1998 Vol. 16, No. 3
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Display Method:
1998, 16(3): 1-5.
Abstract:
The trace fossil Tisoa Serres was unreported previously from China. Over 70 Tisoa specimens have been found in Middle Jurassic Sew a Formation in Qiang tang area, no rthern Tibet. The outcrop is located at 89°54′E in longitude and 32°07′N in latitude. Tisoa specimens consist typically of two closely parallel, cylindrical tubes that constitute the long axis of conical or cylindrical calcareous concretions. Individual tubes 2′～7mm in diameter and lying 1～4 mm apart, a rerarely branched. Calcareous concretions which covered the tubes are 10～25 mm. in di-ameter. One well-preserved specimen shows that Tisoa actually consists of a single U-shaped tube which linked at the basal part, and that the two parallel tubes constituting most specimens are actually the up-per part of a single U-shaped tube. An irregular layer of pyrite in a thin layer of microcrystalline calcite is commonly present along most tubes. The tubes are of ten filled with micrite and sparite, some with iron sulfide, mica and argillaceous as well as arenaceous quartz. Tisoa represents a dwelling burrow probably made by an arthropod. By analysis of sedimentology and palaeoecology, the upper part of Middle Jurassic Sewa Formation which bearing trace fossil Tisoa represents shallow water condition.
The trace fossil Tisoa Serres was unreported previously from China. Over 70 Tisoa specimens have been found in Middle Jurassic Sew a Formation in Qiang tang area, no rthern Tibet. The outcrop is located at 89°54′E in longitude and 32°07′N in latitude. Tisoa specimens consist typically of two closely parallel, cylindrical tubes that constitute the long axis of conical or cylindrical calcareous concretions. Individual tubes 2′～7mm in diameter and lying 1～4 mm apart, a rerarely branched. Calcareous concretions which covered the tubes are 10～25 mm. in di-ameter. One well-preserved specimen shows that Tisoa actually consists of a single U-shaped tube which linked at the basal part, and that the two parallel tubes constituting most specimens are actually the up-per part of a single U-shaped tube. An irregular layer of pyrite in a thin layer of microcrystalline calcite is commonly present along most tubes. The tubes are of ten filled with micrite and sparite, some with iron sulfide, mica and argillaceous as well as arenaceous quartz. Tisoa represents a dwelling burrow probably made by an arthropod. By analysis of sedimentology and palaeoecology, the upper part of Middle Jurassic Sewa Formation which bearing trace fossil Tisoa represents shallow water condition.
1998, 16(3): 14-19.
Abstract:
Time-series sediment trap experiments covering the periods from September 1987 to October 1988 in the northern South China Sea and from December 1990 to April 1995 in the central South China Sea were carried out in order to measure the fluxes and constituents of particulate matter. Particle fluxes in northern and central South China Sea are about 90mg·m-2·day-1 and 85～90mg·m-2·day-1, re-spectively. Significant increases of the fluxes are observed during the periods of northeast and southwest monsoons. The main components of the particulate matter in the central South China Sea are carbonate (25.3%～61.0%), opal (15.3%～49.9%), organic matter (1.6%～12.5%) and lithogenic matter (12.2%～42.0%). Interestingly, in the northern South China Sea, opal only com prised 0.4% ～2.5% of the total fluxes while lithogenic matter occupied 33.0～67.0%. Carbonate, opal and organic matter are mainly derived from recent calcareo us and siliceo us plankton, and as for lithogenic matter, besides fluvial sediment discharge, aeolian transportation may also play an important role to increase lithog enic flux. The decreases of total flux as well as carbo nate, opal, organic matter fluxes with depth are mainly caused by dissolution of carbo nate and opal in water column. Organic matter loss with depth is attributed to dissolution of plankton shells which contain abundant organic matter as well as their biogeochemical degradation processes in water column. The much higher fluxes recorded in deep traps than in shallow traps in some sampling intervals suggest that advect of particulate matter in the water column is very frequent. In comparison with sediments in the deep basin of the South China Sea, it shows that most of the marine biogenic constituents such as carbonate, opal and organic matter dissolved before their reach-ing at the bottom. So it is obviously that the decreases of organic matter in sediments are not only result of decomposition of these organic matter, but also caused by dissolution of carbonate and opal. Lithogenic accumulation rates in sediment are much higher than its fluxes in the deep water column sug-gest that about 30%～60% of the deep basin sediments are contributed by near bottom sediment trans-portation mechanisms such as turbidites, especially in the northern part of the deep South China Sea.
Time-series sediment trap experiments covering the periods from September 1987 to October 1988 in the northern South China Sea and from December 1990 to April 1995 in the central South China Sea were carried out in order to measure the fluxes and constituents of particulate matter. Particle fluxes in northern and central South China Sea are about 90mg·m-2·day-1 and 85～90mg·m-2·day-1, re-spectively. Significant increases of the fluxes are observed during the periods of northeast and southwest monsoons. The main components of the particulate matter in the central South China Sea are carbonate (25.3%～61.0%), opal (15.3%～49.9%), organic matter (1.6%～12.5%) and lithogenic matter (12.2%～42.0%). Interestingly, in the northern South China Sea, opal only com prised 0.4% ～2.5% of the total fluxes while lithogenic matter occupied 33.0～67.0%. Carbonate, opal and organic matter are mainly derived from recent calcareo us and siliceo us plankton, and as for lithogenic matter, besides fluvial sediment discharge, aeolian transportation may also play an important role to increase lithog enic flux. The decreases of total flux as well as carbo nate, opal, organic matter fluxes with depth are mainly caused by dissolution of carbo nate and opal in water column. Organic matter loss with depth is attributed to dissolution of plankton shells which contain abundant organic matter as well as their biogeochemical degradation processes in water column. The much higher fluxes recorded in deep traps than in shallow traps in some sampling intervals suggest that advect of particulate matter in the water column is very frequent. In comparison with sediments in the deep basin of the South China Sea, it shows that most of the marine biogenic constituents such as carbonate, opal and organic matter dissolved before their reach-ing at the bottom. So it is obviously that the decreases of organic matter in sediments are not only result of decomposition of these organic matter, but also caused by dissolution of carbonate and opal. Lithogenic accumulation rates in sediment are much higher than its fluxes in the deep water column sug-gest that about 30%～60% of the deep basin sediments are contributed by near bottom sediment trans-portation mechanisms such as turbidites, especially in the northern part of the deep South China Sea.
