2014 Vol. 32, No. 5
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Display Method:
2014, 32(5): 1-2.
Abstract:
2014, 32(5): 809-815.
Abstract:
The lower Cretaceous hydrothermal sedimentary rocks had been found in Baiyinchagan sag of Inner Mongolia Erlian basin in recent years. The hydrothermal sedimentary rocks were rich in special minerals including clay sized albite, ankerite, natrolite, franquanite, barite, etc., and were only developed in semi-deep to deep lacustrine facies. The hydrothermal sedimentary rock can also be characterized by its log response with extremely high GR(GR=700~1 100 API), which is 2~4 times that of natural gamma value of normal argillaceous, and remarkably fluctuation in resistivity logging from as high as 2 000 Ω·m to 0.2 Ω·m. By the petrologic characteristics of the hydrothermal sedimentary rocks,the detailed analysis of single well core,combined with the corresponding logging response features, four hydrothermal actives can be recognized in Tenggeer-Douhongmu formation in the study area. One hydrothermal process will form a low natural gamma value lithologic section-the peak shape high natural gamma value cyclic deposition. A complete hydrothermal process consists of three stages: ①Early overflow process which precipitate low GR dolomitic or zeolitic fine grain rock with dolomite and zeolite laminae, zebra or interface layer. And ②Jet flow process with increasingly active hydrotherm. The laminae or interface layer of dolomite and zeolite will be deformed or even disrupted and result in dolomitic fine grain rock and clastic rock consisting of dolomitic or zeolitic intraclasts. After the energy of hydrotherm exhausted the hydrothermal activity will return back. ③Sluggish overflow stage and results in argillaceous dolomite rock and partial dolomitic mudstone with extremely high GR response.
The lower Cretaceous hydrothermal sedimentary rocks had been found in Baiyinchagan sag of Inner Mongolia Erlian basin in recent years. The hydrothermal sedimentary rocks were rich in special minerals including clay sized albite, ankerite, natrolite, franquanite, barite, etc., and were only developed in semi-deep to deep lacustrine facies. The hydrothermal sedimentary rock can also be characterized by its log response with extremely high GR(GR=700~1 100 API), which is 2~4 times that of natural gamma value of normal argillaceous, and remarkably fluctuation in resistivity logging from as high as 2 000 Ω·m to 0.2 Ω·m. By the petrologic characteristics of the hydrothermal sedimentary rocks,the detailed analysis of single well core,combined with the corresponding logging response features, four hydrothermal actives can be recognized in Tenggeer-Douhongmu formation in the study area. One hydrothermal process will form a low natural gamma value lithologic section-the peak shape high natural gamma value cyclic deposition. A complete hydrothermal process consists of three stages: ①Early overflow process which precipitate low GR dolomitic or zeolitic fine grain rock with dolomite and zeolite laminae, zebra or interface layer. And ②Jet flow process with increasingly active hydrotherm. The laminae or interface layer of dolomite and zeolite will be deformed or even disrupted and result in dolomitic fine grain rock and clastic rock consisting of dolomitic or zeolitic intraclasts. After the energy of hydrotherm exhausted the hydrothermal activity will return back. ③Sluggish overflow stage and results in argillaceous dolomite rock and partial dolomitic mudstone with extremely high GR response.
2014, 32(5): 823-831.
Abstract:
Tazhong area is located in middle Central uplift in Tarim Basin. The at the north is Manjiaer depression, and the south is Tanggubazi depression. Its strike direction is NW-SE. Based on the datas of seismic, well logging and core, the authors establish the sequence stratigraphic framework and the evolution of the sedimentary facies of Lianglitage Formation in the Tazhong area.The depositional rimmed platform include open platform facies and platform margin facies in Lianglitage Formation depositional stage in the Tazhong area. The open platform facies can be divided into patch reef, grain bank, tide flat, interbank sea, intra-platform bottomland. The platform margin facies can be divided into reef mound, carbonate mud mound, granule shoal, interbank sea. The Lianglitage formation's sedimentary sequence can be dividied into transgressive systems track and highstand systems track, and they contain ten parasequence sets. The transgressive systems track contains parasequence sets from 1 to 4, which are retrogradational stacking or aggradational stacking. Their lithology are mainly mudstone and grainstone with interbed biolithite. The highstand systems track includes parasequence sets from 5 to 10, which are aggradational stacking or progradational stacking. Their lithology are grainstone and biohermal limestone with interbed lime mudstone.In the transgressive systems track, the sedimentary trap gradually cover the whole research area. In the parasequence sets 1 to 2, the Z20—Z11—Z4—T162—T78 wells and the Tazhong NO.1 fault are the boundaries of platform margin/open platform and platform margin/slope. The northwest of T86—Z18—T21 wells is blockmass. In this period, the open platform mainly deposit interbank sea, and the intra-platform bottomland distribute in the T10—T11 wells and T79—T43 wells. The width of platform margin is about 1～10 km, and its length is about 160 km. It also mainly deposit the interbank sea, and the granule shoal develop longitudinal zonality. In the parasequence sets 3 to 4, the blockmass boundary shrink to the western part of Z19—Z17—T45 wells. The Z18—Z20—Z4—T162—T262 wells and the Tazhong NO.1 fault are the boundaries of platform margin, open platform, slope. In this period, the water circulates unobstructedly, so that form the aggradational stacking and retrogradation stacking parasequence sets, which form the thick grainstone and micrite in both platform margin and open platform. The width of platform margin is about 2～10 km, and its length is still about 160 km. Because the deposition range of granule shoal and mud mound gradually expand, the rimmed sedimentary character become obvious.In the highstand systems track, the accretion rate of accommodation is equal to (or smaller than) the rate of sedimentation, so that form the aggradational stacking and progradational stacking. In the parasequence sets 5 to 7, the range of platform margin expand, its width is about 3 km to 14 km, and its length is about 210 km. A lot of carbonate mud mound deposit, and the reef mound deposit in the range of T83 well to T78 well. The granule shoals have the largest sedimentary trap and thickness, longitudinally stacked with the reef mound, so that form the rimmed system of platform margin. The range of intra-platform bottomland diminish, while the range of grain bank expand. The patch reefs deposit in the higher sedimentary topography or previous grain bank. In the parasequence sets 8 to 9, the differentiation of sedimentary topography is obvious, and the uplift of reef-bank complex alternatively distribute with the lower interbank sea. The intra-platform bottomland distribute among the inherited deposit range of patch reef and grain bank in the open platform, and their sedimentary range become maximum in this period. The sedimentary cycle of patch reef and grain bank are 1 to 2, and the thickness is about 50 m to 100 m. The width of platform margin is 4 km to 14 km, and the length is 210 km. The range of T54 well to T78 well deposit lots of reef mound, and the range of T54 well to Z19 well deposit the carbonate mud mound. The granule shoal deposit widely, and it stacked with reef longitudinally form 1 to 2 sedimentary cycle, which the thickness is about 100 m to 200 m. The rimmed platform become a pattern essentially. In the parasequence sets 10, the accretion rate of accommodation is equal to the rate of sedimentation. The open platform mainly deposit the grain bank and interbank sea, and the range of interbank sea diminish apparently. The patch reef only deposit in local area like T77 well、T35 well. The range of platform margin diminish between the Z162—Z4—T62 well to the Tazhong NO.1 fault. Its width is 1 km to 12 km, and the length is about 100 km. It mainly deposit the granule shoal and interbank sea, the reef only deposit in local area. In this period, the depositional topography between platform margin and open platform appear apparently high low differentiation, so the rimmed platform is mature and formalized.
