1997 Vol. 15, No. 3
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Display Method:
1997, 15(3): 1-7.
Abstract:
The study area lies in the Longmenshan area on the western margin of the Yangtz Plate, where the Ping Yipu Formation, Lower Devonian are well exposed. Four depositional systems and three third-or-der T-R cyclic sequences have been distinguished from the formation. In this region, the paleo-geographic pattern along the ancient continental margin of the Yangtz Plate was formed of the transi-tional faoies zone alternating with littoral fades zone. In the vertical sections, the third-order cyclic se-quences were made of different depositional systems sparately in the two facies zones, which the se-quences of foreshore (or tidal)estuary inner-outer shelf delta were developed in the transitional fa-cies zone, and the other sequences of foreshore nearshorer inner shelf(yes or no) foreshore-backshore were developed in the littoral facies zone. The sedimentary evolutional characteristics of thetwo facies zones were different and controlled by different geological conditions, including tectonic activ-ity intensity, rate of tectonic descent and deposition, paleogeographic seat and world sealev el chang e sdining Early Devonian. Because of the world sea-level changes was the main and primary factor to con-trol the evolution of the three cyclic sequences in the formation, the third-order T-R cyclic sequence in the two sedimentary facies zones were synchronous and may be correlated with other oreas, such as theSouth China and the world. According to the evidences above mention, two cyclic sequence models ofancient continental margin of the Yangtz Plate have been advenced in this paper, which were of the ac-tiv e o r relatively stable tectonic descent setting.
The study area lies in the Longmenshan area on the western margin of the Yangtz Plate, where the Ping Yipu Formation, Lower Devonian are well exposed. Four depositional systems and three third-or-der T-R cyclic sequences have been distinguished from the formation. In this region, the paleo-geographic pattern along the ancient continental margin of the Yangtz Plate was formed of the transi-tional faoies zone alternating with littoral fades zone. In the vertical sections, the third-order cyclic se-quences were made of different depositional systems sparately in the two facies zones, which the se-quences of foreshore (or tidal)estuary inner-outer shelf delta were developed in the transitional fa-cies zone, and the other sequences of foreshore nearshorer inner shelf(yes or no) foreshore-backshore were developed in the littoral facies zone. The sedimentary evolutional characteristics of thetwo facies zones were different and controlled by different geological conditions, including tectonic activ-ity intensity, rate of tectonic descent and deposition, paleogeographic seat and world sealev el chang e sdining Early Devonian. Because of the world sea-level changes was the main and primary factor to con-trol the evolution of the three cyclic sequences in the formation, the third-order T-R cyclic sequence in the two sedimentary facies zones were synchronous and may be correlated with other oreas, such as theSouth China and the world. According to the evidences above mention, two cyclic sequence models ofancient continental margin of the Yangtz Plate have been advenced in this paper, which were of the ac-tiv e o r relatively stable tectonic descent setting.
1997, 15(3): 14-17.
Abstract:
Based on sequence stratigraphy work for the outcrops in Tarim Basin, The author sets up theSealevel changes curve of sinian period to Devonian period. Then the author studies the relationship be-tween oxygen isotope and sealevel changes and finds the oxygen isotope ratio' s increase and decredse in-dicating the sealevel' s down and up. The correctness of sealevel changes curve is tested and verified bythe result of oygen isotope. The ranges of sealevel changes are calculated. Finally the author elaboratesthe formation mechanism of sealevel changes of Sinian period to Devonian period in Tarim Basin.
Based on sequence stratigraphy work for the outcrops in Tarim Basin, The author sets up theSealevel changes curve of sinian period to Devonian period. Then the author studies the relationship be-tween oxygen isotope and sealevel changes and finds the oxygen isotope ratio' s increase and decredse in-dicating the sealevel' s down and up. The correctness of sealevel changes curve is tested and verified bythe result of oygen isotope. The ranges of sealevel changes are calculated. Finally the author elaboratesthe formation mechanism of sealevel changes of Sinian period to Devonian period in Tarim Basin.
1997, 15(3): 23-28.
Abstract:
Based on the correlation of the depositional sequences in different orders on the internal YangtzePlate, Yangtze Plate and Huabei Plate, Yangtze Plate and Euramerica Plate, the sea-level curve of theCarboniferous in the main areas of worldwide was worked out. within the Yangtze Plate, the 2nd orderdeposition sequence can be correlated between the Upper Yangtze and Lower Yangtze region, but trans-gression and onlap on the Lower Yangtze region lagged the Upper Yangtze region, the 3rd order deposi-tional sequence can not be correlated because of lacking enough data. In the Huabei Plate, there are one3rd order depositional sequence in the Fusulinella-Fusulina zone and four 3rd order depositional se-quences in the Triticites-Pseuoschwagerina zone, all of them can be correlated with those on the YangtzePlate. Between the Yangtze Plate and the Eurmarican Plate, the 3rd and 4th order can be correlated dur-ing Gzhelian of the Later Carboniferous, but the compositions of the the 4th order depositional sequenceis different because the Yangtze Plate and the North Mid-American continent ( representing the Eurmari-can Plate ) are located in different tectonic setting, the same number of the 4th order depositional se-quences on the two different plates is regarded as the proof of depositional records of synchroneity, whichwas caused by global glacial-eustasy. Those reasons of the similarity and difference on the depositionalsequence orders for the same plate or different plate were discussed both for the glacial period andnonglacial period. The glacial eustasy is the primary factor which controls depositional sequences.There should be global!synchroneity among depositional sequences. But the difference of depositioncondition in the some area will also affect compositions ofdepositional sequences.
Based on the correlation of the depositional sequences in different orders on the internal YangtzePlate, Yangtze Plate and Huabei Plate, Yangtze Plate and Euramerica Plate, the sea-level curve of theCarboniferous in the main areas of worldwide was worked out. within the Yangtze Plate, the 2nd orderdeposition sequence can be correlated between the Upper Yangtze and Lower Yangtze region, but trans-gression and onlap on the Lower Yangtze region lagged the Upper Yangtze region, the 3rd order deposi-tional sequence can not be correlated because of lacking enough data. In the Huabei Plate, there are one3rd order depositional sequence in the Fusulinella-Fusulina zone and four 3rd order depositional se-quences in the Triticites-Pseuoschwagerina zone, all of them can be correlated with those on the YangtzePlate. Between the Yangtze Plate and the Eurmarican Plate, the 3rd and 4th order can be correlated dur-ing Gzhelian of the Later Carboniferous, but the compositions of the the 4th order depositional sequenceis different because the Yangtze Plate and the North Mid-American continent ( representing the Eurmari-can Plate ) are located in different tectonic setting, the same number of the 4th order depositional se-quences on the two different plates is regarded as the proof of depositional records of synchroneity, whichwas caused by global glacial-eustasy. Those reasons of the similarity and difference on the depositionalsequence orders for the same plate or different plate were discussed both for the glacial period andnonglacial period. The glacial eustasy is the primary factor which controls depositional sequences.There should be global!synchroneity among depositional sequences. But the difference of depositioncondition in the some area will also affect compositions ofdepositional sequences.
