amplitude finger, shore shallow lake-braided river delta facies were developed; After the sedimentation of SQd2L, lake basin was in the fault depression-depression transition period, area of lake basin was large, depth of water was shallow, fault activities around the lower uplifts inside the basin weakened obviously, stratum was thin as a whole, lithology were primarily conglomeratic sandstones, medium-fine sandstones and siltstones, monolithic granularity was fine, clastics inside basin were mainly came from Yanshan tectonic belt (regional provenance) in the northwest part of the sag, content of tephra in sandstones reduced visibly, detrital zircons in sandstones were primarily Proterozoic zircons, seismic multi-attributes ichnography show that distribution area of red zone decreased obviously, depositional sequence overlapped toward low uplifts inside basin, sequence characeristics have little differences between the direction parallel and perpendicular to the provenance, sequence was primarily ansymmetrical cycle which took declining half cycle chiefly, it's GR electrical characteristics were low amplitude finger and dentation, proximal fan delta sand bodies transformed gradually to distal braided river delta sand bodies, at the same time, broad shore shallow lake environment was developed. In Paleogene sedimentary filling process of the western slope of Bozhong sag, the consistent changes of the stratigraphic pattern, sedimentary mode and provenance supply mode reflect the inherent law of filling evolution of the rifted basin, provide new clues for evolution and division of rift-subsidence cycles of the rifted basins in the eastern part of our country.
Through comprehensive analysis of U-Pb age analysis of detrital zircons in sandstones, change of the content of tephra component, seismic multi-attributes analysis, sequence stratigraphic framework and sedimentary filling, considering that in the Donger member sedimentary period, the provenance supply mode, the sequence stratigraphic framework and sedimentary filling characteristics of the west of Bozhong sag changed obviously. In the sedimentation of SQd2L and it's earlier stage, lake basin was in the intense rift stage, structure activities were intense, basin was interphase concave-convex, sedimentation rate of the basin was accelerated, depth of water deepened, stratum deposited thickly as a whole, lithology were mainly gray-dark grey mudstones conainning lamina medium-fine sandstones and siltstones, granularity was fine as a whole, provenance was mainly the local provenance like Shijiutuo uplift and Shaleitian uplift and Mesozoic igneous rock basement inside the basin, et al, content of tephra in sandstones was high, Mesozoic zircons were also rich, seismic multi-attributes ichnography show that sandstones in the Shijiutuo uplift and Shaleitian uplift two sides were rich, area of red zone is large, sedimentary sequence was obviously controlled by the lower uplifts inside the basin and faults around them, sequence characteristics have remarkable differences between the direction parallel and perpendicular to the provenance, in the direction parallel to the provenance, sequence at Shaleitian side was ansymmetrical cycle which took declining half cycle as principal, it's GR electrical characteristics were smooth finger, the braided river delta sand bodies which distributed approximately to EW were developed, however, sequence at Shijiutuo uplift side took LST which was rising half cycle as principal, it's GR electrical characteristics were infundibulate and box combination, multi-phase fan delta lobes were developed, in the seismic section passing the fan along the provenance direction at the two uplifts, typical foreset features were visible. In the direction perpendicular to the provenance, however, there mainly no significant difference, sequence was ansymmetrical cycle which took declining half cycle mainly, it's GR electrical characteristics were medium-high amplitude finger, shore shallow lake-braided river delta facies were developed; After the sedimentation of SQd2L, lake basin was in the fault depression-depression transition period, area of lake basin was large, depth of water was shallow, fault activities around the lower uplifts inside the basin weakened obviously, stratum was thin as a whole, lithology were primarily conglomeratic sandstones, medium-fine sandstones and siltstones, monolithic granularity was fine, clastics inside basin were mainly came from Yanshan tectonic belt (regional provenance) in the northwest part of the sag, content of tephra in sandstones reduced visibly, detrital zircons in sandstones were primarily Proterozoic zircons, seismic multi-attributes ichnography show that distribution area of red zone decreased obviously, depositional sequence overlapped toward low uplifts inside basin, sequence characeristics have little differences between the direction parallel and perpendicular to the provenance, sequence was primarily ansymmetrical cycle which took declining half cycle chiefly, it's GR electrical characteristics were low amplitude finger and dentation, proximal fan delta sand bodies transformed gradually to distal braided river delta sand bodies, at the same time, broad shore shallow lake environment was developed. In Paleogene sedimentary filling process of the western slope of Bozhong sag, the consistent changes of the stratigraphic pattern, sedimentary mode and provenance supply mode reflect the inherent law of filling evolution of the rifted basin, provide new clues for evolution and division of rift-subsidence cycles of the rifted basins in the eastern part of our country.
2015, 33(1): 49-59.
doi: 10.14027/j.cnki.cjxb.2015.01.005
Abstract:
At present, piedmont belt in the northern margin of Junggar Basin is one of the key zone in oil-gas exploration fields. For the purpose of explaining the question in the piedmont belt sedimentary research, with the Chunhui exploration area of Hala'alt front edge in the northern margin of Junggar Basin for target, the sedimentary characteristics and provenance of Jurassic Badaowan Formation was studied comprehensively using methods of core, drilling and logging data, and a large number of sedimentologic experiment. The results have confirmed that the coarse clastic sediments belong to the typical proximal deposit, which are mainly from northwest Hala'alt mountains. By analyzing tectonic and depositional histories, combining with recent sediment investigation, two origins of high-psephicity near-source gravel from piedmont zone were concluded, which formed in the littoral environment stage and humid fan environment of retransported stage, respectively. In the end, the humid fan facies model of Jurassic Badaowan Formation in Chunhui exploration area was established.
At present, piedmont belt in the northern margin of Junggar Basin is one of the key zone in oil-gas exploration fields. For the purpose of explaining the question in the piedmont belt sedimentary research, with the Chunhui exploration area of Hala'alt front edge in the northern margin of Junggar Basin for target, the sedimentary characteristics and provenance of Jurassic Badaowan Formation was studied comprehensively using methods of core, drilling and logging data, and a large number of sedimentologic experiment. The results have confirmed that the coarse clastic sediments belong to the typical proximal deposit, which are mainly from northwest Hala'alt mountains. By analyzing tectonic and depositional histories, combining with recent sediment investigation, two origins of high-psephicity near-source gravel from piedmont zone were concluded, which formed in the littoral environment stage and humid fan environment of retransported stage, respectively. In the end, the humid fan facies model of Jurassic Badaowan Formation in Chunhui exploration area was established.
