2013 Vol. 31, No. 3
Display Method:
2013, 31(3): 385-395.
Abstract:
The depositionalstructural transformation and the regional correlation of relevant important strata units from Banxi period to Nanhua glacial period in southeast margin of Yangtze block have been a major focus of debate for a long time. Predecessors had been regarded that they wear conformity without obvious boundary surface between the Danzhou Group and Nanhua glacial deposition in North Guangxi and East Guizhou. However, the authors' survey of some important sections in GuizhouGuangxi neighboring region, such as Jinping Longli section, Liping Zhaoxing section, Congjiang lijiapo section, Sanjiang Silikou section and Luocheng Huangjin section, indicate that the transforming surface from Banxi period into Nanhua glacial period was clearly and sharply, for the upper part and down part of the surface were different completely in rock component, contexture, construction, and depositional facies types. The regional change of the transformation token on that the stratigraphic missing of the Banxi Group and its equivalences with a regressive progradational sequences become more and more obvious from the margin to the interior of Yangtze Block, and in reverse, the sedimentary sequences of the Nanhua glacial period with a transgressing process gradually become more and more integrated from the interior to the margin. We think that this was the depositional records of “Xuefeng Movement” brought forward by predecessor. Therefore, it was more probability and feasibility in the HunanGuizhouGuangxi neighboring region of the southeast margin than the Gorges region in the interior of Yangtze Block to find a relatively integrated sedimentary sequence of Nanhua glacial period, and so the region should be the most favorable area to select the Global Standard Section and Point (GSSP) for “Nanhua System”. At the same time, the available geochronological data suggest that the top boundary of Banxi period should be towards 720Ma, which is close to the onset age of Sturtian Glacial stage, and should not be limited at 780Ma subjectively. The most important is that the depositional sequence of Banxi period was a tact sedimentary cycle standing for the filling of midNeoproterozoic rift basin, and also there was not observable and identifiable hiatus in the sequence. so this sequence should not be dismembered or fragmented, otherwise we will be going against the principle of International Commission on Stratigraphy (ICS) for the classification of Precambrian strata. Therefore, at present, we consider that 720Ma is reasonable for the top boundary age of Banxi Group. And now, the first thing is to get more distinct and clear concept and implication of “Nanhua System”. So it is necessary for its foundation to research and discuss deeply the tectonic settings of the Banxi Group and its equivalences and the depositional transformation from Banxi period to the Nanhua glacial period.
The depositionalstructural transformation and the regional correlation of relevant important strata units from Banxi period to Nanhua glacial period in southeast margin of Yangtze block have been a major focus of debate for a long time. Predecessors had been regarded that they wear conformity without obvious boundary surface between the Danzhou Group and Nanhua glacial deposition in North Guangxi and East Guizhou. However, the authors' survey of some important sections in GuizhouGuangxi neighboring region, such as Jinping Longli section, Liping Zhaoxing section, Congjiang lijiapo section, Sanjiang Silikou section and Luocheng Huangjin section, indicate that the transforming surface from Banxi period into Nanhua glacial period was clearly and sharply, for the upper part and down part of the surface were different completely in rock component, contexture, construction, and depositional facies types. The regional change of the transformation token on that the stratigraphic missing of the Banxi Group and its equivalences with a regressive progradational sequences become more and more obvious from the margin to the interior of Yangtze Block, and in reverse, the sedimentary sequences of the Nanhua glacial period with a transgressing process gradually become more and more integrated from the interior to the margin. We think that this was the depositional records of “Xuefeng Movement” brought forward by predecessor. Therefore, it was more probability and feasibility in the HunanGuizhouGuangxi neighboring region of the southeast margin than the Gorges region in the interior of Yangtze Block to find a relatively integrated sedimentary sequence of Nanhua glacial period, and so the region should be the most favorable area to select the Global Standard Section and Point (GSSP) for “Nanhua System”. At the same time, the available geochronological data suggest that the top boundary of Banxi period should be towards 720Ma, which is close to the onset age of Sturtian Glacial stage, and should not be limited at 780Ma subjectively. The most important is that the depositional sequence of Banxi period was a tact sedimentary cycle standing for the filling of midNeoproterozoic rift basin, and also there was not observable and identifiable hiatus in the sequence. so this sequence should not be dismembered or fragmented, otherwise we will be going against the principle of International Commission on Stratigraphy (ICS) for the classification of Precambrian strata. Therefore, at present, we consider that 720Ma is reasonable for the top boundary age of Banxi Group. And now, the first thing is to get more distinct and clear concept and implication of “Nanhua System”. So it is necessary for its foundation to research and discuss deeply the tectonic settings of the Banxi Group and its equivalences and the depositional transformation from Banxi period to the Nanhua glacial period.
2013, 31(3): 404-412.
Abstract:
A Late Carboniferous coral frame reef developes in Longjiangdong village, Tianlin County, Guangxi Province. The reef basing on the crinoid fragments beach has three separate cycles. The reefbuilder is the fasciculate Diphyphyllum sp. and the reefadherers mainly are crinoids, brachiopods, some kinds of algaes and foraminifers. Reefbuilding communities which just commonly grow together are lack of longterm, stable, complex ecological relationships. The maturity of reef biomes is poor and other reefbuilding ways are absence except Diphyphyllum sp. building the frame. It is formatted only immature stratigraphic reef under polytropic hydrodynamic conditions. The reasons why the Longjiangdong coral reef express such a distinctive characteristic are summarized as the following: the impacts of global geological structure changes in the Middle Carboniferous, the effects of microfloras and algaes in reefbuilding are not obvious, the benthic community is suppressed by crinoids, the reefbuilding capacity of Diphyphyllum sp. is poor for its ecological characteristics.
A Late Carboniferous coral frame reef developes in Longjiangdong village, Tianlin County, Guangxi Province. The reef basing on the crinoid fragments beach has three separate cycles. The reefbuilder is the fasciculate Diphyphyllum sp. and the reefadherers mainly are crinoids, brachiopods, some kinds of algaes and foraminifers. Reefbuilding communities which just commonly grow together are lack of longterm, stable, complex ecological relationships. The maturity of reef biomes is poor and other reefbuilding ways are absence except Diphyphyllum sp. building the frame. It is formatted only immature stratigraphic reef under polytropic hydrodynamic conditions. The reasons why the Longjiangdong coral reef express such a distinctive characteristic are summarized as the following: the impacts of global geological structure changes in the Middle Carboniferous, the effects of microfloras and algaes in reefbuilding are not obvious, the benthic community is suppressed by crinoids, the reefbuilding capacity of Diphyphyllum sp. is poor for its ecological characteristics.
2013, 31(3): 421-429.
Abstract:
According to the observation of petrographic thin sections, the approaches of the heavy mineralogy analysis and the analysis of SHRIMP UPb ages of detrital zircons, which is of the sandstone samples taken from the Dawangou outcrops of Keping area and the drill cores of TP3,TP7 and KQ1 in northern Tarim Basin, as well as using the classic Dickinson Ternary Diagram method and combining with regional geology background analysis, we make a conclusion that the provenance of the sandstones in the Kepingtage Formation of Silurian in the west area of northern Tarim Basin is different from that in the center and east area of northern Tarim Basin. The tectonic setting of the former provenance is the continental island arc environment, and it is composed of the materials from the Proterozoic upper crust. Thus the provenance is inferred to be Tabei uplift. However, the tectonic setting of the latter provenance is the recycled orogens environment and it is composed of the Ordovician materials. So, the provenance is inferred to be Kuluketage uplift. The type of provenance is widely igneous rock. Compared with the center and east area of northern Tarim Basin, the west area is farther to the provenance. These conclusions are of great importance to the reconstruction of paleogeography deposition environment and the analysis of the type and evolution of Tarim Basin.