1998, 16(3): 25-30,37.
Abstract:
The paper mainly discusses the geochemical characteristics and types of the typical coal-typeg as pools of the Upper Paleo zoic, the tectonic environments and exploration prospects in China. North China coal-accumulating area is the most favourable area. Two kinds of tectonic environments and four types of coal-type gas pools have been concluded, self -generated self-reservoired type of ancient burial hill( Suqiao type) and paleogenerated neoreservoired type (Wenliu type ) in tectonically active rift region, combination type ( Ordos type) and self-generated self-reservoired type in tectonically stable region of craton. The four types above should be the major types for exploring coal-type gas in the areas. The coalbed gases are also briefly discussed in the two kinds of tectonic environments.
The paper mainly discusses the geochemical characteristics and types of the typical coal-typeg as pools of the Upper Paleo zoic, the tectonic environments and exploration prospects in China. North China coal-accumulating area is the most favourable area. Two kinds of tectonic environments and four types of coal-type gas pools have been concluded, self -generated self-reservoired type of ancient burial hill( Suqiao type) and paleogenerated neoreservoired type (Wenliu type ) in tectonically active rift region, combination type ( Ordos type) and self-generated self-reservoired type in tectonically stable region of craton. The four types above should be the major types for exploring coal-type gas in the areas. The coalbed gases are also briefly discussed in the two kinds of tectonic environments.
1998, 16(3): 44-51.
Abstract:
Based on the synthetic study of field outcrops and drilling section data, and using new stratigraphic division program, this paper proposes that the paleogeographic pattern of Ordos area was the compound sedimentary system of epiric sea carbonate platform-clastic barrier island-shallow water delta. Influ-enced by aeral tectonic backg round, the late-Paleozoic basin filling included four stages from the filling of the rift bay basin coexisting with shallow-rifting epiric sea, the filling of epiric sea, the filling of par-alic inland sea to the filling of inland lake depression. The evolution of areal paleogeographic pattern was from the compound system deposition of epiric sea carbonate platform-clastic barrier island-shallow wa-ter delta to delta-fluvial system deposition and at last the fluvial-lake system deposition. The develop-ment of sandy reservoir body was controlled by sedimentary envoronments. The sand bodies mainly dis-tribute in the central and northern parts of Ordos area, and mainly the fluvial-delta sand bodies.
Based on the synthetic study of field outcrops and drilling section data, and using new stratigraphic division program, this paper proposes that the paleogeographic pattern of Ordos area was the compound sedimentary system of epiric sea carbonate platform-clastic barrier island-shallow water delta. Influ-enced by aeral tectonic backg round, the late-Paleozoic basin filling included four stages from the filling of the rift bay basin coexisting with shallow-rifting epiric sea, the filling of epiric sea, the filling of par-alic inland sea to the filling of inland lake depression. The evolution of areal paleogeographic pattern was from the compound system deposition of epiric sea carbonate platform-clastic barrier island-shallow wa-ter delta to delta-fluvial system deposition and at last the fluvial-lake system deposition. The develop-ment of sandy reservoir body was controlled by sedimentary envoronments. The sand bodies mainly dis-tribute in the central and northern parts of Ordos area, and mainly the fluvial-delta sand bodies.
1998, 16(3): 58-65.
Abstract:
The northeastern Guizhou and the eastern Yunnan are located on the Upper Yangtze Platform. The present study on seven sections in the region has established nine 3rd order sequences from the Llan-dovery (439 Ma) to the Pridoli (409 Ma), with an average duration of 3.3 Ma. The nine 3rd order se-quences have constituted two 2nd order sequences. The first sequence consists of Longmaxi Fm. and Xi-angshuyuan Fm., extending chronologically from Rhuddanian to Early Telychian, with a distinct type-Ⅰ sequence boundary at the bottom. Basinward, the bottom boundary shows as continuity at Tongzi belong-ing to Gui zhou, while landward to the central Gui zhou old land it becomes an overlap disconformity. Two 3rd order sequences have been recognized in the Lei jiatun Fm. The Majiaochong Fm. (TST) and Rongxi Fm. (HST) make up the fourth sequence. The fifth and the sixth sequences are represented by the Xiushan Fm. and Huixingshao Fm. respectively. The sequence boundary between them, however, is notconcurring with the boundary of the formations. The second to fifth sequences are within the Telychian, and the sixth sequence is early Sheinwoodian in age. The seven to the ninth sequences are represented by the Guandi Fm. the Miaogao Fm. and the Yulongsi Fm. extending chronologically from the Homerian stage belonging to Wenlock to Pridoli. The first sequence and the seventh sequence among these nine se-quences are type-Ⅰ sequences, the others type-Ⅱ sequences. The above mentioned nine sequences are basically controlled by eustatic changes. Owing to the ef-fects of the Caledonian movement, the steady uplifting of the Yangtze Platform during Silurian had ap-parent lyexerted an influence on the formation and the characters of the sequences. From the bottom up-ward, in each of the 3rd order sequences, the ratio of siliciclastics increases continuously with a corre-sponding increase in the thickness of sequence. In all of the third-order sequences, TST and HST are well displayed, but without LST and SMST.
The northeastern Guizhou and the eastern Yunnan are located on the Upper Yangtze Platform. The present study on seven sections in the region has established nine 3rd order sequences from the Llan-dovery (439 Ma) to the Pridoli (409 Ma), with an average duration of 3.3 Ma. The nine 3rd order se-quences have constituted two 2nd order sequences. The first sequence consists of Longmaxi Fm. and Xi-angshuyuan Fm., extending chronologically from Rhuddanian to Early Telychian, with a distinct type-Ⅰ sequence boundary at the bottom. Basinward, the bottom boundary shows as continuity at Tongzi belong-ing to Gui zhou, while landward to the central Gui zhou old land it becomes an overlap disconformity. Two 3rd order sequences have been recognized in the Lei jiatun Fm. The Majiaochong Fm. (TST) and Rongxi Fm. (HST) make up the fourth sequence. The fifth and the sixth sequences are represented by the Xiushan Fm. and Huixingshao Fm. respectively. The sequence boundary between them, however, is notconcurring with the boundary of the formations. The second to fifth sequences are within the Telychian, and the sixth sequence is early Sheinwoodian in age. The seven to the ninth sequences are represented by the Guandi Fm. the Miaogao Fm. and the Yulongsi Fm. extending chronologically from the Homerian stage belonging to Wenlock to Pridoli. The first sequence and the seventh sequence among these nine se-quences are type-Ⅰ sequences, the others type-Ⅱ sequences. The above mentioned nine sequences are basically controlled by eustatic changes. Owing to the ef-fects of the Caledonian movement, the steady uplifting of the Yangtze Platform during Silurian had ap-parent lyexerted an influence on the formation and the characters of the sequences. From the bottom up-ward, in each of the 3rd order sequences, the ratio of siliciclastics increases continuously with a corre-sponding increase in the thickness of sequence. In all of the third-order sequences, TST and HST are well displayed, but without LST and SMST.
