2008 Vol. 26, No. 6
Display Method:
2008, 26(6): 897-903.
Abstract:
The Longmenshan section is a classical Devonian section in the world, and hence becomes the focus of Paleozoic paleocliamte studies. But in the early Devonian, it is short of geochemical isotopic attestation for the paleoenvironment. It will affect the comparison of geochemical signals between the Longmenshan and the other areas in the world, and also hinder the studying of the paleoclimate in Paleozoic. In this study, geochemical signals that came from well preserved brachiopod shells were used to discuss the paleoenvironment. The preservation show: brachiopod shells are well; noncathodoluminscence and Mn<250 μg/g, Sr>400 μg/g. It is witness that diagenetic alteration was small and even not. The δ18O values -4.5‰ ~-9.9‰ was evidently lower than that of other region’s δ18O values (-1.7‰ ~-6.9‰) in the world. And the trace elements Fe and Mn have inverse isochronous trend to the δ18O values. It is possible that the seawater circulation in the Longmenshan was unsmooth, and its δ18O value was desalinized by the input of continental fresh water. Current study will provide a convincing theoretical basis for contrast of isotope and trace elements on the worldwide scale.
The Longmenshan section is a classical Devonian section in the world, and hence becomes the focus of Paleozoic paleocliamte studies. But in the early Devonian, it is short of geochemical isotopic attestation for the paleoenvironment. It will affect the comparison of geochemical signals between the Longmenshan and the other areas in the world, and also hinder the studying of the paleoclimate in Paleozoic. In this study, geochemical signals that came from well preserved brachiopod shells were used to discuss the paleoenvironment. The preservation show: brachiopod shells are well; noncathodoluminscence and Mn<250 μg/g, Sr>400 μg/g. It is witness that diagenetic alteration was small and even not. The δ18O values -4.5‰ ~-9.9‰ was evidently lower than that of other region’s δ18O values (-1.7‰ ~-6.9‰) in the world. And the trace elements Fe and Mn have inverse isochronous trend to the δ18O values. It is possible that the seawater circulation in the Longmenshan was unsmooth, and its δ18O value was desalinized by the input of continental fresh water. Current study will provide a convincing theoretical basis for contrast of isotope and trace elements on the worldwide scale.
2008, 26(6): 913-924.
Abstract:
In the southwest of Sichuan, Upper Permian Formation, the thickness of Emeishan basalts of Zhougongshan and its neighbor area is from 40m to 500m，and it is formed by 12 cyclic basaltic volcanic rock. The volcanic breccias in the bottom and the stomatal basalts in the upper have some reservoir capability in cyclicity. The reservoir spaces mainly are air voids，basaltia jointing split and tectoclase. Generally, they form lower porosities, medium permeability or lower porosities,higher permeability reservoirs. In other sections, if there are not the superposition of tectonic movement，most of them can not form reservoir rocks，during the formation and evolution of this set of reservoirs, the condensation contract fissure of magmatic melt，tectonic rupture，organic maturation and chemical erosion. All of these have promoted the forming of reservoir spaces. But hydrothermal alterations and 4 stage cementation and 3 stage packing action have obvious damage affection to reservoir spaces.
In the southwest of Sichuan, Upper Permian Formation, the thickness of Emeishan basalts of Zhougongshan and its neighbor area is from 40m to 500m，and it is formed by 12 cyclic basaltic volcanic rock. The volcanic breccias in the bottom and the stomatal basalts in the upper have some reservoir capability in cyclicity. The reservoir spaces mainly are air voids，basaltia jointing split and tectoclase. Generally, they form lower porosities, medium permeability or lower porosities,higher permeability reservoirs. In other sections, if there are not the superposition of tectonic movement，most of them can not form reservoir rocks，during the formation and evolution of this set of reservoirs, the condensation contract fissure of magmatic melt，tectonic rupture，organic maturation and chemical erosion. All of these have promoted the forming of reservoir spaces. But hydrothermal alterations and 4 stage cementation and 3 stage packing action have obvious damage affection to reservoir spaces.
2008, 26(6): 933-938.
Abstract:
Provenance analysis is the basis and promise of depositional system and palaeogeography. To some extend provenance analysis is the reference for microfacies and sandbody distribution, sandbody forecast and evaluation. There were several ancient lands around Ordos Basin during Late Triassic, including Yinshan Old Land of the north, Alxa Old Land to the northewest, QilianQinlin Old Land of the south and Longxi Old Land of the southwest and so on. These Old Lands were the main source of the detrital sediment in the Basin. Jiyuan region locate in west of Ordos Basin in Chang6 depositional stage, Provenance analysis especially pointing out the main source orientation is significant for sedimentary facies and sandbody distribution. By the analysis of debris components, heavy minerals assemblage, lithic fragment components, cathodoluminescence image, REE, and paleosalinity recovery, it indicated that northeast were main source orientation and northwest is the subordinate source orientation of the studied area, and southwest supply sediment at the same time.
Provenance analysis is the basis and promise of depositional system and palaeogeography. To some extend provenance analysis is the reference for microfacies and sandbody distribution, sandbody forecast and evaluation. There were several ancient lands around Ordos Basin during Late Triassic, including Yinshan Old Land of the north, Alxa Old Land to the northewest, QilianQinlin Old Land of the south and Longxi Old Land of the southwest and so on. These Old Lands were the main source of the detrital sediment in the Basin. Jiyuan region locate in west of Ordos Basin in Chang6 depositional stage, Provenance analysis especially pointing out the main source orientation is significant for sedimentary facies and sandbody distribution. By the analysis of debris components, heavy minerals assemblage, lithic fragment components, cathodoluminescence image, REE, and paleosalinity recovery, it indicated that northeast were main source orientation and northwest is the subordinate source orientation of the studied area, and southwest supply sediment at the same time.
2008, 26(6): 947-956.
