2007 Vol. 25, No. 3
Display Method:
2007, 25(3): 325-331.
Abstract:
There are many sedimentary facies, which are alluvial fans, terminal fans, fandelta, braideddelta, meanderingdelta, lacustrine facies,lagoon and beach facies，in Cretaceous and Paleogene, Kuche DepressionTabei area, northern Tarim Basin. The lithology assemblages and sedimentary facies are different in north and south zone, also in the east, middle and west segmentation. The north zones are made up of coarse clastics, which are mainly fandelta. The south zones are composed of middle and fine clastics,which are mainly braideddelta. The differences are controlled by palaeostructure, palaeotopographical gradient, palaeoclimate and the distance to provenance.
There are many sedimentary facies, which are alluvial fans, terminal fans, fandelta, braideddelta, meanderingdelta, lacustrine facies,lagoon and beach facies，in Cretaceous and Paleogene, Kuche DepressionTabei area, northern Tarim Basin. The lithology assemblages and sedimentary facies are different in north and south zone, also in the east, middle and west segmentation. The north zones are made up of coarse clastics, which are mainly fandelta. The south zones are composed of middle and fine clastics,which are mainly braideddelta. The differences are controlled by palaeostructure, palaeotopographical gradient, palaeoclimate and the distance to provenance.
2007, 25(3): 343-350.
Abstract:
Mixed deposits, which is composed of terrigenous fragment and carbonate of lagoonal facies, develops extensively in the middle submember of Member 1 of Shahejie Formation of Shanghe Area. This paper definite mixed deposited which includes Hunji sequence, Hunji rock and some sporadic distribution, and as far as mixed deposits in a broad sense, and there is not a concrete standard range, if only it is for the reason the sediment or sedimentary rock deposits to terrigenous fragment and carbonate not for false mixed to sedimentation or transformation of sedimentation, it can be deeply convinced to be mixed deposits. In the study area, the characteristics of mixed deposits are interbedded strata between terrigenous fragment and carbonate of lagoonal facies in high frequency and mixing deposited between terrigenous fragment constituent and carbonate constituent in one layer. Mixed sedimentary type can be divided into 3 categories, blended mixed deposits, salutatory mixed deposits and complex mixed deposits, and the complex mixed deposits can be divided into complex mixed depositsⅠand complex mixed depositsⅡ.In the study area, complex mixed depositsⅠis developing and complex mixed depositsⅡ is not developing. This paper analyses the mixed deposits of study area carefully, such as geological setting, petrological characteristic and depositional environment, etcl, establishes mixed sedimentaary model and discusses controlling factor of the mixed deposits.
Mixed deposits, which is composed of terrigenous fragment and carbonate of lagoonal facies, develops extensively in the middle submember of Member 1 of Shahejie Formation of Shanghe Area. This paper definite mixed deposited which includes Hunji sequence, Hunji rock and some sporadic distribution, and as far as mixed deposits in a broad sense, and there is not a concrete standard range, if only it is for the reason the sediment or sedimentary rock deposits to terrigenous fragment and carbonate not for false mixed to sedimentation or transformation of sedimentation, it can be deeply convinced to be mixed deposits. In the study area, the characteristics of mixed deposits are interbedded strata between terrigenous fragment and carbonate of lagoonal facies in high frequency and mixing deposited between terrigenous fragment constituent and carbonate constituent in one layer. Mixed sedimentary type can be divided into 3 categories, blended mixed deposits, salutatory mixed deposits and complex mixed deposits, and the complex mixed deposits can be divided into complex mixed depositsⅠand complex mixed depositsⅡ.In the study area, complex mixed depositsⅠis developing and complex mixed depositsⅡ is not developing. This paper analyses the mixed deposits of study area carefully, such as geological setting, petrological characteristic and depositional environment, etcl, establishes mixed sedimentaary model and discusses controlling factor of the mixed deposits.
2007, 25(3): 358-364.
Abstract:
Asphalt filling into pore of interparticle and matrix reduced pore space while decreased porosity and permeability during transformation of crude oil into asphalt in Silurian reservoir sandstone in Tazhong area. Impact on reservoir quality of oil/gas filling into reservoir of asphalt sandstones has been studied by means of laboratory simulation. Sandstone with fewer asphalt and lower porosity and permeability at early stage of oil/gas infilling is nonreservoir and oil/gas can not fill in. Sandstone, whose porosity and permeability could be increased at late stage of oil/gas filling when oil with lower viscosity filled into, was effective oil/gas reservoir when more and uniform asphalt filling as well as the low porosity and permeability at early stage of oil/gas infilling. Sandstone, with uniform asphalt filling as well as higher remained porosity at early stage of oil/gas infilling, whose porosity and permeability could be improved as oil with various viscosity filled into. Simulations under laboratory temperature indicate that physical property of crude oil is the key factor for influence of ability of oil/gas refilling into asphalt sandstones. Filling of oil with low viscosity is essential for oil accumulation in Silurian asphalt sandstones.
Asphalt filling into pore of interparticle and matrix reduced pore space while decreased porosity and permeability during transformation of crude oil into asphalt in Silurian reservoir sandstone in Tazhong area. Impact on reservoir quality of oil/gas filling into reservoir of asphalt sandstones has been studied by means of laboratory simulation. Sandstone with fewer asphalt and lower porosity and permeability at early stage of oil/gas infilling is nonreservoir and oil/gas can not fill in. Sandstone, whose porosity and permeability could be increased at late stage of oil/gas filling when oil with lower viscosity filled into, was effective oil/gas reservoir when more and uniform asphalt filling as well as the low porosity and permeability at early stage of oil/gas infilling. Sandstone, with uniform asphalt filling as well as higher remained porosity at early stage of oil/gas infilling, whose porosity and permeability could be improved as oil with various viscosity filled into. Simulations under laboratory temperature indicate that physical property of crude oil is the key factor for influence of ability of oil/gas refilling into asphalt sandstones. Filling of oil with low viscosity is essential for oil accumulation in Silurian asphalt sandstones.
