1990 Vol. 8, No. 3
column
Display Method:
1990, 8(3): 1-21.
Abstract:
The deep lacustrine mudstones are the important source rocks, and the significant evidence ofreconstructing evolutional history of basin and tracing the associated reservoirs as well. In recent ten years,the abundant information contained in deep lacustrine mudstones has been revealed more and more with thedevelopment of science and technology. It is actual necessary to research ;md use the information included inmudstones and form the sysmetric theory directing practice. The research of the lacustrine mudstones in Doug Ying Basin of Bohm Gulf area indicates that the deeplacustrine mudstones comprise at least eight lithofacieses: black shale, calcareous sliced shale, calcareouslaminated shale, homogenerous massive mudstone, graded laminated mudstone, mhomogenerous massivemudstone, chaotic mudstone and deformed mudstone. These rnudstone facieses assemble two categories on the basis of self-generating characteristics, 1. e.autogenic mudstones, including black sliced shale, calcarous sliced shale, calcarous laminated shale andhomogenerous massive mudstone; allogenous mudstones, including graded laminated mudstone,inhomogenerous massive mudstone, chaotic mudstone and deformed mudstone. There are significant differences in six aspects between autogenic mudstones and allogenousmudstones, such as petrologic physics, organic geochemistry, inorganic geochemistry, mineralogic con-stituent, palaeontologic association and geophysics. The autogenic mudstones fully reflect the characteristicsof deep lake, whereas the features of allogenous mudstones show that they are exotic to their depositionalenmronments. The genetic characteristics of two types of mudstones indicate that eight lithotypes can be divided intothree groups according to their genetic processes. The lithofaeieses in the same group are closely related toeach other nn origin, but they are formed in the different evolutional stages of the lake. Therefore, theabove- mentioned two categories of mudstones comprise three genetic serieses: lake- controllingmudstones, fiow-controlling mudstones and slumping mudstones. The lake-controlling mudstones wereformed by slow grain-by-grain vertical accretion of fine-grained suspended particles. The direct originwhich resulted in the different lithotypes was change of lake water nature. The autogenic mudstone, blackshale and calcareous sliced shale, calcareous laminated shale, homogen}rous massive mudstone, wereformed successively as the lake was changed from permanent stratified lake, seasonal stratified lake withbottom anoxic e..vironment into fully mixed aerobic lake. The flow- controlling mudstones consist ofturbidity mudsetones and debris flow mudstone. The former comprise graded laminated mudstone which is the products of turminal stage of sandy tarbidite and inhomogenerous massive mudstone formed by floodturbldity current rich in mud or by redeposition of unconsolidated muddy deposits in the shallow lake. Thegraded laminated mudstone commonly show four types of sequences similar to marine classical muddyturbidite. Debris current mudstone series is chaotic mudstones introduced by redeposition of comsolidaled orsemlconsolidated mudstones. The slumping mudstone series is mostly deformed mudstone initiated by slide orclamp. The association patterns of deep lacustrine mudstones of above-mentioned three genetic types dependon the different evolutional stages and palaeotopography of the basin. The starved stage of the basin wascharacterized by interbeded black shale and calcareous laminated shale with local mud turbidn:es (prevailingmhomogenerous massive mudstone)，covering an extensive area. Association of homoge}aerous massivemudstone with mud turbidite (prevailing graded laminated mudstone) and debris flow mur3stone occurredin setting-compensation equilibrium stage of the basin. In the over-compensatron stage o(' the basin, thelithofaeieses introduced by gravity tlows gradually increased because the basinal slope background wasFormed. During this period slumping mudstone series was of wide distribution.
The deep lacustrine mudstones are the important source rocks, and the significant evidence ofreconstructing evolutional history of basin and tracing the associated reservoirs as well. In recent ten years,the abundant information contained in deep lacustrine mudstones has been revealed more and more with thedevelopment of science and technology. It is actual necessary to research ;md use the information included inmudstones and form the sysmetric theory directing practice. The research of the lacustrine mudstones in Doug Ying Basin of Bohm Gulf area indicates that the deeplacustrine mudstones comprise at least eight lithofacieses: black shale, calcareous sliced shale, calcareouslaminated shale, homogenerous massive mudstone, graded laminated mudstone, mhomogenerous massivemudstone, chaotic mudstone and deformed mudstone. These rnudstone facieses assemble two categories on the basis of self-generating characteristics, 1. e.autogenic mudstones, including black sliced shale, calcarous sliced shale, calcarous laminated shale andhomogenerous massive mudstone; allogenous mudstones, including graded laminated mudstone,inhomogenerous massive mudstone, chaotic mudstone and deformed mudstone. There are significant differences in six aspects between autogenic mudstones and allogenousmudstones, such as petrologic physics, organic geochemistry, inorganic geochemistry, mineralogic con-stituent, palaeontologic association and geophysics. The autogenic mudstones fully reflect the characteristicsof deep lake, whereas the features of allogenous mudstones show that they are exotic to their depositionalenmronments. The genetic characteristics of two types of mudstones indicate that eight lithotypes can be divided intothree groups according to their genetic processes. The lithofaeieses in the same group are closely related toeach other nn origin, but they are formed in the different evolutional stages of the lake. Therefore, theabove- mentioned two categories of mudstones comprise three genetic serieses: lake- controllingmudstones, fiow-controlling mudstones and slumping mudstones. The lake-controlling mudstones wereformed by slow grain-by-grain vertical accretion of fine-grained suspended particles. The direct originwhich resulted in the different lithotypes was change of lake water nature. The autogenic mudstone, blackshale and calcareous sliced shale, calcareous laminated shale, homogen}rous massive mudstone, wereformed successively as the lake was changed from permanent stratified lake, seasonal stratified lake withbottom anoxic e..vironment into fully mixed aerobic lake. The flow- controlling mudstones consist ofturbidity mudsetones and debris flow mudstone. The former comprise graded laminated mudstone which is the products of turminal stage of sandy tarbidite and inhomogenerous massive mudstone formed by floodturbldity current rich in mud or by redeposition of unconsolidated muddy deposits in the shallow lake. Thegraded laminated mudstone commonly show four types of sequences similar to marine classical muddyturbidite. Debris current mudstone series is chaotic mudstones introduced by redeposition of comsolidaled orsemlconsolidated mudstones. The slumping mudstone series is mostly deformed mudstone initiated by slide orclamp. The association patterns of deep lacustrine mudstones of above-mentioned three genetic types dependon the different evolutional stages and palaeotopography of the basin. The starved stage of the basin wascharacterized by interbeded black shale and calcareous laminated shale with local mud turbidn:es (prevailingmhomogenerous massive mudstone)，covering an extensive area. Association of homoge}aerous massivemudstone with mud turbidite (prevailing graded laminated mudstone) and debris flow mur3stone occurredin setting-compensation equilibrium stage of the basin. In the over-compensatron stage o(' the basin, thelithofaeieses introduced by gravity tlows gradually increased because the basinal slope background wasFormed. During this period slumping mudstone series was of wide distribution.
