2007 Vol. 25, No. 4
Display Method:
2007, 25(4): 487-494.
Abstract:
Recent developments in the research on the geology and geochemistry of the newly\|discovered clayey breccias at the top of the Xiaochaka Formation in the Juhuashan, Xiaochaka and Shishuihe areas, Qiangtang Basin, northern Tibet have disclosed that mineral compositions, textures and structures, occurrences and sectional architectures of the clayey breccias agree well with those of the paleo\|weathering crust in these areas. Compared with the bedrocks, the paleo\|weathering crust is characterized by the leaching out of CaO and CO2, and relative enrichment of SiO2, Al2O3, Fe2O3, K2O, Na2O, MnO and P2O5. The clayey weathered residues in the paleo\|weathering crust are characterized by marked enrichment of REEs, much higher contents of LREEs than those of HREEs, markedly positive Ce anomalies and negative Eu anomalies, and a noticeable increase in other element contents besides Mo, Sn and U from the clayey weathered residues. The characteristics cited above have documented that there was a sharp depositional hiatus in the Qiangtang Basin during the Late Triassic.
The discovery of the paleo\|weathering crust at the top of the Upper Triassic Xiaochaka Formation has provided important evidence for the understanding of regional history of crustal, paleoclimatic and paleogeographic evolution, sequence stratigraphic division and correlation and Qiantang petroliferous basin analysis.
Recent developments in the research on the geology and geochemistry of the newly\|discovered clayey breccias at the top of the Xiaochaka Formation in the Juhuashan, Xiaochaka and Shishuihe areas, Qiangtang Basin, northern Tibet have disclosed that mineral compositions, textures and structures, occurrences and sectional architectures of the clayey breccias agree well with those of the paleo\|weathering crust in these areas. Compared with the bedrocks, the paleo\|weathering crust is characterized by the leaching out of CaO and CO2, and relative enrichment of SiO2, Al2O3, Fe2O3, K2O, Na2O, MnO and P2O5. The clayey weathered residues in the paleo\|weathering crust are characterized by marked enrichment of REEs, much higher contents of LREEs than those of HREEs, markedly positive Ce anomalies and negative Eu anomalies, and a noticeable increase in other element contents besides Mo, Sn and U from the clayey weathered residues. The characteristics cited above have documented that there was a sharp depositional hiatus in the Qiangtang Basin during the Late Triassic.
The discovery of the paleo\|weathering crust at the top of the Upper Triassic Xiaochaka Formation has provided important evidence for the understanding of regional history of crustal, paleoclimatic and paleogeographic evolution, sequence stratigraphic division and correlation and Qiantang petroliferous basin analysis.
2007, 25(4): 505-510.
Abstract:
Cyclicity character is one of the most important attributes of depositional strata, and it looks more important in the terrestrial sediments. Rhythmicility or periodicity of the depositional strata is materialized by the transformations of lithological characters in strata ordinally, and it is incarnated by the transformations of ingredient, granularity, color, intensity of the depositional compensation, intensity of oxidationdeoxidation, and the character of biome. Rhythmicility or periodicity of the depositional strata is influenced by the fluctuation of sealevel to a certain extent, but it must be the response of depositional course to the structural activity in extensive significance.
Cyclicity character is one of the most important attributes of depositional strata, and it looks more important in the terrestrial sediments. Rhythmicility or periodicity of the depositional strata is materialized by the transformations of lithological characters in strata ordinally, and it is incarnated by the transformations of ingredient, granularity, color, intensity of the depositional compensation, intensity of oxidationdeoxidation, and the character of biome. Rhythmicility or periodicity of the depositional strata is influenced by the fluctuation of sealevel to a certain extent, but it must be the response of depositional course to the structural activity in extensive significance.
2007, 25(4): 518-525.
Abstract:
Yanqi Basin of Xinjiang is a Mesocenozoic basin, through the lithological analysis on the residual Mesozoic formation of the basin, such conclusion is reached that the source area located in the north of the basin, the debris were transported from the north to the south, so the coarse fragment were deposited in the north while fine clastic in the south; The sedimentary facies in northern basin were braided stream facies while shoreshallow lacustrine stream facies in southern basin; Concurrently, the Jurassic formation is still remained in front of Tianshan mountain of northern basin and on Kulukatag mountain of southern basin; All above show that the primary face of the basin is wider than the present one. On the basis of apatite fission track age, these Mountains began to lift in the middle of lower Crataceous. The four basins, Youedosi basin, Kuqa basin, Yanqi basin and Kumier basin, were coherent and formed the north of the larger Tarim basin before the time. The larger basin was disorganized in Late Crataceous, Yanqi basin and these basins were divided into four separate basins.
Yanqi Basin of Xinjiang is a Mesocenozoic basin, through the lithological analysis on the residual Mesozoic formation of the basin, such conclusion is reached that the source area located in the north of the basin, the debris were transported from the north to the south, so the coarse fragment were deposited in the north while fine clastic in the south; The sedimentary facies in northern basin were braided stream facies while shoreshallow lacustrine stream facies in southern basin; Concurrently, the Jurassic formation is still remained in front of Tianshan mountain of northern basin and on Kulukatag mountain of southern basin; All above show that the primary face of the basin is wider than the present one. On the basis of apatite fission track age, these Mountains began to lift in the middle of lower Crataceous. The four basins, Youedosi basin, Kuqa basin, Yanqi basin and Kumier basin, were coherent and formed the north of the larger Tarim basin before the time. The larger basin was disorganized in Late Crataceous, Yanqi basin and these basins were divided into four separate basins.