Abstract:
For the sedimentation microfacies identification based on the well logging curves of different shapes, three conditions including the invariance of translation and dimension scaling and the modifiability of rotation should be satisfied. In this paper, a new method of sedimentation microfacies identification using the shape of well logging curves which can satisfy the three conditions above was set .Through computing the boundary direction probability density of different shapes of well logging curves, then the wavelet transformation should be made, and few low frequency wavelet descriptors whose direction probability density can be reconstructed can be used as the sedimentation microfacies identification and the wavelet descriptor identification of different sedimentation microfacies can be set at the same time. The wavelet analyze should be made for the direction probability density function of different well logging curve, so the sedimentation microfacies information should be mapped to a reduced dimensionality characteristic vector space consist of few low frequency wavelet descriptors from the high dimensionality characteristic vector space, therefore, the discrepancy information of different sedimentation microfacies can be enlarged. For the complicated problem of sedimentation microfacies identification based on the shapes of well logging curves, this method can degenerate it into a simple problem that judging few low frequency wavelet descriptors and the wavelet descriptors can also be used for the sedimentology analysis.
For the sedimentation microfacies identification based on the well logging curves of different shapes, three conditions including the invariance of translation and dimension scaling and the modifiability of rotation should be satisfied. In this paper, a new method of sedimentation microfacies identification using the shape of well logging curves which can satisfy the three conditions above was set .Through computing the boundary direction probability density of different shapes of well logging curves, then the wavelet transformation should be made, and few low frequency wavelet descriptors whose direction probability density can be reconstructed can be used as the sedimentation microfacies identification and the wavelet descriptor identification of different sedimentation microfacies can be set at the same time. The wavelet analyze should be made for the direction probability density function of different well logging curve, so the sedimentation microfacies information should be mapped to a reduced dimensionality characteristic vector space consist of few low frequency wavelet descriptors from the high dimensionality characteristic vector space, therefore, the discrepancy information of different sedimentation microfacies can be enlarged. For the complicated problem of sedimentation microfacies identification based on the shapes of well logging curves, this method can degenerate it into a simple problem that judging few low frequency wavelet descriptors and the wavelet descriptors can also be used for the sedimentology analysis.
2008, 26(6): 967-974.
Abstract:
Based on studies of regional tectonic setting and observation of drilling cores, softsediment deformation structures of Neogene related to earthquake are recognized in the southwestern margin of the Qaidam Basin. The softsediment deformation structures consist of liquefied sandstone vein，water escape structures，load casts，flame structures，pillow structures，ball structures，pillow beds，microfaults, seismocracks，pinch and swell structures，seismofolds, mixed layers structures and seismic brecciated structures. There are five kinds of sand dikes, such as throatlike sand dikes, venationlike sand dikes, beltlike sand dikes, upward wedge sand dikes and vshape sand dikes. They are caused by shakingfluidization, shakingliquefactionpushing and after shakingpulling softsediments filling in cracks. The load casts，flame structures，pillow structures and ball structures are formed by sinking and instilling caused from oscillation of earthquake along the face between sandy and muddy beds. The seismocracks，microfaults and seismofolds are cracks, faults and folds formed directly by oscillation of earthquake. The pillow beds form by dehydration, sinking and deforming of the sandy beds during earthquake′s oscillation. The integrity of mixed layers structure depends on the magnitude and duration of earthquake. The seismic brecciated structures are made up of autoclastic breccias, plastic breccias and brittle breccias formed by the cracking of basal undisturbed laminate bed because of oscillation of earthquake. The discovery demonstrates that the movement of earthquake was violent on the time of Neogene in the north of Kunlun Orogenic Belt from sedimentology, and it provides a theoretical foundation for the tectonic evolution studies of the Qaidam Basin. Seismic events affect greatly on the physical properties of reservoirs, and the permeability of reservoirs can be improved obviously.
Based on studies of regional tectonic setting and observation of drilling cores, softsediment deformation structures of Neogene related to earthquake are recognized in the southwestern margin of the Qaidam Basin. The softsediment deformation structures consist of liquefied sandstone vein，water escape structures，load casts，flame structures，pillow structures，ball structures，pillow beds，microfaults, seismocracks，pinch and swell structures，seismofolds, mixed layers structures and seismic brecciated structures. There are five kinds of sand dikes, such as throatlike sand dikes, venationlike sand dikes, beltlike sand dikes, upward wedge sand dikes and vshape sand dikes. They are caused by shakingfluidization, shakingliquefactionpushing and after shakingpulling softsediments filling in cracks. The load casts，flame structures，pillow structures and ball structures are formed by sinking and instilling caused from oscillation of earthquake along the face between sandy and muddy beds. The seismocracks，microfaults and seismofolds are cracks, faults and folds formed directly by oscillation of earthquake. The pillow beds form by dehydration, sinking and deforming of the sandy beds during earthquake′s oscillation. The integrity of mixed layers structure depends on the magnitude and duration of earthquake. The seismic brecciated structures are made up of autoclastic breccias, plastic breccias and brittle breccias formed by the cracking of basal undisturbed laminate bed because of oscillation of earthquake. The discovery demonstrates that the movement of earthquake was violent on the time of Neogene in the north of Kunlun Orogenic Belt from sedimentology, and it provides a theoretical foundation for the tectonic evolution studies of the Qaidam Basin. Seismic events affect greatly on the physical properties of reservoirs, and the permeability of reservoirs can be improved obviously.
2008, 26(6): 982-993.
Abstract:
According to seismic, welllogs, outcrop & cores data, we identified sequence stratigraphy boundarys. CretaceousPaleogene strata can be recognized as 3 firstorder sequence, 1 secondorder sequences and 4 thirdorder sequences. Based on the principle of base level cycles，the author distinguished & established sequence stratigraphy framework, sedimentary system setting & evolution in CretaceousPaleogene.That is: 1) Early Cretaceous sequence series(Zhuxiang & Xiangdaopu Formations): a semigraben basin which onlapped in the west & faulted in the east, developed great scale alluvial fanalluvial plaindelta plain on the westernnorthern & westernsouthern respecially. On eastern & easternnorthern growth aseries fandeltas & shore semideepdeep lacustrine. 2) Late Cretaceous sequence series(Zhangqiao Formation): similar with Early Cretaceous basically,buta semigraben basin which onlapped in the south & faulted in the north more salience.3) Paleogene Sequence series(Dingyuan Formation): The north of Feizhong fault uplift since tectonic movement so that bisect the basin, Dingyuan depression on the north and Shucheng depression on the south.