According to the observation of petrographic thin sections, the approaches of the heavy mineralogy analysis and the analysis of SHRIMP UPb ages of detrital zircons, which is of the sandstone samples taken from the Dawangou outcrops of Keping area and the drill cores of TP3,TP7 and KQ1 in northern Tarim Basin, as well as using the classic Dickinson Ternary Diagram method and combining with regional geology background analysis, we make a conclusion that the provenance of the sandstones in the Kepingtage Formation of Silurian in the west area of northern Tarim Basin is different from that in the center and east area of northern Tarim Basin. The tectonic setting of the former provenance is the continental island arc environment, and it is composed of the materials from the Proterozoic upper crust. Thus the provenance is inferred to be Tabei uplift. However, the tectonic setting of the latter provenance is the recycled orogens environment and it is composed of the Ordovician materials. So, the provenance is inferred to be Kuluketage uplift. The type of provenance is widely igneous rock. Compared with the center and east area of northern Tarim Basin, the west area is farther to the provenance. These conclusions are of great importance to the reconstruction of paleogeography deposition environment and the analysis of the type and evolution of Tarim Basin.
2013, 31(3): 440-449.
Abstract:
It has been found that the components of MnO, Na2O, P2O5 and TiO2 in the clastic rock of the Zhujiang Formation in well HZ21 at the Huizhou Depression, Pearl River Mouth Basin are similar to those in PAAS through a comprehensive analysis on the major elements, trace elements and rare earth elements. Comepared with PAAS, a fact that the clastic rock of the Zhujiang Formation is richer in SiO2 while poorer in Al2O3, Fe2O3, K2O and MgO. Referring to the mudstone, the content of Ba is slightly lower than the supracrustal abundance, but it is far higher than lowercrustal abundance; the content of Cr is slightly higher than the supracrustal abundance, but it is far lower than lowercrustal abundance; the content of Th is higher than the supracrustal abundance, and it is far greater than lowercrustal abundance. As regards to the sandstone, the content of Ba is similar to the supracrustal abundance, but it is far higher than lowercrustal abundance; the content of Th is slightly lower than the supracrustal abundance in NSQ1 and NSQ2 while it is far greater than supracrustal abundance in NSQ3 and NSQ4. The REE distribution pattern is similar to that of the upper continental crust, characterized by enrichment of LREE, uniform of HREE and negative Eu anomalies. Eu anomalous value of NSQ1 and NSQ2 is higher than the Eu anomalous value of PASS and it has the opposite situation in NSQ3 and NSQ4. The ratios of major elment and the diagrams of nonmigration trace elments show that the source rocks are mainly felsic, and the principal source of detritus in NSQ1 and NSQ2 are derived from the sedimentary rock and calcareous mudstone, and the principal source of detritus in NSQ3 and NSQ4 are derived from compositon of the granite, alkali basalt, sedimentary rock and calcareous mudstone. According to SiO2 K2O/Na2O, La ThSc discrimination diagrams and the anomalies of Ce, it can be inferred that the tectonic setting of the provenance is similar to that of passive continental margin. The value of Al2O3/Na2O and chemical index of alteration (CIA) suggest that it was warmwet climate in the area, but the degree of dampheat was relatively higher in NSQ1 and NSQ2, and that is one of the reason why the intensity of weathering was relatively strong. But, it has an opposite situation in NSQ3 and NSQ4: the warmwet degree was relatively lower and the intensity of weathering was relatively weak.
It has been found that the components of MnO, Na2O, P2O5 and TiO2 in the clastic rock of the Zhujiang Formation in well HZ21 at the Huizhou Depression, Pearl River Mouth Basin are similar to those in PAAS through a comprehensive analysis on the major elements, trace elements and rare earth elements. Comepared with PAAS, a fact that the clastic rock of the Zhujiang Formation is richer in SiO2 while poorer in Al2O3, Fe2O3, K2O and MgO. Referring to the mudstone, the content of Ba is slightly lower than the supracrustal abundance, but it is far higher than lowercrustal abundance; the content of Cr is slightly higher than the supracrustal abundance, but it is far lower than lowercrustal abundance; the content of Th is higher than the supracrustal abundance, and it is far greater than lowercrustal abundance. As regards to the sandstone, the content of Ba is similar to the supracrustal abundance, but it is far higher than lowercrustal abundance; the content of Th is slightly lower than the supracrustal abundance in NSQ1 and NSQ2 while it is far greater than supracrustal abundance in NSQ3 and NSQ4. The REE distribution pattern is similar to that of the upper continental crust, characterized by enrichment of LREE, uniform of HREE and negative Eu anomalies. Eu anomalous value of NSQ1 and NSQ2 is higher than the Eu anomalous value of PASS and it has the opposite situation in NSQ3 and NSQ4. The ratios of major elment and the diagrams of nonmigration trace elments show that the source rocks are mainly felsic, and the principal source of detritus in NSQ1 and NSQ2 are derived from the sedimentary rock and calcareous mudstone, and the principal source of detritus in NSQ3 and NSQ4 are derived from compositon of the granite, alkali basalt, sedimentary rock and calcareous mudstone. According to SiO2 K2O/Na2O, La ThSc discrimination diagrams and the anomalies of Ce, it can be inferred that the tectonic setting of the provenance is similar to that of passive continental margin. The value of Al2O3/Na2O and chemical index of alteration (CIA) suggest that it was warmwet climate in the area, but the degree of dampheat was relatively higher in NSQ1 and NSQ2, and that is one of the reason why the intensity of weathering was relatively strong. But, it has an opposite situation in NSQ3 and NSQ4: the warmwet degree was relatively lower and the intensity of weathering was relatively weak.
2013, 31(3): 461-467.
Abstract:
As the typical interlayer oxidation zone sandstone type uranium deposit, Shihongtan uranium deposit occurs in the fluvial facies sandstone of the Xishanyao Formation of the middle Jurassic at the Aiding Lake slope in the southwest margin of TurpanHami basin. According to the results of ferrum phases analysis, the formations of iron element in the ore hosting belts include FeCO3, Fe2O3, silicatefacies iron and FeS2whose contents take regular changes in different geochemical subzone. Pyrite, the main form of ferrous iron in the ore hosting belts, has the twoperiod causes, belongs to the sulphate and microbe reducing product. The author analyzed the function of iron geochemical behavior in uranium mineralization process, thought that in the oxidized zone, the iron catalyzed uranium oxidation, dissolution and move, which provided the important source for uranium mineralization. The pyrite of ore belt played the sorption in uranium mineralization process, indicating the similar cause with the bitumionous uranium.
As the typical interlayer oxidation zone sandstone type uranium deposit, Shihongtan uranium deposit occurs in the fluvial facies sandstone of the Xishanyao Formation of the middle Jurassic at the Aiding Lake slope in the southwest margin of TurpanHami basin. According to the results of ferrum phases analysis, the formations of iron element in the ore hosting belts include FeCO3, Fe2O3, silicatefacies iron and FeS2whose contents take regular changes in different geochemical subzone. Pyrite, the main form of ferrous iron in the ore hosting belts, has the twoperiod causes, belongs to the sulphate and microbe reducing product. The author analyzed the function of iron geochemical behavior in uranium mineralization process, thought that in the oxidized zone, the iron catalyzed uranium oxidation, dissolution and move, which provided the important source for uranium mineralization. The pyrite of ore belt played the sorption in uranium mineralization process, indicating the similar cause with the bitumionous uranium.
2013, 31(3): 468-477.