2007, 25(4): 535-544.
Abstract:
According to the cycle architecture of lithology, the Zhiluo Formation is divided into two members (named upper and lower ones) in the scale of whole basin. The figures about member thickness, sandstone thickness and layer numbers of sandstone indicate that: the thickness distribution patterns of sandstone about both upper and lower members are consistent with that of the whole formation, all of them show it is thicker in the west while thinner in the east; the thickness of upper member are thicker than that of lower member, generally. The lower member has less layer numbers of sandstone and bigger thickness of single sandstone layer, while the upper member holds the opposite characteristics. The analysis of detrital components, detritus type,supporting style and regional mapping indicate that: the sandstone of Zhiluo Formation has the characteristics of multiprovenances and proximal deposition. The analysis of grain size shows that the sandstone has the characteristic of fluvial channel deposition. Several types of surface and bedding structures existed in the sandstone of Zhiluo Formation, which reflect the fluvial deposit environment. The vertical sequence of lower member has the typical characteristic of braided stream system, while the upper member reflects the combination characteristic of superimposition of multiple phase meanderingbraided stream system. Via comprehensive analysis, it is considered that the main sedimentary facies of lower member of Zhiluo Formation is braided stream system, and transited to meandering river at latter in the residual basin. While that of the upper member are mainly braidedmeandering stream system, delta and lake. The sandstone deposited in braided channel of lower member of Zhiluo Formation has excellent permeability, connectedness and well bedding, so it is the well reservoir of sandstonetype uranium deposits and hydrocarbon.
According to the cycle architecture of lithology, the Zhiluo Formation is divided into two members (named upper and lower ones) in the scale of whole basin. The figures about member thickness, sandstone thickness and layer numbers of sandstone indicate that: the thickness distribution patterns of sandstone about both upper and lower members are consistent with that of the whole formation, all of them show it is thicker in the west while thinner in the east; the thickness of upper member are thicker than that of lower member, generally. The lower member has less layer numbers of sandstone and bigger thickness of single sandstone layer, while the upper member holds the opposite characteristics. The analysis of detrital components, detritus type,supporting style and regional mapping indicate that: the sandstone of Zhiluo Formation has the characteristics of multiprovenances and proximal deposition. The analysis of grain size shows that the sandstone has the characteristic of fluvial channel deposition. Several types of surface and bedding structures existed in the sandstone of Zhiluo Formation, which reflect the fluvial deposit environment. The vertical sequence of lower member has the typical characteristic of braided stream system, while the upper member reflects the combination characteristic of superimposition of multiple phase meanderingbraided stream system. Via comprehensive analysis, it is considered that the main sedimentary facies of lower member of Zhiluo Formation is braided stream system, and transited to meandering river at latter in the residual basin. While that of the upper member are mainly braidedmeandering stream system, delta and lake. The sandstone deposited in braided channel of lower member of Zhiluo Formation has excellent permeability, connectedness and well bedding, so it is the well reservoir of sandstonetype uranium deposits and hydrocarbon.
2007, 25(4): 545-553.
Abstract:
Mashenmiao and Laogonggou sedimentary strata develop as the bottom of early Cretaceous Yixian Formation in the Yixian basin, western Liaoning province. Mashenmiao sedimentary stratum, which forms under arid palaeoclimate, could be divided into 6 sublayers from the lower to the upper portion, the lower conglomerate sublayers come into being proluvial fan bottom facies and fan surficial streamflood filled facies; the middle part of Mashenmiao layers is ployenous conglomerate containing tuffaceous interlayer; mesotypicbasic vulcanite overlay Mashenmiao sedimentary deposit. The Laogonggou bottom is politic siltstone distal facies of alluvial fan and gritstonepebbly gritstone alluvial facies of proluvial fan to basin centre part, the latter is formed by ephermeral stream's fluviation. Bentonitic siltstone and bentonitecarbonate rock sedimentary deposit are aggraded as the top of Laogonggou stratum; it is a shallow lacustrine sedimentary set. In the initial stage of basin evolution, regional climate is arid and basin margin has high hypsographic feature. There are proluvial fans around basin margin, the flood stream sedimentary process occur on fan surface. In the transition part of fan to lacustrine, there are ephemeral streams; the top facies of Laogonggou indicates a palaeogeographic and palaeoclimatic characteristics of regional aridity, intensive volcanic eruption and lacustrine waterdepth fluctuation. The lower sedimentary of Yixian Formation show form basin margin to centre three facies coexistence paleogeography characteristics of planar, linear and relatively quiescence water mass depositions.
Mashenmiao and Laogonggou sedimentary strata develop as the bottom of early Cretaceous Yixian Formation in the Yixian basin, western Liaoning province. Mashenmiao sedimentary stratum, which forms under arid palaeoclimate, could be divided into 6 sublayers from the lower to the upper portion, the lower conglomerate sublayers come into being proluvial fan bottom facies and fan surficial streamflood filled facies; the middle part of Mashenmiao layers is ployenous conglomerate containing tuffaceous interlayer; mesotypicbasic vulcanite overlay Mashenmiao sedimentary deposit. The Laogonggou bottom is politic siltstone distal facies of alluvial fan and gritstonepebbly gritstone alluvial facies of proluvial fan to basin centre part, the latter is formed by ephermeral stream's fluviation. Bentonitic siltstone and bentonitecarbonate rock sedimentary deposit are aggraded as the top of Laogonggou stratum; it is a shallow lacustrine sedimentary set. In the initial stage of basin evolution, regional climate is arid and basin margin has high hypsographic feature. There are proluvial fans around basin margin, the flood stream sedimentary process occur on fan surface. In the transition part of fan to lacustrine, there are ephemeral streams; the top facies of Laogonggou indicates a palaeogeographic and palaeoclimatic characteristics of regional aridity, intensive volcanic eruption and lacustrine waterdepth fluctuation. The lower sedimentary of Yixian Formation show form basin margin to centre three facies coexistence paleogeography characteristics of planar, linear and relatively quiescence water mass depositions.
