1993 Vol. 11, No. 2
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Display Method:
1993, 11(2): 1-10.
Abstract:
Widely exposed in the western Henan,the Late Proterozoic Luoyu Group consists of sili-ciclastic rocks in the lower section and stromatolite dolostones and dolo-mudstones in the upper section, recording a complete transgressive-regressive depositional sequence. The transgression is demonstrated by the fact that high energy coastal deposits are gradually overlapped by shelf facies,with amalgmated glauconitic sandstones as condensed layers. Trans-gressive section,hower,makes up only 10-15 percent of the Luoyu Group. In contrast,the subsequent regression brought about striking coastal prpgradtion,resulting in a thick vertical stack of facies of outer shelf-inner shelf-beach/barrier islands-lagoon environments in a ascending order. In terms of internal sedimentary structures,siliciclastic rocks are divided into several different facies. Hummocky stratified sandatones,swalley stratified sandstones and thin-bedded Bouma-type fine-grained sandstones are clearly of storm origin. The cross-bedded and parallel-laminated sandstones may be also generated by storm-related ourrents. These distinctive facies and facies associations are widespread and dominate the Luoyu Group, indicative of costal-shelf environments which were influenced mainly by storm events. While sand trn-sport and deposition in inner shelf might be controlled by storm-surf! ebbs,the formation of thin fine-grained Boumatype layers in outer shelf are related to shelf water density (turbidity)currents. The carbonate deposition of Upper Luoyu Group is characterized by development of stromatolites which can be grouped,according to their growth forms,into different types,i. e. .spheroid,dome,columnar and stratiform. A shallowing-upward depositional trend is inferred from the vertical variations of the stromatolite geometry. Thin-layered dolomudstones directly capping stromatolite facies are distingguished by desiccation, solution surfaces, cauliflower chert nodules and tepee structures which provide convincing evidence of subaerial exposure and further attest the shallowing-upword nature of the stromatolite to thin-layered dolomudstone sequence. Alagoon setting for the Upper Luoyu Group mudstone and carbonate deposition is suggested because of its immediate superposition over the beach or barrier islands in a progradational sense. The depositional evolution of Luoyu Group was closely linked to the rifting of southern margin of North China Plateform,and the whole sequence is the products of thermal subsidence phase of a rifted basin in western Henan. The progradation-dominated facies sequence certainly resulted from regression due to low rate of subsidence and relatively rapid fillling of the rifted basin.
Widely exposed in the western Henan,the Late Proterozoic Luoyu Group consists of sili-ciclastic rocks in the lower section and stromatolite dolostones and dolo-mudstones in the upper section, recording a complete transgressive-regressive depositional sequence. The transgression is demonstrated by the fact that high energy coastal deposits are gradually overlapped by shelf facies,with amalgmated glauconitic sandstones as condensed layers. Trans-gressive section,hower,makes up only 10-15 percent of the Luoyu Group. In contrast,the subsequent regression brought about striking coastal prpgradtion,resulting in a thick vertical stack of facies of outer shelf-inner shelf-beach/barrier islands-lagoon environments in a ascending order. In terms of internal sedimentary structures,siliciclastic rocks are divided into several different facies. Hummocky stratified sandatones,swalley stratified sandstones and thin-bedded Bouma-type fine-grained sandstones are clearly of storm origin. The cross-bedded and parallel-laminated sandstones may be also generated by storm-related ourrents. These distinctive facies and facies associations are widespread and dominate the Luoyu Group, indicative of costal-shelf environments which were influenced mainly by storm events. While sand trn-sport and deposition in inner shelf might be controlled by storm-surf! ebbs,the formation of thin fine-grained Boumatype layers in outer shelf are related to shelf water density (turbidity)currents. The carbonate deposition of Upper Luoyu Group is characterized by development of stromatolites which can be grouped,according to their growth forms,into different types,i. e. .spheroid,dome,columnar and stratiform. A shallowing-upward depositional trend is inferred from the vertical variations of the stromatolite geometry. Thin-layered dolomudstones directly capping stromatolite facies are distingguished by desiccation, solution surfaces, cauliflower chert nodules and tepee structures which provide convincing evidence of subaerial exposure and further attest the shallowing-upword nature of the stromatolite to thin-layered dolomudstone sequence. Alagoon setting for the Upper Luoyu Group mudstone and carbonate deposition is suggested because of its immediate superposition over the beach or barrier islands in a progradational sense. The depositional evolution of Luoyu Group was closely linked to the rifting of southern margin of North China Plateform,and the whole sequence is the products of thermal subsidence phase of a rifted basin in western Henan. The progradation-dominated facies sequence certainly resulted from regression due to low rate of subsidence and relatively rapid fillling of the rifted basin.
1993, 11(2): 19-26.
Abstract:
A suit of late Proterozoic Sandstones and shales up to 2800m thick is wide-spreaded in Southern Anhui province. It has been identified by many researchers as a flysch according to a series of characteristics,such as rhythms,grading textures,contemporoneous deformations, sole marks etc.. It lays with a unconformity on Xikou Group of mainly mudstones and is covered by Dunjia coarser detrital deposits and Puling-Jintan volcanic rocks. All above mentioned strata are slightly metamorphosed. The Yanzhanling flysch arenites are debris gray wackes, which are quartz intermediate, plagioclase-rich and very metamorphic lithic. Result of heavy mineral analysis shows that they were derived from igeneous, metamorphic and sedimentary rocks. It is suggested that this flysch deposits have a source area composited of intermediate-acid volcanic rocks,granites,slightly metamorphosed rocks and sedimentary rocks,and also suggested that intermediate-acid magma was erupted during the time of flysch sedimentation, as a thicker intercalations of intermediate-acid are present in the flysch deposits. Using the QFL diagram of Dickinson et al. (1979),the source area of this flysch arenites belong to the domain between magmatic arc and rocyclic erogenic belt. Using the QFL diagram of Crook(1974),the flysch arenites have the andean-type tectonic framework. From 27 samples of flysch arenites,the content of SiO2-is 70. 19%,K2O/Na2O: 0. 84,FeO+MgO:6. 37%,TiO2:0. 74%,Al2O3/SiO2:0. 20, Al2O3/(CaO + Na2O) : 2. 74,according to these data, the flysch can be identified as a andean-type (from Grook, 1974)or active continental margin (from Bhatia, 1983;Roser et al.,1986). From 8 samples of flysch arenites, content of ∑ REE is 184. 29, ∑LREE/∑HREE:8. 21,Eu/Eu* : 0. 69,etc. and the flysch can also be i-dentified as andean-type. Besides,post-flysch deposits-the Puling Formation is a tholeiite-spilite assemblage.locates near the northern side of flysch basin,and the contemporaneous Jingtan Formation is a suit of andesits,dacits and pyroclastic rocks of calc-aikali series .locating near the sourthern side of the flysch basin. So, it can be confirmed that this flysch is of a andean-type developing in a tectonic framework of inter-arc basin.
A suit of late Proterozoic Sandstones and shales up to 2800m thick is wide-spreaded in Southern Anhui province. It has been identified by many researchers as a flysch according to a series of characteristics,such as rhythms,grading textures,contemporoneous deformations, sole marks etc.. It lays with a unconformity on Xikou Group of mainly mudstones and is covered by Dunjia coarser detrital deposits and Puling-Jintan volcanic rocks. All above mentioned strata are slightly metamorphosed. The Yanzhanling flysch arenites are debris gray wackes, which are quartz intermediate, plagioclase-rich and very metamorphic lithic. Result of heavy mineral analysis shows that they were derived from igeneous, metamorphic and sedimentary rocks. It is suggested that this flysch deposits have a source area composited of intermediate-acid volcanic rocks,granites,slightly metamorphosed rocks and sedimentary rocks,and also suggested that intermediate-acid magma was erupted during the time of flysch sedimentation, as a thicker intercalations of intermediate-acid are present in the flysch deposits. Using the QFL diagram of Dickinson et al. (1979),the source area of this flysch arenites belong to the domain between magmatic arc and rocyclic erogenic belt. Using the QFL diagram of Crook(1974),the flysch arenites have the andean-type tectonic framework. From 27 samples of flysch arenites,the content of SiO2-is 70. 19%,K2O/Na2O: 0. 84,FeO+MgO:6. 37%,TiO2:0. 74%,Al2O3/SiO2:0. 20, Al2O3/(CaO + Na2O) : 2. 74,according to these data, the flysch can be identified as a andean-type (from Grook, 1974)or active continental margin (from Bhatia, 1983;Roser et al.,1986). From 8 samples of flysch arenites, content of ∑ REE is 184. 29, ∑LREE/∑HREE:8. 21,Eu/Eu* : 0. 69,etc. and the flysch can also be i-dentified as andean-type. Besides,post-flysch deposits-the Puling Formation is a tholeiite-spilite assemblage.locates near the northern side of flysch basin,and the contemporaneous Jingtan Formation is a suit of andesits,dacits and pyroclastic rocks of calc-aikali series .locating near the sourthern side of the flysch basin. So, it can be confirmed that this flysch is of a andean-type developing in a tectonic framework of inter-arc basin.
1993, 11(2): 34-42.