1997, 15(3): 33-36.
Abstract:
Palaeochannel deposits are a type of special lithosomic body with various forms on seismic profile. I-dentification of the lithosomic body is of difficulty and needs careful observation and detalled analysis.The channel sedimentation is of its own speciality and can form several types of sedimentary sandstoneswhich may be highly productive hydrocarbon reservoirs if they approach source rocks. Channle depositshave been found in many fields in China, and in some of them commercial oil and gas flow of high produc-tion has been discovered by drilling. Therefore, identification of palaeochannel deposition from seismicdata has been an important research subject concerned by many geologists. This paper gave a detaileddiscussion on sedimentary features and seismic facies as well as reflectional characteristics of seismic pro-files of the palaeochannel sedimentation.
Palaeochannel deposits are a type of special lithosomic body with various forms on seismic profile. I-dentification of the lithosomic body is of difficulty and needs careful observation and detalled analysis.The channel sedimentation is of its own speciality and can form several types of sedimentary sandstoneswhich may be highly productive hydrocarbon reservoirs if they approach source rocks. Channle depositshave been found in many fields in China, and in some of them commercial oil and gas flow of high produc-tion has been discovered by drilling. Therefore, identification of palaeochannel deposition from seismicdata has been an important research subject concerned by many geologists. This paper gave a detaileddiscussion on sedimentary features and seismic facies as well as reflectional characteristics of seismic pro-files of the palaeochannel sedimentation.
1997, 15(3): 41-47.
Abstract:
Studies showed that the Silurian sytem in the Tazhong area was deposited in an epicontinental sea tidal flat environment. Combined its depositional feature and setting with the hydrodynamic feature ofepicontinental sea area, an epicontinental sea facies model of clastic deposits of the Silurian system in theTazhong area is established. Furthermore,it can be subdivided into three microfacies: mud flat and mixedflat, and sand flat. Its facies is broad and stable, but there exist no barrier island deposits. Compared withthe flat depositional facies nowadays,it is deposited in deeper water. part of the mud flat and most of themixed flat develop under the water, the hydrodynamics of the sand flat is relatively weak. Tidal currentand hurricane current mainly control the transportation and reconstruction of the clastics, so their de-posits are popular, especially in the sand flat and mixed flat. A vertical coarsing-upward sequence is pre-sent in the transgressive period and cross- bedding is common in the sandstone. In the retrogressive pe-riod, sandstones with good continuity and a stable mud flat are formed in a broad area. Near some of the underwater high land in the sand flat environment, there may exist purer quartz sandstones, which maybe a good reservoir. As an example, the analysis of the Tazhong-11 well shows that it is suitable for the study on the Silurian system in the Tazhong area with this model.
Studies showed that the Silurian sytem in the Tazhong area was deposited in an epicontinental sea tidal flat environment. Combined its depositional feature and setting with the hydrodynamic feature ofepicontinental sea area, an epicontinental sea facies model of clastic deposits of the Silurian system in theTazhong area is established. Furthermore,it can be subdivided into three microfacies: mud flat and mixedflat, and sand flat. Its facies is broad and stable, but there exist no barrier island deposits. Compared withthe flat depositional facies nowadays,it is deposited in deeper water. part of the mud flat and most of themixed flat develop under the water, the hydrodynamics of the sand flat is relatively weak. Tidal currentand hurricane current mainly control the transportation and reconstruction of the clastics, so their de-posits are popular, especially in the sand flat and mixed flat. A vertical coarsing-upward sequence is pre-sent in the transgressive period and cross- bedding is common in the sandstone. In the retrogressive pe-riod, sandstones with good continuity and a stable mud flat are formed in a broad area. Near some of the underwater high land in the sand flat environment, there may exist purer quartz sandstones, which maybe a good reservoir. As an example, the analysis of the Tazhong-11 well shows that it is suitable for the study on the Silurian system in the Tazhong area with this model.
1997, 15(3): 55-61.
Abstract:
The Shitouhezi Formation is a set of non-marine coal-bearing strata, filled in the lower part of theMesozoic- Cenozoic interior basin of Hegang. The strata can be divided into three lithological membersincluding five submembers and 26 small cycles from bottom to the upper part. The first submember wasmainly marked by the alluvial fan and braided stream environments; the second submember the fluvial;the third submemeber the fluvial- delta- lacustrine; the 4th the fluvial again; and the 5th the fluvial andalluvial fan. Vertically, the five submembers respond to the five developing bhases which filled the lowerareas for horizontal ground of the basin- expanding- subsiding stably- subsiding differently- contract-ing of the basin. Richer coal- bearing areas are Locatek to the flank of syndepositional anticline bulge.Coal accumulation was controlled mainly by the periodic fast and slow subsiding of the basin. Coal accu-mulation occurred at each slower and more stable subsiding phase of the episodic subsidence. The excep-tionally thick coal beds are related to the largest swamped deltaic plain.
The Shitouhezi Formation is a set of non-marine coal-bearing strata, filled in the lower part of theMesozoic- Cenozoic interior basin of Hegang. The strata can be divided into three lithological membersincluding five submembers and 26 small cycles from bottom to the upper part. The first submember wasmainly marked by the alluvial fan and braided stream environments; the second submember the fluvial;the third submemeber the fluvial- delta- lacustrine; the 4th the fluvial again; and the 5th the fluvial andalluvial fan. Vertically, the five submembers respond to the five developing bhases which filled the lowerareas for horizontal ground of the basin- expanding- subsiding stably- subsiding differently- contract-ing of the basin. Richer coal- bearing areas are Locatek to the flank of syndepositional anticline bulge.Coal accumulation was controlled mainly by the periodic fast and slow subsiding of the basin. Coal accu-mulation occurred at each slower and more stable subsiding phase of the episodic subsidence. The excep-tionally thick coal beds are related to the largest swamped deltaic plain.
1997, 15(3): 67-71.
Abstract:
A kind of deep formation brine, very rich in potassium, boron and bromine, with reservoir depth of4 300 m approximately, was found in the strata of Leikoupo Formation, Middle Triassic, SichuanProvince. The content of K+in this brine is about 50 g /L, Na+more than 92 g /L, B 2 O 3 more than 12 g /L, Br - more than 2. 36 g /L, and I+about 0. 030 g /L. It has very high value economically and scientifical-ly. The solid phase from evaporating of this brine at 25 ℃ includes KB 5 O 8 · 4H 2 O, K 2 B 4 O 7 · 3H2 O, MgCl 2· 6H 2 O and KMgCl 3 · 6H 2 O. Theδ18O of this brine is from 2. 2 ‰ to 2. 8 ‰ ( SNOW),δ D from - 38 ‰ to- 53 ‰ ( SMOW),δ34S 15. 6 ‰, andδ13B from 13. 5 ‰ to 15. 1 ‰. Based on these geochemical characters,specially isotope of boron, it is suggested that composition of the brine consists of marine brines frommiddle Triassic, nonmarine brines from Upper Triassic and the dissolution of marine evaporites in burialstrata of Middle Triassic.
