2002 Vol. 20, No. 1
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Display Method:
2002, 20(1): 7-12.
Abstract:
The carbonate rocks of Qixia Formation developed extensively on the Lower Yangtze Region have been considered to be deposits of shallow sea carbonate platform for along time. The study indicates, in the case of Chaohu Region, that deposits of Qixia Formation occur mostly in carbonate slope environment. Bedded limestone conglomerates of Swine Limestone and the top limestone members are products of carbonate debris flows and develop on the upper of the carbonate slope. Calcarenite silicon-wackestone of the upper and lower silicon members deposit from contour currents and occur on the lower of the carbonate slope. Calcium-silicon shale (mudstone) developed on the upper and lower silicon members forms in the end of slope and basin environment. Only the limestone of the middle limestone member may deposit in shallow sea carbonate platform environment. This breaks through the traditional idea and is helpful for understanding paleogeographic features and tectonic evolution of Lower Yangtze Plate in Permian period
The carbonate rocks of Qixia Formation developed extensively on the Lower Yangtze Region have been considered to be deposits of shallow sea carbonate platform for along time. The study indicates, in the case of Chaohu Region, that deposits of Qixia Formation occur mostly in carbonate slope environment. Bedded limestone conglomerates of Swine Limestone and the top limestone members are products of carbonate debris flows and develop on the upper of the carbonate slope. Calcarenite silicon-wackestone of the upper and lower silicon members deposit from contour currents and occur on the lower of the carbonate slope. Calcium-silicon shale (mudstone) developed on the upper and lower silicon members forms in the end of slope and basin environment. Only the limestone of the middle limestone member may deposit in shallow sea carbonate platform environment. This breaks through the traditional idea and is helpful for understanding paleogeographic features and tectonic evolution of Lower Yangtze Plate in Permian period
2002, 20(1): 20-24.
Abstract:
There are three interpretations for the cause of formation of nodular limestones.The first interpretation is that they are the beds of carbonate concretions, the second is that they are the result of the differential compaction,and the third is that they are formed by the sedimentation or the synsedimentary faulting.However, in the Da Liang Tang Formating of lower Devenian Series in Du-an,Debao county,Guangxi,a special nodular limestone is mistaken as a rudstone by some people,because the nodular limstone similar to the normal rudstones in its figure and mode of occurrence. The study on its petrology,paleontology,paleostructurs,etc., shows that the rudstone is not simply the beds of carbonate concretions, it was formed neither by the differential compaction nor by the sedimentation and synsedimentary faulting,and the fact is that lot of carbonate nodules were first formed in the poor-oxygen,closed flute facies of shelf platform;then,the differential compaction led to the extremely concave-convex of the bedding surface or the heterogeneity of the beds; finally,the nodules were turned and also transferred by the shearing,flexural slip,flexural flow, process of the limb during forming the dome in the Indo-Chinese epoch, the "rudstone" we see today was produced. Hence,the "rudstone" in Du-an was realy the nodular limstone,and it was the result of sedimentationg,diagenesis and tectonism,etc,and it also shows a kind of sedimentary-diagenetic environment which was the poor-oxygen and closed flute of shelf platform.
There are three interpretations for the cause of formation of nodular limestones.The first interpretation is that they are the beds of carbonate concretions, the second is that they are the result of the differential compaction,and the third is that they are formed by the sedimentation or the synsedimentary faulting.However, in the Da Liang Tang Formating of lower Devenian Series in Du-an,Debao county,Guangxi,a special nodular limestone is mistaken as a rudstone by some people,because the nodular limstone similar to the normal rudstones in its figure and mode of occurrence. The study on its petrology,paleontology,paleostructurs,etc., shows that the rudstone is not simply the beds of carbonate concretions, it was formed neither by the differential compaction nor by the sedimentation and synsedimentary faulting,and the fact is that lot of carbonate nodules were first formed in the poor-oxygen,closed flute facies of shelf platform;then,the differential compaction led to the extremely concave-convex of the bedding surface or the heterogeneity of the beds; finally,the nodules were turned and also transferred by the shearing,flexural slip,flexural flow, process of the limb during forming the dome in the Indo-Chinese epoch, the "rudstone" we see today was produced. Hence,the "rudstone" in Du-an was realy the nodular limstone,and it was the result of sedimentationg,diagenesis and tectonism,etc,and it also shows a kind of sedimentary-diagenetic environment which was the poor-oxygen and closed flute of shelf platform.
2002, 20(1): 34-40.
Abstract:
Cold seepage and venting is a fluid seepage and venting mainly composed of water, hydrocarbon(gas and crude oil), hydrogen sulfide and fine sediments derived below seafloor. Its temperature is similar to sea water and widely occurs on the seafloor of continental slope of active and passive margins. Cold seepage and venting-related chemosynthetic communities are highly in organism density, mainly mussels, clams, tube worms and bacterial mats. The sediments in cold seepage and venting are mostly maed up of carbonates and gas hydrates with minor sulfides and sulphates. The chemosynthetic carbonates occurred as buildup, chimney, cement, nodule, hardgroud and fine vein, and generally as buildup of chemosythetic bioclasts and multi-stage authigenic cements. The carbonate source, sedimentary environment and sedimentations are different with normal carbonates,of which carbon is from sea water. Therefore, using term "Chermoherm" represents the chemosynthetic carbonate buildup to distinguish from the terms of bioherms, lithoherms, pseudobioherms, biostromes of carbonate buildups in normal sea environment,in which the carbon is from sea water. In strata, Chermoherm frequently occurred in abyssal sediment strata as a carbonate buildup containing a lot of fossils of benthic fauna. There are disrupted sedimentary phase and environments in longitudinal and cross strata section, so much as turnover. Carbonate minerals in chemosynthetic carbonates are primarily Mg-calcite, aragonite, and dolomite,which are not different with normal carbonates. Carbon isotope values in chemosynthetic carbonates are very low due to bacteria mediation. Cold seepage and venting occurred along fault zone or permeable beds and at the surface expression of mud volcano and salt diapirism. Cold seepage and venting fluids are derived from formation fluids driven by a combination of (1)pore-space reduction of rapid sedimentation and tectonic compaction, deformation and cementation, and (2)increased buoyancy due to a decrease in pore-fluid density related diagenesis and catagenesis, and gas hydrate decomposition at depth. The sedimentation processes of cold seepage and venting-related carbonates are cementation, filling action and biochemical sedimentation. The hydrocarbon mainly of methane into cold seepage and venting is changed to carbon dioxide by bacteria mediation and deposited chemosynthetic carbonates.
Cold seepage and venting is a fluid seepage and venting mainly composed of water, hydrocarbon(gas and crude oil), hydrogen sulfide and fine sediments derived below seafloor. Its temperature is similar to sea water and widely occurs on the seafloor of continental slope of active and passive margins. Cold seepage and venting-related chemosynthetic communities are highly in organism density, mainly mussels, clams, tube worms and bacterial mats. The sediments in cold seepage and venting are mostly maed up of carbonates and gas hydrates with minor sulfides and sulphates. The chemosynthetic carbonates occurred as buildup, chimney, cement, nodule, hardgroud and fine vein, and generally as buildup of chemosythetic bioclasts and multi-stage authigenic cements. The carbonate source, sedimentary environment and sedimentations are different with normal carbonates,of which carbon is from sea water. Therefore, using term "Chermoherm" represents the chemosynthetic carbonate buildup to distinguish from the terms of bioherms, lithoherms, pseudobioherms, biostromes of carbonate buildups in normal sea environment,in which the carbon is from sea water. In strata, Chermoherm frequently occurred in abyssal sediment strata as a carbonate buildup containing a lot of fossils of benthic fauna. There are disrupted sedimentary phase and environments in longitudinal and cross strata section, so much as turnover. Carbonate minerals in chemosynthetic carbonates are primarily Mg-calcite, aragonite, and dolomite,which are not different with normal carbonates. Carbon isotope values in chemosynthetic carbonates are very low due to bacteria mediation. Cold seepage and venting occurred along fault zone or permeable beds and at the surface expression of mud volcano and salt diapirism. Cold seepage and venting fluids are derived from formation fluids driven by a combination of (1)pore-space reduction of rapid sedimentation and tectonic compaction, deformation and cementation, and (2)increased buoyancy due to a decrease in pore-fluid density related diagenesis and catagenesis, and gas hydrate decomposition at depth. The sedimentation processes of cold seepage and venting-related carbonates are cementation, filling action and biochemical sedimentation. The hydrocarbon mainly of methane into cold seepage and venting is changed to carbon dioxide by bacteria mediation and deposited chemosynthetic carbonates.
2002, 20(1): 47-54.