1990, 8(3): 35-45.
Abstract:
Pingdingshan coal-field, which is located in the middle part of Henan province, is one of the major coal basins in China. The coal-bearing area is 330 km2. The coal-bearing strata are the Taiyuan Formation of Late Carboniferous, Shanxi Formation of early Early Permian and Shihezi Group of late Early to early Late Premian. Mainly discussed in this paper are the depositional environments and coal- forming sedimentary characteristics of Taiyuan Formation. The deposits of Taiyuan Formation are formed, in the mixed carbonate shallow sea and terrigenous clastic seashore. Taiyuan Formation can be divided, from bottom to top, into three members: Lower Limestone Member, Middle Clastic Member and Upper Limestone Member and Upper Limestone Member. The Lower and Upper Limestone Members Also recongnized in Limestone Members are mainly formed on the shore (intertidal zone) grey micrite interbedded with biogenic debris limestone, vertical burrows) and in the shallow sea (dark grey biogenic debris limestone, horizontal burrows). Also recognized in Limestone Members is the tempestite terbidite which interbedded with normal shallow marine carbonate. The vertical sedimentary sequence of Limestone Members is as follows: in the lowre part is the shallow marine limestone and in the upper part are the fine elastics and coal beds (or carbonaceous shale). Often found in the upper part of this sequence is the tidal channel deposits which are more developed in the Upper Limestone Member. The Middle Clastic Member is interpreted as the deposits of barrier island-lagoon-tidal flat system. Extensively developed in the study area are the barrier island facies (quartz sandstone, coarsening upward in grain size, sandbody displaying the belt strike of east to west), tidal channel facies (detritus quartz sandstone, large scale planar crossbedding, erosive base, finning upward both in grain size and sedimentary structure scale, sandbody showing splitting and thinning northwards), lagoon-tidal flat facies (interbedded, lenticular, flaser and bioturbation bedding and vertical burrows). In the lighUof petrographic properties, sedimentary structures etc., the Middle Clastic Member can be recognized as three types of vertical sedimentary sequences, i. e., the vertical sequences which are respectively dominated by barrier island facies, tidal channel facies and lagoon-tidal flat facies. The barrier island facies can be further diviede into regressive sequence (underlain by the shallow marine limestone facies) and transgressive sequence (underlain by the lagoon-tidal flat facies). Generally, there are about 5 to 6 coal seame beds (from 0 to more than 10 beds) in Taiyuan Formation. The average total thickness of coals is 3.36m (from 0.33m to 10.73m, based on the data of 130 wells). In the Lower and Upper Limestone Members, the deposits below the coal beds are often the clastic deposits and rootlet beds, but the roofs of coal beds are dominately by shore and shallow marine limestone, which means that coals are formed on the platform evoluted by the shore and shallow sea when filled by the clastic deposits. In the Middle Clastic Member, the undeveloped, discontinuous and thin flaser coals overlying the barrier island are resulted from the quick regession (because dominated overlying barrier island are the lagoon-tidal flat facies ) or the frequently shifting of barrier island landwards or seawards (refer to the section of vertical sequence). The average group maceral composition of the coals in Taiyuan Formation are vitrinite (70%-90%), inertinite (1.0%-29.8%) andexinite (0-1.0%), so the type of coal is vitrinertite. The inorganic composition of coals is mainly clay types (3.6%-11.8%). The average ash and sulphur content of coals are respectively 10% (from 9.9% to 20.4%) and 4% (from 3.87% to 5.48%). Thus the coals of Taiyuan Formation belong to the low ash (10%-15%) (middle ash content in part) and high sulphur content (higher than 4%) coals. To sum up, it is suggested that the coals of Taiyuan Formation are formed in the brackish to saline water mars
Pingdingshan coal-field, which is located in the middle part of Henan province, is one of the major coal basins in China. The coal-bearing area is 330 km2. The coal-bearing strata are the Taiyuan Formation of Late Carboniferous, Shanxi Formation of early Early Permian and Shihezi Group of late Early to early Late Premian. Mainly discussed in this paper are the depositional environments and coal- forming sedimentary characteristics of Taiyuan Formation. The deposits of Taiyuan Formation are formed, in the mixed carbonate shallow sea and terrigenous clastic seashore. Taiyuan Formation can be divided, from bottom to top, into three members: Lower Limestone Member, Middle Clastic Member and Upper Limestone Member and Upper Limestone Member. The Lower and Upper Limestone Members Also recongnized in Limestone Members are mainly formed on the shore (intertidal zone) grey micrite interbedded with biogenic debris limestone, vertical burrows) and in the shallow sea (dark grey biogenic debris limestone, horizontal burrows). Also recognized in Limestone Members is the tempestite terbidite which interbedded with normal shallow marine carbonate. The vertical sedimentary sequence of Limestone Members is as follows: in the lowre part is the shallow marine limestone and in the upper part are the fine elastics and coal beds (or carbonaceous shale). Often found in the upper part of this sequence is the tidal channel deposits which are more developed in the Upper Limestone Member. The Middle Clastic Member is interpreted as the deposits of barrier island-lagoon-tidal flat system. Extensively developed in the study area are the barrier island facies (quartz sandstone, coarsening upward in grain size, sandbody displaying the belt strike of east to west), tidal channel facies (detritus quartz sandstone, large scale planar crossbedding, erosive base, finning upward both in grain size and sedimentary structure scale, sandbody showing splitting and thinning northwards), lagoon-tidal flat facies (interbedded, lenticular, flaser and bioturbation bedding and vertical burrows). In the lighUof petrographic properties, sedimentary structures etc., the Middle Clastic Member can be recognized as three types of vertical sedimentary sequences, i. e., the vertical sequences which are respectively dominated by barrier island facies, tidal channel facies and lagoon-tidal flat facies. The barrier island facies can be further diviede into regressive sequence (underlain by the shallow marine limestone facies) and transgressive sequence (underlain by the lagoon-tidal flat facies). Generally, there are about 5 to 6 coal seame beds (from 0 to more than 10 beds) in Taiyuan Formation. The average total thickness of coals is 3.36m (from 0.33m to 10.73m, based on the data of 130 wells). In the Lower and Upper Limestone Members, the deposits below the coal beds are often the clastic deposits and rootlet beds, but the roofs of coal beds are dominately by shore and shallow marine limestone, which means that coals are formed on the platform evoluted by the shore and shallow sea when filled by the clastic deposits. In the Middle Clastic Member, the undeveloped, discontinuous and thin flaser coals overlying the barrier island are resulted from the quick regession (because dominated overlying barrier island are the lagoon-tidal flat facies ) or the frequently shifting of barrier island landwards or seawards (refer to the section of vertical sequence). The average group maceral composition of the coals in Taiyuan Formation are vitrinite (70%-90%), inertinite (1.0%-29.8%) andexinite (0-1.0%), so the type of coal is vitrinertite. The inorganic composition of coals is mainly clay types (3.6%-11.8%). The average ash and sulphur content of coals are respectively 10% (from 9.9% to 20.4%) and 4% (from 3.87% to 5.48%). Thus the coals of Taiyuan Formation belong to the low ash (10%-15%) (middle ash content in part) and high sulphur content (higher than 4%) coals. To sum up, it is suggested that the coals of Taiyuan Formation are formed in the brackish to saline water mars
1990, 8(3): 58-65.
