2010 Vol. 28, No. 3
Display Method:
2010, 28(3): 405-411.
Abstract:
The lacustrine stromatolite samples was collected from the Oligocene Yaxicuo Formation in northern Tibetan Plateau. The microtexture features of alternative dark organicrich lamination and light mineralrich lamination distinctly display on polished sections and under microscope observation. The lamination bands occur as wavy and column shapes with step growth episodes. The grayscale values to extract from digitized photographs can be used as a method of lamination couplet counts and thickness measurements. The lamination couplet thickness series are obtained from four sample segments. Individual lamination couplet is interpreted to correspond to annual growth patterns. The periodicities in lamination couplet thickness variations are detected by power spectral analysis. Its significant spectral peaks about 11 years periodicities are related to 11 years sunspot cycle. It is suggested that regular growth rhythms of lacustrine stromatolites may record climate and environmental oscillations forced by sunspot activity.
The lacustrine stromatolite samples was collected from the Oligocene Yaxicuo Formation in northern Tibetan Plateau. The microtexture features of alternative dark organicrich lamination and light mineralrich lamination distinctly display on polished sections and under microscope observation. The lamination bands occur as wavy and column shapes with step growth episodes. The grayscale values to extract from digitized photographs can be used as a method of lamination couplet counts and thickness measurements. The lamination couplet thickness series are obtained from four sample segments. Individual lamination couplet is interpreted to correspond to annual growth patterns. The periodicities in lamination couplet thickness variations are detected by power spectral analysis. Its significant spectral peaks about 11 years periodicities are related to 11 years sunspot cycle. It is suggested that regular growth rhythms of lacustrine stromatolites may record climate and environmental oscillations forced by sunspot activity.
2010, 28(3): 419-425.
Abstract:
Deepwater oil and gas exploration is the most potential area of the worldwide oil and gas exploration, and the tectonic evolution and stratigraphy sequence researches of Passive Continental Margins Deepwater basin have important theory and practice significance. After the integrated researches of typical Passive Continental Margins Deepwater basin, it has been pointed out that Passive Continental Margins Deepwater basin experienced four regional tectonic evolution stages (continental rift onset, continental break up, early continental margins and mature continental margins), and developed three unconformities (Rift onset unconformity, Breakup unconformity and Continental Rise transform unconformity). In addition, it can be identified four tectonosequences (continental rift onset sequence, continental break up sequence, early continental margins sequence and mature continental margins sequence) in these basins.
Deepwater oil and gas exploration is the most potential area of the worldwide oil and gas exploration, and the tectonic evolution and stratigraphy sequence researches of Passive Continental Margins Deepwater basin have important theory and practice significance. After the integrated researches of typical Passive Continental Margins Deepwater basin, it has been pointed out that Passive Continental Margins Deepwater basin experienced four regional tectonic evolution stages (continental rift onset, continental break up, early continental margins and mature continental margins), and developed three unconformities (Rift onset unconformity, Breakup unconformity and Continental Rise transform unconformity). In addition, it can be identified four tectonosequences (continental rift onset sequence, continental break up sequence, early continental margins sequence and mature continental margins sequence) in these basins.
2010, 28(3): 434-440.
Abstract:
The oil and gas exploration of Yanchang Formation in Fuxian area has been constrained by the issue of sediment provenance. The authors make full use of the outcrop, borehole and seismic data of the study area to analysis the six kinds of key parameters indicating the direction of paleoprovenance such as actual measured paleocurrent directions, sand distributed system directions, spatial distribution of extreme exposure signs (coal) and overlying water mark (oil shale), assemblages and distribution characteristics of heavy minerals, foreset structure of delta depositional system (seismic section), regional paleotectonic and paleogeographic characteristics of Ordos basin. Comprehensive studies show that the sediments of Yanchang Formation in Fuxian area come from the northeast of Ordos basin, and there is no provenance system from the south of the study area.
The oil and gas exploration of Yanchang Formation in Fuxian area has been constrained by the issue of sediment provenance. The authors make full use of the outcrop, borehole and seismic data of the study area to analysis the six kinds of key parameters indicating the direction of paleoprovenance such as actual measured paleocurrent directions, sand distributed system directions, spatial distribution of extreme exposure signs (coal) and overlying water mark (oil shale), assemblages and distribution characteristics of heavy minerals, foreset structure of delta depositional system (seismic section), regional paleotectonic and paleogeographic characteristics of Ordos basin. Comprehensive studies show that the sediments of Yanchang Formation in Fuxian area come from the northeast of Ordos basin, and there is no provenance system from the south of the study area.
2010, 28(3): 471-480.
Abstract:
Neoproterozoic Doushantuo Period was very important epoch of phosphorite formation in Yangtze Platform.And phosphorite of Baiguoyuan in the western Hubei was formed by the transgression process' expanding. The Doushantuo Formation of Baiguoyuan was located at the northwestern part of the Huangling anticline,and phosphorite was deposited in the lower part of the Doushantuo Formation.With undertaking the sequence stratigraphic study on the Baiguoyuan section,the Doushantuo Formation and the Dengying Formation which were formed after the Nantuo ice age could be grouped into one secondorder sequence.The Doushantuo Formation contained phosphorites represented a strong transgressive activity after the Nantuo ice age.It could be divided into six thirdorder sequences,and the phosphorite was formed in the first sequence, within which the late transgressive system tract and the early highstand system tract corresponded to subtidal zone,and arenite phosphorite had very high grade.The physical weathering during glacial epoch and chemical weathering during the Doushantuo Period produced the phosphoric material that was input into ocean.The phosphoric seawater was transported to shallow water areas with upwelling caused by transgression, providing the source and power conditions for phosphorite's deposition in the first sequence.The initial transgression was very favour of phosphorite's formation,high grade phosphoria formation corresponds to the maximum transgression.With the application of geochemistry,studying on phosphatic series, the results indicates that organic matter play an important part in the formation of phosphorite.After the great glaciation period, new ecosystem of Doushantuo Period was established,the biological productivity recovered rapidly, providing opportunity for biomineralization.The shalecarbonatite phosphatic series' organic carbon content is between basin phosphorite and platform phosphorite's content, intergrade is characteristic of its.Because the environment was retention basin of semilimitations, the phosphorites of Baiguoyuan were resulted from weak reductionweak oxidation environment. Compared with platform phosphorite of Weng'an,platform phosphorite has the characteristic of low organic carbon content and high P2O5 content as a result of more oxidative environment.Compared with Kunyang phosphorite deposits of early Cambrian located in Yunnan, we could conclude that subtidal zone was favorable area for phosphogenesis,which had high energy and abundant algaes.But phosphorite in Baiguoyuan didn't have the environment of algal beach which belonged to phosphorite deposits in Kunyang.So the phosphorite in Baiguoyuan generated from transgression,biomineralization and so on.