Abstract:
Based on the investigations of 63 species of fossil spores and pollen referred to 34 genera found from the Middle Jurassic Yanan Formation in Dongsheng region of Inner Mongolia, the early Middle Jurassic palynoflora in the region was established in this paper. According to the character of the palynoflora, the early Middle Jurassic paleoecological characteristics, paleoclimatic conditions and sedimentary environment in the study area are discussed. An approach to the original environment of coal, oil and natural gas is also made. The results of this study indicate that the warm and humid climate might be favorable for the origin of coal, oil and natural gas, and the lacustrine-marsh (or swamp) deposits under warm or hot and humid or wet climatic conditions might possess tremendous potentials for the origin of coal, oil and natural gas
Based on the investigations of 63 species of fossil spores and pollen referred to 34 genera found from the Middle Jurassic Yanan Formation in Dongsheng region of Inner Mongolia, the early Middle Jurassic palynoflora in the region was established in this paper. According to the character of the palynoflora, the early Middle Jurassic paleoecological characteristics, paleoclimatic conditions and sedimentary environment in the study area are discussed. An approach to the original environment of coal, oil and natural gas is also made. The results of this study indicate that the warm and humid climate might be favorable for the origin of coal, oil and natural gas, and the lacustrine-marsh (or swamp) deposits under warm or hot and humid or wet climatic conditions might possess tremendous potentials for the origin of coal, oil and natural gas
2002, 20(1): 61-69.
Abstract:
E 3 2 lacustrine stratum, located in Yuejin area, Qaidam Basin, northwestern China, is mainly composed of interbedded /intercalated carbonate rock mudstone. Terrigenous debris-bearing micrite,algea-originated laminated micrite,algea-originated stromatolitic micrite,algea-originated micrite and grainstone could be recognized in the carbonate rock, of which algea-originated laminated micrite and algea-originated stromatolitic micrite developed into good reservoir(oil-bearing) with a mean porosity of 25% and mean permeability of proximate 100×10 -3 μm 2. Meteoric water-seawater mixing dolomitization and dissolution in meteoric vadose zone were the main courses for reservoir development. Based on the research of diagenetic sequence, porosity evolution of the algea-originated laminated micrite and algea-originated stromatolitic micrite have been reconstructed. Furthermore, pore and throat diameters and their combinations have been discussed, which play an important role in petroleum development. The determination of spatial distribution for E 3 2 algal-reef micrite reservoir is very important in petroleum exploration in Yuejin area. Log and seismic data also play important roles in prediction of algal-reef micrite reservoir. High SP and SN values imply the exist of petroleum-bearing algal-reef micrite reservoir, while strong seismic reflection shows the lateral distribution of them. Based on the above discussion, spatial distribution of E 3 2 algal-reef micrite reservoir in Yuejin area have been mapped.
E 3 2 lacustrine stratum, located in Yuejin area, Qaidam Basin, northwestern China, is mainly composed of interbedded /intercalated carbonate rock mudstone. Terrigenous debris-bearing micrite,algea-originated laminated micrite,algea-originated stromatolitic micrite,algea-originated micrite and grainstone could be recognized in the carbonate rock, of which algea-originated laminated micrite and algea-originated stromatolitic micrite developed into good reservoir(oil-bearing) with a mean porosity of 25% and mean permeability of proximate 100×10 -3 μm 2. Meteoric water-seawater mixing dolomitization and dissolution in meteoric vadose zone were the main courses for reservoir development. Based on the research of diagenetic sequence, porosity evolution of the algea-originated laminated micrite and algea-originated stromatolitic micrite have been reconstructed. Furthermore, pore and throat diameters and their combinations have been discussed, which play an important role in petroleum development. The determination of spatial distribution for E 3 2 algal-reef micrite reservoir is very important in petroleum exploration in Yuejin area. Log and seismic data also play important roles in prediction of algal-reef micrite reservoir. High SP and SN values imply the exist of petroleum-bearing algal-reef micrite reservoir, while strong seismic reflection shows the lateral distribution of them. Based on the above discussion, spatial distribution of E 3 2 algal-reef micrite reservoir in Yuejin area have been mapped.
2002, 20(1): 75-79.
Abstract:
Samples are pressure-impregnated with epoxy mixed with a fluorescent dye. So the Laser-induced fluorescence can be observed in thin section with LSCM (Laser scanning confocal microscope ). This technique provides a rapid method for directly obtaining measurement of visual porosity and the size of pores and throats from thin section. The advantages of this method are as follows: 1. The pore size larger than 2μm can be observed 2. The clay matrix in pore space can be differentiated with LSCM but it could not be distinquished with polarized microscope or image analysis during the clay minerals are absorbed with rose fluorescent dyes, so the measmement of visual porosity with LSCM would be more accurate 3. Some fissures in thin section can clearly be observed.
Samples are pressure-impregnated with epoxy mixed with a fluorescent dye. So the Laser-induced fluorescence can be observed in thin section with LSCM (Laser scanning confocal microscope ). This technique provides a rapid method for directly obtaining measurement of visual porosity and the size of pores and throats from thin section. The advantages of this method are as follows: 1. The pore size larger than 2μm can be observed 2. The clay matrix in pore space can be differentiated with LSCM but it could not be distinquished with polarized microscope or image analysis during the clay minerals are absorbed with rose fluorescent dyes, so the measmement of visual porosity with LSCM would be more accurate 3. Some fissures in thin section can clearly be observed.
2002, 20(1): 85-91.
Abstract:
Many red Early Tertiary basins are exposed in the northeastern margin of the Tibetan Plateau due to intracontinental deformation and uplift induced by the Indo-Asian collision. Based on detailed mapping and sedimentologic investigations of two Early Tertiary basins, Nangqian and Xialaxiu, and combining with the comprehensive analysis of tectonism, sedimentation and magmatism, two stages for the tectonic and depositional evolution of the basins are revealed, i.e. the early stage is controlled by thrusting and characterized by coarse-grained alluvial-fan clastic sediments at the bottom and local magmatic activities; and the late stage is controlled by strik-slip and pull-apart and characteristic of fine-grained lacustrine-delta gypsum- sandstones and mudstones interbedded with thin-bedded limestones and widespread igneous activities. There is a clear episodic evolution resulting from the basin tectonic framework, the thickness and structure of sedimentary sequences, sediment constituents and magmatism. The data of the basin paleocurrent and 40 Ar/ 39 Ar dating for igneous rocks in the basins suggest that the sediments in the early Tertiary basins were formed in the period of Late Eocene-Early Oligocene (38～29 Ma). Depositional patterns and magmatic activities in the Early Tertiary basins in the NE margin of the Tibetan Plateau were controlled by thrusting and strike-slipping in the early period of the Indo-Asian collision.
Many red Early Tertiary basins are exposed in the northeastern margin of the Tibetan Plateau due to intracontinental deformation and uplift induced by the Indo-Asian collision. Based on detailed mapping and sedimentologic investigations of two Early Tertiary basins, Nangqian and Xialaxiu, and combining with the comprehensive analysis of tectonism, sedimentation and magmatism, two stages for the tectonic and depositional evolution of the basins are revealed, i.e. the early stage is controlled by thrusting and characterized by coarse-grained alluvial-fan clastic sediments at the bottom and local magmatic activities; and the late stage is controlled by strik-slip and pull-apart and characteristic of fine-grained lacustrine-delta gypsum- sandstones and mudstones interbedded with thin-bedded limestones and widespread igneous activities. There is a clear episodic evolution resulting from the basin tectonic framework, the thickness and structure of sedimentary sequences, sediment constituents and magmatism. The data of the basin paleocurrent and 40 Ar/ 39 Ar dating for igneous rocks in the basins suggest that the sediments in the early Tertiary basins were formed in the period of Late Eocene-Early Oligocene (38～29 Ma). Depositional patterns and magmatic activities in the Early Tertiary basins in the NE margin of the Tibetan Plateau were controlled by thrusting and strike-slipping in the early period of the Indo-Asian collision.
2002, 20(1): 101-105,111.
Abstract:
It is difficult to divide and interpret the fluvial strata because its depositional environment is very special compared with others. The response principle between base level cycle and genetic strata developed by Cross is regarded as the basic theory for high-resolution stratigraphy applications in fluvial strata. The key of high resolution isochronostratigraphic correlation is to identify multi-level base cycles. Short-term base level cycles can be identified by sedimentary microfacies, analysis on the well profiles and the well profile themselves.The mid-term base level cycles also can be identified by stacking patterns of short-term cycles on the base of log curves facies model. Taken the turnround point of base-level cycle as optimal positions in the connected wells' profile isochro nostratigraphic correlation,the high resolution sequence stratigraghic framwork can be established. The paperhas analyzed the evolution principle of fluvial strata and the coupling between base level and sedimentary lateral migration,vetical stacking from the view of base level variation on the established frame work,and pointed out that the environment model is finally different from the classical one.
It is difficult to divide and interpret the fluvial strata because its depositional environment is very special compared with others. The response principle between base level cycle and genetic strata developed by Cross is regarded as the basic theory for high-resolution stratigraphy applications in fluvial strata. The key of high resolution isochronostratigraphic correlation is to identify multi-level base cycles. Short-term base level cycles can be identified by sedimentary microfacies, analysis on the well profiles and the well profile themselves.The mid-term base level cycles also can be identified by stacking patterns of short-term cycles on the base of log curves facies model. Taken the turnround point of base-level cycle as optimal positions in the connected wells' profile isochro nostratigraphic correlation,the high resolution sequence stratigraghic framwork can be established. The paperhas analyzed the evolution principle of fluvial strata and the coupling between base level and sedimentary lateral migration,vetical stacking from the view of base level variation on the established frame work,and pointed out that the environment model is finally different from the classical one.