2015, 33(1): 60-66.
doi: 10.14027/j.cnki.cjxb.2015.01.006
Abstract:
It is common method to utilize the geochemical information in carbonate rocks to study the ancient environment and climate changes in the geological history. As in early 1980s, the whole-rock carbonate was studied as main samples. Recently, more attentions has been attracted by brachiopod fossil shells because of their composition which was the low magnesium calcite with high capacity to resist the diagenetic alteration. In this study, the comparison of δ18O, δ13C and 87Sr/86Sr respectively from brachiopod fossil shells and whole carbonate rocks in Longmen mountian in Sichuan province showed: there was higher δ18O values in brachiopod shells, and similar trend in the evolution of 87Sr/86Sr and δ13C between brachiopod fossil shells and the whole rocks carbonate. These results indicated that the geochemical information in the whole rocks carbonate still could be used to as an indicator for reconstructing the evolution of paleoclimate although there were some differences in the geochemical information between the whole rocks carbonate and brachiopod fossil shells, especially in the period within lack of brachiopod fossil shells.
It is common method to utilize the geochemical information in carbonate rocks to study the ancient environment and climate changes in the geological history. As in early 1980s, the whole-rock carbonate was studied as main samples. Recently, more attentions has been attracted by brachiopod fossil shells because of their composition which was the low magnesium calcite with high capacity to resist the diagenetic alteration. In this study, the comparison of δ18O, δ13C and 87Sr/86Sr respectively from brachiopod fossil shells and whole carbonate rocks in Longmen mountian in Sichuan province showed: there was higher δ18O values in brachiopod shells, and similar trend in the evolution of 87Sr/86Sr and δ13C between brachiopod fossil shells and the whole rocks carbonate. These results indicated that the geochemical information in the whole rocks carbonate still could be used to as an indicator for reconstructing the evolution of paleoclimate although there were some differences in the geochemical information between the whole rocks carbonate and brachiopod fossil shells, especially in the period within lack of brachiopod fossil shells.
2015, 33(1): 67-78.
doi: 10.14027/j.cnki.cjxb.2015.01.007
Abstract:
Carbonate rock is widely developed in the Cambrian system in the west Shandong province but rare studies have been conducted on the diagenesis of the carbonate rock there. It can be inferred from microscopic observation of this study that there exist compaction and cementation as distructive diagenesis and dissolution, pressolution and dolomitization as constructive diagenesis in the studied area. Degrading neomorphism and aggrading neomorphism affect the physical properties of the rock differently, the former one makes little sense to improve the physical properties, while the latter one is conducive to the formation of inter-crystalline pores. Combined with the analysis of fluid inclusions, the Zhangxia Formation comprises four continuously evolved diagenetic systems, including seawater, freshwater, connate water and thermobaric water diagenetic systems where different diagenetic fluid systems and diagenesis types are developed. The seawater diagenetic system is characterized by low diagenetic temperature and single-phase fluid inclusion in the environment of the shallow seabed. Diagenesis in this system mainly involves compaction, micritization/cementation (to form fibriform, coaxial fibriform, coaxial proliferative cements), and dolomitization occurred to the oolite at the seawater-freshwater transition zone. In the freshwater diagenetic system, the early stage witnesses the presence of CaCl2-H2O, NaCl-H2O, MgCl2-H2O and NaCl-MgCl2-H2O low salinity water systems under the actions of isometric calcite cementation and freshwater dissolution; the ancient epidiagenetic stage and the epidiagenetic stage are manifested with the dissolution action. In the connate water diagenetic system, the diagenetic fluid systems are prevailed by NaCl-MgCl2-MgSO4 and KCl-CaCl2-H2O under the actions of cementation and presolution. And the diagenetic fluid systems for thermobaric water diagenetic system are dominated by CaCl2-H2O, NaCl-CaCl2-6H2O, NaCl-MgCl2-MgSO4, MgCl2-H2O and FeCl2-H2O under the modification of cementation, burial dissolution, presolution (in the form of coarse stylolite) and aggrading neomorphism. Both freshwater diagenetic system and thermobaric water diagenetic system are suitable for the development of dissolution. Most dissolved pores caused by selective dissolution in freshwater diagenetic system are merely filled with the cements produced in the later stage. But dissolution in thermobaric water diagenetic system can proliferate by 1%~5% of secondary pores. Both the incompletely filled coarse stylolites that are produced from presolution and the inter-crystalline pores developed under aggrading neomorphism are helpful to improve the physical properties of the carbonate rocks.
Carbonate rock is widely developed in the Cambrian system in the west Shandong province but rare studies have been conducted on the diagenesis of the carbonate rock there. It can be inferred from microscopic observation of this study that there exist compaction and cementation as distructive diagenesis and dissolution, pressolution and dolomitization as constructive diagenesis in the studied area. Degrading neomorphism and aggrading neomorphism affect the physical properties of the rock differently, the former one makes little sense to improve the physical properties, while the latter one is conducive to the formation of inter-crystalline pores. Combined with the analysis of fluid inclusions, the Zhangxia Formation comprises four continuously evolved diagenetic systems, including seawater, freshwater, connate water and thermobaric water diagenetic systems where different diagenetic fluid systems and diagenesis types are developed. The seawater diagenetic system is characterized by low diagenetic temperature and single-phase fluid inclusion in the environment of the shallow seabed. Diagenesis in this system mainly involves compaction, micritization/cementation (to form fibriform, coaxial fibriform, coaxial proliferative cements), and dolomitization occurred to the oolite at the seawater-freshwater transition zone. In the freshwater diagenetic system, the early stage witnesses the presence of CaCl2-H2O, NaCl-H2O, MgCl2-H2O and NaCl-MgCl2-H2O low salinity water systems under the actions of isometric calcite cementation and freshwater dissolution; the ancient epidiagenetic stage and the epidiagenetic stage are manifested with the dissolution action. In the connate water diagenetic system, the diagenetic fluid systems are prevailed by NaCl-MgCl2-MgSO4 and KCl-CaCl2-H2O under the actions of cementation and presolution. And the diagenetic fluid systems for thermobaric water diagenetic system are dominated by CaCl2-H2O, NaCl-CaCl2-6H2O, NaCl-MgCl2-MgSO4, MgCl2-H2O and FeCl2-H2O under the modification of cementation, burial dissolution, presolution (in the form of coarse stylolite) and aggrading neomorphism. Both freshwater diagenetic system and thermobaric water diagenetic system are suitable for the development of dissolution. Most dissolved pores caused by selective dissolution in freshwater diagenetic system are merely filled with the cements produced in the later stage. But dissolution in thermobaric water diagenetic system can proliferate by 1%~5% of secondary pores. Both the incompletely filled coarse stylolites that are produced from presolution and the inter-crystalline pores developed under aggrading neomorphism are helpful to improve the physical properties of the carbonate rocks.