A kind of deep formation brine, very rich in potassium, boron and bromine, with reservoir depth of4 300 m approximately, was found in the strata of Leikoupo Formation, Middle Triassic, SichuanProvince. The content of K+in this brine is about 50 g /L, Na+more than 92 g /L, B 2 O 3 more than 12 g /L, Br - more than 2. 36 g /L, and I+about 0. 030 g /L. It has very high value economically and scientifical-ly. The solid phase from evaporating of this brine at 25 ℃ includes KB 5 O 8 · 4H 2 O, K 2 B 4 O 7 · 3H2 O, MgCl 2· 6H 2 O and KMgCl 3 · 6H 2 O. Theδ18O of this brine is from 2. 2 ‰ to 2. 8 ‰ ( SNOW),δ D from - 38 ‰ to- 53 ‰ ( SMOW),δ34S 15. 6 ‰, andδ13B from 13. 5 ‰ to 15. 1 ‰. Based on these geochemical characters,specially isotope of boron, it is suggested that composition of the brine consists of marine brines frommiddle Triassic, nonmarine brines from Upper Triassic and the dissolution of marine evaporites in burialstrata of Middle Triassic.
1997, 15(3): 89-95.
Abstract:
In this paper, the identification and comparative analysis on the biomarkers of the aliphatic and aro-mati fractions in oil-sands and umderlying brown coal of coal-measures strata of the Baise basin inGuangxi were studied, their biomarker distributive characteristics are extremely similar.Combimed with organic petrological study, it was beieved that hydrocarbons in oil-sands come mainly from the brow n coal. The conclusion of this paper provided a more dependable scientific basis for oilexploration in this area.
In this paper, the identification and comparative analysis on the biomarkers of the aliphatic and aro-mati fractions in oil-sands and umderlying brown coal of coal-measures strata of the Baise basin inGuangxi were studied, their biomarker distributive characteristics are extremely similar.Combimed with organic petrological study, it was beieved that hydrocarbons in oil-sands come mainly from the brow n coal. The conclusion of this paper provided a more dependable scientific basis for oilexploration in this area.
1997, 15(3): 103-109.
Abstract:
The source, distribution and effects of organic acid anions( OAA) in sedimentary basins were notsystematically studied and were poorly understood in China. The paper presented 185 OAA data and 100samples of dissolved Al, Si, Ba and other 12 elements in oilfield waters from Cambrian to Tertiary reser-voirs of the Tarim basin. The above data showed that OAA of high concentration (> 800× 10- 6) oc-curred in reservoirs deep than 4 300 m and nearby unconformities. OAA are thought to be sourced fromthermal maturation of kerogen biodegradation and thermochemical sulfate reduction of crude oils, whichis supported by high reservoir temperature( 115 ℃ to 139 ℃ ), abundance of dissolved H 2 S in oilfield waters( 600 × 10- 6to 780 × 10- 6), and occurrence of tas mats. OAA may contribute 30 % ～ 70 %, up to 92 % oftotal alkalinity; thus it controls pH values of oilfield waters. The concentration of dissolved aluminumranges up from 3. 1 mg /L to 5. 4 mg /L in oil- bearing reservoirs, and it indicates the existence of organ-ic- complexing agents.Selected mineral equilibrium calculation from Carboniferous, Triassic and Jurassic reservoirs wascarried out by computer code SOLMINEQ. 88 for geochemical modeling of water- rock interaction, andshowed that oligioclase is unsaturated and can be dissolved at 81 ℃ to 138 ℃ while kaolinate is over- sat-urated and tends to precipitate at the temperature lower than 132 ℃; quartz is near equilibrium; K-feldspar is stable between 81 ℃ to 105 ℃. From the above, it can be concluded that oligioclase dissolu-tion and kaolinite precipitation are the main diagenesis, and control secondary porosity. And it is consis-tent with the petrographic observation.
The source, distribution and effects of organic acid anions( OAA) in sedimentary basins were notsystematically studied and were poorly understood in China. The paper presented 185 OAA data and 100samples of dissolved Al, Si, Ba and other 12 elements in oilfield waters from Cambrian to Tertiary reser-voirs of the Tarim basin. The above data showed that OAA of high concentration (> 800× 10- 6) oc-curred in reservoirs deep than 4 300 m and nearby unconformities. OAA are thought to be sourced fromthermal maturation of kerogen biodegradation and thermochemical sulfate reduction of crude oils, whichis supported by high reservoir temperature( 115 ℃ to 139 ℃ ), abundance of dissolved H 2 S in oilfield waters( 600 × 10- 6to 780 × 10- 6), and occurrence of tas mats. OAA may contribute 30 % ～ 70 %, up to 92 % oftotal alkalinity; thus it controls pH values of oilfield waters. The concentration of dissolved aluminumranges up from 3. 1 mg /L to 5. 4 mg /L in oil- bearing reservoirs, and it indicates the existence of organ-ic- complexing agents.Selected mineral equilibrium calculation from Carboniferous, Triassic and Jurassic reservoirs wascarried out by computer code SOLMINEQ. 88 for geochemical modeling of water- rock interaction, andshowed that oligioclase is unsaturated and can be dissolved at 81 ℃ to 138 ℃ while kaolinate is over- sat-urated and tends to precipitate at the temperature lower than 132 ℃; quartz is near equilibrium; K-feldspar is stable between 81 ℃ to 105 ℃. From the above, it can be concluded that oligioclase dissolu-tion and kaolinite precipitation are the main diagenesis, and control secondary porosity. And it is consis-tent with the petrographic observation.
1997, 15(3): 133-140.
Abstract:
The terrestrial sediments are well developed in the Turpan-Hami Basin in eastern Xinjiang, whichshow the important petroliferous and coal-bearing significance. Abundant fossil spores and pollen grainsof 97 species assigned to 45 genera are recovered from the Middle Jurassic Xishanyao, Sanjianfang andQiketai Formations of Boreholes PU1 and CN1 in Turpan depression. Three palynological assemblagezones representing Aalenian to Bajocian, early Bathonian and late Bathonian are recognized as: 1) Cy-athidites- Cycadopites- Quadraeculina( CCQ) Zone; 2)Cyathidites- Classopollis-Piceites ( CCP) Zone and 3)Granulatisporites- Classopollis-Podocarpidites( GCP) Zone. The Middle Jurassic palynoflora is dominantedby conifers, ginkgo- cycads as well as ferns. From Aalenian-Bajocian to late Bathonian, ferns representedby Cyatheaceae, Dicksoniaceae and Osmundaceae gradually decreased, while conifers includingConiferales, Pinaceae, Podocarpaceae and especially Cheirolepidiaceae increased in abundance. The paly-noflora indicates a warm and humid climate in Aalenian to Bajocian, and somewhata semi-arid and hotclimate condition in early to middle Bathonian. The warm- humid climate is favorable for the accumula-tion of coal, oil and gas resources,while the arid and hot climate results in the weakness and even termi-nation of hydrocarbon formation.