According to seismic, welllogs, outcrop & cores data, we identified sequence stratigraphy boundarys. CretaceousPaleogene strata can be recognized as 3 firstorder sequence, 1 secondorder sequences and 4 thirdorder sequences. Based on the principle of base level cycles，the author distinguished & established sequence stratigraphy framework, sedimentary system setting & evolution in CretaceousPaleogene.That is: 1) Early Cretaceous sequence series(Zhuxiang & Xiangdaopu Formations): a semigraben basin which onlapped in the west & faulted in the east, developed great scale alluvial fanalluvial plaindelta plain on the westernnorthern & westernsouthern respecially. On eastern & easternnorthern growth aseries fandeltas & shore semideepdeep lacustrine. 2) Late Cretaceous sequence series(Zhangqiao Formation): similar with Early Cretaceous basically,buta semigraben basin which onlapped in the south & faulted in the north more salience.3) Paleogene Sequence series(Dingyuan Formation): The north of Feizhong fault uplift since tectonic movement so that bisect the basin, Dingyuan depression on the north and Shucheng depression on the south.
2008, 26(6): 1005-1013.
Abstract:
By the identified the regional unconformity, sedimentary system conversion, tectonic stress conversion and exposed surface, the authors divided the Late Paleozoic coalbearing measures in northeastern Ordos basin into seven 3rd sequences. Based on the study, the ternary texture of epicontinental sequence indicate that they also consist of lowstand systems tract, transgressive systems tract and highstand systems tract. Some fluvial sandbodies developed in the northern Ordos basin characteristic by filling of valleyincised in the lowstand systems tract that is sheet sandstone such as Jinci sandstone, Qiaotou sandstone and Beichagou sandstone. The position of coal seams in the sequence framework has relationship to the transformation time of sea level change, and develops mainly at the lower part of transgressive systems tract in epicontinental sequence and the upper part of highstand systems tract in nonmarine sequence.
By the identified the regional unconformity, sedimentary system conversion, tectonic stress conversion and exposed surface, the authors divided the Late Paleozoic coalbearing measures in northeastern Ordos basin into seven 3rd sequences. Based on the study, the ternary texture of epicontinental sequence indicate that they also consist of lowstand systems tract, transgressive systems tract and highstand systems tract. Some fluvial sandbodies developed in the northern Ordos basin characteristic by filling of valleyincised in the lowstand systems tract that is sheet sandstone such as Jinci sandstone, Qiaotou sandstone and Beichagou sandstone. The position of coal seams in the sequence framework has relationship to the transformation time of sea level change, and develops mainly at the lower part of transgressive systems tract in epicontinental sequence and the upper part of highstand systems tract in nonmarine sequence.
2008, 26(6): 1021-1026.
Abstract:
Base level is an imaginary level surface and as a matter of fact, a very physical potential energy level at the same time, which controls stratum depositional and conservation by increasing or decreasing accommodation space. Lacustrine sedimentation is mainly controlled by tectonic action. Seismic onlap pinch out boundary is difficult to be used for confirming excursion of the base level. The sediment types and their superimposed features in log data can conversely verify the rangeability of relative accommodation space. In the light of thickness distribution of the sand shale sequence cycle, we can semiquantitatively analysis rangeability of the base level by selecting middle thickness or average thickness of the maximal bearing value area as statistics area, then accounting thickness of sand and shale of every area from bottom to top, and calculating percentage of the mudstone which endowed with different “base level variety numerical value”. The method is suitable to make definite the changing features of accommodation space, to recognize transform surfaces and base level cycle, and to analysis the dominance for precipitation facies partition. It is applied in base level cycle division and comparison of offshore sedimentation sand or sand shale alternate layer to establish high resolution equitime framework.
Base level is an imaginary level surface and as a matter of fact, a very physical potential energy level at the same time, which controls stratum depositional and conservation by increasing or decreasing accommodation space. Lacustrine sedimentation is mainly controlled by tectonic action. Seismic onlap pinch out boundary is difficult to be used for confirming excursion of the base level. The sediment types and their superimposed features in log data can conversely verify the rangeability of relative accommodation space. In the light of thickness distribution of the sand shale sequence cycle, we can semiquantitatively analysis rangeability of the base level by selecting middle thickness or average thickness of the maximal bearing value area as statistics area, then accounting thickness of sand and shale of every area from bottom to top, and calculating percentage of the mudstone which endowed with different “base level variety numerical value”. The method is suitable to make definite the changing features of accommodation space, to recognize transform surfaces and base level cycle, and to analysis the dominance for precipitation facies partition. It is applied in base level cycle division and comparison of offshore sedimentation sand or sand shale alternate layer to establish high resolution equitime framework.
2008, 26(6): 1035-1042.
Abstract:
Investigations of chlorophyll α was carried out in the seawater and sediment in the Chukchi Sea, Chukchi Plateau, the Slopflow area, the Mendeleev Ride and the Canada Basin during the 2nd Chinese National Arctic Research Expedition in the summer of 2003. The results showed that chlorophyll α concentrations were 0.002~39.008 μg/dm3 at the surveyed waters; the surface chlorophyll α concentrations were 0.037~4.644 μg/dm3 and the average value was 0.612 μg/dm3 in the surveyed area. Chlorophyll α concentrations at the depths 20~30 m of the subsurface water were higher than that in the surface and under layer. Chlorophyll α concentration distribution was obviously areal characteristics. The areal arrange order of the watercolumn chlorophyll α concentration is the Chukchi Sea > the Slopflow area > the Chukchi Plateau > the Canada Basin > the Mendeleev Ride. Chlorophyll α concentrations were 0~3.978 μg/g (wet mug) in the sediment of the surveyed stations; and the average value was 0.934 μg/g(wet mug) in 7 surveyed stations. Chlorophyll α concentrations at the surface sediments were higher than that in the underlayer. The areal arrange order of the sediments chlorophyll α concentration is the Chukchi Sea > the Slopflow area > the Mendeleev Ride, and chlorophyll α concentration can not be examined in the sediments of the Chukchi Plateau and the Canada Basin.