2002, 20(1): 112-117.
Abstract:
It is the research goal of the development geology to build up high-resolution isochronous sequence framework, quantitatively study the division and correlation of the reservoir genetic units and provide the basis for developing small-scale flow-units in Daqing oilfield. The paper points out that there are currently two methods on reservoir division and correlation, i.e. base-level cycle and sedimentary cycle, and the marrow of the high-resolution sequence division is the correlation of the base-level cycle. The key of the detailed geological description and correlation of Daqing oilfield is the correlation of sedimentary cycle. Thus, the author expounds the similarities and differences between the high-resolution sequence stratigraphy and detailed geological description and correlation of Daqing oilfield on such aspects as principles, methods and theory. This research also indicates that the theoretic basis of the two methods is cycle and sequence, and their research object is sequence framework and the scale of sedimentary sequence units. The combination of different cycles is very important in correlation of base-level cycle. It can be used in lacustrine facies analysis, but difficult in fluvial facies analysis and with some uncertainties. Sedimentary cycle exists diachronism in fluvial facies and lacustrine facies, but it can be used widely. The movement of base-level cycles of the different grades makes the difference in cycles and scales of sedimentary cycle, resulting in the grade of the sequence, therefore, base-level cycle and sedimentary cycle approach the same object from different ways. Furthermore, the paper discusses two key problems about cycles and correlation, i.e., sequence and boundaries, and their relevant questions. Finally, the author points out their important significances in studying the flow units and distribution of remnant oil.
It is the research goal of the development geology to build up high-resolution isochronous sequence framework, quantitatively study the division and correlation of the reservoir genetic units and provide the basis for developing small-scale flow-units in Daqing oilfield. The paper points out that there are currently two methods on reservoir division and correlation, i.e. base-level cycle and sedimentary cycle, and the marrow of the high-resolution sequence division is the correlation of the base-level cycle. The key of the detailed geological description and correlation of Daqing oilfield is the correlation of sedimentary cycle. Thus, the author expounds the similarities and differences between the high-resolution sequence stratigraphy and detailed geological description and correlation of Daqing oilfield on such aspects as principles, methods and theory. This research also indicates that the theoretic basis of the two methods is cycle and sequence, and their research object is sequence framework and the scale of sedimentary sequence units. The combination of different cycles is very important in correlation of base-level cycle. It can be used in lacustrine facies analysis, but difficult in fluvial facies analysis and with some uncertainties. Sedimentary cycle exists diachronism in fluvial facies and lacustrine facies, but it can be used widely. The movement of base-level cycles of the different grades makes the difference in cycles and scales of sedimentary cycle, resulting in the grade of the sequence, therefore, base-level cycle and sedimentary cycle approach the same object from different ways. Furthermore, the paper discusses two key problems about cycles and correlation, i.e., sequence and boundaries, and their relevant questions. Finally, the author points out their important significances in studying the flow units and distribution of remnant oil.
2002, 20(1): 124-128.
Abstract:
Stalagmites in karst caves are the main carrier of paleoclimatic and paleoenvironmental records with the high resolution.The high resolution information on paleoclimatic change from 46.1ka B.P. to 2.75ka B.P. has been obtained through α-counting U-series dating and carbon and oxygen isotopic analysis of No.1 stalagmite in Xiashuilong cave of Xuanwei city. The record of its ages and δ 18 O value in the change of the vertical section have obvious rhythm characteristics and can be compared with the oxygen isotopic records of deep-sea cores at Ⅲ,ⅡandⅠ stages. It reflects that the climatic changes in Xuanwei area coincides with the fluctuation of global paleoclimatic change.But here is the sensitive area of the climatic change and also the specific region of the reciprocity between East Asian monsoon and Southwest monsoon,and the feature of the climatic change caused by them was obvious in this region.The overall last glaciation from 46.1ka B.P. to 8.1 ka B.P. show warm climate trend in the mass,and 10.25 ka B.P. is the coldest of the end point of Younger Dryas event.The Holocene Megathermal period during 7.1 ka B.P. and 3.7 ka B.P. are the climate of temperate (warm)-wet.The climate during 3.7 ka B.P. and 2.75 ka B.P. has obvious trend of decreasing temperature to follow the weakness of the sun radiation and the Southwest monsoon intension.Furthermore,the cold and warm change of the climate indicate that the main sediment cycles in stalagmite take the periodicity change as ten thousand years, thousand years and hundred years, and sub-cycles in stalagmite show the periodicity change as thousand years and hundred years.
Stalagmites in karst caves are the main carrier of paleoclimatic and paleoenvironmental records with the high resolution.The high resolution information on paleoclimatic change from 46.1ka B.P. to 2.75ka B.P. has been obtained through α-counting U-series dating and carbon and oxygen isotopic analysis of No.1 stalagmite in Xiashuilong cave of Xuanwei city. The record of its ages and δ 18 O value in the change of the vertical section have obvious rhythm characteristics and can be compared with the oxygen isotopic records of deep-sea cores at Ⅲ,ⅡandⅠ stages. It reflects that the climatic changes in Xuanwei area coincides with the fluctuation of global paleoclimatic change.But here is the sensitive area of the climatic change and also the specific region of the reciprocity between East Asian monsoon and Southwest monsoon,and the feature of the climatic change caused by them was obvious in this region.The overall last glaciation from 46.1ka B.P. to 8.1 ka B.P. show warm climate trend in the mass,and 10.25 ka B.P. is the coldest of the end point of Younger Dryas event.The Holocene Megathermal period during 7.1 ka B.P. and 3.7 ka B.P. are the climate of temperate (warm)-wet.The climate during 3.7 ka B.P. and 2.75 ka B.P. has obvious trend of decreasing temperature to follow the weakness of the sun radiation and the Southwest monsoon intension.Furthermore,the cold and warm change of the climate indicate that the main sediment cycles in stalagmite take the periodicity change as ten thousand years, thousand years and hundred years, and sub-cycles in stalagmite show the periodicity change as thousand years and hundred years.
2002, 20(1): 136-143.
Abstract:
The sediment of 4 well's cores of late Quaternary at the continental margin of East China Sea have been systimatically researched, and abundant fossils of diatom, 117 species and varieties in 33 genus, have been found. 12 of diatom zones have been divided according to the characteristics of the diatom pattern, theoptimac Sparation and the corresponding order.They are from buttom to top: 1. Cascinodiscus argus-Cos. wittiomus-Cyclotella striata,2. Cos. blandus-Cyclotella striata diatom zone,3. Cos.excenfricus-Trbliepteychus cocconiformis diatom zone,4. Gomphonema-Cos. blandus-Actnolychus ralfsii diatom zone,5. Cos.-Cyclotella striata-Actinocyclus ralfsii diatom zone,6. Cos. -Actinolychus ralfsii diatom zone,7. diatom poor zone,8. Cos. lineatus-Cos. rothii-Actinolyclus ralfsii diatom zone,9. Gomphonema-Cyclotella striata-Cocconeis placentula var euglypta diatom zone,10. Cos.rothii- Cyclotella striata-Actinolychus ralfsi dialom zone,11.Cymbella affinis-Cyclotella striata-Gomphonema diatom zone,12. Coscinodiscus wittinus-Cyclotella striata-Epithemia hyndmanii diatom zone. Diatom assemblage order patterns of late Quaternary has been set up and the palaeoenvironment evolvution is discussed.
The sediment of 4 well's cores of late Quaternary at the continental margin of East China Sea have been systimatically researched, and abundant fossils of diatom, 117 species and varieties in 33 genus, have been found. 12 of diatom zones have been divided according to the characteristics of the diatom pattern, theoptimac Sparation and the corresponding order.They are from buttom to top: 1. Cascinodiscus argus-Cos. wittiomus-Cyclotella striata,2. Cos. blandus-Cyclotella striata diatom zone,3. Cos.excenfricus-Trbliepteychus cocconiformis diatom zone,4. Gomphonema-Cos. blandus-Actnolychus ralfsii diatom zone,5. Cos.-Cyclotella striata-Actinocyclus ralfsii diatom zone,6. Cos. -Actinolychus ralfsii diatom zone,7. diatom poor zone,8. Cos. lineatus-Cos. rothii-Actinolyclus ralfsii diatom zone,9. Gomphonema-Cyclotella striata-Cocconeis placentula var euglypta diatom zone,10. Cos.rothii- Cyclotella striata-Actinolychus ralfsi dialom zone,11.Cymbella affinis-Cyclotella striata-Gomphonema diatom zone,12. Coscinodiscus wittinus-Cyclotella striata-Epithemia hyndmanii diatom zone. Diatom assemblage order patterns of late Quaternary has been set up and the palaeoenvironment evolvution is discussed.
2002, 20(1): 156-159.