Abstract:
The Xicheng Pb-Zn orefield locates in Gansu Province, is one of the most famous ore-fields in China. Its controlling horizon are Anjiacha and Xihanshui formations of the middle Devonian,and its ore-bearing rocks belong to marine clastic and carbonate rocks. Carbonate rocks characterized wide spreding, multi-rock types, rapid facies changment and good ore-bearing bedds. On the basis of textural origin classification and consulting the types of grains and sedimentary structures,the carbonate rocks can be divided into four types and twenty-six kinds of microfacies: include seven kinds of grainstone(MG1-MG7),six kinds of wackestone (GM1-GM6),nine kinds of mudstone(M1 -M9) and four kinds of hermatobiolith(R1 -R4). The microfacies represent respectively different sedimentary conditions and environments. Ten kinds of microfacies associations have been estabilished according to neighbouring and paragenetic relationship of micro-facies. Each association corresponds a designated sedimentary environment and its evolution: such as (Fig. 1) open platform, uppertidal zone-swamp in restricted platform, sag basin of semi-open platform, reef-fore-reef-reef-back, biogenic bank(or stratigraphic reef)-shallow basin behind bank-shelf and shelf point reef shelf. On the basis of microfacies associations controlling Pb-Zn ore,this paper shows that sag basin of semi-open platform and shollow basin behind the bank are a favourable environments to form Pb-Zn ore.
The Xicheng Pb-Zn orefield locates in Gansu Province, is one of the most famous ore-fields in China. Its controlling horizon are Anjiacha and Xihanshui formations of the middle Devonian,and its ore-bearing rocks belong to marine clastic and carbonate rocks. Carbonate rocks characterized wide spreding, multi-rock types, rapid facies changment and good ore-bearing bedds. On the basis of textural origin classification and consulting the types of grains and sedimentary structures,the carbonate rocks can be divided into four types and twenty-six kinds of microfacies: include seven kinds of grainstone(MG1-MG7),six kinds of wackestone (GM1-GM6),nine kinds of mudstone(M1 -M9) and four kinds of hermatobiolith(R1 -R4). The microfacies represent respectively different sedimentary conditions and environments. Ten kinds of microfacies associations have been estabilished according to neighbouring and paragenetic relationship of micro-facies. Each association corresponds a designated sedimentary environment and its evolution: such as (Fig. 1) open platform, uppertidal zone-swamp in restricted platform, sag basin of semi-open platform, reef-fore-reef-reef-back, biogenic bank(or stratigraphic reef)-shallow basin behind bank-shelf and shelf point reef shelf. On the basis of microfacies associations controlling Pb-Zn ore,this paper shows that sag basin of semi-open platform and shollow basin behind the bank are a favourable environments to form Pb-Zn ore.
1993, 11(2): 51-57.
Abstract:
Banna Formation is the source bedds and host rocks of fine-impregnation gold ore deposits in Northwest Guangxi. The formation is turbidites with 150-5000m thick,and composed of sandstone,siltstone,mudstone and mirl. Through statistical analysis of gold concentration of 240 samples collected from 11 major geological sections and considering sedimentary and petrological characters of those samples,the authors report 7 factors which affect the concentration of gold of Banna Formation; 1:Gold concentration in geological sections is classified into original,barent and enriched type, which include 6 sub-types ;and regionally classified tnto original, barent and enriched area. Among them, part of gold in gold-enriched area is from Jiangnan Uplift and Ermei Basalt Belt. 2: There are little differences among mean concentration of sandstone, siltstone, mud-stone and mirl,but gold concentration in siltstone has comparetively higher variation coefficient,which indicats that gold in siltstone is mobile and easy migrating. 3:Gold concentration is low in the rocks having high percentage of quartz,but the law is only for those samples which have comparetively slight dizginesis. 4:In Bouma Sequence of turbidites,division C has higher variation coefficient of gold. In parts of geological profiles,gold concentration in fine-grain division is higher than that of underlying coarse-grain division. 5: Gold concentration is low in the rocks which had suffered strong chloritization and carbonatization in late diagenetic stage and subsequent stage. 6: Gold distribution in geological sections is classified into stable type and pulsatory type. In pulsatory type,concentration of gold is low in lower parts and higher in upper parts in each petrological member.
Banna Formation is the source bedds and host rocks of fine-impregnation gold ore deposits in Northwest Guangxi. The formation is turbidites with 150-5000m thick,and composed of sandstone,siltstone,mudstone and mirl. Through statistical analysis of gold concentration of 240 samples collected from 11 major geological sections and considering sedimentary and petrological characters of those samples,the authors report 7 factors which affect the concentration of gold of Banna Formation; 1:Gold concentration in geological sections is classified into original,barent and enriched type, which include 6 sub-types ;and regionally classified tnto original, barent and enriched area. Among them, part of gold in gold-enriched area is from Jiangnan Uplift and Ermei Basalt Belt. 2: There are little differences among mean concentration of sandstone, siltstone, mud-stone and mirl,but gold concentration in siltstone has comparetively higher variation coefficient,which indicats that gold in siltstone is mobile and easy migrating. 3:Gold concentration is low in the rocks having high percentage of quartz,but the law is only for those samples which have comparetively slight dizginesis. 4:In Bouma Sequence of turbidites,division C has higher variation coefficient of gold. In parts of geological profiles,gold concentration in fine-grain division is higher than that of underlying coarse-grain division. 5: Gold concentration is low in the rocks which had suffered strong chloritization and carbonatization in late diagenetic stage and subsequent stage. 6: Gold distribution in geological sections is classified into stable type and pulsatory type. In pulsatory type,concentration of gold is low in lower parts and higher in upper parts in each petrological member.
1993, 11(2): 58-54.
Abstract:
Wongfu phosphorus deposits is a kind of sedimentary phosphorus deposits formed in Doushantou formation with era of Sinian,widely associated with silicified rocks which were formed by means of replacing original rock(such as phosphorate,dolomite.etc. )below sedimentary level during the period of penecontemporaneous sedimentation. The characteristics of the silicified rocks in fields are : (1)Spreaded widely .they could be seen in almost all the mined columns. (2)Formed in many formations and along them, the silicified rocks mainly distributed on the top and bottom of the phospharate formation,and a little less in the phosphorate formation. ( 3) Silicification had the characteristics of selected replacement. which were showed by both of selecting formation and lithology. The former means that the top and bottom formations of phosphorate were firstly silicified. The later indicates that some type of rocks were silicified easily. The lithologic sequence in order of silicification is as follows:stromatolithic dolomite-dolomite-stromatolithic phosphorate-clastic phosphorate-black banded laminated phosphorate with colloform structure. (4) The silicified clasts in clastic phosphorate showed that the silicification took place during the period of penecontem-poraneous sedimentation. Under microscope, the silicified rocks mainly consist of coarse, fine,micro-,muddy crystal quartz and chalcedony. However,they were not a diagenetic series. The silicified rocks were divided into slight,strong and crystalized silicified rocks respectively, according to the level of replacement and their texture and structure. The three groups of rocks varied transitionally in space,which shows the characteristics from strong to weak silicification. U/Th is 4. 6-102. 5,∑REE is ranged from 6. 12 to 18. 537ppm.in the silicified rocks LREE/HREE is 7. 283-94. 5,δCe = 0. 251 - 0. 413. There were both positive and negative Eu abnormality (δEu=1. 36 in silicified rocks, δEu = 0. 37 in intense ones). δ18 O of 18. 83 and 20. 80-23. 67 in crystalized and strong silicified rocks respectively. The forming temperature of crystalized and intense silicified rocks is 101 - 105℃ and 66-98℃ respectively .through the isotopic equilibrium fractionation temperature function of quatz-wa-ter.
Wongfu phosphorus deposits is a kind of sedimentary phosphorus deposits formed in Doushantou formation with era of Sinian,widely associated with silicified rocks which were formed by means of replacing original rock(such as phosphorate,dolomite.etc. )below sedimentary level during the period of penecontemporaneous sedimentation. The characteristics of the silicified rocks in fields are : (1)Spreaded widely .they could be seen in almost all the mined columns. (2)Formed in many formations and along them, the silicified rocks mainly distributed on the top and bottom of the phospharate formation,and a little less in the phosphorate formation. ( 3) Silicification had the characteristics of selected replacement. which were showed by both of selecting formation and lithology. The former means that the top and bottom formations of phosphorate were firstly silicified. The later indicates that some type of rocks were silicified easily. The lithologic sequence in order of silicification is as follows:stromatolithic dolomite-dolomite-stromatolithic phosphorate-clastic phosphorate-black banded laminated phosphorate with colloform structure. (4) The silicified clasts in clastic phosphorate showed that the silicification took place during the period of penecontem-poraneous sedimentation. Under microscope, the silicified rocks mainly consist of coarse, fine,micro-,muddy crystal quartz and chalcedony. However,they were not a diagenetic series. The silicified rocks were divided into slight,strong and crystalized silicified rocks respectively, according to the level of replacement and their texture and structure. The three groups of rocks varied transitionally in space,which shows the characteristics from strong to weak silicification. U/Th is 4. 6-102. 5,∑REE is ranged from 6. 12 to 18. 537ppm.in the silicified rocks LREE/HREE is 7. 283-94. 5,δCe = 0. 251 - 0. 413. There were both positive and negative Eu abnormality (δEu=1. 36 in silicified rocks, δEu = 0. 37 in intense ones). δ18 O of 18. 83 and 20. 80-23. 67 in crystalized and strong silicified rocks respectively. The forming temperature of crystalized and intense silicified rocks is 101 - 105℃ and 66-98℃ respectively .through the isotopic equilibrium fractionation temperature function of quatz-wa-ter.