2007, 25(3): 372-379.
Abstract:
Abundant trace fossils are preserved in the alternation of purple and yellow greenish sandstones and mudstones which are formed in littoral and very shallow lake environments in the lower part of Middle Triassic Youfangzhuang Formation, Jiyuan Region, western Henan Province. Six ichnofabrics are found in highenergy zone of lake margin sandstones, they include: Porphyritic bioturbation ichnofabric, Skolithos isp.Planolites montanus ichnofabric,Skolithos verticalis ichnofabric, Planolites beverleyensis ichnofabric,Skolithos isp. Ichnofabric and Palaeophycus annulatus ichnofabric，and can be assigned to Skolithos ichnofacies；three ichnofabrics of Skolithos linearis ichnofabric、Taenidium barrette ichnofabric and rizoliths ichnofabric are recognized from middle and lower energy zone of very shallow lacustrine siltstones and mudstones, they belong to Scoyenia ichnofacies.
Abundant trace fossils are preserved in the alternation of purple and yellow greenish sandstones and mudstones which are formed in littoral and very shallow lake environments in the lower part of Middle Triassic Youfangzhuang Formation, Jiyuan Region, western Henan Province. Six ichnofabrics are found in highenergy zone of lake margin sandstones, they include: Porphyritic bioturbation ichnofabric, Skolithos isp.Planolites montanus ichnofabric,Skolithos verticalis ichnofabric, Planolites beverleyensis ichnofabric,Skolithos isp. Ichnofabric and Palaeophycus annulatus ichnofabric，and can be assigned to Skolithos ichnofacies；three ichnofabrics of Skolithos linearis ichnofabric、Taenidium barrette ichnofabric and rizoliths ichnofabric are recognized from middle and lower energy zone of very shallow lacustrine siltstones and mudstones, they belong to Scoyenia ichnofacies.
2007, 25(3): 386-391.
Abstract:
Banqiao Sag is the halfgraben rift sag. The steep slop belt developed in the northwest side of Banqiao Sag. The article analyzed the sequence patterns and the characteristics of the firstmember of Shahejie Formation in the area of the fault steep slope belt. The scale of the highstand delta front is smaller than the lowstand delta front, but the incise valley and the river deposition developed in the time of the lowstand. The steep slop belt controlled the distribution of the sand bodies, which developed along the direction of the fault and paralleled the steep belt. The steep slop belt also controlled the growth of the good source rocks. So the sand bodies, the good source rocks and the controlling faults together controlled the development and distribution of reservoirs. According to the results, the article sum up the sequence patterns and the characteristics of depositional systems, at last built the model of the reservoirs in the fault steep slope belt.
Banqiao Sag is the halfgraben rift sag. The steep slop belt developed in the northwest side of Banqiao Sag. The article analyzed the sequence patterns and the characteristics of the firstmember of Shahejie Formation in the area of the fault steep slope belt. The scale of the highstand delta front is smaller than the lowstand delta front, but the incise valley and the river deposition developed in the time of the lowstand. The steep slop belt controlled the distribution of the sand bodies, which developed along the direction of the fault and paralleled the steep belt. The steep slop belt also controlled the growth of the good source rocks. So the sand bodies, the good source rocks and the controlling faults together controlled the development and distribution of reservoirs. According to the results, the article sum up the sequence patterns and the characteristics of depositional systems, at last built the model of the reservoirs in the fault steep slope belt.
2007, 25(3): 401-408.
Abstract:
Silurian in Tarim Basin，bounded at the top and base by widely spread regional unconformities，can be divided into 1 secondorder sequence and 5 thirdorder sequences. Three kinds of depositional system assemblages，which represent lowstand systems tract，transgressive systems tract，and highstand systems of the secondorder sequence，are identified in Silurian of Tarim Basin, namely, assemblage of meandering river delta and braided river delta depositional systems，assemblage of offshore and slightly deepwater basin depositional systems, and assemblage of clastic coastal depositional system with no barriers and clastic tidal depositional system with no barriers. Based on the integrated analysis of data of tectonics，sedimentology，palaeontology and palaeoclimatology，the base boundary of sequence 1 and top boundary of sequence 5 are thought to be originated from the pressure of peripheral plates and uplift of basin base. The bottom boundary of sequence 2 belongs to tectonically compressed unconformity that originates from the pressure of plates and decline of basin base. The bottom boundary of sequence 3, sequence 4 and sequence 5 results from integrated effect of change of climate, sediment source and tectonic activity under falling global eustacy.
Silurian in Tarim Basin，bounded at the top and base by widely spread regional unconformities，can be divided into 1 secondorder sequence and 5 thirdorder sequences. Three kinds of depositional system assemblages，which represent lowstand systems tract，transgressive systems tract，and highstand systems of the secondorder sequence，are identified in Silurian of Tarim Basin, namely, assemblage of meandering river delta and braided river delta depositional systems，assemblage of offshore and slightly deepwater basin depositional systems, and assemblage of clastic coastal depositional system with no barriers and clastic tidal depositional system with no barriers. Based on the integrated analysis of data of tectonics，sedimentology，palaeontology and palaeoclimatology，the base boundary of sequence 1 and top boundary of sequence 5 are thought to be originated from the pressure of peripheral plates and uplift of basin base. The bottom boundary of sequence 2 belongs to tectonically compressed unconformity that originates from the pressure of plates and decline of basin base. The bottom boundary of sequence 3, sequence 4 and sequence 5 results from integrated effect of change of climate, sediment source and tectonic activity under falling global eustacy.