Abstract:
A mean direction of-28 °N/132.9° E (α-95 = 4.7, k = 47.1) and a corresponding pole at 42.4 ° N / 350.9 ° E (α-95 = 3.9, K = 67.8) were obtained from 21 out of 33 Upper Permian samples of continental sedimentary rocks collected from the Western Jiuquan Basin, over 1300km west to the places where previous paleomagnetic researches were con- ducted for North China Block. The fair consistency of our results with the preexisting coeval ones demonstrates paleomagnetically that this area was a part of North China Block during Late Permian. If all the preexisting data from both North China and Tarim Blocks are assumed to be precise enough, then the ancient boundary between them should have been west to the Western Jiuquan Basin. The predecessor of Altyn fault or an analoque seems to be the first possible candidate to be chosen as this kind of ancient boundary
A mean direction of-28 °N/132.9° E (α-95 = 4.7, k = 47.1) and a corresponding pole at 42.4 ° N / 350.9 ° E (α-95 = 3.9, K = 67.8) were obtained from 21 out of 33 Upper Permian samples of continental sedimentary rocks collected from the Western Jiuquan Basin, over 1300km west to the places where previous paleomagnetic researches were con- ducted for North China Block. The fair consistency of our results with the preexisting coeval ones demonstrates paleomagnetically that this area was a part of North China Block during Late Permian. If all the preexisting data from both North China and Tarim Blocks are assumed to be precise enough, then the ancient boundary between them should have been west to the Western Jiuquan Basin. The predecessor of Altyn fault or an analoque seems to be the first possible candidate to be chosen as this kind of ancient boundary
1990, 8(3): 75-83.
Abstract:
The Nandqn-Hechi Basin in Cuangxi Province is an elongated extensional basin, which came to existence in a carbonate platform in the Late Palaeozoic Era. During the Late Devonian, the "intra-platform trough" fades, a special type of sedimentary facies, was developed. The siliceous rocks (D31), which are an important part of the facies, were typically deposited by silicon-bearing thermal water. The paper indicates that: (1) Sb (90ppm), As (16ppm), Ag (800ppb) and Ca (100ppm) -richer, and REE (13ppm) -poorer, compared with the element abundances of sedimentary rocks (Sb 1ppm, Ag 9ppm, Ag70ppb, Ga 15ppm, REE184ppm), is one of the most important charecteristics of thermal water sediments. (2) According to the results of Fuzzy Cluster, Factor Analysis and Correspondence Analysis, the relations between types of siliceous rocks and element associations can be described as below: silicalite with argillaceous silicalite shaly argillo-silicalite jasperoid→ → → laminated strcture with massive structure (-As,V) (As,-V) (-Cu,Sb,Ag,V) (Pb,Zn-Ga) (Al2O3,TiO2,K2O,MgO-SiO2) (FeO,MnO) (Fe2O3) (3) From near the spring open of silicon- bearing thermal vater outforward, is such a typical sedimentary and geochemistry sequence as : Sb, As, Ag and Ga rich, V and Cu poor, and good positive correlation between FeO and MnO (r (FeO, MnO) =0.87; n=10, below is the same) →Pb, Zn and Ni relatively rich, and corrlated with Fe2O3 (r (Pb, Fe2O3) =0.91; r (Zn, Fe2O3) =0.88; r (Ni, Fe2O3) =0.71) →V rich, Sb, As and Ag relatively poor, and excellent linear correlation between A12O3, TiO2, K2O, MgO and SiO2 (r (A12O3, TiO2) =0.86; r (A12O3, K2O) =0.99; r (A12O3, MgO = -0.95; r (A12O3, SiO2) =-0.95). (4) Sn is one of the most important ore-forming elements in the basin, and its content (1.1ppm), which is not high compared with Sn abundance of sedimentary rocks (3.9ppm), may be derived partly from silicon-bearing thermal water. (5) The values of δCe, Standardized by the rare earth element average of the shales in Northern America, of jasperoid and sillicalite with laminated structure are higher than those of argillaceous silicalite with massive structure. This suggests that the depositional velocity of siliceous muds near the spring open of thermal water is higher than that far away from the spring open.
The Nandqn-Hechi Basin in Cuangxi Province is an elongated extensional basin, which came to existence in a carbonate platform in the Late Palaeozoic Era. During the Late Devonian, the "intra-platform trough" fades, a special type of sedimentary facies, was developed. The siliceous rocks (D31), which are an important part of the facies, were typically deposited by silicon-bearing thermal water. The paper indicates that: (1) Sb (90ppm), As (16ppm), Ag (800ppb) and Ca (100ppm) -richer, and REE (13ppm) -poorer, compared with the element abundances of sedimentary rocks (Sb 1ppm, Ag 9ppm, Ag70ppb, Ga 15ppm, REE184ppm), is one of the most important charecteristics of thermal water sediments. (2) According to the results of Fuzzy Cluster, Factor Analysis and Correspondence Analysis, the relations between types of siliceous rocks and element associations can be described as below: silicalite with argillaceous silicalite shaly argillo-silicalite jasperoid→ → → laminated strcture with massive structure (-As,V) (As,-V) (-Cu,Sb,Ag,V) (Pb,Zn-Ga) (Al2O3,TiO2,K2O,MgO-SiO2) (FeO,MnO) (Fe2O3) (3) From near the spring open of silicon- bearing thermal vater outforward, is such a typical sedimentary and geochemistry sequence as : Sb, As, Ag and Ga rich, V and Cu poor, and good positive correlation between FeO and MnO (r (FeO, MnO) =0.87; n=10, below is the same) →Pb, Zn and Ni relatively rich, and corrlated with Fe2O3 (r (Pb, Fe2O3) =0.91; r (Zn, Fe2O3) =0.88; r (Ni, Fe2O3) =0.71) →V rich, Sb, As and Ag relatively poor, and excellent linear correlation between A12O3, TiO2, K2O, MgO and SiO2 (r (A12O3, TiO2) =0.86; r (A12O3, K2O) =0.99; r (A12O3, MgO = -0.95; r (A12O3, SiO2) =-0.95). (4) Sn is one of the most important ore-forming elements in the basin, and its content (1.1ppm), which is not high compared with Sn abundance of sedimentary rocks (3.9ppm), may be derived partly from silicon-bearing thermal water. (5) The values of δCe, Standardized by the rare earth element average of the shales in Northern America, of jasperoid and sillicalite with laminated structure are higher than those of argillaceous silicalite with massive structure. This suggests that the depositional velocity of siliceous muds near the spring open of thermal water is higher than that far away from the spring open.