2007, 25(4): 564-573.
Abstract:
The genetic study of the cherts in Erlangping Group is the key to reveal copper polymetallic deposits genesis and tectonic setting of Erlangping Group.By studying the geological and geochemical characters of the three types of cherts in Erlangping Group in the east Qinling orogenic belt, it is believed that the cherts in Erlangping Group are hydrothermal sedimentogenic rocks. The major elements characteristic value (N(Al)/N（Al+Fe+Mn）) indicates that the cherts were formed in different marine environments .The cherts formed at the west of Nanyang basin were deposited in continental margin basin environment, but those formed at the east of Nanyang basin were deposited in pelagic environment and had a little of material from the continental margin. Comprehensive analysis of rare earth elements geochemistry(negative Eu ,Ce anomaly) and geologycharacteristics of the cherts show sthat the cherts of Erlangping Group are formed by the mixing of backarc basin type hydrothermal solutions of low temperature and seawater, so a new evidence is provided to determine the backarc basin tectonic setting of Erlangpin Group.The paragenetic relationship of hydrothermal sedimentogenic cherts and copper polymetallic deposits manifest that the copper polymetallic deposits are formed by the submarine hydrothermal exhalative lithogenesis and mineralization.
The genetic study of the cherts in Erlangping Group is the key to reveal copper polymetallic deposits genesis and tectonic setting of Erlangping Group.By studying the geological and geochemical characters of the three types of cherts in Erlangping Group in the east Qinling orogenic belt, it is believed that the cherts in Erlangping Group are hydrothermal sedimentogenic rocks. The major elements characteristic value (N(Al)/N（Al+Fe+Mn）) indicates that the cherts were formed in different marine environments .The cherts formed at the west of Nanyang basin were deposited in continental margin basin environment, but those formed at the east of Nanyang basin were deposited in pelagic environment and had a little of material from the continental margin. Comprehensive analysis of rare earth elements geochemistry(negative Eu ,Ce anomaly) and geologycharacteristics of the cherts show sthat the cherts of Erlangping Group are formed by the mixing of backarc basin type hydrothermal solutions of low temperature and seawater, so a new evidence is provided to determine the backarc basin tectonic setting of Erlangpin Group.The paragenetic relationship of hydrothermal sedimentogenic cherts and copper polymetallic deposits manifest that the copper polymetallic deposits are formed by the submarine hydrothermal exhalative lithogenesis and mineralization.
2007, 25(4): 589-596.
Abstract:
An ICPMS method is used to determine the contents of rare earth elements of Carboniferous and Permian sedimentary rocks in Bohaiwan Basin. The average REE content of every sample is 290.39 μg/g, and it is obvious higher than the North American shale sample. The δEu is 0.420.83, and the average is 0.67,and the samples are lack of Eu. Most samples content nomal Ce, and δCe is 0.511.22,and the average is 0.97.The rare earth element patterns indicate that the LREE is rich and the HREE is lack,and the HREE patterns are flat. The lack of Ce indicates the ancient water of the upper Carboniferous is oxidable. According to the values of δEu and the REE content and its variation,the material source of Carboniferous and Permian in Bohaiwan Basin was from the Yinshan ancient continent and its province is granite.
An ICPMS method is used to determine the contents of rare earth elements of Carboniferous and Permian sedimentary rocks in Bohaiwan Basin. The average REE content of every sample is 290.39 μg/g, and it is obvious higher than the North American shale sample. The δEu is 0.420.83, and the average is 0.67,and the samples are lack of Eu. Most samples content nomal Ce, and δCe is 0.511.22,and the average is 0.97.The rare earth element patterns indicate that the LREE is rich and the HREE is lack,and the HREE patterns are flat. The lack of Ce indicates the ancient water of the upper Carboniferous is oxidable. According to the values of δEu and the REE content and its variation,the material source of Carboniferous and Permian in Bohaiwan Basin was from the Yinshan ancient continent and its province is granite.
2007, 25(4): 603-611.
Abstract:
245 specimens and samples of aquatic bryophytes were collected from 14 karst waterfalls in southwest Guangxi, P.R.China in November, 2005. The characteristics of bryological biodiversity as follows: (1) It consists of 36 bryophyte taxa in 19 genera and 11 families. Among them, 30 moss taxa in 15 genera and 8 families were founded while 6 liverwort taxa in 4 genera and 3 families were recorded. (2)The life\|forms are Tall turfs (38.89%), Short turfs (19.44%), Mats (13.89%) and Wefts (27.78%). (3)The phytogeographical elements include Cosmopolitans ( 13.57%), North Temperate elements ( 36.11%), Tropical Asia elements( 16.67%), East Asia elements (19.44%) and Endemic to China(13.89% ) . (4)The reproductive systems consist of three types: Dioecious taxa is 83.33%, Synoecious is 13.89% while autoecious 2.78 %. According to the feature of environmental factors and key bryophyte species, 4 ecological types (stream waterfall deposition, river waterfall deposition, dam deposition and cave deposition) and 12 subtypes of biokarst depositions associated with bryophytes can be distinguished.