1998, 16(3): 72-74,79.
Abstract:
Cap rock is the necessary condition of the gas reservoir preservation, and hydrocarbon concentration confining is one important confining mechanism. The geological and mathematical model of natural gas diffusion has been set up system atically. The natural gas diffusion is mainly through the water, so the solubility of the natural gas in water can be regarded as theinitial gas concentration in the cap rock. The solubility of the natural gas can be calculate by the determination of the temperature, pressure and salini-ty of the stratum. The source rock is usually of relatively larger solubility, so it is the best cap rock.
Cap rock is the necessary condition of the gas reservoir preservation, and hydrocarbon concentration confining is one important confining mechanism. The geological and mathematical model of natural gas diffusion has been set up system atically. The natural gas diffusion is mainly through the water, so the solubility of the natural gas in water can be regarded as theinitial gas concentration in the cap rock. The solubility of the natural gas can be calculate by the determination of the temperature, pressure and salini-ty of the stratum. The source rock is usually of relatively larger solubility, so it is the best cap rock.
1998, 16(3): 80-84.
Abstract:
Principles of oil and gas formation fluid dynamic system analysis are briefly described. Fluid dynamic systems are classi fied into four types, including gravity-driven flow, compaction-driven flow, fluid com-partment and no-flowones. Oil and gas pools formation and occurrence for each type are analyzed, along with case studies. It is emphasized that for different types of fluid dynamic systems, the mechanism of oil and gas pools'formation is different, and then, studies on these different types of fluid dynamic systems should have different focus. Finally, it is indicated that the studies on gravity-driven flow and fluid com-partment system types are respectively important for petroleum exploration in the marine basins of southern China and in the deep parts of the basins relatively maturely explored in China.
Principles of oil and gas formation fluid dynamic system analysis are briefly described. Fluid dynamic systems are classi fied into four types, including gravity-driven flow, compaction-driven flow, fluid com-partment and no-flowones. Oil and gas pools formation and occurrence for each type are analyzed, along with case studies. It is emphasized that for different types of fluid dynamic systems, the mechanism of oil and gas pools'formation is different, and then, studies on these different types of fluid dynamic systems should have different focus. Finally, it is indicated that the studies on gravity-driven flow and fluid com-partment system types are respectively important for petroleum exploration in the marine basins of southern China and in the deep parts of the basins relatively maturely explored in China.
1998, 16(3): 92-96.
Abstract:
This paper reviewed some of the important results of the core rock section, cathodo luminescence and X-ray diffraction. The diagenesis in the Rong-37 block of the Lower Tertiary reservoir of are com-paction, cementation, dissolution and replacement. The reservoir pores are destroied by compaction and cementation, and increased by dissolution but they affect reservoir pores in different depth. Secondary pore formation are connected with the sedimentary facies, sandstone origination and lithoclast, etc. The reservoir of Low-Tertiary sandstone′s primary pores decreased by compaction and cementation at eogeneticst age, The depth is from 1000 m to 1600 m, and the primary pore will be lost 5% to 10% . The sandstone porosity were increased by dissolution at late eogeneticst age to early epigeneticst age in depth of 1600 m to 2600 m, but the sandstone porosity are nearly zero at late epigenesis by authigenic mineral. Point bar with the high primary pores compositional and textural maturity would keep a lot of pores after diagenesis. But lands and palus sandstone with the low compositional and textural maturity would loss the chief primary pore by diagensis. Secondary pores is important in the reservoir.
This paper reviewed some of the important results of the core rock section, cathodo luminescence and X-ray diffraction. The diagenesis in the Rong-37 block of the Lower Tertiary reservoir of are com-paction, cementation, dissolution and replacement. The reservoir pores are destroied by compaction and cementation, and increased by dissolution but they affect reservoir pores in different depth. Secondary pore formation are connected with the sedimentary facies, sandstone origination and lithoclast, etc. The reservoir of Low-Tertiary sandstone′s primary pores decreased by compaction and cementation at eogeneticst age, The depth is from 1000 m to 1600 m, and the primary pore will be lost 5% to 10% . The sandstone porosity were increased by dissolution at late eogeneticst age to early epigeneticst age in depth of 1600 m to 2600 m, but the sandstone porosity are nearly zero at late epigenesis by authigenic mineral. Point bar with the high primary pores compositional and textural maturity would keep a lot of pores after diagenesis. But lands and palus sandstone with the low compositional and textural maturity would loss the chief primary pore by diagensis. Secondary pores is important in the reservoir.
1998, 16(3): 102-108.
Abstract:
In Biyang fault-depressed lacustrine basin, the tectonic descent of basement presented antihinge-typed subsidence. Due to the joint effect of lacustrine level change and basement structural subsidence, accommodation change in the steep slope zone of Biyang fault-depressed lacustrine basin only have three possibilities: a. decreasing at southern and northern rim zone but increasing in central zone; b. beingin-variant at southern rim zone but increasing in central zone and at northern rim zone; c. all increasing at southern and northern rim zone and in central zone. In the light of the three cases, the sedimentation-re-sponsed charteristics to the accommodation variation law at different structural positions of the steep slope zone in fault-depressed lacustrine basin have been respectively analy sed at different recharge rate of sediment-source. In this paper, accommodation mechanics to select reference well has been discussed; and by using well B207 as reference well, the terrigenous sequences of the upper member of Eh3 have been di-vided; and by using Fischer diagram, the realized accommodation change curve of the terrigenous se-quences is acquired.