2007, 25(3): 409-416.
Abstract:
The late Cenozoic stratigraphy is widely distributed in the Linxia Basin in the southeastern part of the Tibetan Plateau, China. Especially in 13~4.34 Ma, the Lacustrine sediments are mainly stably fine grain with low energy, the different time scales and sorts of sediment rhythms in this era record much paleoclimatic changes. On basis of research of the element geochemistry of these stably fine lacustrine sediments and sediment rhythmic series in the Linxia Basin, we find four stages of the paleoclimatic evolution throughout the whole time in this basin. Firstly, it is relatively humid at beginning during 13~12 Ma, and then it is still humid with some very short dryevents in the period of 12~7.8 Ma. It turns relatively drier than before in 7.8~6.2 Ma, and at last it becomes drier and drier with high frequency climate oscillations since 6.2 Ma. The climatic reforming in 7.8 Ma is thought as the possible result of the strength of the winter monsoon, and the regulated climatic changes since 6.2 Ma maybe relate to the modern monsoon.
The late Cenozoic stratigraphy is widely distributed in the Linxia Basin in the southeastern part of the Tibetan Plateau, China. Especially in 13~4.34 Ma, the Lacustrine sediments are mainly stably fine grain with low energy, the different time scales and sorts of sediment rhythms in this era record much paleoclimatic changes. On basis of research of the element geochemistry of these stably fine lacustrine sediments and sediment rhythmic series in the Linxia Basin, we find four stages of the paleoclimatic evolution throughout the whole time in this basin. Firstly, it is relatively humid at beginning during 13~12 Ma, and then it is still humid with some very short dryevents in the period of 12~7.8 Ma. It turns relatively drier than before in 7.8~6.2 Ma, and at last it becomes drier and drier with high frequency climate oscillations since 6.2 Ma. The climatic reforming in 7.8 Ma is thought as the possible result of the strength of the winter monsoon, and the regulated climatic changes since 6.2 Ma maybe relate to the modern monsoon.
2007, 25(3): 424-428.
Abstract:
The bottom yellowgrey soilsilt deposits layer at Dingshan sand dune profile originated from the regional dustfall accumulation in the late interstadial of the Last Glacial( 4022 ka BP). Thus the yellowgrey soilsilt had the same origin but had different facis deposits, grain combination are the same and have not characteristic differences; All curves of frequency have character of two apices, the first apex is main and cell value is 832 μm, the second apex is subordinate and cell value is 250500 μm. Cell value of 9.75±0.25Φ~4.25±0.25Φ(1~62.5 μm) have the similar linear change at vertical and compose the first kurtosis, the content changes at different grain vertical is sensitive index on strong and weak changes of winter monsoon; 2.25±0.25Φ~-0.75±0.25Φ (180~2000 μm) have the similar linear change and compose the second kurtosis, the content changes at different grain profiles indicate dry and wet situation at the circumstance of the winter climate and regional dust storm events. At the weak stage of regional dustfall accumulation it had strongly regional dust storm events, indicating that it was dry at local places in the winter.
The bottom yellowgrey soilsilt deposits layer at Dingshan sand dune profile originated from the regional dustfall accumulation in the late interstadial of the Last Glacial( 4022 ka BP). Thus the yellowgrey soilsilt had the same origin but had different facis deposits, grain combination are the same and have not characteristic differences; All curves of frequency have character of two apices, the first apex is main and cell value is 832 μm, the second apex is subordinate and cell value is 250500 μm. Cell value of 9.75±0.25Φ~4.25±0.25Φ(1~62.5 μm) have the similar linear change at vertical and compose the first kurtosis, the content changes at different grain vertical is sensitive index on strong and weak changes of winter monsoon; 2.25±0.25Φ~-0.75±0.25Φ (180~2000 μm) have the similar linear change and compose the second kurtosis, the content changes at different grain profiles indicate dry and wet situation at the circumstance of the winter climate and regional dust storm events. At the weak stage of regional dustfall accumulation it had strongly regional dust storm events, indicating that it was dry at local places in the winter.
2007, 25(3): 437-444.
Abstract:
The analysis of magnetic fabric of the Malan loess, the fifth layer of paleosol which is wellknown for its intensity of weathering and pedogenesis, red clay and matrix indicates that the magnetic fabric parameters P, F of Neogene Red Clay are between Malan loessthe fifth layer of paleosol and matrix with the overlapping boundary as the equation "F=1.01". The average value of L is equal to that of the eolian loess while the average value of Q, which is similar to that of the eolian Malan loess from the aspect of event deposition, approximately corresponds with that of the matrix red clay of hydraulic genesis and is in the transition area when it is in the assembled diagram of magnetic fabric parameters. All above show that the red clay deposits have the similar characters of magnetic fabric values resembling those of eolian deposits without experiencing transportation and also the features of shrouding rock of the fossils undergoing the hydraulic reconstruction thus the conclusion can be reached that red clay is the product of the primary aeolian particles which go through the postdepositional hydraulic process.