245 specimens and samples of aquatic bryophytes were collected from 14 karst waterfalls in southwest Guangxi, P.R.China in November, 2005. The characteristics of bryological biodiversity as follows: (1) It consists of 36 bryophyte taxa in 19 genera and 11 families. Among them, 30 moss taxa in 15 genera and 8 families were founded while 6 liverwort taxa in 4 genera and 3 families were recorded. (2)The life\|forms are Tall turfs (38.89%), Short turfs (19.44%), Mats (13.89%) and Wefts (27.78%). (3)The phytogeographical elements include Cosmopolitans ( 13.57%), North Temperate elements ( 36.11%), Tropical Asia elements( 16.67%), East Asia elements (19.44%) and Endemic to China(13.89% ) . (4)The reproductive systems consist of three types: Dioecious taxa is 83.33%, Synoecious is 13.89% while autoecious 2.78 %. According to the feature of environmental factors and key bryophyte species, 4 ecological types (stream waterfall deposition, river waterfall deposition, dam deposition and cave deposition) and 12 subtypes of biokarst depositions associated with bryophytes can be distinguished.
2007, 25(4): 619-625.
Abstract:
The Qiuli’nanmu Lake is a dried saline lake in central Tibet with many thick mirabilite layers．Saline minerals are suggested to be products of dry and cold environment compared with clays．A detailed mineralogical investigation was carried out with mainly thick mirabilite and thin borax layer and thin clay layer alternately．The stratigraphic variation in the mineralogy of salt lake sediments is an indicator of paleoclimatic fluctuations．Based on the variations of mineralogy, pollen and carbonate，it is suggested that the climate was warm and wet in 27.820.5 ka BP，cold and dry in 20.511.4 ka BP，warm and wet 11.410.1ka B，cold and dry in 10.17.5 ka BP，warm but changed frequently in 7.54.97 ka BP．The Last Glacial Maximum may be appeared in 20.517.5 ka BP．The warm pluses were at 17.517.1 ka BP,15.915.2 ka BP and 14.113.4 ka BP．The “8.2 ka BP cold event” appeared at 8.17.9 ka BP．Borax，a mineral appeared in low temperature，steady and shallow brine water，suggested the same environment during 27.84.97 ka BP in Qiuli’nanmu lake．The changes of summer monsoon led to the climatic conditions in the area. This work gives a mineralogical evidence for the view that Tibet is a sensitive area of climatic changes.
The Qiuli’nanmu Lake is a dried saline lake in central Tibet with many thick mirabilite layers．Saline minerals are suggested to be products of dry and cold environment compared with clays．A detailed mineralogical investigation was carried out with mainly thick mirabilite and thin borax layer and thin clay layer alternately．The stratigraphic variation in the mineralogy of salt lake sediments is an indicator of paleoclimatic fluctuations．Based on the variations of mineralogy, pollen and carbonate，it is suggested that the climate was warm and wet in 27.820.5 ka BP，cold and dry in 20.511.4 ka BP，warm and wet 11.410.1ka B，cold and dry in 10.17.5 ka BP，warm but changed frequently in 7.54.97 ka BP．The Last Glacial Maximum may be appeared in 20.517.5 ka BP．The warm pluses were at 17.517.1 ka BP,15.915.2 ka BP and 14.113.4 ka BP．The “8.2 ka BP cold event” appeared at 8.17.9 ka BP．Borax，a mineral appeared in low temperature，steady and shallow brine water，suggested the same environment during 27.84.97 ka BP in Qiuli’nanmu lake．The changes of summer monsoon led to the climatic conditions in the area. This work gives a mineralogical evidence for the view that Tibet is a sensitive area of climatic changes.
2007, 25(4): 632-639.
Abstract:
The composition and distribution of normal alkane compound in sediments from some rivers with different environmental condition in Tianjin city, northern China, have been investigated. The composition and distribution of middlemolecular weight normal alkane in sediments in different rivers was emphasized in this paper. The origins of middlemolecular weight normal alkane in sediments have been analyzed based on the comparison of normal paraffin hydrocarbon composition among sediment, topsoil, dust fall and TSP. The result shows that the relative content of nC17 or nC19 has obvious predominance compared with other normal paraffin hydrocarbon compound in sediments from different rivers and dust fall. The stable carbon isotope value of nC17 is lower, which is different from the value of normal alkane in fossil fuel (such as oil and coal). The composition predominance of nC17 in topsoil and TSP is not occurrence. It is suggested that the nC17 or nC19 in these samples are derived from aquatic organism, such as algae, in water and surface sediments.
The composition and distribution of normal alkane compound in sediments from some rivers with different environmental condition in Tianjin city, northern China, have been investigated. The composition and distribution of middlemolecular weight normal alkane in sediments in different rivers was emphasized in this paper. The origins of middlemolecular weight normal alkane in sediments have been analyzed based on the comparison of normal paraffin hydrocarbon composition among sediment, topsoil, dust fall and TSP. The result shows that the relative content of nC17 or nC19 has obvious predominance compared with other normal paraffin hydrocarbon compound in sediments from different rivers and dust fall. The stable carbon isotope value of nC17 is lower, which is different from the value of normal alkane in fossil fuel (such as oil and coal). The composition predominance of nC17 in topsoil and TSP is not occurrence. It is suggested that the nC17 or nC19 in these samples are derived from aquatic organism, such as algae, in water and surface sediments.