In Biyang fault-depressed lacustrine basin, the tectonic descent of basement presented antihinge-typed subsidence. Due to the joint effect of lacustrine level change and basement structural subsidence, accommodation change in the steep slope zone of Biyang fault-depressed lacustrine basin only have three possibilities: a. decreasing at southern and northern rim zone but increasing in central zone; b. beingin-variant at southern rim zone but increasing in central zone and at northern rim zone; c. all increasing at southern and northern rim zone and in central zone. In the light of the three cases, the sedimentation-re-sponsed charteristics to the accommodation variation law at different structural positions of the steep slope zone in fault-depressed lacustrine basin have been respectively analy sed at different recharge rate of sediment-source. In this paper, accommodation mechanics to select reference well has been discussed; and by using well B207 as reference well, the terrigenous sequences of the upper member of Eh3 have been di-vided; and by using Fischer diagram, the realized accommodation change curve of the terrigenous se-quences is acquired.
1998, 16(3): 115-118.
Abstract:
Palynofacies is a particular sedimentary organic matter association that can reflect sedimentation and lithogenesis environment. The palynofacies of carbonate rocks of Tertiary Hetaoyuan formation have been studied in detail. Based on the identification and statistics of the organic matter, The carbonate rock series may be divided into five palynofacies zones. Using palynofacies combining with geochemicalindices of organic maturation, the oil potential of these strata has been evaluated.
Palynofacies is a particular sedimentary organic matter association that can reflect sedimentation and lithogenesis environment. The palynofacies of carbonate rocks of Tertiary Hetaoyuan formation have been studied in detail. Based on the identification and statistics of the organic matter, The carbonate rock series may be divided into five palynofacies zones. Using palynofacies combining with geochemicalindices of organic maturation, the oil potential of these strata has been evaluated.
1998, 16(3): 124-131.
Abstract:
The uplifting of whole Yangtze platform occured by the end of Llandovery (Telychian), execpt sev-eral bays around the margin of the platform. The Ningqiang Formation consists of more than 2000 m shales and limestones with faunas form upper griestoniensis Zone to spiral is-grandis Zone. The limestones within this unit may be subdivided into 8 stages according to their origination in ascending order. Reef complexes developed at differentsites on limited carbonate platforms. Reefs, biostromes and lime-mud-mounds cropped out in the different subfacies of the reef complexes. The important reef complexes'building organisms include corals, bryozoans, pelmatozoans, algea and stromatoporoids, and the at tach-ing- reefal organisms are brachiopoda, nutiloidea, trilobite, etc.. The features of the reefal organisms are changable in temporal and spatial distribution. Analysis of typical reef complexes indicate that they are variable in association, shape and growth process. The termination of all limited platforms and reef com-plexes depends on the covering of mudstones.
The uplifting of whole Yangtze platform occured by the end of Llandovery (Telychian), execpt sev-eral bays around the margin of the platform. The Ningqiang Formation consists of more than 2000 m shales and limestones with faunas form upper griestoniensis Zone to spiral is-grandis Zone. The limestones within this unit may be subdivided into 8 stages according to their origination in ascending order. Reef complexes developed at differentsites on limited carbonate platforms. Reefs, biostromes and lime-mud-mounds cropped out in the different subfacies of the reef complexes. The important reef complexes'building organisms include corals, bryozoans, pelmatozoans, algea and stromatoporoids, and the at tach-ing- reefal organisms are brachiopoda, nutiloidea, trilobite, etc.. The features of the reefal organisms are changable in temporal and spatial distribution. Analysis of typical reef complexes indicate that they are variable in association, shape and growth process. The termination of all limited platforms and reef com-plexes depends on the covering of mudstones.
1998, 16(3): 137-140.
Abstract:
Sedimentary environments of Tertiary saline lake and clastic depositional system in Luntai fracture-uplift of Tabei uplift, Tarim basin are studied in detail. In the study area, the depositional patterns were dominated by a rid and semi-arid climate. Two suits of reservoir and seal, respectively Suweiyi Fm. of Pa-leogene and Jidik Fm. of Neogene developed in such conditions, so that their sedimentary and reservoir characteristics had close correlation with the saline deposits, especially the widely distributed anhydrite in this area. Anhydrite was classified into ten sorts according to its occurrence. The sedimentary charac-teristics are summarized in this paper based on the relationship between different structures in anhydrite and environments as the breakthrough point, simultaneously combined with element geochemistry. Five kinds of sedimentary facies were recognized as alluvial fan, sandsheet , ephemeral saline lake, perennial saline lake, ephemeral river and flooded plain, among which the key reservoir sandsheet was subdivided into common, finesorted and gypsificated ones. In conclusion, the author summarized the depositional model of Suweiyi Fm.
Sedimentary environments of Tertiary saline lake and clastic depositional system in Luntai fracture-uplift of Tabei uplift, Tarim basin are studied in detail. In the study area, the depositional patterns were dominated by a rid and semi-arid climate. Two suits of reservoir and seal, respectively Suweiyi Fm. of Pa-leogene and Jidik Fm. of Neogene developed in such conditions, so that their sedimentary and reservoir characteristics had close correlation with the saline deposits, especially the widely distributed anhydrite in this area. Anhydrite was classified into ten sorts according to its occurrence. The sedimentary charac-teristics are summarized in this paper based on the relationship between different structures in anhydrite and environments as the breakthrough point, simultaneously combined with element geochemistry. Five kinds of sedimentary facies were recognized as alluvial fan, sandsheet , ephemeral saline lake, perennial saline lake, ephemeral river and flooded plain, among which the key reservoir sandsheet was subdivided into common, finesorted and gypsificated ones. In conclusion, the author summarized the depositional model of Suweiyi Fm.
1998, 16(3): 147-152.
Abstract:
On the basis of detailed investigation of large quantity of geology sections, the geological event srecorded in the continental Jurassic strata in Northwest China have been systematically studied in this paper. The index bed of the subdivsion and correlation of continental Jurassic are established according to the distribution of coal-bearing rocks, lithologic and sedimentary characteristics and sporo-pollen flora assemblage characteristics, as well as bivalve fossil association features. The forming mechanism of bioevents and cyclic sedimentary bed is due to the change of palaeoclimate and palaeoenvironment effect during that period. The existance of one temperature-rising event is extraordinarily evident during late middle to late Jurassic.
On the basis of detailed investigation of large quantity of geology sections, the geological event srecorded in the continental Jurassic strata in Northwest China have been systematically studied in this paper. The index bed of the subdivsion and correlation of continental Jurassic are established according to the distribution of coal-bearing rocks, lithologic and sedimentary characteristics and sporo-pollen flora assemblage characteristics, as well as bivalve fossil association features. The forming mechanism of bioevents and cyclic sedimentary bed is due to the change of palaeoclimate and palaeoenvironment effect during that period. The existance of one temperature-rising event is extraordinarily evident during late middle to late Jurassic.