Investigations of chlorophyll α was carried out in the seawater and sediment in the Chukchi Sea, Chukchi Plateau, the Slopflow area, the Mendeleev Ride and the Canada Basin during the 2nd Chinese National Arctic Research Expedition in the summer of 2003. The results showed that chlorophyll α concentrations were 0.002~39.008 μg/dm3 at the surveyed waters; the surface chlorophyll α concentrations were 0.037~4.644 μg/dm3 and the average value was 0.612 μg/dm3 in the surveyed area. Chlorophyll α concentrations at the depths 20~30 m of the subsurface water were higher than that in the surface and under layer. Chlorophyll α concentration distribution was obviously areal characteristics. The areal arrange order of the watercolumn chlorophyll α concentration is the Chukchi Sea > the Slopflow area > the Chukchi Plateau > the Canada Basin > the Mendeleev Ride. Chlorophyll α concentrations were 0~3.978 μg/g (wet mug) in the sediment of the surveyed stations; and the average value was 0.934 μg/g(wet mug) in 7 surveyed stations. Chlorophyll α concentrations at the surface sediments were higher than that in the underlayer. The areal arrange order of the sediments chlorophyll α concentration is the Chukchi Sea > the Slopflow area > the Mendeleev Ride, and chlorophyll α concentration can not be examined in the sediments of the Chukchi Plateau and the Canada Basin.
2008, 26(6): 1052-1062.
Abstract:
We have carried out a relatively complete rock magnetism investigation on loess deposit in the eastern Qinling Mountains, central China. 251 and 341 samples were obtained from Shangbaichuan (SBC) and Erlongshan (ELS) loesspaleosol sections at 10 cm and 5cm intervals, respectively. Magnetic susceptibility was measured on all these samples. Isothermal Remanent Magnetization (IRM) and Anhysteretic Remanent Magnetization(ARM) were measured on 24, 26 and 6 samples selected from SBC, ELS and Liuwan (LW) sections, respectively. The thermal properties and hysteresis properties were measured on 14, 14 and 6 samples from SBC, ELS and LW sections. The results indicate that most of loess and paleosol samples are dominated by ferrimagnetic minerals (magnetite and maghemites) and the paleosols have more ferrimagnetic minerals than that in the loess, but there are still some cases that antiferromagnetic minerals (hematite) play a more important role in the magnetic properties. Both of the concentration of ferrimagnetic minerals and antiferromagnetic minerals systematically increase with the intensified degree of pedogenesis. The finegrained ferrimagnetic minerals, which were formed in pedogenesis, are dominated by single domain and/or pseudosingle domain grains which contribute significantly to the magnetic susceptibility enhancement. The results reveal a strong linkage between the magnetic properties and the palaeoclimate. The rock magnetic properties of the three loesspaleosol sections are generally similar to that in the Loess Plateau, but with a minor difference. In addition, the rock magnetic properties among the three loesspaleosol sequences are slightly different; this may be caused by a warmer and more humid climate in this region.
We have carried out a relatively complete rock magnetism investigation on loess deposit in the eastern Qinling Mountains, central China. 251 and 341 samples were obtained from Shangbaichuan (SBC) and Erlongshan (ELS) loesspaleosol sections at 10 cm and 5cm intervals, respectively. Magnetic susceptibility was measured on all these samples. Isothermal Remanent Magnetization (IRM) and Anhysteretic Remanent Magnetization(ARM) were measured on 24, 26 and 6 samples selected from SBC, ELS and Liuwan (LW) sections, respectively. The thermal properties and hysteresis properties were measured on 14, 14 and 6 samples from SBC, ELS and LW sections. The results indicate that most of loess and paleosol samples are dominated by ferrimagnetic minerals (magnetite and maghemites) and the paleosols have more ferrimagnetic minerals than that in the loess, but there are still some cases that antiferromagnetic minerals (hematite) play a more important role in the magnetic properties. Both of the concentration of ferrimagnetic minerals and antiferromagnetic minerals systematically increase with the intensified degree of pedogenesis. The finegrained ferrimagnetic minerals, which were formed in pedogenesis, are dominated by single domain and/or pseudosingle domain grains which contribute significantly to the magnetic susceptibility enhancement. The results reveal a strong linkage between the magnetic properties and the palaeoclimate. The rock magnetic properties of the three loesspaleosol sections are generally similar to that in the Loess Plateau, but with a minor difference. In addition, the rock magnetic properties among the three loesspaleosol sequences are slightly different; this may be caused by a warmer and more humid climate in this region.
2008, 26(6): 1063-1070.
Abstract:
The proved reserves of nonhigh temperatureoriginated natural gas (biogenic gaslow maturity gas)in Tuha basin is already near 100×109 m3, but we didn’t sees the reported about appraises to the effective method of generation quantity and resource quantum yet, this has affected the decisionmaking to its exploration potential and the favorable target. In view of this problem, considering regardless the generation mechanism of biogenic gas and low maturity gas, they were an organic element balance process; this article explored and established element balance method to appraise the gasgenerated amount of biogenic gas and low maturity gas.We use massive actual analysis data of Tuha basin to demarcate and apply this assessment method. The result indicated that biogenic gaslow maturity gas generation rate of ⅡOM is higher than III OM in Tuha basin, the two accumulate separately may reach 134.40ml/g and 83.99ml/g, total generation quantity of biogenic gaslow maturity gas in Tuha basin approximately 1436.28×1012m3; The resource quantum is possibly situated between 7.09×1011m3~24.42×1011m3 it indicated that nonhigh temperature originated natural gas in the Tuha basin has big exploration potential. J2x and J1 and the nearby position in Taibei hollow are the favorable exploration target.