Abstract:
In this paper, the author researched diagenesis and organic inclusion in reservoir. In this area, organic inclusions were mostly formed by recrystalization and metaspmasis and with various phases. They distributed chiefly in dissolved seams and pores in quartz grains and not in structure slot. The organic inclusion abundance in Upper Triassic was more than that in Shaximiao Formation. The homogenization temperature of organic inclusion was between 100℃ and 110℃ in the second interval of Xujiahe Formation and between 90℃ and 100℃ in Shaximiao Formation. The second segment gas reservoir of Xujiahe Formation was formed earlier and underwent the course early from small charge to large charge and late again from adjustment to small charge. The gas reservoir of Shaximiao Formation was formed in the course of Xishan Tectonic Movement.
In this paper, the author researched diagenesis and organic inclusion in reservoir. In this area, organic inclusions were mostly formed by recrystalization and metaspmasis and with various phases. They distributed chiefly in dissolved seams and pores in quartz grains and not in structure slot. The organic inclusion abundance in Upper Triassic was more than that in Shaximiao Formation. The homogenization temperature of organic inclusion was between 100℃ and 110℃ in the second interval of Xujiahe Formation and between 90℃ and 100℃ in Shaximiao Formation. The second segment gas reservoir of Xujiahe Formation was formed earlier and underwent the course early from small charge to large charge and late again from adjustment to small charge. The gas reservoir of Shaximiao Formation was formed in the course of Xishan Tectonic Movement.
2002, 20(1): 165-168.
Abstract:
The geochemistry characters are discussed which between mudstones from deep lacustrine facies and coal measured by hydrous pyrolysis.Lots of differences of the two samples are pointed out by analysis.The mudstones from deep lacustrine facies and coal measure show difficult evolution features by hydrous pyrolysis. The mudstone from deep lacustrine facies has high hydrocarbon yield and is more profitable to liquid oil generation,so it will mainly generate liquid oil in the course of thermal evolution.The saturated hydrocarbon content is more and the nonhydrocarbon content is lower in the residual dissoluble organic matter in the mudstone from deep lacustrine facies than that in coal measures.The ratio of resin to asphalten and the ratio of saturated hydrocarbon to aromatics increase when the temperature rises in the mudstone from deep lacustrine facies.The ratio of resin to asphalten increases and the ratio of saturated hydrocarbon to aromatics varies little or decreases a little when the temperature rises in the mudstone from coal messures. T max of the pyrolyzed(Rock-Eval) mudstones from deep lacustrine facies can not indicate evolution stage,but T max of the pyrolyzed(Rock-Eval) mudstones from the mudstone from coal measures increases as the temperature rises.The carbon isotope of kerogen from the mudstone from deep lacustrine facies is lower distinctly than that of kerogen from mudstone of coal measures. The carbon isotope of kerogen from two samples becomes heavy as the temperature rises.It is obvious that the T max of the mudstone from deep lacustrine facies should be considered carefully when it is used to rekon the maturity of organic matter,and that the variation of isotope carbon of kerogen should also be thought much when it is used to research the type of organic matter.
The geochemistry characters are discussed which between mudstones from deep lacustrine facies and coal measured by hydrous pyrolysis.Lots of differences of the two samples are pointed out by analysis.The mudstones from deep lacustrine facies and coal measure show difficult evolution features by hydrous pyrolysis. The mudstone from deep lacustrine facies has high hydrocarbon yield and is more profitable to liquid oil generation,so it will mainly generate liquid oil in the course of thermal evolution.The saturated hydrocarbon content is more and the nonhydrocarbon content is lower in the residual dissoluble organic matter in the mudstone from deep lacustrine facies than that in coal measures.The ratio of resin to asphalten and the ratio of saturated hydrocarbon to aromatics increase when the temperature rises in the mudstone from deep lacustrine facies.The ratio of resin to asphalten increases and the ratio of saturated hydrocarbon to aromatics varies little or decreases a little when the temperature rises in the mudstone from coal messures. T max of the pyrolyzed(Rock-Eval) mudstones from deep lacustrine facies can not indicate evolution stage,but T max of the pyrolyzed(Rock-Eval) mudstones from the mudstone from coal measures increases as the temperature rises.The carbon isotope of kerogen from the mudstone from deep lacustrine facies is lower distinctly than that of kerogen from mudstone of coal measures. The carbon isotope of kerogen from two samples becomes heavy as the temperature rises.It is obvious that the T max of the mudstone from deep lacustrine facies should be considered carefully when it is used to rekon the maturity of organic matter,and that the variation of isotope carbon of kerogen should also be thought much when it is used to research the type of organic matter.
2002, 20(1): 174-177.
Abstract:
The Holocene strata at Qingfeng section, Jianhu County, Jiangsu Province are 405 cm thick. Most parts of the sediments were thought to be formed in lagoon or bay environments and the bed 6 in coastal low land (4 000～ 2 300 aBP ). A very accurate Holocene sea level change curve with many fluctuations and 2～3 m higher in 6 500～4 000 aBP and 1.5 m lower sea level in 4 000～2 300 aBP than that of the present was drawn by ZHAO Xitao et al. The author put forward different viewpoints on environments and sea levels showed by Qingfeng Section. Bed 1 and the lower part of bed 2 were formed in fresh water marsh environment; the upper part of bed 2 and beds 3, 4 and 5 were formed in intertidal zone. The sediments of bed 6 are products during river flood in estuary. The bed 7 is composed of upper estuary sediments. The sea level since 6 000 aBP should be stable. The very accurate sea level change by foraminiferal thanotocoenose drawn by ZHAO Xitao et al is without the oretical basis and the conclusions on sea level change are unbelievable.
The Holocene strata at Qingfeng section, Jianhu County, Jiangsu Province are 405 cm thick. Most parts of the sediments were thought to be formed in lagoon or bay environments and the bed 6 in coastal low land (4 000～ 2 300 aBP ). A very accurate Holocene sea level change curve with many fluctuations and 2～3 m higher in 6 500～4 000 aBP and 1.5 m lower sea level in 4 000～2 300 aBP than that of the present was drawn by ZHAO Xitao et al. The author put forward different viewpoints on environments and sea levels showed by Qingfeng Section. Bed 1 and the lower part of bed 2 were formed in fresh water marsh environment; the upper part of bed 2 and beds 3, 4 and 5 were formed in intertidal zone. The sediments of bed 6 are products during river flood in estuary. The bed 7 is composed of upper estuary sediments. The sea level since 6 000 aBP should be stable. The very accurate sea level change by foraminiferal thanotocoenose drawn by ZHAO Xitao et al is without the oretical basis and the conclusions on sea level change are unbelievable.
2002, 20(1): 13-19.
Abstract:
North Bohai Bay Basin includes the Huanghua Depression, Cangxian Uplift, Central Hebei Depression and Xialiaohe Depression. In the study area, the Ordovician is 600～800 m thick and mainly consists of limestones and dolostones. The Lower Ordovician is divided into the Yeli Formation and Liangjiashan Formation, and the Middle Ordovician is divided into the Lower Majiagou Formation which is further divided into the upper member and lower member, Upper Majiagou Formation which is further divided into the upper member and lower member, and Fengfeng Formation which is further divided into the upper member and lower member. The Upper Ordovician is missing. The Ordovician is conformable with the underlying Cambrian, and disconformable with the overlying Middle Carboniferous. The contact between the Lower and Middle Ordovician is also disconformable. In the Yeli Age, the study area was mainly a shallow restricted platform, in which there were 2 tidal flats and 5 banks. The deposits are mainly medium to thick bedded limemud limestones intercalated with some penecontemporaneous dolostones and pebble-sized intraclast limestones, with rare fossils.In the Liangjiashan Age, the lithofacies paleogeography was similar to the Yeli Age, and was still mainly a restricted platform, but tidal flats increased to 7. At the end of the Liangjiashan Age, sea level fell quickly, and the whole study area was exposed and the regional disconformity between the Lower and Middle Ordovician was formed. The lithofacies paleogeography throughout the Middle Ordovician showed strong cyclicity. In the early Lower Majiagou Age, transgression occurred, and the whole study area was occupied by tidal flats which included dolomite flats, gypsiferous dolomite flats, limy dolomite flats, limemud flats and dolomitic limemud flats. The deposits are mainly well laminated muddy penecontemporaneous dolostones and limemud limestones. Fossils are rare. In the late Lower Majiagou Age, sea level rose further and the whole study area changed to a shallow restricted platform, in which there were 3 small dolomitic limemud tidal flats. In the early Upper Majiagou Age, sea level fell, and tidal flats again dominated the area, which included limemud flats, dolomitic limemud flats, limy dolomite flats and dolomite flats. In the late Upper Majiagou Age, sea level rose quickly and the whole study area changed to a relatively deep open platform. The deposits are mainly thick bedded fossiliferous limestones. The fossils include cephalopods, brachiopods, echinoderms and gastropods. In the early Fengfeng Age, sea level fell again, and the area changed to tidal flats. In the late Fengfeng Age, transgression occurred, and the whole study area changed to a relatively deep open platform again. During the Ordovician, the study area underwent 4 marine transgression-regression cycles, and in the late Upper Majiagou Age marine transtression reached maximum.