1998, 16(3): 156-160.
Abstract:
When sedimentary environment of corresponding rocks are determined by well logging data, there is of ten a puzzle about their environmental sense because all log-curves are not typical and full of geological information concerning sedimentary envionments. The authors consider that the essence of the inadequate information is the basic mevning of the term "grey" in grey system theory, and propose that an analysis method of cluster of grey comprehensive relationship be applied to deduce sedimentary environments. This method is applied to discriminate S2 sandstone environment in Shanxi Group, situated the Liao City explorating district of Yanggu-Ciping coalfield in Shandong province, with a better result gotten. At the same time, grey comprehensive relationship degree regarded as cluster index has been discussed in this paper
When sedimentary environment of corresponding rocks are determined by well logging data, there is of ten a puzzle about their environmental sense because all log-curves are not typical and full of geological information concerning sedimentary envionments. The authors consider that the essence of the inadequate information is the basic mevning of the term "grey" in grey system theory, and propose that an analysis method of cluster of grey comprehensive relationship be applied to deduce sedimentary environments. This method is applied to discriminate S2 sandstone environment in Shanxi Group, situated the Liao City explorating district of Yanggu-Ciping coalfield in Shandong province, with a better result gotten. At the same time, grey comprehensive relationship degree regarded as cluster index has been discussed in this paper
1998, 16(3): 6-13.
Abstract:
The Early Cretaceous Giabulin Formation, which is distributed along the north margin of the Yarlung Zang bo ophiolite suite, is easy to distinguish in the field. It is characterized by a sequence of ter-rigenous clasticrocks, principally mottled sandstones and conglomerates. Seven types of conglomerate, seven types of sandstone, three types of shale, and one limestone may be classified according to formation and their lithofacies characteristics. They comprise foursedimentary subfacies, from bottom to top: braid-ed river subfacies, fan-delta plain subfacies, fandelt a front subfacies, and profan-delt a subfacies. This progressio n makes up a retrog radational sequence taking together the global Cretaceous transgress con-dition. Paleosalinity of the Giabulin Formation was 12.0‰-20.0‰, and its paleoenvironments were inter-mediate between semi-brackish water and salt water. The sedimentary environments of the braided river of terrestrial facies and the fan-deltas of transitional facies can be concluded from the discussion above. Sediments of the Giabulin Formation were derived chiefly from recycled subduction complexes, and from dissected transitional island arcs. Those provenances were all distributed nearby to the north of the Yarlung Zang bo River. During deposition of the Giabulin Formation, the Tectonic settings was relatively passive in the early stage and active in the late stage.
The Early Cretaceous Giabulin Formation, which is distributed along the north margin of the Yarlung Zang bo ophiolite suite, is easy to distinguish in the field. It is characterized by a sequence of ter-rigenous clasticrocks, principally mottled sandstones and conglomerates. Seven types of conglomerate, seven types of sandstone, three types of shale, and one limestone may be classified according to formation and their lithofacies characteristics. They comprise foursedimentary subfacies, from bottom to top: braid-ed river subfacies, fan-delta plain subfacies, fandelt a front subfacies, and profan-delt a subfacies. This progressio n makes up a retrog radational sequence taking together the global Cretaceous transgress con-dition. Paleosalinity of the Giabulin Formation was 12.0‰-20.0‰, and its paleoenvironments were inter-mediate between semi-brackish water and salt water. The sedimentary environments of the braided river of terrestrial facies and the fan-deltas of transitional facies can be concluded from the discussion above. Sediments of the Giabulin Formation were derived chiefly from recycled subduction complexes, and from dissected transitional island arcs. Those provenances were all distributed nearby to the north of the Yarlung Zang bo River. During deposition of the Giabulin Formation, the Tectonic settings was relatively passive in the early stage and active in the late stage.
1998, 16(3): 20-24.
Abstract:
Halimeda, a genus of calcified green alga (Chlorophyta) of warm seas, is an important producer of carbonate sediment on coral reef areas of Nansha Islands, South China Sea. This study analysed the modern sedimentary characteristic of Halimeda in 52 clastic samples from the 4 geo morphic-sedimentary zones of 8 atolls. Among the 4 zones, i. e., reef front slope, reef flat, lagoon slope and logoon basin floor, Halimeda is the richest in lagoon basin floor and constitutes averagely 32.66% of the sediment, and it ranges from 16% to 75%. Observation under microscope indicates that in the sediment of lagoon basin floor there are most well preserved Halimeda segments and they are deposited in situ. In the sedi-ment of lagoon slope, Halimeda ranges from 8% to 16%, with an average of 9.22%. In reef flat, Hal-imeda composition is low, and ranges from 1%to8%, with an average of 6.06%. From the present da-ta, the contribution of Halimeda to the reef front carbonate producti on is small. The analysed results are consistent with the field investigation. Halimeda of Nansha Islands can grow on any zone of coral reef seither in sand or on solid substrata, the optimum habitat is well closed, big lagoon area, deep wa-ter, weak dynamic, sandy lagoon basin floor, where it develops well in erect. This paper concludes that the sedimentary characteristic of Halimeda on coral reefs of Nansha Islands are in line with its ecologic distributi on. Coral reef drilling research shows that the paleoenvironment setting of the Cenozoic is com-parable with that of recent Halimeda, so the characteristic can be the bases of analysing sedimentary fa-cies of ancient and modern coral reef sediment.
Halimeda, a genus of calcified green alga (Chlorophyta) of warm seas, is an important producer of carbonate sediment on coral reef areas of Nansha Islands, South China Sea. This study analysed the modern sedimentary characteristic of Halimeda in 52 clastic samples from the 4 geo morphic-sedimentary zones of 8 atolls. Among the 4 zones, i. e., reef front slope, reef flat, lagoon slope and logoon basin floor, Halimeda is the richest in lagoon basin floor and constitutes averagely 32.66% of the sediment, and it ranges from 16% to 75%. Observation under microscope indicates that in the sediment of lagoon basin floor there are most well preserved Halimeda segments and they are deposited in situ. In the sedi-ment of lagoon slope, Halimeda ranges from 8% to 16%, with an average of 9.22%. In reef flat, Hal-imeda composition is low, and ranges from 1%to8%, with an average of 6.06%. From the present da-ta, the contribution of Halimeda to the reef front carbonate producti on is small. The analysed results are consistent with the field investigation. Halimeda of Nansha Islands can grow on any zone of coral reef seither in sand or on solid substrata, the optimum habitat is well closed, big lagoon area, deep wa-ter, weak dynamic, sandy lagoon basin floor, where it develops well in erect. This paper concludes that the sedimentary characteristic of Halimeda on coral reefs of Nansha Islands are in line with its ecologic distributi on. Coral reef drilling research shows that the paleoenvironment setting of the Cenozoic is com-parable with that of recent Halimeda, so the characteristic can be the bases of analysing sedimentary fa-cies of ancient and modern coral reef sediment.