Neoproterozoic Doushantuo Period was very important epoch of phosphorite formation in Yangtze Platform.And phosphorite of Baiguoyuan in the western Hubei was formed by the transgression process' expanding. The Doushantuo Formation of Baiguoyuan was located at the northwestern part of the Huangling anticline,and phosphorite was deposited in the lower part of the Doushantuo Formation.With undertaking the sequence stratigraphic study on the Baiguoyuan section,the Doushantuo Formation and the Dengying Formation which were formed after the Nantuo ice age could be grouped into one secondorder sequence.The Doushantuo Formation contained phosphorites represented a strong transgressive activity after the Nantuo ice age.It could be divided into six thirdorder sequences,and the phosphorite was formed in the first sequence, within which the late transgressive system tract and the early highstand system tract corresponded to subtidal zone,and arenite phosphorite had very high grade.The physical weathering during glacial epoch and chemical weathering during the Doushantuo Period produced the phosphoric material that was input into ocean.The phosphoric seawater was transported to shallow water areas with upwelling caused by transgression, providing the source and power conditions for phosphorite's deposition in the first sequence.The initial transgression was very favour of phosphorite's formation,high grade phosphoria formation corresponds to the maximum transgression.With the application of geochemistry,studying on phosphatic series, the results indicates that organic matter play an important part in the formation of phosphorite.After the great glaciation period, new ecosystem of Doushantuo Period was established,the biological productivity recovered rapidly, providing opportunity for biomineralization.The shalecarbonatite phosphatic series' organic carbon content is between basin phosphorite and platform phosphorite's content, intergrade is characteristic of its.Because the environment was retention basin of semilimitations, the phosphorites of Baiguoyuan were resulted from weak reductionweak oxidation environment. Compared with platform phosphorite of Weng'an,platform phosphorite has the characteristic of low organic carbon content and high P2O5 content as a result of more oxidative environment.Compared with Kunyang phosphorite deposits of early Cambrian located in Yunnan, we could conclude that subtidal zone was favorable area for phosphogenesis,which had high energy and abundant algaes.But phosphorite in Baiguoyuan didn't have the environment of algal beach which belonged to phosphorite deposits in Kunyang.So the phosphorite in Baiguoyuan generated from transgression,biomineralization and so on.
2010, 28(3): 489-496.
Abstract:
The deep exploration of Northern Songliao Basin has got a series of breakthrough, such as Xujiaweizi, and so on. For the recognition of deep geology of GulongChangjiaweizi Fault Depression is lower, it is still at the early stage of deep exploration. The Shahezi Formation of the fault depression of GulongChangjiaweizi was filled by a suite of fan delta and lacustrine deposits, is the important reservoir bed and source bed. We utilized multipurposely the data of logging, drilling, seismic and so on, applied the theory of sequence stratigraphy to continental fault depression of lake basin deposit, identified the top and bottom surfaces of the thirdorder sequences of Shahezi Formation, devided it into 2 the thirdorder sequences, and distinguished from highland systems tract, transgression systems tracts, lowstand systems tracts, established the high precision isochronous sequence stratigraphic framework. Based on the geologic configuration of Shahezi Formation and the tectonic background of the strata development, author established the sequence stratigraphic modes of Shehezi Formation: twoway multistage fault terrace sequence stratigraphic model, double halfgraben asymmetric sequence stratigraphic model.
The deep exploration of Northern Songliao Basin has got a series of breakthrough, such as Xujiaweizi, and so on. For the recognition of deep geology of GulongChangjiaweizi Fault Depression is lower, it is still at the early stage of deep exploration. The Shahezi Formation of the fault depression of GulongChangjiaweizi was filled by a suite of fan delta and lacustrine deposits, is the important reservoir bed and source bed. We utilized multipurposely the data of logging, drilling, seismic and so on, applied the theory of sequence stratigraphy to continental fault depression of lake basin deposit, identified the top and bottom surfaces of the thirdorder sequences of Shahezi Formation, devided it into 2 the thirdorder sequences, and distinguished from highland systems tract, transgression systems tracts, lowstand systems tracts, established the high precision isochronous sequence stratigraphic framework. Based on the geologic configuration of Shahezi Formation and the tectonic background of the strata development, author established the sequence stratigraphic modes of Shehezi Formation: twoway multistage fault terrace sequence stratigraphic model, double halfgraben asymmetric sequence stratigraphic model.
2010, 28(3): 509-517.
Abstract:
Though the analysis of clay minerals, major and trace elements of the Carboniferous mudstone samples collected from cores in Bachu, Tazhong and Tahe areas and field outcrops around Xiaohaizi in Bachu and Sishichang in Akesu, palaeosalinity character of water environment when this mudstone was deposited in these regions was revealed by quantitative semiquantitative analysis involving calculation using Adams and Couch palaeosalinity formula, equivalent boron determinate method suggested by Walker and strontiumbarium ratio method. The results indicate the range of palaeosalnity is 4.7‰~33.9‰, and display that the majority of mudstone samples show semisaltwater sedimentary environment and freshwater brackish environment is secondary while saltwater environment is less. In plane view, from northeast of the basin to southwest, the palaeosalinity concentration of mudstone in Mudstone Section, Bachu Formation increased in a general view. Mudstone in Sandstone and Mudstone Section, Kalashayi Formation shows the minimal palaeosalinity concentration in the center and the maximal in the southwest part of the basin, and in the north part of the basin, the palaeosalinity concentration is moderate. Owing to palaeosalinity information extracted form mudstone is one of the indications to determine the sedimentary environment, it can provide important reference in aspect of water character for identifying controversial sedimentary environment of Sandstone and Mudstone Section in Kalashayi Formation and Breccia Section in Bachu Formation. Palaeosalinity of water environment when Carboniferous mudstone was deposited has a good correlation with eustacy and sedimentary facies evolution in this period, and these mudstone was formed in sedimentary environment in which sea level is relatively in fall or slow rise and palaeosalinity is relatively low.
Though the analysis of clay minerals, major and trace elements of the Carboniferous mudstone samples collected from cores in Bachu, Tazhong and Tahe areas and field outcrops around Xiaohaizi in Bachu and Sishichang in Akesu, palaeosalinity character of water environment when this mudstone was deposited in these regions was revealed by quantitative semiquantitative analysis involving calculation using Adams and Couch palaeosalinity formula, equivalent boron determinate method suggested by Walker and strontiumbarium ratio method. The results indicate the range of palaeosalnity is 4.7‰~33.9‰, and display that the majority of mudstone samples show semisaltwater sedimentary environment and freshwater brackish environment is secondary while saltwater environment is less. In plane view, from northeast of the basin to southwest, the palaeosalinity concentration of mudstone in Mudstone Section, Bachu Formation increased in a general view. Mudstone in Sandstone and Mudstone Section, Kalashayi Formation shows the minimal palaeosalinity concentration in the center and the maximal in the southwest part of the basin, and in the north part of the basin, the palaeosalinity concentration is moderate. Owing to palaeosalinity information extracted form mudstone is one of the indications to determine the sedimentary environment, it can provide important reference in aspect of water character for identifying controversial sedimentary environment of Sandstone and Mudstone Section in Kalashayi Formation and Breccia Section in Bachu Formation. Palaeosalinity of water environment when Carboniferous mudstone was deposited has a good correlation with eustacy and sedimentary facies evolution in this period, and these mudstone was formed in sedimentary environment in which sea level is relatively in fall or slow rise and palaeosalinity is relatively low.
2010, 28(3): 525-533.
Abstract:
Since the reefs and banks were found as significant reservoirs from the Upper Ordovician Lianglitag Formation, Tazhong Slopebreak I, debate on the reef aspects of morphology, magnitude, etc. still exist. We analy the regional reef biotic components, community structures and sedimentary backgrounds, and furthermore, synthetically interpret the reef sedimentary successions. Reefs are classified as the catalogues of coralframework reef, stromatoporoidlithisid spongia framework reef, lithisid spongia stromatoporoid framework reef, algae stromatoporoid framework reef respectively based on their biotic differentiations. These reefs differ from the former cases such as the stromatolites of the Precambrian, archeaocyathus reefs of the Cambrian, Calathium reefs of the Early Ordovician as well as the carbonate mudmounds of the Early Ordovician ecologically and lithologically, marked by their higher biodiversity, more complex of the ecological characteristics and magnitude. The reefcomplexes are generally more than tens meters showing in the frillcores. Reefs and banks stack horizontally and vertically. Therefore, extensions of the reefs and banks enhance the widespreading of the reefcomplexes along the Slopebreak.