The terrestrial sediments are well developed in the Turpan-Hami Basin in eastern Xinjiang, whichshow the important petroliferous and coal-bearing significance. Abundant fossil spores and pollen grainsof 97 species assigned to 45 genera are recovered from the Middle Jurassic Xishanyao, Sanjianfang andQiketai Formations of Boreholes PU1 and CN1 in Turpan depression. Three palynological assemblagezones representing Aalenian to Bajocian, early Bathonian and late Bathonian are recognized as: 1) Cy-athidites- Cycadopites- Quadraeculina( CCQ) Zone; 2)Cyathidites- Classopollis-Piceites ( CCP) Zone and 3)Granulatisporites- Classopollis-Podocarpidites( GCP) Zone. The Middle Jurassic palynoflora is dominantedby conifers, ginkgo- cycads as well as ferns. From Aalenian-Bajocian to late Bathonian, ferns representedby Cyatheaceae, Dicksoniaceae and Osmundaceae gradually decreased, while conifers includingConiferales, Pinaceae, Podocarpaceae and especially Cheirolepidiaceae increased in abundance. The paly-noflora indicates a warm and humid climate in Aalenian to Bajocian, and somewhata semi-arid and hotclimate condition in early to middle Bathonian. The warm- humid climate is favorable for the accumula-tion of coal, oil and gas resources,while the arid and hot climate results in the weakness and even termi-nation of hydrocarbon formation.
1997, 15(3): 145-149.
Abstract:
In this paper, a new sediment grain size index, gsi, is proposed as a supplementary time- savingtool of sedimentological analysis of micro- fossils. The gsi is determined according to the grain size rankand composition of sediment at the time of sampling for microfossils. For example, gsis for clay, silt andfine sand are 1. 0, 2. 0 and 3. 0, respctivly, for silty clay, clayey silt are 1. 2 and 1. 8. The reliability ofthis semi- quantitative index system has been confirmed by using correlation analysis of actural Md datagained through conventional instrument analysis of 20sediment samples with their corresiponding gsi da-ta.The correlation coefficient is as high as 0. 9312. As demonstration for practical use of gsi, sedimnto-logical foraminiferal analysis was prformed on 90 samples from Yangtze River mouth and Jiangsu coastalzone where taphonomic processes of foraminiferal taphocoeenoses are important. The demonstration in-dicated the gsi is useful and time- saving for sedimentological study on the base of microfossil.
In this paper, a new sediment grain size index, gsi, is proposed as a supplementary time- savingtool of sedimentological analysis of micro- fossils. The gsi is determined according to the grain size rankand composition of sediment at the time of sampling for microfossils. For example, gsis for clay, silt andfine sand are 1. 0, 2. 0 and 3. 0, respctivly, for silty clay, clayey silt are 1. 2 and 1. 8. The reliability ofthis semi- quantitative index system has been confirmed by using correlation analysis of actural Md datagained through conventional instrument analysis of 20sediment samples with their corresiponding gsi da-ta.The correlation coefficient is as high as 0. 9312. As demonstration for practical use of gsi, sedimnto-logical foraminiferal analysis was prformed on 90 samples from Yangtze River mouth and Jiangsu coastalzone where taphonomic processes of foraminiferal taphocoeenoses are important. The demonstration in-dicated the gsi is useful and time- saving for sedimentological study on the base of microfossil.
1997, 15(3): 153-157,165.
Abstract:
In this paper, the transverse distributive regularity and its controlling factors of clay minerals inTertiary System in Qaidam Basin was carried out. From the marginal facies to the centeral facies of theBasin, the ralative content of interstratified illite/smectite has a tedency of decrease and the ralative con-tent of illite increases obviously. In Neogene system, there are two types of combination of the clay min-erals. The one of them is the combination of randomly interstratified illite/smectite→illite→ chlorite→kaolinite in the marginal facies of the Basin. The other is the combination of ordered interstratified illite /smectite →illite → chlorite→ kaolinite in the central facies of the Basin. In Eogene System have two typesof combination. The one is the composition of ordered interstratified illite/smectite→ illite→ chlorite→kaolinite.The other is the combination without kaolinite. The distributive regularity of clay minerals in NeogeneSystem was controlled chiefly by arid-semiarid peleoclimate, composition of source rock and peleosedi-mentary environment. In Eogene System, because the sediments were buried very deep, it was controllednearly completely by digenesis, but the sedimentary environment still was a its important controlling fac-tor.
In this paper, the transverse distributive regularity and its controlling factors of clay minerals inTertiary System in Qaidam Basin was carried out. From the marginal facies to the centeral facies of theBasin, the ralative content of interstratified illite/smectite has a tedency of decrease and the ralative con-tent of illite increases obviously. In Neogene system, there are two types of combination of the clay min-erals. The one of them is the combination of randomly interstratified illite/smectite→illite→ chlorite→kaolinite in the marginal facies of the Basin. The other is the combination of ordered interstratified illite /smectite →illite → chlorite→ kaolinite in the central facies of the Basin. In Eogene System have two typesof combination. The one is the composition of ordered interstratified illite/smectite→ illite→ chlorite→kaolinite.The other is the combination without kaolinite. The distributive regularity of clay minerals in NeogeneSystem was controlled chiefly by arid-semiarid peleoclimate, composition of source rock and peleosedi-mentary environment. In Eogene System, because the sediments were buried very deep, it was controllednearly completely by digenesis, but the sedimentary environment still was a its important controlling fac-tor.
1997, 15(3): 162-165,157.
Abstract:
This paper took the sandstone reservoirs of Liaohe Oilfield ( Es1, Es3 ) as a case and elaborated howto establish functions between mercury injection pressure ( Pc) and mercury saturation ( SHg), then toconduct some geological applications of these functions. The results indicated that there exists a goodhyperbola relationship between Pc and SHg in the studied area. From these functions one can calculatethe capillary pressue. obtain the capillary pressure curves from porosity and permeability, and computethe permeability and permeability contribution at any SHg intervals.
This paper took the sandstone reservoirs of Liaohe Oilfield ( Es1, Es3 ) as a case and elaborated howto establish functions between mercury injection pressure ( Pc) and mercury saturation ( SHg), then toconduct some geological applications of these functions. The results indicated that there exists a goodhyperbola relationship between Pc and SHg in the studied area. From these functions one can calculatethe capillary pressue. obtain the capillary pressure curves from porosity and permeability, and computethe permeability and permeability contribution at any SHg intervals.
1997, 15(3): 171-173.