Tazhong area is located in middle Central uplift in Tarim Basin. The at the north is Manjiaer depression, and the south is Tanggubazi depression. Its strike direction is NW-SE. Based on the datas of seismic, well logging and core, the authors establish the sequence stratigraphic framework and the evolution of the sedimentary facies of Lianglitage Formation in the Tazhong area.The depositional rimmed platform include open platform facies and platform margin facies in Lianglitage Formation depositional stage in the Tazhong area. The open platform facies can be divided into patch reef, grain bank, tide flat, interbank sea, intra-platform bottomland. The platform margin facies can be divided into reef mound, carbonate mud mound, granule shoal, interbank sea. The Lianglitage formation's sedimentary sequence can be dividied into transgressive systems track and highstand systems track, and they contain ten parasequence sets. The transgressive systems track contains parasequence sets from 1 to 4, which are retrogradational stacking or aggradational stacking. Their lithology are mainly mudstone and grainstone with interbed biolithite. The highstand systems track includes parasequence sets from 5 to 10, which are aggradational stacking or progradational stacking. Their lithology are grainstone and biohermal limestone with interbed lime mudstone.In the transgressive systems track, the sedimentary trap gradually cover the whole research area. In the parasequence sets 1 to 2, the Z20—Z11—Z4—T162—T78 wells and the Tazhong NO.1 fault are the boundaries of platform margin/open platform and platform margin/slope. The northwest of T86—Z18—T21 wells is blockmass. In this period, the open platform mainly deposit interbank sea, and the intra-platform bottomland distribute in the T10—T11 wells and T79—T43 wells. The width of platform margin is about 1～10 km, and its length is about 160 km. It also mainly deposit the interbank sea, and the granule shoal develop longitudinal zonality. In the parasequence sets 3 to 4, the blockmass boundary shrink to the western part of Z19—Z17—T45 wells. The Z18—Z20—Z4—T162—T262 wells and the Tazhong NO.1 fault are the boundaries of platform margin, open platform, slope. In this period, the water circulates unobstructedly, so that form the aggradational stacking and retrogradation stacking parasequence sets, which form the thick grainstone and micrite in both platform margin and open platform. The width of platform margin is about 2～10 km, and its length is still about 160 km. Because the deposition range of granule shoal and mud mound gradually expand, the rimmed sedimentary character become obvious.In the highstand systems track, the accretion rate of accommodation is equal to (or smaller than) the rate of sedimentation, so that form the aggradational stacking and progradational stacking. In the parasequence sets 5 to 7, the range of platform margin expand, its width is about 3 km to 14 km, and its length is about 210 km. A lot of carbonate mud mound deposit, and the reef mound deposit in the range of T83 well to T78 well. The granule shoals have the largest sedimentary trap and thickness, longitudinally stacked with the reef mound, so that form the rimmed system of platform margin. The range of intra-platform bottomland diminish, while the range of grain bank expand. The patch reefs deposit in the higher sedimentary topography or previous grain bank. In the parasequence sets 8 to 9, the differentiation of sedimentary topography is obvious, and the uplift of reef-bank complex alternatively distribute with the lower interbank sea. The intra-platform bottomland distribute among the inherited deposit range of patch reef and grain bank in the open platform, and their sedimentary range become maximum in this period. The sedimentary cycle of patch reef and grain bank are 1 to 2, and the thickness is about 50 m to 100 m. The width of platform margin is 4 km to 14 km, and the length is 210 km. The range of T54 well to T78 well deposit lots of reef mound, and the range of T54 well to Z19 well deposit the carbonate mud mound. The granule shoal deposit widely, and it stacked with reef longitudinally form 1 to 2 sedimentary cycle, which the thickness is about 100 m to 200 m. The rimmed platform become a pattern essentially. In the parasequence sets 10, the accretion rate of accommodation is equal to the rate of sedimentation. The open platform mainly deposit the grain bank and interbank sea, and the range of interbank sea diminish apparently. The patch reef only deposit in local area like T77 well、T35 well. The range of platform margin diminish between the Z162—Z4—T62 well to the Tazhong NO.1 fault. Its width is 1 km to 12 km, and the length is about 100 km. It mainly deposit the granule shoal and interbank sea, the reef only deposit in local area. In this period, the depositional topography between platform margin and open platform appear apparently high low differentiation, so the rimmed platform is mature and formalized.
2014, 32(5): 840-845.
Abstract:
Qinling Mountains as a natural boundary of South-North of China geography, climate, natural environment, and as the Loess Plateau of South barrier. The upper reaches of Hanjiang River valley area is located in the south of Qinling Mountains, belonging to the northern tropical climate. Through the upper reaches of Hanjiang QFC profile susceptibility, loss on the ignition, particle size, Rb/Sr and other physicochemical properties were studied. The results showed that: (1) since the last glacial dust storms may well crossed the Qinling Mountains in the south of accumulation, Loess-Paleosol sequence stratigraphic sequence from top to bottom: MS-L0-S0-Lt-L1-AD; these sediments records recorded a complete terraces of the late Pleistocene climate change information, stratigraphic units by various periods of different periods of different degree of intensity of soil information. (2) Physical and chemical properties were significantly at different stratigraphic units of QFC profile. Such as magnetic susceptibility, LOI, high value of Rb/Sr index average content appear in paleosols, the lower value in the loess layer, and the change of the content of Zr/Rb is just the opposite; these physicochemical properties suggest that the development of paleosol period, hydrothermal conditions into the most suitable period, sediment weathering pedogenesis significantly; in the stage of loess accumulation,cold and dry climate, mainly by the dust deposition, sediment weathering pedogenesis weaker. (3) Qinling Mountains South North Asia tropical upper reaches of Hanjiang River Front terrace profile of chemical weathering intensity change reveals the loess paleosol climate changes: since the last glacial period (about 18～11.5 ka B.P.), climate is dry, frequent sandstorms, sediment in the loess accumulation, pedogenesis weak, forming a typical loess (L1); the early Holocene (about 11.5 ~8.5 ka B.P.), climate change from dry and cold to warm and humid direction, but mainly in the dry and cold, to form a transition layer (Lt); in the Holocene warm period (8.5 ~3.1 Ka B.P.), climate conditions to achieve the optimal stage, with good heat water, biological activity active, pedogenesis is very significant, development of ancient soil S0; Since the late Holocene (3.1 Ka B.P.), climate change from warm humid to cold direction, pedogenesis significantly weakened, sand storms appear more frequently, formed in loess deposits of Holocene loess based (L0). Modern surface layer (MS) in(1.5 Ka B.P.), since the climate warming, and our long-term agricultural tillage disturbance, formed in the Holocene Loess L0 top stack.
Qinling Mountains as a natural boundary of South-North of China geography, climate, natural environment, and as the Loess Plateau of South barrier. The upper reaches of Hanjiang River valley area is located in the south of Qinling Mountains, belonging to the northern tropical climate. Through the upper reaches of Hanjiang QFC profile susceptibility, loss on the ignition, particle size, Rb/Sr and other physicochemical properties were studied. The results showed that: (1) since the last glacial dust storms may well crossed the Qinling Mountains in the south of accumulation, Loess-Paleosol sequence stratigraphic sequence from top to bottom: MS-L0-S0-Lt-L1-AD; these sediments records recorded a complete terraces of the late Pleistocene climate change information, stratigraphic units by various periods of different periods of different degree of intensity of soil information. (2) Physical and chemical properties were significantly at different stratigraphic units of QFC profile. Such as magnetic susceptibility, LOI, high value of Rb/Sr index average content appear in paleosols, the lower value in the loess layer, and the change of the content of Zr/Rb is just the opposite; these physicochemical properties suggest that the development of paleosol period, hydrothermal conditions into the most suitable period, sediment weathering pedogenesis significantly; in the stage of loess accumulation,cold and dry climate, mainly by the dust deposition, sediment weathering pedogenesis weaker. (3) Qinling Mountains South North Asia tropical upper reaches of Hanjiang River Front terrace profile of chemical weathering intensity change reveals the loess paleosol climate changes: since the last glacial period (about 18～11.5 ka B.P.), climate is dry, frequent sandstorms, sediment in the loess accumulation, pedogenesis weak, forming a typical loess (L1); the early Holocene (about 11.5 ~8.5 ka B.P.), climate change from dry and cold to warm and humid direction, but mainly in the dry and cold, to form a transition layer (Lt); in the Holocene warm period (8.5 ~3.1 Ka B.P.), climate conditions to achieve the optimal stage, with good heat water, biological activity active, pedogenesis is very significant, development of ancient soil S0; Since the late Holocene (3.1 Ka B.P.), climate change from warm humid to cold direction, pedogenesis significantly weakened, sand storms appear more frequently, formed in loess deposits of Holocene loess based (L0). Modern surface layer (MS) in(1.5 Ka B.P.), since the climate warming, and our long-term agricultural tillage disturbance, formed in the Holocene Loess L0 top stack.
2014, 32(5): 855-862.
Abstract:
This study discussed the sedimentary geochemistry characteristics and the palaeosedimentary environmental significance of ZK5 core in Yellow River Delta, on the basis of geochemical analyses of 36 sediments samples. Applicating comprehensive analysis of historical geography and sedimentary geology to determine the depositional age of core sediments, and from the bottom to the top of the ZK5 sediment cores was divided into 7 sequences. The results of geochemistry characteristics indicated: K2O, Fe2O3, Al2O3, TiO2, Cr, V, Rb remarkably were positively correlated with each other; SiO2 was apparently negatively correlated with other elements, and weakly negatively correlated with P2O5; Sr and CaO weakly negatively correlated with each other; P2O5 was weakly positively correlated with Al2O3, Fe2O3, K2O, TiO2, CaO. The analytic result of the value of V/Cr revealed that the depth of sedimentary water increased from bottom to top in ZK5 core, and the variation regularities were consistent with the conclusions of sedimentary facies. The analytic result of the value of 102(MgO/Al2O3) and Sr/Ba revealed that the salinity was similar from the bottom to the top of ZK5 core, and belongs to marine sedimentary environment, while water injected from Yellow River. Based on the characters of Rb/Sr and MgO/CaO, climate conditions from NQ1 to NQ7 of ZK5 core have no more change, were deposited in warm-wet climate condition. In summary, the geochemical characteristics and the sedimentary environment are closely correlated, and the geochemical characteristics can be regarded as a mark in the sedimentary facies recognition.