2015, 33(1): 79-90.
doi: 10.14027/j.cnki.cjxb.2015.01.008
Abstract:
Tidal flat sedimentation is mainly controlled by sediment supply and hydrodynamic conditions, and the resultant sedimentary records are valuable in the study of the evolution of coastal environments at various time-scales ranging from several days associated with extreme events to millenniums related to climate changes. A strong storm surge event may destroy a relatively thick sedimentary sequences formed over a long period of time. Therefore, it is important to evaluate the influence of extreme events on the continuity and temporal resolution of tidal flat sedimentary records. In the present contribution, an approach to the modeling of the spatial distribution patterns of tidal flat accretion/erosion, under both fair weather and storm surge conditions, is proposed. This model is applied to the Rudong coast, Jiangsu Province, which is exposed to frequent typhoon attack, to illustrate the sediment dynamic processes and the modification of normal tidally-dominated sedimentary sequences associated with storm surges. The model consists of four parts that deal with the current velocity and near-bed shear stress due to tides or combined tide-typhoon effects, suspended sediment transport and vertical (settling and erosion) fluxes, bedload transport and accretion/erosion, and morphological evolution of the bed, respectively. Driven by the tidal water level curve reconstructed by using the harmonic analysis of the observed data from the study area, the model output reproduced the zonation pattern of intertidal flat sedimentation under the fair weather conditions. Furthermore, its prediction about the tidal flat cross-shore profile associated with a small bed slope, strong tidal currents and a weak time-velocity asymmetry, which is characterized by a “double convexity” shape, is consistent with the observed shape for the study area. According to the model output, the two convexities are located in the vicinity of mean high water and mean low water, respectively. Subsequently, the model was run taking into account both tides and storm surges. Under the condition that a storm surge occurs in association with astronomical spring tides, which occurred over the study area in 1981 (i.e., Typhoon No. 8114), the model prediction is that the bed is subjected to mud accretion over the supratidal zone and the upper part of the intertidal zone, while sand erosion occurs over the lower-middle parts of the intertidal zone. Thus, an erosion surface is formed within the sedimentary sequence, representing the storm effect. This pattern, once again, is consistent with the in-situ observation made following the typhoon event for the area. The model output implies that storm-induced sedimentary record can be found in the upper parts of the tidal flat. It should be noted that the results presented here are only preliminary: a number of detailed morphological parameters about the storm deposit are not available in the model output. In the future, the model may be further improved by taking into account the factors such as the boundary characteristics under extreme shallow water conditions, variability of grain size distribution curves, combined tidal currents and waves, biological activities, tidal creek migration and artificial land reclamation. In combination with inverse methods, the forward modeling will be beneficial to a better interpretation of the formation of tidal flat sedimentary records.
Tidal flat sedimentation is mainly controlled by sediment supply and hydrodynamic conditions, and the resultant sedimentary records are valuable in the study of the evolution of coastal environments at various time-scales ranging from several days associated with extreme events to millenniums related to climate changes. A strong storm surge event may destroy a relatively thick sedimentary sequences formed over a long period of time. Therefore, it is important to evaluate the influence of extreme events on the continuity and temporal resolution of tidal flat sedimentary records. In the present contribution, an approach to the modeling of the spatial distribution patterns of tidal flat accretion/erosion, under both fair weather and storm surge conditions, is proposed. This model is applied to the Rudong coast, Jiangsu Province, which is exposed to frequent typhoon attack, to illustrate the sediment dynamic processes and the modification of normal tidally-dominated sedimentary sequences associated with storm surges. The model consists of four parts that deal with the current velocity and near-bed shear stress due to tides or combined tide-typhoon effects, suspended sediment transport and vertical (settling and erosion) fluxes, bedload transport and accretion/erosion, and morphological evolution of the bed, respectively. Driven by the tidal water level curve reconstructed by using the harmonic analysis of the observed data from the study area, the model output reproduced the zonation pattern of intertidal flat sedimentation under the fair weather conditions. Furthermore, its prediction about the tidal flat cross-shore profile associated with a small bed slope, strong tidal currents and a weak time-velocity asymmetry, which is characterized by a “double convexity” shape, is consistent with the observed shape for the study area. According to the model output, the two convexities are located in the vicinity of mean high water and mean low water, respectively. Subsequently, the model was run taking into account both tides and storm surges. Under the condition that a storm surge occurs in association with astronomical spring tides, which occurred over the study area in 1981 (i.e., Typhoon No. 8114), the model prediction is that the bed is subjected to mud accretion over the supratidal zone and the upper part of the intertidal zone, while sand erosion occurs over the lower-middle parts of the intertidal zone. Thus, an erosion surface is formed within the sedimentary sequence, representing the storm effect. This pattern, once again, is consistent with the in-situ observation made following the typhoon event for the area. The model output implies that storm-induced sedimentary record can be found in the upper parts of the tidal flat. It should be noted that the results presented here are only preliminary: a number of detailed morphological parameters about the storm deposit are not available in the model output. In the future, the model may be further improved by taking into account the factors such as the boundary characteristics under extreme shallow water conditions, variability of grain size distribution curves, combined tidal currents and waves, biological activities, tidal creek migration and artificial land reclamation. In combination with inverse methods, the forward modeling will be beneficial to a better interpretation of the formation of tidal flat sedimentary records.
2015, 33(1): 91-96.
doi: 10.14027/j.cnki.cjxb.2015.01.009
Abstract:
Over the past five decades, the Aral Sea, as the world's fourth largest lake, has a rapid decline of area, a serious decline in quality of the environment and has a devastating impact on most of the Central Asian region. Although the water level of the Aral Sea descent lasted relatively short but had significant changes, in order to understand the detailed process of this change, we collected AS17 shallow drilling core holes from the northern Aral Sea in 1997. Through the comprehensive analysis of mineralogy, ostracods, pollen and other deposits environmental indicators, it shows that the core had a series of significant changes in mineralogical characteristics and biological characteristics, reveals three distinct phases that the Aral Sea depositional environment has experienced during the past nearly 500 years: increase decrease and again increase in salinity, and provides new evidence to the 15th century drought in the Aral Sea.