Abstract:
The well stratificatied and widespread radiolarian silicalite with a fairly great thickness in the Liang- shan region, Hanzhong, is mainly composed. of quartz filling radiolarian cast, aphanitic or microcrystalline chert and quartz as well as a little illite matrix. The average content of SiO 2 in the rock is above 90 %. By analysis of petrological characteristics, the origin of radiolarian silicalite in this region is explained that the distal volcanic product provided SiO , for volcanic product changes, dissolved and released out SiO 2 into sea water where formed a favorable environment for the growth of siliceous organism. The radiolari- an silicalite of the Lower Silurian Longmaxi Formation in this region was formed in the transitive zone between the deepwater continental shelf where the water depth is relatively shallow and the continental slope,in which the sea-water depth is about 200 m.
The well stratificatied and widespread radiolarian silicalite with a fairly great thickness in the Liang- shan region, Hanzhong, is mainly composed. of quartz filling radiolarian cast, aphanitic or microcrystalline chert and quartz as well as a little illite matrix. The average content of SiO 2 in the rock is above 90 %. By analysis of petrological characteristics, the origin of radiolarian silicalite in this region is explained that the distal volcanic product provided SiO , for volcanic product changes, dissolved and released out SiO 2 into sea water where formed a favorable environment for the growth of siliceous organism. The radiolari- an silicalite of the Lower Silurian Longmaxi Formation in this region was formed in the transitive zone between the deepwater continental shelf where the water depth is relatively shallow and the continental slope,in which the sea-water depth is about 200 m.
1997, 15(3): 8-13.
Abstract:
The final purpose of explorion work in petroluem geology is synthetically to appraise acertain field on its structure, deposition and diagenesis in order to find new area and oilfieldfor next exploring step. However, this study in petroleum geology has been Carried out in-dependently for a long time. If we used this method of thinking, It would be very difficultfor us to appraise and predict new field of exploration,especially to determine the locationof exploration well synthetically. Today the main method and content of petroleum explo-ration are to integrate knowledge of multidiscipline for studing a certain qeustion. The au-thor took the Houwujiahu gas fild as the example exposed the diagenesis characteristic ofthis area had set up a integrated model through the study of structure and deposition fea-tures. Furthermore, the author made the detailed research on reserioir development,genesisand distribution of this area. The way and method of established integrated model may beone of the main study content and direction of hydrocarbon exploration in the future.
The final purpose of explorion work in petroluem geology is synthetically to appraise acertain field on its structure, deposition and diagenesis in order to find new area and oilfieldfor next exploring step. However, this study in petroleum geology has been Carried out in-dependently for a long time. If we used this method of thinking, It would be very difficultfor us to appraise and predict new field of exploration,especially to determine the locationof exploration well synthetically. Today the main method and content of petroleum explo-ration are to integrate knowledge of multidiscipline for studing a certain qeustion. The au-thor took the Houwujiahu gas fild as the example exposed the diagenesis characteristic ofthis area had set up a integrated model through the study of structure and deposition fea-tures. Furthermore, the author made the detailed research on reserioir development,genesisand distribution of this area. The way and method of established integrated model may beone of the main study content and direction of hydrocarbon exploration in the future.
1997, 15(3): 18-22.
Abstract:
Based on sedimentary, palaeontological and seismic data, the sequence stratigraphy of the LowerCretaceous in the Suhongtu-Yingen basin has been studied. The Lower Cretaceous is divided into 1 se-quence and lowstand system tract, transgressive system tract as well as highstand system tract. Accord-ing to incumbent style of parasequence, parasequence sets are divided into transgressive style, retrogres-sive style and accretion style. In this region, the lower Cretaceous in divided into 9 parasequence sets, andretrogression parasequence style is developed much better among them. Early period of the Early Creta-ceous has experienced great changes in the Suhongtu-Yingen basin. From Early Cretaceous to Later Cre-taceous, allavial fan, fan delta, shallow lake and deep-lake are developed and turbidity current and debrisflow that belong to lake transgressive stratigraphic sequence of retrogressive style exist in deep-lakemelane mudstone. In late of Early Cretaceous shore-shllow lake has changed into shore-lake swamp andriver that belong to lake retrogressive stratigraphic sequence of transgressive style. In the region, shal-low-deep lake melane mudstone and shale of transgressive system tract that its depth is thick and its or-ganic content is rich and style is good, showing which is important hydrocarbon source rocks. Among fandelta stratigraphic sequence of lowstand system tract, accretion style is more characteristic. In otherwords,its lower part belongs to fan delta plain,its middle belongs to fan delta front and its upper belongsto profan delta. The characteristics reflect that the region might be in the margin of active basin,in whichlake changes from shallow to deep, fan delta retreats with it and rate of subsidence is more rapid thanrate of sedimentation. Reservoir ability of fan delta front is good among them, shore-shallow lake beachsandbody is important gas-oil reservoir body and deep-lake mudstone and shale of transgressive systemtract and shore-lake swampy mudstone of highstand system tract are good cover rock. They have consti-tuted favoruable source-reservoir- cap rocks assemblages.
Based on sedimentary, palaeontological and seismic data, the sequence stratigraphy of the LowerCretaceous in the Suhongtu-Yingen basin has been studied. The Lower Cretaceous is divided into 1 se-quence and lowstand system tract, transgressive system tract as well as highstand system tract. Accord-ing to incumbent style of parasequence, parasequence sets are divided into transgressive style, retrogres-sive style and accretion style. In this region, the lower Cretaceous in divided into 9 parasequence sets, andretrogression parasequence style is developed much better among them. Early period of the Early Creta-ceous has experienced great changes in the Suhongtu-Yingen basin. From Early Cretaceous to Later Cre-taceous, allavial fan, fan delta, shallow lake and deep-lake are developed and turbidity current and debrisflow that belong to lake transgressive stratigraphic sequence of retrogressive style exist in deep-lakemelane mudstone. In late of Early Cretaceous shore-shllow lake has changed into shore-lake swamp andriver that belong to lake retrogressive stratigraphic sequence of transgressive style. In the region, shal-low-deep lake melane mudstone and shale of transgressive system tract that its depth is thick and its or-ganic content is rich and style is good, showing which is important hydrocarbon source rocks. Among fandelta stratigraphic sequence of lowstand system tract, accretion style is more characteristic. In otherwords,its lower part belongs to fan delta plain,its middle belongs to fan delta front and its upper belongsto profan delta. The characteristics reflect that the region might be in the margin of active basin,in whichlake changes from shallow to deep, fan delta retreats with it and rate of subsidence is more rapid thanrate of sedimentation. Reservoir ability of fan delta front is good among them, shore-shallow lake beachsandbody is important gas-oil reservoir body and deep-lake mudstone and shale of transgressive systemtract and shore-lake swampy mudstone of highstand system tract are good cover rock. They have consti-tuted favoruable source-reservoir- cap rocks assemblages.
1997, 15(3): 29-32.
