2016 Vol. 34, No. 3
Display Method:
2016, 34(3): 415-435.
doi: 10.14027/j.cnki.cjxb.2016.03.001
Abstract:
Clearing the relationship among since Mesozoic Tianshan uplift of time sequence, scope, and north and south on both sides of the basin sedimentary evolution, which shows on both sides of Tianshan mountain, Tuha Basin in Junggar Basin and Tarim Basin has important demand to recovery basin protoeype. Through the analysis of a large number of previous apatite fission track dating data, quantitative calculation of gravel transport distance and provenance, the nature of the basin, depositional filling and palaeoclimate changing and the ancient flow, it is believed that of there are four periods of stage uplift of Miocene to Quaternary. They are Late Triassic to Early Jurassic, Late Jurassic - Early Cretaceous and Late Cretaceous to Eocene. The uplift range are two small and two large ones. On the analysis of the Tianshan mountains north and south on both sides of the basin on the basis of lithologic, stratigraphic and sedimentary characteristics, combination of Tianshan uplift mountain range and time, compiled the Early Jurassic to the early - to the south of Tianshan uplift area and its quaternary sedimentary facies evolution, it is considered that Tianshan uplift controlled the four phases of the unified by the early and Middle Jurassic in northern and southern Xinjiang Basin flood lake basin to the Late Jurassic and Early Cretaceous basin began to differentiation, to thoroughly split into independent sedimentary evolution of the basin since Neogene. At the same time, it is clear about the Tianshan mountains between the north and the south on both sides of the basin, hydrocarbon source rocks, reservoir and cap rock important formation to the Tianshan uplift. The understanding of clear and distribution of hydrocarbon source rock, reservoir rock development period is of great significance, also some enlightenment to effectively expanding the scope of oil and gas exploration.
Clearing the relationship among since Mesozoic Tianshan uplift of time sequence, scope, and north and south on both sides of the basin sedimentary evolution, which shows on both sides of Tianshan mountain, Tuha Basin in Junggar Basin and Tarim Basin has important demand to recovery basin protoeype. Through the analysis of a large number of previous apatite fission track dating data, quantitative calculation of gravel transport distance and provenance, the nature of the basin, depositional filling and palaeoclimate changing and the ancient flow, it is believed that of there are four periods of stage uplift of Miocene to Quaternary. They are Late Triassic to Early Jurassic, Late Jurassic - Early Cretaceous and Late Cretaceous to Eocene. The uplift range are two small and two large ones. On the analysis of the Tianshan mountains north and south on both sides of the basin on the basis of lithologic, stratigraphic and sedimentary characteristics, combination of Tianshan uplift mountain range and time, compiled the Early Jurassic to the early - to the south of Tianshan uplift area and its quaternary sedimentary facies evolution, it is considered that Tianshan uplift controlled the four phases of the unified by the early and Middle Jurassic in northern and southern Xinjiang Basin flood lake basin to the Late Jurassic and Early Cretaceous basin began to differentiation, to thoroughly split into independent sedimentary evolution of the basin since Neogene. At the same time, it is clear about the Tianshan mountains between the north and the south on both sides of the basin, hydrocarbon source rocks, reservoir and cap rock important formation to the Tianshan uplift. The understanding of clear and distribution of hydrocarbon source rock, reservoir rock development period is of great significance, also some enlightenment to effectively expanding the scope of oil and gas exploration.
2016, 34(3): 436-451.
doi: 10.14027/j.cnki.cjxb.2016.03.002
Abstract:
End-Guadalupian mass extinction was an independent extinction event before the end-Permian mass extinction. During this biotic crisis, the severity effected on the benthos was believed to be the similar scale as the “Big Five” mass extinction. Recently, owing to the increasing of age data and the precise stratigraphic timescale, more and more researchers began to challenge the severity of this extinction. Meanwhile, the main cause of this extinction, Emeishan LIP, was also questionable. Whether Emeishan LIP was still the main cause of this biotic crisis. In order to figure out this problem, this paper reviews the end-Guadalupian mass extinction, the Emeishan LIP eruption, the C and Sr isotopic changes in Capitanian and the main causes of this mass extinction. Combined with some of the authors' data, they believe that: (1) the impact of end-Guadalupian mass extinction on the benthos was not serious as once to be thought. Decreasing scale of biodiversity was smaller than the “Big Five” mass extinction. (2) the negative excursion of C isotope near the G-LB was affected mostly by diagenesis and facies change. There are two carbon isotopic negative excursions in the mid-Capitanian (excursion amplitude is about 1.0‰ to 1.5‰) and the G-L Boundary (excursion amplitude is about 1.4‰ to 2‰), respectively. (3) The main causes of this mass extinction were probably sea level fall and marine anoxia, instead of Emeishan LIP eruption.
End-Guadalupian mass extinction was an independent extinction event before the end-Permian mass extinction. During this biotic crisis, the severity effected on the benthos was believed to be the similar scale as the “Big Five” mass extinction. Recently, owing to the increasing of age data and the precise stratigraphic timescale, more and more researchers began to challenge the severity of this extinction. Meanwhile, the main cause of this extinction, Emeishan LIP, was also questionable. Whether Emeishan LIP was still the main cause of this biotic crisis. In order to figure out this problem, this paper reviews the end-Guadalupian mass extinction, the Emeishan LIP eruption, the C and Sr isotopic changes in Capitanian and the main causes of this mass extinction. Combined with some of the authors' data, they believe that: (1) the impact of end-Guadalupian mass extinction on the benthos was not serious as once to be thought. Decreasing scale of biodiversity was smaller than the “Big Five” mass extinction. (2) the negative excursion of C isotope near the G-LB was affected mostly by diagenesis and facies change. There are two carbon isotopic negative excursions in the mid-Capitanian (excursion amplitude is about 1.0‰ to 1.5‰) and the G-L Boundary (excursion amplitude is about 1.4‰ to 2‰), respectively. (3) The main causes of this mass extinction were probably sea level fall and marine anoxia, instead of Emeishan LIP eruption.
2016, 34(3): 452-462.