The proved reserves of nonhigh temperatureoriginated natural gas (biogenic gaslow maturity gas)in Tuha basin is already near 100×109 m3, but we didn’t sees the reported about appraises to the effective method of generation quantity and resource quantum yet, this has affected the decisionmaking to its exploration potential and the favorable target. In view of this problem, considering regardless the generation mechanism of biogenic gas and low maturity gas, they were an organic element balance process; this article explored and established element balance method to appraise the gasgenerated amount of biogenic gas and low maturity gas.We use massive actual analysis data of Tuha basin to demarcate and apply this assessment method. The result indicated that biogenic gaslow maturity gas generation rate of ⅡOM is higher than III OM in Tuha basin, the two accumulate separately may reach 134.40ml/g and 83.99ml/g, total generation quantity of biogenic gaslow maturity gas in Tuha basin approximately 1436.28×1012m3; The resource quantum is possibly situated between 7.09×1011m3~24.42×1011m3 it indicated that nonhigh temperature originated natural gas in the Tuha basin has big exploration potential. J2x and J1 and the nearby position in Taibei hollow are the favorable exploration target.
2008, 26(6): 1077-1085.
Abstract:
Nanpu Sag is rich in oil and gas and the main hydrocarbon source rocks of the Eogene are distributed within Es3，Es1 and Ed3 Formations. Based on the sequence stratigraphy study, the hydrocarbongenerating potential and distribution of source rocks in the Eogene sequence stratigraphic framework of Nanpu sag are discussed in this paper by the methods of organic petrology, geochemistry and organic facies. The results show that the heterogeneity of source rocks varies in different systems tracts. The hydrocarbon source rocks which were deposited in the early highstand systems tract and extent systems tract have the best hydrocarbongenerating potential in the SQ9, SQ5SQ8, SQ2 and SQ1 of Eogene, because the characteristics of sedimentation in the different systems tracts affect the type and conservation of organic materials in source rocks.
Nanpu Sag is rich in oil and gas and the main hydrocarbon source rocks of the Eogene are distributed within Es3，Es1 and Ed3 Formations. Based on the sequence stratigraphy study, the hydrocarbongenerating potential and distribution of source rocks in the Eogene sequence stratigraphic framework of Nanpu sag are discussed in this paper by the methods of organic petrology, geochemistry and organic facies. The results show that the heterogeneity of source rocks varies in different systems tracts. The hydrocarbon source rocks which were deposited in the early highstand systems tract and extent systems tract have the best hydrocarbongenerating potential in the SQ9, SQ5SQ8, SQ2 and SQ1 of Eogene, because the characteristics of sedimentation in the different systems tracts affect the type and conservation of organic materials in source rocks.
2008, 26(6): 904-912.
Abstract:
A largescale metazoa framebuilding reef system was developed in the southern Guizhou Province during the LateCarboniferous, which was rarely reported in the geological records after the F/F mass extinction event. The reef structure was mainly built by rugosan corals Fomitchevella, and is, from the bottom to top, composed of four subunits: bioclastic shore, patchy reef and mud mound, bioclastic limestone and Fomitchevella framestone. The organisms in ecosystem of each unit are variable, due to different tropic level in which producers, consumers and decomposers are differentiated in view of their behavior in the food chain, reefbuilder and reefdwellers in view of their functions in the reefbuilding process. The analysis shows that the organisms play different roles in reefbuilding process due to their status in the food chain. According to the contribution of the organisms and energy and macronutrient flow diagram, a new understanding that the coral reef ecosystem rapidly uptake the macronutrient is obtained. According to the composition and the relationship of the organisms, the development process of the ecosystem is supposed based on the organisms and their spatial location relationships, and can be divided into bioclastic shoal stage, patchy reef and mud mound stage, Fomitchevella colonizing stage and Fomitchevelladominant stage. The different behaviors and growth forms of Fomitchevella and Ivanovia cf. manchurica determined their status in the coral reef ecosystem, and the ecosystem maintained survivorship and development of the species by rapidly up taking the macronutrient.
A largescale metazoa framebuilding reef system was developed in the southern Guizhou Province during the LateCarboniferous, which was rarely reported in the geological records after the F/F mass extinction event. The reef structure was mainly built by rugosan corals Fomitchevella, and is, from the bottom to top, composed of four subunits: bioclastic shore, patchy reef and mud mound, bioclastic limestone and Fomitchevella framestone. The organisms in ecosystem of each unit are variable, due to different tropic level in which producers, consumers and decomposers are differentiated in view of their behavior in the food chain, reefbuilder and reefdwellers in view of their functions in the reefbuilding process. The analysis shows that the organisms play different roles in reefbuilding process due to their status in the food chain. According to the contribution of the organisms and energy and macronutrient flow diagram, a new understanding that the coral reef ecosystem rapidly uptake the macronutrient is obtained. According to the composition and the relationship of the organisms, the development process of the ecosystem is supposed based on the organisms and their spatial location relationships, and can be divided into bioclastic shoal stage, patchy reef and mud mound stage, Fomitchevella colonizing stage and Fomitchevelladominant stage. The different behaviors and growth forms of Fomitchevella and Ivanovia cf. manchurica determined their status in the coral reef ecosystem, and the ecosystem maintained survivorship and development of the species by rapidly up taking the macronutrient.
2008, 26(6): 925-932.