2007, 25(4): 640-645.
Abstract:
Oil source of marine crude oils from Tarim Basin is still disputed; However, the research on the reservoir bitumen may provide a new evidence to elucidate oil source. Geochemical characteristics of different strata reservoir bitumen from Well Zhong1 in Katake uplift are discussed here in detail. Pr/Ph ratios of reservoir bitumens from Well Zhong 1 range from 1.14 to 1.39, CPI ratios from 1.01 to 1.08 which indicate no odd even predominance of normal alkanes, OEP ratios from 0.98 to 1.05. The content of gammacerane and C28 sterane of reservoir bitumens from Well Zhong 1 is low, while dibenzothiophene series are abundant. Sterane isomerization maturity parameter and Ts/Ts+Tm ratio indicate that the degree of maturity of reservoir bitumen from
Well Zhong1 is mature to high mature. Based on biomarker distribution difference, it is concluded that reservoir bitumen from Well Zhong1 of which molecular parameters are contrary to those in Cambrian oil from Well Tadong 2 originated from the upper Ordovician source rock.
Oil source of marine crude oils from Tarim Basin is still disputed; However, the research on the reservoir bitumen may provide a new evidence to elucidate oil source. Geochemical characteristics of different strata reservoir bitumen from Well Zhong1 in Katake uplift are discussed here in detail. Pr/Ph ratios of reservoir bitumens from Well Zhong 1 range from 1.14 to 1.39, CPI ratios from 1.01 to 1.08 which indicate no odd even predominance of normal alkanes, OEP ratios from 0.98 to 1.05. The content of gammacerane and C28 sterane of reservoir bitumens from Well Zhong 1 is low, while dibenzothiophene series are abundant. Sterane isomerization maturity parameter and Ts/Ts+Tm ratio indicate that the degree of maturity of reservoir bitumen from
Well Zhong1 is mature to high mature. Based on biomarker distribution difference, it is concluded that reservoir bitumen from Well Zhong1 of which molecular parameters are contrary to those in Cambrian oil from Well Tadong 2 originated from the upper Ordovician source rock.
2007, 25(4): 495-504.
Abstract:
Various processes operate deepwater environment and interplay in very complex way. Gravity (or gravity current) process may act in a variety of ways and systematic evolution may happen between them. Bottom currents (commonly refer as contour current) include those driven by thermocline circulation, those driven by wind, and tidal bottom current running up and down in canyons. Internal wave may be one important geological forces. In all such processes acting either isolate or jointly the type and genesis of sediment of deepwater environment is very complex, and own potential palaeoclimate information and hydrocarbon perspective.
Various processes operate deepwater environment and interplay in very complex way. Gravity (or gravity current) process may act in a variety of ways and systematic evolution may happen between them. Bottom currents (commonly refer as contour current) include those driven by thermocline circulation, those driven by wind, and tidal bottom current running up and down in canyons. Internal wave may be one important geological forces. In all such processes acting either isolate or jointly the type and genesis of sediment of deepwater environment is very complex, and own potential palaeoclimate information and hydrocarbon perspective.
2007, 25(4): 511-517.
Abstract:
Member 2 of Kongdian Formation（Ek2） has been changed by lots of faults, such as Cangdong fault and Xuxi fault, etc. It greatly changed the original basin framework. Black mudstone and oil shale appeared on the uplift, while, stratum rich in gritstone detected in the Sunken area, as the most important characters, become difficult to research. Based on the equitime stratigraphic contrast, and a comprehensive analysis of the thickness, lithofacies, sediment facies, structure and sediment system of Member 2 of Kongdian Formation, conclusions have been made that the lack basin was depress basin, simultaneously, Kongdian uplift belt existed in the center of the basin now was the center of the lack basin and depocenter during the deposition of the Member 2. These conclusions are significant for clearing the basin evolution, its origin, petroleum and natural gas exploration.
Member 2 of Kongdian Formation（Ek2） has been changed by lots of faults, such as Cangdong fault and Xuxi fault, etc. It greatly changed the original basin framework. Black mudstone and oil shale appeared on the uplift, while, stratum rich in gritstone detected in the Sunken area, as the most important characters, become difficult to research. Based on the equitime stratigraphic contrast, and a comprehensive analysis of the thickness, lithofacies, sediment facies, structure and sediment system of Member 2 of Kongdian Formation, conclusions have been made that the lack basin was depress basin, simultaneously, Kongdian uplift belt existed in the center of the basin now was the center of the lack basin and depocenter during the deposition of the Member 2. These conclusions are significant for clearing the basin evolution, its origin, petroleum and natural gas exploration.
2007, 25(4): 526-534.