Abstract:
Carbonate and its carbon isotopes have the potential for distinguishing dust provenance, and but the differences for carbonate and carbon isotopes in different grainsize fractions significantly affect accuracy for identifying dust provenance. Therefore, the study for distribution characteristic of carbonate and carbon isotopes in different grainsize fractions is theory base of dust provenance trace with use of carbonate and carbon isotopes. Samples of sandy land have be collected from horqin sandy land and dumeng sandy land in songnen plain, at one time, samples also are collected from city road loose bare soils. These samples are separated into five different grain size fractions, i. e. bulk sample, >63 μm, 63~30 μm, 30~11 μm, and <11 μm. Then, carbonate volume and carbon isotopic compositions of these samples are measured, respectively. The results show that the varied range of carbonate volume of different grain size fractions in horqin sandy land and dumeng sandy land are fairly minor, although carbonate volume of most samples raise with decreasing grain size, but relations between carbonate volume and grain size are not only a relations that carbonate volume becomes high with decreasing grain size, but also have other much complex relations. The carbonate volume of all road loose bare soils increases with decreasing grain size, and might be caused by join of fine grainsized pollutants such as construction dust. The carbonate volumes of full fractions are similar to that of the >63 μm fraction. It is believed that the carbonate volume of eolian sand and sandland samples undergoing transform of violent pedogenesis decreases with decreasing size of sample particles. The varied scopes of carbon isotopic compositions of different grain size fractions of most samples in dumeng sandy land and road loose bare soils and all samples in Horqin sandy land are fairly minor, and express the characteristics of increase with decreasing grain size, but the varied changes are very slight. The carbonate volumes are not a good dust source region tracer indicator of distinguishing between dumeng sandy land and Horqin sandy land because of not very obvious regional differences of carbonate volumes between dumeng sandy land and Horqin sandy land, and of variations of carbonate volumes in different grain size fractions that is much higher than the different value of carbonate volumes between dumeng sandy land and horqin sandly and. However, there exist the obvious differences between carbon isotopic compositions in dumeng sandy land and Horqin sandy land (63~30 μm grain fraction, specifically), and the differences of δ13C compositions in different grain size fractions are very slight, showing carbonate carbon isotopic compositions in dust fallouts is a better tracing index for indicating eolian dust provenance than carbonate contents. However, the diversity of carbonate carbon isotope compositions in different grainsize fractions maybe increase with increasing distance of dust source regions in west desert and sandy land in China to dust deposit regions, which increase its complexity for identifying dust provenance.
Carbonate and its carbon isotopes have the potential for distinguishing dust provenance, and but the differences for carbonate and carbon isotopes in different grainsize fractions significantly affect accuracy for identifying dust provenance. Therefore, the study for distribution characteristic of carbonate and carbon isotopes in different grainsize fractions is theory base of dust provenance trace with use of carbonate and carbon isotopes. Samples of sandy land have be collected from horqin sandy land and dumeng sandy land in songnen plain, at one time, samples also are collected from city road loose bare soils. These samples are separated into five different grain size fractions, i. e. bulk sample, >63 μm, 63~30 μm, 30~11 μm, and <11 μm. Then, carbonate volume and carbon isotopic compositions of these samples are measured, respectively. The results show that the varied range of carbonate volume of different grain size fractions in horqin sandy land and dumeng sandy land are fairly minor, although carbonate volume of most samples raise with decreasing grain size, but relations between carbonate volume and grain size are not only a relations that carbonate volume becomes high with decreasing grain size, but also have other much complex relations. The carbonate volume of all road loose bare soils increases with decreasing grain size, and might be caused by join of fine grainsized pollutants such as construction dust. The carbonate volumes of full fractions are similar to that of the >63 μm fraction. It is believed that the carbonate volume of eolian sand and sandland samples undergoing transform of violent pedogenesis decreases with decreasing size of sample particles. The varied scopes of carbon isotopic compositions of different grain size fractions of most samples in dumeng sandy land and road loose bare soils and all samples in Horqin sandy land are fairly minor, and express the characteristics of increase with decreasing grain size, but the varied changes are very slight. The carbonate volumes are not a good dust source region tracer indicator of distinguishing between dumeng sandy land and Horqin sandy land because of not very obvious regional differences of carbonate volumes between dumeng sandy land and Horqin sandy land, and of variations of carbonate volumes in different grain size fractions that is much higher than the different value of carbonate volumes between dumeng sandy land and horqin sandly and. However, there exist the obvious differences between carbon isotopic compositions in dumeng sandy land and Horqin sandy land (63~30 μm grain fraction, specifically), and the differences of δ13C compositions in different grain size fractions are very slight, showing carbonate carbon isotopic compositions in dust fallouts is a better tracing index for indicating eolian dust provenance than carbonate contents. However, the diversity of carbonate carbon isotope compositions in different grainsize fractions maybe increase with increasing distance of dust source regions in west desert and sandy land in China to dust deposit regions, which increase its complexity for identifying dust provenance.
2013, 31(3): 486-496.
Abstract:
Based on field data of temperature, turbidity and suspended matter concentration in summer and winter derived from the project named National Coastal Sea Comprehensive Investigation and Evaluation (908ST02), the suspended sediment transport and deposition due to strong regional shear current front off eastern Shandong Peninsula were studied, combined with observation from B1 and B2 sections, circulation simulation in winter by POM model and shallow seismic profile. The results show that the transportation mechanism of suspended matter off eastern Shandong Peninsula is similar to the existing rule in East China Sea: deposition in summer and transport in winter. In summer, not only suspended matter was restricted near bottom by thermocline, but also restricted by the front formed by coastal currents off eastern Shandong Peninsula and northern Yellow Sea cold water mass. Therefore suspended matter mainly deposited in summer. In winter, with the help of strong northeastly wind and the thermocline, the turbidity was high vertical mixing was better off eastern Shandong Peninsula. However, two strong shear current fronts could be found on both sides of the topset of mud wedge, which was respectively generated by northward upwind compensation current along eastern Shandong Peninsula in the middle and lower water, northward Yellow Sea warm currents and southward coastal wind currents above topset of mud wedge. The two strong shear current fronts prevented suspended sediments from bottomset of the mud wedge getting cross eastern Shandong Peninsula continental shelf peripheral, which was helpful to omegashaped (‘Ω’) mud wedge formation off eastern Shandong Peninsula.
Based on field data of temperature, turbidity and suspended matter concentration in summer and winter derived from the project named National Coastal Sea Comprehensive Investigation and Evaluation (908ST02), the suspended sediment transport and deposition due to strong regional shear current front off eastern Shandong Peninsula were studied, combined with observation from B1 and B2 sections, circulation simulation in winter by POM model and shallow seismic profile. The results show that the transportation mechanism of suspended matter off eastern Shandong Peninsula is similar to the existing rule in East China Sea: deposition in summer and transport in winter. In summer, not only suspended matter was restricted near bottom by thermocline, but also restricted by the front formed by coastal currents off eastern Shandong Peninsula and northern Yellow Sea cold water mass. Therefore suspended matter mainly deposited in summer. In winter, with the help of strong northeastly wind and the thermocline, the turbidity was high vertical mixing was better off eastern Shandong Peninsula. However, two strong shear current fronts could be found on both sides of the topset of mud wedge, which was respectively generated by northward upwind compensation current along eastern Shandong Peninsula in the middle and lower water, northward Yellow Sea warm currents and southward coastal wind currents above topset of mud wedge. The two strong shear current fronts prevented suspended sediments from bottomset of the mud wedge getting cross eastern Shandong Peninsula continental shelf peripheral, which was helpful to omegashaped (‘Ω’) mud wedge formation off eastern Shandong Peninsula.
2013, 31(3): 509-515.
Abstract:
Laumontites are important and widespread cements formed in middlelate diagenetic stage in the deepburied glutenites of Xujiaweizi Fault Depression，Songliao Basin. They are later dissolved by organic acids released from kerogens during hydrocarbon generation and expulsion，forming secondary porosities. The secondary porosities within deeply buried glutenites are the main reservoir space of hydrocarbons in the deep formation of Xujiaweizi Fault Depression. In order to predict the distribution of secondary porosity zones，the dissolveprecipitation states of the laumontites and the forming mechanism of secondary porosities in the reservoirs of Yingcheng Formation were studied by using thermodynamic method. Dissolutionprecipitation index DPI was proposed to quantify the dissolution and precipitation of laumontites. The distributions of the secondary porosity zones were predicted by overlapping the DPI contour map over the sedimentary facies map. As the result shows，the secondary porosity zones mainly distributed in the fan delta front or braided fluvial river delta front glutenites，where DPI is greater than 2.5.