Abstract:
In order to investigate the relation between the distribution of mineral elements and sedimentary environment including the salinity and depth of water body, and the evolution of lakebasin, emission spectrograph of inductive coupling plasma was used to intensively testing and dissection the content of mineral elements in the deep death of the Paleogene from the Well Haoke1 in Dongying sag. The involved formation contained the Member 3, Member 4 of Shahejie Formation and Kongdian Formation, in which the main source rocks distributed. The results demonstrate that: in the oxidized sedimentary environment of shallow shorelacustrine the content of Sr, Ca and the parameters of Ca/Mg, Sr/Ba, Sr/Ca have low value response, the content of Fe, Al, Ba, V and the parameter of (Fe+Al)/(Ca+Mg) have high value response; in the brinelake sedimentary environment the content of Mn, Ba,V and the parameters of V/Ni, (Fe+Al)/(Ca+Mg) have low value response, the content of Sr, Na and the parameters of Sr/Ba, Fe/Mn, Sr/Ca have high value response; in the reductive brackish sedimentary environment of halfdeep lacustrine lake the content of K, Na, Fe and the parameters of Fe/Mn have low value response, the content of Ca, Mn have high value response. In the cosedimentary environment of saline deposit and mud of the middle part of Sha4 Formation, the distribution of mineral elements has obvious characteristics of discretion and fluctuation. Sr/Ba, Sr/Ca have obvious high value response in the saline lake and are verified to be good parameters for salinity of waterbody. The parameters of Fe/Mn and (Fe+Al)/(Ca+Mg) are approved to be good parameters for the depth of waterbody and their value increased with deepening of waterbody. The parameters abovementioned should be applied and synthetically analyzed to determine characteristics of geological factors for the parameters were influenced by many geological factors including sedimentary environment and lithologic character.
In order to investigate the relation between the distribution of mineral elements and sedimentary environment including the salinity and depth of water body, and the evolution of lakebasin, emission spectrograph of inductive coupling plasma was used to intensively testing and dissection the content of mineral elements in the deep death of the Paleogene from the Well Haoke1 in Dongying sag. The involved formation contained the Member 3, Member 4 of Shahejie Formation and Kongdian Formation, in which the main source rocks distributed. The results demonstrate that: in the oxidized sedimentary environment of shallow shorelacustrine the content of Sr, Ca and the parameters of Ca/Mg, Sr/Ba, Sr/Ca have low value response, the content of Fe, Al, Ba, V and the parameter of (Fe+Al)/(Ca+Mg) have high value response; in the brinelake sedimentary environment the content of Mn, Ba,V and the parameters of V/Ni, (Fe+Al)/(Ca+Mg) have low value response, the content of Sr, Na and the parameters of Sr/Ba, Fe/Mn, Sr/Ca have high value response; in the reductive brackish sedimentary environment of halfdeep lacustrine lake the content of K, Na, Fe and the parameters of Fe/Mn have low value response, the content of Ca, Mn have high value response. In the cosedimentary environment of saline deposit and mud of the middle part of Sha4 Formation, the distribution of mineral elements has obvious characteristics of discretion and fluctuation. Sr/Ba, Sr/Ca have obvious high value response in the saline lake and are verified to be good parameters for salinity of waterbody. The parameters of Fe/Mn and (Fe+Al)/(Ca+Mg) are approved to be good parameters for the depth of waterbody and their value increased with deepening of waterbody. The parameters abovementioned should be applied and synthetically analyzed to determine characteristics of geological factors for the parameters were influenced by many geological factors including sedimentary environment and lithologic character.
2008, 26(6): 939-946.
Abstract:
There are many thin mud laminas of mmclass in the Cretaceous equal silt stone in Yingtai area, western Songliao Basin, which we call them mudfilms, have a thickness between 0.2 and 3 mm, and the main component is shale while some are carbon dust layers. They are three kinds of conformation of mudfilms on section: close straight line, serrated denticle and irregular curve. There are many micro transmutation structures with the scale less than 3 mm on the surface of mudfilms, we divide all the micro transmutation structures into 9 types: straight line, C/S, circle, ellipse, and leaf of bamboo, ripple mark, twig, mesh and irregular patterns. Some micro transmutation structures are too hard to be breakthrough and so the silt stone up and below the mudfilm can connect each other. The origin of the mud films are mud subsidence or sideway mud erosion in may momentary sedimentary break. There are many causes of formations of the mudfilms such as syndeposit interfere, differential compaction, bedding glide, bioturbation, diagenesis shrink and earthquake activities. The study on the cause of formations and micro transmutation structures of the mudfilms will have an important significance for the research of sedimentary environment and the fine space structure of the reservoirs.
There are many thin mud laminas of mmclass in the Cretaceous equal silt stone in Yingtai area, western Songliao Basin, which we call them mudfilms, have a thickness between 0.2 and 3 mm, and the main component is shale while some are carbon dust layers. They are three kinds of conformation of mudfilms on section: close straight line, serrated denticle and irregular curve. There are many micro transmutation structures with the scale less than 3 mm on the surface of mudfilms, we divide all the micro transmutation structures into 9 types: straight line, C/S, circle, ellipse, and leaf of bamboo, ripple mark, twig, mesh and irregular patterns. Some micro transmutation structures are too hard to be breakthrough and so the silt stone up and below the mudfilm can connect each other. The origin of the mud films are mud subsidence or sideway mud erosion in may momentary sedimentary break. There are many causes of formations of the mudfilms such as syndeposit interfere, differential compaction, bedding glide, bioturbation, diagenesis shrink and earthquake activities. The study on the cause of formations and micro transmutation structures of the mudfilms will have an important significance for the research of sedimentary environment and the fine space structure of the reservoirs.
2008, 26(6): 957-966.
Abstract:
Two genetically distinct dolomite fillings are recognized in Lower Paleozoic dolostone in the Upper CambrianLower Ordovician dolostone of the Central uplift, Tarim basin: rhombus and saddle dolomite fillings, which occur in different diagenetic considerations and have different character. The former crystal exhibits homogeneous, the later crystal is composed of three distinct parts that are rim, clitellum and core. Stratigraphic, petrographic and geochemical date suggest, rhombus dolomite filling deposited steadily and source of Mg2+ is from the altered seawater. However, material source of saddle dolomite filling is hydrothermal dissolution of dolomite. The formation of saddle dolomite filling, three parts of which formed in different phase, is associated with faulting. The deposition of dolomite filling is porosity decreasing, but saddle dolomite is a sign of dissolution.