1990, 8(3): 93-102.
Abstract:
The writer collected 769 data on bulk analysis of carbonate rock and carbonatite from more than 20 country in the world and 21 provinces of china. Results of statistics and calculation indicated that content ranges of main elements between sedimentary carbonate rock and carbonatite are similar. The carbonatite can be distinguished from sedimentary carbonate rock by discriminant analysis. The carbonatite is P2O5-rich and usually content of P2O5 is more thanO. 2%. The number of data, P2O5 0.2%, is 86% of all carbonatite data. But sedimentary carbonate rock is P2O5-poor.The number of data, P2O5 0.2% only makes up 12% in all this rock ' s data. Therefor, content of P2O5 is one important standard for discriminanting genetic type of carbonate rock. When eleven variables are adopted in two set discriminant analysis discriminanting efficiency of various genetic type of calcareous carbonate rocks, dolom tie carbonate rocks and ferruginous carbonate rock is 93.5%, 90.7% and 89.8% separetah When P2O5, Na2O, A12O3, MnO, CaO, K2O and Fe2O3 are used as discri (?) variables in discriminant analysis of step by step, discriminanting effect of casureous carbonate rock is the best and discriminanting efficiency is 94. 5%. While FeO, Fe2O3, Al2O3, and P2O5 are adopted in discriminant analysis for dolomitic carbonate rock, process of calculation. is more simple and discriminanting efficiency reached 96%. Using CaO, P2O5, MgO, SiO2, Fe2O3 and A12O3 for discriminant analysis of ferruginous carbonate rocks, discriminanting efficiency comes up 98. 5%. Generally, discriminanting effect of sedimentary carbonate rocks (near 100%) is better than carbonatite (more than 85%), i.e. sedimentary carbonate rock generally isn' t distinguished. Results of discriminant analysis of limestone and dolomitite from Baiyinobo region indicat that 17 samples of limestone are all distinguished sedimentary carbonate rock, but 3 samples in 57 samples of dolomitite are distinguished sedimentary carbonate rock, making up 5.3% of collecting data, other samples are distinguished carbonatite.The conclusion is in accord with its geological occurrence, geochemical and isotopic composition characteristics.
The writer collected 769 data on bulk analysis of carbonate rock and carbonatite from more than 20 country in the world and 21 provinces of china. Results of statistics and calculation indicated that content ranges of main elements between sedimentary carbonate rock and carbonatite are similar. The carbonatite can be distinguished from sedimentary carbonate rock by discriminant analysis. The carbonatite is P2O5-rich and usually content of P2O5 is more thanO. 2%. The number of data, P2O5 0.2%, is 86% of all carbonatite data. But sedimentary carbonate rock is P2O5-poor.The number of data, P2O5 0.2% only makes up 12% in all this rock ' s data. Therefor, content of P2O5 is one important standard for discriminanting genetic type of carbonate rock. When eleven variables are adopted in two set discriminant analysis discriminanting efficiency of various genetic type of calcareous carbonate rocks, dolom tie carbonate rocks and ferruginous carbonate rock is 93.5%, 90.7% and 89.8% separetah When P2O5, Na2O, A12O3, MnO, CaO, K2O and Fe2O3 are used as discri (?) variables in discriminant analysis of step by step, discriminanting effect of casureous carbonate rock is the best and discriminanting efficiency is 94. 5%. While FeO, Fe2O3, Al2O3, and P2O5 are adopted in discriminant analysis for dolomitic carbonate rock, process of calculation. is more simple and discriminanting efficiency reached 96%. Using CaO, P2O5, MgO, SiO2, Fe2O3 and A12O3 for discriminant analysis of ferruginous carbonate rocks, discriminanting efficiency comes up 98. 5%. Generally, discriminanting effect of sedimentary carbonate rocks (near 100%) is better than carbonatite (more than 85%), i.e. sedimentary carbonate rock generally isn' t distinguished. Results of discriminant analysis of limestone and dolomitite from Baiyinobo region indicat that 17 samples of limestone are all distinguished sedimentary carbonate rock, but 3 samples in 57 samples of dolomitite are distinguished sedimentary carbonate rock, making up 5.3% of collecting data, other samples are distinguished carbonatite.The conclusion is in accord with its geological occurrence, geochemical and isotopic composition characteristics.
1990, 8(3): 110-120.
Abstract:
A clastic rock association is developed in Lower Ordovician in the eastern side ofKangdian oldland, with trace fossils very abundant.The relation between trace fossil associa-tions and sedimentary facies is the central topic to be dealt with in this paper. Thirteen tracefossils are described in the paper, among which there are six new ichnosp.Cruziana regularianov. ichnosp.，C. dimorphiconis nov. ichnosp.，Dimorphichnus ebianensis nov. ichnosp.，D.reticularis nov.ichnosp., Cvlindricum ovatus nov.ichnosn., etc. According to our researches, the area of trace fossils can be divided into the easternpart and the wastern part by a line from Weiyuan, through Yiliang, to Xuanwei. In littoralzone of the western, the trace fossils of Scoyenia, Skolithos and Gruziana occuredalternately, which indicate that the water body of the littoral environment was shallower,and the sea level changed violently(the cyclic change of the supratidal, intertidal andsubtidal) to Meitan age. In the eastern part, such as Guiyang, Hezhang, the trace fossilswere mainly occured in the Meitan age. The abundant trace fossils of Skolithos were occuredin the prolittoral fades of the sedimentary sequence of the sandy progradationad shore in ear-1y Meitan age; the abundant trace fossils of Cruziana were occured in the sandstone and theshale occurring in the Limestone of late Meitan age in Guiyang, which indicate a subtitalmid and high-energy littoral environment, that is to say a linear sandy ridge controlled bytidal current. As a result that the trace fossils associations formed and influenced by the changes oftime and space of water body envisoument，it has the important facios-indicating signifi-cance.