Over the past five decades, the Aral Sea, as the world's fourth largest lake, has a rapid decline of area, a serious decline in quality of the environment and has a devastating impact on most of the Central Asian region. Although the water level of the Aral Sea descent lasted relatively short but had significant changes, in order to understand the detailed process of this change, we collected AS17 shallow drilling core holes from the northern Aral Sea in 1997. Through the comprehensive analysis of mineralogy, ostracods, pollen and other deposits environmental indicators, it shows that the core had a series of significant changes in mineralogical characteristics and biological characteristics, reveals three distinct phases that the Aral Sea depositional environment has experienced during the past nearly 500 years: increase decrease and again increase in salinity, and provides new evidence to the 15th century drought in the Aral Sea.
2015, 33(1): 97-104.
doi: 10.14027/j.cnki.cjxb.2015.01.010
Abstract:
Qinghai Lake is a typical intermontane downfaulted lake in the arid region of northwest China. It is very similar to some continental petroliferous basins, and developed a series of sedimentary facies which are favorable for hydrocarbon accumulation. Thus, researching the sedimentary systems of Qinghai Lake could provide us a good example of paleogeographic recovery in the similar ancient lacustrine basin. In order to analyze the evolution of coastline and sedimentary system of Qinghai Lake, field trip are taken, large amounts of previous data are summed up and 10 pieces of remote sensing images over the past 40 years are interpreted in this study. Meanwhile, on basis of detailed study of hydrodynamics of Qinghai Lake, computer numerical simulation method is used to reveal the sediment transport patterns of Qinghai Lake. There are mainly three clockwise currents in Qinghai Lake; the hydrodynamic characteristics in the beach area are more complicated, sediment transport patterns are consistent with regional hydrodynamic features. It indicates that hydrodynamic condition is the most important factor to affect the sedimentary system of Qinghai Lake. Furthermore, the area including, river estuary, sand island- Haiyan bay, Langjian spit and eastern bay, have the most obvious evolutionary characteristics in Qinghai Lake. It is inferred that the evolution pattern of sedimentary system will keep unchanging under the condition of dry climate in a short time.
Qinghai Lake is a typical intermontane downfaulted lake in the arid region of northwest China. It is very similar to some continental petroliferous basins, and developed a series of sedimentary facies which are favorable for hydrocarbon accumulation. Thus, researching the sedimentary systems of Qinghai Lake could provide us a good example of paleogeographic recovery in the similar ancient lacustrine basin. In order to analyze the evolution of coastline and sedimentary system of Qinghai Lake, field trip are taken, large amounts of previous data are summed up and 10 pieces of remote sensing images over the past 40 years are interpreted in this study. Meanwhile, on basis of detailed study of hydrodynamics of Qinghai Lake, computer numerical simulation method is used to reveal the sediment transport patterns of Qinghai Lake. There are mainly three clockwise currents in Qinghai Lake; the hydrodynamic characteristics in the beach area are more complicated, sediment transport patterns are consistent with regional hydrodynamic features. It indicates that hydrodynamic condition is the most important factor to affect the sedimentary system of Qinghai Lake. Furthermore, the area including, river estuary, sand island- Haiyan bay, Langjian spit and eastern bay, have the most obvious evolutionary characteristics in Qinghai Lake. It is inferred that the evolution pattern of sedimentary system will keep unchanging under the condition of dry climate in a short time.
2015, 33(1): 105-115.
doi: 10.14027/j.cnki.cjxb.2015.01.011
Abstract:
As one of the most pronounced climatic cextremes in the geological history, the mid-Carnian (Late Triassic) extreme climate event, also named the Carnian Pluvial Event (CPE), has been widely recognized from the United States, China, Japan, and many places of Europe over past decades. The known evidence shows that the CPE is characterized by a dramatic increase in rainfalls and could last for nearly one million years. The CPE is represented by the sharp replacement of platform facies carbonates with the siliciclastic succession of mid-Carnian age worldwide. Several scenarios have been proposed to account for the CPE: (1) The plate tectonic activities such as collision and aggregation of the Pangea are believed to have prompted the atmosphere and ocean circulation changes; (2) the coeval large igneous province eruptions such as the Wrangellia Volcanic Province may have triggered a dramatic increase in CO2 contents in atmosphere, which caused a warm, wet climatic condition; (3) Possible global climate disruption such as megamonsoon induced the elevated rainfalls; and integration of all of these factors accounted for the climatic extreme. The strata record from southwestern China suggests that the link among the megamonsoon, tectonic movement and climate changes during the Carnian Stage is worthy studying in detail. In addition, further studies on some critical issues concerning the rise of carbonate compensation depth (CCD), high oceanic productivity reflected by the Carnian black shale, and pulses of humid climate during the mid-Carnian are crucial for better understanding of this deep-time climatic extreme.
As one of the most pronounced climatic cextremes in the geological history, the mid-Carnian (Late Triassic) extreme climate event, also named the Carnian Pluvial Event (CPE), has been widely recognized from the United States, China, Japan, and many places of Europe over past decades. The known evidence shows that the CPE is characterized by a dramatic increase in rainfalls and could last for nearly one million years. The CPE is represented by the sharp replacement of platform facies carbonates with the siliciclastic succession of mid-Carnian age worldwide. Several scenarios have been proposed to account for the CPE: (1) The plate tectonic activities such as collision and aggregation of the Pangea are believed to have prompted the atmosphere and ocean circulation changes; (2) the coeval large igneous province eruptions such as the Wrangellia Volcanic Province may have triggered a dramatic increase in CO2 contents in atmosphere, which caused a warm, wet climatic condition; (3) Possible global climate disruption such as megamonsoon induced the elevated rainfalls; and integration of all of these factors accounted for the climatic extreme. The strata record from southwestern China suggests that the link among the megamonsoon, tectonic movement and climate changes during the Carnian Stage is worthy studying in detail. In addition, further studies on some critical issues concerning the rise of carbonate compensation depth (CCD), high oceanic productivity reflected by the Carnian black shale, and pulses of humid climate during the mid-Carnian are crucial for better understanding of this deep-time climatic extreme.
2015, 33(1): 116-123.
doi: 10.14027/j.cnki.cjxb.2015.01.012
Abstract:
According to relative content of terrigenous clastic rock's components (clay minerals of claystone and clastic composition of sandstone), analyzing paleoclimate of Late Cretaceous - Paleocene Nanxiong Basin in northern Guangdong and southern Jiangxi. The climate index of sandstone clastic components (feldspar/quartz, F/Q) is between 0.02 to 0.14; Clay mineral assemblage is mainly illite, with an average of 79%; Illite crystallinity index and chemical index is 0.25~0.39 and 0.31~0.7. During this period, the climate of the study area is mainly arid climate, with some warm and humid climate intermittent, paleoclimate can be divided into three stages: arid-semiarid Maastrichtian, warm and moist semiarid early Danian, and the semiarid late Danian. Climate evolution is consistent with the same period of global climate change.