North Bohai Bay Basin includes the Huanghua Depression, Cangxian Uplift, Central Hebei Depression and Xialiaohe Depression. In the study area, the Ordovician is 600～800 m thick and mainly consists of limestones and dolostones. The Lower Ordovician is divided into the Yeli Formation and Liangjiashan Formation, and the Middle Ordovician is divided into the Lower Majiagou Formation which is further divided into the upper member and lower member, Upper Majiagou Formation which is further divided into the upper member and lower member, and Fengfeng Formation which is further divided into the upper member and lower member. The Upper Ordovician is missing. The Ordovician is conformable with the underlying Cambrian, and disconformable with the overlying Middle Carboniferous. The contact between the Lower and Middle Ordovician is also disconformable. In the Yeli Age, the study area was mainly a shallow restricted platform, in which there were 2 tidal flats and 5 banks. The deposits are mainly medium to thick bedded limemud limestones intercalated with some penecontemporaneous dolostones and pebble-sized intraclast limestones, with rare fossils.In the Liangjiashan Age, the lithofacies paleogeography was similar to the Yeli Age, and was still mainly a restricted platform, but tidal flats increased to 7. At the end of the Liangjiashan Age, sea level fell quickly, and the whole study area was exposed and the regional disconformity between the Lower and Middle Ordovician was formed. The lithofacies paleogeography throughout the Middle Ordovician showed strong cyclicity. In the early Lower Majiagou Age, transgression occurred, and the whole study area was occupied by tidal flats which included dolomite flats, gypsiferous dolomite flats, limy dolomite flats, limemud flats and dolomitic limemud flats. The deposits are mainly well laminated muddy penecontemporaneous dolostones and limemud limestones. Fossils are rare. In the late Lower Majiagou Age, sea level rose further and the whole study area changed to a shallow restricted platform, in which there were 3 small dolomitic limemud tidal flats. In the early Upper Majiagou Age, sea level fell, and tidal flats again dominated the area, which included limemud flats, dolomitic limemud flats, limy dolomite flats and dolomite flats. In the late Upper Majiagou Age, sea level rose quickly and the whole study area changed to a relatively deep open platform. The deposits are mainly thick bedded fossiliferous limestones. The fossils include cephalopods, brachiopods, echinoderms and gastropods. In the early Fengfeng Age, sea level fell again, and the area changed to tidal flats. In the late Fengfeng Age, transgression occurred, and the whole study area changed to a relatively deep open platform again. During the Ordovician, the study area underwent 4 marine transgression-regression cycles, and in the late Upper Majiagou Age marine transtression reached maximum.
2002, 20(1): 25-29.
Abstract:
The momentum equation of underflows-type turbidity and surge-type turbidity current is compared in this paper,and the result indicates that the surge-type turbidity current entrains water not only through its upper surface but also through its front. At the slope of 0°,5°,10°, surge-type turbidity current experiments reveals that the head of the turbidity current is overhanging and is divided transversely into roughly periodic buttock-shaped lobes and clefts, on account of the mixing, the body of a turbidity current in deep water flows about 25% faster than the head, the moment process of the surge-type turbidity current shows the characteristics of wave, and back-wave transcendental front-wave. the turbidity current consumes itself in the process of mixing into the ambient medium. The flow height and velocity of surge-type turbidity current is proportional to the motion distance and under slope. Close to the bottom of the turbidity current, there is a considerable increase in density and there may even be a thin layer with bed-load flow. There is not such characteristic in the underflow-type turbidity current.
The momentum equation of underflows-type turbidity and surge-type turbidity current is compared in this paper,and the result indicates that the surge-type turbidity current entrains water not only through its upper surface but also through its front. At the slope of 0°,5°,10°, surge-type turbidity current experiments reveals that the head of the turbidity current is overhanging and is divided transversely into roughly periodic buttock-shaped lobes and clefts, on account of the mixing, the body of a turbidity current in deep water flows about 25% faster than the head, the moment process of the surge-type turbidity current shows the characteristics of wave, and back-wave transcendental front-wave. the turbidity current consumes itself in the process of mixing into the ambient medium. The flow height and velocity of surge-type turbidity current is proportional to the motion distance and under slope. Close to the bottom of the turbidity current, there is a considerable increase in density and there may even be a thin layer with bed-load flow. There is not such characteristic in the underflow-type turbidity current.
2002, 20(1): 41-46.
Abstract:
By means of silicon,strontium and carbon isotope, the material origin of hydrothermal sedimentary rocks associated closely with stratiform ore body is discussed in the paper. The value of silicon isotope δ 30 Si NBS-28 for silica rocks ranges from -0.6 ‰to -0.1‰, and it is consistent with the value of sedimentary rocks. The result of silicon isotope indicates that silicon of silica rocks comes mainly from sedimentary pile under Devonian. The value of 87 Sr/ 86 Sr for hydrothermal sedimentary rocks, such as silica rocks, chloritite, baritite and carbonate, changes from 0.709 38 to 0.728 12 and lie between ocean strontium and crust strontium. The composition of strontium of hydrothermal sedimentary rocks belongs to mixed strontium and origins from recycled strontium of underlying sedimentary pile. δ 13 C PDB and δ 18 O PDB of hydrothermal sedimentary carbonate ranges respectively from -2.7‰ to 4.3‰,-10.0 ‰to -2.0‰, and the value of δ 13 C PDB is close to natural carbonate, but δ 18 O PDB of hydrothermal sedimentary carbonate is depleted. The result of silicon and strontium indicates that the composition of hydrothermal sedimentary rocks comes mainly from sedimentary pile underlying Devonian, but its forming manner is exogenous, as well as we can say that the hydrothermal sedimentary rock is entia of endogenetic and exogenetic.
By means of silicon,strontium and carbon isotope, the material origin of hydrothermal sedimentary rocks associated closely with stratiform ore body is discussed in the paper. The value of silicon isotope δ 30 Si NBS-28 for silica rocks ranges from -0.6 ‰to -0.1‰, and it is consistent with the value of sedimentary rocks. The result of silicon isotope indicates that silicon of silica rocks comes mainly from sedimentary pile under Devonian. The value of 87 Sr/ 86 Sr for hydrothermal sedimentary rocks, such as silica rocks, chloritite, baritite and carbonate, changes from 0.709 38 to 0.728 12 and lie between ocean strontium and crust strontium. The composition of strontium of hydrothermal sedimentary rocks belongs to mixed strontium and origins from recycled strontium of underlying sedimentary pile. δ 13 C PDB and δ 18 O PDB of hydrothermal sedimentary carbonate ranges respectively from -2.7‰ to 4.3‰,-10.0 ‰to -2.0‰, and the value of δ 13 C PDB is close to natural carbonate, but δ 18 O PDB of hydrothermal sedimentary carbonate is depleted. The result of silicon and strontium indicates that the composition of hydrothermal sedimentary rocks comes mainly from sedimentary pile underlying Devonian, but its forming manner is exogenous, as well as we can say that the hydrothermal sedimentary rock is entia of endogenetic and exogenetic.
2002, 20(1): 55-60.
Abstract:
Research for the diagenetic lithofacies is based on sedimentary facies, which stress on the observation of diagenetic characteristics in sedimentary rock. Diagenetic lithofacies are distinguished and defined according to the differences of secondary diagenetic textures (including components of cements, cement types, fabric of contraction and solution, pore types and its distribution, etc.). On the basis of analyzing the micro-diagenetic characteristics, the thin sandstone in the middle-mudstone member and the Carboniferous Donghe sandstone are divided into six diagenetic lithofacies. The thin sandstone is composed of the compaction mixing cement facies and the non-compaction mixing cement face; the Donghe sandstone is composed of the solution facies, the primary pore facies, the solution-primary pore mixing facies and the carbonate cement facies. The quality of reservoirs changes with different diagenetic lithofacies. By analyzing and estimating, we conclude that the solution facies is best reservoir(Ⅰ 1), the primary pore face and the solution-primary pore mixing facies is good reservoir(Ⅰ 2), the non-compact cement facies and the non-compact type in the carbonate cement facies are medium reservoirs(Ⅱ), the compact cement facies and the compact type in the carbonate cement facies are bad reservoirs(Ⅲ). On the basis of this study, 8 wells are analyzed in this area by well logs models. As a result, we can see that the distribution of diagenetic lithofacies and different reservoir types distributed vertically and horizontally. Combining distribution characteristics of solution facies and its cause with migration of oil and gas and structure characteristics, we can predict the new oil-bearing area, and propose that the two high points of trap will be favorable for driuing at northwest and southwest from YW3 well, and very likely to gain industrial oil flow.