1998, 16(3): 38-43,51.
Abstract:
Channel bars are of ten observed in the Yellow River Delta and the Sheng LiⅠChannel Bar, which islocated to the morth of the Sheng Li Bridge, is a typical one among them. It is 1 200 meters long and may get 120 meters wide at its broadest part. The spindle-shaped Sheng Li Ⅰ Channel Bar is observed lenticular from its longitudinal or lateral side and cutted by water courses into several parts. The central part is higher than it sends and sides. After a more detailed study, several conclusions, are described as follows: ① there are two quite different kinds of sedimentary units in the channel bar. One of them is that described before, and the other one may consists of sand of muddy gravel dunes nad small water ditches;② channel bar is not the smallest unit in sedimentary facices division. It may be divided into the ordinary channel bar, watercourse, water ditch and eolian deposit facies in the Yellow River Delta, and every fa-cies has its o wn characteristics; ③ climbing beddings are widely developed in the channel bar; ④ sediments in the channel bar are mainly fine-grained sand of silt.
Channel bars are of ten observed in the Yellow River Delta and the Sheng LiⅠChannel Bar, which islocated to the morth of the Sheng Li Bridge, is a typical one among them. It is 1 200 meters long and may get 120 meters wide at its broadest part. The spindle-shaped Sheng Li Ⅰ Channel Bar is observed lenticular from its longitudinal or lateral side and cutted by water courses into several parts. The central part is higher than it sends and sides. After a more detailed study, several conclusions, are described as follows: ① there are two quite different kinds of sedimentary units in the channel bar. One of them is that described before, and the other one may consists of sand of muddy gravel dunes nad small water ditches;② channel bar is not the smallest unit in sedimentary facices division. It may be divided into the ordinary channel bar, watercourse, water ditch and eolian deposit facies in the Yellow River Delta, and every fa-cies has its o wn characteristics; ③ climbing beddings are widely developed in the channel bar; ④ sediments in the channel bar are mainly fine-grained sand of silt.
1998, 16(3): 52-57,65.
Abstract:
The carbon isotope shifts during Upper Permian in the South China drop gradually, and such phe-nomena may correspond to sea level change. There are two 3rd order cycle of carbon isotope stratigraphy of Late Permian. The early one is included in the lower and middle Wujiapingian Stage, while the lateone is included in the upper Wujiapingian and Changhsingian Stage. The carbon isotope curve in Changhsin-gian of South Chian can be distinguished three 4th order cycles from late 3rd order cycle. It is considered that the limestones with high values of δ13C was deposited during highstand of sea level, while those with low values of δ13C was deposited at lowerstand of sea level. Therefore, the 3rd or 4th-cycles of carbon isotope curve correspond to the 3rd or 4th order of sea level change, an interpretation supported by se-qence stratigraphy analysis in South China. Based on carbon isotopic curve, the sea level dropped from Wujiapingian to Changhsingian, that is perfectly conincident with the strongest regressions of the end of Permian in the world. It may indicates that the carbon isotopic curves record the global sea level changes, and may suggests that sediments of the changhsingian limestones deposited in transgression in-duced by regional tectonic subsidence in South China.
The carbon isotope shifts during Upper Permian in the South China drop gradually, and such phe-nomena may correspond to sea level change. There are two 3rd order cycle of carbon isotope stratigraphy of Late Permian. The early one is included in the lower and middle Wujiapingian Stage, while the lateone is included in the upper Wujiapingian and Changhsingian Stage. The carbon isotope curve in Changhsin-gian of South Chian can be distinguished three 4th order cycles from late 3rd order cycle. It is considered that the limestones with high values of δ13C was deposited during highstand of sea level, while those with low values of δ13C was deposited at lowerstand of sea level. Therefore, the 3rd or 4th-cycles of carbon isotope curve correspond to the 3rd or 4th order of sea level change, an interpretation supported by se-qence stratigraphy analysis in South China. Based on carbon isotopic curve, the sea level dropped from Wujiapingian to Changhsingian, that is perfectly conincident with the strongest regressions of the end of Permian in the world. It may indicates that the carbon isotopic curves record the global sea level changes, and may suggests that sediments of the changhsingian limestones deposited in transgression in-duced by regional tectonic subsidence in South China.
1998, 16(3): 66-71.
Abstract:
Seven types high frequency cyclic sequences which have been distinguished in the Upper Cretaceous-Eogene marine carbonate of the southwest Tarim Basin are mainly as follows: undertidal carbonate ramp, platform, platform margin earbonate cyclic sequences and tidal flat cyclic equences which are clas-tic rock mainly. In the region, different kinds of high frequency cyclic sequences represented sedimenta-ry sequences of platform, shore bank and alluvial depositional system which deposited in specific paleo-geographic setting. In the vertical sections, high frequency cyclic sequences stacked upward, in which changing of the kinds of cyclic sequence reflects the evolution of sedimentary enviroment and facies. As a result, in the study area, high frequency sea level change affected on the sedimentary facies changes from the lower unit to the upper unit of high frequency cyclic sequence, and controlled the deposit pro-cession of cyclic sequence. The long periodic sea level changes controlled the stacking patterns of high frequency cyclic sequences, and made the sedimentary environment change from shore bank→carbonate platform→shorebank→river. In a word, stacking of different hierarchy of sea level changes resulted in cyclic sequences of composite sealevel change in the Upper Cretaceous-Eogene of the southwest border, Tarim Basin.