Laumontites are important and widespread cements formed in middlelate diagenetic stage in the deepburied glutenites of Xujiaweizi Fault Depression，Songliao Basin. They are later dissolved by organic acids released from kerogens during hydrocarbon generation and expulsion，forming secondary porosities. The secondary porosities within deeply buried glutenites are the main reservoir space of hydrocarbons in the deep formation of Xujiaweizi Fault Depression. In order to predict the distribution of secondary porosity zones，the dissolveprecipitation states of the laumontites and the forming mechanism of secondary porosities in the reservoirs of Yingcheng Formation were studied by using thermodynamic method. Dissolutionprecipitation index DPI was proposed to quantify the dissolution and precipitation of laumontites. The distributions of the secondary porosity zones were predicted by overlapping the DPI contour map over the sedimentary facies map. As the result shows，the secondary porosity zones mainly distributed in the fan delta front or braided fluvial river delta front glutenites，where DPI is greater than 2.5.
2013, 31(3): 527-535.
Abstract:
The Ordovician Majiagou Formation mainly consists of carbonate rocks originally deposited and karst bareccia. The reservoir space is mainly secondary pores. After deposition dissolution, dolomitization, desiccation, physical compaction, karstification and cementation soon began. Cementation, which mainly occurred under the burial conditions after the middle Carboniferous, is common and important destructional dianenesis for reservoirs. The micritic, equant sparry and poikilotopic calcite and dolomite, infilling moldic pores of anhydrite concretion, and nonfabric selective dissolution pores and fractures, are common cements. The δ18O and δ13C values of micritic dolomite range from 10.98‰ to 0.8‰, averaging 5.54‰; and from 4.76‰ to 5.77‰, averaging 1.51‰, respectively. The δ18O and δ13C values of dolomite cements infilling dissolution pores range from 12.54‰ to 2.67‰, averaging 7.34‰; and from 5.56‰ to 3.48‰, averaging 0.28‰ respectively. The δ18O and δ13C values of calcite cements infilling dissolution pores range from 15.42‰ to 6.02‰, averaging 9.51‰; and from 12.44‰ to 1.33‰, averaging 3.20‰, respectively. The δ18O and δ13C values of dolomite and calcite cements are generally lower than of micritic dolomite, because of late formation, fresh water leaching, burial diagenesis and influence of organic materials. The Na, Sr, Fe and Mn content of micritic dolomite, dolomite cements and calcite cements ranges from 0 to 350 μg/g, averaging 59 μg/g; from 0 to 380 μg/g，averaging 10 μg/g; from 0 to 14 570 μg/g, averaging 1 040μg/g; and from 0 to 4 670 μg/g, averaging 183 μg/g, respectively. The Na, Sr, and Mn content of dolomite and calcite cements is similar with that of micritic dolomite, because all trace elements content is low. Fe content of dolomite and calcite cements is higher than that of micritic dolomite. The homogenization temperatures of fluid inclusions in the cements range 90~140℃. All indicates that the cements formed under reduced conditions with high temperature in the deep burial environments. The most gaseous phase of the fluid inclusions consists of CH4, while the most liquid phase is H2O. The early and late cements formed before and later formation of the natural gas respectively. The cementation developed extensively in the kart depressions.
The Ordovician Majiagou Formation mainly consists of carbonate rocks originally deposited and karst bareccia. The reservoir space is mainly secondary pores. After deposition dissolution, dolomitization, desiccation, physical compaction, karstification and cementation soon began. Cementation, which mainly occurred under the burial conditions after the middle Carboniferous, is common and important destructional dianenesis for reservoirs. The micritic, equant sparry and poikilotopic calcite and dolomite, infilling moldic pores of anhydrite concretion, and nonfabric selective dissolution pores and fractures, are common cements. The δ18O and δ13C values of micritic dolomite range from 10.98‰ to 0.8‰, averaging 5.54‰; and from 4.76‰ to 5.77‰, averaging 1.51‰, respectively. The δ18O and δ13C values of dolomite cements infilling dissolution pores range from 12.54‰ to 2.67‰, averaging 7.34‰; and from 5.56‰ to 3.48‰, averaging 0.28‰ respectively. The δ18O and δ13C values of calcite cements infilling dissolution pores range from 15.42‰ to 6.02‰, averaging 9.51‰; and from 12.44‰ to 1.33‰, averaging 3.20‰, respectively. The δ18O and δ13C values of dolomite and calcite cements are generally lower than of micritic dolomite, because of late formation, fresh water leaching, burial diagenesis and influence of organic materials. The Na, Sr, Fe and Mn content of micritic dolomite, dolomite cements and calcite cements ranges from 0 to 350 μg/g, averaging 59 μg/g; from 0 to 380 μg/g，averaging 10 μg/g; from 0 to 14 570 μg/g, averaging 1 040μg/g; and from 0 to 4 670 μg/g, averaging 183 μg/g, respectively. The Na, Sr, and Mn content of dolomite and calcite cements is similar with that of micritic dolomite, because all trace elements content is low. Fe content of dolomite and calcite cements is higher than that of micritic dolomite. The homogenization temperatures of fluid inclusions in the cements range 90~140℃. All indicates that the cements formed under reduced conditions with high temperature in the deep burial environments. The most gaseous phase of the fluid inclusions consists of CH4, while the most liquid phase is H2O. The early and late cements formed before and later formation of the natural gas respectively. The cementation developed extensively in the kart depressions.
2013, 31(3): 545-552.
Abstract:
Qigu Formation of Jurassic was significant oilbearing strata in Junggar basin, its sequence had developed completely, and the sedimentary facies type was very rich. Comprehensive utilization of core, logging, mud logging and related testing information；In addition，based on the analysis of the sedimentary characteristics, sedimentary microfacies of Qigu Formation in Well blockChe60 have been systematically studied. The results showed that the provenance source of Qigu Formation source came from the northwest and north direction mainly. Target layer was the braided river delta, the sand body of Channel bar was the framework for the reservoir, whose reservoir property was the best; followed channel mouth bar, underwater distributary channel was the most favorable sedimentary facies of Oil and gas migration and accumulation. Results of its research had provided reliable geological basis for development plan and dynamic ananlysis of the oil field.
Qigu Formation of Jurassic was significant oilbearing strata in Junggar basin, its sequence had developed completely, and the sedimentary facies type was very rich. Comprehensive utilization of core, logging, mud logging and related testing information；In addition，based on the analysis of the sedimentary characteristics, sedimentary microfacies of Qigu Formation in Well blockChe60 have been systematically studied. The results showed that the provenance source of Qigu Formation source came from the northwest and north direction mainly. Target layer was the braided river delta, the sand body of Channel bar was the framework for the reservoir, whose reservoir property was the best; followed channel mouth bar, underwater distributary channel was the most favorable sedimentary facies of Oil and gas migration and accumulation. Results of its research had provided reliable geological basis for development plan and dynamic ananlysis of the oil field.
2013, 31(3): 396-403.
Abstract:
The “Shangxitype” iron deposits are wellknown for their wide distribution on North China platform. The origins of the deposits including their mineralization processes and the mineral sources, together with their ages, were once concerned by many geologists. Although the geological problems seem clear, the microbial activity is documented to have influence on the formation of the iron deposits just as the Xuanlong iron deposits. The iron deposits outcropped well in Taiyuan Xishan favors our study, and the ferriferous oolites developped in the iron layer of the Benxi Formation at the Qiligou section became our main study object. Through field observation, thin section examination and analysis of Energy spectrum, the composition and texture of the ferriferous oolites are studied in detail. The oolites are matrixsupported, with 45% of ooids and a few other grains (3%) such as bauxite debris and biotic fragments(shell,etc.) floating in clay minerals. The ooids are wellsorted with the sizes mainly ranging from 0.5 mm to 1 mm in diameter. In the thin section, most of the ooids are round, and some rombic and ovalshaped. The cortical layers of the ooids are mainly composed by micritic hematites, whereas the nuclei consist of micritic hematites or clay minerals, which indicate certain common origin between some nuclei and the matrix. Most of the ooids are characterized by radial structure with 2 or 3 obscure concentric layers, which indicate that the ooids probably formed in a relative stable condition, coinciding with the previous conclusion that the iron deposits formed in the restricted lagoon environment. Additionally, abundant intertwined cyanobacteria filaments are found to aggregate around and envelop most of the ooids and the distribution of ferriferous material (micritic hematites) in the matrix is closely related to these filaments. Spherical cyanobacteria which are interlaid in the intertwined filaments are also recognized under SEM. At the same time, ferriferous clots and pellets are identified in the cortical layers and even the nuclei of the ooids, and the notched margins of some ooids are probably related to microbial activity. All of these characteristics suggest that the microbial activity plays a significant role in the formation of the ferriferous ooids. The microbes are thus proposed to be involved in the formation of the iron deposits which formed in the relative stable lagoon environment.