Since the reefs and banks were found as significant reservoirs from the Upper Ordovician Lianglitag Formation, Tazhong Slopebreak I, debate on the reef aspects of morphology, magnitude, etc. still exist. We analy the regional reef biotic components, community structures and sedimentary backgrounds, and furthermore, synthetically interpret the reef sedimentary successions. Reefs are classified as the catalogues of coralframework reef, stromatoporoidlithisid spongia framework reef, lithisid spongia stromatoporoid framework reef, algae stromatoporoid framework reef respectively based on their biotic differentiations. These reefs differ from the former cases such as the stromatolites of the Precambrian, archeaocyathus reefs of the Cambrian, Calathium reefs of the Early Ordovician as well as the carbonate mudmounds of the Early Ordovician ecologically and lithologically, marked by their higher biodiversity, more complex of the ecological characteristics and magnitude. The reefcomplexes are generally more than tens meters showing in the frillcores. Reefs and banks stack horizontally and vertically. Therefore, extensions of the reefs and banks enhance the widespreading of the reefcomplexes along the Slopebreak.
2010, 28(3): 547-555.
Abstract:
Based on a large number of thinsections, casting thinsections and scanning electron photomicrographs observation , the characteristics of Triassic dissolution in KeBai area, northwestern margin of Junggar Basin are systematically studied. Triassic dissolution is generally developed in KeBai area, with abundant typical phenomena, and reservoir is obviously reformed , so dissolution is the most important type of diagenesis in the study area. The lithology characteristics of "low compositional maturity, lowermiddle textural maturity " provide a sedimentary basis for diagenesis. The dissolution of feldspar is the most common in the area, and cementation is weak, with little calcite and analcime dissolution, quartz is slightly dissolved under alkaline condition. The type of pore space and the vertical evolution of porosity on different walls of the fault belt are determined by dissolution. The intensity and distribution of dissolution was affected by the rock type, matrix content, microfacies and other factors.
Based on a large number of thinsections, casting thinsections and scanning electron photomicrographs observation , the characteristics of Triassic dissolution in KeBai area, northwestern margin of Junggar Basin are systematically studied. Triassic dissolution is generally developed in KeBai area, with abundant typical phenomena, and reservoir is obviously reformed , so dissolution is the most important type of diagenesis in the study area. The lithology characteristics of "low compositional maturity, lowermiddle textural maturity " provide a sedimentary basis for diagenesis. The dissolution of feldspar is the most common in the area, and cementation is weak, with little calcite and analcime dissolution, quartz is slightly dissolved under alkaline condition. The type of pore space and the vertical evolution of porosity on different walls of the fault belt are determined by dissolution. The intensity and distribution of dissolution was affected by the rock type, matrix content, microfacies and other factors.
2010, 28(3): 563-571.
Abstract:
Based on substantial experimental material of reservoir, porosity and permeability parameters of the volcanic reservoir and the quantitative evaluation parameters of heterogeneity of Well Longshen 1 field of Yingtai fault is analyzed. The results show that volcanic reservoir physical properties change a lot in space. It has a strong nonhomogeneous. This makes an effective reservoir prediction of volcanic difficulty. Using the imaging logging, indoor rock identification and casting thin section analysis, this study explores the mechanism and process that the various factors on the formation and transformation of the volcanic reservoir space, points out that lithology of the volcanic rocks is the base of other parameters having an impact on the reservoir properties. Volcanic subfacies are the main control factors of physical, diagenetic and tectonic aspects are an important factor on the physical properties, this makes an effective volcanic reservoir prediction have regulations to abide by.
Based on substantial experimental material of reservoir, porosity and permeability parameters of the volcanic reservoir and the quantitative evaluation parameters of heterogeneity of Well Longshen 1 field of Yingtai fault is analyzed. The results show that volcanic reservoir physical properties change a lot in space. It has a strong nonhomogeneous. This makes an effective reservoir prediction of volcanic difficulty. Using the imaging logging, indoor rock identification and casting thin section analysis, this study explores the mechanism and process that the various factors on the formation and transformation of the volcanic reservoir space, points out that lithology of the volcanic rocks is the base of other parameters having an impact on the reservoir properties. Volcanic subfacies are the main control factors of physical, diagenetic and tectonic aspects are an important factor on the physical properties, this makes an effective volcanic reservoir prediction have regulations to abide by.
2010, 28(3): 579-584.
Abstract:
The youngest discrete population of three zircons from the a Formation yielded a weightedmean 206Pb/238U age of 404.9±4.8 Ma(MSWD=0.11), the youngest discrete one zircon from the b Formation yielded a 206Pb/238U age of 385 5 Ma, and the youngest discrete one zircon from the c Formation yielded a 206Pb/238U age of 375 6 Ma, which can be constrained the maximum depositional age of the Dacaotan Group as 405~375 Ma. This result and the biota fossils data from Dacaotan Group, provide reliable evidence that its depositional age is Late Devonian. According to its lithologic assemblage, sedimentary facies, depositional age, deformation features and sediment provenance, the authors discuss the tectonic implications of Dacaotan Group. In the middle Devonian, an early microcontinent (+magmatic arc) continent collisional orogen was overprinted by Andeantype magmatic arc along the southern convergent margin of North China continent. The large volumes of molasse sediments have been shed into extensional basin in the forearc area at this time, presumably resulted from the combined effects of the collision and the southern oceanic crust subduction northwards. Siliciclastic rocks of the Upper Devonian Dacaotan Group record rapid tectonism denudation and sedimentary response during this period.
The youngest discrete population of three zircons from the a Formation yielded a weightedmean 206Pb/238U age of 404.9±4.8 Ma(MSWD=0.11), the youngest discrete one zircon from the b Formation yielded a 206Pb/238U age of 385 5 Ma, and the youngest discrete one zircon from the c Formation yielded a 206Pb/238U age of 375 6 Ma, which can be constrained the maximum depositional age of the Dacaotan Group as 405~375 Ma. This result and the biota fossils data from Dacaotan Group, provide reliable evidence that its depositional age is Late Devonian. According to its lithologic assemblage, sedimentary facies, depositional age, deformation features and sediment provenance, the authors discuss the tectonic implications of Dacaotan Group. In the middle Devonian, an early microcontinent (+magmatic arc) continent collisional orogen was overprinted by Andeantype magmatic arc along the southern convergent margin of North China continent. The large volumes of molasse sediments have been shed into extensional basin in the forearc area at this time, presumably resulted from the combined effects of the collision and the southern oceanic crust subduction northwards. Siliciclastic rocks of the Upper Devonian Dacaotan Group record rapid tectonism denudation and sedimentary response during this period.
2010, 28(3): 596-610.