doi: 10.14027/j.cnki.cjxb.2016.03.003
Abstract:
Based on literature investigations, research status on hyperpycnal flow was summarized mainly including flowing process, fluid properties, controlling factors, sedimentary characteristics. Sedimentary method among hyperpycnal flow and other gravity flows was discussed and depositional model on “channel-ligule-lobe” was constructed, accompanying with the research example from Mesozoic lacustrine hyperpycnites. Hyperpycnal flow is a kind of sustained turbidity currents generating from flood-river estuary, flowing along the bottom of water for its higher density than catchment basins water. It has frequent occurrences and stable sediments supplies, which triggered by river floods. The phenomenon on the plunging of fluid is the symbolism of formation on hyperpycnal flow. It can make a long-distance transportation along the bottom of the water body, as long as the adequate slope existes at the bottom of basins. Hyperpycnal flow belongs to Newtonian rheology, presenting turbulent state, being supported by fluid turbulence. It has no need of the early accumulation and transportation again on sediments, and event-triggered mechanisms like earthquake, volcano eruption, storm and tsunami. Hyperpycnal flow is controlled by factors of topography, climate and density differences. It takes place in both marine facies and terrestrial lacustrine basin. The current researchers, however, have not paid enough attention to the hyperpycnal flow deposits in terrestrial lacustrine basin，although advantages of lower water density, closer to source areas, enough terrain altitude difference, well developed small and medium sized river and active tectonic movements, always exist in lakes. Hyperpycnal flow appears a diluting tendency from vicinity to distance and corresponds to specific sedimentary structures and sequences. With the hydrodynamic conditions decreased gradually, sediments of hyperpycnal flow present a tendency that grain size much smaller, sand thickness much thinner to the center of basin. Most of them are medium sized sandstone, fine sandstone and siltstone. The distribution is much steady horizontally. And it appears to the shape of fan which consists of “channel-ligule-lobe” accompanying with natural barrier on plane. Channel is linked directly to underwater distributary channel, the place where erosion and filling mainly happened. Channel-ligule in the middle of sedimentary sandbody develops mostly. And lobe at the distal ends can extend a long distance. Hyperpycnites or hyperpycnal flow sediments can be distinguished from turbidites by: well developed micro-erosion surfaces, the combinations of upward-coarsening intervals and upward-fining intervals formed in waxing and waning flows, and rich in terrestrial organic matters. The triggered gravity flows deposits can be the result of the transportation again about the sediments of hyperpycnal flow. The mix of them is good for keeping high density and stability. Thus, hyperpycnal flow can accompany with other gravity flows to form thick sandstones with much more complicated factors. Research on hyperpycnal flow deposits has important scientific values and practical significances to make further researches. It will not only be propitious to fulfill sedimentary theory of deep-water gravity flows and to analyze sedimentary environment, but also in favor of guiding exploration on deep-water unconventional petroleum.
Based on literature investigations, research status on hyperpycnal flow was summarized mainly including flowing process, fluid properties, controlling factors, sedimentary characteristics. Sedimentary method among hyperpycnal flow and other gravity flows was discussed and depositional model on “channel-ligule-lobe” was constructed, accompanying with the research example from Mesozoic lacustrine hyperpycnites. Hyperpycnal flow is a kind of sustained turbidity currents generating from flood-river estuary, flowing along the bottom of water for its higher density than catchment basins water. It has frequent occurrences and stable sediments supplies, which triggered by river floods. The phenomenon on the plunging of fluid is the symbolism of formation on hyperpycnal flow. It can make a long-distance transportation along the bottom of the water body, as long as the adequate slope existes at the bottom of basins. Hyperpycnal flow belongs to Newtonian rheology, presenting turbulent state, being supported by fluid turbulence. It has no need of the early accumulation and transportation again on sediments, and event-triggered mechanisms like earthquake, volcano eruption, storm and tsunami. Hyperpycnal flow is controlled by factors of topography, climate and density differences. It takes place in both marine facies and terrestrial lacustrine basin. The current researchers, however, have not paid enough attention to the hyperpycnal flow deposits in terrestrial lacustrine basin，although advantages of lower water density, closer to source areas, enough terrain altitude difference, well developed small and medium sized river and active tectonic movements, always exist in lakes. Hyperpycnal flow appears a diluting tendency from vicinity to distance and corresponds to specific sedimentary structures and sequences. With the hydrodynamic conditions decreased gradually, sediments of hyperpycnal flow present a tendency that grain size much smaller, sand thickness much thinner to the center of basin. Most of them are medium sized sandstone, fine sandstone and siltstone. The distribution is much steady horizontally. And it appears to the shape of fan which consists of “channel-ligule-lobe” accompanying with natural barrier on plane. Channel is linked directly to underwater distributary channel, the place where erosion and filling mainly happened. Channel-ligule in the middle of sedimentary sandbody develops mostly. And lobe at the distal ends can extend a long distance. Hyperpycnites or hyperpycnal flow sediments can be distinguished from turbidites by: well developed micro-erosion surfaces, the combinations of upward-coarsening intervals and upward-fining intervals formed in waxing and waning flows, and rich in terrestrial organic matters. The triggered gravity flows deposits can be the result of the transportation again about the sediments of hyperpycnal flow. The mix of them is good for keeping high density and stability. Thus, hyperpycnal flow can accompany with other gravity flows to form thick sandstones with much more complicated factors. Research on hyperpycnal flow deposits has important scientific values and practical significances to make further researches. It will not only be propitious to fulfill sedimentary theory of deep-water gravity flows and to analyze sedimentary environment, but also in favor of guiding exploration on deep-water unconventional petroleum.
2016, 34(3): 463-477.
doi: 10.14027/j.cnki.cjxb.2016.03.004
Abstract:
The research of enrichment mechanism of organic matter has great significance in exploring high-quality hydrocarbon source rock and evaluating oil and gas potential in a basin, which becomes more and more important and urgent under the great influence of the exploration and development of unconventional hydrocarbon resources such as shale gas, tight gas and oil shale. However, the overall research degree of organic matter enrichment mechanism is not high, and the research of lacustrine organic matter is relatively lower. With terrestrial basin as the object of the research, based on a detailed investigation of organic matter enrichment mechanism, this paper summarizes systematically the main controls on organic matter enrichment of terrestrial basin from the following aspects including organics production, organics decomposition and preservation, dilution effect of sedimentation on organics, furthermore, the differences of organic matter formation between marine and terrestrial basin are compared and discussed. The research indicates that lacustrine organic production is affected by area illumination rate, nutrient supply, basin topography, climate, aqueous media conditions, seasonal blooming algae, and autotrophic bacteria, etc.; lacustrine organic decomposition and preservation is subject to water stratification, bacterial biomass, inorganic mineral, aqueous medium condition, clay minerals, sedimentation rate, and so on; lacustrine dilution effect of sedimentation on organics is influenced by sedimentation rate. Finally, the paper makes a conclusion that total organic matter content of a terrestrial basin is actually a mutual interaction result of “organics production-organics decomposition-organics dilution”. At the end of this paper, two research areas worthy of paying more attention and in-depth study of this area in the future are put forward, which include, in what condition can autotrophic bacterium yield high productivity, and the impacts of different aqueous medium conditions on organics decomposition and preservation.
The research of enrichment mechanism of organic matter has great significance in exploring high-quality hydrocarbon source rock and evaluating oil and gas potential in a basin, which becomes more and more important and urgent under the great influence of the exploration and development of unconventional hydrocarbon resources such as shale gas, tight gas and oil shale. However, the overall research degree of organic matter enrichment mechanism is not high, and the research of lacustrine organic matter is relatively lower. With terrestrial basin as the object of the research, based on a detailed investigation of organic matter enrichment mechanism, this paper summarizes systematically the main controls on organic matter enrichment of terrestrial basin from the following aspects including organics production, organics decomposition and preservation, dilution effect of sedimentation on organics, furthermore, the differences of organic matter formation between marine and terrestrial basin are compared and discussed. The research indicates that lacustrine organic production is affected by area illumination rate, nutrient supply, basin topography, climate, aqueous media conditions, seasonal blooming algae, and autotrophic bacteria, etc.; lacustrine organic decomposition and preservation is subject to water stratification, bacterial biomass, inorganic mineral, aqueous medium condition, clay minerals, sedimentation rate, and so on; lacustrine dilution effect of sedimentation on organics is influenced by sedimentation rate. Finally, the paper makes a conclusion that total organic matter content of a terrestrial basin is actually a mutual interaction result of “organics production-organics decomposition-organics dilution”. At the end of this paper, two research areas worthy of paying more attention and in-depth study of this area in the future are put forward, which include, in what condition can autotrophic bacterium yield high productivity, and the impacts of different aqueous medium conditions on organics decomposition and preservation.