A clastic rock association is developed in Lower Ordovician in the eastern side ofKangdian oldland, with trace fossils very abundant.The relation between trace fossil associa-tions and sedimentary facies is the central topic to be dealt with in this paper. Thirteen tracefossils are described in the paper, among which there are six new ichnosp.Cruziana regularianov. ichnosp.，C. dimorphiconis nov. ichnosp.，Dimorphichnus ebianensis nov. ichnosp.，D.reticularis nov.ichnosp., Cvlindricum ovatus nov.ichnosn., etc. According to our researches, the area of trace fossils can be divided into the easternpart and the wastern part by a line from Weiyuan, through Yiliang, to Xuanwei. In littoralzone of the western, the trace fossils of Scoyenia, Skolithos and Gruziana occuredalternately, which indicate that the water body of the littoral environment was shallower,and the sea level changed violently(the cyclic change of the supratidal, intertidal andsubtidal) to Meitan age. In the eastern part, such as Guiyang, Hezhang, the trace fossilswere mainly occured in the Meitan age. The abundant trace fossils of Skolithos were occuredin the prolittoral fades of the sedimentary sequence of the sandy progradationad shore in ear-1y Meitan age; the abundant trace fossils of Cruziana were occured in the sandstone and theshale occurring in the Limestone of late Meitan age in Guiyang, which indicate a subtitalmid and high-energy littoral environment, that is to say a linear sandy ridge controlled bytidal current. As a result that the trace fossils associations formed and influenced by the changes oftime and space of water body envisoument，it has the important facios-indicating signifi-cance.
1990, 8(3): 128-140.
Abstract:
Based on observation and statistical analysis of the textural, structural, grainsize and stratigraphic relationship data of ten profiles, we found six types of debris flow facies: Facies A (Coarser) Debris flow layer, which is the main body of debris flow, has a gravel content 25 percent to 50 percent and suspensio and support framwork. Facies B surface mud layer, which is formed by fane sediment floating up to the surface at flat area after the debris flow stopped, is the contemporaneous out-facies of the erosional layer (Facies B) and not be erosioned. The deposit consists of coarser sediment and has dry polygonal ground sometimes. Facies C Erosional layer, which is formed by fluvial erosion reforming on the surace after the debris flow deposited, The deposit appears loosely and porously, and deposit break hiatus. Facies D Basal mudh layer, which is formed by sedimentary bed paving processes in the earlier stage flood before debrcs flow appears. Facies E Mud layer, which is the main deposit body of mud flow in leoss area. By means of statistical analysis, nine local facies models had been found that can satisfy the statistical equire. The facies C.D.A. and B are the most common layers appear in deposit. A complete debris flow succession consists of facies D, A and B layer. The facies C layer is formed by later fluvial erosion and sometimes replaces the facies B. Therefore, a typical facies model of debris flow consists of C, D, A and B layer. The above mentioned models show some difference at different landforms. For example, at the top of debris flow fan, the deposition is strong and the later stage erosion is strong also, therefore, facies A and facies C develope, but on facies B and D. In this situation, facies succession is AC-AC type. At middle and base of a fan, the deposit shows typical facies model, with a well developed facies A, an obvious facies D and a less developed facies C. The facies B sometimes developes at both sides of debris flow valley. The AB planes of gravel in sediment show upper course forward fabric feature. At the margin and flanks of debris flow fan, facies B is well formed, but no fecies C, because the flurial erosion is weak. Apart from the dif- ferent fades succession asemblege in space, the different as emblege of succession appears in different time in some profile, this shows a change in eavironment of the drainage area. The measured profile of Quanjia Valley shows seven successions, which are consisted by facies C developed group and no facies C group, which illustrates the change of climatic cndition.
Based on observation and statistical analysis of the textural, structural, grainsize and stratigraphic relationship data of ten profiles, we found six types of debris flow facies: Facies A (Coarser) Debris flow layer, which is the main body of debris flow, has a gravel content 25 percent to 50 percent and suspensio and support framwork. Facies B surface mud layer, which is formed by fane sediment floating up to the surface at flat area after the debris flow stopped, is the contemporaneous out-facies of the erosional layer (Facies B) and not be erosioned. The deposit consists of coarser sediment and has dry polygonal ground sometimes. Facies C Erosional layer, which is formed by fluvial erosion reforming on the surace after the debris flow deposited, The deposit appears loosely and porously, and deposit break hiatus. Facies D Basal mudh layer, which is formed by sedimentary bed paving processes in the earlier stage flood before debrcs flow appears. Facies E Mud layer, which is the main deposit body of mud flow in leoss area. By means of statistical analysis, nine local facies models had been found that can satisfy the statistical equire. The facies C.D.A. and B are the most common layers appear in deposit. A complete debris flow succession consists of facies D, A and B layer. The facies C layer is formed by later fluvial erosion and sometimes replaces the facies B. Therefore, a typical facies model of debris flow consists of C, D, A and B layer. The above mentioned models show some difference at different landforms. For example, at the top of debris flow fan, the deposition is strong and the later stage erosion is strong also, therefore, facies A and facies C develope, but on facies B and D. In this situation, facies succession is AC-AC type. At middle and base of a fan, the deposit shows typical facies model, with a well developed facies A, an obvious facies D and a less developed facies C. The facies B sometimes developes at both sides of debris flow valley. The AB planes of gravel in sediment show upper course forward fabric feature. At the margin and flanks of debris flow fan, facies B is well formed, but no fecies C, because the flurial erosion is weak. Apart from the dif- ferent fades succession asemblege in space, the different as emblege of succession appears in different time in some profile, this shows a change in eavironment of the drainage area. The measured profile of Quanjia Valley shows seven successions, which are consisted by facies C developed group and no facies C group, which illustrates the change of climatic cndition.
1990, 8(3): 22-34.
Abstract:
Having investigated the detailed organic petrological characteristics of more than 300 hydrocarbon source rocks, including oil source rocks, coals and oil shales, sampled from six typical terrestrial oilfields and 15 coalfields in China, the authors sum up the optical properities of the macerals occurring in these source rocks, and investigate their distribution and origins. Three new macerals are recognized which are called as telalginite C, telalginite D and zoo-soft-organisminite.On the base of this, a petrographic classification of macerals in the terrestrial hydrocarbon source rocks of China has been suggested. This system not only displays the organic petroliogical characteristics of our terre strial source orcks sa well as absorbes the strong points of the influenced classifications in the world, but also pays much attention to the following problems at which the organic petrologists haye been working since the past ten years: 1. This system is based on the research of the polished blacks of whole rocks and the thin- sections of Kerogen, and unifies the two classifications and applies the coal petrological maceral nomenclature. 2.The amorphour kerogen is subdivided as detailed as possible in order to make the widest possible combination of the three factors of of gins, optical properties and hydrocarbon-generationg potential of it, and to corresponed it with shaped organic matter in their precursors. 3.The influence of mature level on optical properties of organic matter is stressed in the classification, and an ther classification system for overmature source orcks is presented, and a great effort is made to corrspond it with the maceral in low mature stage accouding to the thermal evolution characters of macerals. Stage accouding as autoanisotropinite, alloanistropinite, micrinite A and micrinte B are suggested to discrible the secondary macerals in overmature stage formed by differeht kinds of hydrogen-rich macerals during theirthermal evolution.