The analysis of magnetic fabric of the Malan loess, the fifth layer of paleosol which is wellknown for its intensity of weathering and pedogenesis, red clay and matrix indicates that the magnetic fabric parameters P, F of Neogene Red Clay are between Malan loessthe fifth layer of paleosol and matrix with the overlapping boundary as the equation "F=1.01". The average value of L is equal to that of the eolian loess while the average value of Q, which is similar to that of the eolian Malan loess from the aspect of event deposition, approximately corresponds with that of the matrix red clay of hydraulic genesis and is in the transition area when it is in the assembled diagram of magnetic fabric parameters. All above show that the red clay deposits have the similar characters of magnetic fabric values resembling those of eolian deposits without experiencing transportation and also the features of shrouding rock of the fossils undergoing the hydraulic reconstruction thus the conclusion can be reached that red clay is the product of the primary aeolian particles which go through the postdepositional hydraulic process.
2007, 25(3): 456-460.
Abstract:
Distribution of the content of heavy metals in marine sediment in Sansha Bay was analyzed according to the investigation data in 2004, its ecological harm was evaluated with the index method of potential ecological harm. The result showed that the ecological harm of heavy metals was slightly,except the serious pollution of Hg and Cd.Investigation on microelement in surface sediment in Sansha Bay was conducted, too.
Comparison of these results with those from other sea area at home and abroad was made in this paper. The mean values of microelement Fe2O3, Ni and Mn in surface sediment from Sansha Bay were higher than that from continental shelf of northern south china sea, of which the major factor was that metal ores was eroded by rainstorm and variety of microelements was carried into marine surface sediment by river runoff.
In addition, Al2O3 had significant correlation with Fe2O3. The correlation between Al2O3 and Co, Al2O3 and Ni were also significant, showing distinctive geochemistry.
Distribution of the content of heavy metals in marine sediment in Sansha Bay was analyzed according to the investigation data in 2004, its ecological harm was evaluated with the index method of potential ecological harm. The result showed that the ecological harm of heavy metals was slightly,except the serious pollution of Hg and Cd.Investigation on microelement in surface sediment in Sansha Bay was conducted, too.
Comparison of these results with those from other sea area at home and abroad was made in this paper. The mean values of microelement Fe2O3, Ni and Mn in surface sediment from Sansha Bay were higher than that from continental shelf of northern south china sea, of which the major factor was that metal ores was eroded by rainstorm and variety of microelements was carried into marine surface sediment by river runoff.
In addition, Al2O3 had significant correlation with Fe2O3. The correlation between Al2O3 and Co, Al2O3 and Ni were also significant, showing distinctive geochemistry.
2007, 25(3): 461-466.
Abstract:
The geological background of finding the Qingxi oil field in the Qingxi petroleum generation sag of Jiuxi Depression are analyzed, the formation and distribution regularity of the Kulongshan and Liugouzhuang oil reservoirs and it's control factor are researched. On the basis of this study, the thesis raised a new viewpoint that the Kulongshan and Liugouzhuang oil reservoirs of the Qingxi oil field should be the source rock fractured reservoir. At the same time, the specially geological condition of the source rock fractured reservoir's formation and it's research value are demonstrated. The specific significance of the source rock fractured reservoir is that the oil reservoir may be found in the source rock, it's finding and an exhaustive research will extend the oilgas exploring area and enrich the petroleum geology theory. It is a new research task which has great scientific significance and practical value.
The geological background of finding the Qingxi oil field in the Qingxi petroleum generation sag of Jiuxi Depression are analyzed, the formation and distribution regularity of the Kulongshan and Liugouzhuang oil reservoirs and it's control factor are researched. On the basis of this study, the thesis raised a new viewpoint that the Kulongshan and Liugouzhuang oil reservoirs of the Qingxi oil field should be the source rock fractured reservoir. At the same time, the specially geological condition of the source rock fractured reservoir's formation and it's research value are demonstrated. The specific significance of the source rock fractured reservoir is that the oil reservoir may be found in the source rock, it's finding and an exhaustive research will extend the oilgas exploring area and enrich the petroleum geology theory. It is a new research task which has great scientific significance and practical value.
2007, 25(3): 474-481.
Abstract:
The oil and source rocks correlation shows that the crude oil in this region can be classified into three types. Sources of oil in different horizons vary greatly, the first type crude oil which distributed in the deep reservoirs(Ek2-4１) in Kongdian Formation and Wanggu 1 well's Ordovician buried hill reservoirs in the north of Wangjiagang area, and the oil was mainly generated by the source rocks of Kongdian Formation(Ek); the second type oil has geochemiacal features of both the 4th member of Shahejie Formation(Es4) and Ek source rocks in Niuzhuang sag, it was mainly accumulated in the shallow reservoirs(Ek1,2１) in Kongdian Formation, and the third type oil which mainly sourced from the upper Es4 source rocks, always accumulated in the reservoirs of Shahejie Formation .According to the analysis of reservoirforming conditions, it can be seen that the Dingjiawuzi tectonic belt was of good hydrocarbon source conditions; Faults sandbodies and unconformities which formed the complex solid network paths. The reservoirs of sandstones and unconformities were the main pathway of oil and gas lateral migration, faults played diverting, gathering and connecting role. Dingjiawuzi nose-structural belt geological setting, the favorable combination of hydrocarbon generation, migration, accumulation periods and movement stage of faults and the essential seal of faults are the critical factors for the Kongdian Formation hydrocarbon accumulation in Wangjiagang area.