Seven types high frequency cyclic sequences which have been distinguished in the Upper Cretaceous-Eogene marine carbonate of the southwest Tarim Basin are mainly as follows: undertidal carbonate ramp, platform, platform margin earbonate cyclic sequences and tidal flat cyclic equences which are clas-tic rock mainly. In the region, different kinds of high frequency cyclic sequences represented sedimenta-ry sequences of platform, shore bank and alluvial depositional system which deposited in specific paleo-geographic setting. In the vertical sections, high frequency cyclic sequences stacked upward, in which changing of the kinds of cyclic sequence reflects the evolution of sedimentary enviroment and facies. As a result, in the study area, high frequency sea level change affected on the sedimentary facies changes from the lower unit to the upper unit of high frequency cyclic sequence, and controlled the deposit pro-cession of cyclic sequence. The long periodic sea level changes controlled the stacking patterns of high frequency cyclic sequences, and made the sedimentary environment change from shore bank→carbonate platform→shorebank→river. In a word, stacking of different hierarchy of sea level changes resulted in cyclic sequences of composite sealevel change in the Upper Cretaceous-Eogene of the southwest border, Tarim Basin.
1998, 16(3): 75-79.
Abstract:
According to the distribution of the carbon isotopic composition data of over 140 gas samples in dif-ferent places and different beds in Ordos basin, natural gas in the Ordovician weathering crust is more close to the Carbo niferous-Permian coal-typed gas rather than to the Ordovician oil-typed gas represent-ed by the gas in the reservoir under the weathering crust. Plenary distribution of methane carbon isotopic composition of weathering crust gas has a similar feature with that of Carboniferous-Permian gas. Calcu-lation result shows that over 70% of the gas in weathering crust in the Central gas field is from Car-boniferous-Permian beds.
According to the distribution of the carbon isotopic composition data of over 140 gas samples in dif-ferent places and different beds in Ordos basin, natural gas in the Ordovician weathering crust is more close to the Carbo niferous-Permian coal-typed gas rather than to the Ordovician oil-typed gas represent-ed by the gas in the reservoir under the weathering crust. Plenary distribution of methane carbon isotopic composition of weathering crust gas has a similar feature with that of Carboniferous-Permian gas. Calcu-lation result shows that over 70% of the gas in weathering crust in the Central gas field is from Car-boniferous-Permian beds.
1998, 16(3): 85-91.
Abstract:
Results of research on the petrological, petrochemical, rare elements′and trace elements′character-istics of the volcanic event layers in Mid-Taiyuan Formation from middle region of Shanxi and western region of Hebei are presented. Petro-geochemical features, REE distributions, seven-even-numbered- el-ement curves of REE and ratio spiderg rams of trace elements for these pyroclastic rocks perfectly resem-ble, and according to the application of the theory of power function, these pyroclastic rocks considered here should belong to the isochronal products of the same resource, coming from the calc-alk volcanic eruption in island-arc part. The discovery of the isochronal pyroclastic rocks provide the significant in-formation for the division and correlation of strata. In this paper, we can take these volcanic event layers as a marker bed to make regional strata correlation in this area.
Results of research on the petrological, petrochemical, rare elements′and trace elements′character-istics of the volcanic event layers in Mid-Taiyuan Formation from middle region of Shanxi and western region of Hebei are presented. Petro-geochemical features, REE distributions, seven-even-numbered- el-ement curves of REE and ratio spiderg rams of trace elements for these pyroclastic rocks perfectly resem-ble, and according to the application of the theory of power function, these pyroclastic rocks considered here should belong to the isochronal products of the same resource, coming from the calc-alk volcanic eruption in island-arc part. The discovery of the isochronal pyroclastic rocks provide the significant in-formation for the division and correlation of strata. In this paper, we can take these volcanic event layers as a marker bed to make regional strata correlation in this area.
1998, 16(3): 97-101.
Abstract:
Carboni ferous quartz sandstone distributed in the Southwest Depression of the Tarim basin is a set of widespread clastic deposit. During diagenesis, two important secondary structure units were formed in Southwest depression, i. e., Bachu uplift and Maigaiti Slope, which caused the difference in diagenetic sequence of the Carboniferous quartz sandstone in two areas. Under the stable and continuous burial dia-genetic environment, the sandstone reservior in Bachu uplift has a complete diagenetic sequence, and di-agenetic stage could reach B period of late diagenesis and even C period. Thus, the sandstone porosity there was damaged seriously and the average porosity is less than 5%. Conversely, the diagenetic stage of the sandstone in Maigaiti Slope is mainly distributed between A period and B period of the late diagen-esis due to the relatively lower burial depth compared with that in Bachu uplift. Especially, the influence caused by oil emplacement on the sandstone reservior changed the traditional diagenetic environment and made the diagenetic reaction take place in water-oil-rock three phases media which repressed the cemen-tation of some authigenic clay minerals, resulting in the discontinuity of the diagenetic sequence, but, at the same time, many effective porosity was preserved causing the average porosity exceed 7%± in Maigaiei Slope, which is clearly larger than that of the uplift area. For this reason, we believe that the Maigaiti Slope is the most favorable area for the oil exploration work in recent years.
Carboni ferous quartz sandstone distributed in the Southwest Depression of the Tarim basin is a set of widespread clastic deposit. During diagenesis, two important secondary structure units were formed in Southwest depression, i. e., Bachu uplift and Maigaiti Slope, which caused the difference in diagenetic sequence of the Carboniferous quartz sandstone in two areas. Under the stable and continuous burial dia-genetic environment, the sandstone reservior in Bachu uplift has a complete diagenetic sequence, and di-agenetic stage could reach B period of late diagenesis and even C period. Thus, the sandstone porosity there was damaged seriously and the average porosity is less than 5%. Conversely, the diagenetic stage of the sandstone in Maigaiti Slope is mainly distributed between A period and B period of the late diagen-esis due to the relatively lower burial depth compared with that in Bachu uplift. Especially, the influence caused by oil emplacement on the sandstone reservior changed the traditional diagenetic environment and made the diagenetic reaction take place in water-oil-rock three phases media which repressed the cemen-tation of some authigenic clay minerals, resulting in the discontinuity of the diagenetic sequence, but, at the same time, many effective porosity was preserved causing the average porosity exceed 7%± in Maigaiei Slope, which is clearly larger than that of the uplift area. For this reason, we believe that the Maigaiti Slope is the most favorable area for the oil exploration work in recent years.
1998, 16(3): 109-114.