Two genetically distinct dolomite fillings are recognized in Lower Paleozoic dolostone in the Upper CambrianLower Ordovician dolostone of the Central uplift, Tarim basin: rhombus and saddle dolomite fillings, which occur in different diagenetic considerations and have different character. The former crystal exhibits homogeneous, the later crystal is composed of three distinct parts that are rim, clitellum and core. Stratigraphic, petrographic and geochemical date suggest, rhombus dolomite filling deposited steadily and source of Mg2+ is from the altered seawater. However, material source of saddle dolomite filling is hydrothermal dissolution of dolomite. The formation of saddle dolomite filling, three parts of which formed in different phase, is associated with faulting. The deposition of dolomite filling is porosity decreasing, but saddle dolomite is a sign of dissolution.
2008, 26(6): 975-981.
Abstract:
Based on studies of regional tectonic background and the observation of drilling cores, the seismite is recognized which mainly occurred in Cretaceous in South Beir sag, Mongolia. Many kinds of soft sedimentary deformation structures have been found in seismite, such as step microfaults, pleated within layers, liquefaction sandstone veins, vibrational liquefaction deformation structure and seismic breccias. It is the first time that seismite has been found in South Beir sag, Mongolia. The complete vertical sequence of seismite developed in Well Ta219, which include bottom unshaken layer, liquefied sandstone vein bed, vibration liquefaction deformation structure bed, intraclastic parabreccia bed, laddershaped faulted and vibration split bed, seismic turbidite bed and top unshaken layer. It is rare among the reported examples about such complete sequence of seismite in one Well's core, so it is a good example and offers power evidences to study seismism.
Based on studies of regional tectonic background and the observation of drilling cores, the seismite is recognized which mainly occurred in Cretaceous in South Beir sag, Mongolia. Many kinds of soft sedimentary deformation structures have been found in seismite, such as step microfaults, pleated within layers, liquefaction sandstone veins, vibrational liquefaction deformation structure and seismic breccias. It is the first time that seismite has been found in South Beir sag, Mongolia. The complete vertical sequence of seismite developed in Well Ta219, which include bottom unshaken layer, liquefied sandstone vein bed, vibration liquefaction deformation structure bed, intraclastic parabreccia bed, laddershaped faulted and vibration split bed, seismic turbidite bed and top unshaken layer. It is rare among the reported examples about such complete sequence of seismite in one Well's core, so it is a good example and offers power evidences to study seismism.
2008, 26(6): 994-1004.
Abstract:
Abu Gabra Formation of Cretaceous Fula depression, which is formed during the first rifting cycle, can be divided into three secondorder sequences, namely, sequence K1SSI, sequence K1SSII and sequence K1SSIII. They can correspond separately to the strata deposited in the early, middle and late rift period. Of the three secondorder sequences, the sequence K1SSI and sequence K1SSIII can be subdivided into two thirdorder sequences, the sequence K1SSII into three thirdorder sequences. Based on the integrated analysis of seismic data, core and well logging, the distribution of sedimentary facies and the prediction of sedimentary system are achieved. Through investigation, 7 types of sedimentary facies are recognized, namely, fluvial deposit, delta, fan delta, braided delta, proximal sublacustrine fan, lacustrine facies.
Due to the evolution of their sedimentary facies, five chief depositional systems are established in the Fula depression. They are fan delta system in the NE, delta system in the NW, proximal sublacustrine fan in the west, braided delta system in the ES and fluvial system produced in the early period. The distribution and evolution of the depositional systems is controlled by tectonics, probably influenced by paleotopography and paleogeography.
Abu Gabra Formation of Cretaceous Fula depression, which is formed during the first rifting cycle, can be divided into three secondorder sequences, namely, sequence K1SSI, sequence K1SSII and sequence K1SSIII. They can correspond separately to the strata deposited in the early, middle and late rift period. Of the three secondorder sequences, the sequence K1SSI and sequence K1SSIII can be subdivided into two thirdorder sequences, the sequence K1SSII into three thirdorder sequences. Based on the integrated analysis of seismic data, core and well logging, the distribution of sedimentary facies and the prediction of sedimentary system are achieved. Through investigation, 7 types of sedimentary facies are recognized, namely, fluvial deposit, delta, fan delta, braided delta, proximal sublacustrine fan, lacustrine facies.
Due to the evolution of their sedimentary facies, five chief depositional systems are established in the Fula depression. They are fan delta system in the NE, delta system in the NW, proximal sublacustrine fan in the west, braided delta system in the ES and fluvial system produced in the early period. The distribution and evolution of the depositional systems is controlled by tectonics, probably influenced by paleotopography and paleogeography.
2008, 26(6): 1014-1020.
Abstract:
On the principle of baselevel cycling and through the integrated analysis of cores, well logs and 3D seismic data, we divided the Dongying Formation (Ed) in Qingshui Depression into 4 thirdorder sequences, namely Lower Ed3, Upper Ed3, Ed2 and Ed1, and recognized three types of sedimentary systems, i.e. the semideep lacustrine subaqueous fan system, the shallow lacustrinedelta system and the alluvialfloodplain system. On the basis of the sequence identification and the sedimentary system recognition, we then studied the configuration of sedimentary systems and the development of reservoir sandbodies in the sequential context. Finally, after evaluating the oilgeneration, preservation and seal conditions, we concluded that, Lower Ed3 and Upper Ed3 sequences are the most favorable sections vertically, and exploration targets are subwater fans and delta front sands, mainly channel sands, mouth bars and sheet sands.
On the principle of baselevel cycling and through the integrated analysis of cores, well logs and 3D seismic data, we divided the Dongying Formation (Ed) in Qingshui Depression into 4 thirdorder sequences, namely Lower Ed3, Upper Ed3, Ed2 and Ed1, and recognized three types of sedimentary systems, i.e. the semideep lacustrine subaqueous fan system, the shallow lacustrinedelta system and the alluvialfloodplain system. On the basis of the sequence identification and the sedimentary system recognition, we then studied the configuration of sedimentary systems and the development of reservoir sandbodies in the sequential context. Finally, after evaluating the oilgeneration, preservation and seal conditions, we concluded that, Lower Ed3 and Upper Ed3 sequences are the most favorable sections vertically, and exploration targets are subwater fans and delta front sands, mainly channel sands, mouth bars and sheet sands.