The oil and source rocks correlation shows that the crude oil in this region can be classified into three types. Sources of oil in different horizons vary greatly, the first type crude oil which distributed in the deep reservoirs(Ek2-4１) in Kongdian Formation and Wanggu 1 well's Ordovician buried hill reservoirs in the north of Wangjiagang area, and the oil was mainly generated by the source rocks of Kongdian Formation(Ek); the second type oil has geochemiacal features of both the 4th member of Shahejie Formation(Es4) and Ek source rocks in Niuzhuang sag, it was mainly accumulated in the shallow reservoirs(Ek1,2１) in Kongdian Formation, and the third type oil which mainly sourced from the upper Es4 source rocks, always accumulated in the reservoirs of Shahejie Formation .According to the analysis of reservoirforming conditions, it can be seen that the Dingjiawuzi tectonic belt was of good hydrocarbon source conditions; Faults sandbodies and unconformities which formed the complex solid network paths. The reservoirs of sandstones and unconformities were the main pathway of oil and gas lateral migration, faults played diverting, gathering and connecting role. Dingjiawuzi nose-structural belt geological setting, the favorable combination of hydrocarbon generation, migration, accumulation periods and movement stage of faults and the essential seal of faults are the critical factors for the Kongdian Formation hydrocarbon accumulation in Wangjiagang area.
2007, 25(3): 332-342.
Abstract:
Tongren area of Qinghai province is located on the copulae of Qilian and Qinling orogene, of which the structure evolution history is very famous. A continuous PermianTriassic stratum was found in Longwuhe area during this work. In ascending order, this section is divided into Shiguan Formation of upper Permian, Guomugou Formation and Jiangligou Formation of lower Triassic, while Jiangligou Formation is divided into turbidite Member at the lower and tempestite Member at the upper. Primary PermianTriassic Boundary is definited in this work. Sedimentary sequence, sedimentary facies and sediments indicate the Shiguan Formation of upper Permian and Guomugou Formation of lower Triassic are terrigenous clastic turbidite, while the lower parts of Jiangligou Formation of lower Triassic is intraclast turbidite and upper is tempestite. According to the sedimentary facies and geochemistry of interlayer igneous rock, the Shiguan Formation and Guomugou Formation were located at active hemipelagic continental margin, while the Turbidite Member of Jiangligou Formation was located at steady hemipelagic continental margin. The sea level turns down and the sedimentary environment transited into neritic shelf during the tempestite Member of Jiangligou Formation. Based on the sedimentary facies characteristic, this paper reconstructed the eustatic changes during Late Permian and Early Triassic.
Tongren area of Qinghai province is located on the copulae of Qilian and Qinling orogene, of which the structure evolution history is very famous. A continuous PermianTriassic stratum was found in Longwuhe area during this work. In ascending order, this section is divided into Shiguan Formation of upper Permian, Guomugou Formation and Jiangligou Formation of lower Triassic, while Jiangligou Formation is divided into turbidite Member at the lower and tempestite Member at the upper. Primary PermianTriassic Boundary is definited in this work. Sedimentary sequence, sedimentary facies and sediments indicate the Shiguan Formation of upper Permian and Guomugou Formation of lower Triassic are terrigenous clastic turbidite, while the lower parts of Jiangligou Formation of lower Triassic is intraclast turbidite and upper is tempestite. According to the sedimentary facies and geochemistry of interlayer igneous rock, the Shiguan Formation and Guomugou Formation were located at active hemipelagic continental margin, while the Turbidite Member of Jiangligou Formation was located at steady hemipelagic continental margin. The sea level turns down and the sedimentary environment transited into neritic shelf during the tempestite Member of Jiangligou Formation. Based on the sedimentary facies characteristic, this paper reconstructed the eustatic changes during Late Permian and Early Triassic.
2007, 25(3): 351-357.
Abstract:
The Bianping organic reef occurs in the Triticites belt of Maping Formation, Fomitchevella framework builds up its principal part. The type of the Bianping organic reef , a Carboniferous one with corals as dominating reefbuilder, is uncommon in the world. In this paper the Bianping coral reef's growth and sedimentary environments are observed and analyzed by the way of detailed section microfacies analysis.We define and interprete 6 microfacies types. 5 facies are identified in the section as follows: From the bottom up, facies 1: a little protected environment on shallower open platform ; facies 2: shoal in agitated warm water; facies 3: deeper open platform; facies 4: slope above wave base, Fomitchevella growing on facies 4 subsequently, that is facies 5: coral reef; then facies 3, and facies 1. In addition, a sedimentary model similar to typeⅡof shelf margin profile: knoll reef ramps is summarized. Fomitchevella reef’s growth and sedimentary environments are interpreted and analyzed. As a whole, the sedimentary environment of the section should be a subtidal open platform.
The Bianping organic reef occurs in the Triticites belt of Maping Formation, Fomitchevella framework builds up its principal part. The type of the Bianping organic reef , a Carboniferous one with corals as dominating reefbuilder, is uncommon in the world. In this paper the Bianping coral reef's growth and sedimentary environments are observed and analyzed by the way of detailed section microfacies analysis.We define and interprete 6 microfacies types. 5 facies are identified in the section as follows: From the bottom up, facies 1: a little protected environment on shallower open platform ; facies 2: shoal in agitated warm water; facies 3: deeper open platform; facies 4: slope above wave base, Fomitchevella growing on facies 4 subsequently, that is facies 5: coral reef; then facies 3, and facies 1. In addition, a sedimentary model similar to typeⅡof shelf margin profile: knoll reef ramps is summarized. Fomitchevella reef’s growth and sedimentary environments are interpreted and analyzed. As a whole, the sedimentary environment of the section should be a subtidal open platform.
2007, 25(3): 365-371.