This study discussed the sedimentary geochemistry characteristics and the palaeosedimentary environmental significance of ZK5 core in Yellow River Delta, on the basis of geochemical analyses of 36 sediments samples. Applicating comprehensive analysis of historical geography and sedimentary geology to determine the depositional age of core sediments, and from the bottom to the top of the ZK5 sediment cores was divided into 7 sequences. The results of geochemistry characteristics indicated: K2O, Fe2O3, Al2O3, TiO2, Cr, V, Rb remarkably were positively correlated with each other; SiO2 was apparently negatively correlated with other elements, and weakly negatively correlated with P2O5; Sr and CaO weakly negatively correlated with each other; P2O5 was weakly positively correlated with Al2O3, Fe2O3, K2O, TiO2, CaO. The analytic result of the value of V/Cr revealed that the depth of sedimentary water increased from bottom to top in ZK5 core, and the variation regularities were consistent with the conclusions of sedimentary facies. The analytic result of the value of 102(MgO/Al2O3) and Sr/Ba revealed that the salinity was similar from the bottom to the top of ZK5 core, and belongs to marine sedimentary environment, while water injected from Yellow River. Based on the characters of Rb/Sr and MgO/CaO, climate conditions from NQ1 to NQ7 of ZK5 core have no more change, were deposited in warm-wet climate condition. In summary, the geochemical characteristics and the sedimentary environment are closely correlated, and the geochemical characteristics can be regarded as a mark in the sedimentary facies recognition.
2014, 32(5): 873-883.
Abstract:
In order to recognize the provenances, granularity characteristics of peat ash, and further reveal the paleo-enviromental significance of peat ash. Two peat cores in Hani and Gushantun Peat-land in the west foothill of Changbai Mountain are collected. The results of grain size analysis show that the dominant size of peat ash is 1~350 μm. Which means peat ash is mainly composed of different kinds of silt. What is more, the majority probability cumulative curves for particle size distribution are with two sections. At the same time, frequency distribution curves show unimodal type (10~100 μm), bimodal type (10~100 μm, 100~1 000 μm). These show that the transportation ways of peat ash is suspension and saltation. And the grain sizes changed with the hydrologic condition in the peat land. In the dry season, the water power is weak and the peat ash content is relatively fine. But in the wet season, surface runoff carries the coarse particle into the swamp and deposits. Therefore, the peat ash can be used for rebuilding the evolution of paleo-precipitation and it can be a proxy for the summer monsoon. In addition, 9.2 ka, 8ka and 5ka drought events in Holocene are recognized from the grain size changing curve and the curve also reveals a "dry-wet-dry" cycle in the precipitation history. Because these events correspond to the famous cold events, so we may draw the conclusion that dry and cold, warm and wet may be matched in the process of climate change.
In order to recognize the provenances, granularity characteristics of peat ash, and further reveal the paleo-enviromental significance of peat ash. Two peat cores in Hani and Gushantun Peat-land in the west foothill of Changbai Mountain are collected. The results of grain size analysis show that the dominant size of peat ash is 1~350 μm. Which means peat ash is mainly composed of different kinds of silt. What is more, the majority probability cumulative curves for particle size distribution are with two sections. At the same time, frequency distribution curves show unimodal type (10~100 μm), bimodal type (10~100 μm, 100~1 000 μm). These show that the transportation ways of peat ash is suspension and saltation. And the grain sizes changed with the hydrologic condition in the peat land. In the dry season, the water power is weak and the peat ash content is relatively fine. But in the wet season, surface runoff carries the coarse particle into the swamp and deposits. Therefore, the peat ash can be used for rebuilding the evolution of paleo-precipitation and it can be a proxy for the summer monsoon. In addition, 9.2 ka, 8ka and 5ka drought events in Holocene are recognized from the grain size changing curve and the curve also reveals a "dry-wet-dry" cycle in the precipitation history. Because these events correspond to the famous cold events, so we may draw the conclusion that dry and cold, warm and wet may be matched in the process of climate change.
2014, 32(5): 893-900.
Abstract:
Faults and ancient valley-troughs controlled the development of deep sand bodies in Dongying depression by analyzing borehole data, seismic data and previous conclusion. The fault is key element to control the distribution of sand bodies in the northern part of Dongying depression. The sandstone distributes along downthrown side of main faults like skirt sides. The intensity of the faults activity decided the thickness of sandstone, the changing trend line of the fault throw is consistent with the thickness of sandbodies. The intensity of the faults activity also controlled the facies type of sandbodies. The deep faults activity gradually intensified from north to south in Dongying depression due to the northern-faulted and southern-overlapped structural setting, so the facies type of sandbodies are changed from nearshore subaqueous fans in the northern part to braided river deltas in the middle part and to fan deltas in the southern part. The ancient valley-troughs which include the fault troughs and the incised valley with extensive development obviously controlled the distribution of sandbodies in the southern part of Dongying depression as a result of the lack of the deep-large faults. The developing succession of the ancient valley-troughs resulted in the vertical superposition of sand bodies from Sha 4 member to Sha 3 member. At last, the formation patterns of deep sandbodies in Dongying depression were set up according to controlling factors.
Faults and ancient valley-troughs controlled the development of deep sand bodies in Dongying depression by analyzing borehole data, seismic data and previous conclusion. The fault is key element to control the distribution of sand bodies in the northern part of Dongying depression. The sandstone distributes along downthrown side of main faults like skirt sides. The intensity of the faults activity decided the thickness of sandstone, the changing trend line of the fault throw is consistent with the thickness of sandbodies. The intensity of the faults activity also controlled the facies type of sandbodies. The deep faults activity gradually intensified from north to south in Dongying depression due to the northern-faulted and southern-overlapped structural setting, so the facies type of sandbodies are changed from nearshore subaqueous fans in the northern part to braided river deltas in the middle part and to fan deltas in the southern part. The ancient valley-troughs which include the fault troughs and the incised valley with extensive development obviously controlled the distribution of sandbodies in the southern part of Dongying depression as a result of the lack of the deep-large faults. The developing succession of the ancient valley-troughs resulted in the vertical superposition of sand bodies from Sha 4 member to Sha 3 member. At last, the formation patterns of deep sandbodies in Dongying depression were set up according to controlling factors.
2014, 32(5): 912-920.
Abstract:
The sedimentary characteristics of the Suining Formation in Western Sichuan Depression have been studied based on core observation, electron microscope observation, grain size analysis and logging data. It is obvious that the lake was in a stable depression stage, the weather was dry-half dry and the sedimentation was significantly controlled by inflow of periodic flood; a flooded lacustrine sedimentary system formed in the Western Sichuan Depression. Alluvial fan, meandering river, meandering river delta and lacustrine facies formed flood-overlake sediments which have the following features:①lake level changed frequently and sand and mud interbed stratigraphic stacking patterns was formed; ② lacking of widely distributed semi-deep lake to deep lake sediment; ③ fluvial facies is the dominant type of the basin filling; ④the lacustrine basin beared multiple provinces and overlakes, and sandstone was deposited everywhere in the basin. As a new type of depositional model of the Suining Formation in Western Sichuan Depression, flood-overlake has important theoretical and practical significance.
The sedimentary characteristics of the Suining Formation in Western Sichuan Depression have been studied based on core observation, electron microscope observation, grain size analysis and logging data. It is obvious that the lake was in a stable depression stage, the weather was dry-half dry and the sedimentation was significantly controlled by inflow of periodic flood; a flooded lacustrine sedimentary system formed in the Western Sichuan Depression. Alluvial fan, meandering river, meandering river delta and lacustrine facies formed flood-overlake sediments which have the following features:①lake level changed frequently and sand and mud interbed stratigraphic stacking patterns was formed; ② lacking of widely distributed semi-deep lake to deep lake sediment; ③ fluvial facies is the dominant type of the basin filling; ④the lacustrine basin beared multiple provinces and overlakes, and sandstone was deposited everywhere in the basin. As a new type of depositional model of the Suining Formation in Western Sichuan Depression, flood-overlake has important theoretical and practical significance.
2014, 32(5): 930-940.