Having investigated the detailed organic petrological characteristics of more than 300 hydrocarbon source rocks, including oil source rocks, coals and oil shales, sampled from six typical terrestrial oilfields and 15 coalfields in China, the authors sum up the optical properities of the macerals occurring in these source rocks, and investigate their distribution and origins. Three new macerals are recognized which are called as telalginite C, telalginite D and zoo-soft-organisminite.On the base of this, a petrographic classification of macerals in the terrestrial hydrocarbon source rocks of China has been suggested. This system not only displays the organic petroliogical characteristics of our terre strial source orcks sa well as absorbes the strong points of the influenced classifications in the world, but also pays much attention to the following problems at which the organic petrologists haye been working since the past ten years: 1. This system is based on the research of the polished blacks of whole rocks and the thin- sections of Kerogen, and unifies the two classifications and applies the coal petrological maceral nomenclature. 2.The amorphour kerogen is subdivided as detailed as possible in order to make the widest possible combination of the three factors of of gins, optical properties and hydrocarbon-generationg potential of it, and to corresponed it with shaped organic matter in their precursors. 3.The influence of mature level on optical properties of organic matter is stressed in the classification, and an ther classification system for overmature source orcks is presented, and a great effort is made to corrspond it with the maceral in low mature stage accouding to the thermal evolution characters of macerals. Stage accouding as autoanisotropinite, alloanistropinite, micrinite A and micrinte B are suggested to discrible the secondary macerals in overmature stage formed by differeht kinds of hydrogen-rich macerals during theirthermal evolution.
1990, 8(3): 46-57.
Abstract:
Dongpu depression is one of the famous gas-producing areas of China. The principal strata of gas-source rock and reservoir rock is Shahejie formation. To study the potential of formational fluid of this stratum is the main content in this paper. The fluid potential is the mechanical energy possessed by unit mass of fluid,which is composed of two parts, gravity and pressure. The formational fluide always move from higher potential area to the lower, so the area of lower hydrocarbon potential is the direction of secondary migration and the location of accumulation of oil and gas. The characters of ground water pressure system determined the water moving direction and the location of accumulation of oil and gas. According to A. A. Karzaiv,the natural pressure water system is divided into two types: Sedimentary pressure water system and eluvial pressure water system. The former's water moving direction is often centrafugal,while the later's water moving direction is centripetal. The equipotential surfaces of the centripetal flow tilt downward will be favourable to trap oil and gas. The ground water of oil and gas-producing strata in Dongpu depression characterises the centrifudal. The over high pressure in the study area is evident in the deep part, i.e., the formational pressure coefficients in the tectonic lower is evidently larger than that in the tectonic higher, and the fluid potential of the former is larger than that of the later. Therefore,the calculation of fluid potential in Dongpu depression shows that not only in the shallow but also in the deep reservoir rocks,the moving direction of water is towards the tectonic high location,and the gas potential or oil potential are also decreases towards the tectonic high. This character causes the horizontal projects of equipotential surface contours of water,oil and gas are nearly coincide. Because the physical properties of reservoir rock in shallow depth are more homogeneous,and the transportation ability of hydrodynamic is better,so the oil and gas accumulation in Dongpu depression is located at the relative low oil and gas potential area. Generaly,the accumulation of natural gas of deep strata is still controlled by low gas potential. However.the high production wells are always related to the local high potential area such as well Bai 9 but surrounded by the low potential. How can we explain this phenomenon,which appears not coincide with the general hydrodynamic principle of oil and gas migration. The writers suggest it is the effect of less permeable zones. Because of the much smaller weight density of gas than that of oil, former's floating force is much larger than that of later. Gas migration paths are more nearly vertical than oil's under dynamic condition,and hence the slope of gas and water contact surface is smaller than that of oil and water contact surface. If there are open faults at the top of anticline as the Baimiao structure.updip flow direction is detrimental to entrapment oil than to gas,oil is easy to overflow along the faults. This can explain why Baimiao structure mainly produces gas with little oil. Similarly, it can also be used to explain why the S_3~(3+4) strata of Qiaodong block produces gas, not oil.
Dongpu depression is one of the famous gas-producing areas of China. The principal strata of gas-source rock and reservoir rock is Shahejie formation. To study the potential of formational fluid of this stratum is the main content in this paper. The fluid potential is the mechanical energy possessed by unit mass of fluid,which is composed of two parts, gravity and pressure. The formational fluide always move from higher potential area to the lower, so the area of lower hydrocarbon potential is the direction of secondary migration and the location of accumulation of oil and gas. The characters of ground water pressure system determined the water moving direction and the location of accumulation of oil and gas. According to A. A. Karzaiv,the natural pressure water system is divided into two types: Sedimentary pressure water system and eluvial pressure water system. The former's water moving direction is often centrafugal,while the later's water moving direction is centripetal. The equipotential surfaces of the centripetal flow tilt downward will be favourable to trap oil and gas. The ground water of oil and gas-producing strata in Dongpu depression characterises the centrifudal. The over high pressure in the study area is evident in the deep part, i.e., the formational pressure coefficients in the tectonic lower is evidently larger than that in the tectonic higher, and the fluid potential of the former is larger than that of the later. Therefore,the calculation of fluid potential in Dongpu depression shows that not only in the shallow but also in the deep reservoir rocks,the moving direction of water is towards the tectonic high location,and the gas potential or oil potential are also decreases towards the tectonic high. This character causes the horizontal projects of equipotential surface contours of water,oil and gas are nearly coincide. Because the physical properties of reservoir rock in shallow depth are more homogeneous,and the transportation ability of hydrodynamic is better,so the oil and gas accumulation in Dongpu depression is located at the relative low oil and gas potential area. Generaly,the accumulation of natural gas of deep strata is still controlled by low gas potential. However.the high production wells are always related to the local high potential area such as well Bai 9 but surrounded by the low potential. How can we explain this phenomenon,which appears not coincide with the general hydrodynamic principle of oil and gas migration. The writers suggest it is the effect of less permeable zones. Because of the much smaller weight density of gas than that of oil, former's floating force is much larger than that of later. Gas migration paths are more nearly vertical than oil's under dynamic condition,and hence the slope of gas and water contact surface is smaller than that of oil and water contact surface. If there are open faults at the top of anticline as the Baimiao structure.updip flow direction is detrimental to entrapment oil than to gas,oil is easy to overflow along the faults. This can explain why Baimiao structure mainly produces gas with little oil. Similarly, it can also be used to explain why the S_3~(3+4) strata of Qiaodong block produces gas, not oil.