1993, 11(2): 84-90.
Abstract:
Storm current is a special current caused by strom in littoral and sea bottom which has both characters of gravitationsl and tractive current. The limited base effected by storm is called as storm wave base. When sediments deposit on the base,it would be scoured,undercut and disturbed then high density current is formed. When storm fade,grains drop quickly. The sediment and sedimentary structures composition caused by the process is called as tem-pesitites. The storm deposits characters in Paleozoic and Mesozoic marine limestome in Sichuan Basin are being continously studied. The authors first discovered that there are two rather better sequences of tempestites and several layers of para-tempestites in the Lower Triasic Feixianguan Formation (Member 3) in Zhongliang Mountain,Chongqing. The Member 3 with thickness of 102m, is mainly biturbation limestone, micritic limestone and oosparite, belong to open platform facies and shallow facies under open sea shelf envioron-ment. The tempestites discussed was found respectively in the bottom and middle - upper part of the section which thickness is, lower sequences 1. 5m, upper sequences 2. 5m. and para-tempstites 10m. n the tempestites of the area,there are aboundant basal and sedimentary structures as follow mainly: 1. Basal scouring and filling structure:includ crater,qully mold,pocket mould and bowl mould,etc. especially pocket mould tipical with shapes of box,bully and ripple-like. 2. Knotty structure : caused by unhomogeneous distribution of grains and there is obvious difference between knotty and matrix. 3. Swirling structure:developed in para-tempestites,is involution and fold of weakly soli-dated limestone as pushed by storm wave. 4. Massive bedding:one of an important characters of tempestites and with the change of current status there is normally graded bedding developed. 5. Hummocky cross-bedding and bidirectitional cross-bedding:formed on the effected by oscillatory current especially the former is a very important character of storm deposits in the area. 6. Lamination cross-bedding and horizontal bedding:developed in the storm fadding period. The distribution of ooide makes the micro layers and lamina very clear especially in upper sequences. The authors concluded the tempestites sequences of the area as 6 members i. e., A, B, C,D,E and F. Comparision with Aigner sequences, we added the member of hummocky cross-bedding,and also discussed the difference between tempesites sequences and turbidity sequences of Bouma in aspects of sedimentary structures and lithological facies of storm deposits of the member 3,Feixianguan Formation,we divided the tempesites types as follows: 1. Proximal tempestites (lower sequences): lack of one or two members, complicated basal structures,thinner tempestites layer unit,indicates that perhaps sedimentary area located in the storm active centre. 2. Distal tempestites (upper sequences) :whole sequences thicker upper members,it indicates that storm current which has tractive current character kept a long period. 3. Para-tempestites: lack of majority of members, indicates that storm frequently impulsed and tempestites was reformed strongly. Conclusion: 1. There are a few layers of storm diposits in member 3 of Feixiaguan Formation in Zhongliang Mountain area and we could conclude a rather better sequences. 2. Tempestites sequences could mainly be divided into two types,i. e., proximatl and distal tempestites. 3. Both grains and matrix in storm diposits are from the same source. The former was from inner-clastic of limestone and the latter from inner-basin' s carbonate mud. They mixed and sedimented between normal wave base and storm wave base.
Storm current is a special current caused by strom in littoral and sea bottom which has both characters of gravitationsl and tractive current. The limited base effected by storm is called as storm wave base. When sediments deposit on the base,it would be scoured,undercut and disturbed then high density current is formed. When storm fade,grains drop quickly. The sediment and sedimentary structures composition caused by the process is called as tem-pesitites. The storm deposits characters in Paleozoic and Mesozoic marine limestome in Sichuan Basin are being continously studied. The authors first discovered that there are two rather better sequences of tempestites and several layers of para-tempestites in the Lower Triasic Feixianguan Formation (Member 3) in Zhongliang Mountain,Chongqing. The Member 3 with thickness of 102m, is mainly biturbation limestone, micritic limestone and oosparite, belong to open platform facies and shallow facies under open sea shelf envioron-ment. The tempestites discussed was found respectively in the bottom and middle - upper part of the section which thickness is, lower sequences 1. 5m, upper sequences 2. 5m. and para-tempstites 10m. n the tempestites of the area,there are aboundant basal and sedimentary structures as follow mainly: 1. Basal scouring and filling structure:includ crater,qully mold,pocket mould and bowl mould,etc. especially pocket mould tipical with shapes of box,bully and ripple-like. 2. Knotty structure : caused by unhomogeneous distribution of grains and there is obvious difference between knotty and matrix. 3. Swirling structure:developed in para-tempestites,is involution and fold of weakly soli-dated limestone as pushed by storm wave. 4. Massive bedding:one of an important characters of tempestites and with the change of current status there is normally graded bedding developed. 5. Hummocky cross-bedding and bidirectitional cross-bedding:formed on the effected by oscillatory current especially the former is a very important character of storm deposits in the area. 6. Lamination cross-bedding and horizontal bedding:developed in the storm fadding period. The distribution of ooide makes the micro layers and lamina very clear especially in upper sequences. The authors concluded the tempestites sequences of the area as 6 members i. e., A, B, C,D,E and F. Comparision with Aigner sequences, we added the member of hummocky cross-bedding,and also discussed the difference between tempesites sequences and turbidity sequences of Bouma in aspects of sedimentary structures and lithological facies of storm deposits of the member 3,Feixianguan Formation,we divided the tempesites types as follows: 1. Proximal tempestites (lower sequences): lack of one or two members, complicated basal structures,thinner tempestites layer unit,indicates that perhaps sedimentary area located in the storm active centre. 2. Distal tempestites (upper sequences) :whole sequences thicker upper members,it indicates that storm current which has tractive current character kept a long period. 3. Para-tempestites: lack of majority of members, indicates that storm frequently impulsed and tempestites was reformed strongly. Conclusion: 1. There are a few layers of storm diposits in member 3 of Feixiaguan Formation in Zhongliang Mountain area and we could conclude a rather better sequences. 2. Tempestites sequences could mainly be divided into two types,i. e., proximatl and distal tempestites. 3. Both grains and matrix in storm diposits are from the same source. The former was from inner-clastic of limestone and the latter from inner-basin' s carbonate mud. They mixed and sedimented between normal wave base and storm wave base.
1993, 11(2): 99-104.
Abstract:
The suspended load in sea waters off Zhujiang (pearl) River Mouth and on its vicinal shelf was studied by grain-size analysis and mineralogical and microbiological assays on more then 100 specimens collected in four cruises in 1985 and 1986. The distribution of suspended load appears temporal and spatial trends. Average concentration is high in winters (25-26mg/l), low in summers (13-18mg/l), and decreases significantly seaward. Alongshore, the suspended load is enriched in Hanjiang River Mouth, Zhujiang River Mouth,west Guangdong coast,and off southeastern Hainan Island. High concentration is seen also on outer shelf of 100-200m water depth. Localities of high suspended load shift with seasons. The variation of concentration intensifies from sea surface downward both alongshore and on the outer shelf. The dominant components of the suspended loads are minerals; secondary shapeless organisms and biogenic particles. Clay minerals consist of the major portion of the mineral composition; one third of the specimens contains more than 70% of clay minerals. The content of clay minerals increases with the increase of total suspended load. Clastic minarals are mainly quartz and feldspar;secondarily mica, limonite,pyrite,and basaltic glass; ocassionally rutile, tourmalime, amphibole, corundum, glauconite, andcite fluorite, olivin, etc. Contents of the clastic minerals may be up to 15%. Biogenic particles are mainly diatom and secondarily foraminifera, with minor radiolaria, Crustacea, etc. Organisms are seen in all the specimens and particularly rich, with content of 45% and 30% respectively, in two specimens collected in summer from the seawater of 200 -400m depth off southeastern Hainan Island. The content of organisms is in general 1-5%; that of greater than 1% occurs in one third of total specimens, which are distributed in 1) Hanjiang River Mouth during winter rather than summer, especially in the water near the mouth where the content of organisms may reach 10%, 2) Zhujiang River Mouth, where the content of organisms may be up to 9%, 3) the water of 100-200m depth on the outer shelf. The specimens with suspended load greater than 70mg were subject to light-transmissive grain-size analyser of the 15 specimens analyzed, 12 were named silt; the rest three clayey silt. Under microscope the grains of 10-40μ diameter are dominant with many of about 120μ. This indicates a high -energy hydrodynamic conditions in these areas, where high concentration of suspended load is provided not only by Zhujiang and Hanjiang, but also by a-longshore currents. East Guangdong upwelling current, West Guangdong circular current, Nanhai warm current, and outer circular current.