Abstract:
The Upper Jurassic Penglaizhen Formation constitutes important gas reservoir in western Sichuan and the study of provenance of the Penglaizhen sandstones is of great importance in determining the spatial distribution of depositional systems and reservoirs. Owing to the absence of systematic studies, the provenance and lateral distribution of Penglaizhen Formation in the middle part of Western Sichuan have long been speculated upon. Based on detrital mineral analysis, trace element geochemistry, and paleogeomorphology, this study reveals that the sediments of the Penglaizhen Formation were derived from the middle and northern segments of Longmen Shan orogenic belt and Micang Shan orogenic belt. The sediments in the western region of depression are mostly coarse-grained, poor-sorted sandstones with low compositional maturity and porosity, and were sourced from the middle segment of Longmen Shan, indicating southeastward delta depositions close to the source area. The deposits in the middle and eastern parts are generally fine-grained, well-sorted sandstones with high feldspar content, compositional maturity, and porosity, and were supplied from the northern segment of Longmen Shan and Micang Shan, suggesting northeast-to-southwest delta depositions far from their sources. Additionally, it is shown that there existed different provenances during different periods and the dominant provenance transferred from the middle to the northern segment of Longmen Shan from J3p1 to J3p4.
The Upper Jurassic Penglaizhen Formation constitutes important gas reservoir in western Sichuan and the study of provenance of the Penglaizhen sandstones is of great importance in determining the spatial distribution of depositional systems and reservoirs. Owing to the absence of systematic studies, the provenance and lateral distribution of Penglaizhen Formation in the middle part of Western Sichuan have long been speculated upon. Based on detrital mineral analysis, trace element geochemistry, and paleogeomorphology, this study reveals that the sediments of the Penglaizhen Formation were derived from the middle and northern segments of Longmen Shan orogenic belt and Micang Shan orogenic belt. The sediments in the western region of depression are mostly coarse-grained, poor-sorted sandstones with low compositional maturity and porosity, and were sourced from the middle segment of Longmen Shan, indicating southeastward delta depositions close to the source area. The deposits in the middle and eastern parts are generally fine-grained, well-sorted sandstones with high feldspar content, compositional maturity, and porosity, and were supplied from the northern segment of Longmen Shan and Micang Shan, suggesting northeast-to-southwest delta depositions far from their sources. Additionally, it is shown that there existed different provenances during different periods and the dominant provenance transferred from the middle to the northern segment of Longmen Shan from J3p1 to J3p4.
2014, 32(5): 949-956.
Abstract:
This paper mainly discusses the distribution and genesis of secondary pores in Paleogene sandstones in Xihu depression by using a number of the thin section, casting thin section, carbon and oxygen isotopes of carbonate cements, fluid inclusions, clay mineral X-ray diffraction, Laser Scanning Confocal Microscope and porosity and permeability data, combined with regional tectonic sedimentary background. The study results indicate that a large number of secondary pores occurred at two depth ranges of 2 500~3 100 m and 3 500~4 400 m; Organic acids dissolving feldspars minerals mainly leads to the first section of the secondary porosity zone, H2S produced by sulphate thermal oxidation reduction reaction leads to part of the secondary porosity; quartz dissolution and abnormal high pressure leads to the second section of the secondary porosity zone in the alkaline fluid environment. The study concluded that the genesis of secondary pore zone contributes to predict reservoir stratum of high quality.
This paper mainly discusses the distribution and genesis of secondary pores in Paleogene sandstones in Xihu depression by using a number of the thin section, casting thin section, carbon and oxygen isotopes of carbonate cements, fluid inclusions, clay mineral X-ray diffraction, Laser Scanning Confocal Microscope and porosity and permeability data, combined with regional tectonic sedimentary background. The study results indicate that a large number of secondary pores occurred at two depth ranges of 2 500~3 100 m and 3 500~4 400 m; Organic acids dissolving feldspars minerals mainly leads to the first section of the secondary porosity zone, H2S produced by sulphate thermal oxidation reduction reaction leads to part of the secondary porosity; quartz dissolution and abnormal high pressure leads to the second section of the secondary porosity zone in the alkaline fluid environment. The study concluded that the genesis of secondary pore zone contributes to predict reservoir stratum of high quality.
2014, 32(5): 966-972.
Abstract:
As an important oil play in Kunbei area, Qaidam Basin, sandy conglomerate bodies of Lulehe Formation are characterized by strong heterogeneity. As a result, oil enrichment there is mainly under the control of distribution of effective reservoirs developed in sandy conglomerate bodies. Therefore, it is the key problem of petroleum exploration to identify the effective reservoir accurately and figure out its distribution. In this paper, the dominant factor of effective reservoirs in sandy conglomerate bodies is quantitatively studied. Firstly, we used the relationship between oil testing data and petrophysics, and the distribution of oil show in cores, permeability with the limit of 0.7×10-3 μm2 was identified as the decisive parameter for effective reservoirs. Secondly, based on quantitative analysis of factors controlling reservoir formation, matrix content with the limit of 7% was identified as the dominant factor for effective reservoirs in sandy conglomerate bodies of Lulehe Formation. According to the conclusions above, and the relationship between matrix content and mircofacies, the effective reservoirs in sandy conglomerate bodies of Lulehe Formation were deposited by braided channels of alluvial fans, which mainly developed in the upper of single period fan body vertically, and thinning out from the middle to the root and edge zones along the fan radial line horizontally.
As an important oil play in Kunbei area, Qaidam Basin, sandy conglomerate bodies of Lulehe Formation are characterized by strong heterogeneity. As a result, oil enrichment there is mainly under the control of distribution of effective reservoirs developed in sandy conglomerate bodies. Therefore, it is the key problem of petroleum exploration to identify the effective reservoir accurately and figure out its distribution. In this paper, the dominant factor of effective reservoirs in sandy conglomerate bodies is quantitatively studied. Firstly, we used the relationship between oil testing data and petrophysics, and the distribution of oil show in cores, permeability with the limit of 0.7×10-3 μm2 was identified as the decisive parameter for effective reservoirs. Secondly, based on quantitative analysis of factors controlling reservoir formation, matrix content with the limit of 7% was identified as the dominant factor for effective reservoirs in sandy conglomerate bodies of Lulehe Formation. According to the conclusions above, and the relationship between matrix content and mircofacies, the effective reservoirs in sandy conglomerate bodies of Lulehe Formation were deposited by braided channels of alluvial fans, which mainly developed in the upper of single period fan body vertically, and thinning out from the middle to the root and edge zones along the fan radial line horizontally.
2014, 32(5): 981-987.
Abstract:
To clarify the main controlling factors and rules of Haita Basin hydrocarbon accumulation, after in-depth study on the reservoirs, the spatial matching of hydrocarbon accumulation conditions and formation periods, it is found that hydrocarbon accumulated in the main fault depression zones of central Haita Basin can be divided into two types, which are hydrocarbon formed in early period (early hydrocarbon) that mainly distributed in K1n1, K1t and basement rock, and hydrocarbon formed in late period (late hydrocarbon) that mainly distributed in K1d and K1n2. The early hydrocarbon is widespread and more than the late hydrocarbon. Factors that controlled the accumulation of early hydrocarbon are: the distribution of K1n1 oil source area controls the range of early hydrocarbon; early extensional faults control the position where early hydrocarbon accumulated; and sandbody of the fan provides favorable location for early hydrocarbon to accumulate and form reservoir. Whereas factors that controlled the late hydrocarbon are: oil source area distribution controls the range of late hydrocarbon; long period developed faults control accumulation position of late hydrocarbon; and inverted tectonics provide trap structures for the late hydrocarbon to accumulate.
To clarify the main controlling factors and rules of Haita Basin hydrocarbon accumulation, after in-depth study on the reservoirs, the spatial matching of hydrocarbon accumulation conditions and formation periods, it is found that hydrocarbon accumulated in the main fault depression zones of central Haita Basin can be divided into two types, which are hydrocarbon formed in early period (early hydrocarbon) that mainly distributed in K1n1, K1t and basement rock, and hydrocarbon formed in late period (late hydrocarbon) that mainly distributed in K1d and K1n2. The early hydrocarbon is widespread and more than the late hydrocarbon. Factors that controlled the accumulation of early hydrocarbon are: the distribution of K1n1 oil source area controls the range of early hydrocarbon; early extensional faults control the position where early hydrocarbon accumulated; and sandbody of the fan provides favorable location for early hydrocarbon to accumulate and form reservoir. Whereas factors that controlled the late hydrocarbon are: oil source area distribution controls the range of late hydrocarbon; long period developed faults control accumulation position of late hydrocarbon; and inverted tectonics provide trap structures for the late hydrocarbon to accumulate.
2014, 32(5): 797-808.