2008, 26(6): 1027-1034.
Abstract:
The aboudances of the rare earth elements (REEs) of 35 coal samples (including 12 samples of floor and roof seam and 1 gangue sample) in Zibo coalfield were determined by inductively coupleplasma mass spectrometry (ICPMS), and the content of ash and some correlative associated elements are also tested. The contents of the REE, geochemical parameters, spatial distribution and distribution patterns were studied in this paper. Furthermore, the author discussed the characteristics and origin of REE in the samples. The results are as follows: Compared with others areas at home and abroad, the REE are obviously enriched in Zibo coalfield. The REE contents in the Taiyuan Formation are higher than that in the Shanxi Formation. They rise from top to bottom in the coal seam and enrich in the floor and roof and gangue samples. The negative anomalies exists in the value of δEu and normal value in δCe indicate that the sedimentary environment of coal may shallow or close sea. The REE in coal is correlative to the ash contents in those coals, and they have good relativity with the terrigenous elements while weak with the marine elements.
The aboudances of the rare earth elements (REEs) of 35 coal samples (including 12 samples of floor and roof seam and 1 gangue sample) in Zibo coalfield were determined by inductively coupleplasma mass spectrometry (ICPMS), and the content of ash and some correlative associated elements are also tested. The contents of the REE, geochemical parameters, spatial distribution and distribution patterns were studied in this paper. Furthermore, the author discussed the characteristics and origin of REE in the samples. The results are as follows: Compared with others areas at home and abroad, the REE are obviously enriched in Zibo coalfield. The REE contents in the Taiyuan Formation are higher than that in the Shanxi Formation. They rise from top to bottom in the coal seam and enrich in the floor and roof and gangue samples. The negative anomalies exists in the value of δEu and normal value in δCe indicate that the sedimentary environment of coal may shallow or close sea. The REE in coal is correlative to the ash contents in those coals, and they have good relativity with the terrigenous elements while weak with the marine elements.
2008, 26(6): 1043-1052.
Abstract:
Grain size parameter is the most important information of sediment, which can point out the characteristics of distribution and transportation. Based on analysis data of 167 samples which were collected from the north coast of Hangzhou Bay in June 2005 and December 2006, a study on the rules of temporal and spatial changes in properties of seabed surface sediment in strongtide bay is conducted. As well as, through the Grain Size Transport Analysis model, a conveying trend analysis of sediment in this basin has been studied, in the base of which a research of sand sources is primarily discussed. Finally, the response process of tidal flat sediment to the highenergy hydrodynamic environment is also analyzed. The results indicate that: (1) The grain size of tidal flat sediment in north coast of Hangzhou Bay is generally small, and silty clay is the main sediment types in this basin; (2) The vertical difference of grain size characteristics is more obvious than the transversal, and also there is some seasonal variation between flood season and withered season; (3)The results of GSTAmodel show that，the sediment of this basin is mainly from the upstream and the sea waters. As well as , the interregional sediment exchange is another important method to get the balance of sediment supply in this basin；(4) Agency coverage where tide current can stir surface sediment is mostly the Nanhui and Fengxian water area, while the wave stirring agency coverage almost covers the whole section of the research basin, on which the wave height below 1.5m effect most significantly.
Grain size parameter is the most important information of sediment, which can point out the characteristics of distribution and transportation. Based on analysis data of 167 samples which were collected from the north coast of Hangzhou Bay in June 2005 and December 2006, a study on the rules of temporal and spatial changes in properties of seabed surface sediment in strongtide bay is conducted. As well as, through the Grain Size Transport Analysis model, a conveying trend analysis of sediment in this basin has been studied, in the base of which a research of sand sources is primarily discussed. Finally, the response process of tidal flat sediment to the highenergy hydrodynamic environment is also analyzed. The results indicate that: (1) The grain size of tidal flat sediment in north coast of Hangzhou Bay is generally small, and silty clay is the main sediment types in this basin; (2) The vertical difference of grain size characteristics is more obvious than the transversal, and also there is some seasonal variation between flood season and withered season; (3)The results of GSTAmodel show that，the sediment of this basin is mainly from the upstream and the sea waters. As well as , the interregional sediment exchange is another important method to get the balance of sediment supply in this basin；(4) Agency coverage where tide current can stir surface sediment is mostly the Nanhui and Fengxian water area, while the wave stirring agency coverage almost covers the whole section of the research basin, on which the wave height below 1.5m effect most significantly.
2008, 26(6): 1071-1076.
Abstract:
The analytical results of the whole and the monomer paraffin hydrocarbons carbon isotope of the 20 oils from Lunnan and Hadexun oil fields show that the whole carbon isotope of the oils from Lunnan area is more than 32‰, and that of the oils from Hadexun area is less than 32‰, the carbon isotope of monomer paraffin hydrocarbons of the oils from Lunnan area is also heavier than that of the oils from Hadexun area. That the carbon isotope of oils from Lunnan area heavier than that of oils from Lunnan area caused the difference between the oil pools formation in the two areas. The main factor resulted in the carbon isotope of oils from Lunnan area heavier than that of oils from Hadexun area is the mixture between the degraded oil from the Cambrian source rock and the oils from MiddleUpper Ordovician source rock, instead of the different source rocks of the oils.
The analytical results of the whole and the monomer paraffin hydrocarbons carbon isotope of the 20 oils from Lunnan and Hadexun oil fields show that the whole carbon isotope of the oils from Lunnan area is more than 32‰, and that of the oils from Hadexun area is less than 32‰, the carbon isotope of monomer paraffin hydrocarbons of the oils from Lunnan area is also heavier than that of the oils from Hadexun area. That the carbon isotope of oils from Lunnan area heavier than that of oils from Lunnan area caused the difference between the oil pools formation in the two areas. The main factor resulted in the carbon isotope of oils from Lunnan area heavier than that of oils from Hadexun area is the mixture between the degraded oil from the Cambrian source rock and the oils from MiddleUpper Ordovician source rock, instead of the different source rocks of the oils.