2016, 34(3): 478-486.
doi: 10.14027/j.cnki.cjxb.2016.03.005
Abstract:
Two sets of storm deposits, with different sedimentary characteristics, were found at the bottom and the middle of Qingxudong Formation(Lungwangmiaoan Stage, Lower Cambrian)of the Dingtai section, Zunyi, northwestern Guizhou province, which are different from the discovery of the storm deposits that were found mostly at the platform margin in eastern Hunan and western Guizhou. It was the first time that we found storm deposits at the interior of the Yangtze platform in northwestern Guizhou at the same stage. At the bottom, we found erosion surface, coarse lag deposit, hummocky-sunken cross-stratification, ripple bedding, and micrite limestone, which represents the background deposit, and we can recognize three types of storm deposit sequences, and its sedimentary characteristics indicate that it was deposited at middle ramp, between the wave base and the storm wave base. At the middle, we found coarse lag deposit, graded bedding and ripple bedding, and the background deposit is algal clast limestone which develops bird-eye structure, and there are four types of storm deposit sequences that we can recognize, and its sedimentary characteristics indicate that it was deposited at shallow water tidal flat, above the wave base. The discovery of this two sets of storm deposits, which deposited at different settings, not only enrich our understanding of storm deposit, but more impotant is that it can provide us valuable infomation for our study on the evolution of paleolatitude and paleoplate, the isochronostratigraphic correlation and the evolution of paleogeography of the Yangtze platform in the Lungwangmiaoan Stage, Lower Cambrian.
Two sets of storm deposits, with different sedimentary characteristics, were found at the bottom and the middle of Qingxudong Formation(Lungwangmiaoan Stage, Lower Cambrian)of the Dingtai section, Zunyi, northwestern Guizhou province, which are different from the discovery of the storm deposits that were found mostly at the platform margin in eastern Hunan and western Guizhou. It was the first time that we found storm deposits at the interior of the Yangtze platform in northwestern Guizhou at the same stage. At the bottom, we found erosion surface, coarse lag deposit, hummocky-sunken cross-stratification, ripple bedding, and micrite limestone, which represents the background deposit, and we can recognize three types of storm deposit sequences, and its sedimentary characteristics indicate that it was deposited at middle ramp, between the wave base and the storm wave base. At the middle, we found coarse lag deposit, graded bedding and ripple bedding, and the background deposit is algal clast limestone which develops bird-eye structure, and there are four types of storm deposit sequences that we can recognize, and its sedimentary characteristics indicate that it was deposited at shallow water tidal flat, above the wave base. The discovery of this two sets of storm deposits, which deposited at different settings, not only enrich our understanding of storm deposit, but more impotant is that it can provide us valuable infomation for our study on the evolution of paleolatitude and paleoplate, the isochronostratigraphic correlation and the evolution of paleogeography of the Yangtze platform in the Lungwangmiaoan Stage, Lower Cambrian.
2016, 34(3): 487-496.
doi: 10.14027/j.cnki.cjxb.2016.03.006
Abstract:
In gravity depositional area although the sediment grain-size cycle cannot reflect the base-level changes, the flow condition characteristic and types of gravity flow have an apparent response to the landform. Based on this response, our study discusses how to investigate the base level variation in gravity depositional area. A difference in activity rate of the synsedimentary faults that made slope breaks of Teng 1 Formation, southern Wuliyast sag, is shown within different medium cycles through relative paleogeomorphic restoring and analysis of strata thickness. Because of the difference, the landform of the study area underwent a flat to steep process with the accommodation rate changing from slow to fast. Within the process, the flow condition characteristic and deposition location of gravity flow show a regular changes through core observation and 3-D seismic inversion: turbidity current developed and deposited on the bottom part of slope break, as well as weak cohesive debris, during the activity rate of the synsedimentary faults was fast, which led to a steep landform and high creation rate of accommodation; while in the case of low activity rate resulting in flat landform and low creation rate of accommodation, debris developed and deposited wildly on the flat slope. Consequently, our research suggests that the landform variation can be confirmed by the changes of flow regime and taypes of gravity deposition, then the scenario of base level variation can be investigated.
In gravity depositional area although the sediment grain-size cycle cannot reflect the base-level changes, the flow condition characteristic and types of gravity flow have an apparent response to the landform. Based on this response, our study discusses how to investigate the base level variation in gravity depositional area. A difference in activity rate of the synsedimentary faults that made slope breaks of Teng 1 Formation, southern Wuliyast sag, is shown within different medium cycles through relative paleogeomorphic restoring and analysis of strata thickness. Because of the difference, the landform of the study area underwent a flat to steep process with the accommodation rate changing from slow to fast. Within the process, the flow condition characteristic and deposition location of gravity flow show a regular changes through core observation and 3-D seismic inversion: turbidity current developed and deposited on the bottom part of slope break, as well as weak cohesive debris, during the activity rate of the synsedimentary faults was fast, which led to a steep landform and high creation rate of accommodation; while in the case of low activity rate resulting in flat landform and low creation rate of accommodation, debris developed and deposited wildly on the flat slope. Consequently, our research suggests that the landform variation can be confirmed by the changes of flow regime and taypes of gravity deposition, then the scenario of base level variation can be investigated.
2016, 34(3): 497-505.
doi: 10.14027/j.cnki.cjxb.2016.03.007
Abstract:
The deposition time and provenance of Zhaoling Formation in Tangwangling has not been conclusiving since it was found, In order to determine the Zhaoling Formation's assignment, this article has performed studies with the clastic sample from Zhaoling Formation by the method of LA-ICP-MS zircon U-Pb dating, based on the age distribution of zircons this article discussed the deposition time and sedimentary provenance of Zhaoling Formation. The results shows: The detrital zircon ages of Zhaoling Formation mainly include 744~943 Ma(n=6), 1 005~1 412 Ma (n=15), 1 449~2 209 Ma (n=255) and 2 274~2 696 Ma (n=49), the corresponding peak ages are 815 Ma, 1 182 Ma, 1 811 Ma, 2 454 Ma, the minimum age for single detrial zircon is 774 Ma. At the same time, the zircon U-Pb ages shows the deposition time of Zhaoling Formation is similar to Zhengmuguang Formation but not Pingliang Formation, especially lack of the characteristics detrital zircon U-Pb peak age of 454 Ma, they all show that the Zhaoling Formation maximum deposition era is Precambrian. The comparative analyses of zircon U-Pb age shows that the main sources of Zhaoling Formation come from the paleoproterozoic metamorphic basement of North China Craton and Precambrian complex granitic intrusion of North Qinling Mountain, respectively.
The deposition time and provenance of Zhaoling Formation in Tangwangling has not been conclusiving since it was found, In order to determine the Zhaoling Formation's assignment, this article has performed studies with the clastic sample from Zhaoling Formation by the method of LA-ICP-MS zircon U-Pb dating, based on the age distribution of zircons this article discussed the deposition time and sedimentary provenance of Zhaoling Formation. The results shows: The detrital zircon ages of Zhaoling Formation mainly include 744~943 Ma(n=6), 1 005~1 412 Ma (n=15), 1 449~2 209 Ma (n=255) and 2 274~2 696 Ma (n=49), the corresponding peak ages are 815 Ma, 1 182 Ma, 1 811 Ma, 2 454 Ma, the minimum age for single detrial zircon is 774 Ma. At the same time, the zircon U-Pb ages shows the deposition time of Zhaoling Formation is similar to Zhengmuguang Formation but not Pingliang Formation, especially lack of the characteristics detrital zircon U-Pb peak age of 454 Ma, they all show that the Zhaoling Formation maximum deposition era is Precambrian. The comparative analyses of zircon U-Pb age shows that the main sources of Zhaoling Formation come from the paleoproterozoic metamorphic basement of North China Craton and Precambrian complex granitic intrusion of North Qinling Mountain, respectively.