Abstract:
The Lower Permian Taiyuan Formation in North China, well exposed in western Henan and south central of Shanxi province, consists of littoral, neritic, lagoon and tidal flat deposits in the epicontinental sea carbonate platform. It conformably contacts with both the overlaying Middle Permian Shanxi Formation and the underlaying Upper Carboniferous Benxi Formation. The lithology of the Taiyuan Formation mainly composed of thin bedded to middle bedded, grey to dark grey biological clastic limestone, sandstone, siltstone, carbonaceous shale and coal beds. Body fossils are abundant in every layer limestone of the Taiyuan Formation, such as fusulinida, brachiopoda, gastropods, coral, crinoid, and so on. The ichnofossil Zoophycos with high abundance are discovered in carbonate rocks of this stratum, which can be divided into four types-Zoophycos with black, grey, off-white or red fillings based on the different colors of burrow fillings, and other ichnofossils associated with Zoophycos commonly are Chondrites, Nereites, Palaeophycos, Rhizocorallium, Gordia, Taenidium, Teichichnus, Planolites and Thalassinoides. In this paper, representative Zoophycos specimens are chosen from Jiaozuo cross section, western Henan province and Fucheng cross section, southeastern Shanxi province. Specimens used to test are cleaned up with distilled water, and dried in a drying box, then fixed on sample holders with conducting resin, at last coated with gold in ion sputtering apparatus. After specimen preparation, a scanning electron microscopy (SEM, model number: JSM-6390/LV) is used to observe morphology and structure of carbonate micro-shapes in specimens, and Energy Disperse Spectroscopy (EDS, model number: INCA-ENERGY 250) is applied to test their composition. Six kinds of carbonate micro-shapes (single mineral and aggregates) related to microbes are recognized by observing Zoophycos burrow fillings, which are spheroid-like, rhabditiform, areatus, net-like, vase-like and cerebrum-like, most of which show the different microbial structures. Based on spheroids' surface features, individual size and occurrence features, carbonate spheroids can be further divided into four types, including ①Spheroid-like carbonates with smooth surface (type 1),well-preserved, and most are 2 to 15 μm in diameter; ②Spheroid-like carbonates with unshaped surface and fine grain structure (type 2), the diameters of these spheroids range mostly from 2 to 10 μm, their outside surfaces show well-organized fine grain structure, but grain shapes are irregular; ③Spheroid-like carbonates with thorn surface and fine grain structure (type 3), the their diameters are 6 to 9 μm, their outside surfaces display well-organized fine grains; ④Spheroid-like carbonate aggregates (type 4) with smaller diameter, appearing in groups, and distributing intensively, embedded within calcite crystals. The spheroids present as monomer or multi-monomer in types 1-3, but occurred as groups in type 4. Based on surface features, individual shape and branch feature, carbonate micro-shape of rhabditiform can be further divided into six types, i.e., ①net-like rhabditiform with thorn surface (type 1), with obvious branches, showing an irregular network; ②rhabditiform with thorn surface (type 2), arranging in parallel to each other and appearing in groups; ③rhabditiform with spiral form (type 3), showing as a spiral, and occurring separately; ④rhabditiform with biserial form (type 4), arranging closely with smooth surface and occurring separately; ⑤rhabditiform in a straight line with smooth surface (type 5), displaying round cross section and appearing dispersedly; ⑥rhabditiform with smooth surface and expanding tail end (type 6), with tail expanding spheres and appearring independently. Areatus carbonate aggregates appear as druse, and showing granular, needle-like, sheet structures, surrounded by well-crystallized calcite. The monomers of net-like carbonate aggregates varied in shape, which interweave and overlap each other, forming irregular networks. Vase-like carbonate micro-shapes like a vase or a calabash, existing in isolation. Cerebrum-like carbonate micro-shapes, with unshaped fine grain structures on their surface, their composition mainly composed of CaCO3. Above carbonate micro-shapes found in the Zoophycos burrow filling indicates that these burrows is not a simple grazing trace or food storehouse, and it is likely to exsit a set of mutually beneficial and symbiotic relationships between the Zoophycos-maker and microbes. Microcosmic analysis showing, a part of the carbonate micro-shapes found in the Taiyuan Formation contains microbial structures, however, which is not yet enough to determine what kind of microbe species they are. On condition that combining the study of geo-microbial fossils and molecular fossils, it will be helpful to determine biological classification units and ecological characteristics of geo-microbes. This research contributes to explain the relationship between macro-organism and micro-organism, and to explore how the geomicrobial processes affect geochemical processses, and to provide new microcosmic data for finely analyzing the formation process and sedimentary evolution of carbonatite in Taiyuan Formation of the study area.
The Lower Permian Taiyuan Formation in North China, well exposed in western Henan and south central of Shanxi province, consists of littoral, neritic, lagoon and tidal flat deposits in the epicontinental sea carbonate platform. It conformably contacts with both the overlaying Middle Permian Shanxi Formation and the underlaying Upper Carboniferous Benxi Formation. The lithology of the Taiyuan Formation mainly composed of thin bedded to middle bedded, grey to dark grey biological clastic limestone, sandstone, siltstone, carbonaceous shale and coal beds. Body fossils are abundant in every layer limestone of the Taiyuan Formation, such as fusulinida, brachiopoda, gastropods, coral, crinoid, and so on. The ichnofossil Zoophycos with high abundance are discovered in carbonate rocks of this stratum, which can be divided into four types-Zoophycos with black, grey, off-white or red fillings based on the different colors of burrow fillings, and other ichnofossils associated with Zoophycos commonly are Chondrites, Nereites, Palaeophycos, Rhizocorallium, Gordia, Taenidium, Teichichnus, Planolites and Thalassinoides. In this paper, representative Zoophycos specimens are chosen from Jiaozuo cross section, western Henan province and Fucheng cross section, southeastern Shanxi province. Specimens used to test are cleaned up with distilled water, and dried in a drying box, then fixed on sample holders with conducting resin, at last coated with gold in ion sputtering apparatus. After specimen preparation, a scanning electron microscopy (SEM, model number: JSM-6390/LV) is used to observe morphology and structure of carbonate micro-shapes in specimens, and Energy Disperse Spectroscopy (EDS, model number: INCA-ENERGY 250) is applied to test their composition. Six kinds of carbonate micro-shapes (single mineral and aggregates) related to microbes are recognized by observing Zoophycos burrow fillings, which are spheroid-like, rhabditiform, areatus, net-like, vase-like and cerebrum-like, most of which show the different microbial structures. Based on spheroids' surface features, individual size and occurrence features, carbonate spheroids can be further divided into four types, including ①Spheroid-like carbonates with smooth surface (type 1),well-preserved, and most are 2 to 15 μm in diameter; ②Spheroid-like carbonates with unshaped surface and fine grain structure (type 2), the diameters of these spheroids range mostly from 2 to 10 μm, their outside surfaces show well-organized fine grain structure, but grain shapes are irregular; ③Spheroid-like carbonates with thorn surface and fine grain structure (type 3), the their diameters are 6 to 9 μm, their outside surfaces display well-organized fine grains; ④Spheroid-like carbonate aggregates (type 4) with smaller diameter, appearing in groups, and distributing intensively, embedded within calcite crystals. The spheroids present as monomer or multi-monomer in types 1-3, but occurred as groups in type 4. Based on surface features, individual shape and branch feature, carbonate micro-shape of rhabditiform can be further divided into six types, i.e., ①net-like rhabditiform with thorn surface (type 1), with obvious branches, showing an irregular network; ②rhabditiform with thorn surface (type 2), arranging in parallel to each other and appearing in groups; ③rhabditiform with spiral form (type 3), showing as a spiral, and occurring separately; ④rhabditiform with biserial form (type 4), arranging closely with smooth surface and occurring separately; ⑤rhabditiform in a straight line with smooth surface (type 5), displaying round cross section and appearing dispersedly; ⑥rhabditiform with smooth surface and expanding tail end (type 6), with tail expanding spheres and appearring independently. Areatus carbonate aggregates appear as druse, and showing granular, needle-like, sheet structures, surrounded by well-crystallized calcite. The monomers of net-like carbonate aggregates varied in shape, which interweave and overlap each other, forming irregular networks. Vase-like carbonate micro-shapes like a vase or a calabash, existing in isolation. Cerebrum-like carbonate micro-shapes, with unshaped fine grain structures on their surface, their composition mainly composed of CaCO3. Above carbonate micro-shapes found in the Zoophycos burrow filling indicates that these burrows is not a simple grazing trace or food storehouse, and it is likely to exsit a set of mutually beneficial and symbiotic relationships between the Zoophycos-maker and microbes. Microcosmic analysis showing, a part of the carbonate micro-shapes found in the Taiyuan Formation contains microbial structures, however, which is not yet enough to determine what kind of microbe species they are. On condition that combining the study of geo-microbial fossils and molecular fossils, it will be helpful to determine biological classification units and ecological characteristics of geo-microbes. This research contributes to explain the relationship between macro-organism and micro-organism, and to explore how the geomicrobial processes affect geochemical processses, and to provide new microcosmic data for finely analyzing the formation process and sedimentary evolution of carbonatite in Taiyuan Formation of the study area.