The suspended load in sea waters off Zhujiang (pearl) River Mouth and on its vicinal shelf was studied by grain-size analysis and mineralogical and microbiological assays on more then 100 specimens collected in four cruises in 1985 and 1986. The distribution of suspended load appears temporal and spatial trends. Average concentration is high in winters (25-26mg/l), low in summers (13-18mg/l), and decreases significantly seaward. Alongshore, the suspended load is enriched in Hanjiang River Mouth, Zhujiang River Mouth,west Guangdong coast,and off southeastern Hainan Island. High concentration is seen also on outer shelf of 100-200m water depth. Localities of high suspended load shift with seasons. The variation of concentration intensifies from sea surface downward both alongshore and on the outer shelf. The dominant components of the suspended loads are minerals; secondary shapeless organisms and biogenic particles. Clay minerals consist of the major portion of the mineral composition; one third of the specimens contains more than 70% of clay minerals. The content of clay minerals increases with the increase of total suspended load. Clastic minarals are mainly quartz and feldspar;secondarily mica, limonite,pyrite,and basaltic glass; ocassionally rutile, tourmalime, amphibole, corundum, glauconite, andcite fluorite, olivin, etc. Contents of the clastic minerals may be up to 15%. Biogenic particles are mainly diatom and secondarily foraminifera, with minor radiolaria, Crustacea, etc. Organisms are seen in all the specimens and particularly rich, with content of 45% and 30% respectively, in two specimens collected in summer from the seawater of 200 -400m depth off southeastern Hainan Island. The content of organisms is in general 1-5%; that of greater than 1% occurs in one third of total specimens, which are distributed in 1) Hanjiang River Mouth during winter rather than summer, especially in the water near the mouth where the content of organisms may reach 10%, 2) Zhujiang River Mouth, where the content of organisms may be up to 9%, 3) the water of 100-200m depth on the outer shelf. The specimens with suspended load greater than 70mg were subject to light-transmissive grain-size analyser of the 15 specimens analyzed, 12 were named silt; the rest three clayey silt. Under microscope the grains of 10-40μ diameter are dominant with many of about 120μ. This indicates a high -energy hydrodynamic conditions in these areas, where high concentration of suspended load is provided not only by Zhujiang and Hanjiang, but also by a-longshore currents. East Guangdong upwelling current, West Guangdong circular current, Nanhai warm current, and outer circular current.
1993, 11(2): 113-117.
Abstract:
Three new structural tricyclic diterpenes are first reported in this paper. They are examined in the recent sediments of Qinghai Lake and their eluting time is between bicylic ter-panes of long chain and tetracyclic diterpanes of m/z 123 mass chromatogram. They are named as △8.9-sandaracopimaradiene, dihydrorimuene, 13-isopimaradiene through the analysis of broken mechanism of fragments in mass spectrum and the contrast study of synthesized standard spectrum made by Weaver and Wenkert, their molecular ion peaks m/e are 272, 274,272.respectively,and correspond abundant peaks m/z are 257,259,137, respectively. The studied information about natural organic high molecular compounds shows that sandaracopimaric acid and pimaradiene acid had been isolated form resin acid and their structures had been identified. The authours deduce that sandaracopimaric acid and pimaradiene acid are the precursors of △8.9-sandaracopimadariene, 13-isopimaradiene. In addition, many literatures have reported that sandara copimaradiane and pimaradiane have been detected in oil and source rock. Therefore,the three new structural tricyclic diterpenes studied in this paper are the middle transfer productuons form the acids in high plants to alkanes in geologic body, the eveolution process is that acid is transfered into alkene through dehydroxylation and then transfered into alkane through hydrogenation. The detection of △8.9-sandaracopi-maradiene,dihydrori-muene,13-isopimaradiene not only enriched the types of biomarkers but also provided the proof for the transfer process of organic matter from organisms to geological body. These three new structural compounds examined in the recent sediment of Qinghai Lake reflects the information that organic matter in Qinghai Lake is not only derived from the organisms of the lake,but also has the input of terrigenous high plants.
Three new structural tricyclic diterpenes are first reported in this paper. They are examined in the recent sediments of Qinghai Lake and their eluting time is between bicylic ter-panes of long chain and tetracyclic diterpanes of m/z 123 mass chromatogram. They are named as △8.9-sandaracopimaradiene, dihydrorimuene, 13-isopimaradiene through the analysis of broken mechanism of fragments in mass spectrum and the contrast study of synthesized standard spectrum made by Weaver and Wenkert, their molecular ion peaks m/e are 272, 274,272.respectively,and correspond abundant peaks m/z are 257,259,137, respectively. The studied information about natural organic high molecular compounds shows that sandaracopimaric acid and pimaradiene acid had been isolated form resin acid and their structures had been identified. The authours deduce that sandaracopimaric acid and pimaradiene acid are the precursors of △8.9-sandaracopimadariene, 13-isopimaradiene. In addition, many literatures have reported that sandara copimaradiane and pimaradiane have been detected in oil and source rock. Therefore,the three new structural tricyclic diterpenes studied in this paper are the middle transfer productuons form the acids in high plants to alkanes in geologic body, the eveolution process is that acid is transfered into alkene through dehydroxylation and then transfered into alkane through hydrogenation. The detection of △8.9-sandaracopi-maradiene,dihydrori-muene,13-isopimaradiene not only enriched the types of biomarkers but also provided the proof for the transfer process of organic matter from organisms to geological body. These three new structural compounds examined in the recent sediment of Qinghai Lake reflects the information that organic matter in Qinghai Lake is not only derived from the organisms of the lake,but also has the input of terrigenous high plants.
1993, 11(2): 124-132.
Abstract:
Kerogen is the direct original material of oil-forming. To determine the type and the mature degree of kerogen is one of the important work in petroleum geology. While studing the clay minerals of Baise Basin,Guangxi,the authors made some detialed work on the kerogen of this oil-forming region. The type,mature degree,and the evolution process of kerogen was determined through X-ray diffraction and micro-region analysis method,and also by microscopic,atom distribution and infrared work. According to the results of X-ray analysis, the aliphatic degree (Fa) of the kerogen in this region is 0. 28 to 0. 37. On increasing of the depth in the same geological section,the Fa becomes higher, that is, the kerogen evoluted to mature. By calculation, the height of aliphatic nuclei (Lc) is between 16. 60 and 20. 76 A,the layer number (n) of them is 5 to 6. These are the characteristics of type III kerogen. The evolution process of the kerogen in this region was studied using micro-region method,and also using some routine methods. The lower matured kerogen was photoed by microscope, and the distribution of the atoms in it was analyzed by electronic probe. It is shown that the carbon atom in this kind of lower mature kerogen is not homogeneous,normally higher in the center,lower in the outer part. Iron and silica are also concentrated to the center. Most of the Kerogen have FeS2 nuclei,and around the nuclei mainly are clay minerals. The evolution trent of the mature degree of the kerogen is consistent with the evolution trend of the clay minerals,that is,montmorillonite evoluted to illite/montmorillonite. The combining patterns of organic molecules and clay minerals were also discussed. According to the thermodynamics data and some experiments of transforming clay minerals, we qualitatively calculated the water and heat that produced by the montmorillonite to illite. It will let out 30 to 40 grams of water and 100 kcal of heat by 1 mol montmorillonite transform to illite. This may be the medium and dynamic power source of the forming,evolution,and decomposition of kerogen. It is concluded that the clay minerals were the catalytic promoter for organic material evelute to hydrocarbon.
Kerogen is the direct original material of oil-forming. To determine the type and the mature degree of kerogen is one of the important work in petroleum geology. While studing the clay minerals of Baise Basin,Guangxi,the authors made some detialed work on the kerogen of this oil-forming region. The type,mature degree,and the evolution process of kerogen was determined through X-ray diffraction and micro-region analysis method,and also by microscopic,atom distribution and infrared work. According to the results of X-ray analysis, the aliphatic degree (Fa) of the kerogen in this region is 0. 28 to 0. 37. On increasing of the depth in the same geological section,the Fa becomes higher, that is, the kerogen evoluted to mature. By calculation, the height of aliphatic nuclei (Lc) is between 16. 60 and 20. 76 A,the layer number (n) of them is 5 to 6. These are the characteristics of type III kerogen. The evolution process of the kerogen in this region was studied using micro-region method,and also using some routine methods. The lower matured kerogen was photoed by microscope, and the distribution of the atoms in it was analyzed by electronic probe. It is shown that the carbon atom in this kind of lower mature kerogen is not homogeneous,normally higher in the center,lower in the outer part. Iron and silica are also concentrated to the center. Most of the Kerogen have FeS2 nuclei,and around the nuclei mainly are clay minerals. The evolution trent of the mature degree of the kerogen is consistent with the evolution trend of the clay minerals,that is,montmorillonite evoluted to illite/montmorillonite. The combining patterns of organic molecules and clay minerals were also discussed. According to the thermodynamics data and some experiments of transforming clay minerals, we qualitatively calculated the water and heat that produced by the montmorillonite to illite. It will let out 30 to 40 grams of water and 100 kcal of heat by 1 mol montmorillonite transform to illite. This may be the medium and dynamic power source of the forming,evolution,and decomposition of kerogen. It is concluded that the clay minerals were the catalytic promoter for organic material evelute to hydrocarbon.
1993, 11(2): 11-18.