Sediment Distribution and Its Controlling Mechanism in the Littoral Zone of Sigengsha, Hainan, China
2016, 34(3): 506-515.
doi: 10.14027/j.cnki.cjxb.2016.03.008
Abstract:
Owing to the interaction between land and ocean, littoral zones present unique sedimentation. Grain size, as a basic attribute of sediment, is an essential question of sediment dynamics. Grain size is controlled by sediment source and sink, and its parameters play a significant role in determining dynamic relationship between sediment and depositional environment. Sigensha littoral zone is located in the west of Hainan Island, the second largest island of China, extending from the Changhua River delta on the north to the Beili Bay on the south. This zone shows diverse sediment sources, complicated hydrodynamics and variable morphology, where special coastal evolution process is closely connected with its sedimentary environment. A field sampling was conducted in the study area on January 2013 with 185 surface samples collected. Mastersize 2000 laser particle sizer was applied to measure grain sizes all less than 2 mm and the sediments with sizes larger than 2 mm were tested by a comprehensive method, utilizing both sieve analysis and laser particle sizer. Sediment classification and nomenclature were based on Fork method and grain-size parameters were calculated including mean grain size M, standard deviation σ, skewness Sk and kurtosis K. The distribution of grain size parameters in the study area was then acquired by Kriging interpolation. Combined with sediment sources and bathymetric information, the sedimentary environment was divided by using the ternary diagram of Fleming. At last, the controlling mechanism of sediment distribution was investigated combined with hydrodynamic factors and morphology.
The results suggest that the entire study area comprise 12 sediment types, mainly including sandy silt, silt, silty sand and gravel-bearing sand. Sandy silt, the mostly distributed sediment, mainly occurs in the central study area. Silt mainly distributed in the southern study area. Similar to sandy silt, silty sand is also distributed in the central study area. Gravel-bearing sand mostly distributed in the nearshore of the northern study area. Overall, the mean grain size of the study area ranges widely (-0.70 φ to 7.13 φ) and presents a fining trend from north to south. The standard deviation of sediment ranges from 0.30 to 2.73 with mean value of 1.75. It is characterized by a worse-worst-worse trend from north to south. The skewness changes from -0.77 to 0.73 with average of 0.09. The kurtosis range from 0.52 to 4.35 with average of 1.13 and shows mesokurtic to platykurtic pattern. Based on Fleming ternary diagram, combined with sediment sources, hydrodynamic and topographic condition, the study area was divided into three sedimentary districts: Sigengsha nearshore zone, middle Beili Bay zone and Basuo port nearshore zone. In the sediment distribution pattern, the western study area was mainly influenced by strong tidal currents. The nearshore was mostly impacted by wave winnowing and transport and was characterized by fine sediment distributed in the middle and coarse sediment in the two sides. Laterally, the Sigengsha nearshore zone is a high-energy coarse-grained sand area, where sand content is as large as 78.68%, mainly affected by sediments from Changhua River. The Beili Bay zone is a medium-energy transitional area of silty sand and sandy silt, where the grain sizes range widely. The Basuo port nearshore zone is a low-energy area, where silt content occupies 64.43%, and where the sediment is the finest and most likely comes from open sea.
Owing to the interaction between land and ocean, littoral zones present unique sedimentation. Grain size, as a basic attribute of sediment, is an essential question of sediment dynamics. Grain size is controlled by sediment source and sink, and its parameters play a significant role in determining dynamic relationship between sediment and depositional environment. Sigensha littoral zone is located in the west of Hainan Island, the second largest island of China, extending from the Changhua River delta on the north to the Beili Bay on the south. This zone shows diverse sediment sources, complicated hydrodynamics and variable morphology, where special coastal evolution process is closely connected with its sedimentary environment. A field sampling was conducted in the study area on January 2013 with 185 surface samples collected. Mastersize 2000 laser particle sizer was applied to measure grain sizes all less than 2 mm and the sediments with sizes larger than 2 mm were tested by a comprehensive method, utilizing both sieve analysis and laser particle sizer. Sediment classification and nomenclature were based on Fork method and grain-size parameters were calculated including mean grain size M, standard deviation σ, skewness Sk and kurtosis K. The distribution of grain size parameters in the study area was then acquired by Kriging interpolation. Combined with sediment sources and bathymetric information, the sedimentary environment was divided by using the ternary diagram of Fleming. At last, the controlling mechanism of sediment distribution was investigated combined with hydrodynamic factors and morphology.
The results suggest that the entire study area comprise 12 sediment types, mainly including sandy silt, silt, silty sand and gravel-bearing sand. Sandy silt, the mostly distributed sediment, mainly occurs in the central study area. Silt mainly distributed in the southern study area. Similar to sandy silt, silty sand is also distributed in the central study area. Gravel-bearing sand mostly distributed in the nearshore of the northern study area. Overall, the mean grain size of the study area ranges widely (-0.70 φ to 7.13 φ) and presents a fining trend from north to south. The standard deviation of sediment ranges from 0.30 to 2.73 with mean value of 1.75. It is characterized by a worse-worst-worse trend from north to south. The skewness changes from -0.77 to 0.73 with average of 0.09. The kurtosis range from 0.52 to 4.35 with average of 1.13 and shows mesokurtic to platykurtic pattern. Based on Fleming ternary diagram, combined with sediment sources, hydrodynamic and topographic condition, the study area was divided into three sedimentary districts: Sigengsha nearshore zone, middle Beili Bay zone and Basuo port nearshore zone. In the sediment distribution pattern, the western study area was mainly influenced by strong tidal currents. The nearshore was mostly impacted by wave winnowing and transport and was characterized by fine sediment distributed in the middle and coarse sediment in the two sides. Laterally, the Sigengsha nearshore zone is a high-energy coarse-grained sand area, where sand content is as large as 78.68%, mainly affected by sediments from Changhua River. The Beili Bay zone is a medium-energy transitional area of silty sand and sandy silt, where the grain sizes range widely. The Basuo port nearshore zone is a low-energy area, where silt content occupies 64.43%, and where the sediment is the finest and most likely comes from open sea.
2016, 34(3): 516-522.
doi: 10.14027/j.cnki.cjxb.2016.03.009
Abstract:
Both of the 210Pb and sediment grain size in four deep-water multicore sediments which are located in the middle, north and west of Japan Sea are analyzed. The result shows that the sediments mainly consist of silt and clayey silt in the Yamato Ridge, northern part and western slope of Japan Sea over the last 100 years. There is a significant biological disturbance phenomenon of surface sediments in Yamato Ridge and the northern part of the Japan Sea, which does not exist in the western slope. According to the model of Constant Rate of Supply (CRS), we determined the age mode and calculated the sedimentation rate in four multicores. The modern average sedimentation rate in the Japan Sea varied between 0.19~0.42 cm/a, with a lowest value in Yamato Ridge. The mean sediment grain size of four cores showed different vertical patterns, but they simultaneously varied at about 1940 and 1980. We think such simultaneous change is closely related to the variations of Pacific Decadal Oscillation (PDO) and East Asian Summer Monsoon over the last 100 years.