2014, 32(5): 816-822.
Abstract:
One or more suits of thin-medium bedded calcirudites widely distribute in the Devonian Xiejingsi Formation in the East Yangtze Gorges area. Through detailed study of the Changliangzi section in Jianshi county, Yuxiakou section in Changyang county and Guanzhuang section in Yichang city, we found that daisy-like structure developped in the upper gravels, which undoubtedly belongs to storm deposition. In contrast, inversely directed imbrications developed in the lower gravels. Combined with the lateral facies changes and the spatial distribution, we inferred that the lower gravels may represent the global tsunami deposition in the continental margin across the F-F transition, which could be caused by bolide impacts into ocean.
One or more suits of thin-medium bedded calcirudites widely distribute in the Devonian Xiejingsi Formation in the East Yangtze Gorges area. Through detailed study of the Changliangzi section in Jianshi county, Yuxiakou section in Changyang county and Guanzhuang section in Yichang city, we found that daisy-like structure developped in the upper gravels, which undoubtedly belongs to storm deposition. In contrast, inversely directed imbrications developed in the lower gravels. Combined with the lateral facies changes and the spatial distribution, we inferred that the lower gravels may represent the global tsunami deposition in the continental margin across the F-F transition, which could be caused by bolide impacts into ocean.
2014, 32(5): 832-839.
Abstract:
Bishop and Paling mining areas are located in the western belt of Postmasburg Manganese Field, South Africa, in which typical metamorphosed sedimentary deposits developed. Six lithology units are identified for the lithology sequence, they are dolomite unit, iron-manganese mineralization unit, ferruginous fine sandstone/ferruginous conglomerate unit, pelitic siltstone unit, quartzite unit and shale unit from bottom to top, respectively, among which dolomite unit constitutes the base for ore body. There are two types of dolostone. They are Mn-rich dolostone and algal dolostone overlying, and both of them contribute to the karst system. Mass of sinkholes in the karst system provide the main space for the occurrence of depositional sequence. The morphology, size and locality of the original ore are restricted by the sinkholes, resulting in discontinuous lateral continuity. The wad is the weathering residue of the Mn-rich dolomite, and it is overlied unconformably by Mn-rich ores at bottom of the orebody, while the lateral part of the orebody is underlied directly by algal dolomite. Cummulate orebody excessively distributes at the edge of the dolomite slope. The whole development of the manganese field can be divided into three stages. The corroded depression in N-S direction formed during the first stage lays a foundation for the iron and manganese sediment. During the third stage, karstification happens again, resulting in side collapse of original ore, which accumulated on the slope, and finally the cumulate orebodies were formed.
Bishop and Paling mining areas are located in the western belt of Postmasburg Manganese Field, South Africa, in which typical metamorphosed sedimentary deposits developed. Six lithology units are identified for the lithology sequence, they are dolomite unit, iron-manganese mineralization unit, ferruginous fine sandstone/ferruginous conglomerate unit, pelitic siltstone unit, quartzite unit and shale unit from bottom to top, respectively, among which dolomite unit constitutes the base for ore body. There are two types of dolostone. They are Mn-rich dolostone and algal dolostone overlying, and both of them contribute to the karst system. Mass of sinkholes in the karst system provide the main space for the occurrence of depositional sequence. The morphology, size and locality of the original ore are restricted by the sinkholes, resulting in discontinuous lateral continuity. The wad is the weathering residue of the Mn-rich dolomite, and it is overlied unconformably by Mn-rich ores at bottom of the orebody, while the lateral part of the orebody is underlied directly by algal dolomite. Cummulate orebody excessively distributes at the edge of the dolomite slope. The whole development of the manganese field can be divided into three stages. The corroded depression in N-S direction formed during the first stage lays a foundation for the iron and manganese sediment. During the third stage, karstification happens again, resulting in side collapse of original ore, which accumulated on the slope, and finally the cumulate orebodies were formed.
2014, 32(5): 846-854.
Abstract:
The chemical weathering of silicate rocks in continents as an important sink of atmospheric CO2 is of great significance for global environmental change.The chemical index of alteration (CIA) has been widely used as a proxy for chemical weathering in sediment source area. This study presents combined clay minerals and major elements analyses on bulk sediments from a 71-m-long core with high sedimentation rate from northern South Yellow Sea and containing a Late Pleistocene record. After examining the variations of clay minerals and major elements compositions of the core sediment, we develop clay minerals and geochemical proxies to identify the origins of the DLC70-3 Core sediments,especially to discriminate the Yangze River-derived and Yellow River-derived sediment provenances. Further-more, CIA indices are also applied to decipher the chemical weathering record in sediment source area.Results show that combination of clay minerals is given priority to illite, followed by smectite, with low chlorite and kaolinite. In the vast majority of samples the ratios of illite to smectite is less than 6, indicating that the sediments are mainly transported by the Yellow River.The research suggests that the chemical weathering index (CIA) of the sediment in DLC70-3 Core is controlled together by the sea level change and the climate change of the source area, of which the latter one is the major controlling factor. However, the mechanical sedimentary differentiation caused by the sea level change might have affects CIA values at the depth of 27.80~38.00 m corresponding to MIS 4 of coarse grained sediments greatly. CIA values reveal that during MIS 5 and MIS 3 the continental chemical weathering is relatively strong, which is consistent with the trend of summer monsoon and chemical weathering index of the inland Loess Plateau area, especially in the early stage of the MIS 3 (40~60 ka), the record of chemical weathering is very strong, which reflects a strong summer monsoon rainfall process in the Yellow River basin. Although the high resolution paleoenvironmental changes can not be easily reconstructed due to ubiquitous unconformity in the sedimentary strata and weak age controls compared to the deep sea sedimentation, the present study sheds new lights on the understanding of the East Asian palaeomonsoon activity in the Yellow River Basin.
The chemical weathering of silicate rocks in continents as an important sink of atmospheric CO2 is of great significance for global environmental change.The chemical index of alteration (CIA) has been widely used as a proxy for chemical weathering in sediment source area. This study presents combined clay minerals and major elements analyses on bulk sediments from a 71-m-long core with high sedimentation rate from northern South Yellow Sea and containing a Late Pleistocene record. After examining the variations of clay minerals and major elements compositions of the core sediment, we develop clay minerals and geochemical proxies to identify the origins of the DLC70-3 Core sediments,especially to discriminate the Yangze River-derived and Yellow River-derived sediment provenances. Further-more, CIA indices are also applied to decipher the chemical weathering record in sediment source area.Results show that combination of clay minerals is given priority to illite, followed by smectite, with low chlorite and kaolinite. In the vast majority of samples the ratios of illite to smectite is less than 6, indicating that the sediments are mainly transported by the Yellow River.The research suggests that the chemical weathering index (CIA) of the sediment in DLC70-3 Core is controlled together by the sea level change and the climate change of the source area, of which the latter one is the major controlling factor. However, the mechanical sedimentary differentiation caused by the sea level change might have affects CIA values at the depth of 27.80~38.00 m corresponding to MIS 4 of coarse grained sediments greatly. CIA values reveal that during MIS 5 and MIS 3 the continental chemical weathering is relatively strong, which is consistent with the trend of summer monsoon and chemical weathering index of the inland Loess Plateau area, especially in the early stage of the MIS 3 (40~60 ka), the record of chemical weathering is very strong, which reflects a strong summer monsoon rainfall process in the Yellow River basin. Although the high resolution paleoenvironmental changes can not be easily reconstructed due to ubiquitous unconformity in the sedimentary strata and weak age controls compared to the deep sea sedimentation, the present study sheds new lights on the understanding of the East Asian palaeomonsoon activity in the Yellow River Basin.
2014, 32(5): 863-872.
Abstract:
The transportation to a sea of sediment with water founds the linkage mechanism of from "source" to "sink" and the response of surface sediment characteristics in the nearby shelf to factors of incoming sediment from the watershed. Take the response of the surface sediment in the offshore area of the Yangtze River to the characteristics of the incoming sediment from the watershed for example. Results showed that: ①for median grain size, it was large in the east and north while small in the west and south. Silt percentage decreased from northeast to southwest while silt and clay showed trends of increasing from northeast to southwest. And the ratio of clay percentage to silt percentage in the whole area was 0.12~0.83. ②compared to that in 2003~2006, sand percentage in 2008~2011 rose while silt and clay percentages showed trends of dropping, and surface sediment tended to be larger. ③The north part (north of 31°31') of the sand-silt boundary changed alternately during 2003~2007, shifted to the west during 2007~2010 while the south part (south of 31°31') shifted to the west for the whole period of 2003~2010. The shift of the boundary was mainly caused by the deposition of sandy sediment from sea area on argillaceous sediment, with diffusion deposition playing a secondary role. ④The argillaceous zone shrank after the impoundment of the Three Gorges and shifted slightly to the south, which was mainly influenced by the training works and natural factors.