Abstract:
Tsunamis are catastrophic events in a process of evolution of the Earth. Tsunami deposits is benefit for correctly recognizing tsunami behavior and reducing hazard and also is an important subject in the geosciences for understanding the whole truth of natural phenomena and history of the Earth. A tsunami is a water wave train triggered by submarine earthquake, landslide, bolide impact and volcanism with long wavelengths and long periods which differentiate from other waves. The physics of tsunamis generally link four distinct processes: generation, propagation, inundation of onshore areas and backwash. In general, tsunamis seem unlikely that most earthquakegenerated tsunamis can induce a deep water sedimentary imprint, but impactgenerated tsunamis may do so close to source when tsunamis propagate from source to coast. Tsunamis erode coast and transport sediments to onshore, shallow water bay and lagoon and are deposited during runup. Backwash flows follow the maximum landward inundation of individual tsunami waves and are traction flows to seaward. Backwash generally induced not only debris flows and turbidity currents, but also suspended clouds of mud resulting in hemipelagic setting. Because tsunami behavior depends strongly on bathymetric and topographic configurations, tsunami deposits show differences in diverse environment. Detailed sedimentary study had been carried out about onshore finegrain tsunami deposits and storm deposits to differentiate both. Our composited view is that the deposits characterized by (1) fining and thining upward sequences; (2) repeated bidirectional currents; (3) ripup clasts; (4) less well sorted grains; (5) large inland extent；although each of these five points of evidence could be attributed to storm or other depositional processes individually, no sedimentary process except tsunami can account for all of them simultaneously . The emplacement of onshore boulders is usually attributed to highenergy events tsunamis or storms, but the interpretation remains unsolved. However, the boulders ridge complexes may be the result of storms. Siliciclastic tsunamiites in shallow water generally show intercalation of exceptionally highenergy regimen into underlying and overlying lowenergy finegrain background deposits and can be divided into 4 different TnaTnd units. And earthquakegenerated tsunamiites have special characteristics that show seismitestsunamiites sequences while carbonate tsunamiites show scourfill structure related to incoming and backwash flows. The sedimentary process of deep sea tusnamiiites remains unclear. Propagation of tsunami can induce deep sea Mediterranean A type homogenite, but deep sea tsunamiites may mainly be related to backwash, for example the current hot topic KT impactrelated tsunamiites. Although current research promotes the understanding of tsunamis, many open questions remain such as the sedimentary process of tsunamis and identification of tsunami deposits. We believe that further development of tsunamis sedimentology will supply sufficient foundation for it.
Tsunamis are catastrophic events in a process of evolution of the Earth. Tsunami deposits is benefit for correctly recognizing tsunami behavior and reducing hazard and also is an important subject in the geosciences for understanding the whole truth of natural phenomena and history of the Earth. A tsunami is a water wave train triggered by submarine earthquake, landslide, bolide impact and volcanism with long wavelengths and long periods which differentiate from other waves. The physics of tsunamis generally link four distinct processes: generation, propagation, inundation of onshore areas and backwash. In general, tsunamis seem unlikely that most earthquakegenerated tsunamis can induce a deep water sedimentary imprint, but impactgenerated tsunamis may do so close to source when tsunamis propagate from source to coast. Tsunamis erode coast and transport sediments to onshore, shallow water bay and lagoon and are deposited during runup. Backwash flows follow the maximum landward inundation of individual tsunami waves and are traction flows to seaward. Backwash generally induced not only debris flows and turbidity currents, but also suspended clouds of mud resulting in hemipelagic setting. Because tsunami behavior depends strongly on bathymetric and topographic configurations, tsunami deposits show differences in diverse environment. Detailed sedimentary study had been carried out about onshore finegrain tsunami deposits and storm deposits to differentiate both. Our composited view is that the deposits characterized by (1) fining and thining upward sequences; (2) repeated bidirectional currents; (3) ripup clasts; (4) less well sorted grains; (5) large inland extent；although each of these five points of evidence could be attributed to storm or other depositional processes individually, no sedimentary process except tsunami can account for all of them simultaneously . The emplacement of onshore boulders is usually attributed to highenergy events tsunamis or storms, but the interpretation remains unsolved. However, the boulders ridge complexes may be the result of storms. Siliciclastic tsunamiites in shallow water generally show intercalation of exceptionally highenergy regimen into underlying and overlying lowenergy finegrain background deposits and can be divided into 4 different TnaTnd units. And earthquakegenerated tsunamiites have special characteristics that show seismitestsunamiites sequences while carbonate tsunamiites show scourfill structure related to incoming and backwash flows. The sedimentary process of deep sea tusnamiiites remains unclear. Propagation of tsunami can induce deep sea Mediterranean A type homogenite, but deep sea tsunamiites may mainly be related to backwash, for example the current hot topic KT impactrelated tsunamiites. Although current research promotes the understanding of tsunamis, many open questions remain such as the sedimentary process of tsunamis and identification of tsunami deposits. We believe that further development of tsunamis sedimentology will supply sufficient foundation for it.
2010, 28(3): 611-619.
Abstract:
Lanzhou Area is located on the northwestern margin of the Loess Plateau and the northeastern margin of the Tibetan Plateau, which Tertiary stratum are specially significant for the research of the Tibetan Plateau uplifts and the development of the eolian sediment. With a thickness of 210 m, the Gaolan section belongs to the late Tertiary according to the magnetostratigraphy. 901 samples were obtained from the field in a sampling pace of 0.25 m and subsequently the grainsize, magnetic susceptibility and chroma experiments were accomplished in laboratory. The measured particle size data were separated by a mathematical method to gain the components of different origins as well as the ratio of each component. The analytical results of environmental proxies show that Gaolanshan section is eolian deposition with 15 layers of sand accumulated by rivers. The reconstruction results of paleoenvironment imply that the sedimentary stratum of the section had changed from fluvial deposits to eolian deposits at 7 Ma. That means the initial drying of the internal Asia continent begun at least 7 Ma ago, the conclusion of which is consistent with the main Loess Plateau. Lanzhou area was a relatively open plain and structurally stable with a wet and warm climatic condition in 6～5.2 Ma； in 5.2～3.5 Ma, the tectonic activities were frequent thus the septial river sand formed and the climate was dry cold; the lithosphere of Lanzhou area began to become relatively depressed at 3.5 Ma and Wuquan conglomerate is a result of the phase A of QinghaiXizang movement.
Lanzhou Area is located on the northwestern margin of the Loess Plateau and the northeastern margin of the Tibetan Plateau, which Tertiary stratum are specially significant for the research of the Tibetan Plateau uplifts and the development of the eolian sediment. With a thickness of 210 m, the Gaolan section belongs to the late Tertiary according to the magnetostratigraphy. 901 samples were obtained from the field in a sampling pace of 0.25 m and subsequently the grainsize, magnetic susceptibility and chroma experiments were accomplished in laboratory. The measured particle size data were separated by a mathematical method to gain the components of different origins as well as the ratio of each component. The analytical results of environmental proxies show that Gaolanshan section is eolian deposition with 15 layers of sand accumulated by rivers. The reconstruction results of paleoenvironment imply that the sedimentary stratum of the section had changed from fluvial deposits to eolian deposits at 7 Ma. That means the initial drying of the internal Asia continent begun at least 7 Ma ago, the conclusion of which is consistent with the main Loess Plateau. Lanzhou area was a relatively open plain and structurally stable with a wet and warm climatic condition in 6～5.2 Ma； in 5.2～3.5 Ma, the tectonic activities were frequent thus the septial river sand formed and the climate was dry cold; the lithosphere of Lanzhou area began to become relatively depressed at 3.5 Ma and Wuquan conglomerate is a result of the phase A of QinghaiXizang movement.
2010, 28(3): 620-625.