Abstract:
Dolostones are very common in the Lower Paleozoic of eastern North-China Platform, and can be divided into mud-silt-sized crystalline dolostones and fine-coarse crystalline dolostones. The former includes gypsiferous and non-gypsiferous; the later includes equal-crystal and unequal-crystal fine-coarse crystalline dolostones. Gypsiferous mud-silt-sized crystalline dolostones are well laminated,show bird's-eyes and mudcracks,contain gypsum crystals or nodules,and are associated with chicken-wire or laminated gypsum rocks. Based on the analysis of two samples,their δ13C is 0. 42‰-2. 21‰, average 1. 13‰(PDB) ;δ18O is -6. 01‰-4. 77‰, average -5. 39‰(PDB). The low δ18O results from recrystallization in fresh water and/or under high temperatures. These dolostones are similar to the Sabkha penecontemporaneous dolostones in the Persian Gulf,and are formed in supratidal flats by evaporative pumping dolomitizatiom under arid climate. Non-gypsiferous mud-silt -sized crystalline dolostones are similar to the gypsiferous ones in texture and structure, but do not contain gypsum and are not associated with gypsum rocks. Based on the analysis of 17 samples,their δ13C is -3. 69‰-3. 41‰,average 0. 03‰;δ18O - 8. 17‰-4. 04‰,average -5. 91‰. The low δ18O also results from recrystallization in fresh water and/or under high temperatures. These dolostones are similar to the supralittoral penecontemporaneous dolostones on the Bahamian Platform, and are formed in supratidal flats by evaporative pumping dolomitization under humid climate. Equal-crystal fine to coarse crystalline dolostones are composed of dolomites of basically the same size. Euhedral and semi-euhedral dolomites are common,especially when dolomitization is incomplete. Some dolomites show dirty centers and clean marging,and may contaim calcite inclusions. Thses dolomites are formed directly by replacing limestones. Based on analysis of 15 samples,the δ13C is -2. 11‰-2. 10‰,average -0. 40‰;δ18O -8. 49‰-4. 09‰,average -5. 53‰. These dolostones are mostly distributed under the disconformity between the Lower and Middle Ordovician,and are formed by dorag dolomitization. Unequal-crystal fine-coarse crystalline dolostones are composed of dolomites of greatly different size. The dolomites are commonly anhedral. Based on analysis of 5 samples,the 513C is -4. 72‰～-1.08‰,average -2. 83‰;δ18O - 9. 27‰～- 7. 32‰, average -8. 31‰. These dolostones are formed by recrystallization of earlier dolostones in fresh water. Porosities of dolostones in the Lower Paleozoic can be divided into intracrystal pores,in-tercrystal pores,vugs,cast pores,fissures,bird's-eye pores and shrinking fissures. The reser-voiring performance of the dolostones are controlled by many factors,such as the content and size of dolomites,and clay content of the dolostones, non-clayey silt-sized crystalline dolostones show the best reservoiring performance.
Dolostones are very common in the Lower Paleozoic of eastern North-China Platform, and can be divided into mud-silt-sized crystalline dolostones and fine-coarse crystalline dolostones. The former includes gypsiferous and non-gypsiferous; the later includes equal-crystal and unequal-crystal fine-coarse crystalline dolostones. Gypsiferous mud-silt-sized crystalline dolostones are well laminated,show bird's-eyes and mudcracks,contain gypsum crystals or nodules,and are associated with chicken-wire or laminated gypsum rocks. Based on the analysis of two samples,their δ13C is 0. 42‰-2. 21‰, average 1. 13‰(PDB) ;δ18O is -6. 01‰-4. 77‰, average -5. 39‰(PDB). The low δ18O results from recrystallization in fresh water and/or under high temperatures. These dolostones are similar to the Sabkha penecontemporaneous dolostones in the Persian Gulf,and are formed in supratidal flats by evaporative pumping dolomitizatiom under arid climate. Non-gypsiferous mud-silt -sized crystalline dolostones are similar to the gypsiferous ones in texture and structure, but do not contain gypsum and are not associated with gypsum rocks. Based on the analysis of 17 samples,their δ13C is -3. 69‰-3. 41‰,average 0. 03‰;δ18O - 8. 17‰-4. 04‰,average -5. 91‰. The low δ18O also results from recrystallization in fresh water and/or under high temperatures. These dolostones are similar to the supralittoral penecontemporaneous dolostones on the Bahamian Platform, and are formed in supratidal flats by evaporative pumping dolomitization under humid climate. Equal-crystal fine to coarse crystalline dolostones are composed of dolomites of basically the same size. Euhedral and semi-euhedral dolomites are common,especially when dolomitization is incomplete. Some dolomites show dirty centers and clean marging,and may contaim calcite inclusions. Thses dolomites are formed directly by replacing limestones. Based on analysis of 15 samples,the δ13C is -2. 11‰-2. 10‰,average -0. 40‰;δ18O -8. 49‰-4. 09‰,average -5. 53‰. These dolostones are mostly distributed under the disconformity between the Lower and Middle Ordovician,and are formed by dorag dolomitization. Unequal-crystal fine-coarse crystalline dolostones are composed of dolomites of greatly different size. The dolomites are commonly anhedral. Based on analysis of 5 samples,the 513C is -4. 72‰～-1.08‰,average -2. 83‰;δ18O - 9. 27‰～- 7. 32‰, average -8. 31‰. These dolostones are formed by recrystallization of earlier dolostones in fresh water. Porosities of dolostones in the Lower Paleozoic can be divided into intracrystal pores,in-tercrystal pores,vugs,cast pores,fissures,bird's-eye pores and shrinking fissures. The reser-voiring performance of the dolostones are controlled by many factors,such as the content and size of dolomites,and clay content of the dolostones, non-clayey silt-sized crystalline dolostones show the best reservoiring performance.
1993, 11(2): 27-33.
Abstract:
Characteristized by hemipelagic thinly-bedded lime mudstones interbedded with limestone breccias derived from gravity flow,the Middle-Ordovician Jinsushan Formation yields abundant trace fossils,but the are not evently vertical distributed. A brief description is as followsGn ascending order): Member 1, which consists mainly of dolomits,containing no trace fossils. Member 2,which composed of dark gray thinly-bedded lime mudstone,and is characterized by a small amount of tuff,radiolarian chert and well-sorted thinly-bedded calcareite and calcisiltite which represent the equivalent of contourite. Trace fossils are rare,with only one network trace fossil(Neurodictyon n. ichnogen.) and three facies-crossing trace fossils(Chon-drites,Cochlichnus,Gordia) occuring. Member 3,which consists of thinly-bedded lime mudstones interbedded with limestone breccias and yield abundant trace fossils,which includs :Belorhaphe,Chondrties,Cochlichnus, Gordia, Helminthopsis, Helminthoida, Megagrapton, Neurodictyon, Oldliamia, Paleodictyon, Phycodes,Protopaleodictyonand squamodictyon. Member 4.whose lower part consists of dark gray thinly-bedded limestone and the upper,of marl. Like Member 2,it is also contains a small number of trace fossils. Of which,on-ly two ichnogenera-Cochlichnus and Gordia are recognized. Based on the component, relative aboundance and preservational aspect of the trace fossils, in Member 3, the Paleodictyon ichnocoenosis is established, which consists chiefly of network trace fossils represented by the ichnogenus Paleodictyon, and this ichnocoenosis is analogus to Nereites ichnofacies. It is believed that the trace fossil association of the Member 2 belongs also to Nereites ichnofacies. But its water depth may be deeper than that of the Paleodictyon ichnocoenosis and is probably up to one thousand meters. In terms of trace fossils,sedimentary characteristics well as paleontological evidences,it is suggested that the depositional environments of the Member 1 to 4 are shallow-platform, basin margin,lower foreslope,and upper foreslope respectively. As to the sharp change of depositional environments from shallow-platform to basin margin,the possible cause may attribute to the subsidence owing to the tension fracturing of the area during that period.
Characteristized by hemipelagic thinly-bedded lime mudstones interbedded with limestone breccias derived from gravity flow,the Middle-Ordovician Jinsushan Formation yields abundant trace fossils,but the are not evently vertical distributed. A brief description is as followsGn ascending order): Member 1, which consists mainly of dolomits,containing no trace fossils. Member 2,which composed of dark gray thinly-bedded lime mudstone,and is characterized by a small amount of tuff,radiolarian chert and well-sorted thinly-bedded calcareite and calcisiltite which represent the equivalent of contourite. Trace fossils are rare,with only one network trace fossil(Neurodictyon n. ichnogen.) and three facies-crossing trace fossils(Chon-drites,Cochlichnus,Gordia) occuring. Member 3,which consists of thinly-bedded lime mudstones interbedded with limestone breccias and yield abundant trace fossils,which includs :Belorhaphe,Chondrties,Cochlichnus, Gordia, Helminthopsis, Helminthoida, Megagrapton, Neurodictyon, Oldliamia, Paleodictyon, Phycodes,Protopaleodictyonand squamodictyon. Member 4.whose lower part consists of dark gray thinly-bedded limestone and the upper,of marl. Like Member 2,it is also contains a small number of trace fossils. Of which,on-ly two ichnogenera-Cochlichnus and Gordia are recognized. Based on the component, relative aboundance and preservational aspect of the trace fossils, in Member 3, the Paleodictyon ichnocoenosis is established, which consists chiefly of network trace fossils represented by the ichnogenus Paleodictyon, and this ichnocoenosis is analogus to Nereites ichnofacies. It is believed that the trace fossil association of the Member 2 belongs also to Nereites ichnofacies. But its water depth may be deeper than that of the Paleodictyon ichnocoenosis and is probably up to one thousand meters. In terms of trace fossils,sedimentary characteristics well as paleontological evidences,it is suggested that the depositional environments of the Member 1 to 4 are shallow-platform, basin margin,lower foreslope,and upper foreslope respectively. As to the sharp change of depositional environments from shallow-platform to basin margin,the possible cause may attribute to the subsidence owing to the tension fracturing of the area during that period.