The “Shangxitype” iron deposits are wellknown for their wide distribution on North China platform. The origins of the deposits including their mineralization processes and the mineral sources, together with their ages, were once concerned by many geologists. Although the geological problems seem clear, the microbial activity is documented to have influence on the formation of the iron deposits just as the Xuanlong iron deposits. The iron deposits outcropped well in Taiyuan Xishan favors our study, and the ferriferous oolites developped in the iron layer of the Benxi Formation at the Qiligou section became our main study object. Through field observation, thin section examination and analysis of Energy spectrum, the composition and texture of the ferriferous oolites are studied in detail. The oolites are matrixsupported, with 45% of ooids and a few other grains (3%) such as bauxite debris and biotic fragments(shell,etc.) floating in clay minerals. The ooids are wellsorted with the sizes mainly ranging from 0.5 mm to 1 mm in diameter. In the thin section, most of the ooids are round, and some rombic and ovalshaped. The cortical layers of the ooids are mainly composed by micritic hematites, whereas the nuclei consist of micritic hematites or clay minerals, which indicate certain common origin between some nuclei and the matrix. Most of the ooids are characterized by radial structure with 2 or 3 obscure concentric layers, which indicate that the ooids probably formed in a relative stable condition, coinciding with the previous conclusion that the iron deposits formed in the restricted lagoon environment. Additionally, abundant intertwined cyanobacteria filaments are found to aggregate around and envelop most of the ooids and the distribution of ferriferous material (micritic hematites) in the matrix is closely related to these filaments. Spherical cyanobacteria which are interlaid in the intertwined filaments are also recognized under SEM. At the same time, ferriferous clots and pellets are identified in the cortical layers and even the nuclei of the ooids, and the notched margins of some ooids are probably related to microbial activity. All of these characteristics suggest that the microbial activity plays a significant role in the formation of the ferriferous ooids. The microbes are thus proposed to be involved in the formation of the iron deposits which formed in the relative stable lagoon environment.
2013, 31(3): 413-420.
Abstract:
It is significant to study trace fossils for the recovery of paleontological activity patterns，habits and paleoenvironment. They can provide more exact information than body fossils. Trace fossils were found in the Miocene strata from northeast margin of the Qaidam Basin. The fossilbearing horizon is beside Tuosu Lake and Keluke Lake. The specimens occur in a finegrained siltstone. Trace fossils consist of 2 types including at least 4 ichnogenus and 4 ichnospecies: Palaeopycus heberti, Skolithos vertical, Scoyenia gracilis and Taenidium satanassi. The specimens are abundant and clear. Palaeopycus heberti and Skolithos vertical are attributed to Domichnia. Scoyenia gracilis and Taenidium satanassi are attributed to Fodinichnia. Based on the distribution and morphology of the trace fossils and analysis of paleoenvironment, one kind of assemblages is recognized: ScoyeniaTaenidium Skolithos assemblage, presents itself in shallow lacustrine sediments under moist climate. The discovery of trace fossils filled the biological and environmental data in the Qaidam Basin.
It is significant to study trace fossils for the recovery of paleontological activity patterns，habits and paleoenvironment. They can provide more exact information than body fossils. Trace fossils were found in the Miocene strata from northeast margin of the Qaidam Basin. The fossilbearing horizon is beside Tuosu Lake and Keluke Lake. The specimens occur in a finegrained siltstone. Trace fossils consist of 2 types including at least 4 ichnogenus and 4 ichnospecies: Palaeopycus heberti, Skolithos vertical, Scoyenia gracilis and Taenidium satanassi. The specimens are abundant and clear. Palaeopycus heberti and Skolithos vertical are attributed to Domichnia. Scoyenia gracilis and Taenidium satanassi are attributed to Fodinichnia. Based on the distribution and morphology of the trace fossils and analysis of paleoenvironment, one kind of assemblages is recognized: ScoyeniaTaenidium Skolithos assemblage, presents itself in shallow lacustrine sediments under moist climate. The discovery of trace fossils filled the biological and environmental data in the Qaidam Basin.
2013, 31(3): 430-439.
Abstract:
The research shows that there are 5 directions of provenances existed in Chang 7 period of Ordos Basin, that the northeast and southwest are main provenances, northwest, south and west as the secondary provenances. The lithological characteristics of parent rock from synthetic analyzing the light and heavy mineral characteristics and debris feature are inferred. Meanwhile, combining with the method of recovering relationship among heavy minerals reveals the feature of parent rocks. According to the research, the basic magmatic rock and the highgrade metamorphic rock are main part in the rocks of the northeast area; The sedimentary rock and the lowgrade metamorphic rock are main part of the rock in the southwest area; The lowgrade metamorphic rock, dolomite rock and sedimentary rock are main part in the rocks of northwest area; The sedimentary rock and the lowgrade metamorphic rock are main part in the rocks of north area; The sedimentary rock is main part in the rocks of west area. The REE pattern is similar to upper crust and the geochemical diagrams of HfLa/Th, La/ScCo/Th and REELa/Yb indicate that the mudstones come from felsic rock area with less bedrock and andesite. (Gd/Yb)N>2 shows that the provenance of northeast should be from Archean strata, and (Gd/Yb)N<2 shows that the provenance of other areas should be from the strata above Archean. On this basis, by arranging the lithology of bedrock in the margin of Ordos Basin, it recovers that granulitefacies metamorphite series are outcropped in the northeast area. The degree of metamorphism can be greenschistfacies to amphibolitefacies of lowmedium pressure type in the southwest area. The metamorphism has reached granulitefacies to amphibolitefacies and greenschistfacies in the bedrock of northwest area. While greenschist facies to amphibolite facies of low pressure is the important metamorphism in the south area, and granulitefacies on local area. Conclusion demonstrated that the parent rock can correspond to the bedrock in the northeast area, southwest area and west area. The highgrade metamorphic bedrock is developed in the northwest area and south area which were not found at the parent rock in these deposition areas. Therefore, it was inferred that the old bedrock in these areas has not uplifted at Chang 7 period, and not providing source to basin.
The research shows that there are 5 directions of provenances existed in Chang 7 period of Ordos Basin, that the northeast and southwest are main provenances, northwest, south and west as the secondary provenances. The lithological characteristics of parent rock from synthetic analyzing the light and heavy mineral characteristics and debris feature are inferred. Meanwhile, combining with the method of recovering relationship among heavy minerals reveals the feature of parent rocks. According to the research, the basic magmatic rock and the highgrade metamorphic rock are main part in the rocks of the northeast area; The sedimentary rock and the lowgrade metamorphic rock are main part of the rock in the southwest area; The lowgrade metamorphic rock, dolomite rock and sedimentary rock are main part in the rocks of northwest area; The sedimentary rock and the lowgrade metamorphic rock are main part in the rocks of north area; The sedimentary rock is main part in the rocks of west area. The REE pattern is similar to upper crust and the geochemical diagrams of HfLa/Th, La/ScCo/Th and REELa/Yb indicate that the mudstones come from felsic rock area with less bedrock and andesite. (Gd/Yb)N>2 shows that the provenance of northeast should be from Archean strata, and (Gd/Yb)N<2 shows that the provenance of other areas should be from the strata above Archean. On this basis, by arranging the lithology of bedrock in the margin of Ordos Basin, it recovers that granulitefacies metamorphite series are outcropped in the northeast area. The degree of metamorphism can be greenschistfacies to amphibolitefacies of lowmedium pressure type in the southwest area. The metamorphism has reached granulitefacies to amphibolitefacies and greenschistfacies in the bedrock of northwest area. While greenschist facies to amphibolite facies of low pressure is the important metamorphism in the south area, and granulitefacies on local area. Conclusion demonstrated that the parent rock can correspond to the bedrock in the northeast area, southwest area and west area. The highgrade metamorphic bedrock is developed in the northwest area and south area which were not found at the parent rock in these deposition areas. Therefore, it was inferred that the old bedrock in these areas has not uplifted at Chang 7 period, and not providing source to basin.