According to relative content of terrigenous clastic rock's components (clay minerals of claystone and clastic composition of sandstone), analyzing paleoclimate of Late Cretaceous - Paleocene Nanxiong Basin in northern Guangdong and southern Jiangxi. The climate index of sandstone clastic components (feldspar/quartz, F/Q) is between 0.02 to 0.14; Clay mineral assemblage is mainly illite, with an average of 79%; Illite crystallinity index and chemical index is 0.25~0.39 and 0.31~0.7. During this period, the climate of the study area is mainly arid climate, with some warm and humid climate intermittent, paleoclimate can be divided into three stages: arid-semiarid Maastrichtian, warm and moist semiarid early Danian, and the semiarid late Danian. Climate evolution is consistent with the same period of global climate change.
2015, 33(1): 124-133.
doi: 10.14027/j.cnki.cjxb.2015.01.013
Abstract:
High resolution (0.5 cm) grain size analysis by laser particle size analyzer and 210Pb dating of two short cores collected from the mud patches of central part of the southern Yellow Sea (Core YSZD01) and western part of the northern Yellow Sea (Core B45) were performed. Our results show that Core B45, which was deposited from 1913 to 2010, is mainly composed of silt, and its grain size parameters fluctuate vertically. The main sediment of Core YSZD01, which was developed from 1909 to 2012, is mud and sandy mud, and its grain size parameters change little along the core length. Sand fractions in the two cores around 1958, 1971 and 1980 are abruptly increased. We argue that strong cold-air outbreaks probably occurred in the study area, which enhanced ocean hydrodynamics and thereby resulted in abrupt increase in coarse fraction. By the grain size-standard deviation method, we got the environmental sensitive grain size components of Cores B45 and YSZD01, 15.6~71.8 μm and 23.7~500.0 μm, respectively, which are used to indicate variations of the East Asian Monsoon since 1910. The increased percentages of sensitive components during four periods of 1925~1935, 1955~1964, 1974~1977, and 1982~1986, are consistent with significant increase of the East Asian winter monsoon. It seems that the changes in content and fluctuation of sensitive grain size component in the mud patches of the Yellow Sea can be used to indicate variations in intensity and frequency of the East Asian Winter Monsoon.
High resolution (0.5 cm) grain size analysis by laser particle size analyzer and 210Pb dating of two short cores collected from the mud patches of central part of the southern Yellow Sea (Core YSZD01) and western part of the northern Yellow Sea (Core B45) were performed. Our results show that Core B45, which was deposited from 1913 to 2010, is mainly composed of silt, and its grain size parameters fluctuate vertically. The main sediment of Core YSZD01, which was developed from 1909 to 2012, is mud and sandy mud, and its grain size parameters change little along the core length. Sand fractions in the two cores around 1958, 1971 and 1980 are abruptly increased. We argue that strong cold-air outbreaks probably occurred in the study area, which enhanced ocean hydrodynamics and thereby resulted in abrupt increase in coarse fraction. By the grain size-standard deviation method, we got the environmental sensitive grain size components of Cores B45 and YSZD01, 15.6~71.8 μm and 23.7~500.0 μm, respectively, which are used to indicate variations of the East Asian Monsoon since 1910. The increased percentages of sensitive components during four periods of 1925~1935, 1955~1964, 1974~1977, and 1982~1986, are consistent with significant increase of the East Asian winter monsoon. It seems that the changes in content and fluctuation of sensitive grain size component in the mud patches of the Yellow Sea can be used to indicate variations in intensity and frequency of the East Asian Winter Monsoon.
2015, 33(1): 134-141.
doi: 10.14027/j.cnki.cjxb.2015.01.014
Abstract:
Based on 8 U/Th dates, 449 oxygen and carbon isotopic data from stalagmite LM2 from Laomu Cave, West Henan Province, China, a record of the Asian monsoon inter- decadal resolution sequence during 8.2~10.9 ka B.P. was established. The minimum δ18O value is -12‰, the maximum value is -8.2‰ and the vibration amplitude reaches 3.8‰. In the 10.13~10.9 ka B.P. sessions of early Holocene, the stalagmites in Jiuxian Cave, Laomu Cave and Dongshiya Cave reveals that monsoon stable in the period, but the stalagmites of Yamen Cave and Sanbao Cave in the southern China, polar ice cores GRIP record monsoon gradually. Differences of monsoon process of evolution between north and south China in the period may be related to climate response mechanism on the North and South China. Stalagmites LM2 recorded 8.2 ka, 9.5 ka, 10.2 ka and 10.9 ka weak monsoon event. Comparisons of LM2 to previously published early Holocene records show significant phase differences. The record of 9.3 ka weak monsoon event is not obvious in LM-2 stalagmite δ18O curve, but it recorded a weak monsoon event in 9.3~9.6 ka B.P. and similar to DSY09 (2009), Y1, HS-4 record. This indicated there was a weakening monsoon event in this time. The complexity oxygen isotope transport make it the different performance in north and south. In addition, LM2 stalagmite records the beginning of 8.2 ka B.P., the oxygen isotope curve showing a decline stage, and luffing up to 3 ‰, with Zhang et al proposing China "8200 phase" agreement by studying similar Wanxiang Cave. Northern China stalagmite showed the 8.2 ka cold event was staged event, while the south records revealed no showing phase characteristics, the reason for this need to more northern precision stalagmite records for further studying. The LM2 correlate within errors with Greenland ice core records, illustrating Asian monsoon and the North Atlantic climate change have fast atmospheric transmission. The stalagmite in Laomu Cave record confirms earlier work that suggested that Asia Monsoon is closely related to solar activity. Early Holocene Asian monsoon related with changing in solar radiation energy and climate condition on the high northern latitudes.