Both of the 210Pb and sediment grain size in four deep-water multicore sediments which are located in the middle, north and west of Japan Sea are analyzed. The result shows that the sediments mainly consist of silt and clayey silt in the Yamato Ridge, northern part and western slope of Japan Sea over the last 100 years. There is a significant biological disturbance phenomenon of surface sediments in Yamato Ridge and the northern part of the Japan Sea, which does not exist in the western slope. According to the model of Constant Rate of Supply (CRS), we determined the age mode and calculated the sedimentation rate in four multicores. The modern average sedimentation rate in the Japan Sea varied between 0.19~0.42 cm/a, with a lowest value in Yamato Ridge. The mean sediment grain size of four cores showed different vertical patterns, but they simultaneously varied at about 1940 and 1980. We think such simultaneous change is closely related to the variations of Pacific Decadal Oscillation (PDO) and East Asian Summer Monsoon over the last 100 years.
2016, 34(3): 523-530.
doi: 10.14027/j.cnki.cjxb.2016.03.010
Abstract:
Formation and preservation of barite are essential to the biogeochemical processes of Ba in marine environment, which have important value in the field of paleooceanopraphy research. However, researches were mainly concentrated on the deep sea and ocean waters for many years and rarely mentioned in estuaries and coastal waters. In this study, suspended mineral barites were observed systematic by scanning electron microscopy and energy dispersive X-ray spectrometry about five sections including 36 stations in the Yangtze River Estuary and its adjacent areas. Barite particle type, spatial distribution and influencing factors were researched. The results indicate that barite particles can be classified into euhedral crystal, elongated crystal, irregular crystal and aggregate, containing a small amount of Sr, occurring erosion phenomena on most of the barite surface. The size of barite particle is mainly in 0.5~3 μm. Barite particle is more in the surface water than the bottom water and is increasing from shore to the open sea, whose formation is related to microenvironment affected by biological processes. The primary productivity and the settling rate of barite particle are two main factors to influencing the barite distribution in that area.
Formation and preservation of barite are essential to the biogeochemical processes of Ba in marine environment, which have important value in the field of paleooceanopraphy research. However, researches were mainly concentrated on the deep sea and ocean waters for many years and rarely mentioned in estuaries and coastal waters. In this study, suspended mineral barites were observed systematic by scanning electron microscopy and energy dispersive X-ray spectrometry about five sections including 36 stations in the Yangtze River Estuary and its adjacent areas. Barite particle type, spatial distribution and influencing factors were researched. The results indicate that barite particles can be classified into euhedral crystal, elongated crystal, irregular crystal and aggregate, containing a small amount of Sr, occurring erosion phenomena on most of the barite surface. The size of barite particle is mainly in 0.5~3 μm. Barite particle is more in the surface water than the bottom water and is increasing from shore to the open sea, whose formation is related to microenvironment affected by biological processes. The primary productivity and the settling rate of barite particle are two main factors to influencing the barite distribution in that area.
2016, 34(3): 531-542.
doi: 10.14027/j.cnki.cjxb.2016.03.011
Abstract:
A total of 384 Mt/yr of suspended sediment is supplied to ocean by small mountainous rivers in Taiwan (1970—1999), equivalent to the sum of sediment discharge from three major rivers (the Yangtze River, the Yellow River and the Pearl River) in China. Hence, it has an appreciable impact on the sedimentary process of the epicontinental shelf. There are altogether 151 rivers in Taiwan, most of which originate from the Central Range. For our study river basins, the Zhuoshui River and the Lanyang River feed into the Taiwan Strait and the Pacific Ocean, respectively. The Zhuoshui River flows through the western Central Range, the Hsuehshan Range, the Western Foothills and the Coastal Plain in turn. And sequences of the Hsuehshan Range and the western Central Range outcrop in the Lanyang River basin. Heavy mineral types and contents of eight sediment samples from the Zhuoshui River (ZS1~ZS5) and the Lanyang River (LY1~LY3) are analyzed in whole size fraction. Twenty kinds of heavy minerals are identified. The weight percentage of heavy minerals varies from 0.039% to 0.116% in the Zhuoshui River, and from 0.004% to 0.040% in the Lanyang River. On the whole, the weight percentage declines from upstream to downstream.
There is an irregular spatial distribution of heavy mineral assemblages along both rivers. For the Zhuoshui River, the dominated heavy mineral assemblage is pyrite-limonite-magnetite in the upper reaches, zircon-limonite-magnetite-pyrite in the middle reaches, zircon-garnet-limonite-ilmenite-anatase-leucoxene in the lower reaches. For the Lanyang River, the dominated heavy mineral assemblage is zircon-epidote-pyrite in the upper reaches, zircon-magnesite-limonite-leucoxene in the middle reaches, zircon-magnesite-limonite-anatase-pyrite in the lower reaches. Variations of heavy mineral types and contents along the two rivers indicate that most sediments are mainly supplied by proximal source rocks, and signatures of heavy minerals from upstream are masked. Also, there exists difference in contributions to sediments between potential provenances: heavy minerals in the lower reaches of both rivers are mostly derived from Quaternary sediments, and in the upper reaches mainly supplied by Lushan Formation of the Central Range. In addition, because the distribution of heavy mineral assemblages is primarily controlled by source rocks, some heavy mineral indexes (ATi, GZi and ZTR) cannot be used properly in these small mountainous rivers.
The differences in bedrocks between mainland and Taiwan make the heavy mineral assemblages different between both sides of the strait. The typical heavy minerals in the rivers of Chinese mainland, like magnetite and epidote, are not common in the Taiwanese Rivers. However, the enrichment of zircon, magnesite and pyrite in the mouth of the Lanyang River, and the enrichment of zircon and garnet in the mouth of the Zhuoshui River, are there respective characteristics. All these features may offer some reference value for tracing the provenances of sediments in the epicontinental shelf.
A total of 384 Mt/yr of suspended sediment is supplied to ocean by small mountainous rivers in Taiwan (1970—1999), equivalent to the sum of sediment discharge from three major rivers (the Yangtze River, the Yellow River and the Pearl River) in China. Hence, it has an appreciable impact on the sedimentary process of the epicontinental shelf. There are altogether 151 rivers in Taiwan, most of which originate from the Central Range. For our study river basins, the Zhuoshui River and the Lanyang River feed into the Taiwan Strait and the Pacific Ocean, respectively. The Zhuoshui River flows through the western Central Range, the Hsuehshan Range, the Western Foothills and the Coastal Plain in turn. And sequences of the Hsuehshan Range and the western Central Range outcrop in the Lanyang River basin. Heavy mineral types and contents of eight sediment samples from the Zhuoshui River (ZS1~ZS5) and the Lanyang River (LY1~LY3) are analyzed in whole size fraction. Twenty kinds of heavy minerals are identified. The weight percentage of heavy minerals varies from 0.039% to 0.116% in the Zhuoshui River, and from 0.004% to 0.040% in the Lanyang River. On the whole, the weight percentage declines from upstream to downstream.