1990, 8(3): 66-74.
Abstract:
On the basis of geology, petrology and geochemistry, the diagenesis of carbonate rocks in the Middle-Upper Devonian series in Heqing district and its relation to the formation of Pb-Zn ore deposit are studied by means of field investigation and various techniques in laboratory in this pater. In the studied area the outcroped strata are mainly three formation: the Middle Devonian Qiziqiao Formation (D2q), the Upper Dvonian Shetianqiao Formation (D3s) and Xikuangshan Formation (D3x). According to the differences in lithologic characters, Qiziqiao Formation can be subdivided into three members, Shetianqiao Formation and Xikuangshan Formation both into two members. All of them are mainly composed of limestone with few of terrigenous sedimentary rocks. Sedimentary characteristics show that the Middle-Upper Devonian series may be classified into five microfacies (1) intertidal mud flat (including tidal-flat in clear water and tidal-flat in muddy water), (2) grain beach, (3) bioreef, (4) restricted bulf, (5) subtidal tempestite. The field investigation, observation under microscope and distribution characteristics of carbon and oxygen stable isotopes and the trace elements show that the Middle- Upper Devonian carbonate rocks have four principal diagentic manners i. e. : compaction, cementation, neomorphism and dolomization. Compacton is one of the most common diagentic manners, causing decrease of porosity and compact of lime. Neomorphism make micrite enlarge into microsparry and pseudosparry, and considered as the second one. The Middle- Upper Devonian carbonate rocks in studied area experienced four diagenetic environments. They are: (1) Vadose zone of freshwater, (2) Phreatic zone of freshwater, (3) Seawater and (4) Burial- underface dorage zone, among which the influnce of burial-underface dorage zone diagenetic environment is the largest to carbonate rocks in the area. The properties of carbon-oxygen stable isotopes and trace elements suggest that the diagenetic environments of bioreef, grain beach, tidal-flat in clear and subtidal tempestite are open relatively and the diagenetic fluid are active and fresh water flow in. But the diagenetic fluid of tidal-flat in muddy water and restricted gulf are stagnant relatively. As the result of the the open diagenetic environment over ore-bearing strata and the stagnant of diagenetic fluid beneath it, burial-underface dorage diagenesis made mineral elements to be enriched into industrial deposit.
On the basis of geology, petrology and geochemistry, the diagenesis of carbonate rocks in the Middle-Upper Devonian series in Heqing district and its relation to the formation of Pb-Zn ore deposit are studied by means of field investigation and various techniques in laboratory in this pater. In the studied area the outcroped strata are mainly three formation: the Middle Devonian Qiziqiao Formation (D2q), the Upper Dvonian Shetianqiao Formation (D3s) and Xikuangshan Formation (D3x). According to the differences in lithologic characters, Qiziqiao Formation can be subdivided into three members, Shetianqiao Formation and Xikuangshan Formation both into two members. All of them are mainly composed of limestone with few of terrigenous sedimentary rocks. Sedimentary characteristics show that the Middle-Upper Devonian series may be classified into five microfacies (1) intertidal mud flat (including tidal-flat in clear water and tidal-flat in muddy water), (2) grain beach, (3) bioreef, (4) restricted bulf, (5) subtidal tempestite. The field investigation, observation under microscope and distribution characteristics of carbon and oxygen stable isotopes and the trace elements show that the Middle- Upper Devonian carbonate rocks have four principal diagentic manners i. e. : compaction, cementation, neomorphism and dolomization. Compacton is one of the most common diagentic manners, causing decrease of porosity and compact of lime. Neomorphism make micrite enlarge into microsparry and pseudosparry, and considered as the second one. The Middle- Upper Devonian carbonate rocks in studied area experienced four diagenetic environments. They are: (1) Vadose zone of freshwater, (2) Phreatic zone of freshwater, (3) Seawater and (4) Burial- underface dorage zone, among which the influnce of burial-underface dorage zone diagenetic environment is the largest to carbonate rocks in the area. The properties of carbon-oxygen stable isotopes and trace elements suggest that the diagenetic environments of bioreef, grain beach, tidal-flat in clear and subtidal tempestite are open relatively and the diagenetic fluid are active and fresh water flow in. But the diagenetic fluid of tidal-flat in muddy water and restricted gulf are stagnant relatively. As the result of the the open diagenetic environment over ore-bearing strata and the stagnant of diagenetic fluid beneath it, burial-underface dorage diagenesis made mineral elements to be enriched into industrial deposit.
1990, 8(3): 84-92.
Abstract:
As a iind of sedimentary rocks the phosphorite is also regarded as a type of sedimentary mineral deposits so that the study on it is of petrololgical and economic significance. The origin is one of the most important subjects in phosphorite study. Taking the predeccesors ' achievements as starting points and the phosphorite deposits of Doushantuo Stage in Central Guizhou as "dissecting" objects and meanwhile using the theories and the methods of multiple sciences, this paper carried out a systematic study on the origin of the phosphorite from the aspects of the source, the deposition and the enrichment of phosphorus. The Central Guizhou phosphorite-forming region is located in the counties of Xifeng, Kaiyang, Weng' an, Fuquan, Zunyi, Meitan and Yuqing, Guizhou Province where exist two large phosphorite deposits, namely Kaiyang phbsporite deposit and Wengfu phosphorite deposit, and a series of middle to small ones. They are important phopshorite deposits of Doushantuo Stage in the Upper Yangtze region and mainly composed of sand-sized intraclast phosphorite, stromatolite (stratifera) phosphorite and algal pellet phosphorite.The main phosphate-rich environments are intertidal to subtidal ones with higher energy (shoals and algal reefs) on the shallow-water platform margin zone. Analysis of REE, especially the LREE / HREE ratio and the cateforized analysis of REE samples indicate that the phosphorus might be derived from the contemporaneous volcanic materials. The study of the textures and the compositions of phosphorites, ocean geochemistry and biochemistry shows that the assimilation and the fixation of algal is the most possible way of phosphorus deposition after which a series of enriching processes are required to form the phosphorite deposits being worth mining. The enriching processes are multistage and different enriching stages (or ways) lead to the formaion of different types of phosphorites.