Based on 8 U/Th dates, 449 oxygen and carbon isotopic data from stalagmite LM2 from Laomu Cave, West Henan Province, China, a record of the Asian monsoon inter- decadal resolution sequence during 8.2~10.9 ka B.P. was established. The minimum δ18O value is -12‰, the maximum value is -8.2‰ and the vibration amplitude reaches 3.8‰. In the 10.13~10.9 ka B.P. sessions of early Holocene, the stalagmites in Jiuxian Cave, Laomu Cave and Dongshiya Cave reveals that monsoon stable in the period, but the stalagmites of Yamen Cave and Sanbao Cave in the southern China, polar ice cores GRIP record monsoon gradually. Differences of monsoon process of evolution between north and south China in the period may be related to climate response mechanism on the North and South China. Stalagmites LM2 recorded 8.2 ka, 9.5 ka, 10.2 ka and 10.9 ka weak monsoon event. Comparisons of LM2 to previously published early Holocene records show significant phase differences. The record of 9.3 ka weak monsoon event is not obvious in LM-2 stalagmite δ18O curve, but it recorded a weak monsoon event in 9.3~9.6 ka B.P. and similar to DSY09 (2009), Y1, HS-4 record. This indicated there was a weakening monsoon event in this time. The complexity oxygen isotope transport make it the different performance in north and south. In addition, LM2 stalagmite records the beginning of 8.2 ka B.P., the oxygen isotope curve showing a decline stage, and luffing up to 3 ‰, with Zhang et al proposing China "8200 phase" agreement by studying similar Wanxiang Cave. Northern China stalagmite showed the 8.2 ka cold event was staged event, while the south records revealed no showing phase characteristics, the reason for this need to more northern precision stalagmite records for further studying. The LM2 correlate within errors with Greenland ice core records, illustrating Asian monsoon and the North Atlantic climate change have fast atmospheric transmission. The stalagmite in Laomu Cave record confirms earlier work that suggested that Asia Monsoon is closely related to solar activity. Early Holocene Asian monsoon related with changing in solar radiation energy and climate condition on the high northern latitudes.
2015, 33(1): 142-152.
doi: 10.14027/j.cnki.cjxb.2015.01.015
Abstract:
To establish a quantitative geologic database at composite and single channel level for deep water slope channel systems in Angola, the characteristics and their quantitative relationships were carefully studied based on high frequency 3D seismic profile, slice and attribute data of shallow Pliocene deposits. The results indicate that the single channel activity pattern is somewhat similar to the point bar model in a meandering river. It migrates only in lateral direction (orthogonal to the paleocurrent direction) without "downstream sweep" component, and the lateral accretion composites form a "concentric half ring" shape in plane view, whereas the sandbodies fill in the axis by vertical accretion, and thinning towards channel edge. Good positive correlations can be widely observed between width and depth, meander-arc height and sinuosity in single channels. Based on the single channel activity pattern, the composite channel pattern can be classified into 3 types as (Ⅰ) lateral migration, (Ⅱ) inclined migration, and (Ⅲ) swing migration. Type (Ⅰ) develops in higher sinuosity section (sinuosity>1.3), whereas type (Ⅱ) and type (Ⅲ) develops mainly in lower sinuosity section (1
To establish a quantitative geologic database at composite and single channel level for deep water slope channel systems in Angola, the characteristics and their quantitative relationships were carefully studied based on high frequency 3D seismic profile, slice and attribute data of shallow Pliocene deposits. The results indicate that the single channel activity pattern is somewhat similar to the point bar model in a meandering river. It migrates only in lateral direction (orthogonal to the paleocurrent direction) without "downstream sweep" component, and the lateral accretion composites form a "concentric half ring" shape in plane view, whereas the sandbodies fill in the axis by vertical accretion, and thinning towards channel edge. Good positive correlations can be widely observed between width and depth, meander-arc height and sinuosity in single channels. Based on the single channel activity pattern, the composite channel pattern can be classified into 3 types as (Ⅰ) lateral migration, (Ⅱ) inclined migration, and (Ⅲ) swing migration. Type (Ⅰ) develops in higher sinuosity section (sinuosity>1.3), whereas type (Ⅱ) and type (Ⅲ) develops mainly in lower sinuosity section (1
2015, 33(1): 153-159.
doi: 10.14027/j.cnki.cjxb.2015.01.016
Abstract:
The structure and sedimentary characteristics of the 2nd oil series in the 2nd Member of Liushagang Formation in Weizhou12-A oilfield, Weixinan depression, Beibu Gulf basin were very complex. Based on the analysis of the data of well logging, core and seismic data, it is obvious that the provenance of the 2nd oil series in the 2nd Member of Liushagang Formation in Weizhou12-A oilfield is from the southwest Weizhou 12-8 structure ridge; two long-term base level cycle and three medium-term base level cycles were divided, isochronous sequence stratigraphic framework was established; two sedimentary facies were identified by analyzing the differences of sedimentary characteristics of different oil group, the bottom of the 2nd oil series developed fan-delta depositional system, the top developed normal delta depositional system; the evolution sedimentary characteristics was discussed from the aspect of base level cycle.
The structure and sedimentary characteristics of the 2nd oil series in the 2nd Member of Liushagang Formation in Weizhou12-A oilfield, Weixinan depression, Beibu Gulf basin were very complex. Based on the analysis of the data of well logging, core and seismic data, it is obvious that the provenance of the 2nd oil series in the 2nd Member of Liushagang Formation in Weizhou12-A oilfield is from the southwest Weizhou 12-8 structure ridge; two long-term base level cycle and three medium-term base level cycles were divided, isochronous sequence stratigraphic framework was established; two sedimentary facies were identified by analyzing the differences of sedimentary characteristics of different oil group, the bottom of the 2nd oil series developed fan-delta depositional system, the top developed normal delta depositional system; the evolution sedimentary characteristics was discussed from the aspect of base level cycle.
2015, 33(1): 160-169.
doi: 10.14027/j.cnki.cjxb.2015.01.017
Abstract:
The tight sandstone gas of Tarim Basin has a large distribution and great exploration potential, which is an important prospective exploration field of the basin in the future. The Lower Jurassic sandstone in eastern Kuqa depression is commonly tight. It is important for the further exploration and development to strengthen the study of its reservoir characteristics and the main controlling factors. In order to reveal the controlling factors and development mechanism of the Lower Jurassic tight sandstone reservoir in eastern Kuqa depression, by use of the tests of casting section, cathodeluminescence, scanning electron microscope and laser confocal microscopy are applied, together with the geological and logging analyses. The lithology, pore structure characteristics and physical properties are carried out in this paper. The results show that lithic sandstone is the main reservoir rock type, and the rock composition maturity is low while the textural maturity is of medium degree. The pore structure is mainly mesoporous with fine throat and micropore with fine throat. Majority of the porosity values ranges from 4% to 12%, with an average of 8.12%, and the effective air permeability is mainly (0.1~3)×10-3μm2; On the basis of the comprehensive analyses of sedimentation, diagenesis and tectonics of tight reservoir strata, the studies suggest that the reservoir physical property is mainly controlled by sedimentation, diagenesis and tectonism. The main controlling factors are granularity and compaction.