There is an irregular spatial distribution of heavy mineral assemblages along both rivers. For the Zhuoshui River, the dominated heavy mineral assemblage is pyrite-limonite-magnetite in the upper reaches, zircon-limonite-magnetite-pyrite in the middle reaches, zircon-garnet-limonite-ilmenite-anatase-leucoxene in the lower reaches. For the Lanyang River, the dominated heavy mineral assemblage is zircon-epidote-pyrite in the upper reaches, zircon-magnesite-limonite-leucoxene in the middle reaches, zircon-magnesite-limonite-anatase-pyrite in the lower reaches. Variations of heavy mineral types and contents along the two rivers indicate that most sediments are mainly supplied by proximal source rocks, and signatures of heavy minerals from upstream are masked. Also, there exists difference in contributions to sediments between potential provenances: heavy minerals in the lower reaches of both rivers are mostly derived from Quaternary sediments, and in the upper reaches mainly supplied by Lushan Formation of the Central Range. In addition, because the distribution of heavy mineral assemblages is primarily controlled by source rocks, some heavy mineral indexes (ATi, GZi and ZTR) cannot be used properly in these small mountainous rivers.
The differences in bedrocks between mainland and Taiwan make the heavy mineral assemblages different between both sides of the strait. The typical heavy minerals in the rivers of Chinese mainland, like magnetite and epidote, are not common in the Taiwanese Rivers. However, the enrichment of zircon, magnesite and pyrite in the mouth of the Lanyang River, and the enrichment of zircon and garnet in the mouth of the Zhuoshui River, are there respective characteristics. All these features may offer some reference value for tracing the provenances of sediments in the epicontinental shelf.
2016, 34(3): 543-554.
doi: 10.14027/j.cnki.cjxb.2016.03.012
Abstract:
The study area is situated in the southwest of Hangjiahu plain, where the surface water system is developed and most rivers originate from Tianmu mountain and Mogan mountain in the northwest of Zhejiang. The sediment samples were collected from a core drilled at the Beihuqiao (BHQ) of Yuhang town, where the location is 30°22.443' N, 119°56.237' E. The BHQ core is 19.0 m in length, and core sediments are composed of homogeneous gray, clayey silt and silt with a little carbonate nodules except for an intercalation of silty sand in the lower part. No disturbance was observed in the whole core. The part (4.775~19.0 m) of the core was sampled at 2.5 cm increments. Four bulk samples were collected for AMS radiocarbon dating from the organic-rich sediments. And 136 samples were chosen for TOC and δ13Corg analysis at about 10 cm intervals.
Combined with the proxies of grain size parameters, pollen data, C/N radio and age data, and contrasted with researches of surrounding areas, TOC and δ13Corg in organic matter, BHQ core in Zhejiang province are analyzed to interpret the basic environmental information and climate changes during the Early-Middle Holocene. Results reveal that the paleoclimate changes in Hangjiahu plain during the Early-Middle Holocene which can be divided into three periods: (1)11.4~8.7 ka B.P.. Organic carbon isotope increased in the range of -27.24‰ to -23.4‰ and TOC content increased obviously in the range of 0.19% to 0.69%, indicating that the cold-dry climate turned gradually to warm and humid in this period. (2)8.7~8.0 ka B.P.. Compared with the last stage, TOC turned to be negative and fluctuated between 0.2%~1.33%, δ13Corg fluctuated slightly between -24.91‰~-22.93‰ and tended to be positive. As a whole, the climate was dry, and presented cold-dry to humid and warm-dry trend. (3)8.0~4.2 ka B.P.. The major characteristic of the climate in the northern of Zhejiang province was warm and humid, however, some cold-dry events also happened at different time scales in this period. And during the period, TOC and δ13Corg fluctuated in 0.18%~2.18% and -26.33‰~-19.09‰ ranges, respectively. Especially during 8.0~5.7 ka B.P., TOC content improved obviously in 0.43%~2.18% and δ13Corg tended to be negative in -25.79‰~-23.15‰, which indicated the Holocene Megathermal emerged in this region. Meanwhile, there were two cold events occurred in about 5.5 ka B.P. and 4.2 ka B.P.. During these two periods, TOC tended to down and δ13Corg had a positive fluctuation, and they also corresponded with the contemporaneous pollen data and grain sizes parameters.
Combined with multiple climatic proxies of BHQ core and the results of correlation analysis between these proxies, the BHQ core sediments provide a reliable basis interpretation of palaeoclimate. TOC and δ13Corg of BHQ core can be good proxies of paleoclimate in this research zone and indicate the changes of precipitation and temperature respectively. At the same time, this study also effectively suggests the evolution law of paleoenvironment in the northern of Zhejiang province during the Early-Middle Holocene.
The study area is situated in the southwest of Hangjiahu plain, where the surface water system is developed and most rivers originate from Tianmu mountain and Mogan mountain in the northwest of Zhejiang. The sediment samples were collected from a core drilled at the Beihuqiao (BHQ) of Yuhang town, where the location is 30°22.443' N, 119°56.237' E. The BHQ core is 19.0 m in length, and core sediments are composed of homogeneous gray, clayey silt and silt with a little carbonate nodules except for an intercalation of silty sand in the lower part. No disturbance was observed in the whole core. The part (4.775~19.0 m) of the core was sampled at 2.5 cm increments. Four bulk samples were collected for AMS radiocarbon dating from the organic-rich sediments. And 136 samples were chosen for TOC and δ13Corg analysis at about 10 cm intervals.
Combined with the proxies of grain size parameters, pollen data, C/N radio and age data, and contrasted with researches of surrounding areas, TOC and δ13Corg in organic matter, BHQ core in Zhejiang province are analyzed to interpret the basic environmental information and climate changes during the Early-Middle Holocene. Results reveal that the paleoclimate changes in Hangjiahu plain during the Early-Middle Holocene which can be divided into three periods: (1)11.4~8.7 ka B.P.. Organic carbon isotope increased in the range of -27.24‰ to -23.4‰ and TOC content increased obviously in the range of 0.19% to 0.69%, indicating that the cold-dry climate turned gradually to warm and humid in this period. (2)8.7~8.0 ka B.P.. Compared with the last stage, TOC turned to be negative and fluctuated between 0.2%~1.33%, δ13Corg fluctuated slightly between -24.91‰~-22.93‰ and tended to be positive. As a whole, the climate was dry, and presented cold-dry to humid and warm-dry trend. (3)8.0~4.2 ka B.P.. The major characteristic of the climate in the northern of Zhejiang province was warm and humid, however, some cold-dry events also happened at different time scales in this period. And during the period, TOC and δ13Corg fluctuated in 0.18%~2.18% and -26.33‰~-19.09‰ ranges, respectively. Especially during 8.0~5.7 ka B.P., TOC content improved obviously in 0.43%~2.18% and δ13Corg tended to be negative in -25.79‰~-23.15‰, which indicated the Holocene Megathermal emerged in this region. Meanwhile, there were two cold events occurred in about 5.5 ka B.P. and 4.2 ka B.P.. During these two periods, TOC tended to down and δ13Corg had a positive fluctuation, and they also corresponded with the contemporaneous pollen data and grain sizes parameters.
Combined with multiple climatic proxies of BHQ core and the results of correlation analysis between these proxies, the BHQ core sediments provide a reliable basis interpretation of palaeoclimate. TOC and δ13Corg of BHQ core can be good proxies of paleoclimate in this research zone and indicate the changes of precipitation and temperature respectively. At the same time, this study also effectively suggests the evolution law of paleoenvironment in the northern of Zhejiang province during the Early-Middle Holocene.