Abstract:
Upper Paleozoic natural gas reservoir of Ordos Basin consists of lowpermeability sandstone which bears typical secondary porosity. After studying secondary porosity forming cause, it is turned out that there is some direct relation between formation of all kinds of dissolution porosity and dissolution and erosion of volcanic material. Based on the study of petrology, the observation of volcanic material composition, construction and structure, the state and secondary change, we can reach the conclusion that these volcanic materials has the characteristics of simultaneous sedimentation. Combing the formal achievements about simultaneous volcano eruptiverock on basin edge, there is causeeffect relation, which showing volcanic material of the sandstone comes from the simultaneous sedimentary volcanic eruption, which confirms that important geological events in Basinorogen coupling period have great influence on interbasin sedimentation. Not only the simultaneous volcanic material changes the composition of the sandstone, but also offers the dissolution matter for the formation of secondary porosity in these sandstones. The dissolution of volcanic material, with largely unsteady physical and chemical characteristics, led to the formation of dissolution porosity in crystalfragment, in rockfragment, and in ashfragment, as well as eroded kaolinite and chlorite intercrystal porosity in diagenetic period. Meanwhile, remnant, erosion of volcanic material and dissolution differences lead to the heterogeneous reservoir.
Upper Paleozoic natural gas reservoir of Ordos Basin consists of lowpermeability sandstone which bears typical secondary porosity. After studying secondary porosity forming cause, it is turned out that there is some direct relation between formation of all kinds of dissolution porosity and dissolution and erosion of volcanic material. Based on the study of petrology, the observation of volcanic material composition, construction and structure, the state and secondary change, we can reach the conclusion that these volcanic materials has the characteristics of simultaneous sedimentation. Combing the formal achievements about simultaneous volcano eruptiverock on basin edge, there is causeeffect relation, which showing volcanic material of the sandstone comes from the simultaneous sedimentary volcanic eruption, which confirms that important geological events in Basinorogen coupling period have great influence on interbasin sedimentation. Not only the simultaneous volcanic material changes the composition of the sandstone, but also offers the dissolution matter for the formation of secondary porosity in these sandstones. The dissolution of volcanic material, with largely unsteady physical and chemical characteristics, led to the formation of dissolution porosity in crystalfragment, in rockfragment, and in ashfragment, as well as eroded kaolinite and chlorite intercrystal porosity in diagenetic period. Meanwhile, remnant, erosion of volcanic material and dissolution differences lead to the heterogeneous reservoir.
2007, 25(4): 554-563.
Abstract:
Seismic facies of Paleogene in LiaoDong Bay are divided and named mainly based on the reliable internal reflection texture and external shape of the seismic sequence unit. Amplitude, continuity and other seismic parameters are also used in the description of seismic sequence units. In the study area, six seismic sequences are divided and more than seven seismic facies are identified, including parallelsubparallel matshaped, foreset, wedge shaped, filling, lenticular, moundy and hummocky seismic facies, which show differentiation in spatial distribution and hereditability in vertical evolution. The sedimentary facies in the lake environment, including semideepdeep lake subfacies, shallow lake and shore subfacies, fandelta, subaqueous alluvial fan, delta, turbidite, etc. The favorable areas are identified.
Seismic facies of Paleogene in LiaoDong Bay are divided and named mainly based on the reliable internal reflection texture and external shape of the seismic sequence unit. Amplitude, continuity and other seismic parameters are also used in the description of seismic sequence units. In the study area, six seismic sequences are divided and more than seven seismic facies are identified, including parallelsubparallel matshaped, foreset, wedge shaped, filling, lenticular, moundy and hummocky seismic facies, which show differentiation in spatial distribution and hereditability in vertical evolution. The sedimentary facies in the lake environment, including semideepdeep lake subfacies, shallow lake and shore subfacies, fandelta, subaqueous alluvial fan, delta, turbidite, etc. The favorable areas are identified.
2007, 25(4): 583-588.
Abstract:
Numerous iron spherules have been found from coarse sandstone in the bottom of the Changzhougou Formation (1.8Ga) and silicified carbonate rock of the Dahongyu Formation (1.6Ga) of Proterozoic strata of the Ming Tombs District, Beijing. Most of them are round shaped as rod. Surface of iron cosmic spherules are observed by secondary back scanned image without carbon coating showing matallogenic graphs and “gas escape” holes so common during intro\|atmosphere melted and crystallized again. 44 testing points of 30 iron cosmic spherules have been measured by means of electron probe analysis average data as follows(%): FeO 8095; Cr2O3 0.786.56; NiO 0.060.41. Relatively, Cr2O3 is higher in spherules of the Changzhougou Formation but FeO higher in the Dahongyu Formation. However, the helium isotope analysis data are quite different between them. The abnormal of helium isotope made sure of extraterrestrial origin of iron cosmic spherules.
Numerous iron spherules have been found from coarse sandstone in the bottom of the Changzhougou Formation (1.8Ga) and silicified carbonate rock of the Dahongyu Formation (1.6Ga) of Proterozoic strata of the Ming Tombs District, Beijing. Most of them are round shaped as rod. Surface of iron cosmic spherules are observed by secondary back scanned image without carbon coating showing matallogenic graphs and “gas escape” holes so common during intro\|atmosphere melted and crystallized again. 44 testing points of 30 iron cosmic spherules have been measured by means of electron probe analysis average data as follows(%): FeO 8095; Cr2O3 0.786.56; NiO 0.060.41. Relatively, Cr2O3 is higher in spherules of the Changzhougou Formation but FeO higher in the Dahongyu Formation. However, the helium isotope analysis data are quite different between them. The abnormal of helium isotope made sure of extraterrestrial origin of iron cosmic spherules.
2007, 25(4): 597-602.