Abstract:
The stable carbon and oxygen isotopic compositions of lacustrine carbonates can yield useful pale-oenvironmental information. The lacustrine carbonates mainly distribute in the first member (Es1) and the 4th member (Es4) of the Shahejie Formation in the Dongying depression, Shandong. Stable-isotopic analysis of 47 lacustrine carbonate samples have been carried out to reconstract the paleohydrology, pale-ochemistry and paleoproductivity of Dongying Lake during Shahejie Formation depositionnal period. The results show that Dongying Lake is a closed lake during Es1 and Es4 deposition period. The other pale-olimnological characteristics are: Paleosalinity and E/P: middle Es4 lower upper Es4> Es1> upper up-per Es4; Paleolake level: upper upper Es4> Es1> middle Es4 lower upper Es4; Paleoproductivity: Es1> upper upper Es4> middle Es4 lower upper Es4.
The stable carbon and oxygen isotopic compositions of lacustrine carbonates can yield useful pale-oenvironmental information. The lacustrine carbonates mainly distribute in the first member (Es1) and the 4th member (Es4) of the Shahejie Formation in the Dongying depression, Shandong. Stable-isotopic analysis of 47 lacustrine carbonate samples have been carried out to reconstract the paleohydrology, pale-ochemistry and paleoproductivity of Dongying Lake during Shahejie Formation depositionnal period. The results show that Dongying Lake is a closed lake during Es1 and Es4 deposition period. The other pale-olimnological characteristics are: Paleosalinity and E/P: middle Es4 lower upper Es4> Es1> upper up-per Es4; Paleolake level: upper upper Es4> Es1> middle Es4 lower upper Es4; Paleoproductivity: Es1> upper upper Es4> middle Es4 lower upper Es4.
1998, 16(3): 119-123,131.
Abstract:
Saline lakes of Cenozoic are extensively developed in China. There are unique sedimentary environ-ment and condition of hydrocarbon generation in these saline lakes. The geochemical charactristics of source rocks and hydrocarbons generated rom saline lakes sedimentary environment are different to those generated from f reshw ater lacustrine facies and those generated from marine facies. Is is all intro-duce that biomarker assemblage characterisitics, generating condition and geochemical significance of source rocks and crude oils in saline lakes.
Saline lakes of Cenozoic are extensively developed in China. There are unique sedimentary environ-ment and condition of hydrocarbon generation in these saline lakes. The geochemical charactristics of source rocks and hydrocarbons generated rom saline lakes sedimentary environment are different to those generated from f reshw ater lacustrine facies and those generated from marine facies. Is is all intro-duce that biomarker assemblage characterisitics, generating condition and geochemical significance of source rocks and crude oils in saline lakes.
1998, 16(3): 132-136.
Abstract:
According to structure features, the Changxing reefs are classified as mature, semimature and imma-ture reefs. The mature reefs have the characteristics of large scale, complex shape, complete structure, lots of hermatrypic organisms and shallowing sedimentary sequence. The immature reefs have the char-acteristics of small scale, simple shape, incomplete structure, a few hermatrypic organisms and deepening sedimentary sequence. The semimature reefs'characteristics are between the mature reefs and the imma-ture reefs. The mature reefs are distributed over platform edge and transition of platform-flat and plat-form-mulde deep water. The semimature reefs are distributed over transition of platform-flat and plat-form-mulde semideep water. The immaturereefs are distributed over platform-flat and platform-mulde.
According to structure features, the Changxing reefs are classified as mature, semimature and imma-ture reefs. The mature reefs have the characteristics of large scale, complex shape, complete structure, lots of hermatrypic organisms and shallowing sedimentary sequence. The immature reefs have the char-acteristics of small scale, simple shape, incomplete structure, a few hermatrypic organisms and deepening sedimentary sequence. The semimature reefs'characteristics are between the mature reefs and the imma-ture reefs. The mature reefs are distributed over platform edge and transition of platform-flat and plat-form-mulde deep water. The semimature reefs are distributed over transition of platform-flat and plat-form-mulde semideep water. The immaturereefs are distributed over platform-flat and platform-mulde.
1998, 16(3): 141-146.
Abstract:
According to the analysis of micro-characteristics and depositional environment of the main exploit-ed coals, and using the triangular diagram (In the diagram, the significance to indicate coal facies of the minerals in coal, especially authig enicones, has been taken into consideration) and the map of maceral, the authors have found that there is a higher active component and sulfur content in tide-dominated delta plain than that in river-dominated delta plain, and the divergence in the triang ular is small. Besides, the inert component in the coal formed on the tidal flat is high and its distribution is stable, and there is a likeness between different coals formed in the same depositional environment. But there is a difference of microcomposition on the plane because of the various environment.
According to the analysis of micro-characteristics and depositional environment of the main exploit-ed coals, and using the triangular diagram (In the diagram, the significance to indicate coal facies of the minerals in coal, especially authig enicones, has been taken into consideration) and the map of maceral, the authors have found that there is a higher active component and sulfur content in tide-dominated delta plain than that in river-dominated delta plain, and the divergence in the triang ular is small. Besides, the inert component in the coal formed on the tidal flat is high and its distribution is stable, and there is a likeness between different coals formed in the same depositional environment. But there is a difference of microcomposition on the plane because of the various environment.
1998, 16(3): 153-155,160.
Abstract:
Immature organic matter(peat) were pyrolysized at temperatures ranging from 200℃ to 400℃ under high pressure ranging from 0.1 to 2 GPa in a closed system. As the index of maturation, vitrinite reflectance (Ro) of samples was measured. The results display that Ro value of samples tends to rise when temperature increases under constant pressure and the Ro value decreases when pressure increases under constant pressure. These results indicate that pressure is one of factors that influence the maturation of organic matter as important as temperature do, and the pressure can retard the thermal evolution of organic matter. The function of pressure has its interior kinetic principle. The role of pressure in organic maturation process of organic matter can't benig nored as suggested by results of experiment and fact of Geology. It has important theoretical and practical significance on studying the function and influence of pressure by means of pyrolysis
Immature organic matter(peat) were pyrolysized at temperatures ranging from 200℃ to 400℃ under high pressure ranging from 0.1 to 2 GPa in a closed system. As the index of maturation, vitrinite reflectance (Ro) of samples was measured. The results display that Ro value of samples tends to rise when temperature increases under constant pressure and the Ro value decreases when pressure increases under constant pressure. These results indicate that pressure is one of factors that influence the maturation of organic matter as important as temperature do, and the pressure can retard the thermal evolution of organic matter. The function of pressure has its interior kinetic principle. The role of pressure in organic maturation process of organic matter can't benig nored as suggested by results of experiment and fact of Geology. It has important theoretical and practical significance on studying the function and influence of pressure by means of pyrolysis