The transportation to a sea of sediment with water founds the linkage mechanism of from "source" to "sink" and the response of surface sediment characteristics in the nearby shelf to factors of incoming sediment from the watershed. Take the response of the surface sediment in the offshore area of the Yangtze River to the characteristics of the incoming sediment from the watershed for example. Results showed that: ①for median grain size, it was large in the east and north while small in the west and south. Silt percentage decreased from northeast to southwest while silt and clay showed trends of increasing from northeast to southwest. And the ratio of clay percentage to silt percentage in the whole area was 0.12~0.83. ②compared to that in 2003~2006, sand percentage in 2008~2011 rose while silt and clay percentages showed trends of dropping, and surface sediment tended to be larger. ③The north part (north of 31°31') of the sand-silt boundary changed alternately during 2003~2007, shifted to the west during 2007~2010 while the south part (south of 31°31') shifted to the west for the whole period of 2003~2010. The shift of the boundary was mainly caused by the deposition of sandy sediment from sea area on argillaceous sediment, with diffusion deposition playing a secondary role. ④The argillaceous zone shrank after the impoundment of the Three Gorges and shifted slightly to the south, which was mainly influenced by the training works and natural factors.
2014, 32(5): 884-892.
Abstract:
Estuaries are naturally dynamic coastal systems that are unique in their close links to both land-based fluvial and coastal ocean process. Based on the collected large-scale sediment samples of Nandujiang Estuary in August 2011, the characteristics of grain size and associated sediment dynamic process of the Nandujiang Estuary were analyzed, and then depositional modes of the Nandujiang Estuary were further researched by empirical orthogonal function (EOF) method.The studied results show that: surface sediments of the Nandujiang Estuary were mainly composed of sand component. Three distinct depositional modes of the Nandujiang Estuary from land to sea can be seen as follows: ①Mode controlled by dominant wave action with main distribution is limited to the shallow area below 10m isobaths, where the surface sediments are basically composed of silt-sand with poor sorting. ②Mode controlled by coupling actions of runoff and tidal current with main distributed region is ranged from 10m to 20m isobaths, and offshore zone below 20 m isobaths was mainly controlled by the tidal forcing. The depositional mode is composed of coarse sediment component, which is presented as fan appearance. ③Mode controlled by Typhoon or storm tidal actions is distributed over the whole studied area, where the sediments are mainly composed of coarse sand.The first two depositional modes represent commonly sediment dynamics features of the Nandujiang Estuary. The basic pattern is the mode controlled by coupling actions of runoff and tidal current. Moreover, distributed depositional modes from land to sea show that the wave action is dominant in the nearshore zone, and offshore zone is mainly influenced by jet current due to flood action and alongshore tide current. In addition, although Nandujiang Estuary was attributed to wave-dominated estuary in the previous researches, present results reveal that depositional mode of the Nandujiang Estuary could be obvious controlled by different dynamic actions. Estuarine geometry appearance and impacts of barrier actions and narrow tub of the Qiongzhou Strait could be one of the dominant factors on depositional environment changes of the Nandujiang Estuary.
Estuaries are naturally dynamic coastal systems that are unique in their close links to both land-based fluvial and coastal ocean process. Based on the collected large-scale sediment samples of Nandujiang Estuary in August 2011, the characteristics of grain size and associated sediment dynamic process of the Nandujiang Estuary were analyzed, and then depositional modes of the Nandujiang Estuary were further researched by empirical orthogonal function (EOF) method.The studied results show that: surface sediments of the Nandujiang Estuary were mainly composed of sand component. Three distinct depositional modes of the Nandujiang Estuary from land to sea can be seen as follows: ①Mode controlled by dominant wave action with main distribution is limited to the shallow area below 10m isobaths, where the surface sediments are basically composed of silt-sand with poor sorting. ②Mode controlled by coupling actions of runoff and tidal current with main distributed region is ranged from 10m to 20m isobaths, and offshore zone below 20 m isobaths was mainly controlled by the tidal forcing. The depositional mode is composed of coarse sediment component, which is presented as fan appearance. ③Mode controlled by Typhoon or storm tidal actions is distributed over the whole studied area, where the sediments are mainly composed of coarse sand.The first two depositional modes represent commonly sediment dynamics features of the Nandujiang Estuary. The basic pattern is the mode controlled by coupling actions of runoff and tidal current. Moreover, distributed depositional modes from land to sea show that the wave action is dominant in the nearshore zone, and offshore zone is mainly influenced by jet current due to flood action and alongshore tide current. In addition, although Nandujiang Estuary was attributed to wave-dominated estuary in the previous researches, present results reveal that depositional mode of the Nandujiang Estuary could be obvious controlled by different dynamic actions. Estuarine geometry appearance and impacts of barrier actions and narrow tub of the Qiongzhou Strait could be one of the dominant factors on depositional environment changes of the Nandujiang Estuary.
2014, 32(5): 901-911.
Abstract:
Considering the modifications of reservoir property in tectonic compression and volcanic hydrothermal transformation area, according to the outcrop and core data, the experimental analysis, and the well logging information, based on the theory of sandstone dynamic diagenesis, we bring forward this research on the effects of tectonic compression and volcanic hydrothermal transformation in marine sandstone reservoirs. It indicates that clastic particles in Yingmai 35 are obviously more compacted than those in Yingmai 34, the rock porosity is 7%~8% less than the latter. The tectonic compaction in early Hercynian and the volcanic hydrothermal transformation in the late Hercynian had improved the reservoir quality in Yingmai 35. The quartz sandstone reservoirs are obviously affected by the tectonic compression and volcanic hydrothermal transformation. The tectonic compression is controlled by the duration,structural pattern,and the original sedimentary fabric. The volcanic hydrotherm has a zonal influence on the sanstone reservoir quality, influencing area is within the half thickness of the volcanic intrusive, the widely distributed metamorphic mineral is the evidence of the destruction of the reservoir.
Considering the modifications of reservoir property in tectonic compression and volcanic hydrothermal transformation area, according to the outcrop and core data, the experimental analysis, and the well logging information, based on the theory of sandstone dynamic diagenesis, we bring forward this research on the effects of tectonic compression and volcanic hydrothermal transformation in marine sandstone reservoirs. It indicates that clastic particles in Yingmai 35 are obviously more compacted than those in Yingmai 34, the rock porosity is 7%~8% less than the latter. The tectonic compaction in early Hercynian and the volcanic hydrothermal transformation in the late Hercynian had improved the reservoir quality in Yingmai 35. The quartz sandstone reservoirs are obviously affected by the tectonic compression and volcanic hydrothermal transformation. The tectonic compression is controlled by the duration,structural pattern,and the original sedimentary fabric. The volcanic hydrotherm has a zonal influence on the sanstone reservoir quality, influencing area is within the half thickness of the volcanic intrusive, the widely distributed metamorphic mineral is the evidence of the destruction of the reservoir.
2014, 32(5): 921-929.
Abstract:
Delta-fluxoturbidite depositional system has been well developed for the abundant sediment supply in Dongying depression in the middle Es3 period. The study has found that fluxoturbidite thickness h(m) can be established the relationship with delta front characteristics(thickness of the front delta strata H(m), sandstone percentage content x(%) and slope angle of delta front a(°)) and distance of turbidite slip s(m). Using the control variable method to research the single factor analysis to find that distance s(m) which is primary factor, is high negative correlation with fluxoturbidite thickness h(m). The sub-factors which include thickness of the delta front strata H(m), sandstone percentage content x(%) and slope angle a(°), are positively related with h(m). Using the gray relational analysis to calculate the weight coefficients of sub-factors related to the primary factor, to ascertain the gray relation coefficient, and establishes the quantitative prediction model of thickness of fluxoturbidite h(m): h=55.359Q1.522 3,Q=0.355s'+0.223x'+0.221H'+0.201a'(Q is the comprehensive evaluation indices. s', x', H'and a' are distance of turbidite slip, sandstone percentage content, thickness of the front delta strata and slope angle of delta front, which are calculated by using maximum normalization method).
Delta-fluxoturbidite depositional system has been well developed for the abundant sediment supply in Dongying depression in the middle Es3 period. The study has found that fluxoturbidite thickness h(m) can be established the relationship with delta front characteristics(thickness of the front delta strata H(m), sandstone percentage content x(%) and slope angle of delta front a(°)) and distance of turbidite slip s(m). Using the control variable method to research the single factor analysis to find that distance s(m) which is primary factor, is high negative correlation with fluxoturbidite thickness h(m). The sub-factors which include thickness of the delta front strata H(m), sandstone percentage content x(%) and slope angle a(°), are positively related with h(m). Using the gray relational analysis to calculate the weight coefficients of sub-factors related to the primary factor, to ascertain the gray relation coefficient, and establishes the quantitative prediction model of thickness of fluxoturbidite h(m): h=55.359Q1.522 3,Q=0.355s'+0.223x'+0.221H'+0.201a'(Q is the comprehensive evaluation indices. s', x', H'and a' are distance of turbidite slip, sandstone percentage content, thickness of the front delta strata and slope angle of delta front, which are calculated by using maximum normalization method).