Research for the diagenetic lithofacies is based on sedimentary facies, which stress on the observation of diagenetic characteristics in sedimentary rock. Diagenetic lithofacies are distinguished and defined according to the differences of secondary diagenetic textures (including components of cements, cement types, fabric of contraction and solution, pore types and its distribution, etc.). On the basis of analyzing the micro-diagenetic characteristics, the thin sandstone in the middle-mudstone member and the Carboniferous Donghe sandstone are divided into six diagenetic lithofacies. The thin sandstone is composed of the compaction mixing cement facies and the non-compaction mixing cement face; the Donghe sandstone is composed of the solution facies, the primary pore facies, the solution-primary pore mixing facies and the carbonate cement facies. The quality of reservoirs changes with different diagenetic lithofacies. By analyzing and estimating, we conclude that the solution facies is best reservoir(Ⅰ 1), the primary pore face and the solution-primary pore mixing facies is good reservoir(Ⅰ 2), the non-compact cement facies and the non-compact type in the carbonate cement facies are medium reservoirs(Ⅱ), the compact cement facies and the compact type in the carbonate cement facies are bad reservoirs(Ⅲ). On the basis of this study, 8 wells are analyzed in this area by well logs models. As a result, we can see that the distribution of diagenetic lithofacies and different reservoir types distributed vertically and horizontally. Combining distribution characteristics of solution facies and its cause with migration of oil and gas and structure characteristics, we can predict the new oil-bearing area, and propose that the two high points of trap will be favorable for driuing at northwest and southwest from YW3 well, and very likely to gain industrial oil flow.
2002, 20(1): 70-74.
Abstract:
Paleocave systems form an important type of carbonate reservoirs. The studies illustrates that there are widely developed passage caves in the Middle-Upper Ordovician carbonate of Taihe, including branchwork passage, network maze, anastomotic maze, spongework maze and ramiform maze as desoribed by Robert.G.L(1999), and near-surface solution enlarged fractures, sedimentation, rebrecciated chaotic breakdown and collapse as well as mechanical compaction in burial process are probably associated with the formation of collapsed-paleocave system. The approach in terms of chemical composition of carbonate and calcite cement samples and micrographology of calcite crystals associated with karstification has been carried out in Ordovician carbonate of well S60 in Taihe. The results indicates that the carbonate breccias,fractures and sediment fill well developed at the depth of 5 433.20 m～5 435 m belonging to a large-scale paleocave system sedimentation with more than 2 m in height; while the calcites grown in caves at the depth of 5 435m are the products of mixed zone of hypergen fresh water and seawater at the early-middle stage of near-surface karst terrain. Moreover, The author believe that the mineralogic and geochemical studies on carbonate karst process have an important implication for the uncovering the effective depth,periods and intensity of epigenic karst process as well as diagentic sequence and sedimentary environment.
Paleocave systems form an important type of carbonate reservoirs. The studies illustrates that there are widely developed passage caves in the Middle-Upper Ordovician carbonate of Taihe, including branchwork passage, network maze, anastomotic maze, spongework maze and ramiform maze as desoribed by Robert.G.L(1999), and near-surface solution enlarged fractures, sedimentation, rebrecciated chaotic breakdown and collapse as well as mechanical compaction in burial process are probably associated with the formation of collapsed-paleocave system. The approach in terms of chemical composition of carbonate and calcite cement samples and micrographology of calcite crystals associated with karstification has been carried out in Ordovician carbonate of well S60 in Taihe. The results indicates that the carbonate breccias,fractures and sediment fill well developed at the depth of 5 433.20 m～5 435 m belonging to a large-scale paleocave system sedimentation with more than 2 m in height; while the calcites grown in caves at the depth of 5 435m are the products of mixed zone of hypergen fresh water and seawater at the early-middle stage of near-surface karst terrain. Moreover, The author believe that the mineralogic and geochemical studies on carbonate karst process have an important implication for the uncovering the effective depth,periods and intensity of epigenic karst process as well as diagentic sequence and sedimentary environment.
2002, 20(1): 80-84.
Abstract:
Internal-wave and internal-tide deposits are akind of dragging-flow deposits recently found in ancient deep-sea environments. A variety of internal-wave and internal-tide deposits has been identified in the deep-sea deposit along the Hercynian-Indosinian orogeny of the western Qinling Mountains. According to their depositional structures they can be divided into 7 microfacies, 1. Fine- and medium-grained sandstone with bi-directional cross-bedding structure, 2. Siltstone with pinnate cross-lamination structure, 3. Siltstone with fascicular lens superposed cross-lamination structure, 4. Siltstone with complicatedly interweaving bi-directional cross-lamination structure, 5. Siltstone with bi-directional cross-lamination structure, 6. Sand and mud interbed with wave-, vein-and lens-like composite stratification, and 7. Fine sandstone with wave and ripple structure. The present study shows that they are formed in deep-sea turbidite systems of 3 different environments. The distribution of internal-wave and internal-tide deposits in deep sea is characterized by generality, non-abundance and evident selection for layers. All of these characteristics are closely related with their formation and preservation conditions.
Internal-wave and internal-tide deposits are akind of dragging-flow deposits recently found in ancient deep-sea environments. A variety of internal-wave and internal-tide deposits has been identified in the deep-sea deposit along the Hercynian-Indosinian orogeny of the western Qinling Mountains. According to their depositional structures they can be divided into 7 microfacies, 1. Fine- and medium-grained sandstone with bi-directional cross-bedding structure, 2. Siltstone with pinnate cross-lamination structure, 3. Siltstone with fascicular lens superposed cross-lamination structure, 4. Siltstone with complicatedly interweaving bi-directional cross-lamination structure, 5. Siltstone with bi-directional cross-lamination structure, 6. Sand and mud interbed with wave-, vein-and lens-like composite stratification, and 7. Fine sandstone with wave and ripple structure. The present study shows that they are formed in deep-sea turbidite systems of 3 different environments. The distribution of internal-wave and internal-tide deposits in deep sea is characterized by generality, non-abundance and evident selection for layers. All of these characteristics are closely related with their formation and preservation conditions.
2002, 20(1): 92-100.
Abstract:
On the basis of sedimentary comprehensive study of core and well logging, taking the high-resolution sequence stratigraphy theory from Cross T A. As an instruction through the technique of sedimentary dynamic analysis of sequence structure and stacking pattern of base-level cycle and using the classification system of six-grade division scheme of base-level cycle, the authors discuss in detail the high-resolution sequence stratigraphic characteristics of Chang-6 Oil Reservoir Set, Upper Triassic in Zhidan Delta developed in Northern Ordos Basin. In the study mentioned above, four grades and genetic types of base-level cycle interface can be recognized from the formation, which is of different occurrence characteristics, developmental scales and discriminating markers. Depending on the genetic characteristics of base-level cycle interface, the formation may be divided into four order cycle sequences supershort-term,short-term,middle-term and long-term cycle sequences. Among these sequences, the cycle sequences of supershort-term and short-tem may be ubdivided further into three basic types of sequence structure, including up-deepening non-symmetry, up-shallowening non-symmetry and symmetry from up-deepening to up-shallowienng, and into seven subtypes of low or high accommodation and non-complete or nearly complete symmetry. These basic sequence types and subtypes are of various stacking and distribution patterns in differentfacies belts of Zhidan Delta. The middle-term and long-term cycle sequences are usually of symmetric structures which develop complete depositional sequence of lacustrine transgressive-regressive cycle and distribute stably in the different facies belts of the delta. According to the high-resolution isochronostratigrahpic correlation of the turnround boundaries of the multi-order base-level cycles of Chang-6 Oil Reservoir Set, the chronostrata unit frameworks in different time scale can be built, which have different application significance in each stage of hydrocarbon exploration and development.
On the basis of sedimentary comprehensive study of core and well logging, taking the high-resolution sequence stratigraphy theory from Cross T A. As an instruction through the technique of sedimentary dynamic analysis of sequence structure and stacking pattern of base-level cycle and using the classification system of six-grade division scheme of base-level cycle, the authors discuss in detail the high-resolution sequence stratigraphic characteristics of Chang-6 Oil Reservoir Set, Upper Triassic in Zhidan Delta developed in Northern Ordos Basin. In the study mentioned above, four grades and genetic types of base-level cycle interface can be recognized from the formation, which is of different occurrence characteristics, developmental scales and discriminating markers. Depending on the genetic characteristics of base-level cycle interface, the formation may be divided into four order cycle sequences supershort-term,short-term,middle-term and long-term cycle sequences. Among these sequences, the cycle sequences of supershort-term and short-tem may be ubdivided further into three basic types of sequence structure, including up-deepening non-symmetry, up-shallowening non-symmetry and symmetry from up-deepening to up-shallowienng, and into seven subtypes of low or high accommodation and non-complete or nearly complete symmetry. These basic sequence types and subtypes are of various stacking and distribution patterns in differentfacies belts of Zhidan Delta. The middle-term and long-term cycle sequences are usually of symmetric structures which develop complete depositional sequence of lacustrine transgressive-regressive cycle and distribute stably in the different facies belts of the delta. According to the high-resolution isochronostratigrahpic correlation of the turnround boundaries of the multi-order base-level cycles of Chang-6 Oil Reservoir Set, the chronostrata unit frameworks in different time scale can be built, which have different application significance in each stage of hydrocarbon exploration and development.
2002, 20(1): 106-111.