Abstract:
Paleoflood study depends on the flood information drown from paleoflood deposits. Among those,the most valuable one is the paleoflood slack-water deposit. The paleoflood slack-water deposits at thedown reach from the Three Gorges of Yangtze River and from the Sanmen Gorge of the Yellow Riverwere burried and preserved on some terraces in gentle slope. They have slight stratification, which risesup at depositional termination, special grain size as well as the relative amount of every heavy mineral.The features above are also the important mark of looking for and ascertaining the paleoflood slack-wa-ter deposit for paleoflood study on different reaches in different drainage areas.
Paleoflood study depends on the flood information drown from paleoflood deposits. Among those,the most valuable one is the paleoflood slack-water deposit. The paleoflood slack-water deposits at thedown reach from the Three Gorges of Yangtze River and from the Sanmen Gorge of the Yellow Riverwere burried and preserved on some terraces in gentle slope. They have slight stratification, which risesup at depositional termination, special grain size as well as the relative amount of every heavy mineral.The features above are also the important mark of looking for and ascertaining the paleoflood slack-wa-ter deposit for paleoflood study on different reaches in different drainage areas.
1997, 15(3): 37-40.
Abstract:
Siliceous rock can be defined as sedimentary rock which contains about 70 ～ 80 percent authigenicsilica rock with the exception of quartz in sandstone and quartzite. This paper mainly describes the char-acteristics and vertical sequences of storm siliceous of Wumishan Formation in Beijing west mountain.The thichness of Wumishan Formation about 2 168. 55 m. It mainly consists of dolomite interbeded withsiliceous rock. Research shows that there doveloped storm siliceous rock in this area. Its vertical sequenceconsists of bottom unit, lower unit,intermediate unit, upper unit and top unit,i. e., ( a) The bottom unit:50 cm in thickness, gray-black shaly dolomite, normal shallow sea environment, ( b) The lower unit: 25 ～30 cm in thickness, dolorudite with scoured base, which consists of two sedimentary cycles showingcoarse upward seqence, result from early tempestuous current, ( c) Intermediate unit: 20 cm in thickness,storm siliceous rock with surface of scour, siliceous gravel arranged as daisy, which are formed in stromsurge, ( d) Upper unit: 40 cm in thickness, black shaly dolomite, resulting from the last stage of tempestu-ous current, and ( e) Top unit: stromatolithic dolomite interbeded with siliceous strip, wich are formed innormal weather deposit. From bottom unit to top unit, which shows complete process of storm deposit, itcan be regarded as typical sequence. At last, their sedimentary models have been developed.
Siliceous rock can be defined as sedimentary rock which contains about 70 ～ 80 percent authigenicsilica rock with the exception of quartz in sandstone and quartzite. This paper mainly describes the char-acteristics and vertical sequences of storm siliceous of Wumishan Formation in Beijing west mountain.The thichness of Wumishan Formation about 2 168. 55 m. It mainly consists of dolomite interbeded withsiliceous rock. Research shows that there doveloped storm siliceous rock in this area. Its vertical sequenceconsists of bottom unit, lower unit,intermediate unit, upper unit and top unit,i. e., ( a) The bottom unit:50 cm in thickness, gray-black shaly dolomite, normal shallow sea environment, ( b) The lower unit: 25 ～30 cm in thickness, dolorudite with scoured base, which consists of two sedimentary cycles showingcoarse upward seqence, result from early tempestuous current, ( c) Intermediate unit: 20 cm in thickness,storm siliceous rock with surface of scour, siliceous gravel arranged as daisy, which are formed in stromsurge, ( d) Upper unit: 40 cm in thickness, black shaly dolomite, resulting from the last stage of tempestu-ous current, and ( e) Top unit: stromatolithic dolomite interbeded with siliceous strip, wich are formed innormal weather deposit. From bottom unit to top unit, which shows complete process of storm deposit, itcan be regarded as typical sequence. At last, their sedimentary models have been developed.
1997, 15(3): 48-54.
Abstract:
A series of gravity flow sediments composed of terrigenous fine-grained clastic rocks and carbonaterocks, which are the predominant and index lithofacies of the both limited platform basin and front plat-form slop sediments, occur in the Nanyangshan Formation of the Zhen' an-Shanyang district in Shannxi.It is the time space unity among the gravity flow sedimentation, volcano-hydrothermal activity, contem-peraneous fault activity and paleogeography differiating, that gives birth to the limited platform basinsediments dominatedly by gravity flow, with the distinguished features of the terrigenous fine-grainedclastic rocks covered frequently by the carbonate rocks, changing from west to east, containing minorvolcanic tuffaceous and sedimentary-diagentic pyrite, which is the source-bed of the micro-dissiminatedstrata-bound Sb-Au deposits in this district.
A series of gravity flow sediments composed of terrigenous fine-grained clastic rocks and carbonaterocks, which are the predominant and index lithofacies of the both limited platform basin and front plat-form slop sediments, occur in the Nanyangshan Formation of the Zhen' an-Shanyang district in Shannxi.It is the time space unity among the gravity flow sedimentation, volcano-hydrothermal activity, contem-peraneous fault activity and paleogeography differiating, that gives birth to the limited platform basinsediments dominatedly by gravity flow, with the distinguished features of the terrigenous fine-grainedclastic rocks covered frequently by the carbonate rocks, changing from west to east, containing minorvolcanic tuffaceous and sedimentary-diagentic pyrite, which is the source-bed of the micro-dissiminatedstrata-bound Sb-Au deposits in this district.
1997, 15(3): 62-66.
Abstract:
Making use of new mathematical methods such as artificial neural network, fractal geometry andpattern identification, following a geologist' s mode of thinking, the research to interpret microfacies fromthe log data was carried out A software of human-computer interactive interpretation was developed un-der workstation. Combined the superiority of workstation in calculating speed, human-computer interac-tive ability and drawing with the interpreter' s experience and judgement, it provided new technical meansand admirable computer assistant tools for the interpretation of microfacies from the log data. The princi-pal ideas were presented as follows.
Making use of new mathematical methods such as artificial neural network, fractal geometry andpattern identification, following a geologist' s mode of thinking, the research to interpret microfacies fromthe log data was carried out A software of human-computer interactive interpretation was developed un-der workstation. Combined the superiority of workstation in calculating speed, human-computer interac-tive ability and drawing with the interpreter' s experience and judgement, it provided new technical meansand admirable computer assistant tools for the interpretation of microfacies from the log data. The princi-pal ideas were presented as follows.
1997, 15(3): 72-77.