1993, 11(2): 43-50.
Abstract:
Massive dodlostone are widely developed in the strata of Sinian, Cambrian, Ordovician and Carboniferous in the northwestern margin of Trim Basin,three types can be divided according to the shape and size of dolomite in them. 1. Dolostone composed of automorphic rhombohedral dolomite,mainly occur in Ordovi- cian and Carboniferous system. The size of crystal dolomite are mainly 100 - 500μm, two groups of cleavages are developed. Cathodoluminescence colour of which are orange to dark red,there are ring structures shown by dark red and brown,degree of order is high(0. 885 in average) ;the content of CaCO3 is about 51-55% and the oxygen isotope is lighter (the average of δ18O is -8. 73‰PDB). 2. Dolostone composed of hypautomorphic granular dolomite mainly found in Cambrain and Ordovician with grain size of 50-150μm. One group of cleavages always developed in dolomite,the colour of Cathodoluminescence are mainly orange,isotopic composition of oxygen is light (the mean of δ18O is - 7. 55‰PDB). In the miarolitic cavity of this kind of dolo-stone,dolomite with very high automorphic degree are commmonly developed, which has a very high order degree(0. 95 in average) and very light oxygen isotope composition ((δ18O is - 12‰PDB in average),and rings consist of dark red and brown are seen under Cathodoluminescence. 3. Dolostone composed of anhedral microcrystaline dolomite,mainly occured in Sinian and Cambrian,and always accompany by shale and gypsum argillaceous and have laminated bedding and stromatolithic structure. Under electronic microscope,unequiganular dolomite distributed unregularly and there are no cleavages. Cathodoluminescence colour is bright orange,ordering degree of dolomite is low(0. 737 in average)and oxygen isotope composition is heavier(δ18o is -5. 74‰. PDB in average),usually,the contain of CaCo3 is higher. After analysis and study,the author proposed that the dolomite composed of xenomor-phic muddy-micritic dolomite is meta-homogenerous which formed by dolomitization caused by permeation and return flow,the porosity and permeability of which is worse. Dolostone composed of automorphic-hypautomorphic, powder-medium crystalline dolomite is formed by dolomitization of mixing water during early-middle diagenesis,this type of dolostone is the most favourable carbonate reservoir in the study area because of the higher porosity and permeability.
Massive dodlostone are widely developed in the strata of Sinian, Cambrian, Ordovician and Carboniferous in the northwestern margin of Trim Basin,three types can be divided according to the shape and size of dolomite in them. 1. Dolostone composed of automorphic rhombohedral dolomite,mainly occur in Ordovi- cian and Carboniferous system. The size of crystal dolomite are mainly 100 - 500μm, two groups of cleavages are developed. Cathodoluminescence colour of which are orange to dark red,there are ring structures shown by dark red and brown,degree of order is high(0. 885 in average) ;the content of CaCO3 is about 51-55% and the oxygen isotope is lighter (the average of δ18O is -8. 73‰PDB). 2. Dolostone composed of hypautomorphic granular dolomite mainly found in Cambrain and Ordovician with grain size of 50-150μm. One group of cleavages always developed in dolomite,the colour of Cathodoluminescence are mainly orange,isotopic composition of oxygen is light (the mean of δ18O is - 7. 55‰PDB). In the miarolitic cavity of this kind of dolo-stone,dolomite with very high automorphic degree are commmonly developed, which has a very high order degree(0. 95 in average) and very light oxygen isotope composition ((δ18O is - 12‰PDB in average),and rings consist of dark red and brown are seen under Cathodoluminescence. 3. Dolostone composed of anhedral microcrystaline dolomite,mainly occured in Sinian and Cambrian,and always accompany by shale and gypsum argillaceous and have laminated bedding and stromatolithic structure. Under electronic microscope,unequiganular dolomite distributed unregularly and there are no cleavages. Cathodoluminescence colour is bright orange,ordering degree of dolomite is low(0. 737 in average)and oxygen isotope composition is heavier(δ18o is -5. 74‰. PDB in average),usually,the contain of CaCo3 is higher. After analysis and study,the author proposed that the dolomite composed of xenomor-phic muddy-micritic dolomite is meta-homogenerous which formed by dolomitization caused by permeation and return flow,the porosity and permeability of which is worse. Dolostone composed of automorphic-hypautomorphic, powder-medium crystalline dolomite is formed by dolomitization of mixing water during early-middle diagenesis,this type of dolostone is the most favourable carbonate reservoir in the study area because of the higher porosity and permeability.
1993, 11(2): 55-74.
Abstract:
Several Early Silurian storm-wave genesis of bioclastic limestone beds which deposited on the muddy shelf have been recognized from NW Sichuan area. The Early Silurian deposited at the NW margin of the S-China Paleo-plate tectonically and it has the very thick sequence of shale,silty shale,muddy shale and silty sandstone with some reefs, bioherms and stratigraphically discontinuous lenticular and irregular bioclastic limestone beds. The fossils (trilobites, pelmatozoas, brachiopods and some small solitary rugose corals) which are dispersed in surrounding siliclclastic deposites,are the source of the bioclasts for tempestites. The bioclasts result from storm wave-caused winnowing effects and they are lag concentrates. It is one of the very important characteristics of the shallow muddy shelves. Detailed petrographic and stratigraphic analysis reveals 5 distinct tempestite (bioclastic limestone beds) patterns which located at 3 stratigraphic levels, according to 5 different stratigraphic sections. Pattern A:Thick lenticular or irregular bioclastic limestone beds (1-3m thick) with erosion at the bottom. Generally, the beds show three gradding subdivisions from bottom to top (at the Middle-Upper Ningqinag Formation). Pattern B:The small lenticular bisclastic limestone beds with l-20cm thick and 10-50cm long. The petrography of this pattern is similar to the third subdivision of the Pattern A (at the Upper Ningqiang For-mation). Pattern C:The lenticular or irregular bioclastic limestone beds with erosion at the mastem. The lower parts of the beds are mud-teariag bioclaslic limestone and gradually cosfer to the bioclastic grains upwardly. The eds are 5-15cm thick and locate at the gjianwan Formation. Patterm D:The small enticular limestone beds with 2-6cm thick and over 10cm lung, which can be divided into 4 petrographic subdivisions vertically. The first containing thin-shell brachiopod and ostracoda shells.is lag concentrates .the second is rizental lamunar zone,the third is the hummocky cross laminar stratification zone and the woverh is parullet laminar zone(at the Cuijiagou Formation). Pattern E: It is very similar to the Pattern D on the size, the distribution and from the second to the fourth subdivisions of Pattern D petrographically. Because the storm wave is different on energy .frequency and the span of the storm pro cess.several different types of tempestite deposited in this area. The petrographic and paleoe-cologic analysis reveals that the Pattern A and B are proximal and Pattern C.D.E .are distal. Form Pattern A to E,the petrographic characteristics show that the storm energy became weaker and the depth of water increase gradully. The storm wave accumulation of bioclasts can directly influence the structure and dynamics of nature of the sea floor and can change the physical characteristics of benthis habitats. Along with the bioclast accumulations in abundance,the soft muddy sea floor would be transformed into a coarser,firmer and topographically more complex benthic habitat. Many coarser substratum-like and firmer substratum-like epi-organisms,such as encrusting organisns,can settle and develop on it and form the biological hardgrounds. Many reefs and bioherms developed on the biological hardground through the process of taphonomic feedback. Usually, reefs developed on Pattern A tem-pestite.a firm bioherms can be seen on Pattern B,biostrome on Pattern C and Pattern D,E are covered by shale,because the depth of water increased gradually.