The tight sandstone gas of Tarim Basin has a large distribution and great exploration potential, which is an important prospective exploration field of the basin in the future. The Lower Jurassic sandstone in eastern Kuqa depression is commonly tight. It is important for the further exploration and development to strengthen the study of its reservoir characteristics and the main controlling factors. In order to reveal the controlling factors and development mechanism of the Lower Jurassic tight sandstone reservoir in eastern Kuqa depression, by use of the tests of casting section, cathodeluminescence, scanning electron microscope and laser confocal microscopy are applied, together with the geological and logging analyses. The lithology, pore structure characteristics and physical properties are carried out in this paper. The results show that lithic sandstone is the main reservoir rock type, and the rock composition maturity is low while the textural maturity is of medium degree. The pore structure is mainly mesoporous with fine throat and micropore with fine throat. Majority of the porosity values ranges from 4% to 12%, with an average of 8.12%, and the effective air permeability is mainly (0.1~3)×10-3μm2; On the basis of the comprehensive analyses of sedimentation, diagenesis and tectonics of tight reservoir strata, the studies suggest that the reservoir physical property is mainly controlled by sedimentation, diagenesis and tectonism. The main controlling factors are granularity and compaction.
2015, 33(1): 170-182.
doi: 10.14027/j.cnki.cjxb.2015.01.018
Abstract:
Through the analysis of core observations, thin sections, measured physical properties and combined with the homogenization temperature analysis of fluid-inclusion and burial history in the nearshore subaqueous fan of the Es4s in the northern steep zone of the Bonan sag, the evolution characteristics of diagenesis and reservoir properties was studied. The results showed that, the reservoir diagenesis mainly included strong compaction, lime-mud matrix recrystallization, multi-phase of dissolution and cementation, and complicated metasomatism. The reservoirs have experienced multi-phase acidic and alkaline fluid evolution based on the characteristics of diagenetic environment. In the same diagenetic environment, the difference of sedimentary characteristics in different sub/micro-facies of nearshore subaqueous fan controls the difference of diagenetic evolution characteristics, which also determines the difference of the evolution of reservoir physical property. Based on a method of porosity's inversion and back stripping, physical properties of the reservoirs in geological history were restored, it is shown that compaction, carbonate cementation, lime-mud matrix recrystallization, acid dissolution and former hydrocarbon filling exert the most important effect on the evolution of physical properties. The evolution mode of reservoir physical properties in different sub/micro-facies of nearshore subaqueous fan have been established. The conglomerate in inner fan mainly experiences compaction and lime-mud matrix recrystallization, with weak dissolution, so the physical properties of the conglomerate in inner fan keep reducing and the lime-mud matrix recrystallization results in a rapid reduction of physical properties of the conglomerate in inner fan in middle-deep layers. The present physical property of inner fan becomes extremely poor and mainly develops dry layers. Because two stages of acid dissolution reconstruct the reservoirs and the hydrocarbon filling inhibits cementation, the reservoirs far away from mudstone layers in the braided channels of the middle fan develop a great number of primary and secondary pores, have a higher porosity and permeability, and can be effective reservoirs of hydrocarbon. The reservoirs adjacent to mudstone layers in braided channels of the middle fan, the reservoirs in interdistributaries of the middle fan and outer fan develop intensive cementation and metasomatism, therefore they have poor physical property and mainly develop dry layers.
Through the analysis of core observations, thin sections, measured physical properties and combined with the homogenization temperature analysis of fluid-inclusion and burial history in the nearshore subaqueous fan of the Es4s in the northern steep zone of the Bonan sag, the evolution characteristics of diagenesis and reservoir properties was studied. The results showed that, the reservoir diagenesis mainly included strong compaction, lime-mud matrix recrystallization, multi-phase of dissolution and cementation, and complicated metasomatism. The reservoirs have experienced multi-phase acidic and alkaline fluid evolution based on the characteristics of diagenetic environment. In the same diagenetic environment, the difference of sedimentary characteristics in different sub/micro-facies of nearshore subaqueous fan controls the difference of diagenetic evolution characteristics, which also determines the difference of the evolution of reservoir physical property. Based on a method of porosity's inversion and back stripping, physical properties of the reservoirs in geological history were restored, it is shown that compaction, carbonate cementation, lime-mud matrix recrystallization, acid dissolution and former hydrocarbon filling exert the most important effect on the evolution of physical properties. The evolution mode of reservoir physical properties in different sub/micro-facies of nearshore subaqueous fan have been established. The conglomerate in inner fan mainly experiences compaction and lime-mud matrix recrystallization, with weak dissolution, so the physical properties of the conglomerate in inner fan keep reducing and the lime-mud matrix recrystallization results in a rapid reduction of physical properties of the conglomerate in inner fan in middle-deep layers. The present physical property of inner fan becomes extremely poor and mainly develops dry layers. Because two stages of acid dissolution reconstruct the reservoirs and the hydrocarbon filling inhibits cementation, the reservoirs far away from mudstone layers in the braided channels of the middle fan develop a great number of primary and secondary pores, have a higher porosity and permeability, and can be effective reservoirs of hydrocarbon. The reservoirs adjacent to mudstone layers in braided channels of the middle fan, the reservoirs in interdistributaries of the middle fan and outer fan develop intensive cementation and metasomatism, therefore they have poor physical property and mainly develop dry layers.
2015, 33(1): 183-193.
doi: 10.14027/j.cnki.cjxb.2015.01.019
Abstract:
A significant sandstone reservoir at the present burial depths greater than 3 500 m, located in the Wenchang Formation of HZ-A area in Huizhou depression, Pearl River Mouth Basin, was deposited in the braided fluvial delta environment. Based on comprehensive analysis of thin sections, cathodeluminescence microscope, X-ray diffractometor, scanning electronic microscope, physical property analysis and so on, the characteristic of reservoir, diagenesis and pore evolution in Wenchang Formation of HZ-A area were studied in detail. Authors have established a quantitative model for their pore evolution during the geodynamic history by using quantitative analysis method. The results show that the sandstones are mostly lithic sandstone characterized by low compositional and textural maturity. The reservoir has mainly experienced the compaction, early cementation, dissolution and late cementation in sequence and has been at the middle diagenetic A2 stage. Dissolution was the only diagenetic factor resulting in the improvement of reservoir physical property. Both mechanical compaction and late cementation mainly resulted in pore destruction. The original porosity of the reservoir was 35.1% and had the loss of 15.4% by mechanical compaction and the loss of 3.4% due to early cementation. Acid dissolution increased the porosity of 7.2%. The pores were occluded by late clay minerals and carbonate cements, resulting in the reduction of 11.5%. Consequently, the low-porosity and low-permeability reservoir is formed.