Abstract:
Abundant biomarkers( including n-alkanes, acyclic isoprenoid, steranes and terpanes etc. ) have beendetected by GC-MS from the Xiayangao Member of the Early Ordovician Tonggao Formation in the San-du area of the Guizhou Provine. The carbon numbers of n-alkanes range from nC 15 to nC 35 , nC 18 as thehighest peak and nC 29 as the second, nC+ /nC+22 ratios are up to 0. 77 ～ 1. 02, and OEP= 0. 94 ～ 1. 04. Phy-tane is predominant over priatane with a Pr /Ph of 0. 40 ～ 0. 46( average 0. 44) . Hopane series consistmainly of C 27 ～ C 35 -hopanes, a-mong which C 30 -hopane is the most abundant one, and hopane C 27 + C 29 +31 . Tricyclic terpanes are only composed of long-chain ones their carbon numbers ranging from C 20 toC 29 , and strong predominance of C 23 is detected, Steranes consist mainly of C 27 -sterane, C 23 sterane and C29sterane. According to abundance, C 29 -sterane> C27 -sterane> C 28 -sterane, pregnance and 4-methy1 ster-anes are also identified. The composition and distribution of n-alkanes, acyclic isopenoid, terpanes andsteranes, combining with the biota occurring in the same rock samples, seem to show the characteristicsof a reduction environment, and the biomarkers detected from the rock samples might mainly originatefrom algae.
Abundant biomarkers( including n-alkanes, acyclic isoprenoid, steranes and terpanes etc. ) have beendetected by GC-MS from the Xiayangao Member of the Early Ordovician Tonggao Formation in the San-du area of the Guizhou Provine. The carbon numbers of n-alkanes range from nC 15 to nC 35 , nC 18 as thehighest peak and nC 29 as the second, nC+ /nC+22 ratios are up to 0. 77 ～ 1. 02, and OEP= 0. 94 ～ 1. 04. Phy-tane is predominant over priatane with a Pr /Ph of 0. 40 ～ 0. 46( average 0. 44) . Hopane series consistmainly of C 27 ～ C 35 -hopanes, a-mong which C 30 -hopane is the most abundant one, and hopane C 27 + C 29 +31 . Tricyclic terpanes are only composed of long-chain ones their carbon numbers ranging from C 20 toC 29 , and strong predominance of C 23 is detected, Steranes consist mainly of C 27 -sterane, C 23 sterane and C29sterane. According to abundance, C 29 -sterane> C27 -sterane> C 28 -sterane, pregnance and 4-methy1 ster-anes are also identified. The composition and distribution of n-alkanes, acyclic isopenoid, terpanes andsteranes, combining with the biota occurring in the same rock samples, seem to show the characteristicsof a reduction environment, and the biomarkers detected from the rock samples might mainly originatefrom algae.
1997, 15(3): 96-102,66.
Abstract:
Based on the analysis of siderite distribution, occurrence, chemical composition, structural character-istics, carbon- oxygen isotope characteristics and relationship between siderite and hematite, the papermade a systematic study of siderite in the region, and refered that the genesis of siderite in the Xuanlongarea is the result ofganic matter reducing primary hematite during diagenesis. The ferric and ferreous re-lation depends directely on organic Contents which can comvert the ferreous into the ferric by erduction.The above conclusion was also proved by organic geochemistry data.
Based on the analysis of siderite distribution, occurrence, chemical composition, structural character-istics, carbon- oxygen isotope characteristics and relationship between siderite and hematite, the papermade a systematic study of siderite in the region, and refered that the genesis of siderite in the Xuanlongarea is the result ofganic matter reducing primary hematite during diagenesis. The ferric and ferreous re-lation depends directely on organic Contents which can comvert the ferreous into the ferric by erduction.The above conclusion was also proved by organic geochemistry data.
1997, 15(3): 126-132.
Abstract:
Geostatistics was applied to the analysis of the abundance and grade ( such as manganese, copper,cobalt and nickel) of the polymetallic nodules collected from the Clarion-Clipperton Zone in the Pacificand the excellent experimental variograms were obtained. The analytical results showed that the abun-dance range of the smooth nodule enriched area is about 50 ～ 60 km, the continuation of the surface nod-ule distribution is better than that of the rough nodule enriched area. The abundance variation is small inthe area. The four metal ranges or Cu, Co, Ni and Mn in the nodules are approximately 80 ～ 100 km, andthe phenomena of the anisotropy and the hole effects are not apparent; moreover, the abundance range ofthe area dominated by the rough noduies is about 40 ～ 50 km, and it is difficult to fit a smooth curvebased on the points on the experimental variograms of Co, Ni and Mn in the nodules. These metal rangesare nearly 100 km, and and the nost of the experimental variograms showed the phenomena of the shifts,the hole effects and the anisotropy, Considering other practical surver data and information, the majorfactors of affecting the stability of the variogram coule be atteributed to the inhomogeneous distributionof the surface nodules and the abundance variation from place to place. The resource( including the nod-ule and the metal amount) estimation errors calculated in the Kriging and arithmetic average method are1 ～ 2 % in general. The biggest error is less than 7 %. These results were similar to those of the prviouspractice. Research results also showed that the sampling distance of abundance is 28 km× 28 km, thenodule resource estimation error is 29. 45 % for the smooth nodule deposit and 36. 07 % for the rough nodule one, when the distance is reduced to the level of 13 km× 13 km, and the resource estimation erroris 23. 01 % for the rohgh nodule enriched area.
Geostatistics was applied to the analysis of the abundance and grade ( such as manganese, copper,cobalt and nickel) of the polymetallic nodules collected from the Clarion-Clipperton Zone in the Pacificand the excellent experimental variograms were obtained. The analytical results showed that the abun-dance range of the smooth nodule enriched area is about 50 ～ 60 km, the continuation of the surface nod-ule distribution is better than that of the rough nodule enriched area. The abundance variation is small inthe area. The four metal ranges or Cu, Co, Ni and Mn in the nodules are approximately 80 ～ 100 km, andthe phenomena of the anisotropy and the hole effects are not apparent; moreover, the abundance range ofthe area dominated by the rough noduies is about 40 ～ 50 km, and it is difficult to fit a smooth curvebased on the points on the experimental variograms of Co, Ni and Mn in the nodules. These metal rangesare nearly 100 km, and and the nost of the experimental variograms showed the phenomena of the shifts,the hole effects and the anisotropy, Considering other practical surver data and information, the majorfactors of affecting the stability of the variogram coule be atteributed to the inhomogeneous distributionof the surface nodules and the abundance variation from place to place. The resource( including the nod-ule and the metal amount) estimation errors calculated in the Kriging and arithmetic average method are1 ～ 2 % in general. The biggest error is less than 7 %. These results were similar to those of the prviouspractice. Research results also showed that the sampling distance of abundance is 28 km× 28 km, thenodule resource estimation error is 29. 45 % for the smooth nodule deposit and 36. 07 % for the rough nodule one, when the distance is reduced to the level of 13 km× 13 km, and the resource estimation erroris 23. 01 % for the rohgh nodule enriched area.
1997, 15(3): 141-144.
Abstract:
The Middle Pleistocent loes and the Late Pleistocene loess at changshan archipelago were previouslyseen as eolian deposit, which were deposited by north-west monsoon. Comparative analyses on magneticfabric features of them show that the Middle Pleistocene loess belongs to proluvium of talus whose mate-rials prtially came from local crust of weathering and were partially brought to here from the vicinity bywind; the late pleistocene loess belongs to eoilan deposit whose materials were brought to here from ex-posed sea floor nearby by wind. In the Late Pleistocene epoch, surface wind field changed with topogra-phy, and wind dircction may be different in different places.