As a iind of sedimentary rocks the phosphorite is also regarded as a type of sedimentary mineral deposits so that the study on it is of petrololgical and economic significance. The origin is one of the most important subjects in phosphorite study. Taking the predeccesors ' achievements as starting points and the phosphorite deposits of Doushantuo Stage in Central Guizhou as "dissecting" objects and meanwhile using the theories and the methods of multiple sciences, this paper carried out a systematic study on the origin of the phosphorite from the aspects of the source, the deposition and the enrichment of phosphorus. The Central Guizhou phosphorite-forming region is located in the counties of Xifeng, Kaiyang, Weng' an, Fuquan, Zunyi, Meitan and Yuqing, Guizhou Province where exist two large phosphorite deposits, namely Kaiyang phbsporite deposit and Wengfu phosphorite deposit, and a series of middle to small ones. They are important phopshorite deposits of Doushantuo Stage in the Upper Yangtze region and mainly composed of sand-sized intraclast phosphorite, stromatolite (stratifera) phosphorite and algal pellet phosphorite.The main phosphate-rich environments are intertidal to subtidal ones with higher energy (shoals and algal reefs) on the shallow-water platform margin zone. Analysis of REE, especially the LREE / HREE ratio and the cateforized analysis of REE samples indicate that the phosphorus might be derived from the contemporaneous volcanic materials. The study of the textures and the compositions of phosphorites, ocean geochemistry and biochemistry shows that the assimilation and the fixation of algal is the most possible way of phosphorus deposition after which a series of enriching processes are required to form the phosphorite deposits being worth mining. The enriching processes are multistage and different enriching stages (or ways) lead to the formaion of different types of phosphorites.
1990, 8(3): 103-109.
Abstract:
Several stromatolites with different shapes in the lew member of fianziling Formation of Upper Devonian in Fankou Mine have been discovered by the author in recent years. These fossils are of special significance for determining the sedimentary environment. This paper discuses the relationship between the shapes of the stromatolites and the sedimentary environment such as the direction, frequence and range of transgression and the feature of the basin. The stromatolites seen in this area are mostly of Palaeozoic benthons reef-building calcium algae and interstifial cohesion action. The cyclopean of them had formed on environment favorable for mineralization and reef-building. At last the author describes the distribution of stromatolites with different shapes and the evolution of the biota which are similar to the feature of barrier reef of the period in Canning West Australia.
Several stromatolites with different shapes in the lew member of fianziling Formation of Upper Devonian in Fankou Mine have been discovered by the author in recent years. These fossils are of special significance for determining the sedimentary environment. This paper discuses the relationship between the shapes of the stromatolites and the sedimentary environment such as the direction, frequence and range of transgression and the feature of the basin. The stromatolites seen in this area are mostly of Palaeozoic benthons reef-building calcium algae and interstifial cohesion action. The cyclopean of them had formed on environment favorable for mineralization and reef-building. At last the author describes the distribution of stromatolites with different shapes and the evolution of the biota which are similar to the feature of barrier reef of the period in Canning West Australia.
1990, 8(3): 121-127.
Abstract:
A set of typical storm deposits have been recognized in the upper part of early triassic the first member (Fei Xianguan Formation) of Liang Fengya, Chongqing. The lithcharacter of tempestite is dull purple calcirudite and calcarenite which includes greyish white micritic h'mestone. The total thickness of tempestite is 20m, among which any biogenic and trace fossils have not been found. The section can be divided into 11 unit tempestite beds in total and each can be regarded as a complete rhythmic unit of tempestite (Fig. 1) with clear scouring top partly removed 20-40cm in thickness. The lag gravels bed (a) is generally 20-50 cm thick on the scouring plane. The covering deposits upward are the graded bed (b), the evenly bed (c), the hummocky bed (d) and the ripple bed (e). Above the horizontal and wavy bed (f) are normal sediments in fair-weather. A complete sequence of storm deposits from bottom to top may be divided into three parts and six section (Fig. 2, A). According to development degree in the unit and characteristics of lag gravel in the section, three kinds of texture of the section may be divided: 1.the allochthonous lag gravel proximal tempestite; 2.the sedentary type lag gravel proximal tempestite; 3.the repeating type proximal tempestite. The storm deposits formed under the condition from storm peak to wind force subsidence in region. Period of storm peak, tempestuous currents raid semi-solidifying carbonate sediments below the normal wave base so that they become the rip-up intraclasts of different sizes. At the time, the scouring plane of various shapes are formed on the surface of sedimentary. The broken carbonate intraclasts formed the sedentary or allochthonous type lag gravel. The fluid possesses the nature of density flow since storm disturbs to take differential suspension for fine grain. When storm subsided, the suspended matter early or later fall to form the graded bed, the evenly bed, the hummocky bed, the saucer-shaped structures and ripple bed. After the storm stopped, it is sediments in fair-weather. The tempestite is not congenetic material. The particle is the carbonate intraclast in the epicontinental basin while the matrix is the clay and silt in the shoreside. Both of them are formed by mixing below the normal wave base above the storm wave base.
A set of typical storm deposits have been recognized in the upper part of early triassic the first member (Fei Xianguan Formation) of Liang Fengya, Chongqing. The lithcharacter of tempestite is dull purple calcirudite and calcarenite which includes greyish white micritic h'mestone. The total thickness of tempestite is 20m, among which any biogenic and trace fossils have not been found. The section can be divided into 11 unit tempestite beds in total and each can be regarded as a complete rhythmic unit of tempestite (Fig. 1) with clear scouring top partly removed 20-40cm in thickness. The lag gravels bed (a) is generally 20-50 cm thick on the scouring plane. The covering deposits upward are the graded bed (b), the evenly bed (c), the hummocky bed (d) and the ripple bed (e). Above the horizontal and wavy bed (f) are normal sediments in fair-weather. A complete sequence of storm deposits from bottom to top may be divided into three parts and six section (Fig. 2, A). According to development degree in the unit and characteristics of lag gravel in the section, three kinds of texture of the section may be divided: 1.the allochthonous lag gravel proximal tempestite; 2.the sedentary type lag gravel proximal tempestite; 3.the repeating type proximal tempestite. The storm deposits formed under the condition from storm peak to wind force subsidence in region. Period of storm peak, tempestuous currents raid semi-solidifying carbonate sediments below the normal wave base so that they become the rip-up intraclasts of different sizes. At the time, the scouring plane of various shapes are formed on the surface of sedimentary. The broken carbonate intraclasts formed the sedentary or allochthonous type lag gravel. The fluid possesses the nature of density flow since storm disturbs to take differential suspension for fine grain. When storm subsided, the suspended matter early or later fall to form the graded bed, the evenly bed, the hummocky bed, the saucer-shaped structures and ripple bed. After the storm stopped, it is sediments in fair-weather. The tempestite is not congenetic material. The particle is the carbonate intraclast in the epicontinental basin while the matrix is the clay and silt in the shoreside. Both of them are formed by mixing below the normal wave base above the storm wave base.