Abstract:
Through observation of petrological characteristics of fluid inclusions under microscope, the types, shapes, occurrence and colors of fluid inclusions in deep natural gas reservoirs in Minfeng subsag, Dongying sag were described in this paper. The characteristics of hydrocarbonbearing inclusions indicate that evolution of oil and gas in Minfeng area reached high maturity stage. The Raman spectra of hydrocarbonbearing inclusions imply that the accumulation of deep natural gas in Minfeng subsag may be relative to methanerich hydrocarbon fluids. Based on the microthermometry analysis of aqueous inclusions which coexist with hydrocarbonbearing inclusions and reconstruction of burial and thermal history, there were two oil/gas entrapment stages were divided in Minfeng subsag. The first stage mainly occurred during Oligocene Dongying Period, but having not too much contribution. The second accumulation mainly occurred in Pliocene Minghuazhen Period. The latter is the main accumulation period, and mostly occurred smaller than 10 Ma. The analysis of Raman spectroscopy show that hydrocarbonbearing fluids coexist with carbon dioxide in fluid inclusions in deep natural gas reservoirs, confirming that there were acid fluids existed during the accumulation of natural gas. Acid fluids can dissolve calcite cement formed in early diagenesis, consequently improving the growth of induced porosity in deep reservoirs and favor the accumulation of natural gas.
Through observation of petrological characteristics of fluid inclusions under microscope, the types, shapes, occurrence and colors of fluid inclusions in deep natural gas reservoirs in Minfeng subsag, Dongying sag were described in this paper. The characteristics of hydrocarbonbearing inclusions indicate that evolution of oil and gas in Minfeng area reached high maturity stage. The Raman spectra of hydrocarbonbearing inclusions imply that the accumulation of deep natural gas in Minfeng subsag may be relative to methanerich hydrocarbon fluids. Based on the microthermometry analysis of aqueous inclusions which coexist with hydrocarbonbearing inclusions and reconstruction of burial and thermal history, there were two oil/gas entrapment stages were divided in Minfeng subsag. The first stage mainly occurred during Oligocene Dongying Period, but having not too much contribution. The second accumulation mainly occurred in Pliocene Minghuazhen Period. The latter is the main accumulation period, and mostly occurred smaller than 10 Ma. The analysis of Raman spectroscopy show that hydrocarbonbearing fluids coexist with carbon dioxide in fluid inclusions in deep natural gas reservoirs, confirming that there were acid fluids existed during the accumulation of natural gas. Acid fluids can dissolve calcite cement formed in early diagenesis, consequently improving the growth of induced porosity in deep reservoirs and favor the accumulation of natural gas.
2010, 28(3): 635-642.
Abstract:
he Paleogene system in Dongying sag was the representative faulted lakebasin and also the typical cosedimentary system of evaporate and mud rocks in the Eastern of China. To investigate the evolution rule and its controlling factors on the maturation parameters relative to C27 trisnorhopane, the deep formation in the Paleogene System of four deep wells(Well Feng8, Fengshen1, Shi121 and Shi126 ) in the sag were intensively cored, tested and dissected, and the maturation parameters relative to C27 trisnorhopane in the main source rocks(the Member 3, Member 4 in Shahejie Formation and Member 2 in Kongdian Formation in the Paleogene System, the depth across from 2 700 m to 4 200 m) were investigated. The results demonstrate that in the depth across from 2.7 km to 3.572 km, the content of Ts and Ts+Tm(relative to the whole content of ions in the test of mass spectrogram 191) and the value of Ts/Tm, Ts/(Ts+Tm) increase with the buried depth added as a whole except the content of Tm, however in the depth across from 3.572 km to 4.2 km, the distribution of all the above parameters show the reversion. The research turns out besides the close relation between the maturation parameters relative to C27 trisnorhopane and the generation velocity of the isomers, thermal stability and isomerization of the isomers, the cracking of some polymeric compounds contribute to the increase of the relative amount of the Ts; thermodynamic activity control the distribution of these parameters primarily, while the relative low value of Ts/Tm, Ts/(Ts+Tm) in the salted deposition system show the influence of the sedimentary environment on the parameters; the well corresponding of the reversion of the maturation parameters to the high content of the carbonate minerals indicate the restrain and tardy effect of carbonate minerals on the thermal evolution of the organic matter.
he Paleogene system in Dongying sag was the representative faulted lakebasin and also the typical cosedimentary system of evaporate and mud rocks in the Eastern of China. To investigate the evolution rule and its controlling factors on the maturation parameters relative to C27 trisnorhopane, the deep formation in the Paleogene System of four deep wells(Well Feng8, Fengshen1, Shi121 and Shi126 ) in the sag were intensively cored, tested and dissected, and the maturation parameters relative to C27 trisnorhopane in the main source rocks(the Member 3, Member 4 in Shahejie Formation and Member 2 in Kongdian Formation in the Paleogene System, the depth across from 2 700 m to 4 200 m) were investigated. The results demonstrate that in the depth across from 2.7 km to 3.572 km, the content of Ts and Ts+Tm(relative to the whole content of ions in the test of mass spectrogram 191) and the value of Ts/Tm, Ts/(Ts+Tm) increase with the buried depth added as a whole except the content of Tm, however in the depth across from 3.572 km to 4.2 km, the distribution of all the above parameters show the reversion. The research turns out besides the close relation between the maturation parameters relative to C27 trisnorhopane and the generation velocity of the isomers, thermal stability and isomerization of the isomers, the cracking of some polymeric compounds contribute to the increase of the relative amount of the Ts; thermodynamic activity control the distribution of these parameters primarily, while the relative low value of Ts/Tm, Ts/(Ts+Tm) in the salted deposition system show the influence of the sedimentary environment on the parameters; the well corresponding of the reversion of the maturation parameters to the high content of the carbonate minerals indicate the restrain and tardy effect of carbonate minerals on the thermal evolution of the organic matter.
2010, 28(3): 412-418.
Abstract:
Based on the flexural process of elastic lithosphere different from that of viscoelastic lithosphere in foreland basins, this paper provides a solution to acquire the information about lithospheric dynamic property and deformation process by virtue of stratigraphic configurations at the forebulge slope belt. The Kuqa foreland basin，as an example, had gone through tectonic evolution of two thrust period and a quiescence period in the Early Cretaceous. The Kapushaliang Group and Bashenjiqike Formation had respectively developed during thrust and during quiescence. In a single thrust period, accompanied with thrust loading and lithospheric flexural deformation, lithosphere had transformed from elastic property to viscoelastic, and the basin had widen forward to carton and then had narrowed and deepened forward to thrustfault belt. Accordingly, the stratigraphic records at the forebulge slope dipping forward to the foredeep were as follows: during early thrust, the strata gradually onlapped and retrograded forward to carton so as to form a great onlap/truncation bottom unconformity; during the late thrust, the strata gradually shrank and prograded forward to thrustfault belt so as to form a great truncationtoplap top unconformity. During quiescence, the basin was wide and shallow, and the strata appeared parallel and continuous with a few slight truncation unconformities adjacent to thrustfault belt due to lithosphere rebounding.
Based on the flexural process of elastic lithosphere different from that of viscoelastic lithosphere in foreland basins, this paper provides a solution to acquire the information about lithospheric dynamic property and deformation process by virtue of stratigraphic configurations at the forebulge slope belt. The Kuqa foreland basin，as an example, had gone through tectonic evolution of two thrust period and a quiescence period in the Early Cretaceous. The Kapushaliang Group and Bashenjiqike Formation had respectively developed during thrust and during quiescence. In a single thrust period, accompanied with thrust loading and lithospheric flexural deformation, lithosphere had transformed from elastic property to viscoelastic, and the basin had widen forward to carton and then had narrowed and deepened forward to thrustfault belt. Accordingly, the stratigraphic records at the forebulge slope dipping forward to the foredeep were as follows: during early thrust, the strata gradually onlapped and retrograded forward to carton so as to form a great onlap/truncation bottom unconformity; during the late thrust, the strata gradually shrank and prograded forward to thrustfault belt so as to form a great truncationtoplap top unconformity. During quiescence, the basin was wide and shallow, and the strata appeared parallel and continuous with a few slight truncation unconformities adjacent to thrustfault belt due to lithosphere rebounding.