Several Early Silurian storm-wave genesis of bioclastic limestone beds which deposited on the muddy shelf have been recognized from NW Sichuan area. The Early Silurian deposited at the NW margin of the S-China Paleo-plate tectonically and it has the very thick sequence of shale,silty shale,muddy shale and silty sandstone with some reefs, bioherms and stratigraphically discontinuous lenticular and irregular bioclastic limestone beds. The fossils (trilobites, pelmatozoas, brachiopods and some small solitary rugose corals) which are dispersed in surrounding siliclclastic deposites,are the source of the bioclasts for tempestites. The bioclasts result from storm wave-caused winnowing effects and they are lag concentrates. It is one of the very important characteristics of the shallow muddy shelves. Detailed petrographic and stratigraphic analysis reveals 5 distinct tempestite (bioclastic limestone beds) patterns which located at 3 stratigraphic levels, according to 5 different stratigraphic sections. Pattern A:Thick lenticular or irregular bioclastic limestone beds (1-3m thick) with erosion at the bottom. Generally, the beds show three gradding subdivisions from bottom to top (at the Middle-Upper Ningqinag Formation). Pattern B:The small lenticular bisclastic limestone beds with l-20cm thick and 10-50cm long. The petrography of this pattern is similar to the third subdivision of the Pattern A (at the Upper Ningqiang For-mation). Pattern C:The lenticular or irregular bioclastic limestone beds with erosion at the mastem. The lower parts of the beds are mud-teariag bioclaslic limestone and gradually cosfer to the bioclastic grains upwardly. The eds are 5-15cm thick and locate at the gjianwan Formation. Patterm D:The small enticular limestone beds with 2-6cm thick and over 10cm lung, which can be divided into 4 petrographic subdivisions vertically. The first containing thin-shell brachiopod and ostracoda shells.is lag concentrates .the second is rizental lamunar zone,the third is the hummocky cross laminar stratification zone and the woverh is parullet laminar zone(at the Cuijiagou Formation). Pattern E: It is very similar to the Pattern D on the size, the distribution and from the second to the fourth subdivisions of Pattern D petrographically. Because the storm wave is different on energy .frequency and the span of the storm pro cess.several different types of tempestite deposited in this area. The petrographic and paleoe-cologic analysis reveals that the Pattern A and B are proximal and Pattern C.D.E .are distal. Form Pattern A to E,the petrographic characteristics show that the storm energy became weaker and the depth of water increase gradully. The storm wave accumulation of bioclasts can directly influence the structure and dynamics of nature of the sea floor and can change the physical characteristics of benthis habitats. Along with the bioclast accumulations in abundance,the soft muddy sea floor would be transformed into a coarser,firmer and topographically more complex benthic habitat. Many coarser substratum-like and firmer substratum-like epi-organisms,such as encrusting organisns,can settle and develop on it and form the biological hardgrounds. Many reefs and bioherms developed on the biological hardground through the process of taphonomic feedback. Usually, reefs developed on Pattern A tem-pestite.a firm bioherms can be seen on Pattern B,biostrome on Pattern C and Pattern D,E are covered by shale,because the depth of water increased gradually.
1993, 11(2): 75-83.
Abstract:
The volcaniclastic turbidites which are characterized by more than 25% pyroclastic contents and by the Bouma sequence are widely distributed in the Upper Devonian of east Jung-gar, the lower part of the Lower Devonian and the Upper Devonian of west Junggar. In terms of grainsize, they are subdivided into coarse, medium and fine grained volcaniclastic turbidite facies. Twenty sequence structures are recognized, which may be merged in three types; the completed, the continued-uncompleted and the punctuated-uncompleted Bouma sequence, i. e., Tabcde; Tabc or Tab; Tae, Tad or Tabe. Statistical data indicates that the sequence structures of the volcaniclastic turbidites in Northern Xinjiang are dominated by the punctuated-uncompleted Bouma sequences, the thickness frequences are 57. 6%, 73. 3% and 78. 9% respectly in the Zhifang section of east Junggar, the Heishantou section and the Sarburtishan section of west Junggar. The above gradual increasing of frequences corresponds to the strengthening of volcanic, seismic and tectonic activities and to the increasing of distal and fine grained volcaniclastic turbidites in the above sections. The punctuated-uncompleted Bouma sequences of the volcaniclastic turbidites would be formed in the mutual interference of several turbidity current events of in the mutual interference of turbidity current event (s) and other events (volcanic, seismic and tsunami events etc. ). A turbidity current sedimentation would be easily affected by other geologic processes in distal and fine grained turbidite region where a turbidity current energy is lower. In volcanic island are environments, frequent volcanic and seismic events affect easily a turbidity current sedimentation. Therefore, a punctuated-uncompleted sequence of turbidites would be one of the diagnostic indicators of distal and fine grained turbidites, and the turbidity current sedimentation region of polydirections and polyresources and an active tectonic setting.
The volcaniclastic turbidites which are characterized by more than 25% pyroclastic contents and by the Bouma sequence are widely distributed in the Upper Devonian of east Jung-gar, the lower part of the Lower Devonian and the Upper Devonian of west Junggar. In terms of grainsize, they are subdivided into coarse, medium and fine grained volcaniclastic turbidite facies. Twenty sequence structures are recognized, which may be merged in three types; the completed, the continued-uncompleted and the punctuated-uncompleted Bouma sequence, i. e., Tabcde; Tabc or Tab; Tae, Tad or Tabe. Statistical data indicates that the sequence structures of the volcaniclastic turbidites in Northern Xinjiang are dominated by the punctuated-uncompleted Bouma sequences, the thickness frequences are 57. 6%, 73. 3% and 78. 9% respectly in the Zhifang section of east Junggar, the Heishantou section and the Sarburtishan section of west Junggar. The above gradual increasing of frequences corresponds to the strengthening of volcanic, seismic and tectonic activities and to the increasing of distal and fine grained volcaniclastic turbidites in the above sections. The punctuated-uncompleted Bouma sequences of the volcaniclastic turbidites would be formed in the mutual interference of several turbidity current events of in the mutual interference of turbidity current event (s) and other events (volcanic, seismic and tsunami events etc. ). A turbidity current sedimentation would be easily affected by other geologic processes in distal and fine grained turbidite region where a turbidity current energy is lower. In volcanic island are environments, frequent volcanic and seismic events affect easily a turbidity current sedimentation. Therefore, a punctuated-uncompleted sequence of turbidites would be one of the diagnostic indicators of distal and fine grained turbidites, and the turbidity current sedimentation region of polydirections and polyresources and an active tectonic setting.
1993, 11(2): 91-98.
Abstract:
The area of northern Jiangsu and Anhui provinces locates on the southeastern edge of Huabei massif (Sino-Korean massif),and is one of the key areas for the division and correlation of Upper Proterozic in China. Since late 80's,some geologists have reported or studied some storm-deposits of the Upper Proterozoic (Ge Ming et al.,1987;Qiao Xiufu,1987;Qiao Xiufu et al.,1989). However,their researches are concerning only on the storm-deposit levels in Zhangqu Formation and Weiji Formation. Through the research in this area during recent years,the authors have discovered some storm-deposits in Liulaobei Formation,Niyuan Formation, and Wangshan Formation in the Upper Proterozoic. This paper is mainly carried out to approach the characteristics of the newly recognized storm-deposits in some aspects such as types of the tempestites,storm-generated sedimentary structures, sectional textures of tempestites, and sedimentary environment of tempestites. According to our research,the major rock types of the storm-deposits include autochthonous calcirudite,allochthonous calcirudite, turbidite-generated calcisiltite and micritic limestone, etc. Storm-generated sedimentary structures include different scour or truncation structures (e. g., flate, wave-like, complex and irregular, etc. );hummocky cross-stratification (which can be clasificlassified into two types; simple and complex); swaley cross-stration, swaley cross-stration,and thin graded bed. Moreover,the sectional texture of the newly recognized storm-deposits can be classified into 9 types. Most of them are incomplete,and some of them belong to complex ones,which mean the existence of episodical storm activity. The sedimentary environment of tempestites,we think,includes three types:subtidal zone in open shelf, plateform edge gentle ramp,and subtidal zone in confied plateform.
The area of northern Jiangsu and Anhui provinces locates on the southeastern edge of Huabei massif (Sino-Korean massif),and is one of the key areas for the division and correlation of Upper Proterozic in China. Since late 80's,some geologists have reported or studied some storm-deposits of the Upper Proterozoic (Ge Ming et al.,1987;Qiao Xiufu,1987;Qiao Xiufu et al.,1989). However,their researches are concerning only on the storm-deposit levels in Zhangqu Formation and Weiji Formation. Through the research in this area during recent years,the authors have discovered some storm-deposits in Liulaobei Formation,Niyuan Formation, and Wangshan Formation in the Upper Proterozoic. This paper is mainly carried out to approach the characteristics of the newly recognized storm-deposits in some aspects such as types of the tempestites,storm-generated sedimentary structures, sectional textures of tempestites, and sedimentary environment of tempestites. According to our research,the major rock types of the storm-deposits include autochthonous calcirudite,allochthonous calcirudite, turbidite-generated calcisiltite and micritic limestone, etc. Storm-generated sedimentary structures include different scour or truncation structures (e. g., flate, wave-like, complex and irregular, etc. );hummocky cross-stratification (which can be clasificlassified into two types; simple and complex); swaley cross-stration, swaley cross-stration,and thin graded bed. Moreover,the sectional texture of the newly recognized storm-deposits can be classified into 9 types. Most of them are incomplete,and some of them belong to complex ones,which mean the existence of episodical storm activity. The sedimentary environment of tempestites,we think,includes three types:subtidal zone in open shelf, plateform edge gentle ramp,and subtidal zone in confied plateform.
1993, 11(2): 105-112.