2013, 31(3): 450-460.
Abstract:
The dawsonitebearing pyroclastic rock from DamoguaiheYimin Formation in Beier Sag of Hailar Basin was taken as the research object. Polarization microscope, Scanning Electron Microscope, Energy Disperse Spectroscope, alizarin redS staining, Cathode Luminescence and Xray Diffractomer are used in this research to study its rock type, types of authigenic minerals and paragenetic sequences. It is ascertained that the host rock type of dawsonite is tuffite and carbonates are the main authigenic mineral such as dawsonite, ankerite and siderite. Content of dawsonite is up to 25%. The paragenetic sequence is shown as sideriteⅠ→ kaolinite, overgrowth quartz → dawsonite → microcrystalline quartz → calcite → ankerite → sidriteⅡ→ bitumen. Dawsonite is characterized by replacing feldspar, quartz, debris and kaolinite matrix, which is different from porefilling dawsonite found in other field, implicating that these mass in tuffite could provide origin of metal ions, and reacting with diagenetic fluid under the participation of CO2 which results in precipitation of dawsonite. Large amount of carbonates (15%~44%) developed proves that pyroclastic rock owns a relatively well capacity of CO2 fixation.
The dawsonitebearing pyroclastic rock from DamoguaiheYimin Formation in Beier Sag of Hailar Basin was taken as the research object. Polarization microscope, Scanning Electron Microscope, Energy Disperse Spectroscope, alizarin redS staining, Cathode Luminescence and Xray Diffractomer are used in this research to study its rock type, types of authigenic minerals and paragenetic sequences. It is ascertained that the host rock type of dawsonite is tuffite and carbonates are the main authigenic mineral such as dawsonite, ankerite and siderite. Content of dawsonite is up to 25%. The paragenetic sequence is shown as sideriteⅠ→ kaolinite, overgrowth quartz → dawsonite → microcrystalline quartz → calcite → ankerite → sidriteⅡ→ bitumen. Dawsonite is characterized by replacing feldspar, quartz, debris and kaolinite matrix, which is different from porefilling dawsonite found in other field, implicating that these mass in tuffite could provide origin of metal ions, and reacting with diagenetic fluid under the participation of CO2 which results in precipitation of dawsonite. Large amount of carbonates (15%~44%) developed proves that pyroclastic rock owns a relatively well capacity of CO2 fixation.
2013, 31(3): 478-485.
Abstract:
To understand the relationship of distribution characteristic of surface sediment with the sediment supply and the hydrodynamic environment in the middle part of Bohai Sea, 1448 surface sediment samples were selected densely. Some grain size characteristics of the surface sediment sample were analyzed. The results indicate that ten different sediment types were recognized in the studied area, such as gravel, sandy gravel, gravelly sand, sand, silty sand, sandy silt, silt, clayey silt, sandsiltclay and silty clay. Among these ten sediment types, silty sand and clayey silt distribute most widely, while the gravel and silt lesser. The sediment divisions in the middle part of Bohai Sea are composed of Laotieshan Channel, Bozhong Shoal and Liaodong Shoal, Bozhong Plain, Bohai Bay Plain and Western Bohai Gradient Plain. After entering into Bohai Sea, the residual Yellow Sea Warm Current evolves into Bohai Sea Circumfluence, which dominates the pattern of sediment distribution in the middle part of Bohai Sea, and Bohai Strait strong tidal current, Liaodong Bay Circumfluence and Laizhou Bay Circumfluence also play a important role in controlling the sediment distribution pattern. And then the "in north and out south" pattern of sediment exchange is formed, resulted from these dynamic conditions.
To understand the relationship of distribution characteristic of surface sediment with the sediment supply and the hydrodynamic environment in the middle part of Bohai Sea, 1448 surface sediment samples were selected densely. Some grain size characteristics of the surface sediment sample were analyzed. The results indicate that ten different sediment types were recognized in the studied area, such as gravel, sandy gravel, gravelly sand, sand, silty sand, sandy silt, silt, clayey silt, sandsiltclay and silty clay. Among these ten sediment types, silty sand and clayey silt distribute most widely, while the gravel and silt lesser. The sediment divisions in the middle part of Bohai Sea are composed of Laotieshan Channel, Bozhong Shoal and Liaodong Shoal, Bozhong Plain, Bohai Bay Plain and Western Bohai Gradient Plain. After entering into Bohai Sea, the residual Yellow Sea Warm Current evolves into Bohai Sea Circumfluence, which dominates the pattern of sediment distribution in the middle part of Bohai Sea, and Bohai Strait strong tidal current, Liaodong Bay Circumfluence and Laizhou Bay Circumfluence also play a important role in controlling the sediment distribution pattern. And then the "in north and out south" pattern of sediment exchange is formed, resulted from these dynamic conditions.
2013, 31(3): 497-508.
Abstract:
Approximately half of the world's net annual photosynthesis occurs in the oceans (～48 Pg C y-1). Continental margin support 10%~15% of this production. Thus, continental margin seas play the critical role for the energy conversion and carbon cycle in marine ecosystems. However, it is more difficulty to identify the source of these organic matters because continental margin has been affected by both marine currents and terrestrial rivers. The Yellow Sea, a typical semienclosed epicontinental sea, rests on a flat, broad, and tectonically stable seafloor with water depth of average 55 m and maximum 100 m. The Yangtzi River and Yellow River around the Yellow Sea bear remarkably different sizes, water, and sediment discharges; they were regarded to have governed the sediment of major parts of the Yellow Sea during Holocene. This paper is aimed to determine the source, behavior and composition of organic matters access to the understanding the characteristics in nalkanes, total organic carbon, and elements. Another attempt to assess the sediment environment of organic matters and the approaches to discriminate differently sourced organic. The 501 surface sediments from the central part of South Yellow Sea show in detail the characteristics and main factors of the organic matter based on the total organic carbon, grain size, and major elements. There are 64 samples from the above surface sediments detected by GCFID to understand the molecular composition of organic matter in further. The study suggests that the total organic carbon are higher in the eastern part of this region than in the western part area, which affected by the background of the regional circulation patterns in the Yellow Sea, as there are positive correction between the total organic carbon and the concentration of Al2O3, as well as the grain size (median size), although the former seemed more positive. Principal component analysis (PCA) based on correlation was performed using the individual nalkane, as another tool to analyze the compositional distribution of nalkanes in sediment and assess their sources. This analysis identified two principal components registering 71% (Factor 1) and 26% (Factor 2) of total variance, which represents terrestrial plants and marine plank contribution individually. The distribution of nalkanes reveals that the organic matter mainly comes from terrestrial plants, which contain the approximate equal amounts of grassy and woody plant. Marine plank tonic algae organic matter is the second important component, as the isoprenoids indicates the obvious reducing environment related shorter chain nalkanes. Hierarchical cluster examination (HCA) for nalkanes, total organic matter (TOC), grain size (median size) and elements was carried out, grouping the sampled sites. There are three groups samples/sampled sites through HCA analysis in this study area: The Ⅰ group samples may represents primary terrestrial organic matters, the Ⅱ group samples may represents mobile terrestrial organic matters, which were affected by the marine plank input more obviously, and the Ⅲ group samples response anthropogenic factor. The terrestrial organic matters are derived from Yellow Sea which included the old Yellow River and the modern Yellow River. The petroleum pollution input seemed more objective in some sample, and it is common to bacterial production in organic matter of surface sediments. The study shows that it is more precise to combine inorganic geochemical approaches and organic geochemical approaches to understand the origin and dispersal patterns of organic matter in marine sediment, even to establish the fate of terrestrial organic matter in marine environment.