2010, 28(3): 426-433.
Abstract:
Miboshan Formantion in the southern Helan Mountain mainly consisted calcareous breccia, conglomerate, interbedded sandstone or pebbled sandstone, and shale, pebbled shale and grain limestone, and it is very thick Slope facies that is regionally lowgrade metamorphic terrigenous turbidite in deep water, which has experienced different degree deformation and the flysch rhythmic layering and typical Bouma sequence are well developed. Our results shows that the deposition duration of the Middle Ordovician Miboshan Formation is corresponding to the active stage of Helan cold rift, which is particularly important to understand the early Paleozoic tectonic framework and lithofacies paleogeography of Helan Mountain. Our geochemical analysis found that eigenvalue of La, Ce, ∑REE and δEu are similar to that of continental island arc and active continental margin setting. With further information from the tectonic environment and local background, it is concluded that the source of Miboshan Formation is from its southern region of Qilian orogenic belt and its adjacent area of Alashan massif, which is a near source sedimentation that is binary provenance.
Miboshan Formantion in the southern Helan Mountain mainly consisted calcareous breccia, conglomerate, interbedded sandstone or pebbled sandstone, and shale, pebbled shale and grain limestone, and it is very thick Slope facies that is regionally lowgrade metamorphic terrigenous turbidite in deep water, which has experienced different degree deformation and the flysch rhythmic layering and typical Bouma sequence are well developed. Our results shows that the deposition duration of the Middle Ordovician Miboshan Formation is corresponding to the active stage of Helan cold rift, which is particularly important to understand the early Paleozoic tectonic framework and lithofacies paleogeography of Helan Mountain. Our geochemical analysis found that eigenvalue of La, Ce, ∑REE and δEu are similar to that of continental island arc and active continental margin setting. With further information from the tectonic environment and local background, it is concluded that the source of Miboshan Formation is from its southern region of Qilian orogenic belt and its adjacent area of Alashan massif, which is a near source sedimentation that is binary provenance.
2010, 28(3): 441-450.
Abstract:
With the improvement of our national oil/gas exploration, beachbar depositional system has become another kind of favorable reservoir in the continental petroliferous basins, and depositional laws and influential factors are its emphasis and difficulties. This paper, based on highresolution sequence stratigraphy theory, though the analyzing of core, well log, logging curves, divides and correlates strata in the 2nd member of Shahejie Formation. On the basis of identifying and classifying different kinds of sedimentary facies, a fine study about clastic beachbar and organic bank has been done. The results show: ① Organic banks and sand beaches, located in a flat, wide area, have thin single layers and wide distribution; ② Sand bars, located in a slope with a certain angle, and rugged terrain area, have thick single layers and narrow distribution; ③ Palaeotopography and risingdown base level cycles are the controlling factors in beachbar deposits around buried hills of fault basin. Meanwhile, also indicates beachbar deposits around Zhuangxi buried hill have good capacity and petroleum resource potential.
With the improvement of our national oil/gas exploration, beachbar depositional system has become another kind of favorable reservoir in the continental petroliferous basins, and depositional laws and influential factors are its emphasis and difficulties. This paper, based on highresolution sequence stratigraphy theory, though the analyzing of core, well log, logging curves, divides and correlates strata in the 2nd member of Shahejie Formation. On the basis of identifying and classifying different kinds of sedimentary facies, a fine study about clastic beachbar and organic bank has been done. The results show: ① Organic banks and sand beaches, located in a flat, wide area, have thin single layers and wide distribution; ② Sand bars, located in a slope with a certain angle, and rugged terrain area, have thick single layers and narrow distribution; ③ Palaeotopography and risingdown base level cycles are the controlling factors in beachbar deposits around buried hills of fault basin. Meanwhile, also indicates beachbar deposits around Zhuangxi buried hill have good capacity and petroleum resource potential.
2010, 28(3): 462-470.
Abstract:
Based on the knowledge of the sedimentary and tectonic settings in the northeast of the Sichuan basin, using the different methods, such as: outcrop, core, welllogging and seismic, and so on, with the careful analysis of the sequence surfaces, facies section, the stacking pattern, welllogging curves and seismic sequence stratigraphy, and so on, there are 2 thirdorder sequences distinguished in the Feixianguan Formation in the northeast of the Sichuan basin, both of which include the LST, TST and HST. Furthermore, using the theory of the sequence stratigraphy, by establishing the framework of the sequence stratigraphy of the Feixianguan Formation in the northeast of the Sichuan basin, based on the analysis of the control factors of the sequence stratigraphy, the evolution model of the sequence stratigraphy of the Feixianguan Formation is established in the northeast of the Sichuan basin. Furthermore, the distribution of the shoal is discussed in the framework of the sequence evolution; it is important to the further exploration of the hydrocarbon in the northeast of the Sichuan basin.
Based on the knowledge of the sedimentary and tectonic settings in the northeast of the Sichuan basin, using the different methods, such as: outcrop, core, welllogging and seismic, and so on, with the careful analysis of the sequence surfaces, facies section, the stacking pattern, welllogging curves and seismic sequence stratigraphy, and so on, there are 2 thirdorder sequences distinguished in the Feixianguan Formation in the northeast of the Sichuan basin, both of which include the LST, TST and HST. Furthermore, using the theory of the sequence stratigraphy, by establishing the framework of the sequence stratigraphy of the Feixianguan Formation in the northeast of the Sichuan basin, based on the analysis of the control factors of the sequence stratigraphy, the evolution model of the sequence stratigraphy of the Feixianguan Formation is established in the northeast of the Sichuan basin. Furthermore, the distribution of the shoal is discussed in the framework of the sequence evolution; it is important to the further exploration of the hydrocarbon in the northeast of the Sichuan basin.
2010, 28(3): 481-488.
Abstract:
With the theory of highresolution sequence stratigraphy, the baselevel cycles in Chang8 oil set of Yanchang Formation in Jiyuan area of Ordos Basin are recognized as 2 middleterm cyclic sequences(MSC1 and MSC2) and 6 shortterm cyclic sequences(ssc1ssc6) and the sedimentary environment is a shallowwater delta by utilizing the data of well logging, core and rock and mineral analysis. The results indicate that the delta front and predelta of expanded lake developed in Chang82 and delta plain appeared in Chang81 of Jiyuan area. The relationship among the cyclic stacking pattern of various grade of baselevel and the distribution and evolution of sedimentary facies are analyzed and the delta of Jiyuan area is compared with the normal delta. A highresolution sequence stratigraghic framework and stratigraphiclithofacies palaeogeographic maps of Chang81 and Chang82 are established by taking the shortterm cyclic sequence as unit. Compared with the normal delta, the shallowwater delta is charactered by its low A/S, no mouth bar and the microfacies where favorable reservoirs developed is the sandbodies of distributary channel which extended long and mainly developed in the period of the rising half cyclic sequences of shortterm.