Abstract:
Through the comprehensive analysis of out crop, rock cores, well loggings and seismic data, one super-long-term, five long-term and sixteen middle-term base-level cycle sequences are distinguished in Nadu Formation of Baise basin. In this paper, the relationship between the source-reservoir-cap associations and the base-level cycle sequences of Nadu Formation are discussed in detail, and some knowledge is acquired as follows: (1) long-term base-level cycles bear close relation to source-reservoir-cap rock associtations,the main reservoir sand bodies develop in the early-middle stage of the uprising periods and middle-late stage of subsiding periods of the long-term base-level cycle, and the main hydrocarbon source rocks and favourable regional cap rocks develop at the turning position from uprising to subsiding of the long-term base-level cylce; (2) the characteristics of source-reservoir-cap rock associations developed in each long-term base-level cycle are distinctly different and controlled by the frequency, amplitude of the rising and falling of the base-level, facies association, accommodation and A/S ratio; (3) according to the spatial relationship of source rocks, reservoir rocks and cap rocks in the vertical or horizontal section of the formation, three types of basic associations can be divided. The first associations is usually of the type with source rocks in the upper and reservoirs below, the second one with source rocks below and reservoirs in the upper, and the third one with source rocks in other district.
Through the comprehensive analysis of out crop, rock cores, well loggings and seismic data, one super-long-term, five long-term and sixteen middle-term base-level cycle sequences are distinguished in Nadu Formation of Baise basin. In this paper, the relationship between the source-reservoir-cap associations and the base-level cycle sequences of Nadu Formation are discussed in detail, and some knowledge is acquired as follows: (1) long-term base-level cycles bear close relation to source-reservoir-cap rock associtations,the main reservoir sand bodies develop in the early-middle stage of the uprising periods and middle-late stage of subsiding periods of the long-term base-level cycle, and the main hydrocarbon source rocks and favourable regional cap rocks develop at the turning position from uprising to subsiding of the long-term base-level cylce; (2) the characteristics of source-reservoir-cap rock associations developed in each long-term base-level cycle are distinctly different and controlled by the frequency, amplitude of the rising and falling of the base-level, facies association, accommodation and A/S ratio; (3) according to the spatial relationship of source rocks, reservoir rocks and cap rocks in the vertical or horizontal section of the formation, three types of basic associations can be divided. The first associations is usually of the type with source rocks in the upper and reservoirs below, the second one with source rocks below and reservoirs in the upper, and the third one with source rocks in other district.
Paleoclimatic Significance of Grain-size Composition of Neogene Red Earth at Xunyi, Shaanxi Province
2002, 20(1): 118-123.
Abstract:
An approximately continuous section of Late Cenozoic earthy deposits, developed at Xiaqiang Village, Xunyi County, Shaanxi Province, is 230 m in thickness and consists of the complete Quaternary loess-paleosol sequence and its underlying Neogene red earth beds. The loess-paleosol deposits of Quaternary as the aolian genesis has been accepted broadly by geologists. The red earth of Neogene has also been considered to have the same origin as that of loess in recent years. Therefore, the characteristics of the grain-size analysis of the red earth, similar to that of loess, could be used as a substitute index for the paleoclimate study. The climatic evolution of Neogene is discussed in this paper by studying on the grain-size analysis. We choose four groups of grain size data: the mean, 30μm, 63μm and 2μm, which are shown in four curves. Then, we could see (Fig. 2) that these four grain-size curves are all relatively stable and show the features of high-frequency and low-amptitude. Each of these four curves of Neogene red beds can be subdivided into four parts ranging from the bottom up to the top. The first part composed of the 20th bed group has high content of mean, 30μm and 63μm, but low content of 2μm. The second part formed by the bed groups of 19～18th is between the first and third parts, whose content of the mean, 30μm and 63μm is gradually decreasing all the way till the bottom of the third part, while that of the 2μm is increasing till to the highest of the third one. The third part, composed of 17～15th bed groups, has high content of 2μm and low content of mean, 30μm and 63μm; The forth part consisting 14～13th bed groups is relatively stable without obvious undulation, although the content of the mean, 30μm and 63μm is slightly higher, while the 2μm slightly lower than those of the third one. These differences of four parts can also be seen in Fig. 3 the age/depth relations of the different sedimentary ratio of each part. Each curve of Neogene, especially that of 2μm, can further be subdivided into four million-grade cycles, each of these cycles containing many smaller cycles of ten thousand grade. The sharp changes of the curves near the top reveal the different features of grain-size composition of Quaternary from those of Neogene. The curves of coarse particle of Neogene show little changes, which probably means the small uplift of Qin-Tibet Plateau. Winter and also summer monsoon had been primarily formed though rather weak. The average content of 2μm particles is remarkably higher in Neogene red beds than that in Quaternary loess-paleosol, but with a certain fluctuation, suggesting that the Neogene climate was mainly moist and warm and that the strength of summer monsoon had a slight greater change. The grain-size curve of 2μm particles can be divided into four stages. Stage 3, consisting of 17～15th bed-groups, shows the strongest summer monsoon, being the warmest and wettest. However, stages 4, 1 and 2 indicate that the summer monsoon of these stages is relatively weaker than that of stage 3. In other words, the feature of the Late Neogene climate of lLoess Plateau was generally warm and moist. With this background climate there were alterations of warm-wet and cool-dry climate. A distinct change in the curve can be seen since Quaternary, which is indicated by the increase of coarse particles and decrease of 2μm particles. And the curve changed from high-frequency, low-amptitude pattern of Neogene to that of low-frequency, high-amptitude. This obvious change is mainly related to the strong uplift of Qin-Tibet Plateau since Quaternary and also to the formation and expansion of Antarctic ice sheet. The grain-size curves are in agreement with susceptibility curve and strata analysis.
An approximately continuous section of Late Cenozoic earthy deposits, developed at Xiaqiang Village, Xunyi County, Shaanxi Province, is 230 m in thickness and consists of the complete Quaternary loess-paleosol sequence and its underlying Neogene red earth beds. The loess-paleosol deposits of Quaternary as the aolian genesis has been accepted broadly by geologists. The red earth of Neogene has also been considered to have the same origin as that of loess in recent years. Therefore, the characteristics of the grain-size analysis of the red earth, similar to that of loess, could be used as a substitute index for the paleoclimate study. The climatic evolution of Neogene is discussed in this paper by studying on the grain-size analysis. We choose four groups of grain size data: the mean, 30μm, 63μm and 2μm, which are shown in four curves. Then, we could see (Fig. 2) that these four grain-size curves are all relatively stable and show the features of high-frequency and low-amptitude. Each of these four curves of Neogene red beds can be subdivided into four parts ranging from the bottom up to the top. The first part composed of the 20th bed group has high content of mean, 30μm and 63μm, but low content of 2μm. The second part formed by the bed groups of 19～18th is between the first and third parts, whose content of the mean, 30μm and 63μm is gradually decreasing all the way till the bottom of the third part, while that of the 2μm is increasing till to the highest of the third one. The third part, composed of 17～15th bed groups, has high content of 2μm and low content of mean, 30μm and 63μm; The forth part consisting 14～13th bed groups is relatively stable without obvious undulation, although the content of the mean, 30μm and 63μm is slightly higher, while the 2μm slightly lower than those of the third one. These differences of four parts can also be seen in Fig. 3 the age/depth relations of the different sedimentary ratio of each part. Each curve of Neogene, especially that of 2μm, can further be subdivided into four million-grade cycles, each of these cycles containing many smaller cycles of ten thousand grade. The sharp changes of the curves near the top reveal the different features of grain-size composition of Quaternary from those of Neogene. The curves of coarse particle of Neogene show little changes, which probably means the small uplift of Qin-Tibet Plateau. Winter and also summer monsoon had been primarily formed though rather weak. The average content of 2μm particles is remarkably higher in Neogene red beds than that in Quaternary loess-paleosol, but with a certain fluctuation, suggesting that the Neogene climate was mainly moist and warm and that the strength of summer monsoon had a slight greater change. The grain-size curve of 2μm particles can be divided into four stages. Stage 3, consisting of 17～15th bed-groups, shows the strongest summer monsoon, being the warmest and wettest. However, stages 4, 1 and 2 indicate that the summer monsoon of these stages is relatively weaker than that of stage 3. In other words, the feature of the Late Neogene climate of lLoess Plateau was generally warm and moist. With this background climate there were alterations of warm-wet and cool-dry climate. A distinct change in the curve can be seen since Quaternary, which is indicated by the increase of coarse particles and decrease of 2μm particles. And the curve changed from high-frequency, low-amptitude pattern of Neogene to that of low-frequency, high-amptitude. This obvious change is mainly related to the strong uplift of Qin-Tibet Plateau since Quaternary and also to the formation and expansion of Antarctic ice sheet. The grain-size curves are in agreement with susceptibility curve and strata analysis.
2002, 20(1): 129-135.