Abstract:
The integrated information of clay minerals from the Uppermost Permian sediments in the Dongpan Section, Guangxi province is measured by the analyses of the Xray diffraction. Illite crystallinity show that the illite in Bed 9 and Bed 10 is formed in the middlelate diagenetic stage; Vertical distribution of the illite, smectite and the relationship between the contents of illite and illite crystallinity indicate besides terrigenous clast genesis, part of it may derived from smectite. But the clay mineral assemblages and contents are not only related to the diagenesis, also controlled by the sedimentary factors, such as source rock, climate and geography. Illite crystallinity, illite chemical index, the contents of illite and kaolinite, illitesmectite mixedlayers type show that Paleoclimate turn dry and cold into wet and warm and that water medium turn from alkaline to acidic upward 5cm from Beds 9 and 10 boundary.
The integrated information of clay minerals from the Uppermost Permian sediments in the Dongpan Section, Guangxi province is measured by the analyses of the Xray diffraction. Illite crystallinity show that the illite in Bed 9 and Bed 10 is formed in the middlelate diagenetic stage; Vertical distribution of the illite, smectite and the relationship between the contents of illite and illite crystallinity indicate besides terrigenous clast genesis, part of it may derived from smectite. But the clay mineral assemblages and contents are not only related to the diagenesis, also controlled by the sedimentary factors, such as source rock, climate and geography. Illite crystallinity, illite chemical index, the contents of illite and kaolinite, illitesmectite mixedlayers type show that Paleoclimate turn dry and cold into wet and warm and that water medium turn from alkaline to acidic upward 5cm from Beds 9 and 10 boundary.
2007, 25(3): 380-385.
Abstract:
Based on the analysis of core of Subei basin during late Cretaceous and Paleocene Epoch, the authors conclude that Subei Basin was linked with the sea and the deposit was affected by transgression. The causes of marine transgression may be the tension power have predominated the groundstress condition of the east China and develop a series of halfgrabenlike basin which was filled by huge thick sediment of early Tertiary in shelf of HuabeiBohai gulf , Subeisouth yellow sea and East China sea. Consequently, seawater transgresses from East China Sea to yellow sea and connects half grabenlike basin on the shelf and sea during short period. During the sediment of late Cretaceous Taizhou Formation and Paleocene Epoch Funing Formation, Subei Basin have formed dark shale containing lots of ostracoda that include predominated whole basin E1f2 Formation and E1f4 Formation and local K2t2 Formation, which have become main source rocks of the basin. The evidences of paleontology, minerals in rocks and geochemistry can ascertain the environment of lake basin which develops during late Cretaceous and Paleocene Epoch. This environment was generally designated "near sea lake basin" or the layer and member that was transgressed by sea was called "transgression lake basin", whereas, which was generally called inland lake and river alluvium plain during sediment of Eocene Dainan Formation and Sanduo Formation. Based on the analysis and sufficiency cognition of Transgression Lake of late Cretaceous and Paleocene Epoch of Subei Basin, the research is important to not only paleogeographic reconstruction of Subei basin during late Cretaceous and Paleocene Epoch but also the comment to make upon development and distribution of the source rocks and potential of oil and gas generation.
Based on the analysis of core of Subei basin during late Cretaceous and Paleocene Epoch, the authors conclude that Subei Basin was linked with the sea and the deposit was affected by transgression. The causes of marine transgression may be the tension power have predominated the groundstress condition of the east China and develop a series of halfgrabenlike basin which was filled by huge thick sediment of early Tertiary in shelf of HuabeiBohai gulf , Subeisouth yellow sea and East China sea. Consequently, seawater transgresses from East China Sea to yellow sea and connects half grabenlike basin on the shelf and sea during short period. During the sediment of late Cretaceous Taizhou Formation and Paleocene Epoch Funing Formation, Subei Basin have formed dark shale containing lots of ostracoda that include predominated whole basin E1f2 Formation and E1f4 Formation and local K2t2 Formation, which have become main source rocks of the basin. The evidences of paleontology, minerals in rocks and geochemistry can ascertain the environment of lake basin which develops during late Cretaceous and Paleocene Epoch. This environment was generally designated "near sea lake basin" or the layer and member that was transgressed by sea was called "transgression lake basin", whereas, which was generally called inland lake and river alluvium plain during sediment of Eocene Dainan Formation and Sanduo Formation. Based on the analysis and sufficiency cognition of Transgression Lake of late Cretaceous and Paleocene Epoch of Subei Basin, the research is important to not only paleogeographic reconstruction of Subei basin during late Cretaceous and Paleocene Epoch but also the comment to make upon development and distribution of the source rocks and potential of oil and gas generation.
2007, 25(3): 392-400.
Abstract:
According to sequence stratigraphy, on the basis of integrated study on outcrop, well drilling, well logging and seismic data, one thirdorder sequence has been recognized in the Yijianfang Formation. In the upper of the high system tract, at least 5 high frequency sequences have been recognized. And beach facies distribution is depicted both in thirdorder sequence and in high frequency sequence. Then based on the foregoing research, the reservoir in this area has been predicted and conclusions have been made as follows: Vertically, the development of reservoir is controlled by sequence and highfrequency. Flatly, the reservoir develops on the center of the beach which lies in the north of break of slope in the platform. Then by researching the relationship between reservoir qualities and controlling factor, controlling mode of reservoir quality has been set up. At last, by researching the relations between reservoir quality and highfrequency, beach position and tectonic, it can be seen that the fifth highfrequency's reservoir quality is superior to the third, beach center quality is superior to the edge, southwest and south of Tahe oilfield's quality is superior to the east.