With the theory of highresolution sequence stratigraphy, the baselevel cycles in Chang8 oil set of Yanchang Formation in Jiyuan area of Ordos Basin are recognized as 2 middleterm cyclic sequences(MSC1 and MSC2) and 6 shortterm cyclic sequences(ssc1ssc6) and the sedimentary environment is a shallowwater delta by utilizing the data of well logging, core and rock and mineral analysis. The results indicate that the delta front and predelta of expanded lake developed in Chang82 and delta plain appeared in Chang81 of Jiyuan area. The relationship among the cyclic stacking pattern of various grade of baselevel and the distribution and evolution of sedimentary facies are analyzed and the delta of Jiyuan area is compared with the normal delta. A highresolution sequence stratigraghic framework and stratigraphiclithofacies palaeogeographic maps of Chang81 and Chang82 are established by taking the shortterm cyclic sequence as unit. Compared with the normal delta, the shallowwater delta is charactered by its low A/S, no mouth bar and the microfacies where favorable reservoirs developed is the sandbodies of distributary channel which extended long and mainly developed in the period of the rising half cyclic sequences of shortterm.
2010, 28(3): 497-508.
Abstract:
Based on the study of sedimentary facies, biostratigraphy and stack patterns of parasequences, epicontinental depoisit of PermoCarboniferous is divided into 3 sequences in Southern North China, which mean 3 trangressional circles. After that this article reconstructs paleogeography both in sequence and at maximum flood surface. It is found that source area lies in the north, and Sq1 develops a smallscale and shortterm transgression, which is from NE. However, transgression in Sq2 reaches the top almost submerging the whole area, and changes its direction from NE to SE. Sq3 keeps the same landsea distribution with Sq2, while trangressional area retreats to the south. Finally the genesis of paleogeographical evolution is discussed, and it is thought that epicontinental depoisit is dominated by global transgression, and transitional surface between Sq1 and Sq2 results from the synthesis of global sudden transgression, basin basement high in the south and low in the north, and stable source from the north in inactive tectonic setting.
Based on the study of sedimentary facies, biostratigraphy and stack patterns of parasequences, epicontinental depoisit of PermoCarboniferous is divided into 3 sequences in Southern North China, which mean 3 trangressional circles. After that this article reconstructs paleogeography both in sequence and at maximum flood surface. It is found that source area lies in the north, and Sq1 develops a smallscale and shortterm transgression, which is from NE. However, transgression in Sq2 reaches the top almost submerging the whole area, and changes its direction from NE to SE. Sq3 keeps the same landsea distribution with Sq2, while trangressional area retreats to the south. Finally the genesis of paleogeographical evolution is discussed, and it is thought that epicontinental depoisit is dominated by global transgression, and transitional surface between Sq1 and Sq2 results from the synthesis of global sudden transgression, basin basement high in the south and low in the north, and stable source from the north in inactive tectonic setting.
2010, 28(3): 518-524.
Abstract:
In order to analyze the dolomite origin of Paleogene dolomite(Kumugeliemu group)in Kuqa depression, this article take the thin slice to dye, trace element and stable isotope test as method, and system atically analyzed this set of dolomite geochemistry characteristic and their origin. The research indicated that the dolomite mainly divide into the creaming dolomite and micrite (powder crystal) dolomite. The trace element and the isotope characteristic of dolomite indicated that it forms in highsalinity, high Mg/Ca ratio, and the strong reducing water environment. The discontinuity ingression in Kuqa depression western area in early stage of Tertiary Period and the intense evaporation environment causes the water body salinity to be high, and the water has provided the magnesium ion for dolomite's formation in penecontemporaneous time. Combine the deposition and lithic facies characteristic of dolomite, we think the dolomite have two kinds of genetic types: the evaporation dolomitization and reflux dolomitization, creaming dolomite that stem from the evaporation dolomitization mainly distributes in supratidal flat(that is lowenergy environment), creaming micrite (powder crystal) dolomite or creaming dolarenite that stem from the reflux dolomitization distributes in subtidalthe lagoon (that is moderatelow energy environment).
In order to analyze the dolomite origin of Paleogene dolomite(Kumugeliemu group)in Kuqa depression, this article take the thin slice to dye, trace element and stable isotope test as method, and system atically analyzed this set of dolomite geochemistry characteristic and their origin. The research indicated that the dolomite mainly divide into the creaming dolomite and micrite (powder crystal) dolomite. The trace element and the isotope characteristic of dolomite indicated that it forms in highsalinity, high Mg/Ca ratio, and the strong reducing water environment. The discontinuity ingression in Kuqa depression western area in early stage of Tertiary Period and the intense evaporation environment causes the water body salinity to be high, and the water has provided the magnesium ion for dolomite's formation in penecontemporaneous time. Combine the deposition and lithic facies characteristic of dolomite, we think the dolomite have two kinds of genetic types: the evaporation dolomitization and reflux dolomitization, creaming dolomite that stem from the evaporation dolomitization mainly distributes in supratidal flat(that is lowenergy environment), creaming micrite (powder crystal) dolomite or creaming dolarenite that stem from the reflux dolomitization distributes in subtidalthe lagoon (that is moderatelow energy environment).
2010, 28(3): 534-546.
Abstract:
A peculiar characteristic, different segmentations and zones, belongs to foreland basin. In southern margin of Junggar Basin, through a lot of cores of 13 wells describing, reservoir studing and some results of vitrinite reflectance analyzing, there are 3 different factors of reservoir at segmentations and zones in Tertiary. They are different porosity, permeability, compositional maturity and textural maturity. In different segmentations and zones as a research unit in thrust belt, the controlling factors of the different reservoir include ①different sedimentary feeders and sedimentary facies and different sandstone body that belonging at the same sedimentary facies. ②Different Lapidofacies, clay and cement that located at intergrain and dissolution in reservoir.③The main controlling reservoir is buried thermal effect and not the tectonic compression in Palaeogene. And ④because of the Tianshan Mountain’s uplifting in Neogene the tectonic compression changes the main controlling factor of reservoir in southern margin of Junggar Foreland Basin.
A peculiar characteristic, different segmentations and zones, belongs to foreland basin. In southern margin of Junggar Basin, through a lot of cores of 13 wells describing, reservoir studing and some results of vitrinite reflectance analyzing, there are 3 different factors of reservoir at segmentations and zones in Tertiary. They are different porosity, permeability, compositional maturity and textural maturity. In different segmentations and zones as a research unit in thrust belt, the controlling factors of the different reservoir include ①different sedimentary feeders and sedimentary facies and different sandstone body that belonging at the same sedimentary facies. ②Different Lapidofacies, clay and cement that located at intergrain and dissolution in reservoir.③The main controlling reservoir is buried thermal effect and not the tectonic compression in Palaeogene. And ④because of the Tianshan Mountain’s uplifting in Neogene the tectonic compression changes the main controlling factor of reservoir in southern margin of Junggar Foreland Basin.
2010, 28(3): 556-562.
Abstract:
The reservoirs of Ying’er depression in Jiudong basin are characterized by low porosity and low permeability. The general poor physical properties of the reservoirs strictly restrict the exploration in this area. Based on analyses of thin sections, casting thin sections and fluorescence thin sections, Xray diffraction analyses, SEM observations and mercury porosimetry measurements of the reservoir sandstones, this research shows that the main pore types are the intergranular dissolved pore and intragranular dissolved pore of feldspar, siliceous debris, quartz and carbonate cements. Two secondary pore zones are developed in the lower member of Xiagou formation and the top part of Chijinbao formation. Sandstones in the study area are characterized by poor sorting, poor roundness and low mineralogical maturity. These are the characteristics of fast accumulation and closure to provenance of the sediments. Mechanical compaction is the main factor in making the properties of reservoirs poor. Clay minerals and carbonate cements block pores. Cements fill in the pore space and destroy the reservoir property, meanwhile, they provide space for dissolution in the later stage, secondary pore is widely developed because of dissolution of minerals caused by acidic water that released by hydrocarbon generation process and diagenesis processes of clay minerals. It's the main factor that improves the reservoir property in the deep layers of the basin.