2016, 34(3): 555-562.
doi: 10.14027/j.cnki.cjxb.2016.03.013
Abstract:
Ignited by the existence of fluvial, wavy, tidal sediments deposited together in Pearl River mouth-Modaomen, and the land-ocean interaction theory, considering the reality of microfacies definition of delta, we introduced the hydrogeology, geography and geomorphology in to the delta-define scheme, and suggested to integrate fluvial, wavy and tidal microfacies, to re-organize the depositional elements to reconstruct marine delta. This scheme also reveals that referring to the neighbor science like hydrogeology, geography and geomorphology can be fruitful for sedmentological research, especially for petroleum exploration. Based on the field research on Modaomen, those sand bodies which distribute various styles on different orientation show that when we correlate the sand layers during petroleum exploration and development, we should consider the seismic reflection, sedimentary distribution, hydrocarbon-water relations pressure, and even the distance between wells.
Ignited by the existence of fluvial, wavy, tidal sediments deposited together in Pearl River mouth-Modaomen, and the land-ocean interaction theory, considering the reality of microfacies definition of delta, we introduced the hydrogeology, geography and geomorphology in to the delta-define scheme, and suggested to integrate fluvial, wavy and tidal microfacies, to re-organize the depositional elements to reconstruct marine delta. This scheme also reveals that referring to the neighbor science like hydrogeology, geography and geomorphology can be fruitful for sedmentological research, especially for petroleum exploration. Based on the field research on Modaomen, those sand bodies which distribute various styles on different orientation show that when we correlate the sand layers during petroleum exploration and development, we should consider the seismic reflection, sedimentary distribution, hydrocarbon-water relations pressure, and even the distance between wells.
2016, 34(3): 563-570.
doi: 10.14027/j.cnki.cjxb.2016.03.014
Abstract:
Overpressure influence and control of oil and gas reservoir distribution, there is obvious relationship between overpressure distribution and development of gypsum-salt rocks. Study on the development of gypsum-salt rocks in Shizigou area, analysis of regularity of distribution of formation pressure with actual and computational data to the area, for discussing the relationship between gypsum-salt rocks and formation pressure. Gypsum-salt rocks have four sedimentary sequences in the vertical, they were inversely proportional relationship with sandstone, and were proportional relationship with mudstone in the lateral. The formation pressure has the feature of segmentation in the vertical: Ordinary pressure section, pressure coefficient range in 0.9~1.2, it's in up-salt zone; Boost pressure section, pressure coefficient range in 1.3~1.8, it's in inter-salt zone; Excess pressure section, pressure coefficient above 1.8, it's in pre-salt zone. The undeveloped area of gypsum-salt rocks have no this kind of segmentation. Pressure range covered the development range of gypsum-salt rocks. Overpressure decreased as gypsum-salt rocks thickness thinning. Gypsum-salt rocks have obvious control effect for overpressure distribution. Dewatering, compactness, plasticity, flowability, and high thermal conductivity of gypsum-salt rocks are the root cause of formation of overpressure.
Overpressure influence and control of oil and gas reservoir distribution, there is obvious relationship between overpressure distribution and development of gypsum-salt rocks. Study on the development of gypsum-salt rocks in Shizigou area, analysis of regularity of distribution of formation pressure with actual and computational data to the area, for discussing the relationship between gypsum-salt rocks and formation pressure. Gypsum-salt rocks have four sedimentary sequences in the vertical, they were inversely proportional relationship with sandstone, and were proportional relationship with mudstone in the lateral. The formation pressure has the feature of segmentation in the vertical: Ordinary pressure section, pressure coefficient range in 0.9~1.2, it's in up-salt zone; Boost pressure section, pressure coefficient range in 1.3~1.8, it's in inter-salt zone; Excess pressure section, pressure coefficient above 1.8, it's in pre-salt zone. The undeveloped area of gypsum-salt rocks have no this kind of segmentation. Pressure range covered the development range of gypsum-salt rocks. Overpressure decreased as gypsum-salt rocks thickness thinning. Gypsum-salt rocks have obvious control effect for overpressure distribution. Dewatering, compactness, plasticity, flowability, and high thermal conductivity of gypsum-salt rocks are the root cause of formation of overpressure.
2016, 34(3): 571-581.
doi: 10.14027/j.cnki.cjxb.2016.03.015
Abstract:
Mixed sediments of lacustrine carbonate rocks and clastic rocks are developed in the Da'anzhai Member of Ziliujing Formation in Huilong area, western Sichuan. Based on the comprehensive analysis on field outcrops, drilling cores, well logging and microfabric, the sedimentary microfacies of mixed sediments of the study area was finely depicted. The results revealed that the Da'anzhai Member in Huilong area belonged to the lacustrine mixed sedimentary facies consisting of shore-shallow lake and semi-deep lake subfacies, which was further divided into five mixed sedimentary microfacies, including high-energy shelly beach, low-energy shelly beach, sandy shoal, shallow lake and semi-deep lake. Further more, based on the features of mixed sedimentary facies and the evolution process of the Da'anzhai Member in Huilong area in Jurassic Period, the origin and evolution pattern of mixed sediments in the study area was analyzed. It was concluded that the lacustrine mixed sediments in the study area were predominantly controlled by provenance supply and hydrodynamic condition and various type of mixed sediments were formed under the control of five mixed sedimentary microfacies.
Mixed sediments of lacustrine carbonate rocks and clastic rocks are developed in the Da'anzhai Member of Ziliujing Formation in Huilong area, western Sichuan. Based on the comprehensive analysis on field outcrops, drilling cores, well logging and microfabric, the sedimentary microfacies of mixed sediments of the study area was finely depicted. The results revealed that the Da'anzhai Member in Huilong area belonged to the lacustrine mixed sedimentary facies consisting of shore-shallow lake and semi-deep lake subfacies, which was further divided into five mixed sedimentary microfacies, including high-energy shelly beach, low-energy shelly beach, sandy shoal, shallow lake and semi-deep lake. Further more, based on the features of mixed sedimentary facies and the evolution process of the Da'anzhai Member in Huilong area in Jurassic Period, the origin and evolution pattern of mixed sediments in the study area was analyzed. It was concluded that the lacustrine mixed sediments in the study area were predominantly controlled by provenance supply and hydrodynamic condition and various type of mixed sediments were formed under the control of five mixed sedimentary microfacies.
2016, 34(3): 582-593.
doi: 10.14027/j.cnki.cjxb.2016.03.016
Abstract:
Thin sandbodies of subaqueous distributary channels of delta-front are widely developed in Biqian 10 area, Gucheng oil field, Biyang sag. Depending on fine study of reservoir sedimentary microfacies with integrating various data including cores and small well spacing logging data, we characterized the single sand body identification in compound subaqueous distributary channels and established a quantitative prediction model for single sand body scale, then we classified the subaqueous distributary channels into 3 types according to channel scale. Based on the short-term base-level cycle theory of high resolution sequence stratigraphy, the paper analyzes the genesis of subaqueous distributary channel sandstones in the study area. The result shows that in the course of base-level rising, A/S<<1, sandstone genetic type is mainly truncated distributary channel sandstone body, A/S<1(close to 1), sandstone genetic type is mainly integrated distributary channel sandstone body. We identified that there are five main vertical superimposition patterns of single sandbodies, including vertical superposition, lateral superposition, vertical tangency, lateral tangency and vertical separated, and three lateral contact patterns, including interdistributary contact, horizontal overlap contact and lateral superimposition-tangency contact, moreover, each type of logging-facies marks is summarized.