According to sequence stratigraphy, on the basis of integrated study on outcrop, well drilling, well logging and seismic data, one thirdorder sequence has been recognized in the Yijianfang Formation. In the upper of the high system tract, at least 5 high frequency sequences have been recognized. And beach facies distribution is depicted both in thirdorder sequence and in high frequency sequence. Then based on the foregoing research, the reservoir in this area has been predicted and conclusions have been made as follows: Vertically, the development of reservoir is controlled by sequence and highfrequency. Flatly, the reservoir develops on the center of the beach which lies in the north of break of slope in the platform. Then by researching the relationship between reservoir qualities and controlling factor, controlling mode of reservoir quality has been set up. At last, by researching the relations between reservoir quality and highfrequency, beach position and tectonic, it can be seen that the fifth highfrequency's reservoir quality is superior to the third, beach center quality is superior to the edge, southwest and south of Tahe oilfield's quality is superior to the east.
2007, 25(3): 417-423.
Abstract:
A soil profile at the LGT site in the western part of the Guanzhong Basin was studied to illustrate soilforming process and micromorphological features of modern soil. Micromorphology of the thin sections is observed under a petrographic microscope and its image is quantificationally measured by LEICAL Qwin software. Results show that the minerals assemblage of every horizon is very similar, which is mainly composed of Q and Pl. Difference of C/F15μm ratio, mineral content and coarse features is obvious. Coarse grain of the Ap horizon is characterized by higher roundness (1.6361.818), lower aspect ratio (1.8611.909), small size (3541 μm) and some intrusive mass. Shape of coarse grain in BC horizon is characterized by lower roundness (1.8981.982), higher aspect ratio (2.2152.312) and big size (4247μm). BC horizon is characterized by abundant secondarycalcite quantity and slight amount unstable primary minerals such as Cc and Hb and Bi. Pedofeatures mainly consist of clay and calcite and amorphous Fe. Ap horizon is characterized by abundant secondarycarbonate and earthworm excrement and slight amount residual clay. Abundant needleshaped secondary calcite minicrystal is observed in the Ap2 horizon. There are little secondary clay and various secondary calcites in BC horizon. Comparability coefficient, between modern soil and Malan loess L1, is 0.81050.8951 in Ap horizon and 0.90510.9352 in BC horizon, respectively. All the results in this study suggest that Earthcumulic Orthic Anthrosols consists of both upper Ap horizon(040cm), which indicated that loess dung and eolian dust deposition and cultivation occur simultaneously in the process of Ap horizonformation since 2000 years, and lower BC horizon(4075cm), which is aeolian sedimentation in relative aridity period during late Holocene. Abundant needle shaped calcite suggested shortterm stable and dry environment.
A soil profile at the LGT site in the western part of the Guanzhong Basin was studied to illustrate soilforming process and micromorphological features of modern soil. Micromorphology of the thin sections is observed under a petrographic microscope and its image is quantificationally measured by LEICAL Qwin software. Results show that the minerals assemblage of every horizon is very similar, which is mainly composed of Q and Pl. Difference of C/F15μm ratio, mineral content and coarse features is obvious. Coarse grain of the Ap horizon is characterized by higher roundness (1.6361.818), lower aspect ratio (1.8611.909), small size (3541 μm) and some intrusive mass. Shape of coarse grain in BC horizon is characterized by lower roundness (1.8981.982), higher aspect ratio (2.2152.312) and big size (4247μm). BC horizon is characterized by abundant secondarycalcite quantity and slight amount unstable primary minerals such as Cc and Hb and Bi. Pedofeatures mainly consist of clay and calcite and amorphous Fe. Ap horizon is characterized by abundant secondarycarbonate and earthworm excrement and slight amount residual clay. Abundant needleshaped secondary calcite minicrystal is observed in the Ap2 horizon. There are little secondary clay and various secondary calcites in BC horizon. Comparability coefficient, between modern soil and Malan loess L1, is 0.81050.8951 in Ap horizon and 0.90510.9352 in BC horizon, respectively. All the results in this study suggest that Earthcumulic Orthic Anthrosols consists of both upper Ap horizon(040cm), which indicated that loess dung and eolian dust deposition and cultivation occur simultaneously in the process of Ap horizonformation since 2000 years, and lower BC horizon(4075cm), which is aeolian sedimentation in relative aridity period during late Holocene. Abundant needle shaped calcite suggested shortterm stable and dry environment.
2007, 25(3): 429-436.
Abstract:
Comparing the records of two loess profiles, which are located in mideast and west margin of the East Asian Monsoon region, it is found that these records not only captured 20 DansgaardOescher events and 6 Heinrich events, but also were basically synchronous with those of GRIP ice core in the rapid climate fluctuations. And it also suggested that the climate in the East Asian Monsoon region had rapid fluctuations in millennium to century scales in the whole last glacial. But there were still some differences between Shagou Profile in west and Wangguan Profile in east, that is the former were more sensitive to climate change than the latter. With those previous studies of Chinese loess records in the last glacial, it is revealed that the magnitude of DansgaardOeschger cycle decreased gradually from west to east and we suggested it was the effect of westerly and the summer monsoon combination.
Comparing the records of two loess profiles, which are located in mideast and west margin of the East Asian Monsoon region, it is found that these records not only captured 20 DansgaardOescher events and 6 Heinrich events, but also were basically synchronous with those of GRIP ice core in the rapid climate fluctuations. And it also suggested that the climate in the East Asian Monsoon region had rapid fluctuations in millennium to century scales in the whole last glacial. But there were still some differences between Shagou Profile in west and Wangguan Profile in east, that is the former were more sensitive to climate change than the latter. With those previous studies of Chinese loess records in the last glacial, it is revealed that the magnitude of DansgaardOeschger cycle decreased gradually from west to east and we suggested it was the effect of westerly and the summer monsoon combination.