2014, 32(5): 941-948.
Abstract:
In order to analyze diagenetic regularity and its effect to the formation about secondary pore and seek favorable exploration regions, detailed research has been carried on based on casting, scan electron microscope and X-ray diffraction data. The result shows that: be controlled by depositional environment, buried depths and organic acid, both of intensity and distribution range about the compaction, pressure solution, cementation, dissolution and metasomatism occurred in Bonan sag are different in dissimilar regions. The reservoir that distributed in fault zone in the centre of Bonan sag undergo acid and alkali alternately diagenetic environment that is controlled by fault system, distribution of source rock and abnormal overpressure that in the upper section of Es4. For this reason, secondary pore zones formed in the depths between 3 200 m and 4 600 m. The vertical evolution of porosity about reservoir that distributed along the edge of Bonan sag present normal compaction curve. At last, with the guidance of evolution characteristics of secondary pore, combining distribution characteristics of oil-bearing area that have been ascertained, we forecasted the favorable exploration areas including braided channel that distributed in midwest and braided river delta front that distributed in northern of Bonan sag.
In order to analyze diagenetic regularity and its effect to the formation about secondary pore and seek favorable exploration regions, detailed research has been carried on based on casting, scan electron microscope and X-ray diffraction data. The result shows that: be controlled by depositional environment, buried depths and organic acid, both of intensity and distribution range about the compaction, pressure solution, cementation, dissolution and metasomatism occurred in Bonan sag are different in dissimilar regions. The reservoir that distributed in fault zone in the centre of Bonan sag undergo acid and alkali alternately diagenetic environment that is controlled by fault system, distribution of source rock and abnormal overpressure that in the upper section of Es4. For this reason, secondary pore zones formed in the depths between 3 200 m and 4 600 m. The vertical evolution of porosity about reservoir that distributed along the edge of Bonan sag present normal compaction curve. At last, with the guidance of evolution characteristics of secondary pore, combining distribution characteristics of oil-bearing area that have been ascertained, we forecasted the favorable exploration areas including braided channel that distributed in midwest and braided river delta front that distributed in northern of Bonan sag.
2014, 32(5): 957-965.
Abstract:
An analysis between the original water environment of Lvda 21-1 Structure, Bohai Oil Field and the impact of reservoir diagenesis and physical properties has been carried out in this paper. According to the result of normal thin-sections, cast thin-sections, scanning electron microscope and trace element analysis, the original water environment of the Forth Member of Shahejie Formation is mainly brackish, mixing with fresh water in certain period. The rock type is dominated by litchi arkose sandstone, in which there are mainly soluble components. Typical alkaline diagenesis caused by brackish environment have been found in this area, such as dissolved quartz, feldspar overgrowth, chlorite, together with small amount of acidic fluids diagenetic phenomenon. Diagenetic fluid has varied from alkaline to acidic. The impact on the reservoir displays that alkaline fluid provided with a dual effect, and the corrosion caused by acidic fluids is the main reason in improving physical properties.
An analysis between the original water environment of Lvda 21-1 Structure, Bohai Oil Field and the impact of reservoir diagenesis and physical properties has been carried out in this paper. According to the result of normal thin-sections, cast thin-sections, scanning electron microscope and trace element analysis, the original water environment of the Forth Member of Shahejie Formation is mainly brackish, mixing with fresh water in certain period. The rock type is dominated by litchi arkose sandstone, in which there are mainly soluble components. Typical alkaline diagenesis caused by brackish environment have been found in this area, such as dissolved quartz, feldspar overgrowth, chlorite, together with small amount of acidic fluids diagenetic phenomenon. Diagenetic fluid has varied from alkaline to acidic. The impact on the reservoir displays that alkaline fluid provided with a dual effect, and the corrosion caused by acidic fluids is the main reason in improving physical properties.
2014, 32(5): 973-980.
Abstract:
Based on a large number of thin sections, casting thin sections, logging data and core observation, the characteristics of rock components, diagenesis and pore types of Cretaceous Bashijiqike Formation in Kelasu structure zone are systematically studied. The results indicate that the petrological characteristics of sandstone reservoirs are low compositional maturity, middle-well sorted, low-middle textural maturity, sub-angular and sub-round. The effective reservoir spaces are secondary pore and primary pore. The reservoir under went compaction, cementation, dissolution and fissure. The reservoir has mainly entered stage A2-B of the middle diagenetic phase. The cementation is mainly of carbonate character. The mechanical compaction and cementation are the major reasons for reducing storage space. The pore space was affected by the dissolution of calcite cement, feldspar and fragments. Tectonic fracturing gave rise to new reservoir spaces. On the hanging wall of Kelasu fault, the burial depth of strata is shallower, and the storage space is characterized by secondary pores which have formed from the aerial dissolution by the uplifted strata. However, on the foot wall of the Kelasu fault, the burial depth of strata is deeper, and the reservoirs were densified because of compaction and cementation. The solution and fissure are important for improving the quality of the reservoir.
Based on a large number of thin sections, casting thin sections, logging data and core observation, the characteristics of rock components, diagenesis and pore types of Cretaceous Bashijiqike Formation in Kelasu structure zone are systematically studied. The results indicate that the petrological characteristics of sandstone reservoirs are low compositional maturity, middle-well sorted, low-middle textural maturity, sub-angular and sub-round. The effective reservoir spaces are secondary pore and primary pore. The reservoir under went compaction, cementation, dissolution and fissure. The reservoir has mainly entered stage A2-B of the middle diagenetic phase. The cementation is mainly of carbonate character. The mechanical compaction and cementation are the major reasons for reducing storage space. The pore space was affected by the dissolution of calcite cement, feldspar and fragments. Tectonic fracturing gave rise to new reservoir spaces. On the hanging wall of Kelasu fault, the burial depth of strata is shallower, and the storage space is characterized by secondary pores which have formed from the aerial dissolution by the uplifted strata. However, on the foot wall of the Kelasu fault, the burial depth of strata is deeper, and the reservoirs were densified because of compaction and cementation. The solution and fissure are important for improving the quality of the reservoir.
2014, 32(5): 988-995.
Abstract:
Sediment cores in four sites of the red-tide-frequent-occurrence area in East China Sea were selected and source apportionment was calculated using two end-member modeling for δ13CTOC to derive an inventory of marine versus terrestrial organic matter. The n-alkanes and fatty alcohols in sediment cores were analyzed to discuss composition, distribution and origins of organic matter. The results indicate that the n-alkanes have obvious advantages of longer carbon number, and the longer chain n-alkanes have a strong odd-over-even predominance and display bimodal distribution. Downhole variations of total n-alkanes (T-ALK/μg/g) contents are different among four cores. It is indicated by CPI, TAR, Pmar-aq and other n-alkanes that sedimentary organic matter is majorly from terrestrial inputs with predominance of herbaceous plants. The results of n-alkyl alcohol showed that organic matter mainly originated from terrestrial higher plants. The distribution of phytol in four stations are similar suggesting that they may experience through the similar biochemical process and the sedimentary environment may be relatively constant. Donwhole variation in the ratio of brassicasterol and dinoflagellatesterol indicates that red-tide blooms have changed from single diatom type into complex one with diatom and dinoflagellate due to deteriorated eutrophication.
Sediment cores in four sites of the red-tide-frequent-occurrence area in East China Sea were selected and source apportionment was calculated using two end-member modeling for δ13CTOC to derive an inventory of marine versus terrestrial organic matter. The n-alkanes and fatty alcohols in sediment cores were analyzed to discuss composition, distribution and origins of organic matter. The results indicate that the n-alkanes have obvious advantages of longer carbon number, and the longer chain n-alkanes have a strong odd-over-even predominance and display bimodal distribution. Downhole variations of total n-alkanes (T-ALK/μg/g) contents are different among four cores. It is indicated by CPI, TAR, Pmar-aq and other n-alkanes that sedimentary organic matter is majorly from terrestrial inputs with predominance of herbaceous plants. The results of n-alkyl alcohol showed that organic matter mainly originated from terrestrial higher plants. The distribution of phytol in four stations are similar suggesting that they may experience through the similar biochemical process and the sedimentary environment may be relatively constant. Donwhole variation in the ratio of brassicasterol and dinoflagellatesterol indicates that red-tide blooms have changed from single diatom type into complex one with diatom and dinoflagellate due to deteriorated eutrophication.