Abstract:
On the basis of analysis of 116 samples in grain size from high valley flat section in Xianyang and historical book material of Weihe migration time, we knew that the delamination of 120 years' flood deposition of Weihe River is obvious and can be regarded as an indicator of flood and change. The XY profile indicated that there are 16 flood deposition stages, including the top major flood deposition layer formed in 2003 and the other 15 flood deposition layers formed in the ancient flood stages. There is a obvious variety rhythm of granularity along with the depth in the XY. The granularity in the 1st,3rd,5th,7th,9th,11th,13th and 15th layer was thinner than the 2nd,4th,6th,8th,10th,12th,14th and 16th layer in the XY profiles. After thinking over the effect of the heightening landform caused by the accumulating deposition thickness on grain size composition, the order of flood depth and the flood scale of these 16 flood stages was: 12th >15th >6th >9th >16th >1st >5th >14th
>7th >11th >3rd >13th >8th >10th >4th >2nd>. The 12th,15th,6th,9th,16th and 1st were the catastrophic flood stages and the 5th,14th,7th,11th,3rd,13th,8th,10th,4th and 2nd were the big flood stages. The origin of the flood was obviously increased of annual rainfall at the year in some areas in the Weihe basin. The stages in which no flood occurred in high valley flat were of normal rainfall or less rainfall.
On the basis of analysis of 116 samples in grain size from high valley flat section in Xianyang and historical book material of Weihe migration time, we knew that the delamination of 120 years' flood deposition of Weihe River is obvious and can be regarded as an indicator of flood and change. The XY profile indicated that there are 16 flood deposition stages, including the top major flood deposition layer formed in 2003 and the other 15 flood deposition layers formed in the ancient flood stages. There is a obvious variety rhythm of granularity along with the depth in the XY. The granularity in the 1st,3rd,5th,7th,9th,11th,13th and 15th layer was thinner than the 2nd,4th,6th,8th,10th,12th,14th and 16th layer in the XY profiles. After thinking over the effect of the heightening landform caused by the accumulating deposition thickness on grain size composition, the order of flood depth and the flood scale of these 16 flood stages was: 12th >15th >6th >9th >16th >1st >5th >14th
>7th >11th >3rd >13th >8th >10th >4th >2nd>. The 12th,15th,6th,9th,16th and 1st were the catastrophic flood stages and the 5th,14th,7th,11th,3rd,13th,8th,10th,4th and 2nd were the big flood stages. The origin of the flood was obviously increased of annual rainfall at the year in some areas in the Weihe basin. The stages in which no flood occurred in high valley flat were of normal rainfall or less rainfall.
2007, 25(4): 574-582.
Abstract:
Inorganic carbon dioxide and petroleum dual infilling occurred in Wuerxun Depression, Hailaer Basin. Paragenetic sequence of dawsonitebearing sandstone is ascertained and time frame of inorganic carbon dioxide and petroleum is founded through polarizing microscope identification, scanning electron microscope observation, KAr ages measuring of illite and UPb ages testing of magmatite. PreCO2 minerals are mostly quartz overgrowth and kaolinite. Petroleum began to charge during quartz overgrowth growing. As a continuous process, petroleum infilling began from 120 Ma, reached climax during 90\|105 Ma and went on till 63 Ma or later. CO2 infilling, 90 Ma foremost with great difference to magmatic ages such as granite and rhyolite, was later than the time when petroleum charged in large scale. Most of zircon grains from lamprophyre have 206Pb/238U weighted average ages of 46.2±2.1 Ma, representing the time of lamprophyre forming. According to the fact that dawsonite and ankerite are the authigenic minerals forming at latest in sandstone, CO2 infilling was relatively late, possibly 46.2±2.1 Ma or later. The dawsonitebearing sandstone preserved the evidence of oil displaced by CO2.
Inorganic carbon dioxide and petroleum dual infilling occurred in Wuerxun Depression, Hailaer Basin. Paragenetic sequence of dawsonitebearing sandstone is ascertained and time frame of inorganic carbon dioxide and petroleum is founded through polarizing microscope identification, scanning electron microscope observation, KAr ages measuring of illite and UPb ages testing of magmatite. PreCO2 minerals are mostly quartz overgrowth and kaolinite. Petroleum began to charge during quartz overgrowth growing. As a continuous process, petroleum infilling began from 120 Ma, reached climax during 90\|105 Ma and went on till 63 Ma or later. CO2 infilling, 90 Ma foremost with great difference to magmatic ages such as granite and rhyolite, was later than the time when petroleum charged in large scale. Most of zircon grains from lamprophyre have 206Pb/238U weighted average ages of 46.2±2.1 Ma, representing the time of lamprophyre forming. According to the fact that dawsonite and ankerite are the authigenic minerals forming at latest in sandstone, CO2 infilling was relatively late, possibly 46.2±2.1 Ma or later. The dawsonitebearing sandstone preserved the evidence of oil displaced by CO2.
2007, 25(4): 612-618.
Abstract:
The speciation of Cu, Pb, Zn and Cd in sediments and the concentrations of Cu, Pb, Zn and Cd in overlying water, filtered water and pore water of the Nanhai Lake ,which is an abandoned channel of the Yellow River, are analyzed in this paper accompanied with the data of AVS (AcidVolatile Sulfide) and SEM (Simultaneous Extract Metals) in sediments. The data are compared with those of the Yellow River due to the same origin of sediments between the Nanhai Lake and the Yellow River. The investigation was made for the movement and transformation law of heavy metal in solidliquid two phase system. The results show that heavy metals concentration in residual fraction in Nanhai Lake is close to which in the Yellow River. Over 81.1% selected heavy metals are in suspended form in overlying water of the Nanhai Lake and the Yellow River. The high concentration of copper in Nanhai Lake's overly water is released from the sediments. The pore water functions as a pathway for heavy metal mobilization from sediments to water phase. The AVS is the controlling factor on heavy metal precipitation; whereas, the organic complexing agent is the key factor on mobilization of Cu from sediments to water.