Thin sandbodies of subaqueous distributary channels of delta-front are widely developed in Biqian 10 area, Gucheng oil field, Biyang sag. Depending on fine study of reservoir sedimentary microfacies with integrating various data including cores and small well spacing logging data, we characterized the single sand body identification in compound subaqueous distributary channels and established a quantitative prediction model for single sand body scale, then we classified the subaqueous distributary channels into 3 types according to channel scale. Based on the short-term base-level cycle theory of high resolution sequence stratigraphy, the paper analyzes the genesis of subaqueous distributary channel sandstones in the study area. The result shows that in the course of base-level rising, A/S<<1, sandstone genetic type is mainly truncated distributary channel sandstone body, A/S<1(close to 1), sandstone genetic type is mainly integrated distributary channel sandstone body. We identified that there are five main vertical superimposition patterns of single sandbodies, including vertical superposition, lateral superposition, vertical tangency, lateral tangency and vertical separated, and three lateral contact patterns, including interdistributary contact, horizontal overlap contact and lateral superimposition-tangency contact, moreover, each type of logging-facies marks is summarized.
2016, 34(3): 594-605.
doi: 10.14027/j.cnki.cjxb.2016.03.017
Abstract:
Analyzed on casting thin sections, SEM, cathode luminescence, geochemical data, etc and combined with the method of statistics and calculation, we studied the petrologic feature, diagenetic types, sequence, and quantitative evolution of Shanxi Formation in LX area. Based on these researches, we established the types and classification standard of diagenetic facies, and determined the diagenetic facies' distribution of Shanxi Formation in the studied area. The following conclusions were obtained. The compaction and cementation were the main reasons for the densification of Shanxi formation in the studied area. The diagenetic stage was B of middle diagenesis phase. And the diagenetic evolution as follows: Stage A of early diagenesis phase went through the compaction and little carbonate cementation, and stage B was compaction, little cementation and dissolution. Stage A of middle diagenesis phase was mainly experiencing the dissolution and cementation, and stage B was carbonate cementation. The main types of diagenetic facies were moderate compaction, weak cementation, dissolution facies, moderate compaction, moderate cementation, dissolution facies, moderate compaction, strong cementation facies, and strong compaction, matrix strong filling facies. The favorable diagenetic facies was widely distributed in the studied area, which showed that the study area had a good exploration potential. Especially, the moderate compaction, weak cementation, dissolution facies was key area in the next exploration and development of Shanxi Formation in the studied area.
Analyzed on casting thin sections, SEM, cathode luminescence, geochemical data, etc and combined with the method of statistics and calculation, we studied the petrologic feature, diagenetic types, sequence, and quantitative evolution of Shanxi Formation in LX area. Based on these researches, we established the types and classification standard of diagenetic facies, and determined the diagenetic facies' distribution of Shanxi Formation in the studied area. The following conclusions were obtained. The compaction and cementation were the main reasons for the densification of Shanxi formation in the studied area. The diagenetic stage was B of middle diagenesis phase. And the diagenetic evolution as follows: Stage A of early diagenesis phase went through the compaction and little carbonate cementation, and stage B was compaction, little cementation and dissolution. Stage A of middle diagenesis phase was mainly experiencing the dissolution and cementation, and stage B was carbonate cementation. The main types of diagenetic facies were moderate compaction, weak cementation, dissolution facies, moderate compaction, moderate cementation, dissolution facies, moderate compaction, strong cementation facies, and strong compaction, matrix strong filling facies. The favorable diagenetic facies was widely distributed in the studied area, which showed that the study area had a good exploration potential. Especially, the moderate compaction, weak cementation, dissolution facies was key area in the next exploration and development of Shanxi Formation in the studied area.
2016, 34(3): 606-614.
doi: 10.14027/j.cnki.cjxb.2016.03.018
Abstract:
The reservoir-forming situations of source rocks, reservoir rocks, cap rocks and migration condition in Baikouquan Formation lithologic reservoir, west slope of Mahu Depression, are favorable.The valuable trap sealing condition in lateral and upward direction is the key to reservoir-forming. On the basis of making clear the fact that the mud content is the key factor to the reservoir performance of the sand conglomerate reservoir in this area, this paper divided the sand conglomerate reservoir into three lithofacies: poor-mud conglomerate (mud content<5%), mud-bearing conglomerate (mud content 5%~8%) and mud-rich conglomerate (mud content>8%).During the period of early oil-gas injection in early Jurassic, the three lithofacies above mentioned are all the valuable reservoirs. During the period of main oil-gas injection in early Cretaceous, the reservoir performance of the mud-rich conglomerate is obviously worse, and then the mud-rich conglomerate evolved into the sealing block finally, whereas the poor-mud conglomerate and the mud- bearing conglomerate are still acted as valuable reservoir, with the reservoir performance of the former is better than the latter. Fan delta front sub-facies (traction flow) deposition are mainly corresponding to the poor-mud conglomerate, and acted as valuable reservoir during the period of oil-gas injection, and then acted as the main reservoir in T1b lithologic reservoir, west slope of Mahu Depression. The fan delta plain (traction flow) deposition and sandy debris flow (gravity flow) deposition are mainly corresponding to mud-rich conglomerate, mainly acted as the sealing blocks in the bottom and the lateral direction of the large lithologic reservoir with the poor reservoir performance. The two sealing blocks mentioned above, configured with the valuable reservoirs in fan delta front sub-facies (traction flow), jointly constitute the large lithologic reservoir in T1b, west slope of Mahu Depression.
The reservoir-forming situations of source rocks, reservoir rocks, cap rocks and migration condition in Baikouquan Formation lithologic reservoir, west slope of Mahu Depression, are favorable.The valuable trap sealing condition in lateral and upward direction is the key to reservoir-forming. On the basis of making clear the fact that the mud content is the key factor to the reservoir performance of the sand conglomerate reservoir in this area, this paper divided the sand conglomerate reservoir into three lithofacies: poor-mud conglomerate (mud content<5%), mud-bearing conglomerate (mud content 5%~8%) and mud-rich conglomerate (mud content>8%).During the period of early oil-gas injection in early Jurassic, the three lithofacies above mentioned are all the valuable reservoirs. During the period of main oil-gas injection in early Cretaceous, the reservoir performance of the mud-rich conglomerate is obviously worse, and then the mud-rich conglomerate evolved into the sealing block finally, whereas the poor-mud conglomerate and the mud- bearing conglomerate are still acted as valuable reservoir, with the reservoir performance of the former is better than the latter. Fan delta front sub-facies (traction flow) deposition are mainly corresponding to the poor-mud conglomerate, and acted as valuable reservoir during the period of oil-gas injection, and then acted as the main reservoir in T1b lithologic reservoir, west slope of Mahu Depression. The fan delta plain (traction flow) deposition and sandy debris flow (gravity flow) deposition are mainly corresponding to mud-rich conglomerate, mainly acted as the sealing blocks in the bottom and the lateral direction of the large lithologic reservoir with the poor reservoir performance. The two sealing blocks mentioned above, configured with the valuable reservoirs in fan delta front sub-facies (traction flow), jointly constitute the large lithologic reservoir in T1b, west slope of Mahu Depression.