Approximately half of the world's net annual photosynthesis occurs in the oceans (～48 Pg C y-1). Continental margin support 10%~15% of this production. Thus, continental margin seas play the critical role for the energy conversion and carbon cycle in marine ecosystems. However, it is more difficulty to identify the source of these organic matters because continental margin has been affected by both marine currents and terrestrial rivers. The Yellow Sea, a typical semienclosed epicontinental sea, rests on a flat, broad, and tectonically stable seafloor with water depth of average 55 m and maximum 100 m. The Yangtzi River and Yellow River around the Yellow Sea bear remarkably different sizes, water, and sediment discharges; they were regarded to have governed the sediment of major parts of the Yellow Sea during Holocene. This paper is aimed to determine the source, behavior and composition of organic matters access to the understanding the characteristics in nalkanes, total organic carbon, and elements. Another attempt to assess the sediment environment of organic matters and the approaches to discriminate differently sourced organic. The 501 surface sediments from the central part of South Yellow Sea show in detail the characteristics and main factors of the organic matter based on the total organic carbon, grain size, and major elements. There are 64 samples from the above surface sediments detected by GCFID to understand the molecular composition of organic matter in further. The study suggests that the total organic carbon are higher in the eastern part of this region than in the western part area, which affected by the background of the regional circulation patterns in the Yellow Sea, as there are positive correction between the total organic carbon and the concentration of Al2O3, as well as the grain size (median size), although the former seemed more positive. Principal component analysis (PCA) based on correlation was performed using the individual nalkane, as another tool to analyze the compositional distribution of nalkanes in sediment and assess their sources. This analysis identified two principal components registering 71% (Factor 1) and 26% (Factor 2) of total variance, which represents terrestrial plants and marine plank contribution individually. The distribution of nalkanes reveals that the organic matter mainly comes from terrestrial plants, which contain the approximate equal amounts of grassy and woody plant. Marine plank tonic algae organic matter is the second important component, as the isoprenoids indicates the obvious reducing environment related shorter chain nalkanes. Hierarchical cluster examination (HCA) for nalkanes, total organic matter (TOC), grain size (median size) and elements was carried out, grouping the sampled sites. There are three groups samples/sampled sites through HCA analysis in this study area: The Ⅰ group samples may represents primary terrestrial organic matters, the Ⅱ group samples may represents mobile terrestrial organic matters, which were affected by the marine plank input more obviously, and the Ⅲ group samples response anthropogenic factor. The terrestrial organic matters are derived from Yellow Sea which included the old Yellow River and the modern Yellow River. The petroleum pollution input seemed more objective in some sample, and it is common to bacterial production in organic matter of surface sediments. The study shows that it is more precise to combine inorganic geochemical approaches and organic geochemical approaches to understand the origin and dispersal patterns of organic matter in marine sediment, even to establish the fate of terrestrial organic matter in marine environment.
2013, 31(3): 516-526.
Abstract:
Fibrous calcite veins with organic inclusions were considered as indication to oil/gas generation and expelling under overpressure. Abundant fibrous calcite veins contained hydrocarbonbearing inclusions filled in fractures were found in lower Paleozoic hydrocarbon source of black mudstone, clay shale and limestone as well as some faults in Dabashan Foreland Belt. Composition analysis shows that fibrous calcite veins are kind of low magnesium calcite which formed during later diagenesis rather than sedimentary period. 13CVPDB and 18OVPDB of fibrous calcite veins, ranging from -1.9‰ to -4.8‰ and -8.4‰ to -12.8, respectively, are lighter than that of surrounding carbonate rocks, ranging from -1.7‰ to +3.1‰ and -8.7‰ to -4.5‰, show obvious linear relationship, which indicates that fibrous calcite veins were mixture fluid from different source fluids. Fibrous calcite veins contain immiscible fluid inclusions such as solid bitumen, methane bearing liquid fluid inclusion and vaporliquid aqueous inclusions. Bitumen inclusions are residue organic during oil/gas migration. Homogeneous temperatures of vaporliquid aqueous inclusions are from 140 to 196 ℃ with peak of 179℃. Salinities of vaporliquid aqueous inclusions are high with average of 9.7 wt% NaCl. Mehtods of IsoPT phase diagrams of aqueous fluid inclusions and methane inclusions were used to get fluid pressure when fibrous calcite veins formed. The pressure of fibrous calcite vein with hydrocarbonbearing inclusions in Dabashan Foreland Belt is from 150 to 200 MPa, which indicates of abnormal overpressure fluid. Geology and geochemistry features indicate that fibrous calcite veins contained hydrocarbonbearing inclusions are not fluid formed by overpressure of mudrocks source rocks at shallow buried phase. However, combined with the regional sedimentary characteristics and tectonic evolution, it indicates that fibrous calcite veins contained hydrocarbonbearing inclusions were fluid of natural gas drove to expel under overpressure of tectonic stress during InidanChina tectonic movement and Yanshan Foreland tectonics.
Fibrous calcite veins with organic inclusions were considered as indication to oil/gas generation and expelling under overpressure. Abundant fibrous calcite veins contained hydrocarbonbearing inclusions filled in fractures were found in lower Paleozoic hydrocarbon source of black mudstone, clay shale and limestone as well as some faults in Dabashan Foreland Belt. Composition analysis shows that fibrous calcite veins are kind of low magnesium calcite which formed during later diagenesis rather than sedimentary period. 13CVPDB and 18OVPDB of fibrous calcite veins, ranging from -1.9‰ to -4.8‰ and -8.4‰ to -12.8, respectively, are lighter than that of surrounding carbonate rocks, ranging from -1.7‰ to +3.1‰ and -8.7‰ to -4.5‰, show obvious linear relationship, which indicates that fibrous calcite veins were mixture fluid from different source fluids. Fibrous calcite veins contain immiscible fluid inclusions such as solid bitumen, methane bearing liquid fluid inclusion and vaporliquid aqueous inclusions. Bitumen inclusions are residue organic during oil/gas migration. Homogeneous temperatures of vaporliquid aqueous inclusions are from 140 to 196 ℃ with peak of 179℃. Salinities of vaporliquid aqueous inclusions are high with average of 9.7 wt% NaCl. Mehtods of IsoPT phase diagrams of aqueous fluid inclusions and methane inclusions were used to get fluid pressure when fibrous calcite veins formed. The pressure of fibrous calcite vein with hydrocarbonbearing inclusions in Dabashan Foreland Belt is from 150 to 200 MPa, which indicates of abnormal overpressure fluid. Geology and geochemistry features indicate that fibrous calcite veins contained hydrocarbonbearing inclusions are not fluid formed by overpressure of mudrocks source rocks at shallow buried phase. However, combined with the regional sedimentary characteristics and tectonic evolution, it indicates that fibrous calcite veins contained hydrocarbonbearing inclusions were fluid of natural gas drove to expel under overpressure of tectonic stress during InidanChina tectonic movement and Yanshan Foreland tectonics.
2013, 31(3): 536-544.
Abstract:
During the period of the second member of Liushagang Formation, there developed a certain scale of beachbar sandbodies. Based on the analysis of sedimentary characteristics of beachbar sandbodies, the distribution and evolution characteristics of beachbar sandbodies were studied by using the method and technology of seismic sedimentology. According to the controlling of sedimentary model and the demarcation of drilling data, the analysis of seismic property of stratal slice could image the distribution area of beachbar sandbodies well and could also recognize and distinguish the beach sands and bar sands effectively. The analysis of statal slices indicates that the sandbodies were progradation at the early and middle stage of MC1 cycle and the sedimentary areas of beach sands and bar sands were extended and migratory obviously, while the sandbodies were vertical aggradation at the middle and late stage of MC1 cycle and the thickness and area of bar sands increased obviously. The distribution area of sandbodies was comparatively stable and the beach sands and bar sands were vertical aggradation during the process of beachbar development at the period of MC2 cycle. The bar sands of the two cycles were, parallel to each other as strips, mainly distribution at the southeast and centre parts of studying area. In the interest of increasing the successful rate of wells and prove up the development characteristics of main bodies of beachbar sandbodies, the exploration should be emphasis on the bar sands development area in southeast and centre parts of studying area.