The reservoirs of Ying’er depression in Jiudong basin are characterized by low porosity and low permeability. The general poor physical properties of the reservoirs strictly restrict the exploration in this area. Based on analyses of thin sections, casting thin sections and fluorescence thin sections, Xray diffraction analyses, SEM observations and mercury porosimetry measurements of the reservoir sandstones, this research shows that the main pore types are the intergranular dissolved pore and intragranular dissolved pore of feldspar, siliceous debris, quartz and carbonate cements. Two secondary pore zones are developed in the lower member of Xiagou formation and the top part of Chijinbao formation. Sandstones in the study area are characterized by poor sorting, poor roundness and low mineralogical maturity. These are the characteristics of fast accumulation and closure to provenance of the sediments. Mechanical compaction is the main factor in making the properties of reservoirs poor. Clay minerals and carbonate cements block pores. Cements fill in the pore space and destroy the reservoir property, meanwhile, they provide space for dissolution in the later stage, secondary pore is widely developed because of dissolution of minerals caused by acidic water that released by hydrocarbon generation process and diagenesis processes of clay minerals. It's the main factor that improves the reservoir property in the deep layers of the basin.
2010, 28(3): 572-578.
Abstract:
The mineral trapping of CO2 refers to the atmospheric emissions of CO2 gas was injected into the formation of deep aquifers, oil and gas fields, via a series of physical and chemical reactions, CO2 gas will eventually be consolidated in the carbonate minerals. Pyroclastic rocks with high content of magnesium ions and easy to be released and abroad distributing can be used as a promising rock type for mineral trapping,Tongbomiao formation of Tanan sag in Tamuchage basin contain abundant dawsonitebearing volcaniclastic rocks,which further proves the mineral trapping capabilities of pyroclastic rocks .There are three carbonate minerals in pyroclastic rocks after the injection of CO2 , which contain dawsonite ,ferrocalcite and ankerite ,the total content is up to 30% ,which suggests the capacity of CO2 nineral trapping is large enough.
The mineral trapping of CO2 refers to the atmospheric emissions of CO2 gas was injected into the formation of deep aquifers, oil and gas fields, via a series of physical and chemical reactions, CO2 gas will eventually be consolidated in the carbonate minerals. Pyroclastic rocks with high content of magnesium ions and easy to be released and abroad distributing can be used as a promising rock type for mineral trapping,Tongbomiao formation of Tanan sag in Tamuchage basin contain abundant dawsonitebearing volcaniclastic rocks,which further proves the mineral trapping capabilities of pyroclastic rocks .There are three carbonate minerals in pyroclastic rocks after the injection of CO2 , which contain dawsonite ,ferrocalcite and ankerite ,the total content is up to 30% ,which suggests the capacity of CO2 nineral trapping is large enough.
2010, 28(3): 585-595.
Abstract:
Oolitic beach facies of highenergy was widely distributed in the Lower Triassic Strata of South China under the background of carbonate ramp, particularly within a certain quantity of giant ooids. Examined the sizes of giant ooids are mostly between 2mm and 6mm, some up to 12mm, and the nucleus predominantly consist of granular calcite and peloid. All giant ooids exhibit concentric laminae and tangentially oriented crystals, suggesting their originally aragonitic mineralogy. Unites of giant ooidsbearing oolitic and bioclastic limestone deposited alternately, reflected the relative sealevel changes at that time. The occurrence of such giant ooids which diameters over 5mm are commonly developed in the Neoproterozoic, however, were extremely uncommon after the Cambrian. Numerous giant ooids were widespread occured after the endPermian mass extinction, yet eliminated following the radiation of the Mesozoic biotas and the normalization of marine environment. It is implied that giant ooid is a new kind of anachronistic facies, and its occurrence apparently relate to biotas and marine environment at that time. This paper is based on detailed analysis of production background, microscopic structure and sedimentary characteristics of giant ooids, therefore, it is available to aid our understanding of their origin, explore the harsh marine environment and the particular ecosystems under the PaleozoicMesozoic transitional events.
Oolitic beach facies of highenergy was widely distributed in the Lower Triassic Strata of South China under the background of carbonate ramp, particularly within a certain quantity of giant ooids. Examined the sizes of giant ooids are mostly between 2mm and 6mm, some up to 12mm, and the nucleus predominantly consist of granular calcite and peloid. All giant ooids exhibit concentric laminae and tangentially oriented crystals, suggesting their originally aragonitic mineralogy. Unites of giant ooidsbearing oolitic and bioclastic limestone deposited alternately, reflected the relative sealevel changes at that time. The occurrence of such giant ooids which diameters over 5mm are commonly developed in the Neoproterozoic, however, were extremely uncommon after the Cambrian. Numerous giant ooids were widespread occured after the endPermian mass extinction, yet eliminated following the radiation of the Mesozoic biotas and the normalization of marine environment. It is implied that giant ooid is a new kind of anachronistic facies, and its occurrence apparently relate to biotas and marine environment at that time. This paper is based on detailed analysis of production background, microscopic structure and sedimentary characteristics of giant ooids, therefore, it is available to aid our understanding of their origin, explore the harsh marine environment and the particular ecosystems under the PaleozoicMesozoic transitional events.
2010, 28(3): 626-634.
Abstract:
Marine oil shale from the Shengli River oil shale section discovered in 2008 in the Qiangtang basin, northern Tibet, China, was collected systematically and analyzed by means of GCMS. The results indicate that the oil shales from Shengli River area exhibit relatively high values of C31steranes 22S/(22S+22R) \[0.38~0.44\], C29steranes αββ/(ααα+αββ) \[0.37~0.47\] and C31steranes 22S/(22S+22R) \[0.52~0.59\] ratios. These results indicate that the thermal evolutionary phase of organic matter in oil shale has reached oilgenerating window. The relatively high concentrations of C27steranes\[32.82%~43.6%\] and relatively high values of 4methyl sterane to regular sterane ratios\[0.04~0.22\], sterane to hopane ratios\[0.80~1.04\] unanimously indicate that the biological sources of organic matter in oil shale are phytoplankton and bacteria, especially with an important contribution of phytoplankton. The relatively high values of gammacerane index\[0.34~0.50\], homohopane index \[0.076~0.102\] and low pristine to phytane ratios\[0.320.49\]indicate the occlusive water environments are anoxic and relatively hypersaline in the Shengli River area during oil shale deposition.
Marine oil shale from the Shengli River oil shale section discovered in 2008 in the Qiangtang basin, northern Tibet, China, was collected systematically and analyzed by means of GCMS. The results indicate that the oil shales from Shengli River area exhibit relatively high values of C31steranes 22S/(22S+22R) \[0.38~0.44\], C29steranes αββ/(ααα+αββ) \[0.37~0.47\] and C31steranes 22S/(22S+22R) \[0.52~0.59\] ratios. These results indicate that the thermal evolutionary phase of organic matter in oil shale has reached oilgenerating window. The relatively high concentrations of C27steranes\[32.82%~43.6%\] and relatively high values of 4methyl sterane to regular sterane ratios\[0.04~0.22\], sterane to hopane ratios\[0.80~1.04\] unanimously indicate that the biological sources of organic matter in oil shale are phytoplankton and bacteria, especially with an important contribution of phytoplankton. The relatively high values of gammacerane index\[0.34~0.50\], homohopane index \[0.076~0.102\] and low pristine to phytane ratios\[0.320.49\]indicate the occlusive water environments are anoxic and relatively hypersaline in the Shengli River area during oil shale deposition.