A significant sandstone reservoir at the present burial depths greater than 3 500 m, located in the Wenchang Formation of HZ-A area in Huizhou depression, Pearl River Mouth Basin, was deposited in the braided fluvial delta environment. Based on comprehensive analysis of thin sections, cathodeluminescence microscope, X-ray diffractometor, scanning electronic microscope, physical property analysis and so on, the characteristic of reservoir, diagenesis and pore evolution in Wenchang Formation of HZ-A area were studied in detail. Authors have established a quantitative model for their pore evolution during the geodynamic history by using quantitative analysis method. The results show that the sandstones are mostly lithic sandstone characterized by low compositional and textural maturity. The reservoir has mainly experienced the compaction, early cementation, dissolution and late cementation in sequence and has been at the middle diagenetic A2 stage. Dissolution was the only diagenetic factor resulting in the improvement of reservoir physical property. Both mechanical compaction and late cementation mainly resulted in pore destruction. The original porosity of the reservoir was 35.1% and had the loss of 15.4% by mechanical compaction and the loss of 3.4% due to early cementation. Acid dissolution increased the porosity of 7.2%. The pores were occluded by late clay minerals and carbonate cements, resulting in the reduction of 11.5%. Consequently, the low-porosity and low-permeability reservoir is formed.
2015, 33(1): 194-201.
doi: 10.14027/j.cnki.cjxb.2015.01.020
Abstract:
On the basis of a large number of thin-sections, casting thin-sections, and physical property analysis of cores, the article systematically compares Permian-Jurassic reservoir differences between the foot wall and the hanging wall of the Ke-Bai overthrust fault, northwestern margin of Junggar Basin from the perspectives of structural evolution, time-space distribution of the depositional system, diagenesis evolution, and reservoir quality. The formation mechanism of reservoir differences have been discussed. The reservoir on the hanging wall is near to the provenance with coarse grain size and shallow burial depth. The lithologies are conglomerate and sandy conglomerate of alluvial fan and braided river. The compaction is weak and a large number of primary pores are well preserved. The reservoir on the foot wall is far away from the provenance with deeper burial depth and finer grain size. The lithology is sandstone of braided river delta and fan delta front. Zeolites and feldspars are intensely dissolved within some intervals. Comprehensive analysis shows that the reservoir burial history (fracture evolutionary history) controlled facies association, present burial depth, and the formation of secondary porosity in the study area. Depositional systems effected by Ke-Bai fault had a genetic impact on the grain size, compositional maturity and textural maturity of the reservoir rocks, controlling the development of primary pore configuration.
On the basis of a large number of thin-sections, casting thin-sections, and physical property analysis of cores, the article systematically compares Permian-Jurassic reservoir differences between the foot wall and the hanging wall of the Ke-Bai overthrust fault, northwestern margin of Junggar Basin from the perspectives of structural evolution, time-space distribution of the depositional system, diagenesis evolution, and reservoir quality. The formation mechanism of reservoir differences have been discussed. The reservoir on the hanging wall is near to the provenance with coarse grain size and shallow burial depth. The lithologies are conglomerate and sandy conglomerate of alluvial fan and braided river. The compaction is weak and a large number of primary pores are well preserved. The reservoir on the foot wall is far away from the provenance with deeper burial depth and finer grain size. The lithology is sandstone of braided river delta and fan delta front. Zeolites and feldspars are intensely dissolved within some intervals. Comprehensive analysis shows that the reservoir burial history (fracture evolutionary history) controlled facies association, present burial depth, and the formation of secondary porosity in the study area. Depositional systems effected by Ke-Bai fault had a genetic impact on the grain size, compositional maturity and textural maturity of the reservoir rocks, controlling the development of primary pore configuration.
2015, 33(1): 202-210.
doi: 10.14027/j.cnki.cjxb.2015.01.021
Abstract:
There are still some controversies surrounding the security of mudstone upon injection layer of CO2 injection project that implemented by Shenhua Group in the potential target area of CO2 underground embedded, Ordos Basin. Forecast the ability of adjourned carbon sequestration after CO2 penetrate cap rock by research of JX well Yanchang Formation(upon injection layer) that adjacent to injection well of Shenhua Group that the drilling stratigraphic system and rock assemblage are same. The samples of researching layer are mainly feldspar sandstone and lithic feldspar sandstone, followed by lithic sandstone and lithic quartz sandstone, and the rock types of provenance are mainly felsic volcanic rocks, followed by intermediate volcanic rocks and a small amount of quartz sedimentary rock, with componential characteristics of neutral anorthosite at the same time. The parent rocks of sandstone of the upper section(466~534 m) and lower section(666~958 m) suffered weak-medium chemical alteration, maybe they experienced recycling process, but the parent rocks of sandstone in the middle section(534~666 m) did not suffer from chemical alteration and they are likely the first cycle sediment. As the place of adjourned carbon sequestration, Yanchang Formation has the material conditions of achieving CO2 mineral traps and potential of forming dawsonite, calcite, ankerite and siderite which called sequestration mineral.
There are still some controversies surrounding the security of mudstone upon injection layer of CO2 injection project that implemented by Shenhua Group in the potential target area of CO2 underground embedded, Ordos Basin. Forecast the ability of adjourned carbon sequestration after CO2 penetrate cap rock by research of JX well Yanchang Formation(upon injection layer) that adjacent to injection well of Shenhua Group that the drilling stratigraphic system and rock assemblage are same. The samples of researching layer are mainly feldspar sandstone and lithic feldspar sandstone, followed by lithic sandstone and lithic quartz sandstone, and the rock types of provenance are mainly felsic volcanic rocks, followed by intermediate volcanic rocks and a small amount of quartz sedimentary rock, with componential characteristics of neutral anorthosite at the same time. The parent rocks of sandstone of the upper section(466~534 m) and lower section(666~958 m) suffered weak-medium chemical alteration, maybe they experienced recycling process, but the parent rocks of sandstone in the middle section(534~666 m) did not suffer from chemical alteration and they are likely the first cycle sediment. As the place of adjourned carbon sequestration, Yanchang Formation has the material conditions of achieving CO2 mineral traps and potential of forming dawsonite, calcite, ankerite and siderite which called sequestration mineral.