During the period of the second member of Liushagang Formation, there developed a certain scale of beachbar sandbodies. Based on the analysis of sedimentary characteristics of beachbar sandbodies, the distribution and evolution characteristics of beachbar sandbodies were studied by using the method and technology of seismic sedimentology. According to the controlling of sedimentary model and the demarcation of drilling data, the analysis of seismic property of stratal slice could image the distribution area of beachbar sandbodies well and could also recognize and distinguish the beach sands and bar sands effectively. The analysis of statal slices indicates that the sandbodies were progradation at the early and middle stage of MC1 cycle and the sedimentary areas of beach sands and bar sands were extended and migratory obviously, while the sandbodies were vertical aggradation at the middle and late stage of MC1 cycle and the thickness and area of bar sands increased obviously. The distribution area of sandbodies was comparatively stable and the beach sands and bar sands were vertical aggradation during the process of beachbar development at the period of MC2 cycle. The bar sands of the two cycles were, parallel to each other as strips, mainly distribution at the southeast and centre parts of studying area. In the interest of increasing the successful rate of wells and prove up the development characteristics of main bodies of beachbar sandbodies, the exploration should be emphasis on the bar sands development area in southeast and centre parts of studying area.
2013, 31(3): 553-562.
Abstract:
Dishuiquan Area is located in slope area of Kalameili Mountain in the eastern Junggar Basin; at the south are Wucaiwan Depression and Dongdaohaizi Depression; at the west is Dishuiquan Depression.By using of the theory and method of sequence stratigraphy and sedimentology and the data of seismic, well drilling, well logging and core, the authors establish the sequence stratigraphic framework and divide sedimentary facies of Jurassic Badaowan Formation in the Dishuiquan Area. The sequence of Badaowan Formation is one and half, including 5 system tracts divided by two FFS, two MFS and the stable core inner J1b3. The whole experiences the process of retrogradation, progradation and then retrogradation again. Multilevel topographic breaks developed in the Dishuiquan Area in the early Jurassic. Superimposing patterns of system tracts are lowstand system tract, lacustrine transgressive system track and highstand system tract. As is mentioned above, JSB1 is the bottom boundary of the sequence and JSB2 as the top boundary. We divide the middle and lower part with the lower up part of Badaowan Formation into one sequence, from up to down, including lowstand system tract, lacustrine transgressive system track and highstand system tract. Its upper part of the lowstand system tract and lacustrine transgressive system track together with the lower member of Sangonghe Formation of highstand system tract make up another sequence.The Badaowan Group is the first lake influx lake retreat cycle after the late Triassic tectonic uplift, which has the vertical sequence of bottomup development of coarse to fine to coarse complete cycle, and the sedimentary facies perform for the evolution of riverlakedelta. The tectonic activity of Badaowan depositional period is relatively stable, accompanied with regional sublacustrine concussion, and the climate is wet warm. Influenced by ancient water system in the eastern part of the Junggar Basin, the study area constitutes the sedimentary system with eastwest trending. The whole Badaowan Formation deposition in the time and space distribution has the inheritance and variability. The Badaowan Group in the study area mainly developed three kinds of deposition types, which are braided, braided river deltas and lakes, five kinds of sedimentary subfacies types and 10 kinds of sedimentary microfacies type. Braidriver deposits in the study area including the braided channel subfacies and floodplain subfacies, expressed as the peculiar asymmetry of the braided river "dual structure" in vertical. Braided river delta deposition of the study area included braided river delta plain subfacies, braided river delta front subfacies.Viewing from the position of the sand body developing in the sequence, the reservoir sand bodies develop mainly in the low and high system tract, regional mudstone caprock mainly develop in the transgressive systems tract. The Badaowan formation in Dishuiquan area mainly develop two sets of large reservoircap combination.JSQ1 lowstand system tract formation of braided channel sand body has the role of filling the early valleys, also can be used as good reservoir. JSQ1 lake transgressive system tract formation of lacustrine facies mudstone can be used as underlying reservoir favorable cover; JSQ1 high system tract and JSQ2 lowstand system tract formation of braided river delta distributary channel sand body and JSQ2 lake transgressive system tract of lake deposition can be combined to form a reservoir-seal assemblage. Due to the JSQ lowstand system tract developing braided channel sand body, the lateral variation in lithology easy to form the oil and gas lateral occlusion. Therefore, the palaeogeomorphology of valley in study area of Badaowan Formation can be combined with widely distributed braided channel sand body of JSQ1 in the lowstand systems tract to form formation lithologic trap which is the most favorable exploration targets in the study area.
Dishuiquan Area is located in slope area of Kalameili Mountain in the eastern Junggar Basin; at the south are Wucaiwan Depression and Dongdaohaizi Depression; at the west is Dishuiquan Depression.By using of the theory and method of sequence stratigraphy and sedimentology and the data of seismic, well drilling, well logging and core, the authors establish the sequence stratigraphic framework and divide sedimentary facies of Jurassic Badaowan Formation in the Dishuiquan Area. The sequence of Badaowan Formation is one and half, including 5 system tracts divided by two FFS, two MFS and the stable core inner J1b3. The whole experiences the process of retrogradation, progradation and then retrogradation again. Multilevel topographic breaks developed in the Dishuiquan Area in the early Jurassic. Superimposing patterns of system tracts are lowstand system tract, lacustrine transgressive system track and highstand system tract. As is mentioned above, JSB1 is the bottom boundary of the sequence and JSB2 as the top boundary. We divide the middle and lower part with the lower up part of Badaowan Formation into one sequence, from up to down, including lowstand system tract, lacustrine transgressive system track and highstand system tract. Its upper part of the lowstand system tract and lacustrine transgressive system track together with the lower member of Sangonghe Formation of highstand system tract make up another sequence.The Badaowan Group is the first lake influx lake retreat cycle after the late Triassic tectonic uplift, which has the vertical sequence of bottomup development of coarse to fine to coarse complete cycle, and the sedimentary facies perform for the evolution of riverlakedelta. The tectonic activity of Badaowan depositional period is relatively stable, accompanied with regional sublacustrine concussion, and the climate is wet warm. Influenced by ancient water system in the eastern part of the Junggar Basin, the study area constitutes the sedimentary system with eastwest trending. The whole Badaowan Formation deposition in the time and space distribution has the inheritance and variability. The Badaowan Group in the study area mainly developed three kinds of deposition types, which are braided, braided river deltas and lakes, five kinds of sedimentary subfacies types and 10 kinds of sedimentary microfacies type. Braidriver deposits in the study area including the braided channel subfacies and floodplain subfacies, expressed as the peculiar asymmetry of the braided river "dual structure" in vertical. Braided river delta deposition of the study area included braided river delta plain subfacies, braided river delta front subfacies.Viewing from the position of the sand body developing in the sequence, the reservoir sand bodies develop mainly in the low and high system tract, regional mudstone caprock mainly develop in the transgressive systems tract. The Badaowan formation in Dishuiquan area mainly develop two sets of large reservoircap combination.JSQ1 lowstand system tract formation of braided channel sand body has the role of filling the early valleys, also can be used as good reservoir. JSQ1 lake transgressive system tract formation of lacustrine facies mudstone can be used as underlying reservoir favorable cover; JSQ1 high system tract and JSQ2 lowstand system tract formation of braided river delta distributary channel sand body and JSQ2 lake transgressive system tract of lake deposition can be combined to form a reservoir-seal assemblage. Due to the JSQ lowstand system tract developing braided channel sand body, the lateral variation in lithology easy to form the oil and gas lateral occlusion. Therefore, the palaeogeomorphology of valley in study area of Badaowan Formation can be combined with widely distributed braided channel sand body of JSQ1 in the lowstand systems tract to form formation lithologic trap which is the most favorable exploration targets in the study area.