The speciation of Cu, Pb, Zn and Cd in sediments and the concentrations of Cu, Pb, Zn and Cd in overlying water, filtered water and pore water of the Nanhai Lake ,which is an abandoned channel of the Yellow River, are analyzed in this paper accompanied with the data of AVS (AcidVolatile Sulfide) and SEM (Simultaneous Extract Metals) in sediments. The data are compared with those of the Yellow River due to the same origin of sediments between the Nanhai Lake and the Yellow River. The investigation was made for the movement and transformation law of heavy metal in solidliquid two phase system. The results show that heavy metals concentration in residual fraction in Nanhai Lake is close to which in the Yellow River. Over 81.1% selected heavy metals are in suspended form in overlying water of the Nanhai Lake and the Yellow River. The high concentration of copper in Nanhai Lake's overly water is released from the sediments. The pore water functions as a pathway for heavy metal mobilization from sediments to water phase. The AVS is the controlling factor on heavy metal precipitation; whereas, the organic complexing agent is the key factor on mobilization of Cu from sediments to water.
2007, 25(4): 626-631.
Abstract:
Lacustrine sediment samples from QTL01 section of Qingtu lake in NW Tengger Desert, pretreated by removing the organic matter and carbonate, are measured by Malvern 2000. Standard deviations are calculated for samples from the depth of 214~560cm of QTL01 section, and grain size components sensitive to environment are obtained. The result from our study suggests that the content of 60~550 m component is sensitive to local eolian activity and the content variation of <60 m component indicates the changes of river discharges drained into the lake. Based on the grain size analysis and 14C dating, we reconstructed the variations of eolian activity and environment of the studied area during 10~2.5Cal kaBP: From 10 to 7.8Cal kaBP, gradually decreasing eolian activity indicated the area was becoming humid during the early Holocene; From 7.8 to 7.5Cal kaBP, very intense eolian activity suggested a regional dry event; From 7.5 to 5Cal kaBP, weak eolian activity indicated a very humid environment; From 5 to 2.5 Cal kaBP, the gradually weaker eolian activity showed a trend toward aridity in the study area.
Lacustrine sediment samples from QTL01 section of Qingtu lake in NW Tengger Desert, pretreated by removing the organic matter and carbonate, are measured by Malvern 2000. Standard deviations are calculated for samples from the depth of 214~560cm of QTL01 section, and grain size components sensitive to environment are obtained. The result from our study suggests that the content of 60~550 m component is sensitive to local eolian activity and the content variation of <60 m component indicates the changes of river discharges drained into the lake. Based on the grain size analysis and 14C dating, we reconstructed the variations of eolian activity and environment of the studied area during 10~2.5Cal kaBP: From 10 to 7.8Cal kaBP, gradually decreasing eolian activity indicated the area was becoming humid during the early Holocene; From 7.8 to 7.5Cal kaBP, very intense eolian activity suggested a regional dry event; From 7.5 to 5Cal kaBP, weak eolian activity indicated a very humid environment; From 5 to 2.5 Cal kaBP, the gradually weaker eolian activity showed a trend toward aridity in the study area.
2007, 25(4): 646-652.
Abstract:
Various biomarkers in some typical oils from different sags, Beibuwan Basin, have been analyzed, in this paper. The results show that the crude oils from Weixinan Sag and Wushi Sag in the northern basin have relatively lower Pr/Ph ratio, low abundance of oleanane and various rearranged configuration biomarkers, but higher abundance of C26+ long chain tricyclic terpanes with normal pattern in C23 highest peak and C30 4methyl steranes, indicating that their source rocks were deposited under relatively deep and reduced environment with significant algae input. Bun for the crude oils from Fushan Sag and Maichen Sag in the southern basin, it is characteristic of relatively higher Pr/Ph ratio, higher abundance of oleanane and various rearranged configuration biomarkers, but lower abundance of C26+ long chain tricyclic terpanes with steplike decreasing pattern of C19—C26 and C30 4methyl steranes, showing that their source rocks were deposited under relatively shallow and oxidized environment with significant organic matter input from angiosperms. It implies that for northern sags and southern sags in Beibuwan Basin, there are some obvious differences in the depositional environment and organic matter input.
Various biomarkers in some typical oils from different sags, Beibuwan Basin, have been analyzed, in this paper. The results show that the crude oils from Weixinan Sag and Wushi Sag in the northern basin have relatively lower Pr/Ph ratio, low abundance of oleanane and various rearranged configuration biomarkers, but higher abundance of C26+ long chain tricyclic terpanes with normal pattern in C23 highest peak and C30 4methyl steranes, indicating that their source rocks were deposited under relatively deep and reduced environment with significant algae input. Bun for the crude oils from Fushan Sag and Maichen Sag in the southern basin, it is characteristic of relatively higher Pr/Ph ratio, higher abundance of oleanane and various rearranged configuration biomarkers, but lower abundance of C26+ long chain tricyclic terpanes with steplike decreasing pattern of C19—C26 and C30 4methyl steranes, showing that their source rocks were deposited under relatively shallow and oxidized environment with significant organic matter input from angiosperms. It implies that for northern sags and southern sags in Beibuwan Basin, there are some obvious differences in the depositional environment and organic matter input.