Abstract:
The Kaili Biota is the third most diverse Burgess Shale-type biota after the Burgess Shale and Chengjiang biota. In the paper, on the basis of the study on the burial characteristics of fossils, the ecological be-havior of animal and algae, and the analysis of depositional characteristics and the geochemical parameter, we consider that most animals and algae in the Kaili Biota lived at the shallow water, and these organisms are carried into continental shelf by tempesite or turbidity flow and is buried in contnental shelf. At the same time, the burying mechanism of the Kaili biota is put forward in this paper. On the basis of the analyses of sedimentary sequences and taphonomic sequences of fossil in Kaili Fm. bearing-Kaili Biota, and combining research of geochemistry and paleo-ecology and taphonology, the Kaili Biota is considered that most organisms are characterized by ecological behavior of shallow water, these animals and algae living in shallow water were destroyed by event of tempesite or turbidity flow, and carried into deeper shelf, and buried at shelf. Some researches suggested that the Kaili Biota live at 150～200 meters water in depth; they reached this conclusion from lithology and lithofacies, and trace fossil assemblage in Kaili Formation. We disagree with above-mentioned view about the Kaili Biota lived below 150～200 meter deep, but agree that the Kaili Biota uas buried at shelf below 150～200 meter water in depth. Therefore, we consider that most animals and algae in the Kaili biota lived at shallow water, and they were carried into shelf by tempesite or turbidity flow and were buried in shelf. The conclusion is suggested by the following sedimentary characteristics and fossil assemblage in Kaili Fm. 1, A lot of algal fossils (about 20 genus), containing red algae, blue algae, and brown algae, occur in the Kaili Biota. According to ecological distribution of modern algae, so high diverse algae only live at shallow sea (less than 90 meter in depth). 2, Until now, the Kaili Biota contains more than 100 genus animal fossils, so high diverse animals only live at shallow sea (less than 90 meter in depth). 3, Most fossils were persevered at D layer of tempesite or turbidity sequence, this is the fossil buried sequence C, but shelf shale (analogous to E layer of tempesite or turbidite sequence) only contains few fossils. On the basis of fossil distribution in the tempesite or turbidity sequence, we believe that most organisms were carried into shelf from shallow water region by tempesite or turbidity flow.
The Kaili Biota is the third most diverse Burgess Shale-type biota after the Burgess Shale and Chengjiang biota. In the paper, on the basis of the study on the burial characteristics of fossils, the ecological be-havior of animal and algae, and the analysis of depositional characteristics and the geochemical parameter, we consider that most animals and algae in the Kaili Biota lived at the shallow water, and these organisms are carried into continental shelf by tempesite or turbidity flow and is buried in contnental shelf. At the same time, the burying mechanism of the Kaili biota is put forward in this paper. On the basis of the analyses of sedimentary sequences and taphonomic sequences of fossil in Kaili Fm. bearing-Kaili Biota, and combining research of geochemistry and paleo-ecology and taphonology, the Kaili Biota is considered that most organisms are characterized by ecological behavior of shallow water, these animals and algae living in shallow water were destroyed by event of tempesite or turbidity flow, and carried into deeper shelf, and buried at shelf. Some researches suggested that the Kaili Biota live at 150～200 meters water in depth; they reached this conclusion from lithology and lithofacies, and trace fossil assemblage in Kaili Formation. We disagree with above-mentioned view about the Kaili Biota lived below 150～200 meter deep, but agree that the Kaili Biota uas buried at shelf below 150～200 meter water in depth. Therefore, we consider that most animals and algae in the Kaili biota lived at shallow water, and they were carried into shelf by tempesite or turbidity flow and were buried in shelf. The conclusion is suggested by the following sedimentary characteristics and fossil assemblage in Kaili Fm. 1, A lot of algal fossils (about 20 genus), containing red algae, blue algae, and brown algae, occur in the Kaili Biota. According to ecological distribution of modern algae, so high diverse algae only live at shallow sea (less than 90 meter in depth). 2, Until now, the Kaili Biota contains more than 100 genus animal fossils, so high diverse animals only live at shallow sea (less than 90 meter in depth). 3, Most fossils were persevered at D layer of tempesite or turbidity sequence, this is the fossil buried sequence C, but shelf shale (analogous to E layer of tempesite or turbidite sequence) only contains few fossils. On the basis of fossil distribution in the tempesite or turbidity sequence, we believe that most organisms were carried into shelf from shallow water region by tempesite or turbidity flow.
2002, 20(1): 144-150.
Abstract:
Commonly used methods on evaluating the productivity of oil-producing lake have been reviewed and take the Paleogene Lake (refered to as Dongying Lake) in the Dongying depression, Shandong Province, as a case study. These methods include organic carbon analysis, paleontological analysis and stable carbon isotopic analysis. The Paleogene sediment of the Dongying depression mainly composed by the Dongying Formation (Oligocene) and the Shahejie Formation (Eocene-Oligocene).These formations can be subdivided into some members, for example, the Shahejie Formatin is divided into four members including first member(SHA1), second member(SHA2), third member(SHA3) and forth member(SHA4). Both qualitative and quantitative methods show that the level of productivity in the lower-middle SHA 3, upper SHA 4 and SHA 1 are the highest, the second is the upper SHA 3, and the level of productivity in SHA 2 is the lowest. Compared with the productivity of different modern lakes, we concluded that the lake in lower-middle SHA 3, upper SHA 4 and SHA 1 depositional period are hypertropic lake and these lake are the most favorable for the formation of lacustrine oil. The lake in the upper SHA 3 is eutrophic lake and in SHA 2 is Mesotropic Lake. These lakes have poor potential for the formation of lacustrine oil.
Commonly used methods on evaluating the productivity of oil-producing lake have been reviewed and take the Paleogene Lake (refered to as Dongying Lake) in the Dongying depression, Shandong Province, as a case study. These methods include organic carbon analysis, paleontological analysis and stable carbon isotopic analysis. The Paleogene sediment of the Dongying depression mainly composed by the Dongying Formation (Oligocene) and the Shahejie Formation (Eocene-Oligocene).These formations can be subdivided into some members, for example, the Shahejie Formatin is divided into four members including first member(SHA1), second member(SHA2), third member(SHA3) and forth member(SHA4). Both qualitative and quantitative methods show that the level of productivity in the lower-middle SHA 3, upper SHA 4 and SHA 1 are the highest, the second is the upper SHA 3, and the level of productivity in SHA 2 is the lowest. Compared with the productivity of different modern lakes, we concluded that the lake in lower-middle SHA 3, upper SHA 4 and SHA 1 depositional period are hypertropic lake and these lake are the most favorable for the formation of lacustrine oil. The lake in the upper SHA 3 is eutrophic lake and in SHA 2 is Mesotropic Lake. These lakes have poor potential for the formation of lacustrine oil.
2002, 20(1): 160-164.
Abstract:
Rich carbazole compounds, including carbazole, alkylcarbazoles, benzocarbazoles and alkylbenzocarbazoles, were detected by GC/MS in lacustrine oils from Beisantai area, Junggar Basin. Changes in contents of carbazoles and its isomers indicate that there exists an obvious migration fractionation. From Fukang depression to Beisanta uplift, the concentrations of carbazole compounds and its benzocarbazoles have decreased during oil migration, but the relative contents of carbazole, methylcarbazoles and isomers with shield effects have increased. The results indicate that the distributions of carbazole compounds in oils of the same origin are mainly controllted by the oil migration, and they have potential significance in reseaching oil migration.
Rich carbazole compounds, including carbazole, alkylcarbazoles, benzocarbazoles and alkylbenzocarbazoles, were detected by GC/MS in lacustrine oils from Beisantai area, Junggar Basin. Changes in contents of carbazoles and its isomers indicate that there exists an obvious migration fractionation. From Fukang depression to Beisanta uplift, the concentrations of carbazole compounds and its benzocarbazoles have decreased during oil migration, but the relative contents of carbazole, methylcarbazoles and isomers with shield effects have increased. The results indicate that the distributions of carbazole compounds in oils of the same origin are mainly controllted by the oil migration, and they have potential significance in reseaching oil migration.
2002, 20(1): 169-173.
Abstract:
Crude oils in different production stages are analyzed by organic geochemical technology. The oils from Donghe,Tazhong and Lunnan oil field in Tarim basin are collected from different stages in the process of production. In addition, the variation rule of crude oil components is studied and the internal relations between crude oil components and production stages are also investigated. The experiment results indicate that the saturate/aromatics ratio show decreasing trend with production; There is a direct relationship between saturate and NSO + asphaltene with production. The carbon number range or the peak carbon number of normal alkanes in crude oils shift backuard and the light/heavy hydrocarbons ratio show decreasing trendtion.During oil recovery,polar components including various heteroatom-bearing functional groups with basic or acidic property tend to reduce in crude oil Therefore, this investigation has practice significance in researching expelled mechanics from microcosmic points of view, evaluating wetting alteration in crude oils and increasing production ratio of crude oils.
Crude oils in different production stages are analyzed by organic geochemical technology. The oils from Donghe,Tazhong and Lunnan oil field in Tarim basin are collected from different stages in the process of production. In addition, the variation rule of crude oil components is studied and the internal relations between crude oil components and production stages are also investigated. The experiment results indicate that the saturate/aromatics ratio show decreasing trend with production; There is a direct relationship between saturate and NSO + asphaltene with production. The carbon number range or the peak carbon number of normal alkanes in crude oils shift backuard and the light/heavy hydrocarbons ratio show decreasing trendtion.During oil recovery,polar components including various heteroatom-bearing functional groups with basic or acidic property tend to reduce in crude oil Therefore, this investigation has practice significance in researching expelled mechanics from microcosmic points of view, evaluating wetting alteration in crude oils and increasing production ratio of crude oils.