2007, 25(3): 445-455.
Abstract:
Based on 558 surface sediment samples collected in Changjiang Estuary recently, the temporal and spatial characteristics of surface sediment grain size were analyzed, and the distribution of D50 and types were obtained, too. The results showed that few changes of the surface sediment grain size in upper Hengsha Island was showed between flood and dry seasons. The grain size in flood season was coarser than that of dry season in the Turbidity Maximum, and in the mouth of the estuary, the grain size in flood season was finer than that of dry season. The types of surface sediment in upper Hengsha Island and mouth of the estuary were changeless between flood and dry seasons, while in the Turbidity Maximum, it was much more complex and various. Whether in flood season or in dry season, the coarsest surface sediment was in North Channel, then in the North Passage, and the finest surface sediment was in the South Passage. Little difference of surface sediment grain size was showed between spring tide and neap tide, and the difference of mean diameter was about 9.7%. The grain size of different years was changed with the Water discharge and sediment discharge of Datong Station. The grain size of surface sediment in upper North Branch, distributary site of South and North Channels and Turbidity Maximum of South and North Passages were much more changeable in the recent fifteen years. These changes were due to the natural channel processes and human activities. The dynamic sediment environment in Changjiang Estuary was divided by Pejrup triangular diagram, and the grain size characteristics of each sediment environment were discussed. Then, the grain size parameters of surface sediment in Yellow River, Changjiang and Pearl River Estuary were contrasted in this paper.
Based on 558 surface sediment samples collected in Changjiang Estuary recently, the temporal and spatial characteristics of surface sediment grain size were analyzed, and the distribution of D50 and types were obtained, too. The results showed that few changes of the surface sediment grain size in upper Hengsha Island was showed between flood and dry seasons. The grain size in flood season was coarser than that of dry season in the Turbidity Maximum, and in the mouth of the estuary, the grain size in flood season was finer than that of dry season. The types of surface sediment in upper Hengsha Island and mouth of the estuary were changeless between flood and dry seasons, while in the Turbidity Maximum, it was much more complex and various. Whether in flood season or in dry season, the coarsest surface sediment was in North Channel, then in the North Passage, and the finest surface sediment was in the South Passage. Little difference of surface sediment grain size was showed between spring tide and neap tide, and the difference of mean diameter was about 9.7%. The grain size of different years was changed with the Water discharge and sediment discharge of Datong Station. The grain size of surface sediment in upper North Branch, distributary site of South and North Channels and Turbidity Maximum of South and North Passages were much more changeable in the recent fifteen years. These changes were due to the natural channel processes and human activities. The dynamic sediment environment in Changjiang Estuary was divided by Pejrup triangular diagram, and the grain size characteristics of each sediment environment were discussed. Then, the grain size parameters of surface sediment in Yellow River, Changjiang and Pearl River Estuary were contrasted in this paper.
2007, 25(3): 467-473.
Abstract:
First of all, the researchers observed and described hydrocarbon inclusions in Middle Jurassic Zhiluo Formation sandstones in Dongsheng area, northern Ordos basin under microscope and UV fluorescence, and then, carefully selected the sandstone samples containing hydrocarbon inclusions with high abundance. Subsequently, these samples were washed, crushed, extracted for hydrocarbons and analyzed for GC and GCMS and compared with oils extracted from Cretaceous sandstone, Triassic sandstone and source rock, respectively. The results show that C29 ααα sterane 20S/(20S+20R) and C32 αβ hopane 22S/(22S+22R) ratios of the inclusion oils are close to respective equilibrium values. Vitrinite reflectance values were calculated based on methylphenanthrene index(MPI) and have values from 0.64％ to 0.82％, suggesting that the inclusion oils are near mature to mature. Among C27, C28 and C29 ααα20R steranes, C27>C28<C29. C25/C26 tricyclic terpane and regular steranes/17αC29～33 hopanes ratios are relatively low. The values together with those of gammacerane index and homohopane index consistently indicate that the inclusion oils were derived from humicsapropel type organic matter under poor reducing freshwater to semisaline environment. The features are similar to those of organic matter extracted from Triassic sandstone and source rock, but are different from that of Cretaceous sandstone. Thus, it can be concluded that the inclusion oils were mainly derived from Triassic lacustrine facies source rock.
First of all, the researchers observed and described hydrocarbon inclusions in Middle Jurassic Zhiluo Formation sandstones in Dongsheng area, northern Ordos basin under microscope and UV fluorescence, and then, carefully selected the sandstone samples containing hydrocarbon inclusions with high abundance. Subsequently, these samples were washed, crushed, extracted for hydrocarbons and analyzed for GC and GCMS and compared with oils extracted from Cretaceous sandstone, Triassic sandstone and source rock, respectively. The results show that C29 ααα sterane 20S/(20S+20R) and C32 αβ hopane 22S/(22S+22R) ratios of the inclusion oils are close to respective equilibrium values. Vitrinite reflectance values were calculated based on methylphenanthrene index(MPI) and have values from 0.64％ to 0.82％, suggesting that the inclusion oils are near mature to mature. Among C27, C28 and C29 ααα20R steranes, C27>C28<C29. C25/C26 tricyclic terpane and regular steranes/17αC29～33 hopanes ratios are relatively low. The values together with those of gammacerane index and homohopane index consistently indicate that the inclusion oils were derived from humicsapropel type organic matter under poor reducing freshwater to semisaline environment. The features are similar to those of organic matter extracted from Triassic sandstone and source rock, but are different from that of Cretaceous sandstone. Thus, it can be concluded that the inclusion oils were mainly derived from Triassic lacustrine facies source rock.