Abstract:
Sea area around Liaohe Estuary refer the region between Liaohe Estuary to the east and Xiaolinghe Estuary to the west,which's water depth is defined as 10m shallower. Drainages where enter into the sea are liaohe.Shuangtaihe, Dalinghe and Xiaolinghe rivers, characterized by 9.14×109m3/a of total water discharge and 4. 892×107t/a of sediment input. Broad tidal flats and submerged deltas were formed attributed to the large capicity of sediment input. Based on the datd obtained from the seacoast survey in 1983 and the comprehensive investigation of Liaohe Esturay in 1988,the following two aspects are discussed in the present paper. 1. Sedimentary features and grain sige parameters are shown by figures and tables that concerning the sedimental units of different water dinmics in the the sea area around Liaohe estuary, such as tidal flat complexes, submarine delttas, barriers, tidal inlets and tidal furrows. Wheras the tidal flat complexes were mainly effected by tidal currents. From the lower,to middle and higher tidal flat as well as to the submarine delta,the grain size of sediments decrease from silt to muddy silt and sorting become worse,the oblique beddings gradally replaced by horizontal ones,meanwhile organism disturbance strenghened. The formation of the barriers were mainly controlled by wave and tide as well as topograph. The sediments, which's grain size decreasing from outer barrier (coarse sand) to inner barrier (sandy silt, silt),are structured by beddings and small-scaled cross-beddings,featured by ripples on the surface and weak organism disturbance. Tidal inlets distribute as finger gullys on both sides of barries and their V-shaped cross-sections deeper than 5m,that filled with fine sands structured by cross-beddings, shell buildings can be found but no organism disturbance. Tidal burrowes distributed mainly on tidal flats as snaking gullys of U-shaped cross-section obvious mud and sand interlayered structures were formed attributed to the swing of the burrows. 2. Prospecting of tidal flat dynamics. The estimate of tidal flats progression is based on the equilibrium equation of sediment discharge and the sedimentation rates that determined by 210Pb. Take the present height of high and low tidal lines as basis,the duration time needed for reaching the mean height of the supreme is estimated too. For the tidal flats west to Shangtaihe estuary, the duration time and progression rate estimated by the above two methods are 62 and 72 years, 127m/a and 114 m/a respectively,and for those locate between Shangtaihe estuary and Liaohe estuary,the datd are 182 and 193 years,22m/a and 20m/a respectively.
Sea area around Liaohe Estuary refer the region between Liaohe Estuary to the east and Xiaolinghe Estuary to the west,which's water depth is defined as 10m shallower. Drainages where enter into the sea are liaohe.Shuangtaihe, Dalinghe and Xiaolinghe rivers, characterized by 9.14×109m3/a of total water discharge and 4. 892×107t/a of sediment input. Broad tidal flats and submerged deltas were formed attributed to the large capicity of sediment input. Based on the datd obtained from the seacoast survey in 1983 and the comprehensive investigation of Liaohe Esturay in 1988,the following two aspects are discussed in the present paper. 1. Sedimentary features and grain sige parameters are shown by figures and tables that concerning the sedimental units of different water dinmics in the the sea area around Liaohe estuary, such as tidal flat complexes, submarine delttas, barriers, tidal inlets and tidal furrows. Wheras the tidal flat complexes were mainly effected by tidal currents. From the lower,to middle and higher tidal flat as well as to the submarine delta,the grain size of sediments decrease from silt to muddy silt and sorting become worse,the oblique beddings gradally replaced by horizontal ones,meanwhile organism disturbance strenghened. The formation of the barriers were mainly controlled by wave and tide as well as topograph. The sediments, which's grain size decreasing from outer barrier (coarse sand) to inner barrier (sandy silt, silt),are structured by beddings and small-scaled cross-beddings,featured by ripples on the surface and weak organism disturbance. Tidal inlets distribute as finger gullys on both sides of barries and their V-shaped cross-sections deeper than 5m,that filled with fine sands structured by cross-beddings, shell buildings can be found but no organism disturbance. Tidal burrowes distributed mainly on tidal flats as snaking gullys of U-shaped cross-section obvious mud and sand interlayered structures were formed attributed to the swing of the burrows. 2. Prospecting of tidal flat dynamics. The estimate of tidal flats progression is based on the equilibrium equation of sediment discharge and the sedimentation rates that determined by 210Pb. Take the present height of high and low tidal lines as basis,the duration time needed for reaching the mean height of the supreme is estimated too. For the tidal flats west to Shangtaihe estuary, the duration time and progression rate estimated by the above two methods are 62 and 72 years, 127m/a and 114 m/a respectively,and for those locate between Shangtaihe estuary and Liaohe estuary,the datd are 182 and 193 years,22m/a and 20m/a respectively.
1993, 11(2): 118-123.
Abstract:
Modern mud of Dachaidan Lake and the mudstone of the Pliocene sampled from Well Nan-4 both were formed under drought climate. GC and GC-MS had been used to the saturated fraction of hydrocarbons of the samples and the results revealed that;the distribution of bio-markers of the two types sediments are very similar,revealed the similarity of sedimentary environment of them. From the view point of the distribution of saturated hydrocarbon, the maturity parameter of the samples are all very low,OEP and CPI value of mudstone are 4. 5 and 4. 4 respectively,and those of rock samples are 0. 924 and 1. 743 correspondingly. Preference of phytane over pretane are seen in the two sorts of samples also,whereas the Pr/Ph value of mudstone is 0.66 and that of rock profile is 0. 309,and both of them shows the predominance of C22. Diterpanes are simple and featured by m/e 123,predominanted by drrimane and homodr-rimane while long chain triterpanes that characterized by m/e 191 are abundant in the two samples and show a comparatively complete homologues that predominated by C21 and C23. Moreover,except for the triterpane of 13β14α type that normally occurrenced, there is an iso-13β14β triterpane after each peak,the content of which is about half of its hemologue of the same carbon number. Gamacerane that occurrences ordinarilly with high concentration is low in the two samples and the value of Gamacerame over CH+M30 ratio of mud and rock is 0. 203 and 0. 113 respectively. To the distribution of stroid,regular C29 sterane predominance are shown in the samples, this phenomenon is probaly resulted from the halophilic bactera and algea such as diatom under the saline lake facies,rather than the input of higher plants. The innomal variation of the maturitional parameters of sterane and terpane,such as that of mordern mud can even higher than rock,is related with two raesons.i. e., the difference of existing form of bio-markers in the samples;the contents and sorts of mineral matrix can also effect the maturational evolution process of organic matters,for instance,carbonate minerals can postpone the maturational evolution process.
Modern mud of Dachaidan Lake and the mudstone of the Pliocene sampled from Well Nan-4 both were formed under drought climate. GC and GC-MS had been used to the saturated fraction of hydrocarbons of the samples and the results revealed that;the distribution of bio-markers of the two types sediments are very similar,revealed the similarity of sedimentary environment of them. From the view point of the distribution of saturated hydrocarbon, the maturity parameter of the samples are all very low,OEP and CPI value of mudstone are 4. 5 and 4. 4 respectively,and those of rock samples are 0. 924 and 1. 743 correspondingly. Preference of phytane over pretane are seen in the two sorts of samples also,whereas the Pr/Ph value of mudstone is 0.66 and that of rock profile is 0. 309,and both of them shows the predominance of C22. Diterpanes are simple and featured by m/e 123,predominanted by drrimane and homodr-rimane while long chain triterpanes that characterized by m/e 191 are abundant in the two samples and show a comparatively complete homologues that predominated by C21 and C23. Moreover,except for the triterpane of 13β14α type that normally occurrenced, there is an iso-13β14β triterpane after each peak,the content of which is about half of its hemologue of the same carbon number. Gamacerane that occurrences ordinarilly with high concentration is low in the two samples and the value of Gamacerame over CH+M30 ratio of mud and rock is 0. 203 and 0. 113 respectively. To the distribution of stroid,regular C29 sterane predominance are shown in the samples, this phenomenon is probaly resulted from the halophilic bactera and algea such as diatom under the saline lake facies,rather than the input of higher plants. The innomal variation of the maturitional parameters of sterane and terpane,such as that of mordern mud can even higher than rock,is related with two raesons.i. e., the difference of existing form of bio-markers in the samples;the contents and sorts of mineral matrix can also effect the maturational evolution process of organic matters,for instance,carbonate minerals can postpone the maturational evolution process.
1993, 11(2): 133-140.
Abstract:
The black shales and dolostones intercalcated with them had been researched petrologi-cally and geochemically of middle Permian Lucaogou Formation,eastern part of southern. Margin of Junggar Basin. The great similarity between them has been found. Based on the above study and the discussion of carbon and oxygen stable isotopie composition of the dolo-stone,it is concluded that: 1). Special thermodynamical and kinetic condition favorable for the formation of the environment where black shales were formed and organic evolution in then including: A): CO32-,B):Low So42-,C):High Mg2+/Ca2+ ratio and D) :organic-rich alkline and reducing environment. 2) The dolostones may had been precipitated in the evolution process of the environment where black shales were formed,and organic matter,accompaning with the increase of salinity and CO32- content of bottom water.
The black shales and dolostones intercalcated with them had been researched petrologi-cally and geochemically of middle Permian Lucaogou Formation,eastern part of southern. Margin of Junggar Basin. The great similarity between them has been found. Based on the above study and the discussion of carbon and oxygen stable isotopie composition of the dolo-stone,it is concluded that: 1). Special thermodynamical and kinetic condition favorable for the formation of the environment where black shales were formed and organic evolution in then including: A): CO32-,B):Low So42-,C):High Mg2+/Ca2+ ratio and D) :organic-rich alkline and reducing environment. 2) The dolostones may had been precipitated in the evolution process of the environment where black shales were formed,and organic matter,accompaning with the increase of salinity and CO32- content of bottom water.