The Middle Pleistocent loes and the Late Pleistocene loess at changshan archipelago were previouslyseen as eolian deposit, which were deposited by north-west monsoon. Comparative analyses on magneticfabric features of them show that the Middle Pleistocene loess belongs to proluvium of talus whose mate-rials prtially came from local crust of weathering and were partially brought to here from the vicinity bywind; the late pleistocene loess belongs to eoilan deposit whose materials were brought to here from ex-posed sea floor nearby by wind. In the Late Pleistocene epoch, surface wind field changed with topogra-phy, and wind dircction may be different in different places.
1997, 15(3): 150-152.
Abstract:
The 2～ 6μ m particle fractions of loess were employed as the relatively stable dust depositionalflux. On the basis of the relationship between grain size fluctuation and depositional flux variation ofloess, the following dating model was used to calculate ages of loess stratigraphy in the central Chinese loess plateau:Tm = T1+ ( T2 - T 1) ( ∑mi= 1Ci Hi ) /( ∑ni= 1Ci Hi)Abosolute ages calibrated by thermoluminescence and palaeomagnetic reversal boundary wereserved as the time controlling points to obtain detail ages of the Luochuan loess profile, the resultsshowed that our dating model is useful in calibrating detail ages of loess stratigraphy in the central Chi-nese loess plateau.
The 2～ 6μ m particle fractions of loess were employed as the relatively stable dust depositionalflux. On the basis of the relationship between grain size fluctuation and depositional flux variation ofloess, the following dating model was used to calculate ages of loess stratigraphy in the central Chinese loess plateau:Tm = T1+ ( T2 - T 1) ( ∑mi= 1Ci Hi ) /( ∑ni= 1Ci Hi)Abosolute ages calibrated by thermoluminescence and palaeomagnetic reversal boundary wereserved as the time controlling points to obtain detail ages of the Luochuan loess profile, the resultsshowed that our dating model is useful in calibrating detail ages of loess stratigraphy in the central Chi-nese loess plateau.
1997, 15(3): 158-161.
Abstract:
The glauconite formed in the abnormal marine environment was found firstly in the Huagong Forma- tion of the Oligocene, Xihu Depression, East China Sea. It can be divided into three types as follows:granule glauconite, cemented glauconite and clastic pseudomorph glauconite. The first two types wereformed during the sedimentation and the beginning of diagenesis. It was thought by the sedimentarystudies that the Huagong Formation was generally formed in the shoreline lacustrine delta-fluvial deposi-tional systems. But the formation was influenced by marine water or salt-semisalt water in some degree.The re- depositional fossil in the formation, at least a part of it was probably developed and preserved atthe same place. Con-sequently, the age of the Huagong Formation would be probably taken as the EoceneEpoch. Besides the chronos-tratigraphy, the idea would lead to re-analysis for the problems about the e-valuating stages, dimensional dis-tribution of sedimentary systems as well as the prediction of favorablefacies belts for oil and gas.
The glauconite formed in the abnormal marine environment was found firstly in the Huagong Forma- tion of the Oligocene, Xihu Depression, East China Sea. It can be divided into three types as follows:granule glauconite, cemented glauconite and clastic pseudomorph glauconite. The first two types wereformed during the sedimentation and the beginning of diagenesis. It was thought by the sedimentarystudies that the Huagong Formation was generally formed in the shoreline lacustrine delta-fluvial deposi-tional systems. But the formation was influenced by marine water or salt-semisalt water in some degree.The re- depositional fossil in the formation, at least a part of it was probably developed and preserved atthe same place. Con-sequently, the age of the Huagong Formation would be probably taken as the EoceneEpoch. Besides the chronos-tratigraphy, the idea would lead to re-analysis for the problems about the e-valuating stages, dimensional dis-tribution of sedimentary systems as well as the prediction of favorablefacies belts for oil and gas.
1997, 15(3): 166-170.
Abstract:
Some kinds of continental basins were formed during the Mesozoic in the western LiaoningProvince, in which the varied strata occurred. On the basis of recongnizing the sequences of differentbasins in different times and according to the sequence defination, the sequence types including lakebasin sequence, alluvial sequence, desert sequence and volcanic sequence were given through the analysisof geological agents ( such as water, wind and igneous process), sedimentary media and geological envi-ronments. The internal assemblages of different sequences are different and their controlling factors arenot the same. Lake basin sequence is formed through and sedimentation, showing the changes of thesedimentary systems or system tracts in time and space with the lake level variation. A whole sequencemay reflct the cycle of transgressive-regressive processes of the lake. Alluvial sequence developesthrough alluviation in a river basin. The storing water level does not control it directly, but it is influ-enced by groundwater level and controlled by topography and erosional basement level. Desert sequenceis a kind of sequence composed of desert sediments under condition of wind medium. Volcanic sequencecomposed of volcanic, pyroclastic, tuff and sedimentary rocks is formed by the filling of volcanic sub-stances(including sediments) in a basin during the time of volcanic activities. Of the controlling factorsof the sequences in the Mesozoic basins, the western Liaoning Province, the tectonics was the mostdominated. Most of the sdquence boundaries were tectonic surfaces, such as regional angular uncomfor-maties, paralell unconformaties and tectonic transform surfaces. However, the controlling factors a-mong different types of the sequences were different with each other.
Some kinds of continental basins were formed during the Mesozoic in the western LiaoningProvince, in which the varied strata occurred. On the basis of recongnizing the sequences of differentbasins in different times and according to the sequence defination, the sequence types including lakebasin sequence, alluvial sequence, desert sequence and volcanic sequence were given through the analysisof geological agents ( such as water, wind and igneous process), sedimentary media and geological envi-ronments. The internal assemblages of different sequences are different and their controlling factors arenot the same. Lake basin sequence is formed through and sedimentation, showing the changes of thesedimentary systems or system tracts in time and space with the lake level variation. A whole sequencemay reflct the cycle of transgressive-regressive processes of the lake. Alluvial sequence developesthrough alluviation in a river basin. The storing water level does not control it directly, but it is influ-enced by groundwater level and controlled by topography and erosional basement level. Desert sequenceis a kind of sequence composed of desert sediments under condition of wind medium. Volcanic sequencecomposed of volcanic, pyroclastic, tuff and sedimentary rocks is formed by the filling of volcanic sub-stances(including sediments) in a basin during the time of volcanic activities. Of the controlling factorsof the sequences in the Mesozoic basins, the western Liaoning Province, the tectonics was the mostdominated. Most of the sdquence boundaries were tectonic surfaces, such as regional angular uncomfor-maties, paralell unconformaties and tectonic transform surfaces. However, the controlling factors a-mong different types of the sequences were different with each other.
